The effect of low levels of dopants upon the formation and properties of beta-phase molybdenum nitride

The addition of 1 wt% Pd, Au, Ni and Cu dopants has been demonstrated to strongly alter the morphology of beta-phase molybdenum nitride prepared by treatment of MoO₃ with a 3/1 H₂/N₂ mixture at 750 °C. Furthermore, the addition of Pd significantly enhances the surface area and the formation of the nitride phase. It is proposed that the facile formation of molybdenum bronzes in this system is important in this respect. The dopants have also been observed to modify the denitridation characteristics of the beta-phase, with an overall reduction of the proportion of NH₃ formed upon using a 3/1 H₂/Ar mixture with respect to the undoped sample.     

Synthesis of hollow carbon nitride microspheres by an electrodeposition method

Hollow carbon nitride microspheres have been synthesized using a novel liquid phase electrodeposition technique. The microspheres are composed of numerous nanoparticles with size of about 5-30 nm. The diameters of the spheres range from 800 nm to 1.1 μm, and shell thickness is about 80-250 nm. This is the first attempt to synthesize carbon nitride with specific nanostructure by the electrodeposition method, which is proved to be facile and effective, and can be performed in an atmospheric environment and at a rather low temperature. The hollow carbon nitride may have potential applications as lubrication, catalysis, biomolecule adsorption, drug delivery, electronic materials, etc. in the future.     

Efficient and Green Method for the Synthesis of 1,5‐Benzodiazepine and Quinoxaline Derivatives in Water

Various 1,5‐benzodiazepine and quinoxaline derivatives have been synthesized in water with excellent yields using a catalytic amount of indium chloride at room temperature. This synthetic protocol is nontoxic, safe, and environmentally benign.     

Debromination of α‐Bromoketones and vic‐Dibromides Using Indium in the Presence of Carboxylic Acid

Abstract

The debromination of α‐bromoketones and vic‐dibromides using indium metal in the presence of acetic acid at room temperature effectively afforded the corresponding ketones in excellent yield.     

Photoluminescence and optical absorption properties of silicon quantum dots embedded in Si-rich silicon nitride matrices

Silicon nitride (SiN_x) films were prepared with a gas mixture of SiH₄ and NH₃ on Si wafers using the plasma-enhanced chemical vapor deposition (PECVD) method. High-resolution transmission electron microscopy and infrared absorption have been used to reveal the existence of the Si quantum dots (Si QDs) and to determine the chemical composition of the silicon nitride layers. The optical properties of these structures were studied by photoluminescence (PL) spectroscopy and indicate that emission mechanisms are dominated by confined excitons within Si QDs. The peak position of PL could be controlled in the wavelength range from 1.5 to 2.2 eV by adjusting the flow rates of ammonia and silane gases. Absorbance spectra obtained in the transmission mode reveal optical absorption from Si QDs, which is in good correlation with PL properties. These results have implications for future nanomaterial deposition controlling and device applications.     

Structures and electronic properties of SimN8-m（0 〈 m 〈 8） clusters： a density functional theory study

The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.     

Preparation of Nanocrystalline Indium Antimonide Through β-Hydride Elimination from New Indium-Antimony Single-Source Precursors

The 1:1 mole ratio reaction of t-Bu₃In with Sb(SiMe₃)₃ results in the formation of the Lewis acid-base adduct t-Bu₃In Sb(SiMe₃)₃ (1), while the dimeric compound [t-Bu₂InSb(SiMe₃)₂]₂ (2) is isolated from the 1:1 reaction of t-Bu₂InCl with Sb(SiMe₃)₃. Both the 2:1 reactions of t-Bu₂InCl with Sb(SiMe₃)₃ and t-Bu₂InCl with 2 result in the formation of the mixed-bridge compound (3), however, ¹H NMR studies suggest that this compound is unstable in solution. Thermolysis of 1, 2, and t-Bu₃Ga Sb(SiMe₃)₃ (4) results in the formation of nanocrystalline InSb or GaSb through a -hydride elimination pathway.     

硅在cBN单晶合成中的行为

 实验制备了复合氮化物Li₈SiN₄，并对合成温度、合成时间、气流量等因素的影响以及产物的稳定性进行了讨论。研究了Li₈SiN₄作为触媒添加剂时硅在cBN单晶合成中的作用。结果表明：cBN晶体多为截角八面体，晶面致密光滑；硅参与cBN的合成反应，并以SiO₂的形式沉积在cBN表面。