Preparation And Preliminary Application Of Optoelectronic Functional Materials Based On Plasma Treatment Technology

The photoelectrochemical functional materials have been widely used in energy,environment,medicine and other fields,owing to their high photocatalysis or photoelectrochemical(PEC)activities,cost effectiveness,and high physical and chemical stability.In the present thesis,three kinds of photocatalytic materials of nitrogen-doped Cu₂O@CuO and LaPO₄and protonated g-C₃N₄have been synthesized separately for the photocatalytic decomposition of water toward H₂O₂evolution with high efficiency and the sensitive PEC detection of nitrite in urine.The main contents include:(1)An efficient nitrogen-doped Cu₂O@CuO photocatalyst of heterojunction has been constructed for the photocatalytic production of H₂O₂under visible light irradiation(Chapter 2).Octahedral Cu₂O was first synthesized by the glucose reduction and then treated by the N₂plasma,achieving the simultaneous N doping and Cu₂O oxidation,resulting in the nitrogen-doped Cu₂O@CuO heterojunction.It is found that the photocatalytic activity of the as-prepared N-Cu₂O@CuO composite material can depend on the time of N₂plasma treatment,among which the maximum photocatalytic production of H₂O₂can be achieved at the 10-min plasma treatment.The experimental data demonstrated that the generation of N heteroatoms and CuO can promote the highly efficient separation and transfer ability of photogenerated carriers,thereby improving the photocatalytic performances of the photocatalytic materials.(2)A highly-efficient photocatalyst of nitrogen-doped LaPO₄has been synthesized for the photocatalytic production of H₂O₂(Chapter 3).The calcination method was first used to synthesize the urchin-like LaPO₄.Subsequently,the preparation of two kinds of nitrogen-doped LaPO₄materials of Npla-LaPO₄and Ncal-LaPO₄was conducted separately through the calcination route with urea and LaPO₄and the N₂plasma treatment for LaPO₄.The so yielded photocatalysts were separately applied for the photocatalytic decomposition of water for H₂O₂production.By comparison,the introduction of nitrogen heteroatom can effectively adjust the charge distribution on the surfaces of LaPO₄.Moreover,the comparable results of material characterizations indicate that the N atom in Npla-LaPO₄can belong to the substitution N,while Ncal-LaPO₄can be assigned to the adsorbed N.In particular,tit was experimentally found that the photocatalytic H₂O₂production rate of Npla-LaPO₄could be about 2.2 time higher than that of Ncal-LaPO₄.Besides,studies indicate that the replacing N can present an advantage in adjusting the surface charge of LaPO₄,thereby improving its photocatalytic performances.(3)A PEC analysis technique has been established for the detection of nitrite in urine by using protonated g-C₃N₄(pCN)-modified ITO electrode(Chapter 4).Herein,pCN was first obtained by the calcination of urea and protonation for hydrochloric acid.Moreover,the N-doped ITO electrode was obtained by the N₂plasma treatment for ITO electrode,so that the pCN-N/ITO photoelectrochemical sensing platform was constructed for the highly sensitive and selective analysis of nitrite in urine.It was foung that the N₂plasma treatment time could improve the hydrophilicity of ITO and at the same time,promote the separation of photogenerated carriers of ITO,thus enhancing the conductivity of the ITO electrode.Furthermore,due to the hydrogen bonds can be formed between pCN and NO₂^-to facilitate the improved affinity between the sensing material and the analyte.The experimental results manifest that the maximum photocurrent intensity of the pCN-N/ITO electrode can be obtained for the 30-min N₂plasma treatment for ITO,showing the best photoelectrochemical performances in sensing the targeting NO₂^-.The developed pCN-N/ITO sensor can allow for the selective and sensitive analysis of nitrite in urine in the linear range of 0.0080-1000??,with the detection limit low as 5.0 nM.