WorldWideScience

Sample records for colloidal silicon dioxide

  1. Synthesis of silicon carbide at room temperature from colloidal suspensions of silicon dioxide and carbon nanotubes

    Science.gov (United States)

    Zhukalin, D. A.; Tuchin, A. V.; Kulikova, T. V.; Bityutskaya, L. A.

    2015-11-01

    Experimental and theoretical approaches were used for the investigation of mechanisms and conditions of self-organized nanostructures formation in the drying drop of the mixture of colloidal suspensions of nanoscale amorphous silicon dioxide and carbon nanotubes. The formation of rodlike structures with diameter 250-300nm and length ∼4pm was revealed. The diffraction analysis of the obtained nanostructures showed the formation of the silicon carbide phase at room temperature.

  2. Formation of nanostructures from colloidal solutions of silicon dioxide and carbon nanotubes

    Science.gov (United States)

    Zhukalin, D. A.; Tuchin, A. V.; Goloshchapov, D. L.; Bityutskaya, L. A.

    2015-02-01

    The formation of nanostructures from colloidal solutions of amorphous silicon dioxide (SiO2) and carbon nanotubes (CNTs) in evaporating drops at room temperature has been studied. It is established that spherical aggregates with an average diameter of ˜2 μm and rodlike nanostructures with diameters within 250-300 nm and lengths of ˜4 μm are formed under these conditions. The mechanisms of covalent and van der Waals interaction between CNTs and SiO2 are considered in the framework of a phenomenological model of the active center of a closed CNT.

  3. Friction factors of colloidal suspension containing silicon dioxide nanoparticles in water

    Science.gov (United States)

    Tang, Clement; Pant, Sarbottam; Sharif, Md. Tanveer

    2015-11-01

    The purpose of this study is to experimentally characterize the friction factor of a colloidal suspension flow in circular and square tubes. The suspension contained silicon dioxide nanoparticles dispersed in distilled water at 9.58% volume concentration. Rheological measurements indicated that the suspension exhibits non-Newtonian behavior, and could be modelled as a power-law generalized Newtonian fluid. The experimental study showed that, with proper characterization of the consistency and flow behavior indices, the suspension flow friction factors in circular and square tubes exhibit similarities with those of Newtonian fluid flow. In the laminar fully-developed flow region, the Poiseuille numbers are similar to those established for Newtonian fluid flow. In the turbulent region, the Dodge and Metzner relation between the friction factor and a generalized Reynolds number can adequately describe the flow. The onsets of transition to turbulent flow for the suspension vary with the shape of the tube and differ from those of Newtonian fluid flow. The deviations suggest that the flow passage shape and the presence of nanoparticles affect the onset of transition to turbulent flow. Supported by North Dakota NASA EPSCoR.

  4. Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

    KAUST Repository

    Chaieb, Sahraoui

    2015-04-09

    Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

  5. 21 CFR 172.480 - Silicon dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silicon dioxide. 172.480 Section 172.480 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food...

  6. 21 CFR 573.940 - Silicon dioxide.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silicon dioxide. 573.940 Section 573.940 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...

  7. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    Masala, Silvia

    2015-10-13

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 胶态二氧化硅SYLOID244FP固化肉桂挥发油的研究%Study on solidifying volatile oil of cinnamon with colloidal silicon dioxide SYLOID244FP

    Institute of Scientific and Technical Information of China (English)

    蒋艳荣; 张振海; 胡绍英; 贾晓斌

    2013-01-01

    目的:评价胶态二氧化硅SYLOID244FP固化肉桂挥发油的特性.方法:采用SYLOID244FP固化肉桂挥发油,以桂皮醛收率为指标,优选SYLOID244FP用量;采用差示扫描量热法和扫描电镜法对固化粉末进行物相表征;考察SY-LOID244FP对肉桂挥发油中桂皮醛体外溶出和受热稳定性的影响.结果:SYLOID244FP与肉桂挥发油最佳固化比例1∶1,肉桂挥发油被固化之后,体外溶出速率加快,受热稳定性提高.结论:SYLOID244FP吸附固化中药挥发油值得进一步研究.%Objective:To evaluate the properties of solidifying volatile oil of cinnamon with colloidal silicon dioxide SYLOID244FP.Method:Volatile oil of cinnamon was solidified by SYLOID244FP.The amount of SYLOID244FP was optimized with the cinnamaldehyde yield as criteria.Curing powder was characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC).The effects of SYLOID244FP on dissolution in vitro and thermal stability of cinnamaldehyde were studied.Result:The optimum solidification ratio of SYLOID244FP to volatile oil of cinnamon was 1 ∶ 1.Dissolution rate of cinnamaldehyde increasesd and its thermal stability improved after volatile oil of cinnamon was solidified.Conclusion:Solidifying herbal volatile oil with SY-LOID244FP deserves studying further.

  9. Polymer grafting modification of the surface of nano silicon dioxide

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on the composite modification technology of the surface of nano silicon dioxide by non-soap emulsion polymerization, it is verified that there are polymer grafted on the surface of nano silicon dioxide. The modification mechanism and the bonding status on the surface of nano silicon dioxide after modification were suggested via the results of the infrared spectrum, transmission electronic microscope photograph and X-ray photoelectron spectrum. The hydroxyl formed by hydrolyzing of silane coupling agent reacts with hydroxyl on the surface of nano silicon dioxide to form Si-O-Si bonds by losing water molecules and hence the double bonds are introduced onto the surface of nano silicon dioxide. The surface of nano silicon dioxide is grafted with polymer through free radical polymerization between the double bonds on the surface of nano silicon dioxide and styrene under the action of initiating agent. The dispersibility of nano silicon dioxide and the controllability of surface modification of nano silicon dioxide can be greatly improved by the modification process.

  10. Ultrathin, epitaxial cerium dioxide on silicon

    Science.gov (United States)

    Flege, Jan Ingo; Kaemena, Björn; Höcker, Jan; Bertram, Florian; Wollschläger, Joachim; Schmidt, Thomas; Falta, Jens

    2014-03-01

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce2O3 film may very effectively be converted at room temperature to almost fully oxidized CeO2 by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness.

  11. Thermal Oxidation of Structured Silicon Dioxide

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lehrmann; Hansen, Ole; Jensen, Jørgen Arendt

    2014-01-01

    The topography of thermally oxidized, structured silicon dioxide is investigated through simulations, atomic force microscopy, and a proposed analytical model. A 357 nm thick oxide is structured by removing regions of the oxide in a masked etch with either reactive ion etching or hydrofluoric acid....... Subsequent thermal oxidation is performed in both dry and wet ambients in the temperature range 950◦C to 1100◦C growing a 205 ± 12 nm thick oxide in the etched mask windows. Lifting of the original oxide near the edge of the mask in the range 6 nm to 37 nm is seen with increased lifting for increasing...

  12. Multiple Exciton Generation in Colloidal Silicon Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Beard, M. C.; Knutsen, K. P.; Yu, P.; Luther, J. M.; Song, Q.; Metzger, W. K.; Ellingson, R. J.; Nozik, A. M.

    2007-01-01

    Multiple exciton generation (MEG) is a process whereby multiple electron-hole pairs, or excitons, are produced upon absorption of a single photon in semiconductor nanocrystals (NCs) and represents a promising route to increased solar conversion efficiencies in single-junction photovoltaic cells. We report for the first time MEG yields in colloidal Si NCs using ultrafast transient absorption spectroscopy. We find the threshold photon energy for MEG in 9.5 nm diameter Si NCs (effective band gap {identical_to} Eg = 1.20 eV) to be 2.4 {+-} 0.1E{sub g} and find an exciton-production quantum yield of 2.6 {+-} 0.2 excitons per absorbed photon at 3.4E{sub g}. While MEG has been previously reported in direct-gap semiconductor NCs of PbSe, PbS, PbTe, CdSe, and InAs, this represents the first report of MEG within indirect-gap semiconductor NCs. Furthermore, MEG is found in relatively large Si NCs (diameter equal to about twice the Bohr radius) such that the confinement energy is not large enough to produce a large blue-shift of the band gap (only 80 meV), but the Coulomb interaction is sufficiently enhanced to produce efficient MEG. Our findings are of particular importance because Si dominates the photovoltaic solar cell industry, presents no problems regarding abundance and accessibility within the Earth's crust, and poses no significant environmental problems regarding toxicity.

  13. EUV and debris characteristics of a laser-plasma tin-dioxide colloidal target

    Science.gov (United States)

    Kubodera, Shoichi; Kaku, Masanori; Touge, Shunsuke; Katto, Masahito

    2008-10-01

    Characteristics of extreme ultraviolet (EUV) and debris emissions as well as debris reduction have been investigated for a laser-produced plasma (LPP) EUV source by using a colloidal/liquid jet target containing tin dioxide nanoparticles and tin chloride. The amount of deposited debris on a silicon witness plate was determined by a total laser energy irradiated onto a target. Double-pulse laser irradiation was effective for improving the EUV conversion efficiency as a result of plasma regulation. It was, however, not effective for reducing the deposited debris from a colloidal target with nanoparticles. In situ low-temperature heating of the witness plate was effective to reduce the amount of deposited debris. Room-temperature photon processing using an incoherent vacuum ultraviolet excimer lamp at 126 nm deoxidized a deposited tin oxide layer. In addition to these active debris reduction methods, the use of a tin chloride liquid target at a certain concentration passively reduced the amount of deposited debris as a result of production of chlorine atoms that sputtered and/or etched deposition. The EUV CE of more than 1% was observed from a tin chloride target by using double-pulse laser irradiation.

  14. Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions.

    Science.gov (United States)

    Herynková, Kateřina; Šlechta, Miroslav; Šimáková, Petra; Fučíková, Anna; Cibulka, Ondřej

    2016-12-01

    We have prepared colloidal solutions of clusters composed from porous silicon nanoparticles in methanol, water and phosphate-buffered saline (PBS). Even if the size of the nanoclusters is between 60 and 500 nm, due to their highly porous "cauliflower"-like structure, the porous silicon nanoparticles are composed of interconnected nanocrystals having around 2.5 nm in size and showing strong visible luminescence in the orange-red spectral region (centred at 600-700 nm). Hydrophilic behaviour and good solubility of the nanoclusters in water and water-based solutions were obtained by adding hydrogen peroxide into the etching solution during preparation and 16 min long after-bath in hydrogen peroxide. By simple filtration of the solutions with syringe filters, we have extracted smaller nanoclusters with sizes of approx. 60-70 nm; however, these nanoclusters in water and PBS solution (pH neutral) are prone to agglomeration, as was confirmed by zeta potential measurements. When the samples were left at ambient conditions for several weeks, the typical nanocluster size increased to approx. 330-400 nm and then remained stable. However, both freshly filtered and aged samples (with agglomerated porous silicon nanoparticles) of porous silicon in water and PBS solutions can be further used for biological studies or as luminescent markers in living cells.

  15. Agglomeration of Luminescent Porous Silicon Nanoparticles in Colloidal Solutions

    Science.gov (United States)

    Herynková, Kateřina; Šlechta, Miroslav; Šimáková, Petra; Fučíková, Anna; Cibulka, Ondřej

    2016-08-01

    We have prepared colloidal solutions of clusters composed from porous silicon nanoparticles in methanol, water and phosphate-buffered saline (PBS). Even if the size of the nanoclusters is between 60 and 500 nm, due to their highly porous "cauliflower"-like structure, the porous silicon nanoparticles are composed of interconnected nanocrystals having around 2.5 nm in size and showing strong visible luminescence in the orange-red spectral region (centred at 600-700 nm). Hydrophilic behaviour and good solubility of the nanoclusters in water and water-based solutions were obtained by adding hydrogen peroxide into the etching solution during preparation and 16 min long after-bath in hydrogen peroxide. By simple filtration of the solutions with syringe filters, we have extracted smaller nanoclusters with sizes of approx. 60-70 nm; however, these nanoclusters in water and PBS solution (pH neutral) are prone to agglomeration, as was confirmed by zeta potential measurements. When the samples were left at ambient conditions for several weeks, the typical nanocluster size increased to approx. 330-400 nm and then remained stable. However, both freshly filtered and aged samples (with agglomerated porous silicon nanoparticles) of porous silicon in water and PBS solutions can be further used for biological studies or as luminescent markers in living cells.

  16. Cytotoxicity of titanium and silicon dioxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, Stefanie; Scheper, Thomas; Bahnemann, Detlef; Kasper, Cornelia [Institut fuer Technische Chemie, Leibniz Universitaet Hannover, Callinstr.5, 30167 Hannover (Germany)], E-mail: wagner@iftc.uni-hannover.de; Muenzer, Simon; Behrens, Peter [Institut fuer Anorganische Chemie, Leibniz Universitaet Hannover, Callinstr.9, 30167 Hannover (Germany)

    2009-05-01

    Different TiO{sub 2} and SiO{sub 2} nanoparticles have been tested concerning their toxicity on selected mammalian cell lines. Various powders and suspensions, all of which consist of titanium or silicon dioxide nanoparticles have been examined. These particles differ in the crystal structure, the size and the BET-surface area. There was also a classification in fixed particles and in particles easily accessible in solution. With focus on the possible adsorption of the nanoparticles into the human organism, via skin and via respiratory tract, the effects on fibroblasts (NIH-3T3) and on a human lung adenocarcinoma epithelial cell line were examined. Additionally, the particles were tested with HEP-G2 cells, which are often used as model cell line for biocompatibility tests, and PC-12 cells, a rat adrenal pheochromocytoma cell line. The viability of the cells was examined by the MTT-test. The viability results were found to partly depend on the type of cells used. The experimental results show that the adhesion of the cells on the different powders strongly depends on the type of cell lines as well as on the type of powder. It was found that the lower viability of some cells on the powder coatings is not only caused by a cytotoxicity effect of the powders, but is also due to a lower adhesion of the cells on the particle surfaces. Furthermore, it could be shown that the physical properties of the powders cannot be easily correlated to any observed biological effect. While some powders show a significant suppression of the cell growth, others with similar physical properties indicate no toxic effect.

  17. Heteroaggregation of titanium dioxide nanoparticles with natural clay colloids.

    Science.gov (United States)

    Labille, Jérôme; Harns, Carrie; Bottero, Jean-Yves; Brant, Jonathan

    2015-06-02

    To better understand and predict the fate of engineered nanoparticles in the water column, we assessed the heteroaggregation of TiO2 nanoparticles with a smectite clay as analogues for natural colloids. Heteroaggregation was evaluated as a function of water salinity (10(-3) and 10(-1) M NaCl), pH (5 and 8), and selected nanoparticle concentration (0-4 mg/L). Time-resolved laser diffraction was used, coupled to an aggregation model, to identify the key mechanisms and variables that drive the heteroaggregation of the nanoparticles with colloids. Our data show that, at a relevant concentration, nanoparticle behavior is mainly driven by heteroaggregation with colloids, while homoaggregation remains negligible. The affinity of TiO2 nanoparticles for clay is driven by electrostatic interactions. Opposite surface charges and/or high ionic strength favored the formation of primary heteroaggregates via the attachment of nanoparticles to the clay. The initial shape and dispersion state of the clay as well as the nanoparticle/clay concentration ratio also affected the nature of the heteroaggregation mechanism. With dispersed clay platelets (10(-3) M NaCl), secondary heteroaggregation driven by bridging nanoparticles occurred at a nanoparticle/clay number ratio of greater than 0.5. In 10(-1) M NaCl, the clay was preaggregated into larger and more spherical units. This favored secondary heteroaggregation at lower nanoparticle concentration that correlated to the nanoparticle/clay surface area ratio. In this latter case, a nanoparticle to clay sticking efficiency could be determined.

  18. Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

    Science.gov (United States)

    König, Dirk; Hiller, Daniel; Gutsch, Sebastian; Zacharias, Margit; Smith, Sean

    2017-04-01

    All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime and tunnelling current measurements.

  19. A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Liu Chin-Yi

    2010-01-01

    Full Text Available Abstract Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture. We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals (Si NCs from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange, or removal reactions. The Schottky junction device showed a photovoltaic response with a power conversion efficiency of 0.02%, a fill factor of 0.26, short circuit-current density of 0.148 mA/cm2, and open-circuit voltage of 0.51 V.

  20. Simulation and experimental verification of silicon dioxide deposition by PECVD

    Science.gov (United States)

    Xu, Qing; Li, Yu-Xing; Li, Xiao-Ning; Wang, Jia-Bin; Yang, Fan; Yang, Yi; Ren, Tian-Ling

    2017-02-01

    Deposition of silicon dioxide in high-density plasma is an important process in integrated circuit manufacturing. A software named CFD-ACE was used to simulate the mechanism of plasma in the chamber of plasma enhanced chemical vapor deposition (PECVD) system, and the evolution of the feature profile was simulated based on CFD-TOPO. Simulation and experiment of silicon dioxide that deposited in SiH4/N2O mixture by PECVD system was researched. The particle density, energy and angular distribution in the chamber were simulated and discussed. We also studied how the depth/width ratio affected the step coverage of the trench and analyzed the deposition rate of silicon dioxide on the feature scale. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition of thin films. Images of the feature profiles were taken by scanning electron microscope (SEM). The simulation results were in good agreement with experimental, which could guide the semiconductor device manufacture.

  1. Continuous flow ink etching for direct micropattern of silicon dioxide

    Science.gov (United States)

    Xing, Jiyao; Rong, Weibin; Wang, Lefeng; Sun, Lining

    2016-07-01

    A continuous flow ink etching (CFIE) method is presented to directly create micropatterns on a 60 nm thick silicon dioxide (SiO2) layer. This technique employs a micropipette filled with potassium bifluoride (KHF2) aqueous solution to localize SiO2 dissolution in the vicinity of the micropipette tip. Both dot and line features with well-defined edges were fabricated and used as hardmasks for silicon etching. The linear density of etchant ink deposited on the SiO2 can be used to regulate the depth, width and 2D morphology of the line pattern. The characterization of CFIE including the resolution (about 4 μm), reproducibility and capability to form complex structures are reported. This technique provides a simple and flexible alternative to generate the SiO2 hardmask for silicon microstructure fabrication.

  2. Small silicon, big opportunities: the development and future of colloidally-stable monodisperse silicon nanocrystals.

    Science.gov (United States)

    Mastronardi, Melanie L; Henderson, Eric J; Puzzo, Daniel P; Ozin, Geoffrey A

    2012-11-14

    Nanomaterials are becoming increasingly widespread in consumer technologies, but there is global concern about the toxicity of nanomaterials to humans and the environment as they move rapidly from the research laboratory to the market place. With this in mind, it makes sense to intensify the nanochemistry community's global research effort on the synthesis and study of nanoparticles that are purportedly "green". One potentially green nanoparticle that seems to be a most promising candidate in this context is silicon, whose appealing optical, optoelectronic, photonic, and biomedical attributes are recently gaining much attention. In this paper, we outline some of our recent contributions to the development of the growing field of silicon nanocrystals (ncSi) in order to stress the importance of continued study of ncSi as a green alternative to the archetypal semiconductor nanocrystals like CdSe, InAs, and PbS. While a variety of developments in synthetic methods, characterization techniques, and applications have been reported in recent years, the ability to prepare colloidally-stable monodisperse ncSi samples may prove to have the largest impact on the field, as it opens the door to study and access the tunable size-dependent properties of ncSi. Here, we summarize our recent contributions in size-separation methods to achieve monodisperse samples, the characterization of size-dependant property trends, the development of ncSi applications, and their potential impact on the promising future of ncSi.

  3. 3-D patterning of silicon by laser-initiated, liquid-assisted colloidal (LILAC) lithography.

    Science.gov (United States)

    Ulmeanu, M; Grubb, M P; Jipa, F; Quignon, B; Ashfold, M N R

    2015-06-01

    We report a comprehensive study of laser-initiated, liquid-assisted colloidal (LILAC) lithography, and illustrate its utility in patterning silicon substrates. The method combines single shot laser irradiation (frequency doubled Ti-sapphire laser, 50fs pulse duration, 400nm wavelength) and medium-tuned optical near-field effects around arrays of silica colloidal particles to achieve 3-D surface patterning of silicon. A monolayer (or multilayers) of hexagonal close packed silica colloidal particles act as a mask and offer a route to liquid-tuned optical near field enhancement effects. The resulting patterns are shown to depend on the difference in refractive index of the colloidal particles (ncolloid) and the liquid (nliquid) in which they are immersed. Two different topographies are demonstrated experimentally: (a) arrays of bumps, centred beneath the original colloidal particles, when using liquids with nliquidncolloid - and explained with the aid of complementary Mie scattering simulations. The LILAC lithography technique has potential for rapid, large area, organized 3-D patterning of silicon (and related) substrates. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Lock and key colloids through polymerization-induced buckling of monodisperse silicon oil droplets

    NARCIS (Netherlands)

    Sacanna, S.|info:eu-repo/dai/nl/311471676; Irvine, W.T.M.; Rossi, L.|info:eu-repo/dai/nl/314410376; Pine, D.J.

    2011-01-01

    We have developed a new simple method to fabricate bulk amounts of colloidal spheres with well defined cavities from monodisperse emulsions. Herein, we describe the formation mechanism of ‘‘reactive’’ silicon oil droplets that deform to reproducible shapes via a polymerization-induced buckling

  5. Photocatalytic degradation of benzenesulfonate on colloidal titanium dioxide.

    Science.gov (United States)

    Szabó-Bárdos, Erzsébet; Markovics, Otília; Horváth, Ottó; Töro, Norbert; Kiss, Gyula

    2011-02-01

    Titanium dioxide-mediated photocatalyzed degradation of benzenesulfonate (BS) was investigated by monitoring chemical oxygen demand (COD), total organic carbon (TOC) content, sulfate concentration, pH as well as the absorption and emission spectral changes in both argon-saturated and aerated systems. Liquid chromatography-mass spectrometry analysis was utilized for the detection of intermediates formed during the irradiation in the UVA range (λ(max) = 350 nm). The results obtained by these analytical techniques indicate that the initial step of degradation is hydroxylation of the starting surfactant, resulting in the production of hydroxy- and dihydroxybenzenesulfonates. These reactions were accompanied by desulfonation, which increases [H(+)] in both argon-saturated and aerated systems. In accordance with our previous theoretical calculations, the formation of ortho- and meta-hydroxylated derivatives is favored in the first step. The main product of the further oxygenation of these derivatives was 2,5-dihydroxy-benzesulfonate. No decay of the hydroxy species occurred during the 8-h irradiation in the absence of dissolved oxygen. In the aerated system much more efficient desulfonation and hydroxylation, moreover, a significant decrease of TOC took place at the initial stage. Further hydroxylation led to cleavage of the aromatic system, due to the formation of polyhydroxy derivatives, followed by ring fission, resulting in the production of aldehydes and carboxylic acids. Total mineralization was achieved by the end of the 8-h photocatalysis. It has been proved that in this photocatalytic procedure the presence of dissolved oxygen is necessary for the cleavage of the aromatic ring because hydroxyl radicals photochemically formed in the deaerated system too alone are not able to break the C-C bonds.

  6. Repulsive Casimir force between silicon dioxide and superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Phan, Anh D. [Department of Physics, University of South Florida, Tampa, Florida (United States); Viet, N.A. [Institute of Physics, Badinh, Hanoi (Viet Nam)

    2012-06-15

    We present a detailed investigation of the Casimir interaction between the superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (BSCCO) and silicon dioxide with bromobenzene present in between. We found that the dispersion force is repulsive and the magnitude of the force can be changed by varying the thickness of the object and the temperature. The repulsive force would provide a method to deal with stiction problems and provide much significant from the practical point of view. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Electric field dependent dielectric response of alumina/silicone oil colloids

    Science.gov (United States)

    Magallon, Louis; Tsui, Stephen

    2014-03-01

    We investigate the dielectric response of a mixture of alumina nanopowder and silicone oil. Frequency and electric field dependent measurements of another insulating colloid, i.e., urea-coated Ba0.8Rb0.4TiO(C2O4)2 nanoparticles immersed in silicone oil, revealed universal dielectric response (UDR) characteristics and, with the application of high voltage, a negative capacitance. Alumina in silicone oil represents a simpler system in which to perform similar dielectric investigation. This colloid is sandwiched in a parallel plate capacitor cell, and the complex impedance is measured via lock-in amplifier at various frequencies and applied dc biases. Furthermore, we will compare and discuss the dielectric behaviors of different sized suspended alumina particles.

  8. Influence of silicon dioxide capping layers on pore characteristics in nanocrystalline silicon membranes.

    Science.gov (United States)

    Qi, Chengzhu; Striemer, Christopher C; Gaborski, Thomas R; McGrath, James L; Fauchet, Philippe M

    2015-02-06

    Porous nanocrystalline silicon (pnc-Si) membranes are a new class of membrane material with promising applications in biological separations. Pores are formed in a silicon film sandwiched between nm thick silicon dioxide layers during rapid thermal annealing. Controlling pore size is critical in the size-dependent separation applications. In this work, we systematically studied the influence of the silicon dioxide capping layers on pnc-Si membranes. Even a single nm thick top oxide layer is enough to switch from agglomeration to pore formation after annealing. Both the pore size and porosity increase with the thickness of the top oxide, but quickly reach a plateau after 10 nm of oxide. The bottom oxide layer acts as a barrier layer to prevent the a-Si film from undergoing homo-epitaxial growth during annealing. Both the pore size and porosity decrease as the thickness of the bottom oxide layer increases to 100 nm. The decrease of the pore size and porosity is correlated with the increased roughness of the bottom oxide layer, which hinders nanocrystal nucleation and nanopore formation.

  9. UV and visible light active aqueous titanium dioxide colloids stabilized by surfactants.

    Science.gov (United States)

    Pacia, Michał; Warszyński, Piotr; Macyk, Wojciech

    2014-09-07

    Attempts to increase the stability of photocatalytically active nanodispersions of titanium dioxide over a wide range of pH (3-10) were undertaken. Polyethylene glycols (PEGs) with different molecular weights and polyoxyethylenesorbitan monooleate (Tween® 80) were tested as stabilizing agents of TiO2 nanoparticles. The results of DLS measurements proved the stabilizing effect of Tween® 80 while the systems involving PEGs, independently of the polymer concentration, showed a tendency to form aggregates in neutral solutions. The colloids stabilized with Tween® 80 were photosensitized with 2,3-naphthalenediol (nd) or 2-hydroxy-3-naphthoic acid (hn) or catechol (cat). The photocatalytic activity of such colloids has been assessed in an azure B degradation reaction using both UV and visible light. The nd@TiO2 + Tween colloid appeared particularly photoactive upon visible light irradiation. Moreover, the comparison of activities of nd@TiO2 + Tween and TiO2 + Tween revealed a significantly better performance of the former nanodispersion, independently of the irradiation conditions (UV or visible light). This effect has been explained by different structures of micelles formed in the case of TiO2 and nd@TiO2 stabilized with Tween® 80.

  10. Molecular dynamics simulations on surface properties of silicon dioxide melts

    CERN Document Server

    Röder, A

    2000-01-01

    In the present thesis the surface properties of a silicon dioxide melt were studied. As first systems drops (i.e. sytems without periodic boundary conditions) of N=432, 1536, as well as 4608 atoms were considered. The second analyzed geometry corresponds to that of a thin film, i. e. periodic boundary conditions in x- and y-direction were present, while in z-direction one had a free surface. In this case a system of N=1152 atoms was considered. As model potential the two-body potential proposed by Beest, Kramer, and van Santen was applied. For both geometries five temperatures were considered, which lied in the range of 3000 K

  11. Optofluidic taming of a colloidal dimer with a silicon nanocavity

    Energy Technology Data Exchange (ETDEWEB)

    Pin, C.; Renaut, C. [Groupe d' Optique de Champ Proche - LRC CEA n°DSM-08-36, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS n°6303- Université de Bourgogne, Dijon (France); University Grenoble Alpes, INAC-SP2M-SINAPS, F-38000 Grenoble, France and CEA, INAC-SP2M-SINAPS, F-38000 Grenoble (France); University Grenoble Alpes, CNRS, CEA-Leti Minatec, LTM, F-38054 Grenoble Cedex (France); Cluzel, B., E-mail: benoit.cluzel@u-bourgogne.fr; Fornel, F. de [Groupe d' Optique de Champ Proche - LRC CEA n°DSM-08-36, Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS n°6303- Université de Bourgogne, Dijon (France); Peyrade, D. [University Grenoble Alpes, CNRS, CEA-Leti Minatec, LTM, F-38054 Grenoble Cedex (France); Picard, E.; Hadji, E. [University Grenoble Alpes, INAC-SP2M-SINAPS, F-38000 Grenoble, France and CEA, INAC-SP2M-SINAPS, F-38000 Grenoble (France)

    2014-10-27

    We report here the optical trapping of a heterogeneous colloidal dimer above a photonic crystal nanocavity used as an on-chip optical tweezer. The trapped dimer consists of a cluster of two dielectric microbeads of different sizes linked by van der Waals forces. The smallest bead, 1 μm in diameter, is observed to be preferentially trapped by the nanotweezer, leaving the second bead untrapped. The rotational nature of the trapped dimer Brownian motion is first evidenced. Then, in the presence of a fluid flow, control of its orientation and rotation is achieved. The whole system is found to show high rotational degrees of freedom, thereby acting as an effective flow-sensitive microscopic optical ball joint.

  12. In vitro cell tests of pancreatic malignant tumor cells by photothermotherapy based on DMSO porous silicon colloids.

    Science.gov (United States)

    Hong, Chanseok; Lee, Chongmu

    2014-01-01

    Dimethyl sulfoxide porous silicon (DMSO-PSi) colloid in which DMSO was used as a surfactant suitable for inhibiting the agglomeration of PSi nanoparticles was prepared for use in cancer photothermotherapy. The photothermal effect of the DMSO-PSi colloid was found to be high enough to destroy cancer cells (T = ∼52 °C). The mean particle size of the PSi nanoparticles in the DMSO-PSi colloid was 67 nm, which is low enough to flow through blood vessels without causing a blockage. The DMSO-PSi colloid in combination with an NIR laser resulted in a cell viability of 5.70%, which is a sufficiently high cytotoxic effect.

  13. Effect of Surface Treated Silicon Dioxide Nanoparticles on Some Mechanical Properties of Maxillofacial Silicone Elastomer

    Directory of Open Access Journals (Sweden)

    Sara M. Zayed

    2014-01-01

    Full Text Available Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2 on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n=21. One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624, tensile strength (ASTM D412, percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α=0.05. Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer.

  14. Colloidal silicon quantum dots: from preparation to the modification of self-assembled monolayers (SAMs) for bio-applications.

    Science.gov (United States)

    Cheng, Xiaoyu; Lowe, Stuart B; Reece, Peter J; Gooding, J Justin

    2014-04-21

    Concerns over possible toxicities of conventional metal-containing quantum dots have inspired growing research interests in colloidal silicon nanocrystals (SiNCs), or silicon quantum dots (SiQDs). This is related to their potential applications in a number of fields such as solar cells, optoelectronic devices and fluorescent bio-labelling agents. The past decade has seen significant progress in the understanding of fundamental physics and surface properties of silicon nanocrystals. Such understanding is based on the advances in the preparation and characterization of surface passivated colloidal silicon nanocrystals. In this critical review, we summarize recent advances in the methods of preparing high quality silicon nanocrystals and strategies for forming self-assembled monolayers (SAMs), with a focus on their bio-applications. We highlight some of the major challenges that remain, as well as lessons learnt when working with silicon nanocrystals (239 references).

  15. Low-Roughness Plasma Etching of HgCdTe Masked with Patterned Silicon Dioxide

    Science.gov (United States)

    Ye, Z. H.; Hu, W. D.; Yin, W. T.; Huang, J.; Lin, C.; Hu, X. N.; Ding, R. J.; Chen, X. S.; Lu, W.; He, L.

    2011-08-01

    A novel mask technique utilizing patterned silicon dioxide films has been exploited to perform mesa etching for device delineation and electrical isolation of HgCdTe third-generation infrared focal-plane arrays (IRFPAs). High-density silicon dioxide films were deposited at temperature of 80°C, and a procedure for patterning and etching of HgCdTe was developed by standard photolithography and wet chemical etching. Scanning electron microscopy (SEM) showed that the surfaces of inductively coupled plasma (ICP) etched samples were quite clean and smooth. Root-mean-square (RMS) roughness characterized by atomic force microscopy (AFM) was less than 1.5 nm. The etching selectivity between a silicon dioxide film and HgCdTe in the samples masked with patterned silicon dioxide films was greater than 30:1. These results show that the new masking technique is readily available and promising for HgCdTe mesa etching.

  16. Silanization of plasma-grown silicon quantum dots for production of a tunable, stable, colloidal solution

    Science.gov (United States)

    Anderson, Ingrid E.; Shircliff, Rebecca A.; Lee, Benjamin G.; Simonds, Brian; Agarwal, Sumit; Stradins, Paul; Collins, Reuben T.

    2011-09-01

    Nanomaterials have the potential to revolutionize photovoltaics with the promise of new physics, novel architectures and low cost synthesis. Silicon quantum dots, relative to their II-VI counterparts, are understudied due to the difficulty of solution synthesis and chemical passivation. However, silicon is still an attractive solar cell material, providing an optimal band gap, low toxicity, and a very solid body of physical understanding of bulk silicon to draw from. We have synthesized silicon quantum dots with plasma enhanced chemical vapor deposition, and have developed a method for chemical passivation of these silicon quantum dots that can be used on particles created in a variety of ways. This versatile method utilizes oxidation via wet chemical etch and subsequent siloxane bond formation. The attachment of a silane to the SiOx shell leads to stability of the silicon core for over a month in air, and individual particles can be seen with TEM; thus a stable, colloidal suspension is formed. The future for this technique, including increasing quantum yield of the particles by changing the nature of the oxide, will be discussed.

  17. Origin of blue photoluminescence from colloidal silicon nanocrystals fabricated by femtosecond laser ablation in solution

    Science.gov (United States)

    Hao, H. L.; Wu, W. S.; Zhang, Y.; Wu, L. K.; Shen, W. Z.

    2016-08-01

    We present a detailed investigation into the origin of blue emission from colloidal silicon (Si) nanocrystals (NCs) fabricated by femtosecond laser ablation of Si powder in 1-hexene. High resolution transmission electron microscopy and Raman spectroscopy observations confirm that Si NCs with average size 2.7 nm are produced and well dispersed in 1-hexene. Fourier transform infrared spectrum and x-ray photoelectron spectra have been employed to reveal the passivation of Si NCs surfaces with organic molecules. On the basis of the structural characterization, UV-visible absorption, temperature-dependent photoluminescence (PL), time-resolved PL, and PL excitation spectra investigations, we deduce that room-temperature blue luminescence from colloidal Si NCs originates from the following two processes: (i) under illumination, excitons first form within colloidal Si NCs by direct transition at the X or Γ (Γ25 → Γ‧2) point; (ii) and then some trapped excitons migrate to the surfaces of colloidal Si NCs and further recombine via the surface states associated with the Si-C or Si-C-H2 bonds.

  18. Synthetic osteogenic extracellular matrix formed by coated silicon dioxide nanosprings

    Directory of Open Access Journals (Sweden)

    Hass Jamie L

    2012-01-01

    Full Text Available Abstract Background The design of biomimetic materials that parallel the morphology and biology of extracellular matrixes is key to the ability to grow functional tissues in vitro and to enhance the integration of biomaterial implants into existing tissues in vivo. Special attention has been put into mimicking the nanostructures of the extracellular matrix of bone, as there is a need to find biomaterials that can enhance the bonding between orthopedic devices and this tissue. Methods We have tested the ability of normal human osteoblasts to propagate and differentiate on silicon dioxide nanosprings, which can be easily grown on practically any surface. In addition, we tested different metals and metal alloys as coats for the nanosprings in tissue culture experiments with bone cells. Results Normal human osteoblasts grown on coated nanosprings exhibited an enhanced rate of propagation, differentiation into bone forming cells and mineralization. While osteoblasts did not attach effectively to bare nanowires grown on glass, these cells propagated successfully on nanosprings coated with titanium oxide and gold. We observed a 270 fold increase in the division rate of osteoblasts when grow on titanium/gold coated nanosprings. This effect was shown to be dependent on the nanosprings, as the coating by themselves did not alter the growth rate of osteoblast. We also observed that titanium/zinc/gold coated nanosprings increased the levels of osteoblast production of alkaline phosphatase seven folds. This result indicates that osteoblasts grown on this metal alloy coated nanosprings are differentiating to mature bone making cells. Consistent with this hypothesis, we showed that osteoblasts grown on the same metal alloy coated nanosprings have an enhanced ability to deposit calcium salt. Conclusion We have established that metal/metal alloy coated silicon dioxide nanosprings can be used as a biomimetic material paralleling the morphology and biology of

  19. Electrochemical removal of segregated silicon dioxide impurities from yttria stabilized zirconia surfaces at elevated temperatures

    DEFF Research Database (Denmark)

    Andersen, Thomas; Hansen, Karin Vels; Mogensen, Mogens Bjerg;

    2011-01-01

    Here we report on the electrochemical removal of segregated silicon dioxide impurities from Yttria Stabilized Zirconia (YSZ) surfaces at elevated temperatures studied under Ultra High Vacuum (UHV) conditions. YSZ single crystals were heated in vacuum by an applied 18kHz a.c. voltage using the ionic...... and XPS analysis. Silicon enrichment of the surface was only observed at oxygen and water vapor partial pressures above 25mbar and 10mbar, respectively. No silicon was observed on crystals annealed in vacuum and at oxygen and water vapor partial pressures below 10mbar. The YSZ seems to get partially...... electrochemically reduced by the a.c. voltage when no oxidation substances are present. The absence of silicon on the surfaces annealed in vacuum or at low oxygen or water vapor partial pressures was attributed to electrochemical reduction of silicon dioxide to volatile silicon monoxide on the YSZ surface...

  20. Etching Rate of Silicon Dioxide Using Chlorine Trifluoride Gas

    Science.gov (United States)

    Miura, Yutaka; Kasahara, Yu; Habuka, Hitoshi; Takechi, Naoto; Fukae, Katsuya

    2009-02-01

    The etching rate behavior of silicon dioxide (SiO2, fused silica) using chlorine trifluoride (ClF3) gas is studied at substrate temperatures between 573 and 1273 K at atmospheric pressure in a horizontal cold-wall reactor. The etching rate increases with the ClF3 gas concentration, and the overall reaction is recognized to be of the first order. The change of the etching rate with increasing substrate temperature is nonlinear, and the etching rate tends to approach a constant value at temperatures exceeding 1173 K. The overall rate constant is estimated by numerical calculation, taking into account the transport phenomena in the reactor, including the chemical reaction at the substrate surface. The activation energy obtained in this study is 45.8 kJ mol-1, and the rate constant is consistent with the measured etching rate behavior. A reactor system in which there is minimum etching of the fused silica chamber by ClF3 gas can be achieved using an IR lamp heating unit and a chamber cooling unit to maintain a sufficiently low temperature of the chamber wall.

  1. Rain Erosion Behavior of Silicon Dioxide Films Prepared on Sapphire

    Institute of Scientific and Technical Information of China (English)

    Liping FENG; Zhengtang LIU; Wenting LIU

    2005-01-01

    Silicon dioxide (SiO2) films were prepared on sapphire (α-Al2O3) by radio frequency magnetron reactive sputtering in order to in crease both transmission and rain erosion resistant performance of infrared domes of sapphire. Composition and structure of SiO2 films were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD),respectively. The transmittance of uncoated and coated sapphire was measured using a Fourier transform infrared(FTIR) spectrometer. Rain erosion tests of the uncoated and coated sapphire were performed at 211 m/s impact velocity with an exposure time ranging from 1 to 8 min on a whirling arm rig. Results show that the deposited films can greatly increase the transmission of sapphire in mid-wave IR. After rain erosion test, decreases in normalized transmission were less than 1% for designed SiO2 films and the SiO2 coating was strongly bonded to the sapphire substrate. In addition, sapphires coated with SiO2 films had a higher transmittance than uncoated ones after rain erosion.

  2. Electric field enhancement with plasmonic colloidal nanoantennas excited by a silicon nitride waveguide

    CERN Document Server

    Darvishzadeh-Varcheie, Mahsa; Ragan, Regina; Boyraz, Ozdal; Capolino, Filippo

    2016-01-01

    We investigate the feasibility of CMOS-compatible optical structures to develop novel integrated spectroscopy systems. We show that local field enhancement is achievable utilizing dimers of plasmonic nanospheres that can be assembled from colloidal solutions on top of a CMOS-compatible optical waveguide. The resonant dimer nanoantennas are excited by modes guided in the integrated silicon nitride waveguide. Simulations show that 100 fold electric field enhancement builds up in the dimer gap as compared to the waveguide evanescent field amplitude at the same location. We investigate how the field enhancement depends on dimer location, orientation, distance and excited waveguide modes.

  3. Integration of colloidal silicon nanocrystals on metal electrodes in single-electron transistor

    Science.gov (United States)

    Higashikawa, Yasuhiro; Azuma, Yasuo; Majima, Yutaka; Kano, Shinya; Fujii, Minoru

    2016-11-01

    We develop a facile process to integrate colloidal silicon nanocrystals (Si NCs) with metal electrodes in a single-electron transistor by self-assembly. Gold (Au) surface is modified by an amine-terminated self-assembled monolayer to have a positive potential. All-inorganic boron (B) and phosphorus (P) codoped Si NCs, with a negative surface potential and size-controllability, are selectively adsorbed on an amine-terminated Au surface by electrostatic attraction. We demonstrate the fabrication of SETs consisting of electroless-plated Au nanogap electrodes and codoped Si NCs using this process and observation of clear Coulomb diamonds at 9 K.

  4. Effect of different-sized colloids on the transport and deposition of titanium dioxide nanoparticles in quartz sand.

    Science.gov (United States)

    Cai, Li; Peng, Shengnan; Wu, Dan; Tong, Meiping

    2016-01-01

    Colloids (non-biological and biological) with different sizes are ubiquitous in natural environment. The investigations regarding the influence of different-sized colloids on the transport and deposition behaviors of engineered-nanoparticles in porous media yet are still largely lacking. This study investigated the effects of different-sized non-biological and biological colloids on the transport of titanium dioxide nanoparticles (nTiO2) in quartz sand under both electrostatically favorable and unfavorable conditions. Fluorescent carboxylate-modified polystyrene latex microspheres (CML) with sizes of 0.2-2 μm were utilized as model non-biological colloids, while Gram-negative Escherichia coli (∼ 1 μm) and Gram-positive Bacillus subtilis (∼ 2 μm) were employed as model biological colloids. Under the examined solution conditions, both breakthrough curves and retained profiles of nTiO2 with different-sized CML particles/bacteria were similar as those without colloids under favorable conditions, indicating that the copresence of model colloids in suspensions had negligible effects on the transport and deposition of nTiO2 under favorable conditions. In contrast, higher breakthrough curves and lower retained profiles of nTiO2 with CML particles/bacteria relative to those without copresent colloids were observed under unfavorable conditions. Clearly, the copresence of model colloids increased the transport and decreased the deposition of nTiO2 in quartz sand under unfavorable conditions (solution conditions examined in present study). Both competition of deposition sites on quartz sand surfaces and the enhanced stability/dispersion of nTiO2 induced by copresent colloids were found to be responsible for the increased nTiO2 transport with colloids under unfavorable conditions. Moreover, the smallest colloids had the highest coverage on sand surface and most significant dispersion effect on nTiO2, resulting in the greatest nTiO2 transport. Copyright © 2015. Published

  5. Porous silicon photoluminescence modification by colloidal gold nanoparticles: Plasmonic, surface and porosity roles

    Energy Technology Data Exchange (ETDEWEB)

    Mora, M.B. de la; Bornacelli, J. [Instituto de Física, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Nava, R. [Centro de Investigación en Energía, Universidad Nacional Autónoma de México, Temixco, Morelos 62580 (Mexico); Zanella, R. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Reyes-Esqueda, J.A., E-mail: betarina@gmail.com [Instituto de Física, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico)

    2014-02-15

    Metal nanoparticles on semiconductors are of interest because of the tunable effect of the surface plasmon resonance on the physical properties of the semiconductor. In this work, colloidal gold nanoparticles obtained by two different methods, with an average size of 6.1±2.0 nm and 5.0±2.0 nm, were added to luminescent porous silicon by drop casting. The gold nanoparticles interact with porous silicon by modifying its optical properties such as photoluminescence. That being said, plasmon effects are not the only to be taken into account; as shown in this work, surface chemical modification and porosity also play a key role in the final performance of photoluminescence of a porous silicon–gold nanoparticle hybrid system. -- Highlights: • A hybrid material consisting of porous silicon and gold nanoparticles was fabricated. • Porous silicon/gold nanoparticle hybrid material was made by drop casting. • Influence of plasmonics, surface chemical modification and porosity on the optical behavior of our material was analyzed. • Porosity is proposed as a parameter control to obtain the best effects on luminescence of the hybrid plasmonic material.

  6. Pulsed laser deposition of silicon dioxide thin films with silicone targets for fabricating waveguide devices

    Science.gov (United States)

    Okoshi, Masayuki; Kuramatsu, Masaaki; Inoue, Narumi

    2002-06-01

    Silicon dioxide (SiO2) thin films were deposited at room temperature by 193-nm ArF excimer laser ablation of silicone in oxygen atmosphere. Only the side chains of the target were photo-dissociated during ablation to deposit Si-O bonds on a substrate in high laser fluence at about 10 J/cm2. Oxygen gas worked to oxidize the Si-O bonds ejected from the target to from SiO2 thin films at the gas pressure of 4.4 X 10-2 Torr, in addition to reducing the isolated carbon mixed into the films. We also found that the deposited rate could control refractive index of the films. The refractive index of the film deposited at 0.05 nm/pulse is greater than that of the film at 0.1 nm/pulse. Thus, a 0.2-micrometers thick SiO2 cladding film deposited at 0.1 nm/pulse was firstly formed on the whole surface of a 100- micrometers -thick polyester film, and then a 0.6 micrometers -thick SiO2 core film at 0.05 nm/pulse was fabricated in a line on the sample. The sample functioned as a waveguide device for a 633-nm line of He-Ne laser.

  7. Biplot Analysis of Silicon Dioxide on Early Growth of Sunflower

    Directory of Open Access Journals (Sweden)

    Sabaghnia Naser

    2016-06-01

    Full Text Available Research into nanotechnology has advanced in almost all fields of technology and the aim of this study was to evaluate the role of nano-silicon dioxide (nano-SiO2 in germination performance sunflower. Germination and seedling growth are the most important stage of plant development and are critical factors to crop production and are essential to achieve optimum performance. The effects of pre-germination hydration in solutions of nano-SiO2 (0, 0.2, 0.4, 0.6, 0.8, 1 and 1.2 mM for 8 h on germination characteristics of sunflower were investigated. The trait by treatment (TT biplot explained 93% of the total variation of the standardized data (77% and 16% for the first and second principal components, respectively. According to polygon-view of TT biplot, T2 (0.2 mM had the highest values for all of the measured traits except mean germination time and the time to 50% germination. The germination percentage was determined as the best trait and showed the high association with promptness index, energy of germination and germination rate traits. The results of the present study indicated that pre-sowing seed treatments with low concentration of nano-SiO2 had favorable effect sunflower seed germination and seedling early growth. Such a similar outcome could be applied in the future to outline other crops in response to nano-particles as well as to help define tolerance tools for recommendations in stressful conditions in the world.

  8. Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

    Directory of Open Access Journals (Sweden)

    P. Borowicz

    2013-01-01

    Full Text Available Three samples with dielectric layers from high-κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high-κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above, the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide.

  9. Biocompatibility of cerium dioxide and silicon dioxide nanoparticles with endothelial cells

    Directory of Open Access Journals (Sweden)

    Claudia Strobel

    2014-10-01

    Full Text Available Cerium dioxide (CeO2 and silicon dioxide (SiO2 nanoparticles are of widespread use in modern life. This means that human beings are markedly exposed to them in their everyday life. Once passing biological barriers, these nanoparticles are expected to interact with endothelial cells, leading to systemic alterations with distinct influences on human health. In the present study we observed the metabolic impact of differently sized CeO2 (8 nm; 35 nm and SiO2 nanoparticles (117 nm; 315 nm on immortalized human microvascular (HMEC-1 and primary macrovascular endothelial cells (HUVEC, with particular focus on the CeO2 nanoparticles. The characterization of the CeO2 nanoparticles in cell culture media with varying serum content indicated a steric stabilization of nanoparticles due to interaction with proteins. After cellular uptake, the CeO2 nanoparticles were localized around the nucleus in a ring-shaped manner. The nanoparticles revealed concentration and time, but no size-dependent effects on the cellular adenosine triphosphate levels. HUVEC reacted more sensitively to CeO2 nanoparticle exposure than HMEC-1. This effect was also observed in relation to cytokine release after nanoparticle treatment. The CeO2 nanoparticles exhibited a specific impact on the release of diverse proteins. Namely, a slight trend towards pro-inflammatory effects, a slight pro-thrombotic impact, and an increase of reactive oxygen species after nanoparticle exposure were observed with increasing incubation time. For SiO2 nanoparticles, concentration- and time-dependent effects on the metabolic activity as well as pro-inflammatory reactions were detectable. In general, the effects of the investigated nanoparticles on endothelial cells were rather insignificant, since the alterations on the metabolic cell activity became visible at a nanoparticle concentration that is by far higher than those expected to occur in the in vivo situation (CeO2 nanoparticles: 100 µg/mL; SiO2

  10. Uniform delivery of silicon nanoparticles on device quality substrates using spin coating from isopropyl alcohol colloids

    Science.gov (United States)

    Nayfeh, Osama M.; Antoniadis, Dimitri A.; Mantey, Kevin; Nayfeh, Munir H.

    2009-01-01

    Silicon nanoparticles, of predominately 2.9 nm in size, in isopropyl alcohol are spin coated directly on device quality silicon-dioxide layers across 150 mm substrates. Atomic force microscopy (AFM) is used to image the nanoparticle distributions and low levels of agglomeration with apparently regular internanoparticle distances are observed. AFM depth profiling of the nanoparticle size is in agreement with independent high resolution transmission electron microscopy measurements. Hartree-Fock based atomistic simulations confirm the possible formation of Si nanoparticle/isopropanol complexes with a calculated electrostatic binding energy of 30 meV, which is slightly larger than the room temperature thermal agitation energy. The low levels of agglomeration can be explained in terms of such complexes that may regulate the internanoparticle and nanoparticle-solvent interactions.

  11. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures

    KAUST Repository

    Mughal, Asad Jahangir

    2014-01-01

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material\\'s luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon. This journal is

  12. Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures.

    Science.gov (United States)

    Mughal, A; El Demellawi, J K; Chaieb, Sahraoui

    2014-12-14

    Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material's luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon.

  13. High efficiency silicon nanodisk laser based on colloidal CdSe/ZnS QDs

    Directory of Open Access Journals (Sweden)

    Min-Hsiung Shih

    2011-07-01

    Full Text Available Using colloidal CdSe/ZnS quantum dots in the submicron-sized silicon disk cavity, we have developed a visible wavelength nanodisk laser that operates under extremely low threshold power at room temperature. Time-resolved photoluminescence (PL of QDs; nanodisk by e-beam lithography. Observation of lasing action at 594 nm wavelength for quantum dots on a nanodisk (750 nm in diameter cavity and an ultra-low threshold of 2.8 µW. From QD concentration dependence studies we achieved nearly sevenfold increase in spontaneous emission (SE rate. We have achieved high efficient and high SE coupling rate in such a QD nanodisk laser.

  14. Growth and etch rate study of low temperature anodic silicon dioxide thin films.

    Science.gov (United States)

    Ashok, Akarapu; Pal, Prem

    2014-01-01

    Silicon dioxide (SiO2) thin films are most commonly used insulating films in the fabrication of silicon-based integrated circuits (ICs) and microelectromechanical systems (MEMS). Several techniques with different processing environments have been investigated to deposit silicon dioxide films at temperatures down to room temperature. Anodic oxidation of silicon is one of the low temperature processes to grow oxide films even below room temperature. In the present work, uniform silicon dioxide thin films are grown at room temperature by using anodic oxidation technique. Oxide films are synthesized in potentiostatic and potentiodynamic regimes at large applied voltages in order to investigate the effect of voltage, mechanical stirring of electrolyte, current density and the water percentage on growth rate, and the different properties of as-grown oxide films. Ellipsometry, FTIR, and SEM are employed to investigate various properties of the oxide films. A 5.25 Å/V growth rate is achieved in potentiostatic mode. In the case of potentiodynamic mode, 160 nm thickness is attained at 300 V. The oxide films developed in both modes are slightly silicon rich, uniform, and less porous. The present study is intended to inspect various properties which are considered for applications in MEMS and Microelectronics.

  15. Growth and Etch Rate Study of Low Temperature Anodic Silicon Dioxide Thin Films

    Directory of Open Access Journals (Sweden)

    Akarapu Ashok

    2014-01-01

    Full Text Available Silicon dioxide (SiO2 thin films are most commonly used insulating films in the fabrication of silicon-based integrated circuits (ICs and microelectromechanical systems (MEMS. Several techniques with different processing environments have been investigated to deposit silicon dioxide films at temperatures down to room temperature. Anodic oxidation of silicon is one of the low temperature processes to grow oxide films even below room temperature. In the present work, uniform silicon dioxide thin films are grown at room temperature by using anodic oxidation technique. Oxide films are synthesized in potentiostatic and potentiodynamic regimes at large applied voltages in order to investigate the effect of voltage, mechanical stirring of electrolyte, current density and the water percentage on growth rate, and the different properties of as-grown oxide films. Ellipsometry, FTIR, and SEM are employed to investigate various properties of the oxide films. A 5.25 Å/V growth rate is achieved in potentiostatic mode. In the case of potentiodynamic mode, 160 nm thickness is attained at 300 V. The oxide films developed in both modes are slightly silicon rich, uniform, and less porous. The present study is intended to inspect various properties which are considered for applications in MEMS and Microelectronics.

  16. EUV and debris characteristics of a laser-plasma tin dioxide nano-particle colloidal jet target

    Science.gov (United States)

    Kaku, Masanori; Suetake, Sumihiro; Senba, Yusuke; Katto, Masahito; Kubodera, Shoichi

    2008-03-01

    Debris characteristics and its reduction have been investigated for a laser-produced plasma (LPP) extreme ultraviolet (EUV) source using a colloidal jet target containing tin dioxide nano-particles. Dominant deposited debris on a witness plate was found to have a form of oxidized tin (SnO x) originated from nano-particles. Quantitative debris amounts were determined by total laser energy irradiated onto a target, not by laser irradiation modes, such as single or double pulse irradiation. In-situ low-temperature (100°C) heating of a plate was effective to reduce the deposited debris amount, since colloidal debris was easily vaporized by the heat. Another approach to remove the deposited debris was roomtemperature photon processing using incoherent vacuum ultraviolet (VUV) emission at 126 nm. X-ray photoelectron spectroscopy (XPS) analysis has shown that the deposited SnOx debris layer was deoxidized by the 126 nm VUV photon energy.

  17. Microcellular foaming of silicone rubber with supercritical carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Hong, In-Kwon; Lee, Sangmook [Dankook University, Youngin (Korea, Republic of)

    2014-01-15

    In spite of great concern on the industrial application of microcellular silicone rubber foams, such as in electric and medical devices, only a few works can be found about the foaming of silicone rubber. In this study, microcellular silicone rubber foams with a cell size of 12 µm were successfully prepared with curing by heat and foaming by supercritical CO{sub 2} as a green blowing agent. The microcellular silicone rubber foams exhibited a well-defined cell structure and a uniform cell size distribution. The crosslinking and foaming of silicone rubber was carried out separately. After foaming, the silicone rubber foam was cross-linked again to stabilize the foam structure and further improve its mechanical properties. Foaming process of cross-linked silicone rubber should be designed carefully based on the viscoelastic properties because of its elastic volume recovery in the atmosphere. The basic crosslinking condition for small cell size and high cell density was obtained after investigating the rheological behavior during crosslinking.

  18. Follow the track: The effects of silicon dioxide on GTA welding

    NARCIS (Netherlands)

    Schrauwers, A.

    2001-01-01

    Silicon dioxide, in other words sand, turns out to be a highly useful helper for arc welding processes. It can be used as a tracer for a welding robot to follow the weld line and it can also make welding go faster and "deeper". At the Materials Science department of the Delft University of Technolog

  19. Spatial control of direct chemical vapor deposition of graphene on silicon dioxide by directional copper dewetting

    NARCIS (Netherlands)

    van den Beld, Wesley Theodorus Eduardus; van den Berg, Albert; Eijkel, Jan C.T.

    2016-01-01

    In this paper we present a method for the spatial control of direct graphene synthesis onto silicon dioxide by controlled dewetting. The dewetting process is controlled through a combination of using a grooved substrate and conducting copper deposition at an angle. The substrate is then treated

  20. Spatial control of direct chemical vapor deposition of graphene on silicon dioxide by directional copper dewetting

    NARCIS (Netherlands)

    Beld, van den Wesley T.E.; Berg, van den Albert; Eijkel, Jan C.T.

    2016-01-01

    In this paper we present a method for the spatial control of direct graphene synthesis onto silicon dioxide by controlled dewetting. The dewetting process is controlled through a combination of using a grooved substrate and conducting copper deposition at an angle. The substrate is then treated usin

  1. Silanization of Low-Temperature-Plasma Synthesized Silicon Quantum Dots for Production of a Tunable, Stable, Colloidal Solution

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, I. E.; Shircliff, R. A.; Macauley, C.; Smith, D. K.; Lee, B. G.; Agrawal, S.; Stradins, P.; Collins, R. T.

    2012-02-16

    We present a method for grafting silanes onto low-temperature-plasma synthesized silicon quantum dots. The resulting solution of dots is characterized with Fourier transform infrared spectroscopy and transmission electron microscopy, and determined to be a colloidal suspension. The silane is attached at a single point on the quantum dot surface to avoid cross-linking and multilayer formation, and photoluminescence spectroscopy shows the colloidal suspension of dots is stable for over two months in air. The hydroxyl-terminated surfaces required for silanization are created by wet chemical etch, which can be used to tune the luminescence of the silicon dots in the green- to red-wavelength range. We find, however, that the wet etch cannot move the emission into the blue-wavelength range and discuss this observation in terms of the nature of etching process and origin of the emission. In addition, we discuss the photoluminescence quantum yield in the context of other passivation and synthetic techniques.

  2. Silicon Dioxide Coating Deposited by PDPs on PET Films and Influence on Oxygen Transmission Rate

    Institute of Scientific and Technical Information of China (English)

    SUN Yun-Jin; FU Ya-Bo; CHEN Qiang; ZHANG Chun-Mei; SANG Li-Jun; ZHANG Yue-Fei

    2008-01-01

    A silicon dioxide film is deposited on the polyethyleneterephtalate (PET) by a penning discharge plasma source at ambient temperature in a high vacuum chamber.Hexamethyldisiloxane and oxygen are adopted as precursor and reactive reagent to grow a nano-scale silicon dioxide layer on polymer surfaces.For the chemical structure analysis x-ray photoelectron spectroscopy is performed to demonstrate the content of Si,0 and C elements.It is noticed that a higher silicon concentration is contained if Ar plasma is used for pretreatment.X-ray diffraction analysis shows that a micro-crystal silicon dioxide is formed by peak patterns at 25.84° and 21.8°.The barrier properties examined by oxygen transmission rate show that the permeation parameter of the 12-μm-thick PET film drastically decreases from 135 cc/m2 per day for the control one to 0.713 cc/m2 per day for the as-deposited one after Ar plasma treatment.The surface morphology related to the barrier properties of SiOx-coated polymers os also investigated by scanning electron microscopy and atomic force microscopy.

  3. Free Energy Minimization Calculation of Complex Chemical Equilibria. Reduction of Silicon Dioxide with Carbon at High Temperature.

    Science.gov (United States)

    Wai, C. M.; Hutchinson, S. G.

    1989-01-01

    Discusses the calculation of free energy in reactions between silicon dioxide and carbon. Describes several computer programs for calculating the free energy minimization and their uses in chemistry classrooms. Lists 16 references. (YP)

  4. Fully radiative relaxation of silicon nanocrystals in colloidal ensemble revealed by advanced treatment of decay kinetics

    Science.gov (United States)

    Greben, Michael; Khoroshyy, Petro; Liu, Xiangkai; Pi, Xiaodong; Valenta, Jan

    2017-07-01

    A comprehensive study of the spectrally resolved photoluminescence (PL) decay kinetics of dodecyl-passivated colloidal silicon nanocrystals (Si NCs) is presented. The correct treatment of average decay lifetime is demonstrated. We report on importance to distinguish the external quantum efficiency (QE) from the internal QE. The external QE of the ensemble of Si NCs is measured to be ˜60%, while the internal QE of Si NCs emitting around ˜1.5 eV is evaluated to be near unity. This difference between internal and external QE is attributed to a fraction of "dark" (absorbing but non-emitting) Si NCs in the ensemble. This conclusion is based on the analysis of deconvoluted size-selected decay curves retrieved by the presented mathematical procedure. The homogeneous line-broadening is estimated to be around 180 meV by experimentally challenging single-NC PL measurements. In addition, radiative lifetimes are calculated by the envelope function approximation and confirm the observed exponential increase of lifetime with decreasing emission photon energy.

  5. Aluminum-jointed silicon dioxide octagon nanohelix array with desired complex refractive index.

    Science.gov (United States)

    Jen, Yi-Jun; Chen, Chien-Chi; Jheng, Ci-Yao

    2014-06-15

    In this Letter, glancing angle deposition is used to form an aluminum-jointed silicon dioxide octagon nanohelix array as a 3D nanostructured thin film. As a sculptured metal-dielectric composite, the film exhibits a complex refractive index of near unity with a small imaginary part. This structured film is demonstrated as an efficient light absorber to absorb light in a broad band and over a wide range of angles for both polarization states.

  6. Heterogeneous reduction of carbon dioxide by hydride-terminated silicon nanocrystals

    Science.gov (United States)

    Sun, Wei; Qian, Chenxi; He, Le; Ghuman, Kulbir Kaur; Wong, Annabelle P. Y.; Jia, Jia; Jelle, Abdinoor A.; O'Brien, Paul G.; Reyes, Laura M.; Wood, Thomas E.; Helmy, Amr S.; Mims, Charles A.; Singh, Chandra Veer; Ozin, Geoffrey A.

    2016-08-01

    Silicon constitutes 28% of the earth's mass. Its high abundance, lack of toxicity and low cost coupled with its electrical and optical properties, make silicon unique among the semiconductors for converting sunlight into electricity. In the quest for semiconductors that can make chemicals and fuels from sunlight and carbon dioxide, unfortunately the best performers are invariably made from rare and expensive elements. Here we report the observation that hydride-terminated silicon nanocrystals with average diameter 3.5 nm, denoted ncSi:H, can function as a single component heterogeneous reducing agent for converting gaseous carbon dioxide selectively to carbon monoxide, at a rate of hundreds of μmol h-1 g-1. The large surface area, broadband visible to near infrared light harvesting and reducing power of SiH surface sites of ncSi:H, together play key roles in this conversion. Making use of the reducing power of nanostructured hydrides towards gaseous carbon dioxide is a conceptually distinct and commercially interesting strategy for making fuels directly from sunlight.

  7. CMOS-compatible, athermal silicon ring modulators clad with titanium dioxide.

    Science.gov (United States)

    Djordjevic, Stevan S; Shang, Kuanping; Guan, Binbin; Cheung, Stanley T S; Liao, Ling; Basak, Juthika; Liu, Hai-Feng; Yoo, S J B

    2013-06-17

    We present the design, fabrication and characterization of athermal nano-photonic silicon ring modulators. The athermalization method employs compensation of the silicon core thermo-optic contribution with that from the amorphous titanium dioxide (a-TiO(2)) overcladding with a negative thermo-optic coefficient. We developed a new CMOS-compatible fabrication process involving low temperature RF magnetron sputtering of high-density and low-loss a-TiO(2) that can withstand subsequent elevated-temperature CMOS processes. Silicon ring resonators with 275 nm wide rib waveguide clad with a-TiO(2) showed near complete athermalization and moderate optical losses. Small-signal testing of the micro-resonator modulators showed high extinction ratio and gigahertz bandwidth.

  8. Silicon dioxide mask by plasma enhanced atomic layer deposition in focused ion beam lithography

    Science.gov (United States)

    Liu, Zhengjun; Shah, Ali; Alasaarela, Tapani; Chekurov, Nikolai; Savin, Hele; Tittonen, Ilkka

    2017-02-01

    In this work, focused ion beam (FIB) lithography was developed for plasma enhanced atomic layer deposited (PEALD) silicon dioxide SiO2 hard mask. The PEALD process greatly decreases the deposition temperature of the SiO2 hard mask. FIB Ga+ ion implantation on the deposited SiO2 layer increases the wet etch resistivity of the irradiated region. A programmed exposure in FIB followed by development in a wet etchant enables the precisely defined nanoscale patterning. The combination of FIB exposure parameters and the development time provides greater freedom for optimization. The developed process provides high pattern dimension accuracy over the tested range of 90–210 nm. Utilizing the SiO2 mask developed in this work, silicon nanopillars with 40 nm diameter were successfully fabricated with cryogenic deep reactive ion etching and the aspect ratio reached 16:1. The fabricated mask is suitable for sub-100 nm high aspect ratio silicon structure fabrication.

  9. Silicon dioxide with a silicon interfacial layer as an insulating gate for highly stable indium phosphide metal-insulator-semiconductor field effect transistors

    Science.gov (United States)

    Kapoor, V. J.; Shokrani, M.

    1991-01-01

    A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

  10. Hydrogen plasma treatment of silicon dioxide for improved silane deposition.

    Science.gov (United States)

    Gupta, Vipul; Madaan, Nitesh; Jensen, David S; Kunzler, Shawn C; Linford, Matthew R

    2013-03-19

    We describe a method for plasma cleaning silicon surfaces in a commercial tool that removes adventitious organic contamination and enhances silane deposition. As shown by wetting, ellipsometry, and XPS, hydrogen, oxygen, and argon plasmas effectively clean Si/SiO2 surfaces. However, only hydrogen plasmas appear to enhance subsequent low-pressure chemical vapor deposition of silanes. Chemical differences between the surfaces were confirmed via (i) deposition of two different silanes: octyldimethylmethoxysilane and butyldimethylmethoxysilane, as evidenced by spectroscopic ellipsometry and wetting, and (ii) a principal components analysis (PCA) of TOF-SIMS data taken from the different plasma-treated surfaces. AFM shows no increase in surface roughness after H2 or O2 plasma treatment of Si/SiO2. The effects of surface treatment with H2/O2 plasmas in different gas ratios, which should allow greater control of surface chemistry, and the duration of the H2 plasma (complete surface treatment appeared to take place quickly) are also presented. We believe that this work is significant because of the importance of silanes as surface functionalization reagents, and in particular because of the increasing importance of gas phase silane deposition.

  11. Method for one-to-one polishing of silicon nitride and silicon oxide

    Science.gov (United States)

    Babu, Suryadevara V. (Inventor); Natarajan, Anita (Inventor)

    2009-01-01

    The present invention provides a method of removing silicon nitride at about the same removal rate as silicon dioxide by CMP. The method utilizes a polishing slurry that includes colloidal silica abrasive particles dispersed in water and additives that modulate the silicon dioxide and silicon nitride removal rates such that they are about the same. In one embodiment of the invention, the additive is lysine or lysine mono hydrochloride in combination with picolinic acid, which is effective at a pH of about 8. In another embodiment of the invention, the additive is arginine in combination with picolinic acid, which is effective at a pH of about 10.

  12. Synthesis optimization of photonic crystals based on silicon and vanadium dioxides

    Science.gov (United States)

    Akhmadeev, A. A.; Sarandaev, E. V.; Salakhov, M. Kh

    2013-08-01

    The photonic crystal is the material which structure is characterized by periodic distribution of refraction index in the spatial directions, which have the photonic band gaps in a spectrum of own electromagnetic states. There are numerous approaches of the creation of photonic crystals. In the present the optimal conditions of synthesis of photonic crystals based on silicon dioxide as well as the inverse photonic crystals based on vanadium dioxide are investigated. It is known that the synthesis process is influenced by many different factors. We have studied the dependence of the particle size on the concentration of reagents, as well as on the duration of the reaction. These studies are important for the production of samples of photonic crystals with a definite structure.

  13. [Influence of silver/silicon dioxide on infrared absorption spectroscopy of sodium nitrate].

    Science.gov (United States)

    Yang, Shi-Ling; Yue, Li; Jia, Zhi-Jun

    2014-09-01

    Quickly detecting of ocean nutrient was one important task in marine pollution monitoring. We discovered the application of surface-enhanced infrared absorption spectroscopy in the detection of ocean nutrient through researching the evaporation of sodium nitrate solution. The silicon dioxide (SiO2) with highly dispersion was prepared by Stober method, The silver/silica (Ag/SiO2) composite materials were prepared by mixing ammonia solution and silicon dioxide aqueous solution. Three kinds of composite materials with different surface morphology were fabricated through optimizing the experimental parameter and changing the experimental process. The surface morphology, crystal orientation and surface plasmon resonance were investigated by means of the scanning electronic microscope (SEM), X-ray diffraction (XRD), UV-Visible absorption spectrum and infrared ab- sorption spectroscopy. The SEM images showed that the sample A was purified SiO2, sample B and sample C were mixture of silver nanoparticle and silicon dioxide, while sample D was completed nanoshell structure. The absorption spectroscopy showed that there was surface plasmon resonance in the UV-visible region, while there was possibility of surface plasmon resonance in the Infrared absorption region. The effect of Ag/SiO2 composite material on the infrared absorption spectra of sodium nitrite solution was investigated through systematically analyzing the infrared absorption spectroscopy of sodium nitrate solution during its evaporation, i. e. the peak integration area of nitrate and the peak integration area of water molecule. The experimental results show that the integration area of nitrate was enhanced greatly during the evaporation process while the integration area of water molecule decreased continuously. The integration area of nitrate comes from the anti-symmetric stretch vibration and the enhancement of the vibration is attributed to the interface effect of Ag/SiO2 which is consistent with Jensen T

  14. Defects and defect generation in oxide layer of ion implanted silicon-silicon dioxide structures

    CERN Document Server

    Baraban, A P

    2002-01-01

    One studies mechanism of generation of defects in Si-SiO sub 2 structure oxide layer as a result of implantation of argon ions with 130 keV energy and 10 sup 1 sup 3 - 3.2 x 10 sup 1 sup 7 cm sup - sup 2 doses. Si-SiO sub 2 structures are produced by thermal oxidation of silicon under 950 deg C temperature. Investigations were based on electroluminescence technique and on measuring of high-frequency volt-farad characteristics. Increase of implantation dose was determined to result in spreading of luminosity centres and in its maximum shifting closer to boundary with silicon. Ion implantation was shown, as well, to result in increase of density of surface states at Si-SiO sub 2 interface. One proposed model of defect generation resulting from Ar ion implantation into Si-SiO sub 2

  15. Silicon-Based Multiple Microsensors for Sensing Carbon Dioxide, Humidity and Temperature.

    Science.gov (United States)

    Chang, Hsing-Cheng

    A silicon based multiple microsensor for sensing carbon dioxide, humidity and temperature has been investigated. The carbon dioxide microsensor was designed based on gas permeable membrane and ion-sensing field effect transistor structures. The humidity microsensor was designed based on metal-oxide -semiconductor transistor with a polyimide sensing film. The temperature microsensor was also designed based on diode -sensing structure. The multiple microsensors were designed on the same chip and were fabricated by using standard VLSI processing techniques, micromachining processes and compatible polyimide processes. Small dimension, room temperature operation, fast response, and a relatively large chemical reservoir with an inner temperature controlled resistor are some of the special characteristics of this microsensor. Polyimides PMDA-ODA and 6FDA-ODA were chosen for humidity sensing, CO_2 gas selection and for wafer bonding. The polyimide and solid state compatible processes have been developed to reduce the sensor's dimension, simplify the fabrication process, and lower the production cost. A gaseous CO_2 measurement system was developed for measuring the device characteristics. The reaction parameters of the sensors have been analyzed and discussed to explain their sensing mechanisms. A novel polyimide assisted silicon wafer bonding method was investigated. The polyimide PI-2566 (6FDA-ODA) and the adhesion promoter VM-651 (aminopropyltriethoxysilane) were used as an intermediate material to bond two silicon wafers together. By sawing the bonded wafer and measuring the bond strength it was found that this method gave a uniform and strong bond. The bonding temperature was varied from 235^circC to 400 ^circC and the bond absorption characteristics were identified by analyzing the FTIR spectra. The bonding results are discussed and a bond model for the polyimide assisted silicon wafer bonding is suggested. This bonding process is simple and the yield rate is very

  16. Chemical Analysis Method for Magnesia and Magnesia-Alumina Refractories——Gravimetric-Molybdenum Blue Photometric Method for Determination of Silicon Dioxide Content

    Institute of Scientific and Technical Information of China (English)

    Wang Jing

    2007-01-01

    @@ GB/T 5069.3 - 2001 1 Scope This standard specifies the gravimetric-molybdenum blue photometric method for determination of silicon dioxide content. This standard is used for the determination of silicon dioxide content of magnesia and magnesia-alumina refractory materials. Determination range: >5.00%.

  17. High-Temperature Permittivity and Data-Mining of Silicon Dioxide at GHz Band

    Institute of Scientific and Technical Information of China (English)

    YUAN Jie; WEN Bo; HOU Zhi-Ling; LU Ming-Ming; CAO Wen-Qiang; BA Chuan; FANG Xiao-Yong; CAO Mao-Sheng

    2012-01-01

    The high-temperature permittivity of quartz fibre-reinforced silicon dioxide (SiO2/SiO2 ) nano-composites is studied on the basis of the multi-scale theoretical model.We obtain the permittivity of the SiO2/SiO2 at high temperature,which is dependent on the temperature by data-mining.The result shows that the permittivity and loss tangent obtained by data-mining are well consistent with the measured ones.The high-temperature permittivity can be well predicted for SiO2/SiO2 by the as-proposed model and the data-mining method.%The high-temperature permittivity of quartz fibre-reinforced silicon dioxide (SiO2/SiO2) nano-composites is studied on the basis of the multi-scale theoretical model. We obtain the permittivity of the SiO2/SiO2 at high temperature, which is dependent on the temperature by data-mining. The resuJt shows that the permittivity and loss tangent obtained by data-mining are well consistent with the measured ones. The high-temperature permittivity can be well predicted for SiO2/SiO2 by the as-proposed model and the data-mining method.

  18. Light transmission in porous silicon dioxide filled with liquids of different refractive indices

    Institute of Scientific and Technical Information of China (English)

    Jun Li; Xinzheng Zhang; Fan Shi; Yan Xu; Pidong Wang; Xuanyi Yu; Jingjun Xu

    2011-01-01

    Optical transmission at 532 nm from nonabsorbing disordered porous silicon dioxide has been studied experimentally.The transmission behaviors can be adjusted by filling the pores with liquids of different refractive indics, which are analyzed based on the theory of diffusion in a weak scattering regime.In our experiment, the transmission coefficient changes from a value less than 1% to one that is greater than 75%, that is, the opaque sample becomes transparent, which means that the transport mean free path of light within the material has been effectively adjusted.In addition, this method is a useful nondestructive method to derive the refractive index of an unknown bulk porous material.%@@ Optical transmission at 532 nm from nonabsorbing disordered porous silicon dioxide has been studied experimentally.The transmission behaviors can be adjusted by filling the pores with liquids of different refractive indics, which are analyzed based on the theory of diffusion in a weak scattering regime.In our experiment, the transmission coefficient changes from a value less than 1% to one that is greater than 75%, that is, the opaque sample becomes transparent, which means that the transport mean free path of light within the material has been effectively adjusted.In addition, this method is a useful nondestructive method to derive the refractive index of an unknown bulk porous material.

  19. Modification of Shape Memory Polymer Foams Using Tungsten, Aluminum Oxide, and Silicon Dioxide Nanoparticles.

    Science.gov (United States)

    Hasan, S M; Thompson, R S; Emery, H; Nathan, A L; Weems, A C; Zhou, F; Monroe, M B B; Maitland, D J

    Shape memory polymer (SMP) foams were synthesized with three different nanoparticles (tungsten, silicon dioxide, and aluminum oxide) for embolization of cerebral aneurysms. Ultra-low density SMP foams have previously been utilized for aneurysm occlusion, resulting in a rapid, stable thrombus. However, the small cross section of foam struts can potentially lead to fracture and particulate generation, which would be a serious adverse event for an embolic device. The goal of this study was to improve the mechanical properties of the system by physically incorporating fillers into the SMP matrix. Thermal and mechanical characterization suggested minimal changes in thermal transition of the SMP nanocomposites and improved mechanical strength and toughness for systems with low filler content. Actuation profiles of the three polymer systems were tuned with filler type and content, resulting in faster SMP foam actuation for nanocomposites containing higher filler content. Additionally, thermal stability of the SMP nanocomposites improved with increasing filler concentration, and particulate count remained well below accepted standard limits for all systems. Extraction studies demonstrated little release of silicon dioxide and aluminum oxide from the bulk over 16 days. Tungstun release increased over the 16 day examination period, with a maximum measured concentration of approxiately 2.87 μg/mL. The SMP nanocomposites developed through this research have the potential for use in medical devices due to their tailorable mechanical properties, thermal resisitivity, and actuation profiles.

  20. Synthesis of silicon carbide-silicon nitride composite ultrafine particles using a carbon dioxide laser

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Masaaki; Maniette, Yves; Nakata, Yoshinori; Okutani, Takeshi (Government Industrial Development Lab., Hokkaido, Sapporo (Japan))

    1993-05-01

    The synthesis and the structure of silicon carbide-silicon nitride (SiC-Si[sub 3]N[sub 4]) composite ultrafine particles have been studied. SiC-Si[sub 3]N[sub 4] composite ultrafine particles were prepared by irradiating a SiH[sub 4], C[sub 2]H[sub 4], and NH[sub 3] gas mixture with a CO[sub 2] laser at atmospheric pressure. The composition of composite powders changed with the reactant gas flow rate. The carbon and nitrogen content of the powder could be controlled in a wide range from 0 to 30 wt%. The composite powder, which contained 25.3 wt% carbon and 5.8 wt% nitrogen, had a [beta]-SiC structure. As the nitrogen content increased, SiC decreased and amorphous phase, Si[sub 3]N[sub 4], Si appeared. The results of XPS and lattice constant measurements suggested that Si, C, and N atoms were intimately mixed in the composite particles.

  1. Supercritical Carbon Dioxide-Assisted Process for Well-Dispersed Silicon/Graphene Composite as a Li ion Battery Anode

    OpenAIRE

    2016-01-01

    The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. However, the optimal fabrication method for this composite remains a challenge. Here, we developed a novel method using supercritical carbon dioxide (scCO2) to intercalate Si nanoparticles into graphene nanosheets. Silicon was modified with a thin layer of polyaniline, which assisted the dispersion of graphene sheets by introducing π-π interaction. Using scCO2, well-disp...

  2. Thermal oxidation of silicon in a residual oxygen atmosphere—the RESOX process—for self-limiting growth of thin silicon dioxide films

    Science.gov (United States)

    Wright, Jason T.; Carbaugh, Daniel J.; Haggerty, Morgan E.; Richard, Andrea L.; Ingram, David C.; Kaya, Savas; Jadwisienczak, Wojciech M.; Rahman, Faiz

    2016-10-01

    We describe in detail the growth procedures and properties of thermal silicon dioxide grown in a limited and dilute oxygen atmosphere. Thin thermal oxide films have become increasingly important in recent years due to the continuing down-scaling of ultra large scale integration metal oxide silicon field effect transistors. Such films are also of importance for organic transistors where back-gating is needed. The technique described here is novel and allows self-limited formation of high quality thin oxide films on silicon surfaces. This technique is easy to implement in both research laboratory and industrial settings. Growth conditions and their effects on film growth have been described. Properties of the resulting oxide films, relevant for microelectronic device applications, have also been investigated and reported here. Overall, our findings are that thin, high quality, dense silicon dioxide films of thicknesses up to 100 nm can be easily grown in a depleted oxygen environment at temperatures similar to that used for usual silicon dioxide thermal growth in flowing dry oxygen.

  3. Silicon photonic crystals doped with colloidally synthesized lead salt semiconductors nanocrystals.

    Science.gov (United States)

    Gutman, Nadav; Armon, Akiva; Shandalov, Michael; Osherov, Anna; Golan, Yuval; Sa'ar, Amir

    2009-06-01

    The fabrication of two-dimensional and three-dimensional silicon photonic crystals doped with lead salt nanocrystals is reported. The silicon based photonic crystals of macro-porous silicon are fabricated by electro-chemical etching via masked silicon wafers with the periodicity along the third dimension is achieved by modulating the anodization current and voltage. The chemical solution deposition technique has been utilized to deposit thin layers of lead salts (PbS and PbSe) nanocrystals into the pores. Infrared transmission measurements revealed a considerable red-shift of the photonic band gap in a good agreement with numerical calculations.

  4. [Effects of silver and silicon dioxide nanopowders on the development of herpesvirus infection in vitro].

    Science.gov (United States)

    Sopova, E A; Baranov, V I; Gankovskaia, O A; Lavrov, V F; Zverev, V V

    2010-01-01

    Estimation of the potential ability of nanoparticles (NP) to affect human health has generated a need for developing rapid, sensitive, and efficient laboratory tests of the toxicity of nanomaterials. The purpose of the investigation was to study the cytotoxic effect of NP of silver (Ag) and silicon dioxide (SiO2). The transplantable Vero cells treated with NP at different concentrations were used as target cells. Some experiments examined the combined effects of nanopowders and herpes simplex virus type 2 (HSV-2) on Vero cell viability and the direct effect of NP on the reproductive potential of HSV-2 in the culture. SiO2 NPs at concentrations of 1.0 to 0.1 mg/ml were found to cause a marked cytotoxic effect that was in the complete destruction of the cell monolayer. Ag HPs were more toxic than silicon nanopowders and induced a complete degradation of the cell monolayer at substantially lower concentrations. The results of the study formed the basis for the development of a rapid (24-48-hour), reliable, and efficient test for the toxicity of nanomaterials, by using the cultured cells in the laboratory setting. It was also shown that silicon NPs did not noticeably affect the reproductive potential of HSV-2 while nano silver suppressed the capacity of HSV-2 for multiplication, by significantly reducing viral progeny titer in the cell culture.

  5. Crystallization of silicon dioxide and compositional evolution of the Earth's core.

    Science.gov (United States)

    Hirose, Kei; Morard, Guillaume; Sinmyo, Ryosuke; Umemoto, Koichio; Hernlund, John; Helffrich, George; Labrosse, Stéphane

    2017-03-02

    The Earth's core is about ten per cent less dense than pure iron (Fe), suggesting that it contains light elements as well as iron. Modelling of core formation at high pressure (around 40-60 gigapascals) and high temperature (about 3,500 kelvin) in a deep magma ocean predicts that both silicon (Si) and oxygen (O) are among the impurities in the liquid outer core. However, only the binary systems Fe-Si and Fe-O have been studied in detail at high pressures, and little is known about the compositional evolution of the Fe-Si-O ternary alloy under core conditions. Here we performed melting experiments on liquid Fe-Si-O alloy at core pressures in a laser-heated diamond-anvil cell. Our results demonstrate that the liquidus field of silicon dioxide (SiO2) is unexpectedly wide at the iron-rich portion of the Fe-Si-O ternary, such that an initial Fe-Si-O core crystallizes SiO2 as it cools. If crystallization proceeds on top of the core, the buoyancy released should have been more than sufficient to power core convection and a dynamo, in spite of high thermal conductivity, from as early on as the Hadean eon. SiO2 saturation also sets limits on silicon and oxygen concentrations in the present-day outer core.

  6. Focused ion beam milling of nanocavities in single colloidal particles and self-assembled opals

    NARCIS (Netherlands)

    Woldering, Leon A.; Otter, A.M.(Bert); Husken, Bart H.; Vos, Willem L.

    2006-01-01

    We present a new method of realizing single nanocavities in individual colloidal particles on the surface of silicon dioxide artificial opals using a focused ion beam milling technique. We show that both the radius and the position of the nanocavity can be controlled with nanometre precision, to rad

  7. Germanium Nanocrystals Embedded in Silicon Dioxide for Floating Gate Memory Devices

    Directory of Open Access Journals (Sweden)

    A. Bag

    2011-01-01

    Full Text Available Metal-oxide-semiconductor (MOS capacitors with tri-layer structure consisting of rf magnetron sputtered grown germanium (Ge nanocrystals (NCs and silicon dioxide (SiO2 layers sandwiched between thermally grown tunnel and sputtered grown cap oxide layers of SiO2 were fabricated on p-Si substrates. Plane view transmission electron micrographs revealed the formation of spherically shaped and uniformly distributed Ge NCs. The optical and electronic characteristics of tri-layer structures were studied through photoluminescence (PL spectroscopy and capacitance-voltage (C-V measurements, respectively. Frequency dependent electrical properties of the structures have been studied. The optical emission characteristics support the confinement of the carriers in Ge NCs embedded in oxide matrices. An anticlockwise hysteresis in C-V characteristics suggests electron injection and trapping in Ge NCs.

  8. Ultrathin, transferred layers of thermally grown silicon dioxide as biofluid barriers for biointegrated flexible electronic systems

    Science.gov (United States)

    Fang, Hui; Zhao, Jianing; Yu, Ki Jun; Song, Enming; Barati Farimani, Amir; Chiang, Chia-Han; Jin, Xin; Xue, Yeguang; Xu, Dong; Du, Wenbo; Seo, Kyung Jin; Zhong, Yiding; Yang, Zijian; Won, Sang Min; Fang, Guanhua; Choi, Seo Woo; Chaudhuri, Santanu; Huang, Yonggang; Ashraful Alam, Muhammad; Viventi, Jonathan; Aluru, N. R.; Rogers, John A.

    2016-10-01

    Materials that can serve as long-lived barriers to biofluids are essential to the development of any type of chronic electronic implant. Devices such as cardiac pacemakers and cochlear implants use bulk metal or ceramic packages as hermetic enclosures for the electronics. Emerging classes of flexible, biointegrated electronic systems demand similar levels of isolation from biofluids but with thin, compliant films that can simultaneously serve as biointerfaces for sensing and/or actuation while in contact with the soft, curved, and moving surfaces of target organs. This paper introduces a solution to this materials challenge that combines (i) ultrathin, pristine layers of silicon dioxide (SiO2) thermally grown on device-grade silicon wafers, and (ii) processing schemes that allow integration of these materials onto flexible electronic platforms. Accelerated lifetime tests suggest robust barrier characteristics on timescales that approach 70 y, in layers that are sufficiently thin (less than 1 μm) to avoid significant compromises in mechanical flexibility or in electrical interface fidelity. Detailed studies of temperature- and thickness-dependent electrical and physical properties reveal the key characteristics. Molecular simulations highlight essential aspects of the chemistry that governs interactions between the SiO2 and surrounding water. Examples of use with passive and active components in high-performance flexible electronic devices suggest broad utility in advanced chronic implants.

  9. Neutron-activated determination of chlorine, using the /sup 35/Cl(n,p)/sup 35/S reaction as the basis, in thin coatings of silicon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Perezhogin, G.A.

    1988-01-10

    The neutron-activation determination of chlorine in thin coatings of silicon dioxide on silicon has been shown to be possible through the use of the /sup 55/Cl(n, P)/sup 35/S reaction. The detection limit of chlorine is 3 x 10/sup -9/ g (5 x 10/sup 13/ atoms).

  10. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    Directory of Open Access Journals (Sweden)

    Liyun Yu

    2015-10-01

    Full Text Available One prominent method of modifying the properties of dielectric elastomers (DEs is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR has relatively low viscosity, which is favorable for loading inorganic fillers. In the present study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability and dynamic viscosity. Filled silicone elastomers with high loadings of nano-sized titanium dioxide (TiO2 particles were also studied. The best overall performing formulation had 35 wt.% TiO2 nanoparticles in the POWERSIL® XLR LSR, where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz, breakdown strength of 160 V µm−1, tear strength of 5.3 MPa, elongation at break of 190%, a Young’s modulus of 0.85 MPa and a 10% strain response (simple tension in a 50 V μm−1 electric field was obtained.

  11. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-01

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  12. Suppression of ion-implantation induced porosity in germanium by a silicon dioxide capping layer

    Science.gov (United States)

    Tran, Tuan T.; Alkhaldi, Huda S.; Gandhi, Hemi H.; Pastor, David; Huston, Larissa Q.; Wong-Leung, Jennifer; Aziz, Michael J.; Williams, J. S.

    2016-08-01

    Ion implantation with high ion fluences is indispensable for successful use of germanium (Ge) in the next generation of electronic and photonic devices. However, Ge readily becomes porous after a moderate fluence implant ( ˜1 ×1015 ion cm-2 ) at room temperature, and for heavy ion species such as tin (Sn), holding the target at liquid nitrogen (LN2) temperature suppresses porosity formation only up to a fluence of 2 ×1016 ion cm-2 . We show, using stylus profilometry and electron microscopy, that a nanometer scale capping layer of silicon dioxide significantly suppresses the development of the porous structure in Ge during a S n - implant at a fluence of 4.5 ×1016 ion cm-2 at LN2 temperature. The significant loss of the implanted species through sputtering is also suppressed. The effectiveness of the capping layer in preventing porosity, as well as suppressing sputter removal of Ge, permits the attainment of an implanted Sn concentration in Ge of ˜15 at.% , which is about 2.5 times the maximum value previously attained. The crystallinity of the Ge-Sn layer following pulsed-laser-melting induced solidification is also greatly improved compared with that of uncapped material, thus opening up potential applications of the Ge-Sn alloy as a direct bandgap material fabricated by an ion beam synthesis technique.

  13. Thickness-dependent stress in plasma-deposited silicon dioxide films

    Science.gov (United States)

    Au, V.; Charles, C.; Bulla, D. A. P.; Love, J. D.; Boswell, R. W.

    2005-04-01

    Thick silicon dioxide (SiO2) films up to 5 μm have been deposited by helicon activated reactive evaporation (plasma assisted deposition with electron beam evaporation source) as both bilayer and trilayer structures, and the film stress was investigated in the context of optical waveguide fabrication. A model for stress in the SiO2-Si bilayer as a function of film thickness is formulated and interpreted in terms of Volmer-Weber film growth mechanisms. We find that island coalescence begins at a film thickness of less than 165 nm and continues until about 700 nm. Above approximately 1 μm thickness, the film continues growth as a continuous film. The stress in a deposited SiO2 film in an SiO2-Si-SiO2 trilayer structure was investigated by adapting the established Stoney's equation for a trilayer system, and comparing it with a thermally grown SiO2 trilayer. A constant value of stress is obtained for the deposited SiO2 film for film thickness >1μm which was consistently less than both measured and previously reported values of stress in thermally grown SiO2.

  14. Titanium dioxide antireflection coating for silicon solar cells by spray deposition

    Science.gov (United States)

    Kern, W.; Tracy, E.

    1980-01-01

    A high-speed production process is described for depositing a single-layer, quarter-wavelength thick antireflection coating of titanium dioxide on metal-patterned single-crystal silicon solar cells for terrestrial applications. Controlled atomization spraying of an organotitanium solution was selected as the most cost-effective method of film deposition using commercial automated equipment. The optimal composition consists of titanium isopropoxide as the titanium source, n-butyl acetate as the diluent solvent, sec-butanol as the leveling agent, and 2-ethyl-1-hexanol to render the material uniformly depositable. Application of the process to the coating of circular, large-diameter solar cells with either screen-printed silver metallization or with vacuum-evaporated Ti/Pd/Ag metallization showed increases of over 40% in the electrical conversion efficiency. Optical characteristics, corrosion resistance, and several other important properties of the spray-deposited film are reported. Experimental evidence indicates a wide tolerance in the coating thickness upon the overall efficiency of the cell. Considerations pertaining to the optimization of AR coatings in general are discussed, and a comprehensive critical survey of the literature is presented.

  15. Silicon-Doped Titanium Dioxide Nanotubes Promoted Bone Formation on Titanium Implants.

    Science.gov (United States)

    Zhao, Xijiang; Wang, Tao; Qian, Shi; Liu, Xuanyong; Sun, Junying; Li, Bin

    2016-02-26

    While titanium (Ti) implants have been extensively used in orthopaedic and dental applications, the intrinsic bioinertness of untreated Ti surface usually results in insufficient osseointegration irrespective of the excellent biocompatibility and mechanical properties of it. In this study, we prepared surface modified Ti substrates in which silicon (Si) was doped into the titanium dioxide (TiO₂) nanotubes on Ti surface using plasma immersion ion implantation (PIII) technology. Compared to TiO₂ nanotubes and Ti alone, Si-doped TiO₂ nanotubes significantly enhanced the expression of genes related to osteogenic differentiation, including Col-I, ALP, Runx2, OCN, and OPN, in mouse pre-osteoblastic MC3T3-E1 cells and deposition of mineral matrix. In vivo, the pull-out mechanical tests after two weeks of implantation in rat femur showed that Si-doped TiO₂ nanotubes improved implant fixation strength by 18% and 54% compared to TiO₂-NT and Ti implants, respectively. Together, findings from this study indicate that Si-doped TiO₂ nanotubes promoted the osteogenic differentiation of osteoblastic cells and improved bone-Ti integration. Therefore, they may have considerable potential for the bioactive surface modification of Ti implants.

  16. Non-negligible Contributions to Thermal Conductivity From Localized Modes in Amorphous Silicon Dioxide.

    Science.gov (United States)

    Lv, Wei; Henry, Asegun

    2016-10-21

    Thermal conductivity is important for almost all applications involving heat transfer. The theory and modeling of crystalline materials is in some sense a solved problem, where one can now calculate their thermal conductivity from first principles using expressions based on the phonon gas model (PGM). However, modeling of amorphous materials still has many open questions, because the PGM itself becomes questionable when one cannot rigorously define the phonon velocities. In this report, we used our recently developed Green-Kubo modal analysis (GKMA) method to study amorphous silicon dioxide (a-SiO2). The predicted thermal conductivities exhibit excellent agreement with experiments and anharmonic effects are included in the thermal conductivity calculation for all the modes in a-SiO2 for the first time. Previously, localized modes (locons) have been thought to have a negligible contribution to thermal conductivity, due to their highly localized nature. However, in a-SiO2 our results indicate that locons contribute more than 10% to the total thermal conductivity from 400 K to 800 K and they are largely responsible for the increase in thermal conductivity of a-SiO2 above room temperature. This is an effect that cannot be explained by previous methods and therefore offers new insight into the nature of phonon transport in amorphous/glassy materials.

  17. Characterization of magnetic biochar amended with silicon dioxide prepared at high temperature calcination

    Directory of Open Access Journals (Sweden)

    Baig Shams Ali

    2016-09-01

    Full Text Available Calcination is considered to increase the hardness of composite material and prevent its breakage for the effective applications in environmental remediation. In this study, magnetic biochar amended with silicon dioxide was calcined at high temperature under nitrogen environment and characterized using various techniques. X-ray diffraction (XRD analysis revealed elimination of Fe3O4 peaks under nitrogen calcination and formation of Fe3Si and iron as major constituents of magnetic biochar-SiO2 composite, which demonstrated its superparamagnetic behavior (>80 A2·kg−1 comparable to magnetic biochar. Thermogravimetric analysis (TGA revealed that both calcined samples generated higher residual mass (>96 % and demonstrated better thermal stability. The presence of various bands in Fourier transform infrared spectroscopy (FT-IR was more obvious and the elimination of H–O–H bonding was observed at high temperature calcination. In addition, scanning electron microscopy (SEM images revealed certain morphological variation among the samples and the presence of more prominent internal and external pores, which then judged the surface area and pore volume of samples. Findings from this study suggests that the selective calcination process could cause useful changes in the material composites and can be effectively employed in environmental remediation measures.

  18. FTIR Characterization of Fluorine Doped Silicon Dioxide Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    WANG Peng-Fei; DING Shi-Jin; ZHANG Wei; ZHANG Jian-Yun; WANGJi-Tao; WEI William Lee

    2000-01-01

    Fluorine doped silicon dioxide (SiOF) thin films have been prepared by plasma enhanced chemical vapor depo sition. The Fourier transform infrared spectrometry (FTIR) spectra of SiOF films are deliberated to reveal the structure change of SiO2 and the mechanism of dielectric constant reduction after doping fluorine. When F is doped in SiO2 films, the Si-O stretching absorption peak will have a blue-shift due to increase of the partial charge of the O atom. The FTIR spectra indicate that some Si-OH components in the thin film can be removed after doping fluorine. These changes reduce the ionic and orientational polarization, and result in the reduction in dielectric constant of the film. According to Gaussian fitting, it is found that the Si-F2 bonds will appear in the SiOF film with increase of the fluorine content. The Si-F2 structures are liable to react with water, and cause the same increase of absorbed moisture in the film.

  19. Nano-silicon dioxide toxicological characterization on two human kidney cell lines

    Science.gov (United States)

    Paget, V.; Sergent, J. A.; Chevillard, S.

    2011-07-01

    Silicon dioxide nanoparticles (n-SiO2) have recently encountered a wide variety of applications in medicine or engineering but their toxicological effects are poorly understood. In this study, we have used SiO2-25 nm and SiO2-100 nm mono-dispersed nanoparticles labeled with Rhodamine B and TMPyP respectively. These two fluorophores were incorporated during synthesis in order to track nanoparticles cell incorporation. Up-to-date, no evaluation of the toxicological effects of these nanoparticles upon human kidney has been published. As kidney is one of the major traditional retention organs, the aim of our study is to evaluate the potential toxicity of these nanoparticles on two human cell lines from proximal tubule (Caki-1 and Hek293). Our results report that the two cell lines do not show similar responses after 24 hours of exposure to SiO2-nanoparticles disregarding a similar origin in the kidney. Interestingly, our results indicate that for both tested SiO2-nanoparticles, Caki-1 cells present a higher sensitivity in terms of cytotoxicity and genotoxicity than Hek293 cells. Furthermore, our results show that for similar concentration of exposure, SiO2-25 nm seems to be more cytotoxic and genotoxic than SiO2-100nm for both tested cell lines.

  20. Nano-silicon dioxide toxicological characterization on two human kidney cell lines

    Energy Technology Data Exchange (ETDEWEB)

    Paget, V; Sergent, J A; Chevillard, S, E-mail: sylvie.chevillard@cea.fr [Laboratory of Experimental Cancerology, Institute of Cellular and Molecular Radiobiology, CEA, Fontenay-aux-Roses (France)

    2011-07-06

    Silicon dioxide nanoparticles (n-SiO{sub 2}) have recently encountered a wide variety of applications in medicine or engineering but their toxicological effects are poorly understood. In this study, we have used SiO{sub 2}-25 nm and SiO{sub 2}-100 nm mono-dispersed nanoparticles labeled with Rhodamine B and TMPyP respectively. These two fluorophores were incorporated during synthesis in order to track nanoparticles cell incorporation. Up-to-date, no evaluation of the toxicological effects of these nanoparticles upon human kidney has been published. As kidney is one of the major traditional retention organs, the aim of our study is to evaluate the potential toxicity of these nanoparticles on two human cell lines from proximal tubule (Caki-1 and Hek293). Our results report that the two cell lines do not show similar responses after 24 hours of exposure to SiO{sub 2}-nanoparticles disregarding a similar origin in the kidney. Interestingly, our results indicate that for both tested SiO{sub 2}-nanoparticles, Caki-1 cells present a higher sensitivity in terms of cytotoxicity and genotoxicity than Hek293 cells. Furthermore, our results show that for similar concentration of exposure, SiO{sub 2}-25 nm seems to be more cytotoxic and genotoxic than SiO{sub 2}-100nm for both tested cell lines.

  1. Adsorption of Cr(VI onto Hybrid Membrane of Carboxymethyl Chitosan and Silicon Dioxide

    Directory of Open Access Journals (Sweden)

    Yanling Deng

    2017-01-01

    Full Text Available In this study, a new adsorbent material was synthesized by using carboxymethyl chitosan and silicon dioxide. The hybrid membrane was used as an adsorbent for the removal of Cr(VI from aqueous solutions. The adsorption potential of Cr(VI by the hybrid materials was investigated by varying experimental conditions such as pH, contact time, and the dosage of the hybrid membrane. Adsorption isotherms of Cr(VI onto the hybrid membrane were studied with varying initial concentrations under optimum experiment conditions. The surface property of the hybrid membrane was characterized by SEM (scanning electron microscope and Fourier transform infrared spectrometer (FTIR. The concentrations of Cr(VI in solution are determined by ICP-AES (inductively coupled plasma atomic emission spectrometry. The present study investigates the adsorption mechanisms of Cr(VI onto the hybrid membrane. The results provide new insight, demonstrating that the modified hybrid membrane can be an efficient adsorbent for Cr(VI from the aqueous solution.

  2. Direct electrochemistry behavior of Cytochrome c on silicon dioxide nanoparticles-modified electrode

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c′ quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66×10-3 cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.

  3. Silicon dioxide nanoparticles increase macrophage atherogenicity: Stimulation of cellular cytotoxicity, oxidative stress, and triglycerides accumulation.

    Science.gov (United States)

    Petrick, Lauren; Rosenblat, Mira; Paland, Nicole; Aviram, Michael

    2016-06-01

    Nanoparticle research has focused on their toxicity in general, while increasing evidence points to additional specific adverse effects on atherosclerosis development. Arterial macrophage cholesterol and triglyceride (TG) accumulation and foam cell formation are the hallmark of early atherogenesis, leading to cardiovascular events. To investigate the in vitro atherogenic effects of silicon dioxide (SiO2 ), J774.1 cultured macrophages (murine cell line) were incubated with SiO2 nanoparticle (SP, d = 12 nm, 0-20 µg/mL), followed by cellular cytotoxicity, oxidative stress, TG and cholesterol metabolism analyses. A significant dose-dependent increase in oxidative stress (up to 164%), in cytotoxicity (up to 390% measured by lactate dehydrogenase (LDH) release), and in TG content (up to 63%) was observed in SiO2 exposed macrophages compared with control cells. A smaller increase in macrophage cholesterol mass (up to 22%) was noted. TG accumulation in macrophages was not due to a decrease in TG cell secretion or to an increased TG biosynthesis rate, but was the result of attenuated TG hydrolysis secondary to decreased lipase activity and both adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) protein expression (by 42 and 25%, respectively). Overall, SPs showed pro-atherogenic effects on macrophages as observed by cytotoxicity, increased oxidative stress and TG accumulation. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 713-723, 2016.

  4. Adsorption of acids and bases from aqueous solutions onto silicon dioxide particles.

    Science.gov (United States)

    Zengin, Huseyin; Erkan, Belgin

    2009-12-30

    The adsorption of acids and bases onto the surface of silicon dioxide (SiO(2)) particles was systematically studied as a function of several variables, including activation conditions, contact time, specific surface area, particle size, concentration and temperature. The physical properties of SiO(2) particles were investigated, where characterizations were carried out by FT-IR spectroscopy, and morphology was examined by scanning electron microscopy (SEM). The SEM of samples showed good dispersion and uniform SiO(2) particles with an average diameter of about 1-1.5 microm. The adsorption results revealed that SiO(2) surfaces possessed effective interactions with acids and bases, and greatest adsorption capacity was achieved with NaOH, where the best fit isotherm model was the Freundlich adsorption model. The adsorption properties of raw SiO(2) particles were further improved by ultrasonication. Langmuir monolayer adsorption capacity of NaOH adsorbate at 25 degrees C on sonicated SiO(2) (182.6 mg/g) was found to be greater than that of the unsonicated SiO(2) (154.3mg/g). The spontaneity of the adsorption process was established by decreases in DeltaG(ads)(0), which varied from -10.5 to -13.6 kJ mol(-1), in the temperature range 283-338K.

  5. Nano-silicon dioxide mitigates the adverse effects of salt stress on Cucurbita pepo L.

    Science.gov (United States)

    Siddiqui, Manzer H; Al-Whaibi, Mohamed H; Faisal, Mohammad; Al Sahli, Abdulaziz A

    2014-11-01

    Research into nanotechnology, an emerging science, has advanced in almost all fields of technology. The aim of the present study was to evaluate the role of nano-silicon dioxide (nano-SiO2 ) in plant resistance to salt stress through improvement of the antioxidant system of squash (Cucurbita pepo L. cv. white bush marrow). Seeds treated with NaCl showed reduced germination percentage, vigor, length, and fresh and dry weights of the roots and shoots. However, nano-SiO2 improved seed germination and growth characteristics by reducing malondialdehyde and hydrogen peroxide levels as well as electrolyte leakage. In addition, application of nano-SiO2 reduced chlorophyll degradation and enhanced the net photosynthetic rate (Pn ), stomatal conductance (gs ), transpiration rate, and water use efficiency. The increase in plant germination and growth characteristics through application of nano-SiO2 might reflect a reduction in oxidative damage as a result of the expression of antioxidant enzymes, such as catalase, peroxidase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase. These results indicate that nano-SiO2 may improve defense mechanisms of plants against salt stress toxicity by augmenting the Pn , gs , transpiration rate, water use efficiency, total chlorophyll, proline, and carbonic anhydrase activity in the leaves of plants.

  6. Structural and magnetic properties of the nanocomposite materials based on a mesoporous silicon dioxide matrix

    Energy Technology Data Exchange (ETDEWEB)

    Grigor’eva, N. A., E-mail: natali@lns.pnpi.spb.ru [St. Petersburg State University (Russian Federation); Eckerlebe, H. [Helmholtz-Zentrum Geesthacht (Germany); Eliseev, A. A.; Lukashin, A. V.; Napol’skii, K. S. [Moscow State University (Russian Federation); Kraje, M. [Reactor Institute Delft (Netherlands); Grigor’ev, S. V. [St. Petersburg State University (Russian Federation)

    2017-03-15

    The structural and magnetic properties of the mesoporous systems based on silicon dioxide with a regular hexagonal arrangement of pores several microns in length and several nanometers in diameter, which are filled with iron compound nanofilaments in various chemical states, are studied in detail. The studies are performed using the following mutually complementary methods: transmission electron microscopy, SQUID magnetometry, electron spin resonance, Mössbauer spectroscopy, polarized neutron small-angle diffraction, and synchrotron radiation diffraction. It is shown that the iron nanoparticles in pores are mainly in the γ phase of Fe{sub 2}O{sub 3} with a small addition of the α phase and atomic iron clusters. The effective magnetic field acting on a nanofilament from other nanofilaments is 11 mT and has a dipole nature, the ferromagnetic–paramagnetic transition temperature is in the range 76–94 K depending on the annealing temperature of the samples, and the temperature that corresponds to the change in the magnetic state of the iron oxide nanofilaments is T ≈ 50–60 K at H = 0 and T ≈ 80 K at H = 300 mT. It is also shown that the magnetization reversal of an array of nanofilaments is caused by the magnetostatic interaction between nanofilaments at the fields that are lower than the saturation field.

  7. Titanium dioxide antireflection coating for silicon solar cells by spray deposition

    Science.gov (United States)

    Kern, W.; Tracy, E.

    1980-01-01

    A high-speed production process is described for depositing a single-layer, quarter-wavelength thick antireflection coating of titanium dioxide on metal-patterned single-crystal silicon solar cells for terrestrial applications. Controlled atomization spraying of an organotitanium solution was selected as the most cost-effective method of film deposition using commercial automated equipment. The optimal composition consists of titanium isopropoxide as the titanium source, n-butyl acetate as the diluent solvent, sec-butanol as the leveling agent, and 2-ethyl-1-hexanol to render the material uniformly depositable. Application of the process to the coating of circular, large-diameter solar cells with either screen-printed silver metallization or with vacuum-evaporated Ti/Pd/Ag metallization showed increases of over 40% in the electrical conversion efficiency. Optical characteristics, corrosion resistance, and several other important properties of the spray-deposited film are reported. Experimental evidence indicates a wide tolerance in the coating thickness upon the overall efficiency of the cell. Considerations pertaining to the optimization of AR coatings in general are discussed, and a comprehensive critical survey of the literature is presented.

  8. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    DEFF Research Database (Denmark)

    Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    One prominent method of modifying the properties of dielectric elastomers (DEs) is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting...... metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR) has relatively low viscosity, which is favorable for loading inorganic fillers. In the present...... study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV) were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability...

  9. CARBON DIOXIDE SEPARATION BY SELECTIVE PERMEATION.

    Science.gov (United States)

    CARBON DIOXIDE , SEPARATION), (*PERMEABILITY, CARBON DIOXIDE ), POROUS MATERIALS, SILICON COMPOUNDS, RUBBER, SELECTION, ADSORPTION, TEMPERATURE, PRESSURE, POLYMERS, FILMS, PLASTICS, MEMBRANES, HUMIDITY.

  10. Soil microbial community responses to contamination with silver, aluminium oxide and silicon dioxide nanoparticles.

    Science.gov (United States)

    McGee, C F; Storey, S; Clipson, N; Doyle, E

    2017-04-01

    Soil microorganisms are key contributors to nutrient cycling and are essential for the maintenance of healthy soils and sustainable agriculture. Although the antimicrobial effects of a broad range of nanoparticulate substances have been characterised in vitro, little is known about the impact of these compounds on microbial communities in environments such as soil. In this study, the effect of three widely used nanoparticulates (silver, silicon dioxide and aluminium oxide) on bacterial and fungal communities in an agricultural pastureland soil was examined in a microcosm-based experiment using a combination of enzyme analysis, molecular fingerprinting and amplicon sequencing. A relatively low concentration of silver nanoparticles (AgNPs) significantly reduced total soil dehydrogenase and urease activity, while Al2O3 and SiO2 nanoparticles had no effect. Amplicon sequencing revealed substantial shifts in bacterial community composition in soils amended with AgNPs, with significant decreases in the relative abundance of Acidobacteria and Verrucomicrobia and an increase in Proteobacteria. In particular, the relative abundance of the Proteobacterial genus Dyella significantly increased in AgNP amended soil. The effects of Al2O3 and SiO2 NPs on bacterial community composition were less pronounced. AgNPs significantly reduced bacterial and archaeal amoA gene abundance in soil, with the archaea more susceptible than bacteria. AgNPs also significantly impacted soil fungal community structure, while Al2O3 and SiO2 NPs had no effect. Several fungal ribotypes increased in soil amended with AgNPs, compared to control soil. This study highlights the need to consider the effects of individual nanoparticles on soil microbial communities when assessing their environmental impact.

  11. A novel enzymatic microreactor with Aspergillus oryzae β-galactosidase immobilized on silicon dioxide nanosprings.

    Science.gov (United States)

    Schilke, Karl F; Wilson, Kelly L; Cantrell, Timothy; Corti, Giancarlo; McIlroy, David N; Kelly, Christine

    2010-01-01

    The use of silicon dioxide (SiO(2) ) nanosprings as supports for immobilized enzymes in a continuous microreactor is described. A nanospring mat (2.2 cm(2) × 60 μm thick) was functionalized with γ-aminopropyltriethoxysilane, then treated with N-succinimidyl-3-(2-pyridyldithio)-propionate (SPDP) and dithiothreitol (DTT) to produce surface thiol (--SH) groups. SPDP-modified β-galactosidase from Aspergillus oryzae was immobilized on the thiolated nanosprings by reversible disulfide linkages. The enzyme-coated nanospring mat was placed into a 175-μm high microchannel, with the mat partially occluding the channel. The kinetics and steady-state conversion of hydrolysis of o-nitrophenyl β-D-galactosylpyranoside at various substrate flow rates and concentrations were measured. Substantial flow was observed through the nanosprings, for which the Darcy permeability κ ≈ 3 × 10(-6) cm(2) . A simple, one-parameter numerical model coupling Navier-Stokes and Darcy flow with a pseudo-first-order reaction was used to fit the experimental data. Simulated reactor performance was sensitive to changes in κ and the height of the nanospring mat. Permeabilities lower than 10(-8) cm(2) practically eliminated convective flow through the nanosprings, and substantially decreased conversion. Increasing the height of the mat increased conversion in simulations, but requires more enzymes and could cause sealing issues if grown above channel walls. Preliminary results indicate that in situ regeneration by reduction with DTT and incubation with SPDP-modified β-galactosidase is possible. Nanosprings provide high solvent-accessible surface area with good permeability and mechanical stability, can be patterned into existing microdevices, and are amenable to immobilization of biomolecules. Nanosprings offer a novel and useful support for enzymatic microreactors, biosensors, and lab-on-chip devices.

  12. Silicon Dioxide Impedes Antiviral Response and Causes Genotoxic Insult During Calicivirus Replication.

    Science.gov (United States)

    Agnihothram, Sudhakar S; Vermudez, Sheryl Anne; Mullis, Lisa; Townsend, Todd A; Manjanatha, Mugimane G; Azevedo, Marli P

    2016-07-01

    Noroviruses (NoV) are the leading cause of nonbacterial gastroenteritis in humans, and replicate extensively in the human gastrointestinal (GI) tract. Silica (also known as silicon dioxide, SiO2) nanoparticles (NPs) used in processed foods, dairy products, and beverages also accumulate in the GI tract. We investigated the effect of silica NPs on NoV replication and host cell response during virus infection, using murine norovirus (MNV-1) infection of RAW 264.7 murine macrophages. Pretreatment with 10 μg/ml silica significantly reduced the viability of macrophages, but no cumulative effects on viability of macrophages were observed with MNV-1 infection. No difference was observed between exposure to control or silica NPs on either the quantity of viral genome copies or the production of infectious virus in macrophages infected with MNV-1. Silica NPs reduced the ability of macrophages to upregulate genes encoding bone morphogenic proteins (BMPs), chemokine ligands and cytokines for which expression levels were otherwise found to be upregulated in response to MNV-1 infection. Furthermore, silica NPs reduced the levels of proinflammatory cytokines secreted by macrophages in response to MNV infection. Finally, silica NPs with MNV-1 infection produced a genotoxic insult to macrophages. Strikingly, this genotoxic insult was also found to occur as a synergistic effect of silica NPs and feline calicivirus infection in feline kidney epithelial cells. Taken together, our study suggests important safety considerations related to reducing exposure to silica NPs affecting the GI tract in individuals infected with NoVs and possibly other foodborne viruses.

  13. Photochemical reactions of brominated diphenylethers in organic solvents and adsorbed on silicon dioxide in aqueous suspension

    Energy Technology Data Exchange (ETDEWEB)

    Palm, W.U.; Kopetzky, R.; Sossinka, W.; Ruck, W. [Univ. of Lueneburg, Environmental Chemistry, Lueneburg (Germany); Zetzsch, C. [Univ. of Bayreuth, Atmos. Chem. Research, Bayreuth, and Fraunhofer-Inst. of Toxicology and Experimental Medicine, Hannover (Germany)

    2004-09-15

    Polybrominated diphenylethers (BDEs) are in use as flame retardants worldwide and are found as xenobiotics in environmental samples. Photolysis by sunlight, one of the potential abiotic degradation pathways, is found to be rapid in laboratory experiments, especially for deca-BDE, the most prominent BDE as compared to commercial penta- and octa-BDEs. Due to the extremely low water solubility of BDEs, these experiments were mostly performed in organic solvents so far, and a few in environmental matrices (sand and soil) and on dry and hydrated quartz glass. However, detailed UV absorption spectra of deca-BDE and debrominated BDEs in the relevant wavelength range above 300 nm have become available only recently, besides the UV maxima of a number of synthesized congeners at shorter wavelengths and an exploratory study from our laboratory. Other important parameters to assess the abiotic degradation in the environment, such as OH-rate constants and photolytic quantum yields of BDEs are not available. Furthermore, analysis of BDEs was mostly performed by GC-MS, and the capability of HPLC with a diode array detector (DAD) has not yet been exploited. This study presents kinetic results on the photolysis of BDEs in tetrahydrofuran (THF) with detailed photolytic pathways for a tetra-BDE (2,2'4,4'-BDE), a hexa-BDE (2,2'4,4',5,5'-BDE) and deca-BDE. Employing HPLC with a diode array detector (DAD) as analytical tool, quantum yields of BDEs with N{sub Br} = 1-10 are determined. Furthermore, the formation of brominated dibenzofurans (BDFs) was investigated. Since the environmental relevance of photolysis experiments in organic solvents is questionable, first results on photolysis of deca-BDE adsorbed on silicon dioxide particles, suspended in water, are presented.

  14. Semiconductor-metal phase transition of vanadium dioxide nanostructures on silicon substrate: Applications for thermal control of spacecraft

    Energy Technology Data Exchange (ETDEWEB)

    Leahu, G. L., E-mail: roberto.livoti@uniroma1.it; Li Voti, R., E-mail: roberto.livoti@uniroma1.it; Larciprete, M. C., E-mail: roberto.livoti@uniroma1.it; Belardini, A., E-mail: roberto.livoti@uniroma1.it; Mura, F., E-mail: roberto.livoti@uniroma1.it; Sibilia, C.; Bertolotti, M. [Dipartimento di Scienze di Base ed Applicate per l' Ingegneria, Sapienza Università di Roma, Via A. Scarpa 16 00161 Roma (Italy); Fratoddi, I. [Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro, Roma (Italy)

    2014-06-19

    We present a detailed infrared study of the semiconductor-to-metal transition (SMT) in a vanadium dioxide (VO2) film deposited on silicon wafer. The VO2 phase transition is studied in the mid-infrared (MIR) region by analyzing the transmittance and the reflectance measurements, and the calculated emissivity. The temperature behaviour of the emissivity during the SMT put into evidence the phenomenon of the anomalous absorption in VO2 which has been explained by applying the Maxwell Garnett effective medium approximation theory, together with a strong hysteresis phenomenon, both useful to design tunable thermal devices to be applied for the thermal control of spacecraft. We have also applied the photothermal radiometry in order to study the changes in the modulated emissivity induced by laser. Experimental results show how the use of these techniques represent a good tool for a quantitative measurement of the optothermal properties of vanadium dioxide based structures.

  15. Chemical Analysis Methods for Silicon Carbide

    Institute of Scientific and Technical Information of China (English)

    Shen Keyin

    2006-01-01

    @@ 1 General and Scope This Standard specifies the determination method of silicon dioxide, free silicon, free carbon, total carbon, silicon carbide, ferric sesquioxide in silicon carbide abrasive material.

  16. A Monolithically Integrated Gallium Nitride Nanowire/Silicon Solar Cell Photocathode for Selective Carbon Dioxide Reduction to Methane.

    Science.gov (United States)

    Wang, Yichen; Fan, Shizhao; AlOtaibi, Bandar; Wang, Yongjie; Li, Lu; Mi, Zetian

    2016-06-20

    A gallium nitride nanowire/silicon solar cell photocathode for the photoreduction of carbon dioxide (CO2 ) is demonstrated. Such a monolithically integrated nanowire/solar cell photocathode offers several unique advantages, including the absorption of a large part of the solar spectrum and highly efficient carrier extraction. With the incorporation of copper as the co-catalyst, the devices exhibit a Faradaic efficiency of about 19 % for the 8e(-) photoreduction to CH4 at -1.4 V vs Ag/AgCl, a value that is more than thirty times higher than that for the 2e(-) reduced CO (ca. 0.6 %).

  17. Facile synthesis of silicon carbide-titanium dioxide semiconducting nanocomposite using pulsed laser ablation technique and its performance in photovoltaic dye sensitized solar cell and photocatalytic water purification

    Science.gov (United States)

    Gondal, M. A.; Ilyas, A. M.; Baig, Umair

    2016-08-01

    Separation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO2) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet-visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.

  18. Angstrom resolved imaging of charge percolation through the interface between phosphorous doped crystalline silicon and silicon dioxide

    Science.gov (United States)

    Ambal, Kapildep; Rahe, Philipp; Williams, Clayton C.; Boehme, Christoph

    2014-03-01

    Using a high resolution (~100fm/√{ Hz} spectral noise density) scanning probe at T ~4K, we measure currents through the interface between phosphorus doped ([P] ~ 1017-10qualitatively distinct I-V responses, each of which is identified with charge percolation from P donors to the cantilever either with or without different kinds of silicon dangling bond involvement. We acknowledge support by the National Science Foundation, Major Research Instrumentation Program #0959328.

  19. Vanadium dioxide thin films prepared on silicon by low temperature MBE growth and ex-situ annealing

    Science.gov (United States)

    Homm, Pia; van Bilzen, Bart; Menghini, Mariela; Locquet, Jean-Pierre; Ivanova, Todora; Sanchez, Luis; Sanchis, Pablo

    Vanadium dioxide (VO2) is a material that shows an insulator to metal transition (IMT) near room temperature. This property can be exploited for applications in field effect devices, electro-optical switches and nonlinear circuit components. We have prepared VO2 thin films on silicon wafers by combining a low temperature MBE growth with an ex-situ annealing at high temperature. We investigated the structural, electrical and optical characteristics of films with thicknesses ranging from 10 to 100 nm. We have also studied the influence of the substrate cleaning. The films grown with our method are polycrystalline with a preferred orientation in the (011) direction of the monoclinic phase. For the films produced on silicon with a native oxide, an IMT at around 75 °C is observed. The magnitude of the resistance change across the IMT decreases with thickness while the refractive index at room temperature corresponds with values reported in the literature for thin films. The successful growth of VO2 films on silicon with good electrical and optical properties is an important step towards the integration of VO2 in novel devices. The authors acknowledge financial support from the FWO project G052010N10 and EU-FP7 SITOGA project. PH acknowledges support from Becas Chile - CONICYT.

  20. Effect of the Nd content on the structural and photoluminescence properties of silicon-rich silicon dioxide thin films

    Directory of Open Access Journals (Sweden)

    Debieu Olivier

    2011-01-01

    Full Text Available Abstract In this article, the microstructure and photoluminescence (PL properties of Nd-doped silicon-rich silicon oxide (SRSO are reported as a function of the annealing temperature and the Nd concentration. The thin films, which were grown on Si substrates by reactive magnetron co-sputtering, contain the same Si excess as determined by Rutherford backscattering spectrometry. Fourier transform infrared (FTIR spectra show that a phase separation occurs during the annealing because of the condensation of the Si excess resulting in the formation of silicon nanoparticles (Si-np as detected by high-resolution transmission electron microscopy and X-ray diffraction (XRD measurements. Under non-resonant excitation at 488 nm, our Nd-doped SRSO films simultaneously exhibited PL from Si-np and Nd3+ demonstrating the efficient energy transfer between Si-np and Nd3+ and the sensitizing effect of Si-np. Upon increasing the Nd concentration from 0.08 to 4.9 at.%, our samples revealed a progressive quenching of the Nd3+ PL which can be correlated with the concomitant increase of disorder within the host matrix as shown by FTIR experiments. Moreover, the presence of Nd-oxide nanocrystals in the highest Nd-doped sample was established by XRD. It is, therefore, suggested that the Nd clustering, as well as disorder, are responsible for the concentration quenching of the PL of Nd3+.

  1. Errantum: Treatment of human astrocytoma U87 cells with silicon dioxide nanoparticles lowers their survival and alters their expression of mitochondrial and cell signaling proteins

    Directory of Open Access Journals (Sweden)

    Lai JCK

    2010-12-01

    Full Text Available Lai JCK, Ananthakrishnan G, Jandhyam S, et al. Treatment of human astrocytoma U87 cells with silicon dioxide nanoparticles lowers their survival and alters their expression of mitochondrial and cell signaling proteins. Int J Nanomedicine. 2010;5:715–723.The wrong image was used in Figure 5 on page 719.

  2. Nano-hydroxyapatite colloid suspension coated on chemically modified porous silicon by cathodic bias: a suitable surface for cell culture

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Alejandra [Escuela de Quimica, Universidad de Costa Rica, 2060 (Costa Rica); Centro de Electroquimica y Energia Quimica de la Universidad de Costa Rica (CELEQ), Universidad de Costa Rica, 2060 (Costa Rica); Gonzalez, Jerson [Escuela de Quimica, Universidad de Costa Rica, 2060 (Costa Rica); Garcia-Pineres, Alfonso [Escuela de Quimica, Universidad de Costa Rica, 2060 (Costa Rica); Centro de Investigacion en Biologia Celular y Molecular (CIBCM), Universidad de Costa Rica, 2060 (Costa Rica); Montero, Mavis L. [Escuela de Quimica, Universidad de Costa Rica, 2060 (Costa Rica); Centro de Electroquimica y Energia Quimica de la Universidad de Costa Rica (CELEQ), Universidad de Costa Rica, 2060 (Costa Rica); Centro de Ciencia e Ingenieria en Materiales (CICIMA), Universidad de Costa Rica, 2060 (Costa Rica)

    2011-06-15

    The properties of porous silicon make it an interesting material for biological applications. However, porous silicon is not an appropriate surface for cell growth. Surface modification is an alternative that could afford a bioactive material. In this work, we report a method to yield materials by modification of the porous silicon surface with hydroxyapatite of nanometric dimensions, produced using an electrochemical process and coated on macroporous silicon substrates by cathodic bias. The chemical nature of the calcium phosphate deposited on the substrates after the experimental process and the amount of cell growth on these surfaces were characterized. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Choline-sensing carbon paste electrode containing polyaniline (pani)-silicon dioxide composite-modified choline oxidase.

    Science.gov (United States)

    Özdemir, Merve; Arslan, Halit

    2014-02-01

    In this study, a novel carbon paste electrode (CPE) was prepared using the salt form of polyaniline (pani)-silicon dioxide composite that is sensitive to choline. Choline oxidase (ChO) enzyme was immobilized to modified carbon paste electrode (MCPE) by cross-linking with glutaraldehyde. Determination of choline was carried out by the oxidation of enzymatically produced H2O2 at 0.4 V vs. Ag/AgCl. The effects of pH and temperature were investigated, and the optimum parameters were found to be 6.0 and 60°C, respectively. The linear working range of the electrode was 5.0 × 10(-7)-1.0 × 10(-5) M, R(2) = 0.922. The storage stability and operation stability of the enzyme electrode were also studied.

  4. Dielectrophoretic trapping of multilayer DNA origami nanostructures and DNA origami-induced local destruction of silicon dioxide.

    Science.gov (United States)

    Shen, Boxuan; Linko, Veikko; Dietz, Hendrik; Toppari, J Jussi

    2015-01-01

    DNA origami is a widely used method for fabrication of custom-shaped nanostructures. However, to utilize such structures, one needs to controllably position them on nanoscale. Here we demonstrate how different types of 3D scaffolded multilayer origamis can be accurately anchored to lithographically fabricated nanoelectrodes on a silicon dioxide substrate by DEP. Straight brick-like origami structures, constructed both in square (SQL) and honeycomb lattices, as well as curved "C"-shaped and angular "L"-shaped origamis were trapped with nanoscale precision and single-structure accuracy. We show that the positioning and immobilization of all these structures can be realized with or without thiol-linkers. In general, structural deformations of the origami during the DEP trapping are highly dependent on the shape and the construction of the structure. The SQL brick turned out to be the most robust structure under the high DEP forces, and accordingly, its single-structure trapping yield was also highest. In addition, the electrical conductivity of single immobilized plain brick-like structures was characterized. The electrical measurements revealed that the conductivity is negligible (insulating behavior). However, we observed that the trapping process of the SQL brick equipped with thiol-linkers tended to induce an etched "nanocanyon" in the silicon dioxide substrate. The nanocanyon was formed exactly between the electrodes, that is, at the location of the DEP-trapped origami. The results show that the demonstrated DEP-trapping technique can be readily exploited in assembling and arranging complex multilayered origami geometries. In addition, DNA origamis could be utilized in DEP-assisted deformation of the substrates onto which they are attached.

  5. Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

    DEFF Research Database (Denmark)

    Pizzocchero, Filippo; Bøggild, Peter; Booth, Tim

    2013-01-01

    channels, which are aligned with the intersections of the (100) surface of the wafer and the {110} planes on an oxidized silicon wafer, as well as endotaxial copper silicide nanoparticles within the wafer bulk. We apply energy dispersive x-ray spectroscopy, in combination with scanning and transmission......We show that surface arc-discharge deposited carbon plays a critical intermediary role in the breakdown of thermally grown oxide diffusion barriers of 90 nm on a silicon wafer at 1035°C in an Ar/H2 atmosphere, resulting in the formation of epitaxial copper silicide particles in ≈ 10 μm wide...

  6. Supercritical Carbon Dioxide-Assisted Process for Well-Dispersed Silicon/Graphene Composite as a Li ion Battery Anode

    Science.gov (United States)

    Lee, Sang Ha; Park, Sengyoen; Kim, Min; Yoon, Dohyeon; Chanthad, Chalathorn; Cho, Misuk; Kim, Jaehoon; Park, Jong Hyeok; Lee, Youngkwan

    2016-01-01

    The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. However, the optimal fabrication method for this composite remains a challenge. Here, we developed a novel method using supercritical carbon dioxide (scCO2) to intercalate Si nanoparticles into graphene nanosheets. Silicon was modified with a thin layer of polyaniline, which assisted the dispersion of graphene sheets by introducing π-π interaction. Using scCO2, well-dispersed Si/graphene composite was successfully obtained in a short time under mild temperature. The composite showed high cycle performance (1,789 mAh/g after 250 cycles) and rate capability (1,690 mAh/g at a current density of 4,000 mA/g). This study provides a new approach for cost-effective and scalable preparation of a Si/graphene composite using scCO2 for a highly stable lithium battery anode material. PMID:27535108

  7. Supercritical Carbon Dioxide-Assisted Process for Well-Dispersed Silicon/Graphene Composite as a Li ion Battery Anode

    Science.gov (United States)

    Lee, Sang Ha; Park, Sengyoen; Kim, Min; Yoon, Dohyeon; Chanthad, Chalathorn; Cho, Misuk; Kim, Jaehoon; Park, Jong Hyeok; Lee, Youngkwan

    2016-08-01

    The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. However, the optimal fabrication method for this composite remains a challenge. Here, we developed a novel method using supercritical carbon dioxide (scCO2) to intercalate Si nanoparticles into graphene nanosheets. Silicon was modified with a thin layer of polyaniline, which assisted the dispersion of graphene sheets by introducing π-π interaction. Using scCO2, well-dispersed Si/graphene composite was successfully obtained in a short time under mild temperature. The composite showed high cycle performance (1,789 mAh/g after 250 cycles) and rate capability (1,690 mAh/g at a current density of 4,000 mA/g). This study provides a new approach for cost-effective and scalable preparation of a Si/graphene composite using scCO2 for a highly stable lithium battery anode material.

  8. Dielectric elastomer actuators of silicone rubber-titanium dioxide composites obtained by dielectrophoretic assembly of filler particles

    Science.gov (United States)

    Javadi, S.; Razzaghi-Kashani, M.

    2010-04-01

    Formation of controlled morphology of fillers in polymeric composites may be difficult to achieve by conventional methods such as mechanical shear or chemical methods. Tunable structure of filler and anisotropic properties in composites can be obtained by exploiting dielectrophoretic assembly of fillers in a polymer composite by using electric fields. In this study, different concentrations of Titanium Dioxide (TiO2) particles in silicone rubber matrix were assembled in a chain-like structure by using an alternating electric field. Silicone rubber matrix was vulcanized to transform the liquid to solid and maintain the filler structure in the desired direction. Generation of chain structure of filler was verified by Scanning Electron Microscopy (SEM) and equilibrium swelling. It was shown that dielectric permittivity of the oriented composite is higher whereas its dielectric loss factor is lower in the orientation (thickness) direction than those for the composites with random distribution of filler. This phenomenon was in agreement with results of dynamic-mechanical loss factor for these composites, and can be utilized in more efficient dielectric elastomer actuators. Elastic modulus is higher for the structured samples, but presence of titania filler induced a softening effect at higher strains where the actuators are practically being pre-stretched. A critical concentration of filler was distinguished as the percolation point at which the change in dielectric behavior is amplified. Using a simple blocking-force measurement, potential advantages of structured composites over the ones with randomly-distributed filler was explained for potential dielectric elastomer actuator applications.

  9. Facile synthesis of silicon carbide-titanium dioxide semiconducting nanocomposite using pulsed laser ablation technique and its performance in photovoltaic dye sensitized solar cell and photocatalytic water purification

    Energy Technology Data Exchange (ETDEWEB)

    Gondal, M.A., E-mail: magondal@kfupm.edu.sa [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Ilyas, A.M. [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Baig, Umair [Laser Research Group, Physics Department & Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Center of Excellence for Scientific Research Collaboration with MIT, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2016-08-15

    Highlights: • SiC–TiO{sub 2} semiconducting nanocomposites synthesized by nanosecond PLAL technique. • Synthesized nanocomposites were morphologically and optically characterized. • Nanocomposites were applied for the photocatalytic degradation of toxic organic dye. • Photovoltaic performance was investigated in dye sensitized solar cell. - Abstract: Separation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO{sub 2}) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet–visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.

  10. Leakage current conduction and reliability assessment of passivating thin silicon dioxide films on n-4H-SiC

    Science.gov (United States)

    Samanta, Piyas; Mandal, Krishna C.

    2016-09-01

    We have analyzed the mechanisms of leakage current conduction in passivating silicon dioxide (SiO2) films grown on (0 0 0 1) silicon (Si) face of n-type 4H-SiC (silicon carbide). It was observed that the experimentally measured gate current density in metal-oxide-silicon carbide (MOSiC) structures under positive gate bias at an oxide field Eox above 5 MV/cm is comprised of Fowler-Nordheim (FN) tunneling of electrons from the accumulated n-4H-SiC and Poole-Frenkel (PF) emission of trapped electrons from the localized neutral traps in the SiO2 gap, IFN and IPF, respectively at temperatures between 27 and 200 °C. In MOSiC structures, PF mechanism dominates FN tunneling of electrons from the accumulation layer of n-4H-SiC due to high density (up to 1013 cm-2) of carbon-related acceptor-like traps located at about 2.5 eV below the SiO2 conduction band (CB). These current conduction mechanisms were taken into account in studying hole injection/trapping into 10 nm-thick tunnel oxide on the Si face of 4H-SiC during electron injection from n-4H-SiC under high-field electrical stress with positive bias on the heavily doped n-type polysilicon (n+-polySi) gate at a wide range of temperatures between 27 and 200 °C. Holes were generated in the n+-polySi anode material by the hot-electrons during their transport through thin oxide films at oxide electric fields Eox from 5.6 to 8.0 MV/cm (prior to the intrinsic oxide breakdown field). Time-to-breakdown tBD of the gate dielectric was found to follow reciprocal field (1/E) model irrespective of stress temperatures. Despite the significant amount of process-induced interfacial electron traps contributing to a large amount of leakage current via PF emission in thermally grown SiO2 on the Si-face of n-4H-SiC, MOSiC devices having a 10 nm-thick SiO2 film can be safely used in 5 V TTL logic circuits over a period of 10 years.

  11. Electrical and Optical Characterization of Sputtered Silicon Dioxide, Indium Tin Oxide, and Silicon Dioxide/Indium Tin Oxide Antireflection Coating on Single-Junction GaAs Solar Cells

    Directory of Open Access Journals (Sweden)

    Wen-Jeng Ho

    2017-06-01

    Full Text Available This study characterized the electrical and optical properties of single-junction GaAs solar cells coated with antireflective layers of silicon dioxide (SiO2, indium tin oxide (ITO, and a hybrid layer of SiO2/ITO applied using Radio frequency (RF sputtering. The conductivity and transparency of the ITO film were characterized prior to application on GaAs cells. Reverse saturation-current and ideality factor were used to evaluate the passivation performance of the various coatings on GaAs solar cells. Optical reflectance and external quantum efficiency response were used to evaluate the antireflective performance of the coatings. Photovoltaic current-voltage measurements were used to confirm the efficiency enhancement obtained by the presence of the anti-reflective coatings. The conversion efficiency of the GaAs cells with an ITO antireflective coating (23.52% exceeded that of cells with a SiO2 antireflective coating (21.92%. Due to lower series resistance and higher short-circuit current-density, the carrier collection of the GaAs cell with ITO coating exceeded that of the cell with a SiO2/ITO coating.

  12. The effects of different types of nano-silicon dioxide additives on the properties of sludge ash mortar.

    Science.gov (United States)

    Luo, Huan-Lin; Chang, Wei-Che; Lin, Deng-Fong

    2009-04-01

    To improve the drawbacks caused by the sludge ash replacement in mortar, the previous studies have shown that the early strength and durability of sludge ash/cement mortar are improved by adding nano-silicon dioxide (nano-SiO2) to mortar. In this article, three types of nano-SiO2--SS, HS, and SP (manufacturer code names)--were applied to sludge ash/cement mixture to make paste or mortar specimens. The object is to further extend the recycle of the sludge ash by determining the better type of nano-SiO2 additive to improve properties of sludge ash/ cement paste or mortar. The cement was replaced by 0, 10, 20, and 30% of sludge ash, and 0 and 2% of nano-SiO2 additives were added to the sludge ash paste or mortar specimens. Tests such as setting time, compressive strength, scanning electron microscopy, X-ray diffraction, nuclear magnetic resonance, and thermogravimetric analysis/differential thermal analysis were performed in this study. Test results show that nano-SiO2 additives can not only effectively increase the hydration product (calcium silicate hydrate [C-S-H] gel), but also make the crystal structure denser. Among the three types of nano-SiO2 additive, the SS type can best improve the properties of sludge ash/cement paste or mortar, followed by the SP and HS types.

  13. Rheology of dispersions of xanthan gum, locust bean gum and mixed biopolymer gel with silicon dioxide nanoparticles.

    Science.gov (United States)

    Kennedy, Jordan R M; Kent, Katherine E; Brown, Jennifer R

    2015-03-01

    Mixed xanthan gum (XG) and locust bean gum (LBG) biopolymers form thermally reversible gels of interest in tissue engineering and drug delivery. 1% solutions of XG, LBG and 1:1 ratio XG/LBG mixed gels (LX) containing silicon dioxide (SiO2) nanoparticles were rheologically characterized with respect to nanoparticle concentration and temperature. 10% nanoparticles in XG created larger domains of associated polymer, resulting in enhanced viscosity and viscoelastic moduli. In LBG with 10% particles, transient viscosity and a gel-sol transition occurred due to particle bridging and aggregation. In the LX gel, 10% SiO2 particles caused an increase in elasticity. When ramping temperature from 25°C to 85°C, the complex modulus for all solutions containing 10% SiO2 was relatively constant, indicating that nanoparticles counteracted the effect of temperature on the material properties. Understanding the influence of nanoparticle loading on material properties is necessary for biopolymer material development where property prediction and control are critical.

  14. Comparative study of solution-phase and vapor-phase deposition of aminosilanes on silicon dioxide surfaces.

    Science.gov (United States)

    Yadav, Amrita R; Sriram, Rashmi; Carter, Jared A; Miller, Benjamin L

    2014-02-01

    The uniformity of aminosilane layers typically used for the modification of hydroxyl bearing surfaces such as silicon dioxide is critical for a wide variety of applications, including biosensors. However, in spite of many studies that have been undertaken on surface silanization, there remains a paucity of easy-to-implement deposition methods reproducibly yielding smooth aminosilane monolayers. In this study, solution- and vapor-phase deposition methods for three aminoalkoxysilanes differing in the number of reactive groups (3-aminopropyl triethoxysilane (APTES), 3-aminopropyl methyl diethoxysilane (APMDES) and 3-aminopropyl dimethyl ethoxysilane (APDMES)) were assessed with the aim of identifying methods that yield highly uniform and reproducible silane layers that are resistant to minor procedural variations. Silane film quality was characterized based on measured thickness, hydrophilicity and surface roughness. Additionally, hydrolytic stability of the films was assessed via these thickness and contact angle values following desorption in water. We found that two simple solution-phase methods, an aqueous deposition of APTES and a toluene based deposition of APDMES, yielded high quality silane layers that exhibit comparable characteristics to those deposited via vapor-phase methods.

  15. Role of Silicon Dioxide Filler on Mechanical and Dry Sliding Wear Behaviour of Glass-Epoxy Composites

    Directory of Open Access Journals (Sweden)

    Naveed Anjum

    2013-01-01

    Full Text Available The mechanical properties and dry sliding wear behaviour of glass fabric reinforced epoxy (G-E composite with varying weight percentage of silicon dioxide (SiO2 filler have been studied in the present work. The influence of sliding distance, velocity, and applied normal load on dry sliding wear behaviour has been considered using Taguchi's L9 orthogonal array. Addition of SiO2 increased the density, hardness, flexural, and impact strengths of G-E composite. Results of dry sliding wear tests showed increasing wear volume with increase in sliding distance, load, and sliding velocity for G-E and SiO2 filled G-E composites. Taguchi's results indicate that the sliding distance played a significant role followed by applied load, sliding velocity, and SiO2 loading. Scanning electron micrographs of the worn surfaces of composite samples at different test parameters show smooth surface, microploughing, and fine grooves under low load and velocity. However, severe damage of matrix with debonding and fiber breakage was seen at high load and velocity especially in unfilled G-E composite.

  16. Photoemission electron microscopy of arrays of submicron nickel rods in a silicon dioxide matrix

    Science.gov (United States)

    Turishchev, S. Yu.; Parinova, E. V.; Kronast, F.; Ovsyannikov, R.; Malashchenok, N. V.; Streltsov, E. A.; Ivanov, D. K.; Fedotov, A. K.

    2014-09-01

    Arrays of Ni rods (˜500 nm diameter) formed by the ion-track technology in combination with electrochemical deposition into a SiO2 matrix on the surface of single-crystal silicon plates have been investigated using photoemission electron microscopy with high-intensity synchrotron (undulator) radiation. An analysis of the Ni L 2,3 X-ray absorption near-edge structure (XANES) spectra has demonstrated that rod-like structures in pores and connecting bridges between the rods are formed by a metallic nickel phase, which is stable to oxidation by atmospheric oxygen. No formation of intermediate compound phases (nickel silicides and oxides) is observed at the Ni/SiO2 heterojunction, whereas oxidized nickel(II) species are identified on the surface of the SiO2 matrix, which presumably can be attributed to nickel silicate and hydroxide compounds formed upon nickel(II) chemisorption in electrochemical deposition electrolytes.

  17. Application of Aloe vera gel instead of silicon dioxide as organic dielectric material in microelectronics

    Directory of Open Access Journals (Sweden)

    Rana Sardar Masud

    2015-09-01

    Full Text Available Organic materials are now being used in a wide range of microelectronic applications in parallel with inorganic materials, because of their superior properties, environmental safety, and low cost. This paper describes the characterization of Aloe vera gel (AVG, a new organic dielectric material. The surface morphology, spatial distribution of elements, and structural characteristics of an AVG layer were examined using scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX, and X-ray diffraction (XRD, respectively. The resistance of the AVG layer, determined using a four-probe station, was 640 Ω EDX showed that the elements contained in the layer were carbon, oxygen, aluminum, silicon, calcium, potassium, and copper. The XRD results suggested that the sample primarily consisted of bornite (Cu5FeS4, geerite (Cu8S5, sal ammoniac (NH4Cl, and carobbite (KF.

  18. Phase selective growth and characterization of vanadium dioxide films on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Tomo; Okimura, Kunio [School of Engineering, Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292 (Japan); Hajiri, Tetsuya; Kimura, Shin-ichi [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan); Sakai, Joe [GREMAN, UMR 7347 CNRS, Universite Francois Rabelais de Tours, Parc de Grandmont, 37200 Tours (France)

    2013-04-28

    We report on selective growth of VO{sub 2} films with M1, M2, and intermediate T phases on silicon (Si) substrates by using inductively coupled plasma (ICP)-assisted sputtering (ICPS) under particular conditions. The film composed of M2 phase was proved to be under strong in-plane compressive stress, which is consistent with stress-induced M2 phase. Crystalline structural phase transition (SPT) properties of these films were demonstrated together with infrared light transmittance as a measure of insulator-metal transition (IMT) against temperature. Characteristic correlations between SPT and IMT for films with M2 and intermediate-T phases were reported. Ultraviolet photoelectron spectroscopy measurements probed an energy gap of the film in the M2 phase at around 0.4 eV from the Fermi level indicating the presence of a Mott gap.

  19. MOLECULAR DESIGN OF COLLOIDS IN SUPERCRITICAL FLUIDS

    Energy Technology Data Exchange (ETDEWEB)

    Keith P. Johnston

    2009-04-06

    The environmentally benign, non-toxic, non-flammable fluids water and carbon dioxide (CO2) are the two most abundant and inexpensive solvents on earth. Emulsions of these fluids are of interest in many industrial processes, as well as CO2 sequestration and enhanced oil recovery. Until recently, formation of these emulsions required stabilization with fluorinated surfactants, which are expensive and often not environmentally friendly. In this work we overcame this severe limitation by developing a fundamental understanding of the properties of surfactants the CO2-water interface and using this knowledge to design and characterize emulsions stabilized with either hydrocarbon-based surfactants or nanoparticle stabilizers. We also discovered a new concept of electrostatic stabilization for CO2-based emulsions and colloids. Finally, we were able to translate our earlier work on the synthesis of silicon and germanium nanocrystals and nanowires from high temperatures and pressures to lower temperatures and ambient pressure to make the chemistry much more accessible.

  20. Colloidal organization

    CERN Document Server

    Okubo, Tsuneo

    2015-01-01

    Colloidal Organization presents a chemical and physical study on colloidal organization phenomena including equilibrium systems such as colloidal crystallization, drying patterns as an example of a dissipative system and similar sized aggregation. This book outlines the fundamental science behind colloid and surface chemistry and the findings from the author's own laboratory. The text goes on to discuss in-depth colloidal crystallization, gel crystallization, drying dissipative structures of solutions, suspensions and gels, and similar-sized aggregates from nanosized particles. Special emphas

  1. [Changes in proteome profiles of rat liver microsomes induced by silicon dioxide nanoparticles].

    Science.gov (United States)

    Tananova, O N; Arianova, E A; Gmoshinskii, I V; Toropygin, I Yu; Khryapova, E V; Trusov, N V; Khotimchenko, S A; Tutel'yan, V A

    2015-01-01

    The effect of daily intragastric administration of an aqueous dispersion of silicon nanoparticles (NPs) (the dose range from 1.0 mg/kg to 100 mg/kg body weight for 28 days) to rats on the proteomic profile of liver microsomes has been investigated by 2D-electrophoresis followed by subsequent mass spectrometry identification. The liver microsomal fraction was isolated by differential centrifugation and its protein composition was analyzed by 2D-polyacrylamide gel electrophoresis. Identification of protein spots was carried out using MALDI-TOF mass spectrometric analysis. The mass spectrometry analysis revealed the protein GRP78 (78 kD glucose-regulated protein precursor), belonging to the family of heat shock proteins. This protein present in animals of the control group was not detected in NP-treated rats of group 2 (1 mg/kg body weight/day) and group 3 (10 mg/kg body weight/day). This protein predominantly localized in the liver cell endoplasmic reticulum and plasma membrane has the chaperone biological activity. Possible mechanisms of the effects of engineered nanoparticles on biosynthetic processes in the body are discussed.

  2. Sol-gel synthesis of magnesium oxide-silicon dioxide glass compositions

    Science.gov (United States)

    Bansal, Narottam P.

    1988-01-01

    MgO-SiO2 glasses containing up to 15 mol pct MgO, which could not have been prepared by the conventional glass melting method due to the presence of stable liquid-liquid immiscibility, were synthesized by the sol-gel technique. Clear and transparent gels were obtained from the hydrolysis and polycondensation of silicon tetraethoxide (TEOS) and magnesium nitrate hexahydrate when the water/TEOS mole ratio was four or more. The gelling time decreased with increase in magnesium content, water/TEOS ratio, and reaction temperature. Magnesium nitrate hexahydrate crystallized out of the gels containing 15 and 20 mol pct MgO on slow drying. This problem was partially alleviated by drying the gels quickly at higher temperatures. Monolithic gel samples were prepared using glycerol as the drying control additive. The gels were subjected to various thermal treatments and characterized by several methods. No organic groups could be detected in the glasses after heat treatments to approx. 800 C, but trace amounts of hydroxyl groups were still present. No crystalline phase was found from X-ray diffraction in the gel samples to approx. 890 C. At higher temperatures, alpha quartz precipitated out as the crystalline phase in gels containing up to 10 mol pct MgO. The overall activation energy for gel formation in 10MgO-90SiO2 (mol pct) system for water/TEOS mole ratio of 7.5 was calculated to be 58.7 kJ/mol.

  3. Patterning human neuronal networks on photolithographically engineered silicon dioxide substrates functionalized with glial analogues.

    Science.gov (United States)

    Hughes, Mark A; Brennan, Paul M; Bunting, Andrew S; Cameron, Katherine; Murray, Alan F; Shipston, Mike J

    2014-05-01

    Interfacing neurons with silicon semiconductors is a challenge being tackled through various bioengineering approaches. Such constructs inform our understanding of neuronal coding and learning and ultimately guide us toward creating intelligent neuroprostheses. A fundamental prerequisite is to dictate the spatial organization of neuronal cells. We sought to pattern neurons using photolithographically defined arrays of polymer parylene-C, activated with fetal calf serum. We used a purified human neuronal cell line [Lund human mesencephalic (LUHMES)] to establish whether neurons remain viable when isolated on-chip or whether they require a supporting cell substrate. When cultured in isolation, LUHMES neurons failed to pattern and did not show any morphological signs of differentiation. We therefore sought a cell type with which to prepattern parylene regions, hypothesizing that this cellular template would enable secondary neuronal adhesion and network formation. From a range of cell lines tested, human embryonal kidney (HEK) 293 cells patterned with highest accuracy. LUHMES neurons adhered to pre-established HEK 293 cell clusters and this coculture environment promoted morphological differentiation of neurons. Neurites extended between islands of adherent cell somata, creating an orthogonally arranged neuronal network. HEK 293 cells appear to fulfill a role analogous to glia, dictating cell adhesion, and generating an environment conducive to neuronal survival. We next replaced HEK 293 cells with slower growing glioma-derived precursors. These primary human cells patterned accurately on parylene and provided a similarly effective scaffold for neuronal adhesion. These findings advance the use of this microfabrication-compatible platform for neuronal patterning.

  4. Self-assembly of CdSe quantum dots and colloidal titanium dioxide on copolymer microspheres (PS) for CdSe/PS and TiO{sub 2}/CdSe/PS sub-microspheres with yolk–shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Qingchun, E-mail: qczhao@ustc.edu

    2015-07-30

    Highlights: • CdSe/PS sub-microspheres composite were prepared via self-assembly of CdSe quantum dots on modified PS surface. • TiO{sub 2}/CdSe/PS sub-microspheres were prepared via self-assembly of colloidal titanium dioxide on CdSe/PS sub-microspheres surface. • TiO{sub 2}/CdSe/PS sub-microspheres with yolk–shell structure. • TiO{sub 2}/CdSe/PS sub-microspheres with yolk–shell structure can improve the efficiency of charge separation. - Abstract: Semiconductor nanocrystals serve as the building blocks for designing next generation solar cells, chemical/biological sensors, and metal chalcogenides (e.g., CdS, CdSe, PbS, and PbSe) are particularly useful for harnessing size-dependent optical and electronic properties in nanostructures. In this paper, relying on the interaction including van der Waals forces and hydrogen bond, CdSe/PS sub-microspheres composite and TiO{sub 2}/CdSe/PS sub-microspheres with yolk–shell structure were prepared via self-assembly of CdSe quantum dots and colloidal titanium dioxide on modified PS surface. The morphology, structure and composition obtained products were investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy disperse X-ray spectroscopy (EDX). Transmission electron microscopy (TEM) investigations show the CdSe quantum dots and colloidal titanate were assembled on the surface of PS sub-microspheres. CdSe QD-polymer sub-microspheres composites in which the QDs retain their original emission efficiency can be obtained. TiO{sub 2}/CdSe/PS sub-microspheres with yolk–shell structure can improve the efficiency of charge separation.

  5. Pilot-Scale Silicone Process for Low-Cost Carbon Dioxide Capture

    Energy Technology Data Exchange (ETDEWEB)

    Farnum, Rachel; Perry, Robert; Wood, Benjamin

    2014-12-31

    GE Global Research is developing technology to remove carbon dioxide (CO 2) from the flue gas of coal-fired powerplants. A mixture of 3-aminopropyl end-capped polydimethylsiloxane (GAP-1m) and triethylene glycol (TEG) is the preferred CO2-capture solvent. GE Global Research was contracted by the Department of Energy to test a pilot-scale continuous CO2 absorption/desorption system using a GAP-1m/TEG mixture as the solvent. As part of that effort, an Environmental, Health, and Safety (EH&S) assessment for a CO2-capture system for a 550 MW coal-fired powerplant was conducted. Five components of the solvent, CAS#2469-55-8 (GAP-0), CAS#106214-84-0 (GAP-1-4), TEG, and methanol and xylene (minor contaminants from the aminosilicone) are included in this assessment. One by-product, GAP- 1m/SOX salt, and dodecylbenzenesulfonicacid (DDBSA) were also identified foranalysis. An EH&S assessment was also completed for the manufacturing process for the GAP-1m solvent. The chemicals associated with the manufacturing process include methanol, xylene, allyl chloride, potassium cyanate, sodium hydroxide (NaOH), tetramethyldisiloxane (TMDSO), tetramethyl ammonium hydroxide, Karstedt catalyst, octamethylcyclotetrasiloxane (D4), Aliquat 336, methyl carbamate, potassium chloride, trimethylamine, and (3-aminopropyl) dimethyl silanol. The toxicological effects of each component of both the CO2 capture system and the manufacturing process were defined, and control mechanisms necessary to comply with U.S. EH&S regulations are summarized. Engineering and control systems, including environmental abatement, are described for minimizing exposure and release of the chemical components. Proper handling and storage recommendations are made for each chemical to minimize risk to workers and the surrounding community.

  6. Pilot-Scale Silicone Process for Low-Cost Carbon Dioxide Capture

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Surinder; Spiry, Irina; Wood, Benjamin; Hancu, Dan; Chen, Wei

    2014-07-01

    This report presents system and economicanalysis for a carbon-capture unit which uses an aminosilicone-based solvent for CO₂ capture in a pulverized coal (PC) boiler. The aminosilicone solvent is a 60/40 wt/wt mixture of 3-aminopropyl end-capped polydimethylsiloxane (GAP-1m) with tri-ethylene glycol (TEG) as a co-solvent. Forcomparison purposes, the report also shows results for a carbon-capture unit based on a conventional approach using mono-ethanol amine (MEA). The first year removal cost of CO₂ for the aminosilicone-based carbon-capture process is $46.04/ton of CO₂ as compared to $60.25/ton of CO₂ when MEA is used. The aminosilicone- based process has <77% of the CAPEX of a system using MEA solvent. The lower CAPEX is due to several factors, including the higher working capacity of the aminosilicone solvent compared the MEA, which reduces the solvent flow rate required, reducing equipment sizes. If it is determined that carbon steel can be used in the rich-lean heat exchanger in the carbon capture unit, the first year removal cost of CO₂ decreases to $44.12/ton. The aminosilicone-based solvent has a higherthermal stability than MEA, allowing desorption to be conducted at higher temperatures and pressures, decreasing the number of compressor stages needed. The aminosilicone-based solvent also has a lowervapor pressure, allowing the desorption to be conducted in a continuous-stirred tank reactor versus a more expensive packed column. The aminosilicone-based solvent has a lowerheat capacity, which decreases the heat load on the desorber. In summary, the amino-silicone solvent has significant advantages overconventional systems using MEA.

  7. Heterogeneous reactions of methacrolein and methyl vinyl ketone: Kinetics and mechanisms of uptake and ozonolysis on silicon dioxide

    Science.gov (United States)

    Chen, Z. M.; Jie, C. Y.; Li, S.; Wang, H. L.; Wang, C. X.; Xu, J. R.; Hua, W.

    2008-11-01

    Methacrolein (MAC) and methyl vinyl ketone (MVK), two major first-generation products in the oxidation of isoprene, play important roles in tropospheric chemistry. However, little is known about their heterogeneous fate. Here we investigated the heterogeneous reactions of MAC and MVK on particles of silicon dioxide (SiO2), the major constituent of mineral dust in the troposphere, under simulated tropospheric conditions. We first investigated the adsorption and desorption processes. It was found that MAC and MVK molecules were adsorbed onto the surface of SiO2 particles by van der Waals forces and hydrogen bonding forces in a non-reactive state, and the presence of water vapor did not result in the formation of new substances but could decrease the adsorption ability by consuming isolated hydroxyl groups on the surface of SiO2 particles. The initial adsorption and desorption rates, initial uptake coefficients, and adsorption concentrations at equilibrium were determined at different relative humidities. Notably, in the desorption process, a considerable amount of MAC or MVK molecules remained on SiO2 particles in dry air but were almost completely desorbed in high-humid air. We also investigated the heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles, determining product yields at different relative humidities. The heterogeneous ozonolysis of MAC and MVK adsorbed onto SiO2 particles yielded formaldehyde and methylglyoxal as the major secondary carbonyl products and formic acid and acetic acid as the major organic acid products, as in their gas-phase ozonolysis. However, the yield of two major organic peroxides, methyl hydroperoxide and hydroxymethyl hydroperoxide, was much greater in their heterogeneous ozonolysis than in their gas-phase ozonolysis. The mechanisms of heterogeneous ozonolysis of MAC and MVK onto the SiO2 surface are deduced.

  8. Recent Progress in the Development of Supercritical Carbon Dioxide-Soluble Metal Ion Extractants: Aggregation, Extraction, and Solubility Properties of Silicon-Substituted Alkylenediphosphonic Acids

    Energy Technology Data Exchange (ETDEWEB)

    Dietz, Mark L.; McAlister, Daniel R.; Stepinski, Dominique C.; Zalupski, Peter R.; Dzilawa, Julie A.; Barrans, Richard E.; Hess, J.N.; Rubas, Audris V.; Chiarizia, Renato; Lubbers, Christopher M.; Scurto, Aaron M.; Brennecke, Joan F.; Herlinger, Albert W.

    2003-09-11

    Partially esterified alkylenediphosphonic acids (DPAs) have been shown to be effective reagents for the extraction of actinide ions from acidic aqueous solution into conventional organic solvents. Efforts to employ these compounds in supercritical fluid extraction have been hampered by their modest solubility in unmodified supercritical carbon dioxide (SC-CO2). In an effort to design DPAs that are soluble in SC-CO2, a variety of silicon-substituted alkylenediphosphonic acids have been prepared and characterized, and their behavior compared with that of conventional alkyl-substituted reagents. Silicon substitution is shown to enhance the CO2-philicity of the reagents, while other structural features, in particular, the number of methylene groups bridging the phosphorus atoms of the extractant, are shown to exert a significant influence on their aggregation and extraction properties. The identification of DPAs combining desirable extraction properties with adequate solubility in SC-CO2 is shown to be facilitated by the application of molecular connectivity indices.

  9. Self-assembly of CdSe quantum dots and colloidal titanium dioxide on copolymer microspheres (PS) for CdSe/PS and TiO2/CdSe/PS sub-microspheres with yolk-shell structure

    Science.gov (United States)

    Zhao, Qingchun

    2015-07-01

    Semiconductor nanocrystals serve as the building blocks for designing next generation solar cells, chemical/biological sensors, and metal chalcogenides (e.g., CdS, CdSe, PbS, and PbSe) are particularly useful for harnessing size-dependent optical and electronic properties in nanostructures. In this paper, relying on the interaction including van der Waals forces and hydrogen bond, CdSe/PS sub-microspheres composite and TiO2/CdSe/PS sub-microspheres with yolk-shell structure were prepared via self-assembly of CdSe quantum dots and colloidal titanium dioxide on modified PS surface. The morphology, structure and composition obtained products were investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy disperse X-ray spectroscopy (EDX). Transmission electron microscopy (TEM) investigations show the CdSe quantum dots and colloidal titanate were assembled on the surface of PS sub-microspheres. CdSe QD-polymer sub-microspheres composites in which the QDs retain their original emission efficiency can be obtained. TiO2/CdSe/PS sub-microspheres with yolk-shell structure can improve the efficiency of charge separation.

  10. Effect of dispersed hydrophilic silicon dioxide nanoparticles on batch adsorption of benzoic acid from aqueous solution using modified natural vermiculite: An equilibrium study

    Directory of Open Access Journals (Sweden)

    Ehsan Sadeghi Pouya

    2016-10-01

    Full Text Available The equilibrium adsorption of benzoic acid from an aqueous medium on a natural vermiculite-based adsorbent was studied in the presence and absence of hydrophilic silicon dioxide nanoparticles in batchwise mode. The adsorbent was prepared through grinding natural vermiculite in a laboratory vibratory disk mill and the surfactant modification of ground vermiculite by cetyltrimethylammonium bromide, subsequently. The equilibrium isotherm in the presence and absence of nanoparticles was experimentally obtained and the equilibrium data were fitted to the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin models. The results indicated that the dispersion of silicon dioxide nanoparticles at optimum concentration in the liquid phase remarkably increases the removal efficiency. Furthermore, it yields a more favorable equilibrium isotherm and changes the compatibility of equilibrium data from the Langmuir and Temkin equations to just the Langmuir equation. A quadratic polynomial model predicting the equilibrium adsorbent capacity in the presence of nanoparticles as a function of the adsorbate and initial nanoparticle concentrations was successfully developed using the response surface methodology based on the rotatable central composite design. A desirability function was used in order to optimize the values of all variables, independent and dependent ones, simultaneously.

  11. Silicon molybdenum blue spectrophotometric determination of silicon dioxide in arsenic trioxide%硅钼蓝分光光度法测定三氧化二砷中二氧化硅

    Institute of Scientific and Technical Information of China (English)

    谢辉; 赖心; 黄葡英

    2011-01-01

    In this study, hydrochloric acid was added into arsenic trioxide to remove arsenic by heating. The obtained residual was dissolved with sodium hydroxide. After acidification with nitric acid,silicon could form silicon molybdenum yellow complex with molybdate at pH 0. 9 using ammonium molybdate as color developer. With sulfuric acid increase the acidity, the complex was reduced to silicon molybdenum blue complex by ascorbic acid. The content of silicon dioxide was determined by spectrophotometry. The maximum absorption wavelength of silicon molybdenum blue complex was 813 nm. The relative standard deviations (RSD, n=6) were 1. 6 %-1. 9%. The determination results of this method were consistent with those obtained by ICP-AES.%研究了在三氧化二砷中加入盐酸,加热除砷,所得残渣用氢氧化钠溶解,硝酸酸化后,以钼酸铵为显色剂,在pH 0.9条件下,硅与钼酸盐形成硅钼黄络合物,用硫酸提高酸度,以抗坏血酸为还原剂,使硅形成稳定的硅钼蓝络合物,采用分光光度法测定其中的二氧化硅含量.硅钼蓝络合物最大吸收波长位于813 nm处.本法相对标准偏差(RSD)为1.6%~1.9%(n=6),测定结果与.ICP-AES法的结果相一致.

  12. Anisotropic Model Colloids

    Science.gov (United States)

    van Kats, C. M.

    2008-10-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with

  13. Evolvement of cell-substrate interaction over time for cells cultivated on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface

    Science.gov (United States)

    Hsu, Chung-Ping; Hsu, Po-Yen; Wu, You-Lin; Hsu, Wan-Yun; Lin, Jing-Jenn

    2012-09-01

    Since cell-substrate interaction is directly related to the traction force of the cell, the cell property can be judged from the imprint it leaves on the soft substrate surface onto which the cell is cultured. In this letter, the evolvement of the cell-substrate interaction over time was observed by cultivating cells on a 3-aminopropyltriethoxysilane (γ-APTES) modified silicon dioxide (SiO2) surface for different periods of time. The cell-substrate interaction property as a function of time can then be found from the post-cell-removal surface morphology profiles determined by atomic force microscopy (AFM). Different surface morphology profiles were found between normal cells and cancer cells. It was found that the cancer cells tend to form deeper trenches along the circumference of the imprints, while the normal cells do not. In addition, our results indicated that normal cells involve cell-substrate interaction mechanisms that are different from those for cancer cells.

  14. Rapid Determination of Silicon Dioxide Content in Copper Concentrate%铜精矿中二氧化硅含量的快速测定

    Institute of Scientific and Technical Information of China (English)

    戚月花; 张淑玲; 李先和; 万双; 崔鲁

    2016-01-01

    Content of silicon dioxide in copper concentrate was determined by alkali fused silica molybdenum blue spectrophotometric method. It was discussed about the solution conditions, absorption wavelength, solution acidity, water bath time, color and coexisting ions interference conditions on the influence of the absorbance. Sodium hydroxide as solvent,melting for 15 min at 680℃,melting sample effect was the best. The wavelength was selected according to the content of silicon dioxide in sample, detection wavelength was set of 810 nm for the silicon dioxide content of less than 1%, detection wavelength was set of 650 nm for the content of 1%–15%;the color effect was the best with hydrochloric acid solution of 0.15–0.20 mol/L, water bath heating of 60 s,color time of 15 min. Ammonium ferric sulfate was used as a reducing agent. The recoveries of standard addition was between 94.8%–98.8%, the relative standard deviations of five independent sample determination results were 0.26%–4.48%(n=11), the results in standard sample were consistent with the certified values. The method is simple, rapid, accurate and suitable for the determination of silicon dioxide content in the copper concentrate.%采用碱熔样硅钼蓝分光光度法测定铜精矿中二氧化硅的含量。讨论了熔融条件、吸收波长、溶液酸度、水浴加热时间、显色时间以及共存离子干扰等条件对测定结果的影响。确定以氢氧化钠为熔剂,在680℃熔融15 min,熔样效果最佳;根据样品中二氧化硅的含量选择波长,当二氧化硅含量小于1%时,选用810 nm为分析波长,二氧化硅含量为1%~15%时,选用650 nm为分析波长;在酸度为0.15~0.20 mol/L盐酸溶液中,水浴加热60 s,显色15 min,显色效果为最佳。使用硫酸亚铁铵作为还原剂。方法的加标回收率在94.8%~98.8%之间,5个样品独立测定结果的相对标准偏差为0.26%~4.48%(n=11),标准样品测定结果与标

  15. Determination of Silicon Dioxide in Fluorspar by Potassium Fluorosilicate Volumetry%浅淡氟硅酸钾容量法检测萤石二氧化硅

    Institute of Scientific and Technical Information of China (English)

    柳丽娜; 张翠芬; 韩娟伟; 朱秀玉

    2011-01-01

    从检测数据精度和检测效率两方面说明了氟硅酸钾容量法在检测萤石二氧化硅方面的优势。详细介绍了氟硅酸钾容量法的分析化学原理,最后从检测实践方面详细阐述了试验过程中的注意事项,从而有利于更快、更好的进行萤石二氧化硅的检测。%The advantages of determining the silicon dioxide content in fluorspar by potassium fluorosilicate volumetry are described in terms of test data accuracy and testing efficiency, and the attentions to be paid in actual tests are stated in detail to help to make the determination quicker and better.

  16. Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Son, Ji-Su, E-mail: sonjisu@gmail.com [Department of Electrical Engineering and Computer Science, Nagoya University, C3-1 Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Akasaki Research Center, Nagoya University, C3-1 Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi [Department of Electrical Engineering and Computer Science, Nagoya University, C3-1 Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Akasaki Research Center, Nagoya University, C3-1 Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Baik, Kwang Hyeon [Department of Materials Science and Engineering, Hongik University, Jochiwon, Chungnam 339-701 (Korea, Republic of); Seo, Yong Gon; Hwang, Sung-Min [Optoelectronics Laboratory, Korea Electronics Technology Institute, Gyeonggi-do 463-816 (Korea, Republic of)

    2013-11-01

    We report on the characteristics of a-plane GaN films directly grown on optimized silicon-dioxide-patterned r-plane sapphire substrates. Various shapes and sizes of silicon dioxide patterns were considered with the aim of achieving fully coalescent a-plane GaN films with a smooth surface and high crystalline quality. The omega full widths at half maximum of the (11–20) X-ray rocking curve values of optimized a-plane GaN films with regular hexagonal patterns of 1 μm window width and 6 μm mask width were measured to be 597 arc sec along the c-axis direction and 457 arc sec along the m-axis direction. Atomic force microscopy images revealed a significant reduction in the density of submicron pits in the mask region. Plan-view and cross-sectional transmission electron microscopy images showed that basal stacking faults and threading dislocation densities were reduced from ∼ 5.7 × 10{sup 5} cm{sup −1} and ∼ 1 × 10{sup 9} cm{sup −2} in the window region to ∼ 1.8 × 10{sup 5} cm{sup −1} and ∼ 2.1 × 10{sup 8} cm{sup −2} in the mask region, respectively. - Highlights: • Optimal hexagonal patterns (OHP) with 1 μm window width and 6 μm mask width. • Fully coalescent α-plane GaN with smooth surface and high crystalline quality. • Decreased anisotropy and defect density in α-plane GaN with SiO{sub 2} OHP.

  17. Vertically-resolved profiles of mass concentrations and particle backscatter coefficients of Asian dust plumes derived from lidar observations of silicon dioxide.

    Science.gov (United States)

    Noh, Youngmin; Müller, Detlef; Shin, Sung-Kyun; Shin, Dongho; Kim, Young J

    2016-01-01

    This study presents a method to retrieve vertically-resolved profiles of dust mass concentrations by analyzing Raman lidar signals of silicon dioxide (quartz) at 546nm. The observed particle plumes consisted of mixtures of East Asian dust with anthropogenic pollution. Our method for the first time allows for extracting the contribution of the aerosol component "pure dust" contained in the aerosol type "polluted dust". We also propose a method that uses OPAC (Optical Properties of Aerosols and Clouds) and the mass concentrations profiles of dust in order to derive profiles of backscatter coefficients of pure dust in mixed dust/pollution plumes. The mass concentration of silicon dioxide (quartz) in the atmosphere can be estimated from the backscatter coefficient of quartz. The mass concentration of dust is estimated by the weight percentage (38-77%) of mineral quartz in Asian dust. The retrieved dust mass concentrations are classified into water soluble, nucleation, accumulation, mineral-transported and coarse mode according to OPAC. The mass mixing ratio of 0.018, 0.033, 0.747, 0.130 and 0.072, respectively, is used. Dust extinction coefficients at 550nm were calculated by using OPAC and prescribed number concentrations for each of the 5 components. Dust backscatter coefficients were calculated from the dust extinction coefficients on the basis of a lidar ratio of 45±3sr at 532nm. We present results of quartz-Raman measurements carried out on the campus of the Gwangju Institute of Science and Technology (35.10°N, 126.53°E) on 15, 16, and 21 March 2010.

  18. Influence of the ion synthesis and ion doping regimes on the effect of sensitization of erbium emission by silicon nanoclusters in silicon dioxide films

    Science.gov (United States)

    Korolev, D. S.; Kostyuk, A. B.; Belov, A. I.; Mikhaylov, A. N.; Dudin, Yu. A.; Bobrov, A. I.; Malekhonova, N. V.; Pavlov, D. A.; Tetelbaum, D. I.

    2013-11-01

    The photoluminescence spectra of erbium centers in SiO2 films with ion-synthesized silicon nanoclusters under nonresonant excitation were investigated. Erbium was introduced into thermal SiO2 films by ion implantation. The dependences of photoluminescence intensity on the dose, the order of ion implantation of Si and Er, the annealing temperature, and additional Ar+ and P+ ion irradiation regimes, i.e., factors determining the influence of radiation damage and doping on sensitization of erbium luminescence by silicon nanoclusters, were determined. It was found that the sensitization effect and its amplification due to doping with phosphorus are most pronounced under the conditions where nanoclusters are amorphous. The quenching of photoluminescence due to radiation damage in this case manifests itself to a lesser extent than for crystalline nanoclusters. The role of various factors in the observed regularities was discussed in the framework of the existing concepts of the mechanisms of light emission and energy exchange in the system of silicon nanoclusters and erbium centers.

  19. Colloidal polypyrrole

    Science.gov (United States)

    Armes, Steven P.; Aldissi, Mahmoud

    1990-01-01

    Processable electrically conductive latex polymer compositions including colloidal particles of an oxidized, polymerized aromatic heterocyclic monomer, a stabilizing effective amount of a vinyl pyridine-containing polymer and dopant anions and a method of preparing such polymer compositions are disclosed.

  20. Colloidal nematostatics

    Directory of Open Access Journals (Sweden)

    V.M. Pergamenshchik

    2010-01-01

    Full Text Available We give a review of the theory of large distance colloidal interaction via the nematic director field. The new area of nematic colloidal systems (or nematic emulsions has been guided by the analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V.M. Pergamenshchik, V.O. Uzunova, Eur. Phys. J. E, 2007, 23, 161; Phys. Rev. E, 2007, 76, 011707] develops this analogy at the level of charge density and Coulomb interaction. The analogy is shown to lie in common mathematics based on the solutions of Laplace equation. However, the 3d colloidal nematostatics substantially differs from electrostatics both in its mathematical structure and physical implications. The elastic charge is a vector fully determined by the torque exerted upon colloid, the role of Gauss' theorem is played by conservation of the torque components. Elastic multipoles consist of two tensors (dyads. Formulas for the elastic multipoles, the Coulomb-like, dipole-dipole, and quadrupole-quadrupole pair interaction potentials are derived and illustrated by particular examples. Based on the tensorial structure, we list possible types of elastic dipoles and quadrupoles. An elastic dipole is characterized by its isotropic strength, anisotropy, chirality, and its longitudinal component. An elastic quadrupole can be uniaxial and biaxial. Relation between the multipole type and its symmetry is discussed, sketches of some types of multipoles are given. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in nematostatics for arbitrary director tilt at the wall. The method is applied to the charge-wall and dipole-wall interaction.

  1. ‘Reliability of new poly (lactic-co-glycolic acid) membranes treated with oxygen plasma plus silicon dioxide layers for pre-prosthetic guided bone regeneration processes’

    Science.gov (United States)

    Castillo-Dalí, Gabriel; Batista-Cruzado, Antonio; López-Santos, Carmen; Rodríguez-González-Elipe, Agustín; Saffar, Jean-Louis; Lynch, Christopher D.; Gutiérrez-Pérez, José-Luis; Torres-Lagares, Daniel

    2017-01-01

    Background The use of cold plasmas may improve the surface roughness of poly(lactic-co-glycolic) acid (PLGA) membranes, which may stimulate the adhesion of osteogenic mediators and cells, thus accelerating the biodegradation of the barriers. Moreover, the incorporation of metallic-oxide particles to the surface of these membranes may enhance their osteoinductive capacity. Therefore, the aim of this paper was to evaluate the reliability of a new PLGA membrane after being treated with oxygen plasma (PO2) plus silicon dioxide (SiO2) layers for guided bone regeneration (GBR) processes. Material and Methods Circumferential bone defects (diameter: 11 mm; depth: 3 mm) were created on the top of eight experimentation rabbits’ skulls and were randomly covered with: (1) PLGA membranes (control), or (2) PLGA/PO2/SiO2 barriers. The animals were euthanized two months afterwards. A micromorphologic study was then performed using ROI (region of interest) colour analysis. Percentage of new bone formation, length of mineralised bone, concentration of osteoclasts, and intensity of ostheosynthetic activity were assessed and compared with those of the original bone tissue. The Kruskal-Wallis test was applied for between-group com Asignificance level of a=0.05 was considered. Results The PLGA/PO2/SiO2 membranes achieved the significantly highest new bone formation, length of mineralised bone, concentration of osteoclasts, and ostheosynthetic activity. The percentage of regenerated bone supplied by the new membranes was similar to that of the original bone tissue. Unlike what happened in the control group, PLGA/PO2/SiO2 membranes predominantly showed bone layers in advanced stages of formation. Conclusions The addition of SiO2 layers to PLGA membranes pre-treated with PO2 improves their bone-regeneration potential. Although further research is necessary to corroborate these conclusions in humans, this could be a promising strategy to rebuild the bone architecture prior to rehabilitate

  2. Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

    Directory of Open Access Journals (Sweden)

    Keisuke Shibuya

    2015-10-01

    Full Text Available We systematically examined the effects of the substrate temperature (TS and the oxygen pressure (PO2 on the structural and optical properties polycrystalline V O2 films grown directly on Si(100 substrates by pulsed-laser deposition. A rutile-type V O2 phase was formed at a TS ≥ 450 °C at PO2 values ranging from 5 to 20 mTorr, whereas other structures of vanadium oxides were stabilized at lower temperatures or higher oxygen pressures. The surface roughness of the V O2 films significantly increased at growth temperatures of 550 °C or more due to agglomeration of V O2 on the surface of the silicon substrate. An apparent change in the refractive index across the metal–insulator transition (MIT temperature was observed in V O2 films grown at a TS of 450 °C or more. The difference in the refractive index at a wavelength of 1550 nm above and below the MIT temperature was influenced by both the TS and PO2, and was maximal for a V O2 film grown at 450 °C under 20 mTorr. Based on the results, we derived the PO2 versus 1/TS phase diagram for the films of vanadium oxides, which will provide a guide to optimizing the conditions for growth of V O2 films on silicon platforms.

  3. Silicon dioxide obtained by Polymeric Precursor Method; Obtencao de dioxido de silicio pelo Metodo dos Precursores Polimericos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, C.T.; Granado, S.R.; Lopes, S.A.; Cavalheiro, A.A., E-mail: cinthia_quimica@hotmail.com [Universidade Estadual de Mato Grosso do Sul (CPTREN/UEMS), Navirai, MS (Brazil). Centro de Pesquisas Tecnologicas em Recursos Naturais

    2011-07-01

    The Polymeric Precursor Method is able for obtaining several oxide material types with high surface area even obtained in particle form. Several MO{sub 2} oxide types such as titanium, silicon and zirconium ones can be obtained by this methodology. In this work, the synthesis of silicon oxide was monitored by thermal analysis, XRD and surface area analysis in order to demonstrate the influence of the several synthesis and calcining parameters. Surface area values as higher as 370m2/g and increasing in the micropore volume nm were obtained when the material was synthesized by using ethylene glycol as polymerizing agent. XRD analysis showed that the material is amorphous when calcinated at 600°C in despite of the time of calcining, but the material morphology is strongly influenced by the polymeric resin composition. Using Glycerol as polymerizing agent, the pore size increase and the surface area goes down with the increasing in decomposition time, when compared to ethylene glycol. (author)

  4. Colloidal superballs

    NARCIS (Netherlands)

    Rossi, L.

    2012-01-01

    This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and super

  5. Preparation and properties of lauric acid/silicon dioxide composites as form-stable phase change materials for thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Fang Guiyin, E-mail: gyfang@nju.edu.cn [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China); Li Hui [Department of Material Science and Engineering, Nanjing University, Nanjing 210093 (China); Liu Xu [Department of Physics, Nanjing University, Hankou Road 22, Nanjing, Jiangsu 210093 (China)

    2010-08-01

    Form-stable lauric acid (LA)/silicon dioxide (SiO{sub 2}) composite phase change materials were prepared using sol-gel methods. The LA was used as the phase change material for thermal energy storage, with the SiO{sub 2} acting as the supporting material. The structural analysis of these form-stable LA/SiO{sub 2} composite phase change materials was carried out using Fourier transformation infrared spectroscope (FT-IR). The microstructure of the form-stable composite phase change materials was observed by a scanning electronic microscope (SEM). The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that the LA was well dispersed in the porous network of SiO{sub 2}. The DSC results indicated that the melting latent heat of the form-stable composite phase change material is 117.21 kJ kg{sup -1} when the mass percentage of the LA in the SiO{sub 2} is 64.8%. The results of the TGA showed that these materials have good thermal stability. The form-stable composite phase change materials can be used for thermal energy storage in waste heat recovery and solar heating systems.

  6. 容量法快速测定锰矿中二氧化硅含量%Determination of Silicon Dioxide Content in Manganese Ore by Volumetric Method

    Institute of Scientific and Technical Information of China (English)

    张慤; 邓军华; 王一凌; 王翠艳; 曲月华

    2012-01-01

    At present, fluoride potassium silicate Volumetric method analysis silica content in manganese ore has not reported, through experiments optimized the parameters of fluoride potassium silicate Volumetric method: melt-like way, sample weight, volume of acidified et. It can complete the rapid determination of silicon dioxide content in manganese ore. Measurement Results consistent with the certified value and the analysis to satisfy the GB/T 1509 - 2006 permission deviation request, The relative standard deviation of measurement results are less than 1 % .%目前利用氟硅酸钾容量法测定锰矿中二氧化硅含量还没有报道.采用硅氟酸钾容量法,通过称样量、融样方式、酸化体积等条件进行优化实验,实现了容量法快速测定锰矿中二氧化硅的含量.实验数据的相对标准偏差小于1%.测量值与认定值一致,测量结果满足GB/T 1509-2006《锰矿石 硅含量的测定 高氯酸脱水重量法》允许差的要求.

  7. Determination of Glucose by Affinity Adsorption Solid Substrate-room Temperature Phosphorimetry Based on Triticum Vulgare Lectin Labeled with Silicon Dioxide Nanoparticle Containing Fiuorescein Isothiocyanate

    Institute of Scientific and Technical Information of China (English)

    LIU Jia-Ming; LIU Zhen-Bo; LI Zhi-Ming; HE Hang-Xia; LIN Wei-Nü; HUANG Ya-Hong; WANG Fang-Mei

    2008-01-01

    In the presence of heavy atom perturber Pb2+,silicon dioxide nanoparticle containing fluorescein isothiocyanate (FITC-SiO2) could emit a strong and stable room temperature phosphorescence (RTP) signal on the surface of acetyl cellulose membrane (ACM).It was found in the research that a quantitative specific affinity adsorption (AA) reaction between triticum vulgare lectin (WGA) labeled with luminescent nanoparticle and glucose (g)could be carried on the surface of ACM.The product (WGA-G-WGA-FITC-SiO2) of the reaction could emit a stronger RTP signal,and the △Ip had linear correlation to the content of G.According to the facts above,a new method to determine G by affinity adsorption solid substrate room temperature phosphorimetry (AA-SS-RTP) was established,based on WGA labeled with FITC-SiO2.The detection limit (LD) of this method calculated by 3Sb/k was 0.47 pg·spot-1 (corresponding to a concentration value 1.2 × 10-9 g·mL-1,namely 5.3 × 10-9 mol·L-1),the sensitivity was high.Meanwhile,the mechanism for the determination of G by AA-SS-RTP was discussed.

  8. Porous Silicon & Titanium Dioxide Coatings Prepared by Atmospheric Pressure Plasma Jet Chemical Vapour Deposition Technique-A Novel Coating Technology for Photovoltaic Modules

    Directory of Open Access Journals (Sweden)

    S. Bhatt

    2011-01-01

    Full Text Available Atmospheric Pressure Plasma Jet (APPJ is an alternative for wet processes used to make anti reflection coatings and smooth substrate surface for the PV module. It is also an attractive technique because of it’s high growth rate, low power consumption, lower cost and absence of high cost vacuum systems. This work deals with the deposition of silicon oxide from hexamethyldisiloxane (HMDSO thin films and titanium dioxide from tetraisopropyl ortho titanate using an atmospheric pressure plasma jet (APPJ system in open air conditions. A sinusoidal high voltage with a frequency between 19-23 kHz at power up to 1000 W was applied between two tubular electrodes separated by a dielectric material. The jet, characterized by Tg ~ 600-800 K, was mostly laminar (Re ~ 1200 at the nozzle exit and became partially turbulent along the jet axis (Re ~ 3300. The spatially resolved emission spectra showed OH, N2, N2+ and CN molecular bands and O, H, N, Cu and Cr lines as well as the NO2 chemiluminescence continuum (450-800 nm. Thin films with good uniformity on the substrate were obtained at high deposition rate, between 800 -1000 nm.s-1, and AFM results revealed that coatings are relatively smooth (Ra ~ 2 nm. The FTIR and SEM analyses were better used to monitor the chemical composition and the morphology of the films in function of the different experimental conditions.

  9. Solid phase extraction with silicon dioxide microsphere adsorbents in combination with gas chromatography-electron capture detection for the determination of DDT and its metabolites in water samples.

    Science.gov (United States)

    Zhou, Qingxiang; Wu, Wei; Xie, Guohong

    2013-01-01

    The goal of the present study was to investigate the feasibility of silicon dioxide (SiO(2)) microspheres without special modification to enrich dichlorodiphenyltrichloroethane (DDT) and its main metabolites, p,p'-dichlorodiphenyl-2,2-dichloroethylene (p,p'-DDD) and p,p'-dichlorodiphenyldichloroethylene (DDE) in combination with gas chromatography-electron-capture detection. The experimental results indicated that an excellent linear relationship between the recoveries and the concentrations of DDT and its main metabolites was obtained in the range of 0.2-30 ng mL(-1) and the correlation coefficients were in the range of 99.96-99.99%. The detection limits based on the ratio of signal to the baseline noise (S/N = 3) were 2.2, 2.9, 3.8 and 4.1 ng L(-1) for p,p'-DDD, p,p'-DDT, o,p'-DDT, and p,p'-DDE, respectively. The precisions of the proposed method were all below 10% (n = 6). Four real water samples were utilized for validation of the proposed method, and satisfactory spiked recoveries in the range of 72.4-112.9% were achieved. These results demonstrated that the developed method was a simple, sensitive, and robust analytical method for the monitoring of pollutants in the environment.

  10. Adsorption, desorption, and film formation of quinacridone and its thermal cracking product indigo on clean and carbon-covered silicon dioxide surfaces

    Science.gov (United States)

    Scherwitzl, Boris; Lassnig, Roman; Truger, Magdalena; Resel, Roland; Leising, Günther; Winkler, Adolf

    2016-09-01

    The evaporation of quinacridone from a stainless steel Knudsen cell leads to the partial decomposition of this molecule in the cell, due to its comparably high sublimation temperature. At least one additional type of molecules, namely indigo, could be detected in the effusion flux. Thermal desorption spectroscopy and atomic force microscopy have been used to study the co-deposition of these molecules on sputter-cleaned and carbon-covered silicon dioxide surfaces. Desorption of indigo appears at temperatures of about 400 K, while quinacridone desorbs at around 510 K. For quinacridone, a desorption energy of 2.1 eV and a frequency factor for desorption of 1 × 1019 s-1 were calculated, which in this magnitude is typical for large organic molecules. A fraction of the adsorbed quinacridone molecules (˜5%) decomposes during heating, nearly independent of the adsorbed amount, resulting in a surface composed of small carbon islands. The sticking coefficients of indigo and quinacridone were found to be close to unity on a carbon covered SiO2 surface but significantly smaller on a sputter-cleaned substrate. The reason for the latter can be attributed to insufficient energy dissipation for unfavorably oriented impinging molecules. However, due to adsorption via a hot-precursor state, the sticking probability is increased on the surface covered with carbon islands, which act as accommodation centers.

  11. Theory and experiments of electron-hole recombination at silicon/silicon dioxide interface traps and tunneling in thin oxide MOS transistors

    Science.gov (United States)

    Cai, Jin

    2000-10-01

    Surface recombination and channel have dominated the electrical characteristics, performance and reliability of p/n junction diodes and transistors. This dissertation uses a sensitive direct-current current voltage (DCIV) method to measure base terminal currents (IB) modulated by the gate bias (VGB) and forward p/n junction bias (VPN) in a MOS transistor (MOST). Base terminal currents originate from electron-hole recombination at Si/SiO2 interface traps. Fundamental theories which relate DCIV characteristics to device and material parameters are presented. Three theory-based applications are demonstrated on both the unstressed as well as hot-carrier-stressed MOSTs: (1) determination of interface trap density and energy levels, (2) spatial profile of interface traps in the drain/base junction-space-charge region and in the channel region, and (3) determination of gate oxide thickness and impurity doping concentrations. The results show that interface trap energy levels are discrete, which is consistent with those from silicon dangling bonds; in unstressed MOS transistors interface trap density in the channel region rises sharply toward source and drain, and after channel-hot-carrier stress, interface trap density increases mostly in the junction space-charge region. As the gate oxide thins below 3 nm, the gate oxide leakage current via quantum mechanical tunneling becomes significant. A gate oxide tunneling theory which refined the traditional WKB tunneling probability is developed for modeling tunneling currents at low electric fields through a trapezoidal SiO2 barrier. Correlation with experimental data on thin oxide MOSTs reveals two new results: (1) hole tunneling dominates over electron tunneling in p+gate p-channel MOSTs, and (2) the small gate/drain overlap region passes higher tunneling currents than the channel region under depletion to flatband gate voltages. The good theory-experimental correlation enables the extraction of impurity doping concentrations

  12. Soil colloidal behavior

    Science.gov (United States)

    Recent understanding that organic and inorganic contaminants are often transported via colloidal particles has increased interest in colloid science. The primary importance of colloids in soil science stems from their surface reactivity and charge characteristics. Characterizations of size, shape,...

  13. Germanium nanoparticles formed in silicon dioxide layer by multi-energy implantation and oxidation state of Ge atoms

    Science.gov (United States)

    Tsuji, H.; Arai, N.; Gotoh, N.; Minotani, T.; Kojima, K.; Adachi, K.; Kotaki, H.; Ishibashi, T.; Gotoh, Y.; Ishikawa, J.

    2007-04-01

    Ge nanoparticles (NPs) embedded silicon oxide is expected to be promising light emission source, especially, UV - blue light region. We have tried to form Ge NPs in a 100- nm-thick SiO2 layer on Si substrate by multi-energy implantation of Ge negative ions with energies of 50, 20 and 10 keV and doses of 1.4 × 1016, 3.2 × 1015 and 2.2 × 1015 ions/cm2, respectively. Samples were annealed for 1 h at a temperature less than 900oC. By this implantation, Formations of Ge nanoparticles in a surface 50-nm depth region were expected. The depth distribution of implanted Ge atoms in the oxide was measured by XPS (Ge 2p, O 1s, Si 2p) with monochromatic Al K.. and Ar etching at 4 keV. The depth profiles were well agreed with the cross-sectional TEM image. But some extent of Ge atoms diffused to the SiO2/Si interface at 900 oC. The chemical sifted spectra of Ge 2p3/2 showed about 60 % of the oxidation of Ge atom around the end of the range (EOR) even in the as-implanted sample. This oxidation was considered to be due to the excess oxygen atoms near EOR by forward of sputtered oxygen atoms from SiO2 layer. Raman spectra supported this oxidation. In a preliminary investigation of cathode luminescence, the Ge-implanted sample with annealing at 600oC showed CL peak at 3.12 eV (397 nm in wavelength) in UV-blue region at room temperature. This means the Ge-implanted sample has a possibility for light emission in the UV-blue region.

  14. Germanium nanoparticles formed in silicon dioxide layer by multi-energy implantation and oxidation state of Ge atoms

    Energy Technology Data Exchange (ETDEWEB)

    Tsuji, H [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Arai, N [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Gotoh, N [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Minotani, T [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Kojima, K [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Adachi, K [Advanced Technology Research Laboratories, Sharp Corporation, Ichikonomoto, Tenri 632-8567 (Japan); Kotaki, H [Advanced Technology Research Laboratories, Sharp Corporation, Ichikonomoto, Tenri 632-8567 (Japan); Ishibashi, T [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Gotoh, Y [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Ishikawa, J [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)

    2007-04-15

    Ge nanoparticles (NPs) embedded silicon oxide is expected to be promising light emission source, especially, UV - blue light region. We have tried to form Ge NPs in a 100- nm-thick SiO2 layer on Si substrate by multi-energy implantation of Ge negative ions with energies of 50, 20 and 10 keV and doses of 1.4 x 1016, 3.2 x 1015 and 2.2 x 1015 ions/cm{sup 2}, respectively. Samples were annealed for 1 h at a temperature less than 900oC. By this implantation, Formations of Ge nanoparticles in a surface 50-nm depth region were expected. The depth distribution of implanted Ge atoms in the oxide was measured by XPS (Ge 2p, O 1s, Si 2p) with monochromatic Al K.. and Ar etching at 4 keV. The depth profiles were well agreed with the cross-sectional TEM image. But some extent of Ge atoms diffused to the SiO2/Si interface at 900 oC. The chemical sifted spectra of Ge 2p3/2 showed about 60 % of the oxidation of Ge atom around the end of the range (EOR) even in the as-implanted sample. This oxidation was considered to be due to the excess oxygen atoms near EOR by forward of sputtered oxygen atoms from SiO2 layer. Raman spectra supported this oxidation. In a preliminary investigation of cathode luminescence, the Ge-implanted sample with annealing at 600oC showed CL peak at 3.12 eV (397 nm in wavelength) in UV-blue region at room temperature. This means the Ge-implanted sample has a possibility for light emission in the UV-blue region.

  15. Pilot-Scale Silicone Process for Low-Cost Carbon Dioxide Capture Preliminary Techno-Economic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Surinder; Spiry, Irina; Wood, Benjamin; Hance, Dan; Chen, Wei; Kehmna, Mark; McDuffie, Dwayne

    2014-03-31

    This report presents system and economic analysis for a carbon-capture unit which uses an aminosilicone-based solvent for CO{sub 2} capture in a pulverized coal (PC) boiler. The aminosilicone solvent is a 60/40 wt/wt mixture of 3-aminopropyl end-capped polydimethylsiloxane (GAP-1m) with tri-ethylene glycol (TEG) as a co-solvent. For comparison purposes, the report also shows results for a carbon-capture unit based on a conventional approach using mono-ethanol amine (MEA). The first year removal cost of CO{sub 2} for the aminosilicone-based carbon-capture process is $46.04/ton of CO2 as compared to $60.25/ton of CO{sub 2} when MEA is used. The aminosilicone-based process has <77% of the CAPEX of a system using MEA solvent. The lower CAPEX is due to several factors, including the higher working capacity of the aminosilicone solvent compared the MEA, which reduces the solvent flow rate required, reducing equipment sizes. If it is determined that carbon steel can be used in the rich-lean heat exchanger in the carbon capture unit, the first year removal cost of CO{sub 2} decreases to $44.12/ton. The aminosilicone-based solvent has a higher thermal stability than MEA, allowing desorption to be conducted at higher temperatures and pressures, decreasing the number of compressor stages needed. The aminosilicone-based solvent also has a lower vapor pressure, allowing the desorption to be conducted in a continuous-stirred tank reactor versus a more expensive packed column. The aminosilicone-based solvent has a lower heat capacity, which decreases the heat load on the desorber. In summary, the amino-silicone solvent has significant advantages over conventional systems using MEA.

  16. [Investigation on damage of bovine serum albumin (BSA) catalyzed by nano-sized silicon dioxide (SiO2) under ultrasonic irradiation using spectral methods].

    Science.gov (United States)

    Wang, Jun; Ding, Na; Zhang, Zhao-hong; Guo, Ying; Wang, Shi-xian; Xu, Rui; Zhang, Xiang-dong

    2009-04-01

    The damage of bovine serum albumin (BSA) molecules under ultrasonic irradiation in the presence of nano-sized silicon dioxide (SiO2) particles was studied by UV-Vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time, nano-sized SiO2 addition amount, solution acidity (pH) and ultrasonic irradiation power on the damage of BSA molecules in aqueous solution were also detected. For BSA solution of 1.0 x 10(-5) mol x L(-1) at (37.0+/-0.2) degrees C, the UV-Vis spectra of BSA solutions showed that the absorption peaks of BSA displayed obvious hyperchromic effect with the increase in some influence factors such as ultrasonic irradiation time, nano-sized SiO2 addition amount, pH value and ultrasonic irradiation power. However, the fluorescence spectra of BSA solutions showed the phenomenon of fluorescence quenching with the increase in ultrasonic irradiation time, nano-sized SiO2 addition amount, pH value and ultrasonic irradiation power. Moreover, the possible mechanism behind the damage of BSA molecule in the presence of nano-sized SiO2 powders under ultrasonic irradiation was discussed. It was considered that the damage of BSA molecules was attributed to the formation of *OH radicals resulting from the sonoluminescence and high-heat excitation of ultrasonic cavitation. The research results could be of great significance to using sonocatalytic method to treat tumour in clinic application and for developing nano-sized drug in the future.

  17. Implantation of silicon dioxide-based nanocrystalline hydroxyapatite and pure phase beta-tricalciumphosphate bone substitute granules in caprine muscle tissue does not induce new bone formation

    Directory of Open Access Journals (Sweden)

    Ghanaati Shahram

    2013-01-01

    Full Text Available Abstract Background Osteoinductive bone substitutes are defined by their ability to induce new bone formation even at heterotopic implantation sites. The present study was designed to analyze the potential osteoinductivity of two different bone substitute materials in caprine muscle tissue. Materials and methods One gram each of either a porous beta-tricalcium phosphate (β-TCP or an hydroxyapatite/silicon dioxide (HA/SiO2-based nanocrystalline bone substitute material was implanted in several muscle pouches of goats. The biomaterials were explanted at 29, 91 and 181 days after implantation. Conventional histology and special histochemical stains were performed to detect osteoblast precursor cells as well as mineralized and unmineralized bone matrix. Results Both materials underwent cellular degradation in which tartrate-resistant acid phosphatase (TRAP-positive osteoclast-like cells and TRAP-negative multinucleated giant cells were involved. The ß-TCP was completely resorbed within the observation period, whereas some granules of the HA-groups were still detectable after 180 days. Neither osteoblasts, osteoblast precursor cells nor extracellular bone matrix were found within the implantation bed of any of the analyzed biomaterials at any of the observed time points. Conclusions This study showed that ß-TCP underwent a faster degradation than the HA-based material. The lack of osteoinductivity for both materials might be due to their granular shape, as osteoinductivity in goat muscle has been mainly attributed to cylindrical or disc-shaped bone substitute materials. This hypothesis however requires further investigation to systematically analyze various materials with comparable characteristics in the same experimental setting.

  18. Towards Directional Colloidal Interactions

    NARCIS (Netherlands)

    Kamp, M.

    2015-01-01

    Colloids are particles with a size on the scale of microns in at least one dimension. The central theme of this thesis is the synthesis of model colloids with anisotropic interactions - often called `patchy' colloids, as well as the search for new ways to assemble such colloids. Methods to build

  19. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

  20. 基于IBC太阳电池的二氧化硅掩膜研究%Study of Silicon Dioxide Masking Layer in IBC Solar Cell

    Institute of Scientific and Technical Information of China (English)

    李力; 姜辰明; 黄铭; 沈辉

    2014-01-01

    In the fabrication process of interdigitated back contact (IBC)solar cell,one is using SiO2 as a masking layer after boron diffusion and then diffusing phosphorus is used to form local back surface field (LBSF).Under the protection of SiO2 ,the p-type emitter would stay unchanged and the area without SiO2 will become n+LBSF.A gap covered with SiO2 separates the emitter and LBSF.Thickness of ther-mal oxidation SiO2 in different temperatures,from 0 nm to 124 nm,is investigated.Sheet resistance,mi-nority carrier lifetime and diffusion profile by ECV before and after phosphorus diffusion are measured to see the effect of different silicon dioxide masking layers.With all these factors taken into consideration, the best thermal oxidation technique is determined for the following process of the IBC solar cell.%在叉指状背接触太阳电池(IBC电池)的制作过程中,一种办法是以二氧化硅作为掩膜阻挡磷扩散进入已经扩硼的区域,在有二氧化硅保护的区域,p+区保持不变,在没有二氧化硅保护的地方磷扩散进入形成n+背表面场,从而实现在不同区域的不同扩散。该文是研究在不同的的温度下热氧化得到的二氧化硅氧化层的厚度,厚度从0 nm到124 nm,然后通过测量磷扩散前后方阻变化和ECV图像,研究不同厚度下的二氧化硅掩膜对磷扩散的阻挡作用。同时,还测量了在不同情况下硅片的少子寿命,以确定一个最佳的热氧化二氧化硅工艺,为IBC电池工艺的后续研究提供参考。

  1. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    Book Description: Colloidal science and technology is one of the fastest growing research and technology areas. This book explores the cutting edge research in colloidal science and technology that will be usefull in almost every aspect of modern society. This book has a depth of information...... related to historical prospective, synthesis, characterization, theoretical modeling and application of unique class of colloidal materials starting from colloidal gold to coated silica colloid and platinum, titania colloids. This book is unique in its design, content, providing depth of science about...... different colloidal materials and their applications in chemistry, physics, biological, medical sciences and environment. Graduate students, academic and industrial researchers and medical professionals will discover recently developed colloidal materials and their applications in many areas of human...

  2. Use of the Microparticle Nanoscale Silicon Dioxide as an Adjuvant To Boost Vaccine Immune Responses against Influenza Virus in Neonatal Mice

    Science.gov (United States)

    Russell, Ryan F.; McDonald, Jacqueline U.; Lambert, Laura

    2016-01-01

    ABSTRACT Neonates are at a high risk of infection, but vaccines are less effective in this age group; tailored adjuvants could potentially improve vaccine efficacy. Increased understanding about danger sensing by the innate immune system has led to the rational design of novel adjuvants. But differences in the neonatal innate immune response, for example, to Toll-like receptor (TLR) agonists, can reduce the efficacy of these adjuvants in early life. We therefore targeted alternative danger-sensing pathways, focusing on a range of compounds described as inflammasome agonists, including nanoscale silicon dioxide (NanoSiO2), calcium pyrophosphate dihydrate (CPPD) crystals, and muramyl tripeptide (M-Tri-DAP), for their ability to act as adjuvants. In vitro, these compounds induced an interleukin 1-beta (IL-1β) response in the macrophage-like cell line THP1. In vivo, adult CB6F1 female mice were immunized intramuscularly with H1N1 influenza vaccine antigens in combination with NanoSiO2, CPPD, or M-Tri-DAP and subsequently challenged with H1N1 influenza virus (A/England/195/2009). The adjuvants boosted anti-hemagglutinin IgG and IgA antibody levels. Both adult and neonatal animals that received NanoSiO2-adjuvanted vaccines lost significantly less weight and recovered earlier after infection than control animals treated with antigen alone. Administration of the adjuvants led to an influx of activated inflammatory cells into the muscle but to little systemic inflammation measured by serum cytokine levels. Blocking IL-1β or caspase 1 in vivo had little effect on NanoSiO2 adjuvant function, suggesting that it may work through pathways other than the inflammasome. Here we demonstrate that NanoSiO2 can act as an adjuvant and is effective in early life. IMPORTANCE Vaccines can fail to protect the most at-risk populations, including the very young, the elderly, and the immunocompromised. There is a gap in neonatal immunity between the waning of maternal protection and routine

  3. Colloidal Plasmas : Basic physics of colloidal plasmas

    Indian Academy of Sciences (India)

    C B Dwivedi

    2000-11-01

    Colloidal plasma is a distinct class of the impure plasmas with multispecies ionic composition. The distinction lies in the phase distribution of the impurity-ion species. The ability to tailor the electrostatic interactions between these colloidal particles provides a fertile ground for scientists to investigate the fundamental aspects of the Coulomb phase transition behavior. The present contribution will review the basic physics of the charging mechanism of the colloidal particles as well as the physics of the collective normal mode behavior of the general multi-ion species plasmas. Emphasis will be laid on the clarification of the prevailing confusing ideas about distinct qualities of the various acoustic modes, which are likely to exist in colloidal plasmas as well as in normal multi-ion species plasmas. Introductory ideas about the proposed physical models for the Coulomb phase transition in colloidal plasma will also be discussed.

  4. Identification of Al13 on the Colloid Surface Using Surface-Enhanced Raman Spectroscopy.

    Science.gov (United States)

    Li, Ning; Hu, Chengzhi; Fu, Xiaoning; Xu, Xiufang; Liu, Rui; Liu, Huijuan; Qu, Jiuhui

    2017-02-21

    Al13 is the most active polymeric Al species responsible for coagulation at the solid-liquid interface, whereas the detection techniques for Al13 at the interface are currently limited. In this study, for the first time, the identification of Al13 on the silicon dioxide-based colloid surface was realized by using surface-enhanced Raman scattering (SERS), which is an ideal surface method sensitive for single-molecule detection. The high purity Al13 salts were prepared by an electrolysis procedure followed by precipitation or metathesis. Al13-Cln was determined to be feasible for the Raman detection as it exhibited more noticeable signals in comparison to Al13-(SO4)p and Al13-(NO3)m. The peak of Al13-Cln at 635 cm(-1) could be the major characteristic peak of Al13, and the other two peaks at 300 and 987 cm(-1) could be accessorial evidence for the identification. Further, the identification of Al13 adsorbed on the surface of Ag and gold-core/silica-shell colloids was confirmed by the SERS response at the above three wavenumbers with a higher signal-to-noise ratio than the normal Raman scattering. According to the least-squares fitting computed Raman spectra, each of the characteristic peaks was associated with specific vibrational modes.

  5. Microfluidic colloid filtration

    Science.gov (United States)

    Linkhorst, John; Beckmann, Torsten; Go, Dennis; Kuehne, Alexander J. C.; Wessling, Matthias

    2016-03-01

    Filtration of natural and colloidal matter is an essential process in today’s water treatment processes. The colloidal matter is retained with the help of micro- and nanoporous synthetic membranes. Colloids are retained in a “cake layer” – often coined fouling layer. Membrane fouling is the most substantial problem in membrane filtration: colloidal and natural matter build-up leads to an increasing resistance and thus decreasing water transport rate through the membrane. Theoretical models exist to describe macroscopically the hydrodynamic resistance of such transport and rejection phenomena; however, visualization of the various phenomena occurring during colloid retention is extremely demanding. Here we present a microfluidics based methodology to follow filter cake build up as well as transport phenomena occuring inside of the fouling layer. The microfluidic colloidal filtration methodology enables the study of complex colloidal jamming, crystallization and melting processes as well as translocation at the single particle level.

  6. Electron Acceptor Materials Engineering in Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Liu, Huan

    2011-07-15

    Lead sulfide colloidal quantum dot (CQD) solar cells with a solar power conversion efficiency of 5.6% are reported. The result is achieved through careful optimization of the titanium dioxide electrode that serves as the electron acceptor. Metal-ion-doped sol-gel-derived titanium dioxide electrodes produce a tunable-bandedge, well-passivated materials platform for CQD solar cell optimization. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Morphological and structural evolution of the anatase phase of silicon modified titanium dioxide obtained by Sol-gel; Evolucao estrutural e morfologica da fase anatase de dioxido de titanio modificada com silicio obtido pelo Metodo Sol-Gel

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, S.A.; Oliveira, C.T.; Ciola, R.A.; Cavalheiro, A.A., E-mail: silvanicelopes@gmail.com [Universidade Estadual de Mato Grosso do Sul (CPTREN/UEMS), Navirai, MS (Brazil). Centro de Pesquisas Tecnologicas em Recursos Naturais

    2011-07-01

    The photonic efficiency of the titanium dioxide photocatalyst is dependent on the crystalline structure and the anatase phase presents high efficiency in the border region between the UV-B and UV-A, with a redox potential sufficient to generate hydroxyl radicals and superoxide ion in order to oxidate organic compounds. In spite of the organic matter degradation effectiveness, the efficiency can be reduced substantially due to the presence of crystalline defects, which act as premature recombination centers of the electron-hole pair. The increasing of calcining temperature allows the elimination of most of these defects, but the structural ordering at temperatures around 600°C eventually leads to the phase transition toward rutile, which is not photoactive. In this work, it was demonstrated through FTIR and XRD that the silicon modifier presence stabilizes the anatase phase even at temperatures as high as 900°C. (author)

  8. Microcavity arrays for X-ray diffraction studies of ordering phenomena in confined colloid solutions

    NARCIS (Netherlands)

    Diaz, A.; David, C.; Guo, H.; Keymeulen, H.; Pfeiffer, F.; Wegdam, G.; Weitkamp, T.; van der Veen, J.F.

    2005-01-01

    We present a way to fabricate high-aspect-ratio silicon microcavity arrays which can be used for the investigation of confinement-induced ordering phenomena within colloid solutions. In these studies, the microcavity arrays serve as containers for confinement of the colloid. X-ray diffraction measur

  9. UZ Colloid Transport Model

    Energy Technology Data Exchange (ETDEWEB)

    M. McGraw

    2000-04-13

    The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations.

  10. Colloid process engineering

    CERN Document Server

    Peukert, Wolfgang; Rehage, Heinz; Schuchmann, Heike

    2015-01-01

    This book deals with colloidal systems in technical processes and the influence of colloidal systems by technical processes. It explores how new measurement capabilities can offer the potential for a dynamic development of scientific and engineering, and examines the origin of colloidal systems and its use for new products. The future challenges to colloidal process engineering are the development of appropriate equipment and processes for the production and obtainment of multi-phase structures and energetic interactions in market-relevant quantities. The book explores the relevant processes and for controlled production and how they can be used across all scales.

  11. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    different colloidal materials and their applications in chemistry, physics, biological, medical sciences and environment. Graduate students, academic and industrial researchers and medical professionals will discover recently developed colloidal materials and their applications in many areas of human......Book Description: Colloidal science and technology is one of the fastest growing research and technology areas. This book explores the cutting edge research in colloidal science and technology that will be usefull in almost every aspect of modern society. This book has a depth of information...

  12. Determination of silicon dioxide in lead-zinc ore by potassium fluosilicate titration with acid dissolution%酸溶-氟硅酸钾滴定法测定铅锌矿中二氧化硅

    Institute of Scientific and Technical Information of China (English)

    王娜; 滕新华; 王力强; 陈曦; 刘义博; 吴磊

    2015-01-01

    A determination method of silicon dioxide in lead-zinc ore samples was proposed by potassium fluosilicate titration after decomposition with acid. The lead-zinc ore sample was digested with nitric acid and hydrochloric acid successively. Then, the hydrofluoric acid was added to react with silicon dioxide to form fluosilicic acid, which re-acted with excessive potassium nitrate in nitric acid medium to form potassium fluosilicate precipitate. After filtra-tion and washing, the precipitate was dissolved in boiling water. With nitrazine yellow as indictor, the hydrofluoric acid generated by hydrolysis was titrated by sodium hydroxide standard solution to indirectly determine the content of silicon dioxide in lead-zinc ore. The results showed that the interference of much lead in lead-zinc ore could be effectively eliminated when the precipitate was filtrated and washed with 50 g/L potassium nitrate-50% ethanol so-lution after placing for 20 min with 10 mL of nitric acid as precipitation medium and 3. 0 g of potassium nitrate as precipitator. The color mutation at titration endpoint was more obvious when nitrazine yellow was selected as the in-dicator. The proposed method was applied to the determination of silicon dioxide in lead-zinc ore certified reference materials, and the results were consistent with the certified values. The proposed method was also used in the deter-mination of lead-zinc ore actual sample. The relative standard deviation(RSD, n=12) was 0. 5% and 1. 3%, re-spectively. The test was also compared with the conventional gravimetric method, and the results were consistent. The proposed method was applicable for the determination of the mass fraction of silicon dioxide in range of 8%-67% in lead-zinc ore.%提出了酸分解铅锌矿试样,氟硅酸钾滴定法测定试样中二氧化硅的方法。铅锌矿样品依次用硝酸、盐酸消解后,在加入氢氟酸的情况下,二氧化硅与氢氟酸反应形成氟硅酸,

  13. Manipulation of colloidal crystallization

    NARCIS (Netherlands)

    Vermolen, E.C.M.

    2008-01-01

    Colloidal particles (approximately a micrometer in diameter) that are dispersed in a fluid, behave thermodynamically similar to atoms and molecules: at low concentrations they form a fluid, while at high concentrations they can crystallize into a colloidal crystal to gain entropy. The analogy with m

  14. Influence of Silver/Silicon Dioxide on Infrared Absorption Spectroscopy of Sodium Nitrate%银/二氧化硅复合材料对硝酸钠红外吸收光谱特性影响

    Institute of Scientific and Technical Information of China (English)

    杨世玲; 岳莉; 贾志君

    2014-01-01

    对海洋营养盐进行快速检测是海洋污染监控中的一项重要任务。测量了硝酸钠溶液蒸发过程中的红外光谱,发现表面增强红外光谱法在营养盐的快速检测中有重要的应用价值。采用Stober方法制备了二氧化硅纳米颗粒,然后采用银氨溶液与二氧化硅溶液混合的方法制备银/二氧化硅(Ag/SiO2)复合材料,并利用扫描电镜(SEM )、X射线衍射(XRD)以及紫外-可见(UV-Visible)吸收光谱对其进行表征。研究了硝酸钠水溶液干燥过程中Ag/SiO2复合材料对硝酸钠红外吸收光谱的影响,结果表明硝酸根反对称伸缩振动吸收峰的吸收强度得到增强,这可能来自Ag/SiO2薄膜材料的界面效应。%Quickly detecting of ocean nutrient was one important task in marine pollution monitoring .We discovered the applica-tion of surface-enhanced infrared absorption spectroscopy in the detection of ocean nutrient through researching the evaporation of sodium nitrate solution .The silicon dioxide (SiO2 ) with highly dispersion was prepared by Stober method ,The silver/silica (Ag/SiO2 ) composite materials were prepared by mixing ammonia solution and silicon dioxide aqueous solution .Three kinds of composite materials with different surface morphology were fabricated through optimizing the experimental parameter and chan-ging the experimental process .The surface morphology ,crystal orientation and surface plasmon resonance were investigated by means of the scanning electronic microscope (SEM ) ,X-ray diffraction (XRD) ,UV-Visible absorption spectrum and infrared ab-sorption spectroscopy .The SEM images showed that the sample A was purified SiO2 ,sample B and sample C were mixture of silver nanoparticle and silicon dioxide ,while sample D was completed nanoshell structure .The absorption spectroscopy showed that there was surface plasmon resonance in the UV-visible region ,while there was possibility of surface plasmon resonance

  15. 五氧化二铌与二氧化硅作用下氧化铝晶粒的各向异性生长%ANISOTROPIC GRAIN GROWTH OF ALUMINA BY SYNERGISTIC EFFECTS OF NIOBIUM PENTOXIDE AND SILICON DIOXIDE

    Institute of Scientific and Technical Information of China (English)

    尹贻彬; 刘于昌; 蒲锡鹏; 邵鑫; 李文智; 赵利民

    2009-01-01

    研究了少量SiO2和Nb2O5掺杂对α-氧化铝晶粒生长的影响.单一掺杂1 500℃煅烧2h的样品均表现为晶粒的等轴状,且铌掺杂明显促进了氧化铝晶粒的生长.SiO2与Nb2O5的共掺杂则导致晶粒各向异性优势生长.高分辨透射电镜照片表明:在一些晶粒晶界出现0.8~4nm的无定形层,晶界处的液相同样影响晶界能,从而诱导各向异性生长.结果表明:在固定铌含量的基础上,少量二氧化硅使材料的断裂韧度提高42%,抗弯强度提高约80%.%Grain growth caused by doping alpha-alumina with small amounts of silicon dioxide and niobium penroxide added singly or together was investigated in contrast to undoped alumina. When they were sintered at 1500 ℃ for 2 h, the alumina grain for singly doped specimen is equiaxed, and the niobium promotes excessive the grain growth of alumina. But the codoped specimen exhibited anisotropic grain growth and the volume is very large. High resolution transmission electron microscope photograph reveals that a thin amorphous layer (0.8-4 nm) is presented at some grain boundaries. Liquid phase may affect the energy of the grain boundary and induces anisotropic grain growth. The research results also show that when the niobium content is constant, the fracture toughness is enhanced by 42% and the bending strength is increased by 80% via adjusting the silicon contents.

  16. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  17. Colloids in Biotechnology

    CERN Document Server

    Fanun, Monzer

    2010-01-01

    Colloids have come a long way from when Thomas Graham coined the term colloid to describe 'pseudo solutions'. This book enables scientists to close the gap between extensive research and translation into commercial options in biomedicine and biotechnology. It covers biosurfactants and surface properties, phase behavior, and orientational change of surfactant mixtures with peptides at the interface. It also covers adsorption of polymers and biopolymers on the surface and interface, discusses colloidal nanoparticles and their use in biotechnology, and delves into bioadhesion and microencapsulati

  18. The influence of initial defects on mechanical stress and deformation distribution in oxidized silicon

    Directory of Open Access Journals (Sweden)

    Kulinich O. A.

    2008-10-01

    Full Text Available The near-surface silicon layers in silicondioxide silicon systems with modern methods of research are investigated. It is shown that these layers have compound structure and their parameters depend on oxidation and initial silicon parameters. It is shown the influence of initial defects on mechanical stress and deformation distribution in oxidized silicon.

  19. New polypyrrole-carbon nanotubes-silicon dioxide solid-phase microextraction fiber for the preconcentration and determination of benzene, toluene, ethylbenzene, and o-xylene using gas liquid chromatography.

    Science.gov (United States)

    Sarafraz-Yazdi, Ali; Rounaghi, Gholamhossein; Razavipanah, Iman; Vatani, Hossein; Amiri, Amirhassan

    2014-09-01

    For the first time, a polypyrrole-carbon nanotubes-silicon dioxide composite film coated on a steel wire was prepared by an electrochemical method. Scanning electron microscopy images showed that this composite film was even and porous. The prepared fiber was used as an absorbent for the headspace solid-phase microextraction of benzene, toluene, ethylbenzene, and o-xylene, followed by gas chromatographic analysis. This method presented an excellent performance, which was much better than that of a polypyrrole-carbon nanotube fiber. It was found that under the optimized conditions, the linear ranges were 0.01-200 ng/mL with correlation coefficients >0.9953, the detection limits were 0.005-0.020 ng/mL, the relative standard deviations were 3.9-6.4% for five successive measurements with a single fiber, and the reproducibility was 5.5-8.5% (n = 3). Finally, the developed method was successfully applied to real water samples, and the relative recoveries obtained for the spiked water samples were from 91.0 to 106.7%.

  20. Silicon-based photonic integration beyond the telecommunication wavelength range

    OpenAIRE

    2014-01-01

    In this paper we discuss silicon-based photonic integrated circuit technology for applications beyond the telecommunication wavelength range. Silicon-on-insulator and germanium-on-silicon passive waveguide circuits are described, as well as the integration of III-V semiconductors, IV-VI colloidal nanoparticles and GeSn alloys on these circuits for increasing the functionality. The strong nonlinearity of silicon combined with the low nonlinear absorption in the mid-infrared is exploited to gen...

  1. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  2. Confocal microscopy of colloids

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, V; Semwogerere, D; Weeks, Eric R [Department of Physics, Emory University, Atlanta, GA 30322 (United States)

    2007-03-21

    Colloids have increasingly been used to characterize or mimic many aspects of atomic and molecular systems. With confocal microscopy these colloidal particles can be tracked spatially in three dimensions with great precision over large time scales. This review discusses equilibrium phases such as crystals and liquids, and non-equilibrium phases such as glasses and gels. The phases that form depend strongly on the type of particle interaction that dominates. Hard-sphere-like colloids are the simplest, and interactions such as the attractive depletion force and electrostatic repulsion result in more non-trivial phases which can better model molecular materials. Furthermore, shearing or otherwise externally forcing these colloids while under microscopic observation helps connect the microscopic particle dynamics to the macroscopic flow behaviour. Finally, directions of future research in this field are discussed. (topical review)

  3. Photocatalytic Reaction of Sulfur Dioxide with Heptane in the Gas-phase Over Titanium Dioxide

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The photocatalytic reaction of sulfur dioxide with heptane was carried out with the aid of UV-illuminated titanium dioxide ultrafine particles(UFP) at room temperature.The TiO2 UFP was prepared by means of colloidal chemical method.The structure and the surface state of the as-prepared TiO2 UFP via different heat-treatments were studied.As the calcining temperature decreased,the contents of hydroxyl on the surface increased,which could help to enhance the photocatalytic activity of the TiO2 UFP.The mechanism of the photocatalytic reaction of sulfur dioxide with heptane was proposed,in which there was a competition of photocatalytic oxidation between sulfur dioxide and heptane over the TiO2 UFP.It is inferred that the reactive oxygen species play an important role in the photocatalytic reaction of sulfur dioxide with heptane.

  4. Effect of N2 Plasma Annealing on Properties of Fluorine Doped Silicon Dioxide Films with Low Dielectric Constant for Ultra-Large-Scale Integrated Circuits

    Institute of Scientific and Technical Information of China (English)

    张卫; 王鹏飞; 丁士进; 王季陶; 李伟

    2002-01-01

    The influence of N2 plasma annealing on the properties of fluorine doped silicon oxide (SiOF) films is investigated.The stability of the dielectric constant of SiOF film is remarkably improved by the N2 plasma annealing. After enduring a moisture absorption test for six hours in a chamber with 60% humidity at 50℃, the dielectric constant variation of the annealed SiOF films is only 1.5%, while the variation for those SiOF films without annealing is 15.5%. Fourier transform infrared spectroscopic results show that the absorption peaks of Si-OH and H-OH of SiOF films are reduced after the N2 plasma annealing because the annealing can wipe off some unstable Si-F2 bonds in SiOF films. These unstable Si-F2 bonds are suitable to react with water, resulting in the degradation of SiOF film properties. Therefore, the N2 plasma annealing meliorates the properties of SiOF films with low dielectric constant.

  5. Spherical colloidal photonic crystals.

    Science.gov (United States)

    Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze

    2014-12-16

    CONSPECTUS: Colloidal photonic crystals (PhCs), periodically arranged monodisperse nanoparticles, have emerged as one of the most promising materials for light manipulation because of their photonic band gaps (PBGs), which affect photons in a manner similar to the effect of semiconductor energy band gaps on electrons. The PBGs arise due to the periodic modulation of the refractive index between the building nanoparticles and the surrounding medium in space with subwavelength period. This leads to light with certain wavelengths or frequencies located in the PBG being prohibited from propagating. Because of this special property, the fabrication and application of colloidal PhCs have attracted increasing interest from researchers. The most simple and economical method for fabrication of colloidal PhCs is the bottom-up approach of nanoparticle self-assembly. Common colloidal PhCs from this approach in nature are gem opals, which are made from the ordered assembly and deposition of spherical silica nanoparticles after years of siliceous sedimentation and compression. Besides naturally occurring opals, a variety of manmade colloidal PhCs with thin film or bulk morphology have also been developed. In principle, because of the effect of Bragg diffraction, these PhC materials show different structural colors when observed from different angles, resulting in brilliant colors and important applications. However, this angle dependence is disadvantageous for the construction of some optical materials and devices in which wide viewing angles are desired. Recently, a series of colloidal PhC materials with spherical macroscopic morphology have been created. Because of their spherical symmetry, the PBGs of spherical colloidal PhCs are independent of rotation under illumination of the surface at a fixed incident angle of the light, broadening the perspective of their applications. Based on droplet templates containing colloidal nanoparticles, these spherical colloidal PhCs can be

  6. Direct Production of Silicones From Sand

    Energy Technology Data Exchange (ETDEWEB)

    Larry N. Lewis; F.J. Schattenmann: J.P. Lemmon

    2001-09-30

    Silicon, in the form of silica and silicates, is the second most abundant element in the earth's crust. However the synthesis of silicones (scheme 1) and almost all organosilicon chemistry is only accessible through elemental silicon. Silicon dioxide (sand or quartz) is converted to chemical-grade elemental silicon in an energy intensive reduction process, a result of the exceptional thermodynamic stability of silica. Then, the silicon is reacted with methyl chloride to give a mixture of methylchlorosilanes catalyzed by cooper containing a variety of tract metals such as tin, zinc etc. The so-called direct process was first discovered at GE in 1940. The methylchlorosilanes are distilled to purify and separate the major reaction components, the most important of which is dimethyldichlorosilane. Polymerization of dimethyldichlorosilane by controlled hydrolysis results in the formation of silicone polymers. Worldwide, the silicones industry produces about 1.3 billion pounds of the basic silicon polymer, polydimethylsiloxane.

  7. Mid-IR heterogeneous silicon photonics

    Science.gov (United States)

    Roelkens, Gunther; Dave, Utsav; Gassenq, Alban; Hattasan, Nannicha; Hu, Chen; Kuyken, Bart; Leo, Francois; Malik, Aditya; Muneeb, Muhammad; Ryckeboer, Eva; Uvin, Sarah; Hens, Zeger; Baets, Roel G.; Shimura, Yosuke; Gencarelli, Federica; Vincent, Benjamin; Loo, Roger; Van Campenhout, Joris; Cerutti, Laurent; Rodriguez, Jean-Baptiste; Tournié, Eric; Chen, Xia; Nedeljkovic, Milos; Mashanovich, Goran Z.; Shen, Li; Healy, Noel; Peacock, Anna C.; Liu, Xiaoping; Osgood, Richard M.; Green, William

    2013-12-01

    In this paper we discuss silicon-based photonic integrated circuit technology for applications beyond the telecommunication wavelength range. Silicon-on-insulator and germanium-on-silicon passive waveguide circuits are described, as well as the integration of III-V semiconductors, IV-VI colloidal nanoparticle films and GeSn alloys on these circuits for increasing the functionality. The strong nonlinearity of silicon combined with the low nonlinear absorption in the mid-infrared is exploited to generate picosecond pulse based supercontinuum sources and optical parametric oscillators that can be used as spectroscopic sensor sources.

  8. Stabilization of elusive silicon oxides.

    Science.gov (United States)

    Wang, Yuzhong; Chen, Mingwei; Xie, Yaoming; Wei, Pingrong; Schaefer, Henry F; Schleyer, Paul von R; Robinson, Gregory H

    2015-06-01

    Molecular SiO2 and other simple silicon oxides have remained elusive despite the indispensable use of silicon dioxide materials in advanced electronic devices. Owing to the great reactivity of silicon-oxygen double bonds, as well as the low oxidation state of silicon atoms, the chemistry of simple silicon oxides is essentially unknown. We now report that the soluble disilicon compound, L:Si=Si:L (where L: = :C{N(2,6-(i)Pr2C6H3)CH}2), can be directly oxidized by N2O and O2 to give the carbene-stabilized Si2O3 and Si2O4 moieties, respectively. The nature of the silicon oxide units in these compounds is probed by spectroscopic methods, complementary computations and single-crystal X-ray diffraction.

  9. Transformational silicon electronics

    KAUST Repository

    Rojas, Jhonathan Prieto

    2014-02-25

    In today\\'s traditional electronics such as in computers or in mobile phones, billions of high-performance, ultra-low-power devices are neatly integrated in extremely compact areas on rigid and brittle but low-cost bulk monocrystalline silicon (100) wafers. Ninety percent of global electronics are made up of silicon. Therefore, we have developed a generic low-cost regenerative batch fabrication process to transform such wafers full of devices into thin (5 μm), mechanically flexible, optically semitransparent silicon fabric with devices, then recycling the remaining wafer to generate multiple silicon fabric with chips and devices, ensuring low-cost and optimal utilization of the whole substrate. We show monocrystalline, amorphous, and polycrystalline silicon and silicon dioxide fabric, all from low-cost bulk silicon (100) wafers with the semiconductor industry\\'s most advanced high-κ/metal gate stack based high-performance, ultra-low-power capacitors, field effect transistors, energy harvesters, and storage to emphasize the effectiveness and versatility of this process to transform traditional electronics into flexible and semitransparent ones for multipurpose applications. © 2014 American Chemical Society.

  10. Effect of Rheology and Poloxamers Properties on Release of Drugs from Silicon Dioxide Gel-Filled Hard Gelatin Capsules-A Further Enhancement of Viability of Liquid Semisolid Matrix Technology.

    Science.gov (United States)

    Sultana, Misbah; Butt, Mobashar Ahmad; Saeed, Tariq; Mahmood, Rizwan; Ul Hassan, Saeed; Hussain, Khalid; Raza, Syed Atif; Ahsan, Muhammad; Bukhari, Nadeem Irfan

    2016-12-08

    The liquid and semisolid matrix technology, filling liquids, semi-solids and gels in hard gelatin capsule are promising, thus, there is a need of enhanced research interest in the technology. Therefore, the present study was aimed to investigate isoniazid (freely soluble) and metronidazole (slightly soluble) gels filled in hard gelatin capsules for the effect of poloxamers of different viscosities on release of the drugs. Gel of each drug (10% w/w, particle size 180-250 μm), prepared by mixing poloxamer and 8% w/w hydrophilic silicon dioxide (Aerosil® A200), was assessed for rheology, dispersion stability and release profile. Both the drugs remained dispersed in majority of gels for more than 30 days, and dispersions were depended on gels' viscosity, which was further depended on viscosity of poloxamers. A small change in viscosity was noted in gels on storage. FTIR spectra indicated no interactions between components of the gels. The gels exhibited thixotropic and shear-thinning behaviour, which were suitable for filling in hard gelatin capsules without any leakage from the capsules. The release of both drugs from the phase-stable gels for 30 days followed first-order kinetics and was found to be correlated to drugs' solubility, poloxamers' viscosity, polyoxyethylene contents and proportion of block copolymer (poloxamers) in the gels. The findings of the present study indicated that release of drugs of different solubilities (isoniazid and metronidazole) might be modified from gels using different poloxamers and Aerosil® A200.

  11. Colloidal pen lithography.

    Science.gov (United States)

    Xue, Mianqi; Cai, Xiaojing; Chen, Ghenfu

    2015-02-04

    Colloidal pen lithography, a low-cost, high-throughput scanning probe contact printing method, has been developed, which is based on self-assembled colloidal arrays embedded in a soft elastomeric stamp. Patterned protein arrays are demonstrated using this method, with a feature size ranging from 100 nm to several micrometers. A brief study into the specificity reorganization of protein gives evidence for the feasibility of this method for writing protein chips. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Granulated colloidal silicon dioxide-based self-microemulsifying tablets, as a versatile approach in enhancement of solubility and therapeutic potential of anti-diabetic agent: formulation design and in vitro/in vivo evaluation.

    Science.gov (United States)

    Pandey, Vikas; Gilhotra, Ritu M; Kohli, Seema

    2017-06-01

    The current research work was executed with an aim to explore and promote the potential of self-microemusifying drug delivery systems (SMEDDS) in the form of tablets, in order to enhance solubility and oral bioavailability of poorly aqueous soluble drug Repaglinide (RPG). RPG-loaded liquid SMEDDS were developed consisting Labrafil M 1944CS, Kolliphor EL and Propylene glycol, which were then characterized on various parameters. After characterization and optimization, liquid SMEDDS were converted into solid form by adsorbing on Aeroperl® 300 pharma and polyplasdone(TM) XL. Further, selection of suitable excipients was done and mixed with prepared solidified SMEDDS powder followed by the preparation of self-microemulsifying tablets (SMET's) wet granulation-compression method. SMET's were subjected to differential scanning calorimetry (DSC) and particle X-ray diffraction (RXRD) studies, results of which indicated transformation of crystalline structure of RPG because of dispersion of RPG at molecular level in liquid SMEDDS. This was further assured by micrographs obtained from scanning electron microscope. SMET's shown more than 85% (30 min) of in vitro drug release in contrast to conventional marketed tablets (13.2%) and pure RPG drug (3.2%). Results of in vivo studies furnished that SMET's had shown marked decrease in the blood glucose level and prolonged duration of action (up to 8 h) in comparison with conventional marketed tablets and pure RPG drug. In conclusion, SMET's serves as a promising tool for successful oral delivery of poorly aqueous soluble drug(s) such as RPG.

  13. Medical applications of colloids

    CERN Document Server

    Matijevic, Egon

    2008-01-01

    The first book of its type on the medical and biomedical applications of colloids, although there are some related titles on different topicsDiscusses the effects of uniform particles in drug formulations and releaseEvaluates particle transport and deposition in the human body.

  14. Liquid crystal colloids

    Directory of Open Access Journals (Sweden)

    2010-01-01

    Full Text Available This special issue of "Condensed Matter Physics" focuses on the most recent developments in the study of a fascinating soft matter system, representing colloidal particles in a liquid crystalline environment. Furthermore, some articles address pioneering steps in the discovery of liquid crystals going back to 1861 paper by Julius Planer.

  15. Nucleation in food colloids

    Science.gov (United States)

    Povey, Malcolm J. W.

    2016-12-01

    Nucleation in food colloids has been studied in detail using ultrasound spectroscopy. Our data show that classical nucleation theory (CNT) remains a sound basis from which to understand nucleation in food colloids and analogous model systems using n-alkanes. Various interpretations and modifications of CNT are discussed with regard to their relevance to food colloids. Much of the evidence presented is based on the ultrasound velocity spectrometry measurements which has many advantages for the study of nucleating systems compared to light scattering and NMR due to its sensitivity at low solid contents and its ability to measure true solid contents in the nucleation and early crystal growth stages. Ultrasound attenuation spectroscopy also responds to critical fluctuations in the induction region. We show, however, that a periodic pressure fluctuation such as a quasi-continuous (as opposed to a pulse comprising only a few pressure cycles) ultrasound field can alter the nucleation process, even at very low acoustic intensity. Thus care must be taken when using ultrasound techniques that the measurements do not alter the studied processes. Quasi-continuous ultrasound fields may enhance or suppress nucleation and the criteria to determine such effects are derived. The conclusions of this paper are relevant to colloidal systems in foods, pharmaceuticals, agro-chemicals, cosmetics, and personal products.

  16. Binary colloidal crystals

    NARCIS (Netherlands)

    Christova-Zdravkova, C.G.

    2005-01-01

    Binary crystals are crystals composed of two types of particles having different properties like size, mass density, charge etc. In this thesis several new approaches to make binary crystals of colloidal particles that differ in size, material and charge are reported We found a variety of crystal st

  17. Electrodynamics of colloids.

    NARCIS (Netherlands)

    Minor, M.

    1998-01-01

    The goal of the present study is to deepen the insight into the non-equilibrium properties of the electric double layer of colloidal systems. Of basic interest are the ionic mobilities in the different regions of the electric double layer as well as the potential at the plane of shear, i.e., the ele

  18. Viscosity of colloidal suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, E.G.D. [Rockefeller Univ., New York, NY (United States); Schepper, I.M. de [Delft Univ. of Technology (Netherlands)

    1995-12-31

    Simple expressions are given for the effective Newtonian viscosity as a function of concentration as well as for the effective visco-elastic response as a function of concentration and imposed frequency, of monodisperse neutral colloidal suspensions over the entire fluid range. The basic physical mechanisms underlying these formulae are discussed. The agreement with existing experiments is very good.

  19. Colloidal Thermal Fluids

    Science.gov (United States)

    Lotzadeh, Saba

    In this dissertation, a reversible system with a well controlled degree of particle aggregation was developed. By surface modification of colloidal silica with aminosilanes, interactions among the particles were tuned in a controlled way to produce stable sized clusters at different pH values ranges from well-disposed to a colloidal gel. N-[3-(trimethoxysilyl)propyl]ethylenediamine (TMPE) monolayer on particle surface not only removes all the reactive sites to prevent chemical aggregation, also provides steric stabilization in the absence of any repulsion. After surface modification, electrokinetic behavior of silica particles were changed to that of amino groups, positive in acidic pH and neutral at basic pH values. By tuning the pH, the balance between electrostatic repulsion and hydrophobic interactions was reversibly controlled. As a result, clusters with different sizes were developed. The effect of clustering on the thermal conductivity of colloidal dispersions was quantified using silane-treated silica, a system engineered to exhibit reversible clustering under well-controlled conditions. Thermal conductivity of this system was measured by transient hot wire, the standard method of thermal conductivity measurements in liquids. We show that the thermal conductivity increases monotonically with cluster size and spans the entire range between the two limits of Maxwell's theory. The results, corroborated by numerical simulation, demonstrate that large increases of the thermal conductivity of colloidal dispersions are possible, yet fully within the predictions of classical theory. Numerical calculations were performed to evaluate the importance of structural properties of particles/aggregates on thermal conduction in colloidal particles. Thermal conductivity of non-spherical particles including hollow particles, cubic particles and rods was studied using a Monte Carlo algorithm. We show that anisotropic shapes, increase conductivity above that of isotropic

  20. Formation of neptunium(IV)-silica colloids at near-neutral and slightly alkaline pH.

    Science.gov (United States)

    Husar, Richard; Weiss, Stephan; Hennig, Christoph; Hübner, René; Ikeda-Ohno, Atsushi; Zänker, Harald

    2015-01-06

    The reducing conditions in a nuclear waste repository render neptunium tetravalent. Thus, Np is often assumed to be immobile in the subsurface. However, tetravalent actinides can also become mobile if they occur as colloids. We show that Np(IV) is able to form silica-rich colloids in solutions containing silicic acid at concentrations of both the regions above and below the "mononuclear wall" of silicic acid at 2 × 10(-3) M (where silicic acid is expected to start polymerization). These Np(IV)-silica colloids have a size of only very few nanometers and can reach significantly higher concentrations than Np(IV) oxyhydroxide colloids. They can be stable in the waterborne form over longer spans of time. In the Np(IV)-silica colloids, the actinide--oxygen--actinide bonds are increasingly replaced by actinide--oxygen--silicon bonds due to structural incorporation of Si. Possible implications of the formation of such colloids for environmental scenarios are discussed.

  1. Colloidal Double Quantum Dots.

    Science.gov (United States)

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  2. Measurement of the friction between a silver nanowire and the silicon dioxide substrate%银纳米线与二氧化硅衬底表面摩擦力的测量

    Institute of Scientific and Technical Information of China (English)

    吴森; 张峻铭; 刘鸿志; 张锐; 胡晓东

    2016-01-01

    Silver nanowires ( Ag NWs ) are ideal building blocks for nano?photoelectric devices. Understanding the friction mechanism between individual Ag NWs and certain substrate is of great significance to the nano?manufacturing process. In this paper, the atomic force microscopy ( AFM) is applied to study the friction between Ag NWs and silicon dioxide ( SiO2 ) substrate. By using the AFM?based nanomanipulation, an Ag NW with 50 nm in diameter is moved across the SiO2 surface. During the translation, the friction force is recorded by the AFM cantilever probe. In order to increase the accuracy of the force measurement, the lateral spring constant of the AFM cantilever and the sensitivity of optical lever are precisely calibrated by using the wedge method and the lateral force?curve method, respectively. The error introduced by the movement of the AFM scanner is also considered and compensated. The measurement results show that the maximum static friction force per unit between Ag NWs and the SiO2 substrate is 1.07 nN/nm, and the sliding friction per unit is 0.56 nN/nm.%银纳米线是制作纳米光电子器件的理想材料,了解银纳米线与特定衬底间的摩擦特性对于器件的设计和制备工艺具有重要参考价值.本文利用原子力显微镜(AFM)研究银纳米线与二氧化硅衬底表面的摩擦特性,为提高摩擦力测量准确性,依次借助斜面法和横向力曲线分别标定了AFM探针的扭转弹性常数和光杠杆横向灵敏度,同时对扫描器引入的横向误差进行了补偿.利用AFM纳米操纵技术记录了单根银纳米线由静止到整体滑动的全过程,实验测得直径50 nm银纳米线与二氧化硅衬底表面的最大静摩擦线密度和滑动摩擦线密度分别为1.07 nN/nm和0.56 nN/nm.

  3. Development of Doped Microcrystalline Silicon Oxide and its Application to Thin‑Film Silicon Solar Cells

    NARCIS (Netherlands)

    Lambertz, A.

    2015-01-01

    The aim of the present study is the development of doped microcrystalline silicon oxide (µc‑SiOx:H) alloys and its application in thin‑film silicon solar cells. The doped µc‑SiOx:H material was prepared from carbon dioxide (CO2), silane (SiH4), hydrogen (H2) gas mixtures using plasma enhanced

  4. Surface etching, chemical modification and characterization of silicon nitride and silicon oxide - Selective functionalization of Si

    NARCIS (Netherlands)

    Liu, Li Hong; Michalak, David J.; Chopra, Tatiana P.; Pujari, Sidharam P.; Zuilhof, Han

    2016-01-01

    The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be careful

  5. Development of Doped Microcrystalline Silicon Oxide and its Application to Thin‑Film Silicon Solar Cells

    NARCIS (Netherlands)

    Lambertz, A.

    2015-01-01

    The aim of the present study is the development of doped microcrystalline silicon oxide (µc‑SiOx:H) alloys and its application in thin‑film silicon solar cells. The doped µc‑SiOx:H material was prepared from carbon dioxide (CO2), silane (SiH4), hydrogen (H2) gas mixtures using plasma enhanced chemic

  6. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter. PMID:28117325

  7. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter.

  8. Colloidal Covalent Organic Frameworks

    Science.gov (United States)

    2017-01-01

    Covalent organic frameworks (COFs) are two- or three-dimensional (2D or 3D) polymer networks with designed topology and chemical functionality, permanent porosity, and high surface areas. These features are potentially useful for a broad range of applications, including catalysis, optoelectronics, and energy storage devices. But current COF syntheses offer poor control over the material’s morphology and final form, generally providing insoluble and unprocessable microcrystalline powder aggregates. COF polymerizations are often performed under conditions in which the monomers are only partially soluble in the reaction solvent, and this heterogeneity has hindered understanding of their polymerization or crystallization processes. Here we report homogeneous polymerization conditions for boronate ester-linked, 2D COFs that inhibit crystallite precipitation, resulting in stable colloidal suspensions of 2D COF nanoparticles. The hexagonal, layered structures of the colloids are confirmed by small-angle and wide-angle X-ray scattering, and kinetic characterization provides insight into the growth process. The colloid size is modulated by solvent conditions, and the technique is demonstrated for four 2D boronate ester-linked COFs. The diameter of individual COF nanoparticles in solution is monitored and quantified during COF growth and stabilization at elevated temperature using in situ variable-temperature liquid cell transmission electron microscopy imaging, a new characterization technique that complements conventional bulk scattering techniques. Solution casting of the colloids yields a free-standing transparent COF film with retained crystallinity and porosity, as well as preferential crystallite orientation. Collectively this structural control provides new opportunities for understanding COF formation and designing morphologies for device applications. PMID:28149954

  9. Colloidal Covalent Organic Frameworks.

    Science.gov (United States)

    Smith, Brian J; Parent, Lucas R; Overholts, Anna C; Beaucage, Peter A; Bisbey, Ryan P; Chavez, Anton D; Hwang, Nicky; Park, Chiwoo; Evans, Austin M; Gianneschi, Nathan C; Dichtel, William R

    2017-01-25

    Covalent organic frameworks (COFs) are two- or three-dimensional (2D or 3D) polymer networks with designed topology and chemical functionality, permanent porosity, and high surface areas. These features are potentially useful for a broad range of applications, including catalysis, optoelectronics, and energy storage devices. But current COF syntheses offer poor control over the material's morphology and final form, generally providing insoluble and unprocessable microcrystalline powder aggregates. COF polymerizations are often performed under conditions in which the monomers are only partially soluble in the reaction solvent, and this heterogeneity has hindered understanding of their polymerization or crystallization processes. Here we report homogeneous polymerization conditions for boronate ester-linked, 2D COFs that inhibit crystallite precipitation, resulting in stable colloidal suspensions of 2D COF nanoparticles. The hexagonal, layered structures of the colloids are confirmed by small-angle and wide-angle X-ray scattering, and kinetic characterization provides insight into the growth process. The colloid size is modulated by solvent conditions, and the technique is demonstrated for four 2D boronate ester-linked COFs. The diameter of individual COF nanoparticles in solution is monitored and quantified during COF growth and stabilization at elevated temperature using in situ variable-temperature liquid cell transmission electron microscopy imaging, a new characterization technique that complements conventional bulk scattering techniques. Solution casting of the colloids yields a free-standing transparent COF film with retained crystallinity and porosity, as well as preferential crystallite orientation. Collectively this structural control provides new opportunities for understanding COF formation and designing morphologies for device applications.

  10. Flocking ferromagnetic colloids

    Science.gov (United States)

    Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S.

    2017-01-01

    Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks). PMID:28246633

  11. Phosphinate stabilised ZnO and Cu colloidal nanocatalysts for CO2 hydrogenation to methanol.

    Science.gov (United States)

    Brown, N J; Weiner, J; Hellgardt, K; Shaffer, M S P; Williams, C K

    2013-12-07

    Colloidal solutions of ZnO-Cu nanoparticles can be used as catalysts for the reduction of carbon dioxide with hydrogen. The use of phosphinate ligands for the synthesis of the nanoparticles from organometallic precursors improves the reductive stability and catalytic activity of the system.

  12. Increasing entropy for colloidal stabilization

    Science.gov (United States)

    Mo, Songping; Shao, Xuefeng; Chen, Ying; Cheng, Zhengdong

    2016-11-01

    Stability is of paramount importance in colloidal applications. Attraction between colloidal particles is believed to lead to particle aggregation and phase separation; hence, stability improvement can be achieved through either increasing repulsion or reducing attraction by modifying the fluid medium or by using additives. Two traditional mechanisms for colloidal stability are electrostatic stabilization and steric stabilization. However, stability improvement by mixing attractive and unstable particles has rarely been considered. Here, we emphasize the function of mixing entropy in colloidal stabilization. Dispersion stability improvement is demonstrated by mixing suspensions of attractive nanosized titania spheres and platelets. A three-dimensional phase diagram is proposed to illustrate the collaborative effects of particle mixing and particle attraction on colloidal stability. This discovery provides a novel method for enhancing colloidal stability and opens a novel opportunity for engineering applications.

  13. Sustainable steric stabilization of colloidal titania nanoparticles

    Science.gov (United States)

    Elbasuney, Sherif

    2017-07-01

    A route to produce a stable colloidal suspension is essential if mono-dispersed particles are to be successfully synthesized, isolated, and used in subsequent nanocomposite manufacture. Dispersing nanoparticles in fluids was found to be an important approach for avoiding poor dispersion characteristics. However, there is still a great tendency for colloidal nanoparticles to flocculate over time. Steric stabilization can prevent coagulation by introducing a thick adsorbed organic layer which constitutes a significant steric barrier that can prevent the particle surfaces from coming into direct contact. One of the main features of hydrothermal synthesis technique is that it offers novel approaches for sustainable nanoparticle surface modification. This manuscript reports on the sustainable steric stabilization of titanium dioxide nanoparticles. Nanoparticle surface modification was performed via two main approaches including post-synthesis and in situ surface modification. The tuneable hydrothermal conditions (i.e. temperature, pressure, flow rates, and surfactant addition) were optimized to enable controlled steric stabilization in a continuous fashion. Effective post synthesis surface modification with organic ligand (dodecenyl succinic anhydride (DDSA)) was achieved; the optimum surface coating temperature was reported to be 180-240 °C to ensure DDSA ring opening and binding to titania nanoparticles. Organic-modified titania demonstrated complete change in surface properties from hydrophilic to hydrophobic and exhibited phase transfer from the aqueous phase to the organic phase. Exclusive surface modification in the reactor was found to be an effective approach; it demonstrated surfactant loading level 2.2 times that of post synthesis surface modification. Titania was also stabilized in aqueous media using poly acrylic acid (PAA) as polar polymeric dispersant. PAA-titania nanoparticles demonstrated a durable amorphous polymeric layer of 2 nm thickness. This

  14. Jaguar Procedures for Detonation Behavior of Silicon Containing Explosives

    Science.gov (United States)

    Stiel, L. I.; Baker, E. L.; Capellos, C.; Poulos, W.

    2007-12-01

    Improved relationships were developed in this study for the thermodynamic properties of solid and liquid silicon and silicon dioxide for use with JAGUAR thermo-chemical equation of state routines. Analyses of experimental melting temperature curves for silicon and silicon dioxide indicated complex phase behavior and that improved coefficients were required for solid and liquid thermodynamic properties. Advanced optimization routines were utilized in conjunction with the experimental melting point data to establish volumetric coefficients for these substances. The new property libraries resulted in agreement with available experimental values, including Hugoniot data at elevated pressures.

  15. Coupling between bulk- and surface chemistry in suspensions of charged colloids

    Science.gov (United States)

    Heinen, M.; Palberg, T.; Löwen, H.

    2014-03-01

    The ionic composition and pair correlations in fluid phases of realistically salt-free charged colloidal sphere suspensions are calculated in the primitive model. We obtain the number densities of all ionic species in suspension, including low-molecular weight microions, and colloidal macroions with acidic surface groups, from a self-consistent solution of a coupled physicochemical set of nonlinear algebraic equations and non-mean-field liquid integral equations. Here, we study suspensions of colloidal spheres with sulfonate or silanol surface groups, suspended in demineralized water that is saturated with carbon dioxide under standard atmosphere. The only input required for our theoretical scheme are the acidic dissociation constants pKa, and effective sphere diameters of all involved ions. Our method allows for an ab initio calculation of colloidal bare and effective charges, at high numerical efficiency.

  16. Encapsulated liquid sorbents for carbon dioxide capture.

    Science.gov (United States)

    Vericella, John J; Baker, Sarah E; Stolaroff, Joshuah K; Duoss, Eric B; Hardin, James O; Lewicki, James; Glogowski, Elizabeth; Floyd, William C; Valdez, Carlos A; Smith, William L; Satcher, Joe H; Bourcier, William L; Spadaccini, Christopher M; Lewis, Jennifer A; Aines, Roger D

    2015-02-05

    Drawbacks of current carbon dioxide capture methods include corrosivity, evaporative losses and fouling. Separating the capture solvent from infrastructure and effluent gases via microencapsulation provides possible solutions to these issues. Here we report carbon capture materials that may enable low-cost and energy-efficient capture of carbon dioxide from flue gas. Polymer microcapsules composed of liquid carbonate cores and highly permeable silicone shells are produced by microfluidic assembly. This motif couples the capacity and selectivity of liquid sorbents with high surface area to facilitate rapid and controlled carbon dioxide uptake and release over repeated cycles. While mass transport across the capsule shell is slightly lower relative to neat liquid sorbents, the surface area enhancement gained via encapsulation provides an order-of-magnitude increase in carbon dioxide absorption rates for a given sorbent mass. The microcapsules are stable under typical industrial operating conditions and may be used in supported packing and fluidized beds for large-scale carbon capture.

  17. Polymers and colloids

    Energy Technology Data Exchange (ETDEWEB)

    Schurtenberger, P. [ETH Zurich, Inst. fuer Polymere, Zurich (Switzerland)

    1996-11-01

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs.

  18. Thorium colloid analysis by single particle inductively coupled plasma-mass spectrometry.

    Science.gov (United States)

    Degueldre, C; Favarger, P-Y

    2004-04-19

    Thorium colloid analysis in water has been carried out by a single particle mode using inductively coupled plasma mass spectrometry (ICP-MS). The flash of ions due to the ionisation of a thorium colloidal particle in the plasma torch can be detected and measured in a time scan for (232)Th (+ ) or (248)[ThO] (+ ) according to the sensitivity required by the mass spectrometer. The peaks of the recorded intensity of the MS signal can be analysed as a function of the particle size or fraction of the studied element in the colloid phase. The frequency of the flashes is directly proportional to the concentration of particles in the colloidal suspension. After discussing Th colloid detection, on the basis of the intensity of the ion flashes generated in the plasma torch, tests were performed on thorium dioxide colloidal particles. This feasibility study also describes the experimental conditions and the limitation of the plasma design to detect thorium colloids in a single particle analysis mode down to about 10fg.

  19. Explorative analysis of microbes, colloids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Hallbeck, Lotta; Pedersen, Karsten (Microbial Analytics Sweden AB, Goeteborg (Sweden))

    2008-08-15

    potential to transport radionuclides in groundwater. The aim of the study of colloids in the Forsmark 2.3 site investigation was to quantify and determine the composition of colloids in groundwater samples from the boreholes. There are both inorganic and organic colloids, and the site investigation measured both types. - Gases (Chapter 3): Dissolved gases in groundwater contribute to the mass of dissolved species. The distribution and composition of dissolved gases in deep groundwater are important to understand in the safety assessment of a deep geological nuclear waste repository: Micro bubbles of gas may potentially transport radionuclides from the repository to the surface. Oxygen, hydrogen sulphide and carbon dioxide are parts of fundamental redox couples that participate in several solid-aqueous phase transformations such as the precipitation of ferric iron oxides, iron sulphide and calcite. Methane and hydrogen, may serve as sources of energy to various microbiological processes

  20. Light-structured colloidal assemblies

    Science.gov (United States)

    Aubret, Antoine; Mena, Youssef; Ramananarivo, Sophie; Sacanna, Stefano; Palacci, Jeremie; Palacci lab Team; Sacanna lab Team

    2016-11-01

    Self-propelled particles (SPP) are a key tool since they are of relative simplicity as compared to biological micro-entities and provide a higher level of control. They can convert an energy source into motion and work, and exhibit surprising non-equilibrium behavior. In our work, we focus on the manipulation of colloids using light. We exploit osmotic and phoretic effects to act on single and ensemble of colloids. The key mechanism relies on the photocatalytic decomposition of hydrogen peroxide using hematite, which triggers the motion of colloids around it when illuminated. We use hematite particles and particles with photocatalytic inclusions (i.e. SPP). We first show that the interactions between hematite and colloidal tracers can be tuned by adjusting the chemical environment. Furthermore, we report a phototaxic behavior (migration in light gradient) of the particles. From this, we explore the effect of spatio-temporal modulation of the light to control the motion of colloids at the single particle level, and to generate self-assembled colloidal structures through time and space. The so-formed structures are maintained by phoretic and hydrodynamic forces resulting from the motion of each particles. Ultimately, a dynamic light modulation may be a route for the creation of active colloidal motion on a collective scale through the synchronization of the individual motions of SPP. This work is supported by NSF CAREER DMR 1554724.

  1. Colloids in Acute Burn Resuscitation.

    Science.gov (United States)

    Cartotto, Robert; Greenhalgh, David

    2016-10-01

    Colloids have been used in varying capacities throughout the history of formula-based burn resuscitation. There is sound experimental evidence that demonstrates colloids' ability to improve intravascular colloid osmotic pressure, expand intravascular volume, reduce resuscitation requirements, and limit edema in unburned tissue following a major burn. Fresh frozen plasma appears to be a useful and effective immediate burn resuscitation fluid but its benefits must be weighed against its costs, and risks of viral transmission and acute lung injury. Albumin, in contrast, is less expensive and safer and has demonstrated ability to reduce resuscitation requirements and possibly limit edema-related morbidity. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Microfluidic Control Using Colloidal Devices

    Science.gov (United States)

    Terray, Alex; Oakey, John; Marr, David W. M.

    2002-06-01

    By manipulating colloidal microspheres within customized channels, we have created micrometer-scale fluid pumps and particulate valves. We describe two positive-displacement designs, a gear and a peristaltic pump, both of which are about the size of a human red blood cell. Two colloidal valve designs are also demonstrated, one actuated and one passive, for the direction of cells or small particles. The use of colloids as both valves and pumps will allow device integration at a density far beyond what is currently achievable by other approaches and may provide a link between fluid manipulation at the macro- and nanoscale.

  3. Colloids in Paints Colloids and Interface Science, Volume 6

    CERN Document Server

    Tadros, Tharwat F

    2011-01-01

    The first modern approach to relate fundamental research to the applied science of colloids, this series bridges academic research and practical applications, thus providing the information vital to both. Written by the very best scientists in their respective disciplines, this volume describes the role of colloids in paints, highlighting the importance of fundamental research in industrial applications.For surface, polymer and physicochemists, materials scientists, and chemical engineers.

  4. Are All Colloids Same? How to Select the Right Colloid?

    Directory of Open Access Journals (Sweden)

    Sukanya Mitra

    2009-01-01

    Full Text Available The administration of intravenous fluids is one of the most common and universal interventions in medicine. Colloids are an alternative to the frequently used crystalloids, with highly variable use depending on a myriad of clinical variables. A colloid is defined as a high molecular weight (MW substance that largely remains in the intravas-eular compartment, thereby generating an oncotic pressure. Colloids are considered to have a greater intravaseular persistence when compared to crystalloids. All colloids, however, are clearly not the same. Differences in the physi-cochemical properties, pharmacokinetics and safety profile exist amongst various colloids. This review explores the different types of colloids, with their properties and usefulness as well as adverse effects. While all the available colloids are reviewed briefly (e.g., albumin, gelatin, dextran with respect to their pharmacology, indications, advan-tages and disadvantages, particular emphasis is laid on the hydroxyethyl starches (HES because of their rising prominence. It is shown that HES differ widely in their physicochemical and pharmacokinetic properties, composition, usefulness, and especially in their adverse effect profiles. The third generation HES (tetrastarches, in particular, seem to offer a unique combination of safety and efficacy. Several issues related to this are discussed in detail. This review of the available clinical data demonstrates that HES should not be regarded as one homogenous group, and data for one product should not be automatically extrapolated to another. Thus, among the synthetic colloids, the tetrastarches appear to offer the best currently available compromise between efficacy, safety profile, and cost. They also appear to be the best suited for use in the intensive care setting. Finally, balanced (rather than saline-based HES solutions appear promising as a plasma-adapted volume replacement strategy and may further refine the ongoing quest of

  5. Colloidal gels: Clay goes patchy

    Science.gov (United States)

    Kegel, Willem K.; Lekkerkerker, Henk N. W.

    2011-01-01

    Empty liquids and equilibrium gels have so far been only theoretical possibilities, predicted for colloids with patchy interactions. But evidence of both has now been found in Laponite, a widely studied clay.

  6. Active colloids in complex fluids

    CERN Document Server

    Patteson, Alison E; Arratia, Paulo E

    2016-01-01

    We review recent work on active colloids or swimmers, such as self-propelled microorganisms, phoretic colloidal particles, and artificial micro-robotic systems, moving in fluid-like environments. These environments can be water-like and Newtonian but can frequently contain macromolecules, flexible polymers, soft cells, or hard particles, which impart complex, nonlinear rheological features to the fluid. While significant progress has been made on understanding how active colloids move and interact in Newtonian fluids, little is known on how active colloids behave in complex and non-Newtonian fluids. An emerging literature is starting to show how fluid rheology can dramatically change the gaits and speeds of individual swimmers. Simultaneously, a moving swimmer induces time dependent, three dimensional fluid flows, that can modify the medium (fluid) rheological properties. This two-way, non-linear coupling at microscopic scales has profound implications at meso- and macro-scales: steady state suspension proper...

  7. Mechanical Failure in Colloidal Gels

    Science.gov (United States)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form

  8. 78 FR 14540 - Cyromazine, Silica Silicates (Silica Dioxide and Silica Gel), Glufosinate Ammonium, Dioctyl...

    Science.gov (United States)

    2013-03-06

    ... insects at indoor and outdoor sites including a variety of crops. Silicon dioxide is diatomaceous earth, a... example, an English translation must accompany any material that is not in English and a...

  9. Slip Casting and Green Body Evaluation of 6% Yttria, 2% Alumina Silicon Nitride

    Science.gov (United States)

    1991-12-01

    Some Properrie of Aqucouw Silicon Nitride SuN- pensons. Ponrahkovaya Metallurgrya. no. 3 (159), March 1976, p. 37. 7. GREIL. P., NAGEL. A., STADELMANN ...H., and PETZOW, G. Revie%, Colloidal Proce=ing of Silicon Nitride Ceramics. Ceramic Materi- als and Componenls for Engines, p. 319. 8. STADELMANN II

  10. Silicon nanochrystals. Fundamentals, synthesis and applications

    Energy Technology Data Exchange (ETDEWEB)

    Pavesi, Lorenzo [Trento Univ., Povo (Italy). Physics Dept.; Turan, Rasit (eds.) [Middle East Technical Univ., Ankara (Turkey). Dept. of Physics

    2010-07-01

    This unique collection of knowledge represents a comprehensive treatment of the fundamental and practical consequences of size reduction in silicon crystals. This clearly structured reference introduces readers to the optical, electrical and thermal properties of silicon nanocrystals that arise from their greatly reduced dimensions. It covers their synthesis and characterization from both chemical and physical viewpoints, including ion implantation, colloidal synthesis and vapor deposition methods. A major part of the text is devoted to applications in microelectronics as well as photonics and nanobiotechnology, making this of great interest to the high-tech industry. (orig.)

  11. Opto-thermophoretic assembly of colloidal matter.

    Science.gov (United States)

    Lin, Linhan; Zhang, Jianli; Peng, Xiaolei; Wu, Zilong; Coughlan, Anna C H; Mao, Zhangming; Bevan, Michael A; Zheng, Yuebing

    2017-09-01

    Colloidal matter exhibits unique collective behaviors beyond what occurs at single-nanoparticle and atomic scales. Treating colloidal particles as building blocks, researchers are exploiting new strategies to rationally organize colloidal particles into complex structures for new functions and devices. Despite tremendous progress in directed assembly and self-assembly, a truly versatile assembly technique without specific functionalization of the colloidal particles remains elusive. We develop a new strategy to assemble colloidal matter under a light-controlled temperature field, which can solve challenges in the existing assembly techniques. By adding an anionic surfactant (that is, cetyltrimethylammonium chloride), which serves as a surface charge source, a macro ion, and a micellar depletant, we generate a light-controlled thermoelectric field to manipulate colloidal atoms and a depletion attraction force to assemble the colloidal atoms into two-dimensional (2D) colloidal matter. The general applicability of this opto-thermophoretic assembly (OTA) strategy allows us to build colloidal matter of diverse colloidal sizes (from subwavelength scale to micrometer scale) and materials (polymeric, dielectric, and metallic colloids) with versatile configurations and tunable bonding strengths and lengths. We further demonstrate that the incorporation of the thermoelectric field into the optical radiation force can achieve 3D reconfiguration of the colloidal matter. The OTA strategy releases the rigorous design rules required in the existing assembly techniques and enriches the structural complexity in colloidal matter, which will open a new window of opportunities for basic research on matter organization, advanced material design, and applications.

  12. Ultraviolet-visible spectral properties of nanometer zinc oxide colloidal solution

    Institute of Scientific and Technical Information of China (English)

    刘建本; 陈上; 吴竹青; 肖卓炳; 张永康; 黄伯云

    2003-01-01

    Nanometer zinc oxide was prepared by solid phase reaction. And the ultraviolet-visi-ble spectral properties of nanometer zinc oxide colloidal solution dispersed in both water and oilphases were studied. The results show that the absorbance of the colloidal solution to ultravioletlight increases with the decrease of wavelength and reaches about 2.5 at the wavelength of 200nm. When the mass fraction of nanometer zinc oxide becomes lower, the transmittance of the col-loidal solution to visible light gets higher, and it is much higher than that of normal zinc oxide un-der the same conditions, indicating that nanometer zinc oxide dispersed in both water and oil pha-ses has high transmittance to visible light and good shield to ultraviolet light. Therefore it is suit-able for the replacement of organic ultraviolet absorber and titanium dioxide in cosmetics.

  13. Colloidal quantum dot photodetectors

    KAUST Repository

    Konstantatos, Gerasimos

    2011-05-01

    We review recent progress in light sensors based on solution-processed materials. Spin-coated semiconductors can readily be integrated with many substrates including as a post-process atop CMOS silicon and flexible electronics. We focus in particular on visible-, near-infrared, and short-wavelength infrared photodetectors based on size-effect-tuned semiconductor nanoparticles made using quantum-confined PbS, PbSe, Bi 2S3, and In2S3. These devices have in recent years achieved room-temperature D values above 1013 Jones, while fully-depleted photodiodes based on these same materials have achieved MHz response combined with 1012 Jones sensitivities. We discuss the nanoparticle synthesis, the materials processing, integrability, temperature stability, physical operation, and applied performance of this class of devices. © 2010 Elsevier Ltd. All rights reserved.

  14. Colloid Release from Soil Aggregates

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per;

    2012-01-01

    The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

  15. COLLOID RELEASE FROM DIFFERENT SOIL DEPTH

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2013-01-01

    Full Text Available Naturally occurring clay colloidal particles are heavily involved in sediment processes in the subsurface soil. Due to the import ance of these processes in the subsurface environment, the transport of clay colloidal particles has been studied in several disciplines, including soil sciences, petr ology, hydrology, etc. Specifically, in environmental engineering, clay colloid re lease and transport in the sediments have been extensively investigated, which are motiv ated by environmental concerns such as colloid-facilitated contaminant transport in groundwater and the subsurface soil. Clay colloid release is resulted from physical alteration of subsurface sediments. Despite the potential importance of clay colloid activiti es, the detailed mechanisms of release and transport of clay colloidal particles with in natural sediments are poorly understood. Pore medium structure, properties and flow dynamics, etc. are factors that affect clay colloid generation, mobilization, and subse quent transport. Possible mechanisms of clay colloid generation in the sediments in clude precipitation, erosion and mobilization by changes in pore water chemistry and clay colloid release depends on a balance of applied hydrodynamic and resisting adhesive torques and forces. The coupled role of pore water chemistry and fluid hydrodynamics thus play key roles in controlling clay colloid release and transport in the sediment s. This paper investigated clay colloidal particle release and transport, especially th e colloidal particle release mechanisms as well as the process modeling in the sediments. In this research, colloidal particle release from intact sediment columns with variable length was examined and colloidal particle release curves were simulated using an im plicit, finite-difference scheme. Colloidal particle release rate coefficient was found to be an exponential function of the sediment depth. The simulated results demonstrated that transport parameters were

  16. Silicon spintronics.

    Science.gov (United States)

    Jansen, Ron

    2012-04-23

    Worldwide efforts are underway to integrate semiconductors and magnetic materials, aiming to create a revolutionary and energy-efficient information technology in which digital data are encoded in the spin of electrons. Implementing spin functionality in silicon, the mainstream semiconductor, is vital to establish a spin-based electronics with potential to change information technology beyond imagination. Can silicon spintronics live up to the expectation? Remarkable advances in the creation and control of spin polarization in silicon suggest so. Here, I review the key developments and achievements, and describe the building blocks of silicon spintronics. Unexpected and puzzling results are discussed, and open issues and challenges identified. More surprises lie ahead as silicon spintronics comes of age.

  17. Synthesis and Characterization of Supramolecular Colloids.

    Science.gov (United States)

    Vilanova, Neus; De Feijter, Isja; Voets, Ilja K

    2016-04-22

    Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

  18. Colloidal gelation of oppositely charged particles

    NARCIS (Netherlands)

    Russel, E.; Sprakel, J.H.B.; Kodger, T.E.; Weitz, D.A.

    2012-01-01

    Colloidal gelation has been extensively studied for the case of purely attractive systems, but little is understood about how colloidal gelation is affected by the presence of repulsive interactions. Here we demonstrate the gelation of a binary system of oppositely charged colloids, in which repulsi

  19. Effect of oxygen plasma on nanomechanical silicon nitride resonators

    Science.gov (United States)

    Luhmann, Niklas; Jachimowicz, Artur; Schalko, Johannes; Sadeghi, Pedram; Sauer, Markus; Foelske-Schmitz, Annette; Schmid, Silvan

    2017-08-01

    Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

  20. Bonding assembled colloids without loss of colloidal stability

    NARCIS (Netherlands)

    Vutukuri, H.R.; Stiefelhagen, J.C.P.; Vissers, T; Imhof, A.; van Blaaderen, A.

    2012-01-01

    In recent years the diversity of self-assembled colloidal structures has strongly increased, as it is fueled by a wide range of applications in materials science and also in soft condensed-matter physics.[1–4] Some potential applications include photonic bandgap (PBG) crystals, materials for plasmon

  1. Colloids and Nucleation

    Science.gov (United States)

    Ackerson, Bruce

    1997-01-01

    The objectives of the work funded under this grant were to develop a microphotographic technique and use it to monitor the nucleation and growth of crystals of hard colloidal spheres. Special attention is given to the possible need for microgravity studies in future experiments. A number of persons have been involved in this work. A masters student, Keith Davis, began the project and developed a sheet illumination apparatus and an image processing system for detection and analysis. His work on a segmentation program for image processing was sufficient for his master's research and has been published. A post doctoral student Bernie Olivier and a graduate student Yueming He, who originally suggested the sheet illumination, were funded by another source but along with Keith made photographic series of several samples (that had been made by Keith Davis). Data extraction has been done by Keith, Bernie, Yueming and two undergraduates employed on the grant. Results are published in Langmuir. These results describe the sheet lighting technique as one which illuminates not only the Bragg scattering crystal, but all the crystals. Thus, accurate crystal counts can be made for nucleation rate measurements. The strange crystal length scale reduction, observed in small angle light scattering (SALS) studies, following the initial nucleation and growth period, has been observed directly. The Bragg scattering (and dark) crystal size decreases in the crossover region. This could be an effect due to gravitational forces or due to over- compression of the crystal during growth. Direct observations indicate a complex morphology for the resulting hard sphere crystals. The crystal edges are fairly sharp but the crystals have a large degree of internal structure. This structure is a result of (unstable) growth and not aggregation. As yet unpublished work compares growth exponents data with data obtained by SALS. The nucleation rate density is determined over a broad volume fraction range

  2. Synthesis and performance of colloidal silica nano-abrasives with controllable size for chemical mechanical planarization.

    Science.gov (United States)

    Zhang, K L; Song, Z T; Wang, F; Wang, L Y; Feng, S L

    2009-02-01

    Under the analysis of particle growth mechanism, the monodisperse colloidal silica abrasives for chemical mechanical planarization (CMP) slurry were synthesized by the modified ion-exchanged and hydrothermal step-polymerization process. After the colloidal silica with controllable size was synthesized, its microstructure, stability and CMP performance was characterized and tested by SEM, HRTEM, Zeta potential Analyzer and CMP tester. Results show that the spherical, high stable (Zeta potential: -52.8 mV) colloidal silica with controllable size was achieved. About its CMP performance, the polishing rate for silicon double-side CMP is increased to be 317 nm/min and the polished surface roughness (RMS) was reduced to 0.32 nm.

  3. Self-Assembled Structures of Colloidal Silver Nanoparticles on Solid Substrates

    Institute of Scientific and Technical Information of China (English)

    LIU Yulan; HE Shengtai; HUANG Keyang

    2011-01-01

    With a two-phase method,well-dispersed 5.2 nm Ag nanoparticles with narrow size distribution (±0.5 nm) are synthesized.The assembled structures of colloidal Ag nanoparticles on highly oriented pyrolytic graphite (HOPG),silicon chip and microscopic glass have been investigated by atomic force microscopy (AFM).With different spin-coating speeds and concentrations of colloidal silver nanoparticles,various assembly structures could form on those substrates.On HOPG,Ag nanoparticles were absorbed and aligned along single-atom-height step edges to form a linear one-layer structure.And on silicon chip and microscopic glass,one-layer closed packing fractal structure and two-layer closed packing ring were observed respectively.

  4. A short textbook of colloid chemistry

    CERN Document Server

    Jirgensons, B

    1962-01-01

    A Short Textbook of Colloid Chemistry, Second Revised Edition details the factual aspect of colloid chemistry that includes the basic facts, established empirical and mathematical relationships, and practical applications. The chapters of the title are organized into two parts. In the first part, the text discusses the general concepts of colloid chemistry, such as the history and scope, basic terms, and basic methods in experiment with colloids. Part Two covers the technical aspect of colloid chemistry, such as the optical properties, electrical properties, and viscosity. The book will be of

  5. Liquid carbon dioxide absorbents, methods of using the same, and related systems

    Science.gov (United States)

    O'Brien, Michael Joseph; Perry, Robert James; Lam, Tunchiao Hubert; Soloveichik, Grigorii Lev; Kniajanski, Sergei; Lewis, Larry Neil; Rubinsztajn, Malgorzata Iwona; Hancu, Dan

    2016-09-13

    A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO.sub.2 or have a high-affinity for CO.sub.2; and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO.sub.2. The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.

  6. Supramolecular perspectives in colloid science

    NARCIS (Netherlands)

    Cohen Stuart, M.A.

    2008-01-01

    Supramolecular chemistry puts emphasis on molecular assemblies held together by non-covalent bonds. As such, it is very close in spirit to colloid science which also focuses on objects which are small, but beyond the molecular scale, and for which other forces than covalent bonds are crucial. We dis

  7. Colloidal aspects of texture perception

    NARCIS (Netherlands)

    Vliet, van T.

    2010-01-01

    The perception of complex textures in food is strongly related to the way food is processed during eating, and is modulated by other basic characteristics, such as taste and aroma. An understanding at the colloidal level of the basic processes in the mouth is essential in order to link the compositi

  8. Colloidal quantum dot solar cells

    Science.gov (United States)

    Sargent, Edward H.

    2012-03-01

    Solar cells based on solution-processed semiconductor nanoparticles -- colloidal quantum dots -- have seen rapid advances in recent years. By offering full-spectrum solar harvesting, these cells are poised to address the urgent need for low-cost, high-efficiency photovoltaics.

  9. Microbial effects on colloidal agglomeration

    Energy Technology Data Exchange (ETDEWEB)

    Hersman, L.

    1995-11-01

    Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs.

  10. Proteolytic stability in colloidal systems.

    NARCIS (Netherlands)

    Maste, M.C.L.

    1996-01-01

    Proteolytic enzymes in liquid detergents suffer from lack of stability in the sense that activity diminishes with time. Although the phenomenon could be attributed to several factors, the influence of colloidal surfaces on the enzymatic stability was investigated. Besides the types of surfaces that

  11. Enhanced colloidal stability of hydroxyapatite

    Science.gov (United States)

    Borum, La Rhonda Terese

    Hydroxyapatite, Ca10(PO4)6(OH) 2 is the most thermodynamically stable calcium phosphate in physiological environments. Hence, it is the main inorganic mineral found in bone and teeth. Its colloidal stability, however, is poor because hydroxyapatite (HAp) particles exhibit sediment formation upon standing at short time periods, where agglomerates form and lead to non-homogeneous suspensions. Surface modification is a promising method to tailor the colloidal stability of hydroxyapatite for biomaterial applications. Three techniques to modify the HAp surface and enhance the colloidal stability of HAp were investigated. Modified particles were characterized by methods sensitive to surface chemistry changes, such as sedimentation studies, diffuse reflectance Fourier transform infrared spectroscopy (DRIFT), Brunauer-Emmett-Teller (BET) surface area, and electrophoresis. Sedimentation studies demonstrated how effective each technique was in improving the colloidal stability of hydroxyapatite particles. Electrophoresis provided information on electrostatic interactions within each system. The first technique entailed an esterification reaction of the HAp surface with dodecyl alcohol at elevated temperatures. DRIFT results showed that dodecyl groups from the alcohol replaced acidic hydroxyl and phosphate sites on the HAp surface, giving rise to enhanced colloidal stability through steric interactions in ethanol suspensions. TGA curves gave insight to the degree of esterification for the esterified particles. Higher reaction temperatures give rise to a higher degree of esterification resulting in better colloidal stability. The second technique applied a silica coating on the HAp surface by the hydrolysis of tetraethyl orthosilicate in ethanol. Silica was coated onto the HAp surface at 5--75 wt% loading amounts. A combination of acid dissolution and x-ray diffraction (XRD), along with BET showed that the silica coating is complete at 50 wt% silica loading. The silica coating

  12. Optical temperature sensor with enhanced sensitivity by employing hybrid waveguides in a silicon Mach-Zehnder interferometer

    DEFF Research Database (Denmark)

    Guan, Xiaowei; Wang, Xiaoyan; Frandsen, Lars Hagedorn

    2016-01-01

    of the fabricated sensor with silicon/polymer hybrid waveguides is measured to be 172 pm/°C, which is two times larger than a conventional all-silicon optical temperature sensor (∼80 pm/°C). Moreover, a design with silicon/titanium dioxide hybrid waveguides is by calculation expected to have a sensitivity as high...

  13. Oxide film assisted dopant diffusion in silicon carbide

    Energy Technology Data Exchange (ETDEWEB)

    Tin, Chin-Che, E-mail: cctin@physics.auburn.ed [Department of Physics, Auburn University, Alabama 36849 (United States); Mendis, Suwan [Department of Physics, Auburn University, Alabama 36849 (United States); Chew, Kerlit [Department of Electrical and Electronic Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Kuala Lumpur (Malaysia); Atabaev, Ilkham; Saliev, Tojiddin; Bakhranov, Erkin [Physical Technical Institute, Uzbek Academy of Sciences, 700084 Tashkent (Uzbekistan); Atabaev, Bakhtiyar [Institute of Electronics, Uzbek Academy of Sciences, 700125 Tashkent (Uzbekistan); Adedeji, Victor [Department of Chemistry, Geology and Physics, Elizabeth City State University, North Carolina 27909 (United States); Rusli [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)

    2010-10-01

    A process is described to enhance the diffusion rate of impurities in silicon carbide so that doping by thermal diffusion can be done at lower temperatures. This process involves depositing a thin film consisting of an oxide of the impurity followed by annealing in an oxidizing ambient. The process uses the lower formation energy of silicon dioxide relative to that of the impurity-oxide to create vacancies in silicon carbide and to promote dissociation of the impurity-oxide. The impurity atoms then diffuse from the thin film into the near-surface region of silicon carbide.

  14. Effect of High Coal Injection on Low Silicon Ironmaking Process

    Institute of Scientific and Technical Information of China (English)

    JIN Yong-long; XU Nan-ping; WU Shi-ying

    2003-01-01

    The effects of different coal ratios and reaction temperatures on silicon content in hot metal were studied under the condition of high powder coal injection (PCI) ratio in laboratory. The samples of coke taken from tuyere were analyzed by chemical methods. According to the remnant silicon dioxide in different samples, the effect of PCI ratio on silicon content in hot metal was studied in tuyere area. The results can not only certify the traditional theory, but also explain the relation between high PCI ratio and low silicon.

  15. Life at ultralow interfacial tension: Wetting, waves and droplets in demixed colloid-polymer mixtures

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; de Villeneuve, V.W.A.; de Folter, J.W.J.; Schmidt, M.; Hennequin, Y.; Bonn, D.; Indekeu, J.O.; Aarts, D.G.A.L.

    2008-01-01

    Mixtures of colloids and polymers display a rich phase behavior, involving colloidal gas (rich in polymer, poor in colloid), colloidal liquid (poor in polymer, rich in colloid) and colloidal crystal phases (poor in polymer, highly ordered colloids). Recently, the colloidal gas-colloidal liquid inter

  16. Life at ultralow interfacial tension: wetting, waves and droplets in demixed colloid-polymer mixtures

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; de Villeneuve, V.W.A.; de Folter, J.W.J.; Schmidt, M.; Hennequin, Y.; Bonn, D.; Indekeu, J.O.; Aarts, D.G.A.L.

    2008-01-01

    Mixtures of colloids and polymers display a rich phase behavior, involving colloidal gas (rich in polymer, poor in colloid), colloidal liquid (poor in polymer, rich in colloid) and colloidal crystal phases (poor in polymer, highly ordered colloids). Recently, the colloidal gas-colloidal liquid inter

  17. Magnetic Assisted Colloidal Pattern Formation

    Science.gov (United States)

    Yang, Ye

    Pattern formation is a mysterious phenomenon occurring at all scales in nature. The beauty of the resulting structures and myriad of resulting properties occurring in naturally forming patterns have attracted great interest from scientists and engineers. One of the most convenient experimental models for studying pattern formation are colloidal particle suspensions, which can be used both to explore condensed matter phenomena and as a powerful fabrication technique for forming advanced materials. In my thesis, I have focused on the study of colloidal patterns, which can be conveniently tracked in an optical microscope yet can also be thermally equilibrated on experimentally relevant time scales, allowing for ground states and transitions between them to be studied with optical tracking algorithms. In particular, I have focused on systems that spontaneously organize due to particle-surface and particle-particle interactions, paying close attention to systems that can be dynamically adjusted with an externally applied magnetic or acoustic field. In the early stages of my doctoral studies, I developed a magnetic field manipulation technique to quantify the adhesion force between particles and surfaces. This manipulation technique is based on the magnetic dipolar interactions between colloidal particles and their "image dipoles" that appear within planar substrate. Since the particles interact with their own images, this system enables massively parallel surface force measurements (>100 measurements) in a single experiment, and allows statistical properties of particle-surface adhesion energies to be extracted as a function of loading rate. With this approach, I was able to probe sub-picoNewton surface interactions between colloidal particles and several substrates at the lowest force loading rates ever achieved. In the later stages of my doctoral studies, I focused on studying patterns formed from particle-particle interaction, which serve as an experimental model of

  18. Colloid aspects of chemical-mechanical planarization.

    Science.gov (United States)

    Matijević, E; Babu, S V

    2008-04-01

    The essential parts of interconnects for silicon based logic and memory devices consist of metal wiring (e.g. copper), a barrier metal (Ta, TaN), and of insulation (SiO2, low-k polymer). The deposition of the conducting metal cannot be confined to trenches, resulting in additional coverage of Cu and Ta/TaN on the surface of the dielectrics, yielding an electrically conducting continuous but an uneven surface. The surplus metal must be removed until a perfectly flat surface consisting of electrically isolated metal lines is achieved with no imperfections. This task is accomplished by the chemical-mechanical planarization (CMP) process, in which the wafer is polished with a slurry containing abrasives of finely dispersed particles in submicrometer to nanometer size. The slurries also contain dissolved chemicals to modify the surfaces to be planarized. Eventually the final product must be cleared of any adhered particles and debris left after polishing is completed. Obviously the entire process deals with materials and interactions which are the focal subjects of colloid and surface science, such as the natures of abrasive particles and their stability in the slurry, the properties of various surfaces and their modifications, adhesion and detachment of the particles and different methods for the characterization of constituents, as well as elucidation of the relevant interfacial phenomena. This review endeavors to describe the colloid approach to optimize the materials and processes in order to achieve desirable polish rates and final surfaces with no imperfections. Specifically, the effects of the composition, size, shape, and charge of abrasive particles on the polish process and the quality of planarized wafers is described in detail. Furthermore, the interactions of metal surfaces with oxidizing, chelating, and other species which affect the dissolution and surface modification of metal (copper) surfaces are illustrated and related to the planarization process

  19. Colloid Aspects of Chemical-Mechanical Planarization

    Directory of Open Access Journals (Sweden)

    Matijević, E.

    2010-09-01

    Full Text Available The essential parts of interconnects for silicon based logic and memory devices consist of metal wiring (e.g. copper, a barrier metal (Ta, TaN, and of insulation (SiO2 , low-k polymer. The deposition of the conducting metal cannot be confined to trenches, resulting in additional coverage of Cu and Ta/TaN on the surface of the dielectrics, yielding an electrically conducting continuous but an uneven surface. The surplus metal must be removed until a perfectly flat surface consisting of electrically isolated metal lines is achieved with no imperfections. This task is accomplished by the chemical-mechanical planarization (CMP process, in which the wafer is polished with a slurry containing abrasives of finely dispersed particles in submicrometer to nanometer size. The slurries also contain dissolved chemicals to modify the surfaces to be planarized. Eventually the final product must be cleared of any adhered particles and debris left after polishing is completed. Obviously the entire process deals with materials and interactions which are the focal subjects of colloid and surface science, such as the natures of abrasive particles and their stability in the slurry, the properties of various surfaces and their modifications, adhesion and detachment of the particles and different methods for the characterization of constituents, as well as elucidation of the relevant interfacial phenomena. This review endeavors to describe the colloid approach to optimize the materials and processes in order to achieve desirable polish rates and final surfaces with no imperfections. Specifically, the effects of the composition, size, shape, and charge of abrasive particles on the polish process and the quality of planarized wafers is described in detail. Furthermore, the interactions of metal surfaces with oxidizing, chelating, and other species which affect the dissolution and surface modification of metal (copper surfaces are illustrated and related to the

  20. Thermoelectric Properties of Silicon Microchannel Plates Structures

    Energy Technology Data Exchange (ETDEWEB)

    Ci, P L; Shi, J; Wang, F; Sun, L; Xu, S H; Yang, P X; Wang, L W [Laboratory of Polar Materials and Devices, Ministry of Education, and Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China); Chu, Paul K, E-mail: lwwang@ee.ecnu.edu.cn [Department of Physics and Material Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon (Hong Kong)

    2011-02-01

    We have fabricated silicon microchannel plates (MCPs) by photo-assisted electrochemical etching (PAECE) and determined the thermoelectric properties by measuring the Seebeck coefficient of the samples. The samples are composed of regular arrayed lattices with a width of about 5 {mu}m and spacing of about 1 {mu}m. The Seebeck coefficient along the edge of the lattice is 466 {mu}V/K. The silicon MCPs are potential materials for power generation and refrigeration. After oxidation from 30 minutes to 70 minutes and removing the silicon dioxide layer by buffered hydrofluoric acid, the samples show an improved coefficient as high as 1019 {mu}V/K after repeating oxidation and etching 5 times. Our results show that the Seebeck coefficient increases when the wall of the silicon MCPs is thinned.

  1. Stable colloids in molten inorganic salts.

    Science.gov (United States)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dmitri V

    2017-02-15

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other. Electrostatic stabilization of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute-solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute-solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  2. Stable colloids in molten inorganic salts

    Science.gov (United States)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B.; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dmitri V.

    2017-02-01

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other. Electrostatic stabilization of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute–solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute–solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  3. What happens when pharmaceuticals meet colloids.

    Science.gov (United States)

    Xing, Yingna; Chen, Xijuan; Zhuang, Jie; Chen, Xin

    2015-12-01

    Pharmaceuticals (PCs) have been widely detected in natural environment due to agricultural application of reclaimed water, sludge and animal wastes. Their potential risks to various ecosystems and even to human health have caused great concern; however, little was known about their environmental behaviors. Colloids (such as clays, metal oxides, and particulate organics) are kind of substances that are active and widespread in the environment. When PCs meet colloids, their interaction may influence the fate, transport, and toxicity of PCs. This review summarizes the progress of studies on the role of colloids in mediating the environmental behaviors of PCs. Synthesized results showed that colloids can adsorb PCs mainly through ion exchange, complexation and non-electrostatic interactions. During this process the structure of colloids and the stability of PCs may be changed. The adsorbed PCs may have higher risks to induce antibiotic resistance; besides, their transport may also be altered considering they have great chance to move with colloids. Solution conditions (such as pH, ionic strength, and cations) could influence these interactions between PCs and colloids, as they can change the forms of PCs and alter the primary forces between PCs and colloids in the solution. It could be concluded that PCs in natural soils could bind with colloids and then co-transport during the processes of irrigation, leaching, and erosion. Therefore, colloid-PC interactions need to be understood for risk assessment of PCs and the best management practices of various ecosystems (such as agricultural and wetland systems).

  4. Chancellor Water Colloids: Characterization and Radionuclide Association

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Fattah, Amr I. [Los Alamos National Laboratory

    2012-06-18

    Concluding remarks about this paper are: (1) Gravitational settling, zeta potential, and ultrafiltration data indicate the existence of a colloidal phase of both the alpha and beta emitters in the Chancellor water; (2) The low activity combined with high dispersion homogeneity of the Chancellor water indicate that both alpha and beta emitters are not intrinsic colloids; (3) Radionuclides in the Chancellor water, particularly Pu, coexist as dissolved aqueous and sorbed phases - in other words the radionuclides are partitioned between the aqueous phase and the colloidal phase; (4) The presence of Pu as a dissolved species in the aqueous phase, suggests the possibility of Pu in the (V) oxidation state - this conclusion is supported by the similarity of the k{sub d} value of Pu determined in the current study to that determined for Pu(V) sorbed onto smectite colloids, and the similar electrokinetic behavior of the Chancellor water colloids to smectite colloids; (5) About 50% of the Pu(V) is in the aqueous phase and 50% is sorbed on colloids (mass concentration of colloids in the Chancellor water is 0.12 g/L); (6) The k{sub d} of the Pu and the beta emitters (fission products) between aqueous and colloidal phases in the Chancellor water is {approx}8.0 x 10{sup 3} mL/g using two different activity measurement techniques (LSC and alpha spectroscopy); (7) The gravitational settling and size distributions of the association colloids indicate that the properties (at least the physical ones) of the colloids to which the alpha emitters are associated with seem to be different that the properties of the colloids to which the beta emitters are associated with - the beta emitters are associated with very small particles ({approx}50 - 120 nm), while the alpha emitters are associated with relatively larger particles; and (8) The Chancellor water colloids are extremely stable under the natural pH and ionic strength conditions, indicating high potential for transport in the

  5. 分光光度法测定铁矿石中的二氧化硅和五氧化二磷%Spectrophotometric Method For Determination Of Silicon Dioxide In Iron Ore And Phosphorus Pentoxide

    Institute of Scientific and Technical Information of China (English)

    杨莲瑛

    2013-01-01

      试样经碳酸钠、硼酸和四硼酸钠混合助溶剂碱熔,硝酸酸化定容后,以铋磷钼黄分光光度法测定五氧化二磷;在草酸存在下,以硫酸亚铁铵为还原剂,硅钼蓝法测定二氧化硅,本方法操作简单、快速,具有较好的精密度和准确度。%  Sample by sodium carbonate, boric acid and sodium tetraborate cosolvent alkali fusion, the capacity, the nitric acid acidification in bismuth phosphor molybdenum yellow spectrophotometric method determination of phosphorus pentoxide; In the presence of oxalate, reductant of ammonium ferrous sulfate, silica, silicon molybdenum blue method, this method operation is simple, rapid, and has good precision and accuracy.

  6. The carbon dioxide cycle

    Science.gov (United States)

    James, P.B.; Hansen, G.B.; Titus, T.N.

    2005-01-01

    The seasonal CO2 cycle on Mars refers to the exchange of carbon dioxide between dry ice in the seasonal polar caps and gaseous carbon dioxide in the atmosphere. This review focuses on breakthroughs in understanding the process involving seasonal carbon dioxide phase changes that have occurred as a result of observations by Mars Global Surveyor. ?? 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  7. Carbon Dioxide Absorbents

    Science.gov (United States)

    1950-05-17

    carbondioxide content of the solution was then determined. A gas mixture containing 2.6% carbon dioxide and 97.4% nitrogen was prepared in the...which carbon dioxide is removed by heat0 Since this step is usually carried out by "steam stripping ", that is, contacting the solution at its boiling...required to produce the steam required for stripping the carbon dioxide from the s olution. The method ueed in this investigation for determining the

  8. CARBON DIOXIDE REDUCTION SYSTEM.

    Science.gov (United States)

    CARBON DIOXIDE , *SPACE FLIGHT, RESPIRATION, REDUCTION(CHEMISTRY), RESPIRATION, AEROSPACE MEDICINE, ELECTROLYSIS, INSTRUMENTATION, ELECTROLYTES, VOLTAGE, MANNED, YTTRIUM COMPOUNDS, ZIRCONIUM COMPOUNDS, NICKEL.

  9. Dynamics of evaporative colloidal patterning

    OpenAIRE

    Kaplan, Cihan Nadir; Wu, Ning; Mandre, Shreyas; Aizenberg, Joanna; Mahadevan, Lakshminarayanan

    2014-01-01

    Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here, we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying colloidal solution. Direct observations allow us to visualize the dynamics of band and film deposition, where both are made of multiple layers of close packed particles. We further see that there is a transition between banding and filming whe...

  10. Thermophoresis of charged colloidal particles.

    Science.gov (United States)

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-04-01

    Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  11. Thermophoresis of charged colloidal particles

    OpenAIRE

    Fayolle, Sébastien; Bickel, Thomas; Würger, Alois

    2008-01-01

    International audience; Thermally induced particle flow in a charged colloidal suspension is studied in a fluid-mechanical approach. The force density acting on the charged boundary layer is derived in detail. From Stokes' equation with no-slip boundary conditions at the particle surface, we obtain the particle drift velocity and the thermophoretic transport coefficients. The results are discussed in view of previous work and available experimental data.

  12. Implant materials modified by colloids

    Directory of Open Access Journals (Sweden)

    Zboromirska-Wnukiewicz Beata

    2016-03-01

    Full Text Available Recent advances in general medicine led to the development of biomaterials. Implant material should be characterized by a high biocompatibility to the tissue and appropriate functionality, i.e. to have high mechanical and electrical strength and be stable in an electrolyte environment – these are the most important properties of bioceramic materials. Considerations of biomaterials design embrace also electrical properties occurring on the implant-body fluid interface and consequently the electrokinetic potential, which can be altered by modifying the surface of the implant. In this work, the surface of the implants was modified to decrease the risk of infection by using metal colloids. Nanocolloids were obtained using different chemical and electrical methods. It was found that the colloids obtained by physical and electrical methods are more stable than colloids obtained by chemical route. In this work the surface of modified corundum implants was investigated. The implant modified by nanosilver, obtained by electrical method was selected. The in vivo research on animals was carried out. Clinical observations showed that the implants with modified surface could be applied to wounds caused by atherosclerotic skeleton, for curing the chronic and bacterial inflammations as well as for skeletal reconstruction surgery.

  13. Three-dimensional colloidal lithography.

    Science.gov (United States)

    Nagai, Hironori; Poteet, Austen; Zhang, Xu A; Chang, Chih-Hao

    2017-03-24

    Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle-light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd's mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.

  14. Three-dimensional colloidal lithography

    Science.gov (United States)

    Nagai, Hironori; Poteet, Austen; Zhang, Xu A.; Chang, Chih-Hao

    2017-03-01

    Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle–light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd’s mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.

  15. Crystallization of DNA-coated colloids.

    Science.gov (United States)

    Wang, Yu; Wang, Yufeng; Zheng, Xiaolong; Ducrot, Étienne; Yodh, Jeremy S; Weck, Marcus; Pine, David J

    2015-06-16

    DNA-coated colloids hold great promise for self-assembly of programmed heterogeneous microstructures, provided they not only bind when cooled below their melting temperature, but also rearrange so that aggregated particles can anneal into the structure that minimizes the free energy. Unfortunately, DNA-coated colloids generally collide and stick forming kinetically arrested random aggregates when the thickness of the DNA coating is much smaller than the particles. Here we report DNA-coated colloids that can rearrange and anneal, thus enabling the growth of large colloidal crystals from a wide range of micrometre-sized DNA-coated colloids for the first time. The kinetics of aggregation, crystallization and defect formation are followed in real time. The crystallization rate exhibits the familiar maximum for intermediate temperature quenches observed in metallic alloys, but over a temperature range smaller by two orders of magnitude, owing to the highly temperature-sensitive diffusion between aggregated DNA-coated colloids.

  16. Janus Nematic Colloids with Designable Valence

    Directory of Open Access Journals (Sweden)

    Simon Čopar

    2014-05-01

    Full Text Available Generalized Janus nematic colloids based on various morphologies of particle surface patches imposing homeotropic and planar surface anchoring are demonstrated. By using mesoscopic numerical modeling, multiple types of Janus particles are explored, demonstrating a variety of novel complex colloidal structures. We also show binding of Janus particles to a fixed Janus post in the nematic cell, which acts as a seed and a micro-anchor for the colloidal structure. Janus colloidal structures reveal diverse topological defect configurations, which are effectively combinations of surface boojum and bulk defects. Topological analysis is applied to defects, importantly showing that topological charge is not a well determined topological invariant in such patchy nematic Janus colloids. Finally, this work demonstrates colloidal structures with designable valence, which could allow for targeted and valence-conditioned self-assembly at micro- and nano-scale.

  17. COLLOID RELEASE FROM DIFFERENT SOIL DEPTH

    OpenAIRE

    Gang Chen; Yue Niu; Boya Wang; Kamal Tawfiq

    2013-01-01

    Naturally occurring clay colloidal particles are heavily involved in sediment processes in the subsurface soil. Due to the import ance of these processes in the subsurface environment, the transport of clay colloidal particles has been studied in several disciplines, including soil sciences, petr ology, hydrology, etc. Specifically, in environmental engineering, clay colloid re lease and transport in the sediments have been extensively investigated, which are motiv ated by environmental conce...

  18. Thermophoresis of colloids by mesoscale simulations.

    Science.gov (United States)

    Lüsebrink, Daniel; Yang, Mingcheng; Ripoll, Marisol

    2012-07-18

    The motion of a colloid induced by a temperature gradient is simulated by means of multiparticle collision dynamics, a mesoscale simulation technique. Two algorithms to quantify the thermophoretic behavior are employed and contrasted. The validity of the methods is verified as a function of the temperature gradient, system size, and algorithm parameters. The variation of the solvent-colloid interaction from attractive to purely repulsive interestingly results in the change of the colloid behavior from thermophobic to thermophilic.

  19. Colloidal quantum dots: synthesis, properties and applications

    Science.gov (United States)

    Brichkin, S. B.; Razumov, V. F.

    2016-12-01

    Key recent results obtained in studies of a new class of luminophores, colloidal quantum dots, are analyzed. Modern methods for the synthesis and post-synthetic treatment of colloidal quantum dots that make it possible to achieve record high quantum yield of luminescence and to modify their characteristics for specific applications are considered. Currently important avenues of research on colloidal quantum dots and the problems in and prospects for their practical applications in various fields are discussed. The bibliography includes 272 references.

  20. Study of Silicon Nitrate and Tin Dioxide carbon nanotube composite as lithium-ion battery anode, gas sensor and the self-assembly of carbon nanotubes on copper substrates

    Science.gov (United States)

    Hernandez-Lugo, Dionne M.

    Carbon nanotubes since their discovery have been used for many applications. They are predicted to reinforce novel composite materials because of their structural perfection, excellent mechanical properties and low density. CNT can be made into nanowires of different materials or as part of a composite making them beneficial for the incorporation into electrochemical devices. Carbon nanotubes in this study were gown directly on a copper substrate employing hot filament chemical vapor deposition (HFCVD). Bamboo-like carbon nanotubes were made into electrodes reducing the use of inactive materials on the development of working electrodes for electrochemical application. This BCNT were tested as lithium-ion battery anodes assembled together with high capacity materials such as Silicon and Tin Oxide (4200mAh/g and 782 mAh/g). On this study BCNT served as a conductive matrix as well as buffer matrix for the volume expansion brought by cycling silicon and tin oxide. The composite structural properties enhance the surface-to-volume ratio of the electrode demonstrating a desirable electrochemical performance for a lithium-ion battery anode. As a gas sensor electrode CNT was assembled with tin-oxide directly on a copper substrate for the detection of ethanol, methanol, ammonia and H2S. CNT gave a higher surface area and a conductive matrix aiding to the sensing capabilities of the SnO2 increasing the effectiveness of the matrix material for gas detection. Copper is known to produce CNT with a disturb structure. To develop an electrode on copper with well-ordered CNT other techniques need to be used. One way to do this is by chemical modification of the copper substrate with a molecule able to react with the carbon nanotube. For the attachment of well-ordered carbon nanotubes such as SWCNT a self-assembly monolayer technique is chosen. On this study 4-aminothiophenol served as the linker between the copper substrate and the carbon nanotubes. This study let to chemically

  1. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

    Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

  2. Dynamics of Electrically Modulated Colloidal Droplet Transport.

    Science.gov (United States)

    Dey, Ranabir; Ghosh, Udita Uday; Chakraborty, Suman; DasGupta, Sunando

    2015-10-20

    Electrically actuated transport dynamics of colloidal droplets, on a hydrophobic dielectric film covering an array of electrodes, is studied here. Specifically, the effects of the size and electrical properties (zeta-potential) of the colloidal particles on such transport characteristics are investigated. For the colloidal droplets, the application of an electrical voltage leads to additional attenuation of the local dielectric-droplet interfacial tension. This is due to the electrically triggered enhanced colloidal particle adsorption at the dielectric-droplet interface, in the immediate vicinity of the droplet three-phase contact line (TPCL). The extent of such interfacial particle adsorption, and hence, the extent of the consequential reduction in the interfacial tension, is dictated by the combined effects of the three-phase contact line spreading, particle size, the interfacial electrostatic interaction between the colloidal particles (if charged) and the charged dielectric surface above the activated electrode, and the interparticle electrostatic repulsion. The electrical driving force of varying magnitude, stemming from this altered solid-liquid interfacial tension gradient in the presence of the colloidal particles, culminates in different droplet transport velocity and droplet transfer frequency for different colloidal droplets. We substantiate the inferences from our experimental results by a quasi-steady state force balance model for colloidal droplet transport. We believe that the present work will provide an accurate framework for determining the optimal design and operational parameters for digital microfluidic chips handling colloidal droplets, as encountered in a plethora of applications.

  3. Collective motion in populations of colloidal bots

    Science.gov (United States)

    Bartolo, Denis

    One of the origins of active matter physics was the idea that flocks, herds, swarms and shoals could be quantitatively described as emergent ordered phases in self-driven materials. From a somehow dual perspective, I will show how to engineer active materials our of colloidal flocks. I will show how to motorize colloidal particles capable of sensing the orientation of their neighbors and how to handle them in microfluidic chips. These populations of colloidal bots display a non-equilibrium transition toward collective motion. A special attention will be paid to the robustness of the resulting colloidal flocks with respect to geometrical frustration and to quenched disorder.

  4. Fusion bonding of silicon nitride surfaces

    DEFF Research Database (Denmark)

    Reck, Kasper; Østergaard, Christian; Thomsen, Erik Vilain

    2011-01-01

    While silicon nitride surfaces are widely used in many micro electrical mechanical system devices, e.g. for chemical passivation, electrical isolation or environmental protection, studies on fusion bonding of two silicon nitride surfaces (Si3N4–Si3N4 bonding) are very few and highly application...... specific. Often fusion bonding of silicon nitride surfaces to silicon or silicon dioxide to silicon surfaces is preferred, though Si3N4–Si3N4 bonding is indeed possible and practical for many devices as will be shown in this paper. We present an overview of existing knowledge on Si3N4–Si3N4 bonding and new...... results on bonding of thin and thick Si3N4 layers. The new results include high temperature bonding without any pretreatment, along with improved bonding ability achieved by thermal oxidation and chemical pretreatment. The bonded wafers include both unprocessed and processed wafers with a total silicon...

  5. Equilibrium and metastable structures of Nickel/Silicon Dioxide/Silicon and Nickel/Silicon interfaces

    Science.gov (United States)

    Thron, Andrew Malachi

    Solid-state dewetting occurs in thin continuous metal films when capillary instabilities drive the nucleation and growth of holes. Dewetting of thick (>100nm) metals films has extensively been studied and is well understood, however the dewetting of ultra-thin films is not well understood. Recent studies have shown that Ni films less than 5nm thick do not dewet at the same temperatures as thicker Ni films, however it is not well understood why. A fundamental understanding of the dewetting behavior of ultra-thin metal films has key relevance in applications such as catalysis and complimentary metal-oxide semiconductor (CMOS) transistors. Self-assembly of metal islands can be created through the solid-state dewetting of thin metal films on a support substrate. These metal islands are used as catalyst to grow arrays of nanotubes and nanowires. Solid-state dewetting degrades the functional properties of NiSi films, which are used as contacts to the source and drain in CMOS transistors. Once the transistors are processed above 650°C the NiSi film will agglomerate, degrading the contacts to the source and drain. Alloying NiSi with refractory metals increases the dewetting temperature to over 900°C. The effect of Pt on the NiSi/Si interface structure and how the interface structure changes the functional properties of the interface is not understood. In this thesis Transmission Electron Microscopy (TEM) and aberration corrected Scanning TEM (STEM) are used to study the interface structure of ultra-thin films. In-Situ annealing, inside the TEM is used to observe morphological changes in ultra-thin Ni films sputtered onto SiO2/Si substrates. A new Aduro Double tilt heating holder, made by Protochips Inc., is implemented for studying solid-state dewetting, in situ. The Aduro heating holder is based off a Microelectromechanical systems (MEMS) design, where ultra-fast and controlled heating rates are obtained by resistively heating a SiC membrane with a low thermal mass. Advantages and limitations of the Aduro holder, and how to overcome them, are discussed. STEM, TEM, and Electron Energy Loss Spectroscopy (EELS) are used to study the Ni/SiO2/Si interface structure before and after the Ni film has dewetted. Aberration corrected STEM and EELS are used to study the Ni1-xPtxSi /Si interface structure, and how the pre-silicide layer differs from the previously observed diffusion layer. The effect of the Ni1-xPtxSi /Si interface structure on the Schottky barrier height is then discussed based off of the measured Schottky barrier heights.

  6. Carbon Dioxide and Climate.

    Science.gov (United States)

    Brewer, Peter G.

    1978-01-01

    The amount of carbon dioxide in the atmosphere is increasing at a rate that could cause significant warming of the Earth's climate in the not too distant future. Oceanographers are studying the role of the ocean as a source of carbon dioxide and as a sink for the gas. (Author/BB)

  7. Carbon Dioxide Fountain

    Science.gov (United States)

    Kang, Seong-Joo; Ryu, Eun-Hee

    2007-01-01

    This article presents the development of a carbon dioxide fountain. The advantages of the carbon dioxide fountain are that it is odorless and uses consumer chemicals. This experiment also is a nice visual experiment that allows students to see evidence of a gaseous reagent being consumed when a pressure sensor is available. (Contains 3 figures.)…

  8. Analysis of Carbon Dioxide Laser Combined with Silicone Gel in the Treatment of Facial Acne Scar Effect%二氧化碳点阵激光联合硅酮凝胶治疗面部痤疮瘢痕疗效分析

    Institute of Scientific and Technical Information of China (English)

    曾永芳; 鲁元刚; 杨宏珍; 石玉琦; 李玲; 苏静; 李矜然; 刘嘉

    2014-01-01

    Objective:To investigate and analyze the therapeutic effect and adverse reaction of carbon dioxide laser technology[1] combined with silicone gel in acne scars. Methods:Dot matrix laser is a kind of penetration by punctate stripping technology, with high-efficient and carbon dioxide laser deep penetration characteristics, at the same time, with pigmentation reduce and recovery time shortening. 32 patients with facial acne scars were regarded as the research object, including 12 male patients and 20 female patients. All patients were randomly divided into control group and experimental group. All patients were treated with carbon dioxide laser treatment of facial acne scars. After the operation, the control group didn’t use auxiliary drugs, and the experimental group was combined with silicone gel. In the experimental group and the control group, one week after the operation, 1 month, 3 months respectively, the acne scar recovery was recorded through the pictures taken. Results:One week after operation, facial acne scars of the experimental group and the control group have improved, but the experimental group recovered faster. No new scars appeared in patients of the two groups, 2 cases in the control group had pigmentation, and the experimental group had no pigmentation. 1 months and 3 months later, the two groups had no new scar, acne scar total effective rate was 87.5 %(14/16)in experimental group, and acne scar the total effective rate was 62.5% (10/16) in the control group. 2 cases in the control group had pigmentation, experimental group had no pigmentation. Conclusion:The clinical effect of combined carbon dioxide laser silicone gel in the treatment of acne scar[2] is prominent, with little adverse reaction.%目的:探讨二氧化碳点阵激光技术[1]联合硅酮凝胶在面部痤疮瘢痕上的治疗效果及不良反应,并分析。方法:点阵激光是一种通过点状穿透而剥脱的技术,拥有高效能、穿透深的二氧化碳激光

  9. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    OpenAIRE

    Luigjes, B.

    2012-01-01

    This thesis is a study of the preparation and thermodynamic properties of magnetic colloids. First, two types of magnetic model colloids are investigated: composite colloids and single-domain nanoparticles. Thermodynamics of magnetic colloids is studied using analytical centrifugation, including a specially adapted centrifuge for measuring heavy and strongly light absorbing colloids. Magnetic composite colloids can be prepared from thermodynamically stable Pickering emulsions of 3-methacrylox...

  10. Selective porous gates made from colloidal silica nanoparticles

    Directory of Open Access Journals (Sweden)

    Roberto Nisticò

    2015-11-01

    Full Text Available Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS, and using polystyrene-block-poly(ethylene oxide (PS-b-PEO copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field. Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

  11. Silicon Spintronics

    NARCIS (Netherlands)

    Jansen, R.

    2008-01-01

    Integration of magnetism and mainstream semiconductor electronics could impact information technology in ways beyond imagination. A pivotal step is implementation of spin-based electronic functionality in silicon devices. Remarkable progress made during the last two years gives confidence that this

  12. Deposition of latex colloids at rough mineral surfaces: an analogue study using nanopatterned surfaces.

    Science.gov (United States)

    Krishna Darbha, Gopala; Fischer, Cornelius; Michler, Alex; Luetzenkirchen, Johannes; Schäfer, Thorsten; Heberling, Frank; Schild, Dieter

    2012-04-24

    Deposition of latex colloids on a structured silicon surface was investigated. The surface with well-defined roughness and topography pattern served as an analogue for rough mineral surfaces with half-pores in the submicrometer size. The silicon topography consists of a regular pit pattern (pit diameter = 400 nm, pit spacing = 400 nm, pit depth = 100 nm). Effects of hydrodynamics and colloidal interactions in transport and deposition dynamics of a colloidal suspension were investigated in a parallel plate flow chamber. The experiments were conducted at pH ∼ 5.5 under both favorable and unfavorable adsorption conditions using carboxylate functionalized colloids to study the impact of surface topography on particle retention. Vertical scanning interferometry (VSI) was applied for both surface topography characterization and the quantification of colloidal retention over large fields of view. The influence of particle diameter variation (d = 0.3-2 μm) on retention of monodisperse as well as polydisperse suspensions was studied as a function of flow velocity. Despite electrostatically unfavorable conditions, at all flow velocities, an increased retention of colloids was observed at the rough surface compared to a smooth surface without surface pattern. The impact of surface roughness on retention was found to be more significant for smaller colloids (d = 0.3, 0.43 vs. 1, 2 μm). From smooth to rough surfaces, the deposition rate of 0.3 and 0.43 μm colloids increased by a factor of ∼2.7 compared to a factor of 1.2 or 1.8 for 1 and 2 μm colloids, respectively. For a substrate herein, with constant surface topography, the ratio between substrate roughness and radius of colloid, Rq/rc, determined the deposition efficiency. As Rq/rc increased, particle-substrate overall DLVO interaction energy decreased. Larger colloids (1 and 2 μm) beyond a critical velocity (7 × 10(-5) and 3 × 10(-6) m/s) (when drag force exceeds adhesion force) tend to detach from the surface

  13. Fabricating colloidal crystals and construction of ordered nanostructures

    Directory of Open Access Journals (Sweden)

    Sun Zhiqiang

    2006-01-01

    Full Text Available AbstractColloidal crystals of polymeric or inorganic microspheres are of extensive interest due to their potential applications in such as sensing, optics, photonic bandgap and surface patterning. The article highlights a set of approaches developed in our group, which are efficient to prepare colloidal crystals with ordered voids, patterned colloidal crystals on non-planar surfaces, heterogeneous colloidal crystals of different building blocks, colloidal crystals composed of non-spherical polyhedrons, and colloidal crystals of non-close-packed colloidal microspheres in particular. The use of these colloidal crystals as templates for different microstructures range from nanoscale to micron-scale is also summarized.

  14. Silicon nanocrystals as handy biomarkers

    Science.gov (United States)

    Fujioka, Kouki; Hoshino, Akiyoshi; Manabe, Noriyoshi; Futamura, Yasuhiro; Tilley, Richard; Yamamoto, Kenji

    2007-02-01

    Quantum dots (QDs) have brighter and longer fluorescence than organic dyes. Therefore, QDs can be applied to biotechnology, and have capability to be applied to medical technology. Currently, among the several types of QDs, CdSe with a ZnS shell is one of the most popular QDs to be used in biological experiments. However, when the CdSe QDs were applied to clinical technology, potential toxicological problems due to CdSe core should be considered. To eliminate the problem, silicon nanocrystals, which have the potential of biocompatibility, could be a candidate of alternate probes. Silicon nanocrystals have been synthesized using several techniques such as aerosol, electrochemical etching, laser pyrolysis, plasma deposition, and colloids. Recently, the silicon nanocrystals were reported to be synthesized in inverse micelles and also stabilized with 1-heptene or allylamine capping. Blue fluorescence of the nanocrystals was observed when excited with a UV light. The nanocrystals covered with 1-heptene are hydrophobic, whereas the ones covered with allylamine are hydrophilic. To test the stability in cytosol, the water-soluble nanocrystals covered with allylamine were examined with a Hela cell incorporation experiment. Bright blue fluorescence of the nanocrystals was detected in the cytosol when excited with a UV light, implying that the nanocrystals were able to be applied to biological imaging. In order to expand the application range, we synthesized and compared a series of silicon nanocrystals, which have variable surface modification, such as alkyl group, alcohol group, and odorant molecules. This study will provide a wider range of optoelectronic applications and bioimaging technology.

  15. Lithographically patterned silicon nanostructures on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Megouda, Nacera [Institut de Recherche Interdisciplinaire (IRI, USR 3078), Universite Lille1, Parc de la Haute Borne, 50 Avenue de Halley-BP 70478, 59658 Villeneuve d' Ascq and Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, CNRS-8520), Cite Scientifique, Avenue Poincare-B.P. 60069, 59652 Villeneuve d' Ascq (France); Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Unite de Developpement de la Technologie du Silicium (UDTS), 2 Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Alger (Algeria); Piret, Gaeelle; Galopin, Elisabeth; Coffinier, Yannick [Institut de Recherche Interdisciplinaire (IRI, USR 3078), Universite Lille1, Parc de la Haute Borne, 50 Avenue de Halley-BP 70478, 59658 Villeneuve d' Ascq and Institut d' Electronique, de Microelectronique et de Nanotechnologie (IEMN, CNRS-8520), Cite Scientifique, Avenue Poincare-B.P. 60069, 59652 Villeneuve d' Ascq (France); Hadjersi, Toufik, E-mail: hadjersi@yahoo.com [Unite de Developpement de la Technologie du Silicium (UDTS), 2 Bd. Frantz Fanon, B.P. 140 Alger-7 merveilles, Alger (Algeria); Elkechai, Omar [Faculte des Sciences, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); and others

    2012-06-01

    The paper reports on controlled formation of silicon nanostructures patterns by the combination of optical lithography and metal-assisted chemical dissolution of crystalline silicon. First, a 20 nm-thick gold film was deposited onto hydrogen-terminated silicon substrate by thermal evaporation. Gold patterns (50 {mu}m Multiplication-Sign 50 {mu}m spaced by 20 {mu}m) were transferred onto the silicon wafer by means of photolithography. The etching process of crystalline silicon in HF/AgNO{sub 3} aqueous solution was studied as a function of the silicon resistivity, etching time and temperature. Controlled formation of silicon nanowire arrays in the unprotected areas was demonstrated for highly resistive silicon substrate, while silicon etching was observed on both gold protected and unprotected areas for moderately doped silicon. The resulting layers were characterized using scanning electron microscopy (SEM).

  16. Silicon nanocrystal-noble metal hybrid nanoparticles

    Science.gov (United States)

    Sugimoto, H.; Fujii, M.; Imakita, K.

    2016-05-01

    We report a novel and facile self-limiting synthesis route of silicon nanocrystal (Si NC)-based colloidally stable semiconductor-metal (gold, silver and platinum) hybrid nanoparticles (NPs). For the formation of hybrid NPs, we employ ligand-free colloidal Si NCs with heavily boron (B) and phosphorus (P) doped shells. By simply mixing B and P codoped colloidal Si NCs with metal salts, hybrid NPs consisting of metal cores and Si NC shells are spontaneously formed. We demonstrate the synthesis of highly uniform and size controllable hybrid NPs. It is shown that codoped Si NCs act as a reducing agent for metal salts and also as a protecting layer to stop metal NP growth. The process is thus self-limiting. The development of a variety of Si NC-based hybrid NPs is a promising first step for the design of biocompatible multifunctional NPs with broad material choices for biosensing, bioimaging and solar energy conversion.We report a novel and facile self-limiting synthesis route of silicon nanocrystal (Si NC)-based colloidally stable semiconductor-metal (gold, silver and platinum) hybrid nanoparticles (NPs). For the formation of hybrid NPs, we employ ligand-free colloidal Si NCs with heavily boron (B) and phosphorus (P) doped shells. By simply mixing B and P codoped colloidal Si NCs with metal salts, hybrid NPs consisting of metal cores and Si NC shells are spontaneously formed. We demonstrate the synthesis of highly uniform and size controllable hybrid NPs. It is shown that codoped Si NCs act as a reducing agent for metal salts and also as a protecting layer to stop metal NP growth. The process is thus self-limiting. The development of a variety of Si NC-based hybrid NPs is a promising first step for the design of biocompatible multifunctional NPs with broad material choices for biosensing, bioimaging and solar energy conversion. Electronic supplementary information (ESI) available: Additional TEM images and extinction spectra of Si-metal hybrid NPs are shown in Fig. S1

  17. Structural color from colloidal glasses

    Science.gov (United States)

    Magkiriadou, Sofia

    When a material has inhomogeneities at a lengthscale comparable to the wavelength of light, interference can give rise to structural colors: colors that originate from the interaction of the material's microstructure with light and do not require absorbing dyes. In this thesis we study a class of these materials, called photonic glasses, where the inhomogeneities form a dense and random arrangement. Photonic glasses have angle-independent structural colors that look like those of conventional dyes. However, when this work started, there was only a handful of colors accessible with photonic glasses, mostly hues of blue. We use various types of colloidal particles to make photonic glasses, and we study, both theoretically and experimentally, how the optical properties of these glasses relate to their structure and constituent particles. Based on our observations from glasses of conventional particles, we construct a theoretical model that explains the scarcity of yellow, orange, and red photonic glasses. Guided by this model, we develop novel colloidal systems that allow a higher degree of control over structural color. We assemble glasses of soft, core-shell particles with scattering cores and transparent shells, where the resonant wavelength can be tuned independently of the reflectivity. We then encapsulate glasses of these core-shell particles into emulsion droplets of tunable size; in this system, we observe, for the first time, angle-independent structural colors that cover the entire visible spectrum. To enhance color saturation, we begin experimenting with inverse glasses, where the refractive index of the particles is lower than the refractive index of the medium, with promising results. Finally, based on our theoretical model for scattering from colloidal glasses, we begin an exploration of the color gamut that could be achieved with this technique, and we find that photonic glasses are a promising approach to a new type of long-lasting, non-toxic, and

  18. The hydrodynamics of colloidal gelation.

    Science.gov (United States)

    Varga, Zsigmond; Wang, Gang; Swan, James

    2015-12-14

    Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions.

  19. Structured fluids polymers, colloids, surfactants

    CERN Document Server

    Witten, Thomas A

    2010-01-01

    Over the last thirty years, the study of liquids containing polymers, surfactants, or colloidal particles has developed from a loose assembly of facts into a coherent discipline with substantial predictive power. These liquids expand our conception of what condensed matter can do. Such structured-fluid phenomena dominate the physical environment within living cells. This book teaches how to think of these fluids from a unified point of view showing the far-reaching effects ofthermal fluctuations in producing forces and motions. Keeping mathematics to a minimum, the book seeks the simplest expl

  20. Frost Heave in Colloidal Soils

    KAUST Repository

    Peppin, Stephen

    2011-01-01

    We develop a mathematical model of frost heave in colloidal soils. The theory accountsfor heave and consolidation while not requiring a frozen fringe assumption. Two solidificationregimes occur: a compaction regime in which the soil consolidates to accommodate the ice lenses, and a heave regime during which liquid is sucked into the consolidated soil from an external reservoir, and the added volume causes the soil to heave. The ice fraction is found to vary inversely with thefreezing velocity V , while the rate of heave is independent of V , consistent with field and laboratoryobservations. © 2011 Society for Industrial and Applied Mathematics.

  1. Thermodynamic perturbation theory for self assembling mixtures of multi - patch colloids and colloids with spherically symmetric attractions

    OpenAIRE

    Marshall, B. D.; Chapman, W. G.

    2013-01-01

    In this paper we extend our previous theory [B. D. Marshall and W.G. Chapman, J. Chem. Phys. 139, 104904 (2013)] for mixtures of single patch colloids (p colloids) and colloids with spherically symmetric attractions (s colloids) to the case that the p colloids can have multiple patches. The theory is then applied to the case of a binary mixture of bi-functional p colloids which have an A and B type patch and s colloids which are not attracted to other s colloids and are attracted to only patc...

  2. Thermodynamic perturbation theory for self assembling mixtures of multi - patch colloids and colloids with spherically symmetric attractions

    OpenAIRE

    Marshall, B. D.; Chapman, W G

    2013-01-01

    In this paper we extend our previous theory [B. D. Marshall and W.G. Chapman, J. Chem. Phys. 139, 104904 (2013)] for mixtures of single patch colloids (p colloids) and colloids with spherically symmetric attractions (s colloids) to the case that the p colloids can have multiple patches. The theory is then applied to the case of a binary mixture of bi-functional p colloids which have an A and B type patch and s colloids which are not attracted to other s colloids and are attracted to only patc...

  3. Colloid transport in dual-permeability media

    Science.gov (United States)

    It has been widely reported that colloids can travel faster and over longer distances in natural structured porous media than in uniform structureless media used in laboratory studies. The presence of preferential pathways for colloids in the subsurface environment is of concern because of the incre...

  4. Colloidal iron(III) pyrophosphate particles

    NARCIS (Netherlands)

    Rossi, L.; Velikov, K. P.; Philipse, A.P.

    2014-01-01

    Ferric pyrophosphate is a widely used material in the area of mineral fortification but its synthesis and properties in colloidal form are largely unknown. In this article, we report on the synthesis and characterisation of colloidal iron(III) pyrophosphate particles with potential for application a

  5. Structural transitions in condensed colloidal virus phases

    Science.gov (United States)

    Schmidt, Nathan; Barr, Steve; Udit, Andrew; Gutierrez, Leonardo; Nguyen, Thanh; Finn, M. G.; Luijten, Erik; Wong, Gerard

    2010-03-01

    Analogous to monatomic systems colloidal phase behavior is entirely determined by the interaction potential between particles. This potential can be tuned using solutes such as multivalent salts and polymers with varying affinity for the colloids to create a hierarchy of attractions. Bacteriophage viruses are a naturally occurring type of colloidal particle with characteristics difficult to achieve by laboratory synthesis. They are monodisperse, nanometers in size, and have heterogeneous surface charge distributions. We use the MS2 and Qbeta bacteriophages (diameters 27-28nm) to understand the interplay between different attraction mechanisms on nanometer-sized colloids. Small Angle X-ray Scattering (SAXS) is used to characterize the inter-particle interaction between colloidal viruses using several polymer species and different salt types.

  6. 掺杂钙银介孔氧化硅凝胶抗菌止血材料的研究%Study on Hemostatic Materials of Mesoporous Silicon Dioxide Doped Ca and Ag with Antibacterial Properties

    Institute of Scientific and Technical Information of China (English)

    陈于; 李文锐; 徐灿; 苏佳灿; 李明; 刘昌胜

    2012-01-01

    An antibacterial hemostatic material of mesoporous silicon oxide gel doped with Ca and Ag (m-SCA) gel was fabricated by using cetykrimethylammonium bromide(CTAB) as templates and Sol-Gel process. The results showed that m-SCA with mesoporous structure had the surface area of 416 m2/g and pore size of around 2 nm. The m-SCA with high surface area and good clotting function could significantly shorten the prothrombin time (PT) and activated partial thromboplastin time (APTT). The m-SCA containing a small quantity of Ag had no obvious effects on its clotting properties while Ca in m-SCA could promote clotting. The m-SCA doped 0.02wt% Ag without cyto-toxicity had good antibacterial properties against E.coli. Animal experimental results showed that the m-SCA could control hemorrhage and shorten the bleeding time of rabbit ear wound, showing good hemostatic properties. It sug-gestes that the m-SCA is a good hemostatic material with antibacterial properties.%以十六烷基三甲基溴化铵(CTAB)为模板,用溶胶-凝胶法合成了掺杂钙银介孔氧化硅凝胶(m-SCA)抗菌止血材料,结果表明:m-SCA具有介孔结构,比表面积为416 m2/g,孔径在2 nm左右.高比表面积的m-SCA具有很好的凝血功能,能明显缩短血液的凝血酶原时间(PT)和部分凝血活酶时间(APTT).含少量银的m-SCA对其凝血性能没有明显影响,而m-SCA中的钙能促进凝血.含银0.02wt%的m-SCA无细胞毒性,对大肠杆菌有明显的抑制作用.动物试验表明:m-SCA具有很好的止血性能,能阻止兔耳伤口的流血并缩短其流血时间m-SCA是一种有很好应用前景的抗菌止血材料.

  7. Photoinduced Formation of Colloidal Silver in Nitrocellulose Solutions Containing Titanium Alkoxides

    Science.gov (United States)

    Kulak, A. I.; Branitsky, G. A.

    2016-07-01

    The study shows the possibility of photo-induced reduction of silver nitrate and formation of stable colloidal silver particles in an isopropanol-N,N-dimethylacetamide solution of titanium alkoxide (polybutyl titanate) stabilized by nitrocellulose. It is established that titanium alkoxide and the products of its partial hydrolysis in the liquid composition play the role of a photocatalyst for the reduction of silver ions; the introduction of nitric or acetic acid additives to the composition significantly increases its photosensitivity. The films deposited from the liquid composition, previously irradiated with visible or UV light, consist of hydrated titanium dioxide and nitrocellulose with incorporated colloidal silver. Thermal treatment of the films at 150-245°C leads to the decomposition of nitrocellulose and an increase in the absorption by silver particles.

  8. Simultaneous synthesis of anatase colloidal and multiple-branched rutile TiO{sub 2} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Trong Tung; Duong, Ngoc Huyen [School of Engineering Physics, Hanoi University of Science and Technology, Hanoi (Viet Nam); Mai, Xuan Dung [Dept. of Chemistry, Hanoi Pedagogical University No2, Vinh Phuc (Viet Nam)

    2017-03-15

    Facile synthesis of titanium dioxide (TiO{sub 2} ) nanostructures with controllability over their cystallinity, dimensions, and shape is in demand for diverse optoelectronic applications. Anatase colloidal particles and precipitates of rutile bundles were synthesized simultaneously using HCl catalyzed sol–gel process with titanium tetrachloride as Ti precursor. The crystallinity and the morphology of these two separable TiO{sub 2} phases were studied by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The results show that by varying HCl concentration during synthesis, dimensions of colloidal anatase can be tuned from spherical particles with a diameter of 2–5 nm to nanorods of dimension of 4 nm (width) × 14 nm (length). The rutile bundles whose size increased with aging time consisted of multiple branches with elongation along c-axis. Both anatase nanorods and rutile bundles can be applied as highly efficient photocatalysts or electron conduits.

  9. Stable colloids in molten inorganic salts

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao; Dasbiswas, Kinjal; Ludwig, Nicholas B.; Han, Gang; Lee, Byeongdu; Vaikuntanathan, Suri; Talapin, Dimitri V.

    2017-02-16

    A colloidal solution is a homogeneous dispersion of particles or droplets of one phase (solute) in a second, typically liquid, phase (solvent). Colloids are ubiquitous in biological, chemical and technological processes1, 2, homogenizing highly dissimilar constituents. To stabilize a colloidal system against coalescence and aggregation, the surface of each solute particle is engineered to impose repulsive forces strong enough to overpower van der Waals attraction and keep the particles separated from each other2. Electrostatic stabilization3, 4 of charged solutes works well in solvents with high dielectric constants, such as water (dielectric constant of 80). In contrast, colloidal stabilization in solvents with low polarity, such as hexane (dielectric constant of about 2), can be achieved by decorating the surface of each particle of the solute with molecules (surfactants) containing flexible, brush-like chains2, 5. Here we report a class of colloidal systems in which solute particles (including metals, semiconductors and magnetic materials) form stable colloids in various molten inorganic salts. The stability of such colloids cannot be explained by traditional electrostatic and steric mechanisms. Screening of many solute–solvent combinations shows that colloidal stability can be traced to the strength of chemical bonding at the solute–solvent interface. Theoretical analysis and molecular dynamics modelling suggest that a layer of surface-bound solvent ions produces long-ranged charge-density oscillations in the molten salt around solute particles, preventing their aggregation. Colloids composed of inorganic particles in inorganic melts offer opportunities for introducing colloidal techniques to solid-state science and engineering applications.

  10. Colloid-Associated Radionuclide Concentration Limits: ANL

    Energy Technology Data Exchange (ETDEWEB)

    C. Mertz

    2000-12-21

    The purpose and scope of this report is to describe the analysis of available colloidal data from waste form corrosion tests at Argonne National Laboratory (ANL) to extract characteristics of these colloids that can be used in modeling their contribution to the source term for sparingly soluble radioelements (e.g., Pu). Specifically, the focus is on developing a useful description of the following waste form colloid characteristics: (1) composition, (2) size distribution, and (3) quantification of the rate of waste form colloid generation. The composition and size distribution information are intended to support analysis of the potential transport of the sparingly soluble radionuclides associated with the waste form colloids. The rate of colloid generation is intended to support analysis of the waste form colloid-associated radionuclide concentrations. In addressing the above characteristics, available data are interpreted to address mechanisms controlling colloid formation and stability. This report was developed in accordance with the ''Technical Work Plan for Waste Form Degradation Process Model Report for SR'' (CRWMS M&O 2000). Because the end objective is to support the source term modeling we have organized the conclusions into two categories: (1) data analysis conclusions and (2) recommendations for colloid source term modeling. The second category is included to facilitate use of the conclusions from the data analysis in the abstraction of a colloid source term model. The data analyses and conclusions that are presented in this report are based on small-scale laboratory tests conducted on a limited number of waste glass compositions and spent fuel types.

  11. Hollow microsphere with mesoporous shell by Pickering emulsion polymerization as a potential colloidal collector for organic contaminants in water.

    Science.gov (United States)

    Guan, Yinyan; Meng, Xiaohui; Qiu, Dong

    2014-04-08

    Submicrometer hollow microspheres with mesoporous shells were prepared by a simple one-pot strategy. Colloidal silica particles were used as a particle stabilizer to emulsify the oil phase, which was composed of a polymerizable silicon monomer (TPM) and an inert organic solvent (PEA). The low interfacial tension between colloidal silica particles and TPM helped to form a Pickering emulsion with small droplet sizes. After the polymerization of TPM, the more hydrophobic PEA formed a liquid core, leading to a hollow structure after its removal by evaporation. BET results indicated that the shell of a hollow particle was mesoporous with a specific surface area over 400 m(2)·g(-1). With PEA as the core and silica as the shell, each resultant hollow particle had a hydrophobic cavity and an amphiphilic surface, thus serving as a good colloidal collector for hydrophobic contaminants in water.

  12. Diffusion in active magnetic colloids

    Energy Technology Data Exchange (ETDEWEB)

    Taukulis, R.; Cebers, A., E-mail: aceb@tesla.sal.lv

    2014-11-15

    Properties of active colloids of circle swimmers are reviewed. As a particular example of active magnetic colloids the magnetotactic bacteria under the action of a rotating magnetic field is considered. The relation for a diffusion coefficient due to the random switching of the direction of rotation of their rotary motors is derived on the basis of the master equation. The obtained relation is confirmed by the direct numerical simulation of random trajectory of a magnetotactic bacterium under the action of the Poisson type internal noise due to the random switching of rotary motors. The results obtained are in qualitative and quantitative agreement with the available experimental results and allow one to determine the characteristic time between the switching events of a rotary motor of the bacterium. - Highlights: • Magnetotactic bacteria in a rotating field behaves as circle swimmers. • Diffusion coefficient of these swimmers due to the random switching of rotary motors is calculated. • Results are in good qualitative and quantitative agreement with available experimental results.

  13. Dynamics of the colloidal suspensions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-yan; MA Hong-ru

    2006-01-01

    This article offers a survey on our current knowledge of the dynamics of the colloidal suspension,where each particle experiences the friction force with solvent,hydrodynamic interaction,and potential force from surrounding particles and thermodynamic force.It further contains a summary of the basic concepts about microstructures and equilibrium properties,and of analytical and numerical methods,which are relevant for the theoretical description of the suspensions.The description of the dynamics of colloidal particles,based on the generalized Smoluchowski equation,is justified for the time scale accessible in DLS experiments.The combined influence of hard sphere or electrostatic potential and solvent-mediated hydrodynamic interaction on the short-time dynamics of monodisperse suspensions is investigated in detail.A thorough study of tracer-diffusion in hard sphere and charge-stabilized suspensions is presented.Mean-square displacements and long-time tracer-diffusion coefficients are calculated with two alternative approximations,i.e.,a mode-coupling scheme and a single relaxation time ansatz.

  14. Gel trapping of dense colloids.

    Science.gov (United States)

    Laxton, Peter B; Berg, John C

    2005-05-01

    Phase density differences in sols, foams, or emulsions often lead to sedimentation or creaming, causing problems for materials where spatial uniformity over extended periods of time is essential. The problem may be addressed through the use of rheology modifiers in the continuous phase. Weak polymer gels have found use for this purpose in the food industry where they appear to be capable of trapping dispersoid particles in a three-dimensional matrix while displaying water-like viscosities at low shear. Attempts to predict sedimentation stability in terms of particle properties (size, shape, density difference) and gel yield stress have led to qualitative success for suspensions of large particles. The effect of particle size, however, in particular the case in which colloidal dimensions are approached, has not been investigated. The present work seeks to determine useful stability criteria for colloidal dispersions in terms of readily accessible viscoelastic descriptors. Results are reported for systems consisting of 12 microm poly(methyl methacrylate) (PMMA) spheres dispersed in aqueous gellan gum. Monovalent salt concentration is varied to control rheological properties, and sedimentation/centrifugation experiments are performed to determine dispersion stability. Necessary conditions for stability consist of a minimum yield stress together with a value of tan delta less than unity.

  15. Silicon: A Review of Its Potential Role in the Prevention and Treatment of Postmenopausal Osteoporosis

    Directory of Open Access Journals (Sweden)

    Charles T. Price

    2013-01-01

    Full Text Available Physicians are aware of the benefits of calcium and vitamin D supplementation. However, additional nutritional components may also be important for bone health. There is a growing body of the scientific literature which recognizes that silicon plays an essential role in bone formation and maintenance. Silicon improves bone matrix quality and facilitates bone mineralization. Increased intake of bioavailable silicon has been associated with increased bone mineral density. Silicon supplementation in animals and humans has been shown to increase bone mineral density and improve bone strength. Dietary sources of bioavailable silicon include whole grains, cereals, beer, and some vegetables such as green beans. Silicon in the form of silica, or silicon dioxide (SiO2, is a common food additive but has limited intestinal absorption. More attention to this important mineral by the academic community may lead to improved nutrition, dietary supplements, and better understanding of the role of silicon in the management of postmenopausal osteoporosis.

  16. Sampling Artifacts from Conductive Silicone Tubing

    Energy Technology Data Exchange (ETDEWEB)

    Timko, Michael T.; Yu, Zhenhong; Kroll, Jesse; Jayne, John T.; Worsnop, Douglas R.; Miake-Lye, Richard C.; Onasch, Timothy B.; Liscinsky, David; Kirchstetter, Thomas W.; Destaillats, Hugo; Holder, Amara L.; Smith, Jared D.; Wilson, Kevin R.

    2009-05-15

    We report evidence that carbon impregnated conductive silicone tubing used in aerosol sampling systems can introduce two types of experimental artifacts: 1) silicon tubing dynamically absorbs carbon dioxide gas, requiring greater than 5 minutes to reach equilibrium and 2) silicone tubing emits organic contaminants containing siloxane that adsorb onto particles traveling through it and onto downstream quartz fiber filters. The consequence can be substantial for engine exhaust measurements as both artifacts directly impact calculations of particulate mass-based emission indices. The emission of contaminants from the silicone tubing can result in overestimation of organic particle mass concentrations based on real-time aerosol mass spectrometry and the off-line thermal analysis of quartz filters. The adsorption of siloxane contaminants can affect the surface properties of aerosol particles; we observed a marked reduction in the water-affinity of soot particles passed through conductive silicone tubing. These combined observations suggest that the silicone tubing artifacts may have wide consequence for the aerosol community and should, therefore, be used with caution. Gentle heating, physical and chemical properties of the particle carriers, exposure to solvents, and tubing age may influence siloxane uptake. The amount of contamination is expected to increase as the tubing surface area increases and as the particle surface area increases. The effect is observed at ambient temperature and enhanced by mild heating (<100 oC). Further evaluation is warranted.

  17. Fluid-fluid demixing curves for colloid-polymer mixtures in a random colloidal matrix

    Science.gov (United States)

    Annunziata, Mario Alberto; Pelissetto, Andrea

    2011-12-01

    We study fluid-fluid phase separation in a colloid-polymer mixture adsorbed in a colloidal porous matrix close to the θ point. For this purpose we consider the Asakura-Oosawa model in the presence of a quenched matrix of colloidal hard spheres. We study the dependence of the demixing curve on the parameters that characterize the quenched matrix, fixing the polymer-to-colloid size ratio to 0.8. We find that, to a large extent, demixing curves depend only on a single parameter f, which represents the volume fraction which is unavailable to the colloids. We perform Monte Carlo simulations for volume fractions f equal to 40% and 70%, finding that the binodal curves in the polymer and colloid packing-fraction plane have a small dependence on disorder. The critical point instead changes significantly: for instance, the colloid packing fraction at criticality increases with increasing f. Finally, we observe for some values of the parameters capillary condensation of the colloids: a bulk colloid-poor phase is in chemical equilibrium with a colloid-rich phase in the matrix.

  18. Mechanical properties of polymeric composites with carbon dioxide particles

    Science.gov (United States)

    Moskalyuk, O. A.; Samsonov, A. M.; Semenova, I. V.; Smirnova, V. E.; Yudin, V. E.

    2017-02-01

    Nanocomposites consisting of a polymethylmethacrylate or polystyrene matrix with embedded silicon dioxide nanoparticles surface-modified by silazanes have been prepared by melting technology. The influence of particles on viscoelastic properties of the nanocomposites has been studied using dynamic mechanical analysis. It has been revealed that the addition of 20 wt % of SiO2 raises the flexural modulus of the nanocomposites by 30%.

  19. Photochemical manipulation of colloidal structures in liquid-crystal colloids

    Science.gov (United States)

    Yamamoto, T.; Tabe, Y.; Yokoyama, H.

    2007-05-01

    We investigated photochemical manipulation of physical properties and colloidal structures in liquid-crystal (LC) colloids containing azobenzene compounds. In a LC suspension where polymeric particles were dispersed in a host LC, we achieved photochemical control of light-scattering properties of the suspension. In a nematic phase, when the suspension was sandwiched with two glass plates, the film became opaque. This would be attributable to an appearance of both multidomain structures of LC alignment and mismatches of refractive indices between the materials. The opaque state turned into a transparent one when a nematic-to-isotropic phase transition was induced by the trans-to-cis photoisomerization of the azo-dye. This will result from a disappearance of both the multidomain structures and the refractive-index mismatches in the isotropic phase. The transparent film went back into the initial opaque film when the nematic phase was obtained by the cis-to-trans photoisomerization. In a LC emulsion in which glycerol or water droplets were dispersed in liquid crystals, we examined photochemical change of defect structures and inter-droplet distances by the photochemical manner. At the initial state, Saturn ring and hedgehog defects were formed around the droplets. For the glycerol droplets, we observed structural transformations between Saturn ring and boojums on irradiation with ultra-violet and visible light. For the water droplets, the inter-droplet distances varied by changing defect size on the irradiation. These phenomena would result from modulation of anchoring conditions of the droplets by the photoisomerization of the azo-dyes.

  20. Fabrication of size-controllable hexagonal non-close-packed colloidal crystals and binary colloidal crystals by pyrolysis combined with plasma-electron coirradiation of polystyrene colloidal monolayer.

    Science.gov (United States)

    Kim, Jae Joon; Li, Yue; Lee, Eun Je; Cho, Sung Oh

    2011-03-15

    We present an unprecedented and systematic route to controllably fabricate hexagonal non-close-packed (hncp) monolayer colloidal crystals and binary colloidal crystals (BCCs) based on plasma-electron coirradiation of polystyrene colloidal monolayers followed by thermal decomposition. Hncp colloidal crystals with tunable particle sizes and periods could be fabricated by changing the pristine colloidal particle size and the thermal decomposition time. In addition, BCCs and trimodal colloidal crystals that are composed of different-sized colloidal particles can also be fabricated by adding small particles on the prepared hncp colloidal crystals. Both the particle size ratio and the volume fraction of the BCCs can be widely tuned. These hncp colloidal crystals and BCCs have various potential applications as optical and photonic materials as well as in catalysis and sensors.

  1. Phosphate binding by natural iron-rich colloids in streams

    NARCIS (Netherlands)

    Baken, S.; Moens, C.; Griffioen, J.J.; Smolders, E.

    2016-01-01

    Phosphorus (P) in natural waters may be bound to iron (Fe) bearing colloids. However, the natural variation in composition and P binding strength of these colloids remain unclear. We related the composition of "coarse colloids" (colloids in the 0.1-1.2 μm size range) in 47 Belgian streams to the

  2. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    NARCIS (Netherlands)

    Luigjes, B.

    2012-01-01

    This thesis is a study of the preparation and thermodynamic properties of magnetic colloids. First, two types of magnetic model colloids are investigated: composite colloids and single-domain nanoparticles. Thermodynamics of magnetic colloids is studied using analytical centrifugation, including a

  3. Synthesis and Analytical Centrifugation of Magnetic Model Colloids

    NARCIS (Netherlands)

    Luigjes, B.

    2012-01-01

    This thesis is a study of the preparation and thermodynamic properties of magnetic colloids. First, two types of magnetic model colloids are investigated: composite colloids and single-domain nanoparticles. Thermodynamics of magnetic colloids is studied using analytical centrifugation, including a s

  4. Phosphate binding by natural iron-rich colloids in streams

    NARCIS (Netherlands)

    Baken, S.; Moens, C.; Griffioen, J.J.; Smolders, E.

    2016-01-01

    Phosphorus (P) in natural waters may be bound to iron (Fe) bearing colloids. However, the natural variation in composition and P binding strength of these colloids remain unclear. We related the composition of "coarse colloids" (colloids in the 0.1-1.2 μm size range) in 47 Belgian streams to the che

  5. Direct visualization of colloidal liquids

    Science.gov (United States)

    Durand, Richard Vernon

    We have investigated various colloidal systems consisting of aqueous suspensions of micron sized polystyrene particles. These systems are appealing because they provide a fertile testing ground for theories of both the liquid and solid states, as well as for theories describing hydrodynamic interactions. Our first study of colloidal systems was motivated by some interesting observations we made while looking at a suspension under a light microscope. We, as well as other workers, noticed that particles undergoing Brownian motion can appear to linger around each other for long periods of time. The question arose as to whether this lingering was a product of interparticle interactions, or was an artifact due to random thermal motion and projection onto a two dimensional image plane. We found that the latter was true, which drove home the idea that we must be wary of our own biases when making scientific observations. During the course of the research on this lingering behavior, we developed a mathematical technique for generating successively more accurate approximate analytical solutions to initial value linear partial differential equations which are first order in time and have no mixing of spatial and time derivatives. This formalism is especially useful for diffusion problems, since the analytical approximation conserves probability at each order of approximation. Our next experimental effort involved colloidal systems in which the suspending medium was carefully prepared to promote long ranged electrostatic interactions between the particles. The interaction potential in such a suspension has been the topic of much research recently. Using digital video microscopy, as well as techniques we developed allowing the proper analysis of two dimensional data, we found that the interaction length in our samples was surprisingly short ranged compared to what we expected based on our water purification experiments. The problems with projection effects associated with two

  6. Interactions between radioactively labeled colloids and natural particles: Evidence for colloidal pumping

    Science.gov (United States)

    Wen, Liang-Saw; Santschi, Peter H.; Tang, Degui

    1997-07-01

    It has been hypothesized that colloidal forms of trace metals can be reactive intermediaries in the scavenging processes leading to the removal of their particulate forms. A series of radiotracer experiments using natural colloidal organic matter from Galveston Bay, USA were carried out in order to test this hypothesis. Suspended particle uptake of originally colloidally bound trace metals occurred in a matter of hours to days in estuarine waters. After ten days, the majority (>50%) of the colloidal trace metals had been transferred into the particulate phase (≥0.45 μm), except for 65Zn. Two distinctively different temporal regions of removal of colloidal trace metals were identified: a faster reaction during the first four hours, followed by a slower reaction after approximately one day. In a separate river water-seawater mixing experiment, the solid/solution partitioning of the radiotracers was investigated in the absence of suspended matter. About 30% of most of the elements, except Ag and Fe (˜60%), were associated with a newly formed particulate phase after eight days. There were two major trends: (1) the particulate fraction of 59Fe and 110Ag increased while the colloidal fraction decreased, suggesting a colloidal pumping mechanism. (2) The particulate fraction of 54Mn, 133Ba, 65Zn, 109Cd, 113Sn, and 60CO increased while the LMW (≤ 1 kDa) fraction decreased, suggesting a direct uptake into the particulate fraction with less involvement of a transitory colloidal phase. The values of the particle-water ( Kd) and colloid-water partitioning ( Kc) coefficients for most trace metals were similar to those observed in Galveston Bay waters, suggesting complementary results to field studies. The results from these experiments suggested two different pathways for colloidal tracer uptake by particles: (1) colloidal pumping of a major component (e.g., biopolymer) of the colloidal pool and (2) coagulation of trace components (e.g., phytochelatins) with varying

  7. Reducing charge trapping in PbS colloidal quantum dot solids

    Energy Technology Data Exchange (ETDEWEB)

    Balazs, D. M.; Nugraha, M. I.; Bisri, S. Z.; Loi, M. A., E-mail: m.a.loi@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747AG (Netherlands); Sytnyk, M.; Heiss, W. [Institute for Semiconductor and Solid State Physics, University of Linz, Altenbergerstr. 69, Linz 4040 (Austria)

    2014-03-17

    Understanding and improving charge transport in colloidal quantum dot solids is crucial for the development of efficient solar cells based on these materials. In this paper, we report high performance field-effect transistors based on lead-sulfide colloidal quantum dots (PbS CQDs) crosslinked with 3-mercaptopropionic acid (MPA). Electron mobility up to 0.03 cm{sup 2}/Vs and on/off ratio above 10{sup 5} was measured; the later value is the highest in the literature for CQD Field effect transistors with silicon-oxide gating. This was achieved by using high quality material and preventing trap generation during fabrication and measurement. We show that air exposure has a reversible p-type doping effect on the devices, and that intrinsically MPA is an n-type dopant for PbS CQDs.

  8. Reducing charge trapping in PbS colloidal quantum dot solids

    Science.gov (United States)

    Balazs, D. M.; Nugraha, M. I.; Bisri, S. Z.; Sytnyk, M.; Heiss, W.; Loi, M. A.

    2014-03-01

    Understanding and improving charge transport in colloidal quantum dot solids is crucial for the development of efficient solar cells based on these materials. In this paper, we report high performance field-effect transistors based on lead-sulfide colloidal quantum dots (PbS CQDs) crosslinked with 3-mercaptopropionic acid (MPA). Electron mobility up to 0.03 cm2/Vs and on/off ratio above 105 was measured; the later value is the highest in the literature for CQD Field effect transistors with silicon-oxide gating. This was achieved by using high quality material and preventing trap generation during fabrication and measurement. We show that air exposure has a reversible p-type doping effect on the devices, and that intrinsically MPA is an n-type dopant for PbS CQDs.

  9. Site-specific functionalization of anisotropic nanoparticles: from colloidal atoms to colloidal molecules

    DEFF Research Database (Denmark)

    Li, Fan; Yoo, Won Cheol; Beernink, Molly B

    2009-01-01

    Multipodal nanoparticles (NPs) with controlled tethers are promising principal building blocks, useful for constructing more complex materials, much like atoms are connected into more complex molecules. Here we report colloidal sphere templating as a viable means to create tetrapodal NPs with site......-specific tethers. Amorphous sol-gel materials were molded by the template into shaped NPs that mimic tetravalent atoms but on the length scale of colloids. Synthetic methods were developed to modify only the tips of the tetrapods with a range of possible functional groups to generate anisotropic NPs capable...... of directional bonding to other NPs. We also illustrate that sets of tethered "colloidal atoms" can assemble themselves into "colloidal molecules" with precise placement of the modifying colloids. The templating and tethering approaches to these anisotropic colloidal building blocks and the assembly methods...

  10. Oxyhydroxy Silicate Colloids: A New Type of Waterborne Actinide(IV) Colloids

    Science.gov (United States)

    Weiss, Stephan; Hennig, Christoph; Brendler, Vinzenz; Ikeda‐Ohno, Atsushi

    2016-01-01

    Abstract At the near‐neutral and reducing aquatic conditions expected in undisturbed ore deposits or in closed nuclear waste repositories, the actinides Th, U, Np, and Pu are primarily tetravalent. These tetravalent actinides (AnIV) are sparingly soluble in aquatic systems and, hence, are often assumed to be immobile. However, AnIV could become mobile if they occur as colloids. This review focuses on a new type of AnIV colloids, oxyhydroxy silicate colloids. We herein discuss the chemical characteristics of these colloids and the potential implication for their environmental behavior. The binary oxyhydroxy silicate colloids of AnIV could be potentially more mobile as a waterborne species than the well‐known mono‐component oxyhydroxide colloids. PMID:27957406

  11. The Ongoing Controversy: Crystalloids Versus Colloids.

    Science.gov (United States)

    Pierce, Janet D; Shen, Qiuhua; Thimmesch, Amanda

    2016-01-01

    There is still much debate over the optimal fluid to use for resuscitation. Different studies have indicated either crystalloid or colloid is the ideal intravenous solution to administer, based on mortality or various physiological parameters. Older studies found differences between crystalloids and colloids. However, with the evolving science of fluid administration, more recent studies have shown no differences in patient outcomes. This review article will provide an overview of these substances and discuss the advantages, disadvantages, and implications for giving crystalloids and colloids in clinical practice.

  12. Colloid and interface chemistry for nanotechnology

    CERN Document Server

    Kralchevsky, Peter

    2013-01-01

    Colloid and interface science dealt with nanoscale objects for nearly a century before the term nanotechnology was coined. An interdisciplinary field, it bridges the macroscopic world and the small world of atoms and molecules. Colloid and Interface Chemistry for Nanotechnology is a collection of manuscripts reflecting the activities of research teams that have been involved in the networking project Colloid and Interface Chemistry for Nanotechnology (2006-2011), Action D43, the European Science Foundation. The project was a part of the intergovernmental framework for Cooperation in Science an

  13. Carbon Nanomaterials as Antibacterial Colloids

    Directory of Open Access Journals (Sweden)

    Michael Maas

    2016-07-01

    Full Text Available Carbon nanomaterials like graphene, carbon nanotubes, fullerenes and the various forms of diamond have attracted great attention for their vast potential regarding applications in electrical engineering and as biomaterials. The study of the antibacterial properties of carbon nanomaterials provides fundamental information on the possible toxicity and environmental impact of these materials. Furthermore, as a result of the increasing prevalence of resistant bacteria strains, the development of novel antibacterial materials is of great importance. This article reviews current research efforts on characterizing the antibacterial activity of carbon nanomaterials from the perspective of colloid and interface science. Building on these fundamental findings, recent functionalization strategies for enhancing the antibacterial effect of carbon nanomaterials are described. The review concludes with a comprehensive outlook that summarizes the most important discoveries and trends regarding antibacterial carbon nanomaterials.

  14. Colloidal QDs-polymer nanocomposites

    Science.gov (United States)

    Gordillo, H.; Suárez, I.; Rodríguez-Cantó, P.; Abargues, R.; García-Calzada, R.; Chyrvony, V.; Albert, S.; Martínez-Pastor, J.

    2012-04-01

    Nanometer-size colloidal semiconductor nanocrystals, or Quantum Dots (NQD), are very prospective active centers because their light emission is highly efficient and temperature-independent. Nanocomposites based on the incorporation of QDs inside a polymer matrix are very promising materials for application in future photonic devices because they combine the properties of QDs with the technological feasibility of polymers. In the present work some basic applications of these new materials have been studied. Firstly, the fabrication of planar and linear waveguides based on the incorporation of CdS, CdSe and CdTe in PMMA and SU-8 are demonstrated. As a result, photoluminescence (PL) of the QDs are coupled to a waveguide mode, being it able to obtain multicolor waveguiding. Secondly, nanocomposite films have been evaluated as photon energy down-shifting converters to improve the efficiency of solar cells.

  15. Integrated Nanophotonic Silicon Devices for Next Generation Computing Chips

    Science.gov (United States)

    Djordjevic, Stevan

    Development of the computing platform of the future depends largely on high bandwidth interconnects at intra-die level. Silicon photonics, as an innately CMOS compatible technology, is a promising candidate for delivering terabit per second bandwidths through the use of wavelength division multiplex (WDM) signaling. Silicon photonic interconnects offer unmatched bandwidth, density, energy efficiency, latency and reach, compared with the electrical interconnects. WDM silicon photonic links are viewed today as a promising solution for resolving the inter/intra-chip communication bottlenecks for high performance computing systems. Towards its maturity, silicon photonic technology has to resolve the issues of waveguide propagation loss, density of device integration, thermal stability of resonant devices, heterogeneous integration of various materials and many other problems. This dissertation describes the development of integrated photonic technology on silicon and silicon nitride platforms in the increased order of device complexity, from the fabrication process of low loss waveguides and efficient off-chip coupling devices, to the die-size reconfigurable lattice filters for optical signal processing. Particular emphasis of the dissertation is on the demonstration of CMOS-compatible, athermal silicon ring modulators that potentially hold the key to solving the thermal problem of silicon photonic devices. The development of high quality amorphous titanium dioxide films with negative thermo-optic coefficient enabled the fabrication of gigahertz-bandwidth silicon ring modulators that can be made insensitive to ambient temperature changes.

  16. Nanoparticle-based etching of silicon surfaces

    Science.gov (United States)

    Branz, Howard; Duda, Anna; Ginley, David S.; Yost, Vernon; Meier, Daniel; Ward, James S.

    2011-12-13

    A method (300) of texturing silicon surfaces (116) such to reduce reflectivity of a silicon wafer (110) for use in solar cells. The method (300) includes filling (330, 340) a vessel (122) with a volume of an etching solution (124) so as to cover the silicon surface 116) of a wafer or substrate (112). The etching solution (124) is made up of a catalytic nanomaterial (140) and an oxidant-etchant solution (146). The catalytic nanomaterial (140) may include gold or silver nanoparticles or noble metal nanoparticles, each of which may be a colloidal solution. The oxidant-etchant solution (146) includes an etching agent (142), such as hydrofluoric acid, and an oxidizing agent (144), such as hydrogen peroxide. Etching (350) is performed for a period of time including agitating or stirring the etching solution (124). The etch time may be selected such that the etched silicon surface (116) has a reflectivity of less than about 15 percent such as 1 to 10 percent in a 350 to 1000 nanometer wavelength range.

  17. Hemorrhagic Colloid Cyst Presenting with Acute Hydrocephaly

    Science.gov (United States)

    Akhavan, Reza; Zandi, Behrouz; Pezeshki-Rad, Masoud; Farrokh, Donya

    2017-01-01

    Colloid cysts are benign slow-growing cystic lesions located on the roof of the third ventricle that usually present with symptoms related to gradual rise of intracranial pressure. They mostly remain asymptomatic and sometimes grow progressively and cause diverse symptoms associated with increased intracranial pressure such as headache, diplopia, and sixth cranial nerve palsy. Here we report a 47-year-old female who presented to the emergency department with acute severe headache and nausea/vomiting. On MRI examination acute hydrocephaly due to hemorrhagic colloid cyst was detected. Acute hemorrhage in colloid cysts is extremely rare and may present with symptoms of acute increase in the intracranial pressure. Intracystic hemorrhage is very rarely reported as a complication of colloid cyst presenting with paroxysmal symptoms of acute hydrocephaly. PMID:28210514

  18. Solid colloids with surface-mobile linkers.

    Science.gov (United States)

    van der Meulen, Stef A J; Helms, Gesa; Dogterom, Marileen

    2015-06-17

    In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell-cell interactions and cell adhesion processes.

  19. Suspensions of colloidal particles and aggregates

    CERN Document Server

    Babick, Frank

    2016-01-01

    This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between ...

  20. Size determinations of colloidal fat emulsions

    DEFF Research Database (Denmark)

    Kuntsche, Judith; Klaus, Katrin; Steiniger, Frank

    2009-01-01

    Size and size distributions of colloidal dispersions are of crucial importance for their performance and safety. In the present study, commercially available fat emulsions (Lipofundin N, Lipofundin MCT and Lipidem) were analyzed by photon correlation spectroscopy, laser diffraction with adequate...

  1. Linear Optical Properties of Gold Colloid

    Directory of Open Access Journals (Sweden)

    Jingmin XIA

    2015-11-01

    Full Text Available Gold colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The morphology, size of gold nanoparticles and the optical property of colloid were characterized by transmission electron microscope and UV-Vis spectrophotometer, respectively. It shows that the gold nanoparticles are in the shape of spheres with diameters less than 8 nm, and the surface plasmon resonance absorption peak is located at about 438 nm. As the volume fraction of gold particles increases, the intensity of absorption peak strengthens. The optical property of gold colloid was analyzed by Maxwell-Garnett (MG effective medium theory in the company of Drude dispersion model. The results show that the matrix dielectric constant is a main factor, which influences the optical property of gold colloid.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9558

  2. Accelerated purification of colloidal silica sols

    Science.gov (United States)

    Bahnsen, E. B.; Garofalini, S.; Pechman, A.

    1979-01-01

    Accelerated purification process for colloidal sols using heat/deionization scheme, sharply reduces waiting time between deionization cycles from several months to a few days. Process produces same high purity silica sols as conventional methods.

  3. Entropically Driven Colloidal Assembly in Emulsions

    Science.gov (United States)

    Lin, Keng-Hui; Lai, Liang-Jie; Chen, Hui

    2007-03-01

    Using the techniques developed by Manoharan [1], we encapsulate small numbers of colloidal microspheres and polymers in oil-in-water emulsion droplets, remove the oil and generate colloidal clusters covered with polymers. We observe two types of arrangement in the clusters. The first kind is the same as the type reported in [1] of which the clusters are formed without polymer. The second kind is the same as the structure reported in [2] of which the clusters are formed by binary colloidal microspheres. The polymers we put in the emulsions induce depletion interactions between colloidal particles. We will show that two types of structures are from the interplay between the depletion interactions and surface tension. [1] Manoharan, Elsesser, Pine, Science 301, 483(2003). [2] Cho et al. JACS 127, 15968 (2005).

  4. A Course in Colloid and Surface Science.

    Science.gov (United States)

    Scamehorn, John F.

    1984-01-01

    Describes a course for chemical engineers, chemists, and petroleum engineers that focuses on colloid and surface science. Major topic areas in the course include capillarity, surface thermodynamics, adsorption contact angle, micelle formation, solubilization in micelles, emulsions, foams, and applications. (JN)

  5. Hybrid photovoltaics based on semiconductor nanocrystals and amorphous silicon.

    Science.gov (United States)

    Sun, Baoquan; Findikoglu, Alp T; Sykora, Milan; Werder, Donald J; Klimov, Victor I

    2009-03-01

    Semiconductor nanocrystals (NCs) are promising materials for applications in photovoltaic (PV) structures that could benefit from size-controlled tunability of absorption spectra, the ease of realization of various tandem architectures, and, perhaps, increased conversion efficiency in the ultraviolet region through carrier multiplication. The first practical step toward utilization of the unique properties of NCs in PV technologies could be through their integration into traditional silicon-based solar cells. Here, we demonstrate an example of such hybrid PV structures that combine colloidal NCs with amorphous silicon. In these structures, NCs and silicon are electronically coupled, and the regime of this coupling can be tuned by altering the alignment of NC energy states with regard to silicon band edges. For example, using wide-gap CdSe NCs we demonstrate a photoresponse which is exclusively due to the NCs. On the other hand, in devices comprising narrow-gap PbS NCs, both the NCs and silicon contribute to photocurrent, which results in PV response extending from the visible to the near-infrared region. The hybrid silicon/PbS NC solar cells show external quantum efficiencies of approximately 7% at infrared energies and 50% in the visible and a power conversion efficiency of up to 0.9%. This work demonstrates the feasibility of hybrid PV devices that combine advantages of mature silicon fabrication technologies with the unique electronic properties of semiconductor NCs.

  6. Electron-beam deposition of vanadium dioxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Marvel, R.E.; Appavoo, K. [Vanderbilt University, Interdisciplinary Materials Science Program, Nashville, TN (United States); Choi, B.K. [Vanderbilt University, Department of Electrical Engineering and Computer Science, Nashville, TN (United States); Nag, J. [Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States); Haglund, R.F. [Vanderbilt University, Interdisciplinary Materials Science Program, Nashville, TN (United States); Vanderbilt University, Institute for Nanoscale Science and Engineering, Nashville, TN (United States); Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States)

    2013-06-15

    Developing a reliable and efficient fabrication method for phase-transition thin-film technology is critical for electronic and photonic applications. We demonstrate a novel method for fabricating polycrystalline, switchable vanadium dioxide thin films on glass and silicon substrates and show that the optical switching contrast is not strongly affected by post-processing annealing times. The method relies on electron-beam evaporation of a nominally stoichiometric powder, followed by fast annealing. As a result of the short annealing procedure we demonstrate that films deposited on silicon substrates appear to be smoother, in comparison to pulsed laser deposition and sputtering. However, optical performance of e-beam evaporated film on silicon is affected by annealing time, in contrast to glass. (orig.)

  7. Colloidal Silver Not Approved for Treating Animals

    OpenAIRE

    Bagley, Clell

    1997-01-01

    FDA has received reports that products containing colloidal silver are being promoted for use in the treatment of mastitis and other serious disease conditions of dairy cattle, as well as for various conditions of companion animals. For example, FDA’s Center for Veterinary Medicine has received reports from the Agency's regional milk specialists and State inspectors that colloidal silver products have been found on some dairy farms. Also, recent articles in some farm newspapers and journals p...

  8. Colloid Thrusters, Physics, Fabrication and Performance

    Science.gov (United States)

    2005-11-17

    response, including the time for reviewing in. tata needed, and completing and reviewing this collection of information. Send comments regarding this...a discussion with colleagues during the 2nd Colloid Thruster/ Nano Electrojet Workshop (MIT, April 14- 15, 2005, Ref. [11]) an agreement was reached...23 Jul 2003. 11. Second Colloid Thruster/ Nano Electrojet Workshop, CD with a collection of presentations by attendees to this Workshop. MIT, April 14

  9. Colloids with high-definition surface structures

    Science.gov (United States)

    Chen, Hsien-Yeh; Rouillard, Jean-Marie; Gulari, Erdogan; Lahann, Joerg

    2007-01-01

    Compared with the well equipped arsenal of surface modification methods for flat surfaces, techniques that are applicable to curved, colloidal surfaces are still in their infancy. This technological gap exists because spin-coating techniques used in traditional photolithographic processes are not applicable to the curved surfaces of spherical objects. By replacing spin-coated photoresist with a vapor-deposited, photodefinable polymer coating, we have now fabricated microstructured colloids with a wide range of surface patterns, including asymmetric and chiral surface structures, that so far were typically reserved for flat substrates. This high-throughput method can yield surface-structured colloidal particles at a rate of ≈107 to 108 particles per operator per day. Equipped with spatially defined binding pockets, microstructured colloids can engage in programmable interactions, which can lead to directed self-assembly. The ability to create a wide range of colloids with both simple and complex surface patterns may contribute to the genesis of previously unknown colloidal structures and may have important technological implications in a range of different applications, including photonic and phononic materials or chemical sensors. PMID:17592149

  10. Self-replication with magnetic dipolar colloids.

    Science.gov (United States)

    Dempster, Joshua M; Zhang, Rui; Olvera de la Cruz, Monica

    2015-10-01

    Colloidal self-replication represents an exciting research frontier in soft matter physics. Currently, all reported self-replication schemes involve coating colloidal particles with stimuli-responsive molecules to allow switchable interactions. In this paper, we introduce a scheme using ferromagnetic dipolar colloids and preprogrammed external magnetic fields to create an autonomous self-replication system. Interparticle dipole-dipole forces and periodically varying weak-strong magnetic fields cooperate to drive colloid monomers from the solute onto templates, bind them into replicas, and dissolve template complexes. We present three general design principles for autonomous linear replicators, derived from a focused study of a minimalist sphere-dimer magnetic system in which single binding sites allow formation of dimeric templates. We show via statistical models and computer simulations that our system exhibits nonlinear growth of templates and produces nearly exponential growth (low error rate) upon adding an optimized competing electrostatic potential. We devise experimental strategies for constructing the required magnetic colloids based on documented laboratory techniques. We also present qualitative ideas about building more complex self-replicating structures utilizing magnetic colloids.

  11. Inventions Utilizing Microfluidics and Colloidal Particles

    Science.gov (United States)

    Marr, David W.; Gong, Tieying; Oakey, John; Terray, Alexander V.; Wu, David T.

    2009-01-01

    Several related inventions pertain to families of devices that utilize microfluidics and/or colloidal particles to obtain useful physical effects. The families of devices can be summarized as follows: (1) Microfluidic pumps and/or valves wherein colloidal-size particles driven by electrical, magnetic, or optical fields serve as the principal moving parts that propel and/or direct the affected flows. (2) Devices that are similar to the aforementioned pumps and/or valves except that they are used to manipulate light instead of fluids. The colloidal particles in these devices are substantially constrained to move in a plane and are driven to spatially order them into arrays that function, variously, as waveguides, filters, or switches for optical signals. (3) Devices wherein the ultra-laminar nature of microfluidic flows is exploited to effect separation, sorting, or filtering of colloidal particles or biological cells in suspension. (4) Devices wherein a combination of confinement and applied electrical and/or optical fields forces the colloidal particles to become arranged into three-dimensional crystal lattices. Control of the colloidal crystalline structures could be exploited to control diffraction of light. (5) Microfluidic devices, incorporating fluid waveguides, wherein switching of flows among different paths would be accompanied by switching of optical signals.

  12. Complex coacervation between colloidal silica and polyacrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Kawase, Kaoru; Sakami, Hiroshi; Hayakawa, Kiyoshi

    1989-03-01

    Complex coacervation introduced by gamma-ray induced polymerization of acrylamide in colloidal silica was studied. The complex coaservate was formed by polymerization of acrylamide dissolved in a colloidal silica and methanol mixture. Complex coacervation (two-phase separation of the mixture) was observed only when the concentration of methanol was between 33 and 41 percent by volume, and the concentration of colloidal silica did not affect it. Although two phase separation was not influenced by pH change, the content of polyacrylamide was bigger in the equilibrated solution in acidic regions. It was, however, bigger in the complex coacervate at neutral and in alkaline regions. The content of polyacrylamide was also calculated from the particle diameter of complex coacervate measured by small angle X-ray scattering, and the result was well coincided with the analytical result. The stability of the complex coacervate against the addition of salts was better than that of the untreated colloidal silica. The rate of electrophoretic transport of the complex coacervate was also lower than that of the colloidal silica. From these observation it was concluded that the hydrophobic colloidal silica particles were protected by the surrounding hydrophilic polyacrylamide. (author).

  13. Colloids generation from metallic uranium fuel

    Energy Technology Data Exchange (ETDEWEB)

    Metz, C.; Fortner, J.; Goldberg, M.; Shelton-Davis, C.

    2000-07-20

    The possibility of colloid generation from spent fuel in an unsaturated environment has significant implications for storage of these fuels in the proposed repository at Yucca Mountain. Because colloids can act as a transport medium for sparingly soluble radionuclides, it might be possible for colloid-associated radionuclides to migrate large distances underground and present a human health concern. This study examines the nature of colloidal materials produced during corrosion of metallic uranium fuel in simulated groundwater at elevated temperature in an unsaturated environment. Colloidal analyses of the leachates from these corrosion tests were performed using dynamic light scattering and transmission electron microscopy. Results from both techniques indicate a bimodal distribution of small discrete particles and aggregates of the small particles. The average diameters of the small, discrete colloids are {approximately}3--12 nm, and the large aggregates have average diameters of {approximately}100--200 nm. X-ray diffraction of the solids from these tests indicates a mineral composition of uranium oxide or uranium oxy-hydroxide.

  14. Colloids with high-definition surface structures.

    Science.gov (United States)

    Chen, Hsien-Yeh; Rouillard, Jean-Marie; Gulari, Erdogan; Lahann, Joerg

    2007-07-03

    Compared with the well equipped arsenal of surface modification methods for flat surfaces, techniques that are applicable to curved, colloidal surfaces are still in their infancy. This technological gap exists because spin-coating techniques used in traditional photolithographic processes are not applicable to the curved surfaces of spherical objects. By replacing spin-coated photoresist with a vapor-deposited, photodefinable polymer coating, we have now fabricated microstructured colloids with a wide range of surface patterns, including asymmetric and chiral surface structures, that so far were typically reserved for flat substrates. This high-throughput method can yield surface-structured colloidal particles at a rate of approximately 10(7) to 10(8) particles per operator per day. Equipped with spatially defined binding pockets, microstructured colloids can engage in programmable interactions, which can lead to directed self-assembly. The ability to create a wide range of colloids with both simple and complex surface patterns may contribute to the genesis of previously unknown colloidal structures and may have important technological implications in a range of different applications, including photonic and phononic materials or chemical sensors.

  15. Colloidal oatmeal: history, chemistry and clinical properties.

    Science.gov (United States)

    Kurtz, Ellen S; Wallo, Warren

    2007-02-01

    Oatmeal has been used for centuries as a soothing agent to relieve itch and irritation associated with various xerotic dermatoses. In 1945, a ready to use colloidal oatmeal, produced by finely grinding the oat and boiling it to extract the colloidal material, became available. Today, colloidal oatmeal is available in various dosage forms from powders for the bath to shampoos, shaving gels, and moisturizing creams. Currently, the use of colloidal oatmeal as a skin protectant is regulated by the U.S. Food and Drug Administration (FDA) according to the Over-The-Counter Final Monograph for Skin Protectant Drug Products issued in June 2003. Its preparation is also standardized by the United States Pharmacopeia. The many clinical properties of colloidal oatmeal derive from its chemical polymorphism. The high concentration in starches and beta-glucan is responsible for the protective and water-holding functions of oat. The presence of different types of phenols confers antioxidant and anti-inflammatory activity. Some of the oat phenols are also strong ultraviolet absorbers. The cleansing activity of oat is mostly due to saponins. Its many functional properties make colloidal oatmeal a cleanser, moisturizer, buffer, as well as a soothing and protective anti-inflammatory agent.

  16. Interactions between radioactively labeled colloids and natural particles: Evidence for colloidal pumping

    Energy Technology Data Exchange (ETDEWEB)

    Wen, L.S.; Santschi, P.H.; Tang, D. [Texas A & M Univ., Galveston, TX (United States)

    1997-07-01

    It has been hypothesized that colloidal forms of trace metals can be reactive intermediaries in the scavenging processes leading to the removal of their particulate forms. A series of radiotracer experiments using natural colloidal organic matter from Galveston Bay, USA were carried out in order to test this hypothesis. Suspended particle uptake of originally colloidally bound trace metals occurred in a matter of hours to days in estuarine waters. After ten days, the majority ( >50%) of the colloidal trace metals had been transferred into the particulate phase ({ge} 0.45{mu}m), except for {sup 65}Zn. Two distinctively different temporal regions of removal of colloidal trace metals were identified: a faster reaction during the first four hours, followed by a slower reaction after approximately one day. In a separate river water-seawater mixing experiment, the solid/solution partitioning of the radiotracers was investigated in the absence of suspended matter. About 30% of most of the elements, except Ag and Fe ({approximately}60%), were associated with a newly formed particulate phase after eight days. There were two major trends: (1) the particulate fraction of {sup 59}Fe and {sup 110}Ag increased while the colloidal fraction decreased, suggesting a colloidal pumping mechanism. (2) The particulate fraction of {sup 54}Mn, {sup 133}Ba, {sup 65}Zn, {sup 109}Cd, {sup 113}Sn, and {sup 60}Co increased while the LMW({le}1 kDa) fraction decreased, suggesting a direct uptake into the particulate fraction with less involvement of a transitory colloidal phase. The results from these experiments suggested two different pathways for colloidal tracer uptake by particles: (1) colloidal pumping of a major component (e.g., biopolymer) of the colloidal pool and (2) coagulation of trace components (e.g., phytochelatins) with varying affinities for different trace metals. 39 refs., 8 figs., 3 tabs.

  17. Fabrication and Characterization of On-Chip Integrated Silicon Photonic Bragg Grating and Photonic Crystal Cavity Thermometers

    CERN Document Server

    Klimov, Nikolai N; Ahmed, Zeeshan

    2015-01-01

    We report on the fabrication and characterization of photonic-based nanothermometers, a silicon photonic Bragg grating and photonic crystal cavity. When cladded with silicon dioxide layer the sensors have at least eight times better sensitivity compared to the sensitivity of conventional fiber Bragg grating sensors. We demonstrate that these photonic thermometers are a viable temperature sensing solution.

  18. Colloid's influences on microalgae growth as a potential environmental factor

    Institute of Scientific and Technical Information of China (English)

    赵新淮; 张正斌; 刘莲生

    2003-01-01

    The role of colloid as "colloid pump" in the ocean is well known. The important influence of colloid in seawater on the growth of microalga was found in our 1999-2000 study. Colloid concentrates were obtained by employing a cross-flow filtration systen to ultrafilter seawater (which had been pre-filtrated by 0.45 μm acetate cellulose membrane) successively with different membranes. Ultrafiltration retentions (we called them colloid concentrates ) together with control sample ( seawater without colloid) were then inoculated with two species of microalgae and cultivated in selected conditions. Monitoring of microalgae growth during cultivation showed that all colloid concentrates had obvious influence on the growth of the microalgae studied. Addition of Fe(OH)3 colloid or organic colloid (protein or carbohydrate) to the control sample enhanced the microalgae's growth.

  19. Equilibrium sedimentation profile of dilute, salt-free charged colloids.

    Science.gov (United States)

    Wang, Tzu-Yu; Li, Hsien-Tsung; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2008-11-28

    The sedimentation profile of a dilute colloidal solution follows the barometric distribution owing to the balance between gravitational force and thermal fluctuation. However, the electrostatic interactions may lead to significant deviation even in the low volume fraction limit (e.g., 10(-5)). On the basis of Monte Carlo simulations for a dilute, salt-free colloidal dispersion, five regimes can be identified through the resulting colloidal sedimentation profile and the counterion distribution. The electrostatic interactions depends on the Coulomb strength E(c) defined as the ratio of the Bjerrum length to the colloid size. At weak colloid-ion attractions (small E(c)), counterions tend to distribute uniformly in the container. However, both barometric and inflated profiles of colloids can be observed. On the contrary, at strong colloid-ion attraction (large E(c)), counterions accumulate in the vicinity of the colloids. Significant counterion condensation effectively decreases the strength of colloid-colloid repulsion and barometric profile of colloids can be obtained as well. As a result, the sedimentation profile and counterion distribution are indicative of the strength of effective colloid-colloid and colloid-ion interactions. It is also found that local electroneutrality condition is generally not satisfied and charge separation (or internal electric field) is neither a sufficient nor necessary condition for nonbarometric distributions.

  20. Ring formation from a drying sessile colloidal droplet

    Directory of Open Access Journals (Sweden)

    Wenbin Zhang

    2013-10-01

    Full Text Available Ring formation from drying sessile colloidal droplets (∼1.0 mm in size containing microparticles of silicon or polystyrene was investigated with video microscopy. Results show that ring formation begins at the pinned contact line with the growth of an annular nucleus in a line by line way, which recedes inward albeit only slightly, followed by stacking of particles when the flow velocity becomes sufficiently large. The central height of the droplet decreases linearly with evaporation time, which implies that in the early stage, the number of particles arriving at contact line increases with time in a power law N∝t3/(1 + λ, where the parameter λ, according to Deegan's evaporation model, is related to the contact angle via λ=π−2θc2π−2θc. Experimental values of λ agree well with model calculation for small contact angles, but are relatively smaller in the case of large contact angles. ‘Amorphization’ mechanism for the deposit at different stages of evaporation is discussed. Marangoni flow in a droplet on heated substrate introduces a desorption path for particles along the liquid surface, which can partially resolve the ring. Residual particles floating on the liquid surface may leave behind a homogeneous monolayer coating inside the dried spot. A “jump” in the droplet surface area at later stage of evaporation seems inevitably to cause a depletion zone of particles next to the ring. These results may be helpful for the development of strategies towards suppression of coffee ring effect and/or obtaining homogeneous coatings from drying colloidal suspension.

  1. Colloidal Gelation-2 and Colloidal Disorder-Order Transition-2 Investigations Conducted on STS-95

    Science.gov (United States)

    Hoffmann, Monica T.

    2000-01-01

    The Colloidal Gelation-2 (CGEL 2) and Colloidal Disorder-Order Transition-2 (CDOT 2) investigations flew on Space Shuttle Discovery mission STS-95 (also known as the John Glenn Mission). These investigations were part of a series of colloid experiments designed to help scientists answer fundamental science questions and reduce the trial and error involved in developing new and better materials. Industries dealing with semiconductors, electro-optics, ceramics, and composites are just a few that may benefit from this knowledge. The goal of the CGEL 2 investigation was to study the fundamental properties of colloids to help scientists better understand their nature and make them more useful for technology. Colloids consist of very small (submicron) particles suspended in a fluid. They play a critical role in the technology of this country, finding uses in materials ranging from paints and coatings to drugs, cosmetics, food, and drink. Although these products are routinely produced and used, there are still many aspects of their behavior about which scientists know little. Understanding their structures may allow scientists to manipulate the physical properties of colloids (a process called "colloidal engineering") to produce new materials and products. Colloid research may even improve the processing of known products to enhance their desirable properties.

  2. Colloids and polymers in random colloidal matrices: Demixing under good-solvent conditions

    Science.gov (United States)

    Annunziata, Mario Alberto; Pelissetto, Andrea

    2012-10-01

    We consider a simplified coarse-grained model for colloid-polymer mixtures, in which polymers are represented as monoatomic molecules interacting by means of pair potentials. We use it to study polymer-colloid segregation in the presence of a quenched matrix of colloidal hard spheres. We fix the polymer-to-colloid size ratio to 0.8 and consider matrices such that the fraction f of the volume that is not accessible to the colloids due to the matrix is equal to 40%. As in the Asakura-Oosawa-Vrij (AOV) case, we find that binodal curves in the polymer and colloid volume-fraction plane have a small dependence on disorder. As for the position of the critical point, the behavior differs from that observed in the AOV case: While the critical colloid volume fraction is essentially the same in the bulk and in the presence of the matrix, the polymer volume fraction at criticality increases as f increases. At variance with the AOV case, no capillary colloid condensation or evaporation is generically observed.

  3. Drying of thin colloidal films

    Science.gov (United States)

    Routh, Alexander F.

    2013-04-01

    When thin films of colloidal fluids are dried, a range of transitions are observed and the final film profile is found to depend on the processes that occur during the drying step. This article describes the drying process, initially concentrating on the various transitions. Particles are seen to initially consolidate at the edge of a drying droplet, the so-called coffee-ring effect. Flow is seen to be from the centre of the drop towards the edge and a front of close-packed particles passes horizontally across the film. Just behind the particle front the now solid film often displays cracks and finally the film is observed to de-wet. These various transitions are explained, with particular reference to the capillary pressure which forms in the solidified region of the film. The reasons for cracking in thin films is explored as well as various methods to minimize its effect. Methods to obtain stratified coatings through a single application are considered for a one-dimensional drying problem and this is then extended to two-dimensional films. Different evaporative models are described, including the physical reason for enhanced evaporation at the edge of droplets. The various scenarios when evaporation is found to be uniform across a drying film are then explained. Finally different experimental techniques for examining the drying step are mentioned and the article ends with suggested areas that warrant further study.

  4. Carbon dioxide sensor

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Prabir K. (Worthington, OH); Lee, Inhee (Columbus, OH); Akbar, Sheikh A. (Hilliard, OH)

    2011-11-15

    The present invention generally relates to carbon dioxide (CO.sub.2) sensors. In one embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor that incorporates lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3). In another embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor has a reduced sensitivity to humidity due to a sensing electrode with a layered structure of lithium carbonate and barium carbonate. In still another embodiment, the present invention relates to a method of producing carbon dioxide (CO.sub.2) sensors having lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3).

  5. Molecular Recognition in the Colloidal World.

    Science.gov (United States)

    Elacqua, Elizabeth; Zheng, Xiaolong; Shillingford, Cicely; Liu, Mingzhu; Weck, Marcus

    2017-10-06

    Colloidal self-assembly is a bottom-up technique to fabricate functional nanomaterials, with paramount interest stemming from programmable assembly of smaller building blocks into dynamic crystalline domains and photonic materials. Multiple established colloidal platforms feature diverse shapes and bonding interactions, while achieving specific orientations along with short- and long-range order. A major impediment to their universal use as building blocks for predesigned architectures is the inability to precisely dictate and control particle functionalization and concomitant reversible self-assembly. Progress in colloidal self-assembly necessitates the development of strategies that endow bonding specificity and directionality within assemblies. Methodologies that emulate molecular and polymeric three-dimensional (3D) architectures feature elements of covalent bonding, while high-fidelity molecular recognition events have been installed to realize responsive reconfigurable assemblies. The emergence of anisotropic 'colloidal molecules', coupled with the ability to site-specifically decorate particle surfaces with supramolecular recognition motifs, has facilitated the formation of superstructures via directional interactions and shape recognition. In this Account, we describe supramolecular assembly routes to drive colloidal particles into precisely assembled architectures or crystalline lattices via directional noncovalent molecular interactions. The design principles are based upon the fabrication of colloidal particles bearing surface-exposed functional groups that can undergo programmable conjugation to install recognition motifs with high fidelity. Modular and versatile by design, our strategy allows for the introduction and integration of molecular recognition principles into the colloidal world. We define noncovalent molecular interactions as site-specific forces that are predictable (i.e., feature selective and controllable complementary bonding partners

  6. Integrated cooling devices in silicon technology

    Science.gov (United States)

    Perret, C.; Avenas, Y.; Gillot, Ch.; Boussey, J.; Schaeffer, Ch.

    2002-05-01

    Silicon technology has become a good alternative to copper for the elaboration of efficient cooling devices required in power electronics domain. Owing to its high degree of miniaturization, it is expected to provide suitable microchannels and other inlets holes that were not achievable by copper micromachining. Besides, the use of silicon technology provides a variety of bare materials (silicon dioxide, silicon nitride, silicide, etc.) which may be either insulator or conductive, with a good or bad thermal conductivity. This large choice makes it possible to built up rather complex multilayer devices with mechanical properties good enough in comparison with hybrid copper technology heat sinks. Nevertheless, the use of silicon technology, where the microchannel width may reach few tens of microns, raises fundamental features concerning the fluid displacement within such small sections. More precisely, fundamental fluid mechanics studies have to be conducted out in order to get an accurate description of the fluid boundary layers and to provide basic data on the exchange mechanisms occurring at these surfaces. In this paper, we review the operation principles of both single- and double-phase heat exchange devices elaborated in silicon technology. Forced-convection heat sinks as well as integrated micro heat pipes are analyzed. An analytical approach is adopted to evaluate their total thermal resistances as a function of several geometrical parameters. Numerical simulations are then used in order to assess the accuracy of the analytical approach and to evaluate the impact of the fluidic aspects on the whole performance. The optimum devices are then conceived thanks to an appropriate optimization procedure taken into account the several experimental constraints. Reference values of similar copper devices are reminded and the advantages of the silicon integrated approach are highlighted.

  7. Silver-colloid-nucleated cytochrome c superstructures encapsulated in silica nanoarchitectures.

    Science.gov (United States)

    Wallace, Jean Marie; Dening, Brett M; Eden, Kristin B; Stroud, Rhonda M; Long, Jeffrey W; Rolison, Debra R

    2004-10-12

    We recently discovered that self-organized superstructures of the heme protein cytochrome c (cyt. c) are nucleated in buffer by gold nanoparticles. The protein molecules within the superstructure survive both silica sol-gel encapsulation and drying from supercritical carbon dioxide to form air-filled biocomposite aerogels that exhibit gas-phase binding activity for nitric oxide. In this investigation, we report that viable proteins are present in biocomposite aerogels when the nucleating metal nanoparticle is silver rather than gold. Silver colloids were synthesized via reduction of an aqueous solution of Ag+ using either citrate or borohydride reductants. As determined by transmission electron microscopy and UV-visible absorption spectroscopy, the silver nanoparticles vary in size and shape depending on the synthetic route, which affects the fraction of cyt. c that survives the processing necessary to form a biocomposite aerogel. Silver colloids synthesized via the citrate preparation are polydisperse, with sizes ranging from 1 to 100 nm, and lead to low cyt. c viability in the dried bioaerogels (approximately 15%). Protein superstructures nucleated at approximately 10-nm Ag colloids prepared via the borohydride route, including citrate stabilization of the borohydride-reduced metal, retain significant protein viability within the bioaerogels (approximately 45%).

  8. Porous Silicon and Polymer Nanocomposites for Delivery of Peptide Nucleic Acids as Anti-MicroRNA Therapies.

    Science.gov (United States)

    Beavers, Kelsey R; Werfel, Thomas A; Shen, Tianwei; Kavanaugh, Taylor E; Kilchrist, Kameron V; Mares, Jeremy W; Fain, Joshua S; Wiese, Carrie B; Vickers, Kasey C; Weiss, Sharon M; Duvall, Craig L

    2016-09-01

    Self-assembled polymer/porous silicon nanocomposites overcome intracellular and systemic barriers for in vivo application of peptide nucleic acid (PNA) anti-microRNA therapeutics. Porous silicon (PSi) is leveraged as a biodegradable scaffold with high drug-cargo-loading capacity. Functionalization with a diblock polymer improves PSi nanoparticle colloidal stability, in vivo pharmacokinetics, and intracellular bioavailability through endosomal escape, enabling PNA to inhibit miR-122 in vivo.

  9. Colloids in the intensive care unit.

    Science.gov (United States)

    Kruer, Rachel M; Ensor, Christopher R

    2012-10-01

    The most recent published evidence on the use of colloids versus crystalloids in critical care is reviewed, with a focus on population-dependent differences in safety and efficacy. Colloids offer a number of theoretical advantages over crystalloids for fluid resuscitation, but some colloids (e.g., hydroxyethyl starch solutions, dextrans) can have serious adverse effects, and albumin products entail higher costs. The results of the influential Saline Versus Albumin Fluid Evaluation (SAFE) trial and a subsequent SAFE subgroup analysis indicated that colloid therapy should not be used in patients with traumatic brain injury and other forms of trauma due to an increased mortality risk relative to crystalloid therapy. With regard to patients with severe sepsis, two meta-analyses published in 2011, which collectively evaluated 82 trials involving nearly 10,000 patients, indicated comparable outcomes with the use of either crystalloids or albumins. For patients requiring extracorporeal cardiopulmonary bypass (CPB) during heart surgery, the available evidence supports the use of a colloid, particularly albumin, for CPB circuit priming and postoperative volume expansion. In select patients with burn injury, the published evidence supports the use of supplemental colloids if adequate urine output cannot be maintained with a crystalloid-only rescue strategy. The results of the SAFE trial and a subgroup analysis of SAFE data suggest that colloids should be avoided in patients with trauma and traumatic brain injury. There are minimal differences in outcome between crystalloids and hypo-oncotic or iso-oncotic albumin for fluid resuscitation in severe sepsis; in select populations, such as patients undergoing cardiac surgery, the use of iso-oncotic albumin may confer a survival advantage and should be considered a first-line alternative.

  10. Silver nanoparticles-coated glass frits for silicon solar cells

    Science.gov (United States)

    Li, Yingfen; Gan, Weiping; Li, Biyuan

    2016-04-01

    Silver nanoparticles-coated glass frit composite powders for silicon solar cells were prepared by electroless plating. Silver colloids were used as the activating agent of glass frits. The products were characterized by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry. The characterization results indicated that silver nanoparticles with the melting temperature of 838 °C were uniformly deposited on glass frit surface. The particle size of silver nanoparticles could be controlled by adjusting the [Ag(NH3)2]NO3 concentration. The as-prepared composite powders were applied in the front side metallization of silicon solar cells. Compared with those based on pure glass frits, the solar cells containing the composite powders had the denser silver electrodes and the better silver-silicon ohmic contacts. Furthermore, the photovoltaic performances of solar cells were improved after the electroless plating.

  11. Cooperative redox activation for carbon dioxide conversion

    Science.gov (United States)

    Lian, Zhong; Nielsen, Dennis U.; Lindhardt, Anders T.; Daasbjerg, Kim; Skrydstrup, Troels

    2016-12-01

    A longstanding challenge in production chemistry is the development of catalytic methods for the transformation of carbon dioxide into useful chemicals. Silane and borane promoted reductions can be fined-tuned to provide a number of C1-building blocks under mild conditions, but these approaches are limited because of the production of stoichiometric waste compounds. Here we report on the conversion of CO2 with diaryldisilanes, which through cooperative redox activation generate carbon monoxide and a diaryldisiloxane that actively participate in a palladium-catalysed carbonylative Hiyama-Denmark coupling for the synthesis of an array of pharmaceutically relevant diarylketones. Thus the disilane reagent not only serves as the oxygen abstracting agent from CO2, but the silicon-containing `waste', produced through oxygen insertion into the Si-Si bond, participates as a reagent for the transmetalation step in the carbonylative coupling. Hence this concept of cooperative redox activation opens up for new avenues in the conversion of CO2.

  12. Photoelectrochemical Activity of Graphene Supported Titanium Dioxide

    Directory of Open Access Journals (Sweden)

    Rodrigo A. Segura

    2016-01-01

    Full Text Available Thin TiO2 layers grown over few-layers graphene were prepared in order to evaluate the photoinduced chemical response of this composite. Graphene was grown over copper foils by decomposition of acetylene in a standard chemical vapor deposition apparatus. Graphene was subsequently transferred to a silicon substrate, on which the titanium dioxide was grown to form a TiO2/FLG/SiO2/Si composite. The formation of each layered material was verified by Raman spectroscopy and the morphology was characterized by scanning electron microscopy. The photoelectrochemical evaluation of the resulting composite, using it as a photoanode, was accomplished with a potentiostat, a solar simulator, and a three-electrode configuration. The electrochemical response indicates that the new composite preserves the average photoactive properties of the base material and at the same time shows a singular transient response where explicit benefits seem to be derived from the FLG/TiO2 combination.

  13. A new architecture for self-organized silicon nanowire growth integrated on a left angle 100 right angle silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Buttard, D. [Universite Joseph Fourier/IUT-1, Grenoble (France); David, T.; Gentile, P. [CEA-Grenoble/SiNaPS-MINATEC, Grenoble (France); Hertog, M. den; Rouviere, J.L. [CEA-Grenoble/LEMMA-MINATEC, Grenoble (France); Baron, T. [CNRS/LTM, Grenoble (France); Ferret, P. [CEA-DRT/CEA-Grenoble/DOPT, Grenoble (France)

    2008-07-15

    A lithography-independent method for achieving self-organized growth of silicon nanowires by means of a Chemical-Vapor-Deposition process is investigated using a nanoporous alumina template on a left angle 100 right angle oriented silicon substrate. The position of the nanowires is determined by the location of gold colloids, acting as catalysts, which are initially deposited at the bottom of the pores over large areas of the sample. The direction of growth is guided by the pore axis, which is perpendicular to the silicon substrate surface. Results from scanning and transmission electron microscopy are presented and discussed. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  14. Random Surface Texturing of Silicon Dioxide Using Gold Agglomerates

    Science.gov (United States)

    2016-07-01

    cells work by converting sunlight (electromagnetic radiation ) into electricity. Photon absorption needs to occur inside the solar cell’s active...underneath. SEM and AFM were the primary characterization techniques used to evaluate the resulting surfaces, before and after etching, and after

  15. The PL "violet shift" of cerium dioxide on silicon

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    CeO2 thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied from tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of "violet shift" was observed.

  16. Adsorption studies of DNA origami on silicon dioxide

    NARCIS (Netherlands)

    Albrechts, Björn; Hautzinger, Daniel S.; Krüger, Michael; Elwenspoek, Miko; Müller, Kristian M.; Korvink, Jan G.

    2010-01-01

    Self-assembled DNA nanostructures promise low-cost ways to create nanoscale shapes. DNA nanostructures can also be used to position particles with nanometer precision. Yet, reliable and low-cost ways of integrating the structures with MEMS technology still have to be developed and innovations are of

  17. Colloidal spirals in nematic liquid crystals.

    Science.gov (United States)

    Senyuk, Bohdan; Pandey, Manoj B; Liu, Qingkun; Tasinkevych, Mykola; Smalyukh, Ivan I

    2015-12-07

    One of the central experimental efforts in nematic colloids research aims to explore how the interplay between the geometry of particles along with the accompanying nematic director deformations and defects around them can provide a means of guiding particle self-assembly and controlling the structure of particle-induced defects. In this work, we design, fabricate, and disperse low-symmetry colloidal particles with shapes of spirals, double spirals, and triple spirals in a nematic fluid. These spiral-shaped particles, which are controlled by varying their surface functionalization to provide tangential or perpendicular boundary conditions of the nematic molecular alignment, are found inducing director distortions and defect configurations with non-chiral or chiral symmetry. Colloidal particles also exhibit both stable and metastable multiple orientational states in the nematic host, with a large number of director configurations featuring both singular and solitonic nonsingular topological defects accompanying them, which can result in unusual forms of colloidal self-assembly. Our findings directly demonstrate how the symmetry of particle-generated director configurations can be further lowered, or not, as compared to the low point group symmetry of solid micro-inclusions, depending on the nature of induced defects while satisfying topological constraints. We show that achiral colloidal particles can cause chiral symmetry breaking of elastic distortions, which is driven by complex three-dimensional winding of induced topological line defects and solitons.

  18. Colloids with continuously tunable surface charge.

    Science.gov (United States)

    van Ravensteijn, Bas G P; Kegel, Willem K

    2014-09-09

    In this paper, we present a robust way to tune the surface potential of polystyrene colloids without changing the pH, ionic strength, etc. The colloids are composed of a cross-linked polystyrene core and a cross-linked vinylbenzyl chloride layer. Besides the chlorine groups, the particle surface contains sulfate/sulfonate groups (arising from the polymerization initiators) that provide a negative surface potential. Performing a Menschutkin reaction on the surface chlorine groups with tertiary amines allows us to introduce quaternary, positively charged amines. The overall charge on the particles is then determined by the ratio between the sulfate/sulfonate moieties and the quaternary amines. Using this process, we were able to invert the charge in a continuous manner without losing colloidal stability upon passing the isoelectric point. The straightforward reaction mechanism together with the fact that the reaction could be quenched rapidly resulted in a colloidal system in which the ζ potential can be tuned between -80 and 45 mV. As proof of principle, the positively charged particles were used in heterocoagulation experiments with nanometer- and micrometer-sized negatively charged silica particles to create geometrically well-defined colloidal (nano) clusters.

  19. Rheological properties of Cubic colloidal suspensions

    Science.gov (United States)

    Boromand, Arman; Maia, Joao

    2016-11-01

    Colloidal and non-colloidal suspensions are ubiquitous in many industrial application. There are numerous studies on these systems to understand and relate their complex rheological properties to their microstructural evolution under deformation. Although most of the experimental and simulation studies are centered on spherical particles, in most of the industrial applications the geometry of the colloidal particles deviate from the simple hard sphere and more complex geometries exist. Recent advances in microfabrication paved the way to fabricate colloidal particles with complex geometries for applications in different areas such as drug delivery where the fundamental understanding of their dynamics has remained unexplored. In this study, using dissipative particle dynamics, we investigate the rheological properties of cubic (superball) particles which are modeled as the cluster of core-modified DPD particles. Explicit representation of solvent particles in the DPD scheme will conserve the full hydrodynamic interactions between colloidal particles. Rheological properties of these cubic suspensions are investigated in the dilute and semi-dilute regimes. The Einstein and Huggins coefficients for these particles with different superball exponent will be calculate which represent the effect of single particle's geometry and multibody interactions on viscosity, respectively. The response of these suspensions is investigated under simple shear and oscillatory shear where it is shown that under oscillation these particles tend to form crystalline structure giving rise to stronger shear-thinning behavior recently measured experimentally.

  20. Neptunium Colloidal Behaviors in Present of Humic Acids

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The colloidal-borne facilitated transport of actinides is an important part of radionuclide migration investigation in HLW geological disposal. In the present studies, Np colloidal behaviors in present of

  1. Colloidal joints with designed motion range and tunable joint flexibility.

    Science.gov (United States)

    Chakraborty, Indrani; Meester, Vera; van der Wel, Casper; Kraft, Daniela J

    2017-06-14

    The miniaturization of machines towards the micron and nanoscale requires the development of joint-like elements that enable and constrain motion. We present a facile method to create colloidal joints, that is, anisotropic colloidal particles functionalized with surface mobile DNA linkers that control the motion range of bonded particles. We demonstrate quantitatively that we can control the flexibility of these colloidal joints by tuning the DNA linker concentration in the bond area. We show that the shape of the colloidal joint controls the range of motion of bonded particles through a maximisation of the bond area. Using spheres, cubes, and dumbbells, we experimentally realize spherical joints, planar sliders, and hinges, respectively. Finally we demonstrate the potential of the colloidal joints for programmable bottom-up self-assembly by creating flexible colloidal molecules and colloidal polymers. The reconfigurability and motion constraint offered by our colloidal joints make them promising building blocks for the development of switchable materials and nanorobots.

  2. Inorganic passivation and doping control in colloidal quantum dot photovoltaics

    KAUST Repository

    Hoogland, Sjoerd H.

    2012-01-01

    We discuss strategies to reduce midgap trap state densities in colloidal quantum dot films and requirements to control doping type and magnitude. We demonstrate that these improvements result in colloidal quantum dot solar cells with certified 7.0% efficiency.

  3. Six-fold Coordinated Carbon Dioxide VI

    Energy Technology Data Exchange (ETDEWEB)

    Iota, V; Yoo, C; Klepeis, J; Jenei, Z

    2006-03-01

    Under standard conditions, carbon dioxide (CO{sub 2}) is a simple molecular gas and an important atmospheric constituent while silicon dioxide (SiO{sub 2}) is a covalent solid, and represents one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO{sub 2} transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO{sub 2} tridymite. Here, we present the discovery of a new extended-solid phase of carbon dioxide (CO{sub 2}): a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO{sub 2}-II above 50GPa at 530-650K. Together with the previously reported CO{sub 2}-V and a-carbonia, this new extended phase indicates a fundamental similarity between CO{sub 2}--a prototypical molecular solid, and SiO{sub 2}--one of Earth's fundamental building blocks. The phase diagram suggests a limited stability domain for molecular CO{sub 2}-I, and proposes that the conversion to extended-network solids above 40-50 GPa occurs via intermediate phases II, III, and IV. The crystal structure of phase VI suggests strong disorder along the caxis in stishovite-like P4{sub 2}/mnm, with carbon atoms manifesting an average six-fold coordination within the framework of sp{sup 3} hybridization.

  4. Doped Colloidal ZnO Nanocrystals

    Directory of Open Access Journals (Sweden)

    Yizheng Jin

    2012-01-01

    Full Text Available Colloidal ZnO nanocrystals are promising for a wide range of applications due to the combination of unique multifunctional nature and remarkable solution processability. Doping is an effective approach of enhancing the properties of colloidal ZnO nanocrystals in well-controlled manners. In this paper, we analyzed two synthetic strategies for the doped colloidal ZnO nanocrystals, emphasizing our understanding on the critical factors associated with the high temperature and nonaqueous approach. Latest advances of three topics, bandgap engineering, n-type doping, and dilute magnetic semiconductors related to doped ZnO nanocrystals were discussed to reveal the effects of dopants on the properties of the nanocrystalline materials.

  5. Shape-shifting colloids via stimulated dewetting

    Science.gov (United States)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-07-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly.

  6. Targeted delivery of colloids by swimming bacteria

    Science.gov (United States)

    Koumakis, N.; Lepore, A.; Maggi, C.; Di Leonardo, R.

    2013-01-01

    The possibility of exploiting motile microorganisms as tiny propellers represents a fascinating strategy for the transport of colloidal cargoes. However, delivery on target sites usually requires external control fields to steer propellers and trigger cargo release. The need for a constant feedback mechanism prevents the design of compact devices where biopropellers could perform their tasks autonomously. Here we show that properly designed three-dimensional (3D) microstructures can define accumulation areas where bacteria spontaneously and efficiently store colloidal beads. The process is stochastic in nature and results from the rectifying action of an asymmetric energy landscape over the fluctuating forces arising from collisions with swimming bacteria. As a result, the concentration of colloids over target areas can be strongly increased or depleted according to the topography of the underlying structures. Besides the significance to technological applications, our experiments pose some important questions regarding the structure of stationary probability distributions in non-equilibrium systems. PMID:24100868

  7. Plasmonic films based on colloidal lithography.

    Science.gov (United States)

    Ai, Bin; Yu, Ye; Möhwald, Helmuth; Zhang, Gang; Yang, Bai

    2014-04-01

    This paper reviews recent advances in the field of plasmonic films fabricated by colloidal lithography. Compared with conventional lithography techniques such as electron beam lithography and focused ion beam lithography, the unconventional colloidal lithography technique with advantages of low-cost and high-throughput has made the fabrication process more efficient, and moreover brought out novel films that show remarkable surface plasmon features. These plasmonic films include those with nanohole arrays, nanovoid arrays and nanoshell arrays with precisely controlled shapes, sizes, and spacing. Based on these novel nanostructures, optical and sensing performances can be greatly enhanced. The introduction of colloidal lithography provides not only efficient fabrication processes but also plasmonic films with unique nanostructures, which are difficult to be fabricated by conventional lithography techniques.

  8. Charge-transfer processes in semiconductor colloids

    Science.gov (United States)

    Kamat, Prashant V.; Gopidas, K. R.

    1990-04-01

    A picosecond transient absorption spectroscopy technique has been employed to probe the charge transfer processes in Ti02 semiconductor colloids. The trapping of electrons at the TiO surface (Ti4+ sitesY was characterized from the appearance of a broad absorption in the region of 550-750 nm following the 355-nm laser pulse excitation of Ti02 colloids. The lifetime of these trapped charge carriers increased upon incorporation of a hole scavenger in the colloidal semiconductor system. The mechanistic and kinetic details of the charge injection from excited CdS into a large bandgap semiconductor such as AgI and Ti02 have also been inves-' t i ga ted.

  9. Dynamic Assembly of Magnetic Colloidal Vortices

    Energy Technology Data Exchange (ETDEWEB)

    Mohorič, Tomaž; Kokot, Gašper; Osterman, Natan; Snezhko, Alexey; Vilfan, Andrej; Babič, Dušan; Dobnikar, Jure

    2016-04-29

    Magnetic colloids in external time-dependent fields are subject to complex induced many-body interactions governing their self-assembly into a variety of equilibrium and out-of-equilibrium structures such as chains, networks, suspended membranes, and colloidal foams. Here, we report experiments, simulations, and theory probing the dynamic assembly of superparamagnetic colloids in precessing external magnetic fields. Within a range of field frequencies, we observe dynamic large-scale structures such as ordered phases composed of precessing chains, ribbons, and rotating fluidic vortices. We show that the structure formation is inherently coupled to the buildup of torque, which originates from internal relaxation of induced dipoles and from transient correlations among the particles as a result of short-lived chain formation. We discuss in detail the physical properties of the vortex phase and demonstrate its potential in particle-coating applications.

  10. Vector assembly of colloids on monolayer substrates

    Science.gov (United States)

    Jiang, Lingxiang; Yang, Shenyu; Tsang, Boyce; Tu, Mei; Granick, Steve

    2017-06-01

    The key to spontaneous and directed assembly is to encode the desired assembly information to building blocks in a programmable and efficient way. In computer graphics, raster graphics encodes images on a single-pixel level, conferring fine details at the expense of large file sizes, whereas vector graphics encrypts shape information into vectors that allow small file sizes and operational transformations. Here, we adapt this raster/vector concept to a 2D colloidal system and realize `vector assembly' by manipulating particles on a colloidal monolayer substrate with optical tweezers. In contrast to raster assembly that assigns optical tweezers to each particle, vector assembly requires a minimal number of optical tweezers that allow operations like chain elongation and shortening. This vector approach enables simple uniform particles to form a vast collection of colloidal arenes and colloidenes, the spontaneous dissociation of which is achieved with precision and stage-by-stage complexity by simply removing the optical tweezers.

  11. TOPICAL REVIEW: Biological applications of colloidal nanocrystals

    Science.gov (United States)

    Parak, Wolfgang J.; Gerion, Daniele; Pellegrino, Teresa; Zanchet, Daniela; Micheel, Christine; Williams, Shara C.; Boudreau, Rosanne; LeGros, Mark A.; Larabell, Carolyn A.; Alivisatos, A. Paul

    2003-07-01

    Due to their interesting properties, research on colloidal nanocrystals has moved in the last few years from fundamental research to first applications in materials science and life sciences. In this review some recent biological applications of colloidal nanocrystals are discussed, without going into biological or chemical details. First, the properties of colloidal nanocrystals and how they can be synthesized are described. Second, the conjugation of nanocrystals with biological molecules is discussed. And third, three different biological applications are introduced: (i) the arrangement of nanocrystal-oligonucleotide conjugates using molecular scaffolds such as single-stranded DNA, (ii) the use of nanocrystal-protein conjugates as fluorescent probes for cellular imaging, and (iii) a motility assay based on the uptake of nanocrystals by living cells.

  12. Enhanced photoredox chemistry in quantized semiconductor colloids

    Energy Technology Data Exchange (ETDEWEB)

    Nedeljkovic, J.M.; Nenadovic, M.T.; Micic, O.I.; Nozik, A.J.

    1986-01-02

    Optical effects due to size quantization have been observed for HgSe, PbSe, and CdSe colloids in water and acetonitrile with particle diameters of 20-100 A. For diameters less than 50 A, the optical absorption edge of HgSe and PbSe is blue shifted by several volts. The results are consistent with perturbation of the semiconductor band structure due to carrier confinement in very small particles resulting in an increase in the effective band gap. The redox potential of photogenerated carriers is greatly enhanced in such quantized semiconductor particles; reduction reactions that cannot occur in bulk materials can occur in sufficiently small particles. This has been demonstrated with H/sub 2/ evolution in 50-A PbSe and HgSe colloids and CO/sub 2/ reduction in 50-A CdSe colloids. 13 references, 3 figures.

  13. Manipulating semiconductor colloidal stability through doping.

    Science.gov (United States)

    Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

    2014-10-10

    The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.

  14. Highly Elastic and Self-Healing Composite Colloidal Gels.

    Science.gov (United States)

    Diba, Mani; Wang, Huanan; Kodger, Thomas E; Parsa, Shima; Leeuwenburgh, Sander C G

    2017-03-01

    Composite colloidal gels are formed by the pH-induced electrostatic assembly of silica and gelatin nanoparticles. These injectable and moldable colloidal gels are able to withstand substantial compressive and tensile loads, and exhibit a remarkable self-healing efficiency. This study provides new, critical insight into the structural and mechanical properties of composite colloidal gels and opens up new avenues for practical application of colloidal gels.

  15. Colloidal interactions in two-dimensional nematic emulsions

    Indian Academy of Sciences (India)

    N M Silvestre; P Patrício; M M Telo Da Gama

    2005-06-01

    We review theoretical and experimental work on colloidal interactions in two-dimensional (2D) nematic emulsions. We pay particular attention to the effects of (i) the nematic elastic constants, (ii) the size of the colloids, and (iii) the boundary conditions at the particles and the container. We consider the interactions between colloids and fluid (deformable) interfaces and the shape of fluid colloids in smectic-C films.

  16. CARBON DIOXIDE FIXATION.

    Energy Technology Data Exchange (ETDEWEB)

    FUJITA,E.

    2000-01-12

    Solar carbon dioxide fixation offers the possibility of a renewable source of chemicals and fuels in the future. Its realization rests on future advances in the efficiency of solar energy collection and development of suitable catalysts for CO{sub 2} conversion. Recent achievements in the efficiency of solar energy conversion and in catalysis suggest that this approach holds a great deal of promise for contributing to future needs for fuels and chemicals.

  17. Oxyhydroxy Silicate Colloids: A New Type of Waterborne Actinide(IV) Colloids

    OpenAIRE

    Z?nker, Harald; Weiss, Stephan; Hennig, Christoph; Brendler, Vinzenz; Ikeda?Ohno, Atsushi

    2016-01-01

    Abstract At the near?neutral and reducing aquatic conditions expected in undisturbed ore deposits or in closed nuclear waste repositories, the actinides Th, U, Np, and Pu are primarily tetravalent. These tetravalent actinides (AnIV) are sparingly soluble in aquatic systems and, hence, are often assumed to be immobile. However, AnIV could become mobile if they occur as colloids. This review focuses on a new type of AnIV colloids, oxyhydroxy silicate colloids. We herein discuss the chemical cha...

  18. Oxyhydroxy Silicate Colloids: A New Type of Waterborne Actinide(IV) Colloids

    OpenAIRE

    Zänker, Harald; Weiss, Stephan; Hennig, Christoph; Brendler, Vinzenz; Ikeda‐Ohno, Atsushi

    2016-01-01

    Abstract At the near‐neutral and reducing aquatic conditions expected in undisturbed ore deposits or in closed nuclear waste repositories, the actinides Th, U, Np, and Pu are primarily tetravalent. These tetravalent actinides (AnIV) are sparingly soluble in aquatic systems and, hence, are often assumed to be immobile. However, AnIV could become mobile if they occur as colloids. This review focuses on a new type of AnIV colloids, oxyhydroxy silicate colloids. We herein discuss the chemical cha...

  19. Vortexlike topological defects in nematic colloids: chiral colloidal dimers and 2D crystals.

    Science.gov (United States)

    Tkalec, U; Ravnik, M; Zumer, S; Musevic, I

    2009-09-18

    We show that chiral ordering of the underlying complex fluid strongly influences defect formation and colloidal interactions. Nonsingular defect loops with a topological charge -2 are observed, with a cross section identical to hyperbolic vortices in magnetic systems. These loops are binding spontaneously formed pairs of colloidal particles and dimers, which are chiral objects. Chiral dimer-dimer interaction weakly depends on the chirality of dimers and leads to the assembly of 2D nematic colloidal crystals of pure or "mixed" chirality, intercalated with a lattice of nonsingular vortexlike defects.

  20. Chlorine dioxide and hemodialysis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, R.P. (Dartmouth Coll., Hanover, NH (USA). Dept. of Pharmacology and Toxicology)

    1989-05-01

    Because it has little or no tendency to generate carcinogenic trihalomethanes such as chloroform, chlorine dioxide is an attractive alternative to chlorine for drinking water disinfection. There are, however, concerns about its acute toxicity, and the toxic effects of its by-products, chlorite and chlorate. The human experience with chlorine dioxide in both controlled, prospective studies and in actual use situations in community water supplies have as yet failed to reveal adverse health effects. The EPA has recommended standards of 0.06 mg/L for chlorine dioxide and standards of 0.007 mg/L for chlorite and chlorate in drinking water. Among groups who may be at special risk from oxychlorines in drinking water are patients who must undergro chronic extracorporeal hemodialysis. Although even units for home hemodialysis are supposed to be equipped with devices which effectively remove oxychlorines, there is a always a possibility of operator error or equipment failure. When the equipment is adequately maintained, it is likely that dialysis patients will have more intensive exposures from drinking water than from dialysis fluids despite the much larger volumes of water that are involved in dialysis. This paper discusses a hemodialysis and the standards and effects of oxychlorines. 90 refs., 2 tabs.

  1. Clustering and self-assembly in colloidal systems

    NARCIS (Netherlands)

    Smallenburg, F.

    2012-01-01

    A colloidal dispersion consists of small particles called colloids, typically tens of nanometers to a few micrometers in size, suspended in a solvent. Due to collisions with the much smaller particles in the solvent, colloids perform Brownian motion: randomly directed movements that cause the

  2. Interplay between Colloids and Interfaces : Emulsions, Foams and Microtubes

    NARCIS (Netherlands)

    de Folter, J.W.J.

    2013-01-01

    The central theme of this thesis is the interplay between colloids and interfaces. The adsorption of colloids at fluid-fluid interfaces is the main topic and covers Chapters 2-6. Pickering emulsions where colloidal particles act as emulsion stabilizers in the absence of surfactants are studied in a

  3. A general method to coat colloidal particles with titiana

    NARCIS (Netherlands)

    Demirors, A.F.; van Blaaderen, A.; Imhof, A.

    2010-01-01

    We describe a general one-pot method for coating colloidal particles with amorphous titania. Various colloidal particles such as silica particles, large silver colloids, gibbsite platelets, and polystyrene spheres were successfully coated with a titania shell. Although there are several ways of coat

  4. Shape recognition of microbial cells by colloidal cell imprints

    NARCIS (Netherlands)

    Borovicka, J.; Stoyanov, S.D.; Paunov, V.N.

    2013-01-01

    We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called "colloid antibodies", were fabricated by partial fragmentation of silica shells obtained by templating

  5. Introduction to Applied Colloid and Surface Chemistry

    DEFF Research Database (Denmark)

    Kontogeorgis, Georgios; Kiil, Søren

    Colloid and Surface Chemistry is a subject of immense importance and implications both to our everyday life and numerous industrial sectors, ranging from coatings and materials to medicine and biotechnology. How do detergents really clean? (Why can’t we just use water ?) Why is milk “milky” Why do......, to the benefit of both the environment and our pocket. Cosmetics is also big business! Creams, lotions and other personal care products are really just complex emulsions. All of the above can be explained by the principles and methods of colloid and surface chemistry. A course on this topic is truly valuable...

  6. Self-assembly of colloidal surfactants

    Science.gov (United States)

    Kegel, Willem

    2012-02-01

    We developed colloidal dumbbells with a rough and a smooth part, based on a method reported in Ref. [1]. Specific attraction between the smooth parts occurs upon addition of non-adsorbing polymers of appropriate size. We present the first results in terms of the assemblies that emerge in these systems. [4pt] [1] D.J. Kraft, W.S. Vlug, C.M. van Kats, A. van Blaaderen, A. Imhof and W.K. Kegel, Self-assembly of colloids with liquid protrusions, J. Am. Chem. Soc. 131, 1182, (2009)

  7. Binary Colloidal Alloy Test-5: Phase Separation

    Science.gov (United States)

    Lynch, Matthew; Weitz, David A.; Lu, Peter J.

    2008-01-01

    The Binary Colloidal Alloy Test - 5: Phase Separation (BCAT-5-PhaseSep) experiment will photograph initially randomized colloidal samples onboard the ISS to determine their resulting structure over time. This allows the scientists to capture the kinetics (evolution) of their samples, as well as the final equilibrium state of each sample. BCAT-5-PhaseSep studies collapse (phase separation rates that impact product shelf-life); in microgravity the physics of collapse is not masked by being reduced to a simple top and bottom phase as it is on Earth.

  8. Collective sliding states for colloidal molecular crystals

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia [Los Alamos National Laboratory

    2008-01-01

    We study the driving of colloidal molecular crystals over periodic substrates such as those created with optical traps. The n-merization that occurs in the colloidal molecular crystal states produces a remarkably rich variety of distinct dynamical behaviors, including polarization effects within the pinned phase and the formation of both ordered and disordered sliding phases. Using computer simulations, we map the dynamic phase diagrams as a function of substrate strength for dimers and trimers on a triangular substrate, and correlate features on the phase diagram with transport signatures.

  9. Dynamics of colloidal particles in ice

    KAUST Repository

    Spannuth, Melissa

    2011-01-01

    We use x-ray photon correlation spectroscopy (XPCS) to probe the dynamics of colloidal particles in polycrystalline ice. During freezing, the dendritic ice morphology and rejection of particles from the ice created regions of high particle density, where some of the colloids were forced into contact and formed disordered aggregates. The particles in these high density regions underwent ballistic motion, with a characteristic velocity that increased with temperature. This ballistic motion is coupled with both stretched and compressed exponential decays of the intensity autocorrelation function. We suggest that this behavior could result from ice grain boundary migration. © 2011 American Institute of Physics.

  10. Fabrication of anisotropic multifunctional colloidal carriers

    Science.gov (United States)

    Jerri, Huda A.

    The field of colloidal assembly has grown tremendously in recent years, although the direct or template-assisted methods used to fabricate complex colloidal constructions from monodisperse micro- and nanoparticles have been generally demonstrated on model materials. In this work, novel core particle syntheses, particle functionalizations and bottom-up assembly techniques are presented to create functional colloidal devices. Using particle lithography, high-information colloidal vectors have been developed and modified with imaging and targeting agents. Localized nanoscale patches have been reliably positioned on microparticles to serve as foundations for further chemical or physical modifications. Site-specific placement of RGD targeting ligands has been achieved in these lithographed patches. Preferential uptake of these targeted vectors by RGD-specific 3T3 fibroblasts was verified using confocal laser scanning microscopy. A transition was made from the functionalization of model imaging core particles to the lithography of colloidal cartridges, in an effort to construct colloidal syringes with specialized, programmable release profiles. A variety of functional, pH-sensitive fluorescent cores were engineered to respond to solution conditions. When triggered, the diverse composite core microparticles and reservoir microcapsules released embedded fluorescent moieties such as dye molecules, and fluorophore-conjugated nanoparticles. The microcapsules, created using layer-by-layer polyelectrolyte deposition on sacrificial templates, were selectively modified with a robust coating. The pH-responsive anisotropic reservoir microcapsules were extremely stable in solution, and exhibited a "Lazarus" functionality of rehydrating to their original state following desiccation. A snapshot of focused-release of core constituents through the lone opening in colloidal monotremes has been obtained by anisotropically-functionalizing degradable cores with barrier shells. Additionally

  11. Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

    Directory of Open Access Journals (Sweden)

    Jia Ge

    2014-01-01

    Full Text Available We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar n-type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms−1 and an implied open-circuit voltage (Voc of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

  12. Control of iron nanoparticle size by manipulating PEG-ethanol colloidal solutions and spin-coating parameters for the growth of single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    Choon-Ming Seah; Siang-Piao Chai; Satoshi Ichikawa; Abdul Rahman Mohamed

    2013-01-01

    Iron catalyst nanoparticles were prepared on silicon wafers by spin-coating colloidal solutions containing iron nitrate,polyethylene glycol (PEG) and absolute ethanol.The effects of various spin-coating conditions were investigated.The findings showed that the size of the iron particles was governed by the composition of the colloidal solution used and that a high angular speed was responsible for the formation of a thin colloidal film.The effect of angular acceleration on the size and distribution of the iron particles were found to be insignificant.It was observed that a longer spin-coating duration provoked the agglomeration of iron particles,leading to the formation of large particles.We also showed that single-walled carbon nanotubes could be grown from the smallest iron catalyst nanoparticles after the chemical vapor deposition of methane.

  13. Preparation of highly permeable BPPO microfiltration membrane with binary porous structures on a colloidal crystal substrate by the breath figure method.

    Science.gov (United States)

    Yuan, Hua; Yu, Bing; Cong, Hailin; Peng, Qiaohong; Yang, Zhen; Luo, Yongli; Chi, Ming

    2016-01-01

    A highly permeable brominated poly(phenylene oxide) (BPPO) microfiltration membrane with binary porous structures was fabricated by combination of the breath figure and colloidal crystal template methods. The pore size in the bottom layer of the membrane was adjusted by the diameter of SiO2 microspheres in the colloidal crystal template, while the pore size in the top layer of the membrane was adjusted by varying the BPPO concentration in the casting solution. The permeability of the membrane cast on the colloidal crystal substrate was much higher than that of the membrane cast on a bare silicon wafer. The binary porous BPPO membrane with high permeability and antifouling property was used for microfiltration applications.

  14. Doping Silicon Wafers with Boron by Use of Silicon Paste

    Institute of Scientific and Technical Information of China (English)

    Yu Gao; Shu Zhou; Yunfan Zhang; Chen Dong; Xiaodong Pi; Deren Yang

    2013-01-01

    In this work we introduce recently developed silicon-paste-enabled p-type doping for silicon.Boron-doped silicon nanoparticles are synthesized by a plasma approach.They are then dispersed in solvents to form silicon paste.Silicon paste is screen-printed at the surface of silicon wafers.By annealing,boron atoms in silicon paste diffuse into silicon wafers.Chemical analysis is employed to obtain the concentrations of boron in silicon nanoparticles.The successful doping of silicon wafers with boron is evidenced by secondary ion mass spectroscopy (SIMS) and sheet resistance measurements.

  15. Silicon: electrochemistry and luminescence

    NARCIS (Netherlands)

    Kooij, Ernst Stefan

    1997-01-01

    The electrochemistry of crystalline and porous silicon and the luminescence from porous silicon has been studied. One chapter deals with a model for the anodic dissolution of silicon in HF solution. In following chapters both the electrochemistry and various ways of generating visible luminescenc

  16. Silicon: electrochemistry and luminescence

    NARCIS (Netherlands)

    Kooij, Ernst Stefan

    1997-01-01

    The electrochemistry of crystalline and porous silicon and the luminescence from porous silicon has been studied. One chapter deals with a model for the anodic dissolution of silicon in HF solution. In following chapters both the electrochemistry and various ways of generating visible

  17. Silicon: electrochemistry and luminescence

    NARCIS (Netherlands)

    Kooij, Ernst Stefan

    2001-01-01

    The electrochemistry of crystalline and porous silicon and the luminescence from porous silicon has been studied. One chapter deals with a model for the anodic dissolution of silicon in HF solution. In following chapters both the electrochemistry and various ways of generating visible luminescenc

  18. Preparation of electrochemically active silicon nanotubes in highly ordered arrays

    Directory of Open Access Journals (Sweden)

    Tobias Grünzel

    2013-10-01

    Full Text Available Silicon as the negative electrode material of lithium ion batteries has a very large capacity, the exploitation of which is impeded by the volume changes taking place upon electrochemical cycling. A Si electrode displaying a controlled porosity could circumvent the difficulty. In this perspective, we present a preparative method that yields ordered arrays of electrochemically competent silicon nanotubes. The method is based on the atomic layer deposition of silicon dioxide onto the pore walls of an anodic alumina template, followed by a thermal reduction with lithium vapor. This thermal reduction is quantitative, homogeneous over macroscopic samples, and it yields amorphous silicon and lithium oxide, at the exclusion of any lithium silicides. The reaction is characterized by spectroscopic ellipsometry for thin silica films, and by nuclear magnetic resonance and X-ray photoelectron spectroscopy for nanoporous samples. After removal of the lithium oxide byproduct, the silicon nanotubes can be contacted electrically. In a lithium ion electrolyte, they then display the electrochemical waves also observed for other bulk or nanostructured silicon systems. The method established here paves the way for systematic investigations of how the electrochemical properties (capacity, charge/discharge rates, cyclability of nanoporous silicon negative lithium ion battery electrode materials depend on the geometry.

  19. Influence of biofilms on colloid transport: investigations with laponite as a model colloid

    Energy Technology Data Exchange (ETDEWEB)

    Leon-Morales, C.F.; Flemming, H.C.; Leis, A. [Duisburg Univ. (Germany). Inst. for Interface Biotechnology

    2003-07-01

    The synthetic clay mineral laponite RD was used as a model compound to investigate colloid transport in the presence of bacterial biofilms. A complex but pronounced delay in the transport of laponite was observed in colonised porous media, clearly demonstrating the influence of attached bacterial biomass on colloid transport. The transport of laponite under conditions which promoted laponite aggregation was associated with release of attached bacteria; this effect was shown to be independent of ionic strength, indicating that the colloids caused detachment of bacteria. Two major mechanisms are proposed to account for the different colloid transport patterns obtained in the presence or absence of biomass: (1) hydrodynamic effects due to aggregation of laponite and subsequent blockage of a proportion of the flow channels, and (2) sorption of laponite by bacterial biomass. (orig.)

  20. Reaction products of chlorine dioxide.

    OpenAIRE

    Stevens, A A

    1982-01-01

    Inspection of the available literature reveals that a detailed investigation of the aqueous organic chemistry of chlorine dioxide and systematic identification of products formed during water disinfection has not been considered. This must be done before an informed assessment can be made of the relative safety of using chlorine dioxide as a disinfectant alternative to chlorine. Although trihalomethanes are generally not formed by the action of chlorine dioxide, the products of chlorine dioxi...

  1. Reaction products of chlorine dioxide.

    OpenAIRE

    Stevens, A. A.

    1982-01-01

    Inspection of the available literature reveals that a detailed investigation of the aqueous organic chemistry of chlorine dioxide and systematic identification of products formed during water disinfection has not been considered. This must be done before an informed assessment can be made of the relative safety of using chlorine dioxide as a disinfectant alternative to chlorine. Although trihalomethanes are generally not formed by the action of chlorine dioxide, the products of chlorine dioxi...

  2. Process to produce silicon carbide fibers using a controlled concentration of boron oxide vapor

    Science.gov (United States)

    Barnard, Thomas Duncan (Inventor); Lipowitz, Jonathan (Inventor); Nguyen, Kimmai Thi (Inventor)

    2001-01-01

    A process for producing polycrystalline silicon carbide by heating an amorphous ceramic fiber that contains silicon and carbon in an environment containing boron oxide vapor. The boron oxide vapor is produced in situ by the reaction of a boron containing material such as boron carbide and an oxidizing agent such as carbon dioxide, and the amount of boron oxide vapor can be controlled by varying the amount and rate of addition of the oxidizing agent.

  3. Dynamics of Colloids Confined in Microcylinders

    NARCIS (Netherlands)

    Ghosh, Somnath; Wijnperle, Daniël; Mugele, Friedrich Gunther; Duits, Michael H.G.

    2016-01-01

    We studied both global and local effects of cylindrical confinement on the diffusive behavior of hard sphere (HS) colloids. Using confocal scanning laser microscopy (CSLM) and particle tracking, we measured the mean squared displacement (MSD) of 1 micron sized silica particles in water–glycerol.

  4. Colloidal models. A bit of history

    NARCIS (Netherlands)

    Lyklema, J.

    2015-01-01

    This paper offers an anthology on developments in colloid and interface science emphasizing themes that may be of direct or indirect interest to Interfaces Against Pollution. Topics include the determination of Avogadro’s number, development in the insight into driving forces for double layer format

  5. Aggregation kinetics of coalescing polymer colloids.

    Science.gov (United States)

    Gauer, Cornelius; Jia, Zichen; Wu, Hua; Morbidelli, Massimo

    2009-09-01

    The aggregation behavior of a soft, rubbery colloidal system with a relatively low glass transition temperature, T(g) approximately -20 degrees C, has been investigated. It is found that the average gyration and hydrodynamic radii, R(g) and R(h), measured by light scattering techniques, evolve in time in parallel, without exhibiting the crossover typical of rigid particle aggregation. Cryogenic scanning electron microscopy (cryo-SEM) images reveal sphere-like clusters, indicating that complete coalescence between particles occurs during aggregation. Since coalescence leads to a reduction in the total colloidal surface area, the surfactant adsorption equilibrium, and thus the colloidal stability, change in the course of aggregation. It is found that to simulate the observed kinetic behavior based on the population balance equations, it is necessary to assume that all the clusters are spherical and to account for variations in the colloidal stability of each aggregating particle pair with time. This indicates that, for the given system, the coalescence is very fast, i.e., its time scale is much smaller than that of the aggregation.

  6. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  7. Colloidal Toolbox Synthesis of Pt Nanoalloys

    DEFF Research Database (Denmark)

    Spanos, Ioannis

    enhancement of the activity is observeddue to the introduction of an electronic or ligand effect. The above method is however difficult to control and its reproducibility is poor. For thatreason, a colloidal method is used as a toolbox to conduct systematic studies on PtxCo1-xnanoalloys. This method provides...

  8. Designing Zirconium Coated Polystyrene Colloids and Application

    Directory of Open Access Journals (Sweden)

    Diana Chira

    2009-01-01

    Full Text Available A simple technique has been developed to prepare core colloids that are modified using zirconium oxychloride, based on heating a solution of core colloid composites, consisting of poly (ethylenimine (PEI and zirconium oxychloride. The interaction of zirconium oxychloride with the polystyrene (PS core colloids has been investigated using Fourier transform-infrared spectroscopy (FT-IR, energy dispersive X-ray spectroscopy (EDX, and scanning electron microscopy (SEM data. FT-IR studies confirm the occurrence of amine groups present in PEI which are oxidized to carboxyl groups after the reaction. The EDX data and the SEM images confirm the presence of zirconium particles immobilized on the polystyrene surfaces. Demeton, a highly toxic nerve agent, was used due to its ability to easily bind through its organophosphate group illustrating a practical application of the PS-PEI-Zr particles. Attenuated Total Reflection (ATR Spectroscopy was used to assess the interactions between the toxic nerve agent demeton-S and the PS-PEI-Zr particles. The results show that the presented technique for coating polystyrene core colloids with zirconium was successfully accomplished, and the newly formed particles easily bond with demeton agents through the P=O functional group.

  9. Dipolar structures in colloidal magnetite dispersions

    NARCIS (Netherlands)

    Klokkenburg, Mark

    2007-01-01

    Dipolar structures in liquid colloidal dispersions comprising well-defined magnetite (Fe3O4) nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). Compared to conventional ferrofluids, these dispersio

  10. Natural and Synthetic Colloids in Veterinary Medicine.

    Science.gov (United States)

    Brooks, Aimee; Thomovsky, Elizabeth; Johnson, Paula

    2016-06-01

    This review article covers basic physiology underlying the clinical use of natural and artificial colloids as well as provide practice recommendations. It also touches on the recent scrutiny of these products in human medicine and how this may have an effect on their use in veterinary medicine. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Rheology and dynamics of colloidal superballs.

    Science.gov (United States)

    Royer, John R; Burton, George L; Blair, Daniel L; Hudson, Steven D

    2015-07-28

    Recent advances in colloidal synthesis make it possible to generate a wide array of precisely controlled, non-spherical particles. This provides a unique opportunity to probe the role that particle shape plays in the dynamics of colloidal suspensions, particularly at higher volume fractions, where particle interactions are important. We examine the role of particle shape by characterizing both the bulk rheology and micro-scale diffusion in a suspension of pseudo-cubic silica superballs. Working with these well-characterized shaped colloids, we can disentangle shape effects in the hydrodynamics of isolated particles from shape-mediated particle interactions. We find that the hydrodynamic properties of isolated superballs are marginally different from comparably sized hard spheres. However, shape-mediated interactions modify the suspension microstructure, leading to significant differences in the self-diffusion of the superballs. While this excluded volume interaction can be captured with a rescaling of the superball volume fraction, we observe qualitative differences in the shear thickening behavior of moderately concentrated superball suspensions that defy simple rescaling onto hard sphere results. This study helps to define the unknowns associated with the effects of shape on the rheology and dynamics of colloidal solutions.

  12. Dipolar structures in colloidal magnetite dispersions

    NARCIS (Netherlands)

    Klokkenburg, Mark

    2007-01-01

    Dipolar structures in liquid colloidal dispersions comprising well-defined magnetite (Fe3O4) nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). Compared to conventional ferrofluids, these dispersio

  13. Colloidal crystals by electrospraying polystyrene nanofluids

    Science.gov (United States)

    2013-01-01

    This work introduces the electrospray technique as a suitable option to fabricate large-scale colloidal nanostructures, including colloidal crystals, in just a few minutes. It is shown that by changing the deposition conditions, different metamaterials can be fabricated: from scattered monolayers of polystyrene nanospheres to self-assembled three-dimensional ordered nanolayers having colloidal crystal properties. The electrospray technique overcomes the main problems encountered by top-down fabrication approaches, largely simplifying the experimental setup. Polystyrene nanospheres, with 360-nm diameter, were typically electrosprayed using off-the-shelf nanofluids. Several parameters of the setup and deposition conditions were explored, namely the distance between electrodes, nanofluid conductivity, applied voltage, and deposition rate. Layers thicker than 20 μm and area of 1 cm2 were typically produced, showing several domains of tens of microns wide with dislocations in between, but no cracks. The applied voltage was in the range of 10 kV, and the conductivity of the colloidal solution was in the range of 3 to 4 mS. Besides the morphology of the layers, the quality was also assessed by means of optical reflectance measurements showing an 80% reflectivity peak in the vicinity of 950-nm wavelength. PMID:23311494

  14. Cell shape recognition by colloidal cell imprints

    NARCIS (Netherlands)

    Borovička, Josef; Stoyanov, S.D.; Paunov, V.N.

    2015-01-01

    The results presented in this study are aimed at the theoretical estimate of the interactions between a spherical microbial cell and the colloidal cell imprints in terms of the Derjaguin, Landau, Vervey, and Overbeek (DLVO) surface forces. We adapted the Derjaguin approximation to take into accou

  15. Transformative Colloidal Nanomaterials for Mid- Infrared Devices

    Science.gov (United States)

    2015-06-11

    446 (2005) [2] Hillhouse, H.W., Beard, M.C., “Solar cells from colloidal nanocrystals: Fundamentals, materials, devices, and economics ,” Curr. Op...I., Fischer , A., Hoogland, S., Clifford, J., Klem, E., Levina, L., Sargent, EH., “Ultrasensitive solution-cast quantum dot photodetectors

  16. Repeptization and the theory of electrocratic colloids

    NARCIS (Netherlands)

    Frens, G.; Overbeek, J.Th.G.

    1972-01-01

    The coagulation and the repeptization of electrocratic colloids can be treated in one theory provided that the appropriate boundary conditions are chosen. From this version of the DLVO theory it follows that for each sol there exists a critical value Z∞c of the double layer parameter Z∞, Z∞ = zeδ/kT

  17. Colloidal quantum dots as optoelectronic elements

    Science.gov (United States)

    Vasudev, Milana; Yamanaka, Takayuki; Sun, Ke; Li, Yang; Yang, Jianyong; Ramadurai, Dinakar; Stroscio, Michael A.; Dutta, Mitra

    2007-02-01

    Novel optoelectronic systems based on ensembles of semiconductor nanocrystals are addressed in this paper. Colloidal semiconductor quantum dots and related quantum-wire structures have been characterized optically; these optical measurements include those made on self-assembled monolayers of DNA molecules terminated on one end with a common substrate and on the other end with TiO II quantum dots. The electronic properties of these structures are modeled and compared with experiment. The characterization and application of ensembles of colloidal quantum dots with molecular interconnects are considered. The chemically-directed assembly of ensembles of colloidal quantum dots with biomolecular interconnects is demonstrated with quantum dot densities in excess of 10 +17 cm -3. A number of novel photodetectors have been designed based on the combined use of double-barrier quantum-well injectors, colloidal quantum dots, and conductive polymers. Optoelectronic devices including photodetectors and solar cells based on threedimensional ensembles of quantum dots are considered along with underlying phenomena such as miniband formation and the robustness of minibands to displacements of quantum dots in the ensemble.

  18. Geochemistry of colloid systems. For earth scientists

    NARCIS (Netherlands)

    Nickel, E.

    1979-01-01

    The second part of the title of this book gives an indication for whom it has been written. It is a real 'synthesizer'. Throughout ten chapters the reader is introduced into the highly complex matter of colloid chemistry and its role in geochemistry, pedology, oceanography, and geology.

  19. Non-Fickian diffusion in colloidal glasses

    NARCIS (Netherlands)

    Hagen, M.H.J.; Frenkel, D.; Lowe, C.P.

    1998-01-01

    We have studied numerically the decay of the self-dynamic structure factor (SDSF) for a small particle diffusing in a colloidal glass. We show that, in line with theoretical predictions, the super-Burnett coefficient (characterizing the deviation of the fourth moment of the single particle distribut

  20. Phase behavior of colloidal silica rods

    NARCIS (Netherlands)

    Kuijk, A.; Byelov, D.; Petukhov, A.V.; van Blaaderen, A.; Imhof, A.

    2012-01-01

    Recently, a novel colloidal hard-rod-like model system was developed which consists of silica rods [Kuijk et al., JACS, 2011, 133, 2346]. Here, we present a study of the phase behavior of these rods, for aspect ratios ranging from 3.7 to 8.0. By combining real-space confocal laser scanning microscop

  1. Random packing of colloids and granular matter

    NARCIS (Netherlands)

    Wouterse, A.

    2008-01-01

    This thesis deals with the random packing of colloids and granular matter. A random packing is a stable disordered collection of touching particles, without long-range positional and orientational order. Experimental random packings of particles with the same shape but made of different materials sh

  2. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  3. Patchy particles made by colloidal fusion.

    Science.gov (United States)

    Gong, Zhe; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2017-09-18

    Patches on the surfaces of colloidal particles provide directional information that enables the self-assembly of the particles into higher-order structures. Although computational tools can make quantitative predictions and can generate design rules that link the patch motif of a particle to its internal microstructure and to the emergent properties of the self-assembled materials, the experimental realization of model systems of particles with surface patches (or 'patchy' particles) remains a challenge. Synthetic patchy colloidal particles are often poor geometric approximations of the digital building blocks used in simulations and can only rarely be manufactured in sufficiently high yields to be routinely used as experimental model systems. Here we introduce a method, which we refer to as colloidal fusion, for fabricating functional patchy particles in a tunable and scalable manner. Using coordination dynamics and wetting forces, we engineer hybrid liquid-solid clusters that evolve into particles with a range of patchy surface morphologies on addition of a plasticizer. We are able to predict and control the evolutionary pathway by considering surface-energy minimization, leading to two main branches of product: first, spherical particles with liquid surface patches, capable of forming curable bonds with neighbouring particles to assemble robust supracolloidal structures; and second, particles with a faceted liquid compartment, which can be cured and purified to yield colloidal polyhedra. These findings outline a scalable strategy for the synthesis of patchy particles, first by designing their surface patterns by computer simulation, and then by recreating them in the laboratory with high fidelity.

  4. Colloidal dynamics in flow and confinement

    NARCIS (Netherlands)

    Ghosh, Somnath

    2015-01-01

    The aim of this thesis is to understand how the diffusive dynamics and flow behaviors of colloidal hard spheres are influenced by the confinement of nearby walls. The Brownian motion of hard spheres in quiescent bulk fluids is well known, but the presence of confining walls generate new physical phe

  5. Advanced Colloids Experiment (ACE-H-2)

    Science.gov (United States)

    Meyer, William V.; Sicker, Ron; Chmiel, Alan J.; Eustace, John; LaBarbera, Melissa

    2015-01-01

    Increment 43 - 44 Science Symposium presentation of Advanced Colloids Experiment (ACE-H-2) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  6. Advanced Colloids Experiment (ACE-T1)

    Science.gov (United States)

    Meyer, William V.; Sicker, Ron; Brown, Dan; Eustace, John

    2015-01-01

    Increment 45 - 46 Science Symposium presentation of Advanced Colloids Experiment (ACE-T1) to RPO. The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators.

  7. Morphology of colloidal metal pyrophosphate salts

    NARCIS (Netherlands)

    van Leeuwen, Y.M.; Velikov, K.; Kegel, W.K.

    2012-01-01

    We report the preparation and characterization of colloidal particles of several pyrophosphate metal salts, including, for the first time, salts containing multiple metals. These materials are compared in order to determine the influence of the composition and experimental conditions on particle

  8. The glass transition of hard spherical colloids

    Energy Technology Data Exchange (ETDEWEB)

    Pusey, P.N. (Royal Signals and Radar Establishment, Malvern (UK)); Van Megen, W. (Royal Melbourne Inst. of Tech. (Australia). Dept. of Applied Physics)

    1990-03-01

    When suspended in a liquid, hard spherical colloidal particles can show fluid, crystalline and glassy phases. A light scattering study of the dynamics of the metastable fluid and glassy phases is reported. Comparison is made with the predictions of mode-coupling theories applied to the glass transition of simple atomic systems. (orig.).

  9. The chemistry of silicon

    CERN Document Server

    Rochow, E G; Emeléus, H J; Nyholm, Ronald

    1975-01-01

    Pergamon Texts in Organic Chemistry, Volume 9: The Chemistry of Silicon presents information essential in understanding the chemical properties of silicon. The book first covers the fundamental aspects of silicon, such as its nuclear, physical, and chemical properties. The text also details the history of silicon, its occurrence and distribution, and applications. Next, the selection enumerates the compounds and complexes of silicon, along with organosilicon compounds. The text will be of great interest to chemists and chemical engineers. Other researchers working on research study involving s

  10. Assembly of Colloidal Materials Using Bioadhesive Interactions

    Science.gov (United States)

    Hammer, Daniel A.; Hiddessen, Amy L.; Tohver, Valeria; Crocker, John C.; Weitz, David A.

    2002-01-01

    We have pursued the use of biological crosslinking molecules of several types to make colloidal materials at relatively low volume fraction of colloidal particles. The objective is to make binary alloys of colloidal particles, made of two different colloidal particles coated with complementary biological lock-and-key binding molecules, which assemble due to the biological specificity. The long-term goal is to use low affinity lock-and-key biological interactions, so that the can anneal to form crystalline states. We have used a variety of different surface chemistries in order to make colloidal materials. Our first system involved using selectin-carbohydrate (sialyl-Lewis) interactions; this chemistry is derived from immune system. This chemical interaction is of relatively low affinity, with timescales for dissociation of several seconds. Furthermore, the adhesion mediated by these molecules can be reversed by the chelation of calcium atoms; thus assembled structures can be disassembled reversibly. Our second system employed avidin-biotin chemistry. This well-studied system is of high affinity, and is generally irreversible on a laboratory time-scale. Thus, we would expect selectin-carbohydrate interactions at high molecular density and avidin-biotin interactions to give kinetically-trapped structures; however, at low densities, we would expect significant differences in the structure and dynamics of the two materials, owing to their very different release rates. We have also begun to use a third chemistry - DNA hybridization. By attaching single stranded DNA oligonucleotide chains to beads, we can drive the assembly of colloidal materials by hybridization of complementary DNA chains. It is well known that DNA adenosine-thymine (A-T) and guanine-cytosine (G-C) bases hybridize pairwise with a Gibbs free energy change of 1.7 kcal/mol per base; thus, the energy of the assembly can be modulated by altering the number of complementary bases in the DNA chains. Using

  11. Colloid suspension stability and transport through unsaturated porous media

    Energy Technology Data Exchange (ETDEWEB)

    McGraw, M.A.; Kaplan, D.I.

    1997-04-01

    Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media.

  12. Dynamic Colloidal Molecules Maneuvered by Light-Controlled Janus Micromotors.

    Science.gov (United States)

    Gao, Yirong; Mou, Fangzhi; Feng, Yizheng; Che, Shengping; Li, Wei; Xu, Leilei; Guan, Jianguo

    2017-07-12

    In this work, we propose and demonstrate a dynamic colloidal molecule that is capable of moving autonomously and performing swift, reversible, and in-place assembly dissociation in a high accuracy by manipulating a TiO2/Pt Janus micromotor with light irradiation. Due to the efficient motion of the TiO2/Pt Janus motor and the light-switchable electrostatic interactions between the micromotor and colloidal particles, the colloidal particles can be captured and assembled one by one on the fly, subsequently forming into swimming colloidal molecules by mimicking space-filling models of simple molecules with central atoms. The as-demonstrated dynamic colloidal molecules have a configuration accurately controlled and stabilized by regulating the time-dependent intensity of UV light, which controls the stop-and-go motion of the colloidal molecules. The dynamic colloidal molecules are dissociated when the light irradiation is turned off due to the disappearance of light-switchable electrostatic interaction between the motor and the colloidal particles. The strategy for the assembly of dynamic colloidal molecules is applicable to various charged colloidal particles. The simulated optical properties of a dynamic colloidal molecule imply that the results here may provide a novel approach for in-place building functional microdevices, such as microlens arrays, in a swift and reversible manner.

  13. Colloid Mobilization and Transport during Capillary Fringe Fluctuations

    Science.gov (United States)

    Aramrak, Surachet; Flury, Markus

    2016-04-01

    Capillary fringe fluctuations due to changing water tables lead to displacement of air-water interfaces in soils and sediments. These moving air-water interfaces can mobilize colloids. We visualized colloids interacting with moving air-water interfaces during capillary fringe fluctuations by confocal microscopy. We simulated capillary fringe fluctuations in a glass-bead filled column. Confocal images showed that the capillary fringe fluctuations affect colloid transport behavior. Hydrophilic negatively-charged colloids initially suspended in the aqueous phase were deposited at the solid-water interface after a drainage passage, but then were removed by subsequent capillary fringe fluctuations. The colloids that were initially attached to the wet or dry glass bead surface were detached by moving air-water interfaces in the capillary fringe. Hydrophilic negatively-charged colloids did not attach to static air-bubbles, but hydrophobic negatively-charged and hydrophilic positively-charged colloids did.

  14. Cross-interaction drives stratification in drying film of binary colloidal mixtures

    OpenAIRE

    Zhou, Jiajia; Jiang, Ying; Doi, Masao

    2017-01-01

    When a liquid film of colloidal solution consisting of particles of different sizes is dried on a substrate, the colloids often stratify, where smaller colloids are laid upon larger colloids. This phenomenon is counter intuitive because larger colloids which have smaller diffusion constant are expected to remain near the surface during the drying process, leaving the layer of larger colloids on top of smaller colloids. Here we show that the phenomenon is caused by the interaction between the ...

  15. Investigation on the Stability of Aluminosilicate Colloids by Various Analytical Tools

    Energy Technology Data Exchange (ETDEWEB)

    Putri, Kirana Y.; Lee, D. H.; Yun, J. I. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2010-05-15

    Colloids are ubiquitous in natural aquatic systems. Aquatic colloids may play a significant carrier role for radionuclide migration in aquifer systems. Being omnipresent in natural aquatic systems, aluminosilicate colloids are considered as a kernel for various aquatic colloids. Characterization of aluminosilicate colloids formed under various geochemical conditions is of importance to understand their chemical behavior in natural aquatic systems. In this work, a preliminary study on the formation of aluminosilicate colloids with a help of colorimetry and other colloid detection techniques is presented

  16. Glass-silicon column

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Conrad M.

    2003-12-30

    A glass-silicon column that can operate in temperature variations between room temperature and about 450.degree. C. The glass-silicon column includes large area glass, such as a thin Corning 7740 boron-silicate glass bonded to a silicon wafer, with an electrode embedded in or mounted on glass of the column, and with a self alignment silicon post/glass hole structure. The glass/silicon components are bonded, for example be anodic bonding. In one embodiment, the column includes two outer layers of silicon each bonded to an inner layer of glass, with an electrode imbedded between the layers of glass, and with at least one self alignment hole and post arrangement. The electrode functions as a column heater, and one glass/silicon component is provided with a number of flow channels adjacent the bonded surfaces.

  17. Porous silicon gettering

    Energy Technology Data Exchange (ETDEWEB)

    Tsuo, Y.S.; Menna, P.; Al-Jassim, M. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1995-08-01

    We have studied a novel extrinsic gettering method that utilizes the very large surface areas, produced by porous silicon etch on both front and back surfaces of the silicon wafer, as gettering sites. In this method, a simple and low-cost chemical etching is used to generate the porous silicon layers. Then, a high-flux solar furnace (HFSF) is used to provide high-temperature annealing and the required injection of silicon interstitials. The gettering sites, along with the gettered impurities, can be easily removed at the end the process. The porous silicon removal process consists of oxidizing the porous silicon near the end the gettering process followed by sample immersion in HF acid. Each porous silicon gettering process removes up to about 10 {mu}m of wafer thickness. This gettering process can be repeated so that the desired purity level is obtained.

  18. LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE

    Energy Technology Data Exchange (ETDEWEB)

    Markus Flury; James B. Harsh; Fred Zhang; Glendon W. Gee; Earl D. Mattson; Peter C. L

    2012-08-01

    The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface

  19. Carbon dioxide and climate

    Energy Technology Data Exchange (ETDEWEB)

    1990-10-01

    Scientific and public interest in greenhouse gases, climate warming, and global change virtually exploded in 1988. The Department's focused research on atmospheric CO{sub 2} contributed sound and timely scientific information to the many questions produced by the groundswell of interest and concern. Research projects summarized in this document provided the data base that made timely responses possible, and the contributions from participating scientists are genuinely appreciated. In the past year, the core CO{sub 2} research has continued to improve the scientific knowledge needed to project future atmospheric CO{sub 2} concentrations, to estimate climate sensitivity, and to assess the responses of vegetation to rising concentrations of CO{sub 2} and to climate change. The Carbon Dioxide Research Program's goal is to develop sound scientific information for policy formulation and governmental action in response to changes of atmospheric CO{sub 2}. The Program Summary describes projects funded by the Carbon Dioxide Research Program during FY 1990 and gives a brief overview of objectives, organization, and accomplishments.

  20. Reaction products of chlorine dioxide.

    Science.gov (United States)

    Stevens, A A

    1982-01-01

    Inspection of the available literature reveals that a detailed investigation of the aqueous organic chemistry of chlorine dioxide and systematic identification of products formed during water disinfection has not been considered. This must be done before an informed assessment can be made of the relative safety of using chlorine dioxide as a disinfectant alternative to chlorine. Although trihalomethanes are generally not formed by the action of chlorine dioxide, the products of chlorine dioxide treatment of organic materials are oxidized species, some of which also contain chlorine. The relative amounts of species types may depend on the amount of chlorine dioxide residual maintained and the concentration and nature of the organic material present in the source water. The trend toward lower concentrations of chlorinated by-products with increasing ClO2 concentration, which was observed with phenols, has not been observed with natural humic materials as measured by the organic halogen parameter. Organic halogen concentrations have been shown to increase with increasing chlorine dioxide dose, but are much lower than those observed when chlorine is applied. Aldehydes have been detected as apparent by-products of chlorine dioxide oxidation reactions in a surface water that is a drinking water source. Some other nonchlorinated products of chlorine dioxide treatment may be quinones and epoxides. The extent of formation of these moieties within the macromolecular humic structure is also still unknown. PMID:7151750

  1. Comparision of {sup 188}Rhenuim-tin colloid and {sup 188}Rhenium-sulfur colloid as a radiation synovectomy agent

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Y. J.; Jung, J. M.; Kim, Y. J.; Jang, Y. S.; Lee, D. S.; Jung, J. K.; Song, Y. W.; Lee, M. C. [KAERI, Taejon (Korea, Republic of)

    1999-10-01

    Beta-emitting radiocolloids have been used for the treatment of rheumatoid arthritis. As a generator produced beta-emitting radionuclide, the importance of Re-188 for radionuclide therapy is increasing rapidly. We compared the radiochemistry of two {sup 188}Re labeled radiocolloids: {sup 188}Re-tin colloid and {sup 188}Re-sulfur colloid. {sup 188}Re-tin colloid was obtained by reacting 10 mg SnCl{sub 2}{center_dot}H{sub 2}O and {sup 188}Re perrhenate. {sup 188}Re-sulfur colloid was labeled by boiling 40 mg sodium thiosulfate, 0.8 mg Na{sub 2}{center_dot}EDTA, and 0.8 mg potassium perrhenate with {sup 188}Re perrhenate. Radiochemical purity was checked by ITLC-SG/ saline. Labeling efficiencies reached >98% for tin colloid at 2 hr and 89{approx}94% for sulfur colloid at 3 hr. All the preparations were stable for 72 hr in water, serum, and synovial fluid. If labeled at higher temperature, particle size of tin colloid increased. Remained radioactivity of {sup 188}Re-sulfur colloid in disposable polypropylene syringe after injecting to mice was high (62.0{+-}7.0%) due to its hydrophobic nature, although, tin colloid did not show high remained radioactivity (2.9{+-}1.6%). Biodistribution in Antigen induced arthratitis model rabbit after synovial space injection showed that {sup 188}Re-tin colloid was well retained in synovial space for 48 hr. Although, both {sup 188}Re-tin colloid and {sup 188}Re-sulfur colloid might be useful for radionuclide therapy, we concluded that {sup 188}Re-tin colloid is more adventageous over {sup 188}Re-sulfur colloid, due to higher labeling efficency, size-controllable property, and lower residual activity in syringe.

  2. Advanced Colloids Experiment (ACE) Science Overview

    Science.gov (United States)

    Meyer, William V.; Sicker, Ronald J.; Chiaramonte, Francis P.; Luna, Unique J.; Chaiken, Paul M.; Hollingsworth, Andrew; Secanna, Stefano; Weitz, David; Lu, Peter; Yodh, Arjun; hide

    2013-01-01

    The Advanced Colloids Experiment is being conducted on the International Space Station (ISS) using the Light Microscopy Module (LMM) in the Fluids Integrated Rack (FIR). Work to date will be discussed and future plans and opportunities will be highlighted. The LMM is a microscope facility designed to allow scientists to process, manipulate, and characterize colloidal samples in micro-gravity where the absence of gravitational settling and particle jamming enables scientists to study such things as:a.The role that disordered and ordered-packing of spheres play in the phase diagram and equation of state of hard sphere systems,b.crystal nucleation and growth, growth instabilities, and the glass transition, c.gelation and phase separation of colloid polymer mixtures,d.crystallization of colloidal binary alloys,e.competition between crystallization and phase separation,f.effects of anisotropy and specific interactions on packing, aggregation, frustration and crystallization,g.effects of specific reversible and irreversible interactions mediated in the first case by hybridization of complementary DNA strands attached to separate colloidal particles,h.Lock and key interactions between colloids with dimples and spheres which match the size and shape of the dimples,i.finding the phase diagrams of isotropic and interacting particles,j.new techniques for complex self-assembly including scenarios for self-replication, k.critical Casimir forces,l.biology (real and model systems) in microgravity,m.etc. By adding additional microscopy capabilities to the existing LMM, NASA will increase the tools available for scientists that fly experiments on the ISS enabling scientists to observe directly what is happening at the particle level. Presently, theories are needed to bridge the gap between what is being observed (at a macroscopic level when photographing samples) with what is happening at a particle (or microscopic) level. What is happening at a microscopic level will be directly

  3. Simultaneous determination of five quinoxaline-1,4-dioxides in animal feeds using an immunochromatographic strip.

    Science.gov (United States)

    Le, Tao; Zhu, Liqian; Shu, Lihui; Zhang, Lei

    2016-01-01

    An immunochromatographic (ICG) strip was developed for the simultaneous quantitative determination of five quinoxaline-1,4-dioxides in animal feed. For this purpose, polyclonal antibodies (PcAb) with group-specific quinoxaline-1,4-dioxides were conjugated to colloidal gold particles as the detection reagent for ICG strips to test for quinoxaline-1,4-dioxides. This method achieved semi-quantitative detection of quinoxaline-1,4-dioxides within 5-10 min. The visual lower detection limits of the strip for quinocetone, cyadox, carbadox, mequindox and olaquindox were 10, 15, 15, 20 and 20 ng ml(-1), respectively. Using an ICG strip reader, the 50% inhibitions (IC50 values) were calculated to be 9.1, 13.5, 16.6, 20.2 and 21.3 ng ml(-1) for quinocetone, cyadox, carbadox, mequindox and olaquindox, respectively. When used to analyse samples of animal feed, acceptable recovery rates of 77.5-99.5% and coefficients of variation (CVs) of 4.3-10.7% were obtained. Levels measured with the ICG strip for 10 spiked samples were confirmed by HPLC with a high correlation coefficient of 0.9965 (n = 10). In conclusion, the method was rapid and accurate for simultaneous determination of five quinoxaline-1,4-dioxides antibiotics in animal feed.

  4. High efficiency photoluminescence from silicon nanocrystals prepared by plasma synthesis and organic surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Mangolini, L.; Kortshagen, U. [Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Jurbergs, D.; Rogojina, E. [Innovalight Inc., 3303 Octavius Drive Suite 104, Santa Clara, CA 95054 (United States)

    2006-07-01

    An efficient synthesis route for highly luminescent silicon quantum dots is presented. Silicon nanocrystals were synthesized in the gas phase using an argon-silane non-thermal plasma in a continuous flow reactor. Liquid phase surface passivation was used to improve the optical properties and avoid surface oxidation of the silicon quantum dots. Various alkenes, such as octadecene, dodecene and styrene, were covalently bonded to the plasma-produced particles, while strictly avoiding exposure of the raw powder to oxidizing agents. Stable colloidal solutions of silicon quantum dots with ensemble quantum yields between 60% and 70% were achieved. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Mobile linkers on DNA-coated colloids: valency without patches.

    Science.gov (United States)

    Angioletti-Uberti, Stefano; Varilly, Patrick; Mognetti, Bortolo M; Frenkel, Daan

    2014-09-19

    Colloids coated with single-stranded DNA (ssDNA) can bind selectively to other colloids coated with complementary ssDNA. The fact that DNA-coated colloids (DNACCs) can bind to specific partners opens the prospect of making colloidal "molecules." However, in order to design DNACC-based molecules, we must be able to control the valency of the colloids, i.e., the number of partners to which a given DNACC can bind. One obvious, but not very simple approach is to decorate the colloidal surface with patches of single-stranded DNA that selectively bind those on other colloids. Here we propose a design principle that exploits many-body effects to control the valency of otherwise isotropic colloids. Using a combination of theory and simulation, we show that we can tune the valency of colloids coated with mobile ssDNA, simply by tuning the nonspecific repulsion between the particles. Our simulations show that the resulting effective interactions lead to low-valency colloids self-assembling in peculiar open structures, very different from those observed in DNACCs with immobile DNA linkers.

  6. Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media.

    Science.gov (United States)

    Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang

    2015-01-01

    While bismerthiazol [N,N'-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Shape recognition of microbial cells by colloidal cell imprints

    Science.gov (United States)

    Borovička, Josef; Stoyanov, Simeon D.; Paunov, Vesselin N.

    2013-08-01

    We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called ``colloid antibodies'', were fabricated by partial fragmentation of silica shells obtained by templating the targeted microbial cells. We successfully demonstrated the shape and size recognition between such colloidal imprints and matching microbial cells. High percentage of binding events of colloidal imprints with the size matching target particles was achieved. We demonstrated selective binding of colloidal imprints to target microbial cells in a binary mixture of cells of different shapes and sizes, which also resulted in high binding selectivity. We explored the role of the electrostatic interactions between the target cells and their colloid imprints by pre-coating both of them with polyelectrolytes. Selective binding occurred predominantly in the case of opposite surface charges of the colloid cell imprint and the targeted cells. The mechanism of the recognition is based on the amplification of the surface adhesion in the case of shape and size match due to the increased contact area between the target cell and the colloidal imprint. We also tested the selective binding for colloid imprints of particles of fixed shape and varying sizes. The concept of cell recognition by colloid imprints could be used for development of colloid antibodies for shape-selective binding of microbes. Such colloid antibodies could be additionally functionalized with surface groups to enhance their binding efficiency to cells of specific shape and deliver a drug payload directly to their surface or allow them to be manipulated using external fields. They could benefit the pharmaceutical industry in developing selective antimicrobial therapies and formulations.

  8. Memory effects in metal-oxide-semiconductor capacitors incorporating dispensed highly monodisperse 1 nm silicon nanoparticles

    Science.gov (United States)

    Nayfeh, Osama M.; Antoniadis, Dimitri A.; Mantey, Kevin; Nayfeh, Munir H.

    2007-04-01

    Metal-oxide-semiconductor capacitors containing various densities of ex situ produced, colloidal, highly monodisperse, spherical, 1nm silicon nanoparticles were fabricated and evaluated for potential use as charge storage elements in future nonvolatile memory devices. The capacitance-voltage characteristics are well behaved and agree with similarly fabricated zero-nanoparticle control samples and with an ideal simulation. Unlike larger particle systems, the demonstrated memory effect exhibits effectively pure hole storage. The nature of charging, hole type versus electron type may be understood in terms of the characteristics of ultrasmall silicon nanoparticles: large energy gap, large charging energy, and consequently a small electron affinity.

  9. Fully-depleted, back-illuminated charge-coupled devices fabricated on high-resistivity silicon

    Energy Technology Data Exchange (ETDEWEB)

    Holland, Stephen E.; Groom, Donald E.; Palaio, Nick P.; Stover, Richard J.; Wei, Mingzhi

    2002-03-28

    Charge-coupled devices (CCD's) have been fabricated on high-resistivity silicon. The resistivity, on the order of 10,000 {Omega}-cm, allows for depletion depths of several hundred microns. Fully-depleted, back-illuminated operation is achieved by the application of a bias voltage to a ohmic contact on the wafer back side consisting of a thin in-situ doped polycrystalline silicon layer capped by indium tin oxide and silicon dioxide. This thin contact allows for good short wavelength response, while the relatively large depleted thickness results in good near-infrared response.

  10. Photoluminescence from nanoparticles of silicon embedded in an amorphous silicon dioxide matrix

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu-Iwayama, Tsutomu (Aichi Univ. of Education (Japan). Dept. of Materials Science); Nakao, Setsuo; Saitoh, Kazuo (National Industrial Research Inst., Nagoya (Japan)); Itoh, Noriaki (Nagoya Univ. (Japan). Dept. of Physics)

    1994-09-26

    We have investigated visible photoluminescence related to nanometre-sized Si crystals in thermal oxide films grown on a crystalline Si wafer, created by a Si[sup +]-implantation and subsequent annealing in a vacuum at 1100[sup o]C (the temperature at which SiO[sub x] decomposes into Si and SiO[sub 2]). Evidence for the formation of Si nanocrystals by annealing at 1100[sup o]C is presented by transmission electron microscopy. The shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time, while the excitation spectrum of the photoluminescence increases as the photon energy increases and its shape depends on annealing time. The results indicate that the photons are absorbed by nanometre-sized Si crystals, for which the band gap is modified by the quantum confinement, and that the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and SiO[sub 2]. (Author).

  11. The Critical Conditions for the Growth of Silicon Dioxide on Silicon.

    Science.gov (United States)

    Ghidini, Gabriella

    The use of thermally grown SiO(,2) as a coating on Si is wide spread in the modern technology of semiconductor devices. The properties and methods of preparation of SiO(,2) have been studied for many years, but for the increasing importance of high quality thin films of oxide (less than 200 (ANGSTROM)), a better understanding of the initial growth of SiO(,2) will be helpful for the improvement of the actual methods of growing thin films. The subject of this thesis is the study of the critical conditions for the nucleation and growth of SiO(,2) on Si at low oxidant gas (O(,2) gas and H(,2)O vapor) pressures and high temperatures. For O(,2) pressures between 5 x 10('-5) and 5 x 10('-2) Torr and substrate temperatures between 890-1150(DEGREES)C, the critical O(,2) pressure for the nucleation and growth of SiO(,2) was determined as a function of the substrate temperature. The observed critical conditions for growth are consistent with a theoretical model which focuses on the kinetics of SiO(,2) cluster growth and on the thermodynamics of the competing etching reaction leading to the production of SiO. With H(,2)O vapor between 7 x 10('-5) and 3 x 10('-1) Torr and substrate temperature between 890-1280(DEGREES)C two critical behaviours were observed, indicating both the coverage of the surface by some compound (SiO(,x) + H) not passivating completely the surface and the subsequent growth of SiO(,2). A study of the SiO(,2) growth features has also been carried out and evidence for epitaxial growth of cubic (beta)-cristobalite on Si(100) is found. The influence of doping of the Si substrate on the critical conditions for P, B, As heavily-doped samples is also determined. The critical oxygen pressure is only influenced by P atoms, which seem to enhance the nucleation and growth of SiO(,2).

  12. Silicon micro-mold

    Science.gov (United States)

    Morales, Alfredo M.

    2006-10-24

    The present invention describes a method for rapidly fabricating a robust 3-dimensional silicon-mold for use in preparing complex metal micro-components. The process begins by depositing a conductive metal layer onto one surface of a silicon wafer. A thin photoresist and a standard lithographic mask are then used to transfer a trace image pattern onto the opposite surface of the wafer by exposing and developing the resist. The exposed portion of the silicon substrate is anisotropically etched through the wafer thickness down to conductive metal layer to provide an etched pattern consisting of a series of rectilinear channels and recesses in the silicon which serve as the silicon micro-mold. Microcomponents are prepared with this mold by first filling the mold channels and recesses with a metal deposit, typically by electroplating, and then removing the silicon micro-mold by chemical etching.

  13. Colloid Release From Differently Managed Loess Soil

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Schjønning, Per; Møldrup, Per

    2012-01-01

    of the total clay not associated with organic matter. No significant difference in release rate was found for air-dry aggregates. The low-carbon soils initially had a higher content of WSA but were more susceptible to disaggregation than the high-carbon soils. Furthermore, the application of NPK fertilizer had......The content of water-dispersible colloids (WDC) in a soil can have a major impact on soil functions, such as permeability to water and air, and on soil strength, which can impair soil fertility and workability. In addition, the content of WDC in the soil may increase the risk of nutrient loss...... and of colloid-facilitated transport of strongly sorbing compounds. In the present study, soils from the Bad Lauchsta¨dt longterm static fertilizer experiment with different management histories were investigated to relate basic soil properties to the content of WDC, the content of water-stable aggregates (WSA...

  14. Ultrasonic wave interactions with magnetic colloids

    CERN Document Server

    Chapman, J R

    2001-01-01

    fluids have been performed in an effort to determine the relative stability of the fluids. The experimental results have been compared with a combined scattering and hydrodynamic model (Allegra and Hawley 1972) and the ultrasonic anisotropy theory of Skumiel (1997). An on-line quality assurance process is proposed. Originally invented as a method for moving spacecraft fuel in weightless conditions, magnetic colloids or ferrofluids are now used in applications as diverse as the dissipation of heat in the voice coils of a loudspeaker, and for the separation of scrap metal. It has been found that aqueous ferrofluids become unstable after a period of time and with dilution. Therefore, there is a need to characterize the colloidal fluid to study the effects of degradation. Additionally, due to the high cost of ferrofluids and the large volumes required for some applications, the fluid is recycled. It is therefore necessary to develop a system for quality assurance for the fluid reclamation process. Ultrasonic meth...

  15. Laser diffraction analysis of colloidal crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sogami, Ikuo S.; Shinohara, Tadatomi; Yoshiyama, Tsuyoshi [Kyoto Sangyo Univ., Department of Physics, Kyoto (Japan)

    2001-10-01

    Laser diffraction analysis is made on crystallization in salt-free aqueous suspensions of highly-charged colloidal particles for semi-dilute specimens of concentration 0.1-10.0 vol%. Kossel diffraction patterns which represent faithfully accurate information on lattice symmetries in the suspensions enable us to investigate the time evolution of colloidal crystals. The results show that the crystallization proceeds by way of the following intermediate phase transitions: two-dimensional hcp structure {yields} random layer structure {yields} layer structure with one sliding degree of freedom {yields} stacking disorder structure {yields} stacking structure with multivariant periodicity {yields} fcc twin structure with twin plane (111) {yields} normal fcc structure {yields} bcc twin structure with twin plane (11-bar2) or (1-bar12) {yields} normal bcc structure. For concentrated suspensions (>2 vol %), the phase transition ceases to proceed at the normal fcc structure. (author)

  16. Theory of Electrorotation of Clustered Colloidal Particles

    Institute of Scientific and Technical Information of China (English)

    LIU Ren-Ming; HUANG Ji-Ping

    2005-01-01

    When a colloidal suspension is exposed to a strong rotating electric field, an aggregation of the suspended particles is induced to appear. In such clusters, the separation between the suspended particles is so close that one could not neglect the multiple image effect on the electrorotation (ER) spectrum. Since so far the exact multiple image method exists in two dimensions only, rather than in three dimensions, we investigate the ER spectrum of the clustered colloidal particles in two dimensions, in which many cylindrical particles are randomly distributed in a sheet cluster. We report the dependence of the ER spectrum on the materialparameters. It is shown that the multiple image method predicts two characteristic frequencies, at which the rotation speed reaches maximum. To this end, the multiple image method is numerically demonstrated to be in good agreement with the known Maxwell-Garnett approximation.

  17. Colloidal cholesteric liquid crystal in spherical confinement

    Science.gov (United States)

    Li, Yunfeng; Jun-Yan Suen, Jeffrey; Prince, Elisabeth; Larin, Egor M.; Klinkova, Anna; Thérien-Aubin, Héloïse; Zhu, Shoujun; Yang, Bai; Helmy, Amr S.; Lavrentovich, Oleg D.; Kumacheva, Eugenia

    2016-08-01

    The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter.

  18. Ultrasmall colloidal PbS quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, Nick; Wehrung, Michael; O' Dell, Ryan Andrew [Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403 (United States); Sun, Liangfeng, E-mail: lsun@bgsu.edu [Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403 (United States); Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403 (United States)

    2014-09-15

    Ultrasmall colloidal lead sulfide quantum dots can increase the open circuit voltages of quantum-dot-based solar cells because of their large energy gap. Their small size and visible or near infrared light-emitting property make them attractive to the applications of biological fluorescence labeling. Through a modified organometallic route, we can synthesize lead sulfide quantum dots as small as 1.6 nm in diameter. The low reaction temperature and the addition of a chloroalkane cosolvent decrease the reaction rate, making it possible to obtain the ultrasmall quantum dots. - Highlights: • Ultrasmall colloidal PbS quantum dots as small as 1.6 nm in diameter are synthesized. • The quantum dots emit red light with photoluminescence peak at 760 nm. • The growth temperature is as low as 50 °C. • Addition of cosolvent 1,2-dichloroethane in the reaction decreases the reaction rate.

  19. Optoelectronic Applications of Colloidal Quantum Dots

    Science.gov (United States)

    Wang, Zhiping; Zhang, Nanzhu; Brenneman, Kimber; Wu, Tsai Chin; Jung, Hyeson; Biswas, Sushmita; Sen, Banani; Reinhardt, Kitt; Liao, Sicheng; Stroscio, Michael A.; Dutta, Mitra

    This chapter highlights recent optoelectronic applications of colloidal quantum dots (QDs). In recent years, many colloidal QD-based optoelectronic devices, and device concepts have been proposed and studied. Many of these device concepts build on traditional optoelectronic device concepts. Increasingly, many new optoelectronic device concepts have been based on the use of biomolecule QD complexes. In this chapter, both types of structures are discussed. Special emphasis is placed on new optoelectronic device concepts that incorporate DNA-based aptamers in biomolecule QD complexes. Not only are the extensions of traditional devices and concepts realizable, such as QD-based photo detectors, displays, photoluminescent and photovoltaic devices, light-emitting diodes (LEDs), photovoltaic devices, and solar cells, but new devices concepts such a biomolecule-based molecular sensors possible. This chapter highlights a number of such novel QD-based devices and device concepts.

  20. Manipulating colloids with charges and electric fields

    Science.gov (United States)

    Leunissen, M. E.

    2007-02-01

    This thesis presents the results of experimental investigations on a variety of colloidal suspensions. Colloidal particles are at least a hundred times larger than atoms or molecules, but suspended in a liquid they display the same phase behavior, including fluid and crystalline phases. Due to their relatively large size, colloids are much easier to investigate and manipulate, though. This makes them excellent condensed matter model systems. With this in mind, we studied micrometer-sized perspex (‘PMMA’) spheres, labeled with a fluorescent dye for high-resolution confocal microscopy imaging, and suspended in a low-polar mixture of the organic solvents cyclohexyl bromide and cis-decalin. This system offered us the flexibility to change the interactions between the particles from ‘hard-sphere-like’ to long-ranged repulsive (between like-charged particles), long-ranged attractive (between oppositely charged particles) and dipolar (in an electric field). We investigated the phase behavior of our suspensions as a function of the particle concentration, the ionic strength of the solvent and the particles’ charges. In this way, we obtained new insight in the freezing and melting behavior of like-charged and oppositely charged colloids. Interestingly, we found that the latter can readily form large crystals, thus defying the common belief that plus-minus interactions inevitably lead to aggregation. Moreover, we demonstrated that these systems can serve as a reliable model system for classical ionic matter (‘salts’), and that opposite-charge interactions can greatly facilitate the self-assembly of new structures with special properties for applications. On a slightly different note, we also studied electrostatic effects in mixtures of the cyclohexyl bromide solvent and water, both with and without colloidal particles present. This provided new insight in the stabilization mechanisms of oil-water emulsions and gave us control over the self-assembly of various