Gln-GQD-enabled FeCoNiCuAu0.5-high entropy alloy nanoparticles for ultrasensitive and non-invasive electrochemical uric acid detection

Abstract

The limited sensitivity restricts the practical application of the present electrochemical sensors for the detection of uric acid in human sweat. Herein, we report an approach for the construction of FeCoNiCuAu_0.5 high-entropy alloy nanoparticles (FeCoNiCuAu_0.5-HEA) by introducing glutamine-functionalized graphene quantum dots (Gln-GQD). Fe³⁺, Co²⁺, Ni²⁺ and Cu²⁺ are combined with Gln-GQD to form a stable complex, which subsequently coordinated with Au³⁺. This is followed by a two-stage thermal annealing in an N₂ atmosphere. The resulting FeCoNiCuAu_0.5-HEA showed a spherical nanostructure with a small particle size of 47.5 ± 0.63 nm, FCC and BCC phases, and uniform distribution of all the metal elements. The HEA nanoparticles are well dispersed on the three-dimensional graphene framework formed by intertwining of the graphene sheets. The integration of a five-metal element mixture and introduction of Gln-GQD achieved an excellent electron/ion conductivity and good affinity with polar electrolytes and significantly enhanced the catalytic activity. The catalytic activity is more than 2.7-times that of gold nanoparticles. The FeCoNiCuAu_0.5-HEA-based sensor exhibited an ultrasensitive electrochemical response towards uric acid. The differential pulse voltammetric peak current linearly increased with an increase in uric acid concentration in the range of 0.01–1 μM uric acid with a detection limit of 4.3 × 10⁻⁹ M (S/N = 3). The as-proposed analytical method provides the advantages of high sensitivity, selectivity and repeatability for the detection of uric acid in human sweat.