Fabrication And Modification Of Ordered Free-standing Titanium Dioxide Nanomaterials For Photoelectrochemical Sensors

Photoelectrochemical(PEC)sensor,as a newly emerged analytical device that combines electrochemistry with photochemistry,has been developed rapidly in recent years.The performance of PEC sensor depends on the photoelectrically active materials.TiO₂ nanomaterials have been extensively explored to fabricate various PEC sensors for the merits such as good PEC response,high stability and good biocompatibility.However,low inherent conductance,narrow spectral response range and low PEC efficiency of TiO₂ nanomaterials severely limit the performance and applications of PEC sensors.In this paper,PEC sensors were fabricated with ordered self-supporting TiO₂ nanotube arrays(TiO₂ NTAs)modified by carbon quantum dots(CQDs)and graphitic carbon nitride(g-C₃N₄)to improve the conductance and PEC response.The main works are summarized as follows:(1)Ordered self-supporting TiO₂ NTAs were prepared by electrochemical anodization.The average inner diameter of a single nanotube was about 80 nm,the wall thickness was about 50 nm,and the length was about 7?8?m.The CQDs was prepared by electrochemical method,and the particle size of CQDs was about 3?9 nm.Finally,the TiO₂ NTAs/CQDs composite material was successfully obtained by the hydrothermal method.The photocurrent density of TiO₂ NTAs/CQDs is 11.52 times higher than that of TiO₂ NTAs under visible light.Therefore,a PEC sensor was constructed to detect 5-hydroxytryptamine(5-HT).The calibration plot shows a nice linear relationship between the photocurrent density and the log C_5-HT in the range from 0.02 mM to 1 mM with a detection limit of 0.0212 mM(S/N=3),and the detection limit is 0.9508 mM in the range of 1 mM to 7 mM.Besides,the new PEC sensor exhibits excellent performance and displays advantages such as interference and stability.(2)A new of PEC sensor was constructed by TiO₂ NTAs@C/g-C₃N₄ composite material to detect the content of H₂S.Specifically,ordered self-supporting TiO₂ NTAs are prepared by electrochemical anodization,g-C₃N₄ nanosheets are prepared by thermal etching,and then g-C₃N₄ and C are directly decorated on the TiO₂ NTAs by nitrogen annealing.Finally,TiO₂ NTAs@C/g-C₃N₄ composite material was obtained.This material not only has excellent electrochemical activity,but also excellent PEC performance.The detection range of this PEC sensor is 2?M?800?M,the sensitivity is 236.36?A·mM^-1·cm^-2,and the detection limit is 1.97?M(S/N=3).The results show that TiO₂NTAs@C/g-C₃N₄ has good performance,which provides a new idea for PEC analysis.