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991.
Surajit Ghosh Tanusri Pal Daeha Joung Saiful I. Khondaker 《Applied Physics A: Materials Science & Processing》2012,107(4):995-1001
We report the synthesis and characterization of lead sulfide (PbS) decorated reduced graphene oxide (RGO) nanocomposite materials. The materials were synthesized in a one-step solvothermal reaction where the reduction of graphene oxide, synthesis of PbS nanoparticle and decoration of PbS onto RGO were done simultaneously. Structural characterizations reveal that PbS nanoparticles are highly crystalline and a strong interaction exists between RGO and PbS. We also demonstrate fabrication of a near infrared (NIR) photo detector using RGO/PbS nanocomposite film. 相似文献
992.
The cis- and trans-azobenzenes are known as photochromic isomers with the trans- converting into the cis-form and vice versa upon irradiation with specific wavelengths. We have quantum chemically investigated the cis- and trans-forms of substituted azobenzene diradicals, with two nitronyl nitroxides, imino nitoxides, or verdazyls at para positions and serving as monoradical centers, to determine whether they can exhibit a photoassisted magnetic crossover. Geometries of both substituted and unsubstituted molecules have been optimized by density functional (DF) method UB3LYP using the 6-311G(d,p) basis set. Optimization of the geometry of the cis isomers has required special care. Single point singlet, triplet, and broken symmetry calculations have been done using 6-311++G(3df, 3pd) basis set. The magnetic exchange coupling constants have been estimated from the broken symmetry calculations. Absorption wavelengths have been estimated for both substituted and unsubstituted species from time-dependent DF treatment using restricted spin-polarized methodology RB3LYP and 6-311++G(3df, 3pd) basis set. From the similarity in the calculated absorption wavelengths for the unsubstituted and substituted azobenzenes, and the increased oscillator strengths (f) for the substituted species, we predict that the diradical isomers would be strongly photochromic. From our triplet state and broken symmetry calculations, we predict that both the cis- and the trans-diradicals are antiferromagnetically coupled. This prediction is consistent with the spin alternation rule, and the possibility of a magnetic crossover is nonexistent for these species. 相似文献
993.
Santoni MP Pal AK Hanan GS Tang MC Venne K Furtos A Ménard-Tremblay P Malveau C Hasenknopf B 《Chemical communications (Cambridge, England)》2012,48(2):200-202
Pd(II)-directed self-assembly of a 3-pyridyl grafted Lindqvist hexavanadate led to the formation of a unique trimeric species, as confirmed by a variety of techniques, including pulsed-field gradient NMR spectroscopy and high-resolution ESI mass spectrometry. 相似文献
994.
During the last few decades several logic gates, sequential and combinational logic devices, have been developed using light signals. For this work several encoding as well as decoding techniques are proposed for data handling and information processing with optics as information carrying signal. Frequency encoding technique is one such type of encoding processes, which gives a very good response for long distance communication of logically processed data because frequency is a fundamental character of light and it remains unchanged for long distance communication. Here in this paper the authors propose a frequency encoded multiplexer with the proper use of semiconductor optical amplifier in tri-state logic. 相似文献
995.
The self-assembly of non-toxic well-consumed small caffeine molecules into well-defined structures has important implications
for future medical applications seeking to target the transport of small drugs in human body. Particularly, the solvation
of the microenvironments of the self assembly ultimately dictates the interaction with the drug molecules and their therapeutic
efficacy. We present femtosecond-resolved studies of the dynamics of aqueous solvation within self-assembled dimeric structure
of caffeine molecules. We have placed small hydrophobic probes 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl) 4H-pyran
(DCM), coumarin 500 (C500) into the caffeine dimer to enable spectroscopic examinations of the interior. While molecular modeling
and NMR studies of the probes in the caffeine dimers reveal a well-defined location (stacked in between two caffeine molecules),
dynamical light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, densimetric and sonometric experiments explore
the structural evolution of the dimer upon complexation with the probes. We have extended our studies in various temperatures
in order to explore structural evolution of the self assembled structure and consequently the dynamics of solvation in the
interior of the dimer. Picoseconds/femtosecond resolved dynamics and the polarization gated spectroscopic studies unravel
the hydration and energetics associated with activated viscous flow of the confined probes. Our studies indicate that the
interior of the caffeine dimer is well-solvated; however, the dynamics of solvation is retarted significantly compared to
that in bulk water, clearly revealing the dimers maintain some ordered water molecules. We have also explored the consequence
of the retarded dynamics of solvation on the photo-induced electron transfer (ET) reaction of a model probe, 2-(p-toluidino)
naphthalene-6-sulfonate (TNS) encapsulated in the dimer. 相似文献
996.
V. P. Popov L. N. Safronov O. V. Naumova V. A. Volodin I. N. Kupriyanov Yu. N. Pal’yanov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(5):577-581
(111) synthetic HPTP diamond plates are irradiated by H 2 + 50 keV ions in the range of the fluences of 1?13 × 1016 sm?2 and annealed in vacuum at 1 mPa (VPHT, 500?C1600°C) or at high HPHT parameters (4.0?C7.5 GPa, 1200?C1550°C). It is shown by measuring the layer conductivity and Raman light scattering that after VPHT annealing, a buried layer of glassy carbon 10?C100 nm thick with low resistance (??1 kOhm/??) is formed, followed by HPHT with high resistance (??1 MOhm/??) and hopping transport along defects. 相似文献
997.
Ytterbium-sensitized thulium-doped fiber laser with a single-mode output operating at 1900-nm region
S. W. Harun A. Halder M. C. Paul S. M. M. Ali N. Saidin S. S. A. Damanhuri H. Ahmad S. Das M. Pal S. K. Bhadra 《中国光学快报(英文版)》2012,(10):39-41
A single-mode laser is demonstrated using a newly developed double-clad thulium-ytterbium-doped fiber (TYDF) in a linear cavity formed by two fiber Bragg gratings (FBGs). The YTF used is drawn from a D-shape preform fabricated using the modified chemical vapor deposition and solution doping technique. The laser is operated at 1 901.6 nm via the transition of thulium ions from 3F4 to 3H6 with the assistance of ytterbium to thulium ion energy transfer. The efficiencies of the laser are 0.71% and 0.75% at 927- and 905-nm multimode pumping, respectively. The thresholds of the launched pump power for 927- and 905-nm pumping are 1 314 and 1 458 mW, respectively. A 7-mW output is obtained at a 905-nm pump power of 2 400 mW. 相似文献
998.
Manoj Kumar Pal Beena Singh Jaiswar Gautam 《Journal of Thermal Analysis and Calorimetry》2012,107(1):85-96
The influences of nanosized CaCO3 on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated.
Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed
by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO3 and PS/CaCO3 were prepared with different filler loading (0–4 wt%) of CaCO3 nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO3 nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated
by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential
scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation
of CaCO3 nanoparticles could significantly improve the thermal properties of PMMA/CaCO3 and PS/CaCO3 nanocomposites. The glass transition temperature (T
g
) and decomposition temperature (T
d
) of nanocomposites with 4 wt% of CaCO3 nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO3 and 32 and 15 K in the case of PS/CaCO3 nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer
which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption
band in ultraviolet (UV) region is increased with CaCO3 nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers. 相似文献
999.
1000.
Light emitting diodes (LEDs) based on GaN/InGaN material suffer from efficiency droop at high current injection levels. We propose multiple quantum well (MQW) GaN/InGaN LEDs by optimizing the barrier thickness and high–low–high indium composition to reduce the efficiency droop. The simulation results reflect a significant improvement in the efficiency droop by using barrier width of 10 nm and high–low–high indium composition in MQW LED. 相似文献