A Co-TiO 2 nanoribbon array supported on a Ti plate is a high-efficiency catalyst for electrochemical NO 3 – -to-NH 3 conversion, capable of attaining a large NH 3 yield of 1127 μmol h −1 cm −2 and high Faradaic efficiency of 98.2%.
We present a technique for the coherence transfer of laser light through a fiber link, where the optical phase noise induced by environmental perturbation via the fiber link is compensated by remote users. When compensating the fiber noise by remote users, the time base at the remote site independent from that at the local site does not destroy the performance of the fiber output light. Using this technique, we demonstrate the transfer of subhertz-linewidth laser light through a 25-km-long, lab-based spooled fiber. After being compensated, the relative linewidth between the fiber input and output light is 1 mHz, and the relative frequency instability is 4×10-17 at 1 s averaging time and scales down to 2×10-19 at 800 s averaging time. The frequency uncertainty of the light after transferring through the fiber relative to that of the input light is 3.0×10-19. This system is suitable for the simultaneous transfer of an optical signal to a number of end users within a city.
In this paper, a fixed support method for a cryogenic monocrystalline silicon Fabry-Pérot cavity of an ultra-stable laser for space applications is proposed. Through finite element analysis, the vibration sensitivity at the center of the cavity is below 10E-12/g; the fundamental frequency is 381 Hz; the thermal deformation is compensated by applying a preload force of about 3 N*m for a variation of 300 K to 124 K. Based on these analyses, an equal-mass cavity simulator was machined and mounted. The mounting process was then explored to keep its support angle mounting error within 40′. Next, the simulator was vibration tested, and the deviation of the cavity after the test was within 10″. Finally, the thermal deformation of the simulator and the support performance of the PEEK cylinders at 77 K was briefly verified. These works provide an alternative solution for future ultra-stable lasers with cryogenic monocrystalline silicon cavities for space applications.
We report the first examples of ruthenium complexes cis-[(N4)RuIIICl2]+ and cis-[(N4)RuII(OH2)2]2+ supported by chiral tetradentate amine ligands (N4), together with a high-valent cis-dioxo complex cis-[(N4)RuVI(O)2]2+ supported by the chiral N4 ligand mcp (mcp = N,N'-dimethyl-N,N'-bis(pyridin-2-ylmethyl)cyclohexane-1,2-diamine). The X-ray crystal structures of cis-[(mcp)RuIIICl2](ClO4) (1a), cis-[(Me2mcp)RuIIICl2]ClO4 (2a) and cis-[(pdp)RuIIICl2](ClO4) (3a) (Me2mcp = N,N'-dimethyl-N,N'-bis((6-methylpyridin-2-yl)methyl)cyclohexane-1,2-diamine, pdp = 1,1'-bis(pyridin-2-ylmethyl)-2,2'-bipyrrolidine)) show that the ligands coordinate to the ruthenium centre in a cis-α configuration. In aqueous solutions, proton-coupled electron-transfer redox couples were observed for cis-[(mcp)RuIII(O2CCF3)2]ClO4 (1b) and cis-[(pdp)RuIII(O3SCF3)2]CF3SO3 (3c'). Electrochemical analyses showed that the chemically/electrochemically generated cis-[(mcp)RuVI(O)2]2+ and cis-[(pdp)RuVI(O)2]2+ complexes are strong oxidants with E° = 1.11-1.13 V vs. SCE (at pH 1) and strong H-atom abstractors with DO-H = 90.1-90.8 kcal mol-1. The reaction of 1b or its (R,R)-mcp counterpart with excess (NH4)2[CeIV(NO3)6] (CAN) in aqueous medium afforded cis-[(mcp)RuVI(O)2](ClO4)2 (1e) or cis-[((R,R)-mcp)RuVI(O)2](ClO4)2 (1e*), respectively, a strong oxidant with E(RuVI/V) = 0.78 V (vs. Ag/AgNO3) in acetonitrile solution. Complex 1e oxidized various hydrocarbons, including cyclohexane, in acetonitrile at room temperature, affording alcohols and/or ketones in up to 66% yield. Stoichiometric oxidations of alkenes by 1e or 1e* in t BuOH/H2O (5 : 1 v/v) afforded diols and aldehydes in combined yields of up to 98%, with moderate enantioselectivity obtained for the reaction using 1e*. The cis-[(pdp)RuII(OH2)2]2+ (3c)-catalysed oxidation of saturated C-H bonds, including those of ethane and propane, with CAN as terminal oxidant was also demonstrated.
We demonstrate coherent transfer of an ultra-stable optical frequency at 192.8 THz over 50-km spooled fiber. Random phase noise induced by environmental disturbance through fiber is detected and suppressed by feeding a correctional signal into an acousto-optic modulator. After being compensated, the fiber-induced frequency instability is 2×10−17 at 1-s averaging time and reaches 8×10−20 after 16 h. The noise floor of the compensation system could be as low as 2×10−18 at 1-s averaging time.
Abstract Developing low‐cost and efficient nanomaterials to transform nitrogen to ammonia under mild conditions is an attractive topic in chemistry and is significant for sustaining agriculture and life. In this work, the catalytic performance of three types of MoS 2 electrocatalysts is systematically investigated. The density of states shows noticeable improvement in the electrical conductivity for sulfur‐vacancy defective MoS 2 (V S ‐MoS 2 ) than that of pure MoS 2 , as it facilitates the following electrocatalytic nitrogen reduction reaction (NRR). V S ‐MoS 2 possesses excellent NRR catalytic performance with a limiting potential of −0.48 V, an outstanding NH 3 average yield of 29.55 μg h −1 mg cat. −1 at −0.5 V versus reversible hydrogen electrode (RHE), and a high faraday efficiency of 4.58 % at −0.3 V vs RHE. The hydrogenation of *N‐NH to *NH‐NH is the rate determining step of the enzymatic mechanism. These results demonstrate the feasibility of V S ‐MoS 2 for electrocatalytic ammonia synthesis.
A novel catalyst-free halogenative cyclization of N-aryl diazoamides with N-halosuccinimides (NXS) is reported for the synthesis of 3-halooxindoles through a carbene-free mechanism. N-Aryl diazoamides reacted with NXS under mild and catalyst-free conditions to afford the corresponding 3-halooxindoles in good yields. This transformation is proposed to proceed through diazonium ion formation followed by intramolecular Friedel–Crafts alkylation.
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