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981.
Current interest in the fabrication of organic nanostructures on silicon surface is focused on the self-directed growth of 1D molecular lines with predefined position, structure, composition, and the length on the H-terminated Si(100)-(2 x 1) surface. To date, no studies have succeeded in growing the molecular line across the dimer rows on Si(100)-(2 x 1)-H, which is highly desirable. Using scanning tunneling microscopy (STM), we studied a new molecular system (allyl mercaptan, CH2=CH-CH2-SH) that undergoes chain reaction across the dimer row on the Si(100)-(2 x 1)-H surface at 300 K and produces covalently bonded 1D molecular lines. In combination with the previous findings of chain reaction along the rows, the present observations of self-directed growth of 1D molecular lines across the dimer rows on the Si(100)-(2 x 1)-H surface provide a means to connect any two points (through molecular lines) on a 2D surface. 相似文献
982.
Jean-Louis Ripoll Yannick Valle Mohamed Khalid Abdelhak Hakiki 《Journal of heterocyclic chemistry》1992,29(7):1867-1868
4,5-Dihydro-1H,3H-thieno[3,4-c]thiophene and 4,5-dihydro-1H,3H-thieno[3,4-c]furan were synthesized by retro Diels-Alder reactions under flash vacuum thermolysis conditions. 相似文献
983.
Polarity control and residual strain in ZnO epilayers grown by molecular beam epitaxy on (0001) GaN/sapphire 下载免费PDF全文
Md. Barkat Ullah Vitaliy Avrutin Si Qian Li Saikat Das Morteza Monavarian Mykyta Toporkov Ümit Özgür Pierre Ruterana Hadis Morkoç 《固体物理学:研究快报》2016,10(9):682-686
We report on the polarity control of ZnO grown by plasma assisted molecular beam epitaxy on Ga polar (0001) GaN/sapphire templates simply via the oxygen‐to‐Zn (VI/II) ratio during the growth of a thin nucleation layer at 300 °C. Following Zn pre‐exposure, the ZnO layers nucleated with low VI/II ratios (<1.5) exhibited Zn‐polarity. Those nucleated with VI/II ratios above 1.5, exhibited O‐polarity. Supported by scanning transmission electron microscopic imaging, we have unequivocally demonstrated that polarity inversion takes place without formation of any vertical inversion domains and within one monolayer of presumably non‐stoichiometric GaOx formed at the ZnO/GaN interface. A direct correlation between polarity and strain sign of ZnO layers has been found. The Zn‐polar ZnO layers were under tensile biaxial strain, whereas the O‐polar material exhibited compressive strain. Moreover, the amount of residual strain varied linearly with VI/II ratio used during the low‐temperature nucleation layer growth. Strain control with VI/II ratio has been explained by the potential formation of Zn interstitials. 相似文献
984.
Adetayo Abdulmumin Adebisi Md Abdul Maleque Mohammad Yeakub Ali Kamil Adeyemi Bello 《Composite Interfaces》2016,23(6):533-547
AbstractThe influence of reinforcement particle size variation plays a major role on the properties of Al–SiCp composite. Therefore, this study aim to investigate the mechanical and wear performance of single particle size (SPS) and multiple particle size (MPS) Al–SiCp composite prepared by stir casting process. The SPS comprises three categories; fine (15 μm), intermediate (40 μm) and coarse (80 μm) particle sizes and combination of the three sizes accounts for the MPS in the ratio 1:1:2, respectively. Oxidation of the SiCp and addition of 1 wt% Mg during composite processing resulted to interface reaction products such as MgO (magnesium oxide) and MgAl2O4 (magnesium aluminate) which suppresses the potential formation of undesired Al3C4 (aluminium carbide). The study reveals that MPS composite improved the hardness and impact properties with enhanced wear performance compared to SPS composite. Characterization of the composite morphology and phases was performed using scanning electron microscope and X-ray diffraction analysis. This study provides an effective method of optimizing the properties of Al–SiCp composite by integrating MPS with low volume fraction of reinforcement phase. 相似文献
985.
Dr. Md Mokhlesur Rahman Irin Sultana Dr. Tianyu Yang Dr. Zhiqiang Chen Dr. Neeraj Sharma Dr. Alexey M. Glushenkov Prof. Ying Chen 《Angewandte Chemie (International ed. in English)》2016,55(52):16059-16063
A simple, cost‐effective, and easily scalable molten salt method for the preparation of Li2GeO3 as a new type of high‐performance anode for lithium‐ion batteries is reported. The Li2GeO3 exhibits a unique porous architecture consisting of micrometer‐sized clusters (secondary particles) composed of numerous nanoparticles (primary particles) and can be used directly without further carbon coating which is a common exercise for most electrode materials. The new anode displays superior cycling stability with a retained charge capacity of 725 mAh g?1 after 300 cycles at 50 mA g?1. The electrode also offers excellent rate capability with a capacity recovery of 810 mAh g?1 (94 % retention) after 35 cycles of ascending steps of current in the range of 25–800 mA g?1 and finally back to 25 mA g?1. This work emphasizes the importance of exploring new electrode materials without carbon coating as carbon‐coated materials demonstrate several drawbacks in full devices. Therefore, this study provides a method and a new type of anode with high reversibility and long cycle stability. 相似文献
986.
Shyamtanu Chattoraj Md. Asif Amin Saswat Mohapatra Dr. Surajit Ghosh Prof. Dr. Kankan Bhattacharyya 《Chemphyschem》2016,17(1):61-68
In situ generated fluorescent gold nanoclusters (Au‐NCs) are used for bio‐imaging of three human cancer cells, namely, lung (A549), breast (MCF7), and colon (HCT116), by confocal microscopy. The amount of Au‐NCs in non‐cancer cells (WI38 and MCF10A) is 20–40 times less than those in the corresponding cancer cells. The presence of a larger amount of glutathione (GSH) capped Au‐NCs in the cancer cell is ascribed to a higher glutathione level in cancer cells. The Au‐NCs exhibit fluorescence maxima at 490–530 nm inside the cancer cells. The fluorescence maxima and matrix‐assisted laser desorption ionization (MALDI) mass spectrometry suggest that the fluorescent Au‐NCs consist of GSH capped clusters with a core structure (Au8‐13). Time‐resolved confocal microscopy indicates a nanosecond (1–3 ns) lifetime of the Au‐NCs inside the cells. This rules out the formation of aggregated Au–thiolate complexes, which typically exhibit microsecond (≈1000 ns) lifetimes. Fluorescence correlation spectroscopy (FCS) in live cells indicates that the size of the Au‐NCs is ≈1–2 nm. For in situ generation, we used a conjugate consisting of a room‐temperature ionic liquid (RTIL, [pmim][Br]) and HAuCl4. Cytotoxicity studies indicate that the conjugate, [pmim][AuCl4], is non‐toxic for both cancer and non‐cancer cells. 相似文献
987.
Asmat Elahi Abdul Shakoor Muhammad Irfan N. A. Niaz Mukhtar Ahmad Khalid Mahmood 《Polymer Science Series B》2016,58(4):449-456
Zn0.5Ni0.4Cr0.1Fe2O4 nanopowder and its composite with polyaniline were successfully prepared by using wow sol-gel and in situ chemical polymerization respectively. The samples were characterized by X-ray diffraction and field emission scanning electron microscopy. Dielectric properties were investigated as function of frequency by using impedance analyzer. The results showed the presence of the two intended phases. The ac conductivity was found to obey Jonscher’s universal power law. The dielectric constant and loss showed dispersion in low frequency region. Impedance analysis revealed the semiconducting behavior of the investigated samples. 相似文献
988.
Herein, we report the study of the influence of ascorbic acid and temperature on the micellization of a cationic gemini surfactant, hexanediyl-1,6-bis(dimethylcetylammonium bromide), 16-6-16. The critical micelle concentration (CMC) of 16-6-16 was measured by the conductivity method and dye solubilisation technique. A tendency of the CMC values to increase with temperature and upon the adding of ascorbic acid was found. The standard Gibbs energy, standard enthalpy, and standard entropy of micellization of 16-6-16 were evaluated. The results of calculations suggest the decrease of the stability of the 16-6-16 micellar solution in the presence of ascorbic acid. 相似文献
989.
Khalid Saeed 《Accreditation and quality assurance》2016,21(4):305-308
ISO/IEC 17025:2005 states that its requirements are “applicable to all laboratories regardless of the number of personnel” and would therefore include single-operator laboratories. However, there are reservations as to whether these laboratories can comply with all of the requirements without jeopardizing independence of judgement and impartiality. Similarly, there are some requirements of ISO/IEC 17025:2005 including staff supervision, internal communication processes and appointment of deputies that are considered unlikely to apply to a single-operator laboratory. The ISO/IEC 17025:2005 is widely used as the international standard of quality assurance by which accreditation bodies assess the competency of testing and calibration laboratories. There does, however, appear to exist, disagreement amongst accreditation experts when considering single-operator laboratories. Some accreditation bodies accredit single-operator laboratories, whilst others require additional human resources prior to granting accreditation. This discrepancy leads to unfair competition amongst laboratories as a single-operator laboratory by definition needs less resources (both human and financial) to achieve and maintain accreditation, compared with a laboratory where additional human resources need to be sought prior to and in order to maintain accreditation. The ISO/IEC 17025:2005 is in the process of being revised, and this is an opportune moment to address the issues aforementioned with the aim of removing ambiguity and enhancing clarity. In addition, the hope is to assist the accreditation bodies themselves to adopt a consensus approach when granting accreditation towards single-operator laboratories. 相似文献
990.
Md. Saidul Islam Dr. Mohammad Razaul Karim Dr. Kazuto Hatakeyama Hiroshi Takehira Ryo Ohtani Masaaki Nakamura Prof. Michio Koinuma Prof. Shinya Hayami 《化学:亚洲杂志》2016,11(16):2322-2327
A highly stable proton conductor has been developed from carbon sphere oxide (CSO). Carbon sphere (CS) generated from sucrose was oxidized successfully to CSO using Hummers’ graphite oxidation technique. At room temperature and 90 % relative humidity, the proton conductivity of thin layer CSO on microsized comb electrode was found to be 8.7×10?3 S cm?1, which is higher than that for a similar graphene oxide (GO) sample (3.4×10?3 S cm?1). The activation energy (Ea) of 0.258 eV suggests that the proton is conducted through the Grotthuss mechanism. The carboxyl functional groups on the CSO surface are primarily responsible for transporting protons. In contrast to conventional carbon‐based proton conductors, in which the functional groups decompose around 80 °C, CSO has a stable morphology and functional groups with reproducible proton conductivity up to 400 °C. Even once annealed at different temperatures at high relative humidity, the proton conductivity of CSO remains almost unchanged, whereas significant change is seen with a similar GO sample. After annealing at 100 and 200 °C, the respective proton conductivity of CSO was almost the same, and was about ~50 % of the proton conductivity at room temperature. Carbon‐based solid electrolyte with such high thermal stability and reproducible proton conductivity is desired for practical applications. We expect that a CSO‐based proton conductor would be applicable for fuel cells and sensing devices operating under high temperatures. 相似文献