Optimal boron-doped graphene substrate for glucose Raman signal enhancement

TL;DR

The study addresses the challenge of sensitive glucose detection via SERS by evaluating boron-doped graphene substrates. Using first-principles density functional theory and phonon-decomposition analysis, it reveals that a high boron concentration (about 12.5%) markedly strengthens glucose–substrate bonding and yields the largest Raman enhancement, with the molecular orientation relative to the surface playing a critical role. The work demonstrates that phonon-eigenvector analysis is a powerful, generalizable tool for predicting Raman response in substrate–analyte systems, enabling efficient screening of candidates for enhanced SERS performance. This approach has potential implications for developing cost-effective, graphene-based glucose sensors beyond traditional noble-metal substrates.

Abstract

Surface Enhanced Raman Spectroscopy (SERS) is a highly sensitive and selective technique that greatly enhances the signal of an analyte, compared with its signal from classical Raman Spectroscopy, due to its interaction with a substrates surface. It has been shown that low concentration boron-doped graphene (B-graphene) enhances the Raman signal of simple organic molecules like pyridine. Recent studies also suggest that B-graphene can remain thermodynamically stable when doped with significantly higher concentrations of boron than previously observed. In this framework, we use quantum mechanical simulations to investigate the influence of dopant concentration and geometric distribution on the effectiveness of B-doped graphene as a SERS substrate, with glucose as analyte. By combining analysis of interatomic force constants and of phonon eigenvectors composition, we conclude that higher doping concentrations provide a larger enhancement to glucose's Raman signal, while the molecule orientation relative to the surface plays a fundamental role in the Raman response. We suggest that high concentration B-graphene presents itself as a potential substrate for SERS based detection of glucose, while the used phonon-based analysis can be promptly applied for the search of promising candidates as substrate materials for enhanced Raman response.

Figures (6)

• Figure 1: Initial geometries of the studied systems (a) gLowBG, glucose on $1.39\%$ B-graphene, (b) gHighBG, glucose on 12.5$\%$ B-graphene. Brown spheres represent carbon atoms, while red, white and green spheres represent oxygen hydrogen and boron atoms, respectively.
• Figure 2: Relaxed geometries of systems (a) gLowBG - glucose on $1.39\%$ B-graphene and (b) gHighBG - glucose on $12.5\%$ B-graphene.
• Figure 3: Raman spectra of (a) gLowBG (glucose on $1.39\%$ B-graphene) and gG (glucose on pristine graphene) systems, and (b) gHighBG (glucose on $12.5\%$ B-graphene) and gLowBG systems.
• Figure 4: Relaxed geometries of (a) gLowBGF and (b) gHighBGF systems, where the glucose molecule is flipped; i.e. its hydroxymethyl group, highlighted by a red outline, is pointing away from the substrate.
• Figure 5: Raman spectra of (a) gLowBGF and (b) gHighBGF systems. Peak colour gradient indicates the atomic character of the phonon displacements: pure yellow and dark purple colours correspond to contributions from only the glucose molecule or the substrate, respectively.