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71.
The formation of Fe3O4 nanoparticles by hydrothermal process has been studied. X‐ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe3O4 nanoparticles, poly(vinyledene fluoride)‐Fe3O4 composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe3O4 nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe3O4. The conductitivity of the composite films was strongly influenced by the Fe3O4 content; conductivity increased with increase in Fe3O4 content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe3O4 nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
72.
73.
Da-Ren Hang Sk Emdadul Islam Krishna Hari Sharma Shiao-Wei Kuo Cheng-Zu Zhang Jun-Jie Wang 《Nanoscale research letters》2014,9(1):632
Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications. 相似文献
74.
Goutam Kumar Dalapati Terence Kin Shun Wong Yang Li Ching Kean Chia Anindita Das Chandreswar Mahata Han Gao Sanatan Chattopadhyay Manippady Krishna Kumar Hwee Leng Seng Chinmay Kumar Maiti Dong Zhi Chi 《Nanoscale research letters》2012,7(1):1-8
Few-wall carbon nanotubes were synthesized by methane/acetylene decomposition over bimetallic Fe-Mo catalyst with MgO (1:8:40) support at the temperature of 900°C. No calcinations and reduction pretreatments were applied to the catalytic powder. The transmission electron microscopy investigation showed that the synthesized carbon nanotubes [CNTs] have high purity and narrow diameter distribution. Raman spectrum showed that the ratio of G to D band line intensities of I G/I D is approximately 10, and the peaks in the low frequency range were attributed to the radial breathing mode corresponding to the nanotubes of small diameters. Thermogravimetric analysis data indicated no amorphous carbon phases. Experiments conducted at higher gas pressures showed the increase of CNT yield up to 83%. M?ssbauer spectroscopy, magnetization measurements, X-ray diffraction, high-resolution transmission electron microscopy, and electron diffraction were employed to evaluate the nature of catalyst particles. 相似文献
75.
Alireza Samavati Zulkafli Othaman Sib Krishna Ghoshal Mohammad Reza Dousti Mohammed Rafiq Abdul Kadir 《International journal of molecular sciences》2012,13(10):12880-12889
The visible luminescence from Ge nanoparticles and nanocrystallites has generated interest due to the feasibility of tuning band gap by controlling the sizes. Germanium (Ge) quantum dots (QDs) with average diameter ~16 to 8 nm are synthesized by radio frequency magnetron sputtering under different growth conditions. These QDs with narrow size distribution and high density, characterized using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) are obtained under the optimal growth conditions of 400 °C substrate temperature, 100 W radio frequency powers and 10 Sccm Argon flow. The possibility of surface passivation and configuration of these dots are confirmed by elemental energy dispersive X-ray (EDX) analysis. The room temperature strong visible photoluminescence (PL) from such QDs suggests their potential application in optoelectronics. The sample grown at 400 °C in particular, shows three PL peaks at around ~2.95 eV, 3.34 eV and 4.36 eV attributed to the interaction between Ge, GeOx manifesting the possibility of the formation of core-shell structures. A red shift of ~0.11 eV in the PL peak is observed with decreasing substrate temperature. We assert that our easy and economic method is suitable for the large-scale production of Ge QDs useful in optoelectronic devices. 相似文献
76.
Krishna Prasad Rajan Ahmed Al-Ghamdi P. Ramesh G. B. Nando 《Journal of Polymer Research》2012,19(5):9872
Thermoplastic polyurethane (TPU) and polydimethyl siloxane rubber (PDMS) are two major polymers used extensively for biomedical
applications. Blending of these polymers combines the superior mechanical properties, abrasion resistance, solvent resistance
and aging resistance of TPU with chemical stability, inertness, flexibility and biocompatibility of PDMS. In the present investigation,
an 80:20 blend of TPU and PDMS was selected for the preparation of an in situ compatibilized blend using ethylene methyl acrylate
copolymer (EMA) as the compatibilizer. Effect of EMA on blends of ester type and ether type TPU with PDMS was studied. From
the results obtained from torque rheometry, mechanical property evaluation, fourier transform infrared spectroscopy (FTIR),
atomic force microscopy (AFM) and scanning electron microscopy (SEM), it was concluded that 5 wt% of compatibilizer effectively
compatibilized an 80:20 blend of ester type TPU and PDMS, whereas similar blend of ether type TPU required only 2 wt% compatibilizer. 相似文献
77.
Lately, there has been considerable interest in the development of more efficient processes to generate syngas, an intermediate in the production of fuels and chemicals, including methanol, dimethyl ether, ethylene, propylene and Fischer–Tropsch fuels. Steam methane reforming (SMR) is the most widely applied method of producing syngas from natural gas. Dry reforming of methane (DRM) is a process that uses waste carbon dioxide to produce syngas from natural gas. Dry reforming alone has not yet been implemented commercially; however, a combination of steam methane reforming and dry reforming of methane (SMR + DRM) has been used in industry for several years. 相似文献
78.
Zhiqiang Liu Jian Zhou Xiaomin Tang Fujian Liu Jiamin Yuan Guangchao Li Ling Huang Rajamani Krishna Kuan Huang Anmin Zheng 《American Institute of Chemical Engineers》2020,66(8):e16269
Zeolites have been widely used for the processes of adsorption, separation, and catalysis, which are strongly correlated with molecular diffusion. However, the correlation between pore dimension and diffusion properties has not been systematically investigated so far. In this work, the diffusion properties of alkanes in six zeolites with similar pore sizes but different pore dimension have been examined. It is found that the diffusion coefficients of alkanes in zeolites are 2–5 orders of magnitude smaller than that in gas phase. Moreover, the diffusion of alkanes inside zeolites is sensitive to the pore dimension, and can be differentiated by 1-D straight, 1-D tortuous, and 3-D intersecting channels, based on the derived quantitative correlation between the diffusion behavior and pore dimension. Our work may not only provide deep insights into the effects of pore dimension on diffusion, but also benefits for the future design and practical applications of zeolite catalysts. 相似文献
79.
Tiana D. Warren Krishna Patel Jordan L. Rivera James R. Eshleman Marc Ostermeier 《American Institute of Chemical Engineers》2020,66(3):e16688
Improved prodrug-activating enzymes have the potential to increase the therapeutic efficacy of gene-directed enzyme prodrug therapy (GDEPT). Yeast cytosine deaminase (yCD) is commonly used to convert the prodrug 5-fluorocytosine (5-FC) to the chemotherapeutic 5-fluorouracil for GDEPT. Mutagenesis studies on yCD aimed at improving its application in GDEPT have been limited to subsets of residues or have sought to improve a single property of the enzyme. We performed comprehensive site-saturation mutagenesis (CSM) on yCD designed to create all 2,983 possible unique protein mutants with a single amino acid substitution. We identified active variants through Escherichia coli genetic complementation and screened these mutants, and combinations thereof, for increased ability to sensitize E. coli and HT1080 fibrosarcoma cells to 5-FC. Several mutants identified in this study showed increased sensitization ability for both E. coli and HT1080 cells indicating that CSM is an effective directed evolution tool for identifying unexpectedly beneficial mutations. 相似文献
80.
Nina Kubatova Dr. Hendrik R. A. Jonker Dr. Krishna Saxena Dr. Christian Richter Verena Vogel Sandra Schreiber Prof. Dr. Anita Marchfelder Prof. Dr. Harald Schwalbe 《Chembiochem : a European journal of chemical biology》2020,21(1-2):149-156
Past sequencing campaigns overlooked small proteins as they seemed to be irrelevant due to their small size. However, their occurrence is widespread, and there is growing evidence that these small proteins are in fact functionally very important in organisms found in all kingdoms of life. Within a global proteome analysis for small proteins of the archaeal model organism Haloferax volcanii, the HVO_2922 protein has been identified. It is differentially expressed in response to changes in iron and salt concentrations, thus suggesting that its expression is stress-regulated. The protein is conserved among Haloarchaea and contains an uncharacterized domain of unknown function (DUF1508, UPF0339 family protein). We elucidated the NMR solution structure, which shows that the isolated protein forms a symmetrical dimer. The dimerization is found to be concentration-dependent and essential for protein stability and most likely for its functionality, as mutagenesis at the dimer interface leads to a decrease in stability and protein aggregation. 相似文献