Defect-Engineered MoS₂ Nanostructures for Reactive Oxygen Species Generation in the Dark: Antipollutant and Antifungal Performances

Abstract

Meticulous surface engineering of layered structures toward new functionalities is a demanding challenge to the scientific community.Here, we introduce defects on varied MoS 2 surfaces by suitable doping of nitrogen atoms in a sulfur-rich reaction environment, resulting in stable and scalable phase conversion. The experimental characterizations along with the theoretical calculations within the framework of density functional theory establish the impact of nitrogen doping on stabilization of defects and reconstruction of the 2H to 1T phase. The as-synthesized MoS 2 samples exhibit excellent dye removal capacity in the dark, facilitated by a synergistic effect of reactive oxygen species (ROS) generation and adsorption. Positron annihilation spectroscopy and electron paramagnetic resonance studies substantiate the role of defects and associated sulfur vacancies toward ROS generation in the dark. Further, on the basis of its ample ROS generation in the dark and in the light, the commendable antimicrobial activity of the prepared MoS 2 samples against fungal pathogen Alternaria alternata has been demonstrated. Thus, the present study opens up a futuristic avenue to develop newer functional materials through defect engineering by suitable dopants toward superior performances in environment issues.

Oxygen, nitrogen co-doped molybdenum disulphide nanoflowers for an excellent antifungal activity

“…47 This red shift possibly ensues from the lattice distortion invoked by oxygen and nitrogen doping in the samples. This is further reaffirmed by the disorder-prompted symmetry breaking of the E 1 2g mode, causing it to split into the 1+ 2g and E 1À 2g components, 37,48 as shown in Fig. S2 (ESI †).…”

“…NH 3 evolution as a by-product in the thermal decomposition of thiourea accounts for the nitrogen atoms being doped within the MoS 2 lattice, which according to our previous study, are most likely to occupy the S-sites in the Mo-rich limit. 37 However, in order to ensure the incorporation of oxygen into the MoS 2 lattice in addition to the nitrogen atoms, the reaction time had to be substantially brought down to 18 hours. The reduced reaction time effectively rendered the reaction process insufficient for the complete conversion of MoO 3 to MoS 2 .…”

“…However, the d 002 value calculated from the fringes of NMS agrees well with the reported values of 2H-MoS 2 . 37 In addition to this, X-ray diffraction (XRD) studies were carried out on the synthesized samples in order to figure out the crystal structure. The XRD pattern for NMS, as shown in Fig.…”

“…40 Nonetheless, the XRD peaks in ONMS corresponding to the (102) and (110) planes match with those of 2H-MoS 2 . 37 The surface area and porosity of the synthesized samples were ascertained by the adsorption-desorption studies of nitrogen. The isotherm plots for ONMS and NMS are shown in Fig.…”

“…36 However, in all these cases, the bactericidal activities were observed to be engendered by light-dependent stimulations, which would therefore wholly restrain the scope of application of these antimicrobials for disinfection in implantable medical devices. In our previous work, 37 we have shown that the defect sites, which are relatively abundant in MoS 2 , can be advantageously manipulated through nitrogen doping to make them suitable for the generation of reactive oxygen species (ROS) in dark as well, thereby invoking antifungal properties within it. Therefore, it was found that the advantageous design of the material in an appropriate way holds the key to attain success in developing powerful antifungals from MoS 2 nanostructures; this is a relatively new and interesting field of study that requires intensive research work.…”