Characterization of stainless steel assisted bare gold nanoparticles and their analytical potential

• Stainless steel is used as reducing agent to form AuNPs from HAuCl4 solution.
• Bare AuNPs without ligands in their surface have been synthesized.
• AuNPs have been characterized by SEM, TEM, AFM, UV–vis, ICP-OES, EDX.
• Bare AuNPs proved to be very stable without addition of stabilizing agents.
• Their analytical potential to be used as SERS substrates has been demonstrated.

A simple, environmentally friendly, one-pot method to synthesize highly stable bare gold nanoparticles (AuNPs) has been developed. AuNPs have been synthesized from tetrachloroauric acid solution using steel or stainless steel as solid reducing agent, which can be reused. The proposed method yields bare gold nanoparticles at atmospheric pressure and room temperature for potentially producing large quantities. The obtained AuNPs have been characterized by SEM, TEM and AFM finding an average diameter of around 20 nm, polygonal yet nearly spherical shape and a narrow size distribution. The mechanism of reaction has been investigated by UV–vis spectroscopy, ICP-OES and EDX analysis. The obtained dispersed gold nanoparticles proved to be stable if stored a 4 °C for over four months without the addition of a stabilizing agent. Their analytical potential as SERS substrate has been demonstrated and their performance compared with that showed by citrate-coated gold nanoparticles. Thanks to their unique properties, their use as analytical tools provides analytical processes with enhanced selectivity and precision.