The Fabrication Of ZnO Nanoarrays For Photoelectrochemical Catalysis And Biosensing

The shortcoming of the ZnO nanomatrials can be improved by the construction ZnO nanoarrays composites.In this thesis,we prepared several new ZnO nanoarrays composites by the new stratagy and characterized the structure and composition of the materials by X-ray Diffraction?XRD?,Scanning Electron Microscope?SEM?,Transmission Electron Microscope?TEM?,X-ray Photoelectron Spectroscopy?XPS?,Energy Dispersive Spectrometer?EDS?and other techniques.Firstly,the photoelectrochemical?PEC?water splitting property could be modified by the formation of CuO/ZnO heterojunction nanoarrays composites.The absorbtion range of ZnO NRs was extended to the whole visible region by loading narrow bandgap CuO nanoparticles,improving the utilization efficiency of sunlight.In addition,the P-N heterojunction between P-type CuO and N-type ZnO NRs might hinder the recombination of photogenerated electron-hole pairs and improve the photocatalytic efficiency because of formation of the inner electric field in the interface of P-N heterojunctions.Secondly,the properties of Ag/ZnO and Au/ZnO nanoarrays heterojunction would be enhanced by the localized surface plasmon resonance?LSPR?of the modified Ag and Au nanoparticles.Thirdly,we developed ZnO nanorod arrays?ZnO NRs?on 50 nm Au nanofilm.This novel substrate improved the performances for the fluorescence based protein microarray nanalysis.The significant signal enhancement is attributed to the high protein loading capacity with a large surface area of ZnO NRs and to the surface plasmon coupling fluorescence enhancement of Au nanofilm.This ZnO NRs/Au substrate showed prominent advantages of facile mass fabrication,versatility for various fluorophores,and reusability,thus providing great promise for economic,sensitive,and high-throughput disease biomarker screening in early diagnosis.In this thesis,we designed and fabricated several ZnO nanoarrays composites including:CuO/ZnO nanoarrays heterojunction,Ag/ZnO nanoarrays heterojunction,Au/ZnO nanoarrays heterojunction and ZnO NRs/Au film substrate.These ZnO-based nanoarrays composites were applied to the field of photoelectrochemistry and fluorescence enhanced biosensing.The main contents and conclusions include the following parts:1.PEC water splitting offers a promising route for producing chemical energy from abundant solar energy,but a bottleneck remains for PEC practical applications because of the lack of efficient,stable and earth-abundant photoelectrodes.Here,we report simultaneous improvements of the carrier separation and light harvesting by constructing P-N heterojunctions in CuO/ZnO nanoarrays composites.The CuO/ZnO nanoarrays heterojunction photoanode exhibited a significant negative shift of 150mV for the onset potential and an approximately 4-fold enhancement in the photocurrent at 1.23 V vs RHE compared with those of pristine ZnO NRs.This work offers a facile strategy for preparing oxide-based P-N heterojunction photoanodes for enhanced PEC water splitting.2.Developing green,environment-friendly and convenient strategy for constructing the noble metal and semiconductor heterostructure is essential to solve the problems of aggregation of noble metal catalysts and to improve the catalytic properties of semiconductor.Ag/ZnO and Au/ZnO heterostructure nanoarrays composites were successfully prepared by using a photoreduction method in this section.The formation of noble metal/ZnO nanoarrays composites were confirmed by XRD and SEM and EDS.The application of these two nanoarrays composites was preliminarily explored.Ag nanoparticles in the Ag/ZnO heterostructures extended the light absorption range of ZnO from the ultraviolet region to the entire visible region,which has the potential to develop the new kind of spectrum-enhanced and photocatalytic nanomaterials.Au/ZnO heterojunction nanoarrays composites were used for PEC water splitting and the formation of heterojunction,the photocurrent intensity is increased from 0.58 mA cm^-2 to 0.73 mA cm^-2 comparing with ZnO NRs and the on-set potential is reduced by approximate 40 mV.These heterojunction nanoarrays composites are expected to be applied in the fields of spectral enhancement,photoelectrochemistry and PEC biosensing.3.Microarrays require high sensitivity and a broad dynamic range for high-throughput diagnostics and proteomic analysis.We present the fabrication of a kind of novel plasmonic protein microarrays using nanostructured ZnO nanorod arrays?ZnO NRs?on 50 nm Au film that exhibits an enhancement of fluorescence up to 200-fold.The as-prepared plasmonic protein microarrays were used for the detection of the carcinoembryonic antigen?Carcinoembryonic Antigen,CEA?cancer biomarker.The plasmonic enhancement resulted in a detection limit of 27 pg ml^-1 in0.01 M PBS?Phosphate Buffered Saline?and a dynamic range of 100 pg mL^-1 to 100mg mL^-1.The ZnO NRs/Au substrates can be mass-manufactured,which is highly promising for the development of low cost,sensitive,and high-throughput protein assay platform for applications in clinical diagnosis.4.The low sensitivity of protein microarrays has limited the wide application in disagnostics and highthroughput proteomic analysis.We present,for the first time,the exploration of protein microarray analysis on nanostructured plasmonic gold nanograting based grating coupled surface plasmon resonance?GC-SPR?that showed a 10-fold fluorescence enhancement.The as-fabricated plasmonic protein microarray showed a limit of detection?LOD?of 0.36 ng ml^-1 with the dynamic detection range of 1 ng mL^-1 to 100mg mL^-1 for detecting the cancer biomarker of CEA.The LOD determined in this study is one order lower than that of the commercial planar glass substrates,which is attributed to the surface plasmon field enhanced fluorescence?SPFS?from the plasmonic coupling.The highly sensitive and wide dynamic detection range of plasmonic microarrays presents new opportunities in proteomic applications and diagnostics research.