Effect of the mercaptan alkyl chain structure on the structure and electrochemical properties of Au-doped mesoporous carbon materials

A good chelating agent such as mercaptan plays an important role in the synthesis of gold nanoparticles (AuNPs) or Au-doped carbon nano-composites. Herein, a synchronous carbonization-reduction method was employed to synthetize stable and monodispersed AuNPs embedded in the mesoporous carbon framework. A phenolic resin, mercaptan, and HAuCl₄ acted as a carbon source, coordination agent, and gold source, respectively. The effect of the mercaptan chain length on the size of AuNPs and the pore structure of the mesoporous carbon materials was systematically studied. Ultraviolet spectrum analysis revealed that the coordination shifted from Cl–Au to S–Au depending on the mercaptan added to the reaction system. The as-prepared gold nanoparticles@mesoporous carbon materials (AuNPs@MPCs) were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, and N adsorption–desorption. The size of the AuNPs (3.71–12.86 nm) was controlled by changing the alkyl chain length of the mercaptans. The specific surface areas of the obtained AuNPs@MPCs increased from 1440 to 1603 m²/g as the mercaptan chain length increased. Square-wave stripping voltammetry (SWASV) tests on a typical MPTMS-AuNPs@MPC/GCE modified electrode revealed good detection response towards Pb²⁺, with a limit detection as low as 1.96 nM (S/N = 3). This detection limit was significantly lower than the value provided by the World Health Organization. This electrode also showed a relative wide linear detection range (0–2 μM). This good performance was ascribed to the excellent conductivity of AuNPs and the high specific surface area of the carbon materials. This work provides a new research strategy for the one-step synthesis of AuNPs@carbon materials with controllable NP size by using mercaptans with different alkyl chain structure. It can be believe that this approach could be expanded to nano-metal materials other than Au.