Sunlight Induced Synthesis of Reversible and Reusable Biocapped Nanoparticles for Metal Ion Detection and SERS Studies

The present work describes an eco-friendly synthesis of silver and gold nanoparticles using an aqueous extract of the bone powder of a dry marine organism (seahorse), which acts both as a reducing as well as stabilizing agent. The novel photoinduced formation of the nanoparticles (NPs) was characterized by UV–vis absorption, dynamic light scattering, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) experiments. The role of pH on the feasibility of nanoparticle formation has been investigated. The results suggest that photoinduced electron transfer from the amino acids present in the bone extract is responsible for the reduction of the nanoparticle precursors. The as-synthesized nanoparticles have been utilized as “naked eye” sensors for the detection of multiple ions (Cu²⁺, Cr³⁺, V⁴⁺, and UO₂²⁺) at <i>micromolar</i> concentration of the analytes. Furthermore, the NPs were found to enhance the surface Raman peaks from dye molecule (rhodamine 6G) at <i>nanomolar</i> concentration of the analyte. More significantly, a novel and efficient sunlight induced reversible aggregation pathway for the as-synthesized nanoparticles has been demonstrated