In situ Raman spectroscopic monitoring of organic dyes and ferric ions in Fenton reactions on sharp-edged gold nanostar surfaces

Abstract For this report, we compared interfacial spectroscopic tools to monitor in situ Fenton reactions of organic dyes on ascorbic acid-reduced gold nanostars (AuNSs). Ultraviolet-visible (UV–vis) absorption and Raman spectroscopic tools were introduced to check the hydroxyl radical destruction of ethyl violet (EV), which contains a triarylmethane group. AuNSs with sharp edges, tips, and corners were used as efficient surface-enhanced resonance Raman scattering (SERRS) substrates for in situ Fenton reaction monitoring. The SERRS intensity of the EV showed a first-order decay curve with a reaction rate constant value of 0.0263 min −1 , while the decolorization yielded second-order kinetic behavior with a constant value of 0.00430 L/mol min. In addition to the destruction of the organic dyes, the increased number of ferric (III) ions, as a result of the Fenton reactions, was detected via 4-aminobenzo-15-crown-5 (4AB15C5) conjugated with 4-mercaptobenzoic acid (4MBA). We found that the SERRS bands at ∼1500 cm −1 of 4AB15C5 on AuNSs increased after treatment with H 2 O 2 and FeSO 4 . Real industrial textile wastewater samples were then tested to determine whether this Raman method could be applied to detect increases in ferric ions. Our spectroscopic data used SERRS peaks via Fenton reaction results to calculate an estimated ∼65% destruction of the organic dyes.