nanoparticles are a special group of materials with unique features and extensive applications in diverse fields.1 metal nanoparticles , such as those containing gold and silver have recognized importance in chemistry , physics , and biology because of their unique optical , electrical , and photothermal properties.2 the ease of synthesizing gold and silver nanoparticles and their affinity for binding many biological molecules makes them attractive candidates for study .
various physical and chemical methods have been reported over the last two decades for the synthesis of gold and silver nanoparticles , of which chemical approaches , such as chemical reduction , electrochemical techniques , and photochemical reduction , are most widely used .
the green method of nanoparticle synthesis employing plant extracts is a simple and viable alternative to chemical procedures and physical methods.3 chemical and physical methods are harmful because the chemicals used are toxic , flammable , and are not disposed easily of in the environment.4 in recent years , biosynthesis of nanoparticles has received considerable attention due to the growing need to develop clean and nontoxic chemicals , environmentally friendly solvents , and renewable materials.5 utilization of biological systems such as plant extracts for the synthesis of nanoparticles has advantages over chemical and physical methods , because these systems are cost - effective , environment friendly , single - step in nature , and easily scaled up for large - scale synthesis.6 studies have shown that the size , morphology , stability , and physicochemical properties of metal nanoparticles are strongly influenced by the experimental conditions,79 and play pivotal roles in controlling the physical , chemical , optical , and electronic properties of these nanoscopic materials .
this is particularly important for noble metals , such as gold and silver , which have strong surface plasmon resonance oscillations.10 several researchers have reported the use of natural products , inactivated plant biomass , and as living plants such as aloe vera,11 
 carica papaya,12 
 magnolia kobus , diospyros kaki,13 
 medicago sativa,14,15 
 azadirachta indica,16 
 pelargonium graveolens,17 
 chilopsis linearis,18 and tamarindus indica19 for the production of silver and gold nanoparticles ( table 1 ) .
large amounts of nanoparticles can be easily synthesized from plants , and the majority of these are nontoxic .
they have been used in pharmaceutical drug - based industries for treating lymphocytic leukemia , detecting dna , inhibiting bacteria and fungi , and preventing burns and open wound infections.20,21 trianthema decandra , a prostrate , glabrous , succulent annual belonging to the aizoaceae family , is found as a weed throughout most of india.22 the plant has various medicinal properties and has been reported to have antioxidant and antimicrobial properties.23 in the present study , we describe the biosynthesis of gold and silver nanoparticles from aqueous root extract of t. decandra for the first time .
chloroauric acid and silver nitrate were reduced to metallic gold and metallic silver respectively , on reaction with root extract of t. decandra , resulting in synthesis of gold and silver nanoparticles .
the gold and silver nanoparticles formed were characterized using ultraviolet - visible , scanning electron microscopy , energy dispersive x - ray , and fourier transform infrared spectroscopy .
t. decandra l was collected from salem district , tamil nadu , india , during june 2011 .
the plant was taxonomically identified and authenticated by the botanical survey of india , coimbatore , and voucher specimen bsi / src/5/23/10 - 11/tech 975 was deposited at the plant biotechnology laboratory , sri ramaswamy memorial university , for future reference . gold ( iii )
chloride trihydrate ( haucl4 ) and silver nitrate ( agno3 ) were purchased from sigma - aldrich , st louis , mo .
next , 20 g of coarsely powdered material was extracted with 100 ml of double - distilled water .
the extract was stored at 4c until further use . for the synthesis of gold and silver nanoparticles ,
10 ml of 1 mm aqueous haucl4 and agno3 solutions were separately added to 5 ml , 10 ml , and 15 ml of aqueous root extract and incubated in the dark .
the resulting colloidal solutions of gold and silver were then analyzed using ultraviolet - visible spectroscopy .
the colloidal solutions of gold and silver were diluted by adding 2.9 ml of deionized water to 0.1 ml of sample .
bioreduction of haucl4 and agno3 was recorded as a function of time using water as a reference at 3-hour intervals from zero hour up to 24 hours using an ultraviolet - visible spectrophotometer ( perkin - elmer , boston , ma ) in a scanning range of 200 nm to 800 nm . to remove excess gold and silver ions ,
the gold and silver colloids were centrifuged at 10,000 rpm for 15 minutes and washed at least three times with deionized water .
a dried powder of the gold and silver nanoparticles was obtained by freeze - drying .
the air - dried powder form of the synthesized gold and silver nanoparticles was ground with kbr pellets and subjected to fourier transform infrared spectroscopy .
the gold and silver nanoparticles formed were characterized using high resolution field emission scanning electron microscopy ( fe - sem ) .
the samples were prepared by simple drop coating of the suspension of gold and silver nanoparticles separately on a carbon - coated copper grid , by simply dropping a very small amount of the sample on the grid , with excess solution removed using blotting paper .
the film on the scanning electron microscopy grid was then allowed to dry under a mercury lamp for 5 minutes .
energy dispersive x - ray spectroscopy was then performed using the hitachi s-3400 n fe - sem instrument equipped with a thermo energy dispersive x - ray spectroscopy attachment .
the antimicrobial activity of the gold and silver nanoparticles formed was assayed using the standard kirby - bauer disc diffusion method.24 bacterial suspensions of staphylococcus aureus ( mtcc 29213 ) , streptococcus faecalis ( mtcc 0459 ) , enterococcus faecalis ( mtcc 2729 ) , escherichia coli ( mtcc 443 ) , pseudomonas aeruginosa ( mtcc 1035 ) , proteus vulgaris ( mtcc 1771 ) , bacillus subtilis ( mtcc 121 ) , yersinia enterocolitica ( mtcc 840 ) , and the fungus , candida albicans ( mtcc 183 ) , grown overnight were swabbed on separate nutrient agar plates using l - rods .
whatman filter paper ( no 1 ) discs 6 mm in diameter were separately impregnated with 20 l of a 10 mg / ml solution of gold and silver nanoparticles in dimethylsulfoxide .
chloramphenicol and nystatin were used as positive controls for bacteria and the fungus respectively , while dimethylsulfoxide served as a negative control .
diameters of the zones of inhibition were measured using a meter ruler , and the mean value for each organism was recorded and expressed in millimeters .
the data were analyzed by one - way analysis of variance followed by the duncan s multiple range test .
t. decandra l was collected from salem district , tamil nadu , india , during june 2011 .
the plant was taxonomically identified and authenticated by the botanical survey of india , coimbatore , and voucher specimen bsi / src/5/23/10 - 11/tech 975 was deposited at the plant biotechnology laboratory , sri ramaswamy memorial university , for future reference .
gold ( iii ) chloride trihydrate ( haucl4 ) and silver nitrate ( agno3 ) were purchased from sigma - aldrich , st louis , mo .
the shade - dried materials were powdered and passed through a 40-mesh sieve . next , 20 g of coarsely powdered material was extracted with 100 ml of double - distilled water .
for the synthesis of gold and silver nanoparticles , 10 ml of 1 mm aqueous haucl4 and agno3 solutions were separately added to 5 ml , 10 ml , and 15 ml of aqueous root extract and incubated in the dark .
the resulting colloidal solutions of gold and silver were then analyzed using ultraviolet - visible spectroscopy .
the colloidal solutions of gold and silver were diluted by adding 2.9 ml of deionized water to 0.1 ml of sample .
bioreduction of haucl4 and agno3 was recorded as a function of time using water as a reference at 3-hour intervals from zero hour up to 24 hours using an ultraviolet - visible spectrophotometer ( perkin - elmer , boston , ma ) in a scanning range of 200 nm to 800 nm .
to remove excess gold and silver ions , the gold and silver colloids were centrifuged at 10,000 rpm for 15 minutes and washed at least three times with deionized water .
a dried powder of the gold and silver nanoparticles was obtained by freeze - drying .
the air - dried powder form of the synthesized gold and silver nanoparticles was ground with kbr pellets and subjected to fourier transform infrared spectroscopy .
the gold and silver nanoparticles formed were characterized using high resolution field emission scanning electron microscopy ( fe - sem ) .
the samples were prepared by simple drop coating of the suspension of gold and silver nanoparticles separately on a carbon - coated copper grid , by simply dropping a very small amount of the sample on the grid , with excess solution removed using blotting paper .
the film on the scanning electron microscopy grid was then allowed to dry under a mercury lamp for 5 minutes .
energy dispersive x - ray spectroscopy was then performed using the hitachi s-3400 n fe - sem instrument equipped with a thermo energy dispersive x - ray spectroscopy attachment .
the antimicrobial activity of the gold and silver nanoparticles formed was assayed using the standard kirby - bauer disc diffusion method.24 bacterial suspensions of staphylococcus aureus ( mtcc 29213 ) , streptococcus faecalis ( mtcc 0459 ) , enterococcus faecalis ( mtcc 2729 ) , escherichia coli ( mtcc 443 ) , pseudomonas aeruginosa ( mtcc 1035 ) , proteus vulgaris ( mtcc 1771 ) , bacillus subtilis ( mtcc 121 ) , yersinia enterocolitica ( mtcc 840 ) , and the fungus , candida albicans ( mtcc 183 ) , grown overnight were swabbed on separate nutrient agar plates using l - rods .
whatman filter paper ( no 1 ) discs 6 mm in diameter were separately impregnated with 20 l of a 10 mg / ml solution of gold and silver nanoparticles in dimethylsulfoxide .
chloramphenicol and nystatin were used as positive controls for bacteria and the fungus respectively , while dimethylsulfoxide served as a negative control .
diameters of the zones of inhibition were measured using a meter ruler , and the mean value for each organism was recorded and expressed in millimeters .
the data were analyzed by one - way analysis of variance followed by the duncan s multiple range test .
nanoparticles of noble metals are characterized by the presence of bright colors produced by oscillations of the surface electron cloud of these particles .
the formation of gold and silver nanoparticles was observed by monitoring the change in color , ie , a light yellow solution turning to ruby pink when haucl4 was used and a pale yellow solution turning to dark grey when agno3 was used .
the collective oscillations of electrons in a nanoparticle upon interaction with light of suitable energy causes the nanoparticles to attain the color specific to a particular metal .
particle size , shape , and aggregation depend strongly on the frequency of oscillations.25 the reduction kinetics of aqueous chloroaurate ions and silver ions leading to synthesis of gold and silver nanoparticles was compared using different amounts , ie , 5 ml , 10 ml , and 15 ml of root extract of t. decandra ( figures 1 and 2 ) .
gold nanoparticles were synthesized within 3 hours of reaction with the root extract and the components thereof , while more than a 6-hour reaction period was required for synthesis of the silver counterpart .
preliminary phytochemical screening of aqueous extracts of t. decandra showed the presence of various secondary metabolites.26 the bioreduction achieved in the present study is attributed to the metabolites present in the plant .
synthesis of gold nanoparticles was pronounced when 15 ml of root extract was used for bioreduction , while 10 ml of the same root extract was sufficient for production of silver nanoparticles .
the colloidal gold solution showed strong ( 0.15 au ) , weak ( 0.04 au ) , and moderate ( 0.08 au ) absorption peaks with 15 ml , 5 ml , and 10 ml of extract respectively , at 575 nm ( figure 3 ) .
the colloidal silver solution showed strong ( 0.81 au ) , weak ( 0.23 au ) , and moderate ( 0.31 au ) absorbance peaks with 10 ml , 5 ml , and 15 ml of extract respectively at 340 nm ( figure 4 ) .
nanoparticles may grow in a process involving rapid bioreduction and strongly influence surface plasmon resonance in the water extract.27 the results of the present study are in accordance with previous reports , including that by vijayakumar et al27 on artemisia nilagirica , indicating occurrence of a silver band at 340400 nm .
further characterization using fourier transform infrared , scanning electron , and energy dispersive x - ray spectroscopy was carried out for gold nanoparticles formed with 15 ml and silver nanoparticles formed with 10 ml of t. decandra root extract .
the functional groups present in gold nanoparticles detected using fourier transform infrared spectroscopy had absorption peaks located at 1649.33 cm and 1020.12 cm in the region of 10001800 cm characteristic of gold atoms ( figure 5 ) .
two absorption peaks located at 1649.33 cm and 1020 cm are indicative of c = c stretch and aromatic cc bonds , respectively .
distinct peaks in the range of 2344.87 cm and 2364.35 cm correspond to cn stretch , while peaks at 2925.92 cm and 3422.38 cm correspond to ch and oh stretching vibration , respectively .
fourier transform infrared spectroscopy analysis of the silver nanoparticles showed absorption peaks of reduced silver at 1653.96 cm and 1027.44 cm in the region of 10001800 cm ( figure 6 ) .
two absorption peaks located at 1653 cm are associated with the stretch vibration of c = c , and the single absorbance peak located at 1027 cm is assigned to cn stretching vibrations of amine .
further distinct peaks in the region of 2343.972362.27 cm correspond to cn stretch for nitrile groups , while 3447.86 cm corresponds to oh stretching vibration .
scanning electron micrographs ( figure 7 ) for the gold nanoparticles reveal numerous spherical , triangular , hexagonal , and cubic structures produced by reduction of goldions with sizes ranging between 33.7 nm and 99.3 nm . an individual gold nanohexagon with an average edge length of 737 nm is also seen in figure 7b .
very recently , rai et al have demonstrated that the presence of halide ions and modulation of temperature can control the morphology of biologically synthesized gold triangles using lemongrass leaf extract.28 in the present study , nanoparticles resembling triangles with sizes ranging between 33.7 nm and 99.3 nm were produced during bioreduction of haucl4 , which could be attributed to the chloride ions present in it ( figure 7d ) .
spherical silver nanoparticles with diameters of 3694 nm are depicted in the scanning electron micrographs ( figure 8) .
the variation in particle sizes , such as 36 , 47 , 60 , and 94 nm , is possibly due to the fact that the nanoparticles are being formed at different times . water - soluble heterocyclic compounds , including saponin , were mainly responsible for the reduction of silver ions or chloroaurate ions to metallic silver and metallic gold , respectively .
further , it has been shown that the presence of chloride ions during nanosynthesis promotes the growth of nanotriangles . in the present study , reduction of chloroaurate ions produced nanotriangles .
the presence of gold atoms in the gold nanoparticles was further confirmed by energy dispersive x - ray spectroscopy .
the optical absorption peak was observed at approximately 2.2 kev , which is typical of gold nanocrystallite absorption due to surface plasmon resonance .
the current energy dispersive x - ray spectroscopic profile of gold nanoparticles of t. decandra ( figure 9 ) showed strong gold atom signals around 0.30 , 2 , 2.2 , 2.4 , and 9.7 kev .
similarly , the presence of silver atoms in the silver nanoparticles was confirmed using energy dispersive x - ray spectroscopy ( figure 10 ) .
the optical absorption peak was observed at 3 kev , which is typical for silver nanocrystallite absorption due to surface plasmon resonance . in an earlier study ,
individual spherical silver nanoparticles synthesized using alfalfa showed absorption peaks in the range of 2.54 kev.29 the current profile of energy dispersive x - ray spectroscopy for silver nanoparticles of t. decandra indicate strong silver atom signals around 0.20 , 3 , 3.2 , and 3.4 kev .
antimicrobial activity of the synthesized gold and silver nanoparticles was studied using eight different bacteria , namely s. aureus , s. faecalis , e. faecalis , e. coli , p. aeruginosa , p. vulgaris , b. subtilis , y. enterocolitica , and a fungus , c. albicans .
both gold and silver nanoparticles exhibited excellent activity against y. enterocolitica , p. vulgaris , e. coli , s. aureus , and s. faecalis .
zones of inhibition measuring 13.515.5 mm were recorded for the gold nanoparticles , while their silver counterparts recorded zones of 15.520.5 mm .
moderate activity was recorded against the other three bacteria tested ( table 2 , figures 11 and 12 ) .
the growth inhibition of c. albicans was double in silver nanoparticles when compared with gold nanoparticles .
the antibacterial effect was more pronounced in gram - negative bacteria than gram - positive ones .
the antimicrobial activity of colloidal silver particles is influenced by the particle dimensions.30 silver has long been recognized as having an inhibitory effect on microbes present in medical and industrial processes .
the most important application of silver and silver nanoparticles is in medical industry , such as in topical ointments to prevent infection against burns and open wounds.31 gold nanoparticles are harmful to bacteria and fungi .
they bind closely to the surface of microorganisms , causing visible damage to cells , with complete destruction of flagella , stimulated production of biofilm , and aggregation within the biofilm.32 comparison of gold and silver nanoparticle sizes indicates the latter to be smaller than the former .
the smaller particles have greater antimicrobial effects.33 further , the antimicrobial activity in the present study was much higher when compared with previous reports .
silver nanoparticles from polyalthia longifolia , balsamodendron mukul , melia azadirachta , berberis aristata , acorus calamus , embelia ribes , psoralea corylifolia , smilax china , glycyrrhiza glabra , and andropogon muricatus showed activity against e. coli , p. aeruginosa , s. aureus , and c. albicans , with zones of inhibition measuring less than 8 mm in diameter.30,33 the results of the present study are indicative of pronounced antibacterial effects .
they provide an important basis for use of gold and silver nanoparticles synthesized from the root extract of t. decandra in the treatment of human infections associated with the microorganisms used in this study .
nanoparticles of noble metals are characterized by the presence of bright colors produced by oscillations of the surface electron cloud of these particles .
the formation of gold and silver nanoparticles was observed by monitoring the change in color , ie , a light yellow solution turning to ruby pink when haucl4 was used and a pale yellow solution turning to dark grey when agno3 was used .
the collective oscillations of electrons in a nanoparticle upon interaction with light of suitable energy causes the nanoparticles to attain the color specific to a particular metal .
particle size , shape , and aggregation depend strongly on the frequency of oscillations.25 the reduction kinetics of aqueous chloroaurate ions and silver ions leading to synthesis of gold and silver nanoparticles was compared using different amounts , ie , 5 ml , 10 ml , and 15 ml of root extract of t. decandra ( figures 1 and 2 ) .
gold nanoparticles were synthesized within 3 hours of reaction with the root extract and the components thereof , while more than a 6-hour reaction period was required for synthesis of the silver counterpart .
preliminary phytochemical screening of aqueous extracts of t. decandra showed the presence of various secondary metabolites.26 the bioreduction achieved in the present study is attributed to the metabolites present in the plant .
synthesis of gold nanoparticles was pronounced when 15 ml of root extract was used for bioreduction , while 10 ml of the same root extract was sufficient for production of silver nanoparticles .
the colloidal gold solution showed strong ( 0.15 au ) , weak ( 0.04 au ) , and moderate ( 0.08 au ) absorption peaks with 15 ml , 5 ml , and 10 ml of extract respectively , at 575 nm ( figure 3 ) .
the colloidal silver solution showed strong ( 0.81 au ) , weak ( 0.23 au ) , and moderate ( 0.31 au ) absorbance peaks with 10 ml , 5 ml , and 15 ml of extract respectively at 340 nm ( figure 4 ) .
nanoparticles may grow in a process involving rapid bioreduction and strongly influence surface plasmon resonance in the water extract.27 the results of the present study are in accordance with previous reports , including that by vijayakumar et al27 on artemisia nilagirica , indicating occurrence of a silver band at 340400 nm .
further characterization using fourier transform infrared , scanning electron , and energy dispersive x - ray spectroscopy was carried out for gold nanoparticles formed with 15 ml and silver nanoparticles formed with 10 ml of t. decandra root extract .
the functional groups present in gold nanoparticles detected using fourier transform infrared spectroscopy had absorption peaks located at 1649.33 cm and 1020.12 cm in the region of 10001800 cm characteristic of gold atoms ( figure 5 ) .
two absorption peaks located at 1649.33 cm and 1020 cm are indicative of c = c stretch and aromatic cc bonds , respectively .
distinct peaks in the range of 2344.87 cm and 2364.35 cm correspond to cn stretch , while peaks at 2925.92 cm and 3422.38 cm correspond to ch and oh stretching vibration , respectively .
fourier transform infrared spectroscopy analysis of the silver nanoparticles showed absorption peaks of reduced silver at 1653.96 cm and 1027.44 cm in the region of 10001800 cm ( figure 6 ) .
two absorption peaks located at 1653 cm are associated with the stretch vibration of c = c , and the single absorbance peak located at 1027 cm is assigned to cn stretching vibrations of amine .
further distinct peaks in the region of 2343.972362.27 cm correspond to cn stretch for nitrile groups , while 3447.86 cm corresponds to oh stretching vibration .
scanning electron micrographs ( figure 7 ) for the gold nanoparticles reveal numerous spherical , triangular , hexagonal , and cubic structures produced by reduction of goldions with sizes ranging between 33.7 nm and 99.3 nm . an individual gold nanohexagon with an average edge length of 737 nm is also seen in figure 7b .
very recently , rai et al have demonstrated that the presence of halide ions and modulation of temperature can control the morphology of biologically synthesized gold triangles using lemongrass leaf extract.28 in the present study , nanoparticles resembling triangles with sizes ranging between 33.7 nm and 99.3 nm were produced during bioreduction of haucl4 , which could be attributed to the chloride ions present in it ( figure 7d ) .
spherical silver nanoparticles with diameters of 3694 nm are depicted in the scanning electron micrographs ( figure 8) .
the variation in particle sizes , such as 36 , 47 , 60 , and 94 nm , is possibly due to the fact that the nanoparticles are being formed at different times . water - soluble heterocyclic compounds , including saponin , were mainly responsible for the reduction of silver ions or chloroaurate ions to metallic silver and metallic gold , respectively .
further , it has been shown that the presence of chloride ions during nanosynthesis promotes the growth of nanotriangles . in the present study , reduction of chloroaurate ions produced nanotriangles .
the presence of gold atoms in the gold nanoparticles was further confirmed by energy dispersive x - ray spectroscopy .
the optical absorption peak was observed at approximately 2.2 kev , which is typical of gold nanocrystallite absorption due to surface plasmon resonance .
the current energy dispersive x - ray spectroscopic profile of gold nanoparticles of t. decandra ( figure 9 ) showed strong gold atom signals around 0.30 , 2 , 2.2 , 2.4 , and 9.7 kev .
similarly , the presence of silver atoms in the silver nanoparticles was confirmed using energy dispersive x - ray spectroscopy ( figure 10 ) .
the optical absorption peak was observed at 3 kev , which is typical for silver nanocrystallite absorption due to surface plasmon resonance . in an earlier study ,
individual spherical silver nanoparticles synthesized using alfalfa showed absorption peaks in the range of 2.54 kev.29 the current profile of energy dispersive x - ray spectroscopy for silver nanoparticles of t. decandra indicate strong silver atom signals around 0.20 , 3 , 3.2 , and 3.4 kev .
antimicrobial activity of the synthesized gold and silver nanoparticles was studied using eight different bacteria , namely s. aureus , s. faecalis , e. faecalis , e. coli , p. aeruginosa , p. vulgaris , b. subtilis , y. enterocolitica , and a fungus , c. albicans .
both gold and silver nanoparticles exhibited excellent activity against y. enterocolitica , p. vulgaris , e. coli , s. aureus , and s. faecalis .
zones of inhibition measuring 13.515.5 mm were recorded for the gold nanoparticles , while their silver counterparts recorded zones of 15.520.5 mm .
moderate activity was recorded against the other three bacteria tested ( table 2 , figures 11 and 12 ) .
the growth inhibition of c. albicans was double in silver nanoparticles when compared with gold nanoparticles .
the antibacterial effect was more pronounced in gram - negative bacteria than gram - positive ones .
the antimicrobial activity of colloidal silver particles is influenced by the particle dimensions.30 silver has long been recognized as having an inhibitory effect on microbes present in medical and industrial processes .
the most important application of silver and silver nanoparticles is in medical industry , such as in topical ointments to prevent infection against burns and open wounds.31 gold nanoparticles are harmful to bacteria and fungi .
they bind closely to the surface of microorganisms , causing visible damage to cells , with complete destruction of flagella , stimulated production of biofilm , and aggregation within the biofilm.32 comparison of gold and silver nanoparticle sizes indicates the latter to be smaller than the former .
the smaller particles have greater antimicrobial effects.33 further , the antimicrobial activity in the present study was much higher when compared with previous reports .
silver nanoparticles from polyalthia longifolia , balsamodendron mukul , melia azadirachta , berberis aristata , acorus calamus , embelia ribes , psoralea corylifolia , smilax china , glycyrrhiza glabra , and andropogon muricatus showed activity against e. coli , p. aeruginosa , s. aureus , and c. albicans , with zones of inhibition measuring less than 8 mm in diameter.30,33 the results of the present study are indicative of pronounced antibacterial effects .
they provide an important basis for use of gold and silver nanoparticles synthesized from the root extract of t. decandra in the treatment of human infections associated with the microorganisms used in this study .
to summarize , we achieved successful green synthesis of gold and silver nanoparticles using t. decandra root extract .
silver and gold nanoparticles were synthesized under ambient conditions , and characterization of synthesized nanoparticles was carried out by ultraviolet - visible , fourier transform infrared , scanning electron and energy dispersive x - ray spectroscopy .
it is believed that phytochemicals present in t. decandra extract reduce the silver and gold ions into metallic nanoparticles .
 backgroundthere is an increasing commercial demand for nanoparticles due to their wide applicability in various markets , including medicine , catalysis , electronics , chemistry , and energy . in this report 
 , a simple and ecofriendly chemical reaction for the synthesis of gold and silver nanoparticles from trianthema decandra ( aizoaceae ) has been developed.methods and resultson treatment of aqueous solutions containing chloroauric acid or silver nitrate with root extract of t. decandra , stable gold or silver nanoparticles were rapidly formed . 
 the kinetics of reduction of gold and silver ions during the reaction was analyzed by ultraviolet - visible spectroscopy . 
 field emission - scanning electron microscopy showed formation of gold nanoparticles in various shapes , including spherical , cubical , triangular , and hexagonal , while silver nanoparticles were spherical . 
 the size of the gold nanoparticles was 3365 nm and that of the silver nanoparticles was 3674 nm . 
 energy dispersive x - ray and fourier transform infrared spectroscopy confirmed the presence of metallic gold and metallic silver in the respective nanoparticles . 
 the antimicrobial properties of the synthesized nanoparticles were analyzed using the kirby - bauer method . 
 the results show varied susceptibility of microorganisms to the gold and silver nanoparticles.conclusionit is believed that phytochemicals present in t. decandra extract reduce the silver and gold ions into metallic nanoparticles . 
 this strategy reduces the cost of production and the environmental impact . 
 the silver and gold nanoparticles formed showed strong activity against all microorganisms tested . 
Introduction
Materials and methods
Plant materials
Chemicals
Preparation of plant extracts
Synthesis of gold and silver nanoparticles
Ultraviolet-visible spectroscopy
Purification of gold and silver nanoparticles
Fourier transform infrared spectroscopy
FE-SEM and energy dispersive x-ray spectroscopy
Antimicrobial activity
Statistical analysis
Results and discussion
Synthesis and characterization of gold and silver nanoparticles
Antimicrobial activity of gold and silver nanoparticles
Conclusion