Visible-light photoelectrochemical sensor for glutathione based on CoFe2O4-nanosphere-sensitized copper tetraaminophthalocyanine–graphene oxide

A "signal-on" photoelectrochemical sensor based on hierarchical titanium dioxide nanowires/microflowers decorated graphite-like carbon nitride quantum dots for glutathione detection

Glutathione (GSH) is a bioactive tripeptide with important physiological functions in animals, plants, and microorganisms. GSH participates in various biochemical reactions in vivo and is known for its antioxidant, anti-allergy, and detoxification properties. This study introduces an innovative photoelectrochemical (PEC) method for GSH detection, leveraging a fluorine-doped tin oxide (FTO) electrode enhanced by TiO2 nanoflowers and graphitic carbon nitride quantum dots (g-CNQDs). This design formed a type-II heterojunction, which facilitated efficient charge separation and transport. Furthermore, incorporating TiO2 nanoflowers increases the surface area, while adding g-CNQDs led to a narrowing of the semiconductor bandgap. The fabricated electrode exhibits highly attractive photo-electrocatalytic activity towards GSH detection in neutral media at a low potential bias. The developed PEC sensor demonstrates a wide linear range of 1.0 × 10-13 to 5 × 10-5 mol L-1, a low detection limit of 5.0 fmol L-1, and high sensitivity. These remarkable analytical characteristics highlight the potential of this PEC platform for sensitive and selective GSH detection in various biomedical and environmental applications.

An ultra-efficient pretreatment method adopted LPUV/CoFe2O4/PMS-based photolysis for accurate detection of Cd(II) and Pb(II) in water via SWASV

Dissolved organic matter (DOM) is a widely occurring substance in rivers that can strongly complex with heavy metal ions (HMIs), severely interfering with the electrochemical signal of anodic stripping voltammetry (ASV) and reducing the detection accuracy of HMIs in water. In this study, we investigated a novel advanced oxidation process (AOP) that involves the activation of peroxymonosulfate (PMS) using low-pressure ultraviolet (LPUV) radiation and CoFe2O4 photocatalysis. This novel AOP was used for the first time as an effective pretreatment method to break or weaken the complexation between HMIs and DOM, thereby restoring the electrochemical signals of HMIs. The key parameters, including the PMS concentration, CoFe2O4 concentration, and photolysis time, were optimized to be 6 mg/L, 12 mg/L, and 30 s for eliminating DOM interference during the electrochemical analysis of HMIs via LPUV/CoFe2O4-based photolysis. Investigations of the microstructure, surface morphology, specific surface area, and pore volume of CoFe2O4 were conducted to reveal the exceptional signal recovery capability of LPUV/CoFe2O4/PMS-based photolysis in mitigating interference from DOM during HMIs analysis. The PMS activation mechanism, which is critical to the signal recovery process, was elucidated by analyzing the reactive oxygen species (ROS) and the surface elemental composition of CoFe2O4. Additionally, the degradation and transformation behavior of humus-HMIs complexes were analyzed to study the mechanism of ASV signal recovery further. Notably, the detection results of HMIs in actual water samples obtained using the proposed pretreatment method were compared with those obtained from ICP-MS, yielding an RMSE less than 0.04 μg/L, which indicated the satisfactory performance of the proposed pretreatment method for the ASV detection of HMIs in complex actual samples.

Photoelectrochemical sensing of glutathione using bismuth vanadate (BiVO4) decorated with polyaniline (PANI) and cadmium sulfide (CdS)

A ternary nanocomposite photoelectrode composed of cadmium sulfide (CdS), polyaniline (PANI), and bismuth vanadate (BiVO₄) was successfully designed by combining cyclic voltammetry (CV) with electrochemical deposition and high-temperature calcination. The first synthesized CdS/PANI/BiVO₄ composite was used as a photoelectrochemical (PEC) monitoring platform for glutathione (GSH). The ternary CdS/PANI/BiVO₄ nanocomposites exhibited higher PEC activity, which was attributed to the accelerated electron transfer by the loading of CdS and PANI, which enables the material surface to better adsorb the electrons separated by GSH, thereby oxidizing it into GSSH. The photoanodes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy, and photoelectrochemical experiments. Under the optimal experimental conditions, the BiVO₄ electrode modified with CdS and PANI exhibited a linear response in the concentration range of 0.1-20 μM with a sensitivity of 0.669 μA mM^-1 cm^-2 and a detection limit of 40 nM. Moreover, the PEC sensor exhibits good reproducibility and long-term stability. In summary, the designed materials have excellent electrochemical properties, which make them ideal candidates for PEC detection of GSH.

Sensitive photoelectrochemical detection of colitoxin DNA based on NCDs@CuO/ZnO heterostructured nanocomposites with efficient separation capacity of photo-induced carriers

A metal-organic framework (MOF) of Cu-TPA (terephthalic acid) microsphere was prepared, followed by calcinating the MOF precursor of Cu-TPA/ZIF-8 mixture to obtain the CuO/ZnO. N-doped carbon dots (NCDs) were employed to combine the CuO/ZnO composite to form a tripartite heterostructured architecture of NCDs@CuO/ZnO, which led to a fierce enlargement of the photocurrent response. This  was ascribed to the thinner-shell structure of the CuO microsphere and the fact that hollow ZnO particles could sharply promote the incidence intensity of visible light. The more porous defectiveness exposed on CuO/ZnO surface was in favor of rapidly infiltrating electrolyte ions. The p-n type CuO/ZnO composite with more contact interface could abridge the transfer distance of photo-induced electron (e^-1)/hole (h⁺) pairs and repress their recombination availably. NCDs not only could boost electron transfer rate on the electrode interface but also successfully sensitized the CuO/ZnO composite, which resulted in high conversion efficiency of photon-to-electron. The probe DNA (S1) was firmly assembled on the modified ITO electrode surface (S1/NCDs@CuO/ZnO) through an amidation reaction. Under optimal conditions, the prepared DNA biosensor displayed a wide linear range of 1.0 × 10^-6 ~ 7.5 × 10^-1 nM and a low limit of detection (LOD) of 1.81 × 10^-7 nM for colitoxin DNA (S2) measure, which exhibited a better photoelectrochemistry (PEC) analysis performance than that obtained by differential pulse voltammetry techniques. The relative standard deviation (RSD) of the sensing platform for target DNA detection of 5.0 × 10^-2 nM was 6.3%. This proposed DNA biosensor also showed good selectivity, stability, and reproducibility, demonstrating that the well-designed and synthesized photoactive materials of NCDs@CuO/ZnO are promising candidates for PEC analysis.

Simultaneous detection of enrofloxacin and ciprofloxacin in milk using a bias potentials controlling-based photoelectrochemical aptasensor

It is important to develop highly-active photoelectrochemical (PEC) materials and use novel sensing strategy for constructing high-PEC-performance sensors with multiplex detection abilities, owing to the simultaneous presence of multiple antibiotic residues in food. Herein, a bias-potential-based PEC aptasensor was prepared for the trace detection of dual antibiotic analytes, enrofloxacin (ENR) and ciprofloxacin (CIP), which often coexist in milk samples. Here, two materials were developed with excellent PEC performance: three-dimensional nitrogen-doped graphene-loaded copper indium disulfide (CuInS₂/3DNG) and Bi³⁺-doped black anatase titania nanoparticles decorated with reduced graphene oxide (Bi³⁺/B-TiO₂/rGO). By applying different bias potentials to the two materials near one ITO electrode, the cathodic current generated by CuInS₂/3DNH and the anodic current generated by Bi³⁺/B-TiO₂/rGO could be clearly distinguished without interfering with each other. Then, ENR and CIP aptamers were respectively modified onto the surface of CuInS₂/3DNH and Bi³⁺/B-TiO₂/rGO to construct a PEC aptasensor for the sensitive detection of ENR and CIP. Under optimal conditions, the proposed aptasensor exhibited wide linear ranges of ENR (0.01-10000 ng/mL) and CIP (0.01-1000 ng/mL), and relatively low detection limits of 3.3 pg/mL to ENR and CIP (S/N = 3). The aptasensor was successfully applied to the detection of ENR and CIP in milk samples.

Recent advances in electroanalytical drug detection by porphyrin/phthalocyanine macrocycles: developments and future perspectives

Porphyrins and phthalocyanines used to construct sensors for electroanalytical drug detection.