A novel amphiphilic graft copolymer, poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-poly(4-vinyl pyridine) (P(VDF-co-CTFE)-g-P4VP) at 65:35 wt.%, respectively, was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance (1H NMR) and transmission electron microscopy (TEM). Silver bromide (AgBr) nanoparticles were in situ generated within the self-assembled P(VDF-co-CTFE)-g-P4VP graft copolymer. TEM, UV–visible spectroscopy and X-ray diffraction (XRD) analyses support the successful formation of P(VDF-co-CTFE)-g-P4VP nanocomposites consisting of stabilized AgBr nanoparticles mostly 20–40 nm in size, which is presumably due to the capping action of the coordinating pyridine groups of the graft copolymer. The wavenumber of pyridine nitrogen in FT-IR spectra and the glass transition temperature (Tg) of the graft polymer measured by DSC shifted upon the formation of AgBr nanoparticles, indicating specific interactions between the nanoparticles and the graft copolymer matrix. 相似文献
In this study, an anodized tubular TiO2 electrode (ATTE) on titanium foil was prepared and used both as a photoanode and a cathode in an enzymatic photoelectrochemical
system to split water into oxygen and hydrogen. The effect of applied voltage when anodized, thickness of the foil, electrolytes,
annealing temperature, and cathodes was investigated (optimum conditions: 20 V of applied voltage in 0.5 vol.% of hydrofluoric
acid, 0.25-mm foil thickness, and 450–650°C annealing temperature). The samples with higher activities had similar X-ray diffraction
(XRD) patterns, clearly indicating that the samples showing the highest evolution rate were composed of both anatase and rutile,
while those showing a lower evolution rate were made of either anatase or rutile. The ATTE successfully replaced the Pt mesh
cathode and the immobilization of the enzyme enhanced the H2 evolution by 50% (from ca. 66 to 99 μmol/(h × cm2)). Moreover, the use of KOH instead of Tris–HCl buffer in a cathodic compartment further increased the H2 evolution to 115 μmol/(h × cm2). 相似文献
The conformational changes of cyclohexyl acetylene (CHAL) on gold nanoparticle surfaces were investigated by means of concentration- and temperature-dependent surface-enhanced Raman scattering (SERS). Depending on concentrations and temperatures, the spectral changes of the acetylene ν(C≡C) stretching vibration on gold nanoparticles appeared to be more conspicuous than those of cyclohexyl ring modes. The density functional theory (DFT) calculation was performed at the level of B3LYP/6-31G++(d,p) to compare the energetic stability and vibrational frequencies of the various conformers of cyclohexanethiol (CHT) and CHAL. The DFT calculations were also carried out at the level of B3LYP/LACVP** on the CHAL molecule adsorbed on Au clusters at several sites to explain the spectral changes of the acetylene ν(C≡C) stretching vibration. 相似文献
High density energetic salts containing nitrogen rich cations and carbonyl‐ or oxalylbis(diamino‐tetrazole) anions, which were obtained from cyanogen azide and hydrazine, were readily synthesized. In every case, a new family of energetic salts 3 – 14 were characterized by vibrational spectroscopy, multinuclear (1H, 13C, 15N) NMR, elemental analyses, density, differential scanning calorimetry and impact sensitivity. Compound 12 was structured by single crystal X‐ray diffraction. The densities of 3 ‐ 14 , determined by gas pycnometer, range between 1.500 and 1.676 g cm?3. The heats of formation and detonation properties for these stable salts were calculated by using Gaussian 03 and Cheetah 5.0, respectively. 相似文献
An aqueous solution of a poly(ethylene glycol)‐polycaprolactone‐poly(ethylene glycol) (PEG‐PCL‐PEG) with a composition of EG13CL23EG13 undergoes multiple transitions, from sol‐to‐gel (hard gel)‐to‐sol‐to‐gel (soft gel)‐to‐sol, in the concentration range 20.0∼35.0 wt.‐%. Through dynamic mechanical analysis, UV‐vis spectrophotometry, small angle X‐ray scattering, differential scanning calorimetry, microcalorimetry and 13C NMR spectroscopy, the mechanism of these transitions was investigated. The hard gel and soft gel are distinguished by the crystalline and amorphous state of the PCL. The extent of PEG dehydration and the molecular motion of each block also played a critical role in the multiple transitions. This paper suggests a new mechanism for these multiple transitions driven by temperature changes.
We fabricated nano-carbon (NC) doped MgB2 bulks using an in situ process in order to improve the critical current density (Jc) under a high magnetic field and evaluated the correlated effects of the doped carbon content and sintering temperature on the phase formation, microstructure and critical properties. MgB2−xCx bulks with x = 0 and 0.05 were fabricated by pressing the powder into pellets and sintering at 800 °C, 900 °C, or 1000 °C for 30 min.We observed that NC was an effective dopant for MgB2 and that part of it was incorporated into the MgB2 while the other part remained (undoped), which reduced the grain size. The actual C content was estimated to be 68–90% of the nominal content. The NC doped samples exhibited lower Tc values and better Jc(B) behavior than the undoped samples. The doped sample sintered at 900 °C showed the highest Jc value due to its high doping level, small amount of second phase, and fine grains. On the other hand, the Jc was decreased at a sintering temperature of 1000 °C as a result of the formation of MgB4 phase. 相似文献
Abstact A scintillating fiber-optic dosimeter has many advantages such as real-time readout, high-resolution measurement, water-equivalence
and no corrections for temperature, pressure and humidity. Organic scintillator which has water or tissue equivalent characteristics
is very important to measure absorbed dose, dose rate and dose distributions exactly without any corrections and due to its
small size, the sensitive volume enables accurate dose measurements in regions of high dose gradients with high spatial resolution.
In this study, a scintillating fiber-optic dosimeter with an organic scintillator is fabricated to measure high-energy photon
beam from a clinical linear accelerator. And we have measured linear responses of a fiber-optic dosimeter according to dose
rates and monitor units of a clinical linear accelerator. Also, a percent depth dose curve for 6MV photon beam with different
field sizes are obtained. 相似文献
Epidemiological studies have suggested an association between pesticide exposure and Parkinson''s disease. In this study, we examined the neurotoxicity of an organochlorine pesticide, heptachlor, in vitro and in vivo. In cultured SH-SY5Y cells, heptachlor induced mitochondria-mediated apoptosis. When injected into mice intraperitoneally on a subchronic schedule, heptachlor induced selective loss of dopaminergic neurons in the substantia nigra pars compacta. In addition, the heptachlor injection induced gliosis of microglia and astrocytes selectively in the ventral midbrain area. When the general locomotor activities were monitored by open field test, the heptachlor injection did not induce any gross motor dysfunction. However, the compound induced Parkinsonism-like movement deficits when assessed by a gait and a pole test. These results suggest that heptachlor can induce Parkinson''s disease-related neurotoxicities in vivo. 相似文献