Our research unveils a novel and eco-friendly technique for the synthesis of emerging two-dimensional Copper Sulfide (CuS) nanosheets through the sulfidation of surface-modified Cu NPs. These fabricated CuS nanosheets exhibit captivating properties such as fluorescence and surface plasmon resonance (SPR) within the near-infrared (NIR) spectrum, rendering them as remarkable candidates for transformative applications in bioimaging and medical sensing.The structural and optical characterization of the material were carried out, and the morphological characterization using SEM and HRTEM shows the formation of 2D CuS as exfoliated long sheets. The investigation projects a simple and cost-effective method to produce 2D Copper Sulfide (CuS) nanosheets. It is formed through a two-step process, including the synthesis of Cu NPs, and transformation of these colloidal Cu NPs into CuS nanosheets through sulfidation. It is found that the concentrations of sulfur and the surface modifying agents like curcumin and ascorbic acid influence nucleation and promote 2D growth of the nanosheets. The effect of sulfur concentration, pH, and surface modifying agents on SPR properties of the Cu NPs were investigated, and the results are presented here. Additionally, our findings indicate that both seed-mediated syntheses and ligand-assisted surface modification leads to the growth of these CuS nanosheets. The cellular studies show that sulfidation reduces the cellular cytotoxicity of Cu NPs. The sample also exhibits excellent stability and biocompatibility, and it is proved to be a promising candidate for photocatalytic, sensing, and biomedical applications, and hence emerges as a multifunctional 2D material.