Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene:Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles(YP)with center-radial meso-channels were fabricated through a simple and effective method.Al-containing YP-supported NiMo catalysts with different Al amounts(NiMo/AYP-x,x=Si/Al molar proportion)were prepared and dibenzothiophene(DBT)and 4,6-dimethyl-dibenzothiophene(4,6-DMDBT)were employed as the probes to evaluate the hydrodesulfurization(HDS)catalytic performance.The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance.The average pore sizes of series AYP-x supports are above 6.0 nm,which favors the mass transfer of organic sulfides.The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals.Aluminum embedded into the silica framework could facilitate the formation of Lewis(L)and Brønsted(B)acid sites and adjust the metal-support interaction(MSI).Among all the as-synthesized catalysts,NiMo/AYP-20 catalyst shows the highest HDS activities.The improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica,enhanced acidity,moderate MSI,and good accessibility/dispersion of active components.

Synthesis of Silica Particles with Precisely Tailored Diameter

A modified seeded growth process of silica particles with a continuous addition of tetraethyl orthosilicate （TEOS） was presented to control the diameter of silica particles. The diameter of particles was monitored by dynamic light scattering to control the addition of TEOS. The increase in the diameter of the silica particles with time and the addition of TEOS was investigated. The diameter of silica seeds increased from 193 nm to 446 nm in 4 h. The final diameter of silica particles was tailored within the range of ±5 nm to the target diameter. Silica particles with diameter of 446 nm were synthesized and assembled into photonic crystals with a pseudo band gap centered at just 1000 nm. The feasibility and practicability of this modified seeded growth process was verified.

Synthesis of Nanoscale Shell-core Titania Coated Silica Particles in the Presence of Polyether Polyamine and the Phase Transition

The nanoscale titania coated silica was prepared via a two-step precipitating approach, where the nanoscale silica nuclei were first prepared by passing an aqueous solution of sodium silicate through an ion-exchange resin bed, then coated with the precipitation from hydrolyzed butyl titanate in an ethanol-hexane mixture at a low pH value in the presence of poly(ethylene oxide) polyamine salt(PPA) at a high temperature of 90 ℃. In the second-step precipitating process, the spontaneously precipitated titania shell on the silica nuclei was stabilized in the suspension solution with the help of the adsorption of PPA on the particles. A possible precipitating mechanism was suggested. Furthermore, the amorphous titania shell could undergo crystallization from the amorphous to the anatase structure at a high temperature of 650 ℃, and a further phase transition from the anatase to the rutile structure in the different sintering processes at a rising temperature of 750 ℃.

The Effect of Gelatin on the Preparation of Silica Coated Iron Particles

A method is described for coating fine iron particles(~1 μm) with a uniform silica layer, produced by the hydrolysis of tetraethyl orthosilicate. The presence of a small amount of gelatin on the surface of the iron particles facilitates this process. The X ray photoelectron measurements indicated that the gelatin interacted with the surface of the iron particles by means of both nitrogen(in —NH 2 groups) and oxygen(in —COOH groups) and then bound to the silica. The silica coating increases the resistance of the iron particles to oxidation on heating in air, which makes the temperature at which an observable oxidization occurs from 330 ℃ to 400 ℃ raised.

Synthesis and characterization of aluminum particles coated with uniform silica shell

The silica coated aluminum composite particles were prepared by hydrolysis–condensation polymerization of tetraethylorthosilicate(TEOS)on the surface of aluminum particle.The structure,morphology,and properties of the silica coated aluminum were studied.The peaks of Si—O—Si are presented in the Fourier transform infrared(FT-IR)spectrum of the composite particles.The thickness of the silica shell is about 80 nm according to the results of transmission electron microscopy(TEM)and laser particle size analysis,while the mean diameter of the aluminum particle is 7.13μm.The mass fraction of silica in the sample was determined by fluorescent X-ray spectrometry(XRF).Result of the thermogravimetric analysis(TGA)indicates that thermal stability of silica coated aluminum particles is better than that of pure aluminum particles at low temperature while more reactive at high temperature.

MORPHOLOGY EVOLUTION OF POLY(St-co-BuA)/SILICA NANOCOMPOSITE PARTICLES SYNTHESIZED BY EMULSION POLYMERIZATION

Poly（St-co-BuA）/silica nanocomposite latexes were synthesized via conventional emulsion polymerization in the presence of 3-（trimethoxysilyl）propyl methacrylate modified colloidal nano-silica. The effects of surface property, particle size and content of colloidal nano-silica as well as the concentrations of monomer and surfactant on the morphology of nanocomposite latex particles were investigated by transmission electron microscope （TEM） and scanning electron microscope （SEM） in detail. Various interesting morphologies such as grape-like, Chinese gooseberry-like, pomegranate-like and normal core-shell structures were observed. Droplet nucleation mechanism competing with micelle nucleation mechanism was proposed to explain the morphological evolution of the nanocomposite particles.

Enhancement of Heat-Resistance of Carbonyl Iron Particles by Coating with Silica and Consequent Changes in Electromagnetic Properties

Silica-coated carbonyl iron particles （CIPs） are fabricated with the Stober method to improve their heat-resistance and wave-aSsorption properties. The morphology, heat-resistance, electromagnetic properties and microwave absorption of raw-CIPs and silica-coated CIPs are investigated using a scanning electron microscope, an energy dispersive spectrometer, a thermal-gravimetric analyzer, and a network analyzer. The results show that the heat-resistance of silica-coated CIPs is better than that of raw CIFs. The reflection losses exceeding -lOdB of silica-coated CIPs are obtained in the frequency range 9.5-12.4 GHz for the absorber thickness of 2.3 mm, and the same reflection losses of uncoated CIPs reach the data in the lower frequency range for the same thickness. The enhanced microwave absorption of silica-coated CIPs can be ascribed to the combination of proper electromagnetic impedance match and the decrease of dielectric permittivity.

Preparation of Silver Nanoshells on Silica Particles by a Simple Two-step Process

A simple two-step method was developed to prepare silver nanoshells coated on silica paticles. The method involves two steps: concentration of reaction precursor (AgNO3) on particle surfaces and subsequent reduction by formaldehyde. The obtained composite particles were characterized by TEM, ED, and SEM-EDS measurements. The results show that the silver nanoshell is coated on silica particle surface in the form of a polycrystalline (cubic structure) layer with average thickness of 20 nm and weight percentage of 19%.

Synthesis of Mesoporous Silica Nanoparticles with Tunable Shape and Size

The structural and morphological properties of mesoporous silica nanoparticles( MSNs) have dramatical influence on their in vivo biological behaviors,and thereby synthesis of MSNs with well-defined shape and size has recently attracted much more attention in the biomedical field. The synthesis of MSNs with controllable size and shape was presented by controlling the reaction temperature and the concentration of templating agent(cetyltrimethylammonium bromide,CTAB). The results indicated that MSNs were larger in particle size and more round in shape with increasing of the reaction temperature,but their particle size and dispersivity became smaller and poorer as CTAB concentration increased. Therefore,the particle size and shape of MSNs can be tuned by using the optimal synthesis conditions for specific biomedical applications.

Photodegradation and Aggregation Prevention of Natural Melanin Nanoparticles by Silica Coating Method

Melanin, the main photoreceptor in living organics, is largely abundant in pigmented hair tissues. Its promising properties have been widely studied in order to fully explore the corresponding applications. However, the photodegradating and aggregating natures of melanin, to some extent, restrict the development of this eco-friendly biomaterial. This study is conducted to overcome both disadvantages by a mature method that coating the original melanin nanoparticles with silica as shells. The results revealed that the aggregation of the melanin/silica nanoparticles (MSNP) was decreased obviously by a 5 h coating and appeared a uniformly mono-dispersed solution. The MSNP that coated for 20 h provided an efficient protection on the photodegradation of the melanin with a 50% maintenance of the melanin content compared with 16% of original melanin and 2% of MSNP-5 h.

Protein Mediated Silica Particles with pH Controlled Porosity and Morphology

Background: The silica leaching activity of some of the mystifying non-pathogenic BKH1 bacteria present in the cluster of hot springs (temperatures range 35°C - 80°C) at Bakreshwar (West Bengal, India, 23°52'48"N;87°22'40"N) has provided some significant advancements in the field of nanotechnology. The present investigation was designed to synthesis the silica particles using bioremediase protein at different pH conditions. Methods: A secretary bacterial protein bioremediase (UniProt Knowledgebase Accession Number P86277) isolated from a thermophilic non-pathogenic bacterium BKH1 (GenBank Accession No. FJ177512) has been used to synthesis the silica particles at different pH conditions (pH at 3.0, 5.0, 8.0, 10.0, and 12.0 respectively). The silica particles were synthesized by the action of bioremediase protein on Tetra-ethyl-orthosilicate (TEOS) under ambient condition. Morphological and compositional studies of the biosynthesized silica particles were characterized by Field emission scanning electron microscope (FE-SEM) equipped with Energy dispersive X-ray analyser (EDX). Results: The Fourier transformed infra-red (FTIR) spectroscopic analysis confirmed the nature as well as occurrence of several functional groups surrounded on the silica particles. The amorphous nature of the prepared silica particles was confirmed by X-ray diffractometer (XRD) study. The Zeta potential (ζ) study revealed the stability of silica particles in neutral pH environment. The Brunauer-Emmett-Teller (BET) surface area measurement confirmed the porosity variation in all biosynthesized silica particles prepared at different pH conditions. Raman spectra analytically depend on their respective specific surface (BET) area. Thermogravimetry tool was used to monitor the effects of the thermal treatment on the surface properties of all the samples. Conclusions: The method for the synthesis of silica particles at different pH condition using the protein bioremediase has a special implication as it is an environmentally benign, cost-effective and facile technique which may have conceivable application in chromatographic packing. In addition, controlling of size as well as porosity of the silica particles can be achievable by pH as an only variable.

Photoacoustic Studies of Colloidal Silica Particles after MeV Ion-Induced Shape Deformation

Ordered arrays of colloidal submicrometer-sized silica particles deposited onto silicon wafers were irradiated with MeV Si ions. The spherical silica particles turned into oblate particles as a result of the increase of the particle dimension perpendicular to the ion beam direction and the decrease in the parallel direction. Pulsed laser photoacoustic spectroscopy was used to study the structural changes of the silica particles after the ion-induced shape deformation. Our purpose is to correlate the mechanical vibrations generated by the pulsed laser as a function of the Si irradiation parameters: ion energy and fluence. Fast Fourier transform analysis of the photoacoustic signal was carried out in order to obtain the normal vibration modes of the system. The size, size distribution and shape of the silica particles were determined by scanning electron microscopy. Our results revealed significant structural differences between the spherical and the deformed silica particles.

Synthesis of Nanometer-sized Mesoporous Oxide Spheres

A few hundreds nanometer-sized mesoporous silica and alumina spheres were synthesized in organic solvents. The impacts of ammonia, N, N-dimethylformamide (DMF) and stirring speed were also investigated.

Effects of Flame Temperature and SiCl_4 Concentration on Particle Characteristics for Synthetic Silica Glass

Effects of flame temperature and SiCl4 concentration on the particle characteristics were studied.The flame temperature distributions were measured using modified sodium line-reversal technology.The particles were collected by quartz supports and were analyzed by scanning electron microscope（SEM） at different locations along the flame centerline.When the SiCl4 concentration is 16 g/min,the particles first grow and then shrink with the flame temperature increasing.When the SiCl4 concentration is 26 g/min,the flame temperature has little influence on the particle characteristics along the flame and many large spherical particles exist all the way.

Luminescence intensification of lanthanide complexes by silver nanoparticles incorporated in sol-gel matrix

We present how the luminescence of europium RR-2-P-oxides complexes can be increased by interaction of electronic levels of the complex with the radiation field of silver nanoparticles （NPs）. The procedure by which silver NPs are formed in a sol-gel polyurethane matrix precursor was elaborated. The formed Ag NPs were combined with Eu complex incorporated in ormocer matrix. The emission spectra of the complexes without silver NPs were compared with spectra of the same complexes with addition of silver NPs. As the result of the interaction of the electronic levels of lanthaaide ligands with silver plasmons, dramatic increase of luminescence was observed.

Effect of Particle Inhomogeneity on Band-gap of Silica Colloidal Crystals in Vertical Deposition Method

The effect of inhomogeneity of particles on the band-gap of silica colloidal crystals(SCCs) fabricated by vertical deposition method was studied.The optical properties of the crystals were examined.The SEM images and transmission spectrum of the crystals showed that the inhomogeneity of particles not only affected the ordering,but also their mid-gap position.When the volume ratio of S particles(VS) to L particles(VL) in suspension was 1:1,the band-gap of silica colloidal crystals changed with the growth of particles.When the ratio was 2:1,the quality of SCCs on substrate was obviously improved simultaneously with the number decreasing of L particles.Especially,the quality of SCCs at the bottom of substrate was the best and its mid-gap(634 nm) was very close to that of theoretic value of S particles(636 nm).When the ratio was 3:1,the effect of L particles became smaller with the number decreasing of L particles in suspension.The mid-gap position(638 nm) of whole SCCs on substrate were all close to that of theoretic value of S particles(636 nm).

The Effect of Silica Particle Size on the Performance of Color Ink-jet Printing Paper

In this paper,the effects of four sorts of silica with the particle size range of 4～10μm on coated paper properties and printing performance were studied.The results showed that the smaller particle size silica can provide the coated paper with higher density and contrast, better definition and good printing performance.

急性硅肺小鼠模型系统评价

目的基于滴鼻法建立急性硅肺小鼠模型评价方法。方法小鼠麻醉后经鼻吸入的方法给予单次60μl二氧化硅50 mg/ml混悬液复制硅肺小鼠模型,以肺系数、肺干湿比、HE染色和免疫组织化学等作为硅肺小鼠肺损伤评价指标,Masson染色作为纤维化评价指标。结果与对照组相比,硅肺模型组小鼠在滴鼻1~5 d小鼠体重显著下降,运动能力有明显区分,且体重下降与运动距离存在显著相关性。硅肺模型组31 d,肺组织病理学观察到致密的斑片状病灶,提示肺部炎症脓肿并形成硅结节,伴有巨噬细胞和硅颗粒聚集;Masson染色显示纤维化显著,与二氧化硅吸入量呈剂量效应关系。结论采用单次经鼻吸入二氧化硅混悬液,30 d成功建立急性硅肺小鼠模型。

油凝胶改善二氧化硅颗粒薄荷醇的吸附性能

[目的]改善二氧化硅的薄荷醇吸附性能。[方法]采用二氧化硅吸附熔融薄荷醇油凝胶制备附香颗粒,探究棕榈油的添加比例对油凝胶硬度、保油率、热力学特性的影响。对比附香颗粒的微观形态、流动性能及其负载薄荷醇的包封率、贮藏稳定性和释放特性,并评价油凝胶对二氧化硅颗粒的吸附性能改善作用。[结果]当棕榈油添加量为50%,80%时,油凝胶保油率均在90%以上,油凝胶的硬度和熔融峰值温度随棕榈油比例的提高而增大。微观结果显示,附香颗粒表面有油凝胶附着,薄荷醇包封率由73.43%提高至82.05%和91.19%,贮藏终点包封率由30.77%提高至69.83%和80.28%,且有效改善了薄荷醇的缓释性能。[结论]油凝胶能有效改善二氧化硅颗粒的薄荷醇吸附性能。

纳米SiO_(2)颗粒稳定非水相泡沫的排液行为研究

非水相泡沫在石油化工、食品化工、日用化工和生物医药等行业有着广泛的应用,但非水相溶剂本身的低表面张力和低介电常数决定了其难以形成稳定的泡沫,而纳米Si O_(2)颗粒在发泡及稳泡领域的独特优势正得到越来越多的关注。本文通过二氯二甲基硅烷(DCDMS)对14 nm的Si O_(2)颗粒进行表面润湿性改性,研究纳米Si O_(2)颗粒润湿性对非水相泡沫排液行为的影响。研究发现:随纳米Si O_(2)颗粒表面润湿性的增大,在非水相溶剂中形成的泡沫体积呈现先增大后减小的趋势;非水相溶剂极性的增强,其发泡性能呈现逐渐增强的趋势,但在非极性溶剂中不能形成有效的泡沫。所形成的非水相泡沫排液过程分为排液初期、中期、末期三个阶段,随纳米Si O_(2)颗粒表面润湿性的增大,泡沫消泡半衰期呈现先增大后减小的趋势;强极性溶剂泡沫排液半衰期可达45 min,中等极性溶剂泡沫排液半衰期可达60 min,且在光学显微镜下观察到随排液时间的增加,泡沫粒径逐渐增大,形状逐渐趋于多边形。