Recent Progress in Transition-Metal Sulfide Catalyst Regulation for Improved Oxygen Evolution Reaction

Chitosan, which is derived from chitin, is the only known natural alkaline cationic polymer. Chitosan is a biological material that can significantly improve the living standard of the country. It has excellent properties such as good biodegradability, biocompatibility, and cell affinity, and has excellent biological activities such as antibacterial, antioxidant, and hemostasis. In recent years, the demand has increased significantly in many fields and has huge application potential. Due to the poor water solubility of chitosan, its wide application is limited. However, chemical modification of the chitosan matrix structure can improve its solubility and biological activity, thereby expanding its application range. The review covers the period from 1996 to 2022 and was elaborated by searching Google Scholar, PubMed, Elsevier, ACS publications, MDPI, Web of Science, Springer, and other databases. The various chemical modification methods of chitosan and its main activities and application research progress were reviewed. In general, the modification of chitosan and the application of its derivatives have had great progress, such as various reactions, optimization of conditions, new synthetic routes, and synthesis of various novel multifunctional chitosan derivatives. The chemical properties of modified chitosan are usually better than those of unmodified chitosan, so chitosan derivatives have been widely used and have more promising prospects. This paper aims to explore the latest progress in chitosan chemical modification technologies and analyze the application of chitosan and its derivatives in various fields, including pharmaceuticals and textiles, thus providing a basis for further development and utilization of chitosan.

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Progress in Research of Chitosan Chemical Modification Technologies and Their Applications

Optimizing electron distribution and expediting electron transfer efficiency are two of the major strategies for developing non-noble difunctional catalysts in the overall water splitting (OWS). Defect engineering is an emerging technology in catalysis field, and introducing vacancy defects into the crystal structure can promote the electrocatalytic water splitting performance. Hence, the 3D spinel-structured Co 3 O 4 or Co 3 S 4 nanoflowers with anion vacancy are synthesized on nickel foam (V o -Co 3 O 4 @NF, V s -Co 3 S 4 @NF) and compared as electrodes for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Notably, V s -Co 3 S 4 @NF requires merely overpotential of 245 mV to reach 100 mA·cm -2 for OER, 45 mV to reach 10 mA·cm -2 for HER, which exhibit an excellent catalytic activity in alkaline electrolyte. In addition, using V s -Co 3 S 4 @NF as bifunctional catalyst to drive OWS, the current density of 20 mA·cm -2 is reached with a cell voltage of only 1.53 V, along with good stability for successive 200 h test. The sulfur vacancies-rich Co 3 S 4 nanoflowers were grown on nickel foam by hydrothermal and reduction strategies (V s -Co 3 S 4 @NF), and assembled as an efficient bifunctional electrocatalysts for overall water splitting (OWS), which merely required 1.53 V cell voltage to reach 20 mA·cm -2 . More importantly, the V s -Co 3 S 4 @NF act as both the anode and cathode were assembled into a cell, which can also be powered by a self-assembly commercial 1.5 V AA battery, indicating that V s -Co 3 S 4 @NF has potential application in water splitting. • A hydrothermal and reduction strategies is proposed to synthesize sulfur vacancies. • The synergistic effect of sulfur vacancy and the self-assembled 3D structure. • Required only 1.53 V to drive 20 mA·cm -2 for overall water splitting. • Electrocatalytic water splitting by a single self-assembly 1.5 V AA battery. 

Sulfur vacancies engineered self-supported Co3S4 nanoflowers as an efficient bifunctional catalyst for electrochemical water splitting

Recent progressions in biomedical and pharmaceutical applications of chitosan nanoparticles: A comprehensive review.

The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. This review article outlines synthetic techniques, basic characteristics, inherent properties, biomedical applications, and ubiquitous challenges associated to quaternized chitosan.

https://www.mdpi.com/2073-4360/13/15/2514/pdf

Biomedical Applications of Quaternized Chitosan

Immunostimulatory effect of chitosan and quaternary chitosan: A review of potential vaccine adjuvants

Restricted by the sluggish kinetics of the oxygen evolution reaction (OER), efficient OER catalysis remains a challenge. Here, a facile strategy was proposed to prepare a hollow dodecahedron constructed by vacancy-rich spinel Co3S4 nanoparticles in a self-generated H2S atmosphere of thiourea. The morphology, composition, and electronic structure, especially the sulfur vacancy, of the cobalt sulfides can be regulated by the dose of thiourea. Benefitting from the H2S atmosphere, the anion exchange process and vacancy introduction can be accomplished simultaneously. The resulting catalyst exhibits excellent catalytic activity for the OER with a low overpotential of 270 mV to reach a current density of 10 mA cm–2 and a small Tafel slope of 59 mV dec–1. Combined with various characterizations and electrochemical tests, the as-proposed defect engineering method could delocalize cobalt neighboring electrons and expose more Co2+ sites in spinel Co3S4, which lowers the charge transfer resistance and facilitates the formation of Co3+ active sites during the preactivation process. This work paves a new way for the rational design of vacancy-enriched transition metal-based catalysts toward an efficient OER.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c01423

Engineering Sulfur Vacancies in Spinel-Phase Co3S4 for Effective Electrocatalysis of the Oxygen Evolution Reaction

Polycaprolactone (PCL) has been widely used as a scaffold material for tissue engineering. Reliable applications of the PCL scaffolds require overcoming their native hydrophobicity and obtaining the sustained release of signaling factors to modulate cell growth and differentiation. Here, we report a surface modification strategy for electrospun PCL nanofibers using an azide-terminated amphiphilic graft polymer. With multiple alkylation and pegylation on the side chains of poly-L-lysine, stable coating of the graft polymer on the PCL nanofibers was achieved in one step. Using the azide-alkyne “click chemistry”, we functionalized the azide-pegylated PCL nanofibers with dibenzocyclooctyne-modified nanocapsules containing growth factor, which rendered the nanofiber scaffold with satisfied cell adhesion and growth property. Moreover, by specific immobilization of pH-responsive nanocapsules containing bone morphogenetic protein 2 (BMP-2), controlled release of active BMP-2 from the PCL nanofibers was achieved within 21 days. When bone mesenchyme stem cells were cultured on this nanofiber scaffold, enhanced ossification was observed in correlation with the time-dependent release of BMP-2. The established surface modification can be extended as a generic approach to hydrophobic nanomaterials for longtime sustainable release of multiplex signaling proteins for tissue engineering.

Surface Modification of Polycaprolactone Scaffold With Improved Biocompatibility and Controlled Growth Factor Release for Enhanced Stem Cell Differentiation

Immunostimulatory effect of quaternary degree and acetyl group of quaternized chitosan on macrophages RAW 264.7

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Immunostimulatory effect of chitosan and quaternary chitosan: A review of potential vaccine adjuvants

Engineering Sulfur Vacancies in Spinel-Phase Co3S4 for Effective Electrocatalysis of the Oxygen Evolution Reaction

Surface Modification of Polycaprolactone Scaffold With Improved Biocompatibility and Controlled Growth Factor Release for Enhanced Stem Cell Differentiation

Immunostimulatory effect of quaternary degree and acetyl group of quaternized chitosan on macrophages RAW 264.7