Electron momentum spectroscopy of CF2Cl2: experimental and theoretical momentum profiles for outer valence orbitals

Electron momentum distributions for outer valence orbitals of CF2Cl2 have been obtained by (e,2e) electron momentum spectroscopy at an incident energy of 1200 eV + binding energy. The experimental electron momentum profiles are compared with Hartree-Fock and density functional theory (DFT) calculations using B3LYP hybrid functional with the 6-31G and 6-311+G* basis sets. Generally, the shapes of the experimental momentum profiles are well reproduced by DFT calculations using larger basis sets 6-311 + G*. An attempt has been made to clarify the ordering of the outer valence orbitals, which have been in controversy, by comparing experimental results with B3LYP/6-311 + G* calculations.     

GaN-based LEDs for light communication

Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current progresses of GaN-based LEDs for light communications. The modulation bandwidth of GaN-based LEDs has been first improved by optimizing the LED epilayer structures and the modulation bandwidth of 73 MHz was achieved at the driving current density of 40 A/cm² by changing the multi-quantum well structures. After that, in order to increase the current density tolerance, different parallel flip-chip micro-LED arrays were fabricated. With a high injected current density of ～7900 A/cm², a maximum modulation bandwidth of ～227 MHz was obtained with optical power greater than 30 mW. Besides the increase of carrier concentrations, the radiative recombination coefficient B was also enhanced by modifying the photon surrounding environment based on some novel nanostructures such as resonant cavity, surface plasmon, and photonic crystals. The optical 3 dB modulation bandwidth of GaN-based nanostructure LEDs with Ag nanoparticles was enhanced by 2 times compared with GaN-based nanostructure LEDs without Ag nanoparticles. Our results demonstrate that using the QW-SP coupling can effectively help to enhance the carrier spontaneous emission rate and also increase the modulation bandwidth for LEDs, especially for LEDs with high intrinsic IQE. In addition, we discuss the progress of the faster color conversion stimulated by GaN-based LEDs.     

A simple and an efficient strategy to synthesize multi-component nanocomposites for biosensor applications

We demonstrate that core–shell multi-component nanocomposites can be grown in situ at room temperature by a novel one-step approach without adding any reductant and stabilizer. We have presented a one-step method for the synthesis of multi-component nanocomposites in water solution, the multi-component nanocomposites could be produced directly and quickly in an in situ wet-chemical reaction. Here, Au–polypyrrole (PPy)/Prussian blue (PB) nanocomposites have been synthesized successfully under the same circumstance. With the addition of pyrrole monomers into mixture solutions, the autopolymerization of pyrrole into PPy and AuCl₄⁻ was reduced to elemental Au instantaneously as well as simultaneously. At the same time, PB produced along with elemental Au serving as a catalyst. Furthermore, we investigated the performance of Au–PPy/PB nanocomposites as amperometric sensor toward the reduction of H₂O₂, which displayed high sensitivity, fast response and good stability. The peak current of H₂O₂ increased linearly with the concentration of H₂O₂ in the range from 2.5 × 10⁻⁹ to 1.2 × 10⁻⁶ M, and the low detection limit of 8.3 × 10⁻¹⁰ M (S/N = 3) was obtained. Therefore, this work provides a new pathway to design and fabricate novel multi-component nanocomposites, which have unique characteristics and hold great applications in the fields of sensors, electrocatalysis and others.     

Synthesis of graphene on a Ni film by radio-frequency plasma-enhanced chemical vapor deposition

Large-area single-or multilayer graphene of high quality is synthesized on Ni films by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at a relatively low temperature (650℃).In the deposition process,a trace amount of CH4 gas (2-8 sccm (sccm denotes standard cubic centimeter per minute at STP)) is introduced into the PECVD chamber and only a short deposition time (30-60 s) is used.Single-or multilayer graphene is obtained because carbon atoms from the discharging CH4 diffuse into the Ni film and then segregate out at its surface.The layer number of the obtained graphene increases when the deposition time or CH4 gas flow rate is increased.This investigation shows that PECVD is a simple,low-cost,and effective technique to synthesize large-area single-or multilayer graphene,which has potential for application as electronic devices.     

苯丙乳液制备及其电纺微纳米纤维结构的研究

通过乳液聚合的方法制备了水相苯丙乳液(PSBA)，并将其应用于静电纺丝制备出微纳米纤维结构。采用红外光谱、差示扫描量热仪（DSC）和动态光散射仪分析并表征了聚合物的化学组成、热稳定性，并得到了均一稳定的苯丙乳液。通过扫描电镜（SEM）研究了纺丝电压及纺丝液中苯丙乳液与聚乙烯醇（PVA）质量比对苯丙乳液电纺微纳米纤维结构的影响，结果表明，改变纺丝液PSBA、PVA质量比能够得到可控性的纤维结构；纺丝电压对纤维中串珠状结构形成有一定影响，且电压越高，纤维直径越小。     

Holocene climatic and environmental changes recorded in Baahar Nuur Lake core in the Ordos Plateau, Inner Mongolia of China

A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar) and δ 18O (δ 18Ocar) were conducted for retrieving the Holocene chronosequence of climaticchanges based on 15 AMS 14C dates. The record documented four major stages of climate change inthe Ordos Plateau: (IV) a cold and dry condition before ～7.65 14C ka BP; (III) a warm and humid stagebetween ～7.65 and ～5.40 ka BP; (II) a generally drier and cooler climate since ～5.40 ka BP with twohumid events occurring from ～4.70 to ～4.60 ka BP and from ～4.20 to ～3.70 ka BP, and (I) a dry climatecharacterized by complete desiccation of the lake after 3.70 ka BP. Stage III can be further divided intothree sub-stages: (IIIa) a warm and humid episode from ～7.65 to ～6.70 ka BP, (IIIb) a warm and relativelydry episode from ～6.70 to ～6.20 ka BP, and (IIIc) the magthermal and maghumid episode of the Holo-cene from ～6.20 to ～5.40 ka BP.     

4-PEG接枝苯乙烯-马来酸酐交替共聚物的合成及功能化

采用普通自由基聚合和可逆加成一断裂链转移（RAFT）自由基聚合方法合成了对位PEG取代苯乙烯（PEG-g-St）和马来酸酐的交替共聚物（P（（PEG—g—St）-alt-MA））,”CNMR分析表明PEG-g-St和马来酸酐单元采取交替的序列结构．利用反应性基团-马来酸酐单元的水解以及胺解可以制备功能性的PEG聚合物．以月桂胺为模型小分子研究了该聚合物的胺解,得到4-PEG-苯乙烯与羧酸基团以及疏水烷烃的交替序列聚合物,该双亲聚合物在水溶液中形成组装体．     

论工业机器人的发展与应用

随着计算机技术不断向智能化方向发展,机器人应用领域的不断扩展和深化,工业机器人已成为一种高新技术产业,为工业自动化发挥了巨大作用,将对未来生产和社会发展起越来越重要的作用。文章介绍了工业机器人的国内国外的发展状况和应用趋势,以及带来的经济效益。     

In-situ STM observation of the phase transition of two-dimensional 2,5-distyrylpyrazine nanostructure adsorbed on Au(111) in an electrochemical environment

The phase transition of 2,5-distyrylpyrazine (DSP) adsorbed on Au(111) substrate was studied as a function of the substrate potential in 0.1 M HClO 4 , using an in situ scanning tunneling microscope (STM). Depending on the applied electric field, DSP formed three distinctly different, two-dimensionally (2D) ordered, supramolecular nanostructures on the Au(111) surface. In the potential range of 0.55 V < E < 0.75 V, the DSP molecules formed a close-packed stripe pattern with the adlayer structure 1 3 . 8 6 When the potential was reduced to 0.45 V < E < 0.55 V, a ridge-like pattern built from dimer subunits was observed, with the adlayer structure 4 5 . 12 4 Further decreasing in the electrode potential to 0.2 V < E < 0.45 V caused the appearance of a herringbone-like pattern consisting of dimer subunits, with the adlayer structure 9 0 . 3 9 The potential-induced phase transitions revealed the structure-determining role of substrate-adsorbate coordination and intermolecular interaction in forming the distinct 2D adlayer motifs.     

Hydrogen sulfide induced by nitric oxide mediates ethylene-induced stomatal closure of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Pharmacological, laser scanning confocal microscopic (LSCM), real-time PCR and spectrophotographic approaches are used to study the roles of hydrogen sulfide (H2S) and nitric oxide (NO) in signaling transduction of stomatal movement response to ethylene in Arabidopsis thaliana. In the present study, inhibitors of H2S synthesis were found to block ethylene-induced stomatal closure of Arabidopsis. Treatment with ethylene induced H2S generation and increased L-/D-cysteine desulfhydrase (pyridoxal-phosphate-dep...