Highly porous cryogels loaded with bimetallic nanoparticles as an efficient antimicrobial agent and catalyst for rapid reduction of water-soluble organic contaminants

Abstract

The development of robust materials possessing simultaneously antibacterial and catalytic activities for the reduction and removal of organic pollutants from wastewater with enhanced efficacy has received unwavering interest. Herein, highly porous and thermo-responsive cryogels of poly(N-isopropylacrylamide-co-acryamido-2-methylpropane sulfonic acid) have been fabricated via redox-initiated cryo-polymerization. Silver/gold bimetallic nanoparticles were introduced into a bare cryogel through thermal reduction of metal salts. The fabricated bare cryogels and bimetallic integrated cryogel were confirmed with different techniques including fourier transform infrared spectroscopy. The crystallinity of bare cryogels and bimetallic nanoparticles inside cryogel was examined by using powder X-ray diffraction. Thermo-gravimetric analysis confirmed that bimetallic nanoparticle loaded cryogels were thermally more stable than bare cryogels. The macro-porosity of cryogels before and after loading bimetallic nanoparticles were studied by using scanning electron microscopy. Energy dispersive X-ray and X-ray photoelectron spectroscopy were implemented, confirming the presence of metal elements in the synthesized bimetallic hybrid cryogel. Furthermore, the uniform distribution of silver and gold nanoparticles in cryogel was examined with transmission electron microscopy. The fabricated bimetallic nanoparticle loaded cryogel exhibited high antibacterial activities against E. coli and S. aureus as well as the good catalytic capacity for the rapid reduction of p-nitrophenol and rhodamine B. Catalytic activity was also examined at various temperatures, different pH values and catalyst amounts. The activation energy (Ea = 34.41 kJ mol-1), enthalpy change (ΔH = - 31.92 kJ mol-1) and entropy change (ΔS = −145.19 J mol-1 k-1) of catalytic reduction activation were determined using Arrhenius and Eyring equations. The catalytic performance of bimetallic nanoparticle loaded cryogel was also examined in pure water and tap water. The fabricated bimetallic catalyst was highly stable up to five consecutive cycles without any change in their catalytic performance.