SERS Substrates for Ultrasensitive Detection of Malachite Green Using Silver Nanostars

Abstract

Food additives, crucial for enhancing food quality, have raised concerns regarding their potential carcinogenicity, particularly in substances like malachite green (MG), previously removed from the United States Food and Drug Administration approved list due to identified cancer risks. This investigation delves into the nuanced domain of trace detection employing surface-enhanced Raman spectroscopy (SERS), leveraging the localized plasmon of silver nanoparticle substrates. The research involves a comprehensive comparison between solid- and liquid-based SERS substrates. It utilizes diverse morphologies of silver nanostars (AgNSs) for sensitively detecting MG, substances of considerable interest in the food industry despite their acknowledged carcinogenic properties. A comprehensive characterization of diverse AgNS shapes, including TEM analysis and UV-Vis spectra, reveals distinct plasmon resonance peaks influenced by morphology and the surrounding medium. Finite-difference time-domain (FDTD) simulations underscore the influence of core size and arm number on local electric fields, generating robust hot spots along the edges. The surrounding medium also significantly influenced electric field intensity. SERS examinations reveal liquid-based substrates outperforming their solid counterparts, achieving a remarkable limit of detection (LOD) of 37 aM for MG. These findings were extensively examined in light of their consistency with FDTD simulations and the noticeable variations in enhancement factors observed among different configurations of solid substrates. Simultaneously, the study explores the high reproducibility of liquid-based substrates and endeavors to improve the poor reproducibility of the Raman signal by modifying the surface of solid-based substrates.