Enhanced light-harvesting efficiency in Au metal–NiFe2O4 semiconductor hetero-nanostructures with implications for photoelectrochemical sensors towards the sensitive detection of paracetamol in human urine

In this study, Au–NiFe2O4 hetero-nanostructures (Au–NFO HNs) have been successfully developed and proposed as an efficient photoactive material for the construction of a photoelectrochemical sensor for the detection of paracetamol (PCM) under visible light irradiation. When Au NPs were in intimate contact with NFO NFs, a built-in electric field and Schottky barrier at the NFO/Au interface were established and downward band bending occurred. By using monochromatic 532 nm laser excitation, the photo-generated electrons on the NFO conduction band were promptly migrated to the Au Fermi level due to the presence of a built-in electric field and downward band bending, and together with the hot electrons induced by localized surface plasmon resonance characteristics of Au NPs could concurrently contribute to the enhanced photoelectrochemical activity. Furthermore, the Schottky barrier prevents the transfer of photo-generated holes from the valence band of NFO to Au, thereby suppressing the recombination of photo-generated electron–hole pairs and prolonging charge carrier lifetimes. A series of electrochemical kinetic parameters were determined and the results showed that in the presence of visible light irradiation, the interfacial charge transfer ability, electrocatalytic activity, and adsorption/diffusion capacity of Au–NFO HNs-modified electrode were remarkably enhanced compared to the dark environment. As a result, the photoelectrochemical sensing platform based on Au–NFO HNs showed noteworthy analytical performance towards PCM detection in the wide linear ranges from 0.5–200 μM, high electrochemical sensitivity of 1.089 μA μM−1 cm−2, and low detection limit of 0.38 μM. Furthermore, the repeatability, anti-interference ability, and feasibility of the proposed photoelectrochemical sensor were also evaluated. This study will establish a more comprehensive understanding and promote ongoing interest in constructing advanced and efficient plasmonic metal/semiconductor hetero-nanostructures for analytical photoelectrochemistry.