Photoactivated plasmonic nanohybrid fibers with prolonged trapping of excited charge carriers for SERS analysis of biomolecules

Abstract

The quest to enhance Raman spectroscopic signals through the rational design of plasmonic substrates has enabled the detection and characterization of pharmaceutically important molecules with low scattering cross-sections, such as amino acids and proteins, and is helping in making forays into the diverse field of biomedical sciences. This work presents a simple strategy for synthesizing silver nanoparticles-incorporated alumina nanofibers (Ag–AlNFs) utilizing controlled microwave synthesis for enhancing the surface-enhanced Raman chemical enhancement factor through photo-induced charge accumulation at the plasmonic–dielectric interface. The plasmonic–dielectric fibers serve as excellent charge carrier trappers, as evident from the ultrafast transient absorption spectroscopy studies. Apart from chemical enhancement, the increase in electronic surface charge also enables the protein disulfide bonds to capture these electrons and form a transient disulfide electron adduct radical, which converts to free thiol radical on dissociation. This allows protein molecules to bind to the nanoparticle's surface with the favorable silver thiol bond leading to greater surface affinity and larger SERS enhancement. The proposed Ag–AlNFs represent a cost-effective material that can be potentially used to probe biological systems in a label-free manner by photoactivating the SERS substrate for obtaining higher enhancement factors.