Analysis and Large-Scale Synthesis of Bimetallic Nanocube Substrate for Surface Enhanced Raman Scattering

Analysis and Large-Scale Synthesis of Bimetallic Nanocube Substrate for Surface Enhanced Raman Scattering

 

Joshua Weatherston¹, Nolan Worstell¹, Hung-Jen Wu¹

¹Dept. Chemical Engineering, Texas A&M University, USA

Surface Enhanced Raman Scattering (SERS) is a highly sensitive spectroscopic technique capable of identifying surface-adsorbed chemical species at extremely low concentrations, down to single molecule detections. The low detection threshold and the “fingerprint” nature of this vibrational spectroscopic method, as well as its compatibility with equipment found in many research and diagnostic labs, make SERS an ideal candidate for multiplexed biomolecule detection. SERS is a consequence of the large electric field enhancement present near nanostructured surfaces; as such, its signal is dependent on the morphology and dielectric properties of the substrate and the analyte's proximity to the substrate. To create a suitable substrate for high-throughput SERS measurements, highly monodisperse plasmonic silver nanocubes were synthesized and coated with several atomic layers of gold in a large-scale batch synthesis. The theoretical SERS enhancement of Ag@Au core-shell nanocubes, pure Ag nanocubes, hollow Au cages, and other similar structures were calculated using finite element method (FEM), which predicted large enhancement factors. The FEM computation was confirmed by acquiring Raman spectra of the nanocubes functionalized with Raman-active organic dyes. It was found that the Ag@Au nanocubes showed large enhancement factors. Compared with pure silver nanocubes, the gold coated substrate showed greater Raman enhancement, increased resistance to particle degradation, and better compatibility with biological analytes. The multiplexing capabilities of this system were successfully demonstrated by detecting the co-adsorption of multiple dye species on the nanocube surface, including labeled and unlabeled peptide sequences. Furthermore, this platform was used to analyze the enzymatic digestion kinetics of peptide-functionalized nanocubes.

Submitting author: Joshua Weatherston, Dept. Chemical Engineering, Texas A&M University, College Station, TX 77843, USA, Tel: +1-361-232-3982; Email: jdub@tamu.edu