The reactive oxygen species (ROS)-induced inflammatory microenvironment and impaired angiogenesis severely hinder wound healing. Traditional wound dressings fail to address these complex pathological conditions simultaneously. Therefore, the development of novel wound treatment strategies is highly desirable. Herein, carbon dot (CD) nanozymes with a photothermal conversion efficiency of 38.51% and superoxide dismutase-like activity of 13,577 U mg−1 are embedded in polyvinyl alcohol (PVA) to fabricate a multifunctional PVA/CDs hydrogel dressing. The PVA/CDs hydrogel effectively relieves oxidative stress in vitro through scavenging excessive ROS. Under 808 nm near-infrared irradiation, the tunable photothermal response of CDs enables the PVA/CDs hydrogel to exert potent antibacterial activity in vitro through high-temperature photothermal bacterial killing (∼77°C), while mild photothermal heating (∼40°C) promotes the proliferation of human umbilical vein endothelial cells. In a female Kunming mouse model of skin wounds, the PVA/CDs hydrogel demonstrates a significantly accelerated healing process by maintaining a moist microenvironment, alleviating inflammation, and promoting angiogenesis. Furthermore, the PVA/CDs hydrogel exhibits good biocompatibility, supporting its potential as a multifunctional platform for wound healing.
A counterintuitive peak in the in-plane thermal conductivity (κ) of the top layer graphene in twisted bilayer graphene (TBG) was reported at a strain of 0.25%. Without strain, the periodic compressive-tensile combined stress field (σx < 0, σy > 0) is found to govern the dependence of the in-plane κ on the twist angle by deflecting the heat flux, leading to an apparent nonmonotonic dependence of κ on the twist angle. When strain is applied, κ shows an unconventional nonmonotonic evolution—first increasing and then decreasing—which arises from a competition between two distinct mechanisms. On one hand, tensile strain reduces the compressive-tensile combined stress field, and this reduction weakens phonon scattering and prolongs the phonon lifetime. On the other hand, excessive strain induces lattice distortion and longitudinal phonon softening, which results in a decrease of κ. The interplay between these two opposing effects ultimately leads to the anomalous strain-dependent behavior of κ. This work presents a new approach to designing thermal functional devices through torsion and strain engineering.
