Sustainable synthesis of truncated Au-sensors embedded within robust snipped human nails to monitor dye adulteration in real food samples

Natural materials with anomalous molecular machinery and hierarchies are gaining tremendous recognition in the pursuit of environmentally friendly, sustainable supports <i>via</i> noble metal anchoring for the analysis of organic pollutants. Herein, for the first time, we demonstrate the <i>in situ</i> biofabrication of AuNPs stringently tethered within snipped human nails, materialised by the hydroxy amino acids structured within the collagenous nail, which exhibit high reductive potential and Au affinity. Material characterization revealed a firm assemblage of large truncated AuNPs, including triangles, pentagons, hexagons and octagons of sizes between ∼80 and 150 nm, embedded within the highly rigid and compact three-dimensional nail, ensuring durability, shelf-life and stability against diverse physicochemical environments. Furthermore, large truncated AuNPs with sharp edges can intensify localized electromagnetic fields as "<i>hotspots</i>" for the direct SERS detection of organic analytes. This is validated by exposing real dye adulterants at nanomolar regimes, detecting acid orange at concentrations of 0.173-0.206 ppm in red chillies (spice) and 0.087-0.140 ppm of malachite green in green peas (pulse) collected from three distantly far vegetable markets in a radius of ∼37.28 miles. Overall, we present a highly stable, human nail waste biofabricated Au bio-substrate as a sustainable and generalized sensing technique for the identification and quantification of unsafe molecular adulterants in food samples using SERS.