Preparation And Optical Properties Of Tungsten Oxide Nanoflowers

The transition metal oxides with nonstoichiometry show a strong local surface plasmon resonance due to a large number of oxygen vacancies,which have been widely studied in the fields of photocatalysis and electrochromism.In this paper,W₁₈O₄₉ nanomaterials with excellent photochemical properties were successfully prepared by solvothermal method,and their morphology,structure and photoelectric properties were systematically studied.A new idea was provided to explore the potential applications of non-metallic surface plasmon materials in fluorescence enhancement,photocatalysis and optoelectronic devices.The main work is as follows:W₁₈O₄₉ nanomaterials were successfully prepared by solvothermal method,which shows good dispersity,uniform size and stratified flower shape,the diameter was about 500nm.The surface of W₁₈O₄₉ nanoflowers has rich oxygen vacancies and large specific surface area and show strong plasma absorption characteristics in the visible and near infrared regions.At the same time,the unique structure of the material and the nonstoichiometric properties make it have good photoelectric properties.The local surface plasmon resonance effect of W₁₈O₄₉ nanomaterials can significantly enhance the upconversion luminescence properties of rare earth nanoparticles.Through the structure of W₁₈O₄₉/NaYF₄:Yb³⁺,Er³⁺/ITO nano thin films,it is found that there is a near infrared plasma energy-upconversion process.It suggests that the local surface plasmon resonance effect of near infrared light excited W₁₈O₄₉ nanoflowers is the main reason for the green light enhancement of the upconversion nanoparticles.In addition,it is proved that under the negative voltage,the W₁₈O₄₉/NaYF₄:Yb³⁺,Er³⁺/ITO composite thin films have the strongest luminescence combining the electrochromic properties of W₁₈O₄₉ nanomaterials by changing the direction of the applied electric field to regulate the local surface plasmon resonance effect.Using the characteristics of the absorption of W₁₈O₄₉ nanoflowers and the recombination of the emitting parts of the NaYF₄:Yb³⁺,Er³⁺upconversion luminescent materials,the NaYF₄:Yb³⁺,Er³⁺@W₁₈O₄₉ with similar core-shell structure was designed and synthesized,and its photocatalytic properties were explored and studied.Under the same conditions,catalyzing ammonia borane solution for hydrogen production of NaYF₄:Yb³⁺,Er³⁺@W₁₈O₄₉was 30 times enhanced than that of pure ammonia borane,indicating that the similar core-shell structure luminescent particles NaYF₄:Yb³⁺,Er³⁺@W₁₈O₄₉ can be used as a scheme for the preparation of high performance photocatalyst.By changing the reaction temperature and the concentration of the precursor solution,the nanoflowers,nanowires,thorn and sea urchin like nanostructures with different morphology W₁₈O₄₉ are synthesized and used as surface enhanced Raman scattering(Surface Enhanced Raman Scattering,SERS)substrates.The excellent SERS properties of high sensitivity and high detection limit are obtained.The limit detection for R6G of thorn-like W₁₈O₄₉nanostructure is as low as 10^-7 mol/L,the enhancement factor can reach 6×10⁴.