No abstract

Ga2O3 is emerging as an interesting semiconductor for high-power electronics and solar-blind ultraviolet photodetectors because of its ultrawide bandgap and high breakdown field. To fully extend its applications in optoelectronics, it is highly desirable to fabricate a p–n heterojunction. In this work, we report detailed investigations on the epitaxial growth and interface properties of a p–n heterojunction consisting of wide bandgap NiO and β-phase Ga2O3. We show that the NiO(111) layer can be grown on β-Ga2O3(01) thin films, with an epitaxial relationship of NiO(111)||β-Ga2O3(01) and NiO{110}||β-Ga2O3(12). The p–n diode exhibits a large current rectification ratio of about 6 orders of magnitude at ±2.0 V. A detailed X-ray photoemission spectroscopy study reveals a “staggered” band alignment with valence band offsets of 2.1 eV. More interestingly, a large upward built-in potential of 1.1 eV for β-Ga2O3 is observed near the interface region. The valence band offset and large built-in potential formed at the heterointerface provide advantageous energetics for the separation and migration of photogenerated excitons, of particular interest for self-powered solar-blind ultraviolet photodetection.

We demonstrate the 2-D anisotropic formation of ultrathin free-floating Pt nanoplates from the assembly of small nanocrystals using T7 peptide (Ac-TLTTLTN-CONH 2 ). As-formed nanoplates are rich in grain boundaries that can promote their catalytic activities. Furthermore, we demonstrate that a minor number of Pd atoms can selectively deposit on and stabilize the grain boundaries, which leads to enhanced structure stability. The Pd-enhanced Pt polycrystal nanoplates show great oxygen reduction reaction activities with 15.5 times higher specific activity and 13.7 times higher mass activity than current state-of-the-art commercial Pt/C electrocatalysts as well as 2.5 times higher mass activity for hydrogen evolution reaction compared with Pt/C.

The cinobufagin (CB) has a broad spectrum of cytotoxicity to inhibit cell proliferation of various human cancer cell lines, but the molecular mechanisms still remain elusive. Here we observed that CB inhibited the cell proliferation and tumor growth, but induced cell cycle arrest and apoptosis in a dose-dependent manner in non-small cell lung cancer (NSCLC) cells. Treatment with CB significantly increased the reactive oxygen species but decreased the mitochondrial membrane potential in NSCLC cells. These effects were markedly blocked when the cells were pretreated with N-acetylcysteine, a specific reactive oxygen species inhibitor. Furthermore, treatment with CB induced the expression of BAX but reduced that of BCL-2, BCL-XL and MCL-1, leading to an activation of caspase-3, chromatin condensation and DNA degradation in order to induce programmed cell death in NSCLC cells. In addition, treatment with CB reduced the expressions of p-AKTT308 and p-AKTS473 and inhibited the AKT/mTOR signaling pathway in NSCLC cells in a time-dependent manner. Our results suggest that CB inhibits tumor growth by inducing intrinsic apoptosis through the AKT signaling pathway in NSCLC cells.

Systematic control of grain boundary densities in various platinum (Pt) nanostructures was achieved by specific peptide-assisted assembly and coagulation of nanocrystals. A positive quadratic correlation was observed between the oxygen reduction reaction (ORR) specific activities of the Pt nanostructures and the grain boundary densities on their surfaces. Compared to commercial Pt/C, the grain-boundary-rich strain-free Pt ultrathin nanoplates demonstrated a 15.5 times higher specific activity and a 13.7 times higher mass activity. Simulation studies suggested that the specific activity of ORR was proportional to the resident number and the resident time of oxygen on the catalyst surface, both of which correlate positively with grain boundary density, leading to improved ORR activities.