Engineering β-cyclodextrin gels with nanoparticles: tunable assembly and multifunctional applications

Hierarchical gels were developed through the controlled interaction of β-cyclodextrin in good-poor solvent systems, incorporating small amounts of various nanoparticles and nanoclays. These new hierarchical microstructures form through the side-by-side aggregation of β-cyclodextrin lamellar plates. They are stabilized by non-covalent interactions and facilitated by negatively charged nanoparticles or nanoclays. A systematic variation of nanoparticle concentration and solvent composition revealed that gelation occurs even at low concentrations of nanoparticles or nanoclays, significantly altering the typical phase behavior of β-cyclodextrin in DMF-water mixtures. Interestingly, a variety of differently shaped, negatively charged nanoparticles-including nanorods, nanodisks, and nanoplatelets-supported similar hierarchical self-assembly. The smart gels exhibit responsiveness to both temperature and salt, effectively removing cationic dyes. Specifically, temperature-induced phase transitions were demonstrated using three different types of nanoparticles, highlighting their potential use as temperature sensors. By combining β-cyclodextrin with nanoparticles such as cellulose nanocrystals, montmorillonite, and LAPONITE®, we developed composite gels that show improved selectivity and sensitivity for cationic dye detection.