Ngok et al. (2025) fabricate a metal-semiconductor hybrid nanocomposite electrode (ZnO nanorods/α-Fe2O3/Au nanoparticles, denoted ZFA) on fluorine-doped tin oxide (FTO) substrate and evaluate its performance as an electrochemical sensor for arsenate (As(V)) in drinking water. The study optimizes gold nanoparticle concentration and demonstrates that AuNP addition significantly improves electrochemical catalytic activity.
Key numbers
LOD: 2.25 ppb (2.25 µg/L) for As(V) in drinking water — reported as below the WHO guideline value of 10 µg/L for arsenic in drinking water.
Linear range: 0 to 50 mg/L arsenic tested (wide range for calibration purposes).
Detection mode: Linear sweep voltammetry and square wave voltammetry.
Methods (brief)
ZnO nanorods grown by hydrothermal method on FTO substrate; α-Fe2O3 deposited by dip-coating; Au NPs added by hydrothermal route at varying concentrations (0.15–0.75 mM HAuCl4). Characterization by UV-vis, FESEM, XRD, XPS. Electrochemical characterization by LSV and SWV. Three-electrode configuration (Ag/AgCl reference, Pt counter). Drinking water matrix.
Note: this sensor detects As(V) (arsenate) specifically, not As(III) (arsenite). Food arsenic speciation distinguishes inorganic arsenic (iAs = As(III) + As(V)) from organic arsenic species; this sensor measures one of the two inorganic species.
Implications
Testing: LOD of 2.25 ppb As(V) in drinking water is below the WHO 10 ppb guideline, making this relevant for water quality monitoring. For food matrix arsenic testing, both As(III) and As(V) contribute to inorganic arsenic (iAs); a method detecting only As(V) would miss As(III). Full speciation for food compliance requires HPLC-ICP-MS.