Cascaded microsphere‐coupled surface‐enhanced Raman spectroscopy (CMS‐SERS) for ultrasensitive trace‐detection
Yanlin Mi, Yinzhou Yan, Mengyuan Wang, Lixue Yang, Jing He, Yijian Jiang
Abstract
Abstract Surface‐enhanced Raman spectroscopy (SERS) has been widely investigated and employed as a powerful optical analytical technique providing fingerprint vibrational information of molecules with high sensitivity and resolution. In addition to metallic nanostructure, dielectric micro‐/nano‐structures with extraordinary optical manipulation properties have demonstrated capability in enhanced Raman scattering with ultralow energy losses. Here we report a facile cascaded structure composed of a large microsphere (LMS) and a small microsphere array with Ag nanoparticles as a novel hybrid SERS substrate, for the first time. The cascaded microsphere‐coupled SERS substrate provides a platform to increase the molecular concentration, boost the intensity of localized excitation light, and direct the far‐field emission, for giant Raman enhancement. It demonstrates the maximum enhancement factor of Raman intensity greater than 10 8 for the limit of detection down to 10 −11 M of 4‐nitrothiphenol molecules in aqueous solution. The present work inspires a novel strategy to fabricate cascaded dielectric/metallic micro‐/nano‐structures superior to traditional SERS substrates towards practical applications in cost‐effective and ultrahigh‐sensitive trace‐detection.