Eco-Friendly and Efficient Fabrication of Few-Layer Molybdenum Disulfide/Gold Nanocomposites by Chitosan-Assisted Exfoliation for SERS Applications

This study explores the use of chitosan in the sustainable exfoliation of MoS2, optimizing conditions to create effective surface-enhanced Raman scattering (SERS) platforms for optical sensors. Two-dimensional (2D) materials such as molybdenum disulfide (MoS2) have attracted significant attention recently due to their unique electrical, optical, and mechanical properties. However, conventional methods for exfoliating MoS2, such as liquid-phase exfoliation (LPE) with toxic organic solvents, pose environmental and health risks, necessitating the development of more sustainable approaches. Here, we introduce chitosan as a green, multifunctional agent that plays a dual role: acting not only as an eco-friendly exfoliant for producing few-layer MoS2 nanosheets but also as a positively charged linker that drives the electrostatic assembly of Au nanoparticles (AuNPs). Several parameters, such as sonication time and biopolymer concentration, were systematically investigated to tailor the exfoliation efficiency and stability of the MoS2–chitosan biomaterials. This sustainable strategy yields MoS2–Ch1@AuNPs nanocomposites that function as highly active SERS substrates. Importantly, the synergistic interplay between MoS2, chitosan, and AuNPs leads to a substantial enhancement of detection sensitivity toward both crystal violet (limit of detection (LOD) = 10 nM) and glucose (clinically relevant 10 mM), outperforming the individual components (2D MoS2–Ch1 nanosheets or AuNPs alone). Beyond demonstrating high analytical performance, this work establishes a sustainable pathway for the design of biopolymer-mediated 2D nanocomposites bridging sustainability and advanced plasmonic sensing applications.