Fabrication Of Two-dimensional Tungsten Oxide Arrays For Surface-enhanced Raman Scattering Application

Surface-enhanced Raman scattering(SERS)technique has been widely used in the field of single molecule detection and biosensor for its highly sensitive and unharmful to tested samples,playing an important role in modern detecting techniques.At preset,active substrates with excellent SERS are mainly limited to noble metal materials(such as silver,gold),which have been progressively introduced into commercial applications like biomolecule detections.However,SERS technique is badly restricted by the high cost of these substrates.Since silver is oxidizable and it is costly to apply gold into mass production,using metal oxides as active SERS substrates has attracted much attention of scientific researchers.Recently,among various metal oxide materials,tungsten oxide was verified as the most SERS-active materials,whose SERS enhancement factor can be compared with noble metal.Tungsten oxide owns unique crystal structure and can hold the existence of abundant oxygen vacancies,tuning which can affect the photoelectric properties of tungsten oxide,thus realizing SERS-activity promotion by optimizing oxygen vacancies.In this thesis,we use aluminum nanobowl arrays as substrate which is produced by removing the top anodic aluminum oxide layer and produce ordered two-dimensional tungsten oxide nano thin films by magnetron sputtering.After carrying hydrogen annealing under suitable conditions,we obtain the highly SERS-active substrate without ’hot spots’ that are comparable to noble metal substrates.Along with further study on tungsten oxide materials as SERS active substrate it is expected to realize the industrialization of transition metal semiconductors as SERS substrates,upgrading the Raman detecting techniques.The main results in this thesis are as follows:1.We have fabricated ordered two-dimensional tungsten oxide nanomembranes with hexagonal honeycomb structures,which expand the diversity of structures of tungsten oxide thin films.In the meantime,the specific surface area of tungsten oxide thin film materials is increased as well,benefiting further study on optoelectronic properties of tungsten oxide.2.We have realized the control of oxygen vacancies of ordered two-dimensional tungsten oxide nanomembrane,and obtained SERS-active substrates which are highly sentitive..At the same time,the SERS effects of the tungsten oxide nano film materials on R6G molecules are analyzed theoretically,and the SERS mechanisms of the semiconducting materials are discussed.3.The surface modification of ordered two-dimensional tungsten oxide nanomembrane is carried out under hydrogen plasma treated.By comparing with the heat treating experiments,we have studied the impacts of the hydrogen plasma modification on SERS sensitivity of ordered two-dimensional tungsten oxide nanomembranes.The results show that the hydrogen plasma modification goes against to the generation of oxygen vacancies during the hydrogen annealing process in the ordered tungsten oxide nanomembrane and suppresses its SERS effect.