Preparation And Application Of G-C3N4/TiNTs In Photocatalytisis And Photoelectrochemical Biosensor Under Visible-Light Irradiation

As a kind of widely used n-type semiconductor nanomaterials with a wide band gap(E.=3.2 eV),anatase titanium dioxide nanotubes(TiNTs)can only absorb the UV-light(?<387 nm)which accounts for less than 5%of solar light.This greatly limits the use of solar light.In the this study,the small bandgap semiconductor g-C3N4(2.69 eV)is modified on TiNTs.As a result,the response of TiO2 is extended to the visible-light region.We study the photocatalytic activity and photoelectrochemical(PEC)applications of g-C3N4/TiNTs under visible light.In the first chapter,the structure and properties of TiO2 were described briefly.And then the affecting factors,mechanism and applications of TiO2 photocatalytic activity in the degradation of organic materials were introduced.In addition,the principles,classifications and applications of PEC sensing were also described in this chapter in detail.In the end,we summaried the significance of this study briefly.In the second chapter,melamine was used as the precursor to decorate g-C3N4 on TiO2 nanotube which prepared by anodic oxidation decoration by using a one-step chemical vapor deposition technique.We explored two applications of the g-C3N4/TiNTs composite nanomaterials.1)The photocatalytic activities of g-C3N4/TiNTs prepared by different amount of melamine were studied by photocatalytic degradation of A07.We optomized the melamine amount to achieve the best photocatalytical activity under visible light.2)Employing g-C3N4/TiNTs as working electrode,a sensitive PEC sensor for H2O2 detection is established.In the third chapter,Au nanoparticles were modified on g-C3N4/TiNTs to form ternary Au/g-C3N4/TiNTs nanocomposite.This nanotubular composite was studied in the following two aspects.1)The photocatalytic activity of Au/g-C3N4/TiNTs was studied and compared with g-C3N4/TiNTs under visible light.The results showed that as electronic-hole pairs recombination center,the introduce of Au NPs greatly reduced the efficiency of electron-hole separation,and resulted in a highly decreased photocatalytical activity.2)A highly sensitive PEC immunosensor was developed based on Au/g-C3N4/TiNTs electrode.Owing to the synergistic effect of steric effect produced by biotin-avidin system and meanwhile the light absorption effect generated by carbon nanosphere,the PEC sensing system exhibited significantly enhanced sensitivity for the target analyte.The detection linear range of rabbit antigen(RIgG)was 1.0×10-17?5.0×10-7 g mL-1 with the detection limit of 5.5×10-18 g mL-1(S/N=3).