Fuglsangmarcher4396

UV-absorbing rhodopsins are essential for UV vision and sensing in all kingdoms of life. Unlike the well-known visible-absorbing rhodopsins, which bind a protonated retinal Schiff base for light absorption, UV-absorbing rhodopsins bind an unprotonated retinal Schiff base. Thus far, the photoreaction dynamics and mechanisms of UV-absorbing rhodopsins have remained essentially unknown. Here, we report the complete excited- and ground-state dynamics of the UV form of histidine kinase rhodopsin 1 (HKR1) from eukaryotic algae, using femtosecond stimulated Raman spectroscopy (FSRS) and transient absorption spectroscopy, covering time scales from femtoseconds to milliseconds. We found that energy-level ordering is inverted with respect to visible-absorbing rhodopsins, with an optically forbidden low-lying S1 excited state that has Ag- symmetry and a higher-lying UV-absorbing S2 state of Bu+ symmetry. UV-photoexcitation to the S2 state elicits a unique dual-isomerization reaction first, C13═C14 cis-trans isomerization occurs during S2-S1 evolution in less then 100 fs. This very fast reaction features the remarkable property that the newly formed isomer appears in the excited state rather than in the ground state. Second, C15═N16 anti-syn isomerization occurs on the S1-S0 evolution to the ground state in 4.8 ps. We detected two ground-state unprotonated retinal photoproducts, 13-trans/15-anti (all-trans) and 13-cis/15-syn, after relaxation to the ground state. These isomers become protonated in 58 μs and 3.2 ms, respectively, resulting in formation of the blue-absorbing form of HKR1. Our results constitute a benchmark of UV-induced photochemistry of animal and microbial rhodopsins.Porous cubic-like PtCu and PtCuRu nanocrystals, which had a similar porous three-dimensional structure, were successfully prepared via the one-pot method. During the growth of the nanocrystals, cetyltrimethylammonium chloride and ascorbic acid were employed as the structure director and assistant reducing agent, respectively. The structure and possible formation of the nanocrystals were investigated. It is worth mentioning that the PtCuRu nanocrystals demonstrated a much better methanol electro-oxidation ability and ultrahigh stability, which displayed 3.4- and 3-fold higher specific and mass activity, respectively, than the commercial Pt/C. The advantage of PtCuRu nanocrystals was possibly ascribed to the synergistic effect of Cu and the porous structure and, more importantly, the presence of Ru that could more efficiently eliminate the harmful intermediates.Silicon is a known trace contaminant in diamond grown by chemical vapor deposition (CVD) methods. Deliberately Si-doped diamond is currently attracting great interest because of the attractive optical properties of the negatively charged silicon-vacancy (SiV-) defect. This work reports in-depth studies of microwave-activated H2 plasmas containing trace (10-100 ppm) amounts of SiH4, with and without a few % of CH4, operating at pressures and powers relevant for contemporary diamond CVD, using a combination of experiment (spatially resolved optical emission (OE) imaging) and two-dimensional plasma chemical modeling. Key features identified from analysis and modeling of the OE from electronically excited H, H2, Si, and SiH species in the dilute Si/H plasmas include the following (i) fast H-shifting reactions ensure that Si atoms are the most abundant silicon-containing species throughout the entire reactor volume, (ii) the low ionization potentials of all SiHx (x ≤ 4) species and efficient ion conversion reactions ensure that even trace SiH4 additions cause a change in the dominant ions in the plasma volume (from H3+ to SiHx+), with consequences for electron-ion recombination rates and ambipolar diffusion coefficients, and (iii) the total silicon content in the reactor volume can be substantially perturbed by silicon deposition and H atom etching reactions at the reactor walls. The effects of adding trace amounts of SiH4 to a pre-existing C/H plasma are shown to be much less dramatic but include the following (i) a Si substrate or fused silica components within the reactor are a ready (unintended) source of gas-phase Si-containing species, (ii) OE from electronically excited Si atoms should provide a reliable measure of the Si content in the hot plasma region, and (iii) Si atoms and/or SiC2 species are the most abundant gas-phase Si-containing species just above the growing diamond surface and thus the most likely carriers of the silicon incorporated into CVD diamond.The development of robust synthetic routes to stable covalent organic frameworks (COFs) is important to broaden the range of applications for these materials. We report here a simple and efficient three-component assembly reaction between readily available aldehydes, amines, and elemental sulfur via a C-H functionalization and oxidative annulation under transition-metal-free conditions. Five thiazole-linked COFs (TZ-COFs) were synthesized using this method. These materials showed high levels of crystallinity, high specific surface areas, and excellent physicochemical stability. The photocatalytic applications of TZ-COFs were investigated, and TZ-COF-4 gave high sacrificial hydrogen evolution rates from water (up to 4296 μmol h-1 g-1 under visible light irradiation) coupled with high stability and recyclability, with sustained hydrogen evolution for 50 h.The two-dimensional thin metal-organic frameworks (MOF) sheet has emerged as a promising hybrid material for applications in catalysis and optoelectronic devices. However, the small size and large thickness of an MOF sheet still pose barriers toward its potential applications. Herein, a micron-sized ultrathin MOF sheet is synthesized with the assistance of benzoic acid. Benzoic acid promoted the coordination of the porphyrin center with copper ions, reduced H-stacking and J-aggregation between the layers, and induced anisotropic growth of the MOF sheet. The results reveal the growth mechanism and provide a viable method for the synthesis of ultrathin MOF sheet. The as-prepared micron-sized ultrathin MOF sheet has good dispersion and high stability, which can ensure the long-term application properties of this material. GLPG1690 chemical structure The ultrathin thickness in combination with its micron size can make MOF as useful as graphene in practical applications. The synthesis of a micron-sized ultrathin MOF sheet similar to the thickness of graphene can pave the way for effective applications of two-dimensional MOF materials.