We unprecedentedly report that layered MnO₂ nanosheets were in situ formed onto the surface of covalently bonded graphitic carbon nitride/reduced graphene oxide nanocomposite (g-C₃N₄/rGO), forming sheet-on-sheet structured two dimension (2D) graphitic carbon nitride/reduced graphene oxide/layered MnO₂ ternary nanocomposite (g-C₃N₄/rGO/MnO₂) with outstanding catalytic properties on thermal decomposition of ammonium perchlorate (AP). The covalently bonded g-C₃N₄/rGO was firstly prepared by the calcination of graphene oxide-guanidine hydrochloride precursor (GO-GndCl), following by its dispersion into the KMnO₄ aqueous solution to construct the g-C₃N₄/rGO/MnO₂ ternary nanocomposite. FT-IR, XRD, Raman as well as the XPS results clearly demonstrated the chemical interaction between g-C₃N₄, rGO and MnO₂. TEM and element mapping indicated that layered g-C₃N₄/rGO was covered with thin MnO₂ nanosheets. Furthermore, the obtained g-C₃N₄/rGO/MnO₂ nanocomposite exhibited promising catalytic capacity on thermal decomposition of AP. Upon addition of 2 wt % g-C₃N₄/rGO/MnO₂ ternary nanocomposite as catalyst, the thermal decomposition temperature of AP was largely decreased up by 142.5 °C, which was higher than that of pure g-C₃N₄, g-C₃N₄/rGO and MnO₂, respectively, demonstrating the synergistic catalysis of the as-prepared nanocomposite.

Novel graphitic carbon nitride/CuO (g-C₃N₄/CuO) nanocomposite was synthesized through a facile precipitation method. Due to the strong ion-dipole interaction between copper ions and nitrogen atoms of g-C₃N₄, CuO nanorods (length 200–300 nm, diameter 5–10 nm) were directly grown on g-C₃N₄, forming a g-C₃N₄/CuO nanocomposite, which was confirmed via X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Finally, thermal decomposition of ammonium perchlorate (AP) in the absence and presence of the prepared g-C₃N₄/CuO nanocomposite was examined by differential thermal analysis (DTA), and thermal gravimetric analysis (TGA). The g-C₃N₄/CuO nanocomposite showed promising catalytic effects for the thermal decomposition of AP. Upon addition of 2 wt % nanocomposite with the best catalytic performance (g-C₃N₄/20 wt % CuO), the decomposition temperature of AP was decreased by up to 105.5 °C and only one decomposition step was found instead of the two steps commonly reported in other examples, demonstrating the synergistic catalytic activity of the as-synthesized nanocomposite. This study demonstrated a successful example regarding the direct growth of metal oxide on g-C₃N₄ by ion-dipole interaction between metallic ions, and the lone pair electrons on nitrogen atoms, which could provide a novel strategy for the preparation of g-C₃N₄-based nanocomposite.

In this work, a mixing-calcination method was developed to facilely construct MXene/CuO nanocomposite. CuO and MXene were first dispersed in ethanol with sufficient mixing. After solvent evaporation, the dried mixture was calcinated under argon to produce a MXene/CuO nanocomposite. As characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and X-ray photoelectron spectra (XPS), CuO nanoparticles (60–100 nm) were uniformly distributed on the surface and edge of MXene nanosheets. Furthermore, as evaluated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the high-temperature decomposition (HTD) temperature decrease of ammonium perchlorate (AP) upon addition of 1 wt% CuO (hybridized with 1 wt% MXene) was comparable with that of 2 wt% CuO alone, suggesting an enhanced catalytic activity of CuO on thermal decomposition of AP upon hybridization with MXene nanosheets. This strategy could be further applied to construct other MXene/transition metal oxide (MXene/TMO) composites with improved performance for various applications.

Tumor-associated angiogenesis plays a critical role in the pathogenesis of cholangiocarcinoma (CCA). In this study, we examined the biological effects and molecular mechanisms of transcription factor 21 (TCF21) on CCA-associated angiogenesis. TCF21 expression was compared between 15 pairs of peritumor normal tissues and CCA tissues and also between normal bile duct epithelial cells and two CCA cell lines (QBC-939 and TFK-1) using real-time PCR and Western blot. With the use of both CCA cell lines as the model system, we stably expressed TCF21 by lentiviral transduction (Lv-TCF21). In vivo, we monitored xenograft growth from different CCA cells, measured tumor-associated angiogenesis by histological analysis, and determined the expressions and circulatory levels of VEGFA and PDGF-BB by immunohistochemistry and ELISA, respectively. In vitro, we assessed the effects of conditioned medium collected from different CCA cells on the viability, migration, and tube formation of endothelial cells and explored the significance of phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt), as well as ERK1/2 signaling in this process. TCF21 was significantly downregulated in CCA tissues or cell lines. Ectopic expression of TCF21 in CCA cells inhibited xenograft growth or tumor-associated angiogenesis in vivo and targeted the expression and secretion of proangiogenic factors, VEGFA and PDGF-BB. In vitro, the conditioned medium collected from Lv-TCF21 CCA cells significantly reduced the viability, migration, and tube formation of endothelial cells. On the molecular level, the targeting of PI3K/Akt and ERK1/2 signaling mediated the anti-angiogenic activity of TCF21. TCF21 presents growth-inhibitory and anti-angiogenic activities, and thus the elevation of TCF21 expression may provide therapeutic benefits for CCA. NEW & NOTEWORTHY Transcription factor 21 (TCF21) is downregulated in cholangiocarcinoma (CCA) tissues or cells. TCF21 inhibits the growth of xenografts derived from CCA cells. TCF21 suppresses in vivo tumor-associated angiogenesis. TCF21 targets expression and production of proangiogenic factors from CCA cells. The targeting of phosphatidylinositol 3-kinase/protein kinase B and ERK1/2 signaling mediates the anti-angiogenesis of TCF21.