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Signal amplification strategies are of great interest in photoelectrochemical (PEC) sensing research. Herein, we explored a novel approach whereby hole transfer was accelerated from the photosensitive material Blue-TiO 2 (B-TiO 2) to the hole mediator N-hydroxyphthalimide (NHPI). Simultaneously, the introduction of the organic molecule NHPI can promote the efficiency of visible light absorption and expand the absorption range of B-TiO 2. Under visible light irradiation, the photocurrent value of NHPI/B-TiO 2 is 2.7-fold larger than that of B-TiO 2 , which can be ascribed to the acceleration of hole transfer by NHPI. More specifically, NHPI acts as a hole mediator, which effectively transfers photo-generated holes from the valence band (VB) of B-TiO 2 to NHPI. NHPI can be oxidized to phthalimide-N-oxyl radical (PINO*), thereby causing inhibition of photo-generated carrier recombination and enhancement of the photocurrent. Furthermore, a PEC aptasensor for the sensitive detection of diazinon (DIA) was constructed by combining specific aptamers on an NHPI/B-TiO 2 nanocomposite surface. The oxidation product of NHPI, PINO*, oxidizes the DIA captured by the aptamer. Under optimized experimental conditions, the linear range for DIA detection was 0.1–1000 nM, and the detection limit of the NHPI/B-TiO 2 nanocomposite aptamer sensing was 0.03 nM (S/N = 3). Therefore, this proposed method involving the hole mediator can be used as a new strategy to improve the performance of PEC. [Display omitted] • A new strategy for enhancing photoelectrochemical (PEC) signals was developed. • Hole mediator can accelerate photo-generated holes transfer. • Hole mediator can be oxidized by photo-generated holes and promote redox reaction. • Organic molecule have the advantage of high visible light absorption efficiency. • The PEC aptasensor exhibited excellent selectivity and sensitivity for Diazinon. [ABSTRACT FROM AUTHOR]

Residues caused by the abuse of antibiotics will lead to the resistance of bacteria and harm human health through the food chain. Photoelectrochemical (PEC) aptamer sensing technology has been broadly applied in analysis and detection because of its merits of low cost, fast response, high sensitivity, high affinity, and high specificity. Highly active photosensitive materials are suitable for constructing sensitive 'signal-off' type PEC aptasensor. Nitrogen-doped graphene nanosheet-loaded ZnIn 2 S 4 (ZIS/NG) functional material was prepared by a simple one-step solvothermal method. The introduction of NG inhibits the over-assemble of ZIS, forming ZIS/NG 2D/2D Van Der Waals (VDW) heterojunctions. NG cannot only broaden the visible absorption range but accept electrons from ZIS, thus promoting charge separation efficiency. In addition, the as-synthesized ZIS/NG 2D/2D VDW heterojunctions have a good synergy between the two layers, inhibiting electron-hole recombination, improving interfacial charge transfer, and increasing active sites. Hence, the photocurrent of ZIS/NG was significantly higher than that of ZIS. Based on high photocurrent of ZIS/NG, a "signal-off" mode PEC aptasensor was constructed to detect oxytetracycline (OTC), which expressed high sensitivity and selectivity. It can achieve rapid reaction within the linear scope of 1 pmol/L to 5 μmol/L and exhibit relatively low detection limit (0.33 pmol/L). The constructed aptasensor has been applied to detect OTC in chicken with a good recovery. • A novel 2D/2D Heterojunction of ZnIn 2 S 4 /NG was constructed. • The high performance of the composite was suitable for 'signal-off' sensor. • The introduction of NG inhibites the over-aggregation of ZnIn 2 S 4. • A high-performance PEC oxytetracycline aptasensor was successfully established. • The PEC aptasensor exhibited good selectivity and sensitivity. [ABSTRACT FROM AUTHOR]

Exploring efficient methods for microcystin-LR (MC-LR) detection is of great significance for protecting ecological environment safety and human health. Herein, an MC-LR aptasensor was fabricated based on the synergistic amplified cathodic electrochemiluminescence (ECL) of the functional nanocomposite of ZnO quantum dots decorated B, N co-doped graphene (BNG/ZnO). With K 2 S 2 O 8 as co-reactant, a robust cathodic ECL emission of BNG/ZnO was observed based on the synergistic catalytic effect of B, N in graphene. Interestingly, the ECL intensity of BNG/ZnO nanocomposite was 1.8, 2.9, and 5.4 times enhanced than N-doped graphene/ZnO, B-doped graphene/ZnO, and graphene/ZnO, which was because of the difference in the electronegativity of B, C, and N could generate a unique synergistic effect to make graphene-based materials realizing signal amplification. Subsequently, a novel cathodic ECL aptasensor was constructed for sensitive and selective detection of MC-LR with aptamer as the recognition element and BNG/ZnO as the luminous reagent. Under optimized conditions, the linear range of the prepared cathodic ECL aptasensor for MC-LR detection was 0.1–5000 pM, the detection limit was 0.03 pM (S/N = 3). At the same time, the proposed aptasensor had good selectivity and stability and showed satisfactory results in actual water sample analysis. • A novel cathodic ECL aptasensor for MC-LR detection was fabricated based on BNG/ZnO. • The ECL intensity of BNG/ZnO was enhanced than that of BG/ZnO, NG/ZnO, and ZnO QDs. • Synergistic catalysis of B, N in graphene resulted in the amplification ECL of ZnO. • The proposed ECL aptasensor has low detection limit, good selectivity and stability. • Satisfactory results were obtained in the analysis of actual water sample. [ABSTRACT FROM AUTHOR]

• Br doped PEDOT modified carbon paper electrode is constructed through situ thermal polymerization. • The photocurrent of Br doped PEDOT was enhanced due to the doping of Br. • Br doped PEDOT was adopted as photoactive material the first time and was applied in PEC. • The as-prepared electrode can be volume production with good reproducibility. • The constructed Hg2+ PEC sensor exhibited speedy response, outstanding stability, excellent selectivity, wide linear range. Mercury (Hg) is a kind of the most common heavy metals with high toxicity in nature, existing in water, soil, and even food. Hence, it is of great importance to develop a simple, effective way to detect Hg2+. Flexible sensing has attracted extensive attention in recent years, which can be flexibly applied in various detection environments. Poly(3,4-ethylenedioxythiophene) (PEDOT) with conjugation structure which can accelerate the transfer of electrons and inhibit the recombination of carriers is favorable to the photoelectrochemical (PEC) process. Here, Br doped PEDOT modified carbon paper with narrower bandgap was firstly fabricated through situ thermal polymerization which exhibited high photocurrent intensity under visible-light irradiation. The success synthesis of PEDOT was confirmed by SEM, XPS, FT-IR and Raman spectrum. Meanwhile, the as-prepared electrode can be mass produced with good reproducibility. Based on excellent performance of as-prepared electrode of Br doped PEDOT/carbon paper, we constructed a PEC sensing platform for Hg2+ detection with the detection limit of 0.3 nM and linear range from 1 nM to 450 nM. In addition, the PEC sensor exhibited speedy response, outstanding stability, excellent selectivity, wide linear range, and was used for determination of Hg2+ in river water samples with recover range of 97.7–104.5 % and RSD of 2.8–4.7 %. [ABSTRACT FROM AUTHOR]

Ciprofloxacin (CIP) in milk has a harmful effect on human health, it's important to conduct ultra-sensitive selective detection of ciprofloxacin. Herein, an ultrasensitive and selective organic photoelectrochemical transistor (OPECT) CIP aptasensor was constructed using Ti 3 C 2 /TiO 2 composites as gate photoactive materials. Compared with Ti 3 C 2 , TiO 2 , and Ti 3 C 2 /TiO 2 mixed by physical, Ti 3 C 2 /TiO 2 composites exhibits larger capacitance and the OPECT intensity is 3 times of Ti 3 C 2 , 2 times of Ti 3 C 2 /TiO 2 mixed by physical and TiO 2 , which attributed to higher capacitance of Ti 3 C 2 /TiO 2 composites provides high electrostatic charge storage capacity and leads to effective gating, induces more electronic charge in the channel and larger drain currents. Exemplified by CIP as target, the developed sensor achieves sensitive detection with linear range from 3 ng/L to 3 mg/L, detection limit is 1 ng/L. This work completed the detection in real samples, which lays a foundation for the construction of OPECT food safety analysis and detection platform. • TiO 2 /Ti 3 C 2 composites was prepared by one-pot solvent hydrothermal method. • Higher capacitance of TiO 2 /Ti 3 C 2 composites greatly improves the sensitivity of OPECT aptasensor. • A sensitive and stable OPECT aptasensor for CIP detection was fabricated. • This OPECT aptasensor presented excellent performance than traditional PEC aptasensor. [ABSTRACT FROM AUTHOR]

The residual of atrazine (ATZ) can disrupt the production of testosterone in animals, causing chemical castration in animals. Therefore, the monitoring of ATZ residue is essential for human health and ecological balance. Herein, a novel dual-signal amplification photofuel cells (PFC) aptasensor was proposed. The presence of a hole mediator and hollow structure enhances the efficiency of electron-hole pair separation and visible light absorption in the photoanode. Additionally, the effect of dye sensitization plays a crucial role in improving the conversion efficiency of photon-to-electrons in the photocathode. The as-prepared aptasensor realized sensitive detection of ATZ, with a board linear range from 1.0 × 10−13 ∼ 1.0 × 10−6 mol L−1 and a low detection limit of 3.3 × 10−14 mol L−1. The reliability of the as-prepared PFC aptasensor was verified by gas chromatography-mass spectrometry (GC-MS). Therefore, the manufactured PFC aptasensor is a prospective detection method for fruit and vegetables safety analysis. [Display omitted] • A novel dual-signal amplification photofuel cells aptasensor was established. • Hole mediator was used as a novel strategy to improve the P max of PFC system. • The hollow structure contributes to enhancing the output performance of CdS. • NiPc sensitized Cu 7 S 4 was developed as a novel photocathode material. • A high initial P max with a signal-off response aptasensor for ATZ detection. [ABSTRACT FROM AUTHOR]

Synopsis: Successful preparation of VOPc/CN photoactive materials and construction of PEC aptasensor for DCF detection. • Facile method with easy fabrication enabled the visible/NIR light response PEC sensor for rapid DCF detection. • VOPc/CN nanocomposites was first used as photoactive materials. • VOPc/CN based on VOPc sensitizing CN extend spectral range to visible/ NIR light region. • VOPc/CN photoactive materials demonstrated improved photoelectric conversion efficiency. • This biosensor showed a good sensitivity and a wide linear range. A novel photoelectrochemical (PEC) aptasensor for diclofenac detection, based on visible/near-infrared (vis/NIR) light-responsive vanadyl-phthalocyanine/graphitic carbon nitrid nanosheet (VOPc/CN) nanocomposites, was successfully fabricated. In this work, the first coupling of CN and VOPc with a facile solution–phase method was prepared and applied to PEC sensing. The UV–vis diff ;use reflection spectra (DRS) indicated that VOPc is an excellent photosensitizer when applied to the surface of CN. It promoted CN light absorption to the visible-NIR region, which greatly enhanced the light excitation capability. The PEC signal of the VOPc/CN nanocomposites improved 2.7 and 12.42-fold compared with pure VOPc and CN, respectively, indicating that VOPc/CN nanocomposites have good photoelectric activity and enhanced photo-to-current conversion efficiency. As a result, VOPc sensitized CN was introduced as a covalent immobilizing PEC aptasensor for the sensitive and selective determination of diclofenac (DCF). Under optimal conditions, the fabricated PEC biosensor exhibited good PEC performances with high sensitivity, a low detection limit of 0.03 nM (S/N = 3) and a wide linear response, in the range of 0.1-500 nM. This was due to the specific interaction between DCF and the aptamer. It is concluded that VOPc/CN nanocomposites are potentially promising photoactive materials for applications in PEC biosensors, as well as for photocatalysis and other related fields. [ABSTRACT FROM AUTHOR]