Formation of Graphene Oxide Nanocomposites from Carbon Dioxide Using Ammonia Borane

To efficiently recycle CO(2) to economically viable products such as liquid fuels and carbon nanomaterials, the reactivity of CO(2) is required to be fully understood. We have investigated the reaction of CO(2) with ammonia borane (AB), both molecules being able to function as either an acid or a base, to obtain more insights into the amphoteric activity of CO(2). In the present work, we demonstrate that CO(2) can be converted to graphene oxide (GO) using AB at moderate conditions. The conversion consists of two consecutive steps: CO(2) fixation (CO(2) pressure < 3 MPa and temperature < 100 °C) and graphenization (600-750 °C under 0.1 MPa of N(2)). The first step generates a solid compound that contains methoxy (OCH(3)), formate (HCOO) and aliphatic groups while the second graphenization is the pyrolysis of the solid compound to produce graphene oxide-boron oxide nanocomposites, which have been confirmed by micro-Raman spectroscopy, solid state (13)C and (11)B magic angle spinning-nuclear magnetic resonance (MAS-NMR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Our observations also show that the mass of solid product in CO(2) fixation process and raw graphene oxide nanocomposites is twice and 1.2 times that of AB initially charged, respectively. The formation of aliphatic groups without using metal-containing compounds at mild conditions is of great interest to the synthesis of various organic products starting from CO(2.).     

Existence and multiplicity of solutions for a discontinuous problems with critical Sobolev exponents

In this paper, we consider the equation$?{\mathrm{\Delta }}_{p}u=\lambda {|u|}^{p^{?}?2}u+f(x,u)\text{in}{\mathbf{R}}^N,$ with discontinuous nonlinearity, where $1<p<N$, $\lambda >0$ is a real parameter and $p^{?}=\frac{Np}{N?p}$ is the critical Sobolev exponent. Under proper conditions on f, applying the nonsmooth critical point theory for locally Lipschitz functionals, we obtain at least one nontrivial nonnegative solution provided that $\lambda <{\lambda }_0$ and for any $k\in \mathbf{N}$, it has k pairs of nontrivial solutions if $\lambda <{\lambda }_k$, where ${\lambda }_0$ and ${\lambda }_k$ are positive numbers. In particular, we obtain the existence results for f is discontinuous in just one point.     

Liquid-core optical ring-resonator sensors

We have demonstrated a novel sensor architecture based on a liquid-core optical ring-resonator (LCORR) in which a fused silica capillary is utilized to carry the aqueous sample and to act as the ring resonator. The wall thickness of the LCORR is controlled to a few micrometers to expose the whispering gallery mode to the aqueous core. Optical characterization with a water-ethanol mixture shows that the spectral sensitivity of the LCORR sensor is approximately 2.6 nm per refractive index unit. A model based on Mie theory is established to explain the experimental results. The LCORR takes advantage of the high sensitivity, small footprint, and low sample consumption with the ring resonator, as well as the efficient fluidic sample delivery with the capillary, and will open an avenue to future multiplexed sensor array development.     

Density-controlled growth of aligned ZnO nanowires sharing a common contact: a simple, low-cost, and mask-free technique for large-scale applications

An effective, low cost, simple, and mask-free pathway is demonstrated for achieving density control of the aligned ZnO nanowires grown for large-scale applications. By a slight variation of the thickness of the thermally evaporated gold catalyst film, a significant change in the density of aligned ZnO nanowires has been controlled. The growth processes of the nanowires on an Al(0.5)Ga(0.5)N substrate has been studied based on the wetting behavior of gold catalyst with or without source vapor, and the results classify the growth processes into three categories: separated dots initiated growth, continuous layer initiated growth, and scattered particle initiated growth. This study presents an approach for growing aligned nanowire arrays on a ceramic substrate with the simultaneous formation of a continuous conducting electrode at the roots, which is important for device applications, such as field emission.     

Singlet fission for dye-sensitized solar cells: can a suitable sensitizer be found?

We discuss possible improvements in the efficiency of dye-sensitized photovoltaic cells using dyes capable of singlet fission into two triplets, thus producing two electron-hole pairs from a single photon. It is pointed out that, in addition to derivatives of large alternant hydrocarbons, those of biradicals are also likely candidates for a favorable ordering of excited-state energy levels, E(T2), E(S1) > 2E(T1). A large number of potentially favorable structures has been examined by the semiempirical Pariser-Parr-Pople method and some also by the time-dependent density functional theory method. Several likely candidates have been identified for experimental examination.     

Properties of some statistics for AR-ARCH model with application to technical analysis

In this paper, we investigate some popular technical analysis indexes for AR-ARCH model as real stock market. Under the given conditions, we show that the corresponding statistics are asymptotically stationary and the law of large numbers hold for frequencies of the stock prices falling out normal scope of these technical analysis indexes under AR-ARCH, and give the rate of convergence in the case of nonstationary initial values, which give a mathematical rationale for these methods of technical analysis in supervising the security trends.     

利用相位差异技术校准非共光路静态像差

提出了一种用相位差异(PD)技术对自适应光学(AO)系统的非共光路静态像差进行校准的方法。相位差异技术通过采集焦面和离焦面的单帧或多帧短曝光图像来估算波前相位畸变,同时对目标图像进行恢复。在闭环工作条件下,自适应光学系统利用相位差异算法在线检测成像光路的静态像差,并将得到的像差系数转化为变形镜的初始化面形,从而补偿非共光路的静态像差。实验结果表明,校准后的成像质量显著提高,目标半峰全宽降低了约14%,系统残差降低了约72%。成像光路在线检测得到的系统残差与闭环回路实测残差的水平趋于一致,证实了相位差异技术应用于光学检测的能力。该方法具有在无需改变原有自适应光路以及高信噪比条件下便可精确解算系统像差的优点,是大口径光电成像系统较为理想的光学检测技术之一。     

High-peak-power,short-pulse-width,LD end-pumped,passively Q-switched Nd:YAG 946 nm laser

High-peak-power, short-pulse-width diode pumped 946 nm Nd:YAG laser in passively Q-switching operation with Cr⁴⁺:YAG is reported. The highest average output power reaches 3.4 W using the Cr⁴⁺:YAG with initial transmissivity T₀=95%. When the T₀=90% Cr⁴⁺:YAG is employed, the maximum peak power of 31.4 kW with a pulse width of 8.3 ns at 946 nm is generated.     

Phase-sensitive reflection of squeezed vacuum field in optical cavity

We experimentally investigate the optical cavity for various coupled regimes with an injected squeezed vacuum state. We measure the quantum fluctuation spectra of the reflected field of an optical cavity using the homodyne detection and present the spectral dependence on the absorption and dispersion properties of the cavity in the under-coupled, critically-coupled, and over-coupled regimes. The spectra lineshape is phase sensitive with the phase shift induced by the cavity. Moreover, we find that the over-coupled optical cavity has obvious advantage in the manipulation of quantum fluctuation.