Tuning of hydrogen peroxide etching during the synthesis of silver nanoparticles. An application of triangular nanoplates as plasmon sensors for Hg2+ in aqueous solution

Abstract

Abstract A simple method to prepare silver nanoparticles (AgNPs) with different shapes and dimensions was optimized by using a one-step reduction method with NaBH4, TSC and PVP, with H2O2 acting as an oxidation agent, to etch the nanoparticles and produce different morphologies. A series of AgNPs were obtained with different colours, including yellow to green and passing through orange, red, violet and blue, that exhibited different localized surface plasmon resonance (LSPR) as analysed by UV–visible spectroscopy. The dimensions and morphologies of the nanostructures were characterized in detail by scanning electron microscopy (SEM) and dynamic light scattering (DLS) techniques. The characterizations showed different trends in the morphologies, starting from spherical to not well-defined structures, triangular nanoplates, hexagonal nanoplates and ultimately once again showing quasi-spherical shapes. The triangular nanoplates were tested as plasmon sensors for mercury ions in aqueous solution, and they showed an LSPR-blueshift with a change in colour from blue to violet. When a calibration curve was measured in the concentration range from 0.14 to 0.5 mg l−1, the nanoparticles showed good linearity between the Hg2+ concentration in the solutions and the LSPR blueshift, with a correlation factor R2 of 0.9978 and an LOD of 0.013 mg l−1 (64.9 nM).