Electrical devices generate heat at work. The heat should be transferred away immediately by a thermal manager to keep proper functions, especially for high-frequency apparatuses. Besides high thermal conductivity (K), the thermal manager material requires good foldability for the next generation flexible electronics. Unfortunately, metals have satisfactory ductility but inferior K (≤429 W m K ), and highly thermal-conductive nonmetallic materials are generally brittle. Therefore, fabricating a foldable macroscopic material with a prominent K is still under challenge. This study solves the problem by folding atomic thin graphene into microfolds. The debris-free giant graphene sheets endow graphene film (GF) with a high K of 1940 ± 113 W m K . Simultaneously, the microfolds render GF superflexible with a high fracture elongation up to 16%, enabling it more than 6000 cycles of ultimate folding. The large-area multifunctional GFs can be easily integrated into high-power flexible devices for highly efficient thermal management.

Second harmonic generation (SHG) of two-dimensional (2D) layered materials has attracted immense research interests due to the abilities of photon generation, manipulation, transmission, detection, and imaging for the applications of modern on-chip nanophotonic devices. Some layered materials with broken inversion symmetry associated with their 2D nature enable the development of nanophotonic and nanooptoelectronic devices based on the second harmonic generation effect. Recently, many 2D materials with broken inversion symmetry have been discovered, which not only exhibit SHG quantum effects but also greatly promote the development of nanophotonics. In this review, we review the recent developments of all 2D SHG materials, including the graphene-like family, transition metal dichalcogenides, IIIA-VIA compounds and others. We focus on their fabrication, structural characteristics, and generating mechanism and basic characteristics of SHG, associated with the main strategies to tune, modulate, and enhance the SHG of 2D materials. Additionally, several practical applications and possible future research directions of 2D material-based SHG are discussed.

Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) are a promising new therapeutic option for myocardial infarction (MI). The tissue matrix metalloproteinase inhibitor 2, also known as TIMP2, is a member of the tissue inhibitor family of metalloproteinases. Since TIMP2-mediated inhibition of matrix metalloproteinases (MMPs) is a key determinant of post-MI remodeling, we analyzed the therapeutic effects of exosomes derived from TIMP2-overexpressing hucMSCs (huc-exoTIMP2) on the MI rat model. The huc-exoTIMP2 significantly improved in vivo cardiac function as measured by echocardiography and promoted angiogenesis in MI injury. It also restricted extracellular matrix (ECM) remodeling, as indicated by the reduced collagen deposition. In addition, huc-exoTIMP2 administration increased the in situ expression of the antiapoptotic Bcl-2 and decreased that of the proapoptotic Bax and pro-caspase-9 in the infracted myocardium. Meanwhile, huc-exoTIMP2 upregulated superoxide dismutase (SOD) as well as glutathione (GSH) and decreased the malondialdehyde (MDA) level in MI models. In vitro huc-exoTIMP2 pretreatment could inhibit H2O2-mediated H9C2-cardiomyocyte apoptosis and promote human umbilical vein endothelial cell (HUVEC) proliferation, migration, and tube formation, as well as decrease TGFβ-induced MMP2, MMP9, and α-SMA secretion by cardiac fibroblasts (CFs). Besides that, huc-exoTIMP2 pretreatment also increased the expression of Akt phosphorylation in the infarcted myocardium, which may relate to a high level of secreted frizzled-related protein 2 (Sfrp2) in huc-exoTIMP2, indicating a mechanistic basis of its action. Importantly, Sfrp2 knockdown in huc-exoTIMP2 abrogated the protective effects. Taken together, huc-exoTIMP2 improved cardiac function by alleviating MI-induced oxidative stress and ECM remodeling, partly via the Akt/Sfrp2 pathway.

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