Facile preparation of agarose–chitosan hybrid materials and nanocomposite ionogels using an ionic liquid via dissolution, regeneration and sol–gel transition

Abstract

We report simultaneous dissolution of agarose (AG) and chitosan (CH) in varying proportions in an ionic liquid (IL), 1-butyl-3-methylimidazolium chloride [C₄mim][Cl]. Composite materials were constructed from AG–CH–IL solutions using the antisolvent methanol, and IL was recovered from the solutions. Composite materials could be uniformly decorated with silver oxide (Ag₂O) nanoparticles (Ag NPs) to form nanocomposites in a single step by in situ synthesis of Ag NPs in AG–CH–IL sols, wherein the biopolymer moiety acted as both reducing and stabilizing agent. Cooling of Ag NPs–AG–CH–IL sols to room temperature resulted in high conductivity and high mechanical strength nanocomposite ionogels. The structure, stability and physiochemical properties of composite materials and nanocomposites were characterized by several analytical techniques, such as Fourier transform infrared (FTIR), CD spectroscopy, differential scanning colorimetric (DSC), thermogravimetric analysis (TGA), gel permeation chromatography (GPC), and scanning electron micrography (SEM). The result shows that composite materials have good thermal and conformational stability, compatibility and strong hydrogen bonding interactions between AG–CH complexes. Decoration of Ag NPs in composites and ionogels was confirmed by UV-Vis spectroscopy, SEM, TEM, EDAX and XRD. The mechanical and conducting properties of composite ionogels have been characterized by rheology and current–voltage measurements. Since Ag NPs show good antimicrobial activity, Ag NPs –AG–CH composite materials have the potential to be used in biotechnology and biomedical applications whereas nanocomposite ionogels will be suitable as precursors for applications such as quasi-solid dye sensitized solar cells, actuators, sensors or electrochromic displays.