Investigation Of Fabrication And Synthesis Of Au Catalytic ZnO Nanostructures

Nanotechnology will absolutely be dominant in all scientific fields in 21st century, the nanomaterial is the basis of the application of nanotechnology,nanomaterials have received steadily growing interests as a result of their particular and fascinating properties,but also their potential application in many fields.Zinc oxide has been recognized as one of the most important semiconductor materials in scientific research and technological applications,owing to its direct wide bandgap(3.37 eV) and non-centrosymmetric structure.ZnO nanostructures with various morphologies, including nanowires,nanorings,nanobelts,nanorods and nanotubes,have been fabricated by different methods such as wet-chemical method,electrochemical deposition,templating method,radio-frequency magnetron sputtering deposition and metal-organic chemical vapor deposition.Our group has proposed a simple and efficient method to fabricate Straight ZnO nanoporous belts,W-shaped porous ZnO nanobelts and Necklace-shaped ZnO nanostructures.The structure,elemental composition and morphology of the ZnO nanostructures were characterized by a variety of techniques,including X-ray diffraction(XRD),Fourier transform infrared system(FTIR),Scanning electron microscopy(SEM),Fluorescence spectrophotometer,Field-emission transmission electron microscope(FETEM) and selected area electron diffraction(SAED).The formation mechanism of the special ZnO nanostructures were discussed.1.Straight ZnO nanoporous beltsStraight ZnO nanoporous belts with smooth surface and high pore density were successfully synthesized,the simple growth method is applicable to produce high-yield single-crystalline ZnO nanoporous belts with a relatively high purity and at a low cost. The samples have good optical quality.In our experiment,the as-synthesized sample has a high intensity ratio(I_uv:I_vs～10) and no other obvious peaks have been found, which indicates that the as-synthesized ZnO nanoporous belts have good optical quality. The growth mechanism is also briefly discussed,a possible growth mechanism is proposed to understand the formation of the structure,emphasizing the effect of polar orientation on the nucleation and growth of ZnO nanoporous belts.This high-porosity single-crystal belt-like structure has potential applications.2.W-shaped porous ZnO nanobeltsNovel W-shaped porous ZnO nanobelts with the periodical junction angles of about 118°have been successfully synthesized.The growth of W-shaped structure changes from[0001]to[0111]periodically.The structure has smooth surfaces with high porous density.Based on our XRD,electron microscopy and photoluminescence(PL) spectrum study,the growth mechanism of the special ZnO nanostructures is discussed,some oscillations(such as external growth kinetics temperature,partial pressures, supersaturation ratios) could easily disturb the active growth interface and change the chemical potentials,and in consequence,the preferential growth planes might be changed,such as the alternation of[0001]growth plane to[01(?)1]in wurtzite ZnO, and then form W-shaped morphology.3.Necklace-shaped ZnO nanostructuresThe necklace-shaped ZnO nanostructures have been successfully fabricated.For the formation of such ZnO structures,the decomposition of AgNO₃ solution is very important,which could be evaporated and decomposed to AgO_x,Ag and oxygen source (O₂,H₂O and NO₂) to affect the growth in the experiment process.A possible mechanism has been supposed here to explain this phenomenon.The synthesis of this new morphology could enrich our knowledge about wurtzite crystal growth,and it presents a new structural configuration with potential applications.