Plasma-assisted green synthesis of SrTiO3/MoS2/MWCNTs nanohybrids for photocatalytic degradation of phenazopyridine in aqueous and smart polymeric film systems
Reza Ghamarpoor, Akram Fallah, Narges Elmi Fard, Somayeh Salehfekr
Abstract
In this study, an integrated green synthesis approach was developed to fabricate multifunctional SrTiO 3 /MoS 2 /MWCNTs (SMM) nanohybrids for photocatalytic environmental remediation. The process combined plasma-assisted activation, bio-derived precursors, and hydrothermal strategies to achieve high structural control, enhanced surface functionality, and eco-compatibility. Initially, multi-walled carbon nanotubes (MWCNTs) were synthesized via a novel plasma-assisted bio-CVD route using humic acid as a sustainable carbon source. Few-layer MoS 2 nanosheets were subsequently grown on functionalized MWCNTs through a bio-hydrothermal process employing L-cysteine and ammonium molybdate, with dielectric barrier discharge (DBD) plasma pre-treatment to introduce active defect sites. The resulting MoS 2 /MWCNT hybrids were uniformly assembled onto SrTiO 3 nanoparticles via electrostatic self-assembly, followed by secondary hydrothermal growth to ensure strong interfacial coupling. This synergistic strategy enabled the formation of a hierarchical heterostructure with optimized electron transport pathways, visible-light activity, and catalytic functionality. The synthesized nanohybrids were further embedded into epoxy matrices and polymeric films, enabling the development of smart coatings with light-driven pollutant degradation capability. The SMM nanocomposite demonstrates superior photocatalytic degradation of phenazopyridine under UV (95%) and visible light (98%), with a band gap of 2.78 eV. The photocatalytic charge transfer mechanism operates via a Z-scheme under UV light and conventional electron transfer under visible light, facilitated by the synergistic interaction of MoS 2 , MWCNTs, and SrTiO 3 , ensuring efficient charge separation and minimal recombination. Furthermore, incorporating SMM into epoxy resin significantly improves tensile strength, elongation, stiffness, and toughness compared to pure epoxy. Color change analysis (Δb*) under UV and visible light shows significant shifts compared to pure epoxy (i.e., 4.1 UV, 3.5 visible) and other individual composites, highlighting SMM’s (i.e., 41 UV and 45 visible) superior photocatalytic activity. These findings demonstrate the promising future of multifunctional nanohybrid materials in sustainable environmental technologies, paving the way for the next generation of smart coatings and pollution control solutions.