CdSe/TiO2NTs Heterojunction-Based Nonenzymatic Photoelectrochemical Sensor for Glucose Detection

Immobilization of CdTe QDs on Glucose-Imprinted Alg-g-P(AA-co-VPBA) Nanocomposite for Optical Sensing of Glucose

Developing a highly sensitive, selective, and biocompatible nanobiosensor for glucose monitoring remains a significant challenge in biomedical diagnostics. In this research, the design and synthesis of a highly sensitive and selective nanobiosensor for glucose detection were reported, utilizing cadmium telluride quantum dots (CdTe QDs) immobilized on a glucose-imprinted sodium alginate-graft-poly(acrylic acid-copolymer-vinylphenylboronic acid) nanocomposite. The preparation method is notable for its safety, cost-effectiveness, and use of biocompatible materials. The nanobiosensor was synthesized by modifying CdTe QDs with a biopolymer chain comprising acrylic acid, sodium alginate, and vinylphenylboronic acid (VPBA), resulting in a glucose-sensitive and selective sensor with an average hydrodynamic diameter of 32 nm. Glucose detection was achieved through fluorescence quenching of CdTe QDs upon binding glucose molecules to VPBA moieties via cis-diol interactions, facilitating glucose sensing. A linear correlation was established between fluorescence intensity and glucose concentration, with a detection limit of 0.164 μg/mL. The sensor exhibited high specificity for glucose over potential interfering species, including various amino acids, fructose, lactic acid, and metal ions, even at concentrations 100 times higher than glucose. In practical applications, the sensor demonstrated high recovery rates ranging from 98.72 to 101.36% in human serum and urine samples, indicating its efficacy and specificity in complex biological matrices. The nanobiosensor also showed excellent repeatability and reproducibility with a relative standard deviation (RSD) of 1.25 and 1.38% for five replicates, respectively, and stability over 28 days with consistent fluorescence response. These results suggest that the glucose-imprinted Alg-g-P(AA-co-VPBA)/CdTe QDs nanobiosensor is a promising candidate for sensitive, selective, and glucose-monitoring applications.

Feasibility Study of Photoelectrochemical Sensing of Glucose and Urea Using BiVO4 and BiVO4/BiOCl Photoanodes

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.

Effect of Chemical Polishing on the Formation of TiO2 Nanotube Arrays Using Ti Mesh as a Raw Material

As a unique form of TiO2, TiO2 nanotube arrays (TiO2NTAs) have been widely used. TiO2NTAs are usually prepared by Ti foil, with little research reporting its preparation by Ti mesh. In this paper, TiO2NTAs are prepared on a Ti mesh surface via an anodic oxidation method in the F-containing electrolyte. The optimal parameters for the synthesis of TiO2NTAs are as follows: the solvent is ethylene glycol and water; the electrolyte is NH4F (0.175 mol/L); the voltage is 20 V; and the anodic oxidation time is 40 min without chemical polishing. However, there is a strange phenomenon where the nanotube arrays grow only at the intersection of Ti wires, which may be caused by chemical polishing, and the other areas, where TiO2NTAs cannot be observed on the surface of Ti mesh, are covered by a dense TiO2 film. New impurities (the hydrate of TiO2 or other products) introduced by chemical polishing and attaching to the surface of the Ti mesh reduce the current of anodic oxidation and further inhibit the growth of TiO2 nanotubes. Hence, under laboratory conditions, for commercially well-preserved Ti mesh, there is no necessity for chemical polishing. The formation of TiO2NTAs includes growth and crystallization processes. For the growth process, F- ions corrode the dense TiO2 film on the surface of Ti mesh to form soluble complexes ([TiF6]2-), and the tiny pores remain on the surface of Ti mesh. Given the basic photoelectrochemical measurements, TiO2NTAs without chemical polishing have better properties.

Wavelength-dependent photoelectrochemical response demonstrated by the determination of acetaminophen and rutin in differential molecularly imprinted polymers strategy

Herein, the excitation wavelength-dependent responses of the molecularly imprinted polymer (MIP) photoelectrochemical (PEC) sensors were investigated, using acetaminophen (AP), rutin (RT) and perfluorooctanoate (PFOA) as the model templates, pyrrole as functional monomer, CuInS2@ZnS/TiO2 NTs as the basic photoelectrode. With wavelength λ > 240 nm, the photocurrent of MIPPFOA enhanced at higher concentrations of PFOA. With increasing AP concentration, the photocurrents of MIPAP could decline with λ < 271 nm, not change at λ = 270 nm, or increase with λ > 270 nm. As RT concentration increased, the photocurrents of MIPRT could decrease (λ < 431 nm), not change (λ = 431 nm) or increase (λ > 431 nm). The PEC responses depend on the comprehensive interaction of two contrary mechanisms from the template molecules within the MIP membrane. The photocurrent is enhanced by the role of the electron donor for photo-generated holes but attenuated due to the steric hindrance effect and the excitation light intensity loss via absorption or scattering. The apparent molar absorption coefficient of AP and RT within MIP membranes are 9.1-19.4 folds of those measured from dilute solutions. By using a routine UV lamp as the light source, the photocurrents of MIPRT at 254 nm and MIPAP at 365 nm were used to determine RT and AP, with the detection limits of 5.3 and 16 nM, respectively. The interference from the non-specific adsorption of interferents on the surfaces of MIPAP and MIPRT was reduced by one order of magnitude via a differential strategy.