Highly efficient antimicrobial agents based on sulfur-enriched, hydrophilic molybdenum disulfide nano/microparticles and coatings functionalized with palladium nanoparticles

Abstract

In this research the molybdenum disulfide (MoS₂)-based nano/microparticles and coatings were synthesized through a simple, one-step hydrothermal approach without any other additives. Composition, structure, and morphology of the synthesized MoS₂-based materials were investigated using ultraviolet-visible spectroscopy (UV-Vis), inductively coupled plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX) techniques. The fabricated materials exhibited relatively small (Δθ = 18.7 ± 2.5⁰) contact angle and prominent hydrophilic properties, which are attributable to sulfur-enriched MoS₂ composite as evidenced by simultaneous thermal analysis (STA) coupled with mass spectrometric (MS) analysis of evolving gaseous species (TG/DTA-MS) analysis. Such nanostructures exhibit a better adhesion of biomolecules, thus facilitating the interaction between them, as confirmed by highly effective antimicrobial action. The present study examines antimicrobial properties of hydrophilic, sulfur-enriched MoS₂ nano/microparticles as well as MoS₂-based coatings against various humans' pathogenic bacteria such as Salmonella enterica, Pseudomonas aeruginosa, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), Micrococcus luteus, and two Candida yeast strains (C. parapsilosis, C. krusei). The MoS₂-ns (40 μg mL^-1) showed over 90% killing efficiency against S. aureus MRSA bacteria and both Candida yeast when exposed for 24 h. Petal-like MoS₂ microstructures and heterostructured MoS₂/Ti and Pd/MoS₂/Ti coatings also possessed high antimicrobial potential and are considered as a promising antimicrobial agent. The MoS₂-induced production of intracellular reactive oxygen species (ROS) was evidenced by measuring the standard DCF dye fluorescence.

Keywords: Antimicrobial activity; Biofuel cells; MoS(2)/Ti hetero-structures; Molybdenum disulfide (MoS(2)); Pd nanoparticles; Reactive oxygen species.