Supramolecular hydrogel with tunable multi-color and white-light fluorescence from sulfato-β-cyclodextrin and aminoclay

Fullerene-polysaccharide supramolecular hydrogel displaying antioxidation/antiglycation behavior

A fullerene-polysaccharide supramolecular hydrogel was constructed by carrying out a co-assembly of fullerene@hydroxypropyl-β-cyclodextrin, chitosan and bentonite, and displayed good antioxidant and antiglycation properties, and hence showed promising cosmetics applications. Benefitting from the cyclodextrin hydrophobic cavity, hydroxypropyl-β-cyclodextrin formed a stoichiometric 2 : 1 complex with fullerene, effectively enhancing the water solubility and biological activity of fullerene, and the encapsulation ratio of the prepared fullerene was calculated to be 79%. Results of oxygen radical absorbance capacity and pyrogallol autoxidation experiments showed high antioxidant activity displayed by the fullerene@HP-β-CD inclusion complex. The supramolecular inclusion was further co-assembled, using multiple hydrogen bonds and electrostatic interactions, with chitosan and bentonite to form a supramolecular hydrogel; this hydrogel was successfully used in antiglycation, with a glycation end products inhibition rate of 43.99% at a 10% sample concentration. Therefore, the fullerene-polysaccharide ternary co-assembly supramolecular hydrogel showed good antioxidant and antiglycation abilities, and the construction of the polysaccharide supramolecular hydrogel provided a new perspective for raw materials to consider in cosmetics applications.

Multiple Effects of an Anionic Cyclodextrin Macrocycle on the Reversible Isomerization of a Photoactive Guest Dye

Understanding and controlling the reversible isomerization of photoactive molecules in order to obtain a tunable optical response is desirable for many photofunctional applications. This study describes the interesting effects of an anionic cyclodextrin host (sulfated-βCD, SCD) on the photoisomerization and protonation equilibrium of an important hemicyanine dye (trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide, DSP). The SCD host assists in unlocking the photoisomerization potential of DSP by promoting protonation of the dye. It also assists in stabilizing the cis isomer of the protonated dye, thereby significantly delaying the reverse cis to trans isomerization of DSPH⁺. Furthermore, the interplay of both hydrophobic and electrostatic interactions in the complex formation of SCD with DSPH⁺ makes the reverse cis to trans isomerization of DSPH⁺ amenable to influence by the added salt. The stimuli-responsive reversible isomerization of SCD-DSPH⁺ is an interesting case from the perspective of chemical sensing or light operated functional materials with host-guest systems.

Stochastic Binding Dynamics of a Photoswitchable Single Supramolecular Complex

In this work, a real-time precise electrical method to directly monitor the stochastic binding dynamics of a single supramolecule based on the host-guest interaction between a cyclodextrin and an azo compound is reported. Different intermolecular binding states during the binding process are distinguished by conductance signals detected from graphene-molecule-graphene single-molecule junctions. In combination with theoretical calculations, the reciprocating and unidirectional motions in the trans form as well as the restrained reciprocating motion in the cis form due to the steric hindrance is observed, which could be reversibly switched by visible and UV irradiation. The integration of individual supramolecules into nanocircuits not only offers a facile and effective strategy to probe the dynamic process of supramolecular systems, but also paves the way to construct functional molecular devices toward real applications such as switches, sensors, and logic devices.

Simultaneous determination of nitrophenol isomers based on reduced graphene oxide modified with sulfobutylether-β-cyclodextrin

The present study reports the development of an electrochemical sensor based on sulfobutylether-β-cyclodextrin modified reduced graphene oxide hybrid (SBCD-rGO) for simultaneous detection of nitrophenol isomers. First, SBCD-rGO hybrid was synthesized and detailed characterized. Afterwards, a sensor was fabricated via the modification of glassy carbon electrode (GCE) with SBCD-rGO, and its electrochemical detection performances were also investigated. Then, the constructed electrochemical sensor was applied to detect nitrophenol isomers by voltammetry analysis. The results suggested that the sensitivities were 389.26, 280.88 and 217.19 μA/mM for p-nitrophenol (p-NP), m-nitrophenol (m-NP), and o-nitrophenol (o-NP), respectively, and their corresponding detection limits were all about 0.05 μM. Significantly, the combination of voltammetry analysis with the constructed sensor and data analysis by multiple linear regression realized the simultaneous detection of nitrophenol isomers.

Cyclodextrin-Cross-Linked Hydrogels for Adsorption and Photodegradation of Cationic Dyes in Aqueous Solution

Possessing three-dimensional porous structures and tunable mechanical strengths, cyclodextrin-containing polymeric hydrogels are one of the most promising water-based adsorbent materials due to their easy availability, simple chemical modification and environmental friendliness. In this work, two kinds of hydrogels were prepared via the copolymerization with acrylic acid and vinyl-derivatized β-cyclodextrins in water. These two gels have showed good adsorption performance towards cationic dyes through the noncovalent interactions with their anionic backbones and porous network. Meanwhile, pseudo-second-order model was selected to clarify the adsorption kinetics process. Moreover, nano-scaled TiO₂ was doped into these resultant cyclodextrins-based hydrogels to achieve efficient degradation of dyes upon light irradiation. The obtained TiO₂ -loaded hydrogels could exhibit improved adsorption performance and make the adsorbed dyes photo-degraded with the decolorization rates above 95%. It can be envisioned that such cyclodextrin-based soft materials may find applications in dye clearance and water treatment.

Self-healing and acidochromic polyvinyl alcohol hydrogel reinforced by regenerated cellulose

Recently, integration of self-healing, color-tunable, sol-gel converted properties into hydrogel has attracted interest for preparing a reinforced multifunctional hydrogel. Herein, acidochromic regenerated cellulose (ARC) was incorporated into the polyvinyl alcohol/borax (PB) matrix for constructing a tough, self-healing, multicolor and sol-gel converted smart hydrogel (PB/ARC). The mechanical properties of PB/ARC hydrogel were improved after introducing ARC, which could bear a weight of 200 g and had high maximum tensile strength (6.8 times) and compressive strength (2.3 times). PB/ARC hydrogel automatically fused within 15 s after being cut and quickly recovered to the original state after being subjected to high shear strain, showing excellent self-healing ability. The color of hydrogel could be tuned between yellow and purple by altering pH values (5-12). In addition, PB/ARC hydrogel exhibited reversible sol-gel conversion in response to the change of acidity and alkalinity. This study offers a new and facile strategy for developing multifunctional smart hydrogel.

Multicolor luminescent supramolecular hydrogels based on cucurbit[8]uril and OPV derivative

Supramolecular hydrogels have received considerable attention because of their various fascinating applications. Herein, an alkyl chain-modified oligo(p-phenylenevinylene) (Py-OPV) derivative was synthesized. When assembled with cucurbit[7]uril, its fluorescence intensity was enhanced without any change in color. However, the molecules underwent J-type dimerization when encased in the cavity of cucurbit[8]uril, which possessed different emission properties based on the monomer. By simply changing the concentration of cucurbit[8]uril, the fluorescence properties of the assemblies were easily altered. In addition, luminescent supramolecular hydrogels were constructed with Py-OPV and cucurbit[8]uril based on the photopolymerization of acrylamide. By embedding the assembly in the polymer to confine it, hydrogels emitting various tones of blue light were easily constructed. The preparation method of such luminescent hydrogels provides a new reference method for the construction of specific luminescent materials.