查看更多>>摘要：Nonlinear optical (NLO) crystals have been playing an increasingly important role in laser science and technology. The NLO crystals used in the middle infrared (mid-IR) region, compared with the NLO crystals in the other wavelength regions, are still not good enough for the application of high-energy laser. The main defect is that their laser damage thresholds (LDT) are low. Chinese scientists have made a lot of important contributions to the UV and visible NLO crystals. In the last decade, they also did a lot of work on the mid-IR NLO materials. The main purpose of these researches is to increase the LDT and simultaneously balance the other properties.This paper presents a brief summary of their research progress in this topic on three types of materials: chalcogenides, oxides, and halides. The emphasis is put on the design strategy and quality control of the crystals.
查看更多>>摘要：Biocompatible magnetic nanoparticles were prepared by co-precipitation method in the presence of poly (aspartic acid) (PAsp) as stabilizer, which was one of the most extensively studied and used poly(amino acids). As a biocompatible dispersant, PAsp was successfully attached to the Fe3O4 nanoparticles, which was approved by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). From X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) measurement results, it was found that PAsp stabilized iron oxide nanoparticles possess excellent Fe3O4 crystal structure and superparamagnetic property. Compared with trisodium citrate stabilized magnetic nanoparticles, PAsp stabilized magnetic nanoparticles were biocompatible and with lower cytotoxicity, which makes it more applicable in medicine, biology and biomaterial science.
查看更多>>摘要：Transition metal ions (Pb2+, Zn2+, Cd2+, Co2+, Mn2+,Cu2+, Ni2+, Hg2+, Ag+, Fe3+) in water are used to quench emission of 2-(6-oxido-6H-dibenz < c,e > < 1,2 > oxapho-sphorin-6-yl)-1,4-phenylene.bis(p-pentyloxylbenzoate)s (MD5) with aggregation-induced emission enhance-ment (AIEE) in water-acetonitrile (AN) mixture (80:20 by volume). Among all metal ions, Fe3+ exhibits the highest quenching efficiency on AIEE of MD5 even when the concentration of Fe3+ is lower than 1×10-6mol/L. The quenching efficiency of Hg2+ is lower than that of Fe3+ at the same concentration, though MD5 is used to detect Hg3+ efficiently, too. To other metal ions,low quenching efficiency has few relations with a wider concentration range. The UV absorbance spectra show only red shift of absorbance wavelength in the presence of Hg2+ and Fe3+, which indicates a salt-induced J-aggregation. SEM photos reveal larger aggregation and morphological change of nanoparticles of MD5 in water containing Hg2+ and Fe3+, which reduce the surface area of MD5 emission for further aggregation. The selective quenching effect of transition metal ions to emission of MD5 has a potential application in chemical sensors of some metal ions.
查看更多>>摘要：The synthesis of cyclic carbonates or dimethyl carbo-nate (DMC) using CO2 as a building block is a very interesting topic. In this work, we found that the metal-organic framework-5 (MOF-5)/KI was an active and a selective catalytic system for the synthesis of cyclic carbonates from CO2 and epoxides, and MOF-5/KI/K2CO2was efficient for the preparation of DMC from CO2, propylene, and methanol by a sequential route.The impacts of temperature, pressure, and reaction time length on the reactions were investigated, and the mechanism of the reactions is proposed on the basis of the experimental results.
查看更多>>摘要：In this study, different molecular weight (MW) carboxymethyl chitosans (CM-chitosan) nanoparticles were prepared by ionic geliflcation. The particle size of nanoparticles was around 180-250 nm by dynamic light scattering (DLS) and transmission electron microscope (TEM). With the increase of CM-chitosan nanoparticles concentration from 2 to 200 μg/mL, the growth inhibition effects on the keloid fibroblast increased. At theconcentration of 100 ug/mL, CM-chitosan nanoparticles with MW 6.3 kDa had a significant inhibitory effect (inhibition ratio 48.79%) of the proliferation of keloid fibroblast. Compared with CM-chitosan solution, the inhibition of CM-chitosan nanoparticles were lower in prior period and similar in later period. By analyzing the different effects of chitosan, CM-chitosan solution and CM-chitosan nanoparticles on proliferation of keloid fibroblast, we have found that the carboxylmethyl groups of CM-chitosan play an important role in inhibition of proliferation of keloid fibroblast.
查看更多>>摘要：The work aims to study the effect of polycarboxylate type of super plasticizer on the hydration of composite cements. In this paper we have studied the hydration of 20 wt% fly ash (FA) blended Portland cement in the presence of 0.1 wt% super plasticizer (SP). Water consistency, setting times, non-evaporable water con-tents, compressive strength, water percolation, and aircontent measurements were carried out. In addition, X-ray diffraction studies were carried out to understand the hydration process. The results indicated the increase in compressive strength of the FA blended Portland cement in the presence of SP and with the increase of the hydration time.
查看更多>>摘要：Electrospinning is known to be a highly versatile method to produce nanofibers, and several techniques have been developed to align nanoflbers. In this paper,poly(vinyl alcohol) (PVA), poly(vinylpyrrolidone)(PVP), poly(propylene carbonate) (PC), poly(ethylene oxide) (PEO), PVA/Chitosan and PVA/Fe3O4 uniaxially aligned ultrafine fibers were obtained with electrospin-ning method by adding another electric field in the collection area. Alignment of the nanofibers was characterized by the use of digital cameras and feld emission scanning electron microscopy, polarized Fourier transform infrared spectroscopy (FTIR), and wide-angle X-ray diffraction (XRD). The mechanism of fiber alignment was investigated as well.
查看更多>>摘要：Chitosan and sodium alginate have the opposite charges; they can become a gelatin by the electrostatic attraction, High-voltage electrostatic droplet generator method was used to prepare chitosan-sodium alginate microcapsule. Multi-layer chitosan-sodium aiginate microcapsule was prepared through layer-by-layer self-assembly, and the morphology was investigated.In addition, the release property of ofloxacin in microcapsules was studied by UV-Vis microscopy under different conditions such as pH value, layer number, etc. The results showed that the prepared microcapsules have a smooth surface with average particle size about 100 μm. The result of controlled release indicated that the prepared microcapsules are pH-independent, and the rate of release decreased when the layer number increases.
查看更多>>摘要：The well recognized model potential is used to investigate the phonon properties for five glassy Copper alloys viz. Cu57Zr43, Cu60W40, Cu33Y67, Cu43Ti57 and Cu66Ti34. The thermodynamic and elastic properties are also computed from the elastic limits of the phonon dispersion curves (PDC). Three theoretical approaches given by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS) are used in the present study to compute the PDC. Five local field correction functions proposed by Hartree (H), Taylor (T), lchimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are employed to see the effect of exchange and correlation in the aforesaid properties.
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