Search

A photoelectrochemical biosensing strategy for the highly sensitive detection of the flavonoid rutin was developed by synergizing the photoelectrocatalytic properties of hematite (α-Fe2O3) decorated with palladium nanoparticles (PdNPs) and the biocatalysis towards laccase-based reactions. The integration of α-Fe2O3.PdNPs with a polyphenol oxidase as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the photoactive biocomposite can generate a stable photocurrent, which was found to be directly dependent upon the concentration of rutin. Under the optimal experimental conditions, the cathodic photocurrent, measured at 0.33 V vs. Ag/AgCl, from the square-wave voltammograms presented a linear dependence on the rutin concentration within the range of 0.008–30.0 × 10−8 mol L−1 (sensitivity: 1.7 μA·(× 10−8 M−1)·cm−2), with an experimental detection limit (S/N = 3) of 8.4 × 10−11 mol L−1. The proposed biosensor device presented good selectivity towards rutin in the presence of various organic compounds and inorganic ions, demonstrating the potential application of this biosensing platform in complex matrices. This bioanalytical device also exhibited excellent operational and analytical properties, such as intra-day (standard deviation, SD = 0.21%) and inter-day (SD = 1.30%) repeatability, and long storage stability (SD = 2.80% over 30 days). Graphical abstract

A glassy carbon electrode was modified with a TiO2-gold nanoparticle hybrid integrated with multi-walled carbon nanotubes in a dihexadecylphosphate film (TiO2-Au NP-MWCNT-DHP/GCE) and applied to amperometric determination of ascorbic acid (AA). The modified sensor displays fast charge transfer and shows an irreversible anodic behavior for AA by cyclic voltammetry. Under optimal experimental conditions and using amperometry at 0.4 V, the analytical curve presented a statistical linear concentration range for AA from 5.0 to 51 μmol L-1, with a limit of detection of 1.2 μmol L-1. The electrode was successfully applied to the determination of AA in pharmaceutical and fruit juice without the need for major pretreatment of samples. Graphical abstract Schematic of a new sensing platform for ascorbic acid (AA). It is based on a glassy carbon electrode (GCE) modified with TiO2-Au nanoparticles integrated into carbon nanotubes in a dihexadecylphosphate film. The sensor was applied to amperometric determination of AA in juice and pharmaceutical samples.