Gold Nanoparticle‐based Surface‐enhanced Raman Scattering Fe(III) Ion Sensor

Abstract

We performed density functional theory (DFT) calculations of 4‐aminobenzo‐15‐crown‐5 (4AB15C5) in conjugation with 4‐mercaptobenzoic acid (4MCB) with the polarizable continuum model (PCM) while considering the aqueous media. After specific binding of the ferric ion onto the 4MCB–4AB15C5 compound, the Raman frequencies and intensities were estimated by DFT calculations with the PCM. It was predicted that the Raman intensities became significantly increased upon binding of the ferric ion. 4MCB–4AB15C5 could be assembled on gold nanoparticles (AuNPs) via the cleavage of the thiol bond. Colorimetric and UV–Vis absorption spectroscopy indicated that AuNPs became significantly aggregated in the presence of 1–10 mM of the ferric ion. Surface‐enhanced Raman scattering (SERS) of 4MCB–4AB15C5 was used to identify the dissimilar spectral behaviors that yield a difference in intensity in the presence of the ferric ion. These changes were not observed in the other biological ions Zn2+, Mn2+, Fe2+, Na+, K+, Ca2+, Mg2+, NH4 +, and Co2+. This study indicated that 4AB15C5 could be used to detect ferric ions in aqueous AuNP solutions by a combined method of colorimetric, UV–Vis absorption, and Raman spectroscopy. AuNPs–[4MCB–4AB15C5] can thus be utilized as a selective turn‐on sensor to Fe3+ in aqueous solutions above 1 mM.