Preparation,Characterization And Photocatalytic Properties Of TiO₂ Based Thin Films

Os and N co-doped TiO₂ films with various atomic percentages of Os（0 0.30 at.%）were deposited at 600 o C by reactive DC magnetron co-sputtering of Ti-Os metallic target,and their structural,optical and photocatalytic properties were investigated.GO/TiO₂ films（GO doping content: 0 32.5 mg）were prepared by sol-gel spin-coating method.Subsequently,based on optimal GO dopants,Ag-loaded GO/TiO₂ films were synthesizes by sputter-deposited Ag nano-particle films with Ag deposition time from 0 to 90 s on GO/TiO₂ films as substrates.The characterization of the films is carried out using X-ray diffraction（XRD）,Field emission scanning electron microscope（FESEM）,atomic force microscope（AFM）,X-ray photoelectron spectroscopy（XPS）,ultraviolet-visible spectroscopy and photoluminescence（PL）measurements.The photocatalytic performance of the films is evaluated by the amount of decomposition of methylene blue as a function of UV irradiation time.The results are as follows:I Os/N-TiO₂ thin films exhibited a mixed structure of anatase and rutile phases in varying degrees.Combined with SEM observation and XRD structural analysis,it can be concluded that Os doping favors the particle agglomeration,simultaneous crystalline growth of TiO₂,and ART,which is probably attributed to the degree of Os doping.The surface roughness is increased with the increase of Os content.The indirect band gap energies for Os/N-TiO₂ films with Os content of 0,0.17,0.24,0.3 at.% are 3.42 ± 0.02,3.33 ± 0.02,3.24 ±0.02,and 3.22 ± 0.02 e V,respectively.Furthermore,PL investigation further exhibits the effects of Os doping on the electronic structures and defects in N-TiO₂.The indirect transition is observed in both N-TiO₂ and 0.3 at.%Os/N-TiO₂ films.Moreover,the clear visible light response observed in PL spectra implies the deposition of defective N-TiO₂ films with oxygen vacancies.The photocatalytic reaction rate of 0at.%、0.17 at.%、0.24 at.%、0.30 at.% Os/N-TiO₂ films are 0.02min-1、0.0046min-1、0.0034min-1、0.0072min-1 respectively.The photocatalytic activity of N-TiO₂ films are better than Os/N-TiO₂ films.Therefore,it is believed that these effects are directly related to the reduction in photocatalytic activity as measured UV illumination,possible via the introduction of Os metal impurity,which may as nucleation sites for the anatase-to-rutile transformation.II GO/TiO₂ thin films prepared by sol-gel spin coating and annealed at 500°C possesses single anatase phase and smooth interface with the average surface roughness from0.56 to 1.1nm.Raman spectroscopy and XPS analysis further confirm the successfully synthesized GO/TiO₂ films using the sol-gel spin coating method.With the increase of GO content,the optical band gap value of the films is gradually reduced and changes from 3.40 to2.84 e V.The photocatalytic reaction rate of GO/TiO₂ films with GO doping amounts of 0mg,5.2mg,9.1mg,13 mg,and 32.5mg were 0.024min-1,0.036min-1,0.033min-1,0.027min-1,and 0.006 min-1 respectively,indicating optimal GO dopants ranging from 5.2 to 9.1 mg with their photo-degradation performance better than that of pure TiO₂ films.As for Ag loaded GO/TiO₂ thin films（GO content is 5.2 mg）,the photocatalytic performance of the films in a decreasing order is Ag（25s）-GO/TiO₂、Ag（8s）-GO/TiO₂、Ag（40s）-GO/TiO₂、GO/TiO₂、Ag（90s）-GO/TiO₂、Ag-GO/TiO₂,indicating Ag-GO/TiO₂ films（Ag particle deposition time is8 40s）are better than GO/TiO₂ film in the photocatalytic activity.