Label-free and visible-light driven photoelectrochemical sensor with CuCo2O4@CoO Core-shell hybrid rod as photoanode for selective sensing diclofenac

An "on-off-on" photoelectrochemical aptasensor using CoO as a signal label for T-2 toxin detection

T-2 toxin, a mycotoxin commonly found in food, is recognized as one of the most harmful contaminants. Herein, a sensitive photoelectrochemical (PEC) aptasensor based on an "on-off-on" signal response strategy was developed for T-2 detection using WO3/CdIn2S4 as a photoanode. The sensitization of WO3 with CdIn2S4 significantly enhanced the photocurrent, leading to the initial "signal-on" state. As a signal label of probe DNA (pDNA), CoO significantly inhibited the photocurrent response of WO3/CdIn2S4 ("signal-off" state), enhancing the signal recovery space and improving the detection sensitivity. T-2 toxin is preferentially bound to aDNA, releasing the CoO-pDNA complex from the electrode, realizing the "signal-on" state again. This signal switching mechanism enabled a broad detection range from 1 fg mL-1 to 1 μg mL-1 with an ultralow detection limit of 0.434 fg mL-1 (S/N = 3), while the sensor exhibited excellent reproducibility, stability and selectivity. This platform not only provided a robust analytical tool for T-2 toxin detection in food safety but also established a generalizable sensing paradigm adaptable to other mycotoxins by replacing the recognition element.

A biofuel cell of (methyl violet/AuNPs)25/FTO photoanode and bilirubin oxidase/CuCo2O4 bio-photocathode inspired by the photoelectrochemistry activities of fluorescent materials/molecules

Herein, we discuss the idea that fluorescent materials/molecules should logically show potential photoelectrochemistry (PEC) activity, and, in particular, the PEC of fluorescent small molecules (previously usually acting only as dye sensitizers for conventional semiconductors) is explored. After examining the PEC activities of some typical inorganic or organic fluorescent materials/molecules and by adopting methyl violet (MV) with the highest PEC activity among the examined fluorescent small molecules, a new and efficient (MV/Au nanoparticles (AuNPs))25/fluorine-doped tin oxide (FTO) photoanode without conventional semiconductor(s) is prepared by layer-by-layer alternating the electrodeposition of AuNPs and the adsorption of MV. A bilirubin oxidase (BOD)/CuCo2O4/FTO bio-photocathode is prepared by electrodeposition, calcination and cast-coating. Under optimal conditions, a new photoelectrochemical enzymatic biofuel cell (PEBFC) consisting of this photoanode in 0.1 M phosphate buffer solution (PBS) containing 0.1 M ascorbic acid, this bio-photocathode in 0.1 M PBS containing 0.5 mM 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and a Nafion membrane gives an open-circuit voltage of 0.73 V and a maximum power output density of 14.1 μW cm-2, outperforming many reported comparable enzymatic biofuel cells. This fluorescence-activity-based PEC research suggests that new PEC and photocatalysis materials/molecules may be found from the huge library of fluorescent substances, and such a fluorescence-based reference criterion is of some general reference value for exploring potential photoelectric materials/molecules and expanding the applications of fluorescent substances.

CuCo2O4 nanoneedle arrays growth on carbon cloth as a non-enzymatic electrochemical sensor with low detection limit ketoprofen recognition

An electrochemical sensor for detecting ketoprofen was constructed by in-situ grown copper cobaltate (CuCo2O4) nanoneedle arrays on a carbon cloth (CC) substrate. The resulting porous nanoneedle arrays not only expose numerous electrochemically active sites but also significantly enhance the electrochemical apparent active area and current transmission efficiency. By leveraging its electrochemical properties, the sensor achieves an impressive detection limit for ketoprofen of 0.7 pM, with a linear range spanning from 2 pM ~ 2 µM. Furthermore, the sensor exhibits remarkable reproducibility, anti-interference capabilities, and stability. Notably, the developed sensor also performed ketoprofen detection on real samples (including drug formulations and wastewater) and demonstrated excellent recognition ability. These exceptional performances can be attributed to the direct growth of CuCo2O4 nanoneedle arrays on the CC substrate, which facilitates a robust electrical connection, provides abundant electrocatalytic active sites, and expands the apparent active area. Consequently, these improvements contribute to the efficient trace detection capabilities of the ketoprofen sensor.

A Visible-Light-Active CuS/MoS2/Bi2WO6 Aptamer Sensitively Detects the Non-Steroidal Anti-Inflammatory Drug Diclofenac

Diclofenac is a non-steroidal, anti-inflammatory drug and is clinically used for the treatment of osteoarthritis, non-articular rheumatism, etc. This research aimed to demonstrate the creation of an upgraded photoelectrochemical (PEC) aptamer sensor for detecting diclofenac (DCF) with high sensitivity. In this work, photoactive materials and bio-identification components served as visible-light-active CuS/MoS₂/Bi₂WO₆ heterostructures and aptamers, respectively. CuS and MoS₂/Bi₂WO₆ were combined to improve photocurrent responsiveness, which helped the structure of PEC aptasensors. Additionally, the one-pot synthesis of CuS/MoS₂/Bi₂WO₆ was ecologically beneficial. With these optimizations, the photocurrent response of aptamer/CS/CuS/MoS₂/Bi₂WO₆ exhibited linearity between 0.1 and 500 nM DCF. The detection limit was 0.03 nM (S/N = 3). These results suggest that the PEC sensing technique might produce an ultra-sensitive sensor with high selectivity and stability for DCF detection.