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. 2020 Oct 11;10(10):2002.
doi: 10.3390/nano10102002.

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O-AgBiO3 towards Enhanced Selective Photoelectrochemical Detection

Yajun Pang  1   2 , Hao Chen  1 , Jin Yang  1 , Bo Wang  2 , Zhenyu Yang  2 , Jun Lv  2 , Zhenghui Pan  3 , Guangqing Xu  2 , Zhehong Shen  1 , Yucheng Wu  2
Affiliations

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O-AgBiO3 towards Enhanced Selective Photoelectrochemical Detection

Yajun Pang et al. Nanomaterials (Basel). .

Abstract

Due to integrated advances in photoelectrochemical (PEC) functionalities for environment detection applications, one-dimensional (1D) TiO2 nanostructures provide a new strategy (PEC sensors) towards organics detection in wastewater. However, the unidealized selectivity to the oxidation of water and organics limits the PEC detection performance. Herein, we designed a ternary photoanode consisting of Ag2O-AgBiO3/TiO2 nanotube arrays (NTAs) to solve this issue by using a facile one-step precipitation reaction. High oxidation capacity for organics is achieved by regulating the surface free radicals properly through the heterostructure formed between the interface of TiO2 and AgBiO3. More importantly, as a trap for electron capture, Ag2O in this ternary system could not only further improve the separation efficiency of charge carriers, but also capture electrons transferred to the TiO2 conduction band, thus reducing the electrons transferred to the external circuit and the corresponding background photocurrent when detecting organics. As a result, the reconstructed TiO2 NTAs decrease their photocurrent response to water and enhance their response to organics, thus presenting lower oxidation activity to water and higher activity to organics, that is, highly selective oxidation characteristics. This work provides more insights into the impact of charge transfer and surface free radicals on developing promising and efficient PEC sensors for organics.

Keywords: AgBiO3; TiO2 nanotube arrays; high selectivity; organics detection; photoelectrochemical sensors; precipitation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic synthesis process and the corresponding morphology characterization of the co-modified titanium dioxide nanotube arrays (TiO2 NTAs). (a) Schematic representation of a two-step process to prepare co-modified TiO2 NTAs. (b) SEM image of pristine TiO2 NTAs. (c) SEM image, (d) TEM image, and (e) high-magnification TEM image of co-modified TiO2 NTAs.
Figure 2
Figure 2
(a) Raman spectrum of the co-modified materials. XPS spectra of co-modified TiO2 NTAs: high resolution patterns of (b) Bi 4f, (c) Ag 3d, and (d) O 1s.
Figure 3
Figure 3
(a) Light absorption spectra, (b,c) transformed Kubelka–Munk function plotted against photon energy curves, and (d) XPS valance band edge of TiO2 and co-modified materials. (e) Schematic view for electron–hole separations and energy band matching of co-modified TiO2 NTAs under UV light irradiation.
Figure 4
Figure 4
(a–c) Photocurrent of TiO2 and the co-modified TiO2 NTAs in PBS with capture agent added separately. (d) Photoluminescence pattern of terephthalic acid irradiated with ultraviolet light.
Figure 5
Figure 5
Photoelectrochemical (PEC) properties’ characterization. (a,b) Photocurrent and current response of TiO2 and the co-modified TiO2 NTAs. Amperometric response of the constructed PEC sensors to the continuous addition of glucose in PBS: (c) current intensity-time curve, (d) current noise obtained from the high-resolution curve of (c), (e) plots of current increments vs. chemical oxygen demand (COD) range, and (f) comparison of detection performances.
See this image and copyright information in PMC

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