Synthesis and surface functionalization of gold microtubes for SERS detection of dyes

In this study, we report on the synthesis of gold microtube-based substrates and their organic modification with 11-mercaptoundecanoic acid (MUA11) for the use in surface-enhanced Raman spectroscopy (SERS). The main objective of the work was to investigate the influence of organic modification on the optical properties of the substrates and the degree of Raman signal enhancement. The synthesis of gold microtubes was carried out using a chemical template-assisted growth method, resulting in the formation of uniform and continuous gold layers on the porous template surface. The obtained structures were characterized by X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Localized surface plasmon resonance (LSPR) behavior was analyzed through the optical response of the gold microtubes. The presence and efficiency of the organic modification were verified by X-ray photoelectron spectroscopy (XPS). Optical characterization revealed that the substrates with uniformly distributed gold microtubes exhibited a plasmonic resonance around 440-470 nm. To evaluate the analytical performance of the developed substrates, SERS analyses were performed using three model organic dyes: methylene blue, methyl violet, methyl red, in a concentration range from 10^-2 to 10^-6 M.