Composites of Indigenous Nanostructured Layered Materials

Abstract

Naturally occurring nanostructured layered materials are receiving increased attention from researchers in academia and industries owing to their unique characteristic features including naturally controlled nano-scale particle size, higher surface area, cheap, availability, biocompatibility etc. Surface modification o f the nanomaterials with various natural and synthetic materials largely extends their applicability in various fields such as packaging, coating, water purification, antimicrobial agents, cancer nanotherapy etc. However, the potential o f nanostructured kaolinite having layered aluminosilicate structure for diversified applications has largely been unexplored in Bangladesh ahhough it is widely available in the country. In this doctoral research, we have thoroughly investigated the effect o f the modification o f kaolinite in terms o f various physio-chemical properties. Here, we have prepared four different types of composites using different proportions o f kaolinite with starch, choline chloride, poly(methyimethacrylate), and inorganic salt solutions separately. Firstly, we have successfiilly fabricated nanocomposite films through incorporating kaolinite into potato starch. Secondly, self-standing porous composite beads were prepared by modification o f kaolinite with choline chloride. Thirdly, choline chloride-modified kaolinite was incorporated as fillers for preparing nanocomposite films using poly(methylmethacrylate) (PMMA) as a matrix. Finally, metal oxides [c.f. zinc oxide (ZnO), ferric oxide {Fe203)] were anchored onto kaolinite surface via heat treatment. In order to confirm the successfiil modification o f kaolinite, we employed several analytical techniques such as attenuated total reflectance infra-red analysis (ATR-IR), x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). Various useful mechanical properties o f the films were investigated widi a universal testing machine (UTM), whereas, thermogravimetric analysis (TGA) was performed to investigate the improvement in thermal stability. We carefully observed that the incorporation o f both virgin and modified kaolinite into natural and synthetic polymer dramatically improved thermal and mechanical properties o f the films. These films are expected to find widespread applications in packaging industries. Modification o f kaolinite with choline chloride led to the development o f a novel self-standing porous composite bead, which displayed unique fiUration ability for anionic azo dyes (Remazol Red) at alkaline pH. The dye filtration performance was continuously monitored using a UV-Vis spectrophotometer. We strongly believe that this advanced material might contribute significantly in treating effluents from textile indusfries. Lastly, metal oxide-loaded kaolinite showed significantly improved antibacterial action against selective bacteria (Salmonella pullorum Escherichia coli. Pseudomonas aeruginosa) and cytotoxic effect against cancer cells (HeLa and BHK-21). Due to this promising performance, metal oxide-loaded kaolinite might find potential biomedical applications. In conclusion, we firmly state that this study would open new doors for the development o f kaolinite-based technology for the advancement o f materials science.