Synthesis of hybrid materials via photopolymerization of benzoin functionalized silica nanoparticles

Photopolymerization of methyl methacrylate (MMA) was achieved on the surface of silica nanoparticles by “Grafting from” method. Well defined spherical silica nanoparticles prepared by Stöber method was functionalized with isocyanate groups of toluene di-isocyanate in order to achieve both improved dispersion of nanoparticles in organic solvents and further attachment of benzoin photoinitiator moieties onto the surface of silica nanoparticles. FTIR spectroscopy analysis confirmed the covalent bonding of the functional moieties and grafting of polymethylmethacrylate (PMMA) onto the surface of silica nanoparticles. Thermogravimetric analysis indicated the ratios of attached functionalities and PMMA grafting with a good agreement of SEM observations.     

二氧化硅球的制备及其功能化

以正硅酸四乙酯为硅源,分别在碱性和酸性条件下制备了二氧化硅(SiO2)球状粒子;在碱性条件下制备了具有荧光功能的SiO2-FITC复合纳米球;以Sn2+作为敏化剂,在SiO2球表面沉积Ag纳米颗粒,制备了SiO2/Ag核-壳结构纳米粒子。通过透射电子显微镜(TEM)、紫外-可见近红外(UV-vis-NIR)分光光度计,荧光分光光度计对SiO2球,SiO2-FITC荧光纳米球,SiO2/Ag核-壳结构纳米粒子的形貌和光学吸收、荧光发射特性进行了表征。结果表明,碱性环境下制备的SiO2球粒径大小为纳米级,酸性环境下制备的SiO2球粒径大小为微米级,酸性环境下制备的SiO2球比碱性环境下制备的硅球致密。掺入FITC的SiO2球具有荧光发射特性,且发光强度可以控制。Ag纳米颗粒修饰的SiO2/Ag核-壳结构纳米粒子具有等表面等离子体共振吸收特性。     

Grafting polystyrene onto silica nanoparticles via RAFT polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to graft polystyrene (PS) onto silica nanoparticles. A novel route was used to prepare the RAFT agent, 2-butyric acid dithiobenzoate (BDB) by substitution of dithiobenzoate magnesium bromide with sodium 2-bromobutyrate under alkali condition in aqueous solution. Epoxy groups were covalently attached to silica nanoparticles by condensation reaction of 3-glycidyloxypropyltrimethoxysilane (GPS) with the hydroxyl on the silica particle surface. RAFT agent functionalized nanoparticles were produced by ring-open reaction of the epoxy group with the carboxyl group of BDB. Then, PS chains with controlled molecular weights and narrow polydispersities (less than 1.1) were grown from the RAFT agent anchored nanoparticle surface. FT-IR, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) results showed that PS chains grew from silica particles by surface RAFT polymerization.     

银原子修饰铂纳米粒子的制备与其催化活性的研究

以聚乙烯吡咯烷酮（PVP）为保护剂在水溶液中合成了铂（Pt）纳米粒子,利用吸附在Pt纳米粒子表面上的氢还原适量AgNO_3,得到表面修饰了Ag原子的纳米Pt催化剂,并利用苯甲醛的催化加氢反应,考察了Ag原子的修饰量对纳米Pt催化剂的活性影响。实验结果表明：随着Ag原子在Pt纳米粒子表面沉积数量的增加,苯甲醛的转化率先升高后降低,当n（Ag）：n（Pt）为0.005时,纳米Pt催化剂的催化活性最高。     

Diatomite silica nanoparticles for drug delivery

Diatomite is a natural fossil material of sedimentary origin, constituted by fragments of diatom siliceous skeletons. In this preliminary work, the properties of diatomite nanoparticles as potential system for the delivery of drugs in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphological analysis performed by dynamic light scattering and transmission electron microscopy reveals a particles size included between 100 and 300 nm. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery.

PACS

87.85.J81.05.Rm; 61.46. + w     

Effect of gel electrolytes containing silica nanoparticles on aluminum corrosion

We have investigated corrosion of aluminum current collectors in electrolytes containing LiTFSI salt by chronopotentiometry, cyclic voltammetery, chronoamperometry, electrochemical impedance spectroscopy, and optical microscopy. Open-circuit potentials for cells with gel electrolytes containing silica nanoparticles are relatively stable in comparison to the corresponding baseline liquid, which suggests that the Al/electrolyte interface is more stable in presence of silica nanoparticles. Cyclic voltammetery and chronoamperometry data show that the current density for Li/electrolyte/Al cells with gel electrolytes containing fumed silica was less than that for baseline liquid electrolyte. The Nyquist plot for liquid electrolyte after chronoamperometry is semicircular-like, that is a corrosion reaction occurred. After cell disassembly, black particulates are evident and pits are observed on the aluminum foil. In comparison, no corrosion products are observed for cells containing gel electrolytes, and the Nyquist plots indicate that corrosion does not occur appreciably. Gel electrolytes produce impedance spectra with a large phase lag over a wide frequency range, which is not observed for the baseline liquid electrolyte. These phenomena may be interpreted as a good film-coating behavior associated with gel electrolytes, which results in a lower aluminum corrosion rate.     

Surface modification of silica particles assisted by CO2

This paper reports the synthesis of coating silica particles, in order to design hybrid materials with hydrophobic surface properties. The silica particles were prepared in basic conditions under atmosphere of carbon dioxide (CO₂), using tetraethylorthosilicate (TEOS) as a precursor and octyltriethoxysilane (OTES) as a surface modifying agent. It was demonstrated that the contact angles of silica hybrid films could be changed by varying temperature and pressure of CO₂. The investigation of the prepared hybrid materials by dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM), respectively, showed that they consisted mainly of particles with a diameter of 100–250 nm. Fourier transform infrared (FT-IR) spectra indicate that the interaction between the coupling reagents, at different conditions, is mainly through chemical bonding.     

Effect of Ag on the microstructure and electrical properties of ZnO

Various amounts of silver particles, 0.08–7.7 mol%, are mixed with zinc oxide powder and subsequently co-fired at 800–1200 °C. The effects of Ag addition on the microstructural evolution and electrical properties of ZnO are investigated. A small Ag doping amount (<0.76 mol%) promotes the grain growth of ZnO; however, a reversed trend in grain growth is observed for a relatively larger Ag addition (>3.8 mol%). It is evident that a tiny amount of Ag (0.08 mol%) may dissolve into the ZnO lattice. High-resolution TEM observations give direct evidences on the segregation of Ag solutes at the ZnO grain boundaries. The grain boundary resistance of ZnO increases 35-fold with the presence of Ag solute segregates. The Ag-doped ZnO system exhibits a nonlinear electric current–voltage characteristic, confirming the presence of an electrostatic barrier at the grain boundaries. The barrier is approximately 2 V for a single grain boundary.     

二氧化硅含量对硫铝酸盐水泥性能的影响[1]

利用粘土作为校正原料来调整原料中SiO2的含量，从而调整熟料中C4A3S^-的C2S的比例，研究随着熟料中SiO2含量的变化，硫铝酸盐水泥熟料中各矿物成分如何变化以及硫铝酸盐水泥的性能如何变化，借助于XRD射线衍射分析方法和SEM电镜分析方法，对各组试样进行了详细的研究和分析，得出了熟料中SiO2含量对硫铝酸盐水泥性能影响的普遍规律，确定了利用低品位矾土生产硫铝酸盐水泥是可行的。     

硅溶胶结合浇注料的流变性能研究

对高纯硅溶胶电熔莫来石细粉泥浆的流变性能研究表明：这种泥浆是存在触变结构的高浓度胶溶悬浮体系，在受较低剪切力作用时产生的是粘滞流动，总的表现符合Ｂｉｎｇｈａｍ流变方程。研究还表明：少量超细粉的加入不改变泥浆的流变模型，但能有效地改善其流变性能，不同的超细粉影响力不同，且这种改善作用有一最佳加入量（活性ＳｉＯ２超细粉影响力大于活性Ａｌ２Ｏ３微粉，其最佳加入量分别为２％和１０％），超过这一加入量将导致流变常数上升，使其流变性恶化。     

Effects of decomposition-treatment temperature on infiltration pressure of a surface modified nanoporous silica gel

When a nanoporous silica gel surface modified by silyl groups is decomposition-treated at a relatively low temperature, while the network is stable, the organic surface layers can be deactivated. As a result, the degree of hydrophobicity, which can be measured by the liquid infiltration pressure, is lowered. The infiltration and defiltration behaviors of liquid are dependent on the controlled decomposition-treatment time, the liquid composition, as well as the testing temperature. By adding electrolyte or using higher testing temperature, the infiltration pressure can be increased and the defiltration can be promoted.     

SiO_2含量对尖晶石耐火材料高温性能的影响

结合实例阐述了SiO2 含量对尖晶石耐火材料高温性能的影响。认为 :基质中低镁铝比 (接近尖晶石组成 )的尖晶石材料 ,SiO2 含量对高温性能的影响较严重 ;基质中高镁铝比 (MgO/Al2 O3=1～ 3)的尖晶石材料 ,SiO2 含量越低 ,则抗侵蚀性越好。     

Synthesis of silica nanoparticles in a continuous-flow microwave reactor

Monodispersed silica colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetraethylorthosilicate (TEOS) by using a continuous microwave synthesis process. The flow rate was varied from 43 to 101 mL/min in order to establish the optimum conditions required to obtain unagglomerated silica nanopowders. The results were compared with those obtained in batch systems. In particular the mean particle diameter became smaller than 50 nm as the residence time was decreased by increasing the flow rate to 101 mL/min.     

Microstructure and optical properties of Ag/ITO/Ag multilayer films

Transflective and highly conductive Ag/ITO/Ag multilayer films were prepared by magnetron sputtering on glass substrates. The microstructure and optical properties of Ag/ITO/Ag multilayer films were systematically investigated by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible spectroscopy. The optical properties of the multilayer films were significantly influenced by the thickness of the Ag surface layer from 3.0 to 12.6 nm. The multilayer film of Ag9.3nm/ITO142nm/Ag9.3nm shows the best comprehensive property. It could satisfy the requirement for transflective LCD.     

Surface modification of graphene oxide nanoplatelets and its influence on mechanical properties of alumina matrix composites

This paper discusses the effect of modified graphene oxide nanoplatelets (RGO-Al₂O₃) and unmodified graphene oxide nanoplatelets (GO) addition on the microstructure and mechanical properties of alumina matrix composites. The sinters were prepared by powder metallurgy processing using Spark Plasma Sintering to consolidate the powder mixtures. Moreover, the influence of applied reinforcing phase on the fracture mechanism was also investigated. Significant improvement of the fracture toughness (60%) for the composites with 0.5 wt.% RGO-Al₂O₃ compared to the reference sample was observed. Moreover, 20% higher K_IC was noticed for RGO-Al₂O₃ reinforced composites than for Al₂O₃-GO.     

硅微粉酸碱度对镁质浇注料性能的影响

以镁砂为主要原料,使用MgO-SiO2-H2O结合体系,研究了不同酸碱度硅微粉对镁质浇注料流动性和物理性能的影响。结果表明,使用弱酸性硅微粉的镁质浇注料具有良好的流动性和较高的强度,使用中性的硅微粉的镁质浇注料具有更好的流动性保持率。     

Effect of silicone resin on the properties of silica ceramic cores by heating treatment

Silica ceramic cores prepared by heat-press molding were strengthened by impregnating silicone resin. The effect of heating treatment conditions on the properties of silica ceramic cores was analyzed. Results showed that the ambient bending strength increased from 9.3 ± 2.0 MPa to 24.8 ± 1.5 MPa by curing process at low temperature of 250 °C. However, further heating treatment at high temperature ranging from 1150 to 1300 °C made the strength of the samples lower than that of the cured samples owing to the decomposition of silicone resin. But the strength of the samples was still higher than that of raw samples. The increasing heating treatment temperature promoted an increase in the strength by a densification process.     

Controllable fabrication of PS/Ag core-shell-shaped nanostructures

In this paper, based on the previous steps, a facile in situ reduction method was developed to controllably prepare polystyrene/Ag (PS/Ag) core-shell-shaped nanostructures. The crucial procedure includes surface treatment of polystyrene core particles by cationic polyelectrolyte polyethyleneimine, in situ formation of Ag nanoparticles, and immobilization of the Ag nanoparticles onto the surface of the polystyrene colloids via functional group NH from the polyethyleneimine. The experimental parameters, such as the reaction temperature, the reaction time, and the silver precursors were optimized for improvement of dispersion and Ag coat coverage of the core-shell-shaped nanostructures. Ultimately, the optimum parameters were obtained through a series of experiments, and well-dispersed, uniformly coated PS/Ag core-shell-shaped nanostructures were successfully fabricated. The formation mechanism of the PS/Ag core-shell-shaped nanostructures was also explained.     

Thermal properties of diamond/Ag composites fabricated by eletroless silver plating

Thermal management in microelectronic technology has become an important issue due to the increase of device power and integration levels. Diamond and silver were selected for the fabrication of composites with high thermal conductivity and low coefficient of thermal expansion (CTE). Diamond reinforcement powders with varied types, shapes and sizes were electroless plated by silver. Then these powders were hot-pressed in air at 600 °C, 500 MPa for 30 min to produce bulk silver matrix composites. The thermal conductivity and the CTEs of the composite at 20 vol.% are 420 W/m K and 12 ppm/K, respectively. These diamond/Ag composites have potential applications for the high integration electronic devices.     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.