Enhancing the antibacterial activity of transition metal dichalcogenides nanosheets through doping: a study on ReS₂ nanosheets Re(1−x)CoxS2

In this study, ReS₂ and Co-doped ReS₂ thin films were synthesized via aerosol-assisted chemical vapor deposition (AACVD) at 525 °C using single-source precursors: [Re2(μ-S)2(S2CNEt2)4] (1) and [Co(S₂CN(Et)₂)₂] (2). The resulting films were characterized using powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), inductively coupled plasma optical emission spectroscopy (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), confirming the successful formation of Re₁−xCoxS2 alloys. Various feed ratios of precursors (1) and (2) (10%, 20%, 30%, and 50%) were employed for the synthesis of Co-doped ReS2films. ICP-OES quantification revealed actual Co incorporation levels of 0.96%, 2.05%, 6.35%, and 8.19%, corresponding to the respective feed ratios. XRD analysis of the Co-doped films showed systematic shifts in the intensity and position of the (001) diffraction peaks with increasing Co content. A continuous shift was observed from 0.96 to 6.35% Co, while the disappearance of the (001) peak at 8.19% indicated a significant loss of crystallinity, suggesting a transition to an amorphous structure. The interplanar spacing d(001), calculated from XRD data, decreased from 6.119 Å in pure ReS₂ to 5.818 Å at 6.35% Co doping. XPS spectra confirmed the presence of both Co2⁺ and metallic Co⁰, indicating partial substitution of Re by Co in the ReS₂ lattice and the simultaneous formation of Co⁰ clusters. Moreover, the combination of bottom-up AACVD synthesis with top-down liquid-phase exfoliation (LPE) proved to be an effective strategy for producing both pristine and doped ReS₂ nanosheets, demonstrating their potential in biomedical applications. Antibacterial assays of ReS2 and Co-doped ReS2 extracts revealed variable efficacy. The undoped ReS2 extract demonstrated moderate antibacterial activity, with inhibition zones of 8 mm against Pseudomonas aeruginosa and 8.5 mm against Staphylococcus aureus. Upon Co doping, a significant enhancement was observed, particularly at 6.35% Co content, resulting in maximum inhibition zones of 16 mm and 11.5 mm against Pseudomonas aeruginosa and Staphylococcus aureus, respectively.