Ultrasensitive photoelectrochemical aptasensor for diclofenac sodium based on surface-modified TiO2-FeVO4 composite.

Liwei Yang, Lele Li, Fen Li, Hejie Zheng, Tongtong Li, Xiaoqiang Liu, Jichun Zhu, Yanmei Zhou, Subbiah Alwarappan

Analytical and bioanalytical chemistry 2021 Jan

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Herein, a photoelectrochemical (PEC) aptasensing platform was designed by integrating surface oxygen vacancy (OV) defects, Ti3+ self-doping, the heterojunction, and resonance energy transfer (RET) effect into one platform for the detection of diclofenac sodium (DCF). Briefly, OV defects were introduced on TiO2 nanospheres with simultaneous Ti3+ self-doping, followed by a well-separated deposition of FeVO4 nanoparticles on TiO2 to obtain a Ti3+-O-TiO2/FeVO4 heterojunction. The surface modification of OVs, Ti3+ doping, and deposition of FeVO4 were confirmed by SEM, XPS, EPR, DRS, and PEC measurements. The surface OVs and doping of Ti3+ species created a new donor (defect) energy level under the conduction band of TiO2, which minimized the bandgap and thereby improved the visible light absorption of TiO2. Moreover, the capture of photo-excited electrons by surface OVs could hinder the electron-hole recombination. Due to the intimate surface contact and perfect energy matching between TiO2 and FeVO4, the formation of heterojunction decreased the bandgap and facilitated the electron-hole separation of TiO2. All these above events contributed to the enhancement of the PEC signals, which were then quenched by the RET effect between Ti3+-O-TiO2/FeVO4 and Au nanoparticle (AuNP)-labeled cDNA that had been attached to its complementary DCF aptamer on Ti3+-O-TiO2/FeVO4|ITO. The addition of target-DCF detached AuNP-labeled cDNA from the electrode to recover the photocurrent, resulting in a "signal-on" PEC aptasensor that exhibited a 0.1-500-nM linear range and a detection limit of 0.069 nM for DCF, attributed to the excellent amplification of the proposed aptasensing platform.

Citation

Liwei Yang, Lele Li, Fen Li, Hejie Zheng, Tongtong Li, Xiaoqiang Liu, Jichun Zhu, Yanmei Zhou, Subbiah Alwarappan. Ultrasensitive photoelectrochemical aptasensor for diclofenac sodium based on surface-modified TiO2-FeVO4 composite. Analytical and bioanalytical chemistry. 2021 Jan;413(1):193-203