Multilayer Thin-Film Flake Dispersion Gel for Surface-Enhanced Raman Spectroscopy

TL;DR

This paper introduces a multilayer thin-film flake dispersion gel that enhances surface-enhanced Raman spectroscopy (SERS) signals, enabling direct skin biomarker detection with improved sensitivity and safety.

Contribution

The study develops a novel multilayer thin-film flakes dispersion gel that preserves optical properties and enhances SERS signals for biomedical applications.

Findings

SERS signal was 20 times stronger with the multilayer film flakes gel.

The gel allows rapid diffusion of biomolecules like BPY within seconds.

The method is safe and suitable for direct skin application.

Abstract

Ag nanorod arrays/dielectrics/mirror-structured multilayer thin-film are well known, highly sensitive surface-enhanced Raman scattering (SERS) substrates that enhance the Raman scattering cross-section by the interference of light. However, extracting biomarkers directly from human skin using these solid substrates is difficult. To overcome this problem, we propose a multilayer thin-film flake dispersion gel by centrifugal mixing of the multilayer thin-film and hydroxyethyl cellulose (HEC) gel. The multilayer thin-film was prepared by serial bideposition using the dynamic oblique angle deposition technique. The mixing process was optimized to obtain flakes of ~10 {\mu}m so that the optical properties of the multilayer film can be preserved, and there is no risk of adverse effects on humans. The SERS features of the flakes dispersion gel were tested using 4, 4'-bipyridine (BPY). The BPY molecules diffused through the highly porous gel within a few seconds, generating significant SERS signals. The multilayer film flakes dispersion gel showed a SERS signal about 20 times better than the gel-dispersed Ag nanorod arrays without a multilayer film structure. These SERS active flakes dispersion gel can be used directly on the skin surface to collect body fluids from sweat, for biomarker sensing.