Irena Savickaja

This study investigates the photoelectrochemical (PEC) performance of molybdenum-doped bismuth vanadate (Mo-doped BiVO₄) and its heterojunction with the BiOCl layer in glucose and urea sensing. Photoelectrochemical analyses, including cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), revealed that the formation of a heterojunction enhanced charge carrier separation. The impact of the interaction between the surface of the photoanode and analytes on sensing performance was systematically evaluated. Among the tested configurations, Mo-doped BiVO₄ exhibited superior glucose sensing with a limit of detection (LOD) of 0.173 µM, while BiVO₄/BiOCl demonstrated an LOD of 2.474 µM. In the context of urea sensing, Mo-doped BiVO₄ demonstrated an LOD of 0.656 µM, while BiVO₄/BiOCl exhibited an LOD of 0.918 µM. Notably, despite the enhanced PEC activity observed in heterostructured samples, Mo-doped BiVO₄ exhibited superior sensing performance, attributable to good interaction with analytes. The photocurrent response trends—an increase with glucose concentration and a decrease with urea concentration—were attributed to oxidation and adsorption phenomena on the photoanode surface. These findings underscore the critical role of photoanode surface engineering in advancing PEC sensor technology, paving the way for more efficient environmental and biomedical applications.

This study presents the findings of an investigation into the characteristics and capabilities of BiVO₄ and Mo-doped BiVO₄ coatings for the detection of diclofenac (DCF). In this study, a neutral sodium sulfate electrolyte and an alkaline sodium borate buffer were selected, and a range of potentials were employed to ascertain the impact of diverse conditions on the sensing performance of diclofenac. The introduction of Mo-doping had a profound impact on the photoelectrochemical response of the BiVO₄ coating. However, it was observed that Mo-doping resulted in an increase in the adsorption of diclofenac oxidation products on the surface of the photoanode, which in turn led to a negative blocking effect. To evaluate the structural and morphological properties of the coatings, X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and energy dispersive analysis (EDX) were conducted. The photoelectrochemical properties were evaluated through the use of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). An increase in the photocurrent density of BiVO₄ was observed in response to an increase in the concentration of diclofenac within a range of 0.1 to 1 mg L⁻¹ during the sensing experiments. However, at higher concentrations, saturation of diclofenac was observed at the photoelectrode/electrolyte interface. The results of selectivity experiments demonstrated that the nature of the electrolyte has a significant impact on the selectivity of designed photoelectrochemical sensors.

Volatile organic compounds (VOCs) are a notable group of indoor air pollutants released by household products. These substances are commonly employed as solvents in industrial operations, and some of them are recognized or suspected to be cancer-causing or mutagenic agents. Due to their high volatility, VOCs are typically present in surface waters at concentrations below a few micrograms per liter. However, in groundwater, their concentrations can reach levels up to thousands of times higher. This study analyses the applicability of the photoelectrochemical (PEC) sensing of VOCs in aqueous medium. Tungsten oxide and bismuth vanadate photoanodes were tested for PEC sensing of xylene, toluene, and methanol in sodium chloride and sodium sulfate electrolytes. The crystalline structure and morphology of coatings were analyzed using XRD and SEM analyses. Photoelectrochemical properties were evaluated using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The results of the study show that aromatic compounds tend to block the surface of the photoelectrode and interfere with the PEC sensing of other substances. WO₃ photoanode is found to be suitable for the PEC sensing of methanol under the mild conditions in aqueous electrolytes; however, electrode engineering and assay optimization are required to achieve better detection limits.