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

Rokas Žalneravicius^a, Vaclovas Klimas^a, Algimantas Paškevicius^b, Giedre Grinciene^a, Renata Karpicz^a, Arunas Jagminas^a, Arunas Ramanavicius^a,c

Centre for Physical Sciences and Technology, Sauletekio av. 3, LT-10257 Vilnius, Lithuania.

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: Molybdenum disulfide (MoS₂), Pd nanoparticles, Antimicrobial activity, Reactive oxygen species, Biofuel cells, MoS₂/Ti hetero-structures.