Engineering β-Cyclodextrin Gels with Nanoparticles: Tunable Assembly and Multifunctional Applications

Abstract

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 created composite gels that show improved selectivity and sensitivity for cationic dye detection.