Intriguing role of novel ionic liquids in stochastic degradation of chitosan

Carboxymethyl chitosan-quercetin conjugate: A sustainable one-step synthesis and use for food preservation

Bioactive polysaccharide, carboxymethyl chitosan-quercetin (CMCS-q) was prepared by a one-step reaction utilizing Schiff base chemistry. Notably, the presented conjugation method involves neither radical reactions nor auxiliary coupling agents. Physicochemical properties and bioactivity of the modified polymer were studied and compared to those of the pristine carboxymethyl chitosan, CMCS. The modified CMCS-q demonstrated antioxidant activity by TEAC assay and antifungal activity by inhibiting spore germination of plant pathogen Botrytis cynerea. Then, CMCS-q was applied as an active coating on fresh-cut apples. The treatment resulted in enhanced firmness, inhibited browning and improved microbiological quality of the food product. The presented conjugation method allows retaining antimicrobial and antioxidant activity of quercetin moiety in the modified biopolymer. This method can be further used as a platform for binding ketone/aldehyde-containing polyphenols and other natural compounds to form various bioactive polymers.

Synthesis of Se polysaccharide catalyzed by sulfonic acid functionalized ionic liquids: Synergism effect of anion/cation

The rational design and construction of controllable selenylation strategy are important for the study on the structure-activity relationship of Se polysaccharides. Herein, selenized Artemisia sphaerocephala polysaccharides (SePASs) were synthesized by using sulfonic acid functionalized ionic liquids (SFILs) as catalysts in order to study the regulation of the cation/anion constitute on the selenylation efficiency and Se polysaccharide structure. Impressively, SFILs could promote the efficient substitution of seleno-group on the polysaccharide backbone through the synergistic catalysis by cation/anions (Se content up to 5582.7 μg/g). Further, reaction mechanism and potential dissolution effect was supported by DFT calculation and polarized light microscopy. ¹³C NMR and FT-IR spectra analysis of SePASs exhibited that selenite existed in polysaccharides and the substitution position occured at C-6. SEC-MALLS, monosaccharide composition results revealed that strong acidity of SFILs lead to the driving forces toward low molecular mass polysaccharide fragments and synergistic effect of anion/cations in SFILs (-SO₃H group of cations as proton donor, anions as nucleophile) showed regulation on average molecular mass. In addition, the strong attractions between the seleno-groups generated agglomeration of polysaccharide chain, which was proved by applying AFM analysis. Therefore, this work provided a new insight for manipulate Se content and M_W of Se polysaccharides.

Multi-functionalized carbon aerogels derived from chitosan

Carbon aerogels are prepared by a thermal treating-freeze drying approach from chitosan, with glycine hydrochloride ionic liquid (IL) acting as solvent and nitrogen source. Different post-treatments such as ball milling and high temperature carbonization are employed to functionalize the obtained carbon aerogels with tuned properties, making it promising candidates as fluorescence material (NACs-Q), electrode material (FDC-800) and catalyst support (NAC_Pd-C). NACs-Q is water-soluble quantum dot with average particle sizes of 3.8 nm, presenting excitation-/emission-independent and pH-sensitive properties, which could be used as sensor for testing acetone vapor or an "on-off-on" sensor for detections of Fe³⁺ and vitamin C in fruits. FDC-800 exhibits fluffy lamellar structure with developed micro-mesopores and nitrogen-containing groups on their surfaces, which is beneficial for building flexible solid-state supercapacitor with excellent performance, delivering a capacitance of 208F/g at 0.5 A/g, and achieving an energy density of 7.2 W h/kg at a power density of 50 W/kg. Moreover, NAC_Pd-C can be used as catalyst for phenol hydrogenation, and phenol conversion of 100% with cyclohexanone selectivity of 98.3% is achieved, due to the synergetic effects of the Pd active-site, the N-containing groups, and the Lewis acid sites on the support.