one - dimensional ( 1d ) nanostructures such as wires , rods , belts , and tubes , whose lateral dimensions fall anywhere in the range of 1100 nm , have become the focus of intensive research , owing to their unique applications in mesoscopic physics and fabrication of nanoscale devices [ 1 - 6 ] . among one - dimensional ( 1d ) nanostructures , nanobelts ( or nanoribbons ) , a relatively new family of 1d nanostructures with a rectangular cross section , have received increasing attention since the discovery of novel oxide semiconductor nanobelts [ 4 - 8 ] .
a variety of functional oxide   and sulfide [ 10 - 17 ] nanobelts have been successfully fabricated by simple thermal evaporation .
the methods used in 1d nanostructure synthesis and hydrothermal processes have emerged as powerful tools for the fabrication of anisotropic nanomaterials with some significant advantages , such as controllable particle size and low - temperature , cost - effective , and less - complicated techniques . under hydrothermal conditions , many starting materials can undergo quite unexpected reactions , which are often accompanied by the formation of nanoscopic morphologies that are not accessible by classical routes . in recent years , 1d nanomaterials such as ln(oh)3[19 - 21 ] , cdwo4 , moo3 , and dy(oh)3
cadmium hydroxide , cd(oh)2 , is a wide band gap semiconductor   with a wide range of possible applications including solar cells , photo transistors and diodes , transparent electrodes , sensors , etc . .
cadmium hydroxide is also the precursor to prepare cadmium oxide . as a consequence , numerous techniques
have been proposed to synthesize nano - sized cd(oh)2 particles with promising control of properties [ 25 - 28 ] . however , up to now , to our best knowledge , the synthesis of cd(oh)2 nanobelts by hydrothermal process has not been reported .
herein , we report the preparation of cadmium hydroxide nanobelts by the conventional polyol assisted hydrothermal process .
in a typical procedure ; cdcl2  2h2o ( 0.2281 g ) was dissolved in 32 ml of distilled water , and then nh3  h2o ( 25 wt.% , 5 ml ) was slowly added into the solution and stirred for about 10 min , and a transparent cd(nh3)4solution was formed . then , the above solution was loaded into a 50-ml teflon - lined autoclave , which was then filled with 8 ml of glycol .
the autoclave was sealed , warmed up at a speed of 3 c / min and maintained at 100 c for 6 h , and was then cooled to room temperature on standing .
the white precipitate was filtered off , washed with absolute ethanol and distilled water for several times , and then dried in vacuum at 40 c for 4 h. x - ray diffraction ( xrd ) patterns were carried out on a japan rigaku d / max ra x - ray diffractometer equipped with graphitemonochromatized high - intensity cu ka radiation ( = 1.541784  ) . the accelerating voltage was set at 50 kv , with 100 ma flux at a scanning rate of 0.06/s in the 2 range 1080. the x - ray photoelectron spectra ( xps ) were collected on an escalab mkii x - ray photoelectron spectrometer using nonmonochromatized mg kr x - ray as the excitation source .
the field emission scanning electron microscopy ( fe - sem ) images were taken on a jeol jsm-6700fsem .
the transmission electron microscopy ( tem ) images were characterized by hitachi h-800 transmission electron microscope with a tungsten filament and an accelerating voltage of 200 kv .
1 ) from the as - synthesized bulk samples reveals the crystal structure and phase purity of the products .
all the diffraction peaks can be indexed to the hexagonal cd(oh)2with cell constantsa = 3.4942,c = 4.7102 , which are consistent with the values in the literature ( jcpds 31 - 0228 ) .
the abnormally intensified ( 100 ) peak in the xrd pattern also indicates that the belt - like product comprises 1d cd(oh)2crystals preferentially grown along the   direction .
powder xrd patterns of the products figure 2 shows the xps spectra of the as - obtained cd(oh)2 sample . a survey spectrum shown in fig .
2a , indicates the presence of cd and o as well as c from reference .
there are no peaks for other impurities , indicating that the as - obtained product is relatively pure .
high - resolution spectra are also taken for the cd 3d region and the o 1s region to determine the valency state and atomic ratio .
the binding energies of cd(3d5/2 ) and o(1s ) were found to be 405.30 and 531.25 ev , respectively .
all the above observed binding energy values are in good agreement with the reported data .
quantification of the xps peaks gives the molar ratio of cd : o as 1:2.02 , close to the stoichiometry of cd(oh)2 .
3a ) shows that the as - synthesized products consist of a large quantity of 1d nanostructures with lengths from several tens to several hundreds of micrometers ; some of them even have lengths of the order of millimeters . a representative high magnification sem image ( fig .
3b ) of several curved cd(oh)21d nanostructures reveals that their geometrical shape is belt - like , which is distinct from those of previously reported nanowires , and their thickness is about 3050 nm .
( b ) high - magnification image of curved nanobelts tem and saed studies of the as - synthesized products provide further insight into the belt - like cd(oh)2nanostructures .
the nanobelts are uniform in width and thickness , and their typical widths and thickness are in the range of 60250 nm and 1030 nm , respectively . the saed pattern ( inset in fig .
4b ) taken from the straight section of the curved nanobelt demonstrates that this particular nanobelt is a single crystal .
( b ) single curved cd(oh)2 nanobelt for the polyol process , glycol was selected as the solvent because of its excellent viscosity , which makes it possible to mix the reagents homogeneously . in the process
, glycol can provide reaction conditions adequate to greatly enhance solubility , diffusion , and crystallization , but is still mild to leave molecular building blocks to bring about the formation of the solid - state phase .
at reaction temperature , the diffusion of ions in glycol is more rapid than in other polyol , such as glycerine and diethylene glycol ; this leads to acceleration in the solubility of starting materials and in the following crystal growth .
the concentrations of glycol of about 2030 vol.% , were found to be favorable for the formation of the cd(oh)2 nanobelts in high yield . such viscosity had a good effect on prohibiting aggregation of cd(oh)2particles and then resulted in a relatively stable suspension .
control reactions at a low concentration of glycol ( 3 ml ) would plate out a large amount of the cd(oh)2 nanorods ( fig .
5a ) . at very high concentrations ( 20 ml glycol ) , however , only the aggregated particles were observed ( fig .
when glycerine was used , nanobelts were not obtained due to the high viscosity of solvent .
, we can clearly see that the viscosity is of importance to the structure of the final product .
sem images of cd(oh)2 samples using different concentrations of glycol : ( a ) 3 ml ; ( b ) 20 ml the optical absorption spectrum of our sample is shown in fig .
compared to other researcher s work , the absorption edge obviously shifts toward shorter wavelength , i.e. , blue shift .
the absorption band gap eg can be determined by the following equation : ( h)= b(h  eg ) , in which h is the photo energy ,  is the absorption coefficient , b is a constant relative to the material , and n is either 2 for a direct transition or 1/2 for an indirect transition .
the ( h ) ~ h curve for the samples shown in fig . 6 insert reveals that the band gap of the samples is about 4.45 ev , which is larger than the reported value for cd(oh)2 thin film ( eg = 2.75 ev ) , but is less than the reported value for nanostrands , which have a constant width of 1.9 nm ( eg = 4.76 ev )   due to the quantum size effect . optical absorption spectrum and ( h ) ~ h curve for the cd(oh)2 nanobelts
in summary , cd(oh)2nanobelts with a uniform diameter have been successfully prepared in high yield through a rapid polyol process .
it was found that the viscosity of the solvent played an important role in determining the morphology .
we believe that it should be possible to synthesize other similar patterns by choosing an appropriate solvent .
the optical absorption spectrum indicates that the cd(oh)2nanobelts have a direct band gap of 4.45 ev .
this work was supported by a grant - in - aid for scientific research from the japan society for the promotion of science ( jsps ) and the crest program of the japan science and technology agency ( jst ) .
we are grateful to young and middle aged academic leaders of jiangsu province universities  blue and green blue project .
 we are grateful to the electron microscope and x - ray diffraction facilities of university of science & technology of china for assistance in xrd and sem measurement .
 cd(oh)2nanobelts have been synthesized in high yield by a convenient polyol method for the first time . 
 xrd , xps , fesem , and tem were used to characterize the product , which revealed that the product consisted of belt - like crystals about 40 nm in thickness and length up to several hundreds of micrometers . 
 studies found that the viscosity of the solvent has important influence on the morphology of the final products . 
 the optical absorption spectrum indicates that the cd(oh)2nanobelts have a direct band gap of 4.45 ev . 
Introduction
Materials and Methods
Results and Discussion
Conclusions
Acknowledgment