Achieving good stability while maintaining excellent properties is one of the main challenges for enhancing the competitiveness of luminescent perovskite CsPbX 3 (X=Cl, Br, I) nanocrystals (NCs). Here, we propose a facile strategy to synthesize ceramic-like stable and highly luminescent CsPbBr 3 NCs by encapsulating them into silica derived from molecular sieve templates at high temperature (600-900 o C). The obtained CsPbBr 3 -SiO 2 powders not only show high photoluminescence quantum yield (~71%), but also show an exceptional stability comparable to the ceramic Sr 2 SiO 4 :Eu 2+ green phosphor. They can maintain 100% of their photoluminescence value under illumination on blue light-emitting diodes (LEDs) chips (20 mA, 2.7 V) for 1000 h, and can also survive in a harsh hydrochloric acid aqueous solution (1 M) for 50 days. We believe that the above robust stabilities will significantly enhance the potential of perovskite CsPbX 3 NCs to be practically applied in LEDs and backlight displays.
A series of graphene oxide (GO)−cadmium sulfide (CdS) nanocomposites were fabricated via a facile precipitation process by using Cd(Ac) 2 , Na 2 S, and prefabricated GO as raw materials. The obtained GO−CdS nanocomposites are composed of CdS nanoparticles with an average diameter of ca.10 nm, which are well dispersed and immobilized on GO sheets. By using Na 2 S/Na 2 SO 3 as sacrificial reagent, the GO−CdS nanocomposites exhibit higher photoactivity for hydrogen production than the bare CdS under visiblelight irradiation. Among various composite photocatalysts prepared, 5 wt % GO−CdS shows maximum hydrogen production efficiency. Our findings demonstrate that the coupled GO can serve as CdS supporting matrix, cocatalyst, and electron acceptor for effective charge separation, and therefore provide an inexpensive means to achieve high-performance visible-light-driven photocatalysts for hydrogen production without noble metal-loading.
Singlet oxygen ( 1 O 2 ) is considered one of the most effective and selective oxygen agents. However, it is always obtained with the help of heavy atoms in the photosensitizers to sensitize 3 O 2 . Herein, metal−nitrogen (M−Nx) doped 1 O 2 photosensitizers were readily prepared from metal−nitrogen complex. Their relative metal centers (e.g., Co) chelated with the N/C moiety (Co−Nx/C) provide the primary active sites for 1 O 2 generation and selective oxidation. The structures of Co−Nx active sites are investigated by scanning and transmission electron microscopy and X-ray photoelectron, Fourier transform infrared, and X-ray absorption fine structure spectroscopy. Their functions for 1 O 2 generation are confirmed by electrons spin resonance, 1 O 2 emission, KSCN poisoning test, and H 2 SO 4 etching test. These Co−Nx photosensitizers show excellent selective photooxidation abilities for 1,5-dihydroxynaphthalene after irradiation by a light-emitting diode lamp. After simple concentration and filtration, it is easy to obtain the pure product (juglone), which is confirmed by 1 H NMR spectroscopy. On the basis of density functional theory calculations, metal (e.g., Co) chelated with N/C moiety, especially for the Co−pyridinic N structure, could effectively reduce the singlet−triplet energy gap (ΔE ST ). It is speculated that this strategy for lowering ΔE ST could benefit intersystem crossing from the singlet state to the triplet state and efficient sensitization of 3 O 2 (triplet state) into 1 O 2 for selective photooxidation.
Drug resistance of mutations V32I, G48V, I50V, I54V, and I84V in HIV-1 protease (PR) was found in clinical treatment of HIV patients with the drug amprenavir (APV). In order to elucidate the molecular mechanism of drug resistance associated with these mutations, the thermodynamic integration (TI) and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) methods were applied to calculate binding free energies of APV to wild-type PR and these mutated PRs. The relative binding free energy differences from the TI calculations reveal that the decrease in van der Waals interactions of APV with mutated PRs relative to the wild-type PR mainly drives the drug resistance. This result is in good agreement with the previous experimental results and is also consistent with the results from MM-PBSA calculations. Analyses based on molecular dynamics trajectories show that these mutations can adjust the shape and conformation of the binding pocket, which provides main contributions to the decrease in the van der Waals interactions of APV with mutated PRs. The present study could provide important guidance for the design of new potent inhibitors that could alleviate drug resistance of PR due to mutations.
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