Potential applications of graphene

Potential graphene applications include lightweight, thin, and flexible electric/photonics circuits, solar cells, and various medical, chemical and industrial processes enhanced or enabled by the use of new graphene materials.
In 2008, graphene produced by exfoliation was one of the most expensive materials on Earth, with a sample the area of a cross section of a human hair costing more than $1,000 as of April 2008 (about $100,000,000/cm2). Since then, exfoliation procedures have been scaled up, and now companies sell graphene in large quantities. The price of epitaxial graphene on silicon carbide is dominated by the substrate price, which was approximately $100/cm2 as of 2009. Hong and his team in South Korea pioneered the synthesis of large-scale graphene films using chemical vapour deposition (CVD) on thin nickel layers, which triggered research on practical applications, with wafer sizes up to reported. By 2017, graphene electronics were being manufactured in a commercial fab on a 200 mm line.
In 2013, the European Union made a €1 billion grant to be used for research into potential graphene applications. In 2013 the Graphene Flagship consortium formed, including Chalmers University of Technology and seven other European universities and research centers, along with Nokia.
Medicine.
Researchers in 2011 discovered the ability of graphene to accelerate the osteogenic differentiation of human mesenchymal stem cells without the use of biochemical inducers.
In 2015 researchers used graphene to create biosensors with epitaxial graphene on silicon carbide. The sensors bind to 8-hydroxydeoxyguanosine (8-OHdG) and is capable of selective binding with antibodies. The presence of 8-OHdG in blood, urine and saliva is commonly associated with DNA damage. Elevated levels of 8-OHdG have been linked to increased risk of several cancers. By the next year, a commercial version of a graphene biosensor was being used by biology researchers as a protein binding sensor platform.
In 2016 researchers revealed that uncoated graphene can be used as neuro-interface electrode without altering or damaging properties such as signal strength or formation of scar tissue. Graphene electrodes in the body are significantly more stable than electrodes of tungsten or silicon because of properties such as flexibility, bio-compatibility and conductivity.
Tissue engineering.
Graphene has been investigated for tissue engineering. It has been used as a reinforcing agent to improve the mechanical properties of biodegradable polymeric nanocomposites for engineering bone tissue applications. Dispersion of low weight % of graphene (≈0.02 wt.%) increased in compressive and flexural mechanical properties of polymeric nanocomposites. The addition of graphene nanoparticles in the polymer matrix lead to improvements in the crosslinking density of the nanocomposite and better load transfer from the polymer matrix to the underlying nanomaterial thereby increasing the mechanical properties.
Contrast agents, bioimaging.
Functionalized and surfactant dispersed graphene solutions have been designed as blood pool MRI contrast agents. Further, iodine and manganese incorporating graphene nanoparticles have served as multimodal MRI-computerized tomograph (CT) contrast agents. Graphene micro- and nano-particles have served as contrast agents for photoacoustic and thermoacoustic tomography. Graphene has also been reported to be efficiently taking up cancerous cells thereby enabling the design of drug delivery agents for cancer therapy. Graphene nanoparticles of various morphologies such as graphene nanoribbons, graphene nanoplatelets and graphene nanoonions are non-toxic at low concentrations and do not alter stem cell differentiation suggesting that they may be safe to use for biomedical applications.
Polymerase chain reaction.
Graphene is reported to have enhanced PCR by increasing the yield of DNA product.<ref name="doi10.1088/0957-4484/23/45/455106"></ref> Experiments revealed that graphene's thermal conductivity could be the main factor behind this result. Graphene yields DNA product equivalent to positive control with up to 65% reduction in PCR cycles.
Devices.
Graphene's modifiable chemistry, large surface area per unit volume, atomic thickness and molecularly gatable structure make antibody-functionalized graphene sheets excellent candidates for mammalian and microbial detection and diagnosis devices. Graphene is so thin that water has near-perfect wetting transparency which is an important property particularly in developing bio-sensor applications. This means that a sensor coated in graphene has as much contact with an aqueous system as an uncoated sensor, while remaining protected mechanically from its environment.
Integration of graphene (thickness of ) layers as nanoelectrodes into a nanopore can potentially solve a bottleneck for nanopore-based single-molecule DNA sequencing.
On November 20, 2013 the Bill & Melinda Gates Foundation awarded $100,000 'to develop new elastic composite materials for condoms containing nanomaterials like graphene'.
In 2014, graphene-based, transparent (across infrared to ultraviolet frequencies), flexible, implantable medical sensor microarrays were announced that allow the viewing of brain tissue hidden by implants. Optical transparency was greater than 90%. Applications demonstrated include optogenetic activation of focal cortical areas, "in vivo" imaging of cortical vasculature via fluorescence microscopy and 3D optical coherence tomography.
Drug delivery.
Researchers at Monash University discovered that a sheet of graphene oxide can be transformed into liquid crystal droplets spontaneously—like a polymer—simply by placing the material in a solution and manipulating the pH. The graphene droplets change their structure in the presence of an external magnetic field. This finding raises the possibility of carrying a drug in graphene droplets and releasing the drug upon reaching the targeted tissue by making the droplets change shape in a magnetic field. Another possible application is in disease detection if graphene is found to change shape at the presence of certain disease markers such as toxins.
A graphene ‘flying carpet’ was demonstrated to deliver two anti-cancer drugs sequentially to the lung tumor cells (A549 cell) in a mouse model. Doxorubicin (DOX) is embedded onto the graphene sheet, while the molecules of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) are linked to the nanostructure via short peptide chains. Injected intravenously, the graphene strips with the drug payload preferentially concentrate to the cancer cells due to common blood vessel leakage around the tumor. Receptors on the cancer cell membrane bind TRAIL and cell surface enzymes clip the peptide thus release the drug onto the cell surface. Without the bulky TRAIL, the graphene strips with the embedded DOX are swallowed into the cells. The intracellular acidic environment promotes DOX's release from graphene. TRAIL on the cell surface triggers the apoptosis while DOX attacks the nucleus. These two drugs work synergistically and were found to be more effective than either drug alone.
The development of nanotechnology and molecular biology has provided the improvement of nanomaterials with speciﬁc properties which are now able to overcome the weaknesses of traditional disease diagnostic and therapeutic procedures. In recent years, more attention has been devoted to designing and the development of new methods for realizing sustained release of diverse drugs. Since each drug has a plasma level above which is toxic and below which is ineﬀective and in conventional drug delivery, the drug concentration in the blood rises quickly and then declines, the main aim of an ideal drug delivery system (DDS) is to maintain the drug within a desired therapeutic range after a single dose, and/or target the drug to a speciﬁc region while simultaneously lowering the systemic levels of the drug. Graphene–based materials such as graphene oxide (GO) have considerable potential for several biological applications including the development of new drug release system. GOs are an abundance of functional groups such as hydroxyl, epoxy, and carboxyl on its basal surface and edges that can be also used to immobilize or load various biomolecules for biomedical applications. On the other side, biopolymers have frequently been used as raw materials for designing drug delivery formulations owing to their excellent properties, such as non-toxicity, biocompatibility, biodegradability and environmental sensitivity, etc. Protein therapeutics possess advantages over small molecule approaches including high target speciﬁcity and low oﬀ target eﬀects with normal biological processes. Human serum albumin (HSA) is one of the most abundant blood proteins. It serves as a transport protein for several endogenous and exogenous ligands as well as various drug molecules. HSA nanoparticles have long been the center of attention in the pharmaceutical industry due to their ability to bind to various drug molecules, high storage stability and in vivo application, non–toxicity and antigenicity, biodegradability, reproducibility, scale–up of the production process and a better control over release properties. In addition, signiﬁcant amounts of drugs can be incorporated into the particle matrix because of the large number of drug binding sites on the albumin molecule. Therefore, the combination of HSA-NPs and GO-NSs could be useful for reducing the cytotoxicity of GO-NSs and the enhancement of drug loading and sustained drug release in cancer therapy.
Biomicrorobotics.
Researchers demonstrated a nanoscale biomicrorobot (or cytobot) made by cladding a living endospore cell with graphene quantum dots. The device acted as a humidity sensor.
Testing.
In 2014 a graphene based blood glucose testing product was announced.
Toxicity.
The toxicity of graphene has been extensively debated in the literature. The most comprehensive review on graphene toxicity published by Lalwani "et al." summarizes current knowledge of the "in vitro", "in vivo", antimicrobial, and environmental toxicities of graphene, and highlights the various mechanisms of graphene toxicity.
Results show that the toxicity of graphene is dependent on several factors such as shape, size, purity, post-production processing steps, oxidative state, functional groups, dispersion state, synthesis methods, route and dose of administration, and exposure times.
Electronics.
Graphene has a high carrier mobility, and low noise, allowing it to be used as the channel in a field-effect transistor. Unmodified graphene does not have an energy band gap, making it unsuitable for digital electronics. However, modifications (e.g. Graphene nanoribbons) have created potential uses in various areas of electronics.
Transistors.
Graphene transistors have been built that are chemically controlled, and others that are voltage controlled.
Graphene exhibits a pronounced response to perpendicular external electric fields, potentially forming field-effect transistors (FET). A 2004 paper documented FETs with an on-off ratio of ≈30 at room temperature. A 2006 paper announced an all-graphene planar FET with side gates. Their devices showed changes of 2% at cryogenic temperatures. The first top-gated FET (on–off ratio of <2) was demonstrated in 2007. Graphene nanoribbons may prove generally capable of replacing silicon as a semiconductor.
 for graphene-based electronics was issued in 2006. In 2008, researchers at MIT Lincoln Lab produced hundreds of transistors on a single chip and in 2009, very high frequency transistors were produced at Hughes Research Laboratories.
A 2008 paper demonstrated a switching effect based on a reversible chemical modification of the graphene layer that gives an on–off ratio of greater than six orders of magnitude. These reversible switches could potentially be employed in nonvolatile memories. In 2008, the smallest transistor so far, one atom thick, 10 atoms wide was made of graphene. IBM announced in December 2008 that they had fabricated and characterized graphene transistors operating at GHz frequencies.
In 2009, researchers demonstrated four different types of logic gates, each composed of a single graphene transistor. In May 2009, an n-type transistor was announced meaning that both n and p-type graphene transistors had been created. A functional graphene integrated circuit was demonstrated—a complementary inverter consisting of one p- and one n-type graphene transistor. However, this inverter suffered from a very low voltage gain. Typically, the amplitude of the output signal is about 40 times less than that of the input signal. Moreover, none of these circuits operated at frequencies higher than 25 kHz.
In the same year, tight-binding numerical simulations demonstrated that the band-gap induced in graphene bilayer field effect transistors is not sufficiently large for high-performance transistors for digital applications, but can be sufficient for ultra-low voltage applications, when exploiting a tunnel-FET architecture.
In February 2010, researchers announced graphene transistors with an on-off rate of 100 gigahertz, far exceeding the rates of prior attempts, and exceeding the speed of silicon transistors with an equal gate length. The devices were made with conventional silicon-manufacturing equipment. According to a January 2010 report, graphene was epitaxially grown on SiC in a quantity and with quality suitable for mass production of integrated circuits. At high temperatures, the quantum Hall effect could be measured in these samples. IBM built 'processors' using 100 GHz transistors on graphene sheets.
In June 2011, IBM researchers announced that they had succeeded in creating the first graphene-based integrated circuit, a broadband radio mixer. The circuit handled frequencies up to 10 GHz. Its performance was unaffected by temperatures up to 127 °C. In November researchers used 3d printing (additive manufacturing) as a method for fabricating graphene devices.
In 2013, researchers demonstrated graphene's high mobility in a detector that allows broad band frequency selectivity ranging from the THz to IR region (0.76–33 THz) A separate group created a terahertz-speed transistor with bistable characteristics, which means that the device can spontaneously switch between two electronic states. The device consists of two layers of graphene separated by an insulating layer of boron nitride a few atomic layers thick. Electrons move through this barrier by quantum tunneling. These new transistors exhibit "negative differential conductance", whereby the same electric current flows at two different applied voltages. In June, an 8 transistor 1.28 GHz ring oscillator circuit was described.
The negative differential resistance experimentally observed in graphene field-effect transistors of conventional design allows for construction of viable non-Boolean computational architectures with graphene. The negative differential resistance—observed under certain biasing schemes—is an intrinsic property of graphene resulting from its symmetric band structure. The results present a conceptual change in graphene research and indicate an alternative route for graphene's applications in information processing.
In 2013 researchers created transistors printed on flexible plastic that operate at 25 gigahertz, sufficient for communications circuits and that can be fabricated at scale. The researchers first fabricated non-graphene-containing structures—the electrodes and gates—on plastic sheets. Separately, they grew large graphene sheets on metal, then peeled it and transferred it to the plastic. Finally, they topped the sheet with a waterproof layer. The devices work after being soaked in water, and are flexible enough to be folded.
In 2015 researchers devised a digital switch by perforating a graphene sheet with boron-nitride nanotubes that exhibited a switching ratio of 105 at a turn-on voltage of 0.5 V. Density functional theory suggested that the behavior came from the mismatch of the density of states.
Trilayer.
An electric field can change trilayer graphene's crystal structure, transforming its behavior from metal-like into semiconductor-like. A sharp metal scanning tunneling microscopy tip was able to move the domain border between the upper and lower graphene configurations. One side of the material behaves as a metal, while the other side behaves as a semiconductor. Trilayer graphene can be stacked in either Bernal or rhombohedral configurations, which can exist in a single flake. The two domains are separated by a precise boundary at which the middle layer is strained to accommodate the transition from one stacking pattern to the other.
Silicon transistors function as either p-type or n-type semiconductors, whereas graphene could operate as both. This lowers costs and is more versatile. The technique provides the basis for a field-effect transistor. Scalable manufacturing techniques have yet to be developed.
In trilayer graphene, the two stacking configurations exhibit very different electronic properties. The region between them consists of a localized strain soliton where the carbon atoms of one graphene layer shift by the carbon–carbon bond distance. The free-energy difference between the two stacking configurations scales quadratically with electric field, favoring rhombohedral stacking as the electric field increases.
This ability to control the stacking order opens the way to new devices that combine structural and electrical properties.
Graphene-based transistors could be much thinner than modern silicon devices, allowing faster and smaller configurations.
Transparent conducting electrodes.
Graphene's high electrical conductivity and high optical transparency make it a candidate for transparent conducting electrodes, required for such applications as touchscreens, liquid crystal displays, inorganic photovoltaics cells, organic photovoltaic cells, and organic light-emitting diodes. In particular, graphene's mechanical strength and flexibility are advantageous compared to indium tin oxide, which is brittle. Graphene films may be deposited from solution over large areas.
Large-area, continuous, transparent and highly conducting few-layered graphene films were produced by chemical vapor deposition and used as anodes for application in photovoltaic devices. A power conversion efficiency (PCE) up to 1.7% was demonstrated, which is 55.2% of the PCE of a control device based on indium tin oxide. However, the main disadvantage brought by the fabrication method will be the poor substrate bondings that will eventually lead to poor cyclic stability and cause high resistivity to the electrodes.
Organic light-emitting diodes (OLEDs) with graphene anodes have been demonstrated. The device was formed by solution-processed graphene on a quartz substrate. The electronic and optical performance of graphene-based devices are similar to devices made with indium tin oxide. In 2017 OLED electrodes were produced by CVD on a copper substrate.
A carbon-based device called a light-emitting electrochemical cell (LEC) was demonstrated with chemically-derived graphene as the cathode and the conductive polymer Poly(3,4-ethylenedioxythiophene) (PEDOT) as the anode. Unlike its predecessors, this device contains only carbon-based electrodes, with no metal.
In 2014 a prototype graphene-based flexible display was demonstrated.
In 2016 researchers demonstrated a display that used interferometry modulation to control colors, dubbed a "graphene balloon device" made of silicon containing 10 μm circular cavities covered by two graphene sheets. The degree of curvature of the sheets above each cavity defines the color emitted. The device exploits the phenomena known as Newton's rings created by interference between light waves bouncing off the bottom of the cavity and the (transparent) material. Increasing the distance between the silicon and the membrane increased the wavelength of the light. The approach is used in colored e-reader displays and smartwatches, such as the Qualcomm Toq. They use silicon materials instead of graphene. Graphene reduces power requirements.
Frequency multiplier.
In 2009, researchers built experimental graphene frequency multipliers that take an incoming signal of a certain frequency and output a signal at a multiple of that frequency.
Optoelectronics.
Graphene strongly interacts with photons, with the potential for direct band-gap creation. This is promising for optoelectronic and nanophotonic devices. Light interaction arises due to the Van Hove singularity. Graphene displays different time scales in response to photon interaction, ranging from femtoseconds (ultra-fast) to picoseconds. Potential uses include transparent films, touch screens and light emitters or as a plasmonic device that confines light and alters wavelengths.
Hall effect sensors.
Due to extremely high electron mobility, graphene may be used for production of highly sensitive Hall effect sensors. Potential application of such sensors is connected with DC current transformers for special applications. New record high sensitive Hall sensors are reported in April 2015. These sensors are two times better than existing Si based sensors.
Quantum dots.
Graphene quantum dots (GQDs) keep all dimensions less than 10 nm. Their size and edge crystallography govern their electrical, magnetic, optical, and chemical properties. GQDs can be produced via graphite nanotomy or via bottom-up, solution-based routes (Diels-Alder, cyclotrimerization and/or cyclodehydrogenation reactions). GQDs with controlled structure can be incorporated into applications in electronics, optoelectronics and electromagnetics. Quantum confinement can be created by changing the width of graphene nanoribbons (GNRs) at selected points along the ribbon. It is studied as a catalyst for fuel cells.
Organic electronics.
A semiconducting polymer (poly(3-hexylthiophene) placed on top of single-layer graphene vertically conducts electric charge better than on a thin layer of silicon. A 50 nm thick polymer film conducted charge about 50 times better than a 10 nm thick film, potentially because the former consists of a mosaic of variably-oriented crystallites forms a continuous pathway of interconnected crystals. In a thin film or on silicon, plate-like crystallites are oriented parallel to the graphene layer. Uses include solar cells.
Spintronics.
Large-area graphene created by chemical vapor deposition (CVD) and layered on a SiO2 substrate, can preserve electron spin over an extended period and communicate it. Spintronics varies electron spin rather than current flow. The spin signal is preserved in graphene channels that are up to 16 micrometers long over a nanosecond. Pure spin transport and precession extended over 16 μm channel lengths with a spin lifetime of 1.2 ns and a spin diffusion length of ≈6 μm at room temperature.
Spintronics is used in disk drives for data storage and in magnetic random-access memory. Electronic spin is generally short-lived and fragile, but the spin-based information in current devices needs to travel only a few nanometers. However, in processors, the information must cross several tens of micrometers with aligned spins. Graphene is the only known candidate for such behavior.
Conductive ink.
In 2012 Vorbeck Materials started shipping the Siren anti-theft packaging device, which uses their graphene-based Vor-Ink circuitry to replace the metal antenna and external wiring to an RFID chip. This was the world's first commercially available product based on graphene.
Light processing.
Optical modulator.
When the Fermi level of graphene is tuned, its optical absorption can be changed. In 2011, researchers reported the first graphene-based optical modulator. Operating at without a temperature controller, this modulator has a broad bandwidth (from 1.3 to 1.6 μm) and small footprint (~).
A Mach-Zehnder modulator based on a hybrid graphene-silicon waveguide has been demonstrated recently, which can process signals nearly chirp-free. An extinction up to 34.7 dB and a minimum chirp parameter of -0.006 are obtained. Its insertion loss is roughly -1.37 dB.
Ultraviolet lens.
A hyperlens is a real-time super-resolution lens that can transform evanescent waves into propagating waves and thus break the diffraction limit. In 2016 a hyperlens based on dielectric layered graphene and h-boron nitride (h-BN) can surpass metal designs. Based on its anisotropic properties, flat and cylindrical hyperlenses were numerically verified with layered graphene at 1200 THz and layered h-BN at 1400 THz, respectively. In 2016 a 1-nm thick graphene microlens that can image objects the size of a single bacterium. The lens was created by spraying a sheet of graphene oxide solution, then molding the lens using a laser beam. It can resolve objects as small as 200 nanometers, and see into the near infrared. It breaks the diffraction limit and achieve a focal length less than half the wavelength of light. Possible applications include thermal imaging for mobile phones, endoscopes, nanosatellites and photonic chips in supercomputers and superfast broadband distribution.
Infrared light detection.
Graphene reacts to the infrared spectrum at room temperature, albeit with sensitivity 100 to 1000 times too low for practical applications. However, two graphene layers separated by an insulator allowed an electric field produced by holes left by photo-freed electrons in one layer to affect a current running through the other layer. The process produces little heat, making it suitable for use in night-vision optics. The sandwich is thin enough to be integrated in handheld devices, eyeglass-mounted computers and even contact lenses.
Photodetector.
A graphene/n-type silicon heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity. By introducing a thin interfacial oxide layer, the dark current of graphene/n-Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n-Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 1013 cm Hz1/2 W2 at the peak wavelength of 890 nm in vacuum. In addition, the improved graphene/n-Si heterojunction photodetectors possess high responsivity of 0.73 A W−1 and high photo-to-dark current ratio of ≈107. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors. Recently, a graphene/si Schottky photodetector with record-fast response speed (< 25 ns) from wavelength 350 nm to 1100 nm are presented. The photodetectors exhibit excellent long-term stability even stored in air for more than 2 years. These results not only advance the development of high-performance photodetectors based on the graphene/Si Schottky junction, but also have important implications for mass-production of graphene-based photodetector array devices for cost-effective environmental monitoring, medical images, free-space communications, photoelectric smart-tracking, and integration with CMOS circuits for emerging interest-of-things applications, etc.
Energy.
Generation.
Ethanol distillation.
Graphene oxide membranes allow water vapor to pass through, but are impermeable to other liquids and gases. This phenomenon has been used for further distilling of vodka to higher alcohol concentrations, in a room-temperature laboratory, without the application of heat or vacuum as used in traditional distillation methods.
Solar cells.
Charge conductor.
Graphene solar cells use graphene's unique combination of high electrical conductivity and optical transparency. This material absorbs only 2.6% of green light and 2.3% of red light. Graphene can be assembled into a film electrode with low roughness. These films must be made thicker than one atomic layer to obtain useful sheet resistances. This added resistance can be offset by incorporating conductive filler materials, such as a silica matrix. Reduced conductivity can be offset by attaching large aromatic molecules such as pyrene-1-sulfonic acid sodium salt (PyS) and the disodium salt of 3,4,9,10-perylenetetracarboxylic diimide bisbenzenesulfonic acid (PDI). These molecules, under high temperatures, facilitate better π-conjugation of the graphene basal plane.
Light collector.
Using graphene as a photoactive material requires its bandgap to be 1.4–1.9 eV. In 2010, single cell efficiencies of nanostructured graphene-based PVs of over 12% were achieved. According to P. Mukhopadhyay and R. K. Gupta organic photovoltaics could be "devices in which semiconducting graphene is used as the photoactive material and metallic graphene is used as the conductive electrodes".
In 2008, chemical vapor deposition produced graphene sheets by depositing a graphene film made from methane gas on a nickel plate. A protective layer of thermoplastic is laid over the graphene layer and the nickel underneath is then dissolved in an acid bath. The final step is to attach the plastic-coated graphene to a flexible polymer sheet, which can then be incorporated into a PV cell. Graphene/polymer sheets range in size up to 150 square centimeters and can be used to create dense arrays.
Silicon generates only one current-driving electron for each photon it absorbs, while graphene can produce multiple electrons. Solar cells made with graphene could offer 60% conversion efficiency.
Electrode.
In 2010, researchers first reported creating a graphene-silicon heterojunction solar cell, where graphene served as a transparent electrode and introduced a built-in electric field near the interface between the graphene and n-type silicon to help collect charge carriers. In 2012 researchers reported efficiency of 8.6% for a prototype consisting of a silicon wafer coated with trifluoromethanesulfonyl-amide (TFSA) doped graphene. Doping increased efficiency to 9.6% in 2013. In 2015 researchers reported efficiency of 15.6% by choosing the optimal oxide thickness on the silicon. This combination of carbon materials with traditional silicon semiconductors to fabricate solar cells has been a promising field of carbon science.
In 2013, another team reported 15.6% percent by combining titanium oxide and graphene as a charge collector and perovskite as a sunlight absorber. The device is manufacturable at temperatures under using solution-based deposition. This lowers production costs and offers the potential using flexible plastics.
In 2015, researchers developed a prototype cell that used semitransparent perovskite with graphene electrodes. The design allowed light to be absorbed from both sides. It offered efficiency of around 12 percent with estimated production costs of less than $0.06/watt. The graphene was coated with PEDOT:PSS conductive polymer (polythiophene) polystyrene sulfonate). Multilayering graphene via CVD created transparent electrodes reducing sheet resistance. Performance was further improved by increasing contact between the top electrodes and the hole transport layer.
Fuel cells.
Appropriately perforated graphene (and hexagonal boron nitride hBN) can allow protons to pass through it, offering the potential for using graphene monolayers as a barrier that blocks hydrogen atoms but not protons/ionized hydrogen (hydrogen atoms with their electrons stripped off). They could even be used to extract hydrogen gas out of the atmosphere that could power electric generators with ambient air.
The membranes are more effective at elevated temperatures and when covered with catalytic nanoparticles such as platinum.
Graphene could solve a major problem for fuel cells: fuel crossover that reduces efficiency and durability.
In methanol fuel cells, graphene used as a barrier layer in the membrane area, has reduced fuel cross over with negligible proton resistance, improving the performance.
At room temperature, proton conductivity with monolayer hBN, outperforms graphene, with resistivity to proton flow of about 10 Ω cm2 and a low activation energy of about 0.3 electronvolts. At higher temperatures, graphene outperforms with resistivity estimated to fall below 10−3 Ω cm2 above 250 degrees Celsius.
In another project, protons easily pass through slightly imperfect graphene membranes on fused silica in water. The membrane was exposed to cycles of high and low pH. Protons transferred reversibly from the aqueous phase through the graphene to the other side where they undergo acid–base chemistry with silica hydroxyl groups. Computer simulations indicated energy barriers of 0.61–0.75 eV for hydroxyl-terminated atomic defects that participate in a Grotthuss-type relay, while pyrylium-like ether terminations did not. Recently, Paul and co-workers at IISER Bhopal demonstrated solid state proton conduction for oxygen functionalized few-layer graphene (8.7x10−3 S/cm) with a low activation barrier (0.25 eV).
Thermoelectrics.
Adding 0.6% graphene to a mixture of lanthanum and partly reduced strontium titanium oxide produces a strong Seebeck at temperatures ranging from room temperature to 750 °C (compared to 500–750 without graphene). The material converts 5% of the heat into electricity (compared to 1% for strontium titanium oxide.)
Condenser coating.
In 2015 a graphene coating on steam condensers quadrupled condensation efficiency, increasing overall plant efficiency by 2–3 percent.
Storage.
Supercapacitor.
Due to graphene's high surface-area-to-mass ratio, one potential application is in the conductive plates of supercapacitors.
In February 2013 researchers announced a novel technique to produce graphene supercapacitors based on the DVD burner reduction approach.
In 2014 a supercapacitor was announced that was claimed to achieve energy density comparable to current lithium-ion batteries.
In 2015 the technique was adapted to produce stacked, 3-D supercapacitors. Laser-induced graphene was produced on both sides of a polymer sheet. The sections were then stacked, separated by solid electrolytes, making multiple microsupercapacitors. The stacked configuration substantially increased the energy density of the result. In testing, the researchers charged and discharged the devices for thousands of cycles with almost no loss of capacitance. The resulting devices were mechanically flexible, surviving 8,000 bending cycles. This makes them potentially suitable for rolling in a cylindrical configuration.  Solid-state polymeric electrolyte-based devices exhibit areal capacitance of >9 mF/cm2 at a current density of 0.02 mA/cm2, over twice that of conventional aqueous electrolytes.
Also in 2015 another project announced a microsupercapacitor that is small enough to fit in wearable or implantable devices. Just one-fifth the thickness of a sheet of paper, it is capable of holding more than twice as much charge as a comparable thin-film lithium battery. The design employed laser-scribed graphene, or LSG with manganese dioxide. They can be fabricated without extreme temperatures or expensive “dry rooms”. Their capacity is six times that of commercially available supercapacitors. The device reached volumetric capacitance of over 1,100 F/cm3. This corresponds to a specific capacitance of the constituent MnO2 of 1,145 F/g, close to the theoretical maximum of 1,380 F/g. Energy density varies between 22 and 42 Wh/l depending on device configuration.
In May 2015 a boric acid-infused, laser-induced graphene supercapacitor tripled its areal energy density and increased its volumetric energy density 5-10 fold. The new devices proved stable over 12,000 charge-discharge cycles, retaining 90 percent of their capacitance. In stress tests, they survived 8,000 bending cycles.
Batteries.
Silicon-graphene anode lithium ion batteries were demonstrated in 2012.
Stable lithium ion cycling was demonstrated in bi- and few layer graphene films grown on nickel substrates, while single layer graphene films have been demonstrated as a protective layer against corrosion in battery components such as the battery case. This creates possibilities for flexible electrodes for microscale Li-ion batteries, where the anode acts as the active material and the current collector.
Researchers built a lithium-ion battery made of graphene and silicon, which was claimed to last over a week on one charge and took only 15 minutes to charge.
In 2015 argon-ion based plasma processing was used to bombard graphene samples with argon ions. That knocked out some carbon atoms and increased the capacitance of the materials three-fold. These “armchair” and “zigzag” defects are named based on the configurations of the carbon atoms that surround the holes.
In 2016, Huawei announced graphene-assisted lithium-ion batteries with greater heat tolerance and twice the life span of "traditional" Lithium-Ion batteries, the component with the shortest life span in mobile phones.
Sensors.
Biosensors.
Graphene does not oxidize in air or in biological fluids, making it an attractive material for use as a biosensor. A graphene circuit can be configured as a field effect biosensor by applying biological capture molecules and blocking layers to the graphene, then controlling the voltage difference between the graphene and the liquid that includes the biological test sample. Of the various types of graphene sensors that can be made, biosensors were the first to be available for sale.
Pressure sensors.
The electronic properties of graphene/h-BN heterostructures can be modulated by changing the interlayer distances via applying external pressure, leading to potential realization of atomic thin pressure sensors. In 2011 researchers proposed an in-plane pressure sensor consisting of graphene sandwiched between hexagonal boron nitride and a tunneling pressure sensor consisting of h-BN sandwiched by graphene. The current varies by 3 orders of magnitude as pressure increases from 0 to 5 nN/nm². This structure is insensitive to the number of wrapping h-BN layers, simplifying process control. Because h-BN and graphene are inert to high temperature, the device could support ultra-thin pressure sensors for application under extreme conditions.
In 2016 researchers demonstrated a biocompatible pressure sensor made from mixing graphene flakes with cross-linked polysilicone (found in silly putty).
NEMS.
Nanoelectromechanical systems (NEMS) can be designed and characterized by understanding the interaction and coupling between the mechanical, electrical, and the van der Waals energy domains. Quantum mechanical limit governed by Heisenberg uncertainty relation decides the ultimate precision of nanomechanical systems. Quantum squeezing can improve the precision by reducing quantum fluctuations in one desired amplitude of the two quadrature amplitudes. Traditional NEMS hardly achieve quantum squeezing due to their thickness limits. A scheme to obtain squeezed quantum states through typical experimental graphene NEMS structures taking advantages of its atomic scale thickness has been proposed.
Molecular absorption.
Theoretically graphene makes an excellent sensor due to its 2D structure. The fact that its entire volume is exposed to its surrounding environment makes it very efficient to detect adsorbed molecules. However, similar to carbon nanotubes, graphene has no dangling bonds on its surface. Gaseous molecules cannot be readily adsorbed onto graphene surfaces, so intrinsically graphene is insensitive. The sensitivity of graphene chemical gas sensors can be dramatically enhanced by functionalization, for example, coating the film with a thin layer of certain polymers. The thin polymer layer acts like a concentrator that absorbs gaseous molecules. The molecule absorption introduces a local change in electrical resistance of graphene sensors. While this effect occurs in other materials, graphene is superior due to its high electrical conductivity (even when few carriers are present) and low noise, which makes this change in resistance detectable.
Piezoelectric effect.
Density functional theory simulations predict that depositing certain adatoms on graphene can render it piezoelectrically responsive to an electric field applied in the out-of-plane direction. This type of locally engineered piezoelectricity is similar in magnitude to that of bulk piezoelectric materials and makes graphene a candidate for control and sensing in nanoscale devices.
Body motion.
Promoted by the demand for wearable devices, graphene has been proved to be a promising material for potential applications in flexible and highly sensitive strain sensors. An environment-friendly and cost-effective method to fabricate large-area ultrathin graphene films is proposed for highly sensitive flexible strain sensor. The assembled graphene films are derived rapidly at the liquid/air interface by Marangoni effect and the area can be scaled up. These graphene-based strain sensors exhibit extremely high sensitivity with gauge factor of 1037 at 2% strain, which represents the highest value for graphene platelets at this small deformation so far.
Rubber bands infused with graphene ("G-bands") can be used as inexpensive body sensors. The bands remain pliable and can be used as a sensor to measure breathing, heart rate, or movement. Lightweight sensor suits for vulnerable patients could make it possible to remotely monitor subtle movement. These sensors display -fold increases in resistance and work at strains exceeding 800%. Gauge factors of up to 35 were observed. Such sensors can function at vibration frequencies of at least 160 Hz. At 60 Hz, strains of at least 6% at strain rates exceeding 6000%/s can be monitored.
Magnetic.
In 2015 researchers announced a graphene-based magnetic sensor 100 times more sensitive than an equivalent device based on silicon (7,000 volts per amp-tesla). The sensor substrate was hexagonal boron nitride. The sensors were based on the Hall effect, in which a magnetic field induces a Lorentz force on moving electric charge carriers, leading to deflection and a measurable Hall voltage. In the worst case graphene roughly matched a best case silicon design. In the best case graphene required lower source current and power requirements.
Environmental.
Contaminant removal.
Graphene oxide is non-toxic and biodegradable. Its surface is covered with epoxy, hydroxyl, and carboxyl groups that interact with cations and anions. It is soluble in water and forms stable colloid suspensions in other liquids because it is amphiphilic (able to mix with water or oil). Dispersed in liquids it shows excellent sorption capacities. It can remove copper, cobalt, cadmium, arsenate, and organic solvents.
Water filtration.
Research suggests that graphene filters could outperform other techniques of desalination by a significant margin.
Permeation barrier.
Instead of allowing the permeation, blocking is also necessary. Gas permeation barriers are important for almost all applications ranging from food, pharmaceutical, medical, inorganic and organic electronic devices, etc. packaging. It extends the life of the product and allows keeping the total thickness of devices small. Being atomically thin, defectless graphene is impermeable to all gases. In particular, ultra-thin moisture permeation barrier layers based on graphene are shown to be important for organic-FETs and OLEDs. Graphene barrier applications in biological sciences are under study.
Other.
Plasmonics and metamaterials.
Graphene accommodates a plasmonic surface mode, observed recently via near field infrared optical microscopy techniques and infrared spectroscopy Potential applications are in the terahertz to mid-infrared frequencies, such as terahertz and midinfrared light modulators, passive terahertz filters, mid-infrared photodetectors and biosensors.
Lubricant.
Scientists discovered using graphene as a lubricant works better than traditionally used graphite. A one atom thick layer of graphene in between a steel ball and steel disc lasted for 6,500 cycles. Conventional lubricants lasted 1,000 cycles.
Radio wave absorption.
Stacked graphene layers on a quartz substrate increased the absorption of millimeter (radio) waves by 90 per cent over 125–165 GHz bandwidth, extensible to microwave and low-terahertz frequencies, while remaining transparent to visible light. For example, graphene could be used as a coating for buildings or windows to block radio waves. Absorption is a result of mutually coupled Fabry–Perot resonators represented by each graphene-quartz substrate. A repeated transfer-and-etch process was used to control surface resistivity.
Redox.
Graphene oxide can be reversibly reduced and oxidized via electrical stimulus. Controlled reduction and oxidation in two-terminal devices containing multilayer graphene oxide films are shown to result in switching between partly reduced graphene oxide and graphene, a process that modifies electronic and optical properties. Oxidation and reduction are related to resistive switching.
Nanoantennas.
A graphene-based plasmonic nano-antenna (GPN) can operate efficiently at millimeter radio wavelengths. The wavelength of surface plasmon polaritons for a given frequency is several hundred times smaller than the wavelength of freely propagating electromagnetic waves of the same frequency. These speed and size differences enable efficient graphene-based antennas to be far smaller than conventional alternatives. The latter operate at frequencies 100–1000 times larger than GPNs, producing 0.01–0.001 as many photons.
An electromagnetic (EM) wave directed vertically onto a graphene surface excites the graphene into oscillations that interact with those in the dielectric on which the graphene is mounted, thereby forming surface plasmon polaritons (SPP). When the antenna becomes resonant (an integral number of SPP wavelengths fit into the physical dimensions of the graphene), the SPP/EM coupling increases greatly, efficiently transferring energy between the two.
A phased array antenna 100 µm in diameter could produce 300 GHz beams only a few degrees in diameter, instead of the 180 degree radiation from tsa conventional metal antenna of that size. Potential uses include smart dust, low-power terabit wireless networks and photonics.
A nanoscale gold rod antenna captured and transformed EM energy into graphene plasmons, analogous to a radio antenna converting radio waves into electromagnetic waves in a metal cable. The plasmon wavefronts can be directly controlled by adjusting antenna geometry. The waves were focused (by curving the antenna) and refracted (by a prism-shaped graphene bilayer because the conductivity in the two-atom-thick prism is larger than in the surrounding one-atom-thick layer.)
The plasmonic metal-graphene nanoantenna was composed by inserting a few nanometers of oxide between a dipole gold nanorod and the monolayer graphene. The used oxide layer here can reduce the quantum tunelling effect between graphene and metal antenna. With tuning the chemical potential of the graphene layer through field effect transistor architecture, the in-phase and out-phase mode coupling between graphene palsmonics and metal plasmonics is realized. The tunable properties of the plasmonic metal-graphene nanoantenna can be switched on and off via modifying the electrostatic gate-voltage on graphene.
Sound transducers.
Graphene's light weight provides relatively good frequency response, suggesting uses in electrostatic audio speakers and microphones. In 2015 an ultrasonic microphone and speaker were demonstrated that could operate at frequencies from 20 Hz–500 kHz. The speaker operated at a claimed 99% efficiency with a flat frequency response across the audible range. One application was as a radio replacement for long-distance communications, given sound's ability to penetrate steel and water, unlike radio waves.
Waterproof coating.
Graphene could potentially usher in a new generation of waterproof devices whose chassis may not need to be sealed like today's devices.
Coolant additive.
Graphene's high thermal conductivity suggests that it could be used as an additive in coolants. Preliminary research work showed that 5% graphene by volume can enhance the thermal conductivity of a base fluid by 86%. Another application due to graphene's enhanced thermal conductivity was found in PCR.
Reference material.
Graphene's properties suggest it as a reference material for characterizing electroconductive and transparent materials. One layer of graphene absorbs 2.3% of red light.
This property was used to define the "conductivity of transparency" that combines sheet resistance and transparency. This parameter was used to compare materials without the use of two independent parameters.
Thermal management.
In 2011, researchers reported that a three-dimensional, vertically aligned, functionalized multilayer graphene architecture can be an approach for graphene-based thermal interfacial materials (TIMs) with superior thermal conductivity and ultra-low interfacial thermal resistance between graphene and metal.
Graphene-metal composites can be used in thermal interface materials.
Adding a layer of graphene to each side of a copper film increased the metal's heat-conducting properties up to 24%. This suggests the possibility of using them for semiconductor interconnects in computer chips. The improvement is the result of changes in copper's nano- and microstructure, not from graphene's independent action as an added heat conducting channel. High temperature chemical vapor deposition stimulates grain size growth in copper films. The larger grain sizes improve heat conduction. The heat conduction improvement was more pronounced in thinner copper films, which is useful as copper interconnects shrink.
Attaching graphene functionalized with silane molecules increases its thermal conductivity ("κ") by 15–56% with respect to the number density of molecules. This is because of enhanced in-plane heat conduction resulting from the simultaneous increase of thermal resistance between the graphene and the substrate, which limited cross-plane phonon scattering. Heat spreading ability doubled.
However, mismatches at the boundary between horizontally adjacent crystals reduces heat transfer by a factor of 10.
Structural material.
Graphene's strength, stiffness and lightness suggested it for use with carbon fiber. Graphene has been used as a reinforcing agent to improve the mechanical properties of biodegradable polymeric nanocomposites for engineering bone tissue.
Catalyst.
In 2014, researchers at the University of Western Australia discovered nano sized fragments of graphene can speed up the rate of chemical reactions. In 2015, researchers announced an atomic scale catalyst made of graphene doped with nitrogen and augmented with small amounts of cobalt whose onset voltage was comparable to platinum catalysts. In 2016 iron-nitrogen complexes embedded in graphene were reported as another form of catalyst. The new material was claimed to approach the efficiency of platinum catalysts. The approach eliminated the need for less efficient iron nanoparticles.
Aviation.
In 2016, researchers developed a prototype de-icing system that incorporated unzipped carbon nanotube graphene nanoribbons in an epoxy/graphene composite. In laboratory tests, the leading edge of a helicopter rotor blade was coated with the composite, covered by a protective metal sleeve. Applying an electrical current heated the composite to over 200 °F (93 °C), melting a 1 cm (0.4 in)-thick ice layer with ambient temperatures of a -4 °F (-20 °C).


Unquadennium


Ebselen

Ebselen (also called PZ 51, DR3305, and SPI-1005), is a synthetic organoselenium drug molecule with anti-inflammatory, anti-oxidant and cytoprotective activity. It acts as a mimic of glutathione peroxidase and can also react with peroxynitrite. It is being investigated as a possible treatment for reperfusion injury and stroke, hearing loss and tinnitus, and bipolar disorder.
Additionally, ebselen may be effective against "Clostridioides difficile" infections and has been shown to have antifungal activity against "Aspergillus fumigatus".
Ebselen is a potent scavenger of hydrogen peroxide as well as hydroperoxides including membrane bound phospholipid and cholesterylester hydroperoxides. Several ebselen analogs have been shown to scavenge hydrogen peroxide in the presence of thiols.
Possible anti-COVID-19 activity.
Preliminary studies demonstrate that Ebselen exhibits promising inhibitory activity against COVID-19 in cell-based assays. The effect was attributed to irreversible inhibition of the main protease via a covalent bond formation with the thiol group of the active center's cysteine (Cys-145).
Synthesis.
Generally, synthesis of the characteristic scaffold of ebselen, the benzoisoselenazolone ring system, can be achieved either through reaction of primary amines (RNH2) with 2-(chloroseleno)benzoyl chloride (Route I), by "ortho"-lithiation of benzanilides followed by oxidative cyclization (Route II) mediated by cupric bromide (CuBr2), or through the efficient Cu-catalyzed selenation / heterocyclization of o-halobenzamides, a methodology developed by Kumar "et al." (Route III).


Deuterated ethanol

Deuterated ethanol (C2D5OD) is a form (called an isotopologue) of ethanol (C2H5OH) in which the hydrogen atom ("H") is replaced with deuterium (heavy hydrogen) isotope ("D"). Deuterated ethanol is an uncommon solvent used in NMR spectroscopy.


Organotitanium compound

Organotitanium compounds in organometallic chemistry contain carbon-to-titanium chemical bonds. Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis and reactions. They are reagents in organic chemistry and are involved in major industrial processes.
Brief history.
Although the first attempt to prepare an organotitanium compound dates back to 1861, the first example was not reported until 1954. In that year titanocene dichloride was described by Wilkinson and Birmingham. Independently, titanium-based Ziegler–Natta catalysts were described leading to major commercial applications, for which the 1963 Nobel Prize in Chemistry was awarded. This technology underscored the technical significance of organotitanium chemistry.
Properties.
The titanium electron configuration ([Ar]3d24s2) vaguely resembles that of carbon and like carbon, the +4 oxidation state dominates. Titanium is however a much larger element than carbon, reflected by the Ti-C bond lengths being about 30% longer, e.g. 210 pm in tetrabenzyltitanium vs a typical C-C bond of 155 pm. Simple tetraalkyltitanium compounds however are not typically isolable, owing to the large size of titanium and the electron-deficient nature of its tetrahedral complexes. More abundant and more useful than the simple tetraalkyl compounds are mixed ligand complexes with alkoxide and cyclopentadienyl coligands. Titanium is capable of forming complexes with high coordination numbers.
In terms of oxidation states, most organotitanium chemistry, in solution at least, focuses on derivatives of Ti(IV) and Ti(III). Ti(II) compounds are rarer, examples being titanocene dicarbonyl and Ti(CH3)2(dmpe)2. [Ti(CO)6]2− is formally a complex of Ti(-II). Although Ti(III) is involved in Ziegler–Natta catalysis, the organic derivatives of Ti(III) are uncommon. One example is the dimer [Cp2TiIIICl]2.
Due to the low electronegativity of titanium, Ti-C bonds are polarized toward carbon. Consequently, alkyl ligands in many titanium compounds are nucleophilic. Titanium is characteristically oxophilic, which recommends the use of air-free techniques. On the other hand, high oxophilicity means that titanium alkyls are effective for abstracting or exchanging organyl ligands for oxo groups, as discussed below.
Compounds.
Alkyl titanium chlorides and alkoxides.
Simple alkyl complexes of titanium, e.g. Ti(CH2C6H5)4, are rare. Several mixed alkyl-titanium-halides and alkyl-titanium-alkoxides are utilized in organic synthesis, even if they are not often well characterized. At least from the commercial perspective, the most useful organotitanium compounds are generated by combining titanium(III) chloride and diethylaluminium chloride. As Ziegler–Natta catalysts, such species efficiently catalyze the polymerization of ethylene. The process is heterogeneous and no organotitanium intermediates have been well characterized for this process.
Numerous organotitanium reagents are produced by combining titanium tetrachloride, titanium tetraalkoxides, or mixtures thereof with organolithium, organomagnesium, and organozinc compounds. Such compounds find occasional use as stoichiometric reagents in organic synthesis. "Methyltitanium trichloride", nominally CH3TiCl3, can be prepared by treating titanium(IV) chloride with dimethylzinc in dichloromethane at -78 °C. It delivers a methyl groups to carbonyl compounds and alkyl halides. "Methyltriisopropoxytitanium" is a related reagent. A dialkyltitanium species is implicated for Ti-promoted cyclopropanations starting from a Grignard reagent and an ester. This reaction is the basis of the Kulinkovich reaction:
"Lombardo's reagent" is used for methylenation. It is functionally related to the "Dibromomethane-Zinc-Titanium(IV) Chloride" reagent. This chemistry addresses a shortcoming of the Wittig reagent by methylenating enolisable carbonyl groups without loss of stereochemical integrity (Lombardo Methylenation). It can for example also be applied in a conversion of a ketene into an allene:
Titanocene derivatives.
Attempted synthesis of "titanocene", i.e. Ti(C5H5)2, produces a fulvalene complex. The titanocene dimer was recognised in the 1970s but not structurally characterised until 1992, and the investigations led to many innovations on cyclopentadienyl complexes of titanium. Only in 1998 was a true titanocene derivative identified, the paramagnetic species (C5Me4SiMe3)2Ti.
In contrast to titanocene itself, titanocene dichloride and to some extent titanocene monochloride have rich and well defined chemistries. Tebbe's reagent, prepared from titanocene dichloride and trimethylaluminium, is used as a methylenation agent (conversion of R2C=O to R2C=CH2).
Tebbe's reagent adds simple alkenes to give titanocyclobutanes, which can be regarded as stable olefin metathesis intermediates. These compounds are reagents in itself such as "1,1-bis(cyclopentadienyl)-3,3-dimethyltitanocyclobu"tane, the adduct of Tebbe's reagent with isobutene catalysed with 4-dimethylaminopyridine.
The Petasis reagent or "dimethyl titanocene" (1990) is prepared from titanocene dichloride and methyllithium in diethyl ether. Compared to Tebbe's reagent it is easier to prepare and easier to handle. It is also a methylenation reagent.
The Nugent-RajanBabu reagent is a one-electron reductant used in synthetic organic chemistry for the generation of alcohols via anti-Markovnikov ring-opening of epoxides, and is generated as a dimer [(η5-Cp)2Ti(μ-Cl)]2 and used "in situ" from titanocene dichloride.
MonoCp compounds.
Less useful in organic chemistry but still prominent are many derivatives of (cyclopentadienyl)titanium trichloride, (C5H5)TiCl3. This piano-stool complex is obtained by the redistribution reaction of titanocene dichloride and titanium tetrachloride. With an electron count of 12, it is far more electrophilic than the 16e titanocene dichloride.
Arene complexes.
Titanium tetrachloride reacts with hexamethylbenzene to give [(η6-C6Me6)TiCl3]+ salts. Reduced arene complexes include the oxidation states −1, 0, +1.
Carbonyl complexes.
Salts of [Ti(CO)6]2− is known.


Georgerobinsonite

Georgerobinsonite, named for George Willard Robinson, is a lead chromate mineral with formula Pb4(CrO4)2(OH)2FCl. It exhibits very small, transparent crystals with a bright orange-red color. It was obtained from the Mammoth-St. Anthony Mine in Arizona in the 1940s and identified in 2009.
History.
The type specimen for georgerobinsonite was found in the Mammoth-St. Anthony Mine in Tiger, Arizona. The sample was collected by Dan Mayers in 1943 or 1944. At this time, the mine was operating at a level where a number of exotic minerals have been discovered. The exact location of its origin is unknown, but it is likely from the Collins vein at the 500 level.
The sample, labelled M 117 by Mayers, was donated along with many others to the Department of Mineralogy at Harvard. Professor Heinrich Meixner obtained it in the 1950s in an exchange with the curator of Harvard's mineral collection, Professor C. Frondel. Werner H. Paar then acquired it in the early 1970s. Several years prior to 2011, reexamination of M 117 revealed very small crystals of an orange-red mineral. They were initially misidentified as wulfenite, but later determined to be a new mineral species.
In November 2009, the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA) designated the mineral as IMA 2009-068. The IMA later approved georgerobinsonite as the recommended name. Georgerobinsonite is named for George Willard Robinson, A. E. Seaman Mineral Museum curator since 1996 and mineralogy professor at Michigan Technological University.
Properties.
Georgerobinsonite is a soft, brittle mineral that forms crystals less than across. The mineral possesses a pale-orange streak and an adamantine luster. It is most strongly associated with cerussite and diaboleite.


Yttrium nitride

Yttrium nitride, YN, is a nitride of yttrium.
Yttrium nitride is hard ceramic material similar to titanium nitride and zirconium nitride.
The nitrides of lanthanum, scandium, and yttrium show semiconducting properties and additionally the lattice structure of YN differs only by 8% from that of gallium nitride. This makes YN a possible buffer layer between a substrate and the GaN layer during GaN crystal growth.


Ulexite

Ulexite (NaCaB5O6(OH)6·5H2O, hydrated sodium calcium borate hydroxide), sometimes known as TV rock, is a mineral occurring in silky white rounded crystalline masses or in parallel fibers. The natural fibers of ulexite conduct light along their long axes, by internal reflection. Ulexite was named for the German chemist Georg Ludwig Ulex (1811–1883) who first discovered it.
Ulexite is a structurally complex mineral, with a basic structure containing chains of sodium, water and hydroxide octahedra. The chains are linked together by calcium, water, hydroxide and oxygen polyhedra and massive boron units. The boron units have a formula of [B5O6(OH)6]3– and a charge of −3. They are composed of three borate tetrahedra and two borate triangular groups.
Ulexite is found in evaporite deposits and the precipitated ulexite commonly forms a "cotton ball" tuft of acicular crystals. Ulexite is frequently found associated with colemanite, borax, meyerhofferite, hydroboracite, probertite, glauberite, trona, mirabilite, calcite, gypsum and halite. It is found principally in California and Nevada, US; Tarapacá Region in Chile, and Kazakhstan. Ulexite is also found in a vein-like bedding habit composed of closely packed fibrous crystals.
Ulexite is also known as TV rock due to its unusual optical characteristics. The fibers of ulexite act as optical fibers, transmitting light along their lengths by internal reflection. When a piece of ulexite is cut with flat polished faces perpendicular to the orientation of the fibers, a good-quality specimen will display an image of whatever surface is adjacent to its other side.
The fiber-optic effect is the result of the polarization of light into slow and fast rays within each fiber, the internal reflection of the slow ray and the refraction of the fast ray into the slow ray of an adjacent fiber. An interesting consequence is the generation of three cones, two of which are polarized, when a laser beam obliquely illuminates the fibers. These cones can be seen when viewing a light source through the mineral.
Ulexite decomposes/dissolves in hot water.
Chemical composition.
Ulexite is a borate mineral because its formula (NaCaB5O6(OH)6·5H2O) contains boron and oxygen. The isolated borate polyanion [B5O6(OH)6]3− has five boron atoms, therefore placing ulexite in the pentaborate group.
Related minerals.
Borate minerals are rare because their main component, boron, makes up less than 10 ppm (10 mg/kg) of Earth's crust. Because boron is a trace element, the majority of borate minerals occur only in one specific geologic environment: geologically active intermontane basins. Borates are formed when boron bearing solutions, caused from the leaching of pyroclastic rocks, flow into isolated basins where evaporation then takes place. Over time, borates deposit and form into stratified layers. Ulexite occurs in salt playas and dry saline lakes in association with large-scale gypsum deposits and Na-Ca borates. There are no known polymorphs of ulexite nor does ulexite form a solid solution series with any other minerals.
According to Stamatakis "et al". (2009) Na, Ca, and Na-Ca borates are found in relation to ulexite. These minerals are:
More common minerals that are not borates, but also form in evaporite deposits are:
Morphology.
Ulexite commonly forms small, rounded masses resembling cotton balls. Crystals are rare but will form fibrous, elongated crystals either oriented parallel or radial to each other. Crystals may also be acicular, resembling needles (Anthony et al., 2005). The point group of ulexite is 1, which means that the crystals show very little symmetry as there are no rotational axes or mirror planes. Ulexite is greatly elongated along [001]. The most common twinning plane is (010). Ulexite collected from the Flat Bay gypsum quarry in Newfoundland exhibits acicular "cotton balls" of crystals with a nearly square cross-section formed by the equal development of two pinacoids. The crystals are about 1-3 µm thick and 50-80 µm long, arranged in loosely packed, randomly oriented overlapping bundles (Papezil and Fong, 1975). In general, the crystals have six to eight faces with three to six terminal faces (Murdoch, 1940).
Optical properties.
In 1956, John Marmon observed that fibrous aggregates of ulexite project an image of an object on the opposite surface of the mineral. This optical property is common for synthetic fibers, but not in minerals, giving ulexite the nickname "TV rock". According to Baur et al. (1957), this optical property is due to the reflections along twinned fibers, the most prominent twinning plane being on (010). The light is internally reflected over and over within each of the fibers that are surrounded by a medium of a lower refractive index (Garlick, 1991). This optical effect is also the result of the large spaces formed by the sodium octahedral chains in the mineral structure. Synthetic fibers used for fiber optics transmit images along a bundle of threadlike crystals the same way naturally occurring ulexite reproduces images due to the existence of different indices of refractions between fibers. Additionally, if the object is colored, all of the colors are reproduced by ulexite. Parallel surfaces of ulexite cut perpendicular to the fibers produce the best image, as distortion in the size of the projected image will occur if the surface is not parallel to the mineral. Curiously, "in situ" samples of ulexite are capable of producing a decent, rough image. Satin spar gypsum also exhibits this optical effect; however, the fibers are too coarse to transmit a decent image. The thickness of the fibers is proportional to the sharpness of the projected image.
Ulexite also displays concentric circles of light if held up to a light source, a strange optical property first observed by G. Donald Garlick (1991). This effect can also be produced by shining a laser pointer at a slightly oblique angle through a piece of ulexite. This optical behavior is a consequence of the different refractive indices of ulexite in different directions of polarization. Microscopic analysis of ulexite also yields cones of light that clearly emerge from each grain that is thicker than 0.1 mm under the Bertrand lens.
Ulexite is colorless and nonpleochroic in thin sections with low relief. Being triclinic, ulexite is optically biaxial. Interference figures yield addition on the concave side of the isogyers, causing ulexite to be biaxial positive. Ulexite has a high 2V that ranges between 73° - 78° and a maximum birefringence of up to 0.0300 (Anthony et al., 2005). According to Moore and Potter (1963), the orientation of the fibers around the c-axis is completely random based on the variations in extinctions viewed under cross polarization. Ulexite displays polysynthetic twinning parallel to the elongation, along {010} and {100} (Murdoch, 1940). In thin sections cut parallel to the fibers, ulexite grains display both length-fast and length-slow orientations in equal quantities because the intermediate axis (y) of the indicatrix is roughly parallel to the elongation of the fibers along the crystallographic c-axis (Moore and Potter, 1963).
Structure.
Ulexite crystals contain three structural groups, isolated pentaborate polyanions, calcium coordinated polyhedra, and sodium coordinated octahedra that are joined together and cross-linked by hydrogen bonding. The Ca-coordination polyhedra share edges to form chains which are separate from the Na-coordination octahedral chains. There are 16 distinct hydrogen bonds that have an average distance of 2.84 Å. Boron is coordinated to four oxygens in a tetrahedra arrangement and also to three oxygens in a triangular arrangement with average distances of 1.48 and 1.37 Å, respectively. Each Ca2+ cation is surrounded by a polyhedron of eight oxygen atoms. The average distance between calcium and oxygen is 2.48 Å. Each Na+ is coordinated by an octahedron of two hydroxyl oxygens and four water molecules, with an average distance of 2.42 Å (Clark and Appleman 1964). The octahedral and polyhedral chains parallel to c, the elongate direction, cause the fibrous habit of ulexite and the fiber optical properties.
Significance.
Boron is a trace element within the lithosphere that has an average concentration of 10 ppm, although large areas of the world are boron deficient. Boron is never found in the elemental state in nature, however boron naturally occurs in over 150 minerals. The three most important minerals from a worldwide commercial standpoint based on abundance are tincal (also known as borax), ulexite, and colemanite (Ekmekyaper et al., 2008). High concentrations of economically significant boron minerals generally occur in arid areas that have a history of volcanism. Ulexite is mined predominately from the Borax mine in Boron, California.
The boron concentration of ulexite is commercially significant because boron compounds are used in producing materials for many branches of industry. Boron is primarily used in the manufacturing of fiberglass along with heat resistant borosilicate glasses such as traditional Pyrex, car headlights, and laboratory glassware. Borosilicate glass is desirable because adding B2O3 lowers the expansion coefficient, therefore increasing the thermal shock resistance of the glass. Boron and its compounds are also common ingredients in soaps, detergents, and bleaches, which contributes to the softening of hard water by attracting the calcium ions. Boron usage in alloy and metal production has been increasing because of its excellent metal oxide solubilizing ability. Boron compounds are used as a reinforcing agent in order to harden metals for use in military tanks and armor. Boron is used extensively for fire retardant materials. Boron is an essential element for plant growth and is frequently used as a fertilizer, however in large concentrations boron can be toxic, and therefore boron is a common ingredient in herbicides and insecticides. Boron is also found in chemicals used to treat wood and as protective coatings and pottery glazes. Additionally when ulexite is dissolved in a solution of carbonate, calcium carbonate forms as a by-product. This by-product is used in large amounts by the pulp and paper industry as a paper filler and as a coating for paper that allows for improved printability (Demirkiran and Kunkul, 2011).
Recently, as more attention is being given to obtaining new sources of energy, the use of hydrogen as a fuel for cars has come to the forefront. The compound sodium borohydride (NaBH4) is currently being considered as an excellent hydrogen storage medium due to its high theoretical hydrogen yield by weight for future use in cars. Piskin (2009) validates that the boron concentration in ulexite can be used as the boron source or the starting material in the synthesis of sodium borohydride (NaBH4).
Historical.
Ulexite has been recognized as a valid mineral since 1840, after George Ludwig Ulex, for whom the mineral was named, provided the first chemical analysis of the mineral. In 1857, Henry How, a professor at King's College in Windsor, Nova Scotia discovered borate minerals in the gypsum deposits of the Lower Carboniferous evaporate deposits in the Atlantic Provinces of Canada where he noted the presence of a fibrous borate that he termed natro-boro-calcite, which was actually ulexite (Papezik and Fong, 1975).
Murdoch examined the crystallography of ulexite in 1940. The crystallography was reworked in 1959 by Clark and Christ and their study also provided the first powder x-ray diffraction analysis of ulexite. In 1963 ulexite's remarkable fiber optics qualities were explained by Weichel-Moore and Potter. Their study highlighted the existence in nature of mineral structures exhibiting technologically required characteristics. Lastly, Clark and Appleman described the structure of ulexite correctly in 1964.


YF-75D

The YF-75D is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in a closed expander cycle. It is China's third generation of upper stage cryogenic propellant engine, after the YF-73 and the YF-75. It is used in a dual engine mount in the H5-2 second stage of the Long March 5 launch vehicles. Within the mount, each engine can gimbal individually to enable thrust vectoring control. As its predecessor, the YF-75 it can adjust its mixture ratio to optimize propellant consumption. But as an additional improvement, it can do multiple restarts, against the single one of its predecessor.
The combustion chamber required a redesign to keep the power balance. Since the expander cycle uses the heat extracted from the cooling circuits to drive the turbines, the chamber had to be lengthened and the cooling passages redesigned. The engine uses a redesigned hydrogen turbine. It uses an axial two-staged low pressure ratio subsonic turbine that operates at 65,000rpm, which is between the second and third critical speed. It rests on dual elastic support dampers around the ceramic ball bearings.


Organovanadium chemistry

Organovanadium chemistry is the chemistry of organometallic compounds containing a carbon to vanadium (V) chemical bond. Organovanadium compounds find only minor use as reagents in organic synthesis but are significant for polymer chemistry as catalysts.
Oxidation states for vanadium are +2, +3, +4 and +5. Low valency vanadium is usually stabilized with carbonyl ligands. Oxo derivatives are relatively common, unlike the organic complexes of neighboring elements.
Compound classes.
Carbonyls.
Vanadium carbonyl can be prepared by reductive carbonylation of vanadium salts:
The salt can be oxidized to the 17e binary carbonyl V(CO)6.
Cyclopentadienyl derivatives.
Vanadocene dichloride, the first organovanadium complexes to be reported, is prepared from sodium cyclopentadienyl and vanadium tetrachloride:
Reduction of this compound gives the parent vanadocene (Cp)2V:
Vanadocene is the lightest transition metal metallocene that is isolable at room temperature. Vanadocene reacts with high pressures of carbon monoxide to give CpV(CO)4. Photolysis of the tetracarbonyl gives Cp2V2(CO)5. Several analogous indenyl complexes are known.
Monocyclopentadienyl vanadium chlorides include CpVCl3 and the diamagnetic CpVOCl2.
Arene complexes.
Vanadium forms a variety of arene complexes, e.g. with benzene:
Alkyl and aryl derivatives.
A handful of alkyl and aryl complexes exist. The reactive species V(mesityl)3 forms from VCl3:
This species binds CO and, under appropriate conditions, N2. V(mesityl)3 adds a fourth mesityl group and the resulting "ate complex" can be oxidized to the vanadium(IV) derivative:
The tetrakis(norbornyl) complex is also known.
Vanadium oxytrichloride is a starting material for organovanadium(IV) and organovanadium(V) compounds:
Catalysts and reagents.
Well-defined vanadium compounds do not appear as catalysts in any commercial process. However organovanadium species are clearly implicated as catalysts for the production of butadiene-based rubbers. These catalysts are generated in situ by treating soluble coordination complexes such as vanadium(III) acetylacetonate with organoaluminium activators.


Teflurane

Teflurane (INN, USAN, code name Abbott 16900) is a halocarbon drug which was investigated as an inhalational anesthetic but was never marketed. Its clinical development was terminated due to a high incidence of cardiac arrhythmias in patients, similarly to the cases of halopropane and norflurane.
Chemistry.
Teflurane is 2-bromo-1,1,1,2-tetrafluoroethane, a haloalkane. It is a gas at standard conditions. The compound is chiral.


Tlalocite

Tlalocite is a rare and complex tellurate mineral with the formula Cu10Zn6(TeO4)2(TeO3)(OH)25Cl · 27 H2O. It has a Mohs hardness of 1, and a cyan color. It was named after Tlaloc, the Aztec god of rain, in allusion to the high amount of water contained within the crystal structure. It is not to be confused with quetzalcoatlite, which often looks similar in color and habit.
Occurrence.
Tlalocite was first identified in the Bambollite mine (La Oriental), Moctezuma, Municipio de Moctezuma, Sonora, Mexico and it was approved by the IMA in 1974. It often occurs together with tenorite, azurite, malachite and tlapallite. It is found in partially oxidized portions of tellurium-bearing hydrothermal veins.


Sulfite

Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid (sulfurous acid) is elusive, its salts are widely used.
Sulfites are substances that naturally occur in some foods and the human body. They are also used as regulated food additives. When in food or drink, sulfites are often lumped together with sulfur dioxide.
Structure.
The structure of the sulfite anion can be described with three equivalent resonance structures. In each resonance structure, the sulfur atom is double-bonded to one oxygen atom with a formal charge of zero (neutral), and sulfur is singly bonded to the other two oxygen atoms, which each carry a formal charge of −1, together accounting for the −2 charge on the anion. There is also a non-bonded lone pair on the sulfur, so the structure predicted by VSEPR theory is trigonal pyramidal, as in ammonia (NH3). In the hybrid resonance structure, the S−O bonds are equivalently of bond order one and one-third.
Evidence from 17O NMR spectroscopic data suggests that protonation of the sulfite ion gives a mixture of isomers:
Commercial uses.
Sulfites are used as a food preservative or enhancer. They may come in various forms, such as:
Wine.
Sulfites occur naturally in all wines to some extent. Sulfites are commonly introduced to arrest fermentation at a desired time, and may also be added to wine as preservatives to prevent spoilage and oxidation at several stages of the winemaking. Sulfur dioxide (SO2) protects wine not only from oxidation, but also from bacteria.
Organic wines are not necessarily sulfite-free, but generally have lower amounts and regulations stipulate lower maximum sulfite contents for these wines. In general, white wines contain more sulfites than red wines and sweeter wines contain more sulfites than drier ones.
In the United States, wines bottled after mid-1987 must have a label stating that they contain sulfites if they contain more than 10 parts per million (ppm).
In the European Union an equivalent regulation came into force in November 2005. This includes sulfur dioxide, and the limit is on the milligrams per kilogram or per litre of sulfur dioxide equivalent. In 2012, a new regulation for organic wines came into force. In the United Kingdom, similar laws apply. Bottles of wine that contain over 10 mg/L (ppm) of "sulfites" (or sulfur dioxide) are required to bear "contains sulphites" on the label. This does not differ if sulfites are naturally occurring or added in the winemaking process.
Other foods.
Sulfites are often used as preservatives in dried fruits, preserved radish, and dried potato products.
Most beers no longer contain sulfites, although some alcoholic ciders contain them. Although shrimp are sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label. In 1986, the Food and Drug Administration in the United States banned the addition of sulfites to all fresh fruit and vegetables that are eaten raw.
E numbers.
E numbers for sulfites as food additives are:
Health effects.
Allergic reactions to sulfites appear to be very rare in the general population, but more common in hyperallergic individuals.
Sulfites are counted among the top nine food allergens, but a reaction to sulfite is not a true allergy. Some people have positive skin allergy tests to sulfites indicating true (IgE-mediated) allergy. Chronic skin conditions in the hands, perineum, and face have been reported in individuals that regularly use cosmetics or medications containing sulfites. Occupational exposure to sulfites has been reported to cause persistent skin symptoms.
It may cause breathing difficulty within minutes after eating a food containing it. Asthmatics and possibly people with salicylate sensitivity (or aspirin sensitivity) are at an elevated risk for reaction to sulfites. Anaphylaxis and life-threatening reactions are rare. Other potential symptoms include sneezing, swelling of the throat, hives, and migraine.
A 2017 study has shown negative impacts of sulfites on bacteria found in the human microbiome.
Use and labeling regulations.
In 1986, the U.S. Food and Drug Administration banned the use of sulfites as preservatives on foods intended to be eaten fresh (such as salad ingredients). This has contributed to the increased use of erythorbic acid and its salts as preservatives.
Generally, U.S. labeling regulations do not require products to indicate the presence of sulfites in foods unless it is added specifically as a preservative; still, many companies voluntarily label sulfite-containing foods. Sulfites used in food processing (but not as a preservative) are required to be listed if they are not incidental additives (21 CFR 101.100(a)(3)), and if there are more than 10 ppm in the finished product (21 CFR 101.100(a)(4))
Products likely to contain sulfites at less than 10 ppm (fruits and alcoholic beverages) do not require ingredients labels, and the presence of sulfites usually is undisclosed.
In Australia and New Zealand, sulfites must be declared in the statement of ingredients when present in packaged foods in concentrations of 10 mg/kg (ppm) or more as an ingredient; or as an ingredient of a compound ingredient; or as a food additive or component of a food additive; or as a processing aid or component of a processing aid.
Sulfites that can be added to foods in Canada are potassium bisulfite, potassium metabisulfite, sodium bisulfite, sodium dithionite, sodium metabisulfite, sodium sulfite, sulfur dioxide and sulfurous acid. These can also be declared using the common names sulfites, sulfates, sulfiting agents.
In the European Union, "EU law requires food labels to indicate “contains sulfites” (when exceeding 10 milligrams per kilogram or per litre) without specifying the amount".
Metabolic diseases.
High sulfite content in the blood and urine of babies can be caused by molybdenum cofactor deficiency disease which leads to neurological damage and early death unless treated. Treatment, requiring daily injections, became available in 2009.


Radium emanation


Early Cambrian geochemical fluctuations

The start of the Cambrian period is marked by 'fluctuations' in a number of geochemical records, including Strontium, Sulfur and Carbon isotopic excursions. While these anomalies are difficult to interpret, a number of possibilities have been put forward. They probably represent changes on a global scale, and as such may help to constrain possible causes of the Cambrian explosion.
The chemical signature may be related to continental break-up, the end of a "global glaciation", or a catastrophic drop in productivity caused by a mass extinction just before the beginning of the Cambrian.
Isotopes.
Isotopes are different forms of elements; they have a different number of neutrons in the nucleus, meaning they have very similar chemical properties, but different mass. The weight difference means that some isotopes are discriminated against in chemical processes – for example, plants find it easier to incorporate the lighter 12C than heavy 13C. Other isotopes are only produced as a result of the radioactive decay of other elements, such as 87Sr, the daughter isotope of 87Rb. Rb, and therefore 87Sr, is common in the crust, so abundance of 87Sr in a sample of sediment (relative to 86Sr) is related to the amount of sediment which originated in the crust, as opposed to from the oceans.
The ratios of three major isotopes, 87Sr / 86Sr, 34S / 32S and 13C / 12C, undergo dramatic fluctuations around the beginning of the Cambrian.
Carbon isotopes.
Carbon has 2 stable isotopes, carbon-12 (12C) and carbon-13 (13C). The ratio between the two is denoted , and represents a number of factors.
Because organic matter preferentially takes up the lighter 12C, an increase in productivity increases the of the rest of the system, and vice versa. Some carbon reservoirs are very isotopically light: for instance, biogenic methane, produced by bacterial decomposition, has a of −60‰ – vast, when 1‰ is a large fluctuation! An injection of carbon from one of these reservoirs could therefore account for the early Cambrian drop in .
Causes often suggested for changes in the ratio of 13C to 12C found in rocks include:
Strontium isotopes.
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Sulfur isotopes.
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Other chemical fluctuations.
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Coccolith

Coccoliths are individual plates of calcium carbonate formed by coccolithophores (single-celled algae such as "Emiliania huxleyi") which are arranged around them in a "coccosphere".
Formation and composition.
Coccoliths are formed within the cell in vesicles derived from the golgi body. When the coccolith is complete these vesicles fuse with the cell wall and the coccolith is exocytosed and incorporated in the coccosphere. The coccoliths are either dispersed following death and breakup of the coccosphere, or are shed continually by some species. They sink through the water column to form an important part of the deep-sea sediments (depending on the water depth). Thomas Huxley was the first person to observe these forms in modern marine sediments and he gave them the name 'coccoliths' in a report published in 1858.
Coccoliths are composed of calcium carbonate as the mineral calcite and are the main constituent of chalk deposits such as the white cliffs of Dover (deposited in Cretaceous times), in which they were first described by Henry Clifton Sorby in 1861.
Types.
There are two main types of coccoliths, heterococcoliths and holococcoliths. Heterococcoliths are formed of a radial array of elaborately shaped crystal units. Holococcoliths are formed of minute (ca 0.1 micrometre) calcite rhombohedra, arranged in continuous arrays. The two coccolith types were originally thought to be produced by different families of coccolithophores. Now, however, it is known through a mix of observations on field samples and laboratory cultures, that the two coccolith types are produced by the same species but at different life cycle phases. Heterococcoliths are produced in the diploid life-cycle phase and holococcoliths in the haploid phase. Both in field samples and laboratory cultures, there is the possibility of observing a cell covered by a combination of heterococcoliths and holococcoliths. This indicates the transition from the diploid to the haploid phase of the species. Such combination of coccoliths has been observed in field samples, with many of them coming from the Mediterranean.
Shape.
Coccoliths are also classified depending on shape. Common shapes include:
Function.
Although coccoliths are remarkably elaborate structures whose formation is a complex product of cellular processes, their function is unclear. Hypotheses include defence against grazing by zooplankton or infection by bacteria or viruses; maintenance of buoyancy; release of carbon dioxide for photosynthesis; to filter out harmful UV light; or in deep-dwelling species, to concentrate light for photosynthesis.
Fossil record.
Because coccoliths are formed of low-Mg calcite, the most stable form of calcium carbonate, they are readily fossilised. They are found in sediments together with similar microfossils of uncertain affinities (nanoliths) from the Upper Triassic to recent. They are widely used as biostratigraphic markers and as paleoclimatic proxies. Coccoliths and related fossils are referred to as "calcareous nanofossils" or "calcareous nannoplankton (nanoplankton)".


Steinmetzite

Steinmetzite is a very rare phosphate mineral with formula Zn2Fe(PO4)2(OH)•3H2O. It was discovered among pegmatites of Hagendorf in Germany, that are famous for rare phosphate minerals. Steinmetzite is chemically related to phosphophyllite and other zinc iron phosphates, namely plimerite and zinclipscombite.


Potassium salicylate

Potassium salicylate is the potassium salt of salicylic acid.


Magnesium sulfite

Magnesium sulfite is the magnesium salt of sulfurous acid with the formula . Its most common hydrated form has 6 water molecules making it a hexahydrate, ·6. When heated above , it is dehydrated to magnesium sulfite trihydrate, or ·3. The anhydrous form is hygroscopic, meaning that it readily absorbs water from the air.
References.
solubility tables of MgSO3 hydrates PDF


Magnesium aspartate

Magnesium aspartate, the chelated magnesium salt of aspartic acid, it is a mineral supplement.
Chemical Action.
This form of magnesium supplementation has increased bioavailability compared to oxide and citrate. There were some promising clinical trials conducted in the 1960s that found a combination of magnesium and potassium aspartates had a positive effect on fatigue and they reduced muscle hyper-excitability.
In its evaluation in 2005, the AFC Panel concluded that in humans the bioavailability of magnesium from magnesium L-aspartate was similar to that from other organic magnesium salts and the more soluble inorganic magnesium salts. Overall, it was concluded that organic salts of magnesium have the greatest water solubility and demonstrate a greater oral absorption and bioavailability compared to less soluble magnesium preparations such as magnesium oxide, magnesium hydroxide, magnesium carbonate and magnesium sulphate.
Dosage.
Magnesium-L-aspartate 1230 mg (magnesium 122 mg) up to 3 times/day
Dosage adjustment in renal impairment: Patients with severe kidney failure should not receive magnesium due to toxicity from accumulation.
Magnesium supplements and other magnesium containing products, such as antacids, can bind with prescription medicines, reducing their effectiveness.
Safety.
When considering aspartate sources individually, the levels of exposure estimated in this opinion amount up to 6 g/day for calcium aspartate (equivalent to 100 mg/kg bw/day for a 60 kg individual), 5.8 g/day for magnesium aspartate (equivalent to 97 mg/kg bw/day), 4 g/day for potassium aspartate (equivalent to 67 mg/kg bw/day), 0.05 g/day for zinc aspartate (0.8 mg/kg bw/day) and 0.008 g/day for copper aspartate (0.1 mg/kg bw/day). These values are all below those reported to induce amino acid imbalance in intervention trials (6.3 g aspartate/day) and they are, respectively, 7, 7.2, 10.5, 875 and 7000 times lower than the NOAEL for aspartate identified from a 90-day rat study. Based on these margins of safety, the Panel concludes that the use of zinc and copper aspartate, as sources of zinc and copper at the proposed use levels, are not of safety concern but that the use of calcium, magnesium and potassium aspartate could be of safety concern because the margins of safety are considered too low. The Panel notes that if all sources would be used simultaneously, combined exposure will be 16 g/day (equivalent to 267 mg/kg bw/day), which is above the reported amounts inducing amino acid imbalance in intervention trials (6.3 g/day). Furthermore, this value is only 3 times lower than the NOAEL from the rat study and due to the low margin of safety the Panel considers this of safety concern. The Panel estimates that the exposure to aspartate from these food supplements should be added to the aspartate exposure arising from the diet.
Based on US data, estimates of the mean exposure to aspartic acid arising from the diet are 4.1 g/day (children 1-3 year old) to 9.3 g/day (males 19-30 year old) and at the 95th percentile 6.6 g/day (children 4-8 year old) to 12.9 g/day (males 19-50 year old). Under these conditions, estimates of maximum daily exposure to aspartate ions from the diet (13 g/day) and from calcium or magnesium aspartate supplements would be approximately 19 g/day6, and from potassium aspartate would be 17 g/day. Aspartate exposure estimates from zinc or copper supplementation would not significantly change aspartate exposure from the diet.
Taken individually these levels of exposure are lower than those reported to induce amino acid imbalance in intervention trials, when aspartate exposure from the diet is also taken into consideration (19.3 g/day). However, when considering the potential total intake of aspartic ions arising from the diet and from a potential multi-mineral combination of all food supplements the exposure could add up to 29 g/day. In line with the SCF concerns, the Panel considers that the use of L-amino acids in food supplements should not give rise to a nutritional imbalance of the amino acids. Thus the Panel concludes that under these conditions aspartate ion exposure from a multi-mineral combination of this type could be of safety concern.


Thallous malonate

Thallous malonate is a chemical compound composed mainly of Thallium. It is an extremely hazardous substance and is on the List of extremely hazardous substances.


Triphosphoric acid

Triphosphoric acid (also tripolyphosphoric acid), with formula H5P3O10, is a condensed form of phosphoric acid. In the family of phosphoric acids, it is the next polyphosphoric acid after pyrophosphoric acid, H4P2O7, also called diphosphoric acid.
Compounds such as ATP (adenosine triphosphate) are esters of triphosphoric acid.
Triphosphoric acid has not been obtained in crystalline form. The equilibrium mixture with an overall composition corresponding to H5P3O10 contains about 20% of triphosphoric acid. A solution of the pure species can be obtained by ion exchange of the sodium salt, sodium triphosphate, at 0 °C.
Triphosporic acid is a pentaprotic acid, meaning that it can release five protons in basic enough conditions. Various p"K"a values are reported, 1.0 ; 2.2 ; 2.3 ; 5.7 ; 8.5, 1.0 ; 2.2 ; 2.3 ; 3.7 ; 8.5


Diphenyldichloromethane

Diphenyldichloromethane is an organic compound with the formula (C6H5)2CCl2. It is a colorless solid that is used as a precursor to other organic compounds.
Synthesis.
It is prepared from carbon tetrachloride and anhydrous aluminium chloride as catalyst in a double Friedel-Crafts alkylation of benzene. Alternatively,
benzophenone is treated with phosphorus pentachloride:
Reactions.
It undergoes hydrolysis to benzophenone.
It is used in the synthesis of tetraphenylethylene,
diphenylmethane imine hydrochloride and benzoic anhydride.


Diborane(4)

Diborane(4) is a transient inorganic compound with the chemical formula . Stable derivatives are known.
Diborane(4) has been produced by abstraction of two hydrogen atoms from diborane(6) using atomic fluorine and detected by photoionization mass spectrometry. Computational studies predict a structure in which are two hydrogen atoms bridging the two boron atoms via three-centre two-electron bonds in addition to the 2-centre, 2-electron bond between the two boron atoms and one terminal hydrogen atom bonded to each boron atom.
Several stable derivatives of diborane(4) have been reported.


Carbon respiration

Carbon respiration (also called carbon emissions and carbon releases) is used in combination with carbon fixation to gauge carbon flux (as CO2) between atmospheric carbon and the global carbon cycle
Basic process.
Carbon is released to the atmosphere through the burning of fossil fuels, organic respiration, wood burning, and volcanic eruptions. The uptake of carbon from the atmosphere occurs through carbon dissolution into the oceans, Photosynthesis, and the consequent storing of carbon in various forms such as peat bogs, oil accumulation, and formation of minerals such as coal and copper. It also happens when carbohydrates are changed into carbon dioxide.
Carbon flux ratio.
The calculation of the annual net difference between carbon release and carbon storage constitutes the annual global atmospheric carbon accumulation rate. Using this method, the annual carbon flux ratio has been calculated to be approaching zero. This means the carbon respiration rate and carbon storage rate are in balance when generating a global estimate of this figure.
Annual net carbon flux has been grossly calculated to be close to zero, implying the carbon release and carbon fixation rates are roughly in balance worldwide. This finding is contradicted by measuring the concentrations of carbon dioxide in the atmosphere, an important indication that the balance is tipped toward emissions. Using this data, atmospheric concentrations appear to have increased rapidly over the past 100 years and are currently higher than ever in human history, suggesting that more carbon is being released than can be absorbed on earth.


Potassium selenate

Potassium selenate, , is an odorless, white solid that forms as the potassium salt of selenic acid. It is used in photography.
Preparation.
Potassium selenate is produced by the reaction of selenium trioxide and potassium hydroxide.
Alternatively, it can be made by reacting selenous acid with potassium hydroxide, and then oxidizing the resulting potassium selenite with bromine.