Preparation Of Au Nanoparticles Decorated Ordered ZnO Nanorod Arrays And Their Catalytic Test Under Visible Light

Nanomaterials display a lot of unique properties and advantages that traditional materials do not possess,e.g.large specific surface area,quantum effects,and enhanced photoelectric conversion efficiency.Recently,with the advance of research and the great development of material processing,the fabrication and application of nanomaterials have made great progress.Meanwhile,nanomaterials have been widely used in many fields,e.g.optical devices,electronic devices,biomedicine,etc.,becoming one of the most investigated area.The morphology,size,and even crystal structure of semiconductor nanomaterials can be adjusted to improve the performance by changing the fabrication methods and the parameters during preparation.The nanorod arrays,due to its controllable morphology and ordered structure,can result in higher light absorption efficiency,and have attracted considerable attention in recent years.Surface plasmon resonance（SPR）effect can be excited on noble metal nanomaterials under visible light.If the semiconductor nanorod arrays are decorated with noble metal nanomaterials,the photoelectric performance could be further improved.Here,zinc oxide（ZnO）nanorod arrays were grown on Ga N epitaxy on（0001）sapphire substrates,and then ZnO nanorods were used as a carrier to decorate gold nanoparticles（Au NPs）to form Au-ZnO composites.Surface enhanced Raman spectroscopy（SERS）was used to study the photocatalytic properties of Au-ZnO nanomaterials.The main contents are as follows.（1）Polystyrene（PS）nanospheres were used to self-assemble a close-packed monolayer on the surface of water through the Langmuir-Blodgett（LB）method,and then it was deposited on a Ga N（0001）substrate.Subsequently,radio frequency（RF）magnetron sputtering of Si O₂ was used to reduce the size of PS nanospheres by plasma etching and cover the interstitial space between PS nanospheres by Si O₂,which can prevent the growth of ZnO there.After removing the PS nanospheres by dichloromethane,periodic seed sites were accomplished for following ZnO growth.The test results show that the ZnO nanorods grown by hydrothermal method were hexagonal and had a wurtzite crystal structure,and meanwhile the nanorods grew perpendicular to the substrate along the[0001]crystal direction.Moreover,the relationship between size and morphology of nanorods versus growth temperature was studied.It was observed that the size of ZnO nanorods was greatly affected by the growth temperature.ZnO nanorods didn’t grow if the growth temperature was too low.Moreover,if the growth temperature was too high,incomplete growth could be observed on the top of ZnO nanorods.（2）Various characterization methods,e.g.scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,ultraviolet-visible（UV-VIS）spectroscopy,etc.,have been used to analyze the morphology,crystal structure,chemical composition and electronic structure of the ZnO nanorod arrays.（3）Au NPs was deposited on ZnO nanorods and their catalytic performance under visible light was studied.We found that the ZnO nanorod arrays could change the propagation direction of incident light by scattering,which resulted in the increase of light absorption efficiency.In addition,the periodic structure of ordered ZnO nanorod array could make the incident light occur interference effects during the propagation process,and thus increase the light intensity in some areas.Although ZnO could not be excited by visible light,the increased light intensity can elevate the electric field intensity caused by surface plasmon on Au NPs,thus enhancing the photocatalytic properties.By using SERS to investigate the oxidation of p-aminothiophenol（PATP）to p,p’-dimercaptoazobenzene（DMAB）as a model transformation the enhancement of photocatalytic properties under visible light on Au NPs decorated ordered ZnO nanorod arrays were preliminary studied.