3D Interior Plasmonic Nanocavities for Sensitive and Selective Recognition of Hazardous Substances in Plastic Products

Surface-enhanced Raman scattering (SERS) utilizing plasmonic nanomaterials and nanostructured substrates has been extensively investigated to directly recognize substances because the energy differences between the incident and scattered lights correspond to the molecular vibrational energy states of the substances. SERS performance is dominantly derived from electric fields confined in dielectric media, called hotspots, between adjacent plasmonic nanostructures. Recently, the 3D interior hotspots templated with dielectric media surrounded by plasmonic materials have attracted great attention [1]. Various electrochemical techniques such as catalytic reaction, electrodeposition, and galvanic reaction (GR) have been exploited to realize the 3D interior hotspots. Particularly, a GR process spontaneously originates from energy differences in the reduction potential of two or more materials [2]. An imbalanced atomic exchange strategically defines narrow hollow regions which have dual functions of electric field confinement domains and molecular diffusion paths. For deeper comprehension of interior hotspots, the Ag nanocavities galvanically replaced by Au (Au/AgNC) on the silicon substrates were prepared. The proposed Au/AgNC platforms were used to trace hazardous substances such as phthalates. The activation of interior hotspots with superior density in a unit volume enabled reliable sensing operations at ppb levels. From the collected dataset, a machine-learning model was designed to predict various combinations (i.e., single, binary, ternary, and quaternary) of four major phthalates. Subtle differences in the phthalates’ spectral characteristics were successfully classified using a machine learning algorithm based on a principal component analysis–linear discriminant analysis model.<br/> <br/>References<br/>I.-B. Ansah, S.-H. Lee, J.-Y. Yang, C.W. Moon, S. Jung, H.S. Jung, M.-Y. Lee T. Kang, S. Lee. D.-H. Kim, S.-G. Park, In-situ fabrication of 3D interior hotspots templated with a protein@Au core–shell structure for label-free and on-site SERS detection of viral diseases, <i>Biosens. Bioelectron.</i> <b>220</b> 114930 (2023).<br/>I.-B. Ansah, S.-H. Lee, C.W. Moon, J.-Y. Yang, J. Park, S.-Y. Nam, S. Lee. D.-H. Kim, S.-G. Park, Nanoscale crack generation of Au/Ag nanopillars by in situ galvanic replacement for sensitive, label-free, and rapid SERS detection of toxic substances, <i>Sens. Actuators, B.</i> <b>379</b> 133172 (2023).