A novel and stable Raman probe for sensing Fe (III)

Abstract

We developed a highly sensitive surface-enhanced Raman scattering (SERS) technique for determining Fe3+ ions via synthesis of inositol hexaphosphate (IP6) capped silver nanoparticles (AgNPs). IP6 (1.98nm thickness) coated on the surface of AgNPs not only provided a protection layer to stabilize silver substrate but also specifically anchoring sites of phosphates to capture Fe3+ ions from aqueous solution. Rhodamine 6G (R6G) was used as a Raman indicator in this case and the scattering intensity of R6G in Raman probe increased with adding Fe3+ ions. A possible mechanism is that IP6 bound with Fe3+ narrowed the gap of neighboring AgNPs to produce plenty of SERS “hot spots”. Due to the controllable aggregation of IP6@R6G–AgNPs by Fe3+, it presents a widely linear range of 11.2–39.2ppm for analyzing the Fe3+ ions. This Raman-based method for detecting Fe3+ showed a high selectivity in the presence of other metal ions in same solution involving Mg2+, Cu2+, Ca2+, Pb2+, Co2+, Na+, Zn2+, K+, Li+, Mn2+ and Fe2+. Under optimal conditions, the limit of detection (LOD) for SERS testing Fe3+ could be down to 0.28ppm. As a practical application, the Raman assay for the determination of Fe3+ in river water was carried out.