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

• We synthesize a novel structure of IP6@R6G–AgNPs as Fe (III) Raman probe.
• The Raman probe is a simple and sensitive method to detect Fe (III) in water.
• The Raman probe shows a good capability against interference from other metal ions.

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 (1.98 nm 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 11.2–39.2 ppm 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 0.28 ppm. As a practical application, the Raman assay for the determination of Fe3+ in river water was carried out.

A novel core@shell structure of IP6@R6G–AgNPs is constructed. IP6@R6G–AgNPs-based Raman assay shows highly selective determination of trace Fe (III) in river water. A mechanism is that Fe (III) bound IP6 in shell controllably produce “hot spots” of AgNPs to realize quantitative analysis of Fe (III).Figure optionsDownload as PowerPoint slide