Enhanced second-harmonic generation in AlGaAs microring resonators

Highly efficient second-harmonic generation can be achieved by harnessing resonance effects in microring resonator structures. We propose an angular quasi-phase-matching scheme based on the position dependence of polarization inside the ring resonator.     

La2NiO4／Al2O3催化剂上CH4／CO2的重整

 通过溶胶－凝胶方法制备了尖晶石结构的La2NiO4／Al2O3催化剂，采用BET，XRD和TG表征了催化剂的孔分布、比表面积、体相组成以及凝胶样品的热失重和热分解过程．将催化剂应用于CH4／CO2重整反应制合成气，考察了惰性气体和反应温度对转化率、选择性以及积碳的影响．结果表明，在高空速（GHSV＝4．8×104ml／（g·h））下，CH4和CO2转化率分别为51％和60％，CO和H2的选择性约为98％和92％，惰性气体He的引入明显地提高了CH4和CO2的转化率．     

pH‐Controllable Supramolecular Systems

Proton, all that matters! This Focus Review surveys representative examples of pH‐controllable supramolecular systems with interesting features and state‐of‐the‐art applications, which can lead to the construction of meaningful molecular machines for electronic and biological applications that can be controlled by simple perturbation with acid and base.

     

Palladium-catalyzed direct and regioselective C-H bond functionalization/oxidative acetoxylation of indoles

The first general examples of palladium-catalyzed direct and selective oxidative C3-acetoxylation of indoles are presented. The mild reaction conditions (70 °C and with weak base, KOAc) in this indole C-H-acetoxylation are notable.     

The lewis acidic ruthenium-complex-catalyzed addition of beta-diketones to alcohols and styrenes is in fact Brønsted acid catalyzed

The perchlorate salt of the dicationic bipy–ruthenium complex cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂]²⁺ effectively catalyzes addition of β‐diketones to secondary alcohols and styrenes to yield the α‐alkylated β‐diketones. In a catalytic addition reaction of acetylacetone to 1‐phenylethanol, the κ²‐acetylacetonate complex [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ was isolated after the catalysis; this complex is readily synthesized by reacting cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with acetylacetone. [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ is unreactive toward 1‐phenylethanol in the presence of HClO₄; it also fails to catalyze the addition of acetylacetone to 1‐phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of β‐diketones to the secondary alcohols is in fact catalyzed by the Brønsted acid HClO₄, which is generated by the reaction of cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with the β‐diketone.     

Equation of state and structural changes in diaminodinitroethylene under compression

Structural changes in 1,1-diamino-2,2-dinitroethylene (DADNE, FOX-7) compressed to high pressure in diamond anvil cells were investigated using angle-dispersive x-ray diffraction analysis, Raman spectroscopy, and optical polarizing microscopy. The x-ray results show several changes above 1 GPa. When the x-ray data are indexed according to the ambient-pressure structure, DADNE shows anisotropic compression, with higher compression along the b axis than along the a or c axis. An ambient-temperature isothermal equation of state of DADNE was generated from these data. In addition, the experimentally obtained Raman spectra were matched with vibrational normal modes calculated using quantum chemistry calculations. The shifts in vibrational modes indicate changes in H-wagging vibrations with pressure.