Structural regulation of amorphous molybdenum sulfide by atomic palladium doping for hydrogen evolution.

Molybdenum sulfide materials have long been considered as attractive non-precious-metal electrocatalysts for the hydrogen evolution reaction (HER). However, comparing with the crystalline counterpart, amorphous MoSx has been less investigated previously. We here propose to increase the catalytical activity of a-MoSx by raising the reactant concentration at the catalytic interface via a chemical doping approach. The reconstruction of coordination structure of a-MoSx via Pd doping induces the formation of abundant unsaturated S atoms. Moreover, the reactant friendly catalytic interface is constructed through introducing hydrophilic groups to a-MoSx. The doped a-MoSx catalyst exhibits significantly enhanced HER activity in both acid and alkaline media.

Chitin nanocrystals stabilized liquid metal for highly stretchable and anti-freeze hydrogels as flexible strain sensor.

Conductive hydrogels show extensive applications in flexible electronics and biomedical areas, but it is a challenge to simultaneously achieve high mechanical properties, satisfied electrical conductivity, good biocompatibility, self-recovery and anti-freezing properties through a simple preparation method. Herein, chitin nanocrystals (ChNCs) were employed to encapsulate liquid metal nanoparticles (LMNPs) to ensure the dispersion stability of LMNPs in a hydrogel system composed of polyacrylamide (PAM) and polyvinyl alcohol (PVA). The synergistic effect of ChNCs-stabilized LMNPs imparts remarkable conductivity to the hydrogel, making it an effective strain sensor for human motion. With 1 % LMNPs, the composite hydrogel stretches up to 2100 %, showing excellent stretchability. Under 10 cycles of 200 % strain, hysteresis loop curves overlap, indicating outstanding fatigue resistance. The hydrogel exhibits remarkable self-recovery, enduring 1400 % deformation without rupture. In addition, its effective antifreeze properties result from immersion in a glycerol-water solvent. Even at -20 °C and 60 °C, the hydrogel maintains stable, reproducible resistance changes at 150 % tensile strain. Therefore, the high-performance conductive hydrogel containing ChNCs stabilized LM has promising applications in flexible wearable sensing devices.

Microencapsulated phase change material with chitin nanocrystals stabilized Pickering emulsion for thermal energy storage.

The leakage during the phase change process and low thermal conductivity of PCMs limit their application area. In this study, Pickering emulsion stabilized with chitin nanocrystals (ChNCs) was used to prepare paraffin wax (PW) microcapsules by forming a dense melamine-formaldehyde resin shell on the surface of droplets. The PW microcapsules were then loaded into the metal foam to endow high thermal conductivity to the composite. The PW emulsions could be formed at low concentrations of ChNCs (0.3 wt%), and the PW microcapsules exhibits a favorable thermal cycling stability and a satisfactory latent heat-storage capacity over 170 J/g. Most importantly, the encapsulation of the polymer shell not only endows the microcapsules with high encapsulation efficiency of 98.8 %, non-leakage properties under prolonged high temperature conditions, but also with high flame retardancy. In addition, the composite of PW microcapsules/copper foam shows satisfactory performance in terms of thermal conductivity, thermal storage capacity and thermal reliability, which can be used for effective temperature regulation of heat generating materials. This study provides new design strategy of natural and sustainable nanomaterials stabilized PCMs, which shows promising application in the field of energy management and thermal equipment temperature regulation.

Gold@Halloysite nanotubes-chitin composite hydrogel with antibacterial and hemostatic activity for wound healing.

Infection and healing of wounds after injury has always been an unavoidable problem in daily life, so design of a biomaterial with antibacterial and good wound healing properties is highly needed. Herein, a wound healing hydrogel dressing with halloysite clay and chitin as the main components was prepared, which combines the advantages of the biomacromolecule and clay. Halloysite nanotubes (HNTs) are extremely biocompatible clay materials with a hollow tubular structure, and the inner and outer surfaces of HNTs are composed of SiOx and AlOx layers with different charges. Au nanoparticles with diameter in 5-10 nm were filled into the HNTs' lumen to endow photothermal effect of the clay materials. Au@HNTs was then mixed with chitin solution to prepare flexible composite hydrogel by crosslinking by epichlorohydrin. The antibacterial properties, biocompatibility and hemostatic properties of the hydrogel material were investigated by antibacterial experiments, cell experiments, mouse liver and tail hemostatic experiments. After infecting the back wound of mice with Staphylococcus aureus, the hydrogel was applied to the wound to further verify the killing effect on bacteria and wound healing effect of the hydrogel material in vivo. The Au@HNTs-chitin composite hydrogel exhibits high antibacterial and hemostatic activity as well as promoting wound healing function with low cytotoxicity. This study is significant for the development of high-performance wound dressings based on two commonly used biocompatible materials, which shows promising application in wound sterilization and healing.

Cell Membrane-Coated Halloysite Nanotubes for Target-Specific Nanocarrier for Cancer Phototherapy.

Naturally-occurring halloysite nanotubes (HNTs) have many advantages for constructing target-specific delivery of phototherapeutic agents. Here, HNTs were labeled with fluorescein isothiocyanate (FITC) and loaded with the type-II photosensitizer indocyanine green (ICG) for phototherapy. HNTs-FITC-ICG was structurally stable due to presence of HNTs as the nanocarrier and protective agent. The nanocarrier was further wrapped with red blood cell membrane (RBCM) to enhance the biocompatibility. The HNTs-FITC-ICG-RBCM nanocarrier show high cytocompatibility and hemocompatibility. Due to the photothermal effect of ICG, a significant temperature rising was achieved by irradiation of the nanocarrier using 808 nm laser. The photothermal temperature rising was used to kill the cancer cells effectively. The HNTs-FITC-ICG-RBCM nanocarrier was further linked with anti-EpCAM to endow it with targeting therapy performance against breast cancer, and the anti-EpCAM-conjugated nanocarrier exhibited significantly tumor-specific accumulation. The RBCM-coated and biocompatible HNTs nanocarrier is a promising candidate for target-specific therapy of cancer.

pH/Reduction Dual-Stimuli-Responsive Cross-Linked Micelles Based on Multi-Functional Amphiphilic Star Copolymer: Synthesis and Controlled Anti-Cancer Drug Release.

Novel approach has been constructed for preparing the amphiphilic star copolymer pH/reduction stimuli-responsive cross-linked micelles (SCMs) as a smart drug delivery system for the well-controlled anti-tumor drug doxorubicin (DOX) release. The SCMs had a low CMC value of 5.3 mg/L. The blank and DOX-loaded SCMs both had a spherical shape with sizes around 100-180 nm. In addition, the good stability and well pH/reduction-sensitivity of the SCMs were determined by dynamic light scattering (DLS) as well. The SCMs owned a low release of DOX in bloodstream and normal tissues while it had a fast release in tumor higher glutathione (GSH) concentration and/or lower pH value conditions, which demonstrates their pH/reduction dual-responsiveness. Furthermore, we conducted the thermodynamic analysis to study the interactions between the DOX and polymer micelles in the DOX release process. The values of the thermodynamic parameters at pH 7.4 and at pH 5.0 conditions indicated that the DOX release was endothermic and controlled mainly by the forces of an electrostatic interaction. At pH 5.0 with 10 mM GSH condition, electrostatic interaction, chemical bond, and hydrophobic interactions contributed together on DOX release. With the low cytotoxicity of blank SCMs and well cytotoxicity of DOX-loaded SCMs, the results indicated that the SCMs could form a smart cancer microenvironment-responsive drug delivery system. The release kinetic and thermodynamic analysis offer a theoretical foundation for the interaction between drug molecules and polymer matrices, which helps provide a roadmap for the oriented design and control of anti-cancer drug release for cancer therapy.