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Sample records for si-implanted sio2 layers

  1. Thickness and composition of ultrathin SiO2 layers on Si

    NARCIS (Netherlands)

    van der Marel, C; Verheijen, M.A.; Tamminga, Y; Pijnenburg, RHW; Tombros, N; Cubaynes, F

    2004-01-01

    Ultrathin SiO2 layers are of importance for the semiconductor industry. One of the techniques that can be used to determine the chemical composition and thickness of this type of layers is x-ray photoelectron spectroscopy (XPS). As shown by Seah and Spencer [Surf. Interface Anal. 33, 640 (2002)], it

  2. Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

    Science.gov (United States)

    Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

    2017-09-13

    Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

  3. Densification of ∼5 nm-thick SiO2 layers by nitric acid oxidation

    Science.gov (United States)

    Choi, Jaeyoung; Joo, Soyeong; Park, Tae Joo; Kim, Woo-Byoung

    2017-08-01

    Low-temperature nitric acid (HNO3) oxidation of Si (NAOS) has been used to improve the interface and electrical properties of ∼5 nm-thick SiO2/Si layers produced by plasma-enhanced chemical vapor deposition (PECVD). Investigations of the physical properties and electrical characteristics of these thin films revealed that although their thickness is not changed by NAOS, the leakage current density at a gate bias voltage of -1 V decreases by about two orders of magnitude from 1.868 × 10-5 A/cm2. This leakage current density was further reduced by post-metallization annealing (PMA) at 250 °C for 10 min in a 5 vol.% hydrogen atmosphere, eventually reaching a level (5.2 × 10-8 A/cm2) approximately three orders of magnitude less than the as-grown SiO2 layer. This improvement is attributed to a decrease in the concentration of suboxide species (Si1+, Si2+ and Si3+) in the SiO2/Si interface, as well as a decrease in the equilibrium density of defect sites (Nd) and fixed charge density (Nf). The barrier height (Vt) generated by a Poole-Frenkel mechanism also increased from 0.205 to 0.371 eV after NAOS and PMA. The decrease in leakage current density is therefore attributed to a densification of the SiO2 layer in combination with the removal of OH species and increase in interfacial properties at the SiO2/Si interface.

  4. Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

    Directory of Open Access Journals (Sweden)

    Liliana Kotte

    2014-12-01

    Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

  5. Plasmonic properties of implanted Ag nanoparticles in SiO2 thin layer by spectroscopic ellipsometry

    Science.gov (United States)

    Battie, Yann; En Naciri, Aotmane; Chaoui, Nouari; Le Gall, Yann; Muller, Dominique; Carrada, Marzia; Mathiot, Daniel

    2017-08-01

    We report an uncommon study of the insertion of distributions of both volume fraction and depolarization factors in the modeling of the plasmonic properties of implanted Ag nanoparticles (Ag-NPs) in a SiO2 layer when using spectroscopic ellipsometry (SE) characterization. The Ag-NPs were embedded in the SiO2 matrix by Ag+ ion implantation at various doses of 0.5 × 1016, 1 × 1016, 2 × 1016, and 5 × 1016 ions cm-2. The formation of the Ag-NPs in a host matrix of SiO2 was controlled by transmission electron microscopy (TEM). The Ag-NPs are self-organized in the layer, and their mean radius ranges between 2 and 20 nm. The optical properties of layers were extracted by modeling the SE parameters by taking into account the depth profile concentration of Ag-NPs. The mixture of SiO2 and Ag-NP inclusions was modeled as an effective medium according to the shape distributed effective medium theory (SDEMT). In addition to the optical responses, it is shown that this model enables the explanation of the impact of NP shape distribution on the plasmon band and provides precious information about the NP shape characteristics. A good agreement was obtained between ellipsometry and TEM results. The distribution of the volume fraction in the film was found to lead to a gradient of effective dielectric function which was determined by the SDEMT model. The effective dielectric function reveals distinct Ag plasmon resonance varying as the Ag+ ions dose is varied. The real part of the dielectric function shows a significant variation around the plasmon resonance in accordance with the Kramers-Kronig equations. All determined optical parameters by SDEMT are provided and discussed. We highlight that SE combined with SDEMT calculations can be considered as a reliable tool for the determination of the NP shape and volume fraction distributions without the need of TEM.

  6. Sol-gel preparation of self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective coating for solar glass

    Science.gov (United States)

    Lin, Wensheng; Zheng, Jiaxian; Yan, Lianghong; Zhang, Xinxiang

    2018-03-01

    Self-cleaning SiO2-TiO2/SiO2-TiO2 double-layer antireflective (AR) coating is prepared by sol-gel process. SiO2 sol is prepared by using tetraethyl orthosilicate (TEOS) as precursor and ammonia as catalyst, while TiO2 sol was prepared by using tetrabutyl orthotitanate (TBOT) as precursor and hydrochloric acid as catalyst. The effect of TiO2 content on refractive index, abrasion-resistance and photo-catalytic activity of SiO2-TiO2 hybrid thin films or powders is systematically investigated. It is found that the refractive index of SiO2-TiO2 hybrid thin films increases gradually from 1.18 to 1.53 as the weight ratio of TiO2 to SiO2 increased from 0 to 1.0. The SiO2-TiO2 hybrid thin film and powder possesses good abrasion-resistance and photo-catalytic activity, respectively, as the weight ratio of TiO2 to SiO2 is 0.4. The degradation degree of Rhodamine B by SiO2-TiO2 hybrid powder is 88.3%. Finally, SiO2-TiO2/SiO2-TiO2 double-layer AR coating with high transmittance, abrasion-resistance and self-cleaning property is realized.

  7. Realization of Colored Multicrystalline Silicon Solar Cells with SiO2/SiNx:H Double Layer Antireflection Coatings

    Directory of Open Access Journals (Sweden)

    Minghua Li

    2013-01-01

    Full Text Available We presented a method to use SiO2/SiNx:H double layer antireflection coatings (DARC on acid textures to fabricate colored multicrystalline silicon (mc-Si solar cells. Firstly, we modeled the perceived colors and short-circuit current density (Jsc as a function of SiNx:H thickness for single layer SiNx:H, and as a function of SiO2 thickness for the case of SiO2/SiNx:H (DARC with fixed SiNx:H (refractive index n=2.1 at 633 nm, and thickness = 80 nm. The simulation results show that it is possible to achieve various colors by adjusting the thickness of SiO2 to avoid significant optical losses. Therefore, we carried out the experiments by using electron beam (e-beam evaporation to deposit a layer of SiO2 over the standard SiNx:H for 156×156 mm2 mc-Si solar cells which were fabricated by a conventional process. Semisphere reflectivity over 300 nm to 1100 nm and I-V measurements were performed for grey yellow, purple, deep blue, and green cells. The efficiency of colored SiO2/SiNx:H DARC cells is comparable to that of standard SiNx:H light blue cells, which shows the potential of colored cells in industrial applications.

  8. Self-assembly preparation of SiO2@Ni-Al layered double hydroxide composites and their enhanced electrorheological characteristics

    OpenAIRE

    Xuqiang Ji; Wenling Zhang; Lei Shan; Yu Tian; Jingquan Liu

    2015-01-01

    The core-shell structured SiO2@Ni-Al layered double hydroxide (LDH) composites were prepared via self-assembly of Ni-Al LDH on the surface of SiO2 spheres. Only coating a layer of ultrathin Ni-Al LDH sheet, the resulting SiO2@Ni-Al LDH composites exhibit significantly enhanced electrorheological (ER) characteristics compared to conventional bare SiO2 spheres. The monodispersed SiO2 spheres with average diameters of 260?nm were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS), ...

  9. Ultraviolet-enhanced light emitting diode employing individual ZnO microwire with SiO2 barrier layers

    Science.gov (United States)

    Xu, Yingtian; Xu, Li; Dai, Jun; Ma, Yan; Chu, Xianwei; Zhang, Yuantao; Du, Guotong; Zhang, Baolin; Yin, Jingzhi

    2015-05-01

    This paper details the fabrication of n-ZnO single microwire (SMW)-based high-purity ultraviolet light-emitting diodes (UV-LEDs) with an added SiO2 barrier layer on the p-Si substrate. However, the current-voltage (I-V) curve exhibited non-ideal rectifying characteristics. Under forward bias, both UV and visible emissions could be detected by electroluminescence (EL) measurement. When bias voltage reached 60 V at room temperature, a UV emission spike occurred at 390 nm originating from the n-ZnO SMW. Compared with the EL spectrum of the n-ZnO SMW/p-Si heterojunction device without the SiO2 barrier layer, we saw improved UV light extraction efficiency from the current-blocking effect of the SiO2 layer. The intense UV emission in the n-ZnO SMW/SiO2/p-Si heterojunction indicated that the SiO2 barrier layer can restrict the movement of electrons as expected and result in effective electron-hole recombination in ZnO SMW.

  10. Enhanced Visible Transmittance of Thermochromic VO2 Thin Films by SiO2 Passivation Layer and Their Optical Characterization

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    Jung-Hoon Yu

    2016-07-01

    Full Text Available This paper presents the preparation of high-quality vanadium dioxide (VO2 thermochromic thin films with enhanced visible transmittance (Tvis via radio frequency (RF sputtering and plasma enhanced chemical vapor deposition (PECVD. VO2 thin films with high Tvis and excellent optical switching efficiency (Eos were successfully prepared by employing SiO2 as a passivation layer. After SiO2 deposition, the roughness of the films was decreased 2-fold and a denser structure was formed. These morphological changes corresponded to the results of optical characterization including the haze, reflectance and absorption spectra. In spite of SiO2 coating, the phase transition temperature (Tc of the prepared films was not affected. Compared with pristine VO2, the total layer thickness after SiO2 coating was 160 nm, which is an increase of 80 nm. Despite the thickness change, the VO2 thin films showed a higher Tvis value (λ 650 nm, 58% compared with the pristine samples (λ 650 nm, 43%. This enhancement of Tvis while maintaining high Eos is meaningful for VO2-based smart window applications.

  11. Shallow boron-doped layer formation by boron diffusion from poly-Si through thin SiO2

    Science.gov (United States)

    Miyake, Masayasu

    1994-06-01

    This paper discusses boron doping using metal oxide semiconductor structure (poly-Si/SiO2/Si). The thin SiO2 layer acts as a stopper to poly-Si removal after doping. When boron implantation is used for poly-Si doping, shallow boron-doped layers suitable for base application can be formed by wet O2-ambient drive-in. When BF2 implantation is used, shallow boron-doped layers can be formed even by N2-ambient drive-in. The surface boron concentration of boron-doped layers increases with dose and saturates, since boron concentration in poly-Si in the region near the interface with SiO2 also increases with dose and saturates. An estimate of the boron diffusion coefficient in SiO2, D(sub ox), shows that it increases by about one order of magnitude both for boron implantation with subsequent wet O2-ambient drive-in and for BF2 implantation with subsequent N2-ambient drive-in.

  12. Electron microscopy studies of the intermediate layers at the SiO2/GaN interface

    Science.gov (United States)

    Mitsuishi, Kazutaka; Kimoto, Koji; Irokawa, Yoshihiro; Suzuki, Taku; Yuge, Kazuya; Nabatame, Toshihide; Takashima, Shinya; Ueno, Katsunori; Edo, Masaharu; Nakagawa, Kiyokazu; Koide, Yasuo

    2017-11-01

    As the first step toward understanding the electrical properties of SiO2/GaN systems, the interface was characterized using high-resolution scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). An epitaxial crystalline intermediate layer with a thickness of ∼1.5 nm was observed at the SiO2/GaN interface. STEM-EDS analyses revealed that this intermediate layer contained gallium and oxygen and mostly comprised the ε-Ga2O3 phase. The ε-Ga2O3/GaN interface was atomically smooth and free from misfit dislocations despite lattice mismatch of ∼8.0%, suggesting that the initial oxidation of GaN surfaces is crucial to achieve good interfacial properties.

  13. Atomic Layer Deposition of SiO2 for the Performance Enhancement of Fin Field Effect Transistors

    Science.gov (United States)

    Endo, Kazuhiko; Ishikawa, Yuki; Matsukawa, Takashi; Liu, Yongxun; O'uchi, Shin-ichi; Sakamoto, Kunihiro; Tsukada, Junichi; Yamauchi, Hiromi; Masahara, Meishoku

    2013-11-01

    Atomic layer deposition (ALD) of SiO2 by using a tetraethoxysilane (TEOS) or a bis(ethylmethylamino)silane (BEMAS) have been studied for the side-wall spacer formation of the fin field effect transistor (FinFET). The ALD-SiO2 can be deposited conformally at 50 °C for the TEOS and at 250 °C for the BEMAS precursor. As a result, FinFETs with a 25-nm-long extension of the source/drain using the ALD grown SiO2 sidewall spacer have been successfully fabricated. The performance of the FinFET has been successfully improved by reduction of the parasitic resistance.

  14. Experimental and theoretical investigation of the effect of SiO2 content in gate dielectrics on work function shift induced by nanoscale capping layers

    KAUST Repository

    Caraveo-Frescas, J. A.

    2012-09-10

    The impact of SiO2 content in ultrathin gate dielectrics on the magnitude of the effective work function (EWF) shift induced by nanoscale capping layers has been investigated experimentally and theoretically. The magnitude of the effective work function shift for four different capping layers (AlN, Al2O3, La2O3, and Gd2O3) is measured as a function of SiO2 content in the gate dielectric. A nearly linear increase of this shift with SiO2 content is observed for all capping layers. The origin of this dependence is explained using density functional theory simulations.

  15. Effect of ring-shaped SiO2 current blocking layer thickness on the external quantum efficiency of high power light-emitting diodes

    Science.gov (United States)

    Zhou, Shengjun; Liu, Mengling; Hu, Hongpo; Gao, Yilin; Liu, Xingtong

    2017-12-01

    A ring-shaped SiO2 CBL underneath the p-electrode was employed to enhance current spreading of GaN-based light-emitting diodes (LEDs). Effects of ring-shaped SiO2 current blocking layer (CBL) thickness on optical and electrical characteristics of high power LEDs were investigated. A 190-nm-thick ring-shaped SiO2 CBL with inclined sidewalls was obtained using a combination of a thermally reflowed photoresist technique and an inductively coupled plasma (ICP) etching process, allowing for the deposition of conformal indium tin oxide (ITO) transparent conductive layer on sidewalls of ring-shaped SiO2 CBL. It was indicated that the external quantum efficiency (EQE) of high power LEDs increased with increasing thickness of ring-shaped SiO2 CBL. The EQE of high power LED with 190-nm-thick ring-shaped SiO2 CBL was 12.7% higher than that of high power LED without SiO2 CBL. Simulations performed with commercial SimuLED software package showed that the ring-shaped SiO2 CBL could significantly alleviate current crowding around p-electrode, resulting in enhanced current spreading over the entire high power LED structure.

  16. Formation of Transparent SiO2 Protective Layer on Polycarbonate by 157 nm F2 Laser for Lightweight Automobile Window

    Science.gov (United States)

    Yoshihiko Nojima,; Masayuki Okoshi,; Hidetoshi Nojiri,; Narumi Inoue,

    2010-07-01

    A transparent, hard silica glass (SiO2) layer was formed on a conventional protective coat made of silicone ([SiO(CH3)2]n) on a polycarbonate plate by the 157 nm F2 laser-induced photochemical modification of silicone into SiO2. An optimum laser irradiation time of the F2 laser was found to form a crack-free SiO2 layer. The high optical transparency of the samples in the visible light region remained unchanged after the F2 laser irradiation. In the Taber abrasion test, the SiO2 layer markedly reduced the number of scratches, resulting in a low haze value. The haze values of the samples also depend on the thickness of the silicone protective coat underneath the SiO2 protective layer. As a result, the difference of haze value (δHz) was successfully reduced to 3.6%, compared with these of the nonirradiated sample and a bare polycarbonate plate of approximately 11.3 and 41.3%, respectively, which is comparable to the case of a bare silica glass of approximately 1.6%. In addition, the thickness of the SiO2 protective layer was estimated to be approximately 0.44 μm for the 30-s laser irradiation by immersing the samples in 1 wt % hydrogen fluoride aqueous solution and measuring the depth using a surface profilometer.

  17. Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer

    Science.gov (United States)

    Johannes, Daniel; Webber, Robert

    2013-01-01

    Adiabatic demagnetization refrigerators (ADR) are operated in space to cool detectors of cosmic radiation to a few 10s of mK. A key element of the ADR is a superconducting magnet operating at about 0.3 K that is continually energized and de-energized in synchronism with a thermal switch, such that a piece of paramagnetic salt is alternately warm in a high magnetic field and cold in zero magnetic field. This causes the salt pill or refrigerant to cool, and it is able to suck heat from an object, e.g., the sensor, to be cooled. Current has to be fed into and out of the magnets from a dissipative power supply at the ambient temperature of the spacecraft. The current leads that link the magnets to the power supply inevitably conduct a significant amount of heat into the colder regions of the supporting cryostat, resulting in the need for larger, heavier, and more powerful supporting refrigerators. The aim of this project was to design and construct high-temperature superconductor (HTS) leads from YBCO (yttrium barium copper oxide) composite conductors to reduce the heat load significantly in the temperature regime below the critical temperature of YBCO. The magnet lead does not have to support current in the event that the YBCO ceases to be superconducting. Cus - tomarily, a normal metal conductor in parallel with the YBCO is a necessary part of the lead structure to allow for this upset condition; however, for this application, the normal metal can be dispensed with. Amorphous silicon dioxide is deposited directly onto the surface of YBCO, which resides on a flexible substrate. The silicon dioxide protects the YBCO from chemically reacting with atmospheric water and carbon dioxide, thus preserving the superconducting properties of the YBCO. The customary protective coating for flexible YBCO conductors is silver or a silver/gold alloy, which conducts heat many orders of magnitude better than SiO2 and so limits the use of such a composite conductor for passing current across a thermal gradient with as little flow of heat as possible to make an efficient current lead. By protecting YBCO on a flexible substrate of low thermal conductivity with SiO2, a thermally efficient and flexible current lead can be fabricated. The technology is also applicable to current leads for 4 K superconducting electronics current biasing. A commercially available thin-film YBCO composite tape conductor is first stripped of its protective silver coating. It is then mounted on a jig that holds the sample flat and acts as a heat sink. Silicon dioxide is then deposited onto the YBCO to a thickness of about 1 micron using PECVD (plasma-enhanced chemical vapor deposition), without heating the YBCO to the point where degradation occurs. Since SiO2 can have good high-frequency electrical properties, it can be used to coat YBCO cable structures used to feed RF signals across temperature gradients. The prime embodiment concerns the conduction of DC current across the cryogenic temperature gradient. The coating is hard and electrically insulating, but flexible.

  18. Picosecond Photoacoustic Metrology of SiO2 and LiNbO3 Layer Systems Used for High Frequency Surface-Acoustic-Wave Filters

    Directory of Open Access Journals (Sweden)

    Delia Brick

    2017-08-01

    Full Text Available Many applications of thin films necessitate detailed information about their thicknesses and sound velocities. Here, we study SiO2/LiNbO3 layer systems by picosecond photoacoustic metrology and measure the sound velocities of the respective layers and the film thickness of SiO2, which pose crucial information for the fabrication of surface-acoustic-wave filters for communication technology. Additionally, we utilize the birefringence and the accompanying change in the detection sensitivity of coherent acoustic phonons in the LiNbO3 layer to infer information about the LiNbO3 orientation and the layer interface.

  19. DIFFUSION AT THE INTERFACE BETWEEN Ag DOPED SiO2 LAYERS AND THE GLASS SUBSTRATE

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    JOSEF MATOUŠEK

    2011-03-01

    Full Text Available Silica layers containing silver were prepared by the sol-gel method and deposited on the Float glass substrate. Heat treatment at different temperatures (60 and 550°C and time periods (1 to 6 hours followed afterwards. Silica layer texture without any particles was observed by electron microscopy. Silver, sodium, tin and silicon concentration profiles on “tin” side of Float glass substrates and in the deposited layers were evaluated by the help of Secondary Neutral Mass Spectrometry and discussed with respect to diffusion process taking place at the interface of the system substrate-layer. The concentration profiles of Ag and Na confirmed exchange diffusion mechanism at 550°C by which silver moves quickly from the surface layer into glass substrate.

  20. Nanomechanical and Macrotribological Properties of CVD-Grown Graphene as a Middle Layer between Metal Pt Cylinders and SiO2/Si Substrate

    Directory of Open Access Journals (Sweden)

    Hongyan Wu

    2015-01-01

    Full Text Available The CVD-grown graphene as a middle layer was introduced between Pt cylinders and SiO2/Si to extend the application of graphene for improving the wear performance of microelectromechanical systems. Periodic arrays of Pt cylinders were prepared on the graphene/SiO2/Si (Pt/graphene and SiO2/Si substrate (Pt/SiO2 using the magnetron sputtering technique. To characterize Pt/graphene and Pt/SiO2, nanoindentation and macrotribological tests were performed. The results showed that the friction coefficient was lower and the wear lifetime of Pt/graphene was longer than those of Pt/SiO2. Graphene, as a middle layer, was not only observed to have significant influence on the mechanical properties (i.e., microhardness and elastic modulus, but also found to improve the adhesive strength between SiO2/Si and Pt cylinders.

  1. Effect of SiO2 buffer layers on the structure of SrTiO3 films grown on silicon by pulsed laser deposition

    OpenAIRE

    Tejedor, P.; Fuenzalida, V. M.; Briones Fernández-Pola, Fernando

    1996-01-01

    Thin films of SrTiO3 were grown by pulsed laser deposition on Si and SiO2/Si at 35 and 650°C in a 50 mTorr oxygen discharge (300 V). The effect of introducing a SiO2 buffer layer between the Si substrate and the complex oxide on the crystallinity and microstructure of the SrTiO3 films was investigated at both deposition temperatures. All films grown at 35°C were amorphous. Surface morphology examination by scanning electron microscopy (SEM) showed that these films were continuous and homogene...

  2. Improvements in the laser damage behavior of Ta2O5/SiO2 interference coatings by modification of the top layer design

    Science.gov (United States)

    Patel, D.; Schiltz, D.; Langton, P. F.; Emmert, L.; Acquaroli, L. N.; Baumgarten, C.; Reagan, B.; Rocca, J. J.; Rudolph, W.; Markosyan, A.; Route, R. R.; Fejer, M.; Menoni, C. S.

    2013-11-01

    We have investigated the properties and laser damage behavior of Ta2O5/SiO2 quarter wave stacks designed for λ=1 μm operation by substituting the Ta2O5 layer by either Y2O3 or HfO2 and the SiO2 by Al2O3 in the top 3 pairs of the multilayer stack. The high reflectors were deposited by dual ion beam sputtering. Laser damage at 1 μm using 350 ps showed enhanced performance when the Ta2O5/SiO2 stack had HfO2 or Y2O3 in its top few pairs.

  3. Sensitivity enhancement of surface plasmon resonance sensor based on graphene-MoS2 hybrid structure with TiO2-SiO2 composite layer

    Science.gov (United States)

    Maurya, J. B.; Prajapati, Y. K.; Singh, V.; Saini, J. P.

    2015-11-01

    In this paper, surface plasmon resonance (SPR) sensor based on graphene-MoS2 hybrid structure with composite layer of TiO2-SiO2 is presented. The angular interrogation method is used for the analysis of reflected light from the sensor. For the calculation of the sensitivity, first of all the thicknesses of TiO2, SiO2 and gold layers are optimized for the monolayer graphene and MoS2. Thereafter, at these optimum thicknesses the reflectance curves are plotted for different sensor structure and comparison of change in resonance angle is made among these structures. It is observed that the sensitivity of the graphene-MoS2-based sensor is enhanced by 9.24 % with respect conventional SPR sensor. The sensitivity is further enhanced by including TiO2-SiO2 composite layer between prism base and metal layer and observed that the enhanced sensitivity for this sensor is 12.82 % with respect to conventional SPR sensor and 3.28 % with respect to graphene-MoS2-based SPR sensor. At the end of this paper, the variation of the sensitivity and minimum reflectance is plotted with respect to sensing layer refractive index at the optimum thickness of all the layers and optimum number of MoS2 and graphene layers. It is also observed that four layers of MoS2 and monolayer graphene are best selection for the maximum enhancement of the sensitivity.

  4. Conformal SiO2 coating of sub-100 nm diameter channels of polycarbonate etched ion-track channels by atomic layer deposition

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    Nicolas Sobel

    2015-02-01

    Full Text Available Polycarbonate etched ion-track membranes with about 30 µm long and 50 nm wide cylindrical channels were conformally coated with SiO2 by atomic layer deposition (ALD. The process was performed at 50 °C to avoid thermal damage to the polymer membrane. Analysis of the coated membranes by small angle X-ray scattering (SAXS reveals a homogeneous, conformal layer of SiO2 in the channels at a deposition rate of 1.7–1.8 Å per ALD cycle. Characterization by infrared and X-ray photoelectron spectroscopy (XPS confirms the stoichiometric composition of the SiO2 films. Detailed XPS analysis reveals that the mechanism of SiO2 formation is based on subsurface crystal growth. By dissolving the polymer, the silica nanotubes are released from the ion-track membrane. The thickness of the tube wall is well controlled by the ALD process. Because the track-etched channels exhibited diameters in the range of nanometres and lengths in the range of micrometres, cylindrical tubes with an aspect ratio as large as 3000 have been produced.

  5. Area-selective atomic layer deposition of Ru on electron-beam-written Pt(C) patterns versus SiO2 substratum

    Science.gov (United States)

    Junige, Marcel; Löffler, Markus; Geidel, Marion; Albert, Matthias; Bartha, Johann W.; Zschech, Ehrenfried; Rellinghaus, Bernd; van Dorp, Willem F.

    2017-09-01

    Area selectivity is an emerging sub-topic in the field of atomic layer deposition (ALD), which employs opposite nucleation phenomena to distinct heterogeneous starting materials on a surface. In this paper, we intend to grow Ru exclusively on locally pre-defined Pt patterns, while keeping a SiO2 substratum free from any deposition. In a first step, we study in detail the Ru ALD nucleation on SiO2 and clarify the impact of the set-point temperature. An initial incubation period with actually no growth was revealed before a formation of minor, isolated RuO x islands; clearly no continuous Ru layer formed on SiO2. A lower temperature was beneficial in facilitating a longer incubation and consequently a wider window for (inherent) selectivity. In a second step, we write C-rich Pt micro-patterns on SiO2 by focused electron-beam-induced deposition (FEBID), varying the number of FEBID scans at two electron beam acceleration voltages. Subsequently, the localized Pt(C) deposits are pre-cleaned in O2 and overgrown by Ru ALD. Already sub-nanometer-thin Pt(C) patterns, which were supposedly purified into some form of Pt(O x ), acted as very effective activation for the locally restricted, thus area-selective ALD growth of a pure, continuous Ru covering, whereas the SiO2 substratum sufficiently inhibited towards no growth. FEBID at lower electron energy reduced unwanted stray deposition and achieved well-resolved pattern features. We access the nucleation phenomena by utilizing a hybrid metrology approach, which uniquely combines in-situ real-time spectroscopic ellipsometry, in-vacuo x-ray photoelectron spectroscopy, ex-situ high-resolution scanning electron microscopy, and mapping energy-dispersive x-ray spectroscopy.

  6. SiO $ _2 $/TiO $ _2 $ multi-layered thin films with self-cleaning and ...

    Indian Academy of Sciences (India)

    Self-cleaning, high transmittance glazing was obtained by cold spray deposition for glazings. The thin films contain TiO 2 , SiO 2 and Au nanoparticles in different structures which allow for tailoring the optical, hydrophilic and photocatalytic properties. The crystallinity, morphology and surface energy were correlated with the ...

  7. SiO2/bi-layer GZO/Ag structures for near-infrared broadband wide-angle perfect absorption

    Science.gov (United States)

    Zhu, Chaoting; Li, Jia; Yang, Ye; Huang, Jinhua; Lu, Yuehui; Zhao, Xunna; Tan, Ruiqin; Dai, Ning; Song, Weijie

    2016-10-01

    In this work, near-infrared (NIR) perfect absorbers with a silicon dioxide (SiO2)/gallium-doped zinc oxide (GZO)/silver (Ag) multi-layer structure were designed and experimentally demonstrated. The results show that a broadband perfect absorption (PA) from 1.24 µm to 1.49 µm was achieved by adopting bi-layer GZO thin films with different carrier concentrations. This absorption remained higher than 97% for incident angles up to 60°. The perfect NIR absorber reported here has a simple structure as well as broadband and wide-angle absorption features, which is promising for practical applications.

  8. Structural and electronic properties of the transition layer at the SiO2/4H-SiC interface

    Directory of Open Access Journals (Sweden)

    Wenbo Li

    2015-01-01

    Full Text Available Using first-principles methods, we generate an amorphous SiO2/4H-SiC interface with a transition layer. Based this interface model, we investigate the structural and electronic properties of the interfacial transition layer. The calculated Si 2p core-level shifts for this interface are comparable to the experimental data, indicating that various SiCxOy species should be present in this interface transition layer. The analysis of the electronic structures reveals that the tetrahedral SiCxOy structures cannot introduce any of the defect states at the interface. Interestingly, our transition layer also includes a C-C=C trimer and SiO5 configurations, which lead to the generation of interface states. The accurate positions of Kohn-Sham energy levels associated with these defects are further calculated within the hybrid functional scheme. The Kohn-Sham energy levels of the carbon trimer and SiO5 configurations are located near the conduction and valence band of bulk 4H-SiC, respectively. The result indicates that the carbon trimer occurred in the transition layer may be a possible origin of near interface traps. These findings provide novel insight into the structural and electronic properties of the realistic SiO2/SiC interface.

  9. Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

    Science.gov (United States)

    Kim, Hyungki; Song, Intek; Park, Chibeom; Son, Minhyeok; Hong, Misun; Kim, Youngwook; Kim, Jun Sung; Shin, Hyun-Joon; Baik, Jaeyoon; Choi, Hee Cheul

    2013-08-27

    We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer. The overall quality of graphene grown by Cu-vapor-assisted CVD is comparable to that of the graphene grown by regular metal-catalyzed CVD on a Cu foil. While Cu vapor induces the nucleation and growth of SLG on an amorphous substrate, the resulting SLG is confirmed to be Cu-free by synchrotron X-ray photoelectron spectroscopy. The SLG grown by Cu-vapor-assisted CVD is fabricated into field effect transistor devices without transfer steps that are generally required when SLG is grown by regular CVD process on metal catalyst substrates. This method has overcome two important hurdles previously present when the catalyst-free CVD process is used for the growth of SLG on fused quartz and hexagonal boron nitride substrates, that is, high degree of structural defects and limited size of resulting graphene, respectively.

  10. Ta2O5/ Al2O3/ SiO2 - antireflective coating for non-planar optical surfaces by atomic layer deposition

    Science.gov (United States)

    Pfeiffer, K.; Schulz, U.; Tünnermann, A.; Szeghalmi, A.

    2017-02-01

    Antireflective coatings are essential to improve transmittance of optical elements. Most research and development of AR coatings has been reported on a wide variety of plane optical surfaces; however, antireflection is also necessary on nonplanar optical surfaces. Physical vapor deposition (PVD), a common method for optical coatings, often results in thickness gradients on strongly curved surfaces, leading to a failure of the desired optical function. In this work, optical thin films of tantalum pentoxide, aluminum oxide and silicon dioxide were prepared by atomic layer deposition (ALD), which is based on self-limiting surface reactions. The results demonstrate that ALD optical layers can be deposited on both vertical and horizontal substrate surfaces with uniform thicknesses and the same optical properties. A Ta2O5/Al2O3/ SiO2 multilayer AR coating (400-700 nm) was successfully applied to a curved aspheric glass lens with a diameter of 50 mm and a center thickness of 25 mm.

  11. Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method.

    Science.gov (United States)

    Dufour, Christian; Cardin, Julien; Debieu, Olivier; Fafin, Alexandre; Gourbilleau, Fabrice

    2011-04-04

    By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λpump = 488 nm) and signal (λsignal = 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.

  12. Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method

    Directory of Open Access Journals (Sweden)

    Dufour Christian

    2011-01-01

    Full Text Available Abstract By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λ pump = 488 nm and signal (λ signal = 1064 nm waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.

  13. Determination of SiO2 and C layers on a monocrystalline silicon sphere by reference-free x-ray fluorescence analysis

    Science.gov (United States)

    Hönicke, Philipp; Holfelder, Ina; Kolbe, Michael; Lubeck, Janin; Pollakowski-Herrmann, Beatrix; Unterumsberger, Rainer; Weser, Jan; Beckhoff, Burkhard

    2017-08-01

    The redefinition of the kilogram will be based on Planck’s constant, which can be calculated from Avogadro’s constant, and hence by ‘counting’ the silicon atoms in a monocrystalline 28Si sphere weighing one kilogram. To reduce the influence of the surface layers on the determined value requires, amongst other issues, an accurate quantification of these layers on the 28Si spheres. Apart from the native SiO2 layer, carbonaceous contamination layers and adsorbed water molecules are expected to be crucial in determining the surface composition. The overall mass contribution of these surface layers must be determined with an accuracy below 10% in order to be able to meet the targeted uncertainty budget for the redefinition. In this work, we performed a quantification of these surface layers, applying reference-free x-ray fluorescence spectrometry using a modified manipulator within an ultra-high vacuum chamber. Using this setup, we are able to quantitatively assess the surface of the spheres on a large area (about 20%) with quantification uncertainties below the required target of 10% for oxygen and carbon in order to meet an absolute uncertainty value of the mass below 10 µg.

  14. SiO2/TiO2 multi-layered thin films with self-cleaning and enhanced ...

    Indian Academy of Sciences (India)

    6 axes robot (ABB, model IRB5400) with a control software. (ABB, IRC5P control system) and a heating ceramic plate. (Ceram, model HP1212M). The glass substrate was initially cleaned by ultra-sonication in alcohol and then dried using compressed air. The multi-layered thin films were obtained by successive deposition ...

  15. Interfacial Layer Growth Condition Dependent Carrier Transport Mechanisms in HfO2/SiO2 Gate Stacks

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, S. K.; Misra, D.

    2012-06-04

    The temperature and field dependent leakage current in HfO{sub 2}/SiO{sub 2} gate stack for in situ steam grown and chemical interfacial layers (ILs) are studied in the temperature range of 20 C to 105 C. Poole-Frenkel mechanism in high field whereas Ohmic conduction in low field region are dominant for both devices. Leakage current decreases whereas both trap energy level ({phi}{sub t}) and activation energy (E{sub a}) increase for chemically grown IL devices. The trap level energy, ({phi}{sub t}) -0.2 eV, indicates that doubly charged oxygen vacancies (V{sup 2-}) are the active electron traps which contribute to the leakage current in these gate stacks.

  16. Observing the semiconducting band-gap alignment of MoS2 layers of different atomic thicknesses using a MoS2/SiO2/Si heterojunction tunnel diode

    NARCIS (Netherlands)

    Nishiguchi, K.; Castellanos-Gomez, A.; Yamaguchi, H.; Fujiwara, A.; Van der Zant, H.S.J.; Steele, G.A.

    2015-01-01

    We demonstrate a tunnel diode composed of a vertical MoS2/SiO2/Si heterostructure. A MoS2 flake consisting four areas of different thicknesses functions as a gate terminal of a silicon field-effect transistor. A thin gate oxide allows tunneling current to flow between the n-type MoS2 layers and

  17. Negative refractive behaviors of 2D triangular-lattice photonic crystals by structure of SiO2/TiO2 layers

    Science.gov (United States)

    Li, Mengxue; Liu, Mengnan; Jiang, Chengyi; Liu, Tongtong; Sun, Peng; Wan, Yong

    2018-01-01

    In this paper, we propose a two-dimensional (2-D) triangular lattice photonic crystal plate by close-packed SiO2/ TiO2 layers with the stacking mode of ABABABA. By using the finite-difference time-domain (FDTD) method, negative refraction of a single Gaussian beam incident plate with different angles are respectively demonstrated; clear image spots of a point source with normalized frequency ω=0.3605(2πc/a) vertical incident media plate are obtained in the image plane. It can be found that the imaging properties are as same as the isotropic homogeneous medium with refractive index n=-1. The measurement results show that when the distance between the image and the upper surface of the sample V is 5.12a, 3.09a and 1.15a, the distance between the source and the lower surface of the sample U is a, 3a and 5a, respectively. This means that the sum of U and V is mostly equal to the thickness of the plate L and the negative effect of near-perfect lens is realized. This proposed structure with negative refraction properties may have great applications for the design of photonic crystal focusing devices.

  18. Total Ionizing Dose Effects of Si Vertical Diffused MOSFET with SiO2 and Si3N4/SiO2 Gate Dielectrics

    Directory of Open Access Journals (Sweden)

    Jiongjiong Mo

    2017-01-01

    Full Text Available The total ionizing dose irradiation effects are investigated in Si vertical diffused MOSFETs (VDMOSs with different gate dielectrics including single SiO2 layer and double Si3N4/SiO2 layer. Radiation-induced holes trapping is greater for single SiO2 layer than for double Si3N4/SiO2 layer. Dielectric oxidation temperature dependent TID effects are also studied. Holes trapping induced negative threshold voltage shift is smaller for SiO2 at lower oxidation temperature. Gate bias during irradiation leads to different VTH shift for different gate dielectrics. Single SiO2 layer shows the worst negative VTH at VG=0 V, while double Si3N4/SiO2 shows negative VTH shift at VG=-5 V, positive VTH shift at VG=10 V, and negligible VTH shift at VG=0 V.

  19. Photocatalytic Property of Fe3O4/SiO2/TiO2 Core-Shell Nanoparticle with Different Functional Layer Thicknesses

    Directory of Open Access Journals (Sweden)

    Junyang Li

    2014-01-01

    Full Text Available This study examined the different properties of Fe3O4/SiO2/TiO2 (FST core-shell nanoparticles encapsulated for one to five different times, represented as FST1 to FST5, respectively. These FST nanoparticles were obtained using the carbon reduction and sol-gel methods, and their properties were characterized by various tools, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibratory sample magnetometer, laser granularity apparatus, and specific surface area analyzer. The relationship between irradiation time and decoloration ratio indicates that FST2 demonstrated significant efficiency in the decolorization of methyl orange (MO under UV light. Further study on recycle activity showed that FST2 had a high decoloration rate after four cycles of photocatalysis, and its degradation of MO was well aligned with the apparent first-order kinetic equation. Furthermore, FST2 exhibited the highest apparent rate in the first cycle. All these results demonstrate that the recoverable FST2 possessed excellent photocatalytic activity while maintaining outstanding stability for further applications, such as managing environmental pollution.

  20. TEM and STEM Studies on the Cross-sectional Morphologies of Dual-/Tri-layer Broadband SiO2Antireflective Films.

    Science.gov (United States)

    Wang, Shuangyue; Yan, Hongwei; Li, Dengji; Qiao, Liang; Han, Shaobo; Yuan, Xiaodong; Liu, Wei; Xiang, Xia; Zu, Xiaotao

    2018-02-12

    Dual-layer and tri-layer broadband antireflective (AR) films with excellent transmittance were successfully fabricated using base-/acid-catalyzed mixed sols and propylene oxide (PO) modified silica sols. The sols and films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), transmission electron microscope (TEM), and scanning transmission electron microscope (STEM). FTIR and TEM results suggest that the PO molecules were covalently bonded to the silica particles and the bridge structure existing in PO modified silica sol is responsible for the low density of the top layer. The density ratio between different layers was measured by cross-sectional STEM, and the results are 1.69:1 and 2.1:1.7:1 from bottom-layer to top-layer for dual-layer and tri-layer films, respectively. The dual-layer film demonstrates good stability with 99.8% at the central wavelength of 351 nm and nearly 99.5% at the central wavelength of 1053 nm in laser system, and for the tri-layer AR film, the maximum transmittance reached nearly 100% at both the central wavelengths of 527 and 1053 nm.

  1. Effect of substrate temperature on self-assisted GaAs nanowires grown by Molecular Beam Epitaxy on GaAs (111)B substrates without SiO2 layer

    Science.gov (United States)

    Vorathamrong, Samatcha; Ratanathammaphan, Somchai; Panyakeow, Somsak; Praserthdam, Piyasan; Tongyam, Chiraporn

    2017-11-01

    In this work, we demonstrate a self-assisted VLS growth of GaAs nanowires directly on GaAs (111)B substrates without assistance of SiO2 layer. We believe that with this technique, we can overcome some inherent problems that usually occur in conventional self-assisted VLS growth and simplify the process. Moreover, to study the effect of substrate temperature, each nanowire sample was fabricated at the different temperature from 400 °C to 600 °C using Molecular Beam Epitaxy (MBE) technique. Surface morphology, elemental composition, and crystal structure of nanowire samples were characterized by Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray Diffraction Analysis (XRD) respectively.

  2. Design and sol-gel preparation of SiO2/TiO2 and SiO2/SnO2/SiO2-SnO2 multilayer antireflective coatings

    Science.gov (United States)

    Wang, Jindi; Ge, Juanjuan; Hou, Haigang; Wang, Mingsong; Liu, Guiwu; Qiao, Guanjun; Wang, Yongsheng

    2017-11-01

    Interference-type antireflective coatings with homogeneous multilayers have been designed and prepared. Optical thin film design of a 6-layer SiO2/TiO2 and a tri-layer SiO2/SnO2/SiO2-SnO2 was investigated. The optical constants of the source materials for optical design were directly extracted from the sol-gel-prepared oxide thin films. The designed 6-layer SiO2/TiO2 exhibits a high average transmittance (98.3%) over a large bandwidth (400-700 nm) compared to a starting λ/4-λ/2 stack of SiO2/TiO2. Sol-gel coating of sub-10 nm ultrathin film for the multilayer was circumvented by employing diluted sols. A λ/4-λ/4-λ/4 stack of SiO2/SnO2/SiO2-SnO2 was also constructed, with its antireflective performance optimized by tuning the refractive index of the SiO2-SnO2 composite layer. In spite of some thickness deviation from the design value, a peak transmittance of 98.2% and 98.6% has been reached for the sol-gel SiO2/TiO2 and SiO2/SnO2/SiO2-SnO2 multilayers, respectively. The results obtained in this work demonstrate the great advantage of combining design with sol-gel preparation for antireflective coatings.

  3. Modulating the size of ZnO nanorods on SiO2 substrates by incorporating reduced graphene oxide into the seed layer solution

    Directory of Open Access Journals (Sweden)

    Tzu-Yi Yu

    2017-06-01

    Full Text Available In this research, reduced graphene oxide was incorporated into the ZnO seed layer to modulate the rod diameter of ZnO nanorods (NRs during solgel/hydrothermal growth. To characterize the reduced graphene oxide incorporated ZnO NRs, multiple material analysis techniques including field-emission scanning electron microscopy, surface contact angle measurements, X-ray diffraction, and photoluminescence were used to explore distinct properties of these size modulatable NRs. Results indicate ZnO NRs with smaller diameters could be observed with more reduced graphene oxide added into the ZnO seed layer. Furthermore, better crystallinity, higher hydrophobicity and lower defect concentration could be obtained with more amount of reduced graphene oxide added into the ZnO seed layer. The modulatable reduced graphene oxide-incorporated ZnO NRs growth is promising for future ZnO NRs based nanodevice applications.

  4. Modulating the size of ZnO nanorods on SiO2 substrates by incorporating reduced graphene oxide into the seed layer solution

    Science.gov (United States)

    Yu, Tzu-Yi; Wei, Min Ruei; Weng, Chen Yuan; Su, Wei Ming; Lu, Chien Cheng; Chen, Yu Tzu; Chen, Hsiang

    2017-06-01

    In this research, reduced graphene oxide was incorporated into the ZnO seed layer to modulate the rod diameter of ZnO nanorods (NRs) during solgel/hydrothermal growth. To characterize the reduced graphene oxide incorporated ZnO NRs, multiple material analysis techniques including field-emission scanning electron microscopy, surface contact angle measurements, X-ray diffraction, and photoluminescence were used to explore distinct properties of these size modulatable NRs. Results indicate ZnO NRs with smaller diameters could be observed with more reduced graphene oxide added into the ZnO seed layer. Furthermore, better crystallinity, higher hydrophobicity and lower defect concentration could be obtained with more amount of reduced graphene oxide added into the ZnO seed layer. The modulatable reduced graphene oxide-incorporated ZnO NRs growth is promising for future ZnO NRs based nanodevice applications.

  5. Estimation of silver nanoparticles size in SiO2 sol-gel layers by use of UV-VIS spectroscopy

    Directory of Open Access Journals (Sweden)

    Marek Novotný

    2011-12-01

    Full Text Available Silica glass layers containing silver nanoparticles were prepared by the sol-gel method. The layers were deposited on a glass substrate by the dip-coating method, dried and heat treated at various temperatures. The average silver particle size was determined from absorption spectra according to Mie’s theory. A good correlation was found between the calculated values and analysis of HRTEM images. A very narrow size distribution was obtained by this procedure. The average particle size of silver particles fell between 1 and 2 nm for dried samples; in case of glasses treated at 500 and 550°C the size ranged between 2 and 4 nm.

  6. Modulating the size of ZnO nanorods on SiO2 substrates by incorporating reduced graphene oxide into the seed layer solution

    OpenAIRE

    Tzu-Yi Yu; Min Ruei Wei; Chen Yuan Weng; Wei Ming Su; Chien Cheng Lu; Yu Tzu Chen; Hsiang Chen

    2017-01-01

    In this research, reduced graphene oxide was incorporated into the ZnO seed layer to modulate the rod diameter of ZnO nanorods (NRs) during solgel/hydrothermal growth. To characterize the reduced graphene oxide incorporated ZnO NRs, multiple material analysis techniques including field-emission scanning electron microscopy, surface contact angle measurements, X-ray diffraction, and photoluminescence were used to explore distinct properties of these size modulatable NRs. Results indicate ZnO N...

  7. Reduction of interface traps between poly-Si and SiO2 layers through the dielectric recovery effect during delayed pulse bias stress

    Science.gov (United States)

    Lee, Dong Uk; Pak, Sangwoo; Lee, Daemyoung; Kim, Yihun; Yang, Haechang; Hong, Sanghoo; Lee, Seungjun; Kim, Eun Kyu

    2017-06-01

    We investigate the interface trap behavior between tunneling oxide and poly-Si channel layer post erase/write cycling with a delayed pulse by using deep level transient spectroscopy. For comparison of the defect states depending on the stress pulses, a Schottky and a metal-oxide semiconductor device were fabricated. A defect state at about E c -0.51 eV in the Schottky device was measured before the annealing process. Three-hole trap states with activation energies of E v +0.28 eV, E v +0.53 eV, and E v +0.76 eV appeared after the post-annealing process. The electron trap was about E c -0.15 eV after erase/write 3000 cycling was applied at ±10 V for 100 ms at 25 °C and 85 °C. These defect states may have an effect on the charge loss behavior of the electrons localized in the charge trap layer at the retention mode of three-dimensional non-volatile memory devices. Dramatically, after the endurance stress was applied with a delayed pulse of 300 cycling at 85 °C for 50.4 h, no interface traps of the deep level transient spectroscopy spectra appeared. Dielectric recovery can decrease the density of the interface trap and improve the retention properties. This may have been caused by the passivation effect on the dangling bond of the interface traps.

  8. RESEARCH PROCESS PLASMA ETCHING SIO2 MEMBRANE

    Directory of Open Access Journals (Sweden)

    T. A. Ismailov

    2014-01-01

    Full Text Available The article discusses the results of plasma chemical etching of silicon dioxide in the fluorine-containing medium in the manufacture of semiconductor devices. Delivered and processed to obtain the solution of the smoothed microrelief contact windows in SiO2 other materials. The solution of the problem is closely connected with the problem of an isotropic plasma chemical etching, when the rate of lateral (horizontal equal to the speed of the vertical etching, which allows to obtain smooth wall structures with maximum care dimensions on the border with photoresist or other masking coating. 

  9. Electrical characteristics of SiO2/ZrO2 hybrid tunnel barrier for charge trap flash memory

    Science.gov (United States)

    Choi, Jaeho; Bae, Juhyun; Ahn, Jaeyoung; Hwang, Kihyun; Chung, Ilsub

    2017-08-01

    In this paper, we investigate the electrical characteristics of SiO2/ZrO2 hybrid tunnel oxide in metal-Al2O3-SiO2-Si3N4-SiO2-silicon (MAONOS) structure in an effort to improve program and erase speed as well as retention characteristics. Inserting ZrO2 into the conventional MAONOS structure increased the programmed V th variation to 6.8 V, and increased the erased V th variation to -3.7 V at 17 MV/cm. The results can be understood in terms of reducing the Fowler-Nordheim (F/N) tunneling barrier due to high-k ZrO2 in the tunneling oxide. In addition, Zr diffusion in SiO2 caused the formation of Zr x Si1- x O2 at the interface region, which reduced the energy band gap of SiO2. The retention property of the hybrid tunnel oxide varied depending on the thickness of SiO2. For thin SiO2 less than 30 Å, the retention properties of the tunneling oxides were poor compared with those of the SiO2 only tunneling oxides. However, the hybrid tunneling oxides with SiO2 thickness thicker than 40 Å yielded improved retention behavior compared with those of the SiO2-only tunneling oxides. The detailed analysis in charge density of ZrO2 was carried out by ISPP test. The obtained charge density was quite small compared to that of the total charge density, which indicates that the inserted ZrO2 layer serves as a tunneling material rather than charge storage dielectric.

  10. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy

    Directory of Open Access Journals (Sweden)

    Volodymyr Tkachenko

    2016-11-01

    Full Text Available Control of liquid crystal (LC orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles.

  11. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy.

    Science.gov (United States)

    Tkachenko, Volodymyr; Marino, Antigone; Otón, Eva; Bennis, Noureddine; Otón, Josè Manuel

    2016-01-01

    Control of liquid crystal (LC) orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN) displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles.

  12. Morphology of SiO2 films as a key factor in alignment of liquid crystals with negative dielectric anisotropy

    Science.gov (United States)

    Marino, Antigone; Otón, Eva; Bennis, Noureddine; Otón, Josè Manuel

    2016-01-01

    Control of liquid crystal (LC) orientation using a proper SiO2 alignment layer is essential for the optimization of vertically aligned nematic (VAN) displays. With this aim, we studied the optical anisotropy of thin SiO2 films by generalized ellipsometry as a function of deposition angle. The columnar SiO2 structure orientation measured by a noninvasive ellipsometry technique is reported for the first time, and its morphology influence on the LC alignment is demonstrated for large deposition angles. PMID:28144524

  13. Metastable ultrathin crystal in thermally grown SiO2 film on Si substrate

    Directory of Open Access Journals (Sweden)

    Koji Kimoto

    2012-12-01

    Full Text Available A silicon dioxide film on a silicon substrate is the most essential element in semiconductor devices and various advanced materials. We have elucidated the atomic structure of SiO2 films using low-dose scanning transmission electron microscopy (STEM. We have visualized a metastable crystalline SiO2 layer near a silicon substrate, which was not revealed in previous studies probably due to the vitrification caused by electron irradiation. Our experimental results also suggest a crystallographic nature of various surface oxides.

  14. A novel growth mode of alkane films on a SiO2 surface

    DEFF Research Database (Denmark)

    Mo, H.; Taub, H.; Volkmann, U.G.

    2003-01-01

    Synchrotron X-ray specular scattering measurements confirm microscopically a structural model recently inferred by very-high-resolution ellipsometry of a solid dotriacontane (n-C32H66 or C32) film formed by adsorption from solution onto a SiO2 surface. Sequentially, one or two layers adsorb...... on the SiO2 surface with the long-axis of the C32 molecules oriented parallel to the interface followed by a C32 monolayer with the long-axis perpendicular to it. Finally, preferentially oriented bulk particles nucleate having two different crystal structures. This growth model differs from that found...

  15. Ultrathin Microporous SiO2 Membranes Photodeposited on Hydrogen Evolving Catalysts Enabling Overall Water Splitting

    KAUST Repository

    Bau, Jeremy A.

    2017-10-17

    Semiconductor systems for photocatalytic overall water splitting into H2 and O2 gases typically require metal cocatalyst particles, such as Pt, to efficiently catalyze H2 evolution. However, such metal catalyst surfaces also serve as recombination sites for H2 and O2, forming H2O. We herein report the photon-induced fabrication of microporous SiO2 membranes that can selectively restrict passage of O2 and larger hydrated ions while allowing penetration of protons, water, and H2. The SiO2 layers were selectively photodeposited on Pt nanoparticles on SrTiO3 photocatalyst by using tetramethylammonium (TMA) as a structure-directing agent (SDA), resulting in the formation of core–shell Pt@SiO2 cocatalysts. The resulting photocatalyst exhibited both improved overall water splitting performance under irradiation and with no H2/O2 recombination in the dark. The function of the SiO2 layers was investigated electrochemically by fabricating the SiO2 layers on a Pt electrode via an analogous cathodic deposition protocol. The uniform, dense, yet amorphous layers possess microporosity originating from ring structures formed during the hydrolysis of the silicate precursor in the presence of TMA, suggesting a double-role for TMA in coordinating silicate to cathodic surfaces and in creating a microporous material. The resulting layers were able to function as a molecular sieve, allowing for exclusive H2 generation while excluding unwanted side reactions by O2 or ferricyanide. The SiO2 layer is stable for extended periods of time in photocatalytic conditions, demonstrating promise as a nontoxic material for selective H2 evolution.

  16. Reflectance modulation using SiO2/TiO2 multilayer structures prepared by sol-gel spin coating process for optical applications

    Science.gov (United States)

    Dubey, R. S.; Ganesan, V.

    2017-11-01

    Passive devices made of SiO2/TiO2 bilayers have been demanded for the molding of electromagnetic waves in optical waveguides, microcavities, solar cells, sensors and so on. Here, we present the fabrication and characterization of SiO2/TiO2 multilayer structures as reflectors. The refractive indices were found to be 1.43 & 2.0 with thicknesses 230 & 70 nm corresponding to the SiO2 and TiO2 films respectively. AFM surface topography study showed little bit large surface roughness of the TiO2 as compared to SiO2 film due to its large grain size. The corresponding reflectance enhancement was noticed with the increased number of bilayers of SiO2/TiO2 films. Furthermore, six alternate layers of SiO2/TiO2 demonstrated the as much as 78% reflectance in the near-infrared wavelength range.

  17. Photocatalytic activity of the binary composite CeO2/SiO2 for degradation of dye

    Science.gov (United States)

    Phanichphant, Sukon; Nakaruk, Auppatham; Channei, Duangdao

    2016-11-01

    In this study, CeO2 photocatalyst was modified by composite with SiO2 to increase efficiency and improve photocatalytic activity. The as-prepared SiO2 particles have been incorporated into the precursor mixture of CeO2 by homogeneous precipitation and subsequent calcination process. The phase compositions of CeO2 before and after compositing with SiO2 were identified by X-ray diffraction (XRD). The morphology and particle size of CeO2/SiO2 composite was analyzed by high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed SiO2 spheres with the particle size approximately 100-120 nm, and a uniform layer of CeO2 nanoparticles with a diameter of about 5-7 nm that were fully composite to the surfaces of SiO2. The X-ray photoelectron spectroscopy (XPS) technique was carried out in order to characterize the change in valence state and composite characteristic by shifted peaks of binding energies. The photocatalytic activity was studied through the degradation of Rhodamine B in aqueous solution under visible light exposure. The highest photocatalytic efficiency of CeO2/SiO2 composite was also obtained. To explain the high photocatalytic efficiency of CeO2/SiO2 composite, the proposed mechanism involves the high surface properties of the CeO2/SiO2 composite, as measured by Brunauer-Emmett-Teller (BET) method.

  18. Surface Crystallization of a MgO/Y2O3/SiO2/Al2O3/ZrO2 Glass: Growth of an Oriented β-Y2Si2O7 Layer and Epitaxial ZrO2

    Science.gov (United States)

    Wisniewski, Wolfgang; Seidel, Sabrina; Patzig, Christian; Rüssel, Christian

    2017-03-01

    The crystallization behavior of a glass with the composition 54.7 SiO2·10.9 Al2O3·15.0 MgO·3.4 ZrO2·16.0 Y2O3 is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and (scanning) transmission electron microscopy [(S)TEM] including energy-dispersive X-ray spectrometry (EDXS). This glass shows the sole surface crystallization of four different yttrium silicates of the composition Y2Si2O7 (YS). The almost simultaneous but independent nucleation of α-, β-, δ-, and ε-YS at the surface is followed by growth into the bulk, where ε-YS quickly dominates a first crystallized layer. An accumulation of Mg at the growth front probably triggers a secondary nucleation of β-YS, which forms a thin compact layer before fragmenting into a highly oriented layer of fine grained crystals occupying the remaining bulk. The residual glass between the YS growth structures allows the crystallization of indialite, yttrium stabilized ZrO2 (Y-ZrO2) and very probably μ-cordierite during cooling. Hence, this glass basically shows the inverted order of crystallization observed in other magnesium yttrium alumosilicate glasses containing less Y2O3. An epitaxial relationship between Y-ZrO2 and ε-YS is proven and multiple twinning relationships occur in the YS phases.

  19. Role of surface-reaction layer in HBr/fluorocarbon-based plasma with nitrogen addition formed by high-aspect-ratio etching of polycrystalline silicon and SiO2 stacks

    Science.gov (United States)

    Iwase, Taku; Matsui, Miyako; Yokogawa, Kenetsu; Arase, Takao; Mori, Masahito

    2016-06-01

    The etching of polycrystalline silicon (poly-Si)/SiO2 stacks by using VHF plasma was studied for three-dimensional NAND fabrication. One critical goal is achieving both a vertical profile and high throughput for multiple-stack etching. While the conventional process consists of multiple steps for each stacked layer, in this study, HBr/fluorocarbon-based gas chemistry was investigated to achieve a single-step etching process to reduce process time. By analyzing the dependence on wafer temperature, we improved both the etching profile and rate at a low temperature. The etching mechanism is examined considering the composition of the surface reaction layer. X-ray photoelectron spectroscopy (XPS) analysis revealed that the adsorption of N-H and Br was enhanced at a low temperature, resulting in a reduced carbon-based-polymer thickness and enhanced Si etching. Finally, a vertical profile was obtained as a result of the formation of a thin and reactive surface-reaction layer at a low wafer temperature.

  20. Transparent, Adherent, and Photocatalytic SiO2-TiO2 Coatings on Polycarbonate for Self-Cleaning Applications

    Directory of Open Access Journals (Sweden)

    Sanjay S. Latthe

    2014-07-01

    Full Text Available Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO2-TiO2 coatings on polycarbonate (PC substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO2-TiO2 coatings. The effect of different vol% of SiO2 in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO2 in TiO2 showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO2 in TiO2. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20 of SiO2 in TiO2 showed high transparency in the visible range.

  1. Hydroxyapatite-TiO2-SiO2-Coated 316L Stainless Steel for Biomedical Application

    Science.gov (United States)

    Sidane, Djahida; Khireddine, Hafit; Bir, Fatima; Yala, Sabeha; Montagne, Alex; Chicot, Didier

    2017-07-01

    This study investigated the effectiveness of titania (TiO2) as a reinforcing phase in the hydroxyapatite (HAP) coating and silica (SiO2) single layer as a bond coat between the TiO2-reinforced hydroxyapatite (TiO2/HAP) top layer and 316L stainless steel (316L SS) substrate on the corrosion resistance and mechanical properties of the underlying 316L SS metallic implant. Single layer of SiO2 film was first deposited on 316L SS substrate and studied separately. Water contact angle measurements, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrophotometer analysis were used to evaluate the hydroxyl group reactivity at the SiO2 outer surface. The microstructural and morphological results showed that the reinforcement of HAP coating with TiO2 and SiO2 reduced the crystallite size and the roughness surface. Indeed, the deposition of 50 vol pct TiO2-reinforced hydroxyapatite layer enhanced the hardness and the elastic modulus of the HAP coating, and the introduction of SiO2 inner layer on the surface of the 316L SS allowed the improvement of the bonding strength and the corrosion resistance as confirmed by scratch studies, nanoindentation, and cyclic voltammetry tests.

  2. Investigation of Leakage Current Mechanisms in La2O3/SiO2/4H-SiC MOS Capacitors with Varied SiO2 Thickness

    Science.gov (United States)

    Wang, Yucheng; Jia, Renxu; Zhao, Yanli; Li, Chengzhan; Zhang, Yuming

    2016-11-01

    In this study, the material and electrical properties of La2O3/SiO2/4H-SiC metal-oxide-semiconductor (MOS) capacitors are systematically characterized. Thermal oxidization SiO2 with varying thickness (0 nm, 3.36 nm, 5 nm, 8 nm, and 30 nm) were coated with La2O3 using atomic layer deposition on n-type 4H-SiC. The stacking oxides were measured using atomic force microscopy, transmission electron microscopy, and x-ray photoelectron spectroscopy, and the MOS capacitors were measured by capacitance-voltage and current-voltage measurements. The results demonstrate that the main gate current leakage mechanisms are dependent on the thickness of the SiO2 oxide under the applied electric field. The primary mechanism for current leakage from the La2O3/4H-SiC MOS capacitor follows the Schottky emission mechanism due to its low conduction band offset. In contrast, the current leakage mechanism for the capacitor with a 3.36 nm SiO2 layer follows the Poole-Frenkel emission mechanism on account of its high trap charge density in the gate dielectric and at the interface. When the thickness of the SiO2 layer increases to 8 nm, lower leakage current is observed by reason of the low trap charge density and high conduction band offset when E ≤ 5 MV/cm. As the electric field strength increases to 5 MV/cm and 5.88 MV/cm (30 nm SiO2: 4.8 MV/cm), the main current leakage mechanism changes to the Fowler-Nordheim tunneling mechanism, which indicates that the La2O3/SiO2 stacking structure can improve the properties of MOS capacitors.

  3. Three-dimensional conductive networks based on stacked SiO2@graphene frameworks for enhanced gas sensing.

    Science.gov (United States)

    Huang, Da; Yang, Zhi; Li, Xiaolin; Zhang, Liling; Hu, Jing; Su, Yanjie; Hu, Nantao; Yin, Guilin; He, Dannong; Zhang, Yafei

    2017-01-07

    Graphene is an ideal candidate for gas sensing due to its excellent conductivity and large specific surface areas. However, it usually suffers from sheet stacking, which seriously debilitates its sensing performance. Herein, we demonstrate a three-dimensional conductive network based on stacked SiO2@graphene core-shell hybrid frameworks for enhanced gas sensing. SiO2 spheres are uniformly encapsulated by graphene oxide (GO) through an electrostatic self-assembly approach to form SiO2@GO core-shell hybrid frameworks, which are reduced through thermal annealing to establish three-dimensional (3D) conductive sensing networks. The SiO2 supported 3D conductive graphene frameworks reveal superior sensing performance to bare reduced graphene oxide (RGO) films, which can be attributed to their less agglomeration and larger surface area. The response value of the 3D framework based sensor for 50 ppm NH3 and 50 ppm NO2 increased 8 times and 5 times, respectively. Additionally, the sensing performance degradation caused by the stacking of the sensing materials is significantly suppressed because the graphene layers are separated by the SiO2 spheres. The sensing performance decays by 92% for the bare RGO films when the concentration of the sensing material increases 8 times, while there is only a decay of 25% for that of the SiO2@graphene core-shell hybrid frameworks. This work provides an insight into 3D frameworks of hybrid materials for effectively improving gas sensing performance.

  4. Antireflection and SiO2 Surface Passivation by Liquid-Phase Chemistry for Efficient Black Silicon Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, H. C.; Oh, J.; Zhang, Y.; Kuznetsov, O. A.; Flood, D. J.; Branz, H. M.

    2012-06-01

    We report solar cells with both black Si antireflection and SiO2 surface passivation provided by inexpensive liquid-phase chemistry, rather than by conventional vacuum-based techniques. Preliminary cell efficiency has reached 16.4%. Nanoporous black Si antireflection on crystalline Si by aqueous etching promises low surface reflection for high photon utilization, together with lower manufacturing cost compared to vacuum-based antireflection coating. Ag-nanoparticle-assisted black Si etching and post-etching chemical treatment recently developed at NREL enables excellent control over the pore diameter and pore separation. Performance of black Si solar cells, including open-circuit voltage, short-circuit current density, and blue response, has benefited from these improvements. Prior to this study, our black Si solar cells were all passivated by thermal SiO2 produced in tube furnaces. Although this passivation is effective, it is not yet ideal for ultra-low-cost manufacturing. In this study, we report, for the first time, the integration of black Si with a proprietary liquid-phase deposition (LPD) passivation from Natcore Technology. The Natcore LPD forms a layer of <10-nm SiO2 on top of the black Si surface in a relatively mild chemical bath at room temperature. We demonstrate black Si solar cells with LPD SiO2 with a spectrum-weighted average reflection lower than 5%, similar to the more costly thermally grown SiO2 approach. However, LPD SiO2 provides somewhat better surface-passivation quality according to the lifetime analysis by the photo-conductivity decay measurement. Moreover, black Si solar cells with LPD SiO2 passivation exhibit higher spectral response at short wavelength compared to those passivated by thermally grown SiO2. With further optimization, the combination of aqueous black Si etching and LPD could provide a pathway for low-cost, high-efficiency crystalline Si solar cells.

  5. Preparation of SiO2-Protecting Metallic Fe Nanoparticle/SiO2 Composite Spheres for Biomedical Application

    Directory of Open Access Journals (Sweden)

    Pin-Wei Hsieh

    2015-11-01

    Full Text Available Functionalized Fe nanoparticles (NPs have played an important role in biomedical applications. In this study, metallic Fe NPs were deposited on SiO2 spheres to form a Fe/SiO2 composite. To protect the Fe from oxidation, a thin SiO2 layer was coated on the Fe/SiO2 spheres thereafter. The size and morphology of the SiO2@Fe/SiO2 composite spheres were examined by transmission electron microscopy (TEM. The iron form and its content and magnetic properties were examined by X-ray diffraction (XRD, inductively-coupled plasma mass spectrometry (ICP-MS and a superconducting quantum interference device (SQUID. The biocompatibility of the SiO2@Fe/SiO2 composite spheres was examined by Cell Counting Kit-8 (CCK-8 and lactate dehydrogenase (LDH tests. The intracellular distribution of the SiO2@Fe/SiO2 composite spheres was observed using TEM. XRD analysis revealed the formation of metallic iron on the surface of the SiO2 spheres. According to the ICP-MS and SQUID results, using 0.375 M FeCl3·6H2O for Fe NPs synthesis resulted in the highest iron content and magnetization of the SiO2@Fe/SiO2 spheres. Using a dye loading experiment, a slow release of a fluorescence dye from SiO2@Fe/SiO2 composite spheres was confirmed. The SiO2@Fe/SiO2 composite spheres co-cultured with L929 cells exhibit biocompatibility at concentrations <16.25 µg/mL. The TEM images show that the SiO2@Fe/SiO2 composite spheres were uptaken into the cytoplasm and retained in the endosome. The above results demonstrate that the SiO2@Fe/SiO2 composite spheres could be used as a multi-functional agent, such as a magnetic resonance imaging (MRI contrast agent or drug carriers in biomedical applications.

  6. Reactive sputtering deposition of SiO2 thin films

    Directory of Open Access Journals (Sweden)

    IVAN RADOVIC

    2008-01-01

    Full Text Available SiO2 layers were deposited in a UHV chamber by 1 keV Ar+ ion sputtering from a high purity silicon target, using different values of the oxygen partial pressure (5×10-6–2×10-4 mbar and of the ion beam current on the target (1.67–6.85 mA. The argon partial pressure during operation of the ion gun was 1×10-3 mbar. The substrate temperature was held at 550 °C and the films were deposited to a thickness of 12.5–150 nm, at a rate from 0.0018–0.035 nm s-1. Structural characterization of the deposited thin films was performed by Rutherford backscattering spectrometry (RBS analysis. Reactive sputtering was proved to be efficient for the deposition of silica at 550 °C, an oxygen partial pressure of 2×10-4 mbar (ion beam current on the target of 5 mA or, at a lower deposition rate, ion beam current of 1.67 mA and an oxygen partial pressure of 6×10-5 mbar. One aspect of these investigations was to study the consumption of oxygen from the gas cylinder, which was found to be lower for higher deposition rates.

  7. Preparation, chromatographic evaluation and application of adenosine 5'-monophosphate modified ZrO2/SiO2 stationary phase in hydrophilic interaction chromatography.

    Science.gov (United States)

    Wang, Qing; Luo, Zhi-Yuan; Ye, Mao; Wang, Yu-Zhuo; Xu, Li; Shi, Zhi-Guo; Xu, Lanying

    2015-02-27

    The zirconia-coated silica (ZrO2/SiO2) material was obtained by coupling layer-by-layer (LbL) self-assembly method and sol-gel technology, to take dual advantages of the suitable porous structure of SiO2 and basic resistance of ZrO2. Adenosine 5'-monophosphate (5'-AMP) was then self-assembled onto ZrO2/SiO2 via Lewis acid-base interaction, generating 5'-AMP-ZrO2/SiO2. The chromatographic properties of 5'-AMP-ZrO2/SiO2 were systemically studied by evaluating the effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the 5'-AMP-ZrO2/SiO2 possessed hydrophilic interaction chromatographic (HILIC) property comprising hydrophilic, hydrogen-bonding, electrostatic and ion-exchange interactions. For basic analytes, the column efficiency of ZrO2/SiO2 and 5'-AMP-ZrO2/SiO2 was superior to the bare ZrO2, and different selectivity was obtained after the introduction of 5'-AMP. For acidic analytes, good resolution was obtained on 5'-AMP-ZrO2/SiO2 while the analysis failed on the bare ZrO2 column owing to strong adsorption. Hence, the proposed 5'-AMP-ZrO2/SiO2 had great potential in analyzing acidic compounds in HILIC mode. It was an extended application of ZrO2 based SP. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Ordering at Si(111)/o-Si and Si(111)/SiO2 Interfaces

    DEFF Research Database (Denmark)

    Robinson, I. K.; Waskiewicz, W. K.; Tung, R. T.

    1986-01-01

    X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(111)/a-Si and Si(111)/SiO2 examples there are features in the perpendicular-momentum-transfer dependence which are not expec......X-ray diffraction has been used to measure the intensity profile of the two-dimensional rods of scattering from a single interface buried inside a bulk material. In both Si(111)/a-Si and Si(111)/SiO2 examples there are features in the perpendicular-momentum-transfer dependence which...... are not expected from an ideal sharp interface. The diffraction profiles are explained by models with partially ordered layers extending into the amorphous region. In the Si(111)/a-Si case there is clear evidence of stacking faults which are attributed to residual 7×7 reconstruction....

  9. Effect of different oxide thickness on the bending Young's modulus of SiO2@SiC nanowires.

    Science.gov (United States)

    Ma, Jinyao; Liu, Yanping; Hao, Peida; Wang, Jin; Zhang, Yuefei

    2016-01-07

    The surface or sheath effect on core-shell nanowires plays an important role in the nanomechanical test. In the past few years, SiC nanowires have been synthesized using various methods with an uneven and uncontrollable amorphous silicon dioxide sheath. The bending Young's modulus of the SiC nanowires has scarcely been measured, and the effect of the oxide sheath has not been taken into account. In this paper, SiO2-coated SiC (SiO2@SiC) nanowires were synthesized using the chemical vapor deposition method, followed by thermal reduction. Scanning electron microscopy and transmission electron microscopy show that the SiO2@SiC nanowires in this paper have diameters ranging from 130 ~ 150 nm, with the average thickness of SiO2 layer approximately 14 nm. After different processing times with 1 mol/L NaOH, approximately 5 nm, 9 nm, 14 nm silicon dioxide layers were obtained. The results of the three-point-bending test show that the modulus of SiO2@SiC nanowires is found to clearly decrease with the increase in oxide thickness and the influence of the oxide sheath should not be ignored when the layer thickness is above 5 nm. Young's modulus of the SiO2@SiC nanowires calculated in this study by the core-shell structure model is in good agreement with the theoretical value.

  10. Deposition of conductive TiN shells on SiO2 nanoparticles with a fluidized bed ALD reactor

    NARCIS (Netherlands)

    Didden, A.; Hillebrand, P.; Wollgarten, M.; Dam, B.; Van de Krol, R.

    2016-01-01

    Conductive TiN shells have been deposited on SiO2 nanoparticles (10–20 nm primary particle size) with fluidized bed atomic layer deposition using TDMAT and NH3 as precursors. Analysis of the powders confirms that shell growth saturates at approximately 0.4 nm/cycle at TDMAT doses of >1.2 mmol/g of

  11. Current Tunnelling in MOS Devices with Al2O3/SiO2 Gate Dielectric

    Directory of Open Access Journals (Sweden)

    A. Bouazra

    2008-01-01

    Full Text Available With the continued scaling of the SiO2 thickness below 2 nm in CMOS devices, a large direct-tunnelling current flow between the gate electrode and silicon substrate is greatly impacting device performance. Therefore, higher dielectric constant materials are desirable for reducing the gate leakage while maintaining transistor performance for very thin dielectric layers. Despite its not very high dielectric constant (∼10, Al2O3 has emerged as one of the most promising high-k candidates in terms of its chemical and thermal stability as its high-barrier offset. In this paper, a theoretical study of the physical and electrical properties of Al2O3 gate dielectric is reported including I(V and C(V characteristics. By using a stack of Al2O3/SiO2 with an appropriate equivalent oxide thickness of gate dielectric MOS, the gate leakage exhibits an important decrease. The effect of carrier trap parameters (depth and width at the Al2O3/SiO2 interface is also discussed.

  12. Diffusive charge transport in graphene on SiO 2

    Science.gov (United States)

    Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

    2009-07-01

    We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

  13. Structural enhancement of ZnO on SiO2 for photonic applications

    Directory of Open Access Journals (Sweden)

    Marcel Ruth

    2013-07-01

    Full Text Available Multi-layer thin films are often the basis of photonic devices. Zinc oxide (ZnO with its excellent optoelectronic properties can serve as a high quality emitter in structures like microdisks or photonic crystals. Here, we present a detailed study on the enhancement of the structural properties of low-temperature MBE grown ZnO on silica (SiO2. By thermal annealing a grain coalescence of the initially polycrystalline layer leads to an enhancement of the electronic structure, indicated by a blue shift of the photoluminescence (PL signal maximum. Oxygen atmosphere during the annealing process prevents the creation of intrinsic defects by out-diffusion. Pre-annealing deposited SiO2 capping layers instead obstruct the recrystallization and lead to less intense emission. While thin capping layers partially detach from the ZnO film at high temperatures and cause higher surface roughness and the weakest emission, thicker layers remain smoother and exhibit a significantly stronger photoluminescence.

  14. Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

    Science.gov (United States)

    Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

    2016-11-15

    Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Ag-Decorated Fe3O4@SiO2 Nanorods: Synthesis, Characterization, and Applications in Degradation of Organic Dyes

    Directory of Open Access Journals (Sweden)

    Chao Li

    2016-01-01

    Full Text Available Well-dispersed Ag nanoparticles (NPs are successfully decorated on Fe3O4@SiO2 nanorods (NRs via a facile step-by-step strategy. This method involves coating α-Fe2O3 NRs with uniform silica layer, reduction in 10% H2/Ar atmosphere at 450°C to obtain Fe3O4@SiO2 NRs, and then depositing Ag NPs on the surface of Fe3O4@SiO2 NRs through a sonochemical step. It was found that the as-prepared Ag-decorated magnetic Fe3O4@SiO2 NRs (Ag-MNRs exhibited a higher catalytic efficiency than bare Ag NPs in the degradation of organic dye and could be easily recovered by convenient magnetic separation, which show great application potential for environmental protection applications.

  16. Surface properties of SiO2 with and without H2O2 treatment as gate dielectrics for pentacene thin-film transistor applications

    Science.gov (United States)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of H2O2 treatment on the surface properties of SiO2 is studied. H2O2 treatment leads to the formation of Si(sbnd OH)x at the SiO2 surface that serves to reduce the number of trap states, inducing the shift of the Fermi level toward the conduction band minimum. H2O2 treatment also leads to a noticeable reduction in the value of the SiO2 capacitance per unit area. The effect of SiO2 layers with H2O2 treatment on the behavior of carrier transports for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. Experimental identification confirms that the shift of the threshold voltage towards negative gate-source voltages is due to the reduced number of trap states in SiO2 near the pentacene/SiO2 interface. The existence of a hydrogenated layer between pentacene and SiO2 leads to a change in the pentacene-SiO2 interaction, increasing the value of the carrier mobility.

  17. Surface Property and Stability of Transparent Superhydrophobic Coating Based on SiO2-Polyelectrolyte Multilayer

    Directory of Open Access Journals (Sweden)

    Sunisa JINDASUWAN

    2016-05-01

    Full Text Available Artificial superhydrophobic films were deposited onto a glass slide by performing layer-by-layer deposition of 3.5 bilayers of poly(allylamine hydrochloride/ poly(acrylic acid polyelectrolyte, followed by a layer of SiO2 nanoparticles of various amounts to enhance the surface roughness and a fluorosilane to reduce the surface free energy. Higher SiO2 content incorporated into the films resulted in rougher surface and higher water contact angle. The total surface free energy determined by using the Owens-Wendt equation dramatically decreased from 31.46 mJ·m-2 for the film having the relatively flat surface to only 1.16 mJ·m-2 for the film having the highest surface roughness of 60.2 ± 1.1 nm. All the films were optically transparent and had excellent adhesion based on the peel test. Indoor and accelerated weathering tests revealed good weathering stability.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12952

  18. Atomic force microscopy measurements of topography and friction on dotriacontane films adsorbed on a SiO2 surface

    DEFF Research Database (Denmark)

    Trogisch, S.; Simpson, M.J.; Taub, H.

    2005-01-01

    We report comprehensive atomic force microscopy (AFM) measurements at room temperature of the nanoscale topography and lateral friction on the surface of thin solid films of an intermediate-length normal alkane, dotriacontane (n-C32H66), adsorbed onto a SiO2 surface. Our topographic and frictional...... images, recorded simultaneously in the contact mode, reveal a multilayer structure in which one to two layers of molecules adsorb adjacent to the SiO2 surface oriented with their long axis parallel to the interface followed by partial layers of molecules oriented perpendicular to the surface...... their location. Above a minimum size, the bulk particles are separated from islands of perpendicularly oriented molecules by regions of exposed parallel layers that most likely extend underneath the particles. We find that the lateral friction is sensitive to the molecular orientation in the underlying...

  19. Preparation, characterization, and infrared emissivity property of optically active polyurethane/TiO 2/SiO 2 multilayered microspheres

    Science.gov (United States)

    Yang, Yong; Zhou, Yuming; Ge, Jianhua; Wang, Yongjuan; Zhu, Yunxia

    2011-10-01

    Optically active polyurethane/titania/silica (LPU/TiO 2/SiO 2) multilayered core-shell composite microspheres were prepared by the combination of titania deposition on the surface of silica spheres and subsequent polymer grafting. LPU/TiO 2/SiO 2 was characterized by FT-IR, UV-vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), SEM and TEM, and the infrared emissivity value (8-14 μm) was investigated in addition. The results indicated that titania and polyurethane had been successfully coated onto the surfaces of silica microspheres. LPU/TiO 2/SiO 2 exhibited clearly multilayered core-shell construction. The infrared emissivity values reduced along with the increase of covering layers thus proved that the interfacial interactions had direct influence on the infrared emissivity. Besides, LPU/TiO 2/SiO 2 multilayered microspheres based on the optically active polyurethane took advantages of the orderly secondary structure and strengthened interfacial synergistic actions. Consequently, it possessed the lowest infrared emissivity value.

  20. Fabrication and characterization of suspended beam structures for SiO2 photonic MEMS

    NARCIS (Netherlands)

    Peters, T.J.; Tichem, M.

    2015-01-01

    This paper proposes a microfabrication process for the reliable release of SiO2 beam structures. These structures are intended to be utilized in SiO2 photonic MEMS. A major fabrication challenge is the release of thick (>10 ?m) SiO2 structures with high yield. A single mask process is developed

  1. Fabrication of core/shell structured SiO2/Zn2SiO4:Mn2+ composite and its photoluminescence properties

    Science.gov (United States)

    Park, Jehong; Kim, Jongsu; Kwon, Hansang

    2017-10-01

    Core/shell structured SiO2/Zn2SiO4:Mn2+ composite was prepared by thermal-diffusion reaction between SiO2 and Zn1-xMnxO particles, which is a low cost solid-state method. The X-ray diffraction and scanning electron microscope results showed that a 5- μm-thick dense Zn2SiO4:Mn2+ layer was successfully formed on the surface of the SiO2 particles. The PL spectrum of the SiO2/Zn2SiO4:Mn2+ composite revealed a green emission peak at 526 nm with PL intensity 20% higher than that of the conventional Zn2SiO4:Mn2+ particles. In addition, the decay time of the SiO2/Zn2SiO4:Mn2+ composite was shorter ( τ 10% = 7 ms) than that of the conventional Zn2SiO4:Mn2+ particles ( τ 10% =12 ms), which is owing to the relaxation of forbidden transition of Mn2+ ions due to the localized stress of Mn2+ ions arising from the surface tension in the SiO2/Zn2SiO4:Mn2+ composite.

  2. Leakage radiation spectroscopy of organic/dielectric/metal systems: influence of SiO2 on exciton-surface plasmon polariton interaction

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Kawalec, Tomasz; Kostiučenko, Oksana

    excitons and surface plasmon polaritons (SPPs) of the metal/dielectric boundary. The presence of the SiO2 layer considerably changes the dispersion curve in comparison to the one of the Ag/p-6P/air system. However, the Ag/SiO2/p-6P/air stack forms a stable structure allowing construction of organic......Leakage radiation spectroscopy of organic para-Hexaphenylene (p-6P) molecules has been performed in the spectral range 420-675 nm which overlaps with the p-6P photoluminescence band. The p-6P was deposited on 40 nm silver (Ag) films on BK7 glass, covered with SiO2 layers. The SiO2 layer thickness...

  3. Surface-modification of SiO 2 nanoparticles with oleic acid

    Science.gov (United States)

    Li, Zongwei; Zhu, Yongfa

    2003-04-01

    SiO 2 nanoparticles modified by oleic acid (OA) were prepared using surface-modification method in this work. Infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS) were used to investigate the structure of the modified SiO 2 nanoparticles. Effects on coverage and dispersion in oil by OA concentration were also studied. The results indicate that OA-modified SiO 2 nanoparticles are capable of dispersing stably in mineral oil and the OA is bonded to the surface of SiO 2 nanoparticles through esterification. The optimal reaction temperature and the proportion of OA to SiO 2 were established.

  4. Interactions of atomic hydrogen with amorphous SiO2

    Science.gov (United States)

    Yue, Yunliang; Wang, Jianwei; Zhang, Yuqi; Song, Yu; Zuo, Xu

    2018-03-01

    Dozens of models are investigated by the first-principles calculations to simulate the interactions of an atomic hydrogen with a defect-free random network of amorphous SiO2 (a-SiO2) and oxygen vacancies. A wide variety of stable configurations are discovered due to the disorder of a-SiO2, and their structures, charges, magnetic moments, spin densities, and density of states are calculated. The atomic hydrogen interacts with the defect-free a-SiO2 in positively or negatively charged state, and produces the structures absent in crystalline SiO2. It passivates the neutral oxygen vacancies and generates two neutral hydrogenated E‧ centers with different Si dangling bond projections. Electron spin resonance parameters, including Fermi contacts, and g-tensors, are calculated for these centers. The atomic hydrogen interacts with the positive oxygen vacancies in dimer configuration, and generate four different positive hydrogenated defects, two of which are puckered like the Eγ‧ centers. This research helps to understand the interactions between an atomic hydrogen, and defect-free a-SiO2 and oxygen vacancies, which may generate the hydrogen-complexed defects that play a key role in the degeneration of silicon/silica-based microelectronic devices.

  5. Effect of Commercial SiO2 and SiO2 from rice husk ash loading on biodegradation of Poly (lactic acid) and crosslinked Poly (lactic acid)

    Science.gov (United States)

    Prapruddivongs, C.; Apichartsitporn, M.; Wongpreedee, T.

    2017-09-01

    In this work, biodegradation behavior of poly (lactic acid) (PLA) and crosslinked PLA filled with two types of SiO2, precipitated SiO2 (commercial SiO2) and SiO2 from rice husk ash, were studied. Rice husks were first treated with 2 molar hydrochloric acid (HCl) to produce high purity SiO2, before burnt in a furnace at 800°C for 6 hours. All components were melted bending by an internal mixer then hot pressed using compression molder to form tested specimens. FTIR spectra of SiO2 and PLA samples were investigated. The results showed the lack of silanol group (Si-OH) of rice husk ash after steric acid surface modification, while the addition of particles can affect the crosslinking of the PLA. For biodegradation test by evaluating total amount of carbon dioxide (CO2) evolved during 60 days incubation at a controlled temperature of 58±2°C, the results showed that the biodegradation of crosslinked PLA occurred slower than the neat PLA. However, SiO2 incorporation enhanced the degree of biodegradation In particular, introducing commercial SiO2 in PLA and crosslinked PLA tended to clearly increase the degree of biodegradation as a consequence of the more accelerated hydrolysis degradation.

  6. Phosphorous passivation of the SiO 2/4H-SiC interface

    Science.gov (United States)

    Sharma, Y. K.; Ahyi, A. C.; Issacs-Smith, T.; Shen, X.; Pantelides, S. T.; Zhu, X.; Feldman, L. C.; Rozen, J.; Williams, J. R.

    2012-02-01

    We describe experimental and theoretical studies to determine the effects of phosphorous as a passivating agent for the SiO 2/4H-SiC interface. Annealing in a P 2O 5 ambient converts the SiO 2 layer to PSG (phosphosilicate glass) which is known to be a polar material. Higher mobility (approximately twice the value of 30-40 cm 2/V s obtained using nitrogen introduced with an anneal in nitric oxide) and lower threshold voltage are compatible with a lower interface defect density. Trap density, current-voltage and bias-temperature stress (BTS) measurements for MOS capacitors are also discussed. The BTS measurements point to the possibility of an unstable MOSFET threshold voltage caused by PSG polarization charge at the O-S interface. Theoretical considerations suggest that threefold carbon atoms at the interface can be passivated by phosphorous which leads to a lower interface trap density and a higher effective mobility for electrons in the channel. The roles of phosphorous in the passivation of correlated carbon dangling bonds, for SiC counter-doping, for interface band-tail state suppression, for Na-like impurity band formation and for substrate trap passivation are also discussed briefly.

  7. Analysis of piezoelectric boundary acoustic wave in Cu electrode/Y-cut X-propagating LiNbO3 substrate structure partially covered with SiO2.

    Science.gov (United States)

    Wang, Yiliu; Hashimoto, Ken-ya; Omori, Tatsuya; Yamaguchi, Masatsune

    2011-03-01

    This paper describes the existence of piezoelectric boundary acoustic wave (PBAW) propagating in a Cu electrode/Y-cut X-propagating (YX) LiNbO(3) substrate structure partially covered with a SiO2 layer. In the analysis, two types of structures are taken into consideration: one is the so-called slotted structure with SiO2 pillars placed in the grating slots; the other is the so-called topped structure with SiO(2) pillars placed on the top of grating electrodes. The top surface could be fully covered with an additional layer (like epoxy) to bridge the grating slots for encapsulation. Results show that SH-type PBAW begins to propagate in the slotted structure when the SiO(2) thickness exceeds 0.3 wavelength. Strong electromechanical coupling factor K(2) of 21%, and temperature coefficient of velocity (TCV) of -33 ppm/°C are obtained. In the topped structure, on the other hand, the boundary acoustic wave mode is not supported. Instead, the thickness resonance modes in the SiO2 pillar do exist. Comparison of the obtained results with those in the structure fully covered with the SiO(2) layer indicates that, as for the PBAW mode, the slotted structure offers improved K(2) but with worse TCV compared with the fully covered SiO(2) structure.

  8. SiO2-Ag-SiO2 core/shell structure with a high density of Ag nanoparticles for CO oxidation catalysis.

    Science.gov (United States)

    Feng, Xiaoqian; Li, Hongmo; Zhang, Qing; Zhang, Peng; Song, Xuefeng; Liu, Jing; Zhao, Liping; Gao, Lian

    2016-11-11

    SiO2-Ag-SiO2, a sandwiched core/shell structure with a layer of Ag nanoparticles (∼4 nm) encapsulated between a shallow SiO2 surface layer and a SiO2 submicrosphere substrate (∼200 nm), has been synthesized from [Formula: see text] and SiO2 spheres by a facile one-pot hydrothermal method. The composite is proposed to result from the dynamic balance between the [Formula: see text] reduction and the dissolution-redeposition of SiO2 in mild basic media. The synthetic mechanism and the roles of the reaction time, temperature, and the amount of ammonia in the formation of this unique structure are investigated and discussed. The composite structure shows superior catalytic performance in CO oxidation to the control Ag/SiO2 structure prepared by impregnation. Pre-treatment by O2 at 600 °C significantly improves the catalytic performance of the composite structure and preserves the nanocomposite structure well.

  9. Direct fabrication of hybrid nanofibres composed of SiO2-PMMA nanospheres via electrospinning.

    Science.gov (United States)

    Zhang, Ran; Shang, Tinghua; Yang, Guang; Jia, Xiaolong; Cai, Qing; Yang, Xiaoping

    2016-08-01

    The direct fabrication of hybrid nanofibres composed of poly(methyl methacrylate)-grafted SiO2 (SiO2-PMMA) nanospheres via electrospinning was investigated in detail. SiO2-PMMA nanospheres were successfully prepared, with the SiO2 nanospheres synthesized via the Stober method, followed by in situ surface-initiated atom transfer radical polymerization of methyl methacrylate (MMA). Electrospinning was carried out with N,N-dimethylformamide (DMF) as the solvent to disperse SiO2-PMMA nanospheres. The size of the SiO2 core, the molecular weight of the PMMA shell and the concentration of the SiO2-PMMA/DMF solution all had substantial effects on the morphology and structure of electrospun nanofibres composed of SiO2-PMMA nanospheres. When these determining factors were well-tailored, it was found that one-dimensional necklace-like nanofibres were obtained, with SiO2-PMMA nanospheres aligned one by one along the fibre. The successful fabrication of nanofibres by directly electrospinning the SiO2-PMMA/DMF solution verified that polymer-grafted particles possess polymer-like characteristics, which endowed them with the ability to be processed into desirable shapes and structures. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Controlled synthesis of monodisperse SiO(2)--TiO(2) microspheres with a yolk-shell structure as effective photocatalysts.

    Science.gov (United States)

    Yoo, Jung Bo; Yoo, Hyo Jin; Lim, Byung Wook; Lee, Kang Hyuk; Kim, Mi Hyun; Kang, Donghyeon; Hur, Nam Hwi

    2012-12-01

    Monodisperse yolk-shell SiO(2) -TiO(2) microspheres were synthesized using core-shell silica microspheres as templates. In the absence of prior surface modifications, a uniform coating of the TiO(2) layer on the core-shell silica was achieved through a sol-gel route. Mesoporous silica shells between the outer TiO(2) shell and the SiO(2) core were selectively removed by using a weak base, yielding yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @TiO(2) ). Using the same templates, we synthesized Pt-encased microspheres (SiO(2) @Pt-TiO(2) ), in which Pt nanoparticles are embedded between the SiO(2) core and the TiO(2) shell. Selective etching of the silica shells in SiO(2) @Pt-TiO(2) yields Pt-encased yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @TiO(2) ), which contain void spaces suitable for use as nanoreactors. The ys-SiO(2) @TiO(2) catalyst shows enhanced hydrogen production from water under UV-light irradiation presumably as a result of multiple reflections within the void spaces and can be reused without losing their activity. Moreover, this core-shell template method is effective for the synthesis of other yolk-shell microspheres with different metal oxides. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  12. Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm3+ and SiO2:Ho3+, Tm3+ systems

    CSIR Research Space (South Africa)

    Dhlamini, MS

    2012-05-01

    Full Text Available .physb.2011.09.091 Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm 3+ and SiO2:Ho 3+, Tm3+ systems M.S. Dhlamini, G.H. Mhlongo, H.C. Swart, O.M. Ntwaeaborwa, K.T. Hillie ABSTRACT: Cathodoluminescence (CL) properties of Si...O2 powders activated with thulium (Tm3+) and holmium (Ho3+) ions prepared by a sol–gel process were investigated. Different molar concentrations of Tm3+ co-doped with Ho3+ were studied. The 460 nm peak was monitored and the influence of the beam...

  13. Synthesis of TiO 2-doped SiO 2 composite films and its applications

    Indian Academy of Sciences (India)

    The TiO2-doped SiO2 composite films were prepared by two-step sol–gel method and then it was applied in the degradation of methylene red (MR) as photocatalysts. In XRD, FT–IR, and TEM investigations of these TiO2-doped SiO2 composite films, the titanium oxide species are highly dispersed in the SiO2 matrixes and ...

  14. Microstructure and mechanical properties of SiO2-BN ceramic and Invar alloy joints brazed with Ag–Cu–Ti+TiH2+BN composite filler

    OpenAIRE

    Y. Wang; Z.W. Yang; L.X. Zhang; D.P. Wang; J.C. Feng

    2016-01-01

    Ag–Cu–Ti + TiH2+BN composite filler was prepared to braze SiO2-BN ceramic and Invar alloy. The interfacial microstructure, mechanical properties, and residual stress distribution of the brazed joints were investigated. The results show that a wave-like Fe2Ti–Ni3Ti structure appears in the Invar substrate and a thin TiN–TiB2 reaction layer forms adjacent to the SiO2-BN ceramic. The added BN particles react with Ti to form TiN–TiB fine-particles, which is beneficial to refine the microstructure...

  15. Anomalous temperature dependence of photoluminescence in GeO x films and GeO x /SiO2 nano-heterostructures

    Science.gov (United States)

    Marin, D. V.; Volodin, V. A.; Rinnert, H.; Vergnat, M.

    2012-06-01

    The optical properties of GeO x film and GeO x /SiO2 multilayer heterostructures (with thickness of GeO x layers down to 1 nm) were studied with the use of Raman scattering and infrared spectroscopy, ellipsometry and photoluminescence spectroscopy including temperature dependence of photoluminescence. The observed photoluminescence is related to defect (dangling bonds) in GeO x and interface defects for the case of GeO x /SiO2 multilayer heterostructures. From analysis of temperature dependence of photoluminescence intensity, it was found that rate of nonradiative transitions in GeO x film has Berthelot type, but anomalous deviations from Berthelot type temperature dependence were observed in temperature dependences of photoluminescence intensities for GeO x /SiO2 multilayer heterostructures.

  16. Corrosion Behavior of Nickel Alloy (ASTM A 494 M) Reinforced with Fused SiO2 Chilled Metal Matrix Composites (MMCs) for Marine Applications

    Science.gov (United States)

    Hemanth, Joel, Dr.

    2017-08-01

    This paper presents the results obtained and the discussions made from a series of corrosion experiments involving Nickel alloy (ASTM A 494 M) reinforced with fused SiO2, size of the particles dispersed varies from 80-120 µm and amount of addition varies from 3 to 12 wt.% in steps of 3 wt.%. The resulting chilled MMCs are solidified under the influence of copper chill of 25 mm thickness to study the effect of corrosion behavior. Corrosion resistance was found to increase significantly with increase in SiO2 content in chilled MMCs. Nevertheless, even with high SiO2 content corrosion attack ie., pitting was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages, due to the formation of an adherent protective layer on the MMCs developed.

  17. Study of pool boiling of distilled water on SiO2 nanoparticle-coated wire

    Science.gov (United States)

    Pryazhnikov, M. I.; Minakov, A. V.

    2017-11-01

    Experimental results of pool boiling of distilled water on bare nichrome wire and SiO2 nanoparticle-coated wire are presented. Nano-coated wires were obtained by first boiling them in SiO2-water nanofluid. The nanofluid was prepared based on distilled water and SiO2 nanoparticles. The average size of the nanoparticles was 100 nm. The volume concentration of particles was equal 2%. Boiling curves of distilled water were obtained on bare nichrome wire and SiO2 nanoparticles coated wire. The coating increased the critical heat flux during boiling of water.

  18. Synthesis and catalytic performance of SiO2@Ni and hollow Ni microspheres

    Science.gov (United States)

    Liu, Xin; Liu, Yanhua; Shi, Xueting; Yu, Zhengyang; Feng, Libang

    2016-11-01

    Nickel (Ni) catalyst has been widely used in catalytic reducing reactions such as catalytic hydrogenation of organic compounds and catalytic reduction of organic dyes. However, the catalytic efficiency of pure Ni is low. In order to improve the catalytic performance, Ni nanoparticle-loaded microspheres can be developed. In this study, we have prepared Ni nanoparticle-loaded microspheres (SiO2@Ni) and hollow Ni microspheres using two-step method. SiO2@Ni microspheres with raspberry-like morphology and core-shell structure are synthesized successfully using SiO2 microsphere as a template and Ni2+ ions are adsorbed onto SiO2 surfaces via electrostatic interaction and then reduced and deposited on surfaces of SiO2 microspheres. Next, the SiO2 cores are removed by NaOH etching and the hollow Ni microspheres are prepared. The NaOH etching time does no have much influence on the crystal structure, shape, and surface morphology of SiO2@Ni; however, it can change the phase composition evidently. The hollow Ni microspheres are obtained when the NaOH etching time reaches 10 h and above. The as-synthesized SiO2@Ni microspheres exhibit much higher catalytic performance than the hollow Ni microspheres and pure Ni nanoparticles in the catalytic reduction of methylene blue. Meanwhile, the SiO2@Ni catalyst has high stability and hence it can be recycled for reuse.

  19. Luminescent SiO2 particles: porous structure of matrix and stability of quantum dots.

    Science.gov (United States)

    Yang, Ping; Wang, Yingzi; Zhang, Lipeng

    2013-04-01

    Luminescent CdSe/Cd0.5Zn0.5S quantum dots (QDs) with narrow size distribution and high photoluminescence (PL) efficiency were fabricated via a two-step organic synthesis. The QDs were coated with a SiO2 shell by a reverse micelle route. The thickness of SiO2 shell on the QDs was adjusted for investigating the effect of the porous structure of SiO2 matrix on the stability of the QDs. When the shell thickness of SiO2 shells is less than 5 nm, the pores of SiO2 shell are type II (cylindrical pores). In contrast, the pores of SiO2 shell are type IV (one-neck-flask-shaped pores) while the shell thickness is 10 nm. The stability of SiO2-coated QDs was investigated in phosphate-buffered saline (PBS, pH - 7.4) buffer solutions using various phosphate concentrations. The QDs coated with a SiO2 shell with type IV pores revealed high stability compared with those with type II pores. This is ascribed that cylindrical pores (type II) accelerated the transfer of ions in SiO2 shells compared with type IV pores.

  20. Preparation, and Luminescence Properties of SiO2@Sm(MABA-Siphen Core-Shell Structure Nanometer Composite

    Directory of Open Access Journals (Sweden)

    Feng Li-Na

    2018-01-01

    Full Text Available A novel ternary samarium complex was prepared using HOOCC6H4N(CONH(CH23Si- (OCH2CH332 (MABA-Si as first ligand, and phen as second ligand. The corresponding SiO2@Sm(MABA-Siphen core-shell structure nanometer composite was synthesized as well, and the silica spheres was the core, and the ternary samarium complex was the shell layer. The ternary samarium complex has been characterized by element analysis, molar conductivity and IR spectra. The results show that the chemical formula of the complex is Sm(MABA-Si(phen2(ClO43·2H2O. The fluorescent spectra illustrat that the luminescence properties of the samarium complex are superior. The core-shell structure of SiO2@Sm(MABA-Siphen nanometer composite is characterized by SEM, TEM and IR spectra. The SiO2@Sm(MABA-Siphen core-shell structure composites exhibit stronger emission intensity than the ternary samarium complex. The fluorescence lifetime of the complex and core-shell structure composite is measured as well.

  1. Reduction in interface state density of SiO2/Si-IPL/InP by fluorine and sulfur passivations

    Science.gov (United States)

    Yen, Chih-Feng; Lee, Ming-Kwei

    2014-12-01

    The characteristics of a liquid-phase-deposited SiO2 film on InP were investigated. The mixture of H2SiF6 and H3BO3 aqueous precursors was used as the growth solution. SiO2 on InP with (NH4)2S treatment showed good electrical characteristics owing to the reduction of native oxides and sulfur passivation. The electrical characteristics were further improved with an ultrathin Si interface passivation layer (IPL) through reductions in Fermi-level pinning and interface state density. Moreover, during the SiO2 deposition, the HF in the growth solution simultaneously and effectively removed native oxides from the Si-IPL and provided fluorine passivation on it. The Al/SiO2/Si-IPL/(NH4)2S-treated InP MOS capacitor showed superior electrical properties. The leakage current density reached 6.9 × 10-9 and 1.6 × 10-7 A/cm2 at ±2 V. The interface state density reached 3.6 × 1011 cm-2 eV-1 with low frequency dispersion of 12.3%.

  2. Surface texturing effect on crack suppression of SiO2 film formed by F2 laser-induced photochemical surface modification of silicone on polycarbonate under heat resistance test

    Science.gov (United States)

    Nojiri, Hidetoshi; Okoshi, Masayuki

    2017-08-01

    A crack-free SiO2 film was successfully fabricated on silicone-coated polycarbonate (PC) even under heat resistance tests at 100 and 120 °C for 3 h by an additional rubbing treatment with steel wool for use as an automobile window material. The SiO2 film was formed by 157 nm F2 laser-induced photochemical surface modification of silicone on PC. The modified SiO2 layer was also zoned with a mesh mask during the laser irradiation. The zoned SiO2 layer was effective for suppressing cracks during laser irradiation. However, even the zoned layer caused cracks under heat resistance tests. A mechanism of the cracking was analyzed on the basis of observations of sample surfaces by confocal laser microscopy. The rubbed samples showed high heat resistance. By atomic force microscopy, the surface of the modified SiO2 layer was clearly observed to be textured, which reduced the large difference in the thermal expansion coefficient between SiO2 and silicone on PC, thus maintaining optical transparency.

  3. Interface States Densities Effect at SiO2/ Polysilicon and SiO2/ Monosilicon Surfaces on N-polysilicon /Oxide/ P-Monosilicon Capacitance

    Directory of Open Access Journals (Sweden)

    H. Dib

    2014-05-01

    Full Text Available the interface states have a very significant role in the components containing MOS structures. In this paper we study the interface states densities effect at SiO2/ N-polysilicon and SiO2/ P- monosilicon surfaces on metal/polysilicon /oxide/ monosilicon capacitance. The numerical solution of poisson's equation and the determination of the charge variation in the structure induced by application of external bias (Vg allow simulating the capacitance-voltage MSPOS characteristics. The results show that the interface states at SiO2/ polysilicon and SiO2/ monosilicon surfaces translate the CT (V curve about positive voltage and cause the increase of the minimum value of capacitance. The effect of interface states on C (V curves is neglected for the polysilicon doping concentration in order to 1019 cm-3. For this doping level, the C (V curves are identical to the C (V of the monocristalline MOS structure.

  4. Characterization of Fe3O4/SiO2/Gd2O(CO3)2 core/shell/shell nanoparticles as T1 and T2 dual mode MRI contrast agent.

    Science.gov (United States)

    Yang, Meicheng; Gao, Lipeng; Liu, Kai; Luo, Chunhua; Wang, Yiting; Yu, Lei; Peng, Hui; Zhang, Wen

    2015-01-01

    Core/shell/shell structured Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles were successfully synthesized. Their properties as a new type of T1-T2 dual model contrast agent for magnetic resonance imaging were investigated. Due to the introduce of a separating SiO2 layer, the magnetic coupling between Gd2O(CO3)2 and Fe3O4 could be modulated by the thickness of SiO2 layer and produce appropriate T1 and T2 signal. Additionally, the existence of Gd(3+) enhances the transverse relaxivity of Fe3O4 possibly because of the magnetic coupling between Gd(3+) and Fe3O4. The Fe3O4/SiO2/Gd2O(CO3)2 nanoparticles exhibit good biocompatibility, showing great potential for biomedical applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Functionalized sio2 microspheres for extracting oil from produced water

    KAUST Repository

    Mishra, Himanshu

    2017-03-16

    Functionalized material, methods of producing the functionalized material, and use thereof for separation processes such as but not limited to use for separating and extracting a dissolved organic foulant, charged contaminant or oily matter or any combination thereof from water, such as produced water, are provided. In an embodiment, the functionalized material is a mineral material, such as mica, silica (e.g. an SiO2 microsphere) or a metal oxide, and the outer surface of the material is functionalized with an alkyl chain or a perfluorinated species. In an embodiment, the method of making the functionalized material, includes: a) providing a mineral material; b) providing an alkyl chain and/or a perfluorinated species, the alkyl chain or perfluorinated species selected to dissolve organic foulants, charged contaminants or oily matter from water or any combination thereof; c) hydroxylating the material via a concentrated acid solution or a basic solution; and d) grafting the alkyl chain and/or the perfluorinated species onto the material via a silanation reaction.

  6. Synthesis and properties of spherical catalysts TiO2-SiO2/MxOy (M = Co and Cr)

    Science.gov (United States)

    Rogacheva, Anastasiya; Shamsutdinova, Anastasiya; Brichkov, Anton; Larina, Tatyana; Paukshtis, Eugeny; Kozik, Vladimir

    2017-11-01

    Layered spherical materials were obtained, the inner layer of which is represented by oxides of cobalt or chromium, and external oxides of titanium and silicon. D-metals were fixed on the surface of the polymer substrate through sorption from aqueous solutions of the corresponding salts. The outer layer of the oxide titanium-silicon matrix was obtained by the sol-gel method. Aggregative stability of sols was controlled by viscosimetry. The influence of the components on the stability of sol solutions has been established. The time interval for the stability of sols is in the range of 400-1000 h. The laminated structure, material characteristics are studied using 3D-microtomography. The catalytic activity of the obtained TiO2-SiO2/Cr2O3 and TiO2-SiO2/Co3O4 samples was compared to the n-heptane oxidation reaction. The maximum heptane conversion for the TiO2-SiO2/Co3O4 sample is 80 % at a temperature of 600 °C, for the TiO2-SiO2/Cr2O3 sample, the conversion of n-heptane reaches 100 % at 400 °C.

  7. Enhanced germanium precipitation and nanocrystal growth in the Ge+ ion-implanted SiO2 films during high-pressure annealing

    Science.gov (United States)

    Tyschenko, Ida E.; Volodin, Vladimir A.; Cherkov, Alexander G.

    2016-12-01

    The effect of pressure employed during subsequent annealing of the Ge+-ion implanted SiO2 layers on the Ge nanocrystal formation was studied. Ge+ ions implanted in the thin SiO2 layers formed Gauss-like profiles with a Ge peak concentration varied from 1 to 12 at%. Subsequent annealing was carried out at temperature 600-1130 °C under pressures 1-1.2×104 bar. Strong effect of the pressure on the Ge atom distribution was obtained. High-temperature annealing under pressure within the range of 1-103 bar resulted in the out-diffusion of germanium from the SiO2 layer to the Si substrate. As the pressure reached 1.2×104 bar, Ge migration to the Si/SiO2 interface was prevented. At that, the Ge nanocrystal growth within the ion-implanted region of the SiO2 film took place. The nanocrystal size was investigated as a function both of the Ge atom concentration and the annealing temperature. The obtained results show a diffusion-controlled nanocrystal growth mechanism. The high-pressure (1.2×104 bar) diffusion coefficient of germanium in silicon dioxide was estimated as a function of the temperature and expressed by D=1.1×10-10 exp(-1.43 eV/kT) cm2/s.

  8. Design and Synthesis of Hierarchical SiO2@C/TiO2 Hollow Spheres for High-Performance Supercapacitors.

    Science.gov (United States)

    Zhang, Ying; Zhao, Yan; Cao, Shunsheng; Yin, Zhengliang; Cheng, Li; Wu, Limin

    2017-09-06

    TiO2 has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO2@C/TiO2 (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO2 such as cycle stability and SiO2 with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO2 layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g-1 at 1 A g-1 which is higher than those for hollow TiO2 (113 F g-1) and SiO2/TiO2 (252 F g-1) electrodes, and substantially higher than those of all the previously reported TiO2-based electrodes.

  9. Van der Waals epitaxial growth of MoS2 on SiO2/Si by chemical vapor deposition

    KAUST Repository

    Cheng, Yingchun

    2013-01-01

    Recently, single layer MoS2 with a direct band gap of 1.9 eV has been proposed as a candidate for two dimensional nanoelectronic devices. However, the synthetic approach to obtain high-quality MoS2 atomic thin layers is still problematic. Spectroscopic and microscopic results reveal that both single layers and tetrahedral clusters of MoS2 are deposited directly on the SiO2/Si substrate by chemical vapor deposition. The tetrahedral clusters are mixtures of 2H- and 3R-MoS2. By ex situ optical analysis, both the single layers and tetrahedral clusters can be attributed to van der Waals epitaxial growth. Due to the similar layered structures we expect the same growth mechanism for other transition-metal disulfides by chemical vapor deposition. © 2013 The Royal Society of Chemistry.

  10. Water droplet behavior on superhydrophobic SiO2 nanocomposite films during icing/deicing cycles

    NARCIS (Netherlands)

    Lazauskas, A.; Guobiene, A.; Prosycevas, I.; Baltrusaitis, V.; Grigaliunas, V.; Narmontas, P.; Baltrusaitis, Jonas

    2013-01-01

    This work investigates water droplet behavior on superhydrophobic (water contact angle value of 162 ± 1°) SiO2 nanocomposite films subjected to repetitive icing/deicing treatments, changes in SiO2 nanocomposite film surface morphology and their non-wetting characteristics. During the experiment,

  11. Structural verification and optical characterization of SiO2–Au–Cu2O ...

    Indian Academy of Sciences (India)

    Administrator

    attention due to their novel properties in light harvesting and photo manipulating and their application in photonic components (Costi et al 2010). On the other ..... the peak spans from Au absorption peak to SiO2–Au absorption peak. It is worth noticing that when SiO2–Au absorption is measured, the measurement takes ...

  12. Preparation and characterization of core-shell structure of SiO2@Cu antibacterial agent.

    Science.gov (United States)

    Zhang, Nianchun; Gao, Yanhong; Zhang, Hui; Feng, Xuan; Cai, Huaihong; Liu, Yingliang

    2010-12-01

    A simple, low cost and convenient method was used to prepare SiO2@Cu core-shell composite using SiO2 spheres as the core and copper nanoparticles as the shell. A uniform spherical particle of SiO2 was fabricated according to an improved Stöber method. The SiO2 spheres served as a support for the immobilization of copper by reducing Cu2+ in aqueous solution using Fe power. The chemical structures and morphologies of the SiO2 and SiO2@Cu composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). E. coli (Escherichia coli), S. aureus (Staphylococcus aureus) and C. albicans (Candida albicans) were utilized to test its antibacterial effect. Results of XRD, TEM and XPS demonstrated that the copper nanoparticles shell supported on the surface of SiO2 spheres. With regard to the antibacterial effect, E. coli was more easily killed than S. aureus and C. albicans after 24 h incubation, and the pictures of TEM showed obviously morphological changes of the antibacterial activity. The results demonstrated that Cu supported on the surface of SiO2 spheres without aggregation, which was proved to be a good novel antibacterial material. Crown Copyright © 2010. Published by Elsevier B.V. All rights reserved.

  13. The release of TiO2 and SiO2 nanoparticles from nanocomposites

    NARCIS (Netherlands)

    Reijnders, L.

    2009-01-01

    There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO2 or amorphous SiO2 nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO2 and TiO2 nanoparticles can be hazardous. Thus, in the design of

  14. Síntese e caracterização de nanocompósitos Ni: SiO2 processados na forma de filmes finos Synthesis and characterization of Ni: SiO2 nanocomposites processed as thin films

    Directory of Open Access Journals (Sweden)

    Paulo Sérgio Gouveia

    2005-10-01

    Full Text Available We have produced nanocomposite films of Ni:SiO2 by an alternative polymeric precursor route. Films, with thickness of ~ 1000 nm, were characterized by several techniques including X-ray diffraction, scanning electron microscopy, atomic force microscopy, flame absorption atomic spectrometry, and dc magnetization. Results from the microstructural characterizations indicated that metallic Ni-nanoparticles with average diameter of ~ 3 nm are homogeneously distributed in an amorphous SiO2 matrix. Magnetization measurements revealed a blocking temperature T B ~ 7 K for the most diluted sample and the absence of an exchange bias suggesting that Ni nanoparticles are free from an oxide layer.

  15. Seed-mediated photodeposition route to Ag-decorated SiO2@TiO2 microspheres with ideal core-shell structure and enhanced photocatalytic activity

    Science.gov (United States)

    Ma, Jianqi; Guo, Xiaohua; Ge, Hongguang; Tian, Guanghui; Zhang, Qiang

    2018-03-01

    Ag-decorated SiO2@TiO2 microspheres (SiO2@TiO2-Ag) with ideal core-shell structure and enhanced photocatalytic activity were successfully fabricated by combining both coating anatase TiO2 on the surface of SiO2 spheres and subsequent depositing face-centered cubic Ag nanoparticles (NPs) on the coated TiO2 surface via novel sol-gel method and Ag-seed-mediated photodeposition (PD) route, respectively. The morphology, structure, composition and optical properties of the resulting composites were characterized in detail. The results reveal that the monodisperse SiO2 spheres of ∼260 nm were covered uniformly and perfectly by the TiO2 nanoparticle coating layer with the thickness of ca. 55 nm by the novel sol-gel method. Further, homogeneously and highly dispersed Ag NPs with an average size of 8 ± 1.5 nm were strongly anchored onto the TiO2 surface in SiO2@TiO2 core-shell spheres by the modified PD process (Ag-seed-mediated PD route), whereas polydispersed Ag aggregates and detached Ag NPs were irregularly deposited over the TiO2 surface in previous works, which is the inherent problem and has not been effectively solved for depositing noble metal NPs such as Au, Ag, Pt, Pd on TiO2 surface by conventional PD method. The formation mechanism of small and uniformly dispersed Ag NPs with narrow size distribution via the modified PD method is tentatively explained by both nucleation kinetics and growth kinetics. The key reason is that the pre-deposited seeds firmly tethered on SiO2@TiO2 spheres served as nucleation sites and anchoring points for the further nucleation and subsequent growth of Ag via photoreduction of Ag+.

  16. Role of bovine serum albumin and humic acid in the interaction between SiO2 nanoparticles and model cell membranes.

    Science.gov (United States)

    Wei, Xiaoran; Qu, Xiaolei; Ding, Lei; Hu, Jingtian; Jiang, Wei

    2016-12-01

    Silica nanoparticles (SiO2 NPs) can cause health hazard after their release into the environment. Adsorption of natural organic matter and biomolecules on SiO2 NPs alters their surface properties and cytotoxicity. In this study, SiO2 NPs were treated by bovine serum albumin (BSA) and humic acid (HA) to study their effects on the integrity and fluidity of model cell membranes. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes in order to avoid the interference of cellular activities. The microscopic observation revealed that the BSA/HA treated (BSA-/HA-) SiO2 NPs took more time to disrupt membrane than untreated-SiO2 NPs, because BSA/HA adsorption covered the surface SiOH/SiO- groups and weakened the interaction between NPs and phospholipids. The deposition of SiO2 NPs on membrane was monitored by a quartz crystal microbalance with dissipation (QCM-D). Untreated- and HA-SiO2 NPs quickly disrupted the SUV layer on QCM-D sensor; BSA-SiO2 NPs attached on the membranes but only caused slow vesicle disruption. Untreated-, BSA- and HA-SiO2 NPs all caused the gelation of the positively-charged membrane, which was evaluated by the generalized polarity values. HA-SiO2 NPs caused most serious gelation, and BSA-SiO2 NPs caused the least. Our results demonstrate that the protein adsorption on SiO2 NPs decreases the NP-induced membrane damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Stability and lattice dynamics of SiO2 cristobalite

    Science.gov (United States)

    Coh, Sinisa; Vanderbilt, David

    2008-03-01

    Among the phases of SiO2 are alpha and beta cristobalite. Despite early indications that the higher-temperature beta phase might be cubic (Fd3m), it is now accepted that it is in fact tetragonal (I42d), and that the experiments suggesting a cubic structure were averaging spatially or dynamically over tetragonal domains. Recently, Zhang and Scott (J. Phys. Cond.Matt. 19, 275201) suggested that the lower-temperature alpha phase, widely accepted to be tetragonal (P41212), might be an artifact in a similar way. With this motivation we investigate the energy landscape in the vicinity of cristobalite phases using first-principles calculations. We use the ABINIT implementation of density-functional theory in a plane-wave pseudopotential framework. We find that both the P41212 alpha and I42d beta phases are local minima, thus reinforcing that the identification of the alpha phase as belonging to the P41212 structure. We compute the frequencies of phonon modes at high-symmetry k-points in both structures and compare with experiment. We also identify a minimum-energy path connecting the alpha and beta phases through an intermediate orthorhombic phase (P212121), and find a surprisingly low barrier of ˜5,eV per formula unit. We note that a simple rigid-unit mode picture gives a good rough description of these energetics, and we map out the minimum-energy path in the space of rigid unit rotations in a physically insightful way.

  18. Reactive HiPIMS deposition of SiO2/Ta2O5 optical interference filters

    Science.gov (United States)

    Hála, Matěj; Vernhes, Richard; Zabeida, Oleg; Klemberg-Sapieha, Jolanta-Ewa; Martinu, Ludvik

    2014-12-01

    In this contribution, based on the detailed understanding of the processes at the target during reactive high power impulse magnetron sputtering (HiPIMS), we demonstrate the deposition of both low- and high-index films and their implementation in optical interference filters with enhanced performance. We first investigate strategies for stabilizing the arc-free HiPIMS discharges above Si and Ta targets in the presence of oxygen. We show that hysteresis can be suppressed for these two target materials by suitable pulse-management strategies, ensuring good process stability without having to rely on any feedback control. Afterwards, we discuss the room temperature deposition of optically transparent SiO2 and Ta2O5 single layers as well as the fabrication of SiO2/Ta2O5 stacks such as 7 layer Bragg reflectors and 11 layer Fabry-Perot interference filters. We also analyze the optical and mechanical characteristics of these various coatings and compare them with their counterparts obtained by radio-frequency magnetron sputtering (RFMS). Among other findings, we observe that the coatings prepared by HiPIMS present higher refractive index and lower surface roughness values, suggesting a denser microstructure. In addition, the HiPIMS-deposited optical filters exhibit a better optical performance than their counterparts fabricated by RFMS, but it is especially with respect to the mechanical properties such as scratch resistance and low residual stress, that the coatings prepared by HiPIMS present the most dramatic improvements (up to 42% and 72% enhancement, respectively). Finally, we show that the stress values obtained for the HiPIMS-deposited SiO2 and Ta2O5 coatings are lower than for other deposition techniques commonly used in the fabrication of optical interference filters.

  19. Preparation, characterization, and thermal stability of B2O3-SiO2

    Directory of Open Access Journals (Sweden)

    Winda Fitriana

    2017-06-01

    Full Text Available Preparation of B2O3-SiO2 compound by inorganic synthesis was carried out. B2O3-SiO2 was characterized by FT-IR spectro-photometer, analysis of crystallinity by XRD, and test of acidity. B2O3-SiO2 was also tested by thermal stability with temperature range at 300-700 ⁰C. The results showed that the FT-IR spectrum of B2O3-SiO2 has some vibrations of B-O, Si-O-Si, Si-O-B stretching, and Si-O-B bending at 1442.8 cm-1, 779.2 cm-1, 925.8 cm-1, and 648.1 cm-1. The X-Ray diffraction pattern results showed that the analysis of B2O3-SiO2 has high crystallinity with two peaks diffraction identified at 26.6⁰ and 20.9⁰. The thermal stability test of B2O3-SiO2 showed that B2O3-SiO2 has high thermal stability with temperature range at 300-700 ⁰C. The results showed that the acidity analysis of B2O3-SiO2 has potential number 122.71 mV so that indicated B2O3-SiO2 was high acidity. Keywords : boric oxide, silica dioxide, boric silica, B2O3-SiO2

  20. About electrical properties of passivated SiO2/Si structures prepared electro-chemically in HClO4 solutions

    Science.gov (United States)

    Pinčík, Emil; Kobayashi, Hikaru; Rusnák, Jaroslav; Takahashi, Masao; Brunner, Robert

    2013-03-01

    The contribution mainly presents results obtained on passivated SiO2/Si structures prepared in HClO4 solutions. The cleaned Si (1 0 0) wafers were immersed in 1 M HClO4 aqueous solutions and oxidized under positive bias. Results obtained on wet chemically prepared SiO2/Si structures are compared with corresponding ones obtained on MOS formed by thermal oxidation at 850 °C. Resulting oxide thicknesses of the layer prepared by electrochemical and thermal manners are ˜15 nm and ˜7.5 nm, respectively. All of prepared SiO2/Si structures were passivated in HCN or KCN solutions. Low density of interface defect states below the level of ˜1011 eV-1 cm-2 was determined on structures with the SiO2 layer prepared electrochemically, passivated in aqueous HCN solutions, and annealed in vacuum at low temperatures. It has been shown that residual interface electron traps detected by Q-DLTS or C-V method after passivation procedures on electrochemically prepared samples can be partly transformed to mobile and/or immobile charged particles which shift the flat-band voltage of MOS and increase the magnitude of hysteresis of C-V curves.

  1. Synthesis of monodisperse spherical core-shell SiO2-SrAl2Si2O8: Eu2+ phosphors by hydrothermal homogeneous precipitation method.

    Science.gov (United States)

    Li, Yidong; Xiao, Liyuan; Liu, Yingliang; Ai, Pengfei; Chen, Xiaobo

    2010-08-01

    Nanocrystalline SrAl2Si2O8 :Eu2+ phosphor layers were coated on nonaggregated, monodisperse and spherical SiO2 particles using a hydrothermal homogeneous precipitation. After annealing at 1100 °C, core-shell SiO2@SrAl2Si2O8 :Eu2+ particles were obtained. They were characterized with x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. XRD analysis confirmed the formation of SiO2 @SrAl2Si2O8 :Eu2+ particles; it indicated that the SrAl2Si2O8 :Eu2+ shells on SiO2 particles consisted of hexagonal crystallites. The core-shell phosphors obtained are well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the coated layer is approximately 20-40 nm. Under ultraviolet excitation (361 nm), the particles emit blue light at about 440 nm due to the Eu2+ ions in their shells.

  2. Synthesis of monodisperse spherical core-shell SiO2-SrAl2Si2 O8:Eu2+ phosphors by hydrothermal homogeneous precipitation method

    Directory of Open Access Journals (Sweden)

    Yidong Li, Liyuan Xiao, Yingliang Liu, Pengfei Ai and Xiaobo Chen

    2010-01-01

    Full Text Available Nanocrystalline SrAl2Si2 O8 :Eu2+ phosphor layers were coated on nonaggregated, monodisperse and spherical SiO2 particles using a hydrothermal homogeneous precipitation. After annealing at 1100 °C, core-shell SiO2@SrAl2 Si2 O8 :Eu2+ particles were obtained. They were characterized with x-ray diffraction (XRD, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. XRD analysis confirmed the formation of SiO2 @SrAl2 Si2 O8 :Eu2+ particles; it indicated that the SrAl2 Si2 O8 :Eu2+ shells on SiO2 particles consisted of hexagonal crystallites. The core-shell phosphors obtained are well-dispersed submicron spherical particles with a narrow size distribution. The thickness of the coated layer is approximately 20–40 nm. Under ultraviolet excitation (361 nm, the particles emit blue light at about 440 nm due to the Eu2+ ions in their shells.

  3. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Liu Jian

    2009-01-01

    Full Text Available Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  4. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays.

    Science.gov (United States)

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-10-29

    Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  5. Highly luminescent hybrid SiO2-coated CdTe quantum dots: synthesis and properties.

    Science.gov (United States)

    Liu, Ning; Yang, Ping

    2013-01-01

    Novel hybrid SiO2-coated CdTe quantum dots (QDs) were created using CdTe QDs coated with a hybrid SiO2 shell containing Cd(2+) ions and a sulfur source via a sol-gel process in aqueous solution. Aqueous CdTe QDs with tunable emitting color created through a reaction between cadmium chloride and sodium hydrogen telluride was used as cores for the preparation of hybrid SiO2-coated CdTe QDs. In our experiments we found that the surface state of the cores and preparation conditions that affect the formation of the hybrid SiO2 shell also greatly affect photoluminescence of the hybrid SiO2-coated CdTe QDs. The generation of CdS-like clusters in the vicinity of the CdTe QDs, caused the quantum size effect of the QDs to be greatly reduced, which changes photoluminescence properties of the hybrid QDs fundamentally. Namely, the novel hybrid SiO2 shell played an important role in generating a series of specific optical properties. In addition, the novel hybrid SiO2 shell can be created if no CdTe QD is added. In order to gain an insight into the inter structure of the hybrid shell, we characterized the hybrid SiO2-coated CdTe QDs using X-ray diffraction analysis and discuss the formation mechanism of such a hybrid structure. This work is significant because the novel hybrid SiO2-coated CdTe QDs with its excellent properties can be used in many applications, such as biolabeling and optoelectronic devices. Copyright © 2013 John Wiley & Sons, Ltd.

  6. Kinetics of Valeric Acid Ketonization and Ketenization in Catalytic Pyrolysis on Nanosized SiO2 , γ-Al2 O3 , CeO2 /SiO2 , Al2 O3 /SiO2 and TiO2 /SiO2.

    Science.gov (United States)

    Kulyk, Kostiantyn; Palianytsia, Borys; Alexander, John D; Azizova, Liana; Borysenko, Mykola; Kartel, Mykola; Larsson, Mats; Kulik, Tetiana

    2017-07-19

    Valeric acid is an important renewable platform chemical that can be produced efficiently from lignocellulosic biomass. Upgrading of valeric acid by catalytic pyrolysis has the potential to produce value added biofuels and chemicals on an industrial scale. Understanding the different mechanisms involved in the thermal transformations of valeric acid on the surface of nanometer-sized oxides is important for the development of efficient heterogeneously catalyzed pyrolytic conversion techniques. In this work, the thermal decomposition of valeric acid on the surface of nanoscale SiO2 , γ-Al2 O3 , CeO2 /SiO2 , Al2 O3 /SiO2 and TiO2 /SiO2 has been investigated by temperature-programmed desorption mass spectrometry (TPD MS). Fourier transform infrared spectroscopy (FTIR) has also been used to investigate the structure of valeric acid complexes on the oxide surfaces. Two main products of pyrolytic conversion were observed to be formed depending on the nano-catalyst used-dibutylketone and propylketene. Mechanisms of ketene and ketone formation from chemisorbed fragments of valeric acid are proposed and the kinetic parameters of the corresponding reactions were calculated. It was found that the activation energy of ketenization decreases in the order SiO2 >γ-Al2 O3 >TiO2 /SiO2 >Al2 O3 /SiO2 , and the activation energy of ketonization decreases in the order γ-Al2 O3 >CeO2 /SiO2 . Nano-oxide CeO2 /SiO2 was found to selectively catalyze the ketonization reaction. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    OpenAIRE

    Liu, Jian; Wang, Chunrui; Xie, Qingqing; Cai, Junsheng; Zhang, Jing

    2009-01-01

    Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondar...

  8. Defects at the Si(001 )/a -SiO2 interface: Analysis of structures generated with classical force fields and density functional theory

    Science.gov (United States)

    Mehes, E.; Patterson, C. H.

    2017-09-01

    Defects at the Si(001 )/a -SiO2 interface were simulated using a combination of classical force field molecular dynamics and first-principles total-energy minimization techniques. The second generation charge-optimized many-body potential COMB10 was used to generate a -SiO2 which was placed on an ideally terminated Si(001) surface and briefly annealed before being relaxed using density functional theory. Si dimers form at the Si interface on relaxation unless the Si surface has been oxidized. Pb 1 defects form when Si dimers do not bond to O atoms in the a -SiO2 layer. Mismatch in Si atom pairings at the dimerized surface leads to Si2O ≡Si . defects at the interface which may be the structure of a defect denoted S in electron-spin resonance (ESR) studies. Relatively few Pb 0 defects with a magnetic moment form at the Si interface. a -SiO2 generated by heating and quenching a system with periodic boundary conditions is free of E' defects. Afterward, this structure is placed on the Si surface and allowed to relax. The main type of E' defect which forms is a forward oriented Eα' defect. ESR hyperfine parameters for each defect category are calculated and compared to experimental data. Defect densities of states are calculated and compared to experiment.

  9. Synthesis of Hierarchical ZnFe2O4@SiO2@RGO Core-Shell Microspheres for Enhanced Electromagnetic Wave Absorption.

    Science.gov (United States)

    Feng, Jiantao; Hou, Yanhui; Wang, Yechen; Li, Liangchao

    2017-04-26

    Hierarchical structured ZnFe2O4@SiO2@RGO core-shell nanocomposites were prepared via a "coating-coating" route, and its structure, composition and electromagnetic properties were characterized. Compared with the binary composites of ZnFe2O4@SiO2, the hierarchical ZnFe2O4@SiO2@RGO ternary composites exhibited enhanced electromagnetic wave (EMW) absorption properties in terms of the effective bandwidth and minimum reflection loss (RL). Furthermore, EMW absorption properties of the prepared samples can be tuned by changing RGO content and thickness of SiO2 layer to reach the best impedance match. The minimum RL of the sample with a thickness of 2.8 mm can reach -43.9 dB at 13.9 GHz, and its effective bandwidth (RL ≤ -10 dB) was up to 6 GHz. Hence, the obtained products can be a new candidate for lightweight EMW absorbing materials.

  10. Novel Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites: High-efficiency and magnetic recyclable catalysts for organic dye degradation

    Science.gov (United States)

    Li, Chao; Sun, Jun-Jie; Chen, Duo; Han, Guang-Bing; Yu, Shu-Yun; Kang, Shi-Shou; Mei, Liang-Mo

    2016-08-01

    A facile step-by-step approach is developed for synthesizing the high-efficiency and magnetic recyclable Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites. This method involves coating Fe2O3 nanorods with a uniform silica layer, reduction in 10% H2/Ar atmosphere to transform the Fe2O3 into magnetic Fe3O4, and finally depositing Ag@Ni core-shell nanoparticles on the L-lysine modified surface of Fe3O4@SiO2 nanorods. The fabricated nanocomposites are further characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscope, Fourier transform infrared spectroscopy, and inductively coupled plasma mass spectroscopy. The Fe3O4@SiO2@Ag@Ni trepang-like nanocomposites exhibit remarkably higher catalytic efficiency than monometallic Fe3O4@SiO2@Ag nanocomposites toward the degradation of Rhodamine B (RhB) at room temperature, and maintain superior catalytic activity even after six cycles. In addition, these samples could be easily separated from the catalytic system by an external magnet and reused, which shows great potential applications in treating waste water. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11174183), the 111 Project (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

  11. Synthesis and Electrochemical Properties of Carbon Nanofibers and SiO2/Carbon Nanofiber Composite on Ni-Cu/C-Fiber Textiles.

    Science.gov (United States)

    Nam, Ki-Mok; Park, Heai-Ku; Lee, Chang-Seop

    2015-11-01

    In this study, carbon nanofibers (CNFs) were grown by chemical vapor deposition on C-fiber textiles that had Ni and Cu catalyst deposited via electrophoretic deposition. Before the CNFs were coated with silica layer via hydrolysis of TEOS (Tetraethyl orthosilicate), the carbon nanofibers were oxidized by nitric acid. Due to oxidation, the hydroxyl group was created on the carbon nanofibers and this was used as an activation site for the SiO2. The physicochemical properties of the grown carbon nanofibers were investigated with Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), X-ray Diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The structures of SiO2-coated carbon nanofibers were characterized by XPS and TEM. The electrochemical properties and the capacitance of the materials were investigated by galvanostatic charge-discharge and cyclic voltammetry. Different types of carbon nanofibers were grown upon the deposition utilizing catalysts, with the SiO2 uniformly coated on the surface of carbon nanofibers. When used as an anode material for the Li secondary battery, the SiO2/CNFs composite had a lower capacity maintenance and a greater discharge capacity as compared to the carbon nanofibers.

  12. Advanced Cu chemical displacement technique for SiO2-based electrochemical metallization ReRAM application.

    Science.gov (United States)

    Chin, Fun-Tat; Lin, Yu-Hsien; You, Hsin-Chiang; Yang, Wen-Luh; Lin, Li-Min; Hsiao, Yu-Ping; Ko, Chum-Min; Chao, Tien-Sheng

    2014-01-01

    This study investigates an advanced copper (Cu) chemical displacement technique (CDT) with varying the chemical displacement time for fabricating Cu/SiO2-stacked resistive random-access memory (ReRAM). Compared with other Cu deposition methods, this CDT easily controls the interface of the Cu-insulator, the switching layer thickness, and the immunity of the Cu etching process, assisting the 1-transistor-1-ReRAM (1T-1R) structure and system-on-chip integration. The modulated shape of the Cu-SiO2 interface and the thickness of the SiO2 layer obtained by CDT-based Cu deposition on SiO2 were confirmed by scanning electron microscopy and atomic force microscopy. The CDT-fabricated Cu/SiO2-stacked ReRAM exhibited lower operation voltages and more stable data retention characteristics than the control Cu/SiO2-stacked sample. As the Cu CDT processing time increased, the forming and set voltages of the CDT-fabricated Cu/SiO2-stacked ReRAM decreased. Conversely, decreasing the processing time reduced the on-state current and reset voltage while increasing the endurance switching cycle time. Therefore, the switching characteristics were easily modulated by Cu CDT, yielding a high performance electrochemical metallization (ECM)-type ReRAM.

  13. Synthesis of SiO2 nanopowders containing quartz and cristobalite phases from silica sands

    Directory of Open Access Journals (Sweden)

    Munasir

    2015-03-01

    Full Text Available In this study, extraction and synthesis of SiO2 nanoparticles from silica sands have been conducted by means of two different methods, i.e. dry method (method 1 and hydrothermal process (method 2. The basic difference between the two methods is in the extraction step. The two methods were compared in terms of being more efficient, economical, and superior in obtaining SiO2 nanoparticles. The SiO2 nanoparticles were characterized in terms of phase purity, crystallinity, Si-O functional bonding as well as particles size and morphology. The most interesting fact in this study was the formation of both quartz and cristobalite phases within all prepared SiO2 nanoparticles.

  14. Enhanced luminous transmittance of thermochromic VO2 thin film patterned by SiO2 nanospheres

    Science.gov (United States)

    Zhou, Liwei; Liang, Jiran; Hu, Ming; Li, Peng; Song, Xiaolong; Zhao, Yirui; Qiang, Xiaoyong

    2017-05-01

    In this study, an ordered SiO2 nanosphere array coated with vanadium dioxide (VO2) has been fabricated to enhance transmittance with the potential application as an energy-efficient coating in the field of smart windows. SiO2 arrays were formed using the methods of self-assembly, and VO2 thin films were prepared by rapid thermal annealing (RTA) of sputtered vanadium films. VO2@SiO2 arrays were characterized by scanning electron microscopy, X-ray diffraction, a four-point probe, and UV-vis-NIR spectrophotometry. Compared with the planar films, the films deposited on 300 nm diameter SiO2 nanospheres can offer approximately 18% enhancement of luminous transmission (Tlum) because the diameter is smaller than the given wavelength and the protuberance of the surface array behaves as a gradation of refractive index producing antireflection. The solar regulation efficiency was not much deteriorated.

  15. Facile synthesis of microporous SiO2/triangular Ag composite nanostructures for photocatalysis

    Science.gov (United States)

    Sirohi, Sidhharth; Singh, Anandpreet; Dagar, Chakit; Saini, Gajender; Pani, Balaram; Nain, Ratyakshi

    2017-09-01

    In this article, we present a novel fabrication of microporous SiO2/triangular Ag nanoparticles for dye (methylene blue) adsorption and plasmon-mediated degradation. Microporous SiO2 nanoparticles with pore size amine groups. Amine-functionalized microporous silica was used for adsorption of triangular silver (Ag) nanoparticles. The synthesized microporous SiO2 nanostructures were investigated for adsorption of different dyes including methylene blue, congo red, direct green 26 and curcumin crystalline. Amine-functionalized microporous SiO2/triangular Ag nanostructures were used for plasmon-mediated photocatalysis of methylene blue. The experimental results revealed that the large surface area of microporous silica facilitated adsorption of dye. Triangular Ag nanoparticles, due to their better charge carrier generation and enhanced surface plasmon resonance, further enhanced the photocatalysis performance.

  16. Facile synthesis of microporous SiO2/triangular Ag composite nanostructures for photocatalysis

    Science.gov (United States)

    Sirohi, Sidhharth; Singh, Anandpreet; Dagar, Chakit; Saini, Gajender; Pani, Balaram; Nain, Ratyakshi

    2017-11-01

    In this article, we present a novel fabrication of microporous SiO2/triangular Ag nanoparticles for dye (methylene blue) adsorption and plasmon-mediated degradation. Microporous SiO2 nanoparticles with pore size silica was used for adsorption of triangular silver (Ag) nanoparticles. The synthesized microporous SiO2 nanostructures were investigated for adsorption of different dyes including methylene blue, congo red, direct green 26 and curcumin crystalline. Amine-functionalized microporous SiO2/triangular Ag nanostructures were used for plasmon-mediated photocatalysis of methylene blue. The experimental results revealed that the large surface area of microporous silica facilitated adsorption of dye. Triangular Ag nanoparticles, due to their better charge carrier generation and enhanced surface plasmon resonance, further enhanced the photocatalysis performance.

  17. Analysis of SiO2 nanoparticles binding proteins in rat blood and brain homogenate.

    Science.gov (United States)

    Shim, Kyu Hwan; Hulme, John; Maeng, Eun Ho; Kim, Meyoung-Kon; An, Seong Soo A

    2014-01-01

    A multitude of nanoparticles, such as titanium oxide (TiO2), zinc oxide, aluminum oxide, gold oxide, silver oxide, iron oxide, and silica oxide, are found in many chemical, cosmetic, pharmaceutical, and electronic products. Recently, SiO2 nanoparticles were shown to have an inert toxicity profile and no association with an irreversible toxicological change in animal models. Hence, exposure to SiO2 nanoparticles is on the increase. SiO2 nanoparticles are routinely used in numerous materials, from strengthening filler for concrete and other construction composites, to nontoxic platforms for biomedical application, such as drug delivery and theragnostics. On the other hand, recent in vitro experiments indicated that SiO2 nanoparticles were cytotoxic. Therefore, we investigated these nanoparticles to identify potentially toxic pathways by analyzing the adsorbed protein corona on the surface of SiO2 nanoparticles in the blood and brain of the rat. Four types of SiO2 nanoparticles were chosen for investigation, and the protein corona of each type was analyzed using liquid chromatography-tandem mass spectrometry technology. In total, 115 and 48 plasma proteins from the rat were identified as being bound to negatively charged 20 nm and 100 nm SiO2 nanoparticles, respectively, and 50 and 36 proteins were found for 20 nm and 100 nm arginine-coated SiO2 nanoparticles, respectively. Higher numbers of proteins were adsorbed onto the 20 nm sized SiO2 nanoparticles than onto the 100 nm sized nanoparticles regardless of charge. When proteins were compared between the two charges, higher numbers of proteins were found for arginine-coated positively charged SiO2 nanoparticles than for the negatively charged nanoparticles. The proteins identified as bound in the corona from SiO2 nanoparticles were further analyzed with ClueGO, a Cytoscape plugin used in protein ontology and for identifying biological interaction pathways. Proteins bound on the surface of nanoparticles may affect functional and conformational properties and distributions in complicated biological processes.

  18. Electrical behavior of MIS devices based on Si nanoclusters embedded in SiOxNy and SiO2 films

    Directory of Open Access Journals (Sweden)

    Debieu Olivier

    2011-01-01

    Full Text Available Abstract We examined and compared the electrical properties of silica (SiO2 and silicon oxynitride (SiOxNy layers embedding silicon nanoclusters (Sinc integrated in metal-insulator-semiconductor (MIS devices. The technique used for the deposition of such layers is the reactive magnetron sputtering of a pure SiO2 target under a mixture of hydrogen/argon plasma in which nitrogen is incorporated in the case of SiOxNy layer. Al/SiOxNy-Sinc/p-Si and Al/SiO2-Sinc/p-Si devices were fabricated and electrically characterized. Results showed a high rectification ratio (>104 for the SiOxNy-based device and a resistive behavior when nitrogen was not incorporating (SiO2-based device. For rectifier devices, the ideality factor depends on the SiOxNy layer thickness. The conduction mechanisms of both MIS diode structures were studied by analyzing thermal and bias dependences of the carriers transport in relation with the nitrogen content.

  19. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 spheres have been prepared by an in situ reaction using different molar ratios of Fe3+/Fe2+ (50–200%). It has been observed that morphology of the assembly and properties of these hybrid materials composed of SiO2 as core and Fe3O4 ...

  20. SiO2–CaO–P2O5

    Indian Academy of Sciences (India)

    Abstract. Bioactive glasses in the systems SiO2–CaO–P2O5–MgO (BGZn0) and SiO2–CaO–P2O5–MgO–ZnO. (BGZn5), were prepared by sol–gel method and then characterized. Surface reactivity was studied in simulated body fluid (SBF) to determine the effect of zinc (Zn) addition as a trace element. The effect of Zn ...

  1. Nano-Ticl 4 .SiO 2 : a Versatile and Efficient Catalyst for Synthesis of ...

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 has been found to be an extremely efficient catalyst for the preparation of 3,4-dihydropyrimidinones/thiones via three-component reactions of an aldehyde, β-ketoester or β-diketone and urea or thiourea under mild conditions. Nano-TiCl4.SiO2 as a solid Lewis acid has been synthesized by reaction of ...

  2. Tetrazoles in the Presence of Nano-TiCl 4 .SiO 2

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 was found to be an extremely efficient catalyst for the preparation of 5-substituted 1H-tetrazole derivatives. Nano-TiCl4.SiO2 is a solid Lewis-acid was synthesized by the reaction of nano-SiO2 and TiCl4. The structure characterization of this acid was achieved with X-ray diffraction, thermogravimetric ...

  3. Thermal conduction across a boron nitride and SiO2 interface

    Science.gov (United States)

    Li, Xinxia; Yan, Yaping; Dong, Lan; Guo, Jie; Aiyiti, Adili; Xu, Xiangfan; Li, Baowen

    2017-03-01

    The need for efficient heat removal and superior thermal conduction in nano/micro devices has triggered tremendous studies in low-dimensional materials with high thermal conductivity. Hexagonal boron nitride (h-BN) is believed to be one of the candidates for thermal management and heat dissipation due to its novel physical properties, i.e. as a thermal conductor and electrical insulator. Here we report the interfacial thermal resistance between few-layer h-BN and its SiO2 substrate using the differential 3ω method. The measured interfacial thermal resistance is around ~1.6  ×  10-8 m2K W-1 for monolayer h-BN and ~3.4  ×  10-8 m2K W-1 for 12.8 nm-thick h-BN in metal/h-BN/SiO2 interfaces. Our results suggest that the voids and gaps between the substrate and thick h-BN flakes limit the interfacial thermal conduction. This work provides a deeper understanding of utilizing h-BN flakes as a lateral heat spreader in electronic and optoelectronic nano/micro devices with further miniaturization and integration.

  4. Dewetting induced Au-Ge composite nanodot evolution in SiO2

    Science.gov (United States)

    Datta, D. P.; Chettah, A.; Siva, V.; Kanjilal, D.; Sahoo, P. K.

    2018-01-01

    A composite nanostructure comprising of Au and Ge gradually evolves on SiO2 surface when a bilayer of Au and Ge is irradiated by medium keV Xe-ion beam. The morphology progresses through different stages from nucleating patches to extended islands and finally a Au-Ge composite nanodot array develops on the insulator surface. While ion energy and fluence are found to determine dimensions of the nanostructures, existence of a characteristic lateral length scale is also detected at every stage of evolution. Through morphological and compositional analysis, the observed evolution is understood as an effect of ion beam induced dewetting of Au top layer. Numerical estimation based on the unified thermal spike model using the present experimental condition demonstrates formation of molten zones around the ion track due to nuclear and electronic energy deposition in the target. Dewetting results from mass flow onto the surface driven by local melting along the ion track and combines with sputter erosion of the bilayer film to lead to composite nanodot evolution. The generality of the ion induced processes provides possible route towards metal-semiconductor hybrid nanostructure synthesis on insulator surface.

  5. Synthesis and Characterization of Microwave Absorber SiO2 by Sol-Gel Methode

    Science.gov (United States)

    Wardiyati, S.; Adi, W. A.; Deswita

    2017-05-01

    In recent years, information technology is growing rapidly, such as communication devices. However, there are still many shortcomings, for example, confidential information leaks caused by the leakage of electromagnetic waves used. A coating of electromagnetic materials or formation composite of electromagnetic material with other materials such as SiO2 is needed to overcome these problems. For such needs, it is necessary to study the manufacture of SiO2 which is simple, cheap, and effective. In this research, manufacture of SiO2 by sol-gel method used a solution of sodium silicate (Na2SiO3) as precursors and H2SO4 as a catalyst. The parameters tested in this experiment is the effect of sintering temperature on the properties of the resulting SiO2. The purpose of this study was to obtain an amorphous SiO2 powder, which is in nano-sized and has a high surface area. The characterization of prepared samples were performed by using an X-ray Diffraction (XRD), Fourier Transmission Infra Red (FTIR), Scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), Transmission Electron Microscopy (TEM), and Surface Area Analyzer (SAA). Based on the experimental results, the SiO2 amorphous structure was obtained with a particle size of 15-20 nm, the surface area of 298 m2/g, and sintering temperature of 100 °C.

  6. Study of SiO2/4H-SiC interface nitridation by post-oxidation annealing in pure nitrogen gas

    Directory of Open Access Journals (Sweden)

    Atthawut Chanthaphan

    2015-09-01

    Full Text Available An alternative and effective method to perform interface nitridation for 4H-SiC metal-oxide-semiconductor (MOS devices was developed. We found that the high-temperature post-oxidation annealing (POA in N2 ambient was beneficial to incorporate a sufficient amount of nitrogen atoms directly into thermal SiO2/SiC interfaces. Although N2-POA was ineffective for samples with thick thermal oxide layers, interface nitridation using N2-POA was achieved under certain conditions, i.e., thin SiO2 layers (1350°C. Electrical characterizations of SiC-MOS capacitors treated with high-temperature N2-POA revealed the same evidence of slow trap passivation and fast trap generation that occurred in NO-treated devices fabricated with the optimized nitridation conditions.

  7. Photocatalytic hydrogen production using visible-light-responsive Ta 3N5 photocatalyst supported on monodisperse spherical SiO2 particulates

    KAUST Repository

    Liu, Xiaoming

    2014-01-01

    Fine nanoparticles of Ta3N5 (10-20 nm) were synthesized on the surfaces of SiO2 spheres with a diameter of ∼550 nm. A sol-gel method was used to modify the surface of SiO2 with Ta2O5 from TaCl5 dissolved in ethanol in the presence of citric acid and polyethylene glycol. The resulting oxide composites were treated in an NH3 flow at 1123 K to form core-shell structured Ta3N5/SiO2 sub-microspheres. The obtained samples were characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDX), transmission electron microscopy (TEM), and photocatalytic activity measurements for H 2 evolution from an aqueous methanol solution. The XRD results demonstrate the expected sequential formation of Ta2O5 layers, followed by Ta3N5 after nitridation on the Ta 2O5/SiO2 composite. SEM and TEM observations indicate that the obtained Ta3N5/SiO2 sub-microspheres have a uniform size distribution with high crystallinity and an obvious core-shell structure. The presence of support maintained the intrinsic photocatalytic activity of Ta3N5 nanoparticles, but it did drastically improve the dispersion of the photocatalysts in the solution. This study proposes the use of an inert support in photocatalytic reactors to improve ease of handling the powder photocatalyst for gas-phase photocatalysis and the suspension of the solution, controlling nature of light harvesting and degree of scattering of the photoreactor. © 2013 Elsevier Ltd. All rights reserved.

  8. Optical characterization of surface plasmon resonance of Pt nanoparticles in TiO2-SiO2 nanocomposite films

    Science.gov (United States)

    Kang, T. D.; Yoon, Jong-Gul

    2017-10-01

    The surface plasmon resonance (SPR) of Pt nanoparticles (NPs) in TiO2-SiO2 nanocomposite films, in which Pt NPs of about 5 nm are incorporated, is investigated by using spectroscopic ellipsometry. After obtaining the dielectric functions of Pt NPs from the Pt-SiO2 nanocomposite film, Pt-TiO2-SiO2 nanocomposite films are analyzed by applying a homogenous single layer model with an effective medium approximation. The effects of Pt NPs on the optical properties of the nanocomposite films are clearly revealed in the imaginary part of the dielectric functions, showing an increase in broadband absorption near the band gap of the films with the increasing volume fraction of Pt NPs in the films. Particularly, the maximum of extinction cross-section of Pt NPs in the films coincides with the broadband absorption, indicating that the localized SPR of Pt NPs is responsible for the enhanced light absorption at the visible-light wavelengths. This work emphasizes that, although SPR absorption of Pt NPs is not so distinctive in the visible-light wavelengths, proper tuning of the dielectric environment as well as the volume fraction of Pt NPs can enhance the photoactivity of the nanocomposite films.

  9. SiO2 and TiO2 nanoparticles synergistically trigger macrophage inflammatory responses.

    Science.gov (United States)

    Tsugita, Misato; Morimoto, Nobuyuki; Nakayama, Masafumi

    2017-04-11

    Silicon dioxide (SiO2) nanoparticles (NPs) and titanium dioxide (TiO2) NPs are the most widely used inorganic nanomaterials. Although the individual toxicities of SiO2 and TiO2 NPs have been extensively studied, the combined toxicity of these NPs is much less understood. In this study, we observed unexpected and drastic activation of the caspase-1 inflammasome and production of IL-1β in mouse bone marrow-derived macrophages stimulated simultaneously with SiO2 and TiO2 NPs at concentrations at which these NPs individually do not cause macrophage activation. Consistent with this, marked lung inflammation was observed in mice treated intratracheally with both SiO2 and TiO2 NPs. In macrophages, SiO2 NPs localized in lysosomes and TiO2 NPs did not; while only TiO2 NPs produced ROS, suggesting that these NPs induce distinct cellular damage leading to caspase-1 inflammasome activation. Intriguingly, dynamic light scattering measurements revealed that, although individual SiO2 and TiO2 NPs immediately aggregated to be micrometer size, the mixture of these NPs formed a stable and relatively monodisperse complex with a size of ~250 nm in the presence of divalent cations. Taken together, these results suggest that SiO2 and TiO2 NPs synergistically induce macrophage inflammatory responses and subsequent lung inflammation. Thus, we propose that it is important to assess the synergistic toxicity of various combinations of nanomaterials.

  10. Development of nano SiO2 incorporated nano zinc phosphate coatings on mild steel

    Science.gov (United States)

    Tamilselvi, M.; Kamaraj, P.; Arthanareeswari, M.; Devikala, S.; Selvi, J. Arockia

    2015-03-01

    This paper reports the development of nano SiO2 incorporated nano zinc phosphate coatings on mild steel at low temperature for achieving better corrosion protection. A new formulation of phosphating bath at low temperature with nano SiO2 was attempted to explore the possibilities of development of nano zinc phosphate coatings on mild steel with improved corrosion resistance. The coatings developed were studied by Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Electrochemical measurements. Significant variation in the coating weight, morphology and corrosion resistance was observed as nano SiO2 concentrations varied from 0.5-4 g/L. The results showed that, the nano SiO2 in the phosphating solution changed the initial potential of the interface between mild steel substrate and phosphating solution and reduce the activation energy of the phosphating process, increase the nucleation sites and yielded zinc phosphate coatings of higher coating weight, greater surface coverage and enhanced corrosion resistance. Better corrosion resistance was observed for coatings derived from phosphating bath containing 1.5 g/L nano SiO2. The new formulation reported in the present study was free from Ni or Mn salts and had very low concentration of sodium nitrite (0.4 g/L) as accelerator.

  11. Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

    Science.gov (United States)

    Tseng, Kuang-Hung; Chen, Kuan-Lung

    2012-08-01

    This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

  12. Integrated nanophotonic hubs based on ZnO-Tb(OH)3/SiO2 nanocomposites

    Science.gov (United States)

    Lin, Hsia Yu; Cheng, Chung Liang; Lin, Yu Shen; Hung, Yann; Mou, Chung Yuan; Chen, Yang Fang

    2011-08-01

    Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH)3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH)3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH)3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH)3/SiO2 as well as SnO2-Tb(OH)3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  13. Integrated nanophotonic hubs based on ZnO-Tb(OH3/SiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Lin Yu

    2011-01-01

    Full Text Available Abstract Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH3/SiO2 as well as SnO2-Tb(OH3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  14. Structure and growth of dotriacontane films on SiO_2 and Ag(111) surfaces: synchrotron X-ray scattering and molecular dynamics simulations

    DEFF Research Database (Denmark)

    Mo, H.; Trogisch, S.; Taub, H.

    2004-01-01

    We report synchrotron X-ray scattering experiments and molecular dynamics simulations of the structure and growth mode of dotriacontane (n-C32H(66) or C32) films adsorbed on Ag(111) and SiO2-coated Si(100) substrates. On the SiO2 surface, the X-ray measurements confirm a structural model...... oriented bulk particles nucleate consistent with a Stranski-Krastanov growth mode. On the Ag(l 11) surface, we again observe one or two layers of the "parallel" film but no evidence of the perpendicular monolayer before nucleation of the preferentially oriented bulk particles. We compare the experimentally...... observed structures with molecular dynamics simulations of a multilayer film of the homologous C24 molecule. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  15. Graphene/SiO2 nanocomposites: The enhancement of photocatalytic and biomedical activity of SiO2 nanoparticles by graphene

    Science.gov (United States)

    Arshad, Aqsa; Iqbal, Javed; Mansoor, Qaisar; Ahmed, Ishaq

    2017-06-01

    The exceptional conducting nature of graphene makes it a viable candidate for enhancing the effectiveness of photocatalytic and biomedical nanomaterials. Herein, the immobilization of monodispersed silicon dioxide (SiO2) nanoparticles on multiple graphene layers is demonstrated for intercalation of graphene nanoplatelets. Interestingly, the addition of graphene nanoplatelets with SiO2 nanoparticles enhances the photocatalytic efficiency from 46% to 99%. For biomedical applications, it is found that 75% of Gram positive and 50% of Gram negative bacteria have been killed; hence, bacterial proliferation is significantly restricted. Further, the cytotoxicity study reveals that the synthesised nanocomposites are non-toxic for both normal (human corneal epithelial cells) and cancerous (MCF-7, HEp-2) cell lines which signify their potential as carriers for drug delivery. The prepared nanocomposites with a controlled amount of carbon in the form of graphene can be employed for photocatalysis based waste water remediation, biomedicine, and nanodrug delivery.

  16. Preparation and Characterization of ZnO Nanoparticles Supported on Amorphous SiO2

    Directory of Open Access Journals (Sweden)

    Ying Chen

    2017-08-01

    Full Text Available In order to reduce the primary particle size of zinc oxide (ZnO and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2 by the hydrogen bond association between hydroxyl groups in the hydrothermal process. After calcining the precursors, dehydration condensation among hydroxyl groups occurred and ZnO nanoparticles supported on amorphous SiO2 (ZnO–SiO2 were prepared. Furthermore, the SEM and TEM observations showed that ZnO nanoparticles with a particle size of 3–8 nm were uniformly and dispersedly loaded on the surface of amorphous SiO2. Compared with pure ZnO, ZnO–SiO2 showed a much better antibacterial performance in the minimum inhibitory concentration (MIC test and the antibacterial properties of the paint adding ZnO–SiO2 composite.

  17. Ion assisted deposition of SiO2 film from silicon

    Science.gov (United States)

    Pham, Tuan. H.; Dang, Cu. X.

    2005-09-01

    Silicon dioxide, SiO2, is one of the preferred low index materials for optical thin film technology. It is often deposited by electron beam evaporation source with less porosity and scattering, relatively durable and can have a good laser damage threshold. Beside these advantages the deposition of critical optical thin film stacks with silicon dioxide from an E-gun was severely limited by the stability of the evaporation pattern or angular distribution of the material. The even surface of SiO2 granules in crucible will tend to develop into groove and become deeper with the evaporation process. As the results, angular distribution of the evaporation vapor changes in non-predicted manner. This report presents our experiments to apply Ion Assisted Deposition process to evaporate silicon in a molten liquid form. By choosing appropriate process parameters we can get SiO2 film with good and stable property.

  18. Preparation and Characterization of ZnO Nanoparticles Supported on Amorphous SiO2

    Science.gov (United States)

    Chen, Ying; Ding, Hao; Sun, Sijia

    2017-01-01

    In order to reduce the primary particle size of zinc oxide (ZnO) and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2) by the hydrogen bond association between hydroxyl groups in the hydrothermal process. After calcining the precursors, dehydration condensation among hydroxyl groups occurred and ZnO nanoparticles supported on amorphous SiO2 (ZnO–SiO2) were prepared. Furthermore, the SEM and TEM observations showed that ZnO nanoparticles with a particle size of 3–8 nm were uniformly and dispersedly loaded on the surface of amorphous SiO2. Compared with pure ZnO, ZnO–SiO2 showed a much better antibacterial performance in the minimum inhibitory concentration (MIC) test and the antibacterial properties of the paint adding ZnO–SiO2 composite. PMID:28796157

  19. SiO2 Glass Density to Lower-Mantle Pressures

    DEFF Research Database (Denmark)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste

    2017-01-01

    The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past...... and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range...... for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60...

  20. Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

    Directory of Open Access Journals (Sweden)

    M. Kamran

    2017-02-01

    Full Text Available Effect of silica (SiO2 coating concentration on structural and magnetic properties of multiferroic cobalt chromite (CoCr2O4 nanoparticles have been studied. The nanoparticles with average crystallite size in the range 19 to 28 nm were synthesised by sol-gel method. X-ray diffraction (XRD analysis has verified the composition of single-phase cubic normal spinel structure of CoCr2O4 nanoparticles. The average crystallite size and cell parameter decreased with increasing SiO2 concentration. TEM image revealed that the shape of nanoparticles was non-spherical. Zero field cooled/field cooled (ZFC/FC curves revealed that nanoparticles underwent a transition from paramagnetic (PM state to collinear short-range ferrimagnetic (FiM state, and this PM–FiM transition temperature decreased from 101 to 95 K with increasing SiO2 concentration or decreasing crystallite size. A conical spin state at Ts = 27 K was also observed for all the samples which decreased with decreasing average crystallite size. Low temperature lock-in transition was also observed in these nanoparticles at 12 K for uncoated nanoparticles which slightly shifted towards low temperature with decreasing average crystallite size. Saturation magnetization (Ms showed decreasing trend with increasing SiO2 concentration, which was due to decrease in average crystallite size of nanoparticles and enhanced surface disorder in smaller nanoparticles. The temperature dependent AC-susceptibility also showed the decrease in the transition temperature (Tc, broadening of the Tc peak and decrease in magnetization with increasing SiO2 concentration or decreasing average crystallite size. In summary, the concentration of SiO2 has significantly affected the structural and magnetic properties of CoCr2O4 nanoparticles.

  1. Magnetic studies of SiO2 coated CoFe2O4 nanoparticles

    Science.gov (United States)

    Limaye, Mukta V.; Singh, Shashi B.; Das, Raja; Poddar, Pankaj; Abyaneh, Majid K.; Kulkarni, Sulabha K.

    2017-11-01

    Oleic acid capped CoFe2O4 nanoparticles which exhibit a high coercivity of ∼9.47 kOe at room temperature were coated with a robust coating of SiO2. We have used chemical synthesis method to obtain SiO2 coated CoFe2O4 nanoparticles with different weight percentages of CoFe2O4 in SiO2 (1.5, 3.1 and 4.8 wt.%). The morphological investigation of the coated nanoparticles by transmission electron microscopy shows that the particles are spherical with average size ∼160 nm. Infrared spectroscopy reveals that oleic acid capping on the surface of CoFe2O4 nanoparticles is retained after silica coating process. The complete coating of SiO2 on CoFe2O4 nanoparticles is confirmed by X-ray photoelectron spectroscopy as there is no signature of cobalt or iron ions on the surface. Magnetic measurements show that coercivity of SiO2 coated CoFe2O4 particles remains more or less unaffected as in CoFe2O4 nanoparticles at room temperature. In addition, the temperature dependent magnetic measurements show that at 5 K the CoFe2O4 and SiO2 coated 1.5 wt.% CoFe2O4 samples exhibit a very high value of coercivity (∼20 kOe) which is more than twice as compared to room temperature coercivity value (∼9.47 kOe). We conclude that silica coating in our study does not significantly affect the coercivity of CoFe2O4 nanoparticles.

  2. SiO2 Glass Density to Lower-Mantle Pressures

    Science.gov (United States)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste; Collings, Ines E.; Jennings, Eleanor S.; Blanchard, Ingrid; Kantor, Innokenty; Kurnosov, Alexander; Cotte, Marine; Dane, Thomas; Burghammer, Manfred; Rubie, David C.

    2017-11-01

    The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60 GPa. The density data present two discontinuities at ˜17 and ˜60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5 /6 coordination and from 5 /6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at ˜40 GPa , and its density becomes identical to that of MgSiO3 glass above 80 GPa. Our results on SiO2 glass may suggest that a variation of SiO2 content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

  3. Photoluminescent Au-Ge composite nanodots formation on SiO2 surface by ion induced dewetting

    Science.gov (United States)

    Datta, D. P.; Siva, V.; Singh, A.; Kanjilal, D.; Sahoo, P. K.

    2017-09-01

    Medium energy ion irradiation on a bilayer of Au and Ge on SiO2 is observed to result in gradual morphological evolution from an interconnected network to a nanodot array on the insulator surface. Structural and compositional analyses reveal composite nature of the nanodots, comprising of both Au and Ge. The growing nanostructures are found to be photoluminescent at room temperature where the emission intensity and wavelengths vary with morphology. The growth of such nanostructures can be understood in terms of dewetting of the metal layer under ion irradiation due to ion-induced melting along the ion tracks. The visible PL emission is found to be related with evolution of the Au-Ge nanodots. The study indicates a route towards single step synthesis of metal-semiconductor nanodots on insulator surface.

  4. Negative differential resistance effect induced by metal ion implantation in SiO2 film for multilevel RRAM application

    Science.gov (United States)

    Wu, Facai; Si, Shuyao; Shi, Tuo; Zhao, Xiaolong; Liu, Qi; Liao, Lei; Lv, Hangbing; Long, Shibing; Liu, Ming

    2018-02-01

    Pt/SiO2:metal nanoparticles/Pt sandwich structure is fabricated with the method of metal ion (Ag) implantation. The device exhibits multilevel storage with appropriate R off/R on ratio, good endurance and retention properties. Based on transmission electron microscopy and energy dispersive spectrometer analysis, we confirm that Pt nanoparticles are spurted into SiO2 film from Pt bottom electrode by Ag implantation; during electroforming, the local electric field can be enhanced by these Pt nanoparticles, meanwhile the Ag nanoparticles constantly migrate toward the Pt nanoparticles. The implantation induced nanoparticles act as trap sites in the resistive switching layer and play critical roles in the multilevel storage, which is evidenced by the negative differential resistance effect in the current–voltage (I–V) measurements.

  5. A microbiological evaluation of SiO2-coated textiles in hospital interiors

    DEFF Research Database (Denmark)

    Mogensen, Jeppe; Jørgensen, Poul-Erik; Thomsen, Trine Rolighed

    2016-01-01

    . From this perspective, the purpose of this paper is therefore to address focus on alternative passive coatings that without actively killing the bacteria provide a hydrophobic and easy-to-clean textile surface. The paper relates to an in-situ study evaluating the effect and cleaning potential of SiO2...... contact plates through a three-week period. By determining the level of contamination on these surfaces, the study illustrates that the SiO2-coated textile is possible to clean to an acceptable level below the critical limit value of 2,5 Colony Forming Units (CFU) per cm2. In comparison, the traditional...

  6. Understanding the remarkable luminescence enhancement via SiO2 coating on TiO2:Eu3+ nanofibers.

    Science.gov (United States)

    Chang, Meiqi; Song, Yanhua; Sheng, Ye; Chen, Jie; Zou, Haifeng

    2017-07-05

    TiO2:Eu3+ nanofibers diameters can be tuned by changing the mixed solvent ratio are synthesized via the electrospinning technique. Concentration quenching phenomena and the relationship of the PL intensity ratio I(5D0-7F2)/I(5D0-7F1) with the Eu doping concentration are discussed. Notably, the luminescence intensity is enhanced by about 7.8 fold by coating SiO2 gel layer on the TiO2:Eu3+ nanofibers, which is successfully performed via a sol-gel process followed by calcination. Furthermore, these fibers are characterized systematically via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectroscopy. Additionally, their Judd-Ofelt and spectral parameters are calculated to investigate their local structures. The relatively low Ω2 value of the coated samples reveals a decrease in covalency in the Eu-O bonds and an increase in the symmetric nature of Eu3+, which indicate that the perturbation effect of the crystal field in the solid system is larger than that of the uncoated samples. FT-IR analysis indicates the formation of Ti-O-Si bonds, which provide the ligand field in the interface between the TiO2:Eu3+ nanofibers and SiO2 layer and can repair the surface unsaturated bonds. This reduces the selection rules for radiative transitions, thereby the state of the Eu3+ ions is converted from dormant to activated. Moreover, the silica coating stabilizes the surface of the TiO2:Eu3+ nanofibers and eliminates the surface defects. Finally, a detailed mechanism is proposed to explain the luminescence enhancement behavior.

  7. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    OpenAIRE

    Yu-An Chen; Cheng-Huang Kuo; Li-Chuan Chang; Ji-Pu Wu

    2014-01-01

    GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2) and (1 0 2) peaks decreased from 485 ar...

  8. Design and preparation of binary-binary SnO2-ZnO:F/MgF2/SiO2 transparent conducting oxide coatings

    Directory of Open Access Journals (Sweden)

    S Hadavi

    2012-12-01

    Full Text Available   In this study, we prepared the binary-binary TCO compounds of SnO2-ZnO by the spray pyrolysis technique. We also investigated the role of MgF2/SiO2 antireflection coatings in reducing optical reflectance in the visible region of TCO. Before preparation , we simulated the optical transmition of the films for optimizing the layer thicknesses. The results of this study showed increasing of optical transmittance in the visible region of TCO by adding antireflection coating layers.

  9. Improvement in crystal quality and optical properties of n-type GaN employing nano-scale SiO2 patterned n-type GaN substrate.

    Science.gov (United States)

    Jo, Min Sung; Sadasivam, Karthikeyan Giri; Tawfik, Wael Z; Yang, Seung Bea; Lee, Jung Ju; Ha, Jun Seok; Moon, Young Boo; Ryu, Sang Wan; Lee, June Key

    2013-01-01

    n-type GaN epitaxial layers were regrown on the patterned n-type GaN substrate (PNS) with different size of silicon dioxide (SiO2) nano dots to improve the crystal quality and optical properties. PNS with SiO2 nano dots promotes epitaxial lateral overgrowth (ELOG) for defect reduction and also acts as a light scattering point. Transmission electron microscopy (TEM) analysis suggested that PNS with SiO2 nano dots have superior crystalline properties. Hall measurements indicated that incrementing values in electron mobility were clear indication of reduction in threading dislocation and it was confirmed by TEM analysis. Photoluminescence (PL) intensity was enhanced by 2.0 times and 3.1 times for 1-step and 2-step PNS, respectively.

  10. Microstructure and mechanical properties of SiO2-BN ceramic and Invar alloy joints brazed with Ag–Cu–Ti+TiH2+BN composite filler

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2016-03-01

    Full Text Available Ag–Cu–Ti + TiH2+BN composite filler was prepared to braze SiO2-BN ceramic and Invar alloy. The interfacial microstructure, mechanical properties, and residual stress distribution of the brazed joints were investigated. The results show that a wave-like Fe2Ti–Ni3Ti structure appears in the Invar substrate and a thin TiN–TiB2 reaction layer forms adjacent to the SiO2-BN ceramic. The added BN particles react with Ti to form TiN–TiB fine-particles, which is beneficial to refine the microstructure of the brazing seam and to greatly inhibit the brittle compounds formation. The interfacial microstructure at various brazing temperatures was analyzed, and the mechanism for the interfacial reactions responsible for the bonding was proposed. The maximum shear strength of the joints brazed with the composite filler at 880 °C for 10 min is 39 MPa, which is 30% greater than that brazed with Ag–Cu–Ti alloy. The improvement of the joint strength is attributed to the variation of joint microstructure and the reduction of tensile stresses induced in the SiO2-BN ceramic. The finite element analysis indicates that the peak tensile stress decreases from 230 to 142 MPa due to the addition of BN particles in the ceramic.

  11. In-situ formation of SiC nanocrystals by high temperature annealing of SiO2/Si under CO: A photoemission study

    Science.gov (United States)

    D'angelo, M.; Deokar, G.; Steydli, S.; Pongrácz, A.; Pécz, B.; Silly, M. G.; Sirotti, F.; Cavellin, C. Deville

    2012-04-01

    We have studied CO interaction with SiO2/Si system at high temperature (~ 1100 °C) and 350 mbar by core-level photoemission. Even for short annealing time (5 min) the signal from Si2p and C1s core levels shows a clear change upon CO treatment. Shifted components are attributed to formation of SiC. This is confirmed by TEM imaging which further shows that the silicon carbide is in the form of nano-crystals of the 3C polytype. Photoemission spectroscopy moreover reveals the formation of silicon oxicarbide which could not be evidenced by other methods. Combining these results with previous Nuclear Resonance Profiling study gives a deeper insight into the mechanisms involved in the nanocrystals growth and especially for the reaction equation leading to SiC formation. We show that CO diffuses as a molecule through the silica layer and reacts with the silicon substrate according the following reaction: 4 CO + 4 Si → SiO2 + 2SiC + SiO2C2.

  12. Deprotection of Acetals and Ketals by Silica Sulfuric Acid and Wet SiO2

    Directory of Open Access Journals (Sweden)

    Abdolhamid Bamoniri

    2002-10-01

    Full Text Available Neat chlorosulfonic acid reacts with silica gel to give silica sulfuric acid in which sulfuric acid is immobilized on the surface of silica gel via covalent bonds. A combination of silica sulfuric acid and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under thermal conditions.

  13. SnO 2 /SiO 2 Nanocomposite Catalyzed One-pot, Four-component ...

    African Journals Online (AJOL)

    Nanocomposite (SnO2/SiO2) catalytic material has been synthesized by using the sol-gel method. The prepared catalytic materials were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform ...

  14. Surface texture modification of spin-coated SiO2 xerogel thin films ...

    Indian Academy of Sciences (India)

    These as deposited and surfacemodified films were characterized by ellipsometer, Fourier transform infrared (FTIR) spectrometer and contact angle meter. The presence of 2900 and 850 cm-1 peaks of CH3 vibrations in FTIR spectra of surface-modified films confirms the hydrphobisation of SiO2 surface. The maximum ...

  15. HClO4-SiO2 catalyzed per-O-acetylation of carbohydrates.

    Science.gov (United States)

    Misra, Anup Kumar; Tiwari, Pallavi; Madhusudan, Soni Kamlesh

    2005-02-07

    An efficient per-O-acetylation of carbohydrates catalyzed by HClO4-SiO2 is reported using a stoichiometric quantity of acetic anhydride avoiding the use of pyridine and excess acetic anhydride under solvent-free conditions.

  16. SiO2 Glass Density to Lower-Mantle Pressures

    DEFF Research Database (Denmark)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste

    2017-01-01

    and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range...... for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60...... GPa. The density data present two discontinuities at similar to 17 and similar to 60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at similar to 40 GPa, and its density...

  17. Nano-TiCl4/SiO2: an efficient heterogeneous solid acid catalyst for ...

    Indian Academy of Sciences (India)

    Mirjalili

    Nano-TiCl4/SiO2: an efficient heterogeneous solid acid catalyst for the one pot cascade five-component synthesis of densely functionalized tetrahydropyridines. ABDOLHAMID BAMONIRIa,*, BI BI FATEMEH MIRJALILIb and REZA TARAZIANa. aDepartment of Organic Chemistry, Faculty of Chemistry, University of Kashan, ...

  18. Nano-TiCl4/SiO2: An efficient heterogeneous solid acid catalyst for ...

    Indian Academy of Sciences (India)

    Abstract. Nano-TiCl4/SiO2 was found to be an inexpensive and efficient heterogeneous solid acid catalyst for the synthesis of one-pot cascade synthesis of highly functionalized asymmetric tetrahydropyridines from the five-component condensation reaction of the para-substituted anilines and aromatic aldehydes with ethyl.

  19. Theory of Al2O3 incorporation in SiO2

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2002-01-01

    Different possible forms of Al2O3 units in a SiO2 network are studied theoretically within the framework of density-functional theory. Total-energy differences between the various configurations are obtained, and simple thermodynamical arguments are used to provide an estimate of their relative...

  20. Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

    NARCIS (Netherlands)

    Kulazynski, M.; van Ommen, J.G.; Trawczynski, J.; Walendziewski, J.

    2002-01-01

    Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures

  1. Hazards of TiO2 and amorphous SiO2 nanoparticles

    NARCIS (Netherlands)

    Reijnders, L.; Kahn, H.A.; Arif, I.A.

    2012-01-01

    TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

  2. Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

    Directory of Open Access Journals (Sweden)

    Mohammad W. Kadi

    2013-01-01

    Full Text Available ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

  3. Structure and chemistry of grain boundaries in SiO2-doped TZP

    Directory of Open Access Journals (Sweden)

    Yuichi Ikuhara, Takahisa Yamamoto, Akihide Kuwabara, Hidehiro Yoshida and Taketo Sakuma

    2001-01-01

    Full Text Available The addition of glass phase can control the grain boundary structure and hence the mechanical properties of tetragonal zirconia polycrystals (TZP. To reveal the effect of the glass dopant on the high-temperature deformation behavior of TZP, SiO2-doped TZP, (SiO2–Al2O3-doped TZP, (SiO2–MgO-doped TZP and undoped TZP were prepared and their grain boundary structure, chemical composition and chemical bonding state were investigated by high resolution electron microscopy (HREM, energy dispersive X-ray spectroscopy (EDS and electron energy loss spectroscopy (EELS using a field-emission-type transmission electron microscope (FE-TEM. It was found that no amorphous film was formed along the grain boundaries in any of the specimens examined, but amorphous pockets formed at multiple grain boundary junctions in three kinds of glass-doped specimens. In the glass-doped specimens, the segregation of yttrium, silicon and the added metal ions (Al3+ or Mg2+ was observed over a width of several nm across the grain boundaries. The addition of pure SiO2 much enhanced the ductility in TZP, although further addition of a small amount of Al2O3 or MgO to SiO2 phase resulted in a marked reduction in the tensile ductility of SiO2-doped TZP. EELS measurements and molecular orbital (MO calculations using a cluster model revealed that the ductility of TZP was related to the bond overlap population (BOP at the grain boundaries, which was influenced by the kinds of segregated dopants. That is, the presence of Si4+ increases the BOP, strengthening the grain boundary bonding strength and thus preventing cavity formation, but Al3+ and Mg2+ decrease the BOP, enhancing the grain boundary cavitation and thus reducing the ductility. Furthermore, the dynamic behavior of SiO2 in TZP was observed using a TEM in situ heating technique, and the results supported the fact that that Si segregates along the grain boundaries.

  4. Estructura y porosidad de recubrimientos híbridos de SiO2

    Directory of Open Access Journals (Sweden)

    Durán, A.

    2001-02-01

    Full Text Available Morphology and volumetric fraction of pores (Vp, determine several properties of sol-gel coatings. In this work, two methodologies for porosity characterisation of sol-gel hybrid SiO2 coatings as a function of starting compositions and thermal treatment conditions are proposed. Vp was determined from ellipsometric measurement of the refractive index (n. A theoretical correction of n for SiO2 for hybrid system is suggested by employing additive molar properties. An FT-IR method that involves the analysis and fitting of infrared spectra between 1300-960 cm-1 is derived from previous results. From the thermal evolution of the FT-IR spectra different signals and its evolution were assigned to optical modes activated by porosity and SiO2 network densification. Correspondence between thermal evolution of porosity obtained by means of both of the studied methodologies supports these assignments.El estudio de la porosidad de los recubrimientos híbridos de SiO2 obtenidos por sol-gel es importante dado que tanto el porcentaje como la morfología de los poros determinan sus propiedades más significativas. En este trabajo se presentan dos metodologías para caracterizar la porosidad en capas de MTES/TEOS en función del tratamiento térmico y la composición. En primer lugar se ha determinado el porcentaje de porosidad mediante elipsometría, modificando el índice de refracción del SiO2 vítreo para un sistema híbrido, utilizando el concepto de propiedades molares aditivas, empleado habitualmente en el estudio de mezclas poliméricas. Por otro lado, se analizó y optimizó un método que involucra el análisis de los espectros FT-IR de las capas de SiO2 en la región comprendida entre 1300 y 960 cm-1. El ajuste y deconvolución de los espectros ha permitido determinar cuando son necesarias una o dos curvas para ajustar el hombro que afecta a la banda principal del SiO2 (a 1080cm-1 aproximadamente, y su evolución con la temperatura. Una de las bandas se ha asignado a la porosidad de la capa y la otra a la densificación de la red. Ambas metodologías conducen a resultados coherentes y similares, probando la consistencia de los modelos.

  5. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  6. Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

    KAUST Repository

    Zhang, Dongen

    2013-01-01

    Photocatalysis provides a \\'green\\' approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production. © 2013 The Royal Society of Chemistry.

  7. Diffusion of carbon oxides in SiO2 during SiC oxidation

    Science.gov (United States)

    Akiyama, Toru; Nakamura, Kohji; Ito, Tomonori; Kageshima, Hiroyuki; Uematsu, Masashi

    2013-03-01

    SiC is a wide-band-gap semiconductor and has an advantage to fabricate electronic devices such as MOSFETs due to the ability to thermally oxidize to SiO2. Despite many studies conducted on the oxidation of SiC, the kinetics such as diffusion and interface reaction is not fully understood. Here, we focus on the diffusion process during SiC oxidation, and clarify the diffusion mechanism of carbon oxides (CO and CO2) in SiO2 by means of density functional calculations. Our calculations demonstrate that the CO without any chemical bonds with host SiO2 is stabilized while the CO2 is incorporated between Si-O bonds of SiO2 to form a carbonate group. The energy of CO2 is found to be lower than that of CO by 3.7 eV, indicating that the most stable form of carbon oxides in SiO2 is CO2. Furthermore, the calculated energy barriers for diffusion of CO and CO2 are found to be 0.1 and 1.8 eV, respectively. These results thus imply that CO molecules easily react with oxidant such as O2 to form CO2 and the outward diffusion of resultant CO2 is rate-limiting. Indeed, the estimated activation energy for CO2 diffusion (3.5 eV) reasonably agrees with that for Si-face SiC (3.1 eV) obtained by Deal-Grove model considering product gas out-diffusion. This work was supported in part by Grant-in-Aid for Scientific Research (No. 24560025) from the Japan Society for the Promotion of Science.

  8. Ti(IV) carrying polydopamine-coated, monodisperse-porous SiO2 microspheres with stable magnetic properties for highly selective enrichment of phosphopeptides.

    Science.gov (United States)

    Salimi, Kouroush; Usta, Duygu Deniz; Çelikbıçak, Ömür; Pinar, Asli; Salih, Bekir; Tuncel, Ali

    2017-05-01

    A marked decrease in the saturation magnetization by the formation of functional shells around the magnetic core is an important disadvantage of magnetic core-shell nanoparticles. Another drawback of Ti(IV)-functionalized immobilized metal affinity chromatography (IMAC) sorbents is the acidic character of the binding medium used for Ti4+ attachment onto composite magnetic nanoparticles, which causes an additional decrease in the saturation magnetization owing to the chemical interaction between the acidic moiety and the magnetic core. An IMAC sorbent in the form of magnetic microspheres with superior and stable magnetic properties with respect to magnetic core-shell nanoparticles was designed for phosphopeptide enrichment. Magnetic, monodisperse-porous silica microspheres (MagSiO2) 6μm in size were synthesized by a new staged-shape template hydrolysis-condensation protocol. A porous-silica shell layer was generated around the microspheres to protect the magnetic core from the acidic medium during Ti4+ attachment (MagSiO2@SiO2). The MagSiO2@SiO2 microspheres were coated with a polydopamine shell (MagSiO2@SiO2@PDA) and Ti4+ was attached onto the composite microspheres (MagSiO2@SiO2@PDA@Ti(IV)). Formation of the PDA layer and Ti4+ attachment did not cause any significant decrease in the saturation magnetization. The platform exhibited excellent performance for phosphopeptide enrichment from the digests of phosphorylated proteins. Selectivity was investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The detection limit for phosphopeptide enrichment by the MagSiO2@SiO2@PDA@Ti(IV) microspheres from the tryptic digests of β-casein was 50 fmol/mL. Usability of the proposed magnetic sorbent with complex biological samples was demonstrated by successful enrichment of four phosphopeptides from human serum. The proposed sorbent showed stable performance over five repeated uses. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Redistribution of valence and conduction band states depending on the method of modification of SiO2 structure.

    Science.gov (United States)

    Konashuk, A S; Filatova, E O

    2017-10-04

    The effect of introducing porosity and the insertion of methyl groups in SiO4 tetrahedra on the distribution of valence and conduction band states of SiO2 was studied using high-resolution near edge X-ray absorption fine structure spectroscopy (NEXAFS) and soft X-ray photoelectron spectroscopy (XPS). Alignment of NEXAFS spectra and valence band XPS spectra in a common energy scale was performed using binding energies of the initial levels obtained by XPS. It was established that the insertion of methyl groups into SiO4 tetrahedra leads to a significant shift of the top of the valence band EV to smaller binding energies due to the reduction of the electronegativity of the nearest surrounding neighbors of the Si atoms, while introducing porosity changes the position of EV only slightly. The position of the bottom of the conduction band is affected by neither the introduction of porosity nor the insertion of methyl groups. The formation of the π*C[double bond, length as m-dash]C state near the Fermi level, caused by the presence of porogen residues in the structure of organosilicate glass (OSG) and responsible for the leakage currents, was revealed. It was found that high level porosity in OSG films induces a significant variation of Si-O-Si valence angles. A number of Si-O dangling bonds were found in the surface layers of por-SiO2, while methyl groups effectively passivated these dangling bonds in OSG films. The obtained results are important for understanding the regularities of electronic structure formation in SiO2-based low-k dielectrics, which is necessary for the reduction of energy dissipated in semiconductor integrated circuits (ICs).

  10. Sensitizing effects of ZnO quantum dots on red-emitting Pr3+-doped SiO2 phosphor

    CSIR Research Space (South Africa)

    Mbule, PS

    2012-05-01

    Full Text Available In this study, red cathodoluminescence (CL) ( emission=614 nm) was observed from Pr3+ ions in a glassy (amorphous) SiO2 host. This emission was enhanced considerably when ZnO quantum dots (QDs) were incorporated in the SiO2:Pr3+ suggesting...

  11. Preparation of Raspberry-like Superhydrophobic SiO2 Particles by Sol-gel Method and Its Potential Applications

    Directory of Open Access Journals (Sweden)

    Xu Gui-Long

    2011-12-01

    Full Text Available Raspberry‐like SiO2 particles with a nano‐micro‐binary structure were prepared by a simple sol‐gel method using tetraethoxysilane (TEOS and methyltriethoxysilane (MTES as precursors. The chemical components and morphology of the SiO2 particles were characterized by Fourier transform infrared spectroscopy (FT‐IR and a Transmission electron microscope (TEM. The surface topography and wetting behaviour of the raspberry‐like SiO2 surface were observed with a Scanning electron microscope (SEM and studied by the water/oil contact angle (CA, respectively. The thermal stability of the prepared SiO2 particles was characterized by TGA analysis. The results show that the highly dispersed SiO2 particles initially prepared by the sol‐gel method turn into raspberry‐like particles with during the aging process. The raspberry‐like SiO2 particles show superhydrophobicity and superoleophilicity across a wide range of pH values. The SiO2 particles were thermally stable up to 475°C, while above this temperature the hydrophobicity decreases and finally becomes superhydrophobic when the temperature reaches 600°C. The raspberry‐like SiO2 particles which were prepared have potential applications in the fields of superhydrophobic surfaces, water‐oil separation, anti‐corrosion and fluid transportation.

  12. Ethanol-to-Butadiene Conversion over SiO2-MgO Catalysts: Synthesis-Structure-Performance Relationships

    NARCIS (Netherlands)

    Angelici, C.

    2015-01-01

    The work presented in this PhD Thesis provides new insights into the underlying reasons that make SiO2-MgO materials excellent catalysts for the ethanol-to-butadiene Lebedev process. In particular, the preparation technique of choice affects the structural properties of the resulting SiO2-MgO

  13. Effect of nano SiO2 particles on the morphology and mechanical properties of POSS nanocomposite dental resins

    Science.gov (United States)

    Liu, Yizhi; Sun, Yi; Zeng, Fanlin; Xie, Weili; Liu, Yang; Geng, Lin

    2014-12-01

    Nanocomposite dental resins composed of polyhedral oligomeric silsesquioxane nanocomposite matrix and 0, 0.5,1, 1.5 and 2 wt% nano SiO2 as filler were prepared by light curing method. The nanocomposite resins were characterized by performing compressive, three-point flexure, nanoindentation and nanoscratch testings as well as optical microscopy and scanning electron microscope analysis. The effects of different nano SiO2 contents were studied on compressive strength, flexural strength, hardness and resistance of composite resin. From the mechanical results, it was found that nano SiO2 effectively enhanced the mechanical properties of the composite resins at low content. With the increase of the nano SiO2 content, the mechanical properties decreased. It was attributed to the content of nano SiO2 and dispersion of nanoparticles in matrix.

  14. New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity.

    Science.gov (United States)

    Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

    2017-01-01

    Highly transparent, energy-saving, and superhydrophobic nanostructured SiO2/VO2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO2 layer and a top protective layer that consists of SiO2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO2 layer. The transmittance of the composite films in visible region (Tlum) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO2 films and tungsten-doped VO2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO2/VO2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW . cm-2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

  15. Fabrication of multifunctional SiO2@GN-serum composites for chemo-photothermal synergistic therapy.

    Science.gov (United States)

    Liu, Yuwei; Bai, Jing; Jia, Xiaodan; Jiang, Xiue; Guo, Zhuo

    2015-01-14

    Recently, the chemo-photothermal synergistic therapy has become a potential method for cancer treatment. Herein, we developed a multifunctional nanomaterial for chemo-photothermal therapeutics based on silica and graphene core/shell structure (SiO2@GN) because of the ability of GN to convert light energy into heat. Serum protein was further modified onto the surface of GN (SiO2@GN-Serum) to improve the solubility and stability of GN-based nanoparticles in physiological conditions. The as-synthesized SiO2@GN-Serum nanoparticles (NPs) have been revealed to have high photothermal conversion efficiency and stability, as well as high storage and release capacity for anticancer drug doxorubicin (SiO2@GN-Serum-Dox). The therapeutic efficacy of SiO2@GN-Serum-Dox has been evaluated in vitro and in vivo for cervical cancer therapy. In vitro cytotoxicity tests demonstrate that SiO2@GN-Serum NPs have excellent biocompatibility. However, SiO2@GN-Serum-Dox NPs show higher cytotoxicity than SiO2@GN-Serum and free Dox under irradiation with NIR laser at 1.0 W/cm(2) for 5 min owing to both SiO2@GN-Serum-mediated photothermal ablation and cytotoxicity of light-triggered Dox release. In mouse models, the tumor growth is significantly inhibited by chem-photothermal effect of SiO2@GN-Serum-Dox. Overall, compared with single chemotherapy or photothermal therapy, the combined treatment demonstrates better therapeutic efficacy. Our results suggest a promising GN-based core/shell nanostructure for biomedical applications.

  16. Interface engineered carbon nanotubes with SiO2 for flexible infrared detectors

    Science.gov (United States)

    Huang, Zhenlong; Gao, Min; Pan, Taisong; Wei, Xianhua; Chen, Chonglin; Lin, Yuan

    2017-08-01

    Nitrogen-doped/non-doped carbon nanotubes (CNTs) were integrated on SiO2/Si and PMMA substrates for understanding the infrared sensing mechanisms. The nanotube structures on SiO2 substrates exhibit a much shorter response time (about 40 ms) than those directly on PMMA substrates (about 1200 ms), indicating the interface effects between CNTs and the substrates. The infrared responses for both structures show a linear relationship with the light power density even at the radiation power as low as 0.1 mW/mm2. Moreover, a new concept flexible IR detector was designed and fabricated by transferring the CNTs/SiO2 structure onto the PMMA substrate, which exhibits both short response time (50 ms) and good flexibility. The successful detection of human finger movements indicates the practical applications of the CNT-based detectors for the detection of weak thermal or far infrared radiation.

  17. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    Science.gov (United States)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  18. Versatile superamphiphobic cotton fabrics fabricated by coating with SiO2/FOTS

    Science.gov (United States)

    Li, Deke; Guo, Zhiguang

    2017-12-01

    A multifunctional superamphiphobic cotton fabric was fabricated by coating silica nanoparticles on the cotton fabric surface and further modification by 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS). The fluctuant woven fabric and the fluffy spherical SiO2 nanoparticles constructed a dual micro/nano-structures. The surface free energy of the fabric composite was reduced by FOTS modifier. The interplay of the structured and perfluorinated SiO2 nanoparticles could not only endow the fabric highly liquid repellent ability, but could also to enhance the coating stability. The prepared cotton fabrics exhibited high liquid repellency to water, colza oil and n-hexadecane with lower surface tension, showing a contact angle of 158°, 152°, and 153°, respectively. The results demonstrated that superamphiphobic cotton fabric possessed desirable chemical and mechanical durability, self-cleaning and self-healing property, the robust and multifunctional fabric would find innovative opportunities for practical applications.

  19. Immobilized Aspergillus niger Lipase with SiO2 Nanoparticles in Sol-Gel Materials

    Directory of Open Access Journals (Sweden)

    Li Xu

    2016-09-01

    Full Text Available Lipase from Aspergillus niger was “doubly immobilized” with SiO2 nanoparticles in sol-gel powders prepared via the base-catalyzed polymerization of tetramethoxysilane (TMOS and methyltreimethoxysilane (MTMS. The hydrolytic activity of the immobilized lipase was measured using the p-nitrophenyl palmitate hydrolysis method. The results showed that the optimum preparation conditions for the gels were made using a MTMS/TMOS molar ratio of 5, 60 mg of SiO2 nanoparticles, a water/silane molar ratio of 12, 120 mg of enzyme supply, and 120 μL of PEG400. Under the optimal conditions, the immobilized lipase retained 92% of the loading protein and 94% of the total enzyme activity. Characteristic tests indicated that the immobilized lipase exhibited much higher thermal and pH stability than its free form, which shows great potential for industrial applications.

  20. Uniform fabrication of Ge nanocrystals embedded into SiO2 film via neutron transmutation doping

    Directory of Open Access Journals (Sweden)

    Wei Liu

    2014-06-01

    Full Text Available Nanocrystalline 74Ge embedded SiO2 films were prepared by employing ion implantation and neutron transmutation doping methods. Transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence of the obtained samples were measured. The existence of As dopants transmuted from 74Ge is significant to guarantee the uniformity and higher volume density of Ge nanocrystals by tuning the system׳s crystallinity and activating mass transfer process. It was observed that the photoluminescence intensity of Ge nanocrystals increased first then decreased with the increase of arsenic concentration. The optimized fluence of neutron transmutation doping was found to be 5.5×1017 cm−2 to achieve maximum photoluminescence emission in Ge embedded SiO2 film. This work opens a route in the three-dimensional nanofabrication of uniform Ge nanocrystals.

  1. Synthesis of biomorphic SiC and SiO2 ceramics

    Directory of Open Access Journals (Sweden)

    ADELA EGELJA

    2008-07-01

    Full Text Available Coniferous wood (fir was transformed by pyrolysis into carbon preforms, which were subsequently converted into biomorphic ceramics by the pressure infiltration technique with colloidal silica. An in situ reaction between the silica and the carbon template occurred in the cellular wall at a high sintering temperature. Depending on the employed atmosphere, non-oxide (SiC or oxide (SiO2 ceramics were obtained. The morphology of the resulting porous ceramics and their phase composition were investigated by scanning electron microscopy (SEM/EDX and X-ray diffraction (XRD. The experimental results showed that the biomorphic cellular morphology of the wood maintained in both the SiC and silica ceramics, which consisted of only the b-SiC phase and SiO2, respectively.

  2. Si nanocrystals embedded in SiO2: Optical studies in the vacuum ultraviolet range

    DEFF Research Database (Denmark)

    Pankratov, V.; Osinniy, Viktor; Kotlov, A.

    2011-01-01

    Photoluminescence excitation and transmission spectra of Si nanocrystals of different diameters embedded in a SiO2 matrix have been investigated in the broad visible-vacuum ultraviolet spectral range using synchrotron radiation. The dependence of the photoluminescence excitation spectra...... on the nanocrystals size was experimentally established. It is shown that the photoluminescence excitation and absorption spectra are significantly blueshifted with decreasing Si nanocrystal size. A detailed comparison of photoluminescence excitation and absorption spectra with data from theoretical modeling has been...... done. It is demonstrated that the experimentally determined blueshift of the photoluminescence excitation and absorption spectra is larger than the theoretical predictions. The influence of point defects in the SiO2 matrix on the optical and luminescence properties of the embedded Si nanocrystals...

  3. Effect of SiO2 Overlayer on WO3 Sensitivity to Ammonia

    Directory of Open Access Journals (Sweden)

    Vibha Srivastava

    2010-06-01

    Full Text Available Ammonia gas sensing properties of tungsten trioxide thick film sensor was investigated. The doping of noble catalysts such as Pt, Pd, Au enhanced the gas sensitivity. Platinum doping was found to result in highest sensitivity. Remarkable sensitivity enhancement was realized by coating WO3 thick film sensors with SiO2 overlayer. Sol gel process derived silica overlayer increased ammonia gas sensitivity for doped as well as undoped sensor.

  4. Preparation of xerogel SiO2 from roasted iron sand under various acidic solution

    Science.gov (United States)

    Ramelan, A. H.; Wahyuningsih, S.; Ismoyo, Y. A.; Pranata, H. P.; Munawaroh, H.

    2016-11-01

    Xerogel SiO2 had been prepared from roasted iron sand through variation of Na2CO3 addition and sol-gel process under various acidic solution. Roasting treatment was carried out on the compositional variation of iron sand:Na2CO3 = 1:2; 1:1 and 2:1 at 1100 °C. While the sol-gel process was conducted at room temperature and neutralized using HCl 0.1 M and 6 M. The color characteristics of roasted iron sand shown light brown, dark brown and dark gray of the compositional variation of iron sand:Na2CO3 = 1:2; 1:1 and 2:1, respectively. In addition, the levels of thoughness increased by increasing the ratio of sand in the composition of the mixture. The best composition of roasted treatment was at a variety of iron sand:Na2SiO3 = 1:2 with 57.72% had been dissolved in hot water. The addition of Na2CO3 will influence the Na2SiO3 formation, because of the increase of Na2CO3 capable produced the iron sand decomposition product. Na2SiO3 gel had been produced after it was neutralized with certain amount of HCl solution. The neutralization was more effective if using high concentration of HCl because of the formation of gel SiO2 will be easier occurred. The results of SiO2 had been identified by the FTIR spectra, which an absorption spectra of Si-O-Si asymmetric stretching at 1098.51 cm-1, symmetric stretching of Si-O-Si at 804.35 cm-1 and the bending O-Si-O at 469.69 cm'1. The result of SiO2 content by XRF analysis is about 85.15%.

  5. Vaporization of SiO2 and MgSiO3

    Science.gov (United States)

    Stixrude, L. P.; Xiao, B.

    2016-12-01

    Vaporization of SiO2 and MgSiO3B Xiaoa and L Stixrude*a, a Department of Earth Sciences, University College London, WC1E 6BT London, UK *presenting author, email: l.stixrude@ucl.ac.uk Vaporization is an important process in Earth's earliest evolution during which giant impacts are thought to have produced a transient silicate atmosphere. As experimental data are very limited, little is known of the near-critical vaporization of Earth's major oxide components: MgO and SiO2. We have performed novel ab initio molecular dynamics simulations of vapor-liquid coexistence in the SiO2 and MgSiO3 systems. The simulations, based on density functional theory using the VASP code, begin with a suitably prepared liquid slab embedded in a vacuum. During the dynamical trajectory in the canonical ensemble, we see spontaneous vaporization, leading eventually to a steady-state chemical equilibrium between the two coexisting phases. We locate the liquid-vapor critical point at 6600 K and 0.40 g/cm3 for MgSiO3 and 5300 K and 0.43 g/cm3 for SiO2. By carefully examining the trajectories, we determine the composition and speciation of the vapor. For MgSiO3, We find that the vapor is significantly richer in Mg, O, and atomic (non-molecular) species than extrapolation of low-temperature experimental data has suggested. These results will have important implications for our understanding of the initial chemistry of the Earth and Moon and the initial thermal state of Earth.

  6. Measurements of SiO2 glass surface parameters by methods of microscopy

    Science.gov (United States)

    Gavars, Eduards; Svagere, Anda; Skudra, Atis; Zorina, Natalia; Poplausks, Raimonds

    2012-08-01

    In this research we compare chemical and plasma treatment methods for surface of SiO2 glass. For chemical treatment of surface tequila and alcohol were used but for plasma treatment - Ar+As and Ar+Se plasmas. Surface topography was analyzed using atomic force microscope. Comparison of chemical and plasma treatment methods shows that surface treated with plasma is smoother. Because of their various chemical compositions tequila and alcohol show different results.

  7. Measured electrical charge of SiO2 in polar and nonpolar media.

    Science.gov (United States)

    Kokot, G; Bespalova, M I; Krishnan, M

    2016-11-21

    We present measurements of the net electrical surface charge of silicon dioxide (SiO2) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase.

  8. Stabilization of SiO2 nanoparticle foam system and evaluation of its performance

    Science.gov (United States)

    Sun, Chong; Fan, Zhenzhong; Liu, Qingwang; Wang, Jigang; Xu, Jianjun

    2017-05-01

    As tertiary recovery is applied in the oil field, foam flooding technology plays an important role in the oil field. Steam flooding is easy to generate a series of problems such as excessive pressure, gas channelling, heat loss ect. The foam flooding can be better used in the formation of plugging and profile control. However, the foam is not stabilizing in thermodynamics and breaks easily while it encounters oil. So the emphasis of the research is how to make the foam stable. The Warning Blender method is used to evaluate the foam In the course of experiment, which verifies that the modified Nano SiO2 solid not only works very well in coordination with SDS solution but also contributes to the generation of stable foam in solution. The optimum concentration of SDS is determined by 0.5%, and the best concentration is 1.4% of H20 type SiO2 particles that the concentration is 79.26°. Finally, the 0.5%SDS+1.4%H2O type SiO2 is chosen as the complete foam flooding system, and the performance of salt tolerance and oil displacement of composite foam system is evaluated. It is concluded that the stability of foam is the key to improve the oil recovery.

  9. Optical reset modulation in the SiO2/Cu conductive-bridge resistive memory stack

    Science.gov (United States)

    Kawashima, T.; Zhou, Y.; Yew, K. S.; Ang, D. S.

    2017-09-01

    We show that the negative photoconductivity property of the nanoscale filamentary breakdown path in the SiO2 electrolyte of the SiO2/Cu conductive bridge resistive random access memory (CBRAM) stack is affected by the number of positive-voltage sweeps applied to the Cu electrode (with respect to a non-metal counter electrode). The path's photo-response to white light, of a given intensity, is suppressed with an increasing number of applied positive-voltage sweeps. When this occurs, the path may only be disrupted by the light of a higher intensity. It is further shown that the loss of the path's photosensitivity to the light of a given intensity can be recovered using a negative-voltage sweep (which eliminates the path), followed by the reformation of the path by a positive-voltage sweep. The above behavior is, however, not seen in the SiO2/Si stack (which involves a non-metal Si electrode), suggesting that the photo-response modulation effect is related to the Cu electrode. The demonstrated reversible electrical modulation of the path's photo-response may afford greater flexibility in the electro-optical control of the CBRAM device.

  10. Improving Passivation Process of Si Nanocrystals Embedded in SiO2 Using Metal Ion Implantation

    Directory of Open Access Journals (Sweden)

    Jhovani Bornacelli

    2013-01-01

    Full Text Available We studied the photoluminescence (PL of Si nanocrystals (Si-NCs embedded in SiO2 obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm inside the SiO2 achieving a robust and better protected system. After metal ion implantation (Ag or Au, and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO2 matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H2/N2 and Ar to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.

  11. Solid-phase extraction of antimony using chemically modified SiO2-PAN nanoparticles.

    Science.gov (United States)

    Kaur, Anupreet; Gupta, Usha

    2010-01-01

    A new analytical method using 1-(2-pyridylazo)-2-naphthol (PAN)-modified SiO2 nanoparticles as solid-phase extractant has been developed for the preconcentration of trace amounts of Sb(III) in different water samples. Conditions of the analysis such as preconcentration factor, effect of pH, sample volume, shaking time, elution conditions, and effects of interfering ions for the recovery of the analyte were investigated. The adsorption capacity of nanometer SiO2-PAN was found to be 186.25 micromol/g at optimum pH and the LOD (3sigma) was 0.60 microg/L. The extractant showed rapid kinetic sorption. The adsorption equilibrium of Sb(III) on nanometer SiO2-PAN was achieved in 10 min. Adsorbed Sb(III) was easily eluted with 4 mL 2 M hydrochloric acid. The maximum preconcentration factor was 62.20. The method was applied for the determination of trace amounts of Sb(III) in various water samples (tap, mineral water, and industrial effluents).

  12. SiO2 nanoparticles change colour preference and cause Parkinson's-like behaviour in zebrafish.

    Science.gov (United States)

    Li, Xiang; Liu, Bo; Li, Xin-Le; Li, Yi-Xiang; Sun, Ming-Zhu; Chen, Dong-Yan; Zhao, Xin; Feng, Xi-Zeng

    2014-01-22

    With advances in the development of various disciplines, there is a need to decipher bio-behavioural mechanisms via interdisciplinary means. Here, we present an interdisciplinary study of the role of silica nanoparticles (SiO2-NPs) in disturbing the neural behaviours of zebrafish and a possible physiological mechanism for this phenomenon. We used adult zebrafish as an animal model to evaluate the roles of size (15-nm and 50-nm) and concentration (300 μg/mL and 1000 μg/mL) in SiO2-NP neurotoxicity via behavioural and physiological analyses. With the aid of video tracking and data mining, we detected changes in behavioural phenotypes. We found that compared with 50-nm nanosilica, 15-nm SiO2-NPs produced greater significant changes in advanced cognitive neurobehavioural patterns (colour preference) and caused potentially Parkinson's disease-like behaviour. Analyses at the tissue, cell and molecular levels corroborated the behavioural results, demonstrating that nanosilica acted on the retina and dopaminergic (DA) neurons to change colour preference and to cause potentially Parkinson's disease-like behaviour.

  13. Preparation and morphology of porous SiO2 ceramics derived from fir flour templates

    Directory of Open Access Journals (Sweden)

    ZHONG LI

    2010-03-01

    Full Text Available The preparation of SiO2 ceramics with controllable porous structure from fir flour templates via sol–gel processing was investigated. The specific size the fir flour, which was treated with 20 % NaOH solution, was infiltrated with a low viscous silica sol and subsequently calcined in air, which resulted in the formation of highly porous SiO2 ceramics. X-Ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and field emission scanning electron microscopy (FESEM were employed to investigate the microstructure and phase formation during processing as well as of the SiO2 ceramics. N2 adsorption measurements were used to analyze the pore size distributions (PSD of the final ceramics. The results indicated that the surface topography was changed and the proportion of the amorphous material was increased in NaOH-treated fir flour. The final oxide products retained ordered structures of the pores and showed unique pore sizes and distributions with hierarchy on the nanoscale derived from the fir flour.

  14. Measured electrical charge of SiO2 in polar and nonpolar media

    Science.gov (United States)

    Kokot, G.; Bespalova, M. I.; Krishnan, M.

    2016-11-01

    We present measurements of the net electrical surface charge of silicon dioxide (SiO2) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase.

  15. Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@SiO2/TiO2) for reusing of textile wastewater

    OpenAIRE

    Laleh Enayati Ahangar; Karim Movassaghi; Masoomeh Emadi; Fatemeh Yaghoobi

    2016-01-01

    In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2) under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions....

  16. The structural studies of Ag containing TiO2-SiO2 gels and thin films deposited on steel

    Science.gov (United States)

    Adamczyk, Anna; Rokita, Magdalena

    2016-06-01

    FTIR spectroscopic structural studies of titania-silica monolith samples as well as thin films deposited on steel were described in this work. Thin films were synthesized by the sol-gel method applying the dip coating as separate one-component TiO2 and/or SiO2 layers or as two-component TiO2-SiO2 thin films. Silver nanoparticles were incorporated into the structure from pure SiO2 sol, deposited then as an additional layer in those hybrid multilayers systems. Except the spectroscopic studies, XRD diffraction, SEM microscopy with EDX analysis and AFM microscopy were applied. The structural studies allow to describe and compare the structure and the morphology of thin films, as well those Ag free as Ag containing ones, also by the comparison with the structure of bulk samples. In FTIR spectra, the band observed at about 613 cm-1 can be connected with the presence of the non-tetrahedral cation in the structure and is observed only in the spectra of Ag containing bulk samples and thin films. The bands at 435-467 cm-1 are due to the stretching vibrations of Ti-O bonds or as well to the bending vibrations of O-Si-O one. In the ranges of 779-799 cm-1 and 1027-1098 cm-1, the bands ascribed to the symmetric stretching vibrations and asymmetric vibrations of Si-O-Si connections, respectively, are observed. SEM and AFM images gave the information on the microstructure and the topography of samples surface. XRD measurements confirmed the presence of only amorphous phase in samples up to 500 °C and allowed to observe the tendency of their crystallization.

  17. Magnetic decoupling of Fe coverage across atomic step of MoS2 flakes on SiO2 surface

    Science.gov (United States)

    Hsu, Chuan-Che; Lin, Zong-You; Chang, Po-Chun; Chiu, Hsiang-Chih; Chen, Hsiao-Wen; Liu, Hsiang-Lin; Bisio, Francesco; Lin, Wen-Chin

    2017-10-01

    In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS2 flakes were fabricated on SiO2/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes had a mean lateral size of 10-20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS2 flakes. Although the Fe coverage was much thicker than the MoS2 atomic step height (˜0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 were expected, a magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (H c ) was 28  ±  5 Oe, while in contrast, the H c of 3.6 nm Fe/SiO2 ranged 58  ±  5 Oe. With a thicker Fe coverage of 7.0 nm, the H c of Fe/MoS2 and Fe/SiO2 converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS2 for future spintronic applications.

  18. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    OpenAIRE

    Ling Wang; Huidan Zeng; Bin Yang; Feng Ye; Jianding Chen; Guorong Chen; Andew T. Smith; Luyi Sun

    2017-01-01

    Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms?pm2), the maximum Stark splitting manifold of 2F7/2 level (781 cm...

  19. Manufacturing, Microstructure and Corrosion Resistance of Electrophoretically Deposited SiO2 and Ni/SiO2 Coatings On X2CrNiMo17–12–2 Steel

    Directory of Open Access Journals (Sweden)

    Ratajski T.

    2016-06-01

    Full Text Available The SiO2 and Ni/SiO2 coatings were electrophoretically deposited on X2CrNiMo17-12-2 steel using ethanol-based suspensions of the SiO2 and Ni powders. The influence of the zeta potential and concentration of the suspensions, the applied voltage and deposition time on the quality of the coatings was studied. Microstructure of the plan-view and cross sections of the coatings was investigated using scanning electron microscopy. The plan-view images revealed the uniform microstructure of the coatings with sporadically observed cracks, pores as well SiO2 and Ni agglomerates. On the cross-sections, the Cr2O3 layer, resulted from oxidation of the substrate during sintering of the coatings was observed. The polarization tests have shown that SiO2 and Ni/SiO2 coatings improve the corrosion resistance of the X2CrNiMo17-12-2 steel in 3.5% NaCl aqueous solution.

  20. Energy transfer between doubly doped Er3+, Tm3+and Ho3+ rare earth ions in SiO2 nanoparticles

    CSIR Research Space (South Africa)

    Dhlamini, MS

    2011-04-01

    Full Text Available ) colours were measured from both SiO2:Er3+,Tm3+ and SiO2:Ho3+,Tm3+ systems. The change in the intensities of the emission peaks in both the SiO2:Ho3+,Tm3+ and SiO2:Er3+,Tm3+ systems with the change in accelerating beam voltage is shown. Energy transfer from...

  1. The creation of Au nanoscale surface patterns by the low energy Ar+ beam irradiation of Au clusters evaporated onto a SiO2/Si surface

    Science.gov (United States)

    Yang, D.-Q.; Sacher, E.; Meunier, M.

    2005-02-01

    Ex-situ contact-mode atomic force microscopy (C-AFM) was used to study the evolution of the topography of nanoscale Au clusters, deposited onto SiO2/Si surfaces, as a function of Ar+ beam irradiation. Various nanoscale Au surface patterns were created, at an ion beam energy of 2.5 keV, by controlling the ion beam conditions. These patterns include ordered or disordered spheres as well as a nanoporous metal layer. We found that the original (˜ 4 nm) clusters coalesced, under the ion beam, to form both larger clusters (˜ 9 nm) and a nanoporous interphase layer (˜ 6.5 nm). Under continued irradiation, both the original clusters and the nanoporous layer were absorbed into the larger clusters.

  2. Fabrication of cube-like Fe3O4@SiO2@Ag nanocomposites with high SERS activity and their application in pesticide detection

    Science.gov (United States)

    Li, Lei; Zhao, Aiwu; Wang, Dapeng; Guo, Hongyan; Sun, Henghui; He, Qinye

    2016-07-01

    The cube-like Fe3O4@SiO2@Ag (FSA) nanocomposites with great SERS activity have been successfully synthesized by a layer-by-layer procedure in this paper. The cube-like Fe3O4@SiO2 core-shell structures were prepared via a new route and Ag nanoparticles were introduced onto their surface through a one-pot hydrothermal reaction. By controlling the reaction time, the coverage rate of Ag on the FSA surface could be tuned, and then a series of FSA composites were obtained. The SERS properties of these FSA composites were investigated using p-aminothiophenol ( p-ATP) as the probe molecule. It was found that the FSA composites synthesized with a reaction time of 6 h showed the best SERS performance, and the detection limit for p-ATP could reach 1 × 10-7 M. For practical application, the FSA composites were also used to detect thiram, one of the dithiocarbamate fungicides that has been widely used as a pesticide in agriculture. The detection limit is as low as 1 × 10-6 M (0.24 ppm), lower than the maximal residue limit of 7 ppm in fruit prescribed by the US Environmental Protection Agency. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the FSA composite a perfect choice for practical SERS detection applications.

  3. Water adsorption, solvation and deliquescence of alkali halide thin films on SiO2 studied by ambient pressure X-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arima, Kenta; Jiang, Peng; Deng, Xingyi; Bluhm, Henrik; Salmeron, Miquel

    2010-03-31

    The adsorption of water on KBr thin films evaporated onto SiO2 was investigated as a function of relative humidity (RH) by ambient pressure X-ray photoelectron spectroscopy. At 30percent RH adsorbed water reaches a coverage of approximately one monolayer. As the humidity continues to increase, the coverage of water remains constant or increases very slowly until 60percent RH, followed by a rapid increase up to 100percent RH. At low RH a significant number of the Br atoms are lost due to irradiation damage. With increasing humidity solvation increases ion mobility and gives rise to a partial recovery of the Br/K ratio. Above 60percent RH the increase of the Br/K ratio accelerates. Above the deliquescence point (85percent RH), the thickness of the water layer continues to increase and reaches more than three layers near saturation. The enhancement of the Br/K ratio at this stage is roughly a factor 2.3 on a 0.5 nm KBr film, indicating a strong preferential segregation of Br ions to the surface of the thin saline solution on SiO2.

  4. Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

    Science.gov (United States)

    Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

    2016-01-27

    We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7).

  5. Photocatalytic Removal of Phenol under Natural Sunlight over N-TiO2-SiO2 Catalyst: The Effect of Nitrogen Composition in TiO2-SiO2

    Directory of Open Access Journals (Sweden)

    Viet-Cuong Nguyen

    2009-01-01

    Full Text Available In this present work, high specific surface area and strong visible light absorption nitrogen doped TiO2-SiO2 photocatalyst was synthesized by using sol-gel coupled with hydrothermal treatment method. Nitrogen was found to improve the specific surface area while it also distorted the crystal phase of the resulting N-TiO2-SiO2 catalyst. As the N/ (TiO2-SiO2 molar ratio was more than 10%, the derived catalyst presented the superior specific surface area up to 260 m2/g. Nevertheless, its photoactivity towards phenol removal was observed to significantly decrease, which could results from the too low crystallinity. The nitrogen content in N-TiO2-SiO2 catalyst was therefore necessary to be optimized in terms of phenol removal efficiency and found at ca. 5%. Under UVA light and natural sunlight irradiation of 80 min, N(5%-TiO2-SiO2 catalyst presented the phenol decomposition efficiencies of 68 and 100%, respectively. It was also interestingly found in this study that the reaction rate was successfully expressed using a Langmuir-Hinshelwood (L-H model, indicating the L-H nature of photocatalytic phenol decomposition reaction on the N-TiO2-SiO2 catalyst.

  6. Cathodoluminescence properties of SiO2:Pr3+and ZnO.SiO2:Pr3+ phosphor nanopowders

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2010-10-01

    Full Text Available O nanoparticles in Pr3+-doped SiO2 using a sol–gel process is reported. SiO2:Pr 3+ gels, with or without ZnO nanoparticles, were dried at room temperature and annealed at 600 °C. On the basis of the X-ray Diffraction (XRD) results, the SiO2 was amorphous... of 1-5 keV and a fixed beam current of 8.5 μA. The effects of accelerating voltage on the CL intensity and the CL degradation of SiO2:Pr 3+ and ZnO·SiO2:Pr 3+were also investigated using Auger electron spectroscopy coupled with an Ocean Optics S2000...

  7. Efficient VEGF targeting delivery of DOX using Bevacizumab conjugated SiO2@LDH for anti-neuroblastoma therapy.

    Science.gov (United States)

    Zhu, Rongrong; Wang, Zhaoqi; Liang, Peng; He, Xiaolie; Zhuang, Xizhen; Huang, Ruiqi; Wang, Mei; Wang, Qigang; Qian, Yechang; Wang, Shilong

    2017-11-01

    Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and is highly expressed in carcinoma, which make it an important target for tumor targeting therapy. Neuroblastoma is the main cause for cancer-related death in children. Like most solid tumors, it is also accompanied with the overexpression of VEGF. Doxorubicin Hydrochloride (DOX), a typical chemotherapeutic agent, exhibits efficient anticancer activities for various cancers. However, DOX, without targeting ability, usually causes severe damage to normal tissues. To overcome the shortages, we designed a novel nano-composite, which is Bevacizumab (Bev) modified SiO2@LDH nanoparticles (SiO2@LDH-Bev), loading with DOX to achieve targeting ability and curative efficiency. SiO2@LDH-DOX and SiO2@LDH-Bev-DOX nanoparticles were synthesized and the physicochemical properties were characterized by TEM detection, Zeta potential analysis, FTIR, Raman and XPS analysis. Then in vitro and in vivo anti-neuroblastoma efficiency, targeting ability and mechanisms of anti-carcinoma and anti-angiogenesis of SiO2@LDH-Bev-DOX were explored. Our results indicated that we obtained the core-shell structure SiO2@LDH-Bev with an average diameter of 253±10nm and the amount of conjugated Bev was 4.59±0.38μg/mg SiO2@LDH-Bev. SiO2@LDH-Bev-DOX could improve the cellular uptake and the targeting effect of DOX to brain and tumor, enhance the anti-neuroblastoma and anti-angiogenesis efficiency both in vitro and in vivo, and alleviate side effects of DOX sharply, especially hepatic injury. In addition, we also demonstrated that angiogenesis inhibitory effect was mediated by DOX and VEGF triggered signal pathways, including PI3K/Akt, Raf/MEK/ERK, and adhesion related pathways. In summary, SiO2@LDH-Bev could be a potential VEGF targeting nanocarrier applied in VEGF positive cancer therapy. This paper explored that a novel core-shell structure nanomaterial SiO2@LDH and modified SiO2@LDH with Bevacizumab (Bev) to form a new tumor vasculature targeting nanocarrier SiO2@LDH-Bev as vector of DOX, which was not reported before. The results indicated that SiO2@LDH-Bev could improve the VEGF targeting ability, anti-neuroblastoma and anti-angiogenesis efficiency of DOX. At the same time, SiO2@LDH-Bev-DOX could erase the cardiac toxicity and hepatic injury coming from DOX. Tube formation showed SiO2@LDH-Bev-DOX had the strongest effect on inhibiting angiogenesis among all the four formulations. SiO2@LDH-Bev-DOX could downregulate expression of p-VEGFR and inhibit activation of the Raf/MEK/ERK, p38MAPK, PI3K/Akt and FAK signaling pathways to achieve the goal of anti-angiogenesis. This work provides a novel system for the safe and efficient use of Bev and DOX on Neuroblastoma and explores the mechanism of the function of nano carrier in cancer therapy both in vitro and in vivo. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. Nano-regime Length Scales Extracted from the First Sharp Diffraction Peak in Non-crystalline SiO2 and Related Materials: Device Applications

    Directory of Open Access Journals (Sweden)

    Phillips James

    2010-01-01

    Full Text Available Abstract This paper distinguishes between two different scales of medium range order, MRO, in non-crystalline SiO2: (1 the first is ~0.4 to 0.5 nm and is obtained from the position of the first sharp diffraction peak, FSDP, in the X-ray diffraction structure factor, S(Q, and (2 the second is ~1 nm and is calculated from the FSDP full-width-at-half-maximum FWHM. Many-electron calculations yield Si–O third- and O–O fourth-nearest-neighbor bonding distances in the same 0.4–0.5 nm MRO regime. These derive from the availability of empty Si dπ orbitals for back-donation from occupied O pπ orbitals yielding narrow symmetry determined distributions of third neighbor Si–O, and fourth neighbor O–O distances. These are segments of six member rings contributing to connected six-member rings with ~1 nm length scale within the MRO regime. The unique properties of non-crystalline SiO2 are explained by the encapsulation of six-member ring clusters by five- and seven-member rings on average in a compliant hard-soft nano-scaled inhomogeneous network. This network structure minimizes macroscopic strain, reducing intrinsic bonding defects as well as defect precursors. This inhomogeneous CRN is enabling for applications including thermally grown ~1.5 nm SiO2 layers for Si field effect transistor devices to optical components with centimeter dimensions. There are qualitatively similar length scales in nano-crystalline HfO2 and phase separated Hf silicates based on the primitive unit cell, rather than a ring structure. Hf oxide dielectrics have recently been used as replacement dielectrics for a new generation of Si and Si/Ge devices heralding a transition into nano-scale circuits and systems on a Si chip.

  9. Thermal conductivity and electrical properties of hybrid SiO2-graphene naphthenic mineral oil nanofluid as potential transformer oil

    Science.gov (United States)

    Qing, Soo Hui; Rashmi, W.; Khalid, M.; Gupta, T. C. S. M.; Nabipoor, M.; Taghi Hajibeigy, Mohammad

    2017-01-01

    Hybrid SiO2-graphene nanoparticles were synthesised by sol gel centrifugation technique under four different pH levels ranging from 9 to 12. Stability, thermal conductivity, viscosity and electrical conductivity of hybrid SiO2-graphene and pure graphene dispersed in naphthenic oil were investigated. Nanofluids were synthesied at three different nanoparticle concentrations (0.01, 0.04 and 0.08 wt%) while the temperature was varied from 20 °C to 100 °C. Field emission scanning electron microscopy (FESEM), x-ray spectroscopy and Fourier transform infrared (FTIR) spectrometer show successful coating of SiO2 on graphene surface. The growth units and size distribution of SiO2 nanoparticles increased with pH level. Moreover, the presence of SiO2 improved the dispersion behaviour of the nanofluid as confirmed by visual observation and UV-Vis studies. Zeta potential measurements show the hybrid nanofluids at pH 11 are most stable due to its optimum amount and size of SiO2 coated on graphene surface while at pH 12 shows least stability due to precipitation. The presence of SiO2 on graphene further enhanced the thermal conductivity by 80% at pH 9. Also, the viscosity of hybrid nanofluids was higher than pure graphene based nanofluids due to increase in density and particle size. Moreover, the addition of hybrid SiO2-graphene nanoparticles significantly reduced the electrical conductivity enhancement of base fluid from 557% to 97%.

  10. Preparation and characterization of silane-modified SiO2particles reinforced resin composites with fluorinated acrylate polymer.

    Science.gov (United States)

    Liu, Xue; Wang, Zengyao; Zhao, Chengji; Bu, Wenhuan; Na, Hui

    2018-01-10

    A series of fluorinated dental resin composites were prepared with two kinds of SiO 2 particles. Bis-GMA (bisphenol A-glycerolate dimethacrylate)/4-TF-PQEA (fluorinated acrylate monomer)/TEGDMA (triethylene glycol dimethacrylate) (40/30/30, wt/wt/wt) was introduced as resin matrix. SiO 2 nanopartices (30nm) and SiO 2 microparticles (0.3µm) were silanized with 3-methacryloxypropyl trimethoxysilane (γ-MPS) and used as fillers. After mixing the resin matrix with 0%, 10%, 20%, 30% SiO 2 nanopartices and 0%, 10%, 20%, 30%, 40%, 50% SiO 2 microparticles, respectively, the fluorinated resin composites were obtained. Properties including double bond conversion (DC), polymerization shrinkage (PS), water sorption (W p ), water solubility (W y ), mechanical properties and cytotoxicity were investigated in comparison with those of neat resin system. The results showed that, filler particles could improve the overall performance of resin composites, particularly in improving mechanical properties and reducing PS of composites along with the addition of filler loading. Compared to resin composites containing SiO 2 microparticles, SiO 2 nanoparticles resin composites had higher DC, higher mechanical properties, lower PS and lower W p under the same filler content. Especially, 50% SiO 2 microparticles reinforced resins exhibited the best flexural strength (104.04 ± 7.40MPa), flexural modulus (5.62 ± 0.16GPa), vickers microhardness (37.34 ± 1.13 HV), compressive strength (301.54 ± 5.66MPa) and the lowest polymerization (3.42 ± 0.22%). Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Experimental research of stability of emulsion systems with SIO2 nanoparticles.

    Directory of Open Access Journals (Sweden)

    Zeigman Yury Veniaminovich

    2017-10-01

    Full Text Available Since the beginning of the 21st century scientific research devoted to properties of nanosized particles and their industrial application in the industry of oil and gas fields development has been rapidly evolving. The use of nanosized particles can significantly rise efficiency of technological solutions, and that fact determines this research area as the most promising today. In the area of oil and gas fields development one of the general application for nanoparticles is the development of high-performance technological fluids with new or improved physico-chemical properties. The ability of nanoparticles to modify wettability of the rock surface and to be fixed on the adsorption-solvation stratums of globules makes them a unique tool to regulate physicochemical properties of technological fluids and physical properties of rocks.The article reveals the results of a new stage in the research of physical properties of emulsion systems with silicon dioxide nanoparticles (SiO2. The research carried out within the framework of international project «Development and implementation of water-blocking agents based on the SiO2 nanoparticles application». The results of comparative tests of stability of classical emulsions (O/W and W/O types and emulsion systems modified with SiO2 nanoparticles with different wettability characteristics (hydrophilic or hydrophobic are presented. According to the results of comparative tests, it has been determined that the stability of most samples of modified emulsion systems containing hydrophilic or hydrophobic silica nanoparticles exceeds the stability of classical emulsions by more than 100%. In the course of comparative studies, the following types of experiments were performed: measurement of aggregate stability, electrostability and thermal stability of samples. The paper is a continuation of the complex research which has been published in [1].

  12. Evolution of size distribution and structure of Si and SiO2 nanoparticles: laser-assisted formation and fragmentation

    Science.gov (United States)

    Eidelman, K.; Gudkov, D.; Segbefia, O.; Ageev, E.; Krivonosov, A.; Matuhina, A.

    2017-11-01

    In this work, Si and SiO2, nanoparticles (NPs) was prepared by pulsed laser ablation (PLA) in distilled water. The radiation of a ytterbium fiber laser (repetition rate f = 50 kHz, wavelength λ = 1064 nm and pulse duration τ = 8 ns and 100 ns) at different laser intensities was utilized to ablate the Si target (99.999%, cubic, 7×7 mm2) under liquid layer to synthesize and to fragment the silicon colloidal NPs. Studies of morphology and size distribution of silica NPs were conducted using Transmission Electron Microscopy (TEM). The NPs of crystalline and amorphous phases were founded. Most of the NPs in the nano colloids were found to have dimensions less than 100 nm, and a few of them were between 100 nm and 700 nm. Dependence of average NP size on the number of laser passes was revealed. The average size of the nanoparticles obtained by TEM was confirmed by dynamic light scattering (DLS) measurements.

  13. MnF2/SiO2 Transport Properties of Quasiperiodic Photonic Crystals for Potential Catalytic Applications

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    Qiang Zhang

    2015-01-01

    Full Text Available Magnetically recyclable materials should be ideal support in photocatalytic system because they permit the photocatalysts to be recovered rapidly and efficiently by applying an external magnetic field such as, MnF2. In this paper, MnF2 and SiO2 layers constitute a one-dimensional quasiperiodic photonic crystal according to Fibonacci. When the electromagnetic wave irradiates obliquely, the transmission peak moves to higher frequency direction with the angle increasing. Both the number of transmission peaks and the transmission peaks of double-forked structure increase with the increase of structural progression. We also found that the polarization of electromagnetic waves has influence on the transmission properties; TM wave transmission peak half wide is significantly greater than TE wave transmission peak half wide. The band gap near antiferromagnetic (AF resonance frequency becomes narrow as the intensity of the applied static magnetic field increases. The as-prepared photonic crystal has tremendous potential practical use to eliminate organic pollutants from wastewater.

  14. Investigation of solar cell performance using multilayer thin film structure (SiO2/Si3N4 and grating

    Directory of Open Access Journals (Sweden)

    R.S. Dubey

    Full Text Available Thin film silicon solar cells are the better choice due to their low cost as compared to the crystalline solar cells. However, thin film silicon solar cells are suffering from a problem of weak absorption of incident light and hence, light trapping mechanism is essential for the harvesting of maximum solar radiation. In this paper, we present the performance of solar cell using an efficient back reflector composed of multilayer thin film (SiO2/Si3N4 and a diffraction grating. The use of a back reflector showed enhanced light absorption due to the folding of unabsorbed light coming to it after crossing the active region in a wide wavelength range. Further, the effect of active layer thickness and grating height were also discussed for the optimal performance of the solar cell. In the case of magnetic transverse mode, a relative enhancement in cell efficiency about 79 and 21% respectively have been observed with respect to a planar and SC4 solar cells. Keywords: Dielectric multilayer film structure, Bragg reflectors, Reflection, Thin film silicon solar cells, Absorption

  15. An ab initio investigation of Bi2Se3 topological insulator deposited on amorphous SiO2.

    Science.gov (United States)

    de Oliveira, I S S; Scopel, W L; Miwa, R H

    2017-02-01

    We use first-principles simulations to investigate the topological properties of Bi2Se3 thin films deposited on amorphous SiO2, Bi2Se3/a-SiO2, which is a promising substrate for topological insulator (TI) based device applications. The Bi2Se3 films are bonded to a-SiO2 mediated by van der Waals interactions. Upon interaction with the substrate, the Bi2Se3 topological surface and interface states remain present, however the degeneracy between the Dirac-like cones is broken. The energy separation between the two Dirac-like cones increases with the number of Bi2Se3 quintuple layers (QLs) deposited on the substrate. Such a degeneracy breaking is caused by (i) charge transfer from the TI to the substrate and charge redistribution along the Bi2Se3 QLs, and (ii) by deformation of the QL in contact with the a-SiO2 substrate. We also investigate the role played by oxygen vacancies ([Formula: see text]) on the a-SiO2, which increases the energy splitting between the two Dirac-like cones. Finally, by mapping the electronic structure of Bi2Se3/a-SiO2, we found that the a-SiO2 surface states, even upon the presence of [Formula: see text], play a minor role on gating the electronic transport properties of Bi2Se3.

  16. Experimental study of viscosity properties of emulsion system with SiO2 nanoparticles.

    Directory of Open Access Journals (Sweden)

    ZEIGMAN Yury Veniaminovich,

    2017-04-01

    Full Text Available When oil production is increasing due to intensive oilfield development methods supporting seam pressure by water injection oil producers face the problem of displacement agent break in more permeable intervals of petroleum reservoir. That leads to dramatic increase of product inundation for well stock and decrease of economic efficiency for well performance. Nowadays the petroleum engineers have proposed more than 100 technologies designed to restrict water inflows and flooding agent to bottom-hole zone of the production wells. The water inflows restriction technologies are distinguished by the type of applied chemical compositions and the way how the chemical compositions are delivered to bottom-hole zone. The analysis of the currently applied chemical compositions has allowed authors to reveal the common feature. The common feature is that the currently applied chemical compositions are non-selective and they produce isolating or blocking effect onto water-saturated and oil-saturated zones of the petroleum reservoir. The application of the nonselective high-stability chemical compositions leads to uncontrolled colmatation of all treated intervals and makes it difficult to involve them into filtration process in future. This work presents the technology for the selective reservoir stimulation based on emulsion systems with SiO2 nanoparticles content and gelling acid composition. The technology was developed for complex impact on formation system, that achieved by blocking water-saturated intervals of reservoir and stimulation of less permeable oil-saturated intervals of reservoir. The paper shows the results of complex laboratory experiments to study viscosity parameters of emulsion systems with SiO2 nanoparticles content. The results of the experiments revealed the ability of the SiO2 nanoparticles to rise dynamic viscosity of the different type of emulsion systems: oil in water and water in oil. Test for thermostability of the modified emulsion systems showed stability of the systems under 80о C. In addition, the modified emulsion systems kept the ability to decrease significantly viscosity in the reaction with hydrocarbons, i.e. the emulsion systems with SiO2 nanoparticles are selective compositions for the water-inflows restriction.

  17. The Obtaining of Nano Oxide Systems SiO2-REE with Alkoxide Technology

    Science.gov (United States)

    Amelina, Anna; Grinberg, Evgenii

    A lot of oxides systems with REE as dopants are used in catalytic processes in organic synthesis. They are very perspectives as thermostable coating in aerospace technics. These systems are usually based on silicon or aluminium oxides and doped with rare-earth elements. This systems can be produced by different methods. One of the most perspective of them is “sol-gel”-method with silicium, aluminium and rare-earth alkoxides as a precursor of doped silica and alumina, or their derivatives. Thus the obtaining of composite SiO _{2} - REE oxide materials by the hydrolysis doped with rare-earth elements was suggested. Some of alcoholate derivatives such as El(OR)n were used in this processes. The SiO _{2}- REE oxides were precipitated during the sol-gel process, where tetraethoxysilane (TEOS) as used as SiO _{2} sources. Also it is known that alkoxides of alkali metals, including lithium alkoxides, are widely used in industry and synthetic chemistry, as well as a source of lithium in various mixed oxide compositions, such as lithium niobate, lithium tantalate or lithium silicate. Therefore, we attempted to obtain the lithium silicate, which is also doped with rare-earth elements. Lithium silicate was obtained by alkaline hydrolysis of tetraethoxysilane with lithium alkoxide. Lithium alkoxide were synthesized by dissolving at metal in the corresponding alcohol are examined. The dependence of the rate of dissolving of the metal on the method of mixing of the reaction mixture and the degree of metal dispersion was investigated. The mathematical model of the process was composed and also optimization of process was carried out. Some oxide SiO _{2}, Al _{2}O _{3} and rare-earth nanostructured systems were obtained by sol-gel-method. The size of particle was determined by electron and X-ray spectroscopy and was in the range of 5 - 15 nm. Purity of this oxide examples for contaminating of heavy metals consists n.(1E-4...1E-5) wt%. Sols obtained by this method may be used for producing of thin coats on ceramics and metallic surfaces.

  18. Experimental investigation of bubble formation during capillary filling of SiO2 nanoslits

    DEFF Research Database (Denmark)

    Thamdrup, Lasse Højlund; Persson, Karl Fredrik; Bruus, Henrik

    2007-01-01

    Experimental results are presented regarding the influence of bubble formation on the capillary filling speed of water in SiO2 nanoslits with heights ranging from 33 to 158 nm. The formation of an isolated pinned bubble in a nanoslit with a height of 111 nm causes an immediate decrease...... in the filling speed. In nanoslits with heights below 100 nm, pinned bubbles are continuously formed at the advancing liquid meniscus. This observed increase in bubble density, which increases the fluidic resistance, quantitatively coincides with an observed reduction of the filling speed during filling...

  19. Influence of SiO2 Particles on Microstructures and Properties of Ni-W-P-CeO2-SiO2 Nano-Composite Coatings

    Institute of Scientific and Technical Information of China (English)

    Xu Ruidong; Wang Junli; Guo Zhongcheng; Wang Hua

    2007-01-01

    Ni-W-P-CeO2-SiO2 nano-composite coatings were prepared on the carbon steel surface by pulse co-deposition of nickel, tungsten, phosphorus, nano-CeO2 and nano-SiO2 particles. The influence of nano-SiO2 particles concentrations in electrolyte on microstructures and properties of the nano-composite coatings were researched, and the characteristics were assessed by chemical compositions, element distribution, deposition rate, microhardness and microstructures. The results indicate that when nano-SiO2 particles concentrations in electrolyte are controlled at 20g·L-1, the deposition rate with 27.07μm·h-1 and the microhardness with 666 Hv of the nano-composite coatings are highest, element line scanning and area scanning analyses show that the average contents of elements W, P, Si and Ce in the nano-composite coatings are close. displaying that the distribution of every element within the nano-composite coatings is even. An increase in nano-SiO2 particles concentrations in electrolyte (when lower than 20g·L-1) leads to refinement in grain structure of nano-composite coatings, but when it improved to 30g·L-1, the crystallite sizes increase again and in the meantime there are a lot of small boss with nodulation shape appearing on the surface of nano-composite coatings.

  20. Preparation of CaCO3-SiO2 composite with core-shell structure and its application in silicone rubber

    OpenAIRE

    Cui Chenglin; Ding Hao; Cao Li; Chen Daimei

    2015-01-01

    A new CaCO3-SiO2 composite with core-shell structure was successfully prepared by mechano-chemistry method (MCM). SEM and FTIR indicated that SiO2 particles were homogeneously immobilized on the surface of CaCO3. The well dispersion of this CaCO3-SiO2 composite into silicone rubber can not only reduce the usage amount of SiO2, but also improve the mechanical properties of silicone rubber. By the calculation, the theoretical numbers of the SiO2 particles is about 10 times as large as that of C...

  1. Formation Mechanism of SiO2-Type Inclusions in Si-Mn-Killed Steel Wires Containing Limited Aluminum Content

    Science.gov (United States)

    Wang, Kunpeng; Jiang, Min; Wang, Xinhua; Wang, Ying; Zhao, Haoqian; Cao, Zhanmin

    2015-10-01

    The origin, formation mechanism, and evolution of SiO2-type inclusions in Si-Mn-killed steel wires were studied by pilot trials with systematical samplings at the refining ladle, casting tundish, as-cast bloom, reheated bloom, and hot-rolled rods. It was found that the inclusions in tundish were well controlled in the low melting point region. By contrast, MnO-SiO2-Al2O3 inclusions in the as-cast bloom were with compositions located in the primary region of SiO2, and most CaO-SiO2-Al2O3-MnO inclusions lied in primary phase region of anorthite. Therefore, precipitation of SiO2 particles in MnO-SiO2-Al2O3 inclusions can be easier than in CaO-SiO2-Al2O3-MnO inclusions to form dual-phase inclusions in the as-cast bloom. Thermodynamic calculation by the software FactSage 6.4 (CRCT-ThermFact Inc., Montréal, Canada) showed that mass transfer between liquid steel and inclusions resulted in the rise of SiO2 content in inclusions from tundish to as-cast bloom and accelerated the precipitation of pure SiO2 phase in the formed MnO-SiO2-Al2O3 inclusions. As a result, the inclusions characterized by dual-phase structure of pure SiO2 in MnO-SiO2-Al2O3 matrix were observed in both as-cast and reheated blooms. Moreover, the ratio of such dual-phase SiO2-type inclusions witnessed an obvious increase from 0 to 25.4 pct before and after casting, whereas it changed little during the reheating and rolling. Therefore, it can be reasonably concluded that they were mainly formed during casting. Comparing the evolution of the inclusions composition and morphology in as-cast bloom and rolled products, a formation mechanism of the SiO2-type inclusions in wire rods was proposed, which included (1) precipitation of SiO2 in the formed MnO-SiO2-Al2O3 inclusion during casting and (2) solid-phase separation of the undeformed SiO2 precipitation from its softer MnO-SiO2-Al2O3 matrix during multipass rolling.

  2. Proton trapping and diffusion in SiO 2 thin films: a first-principles study

    Science.gov (United States)

    Zhang, Qiming; Tang, Shaoping; Wallace, Robert M.

    2001-03-01

    The behavior of mobile protons at the Si/SiO 2 interface has drawn substantial interest since it was found to play the critical role in a proposed non-volatile memory device based on Si/SiO 2/Si structures. We have investigated the bonding and diffusion properties of a proton at the interface by a first-principles local density cluster total energy approach. A 73-atom cluster model is used to simulate the Si/SiO 2 interface that is constructed from β-cristobalite SiO 2 on the Si(0 0 1) surface. In agreement with previous calculations of protons in bulk Si, the SiSi bond center is found to be a stable site for a proton on the Si side of the Si/SiO 2 interface. On the SiO 2 side, the proton is found to bond with O atoms. Furthermore, it is found that the binding energy of protonoxygen bond decreases as the proton penetrates into the oxide. Thus, an energy well is formed which confines protons in silicon oxide region in a Si/SiO 2/Si structure. The calculated diffusion barrier for proton hopping between the neighboring binding sites is 0.73 eV in LDA and 1.15 eV in GGA, in good agreement with the experimental activation energy.

  3. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  4. Environment assisted photoconversion of luminescent surface defects in SiO2 nanoparticles

    Science.gov (United States)

    Spallino, Luisa; Spera, Monia; Vaccaro, Lavinia; Agnello, Simonpietro; Gelardi, Franco M.; Zatsepin, Anatoly F.; Cannas, Marco

    2017-10-01

    Time-resolved photoluminescence investigation on SiO2 nanoparticles was carried out in controlled atmosphere, with the aim to discern the effects induced on the typical blue luminescence band by high power UV Nd:YAG laser photons (4.66 eV) and by some selected molecular species of the air (O2, N2, CO2, H2O). These factors ultimately determine both the brightness and photostability of the emitting defect, so as to limit the unique and attracting potentialities offered by this system in many applicative fields. Here it is highlighted that the effects due to photons and molecules, singularly considered, are not additive, the radiation being more dramatic in reducing the emission efficiency. Moreover, by analyzing the kinetics to convert the defects in a non-luminescent configuration both by the direct (photon-defect) and indirect (photon-molecule-defect) interactions, the threshold bleaching fluence is derived, ranging between 5000 J/cm2 (in a vacuum) and 60 J/cm2 (in air). These results indicate that an outstanding enhancement of the defect photostability is gained by passing from ambient atmosphere to vacuum condition, leading to foresee an immediate and relevant improvement in the field of the single-emitter spectroscopy based on the visible emission of SiO2 nanoparticles.

  5. La cascarilla de arroz como fuente de SiO2

    Directory of Open Access Journals (Sweden)

    Claudia Andrea Arcos

    2007-01-01

    Full Text Available La cascarilla de arroz calcinada presenta un alto contenido de sílice. Este trabajo estudió la naturaleza de la fracción orgánica donde se nuclean los complejos de sílice y las condiciones óptimas para la síntesis de SiO2. La cascarilla de arroz y la sílice se analizaron utilizando microscopía electrónica de barrido (MEB, difracción de rayos de X (DRX, infrarrojo con transformada de Fourier (FTIR y análisis térmico diferencial (ATD. La cascarilla fue tratada con HCl para eliminar impurezas como Fe, Na, K, entre otros. Los resultados obtenidos muestran que en la parte externa de la cascarilla, constituida de celulosa, se nuclea la sílice, y el SiO2 obtenido de la misma es amorfo, con un alto valor de superficie específica (~277 m2/g, morfología no definida y tamaño nanométrico (< 200 nm.

  6. Effect of relative humidity on the deposition and coagulation of aerosolized SiO2 nanoparticles

    Science.gov (United States)

    Wang, Youfeng; Chen, Lan; Chen, Rui; Tian, Guolan; Li, Dexing; Chen, Chunying; Ge, Xiujie; Ge, Guanglu

    2017-09-01

    The temporal evolution of aerosolized SiO2 nanoparticles (NPs) released into an environmental test chamber has been investigated to interrogate the effect of relative humidity (RH) on the deposition and coagulation of the nanoparticles. The size-resolved deposition rate and Brownian coagulation coefficient for the particles at RH of 10%, 27%, 40%, 54%, and 64% are estimated. The results show that the effect of RH on the deposition rate is size-dependent; for particle diameter (Dp) 70 nm, it grows as the RH rises. Generally, both low and high RH tends to enhance the deposition rate, and the minimum rate appears at moderate RH ( 54%). Electrostatic repulsion is probable for the inter-particles interaction at the low RH while the surface roughness due to water molecular adsorption is a main reason for the particle-wall interaction at higher RH. The increasing coagulation coefficient at high humidity correlates to the strong inter-particle adhesion, which may be caused by the water molecular adsorption on the hydrophilic surfaces of the SiO2 NPs due to the formation of nanometer-thick water film. This study suggests that air humidity plays unignorable roles in particle deposition and coagulation.

  7. Structure and magnetic properties of granular NiZn-ferrite - SiO2

    Directory of Open Access Journals (Sweden)

    Albuquerque Adriana Silva de

    1999-01-01

    Full Text Available Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthesized by sol-gel processing. Samples with ferrite volumetric fraction x ranging from 6% to 78% were prepared, and characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Our results show the formation of pure stoichiometric NiZn-ferrite in the SiO2 matrix for x < 34%. Above these fraction, our samples presented also small amounts of Fe2O3. Mössbauer spectroscopy revealed the superparamagnetic behaviour of the ferrimagnetic NiZn-ferrite nanoparticles. The combination of different ferrite concentration and heat treatments allowed the obtaintion of samples with saturation magnetization between 1.3 and 68 emu/g and coercivity ranging from 0 to 123 Oe, value which is two orders of magnitude higher than the coercivity of bulk NiZn-ferrite.

  8. Formation of ZnO nanostructures grown on Si and SiO2 substrates.

    Science.gov (United States)

    Lee, Seungjin; Park, Eunkyung; Lee, Jongtack; Park, Taehee; Lee, Sang-Hwa; Kim, Jae-Yong; Yi, Whikun

    2013-09-01

    ZnO nanorods are grown on Si-based substrate by chemical bath deposition method in aqueous solution using zinc nitrate hexahydrate. Various substrates having different surface morphology are used to evaluate their effect on growing ZnO nanorods, such as flat Si(100) wafer, small and large textured-Si wafer, porous silicon, flat SiO2 wafer, small and large textured-SiO2 wafer. The length, diameter, geometry, and coverage density of ZnO nanorods are investigated by field-emission scanning electron microscopy and summarized. SiO2 is a preferred substrate for the growth of ZnO nanorods to Si if the surface morphology of substrate is same, and the textured surface has much higher coverage density (> 95%) than the flat surface. Each nanorod is vertically grown along the c-axis on the top of each pyramid face for textured substrate, and forms the 3D sea sponge-like ZnO structure. The characteristics of ZnO nanorods grown on various substrates are analyzed by grazing-angle X-ray diffraction (XRD) and photoluminescence (PL) measurements.

  9. Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

    Directory of Open Access Journals (Sweden)

    Giyjaz E. Bekmukhamedov

    2016-10-01

    Full Text Available Due to the continuously rising demand for C3–C5 olefins it is important to improve the performance of catalysts for dehydrogenation of light alkanes. In this work the effect of modification by SiO2 on the properties of the alumina support and the chromia-alumina catalyst was studied. SiO2 was introduced by impregnation of the support with a silica sol. To characterize the supports and the catalysts the following techniques were used: low-temperature nitrogen adsorption; IR-spectroscopy; magic angle spinning 29Si nuclear magnetic resonance; temperature programmed desorption and reduction; UV-Vis-, Raman- and electron paramagnetic resonance (EPR-spectroscopy. It was shown that the modifier in amounts of 2.5–7.5 wt % distributed on the support surface in the form of SiOx-islands diminishes the interaction between the alumina support and the chromate ions (precursor of the active component. As a result, polychromates are the compounds predominantly stabilized on the surface of the modified support; under thermal activation of the catalyst and are reduced to the amorphous Cr2O3. This in turn leads to an increase in the activity of the catalyst in the dehydrogenation of isobutane.

  10. Sol-hydrothermal synthesis of inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite and its preferential photocatalytic degradation towards target contaminant.

    Science.gov (United States)

    Deng, Fang; Liu, Yin; Luo, Xubiao; Wu, Shaolin; Luo, Shenglian; Au, Chaktong; Qi, Ruoxi

    2014-08-15

    Inorganic-framework molecularly imprinted TiO2/SiO2 nanocomposite (MIP-TiO2/SiO2) was successfully prepared by sol-hydrothermal method using 4-nitrophenol as template. The morphology, structure, optical property, zeta-potential and photocurrent of MIP-TiO2/SiO2 were characterized. The adsorption performance and photocatalytic selectivity were also studied. MIP-TiO2/SiO2 shows higher adsorption capacity and selectivity than the non-imprinted TiO2/SiO2 (NIP-TiO2/SiO2). Kinetics results show that the adsorption equilibrium of 4-nitrophenol on MIP-TiO2/SiO2 is established within 20 min, and the adsorption process obeys the pseudo-second-order model. Moreover, MIP-TiO2/SiO2 can completely degrade 4-nitrophenol within 30 min, while NIP-TiO2/SiO2 takes 110 min. It was found that the MIP-TiO2/SiO2 photocatalyst shows molecular recognition ability, leading to selective adsorption and molecular recognitive photocatalytic degradation of 4-nitrophenol. Furthermore, because of its inorganic framework, MIP-TiO2/SiO2 shows excellent reusability. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Void Shapes Controlled by Using Interruption-Free Epitaxial Lateral Overgrowth of GaN Films on Patterned SiO2 AlN/Sapphire Template

    Directory of Open Access Journals (Sweden)

    Yu-An Chen

    2014-01-01

    Full Text Available GaN epitaxial layers with embedded air voids grown on patterned SiO2 AlN/sapphire templates were proposed. Using interruption-free epitaxial lateral overgrowth technology, we realized uninterrupted growth and controlled the shape of embedded air voids. These layers showed improved crystal quality using X-ray diffraction and measurement of etching pits density. Compared with conventional undoped-GaN film, the full width at half-maximum of the GaN (0 0 2 and (1 0 2 peaks decreased from 485 arcsec to 376 arcsec and from 600 arcsec to 322 arcsec, respectively. Transmission electron microscopy results showed that the coalesced GaN growth led to bending threading dislocation. We also proposed a growth model based on results of scanning electron microscopy.

  12. Enhanced photoluminescence of core-shell CoFe2O4/SiO2/Y2O3:Eu3+ composite by remanent magnetization

    Science.gov (United States)

    Jia, Yanmin; Zhou, Zhihua; Wei, Yongbin; Wu, Zheng; Wang, Haihang; Chen, Jianrong; Zhang, Yihe; Liu, Yongsheng

    2013-12-01

    A core-shell cobalt ferrite/silicon dioxide/europium ion-doped Y2O3 (CoFe2O4/SiO2/Y2O3:Eu3+) composite was synthesized by a facile layer-by-layer method. Magnetization of the composite under an external magnetic field of approximately 0.25 T enhanced the photoluminescence (PL) intensity by 56%. The remanent magnetization of the CoFe2O4 core increased the excited charge-transfer transition between O2- and Eu3+ in the Y2O3:Eu3+ shell, thus enhancing the probability of radiative transition (5D0→7F2) of Eu3+ ions and leading to enhanced PL. Remanent magnetization is a noncontact, easy-to-operate technique with high growth amplitude and potential for practical application for smart display devices.

  13. Synthesis of surface molecular imprinting polymer on SiO2-coated CdTe quantum dots as sensor for selective detection of sulfadimidine

    Science.gov (United States)

    Zhou, Zhiping; Ying, Haiqin; Liu, Yanyan; Xu, Wanzhen; Yang, Yanfei; Luan, Yu; Lu, Yi; Liu, Tianshu; Yu, Shui; Yang, Wenming

    2017-05-01

    This paper demonstrates a facile method to synthesize surface molecular imprinting polymer (MIP) on SiO2-coated CdTe QDs for selective detection of sulfadimidine (SM2). The fluorescent MIP sensor was prepared using cadmium telluride quantum dots (CdTe QDs) as the material of fluorescent signal readout, sulfadimidine as template molecule, 3-aminopropyltriethoxysilane (APTES) as functional monomer and tetraethyloxysilane (TEOS) as cross-linking agent. The CdTe cores were embed in the silicon shells by a sol-gel reaction and then the molecular imprinting layers were immobilized on the surface of the SiO2-coated CdTe QDs. Under the optimized conditions, the relative fluorescent intensity weakened in a linear way with the increasing concentration of sulfadimidine in the range of 10-60 μmol L-1. The practical application of the fluorescent MIP sensor was evaluated by means of analyzing sulfadimidine in the real milk samples. The recoveries were at the range of 90.3-99.6% and the relative standard deviation (RSD) ranged from 1.9 to 3.1%, which indicates the successful synthesis of the fluorescent MIP sensor. This sensor provides an alternative solution for selective determination of sulfadimidine from real milk samples.

  14. Colloidal GdVO4:Eu3+@SiO2 nanocrystals for highly selective and sensitive detection of Cu2+ ions

    Science.gov (United States)

    Liang, Yanjie; Noh, Hyeon Mi; Park, Sung Heum; Choi, Byung Chun; Jeong, Jung Hyun

    2018-03-01

    Nowadays, in view of health and safety demands, the controlled design of selective and sensitive sensors for Cu2+ detection is of considerable importance. Therefore, we construct herein core-shell colloidal GdVO4:Eu3+@SiO2 nanocrystals (NCs) as optical sensor for the detection of Cu2+, which were synthesized by a facile hydrothermal reaction and encapsulated with a uniform layer of ultrathin silica through a sol-gel strategy. The NCs present strong red emission due to energy transfer from VO43- groups to Eu3+ when exciting with ultraviolet (UV) light. This intense red emission from Eu3+ could be selectively quenched in the presence of Cu2+ in comparison to other metal ions and the limit of detection is as low as 80 nM in aqueous solution. It is revealed that the spectral overlap between the emission band of NCs and the absorption of Cu2+ accounts for this intriguing luminescence behavior. The detection ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA) with the recovery of almost 100% of the original luminescence. The luminescence quenching and recovery processes can be performed repeatedly with good sensing ability. These remarkable performances allow the colloidal GdVO4:Eu3+@SiO2 NCs a promising fluorescence chemosensor for detecting Cu2+ ions in aqueous solution.

  15. Surface molecular imprinting on hybrid SiO2-coated CdTe nanocrystals for selective optosensing of bisphenol A and its optimal design

    Science.gov (United States)

    Qiu, Chunxiao; Xing, Youhong; Yang, Wenming; Zhou, Zhiping; Wang, Yingchun; Liu, Hong; Xu, Wanzhen

    2015-08-01

    Twenty molecular dynamics (MD) simulations of molecular imprinting prepolymerization systems had been performed to optimize the imprinting shell of the fluorescent sensor. The results revealed that the system with a Bisphenol A (BPA): 3-aminopropyltriethoxysilane (APTES): tetraethylorthosilicate (TEOS) mole ratio of 10:15:60 had the most stable template (T)-functional monomer (FM) cluster. Correspondingly, five kinds of imprinted and non-imprinted polymers were synthesized to assess the reliability and validity of the simulation results. Hybrid SiO2-coated CdTe NCs (HS-QD) were synthesized by a simple reflux procedure including a sol-gel reaction that resulted in the formation of a hybrid SiO2 layer with CdS-like clusters on a CdTe core. Based on the optimal component ratio of the prepolymerization system, MIP shells were anchored on the surface of HS-QD to build a fluorescent MIP sensor. A linear relationship between relative fluorescence intensity and the concentration of BPA had been obtained covering the concentration range of 0.05-10 μmol L-1 with a limit of detection of 6 nmol L-1. The feasibility of the fluorescent sensor was successfully evaluated through the analysis of BPA in river water and milk. The recoveries are above 96.31%, and the relative standard deviation (RSD) ranged from 1.55% to 2.78%.

  16. Facile synthesis of SiO2@CuxO@TiO2 heterostructures for catalytic reductions of 4-nitrophenol and 2-nitroaniline organic pollutants

    Science.gov (United States)

    Zelekew, Osman Ahmed; Kuo, Dong-Hau

    2017-01-01

    Herein, we designed the p-type CuxO (x = 1 or 2) nanoparticles deposited on SiO2 spherical particle inside and coated with thin layered n-type TiO2 semiconductors outside for reduction purpose. The composite material, abbreviated as SiO2@CuxO@TiO2, was characterized. The catalytic performance of the composite was tested for the reductions of 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA). Complete reductions of 4-NP and 2-NA took, 210 and 150 s, respectively. The catalytic efficiency of the composite material may be associated with electron and hole separation resulted from the p-n junction formation between p-type CuxO and n-type TiO2 and the built-in electric field. Moreover, the hydride ion and electrons released from NaBH4 together with outward electrons from n-type TiO2, synergistically, are also responsible for the reduction of nitro aromatic compounds. Our design of composite material from low-priced metal oxides was successful towards reduction of nitro-aromatic compounds.

  17. A theoretical study on the thermal oxidation of silicon carbide: Chemical species at the SiO2/SiC interface

    Science.gov (United States)

    Tajima, Nobuo; Kaneko, Tomoaki; Nara, Jun; Yamasaki, Takahiro; Schimizu, Tatsuo; Kato, Koichi; Ohno, Takahisa

    Silicon carbide (SiC) is potentially a suitable candidate of the channel materials of power devices since it has wide bandgap, high electron mobility, and thermal conductivity. Furthermore, it is favorable for device fabrication as it can be thermally oxidized to create insulating silicon oxide (SiO2) layer. However, the SiC devices of current technology do not show acceptable performance because of a defective nature of the created SiO2/SiC stacking structure, which causes problems such as channel mobility degradation, threshold voltage increase, and leakage current. The origins of the defective nature are not understood so far, though it is presumed that they are rather concentrated at the interface. In the present study, we have performed first principles calculations to know the chemical species possibly produced at the oxide interface of thermally oxidized SiC. The First principles simulation code PHASE/0 (http://www.ciss.iis.u-tokyo.ac.jp/riss/english/project/device/) was used in the theoretical calculations. A portion of this research was supported by the Grant from MEXT's project and carried out in partnership with the University of Tokyo.

  18. TiO2 nanoparticles doped SiO2 films with ordered mesopore channels: a catalytic nanoreactor.

    Science.gov (United States)

    Saha, Jony; Mitra, Anuradha; Dandapat, Anirban; De, Goutam

    2014-04-07

    Titanium dioxide (TiO2) incorporated ordered 2D hexagonal mesoporous silica (SiO2) films on a glass substrate were fabricated for use as a catalytic nanoreactor. Films were prepared using a tetraethyl orthosilicate (TEOS) derived SiO2 sol and a commercially available dispersion of TiO2 nanoparticles (NPs) in the presence of pluronic P123 as the structure directing agent. The effect of TiO2 doping (4-10 mol% with respect to the equivalent SiO2) into the ordered mesoporous SiO2 matrix was thoroughly investigated. The undoped SiO2 film showed a mesostructural transformation after heat-treatment at 350 °C whereas incorporation of TiO2 restricted such a transformation. Among all the TiO2 incorporated films, TEM showed that the 7 equivalent mol% TiO2 doped SiO2 film (ST-7) had an optimal composition which could retain the more organized 2D hexagonal (space group p6mm)-like mesostructures after heat-treatment. The catalytic activities of the TiO2 doped (4-10 mol%) films were investigated for the reduction of toxic KMnO4 in an aqueous medium. ST-7 film showed the maximum catalytic activity, as well as reusability. A TEM study on the resultant solution after KMnO4 reduction revealed the formation of MnO2 nanowires. It was understood that the embedded TiO2 NPs bonded SiO2 matrix increased the surface hydroxyl groups of the composite films resulting in the generation of acidic sites. The catalytic process can be explained by this enhanced surface acidity. The mesoporous channel of the ST-7 films with TiO2 doping can be used as a nanoreactor to form extremely thin MnO2 nanowires.

  19. Robust SiO2-modified CoFe2O4 hollow nanofibers with flexible room temperature magnetic performance.

    Science.gov (United States)

    Jing, Panpan; Pan, Lining; Du, Jinlu; Wang, Jianbo; Liu, Qingfang

    2015-05-21

    A range of robust SiO2-modified CoFe2O4 hollow nanofibers with high uniformity and productivity were successfully prepared via polyvinylpyrrolidone-sol assisted electrospinning followed by annealing at a high temperature of 1000 °C, and they were characterized using scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction and X-ray photoelectron spectroscopy in detail. It was demonstrated that amorphous SiO2 has a significant influence on not only the surface morphology, microstructure and crystalline size but also the room temperature magnetic performance of the inverse spinel CoFe2O4 nanofibers. The pure CoFe2O4 sample shows a particle chain rod-shape appearance but the SiO2-modified CoFe2O4 sample shows a robust hollow fibrous structure. With increasing SiO2 content, an increase at first and then a decrease in coercivity (Hc) and monotonously a decrease in saturation magnetization (Ms) have been determined in the obtained modified CoFe2O4 hollow nanofibers. A maximum Ms of about 80 emu g(-1) and a maximum Hc of about 1477 Oe could be, respectively, acquired from the pure CoFe2O4 nanorods and the modified CoFe2O4 hollow nanofibers with about 14.9% SiO2. The changes in Ms, Hc and the structure evolution mechanism of these SiO2-modified CoFe2O4 hollow nanofibers have been elaborated systematically. Furthermore, it is suggested that amorphous SiO2 enables effectively improving the structure endurance of 1D electrospun inorganic oxide hollow nanostructures being subjected to high temperatures.

  20. Laser Resistance of Ta2O5/SiO2 and ZrO2/SiO2 Optical Coatings under 2 μm Femtosecond Pulsed Irradiation

    Science.gov (United States)

    Liu, Na; Wang, Ying-Jian; Zhou, Ming; Jing, Xu-Feng; Wang, Yan-Zhi; Cui, Yun; Jin, Yun-Xia

    2010-07-01

    Ta2 O5/SiO2 and ZrO2/SiO2 high reflecting (HR) coatings are prepared by ion beam sputtering and electron beam evaporation, respectively. The laser-induced damage thresholds (LIDTs) of these samples are investigated with 2 μm femtosecond pulse lasers (80 fs, 1 kHz). It is found that the Ta1O5/SiO2 HR coating has a higher capability of laser damage resistance than the ZrO2/SiO2 HR coating in the 2 μm femtosecond regime. The scanning electron microscope results show that the damage sites of the ZrO2/SiO2 HR coating have a relatively porous structure, the loose structure of coatings will provide more sites for water molecules, and the LIDTs of HR coatings will be reduced as a result of the strong water absorption at the wavelength of 2μm.

  1. Twisted bi-layer graphene: microscopic rainbows.

    Science.gov (United States)

    Campos-Delgado, J; Algara-Siller, G; Santos, C N; Kaiser, U; Raskin, J-P

    2013-10-11

    Blue, pink, and yellow colorations appear from twisted bi-layer graphene (tBLG) when transferred to a SiO2 /Si substrate (SiO2 = 100 nm-thick). Raman and electron microscope studies reveal that these colorations appear for twist angles in the 9-15° range. Optical contrast simulations confirm that the observed colorations are related to the angle-dependent electronic properties of tBLG combined with the reflection that results from the layered structure tBLG/100 nm-thick SiO2 /Si. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Effect of SiO2, PVA and glycerol concentrations on chemical and mechanical properties of alginate-based films.

    Science.gov (United States)

    Yang, Manli; Shi, Jinsheng; Xia, Yanzhi

    2017-11-01

    Sodium alginate (SA)/polyvinyl alcohol (PVA)/SiO2 nanocomposite films were prepared by in situ polymerization through solution casting and solvent evaporation. The effect of different SA/PVA ratios, SiO2, and glycerol content on the mechanical properties, water content, water solubility, and water vapor permeability were studied. The nanocomposite films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermal stability (thermogravimetric analysis/differential thermogravimetry) analyses. The nanocomposites showed the highest values of mechanical properties, such as SA/PVA ratio, SiO2, and glycerol content was 7:3, 6wt.%, and 0.25g/g SA, respectively. The tensile strength and elongation at break (E%) of the nanocomposites increased by 525.7% and 90.7%, respectively, compared with those of the pure alginate film. The Fourier transform infrared spectra showed a new SiOC band formed in the SA/PVA/SiO2 nanocomposite film. The scanning electron microscopy image revealed good adhesion between SiO2 and SA/PVA matrix. After the incorporation of PVA and SiO2, the water resistance of the SA/PVA/SiO2 nanocomposite film was markedly improved. Transparency decreased with increasing PVA content but was enhanced by adding SiO2. Copyright © 2017. Published by Elsevier B.V.

  3. Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

    Science.gov (United States)

    Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

    2017-09-01

    Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

  4. Preparation and characterization of novel PA6/SiO2 composite microsphere applied for selective laser sintering

    Directory of Open Access Journals (Sweden)

    G. X. Wang

    2018-01-01

    Full Text Available The high cost and less variety of raw materials has greatly restricted the wide application of selective laser sintering (SLS technology. In order to make the material cheaper and more diverse, PA6 is the most preferable material. In this work, a new PA6/SiO2 composite microsphere used for SLS was designed and fabricated. To construct the material, PA6 porous microspheres with diameters of 20–80 µm and a certain pore volume were firstly prepared by the dissolution precipitation method. Then, SiO2 was generated in situ in the PA6 porous microsphere framework, thus achieving a special structured PA6/SiO2 composite microsphere. These microspheres with much well dispersed SiO2 in PA6 matrices formed a powder with high bulk density and good electron conductivity. The particle size and weight fraction of the two components can be well controlled by adjusting the experimental conditions. Differential scanning calorimetry (DSC data showed that the composite powder had a larger sintering window, which would be beneficial for SLS processing. The introduction of SiO2 reduced the rate of water absorption in the composite powder, which could improve the accuracy of SLS forming. This work has certain significance as a reference for the design and development of SLS polymer-based composite materials.

  5. VO x /SiO 2 Catalyst Prepared by Grafting VOCl 3 on Silica for Oxidative Dehydrogenation of Propane

    KAUST Repository

    Zhu, Haibo

    2015-09-07

    The VOx/SiO2 catalysts for oxidative dehydrogenation of propane were synthesized by a simple grafting method. The VOCl3 was first grafted at the surface of SiO2, which was dehydrated at different temperature (from 200 to 1000°C). The formed grafted complexes were then calcined in air, leading to the formation of VOx/SiO2 catalysts. The synthesized catalysts were characterized by nitrogen adsorption, SEM, Raman spectroscopy, temperature-programmed reduction, and extended X-ray absorption fine structure analysis. The SiO2 pretreatment temperature has an evident effect on the loading and dispersion of VOx on SiO2, which finally affects their catalytic performance. High SiO2 treatment temperature is beneficial to dispersing the vanadium oxide species at the SiO2 surface. These materials are efficient catalysts for the catalytic oxidative dehydrogenation of propane to propylene. The best selectivity to propylene is achieved on the VOx/SiO2-(1000) catalyst. The high selectivity and activity are well maintained for three days catalytic reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Magnesium Removal from an Aluminum A-332 Molten Alloy Using Enriched Zeolite with Nanoparticles of SiO2

    Directory of Open Access Journals (Sweden)

    R. Muñoz-Arroyo

    2014-01-01

    Full Text Available In order to improve the Mg removal from an A-380 molten alloy, mixtures of zeolite and SiO2 nanoparticles (SiO2(NPs were tested. Zeolite was enriched with 2.5, 5, 7.5, 10, or 12.5 wt-% of amorphous SiO2(NPs. The SiO2(NPs and zeolite were mixed for 30 min in ethanol for each experiment and then dried in a furnace at 80°C for 12 h. The enriched zeolites were analyzed by scanning electron microscopy, transmission electron microscopy, and N2 gas adsorption analysis. The Mg removal was carried out injecting each mixture into the molten aluminum alloy at 750°C using argon. The Mg content of the molten alloy was measured after different periods of the injection time. Zeolites enriched with 2.5 and 5 wt-% of SiO2(NPs were demonstrated to be the better mixtures, removing Mg from an initial content of 1.6 to a final content of 0.0002 and 0.0101 wt-%, respectively, in 45 min of injection.

  7. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Science.gov (United States)

    Wang, Ling; Zeng, Huidan; Yang, Bin; Ye, Feng; Chen, Jianding; Chen, Guorong; Smith, Andew T.; Sun, Luyi

    2017-01-01

    Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm2), the maximum Stark splitting manifold of 2F7/2 level (781 cm−1), and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers. PMID:28772601

  8. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Directory of Open Access Journals (Sweden)

    Ling Wang

    2017-02-01

    Full Text Available Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms, the highest gain coefficient (1.10 ms·pm2, the maximum Stark splitting manifold of 2F7/2 level (781 cm−1, and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers.

  9. Synthesis of SiO2-Coated Core-Shell ZnO Composites for Preparing High-Voltage Varistors

    Science.gov (United States)

    Qu, Xiao; Yao, Da-Chuan; Liu, Jin-Ran; Wang, Mao-Hua; Zhang, Han-Ping

    2018-01-01

    Monodispersed ZnO composite microspheres were successfully prepared by a facile ultrasound irradiation method. Then, the uniform core-shell structured composites were synthesized through the hydrolysis of tetraethyl orthosilicate on the surface of the ZnO composite microspheres. Microstructural studies of the as-obtained powders were carried out using the techniques of the x-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy with energy dispersive x-ray spectroscopy. The results show that the pink ZnO composite powders as the core were spherical structures with the size of approximately 100 nm, and the SiO2 shell was fully coated on the surface of the core. On the basis of these results, the effect of SiO2 content on the thickness of the synthesized composites and microstructure, as well as the electrical properties of the ZnO varistors sintered in air at 1150°C for 2 h, were fully studied. In particular, the ZnO varistor prepared with the appropriate amount of the SiO2 coating (˜40 nm) leads to a superior electrical performance with the high breakdown voltage of 418 V mm-1 and an excellent nonlinear coefficient of 70.7, compared with the varistors obtained without the SiO2 coating. The high performance is attributed to the smaller and more homogeneous ZnO grains obtained via the SiO2 coating.

  10. Synthesis and Characterization of SiO2-Carbon Nanotube Hybrides Using a Sol-Gel Method

    Directory of Open Access Journals (Sweden)

    N. Montakhab

    2012-10-01

    Full Text Available This work is focused on synthesis of SiO2- CNT hybrides via sol-gel method. Homogeneous distribution of carbon nanotubes within silicon matrix was obtained by mixing the functionalized carbon nanotube (CNTCOOH with active silicic acid followed by titration to the solution of sodium silicate (Na2SiO3 under the average temperature condition of 80?C. Different ratios of multi-walled carbon nanotubes and various concentrations of colloidal silica were used for synthesis of SiO2-CNT. Powder X-Ray Diffraction (XRD and Scanning Electron Microscopy (SEM used for studying the structure and morphological characteristics of the synthesized SiO2-CNT hybrids. The results showed that the various morphologies of SiO2-CNTs are obtained with different ratio of precursors. The SEM images indicated the formation of uniform nanoparticles, nanowires and nanotube structures in various samples. In addition, the hydrogen storage capacity and thermal conductivity of SiO2-CNT hybrides were determined and presented in this article. Also total pore volume and BET surface area were calculated for these composites.

  11. Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

    Directory of Open Access Journals (Sweden)

    Rogéria R. Gonçalves

    1999-01-01

    Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

  12. The influence of SiO2 and SiO2-TiO2 intermediate coatings on bond strength of titanium and Ti6Al4V alloy to dental porcelain.

    Science.gov (United States)

    Bieniaś, Jarosław; Surowska, Barbara; Stoch, Anna; Matraszek, Halina; Walczak, Mariusz

    2009-09-01

    The purpose of this study was to evaluate the bond strength of commercially pure CPTi and Ti6Al4V alloy with SiO2 and SiO2-TiO2 intermediate coatings to Triceram low-fusing dental porcelain. The multilayered systems were characterized from the standpoint of microstructure analysis (SEM), the mode of failure, the nature of bonding and the influence of intermediate coatings on the improvement of bond strength. The SiO2 and SiO2-TiO2 intermediate coatings were applied on the substrate materials by the sol-gel dipping technique. The metal-ceramic bond strength was investigated according to ISO 9693 standards using the three-point flexure bond test. Statistically significant higher bond strength of the metal-porcelain for Ti6A14V alloy (28.24 MPa), Ti6Al4V/SiO2 (32.17 MPa) and Ti6Al4V/SiO2-TiO2 (36.09 MPa) was noted in comparison to CPTi (23.04 MPa), CPTi/SiO2 (27.98 MPa) and CPTi/SiO2-TiO2 (28.84 MPa), respectively. The nature of metal-intermediate coating-porcelain bonding was both mechanical and chemical. The failure in all systems was cohesive and adhesive, mainly adhesive. The application of SiO2 and SiO2-TiO2 intermediate coatings, produced by the sol-gel method, to both CPTi and Ti6Al4V alloy significantly improves the bond strength of metal-porcelain systems in comparison to the metal substrate only after sandblasting, and may have clinical use.

  13. Rational Design and Construction of Well-Organized Macro-Mesoporous SiO2/TiO2 Nanostructure toward Robust High-Performance Self-Cleaning Antireflective Thin Films.

    Science.gov (United States)

    Jin, Binbin; He, Junhui; Yao, Lin; Zhang, Yue; Li, Jing

    2017-05-24

    Antireflection (AR) thin films on optical substrates are of great significance in high-performance optoelectronic devices. Here, we present a rational design and construction of well-organized macro-mesoporous nanostructure toward robust high-performance self-cleaning antireflective thin films on the basis of effective medium theory and finite difference time domain (FDTD) simulations that combine the optical design principle. A hierarchical macro-mesoporous SiO2 thin film with very high porosity and gradient refractive indexes works as a λ/4-wavelength AR layer and significantly suppresses the reflection in the range from 350 to 1200 nm. Even after dip-coating a layer of high refractive index TiO2 nanocrystals, the nanostructured thin film still exhibits broadband AR properties which are much superior to conventional flat SiO2/TiO2 thin films, especially in the range of 350-500 nm. In addition, the obtained thin film exhibits photocatalytic self-cleaning and durable superhydrophilicity. The advantages brought by the well-organized macro-mesoporous structure are also testified through comparing to the solely mesoporous SiO2/TiO2 film counterpart. Moreover, the pencil hardness test and sandpaper abrasion test show favorable robustness and functional durability of the thin film, which make it extremely attractive for practical applications in optical devices, display devices, and photovoltaic cells.

  14. A metal/Ba0.6Sr0.4TiO3/SiO2/Si single film device for charge trapping memory towards a large memory window

    Science.gov (United States)

    Zhang, Yuanyuan; Yang, Tao; Yan, Xiaobing; Zhang, Zichang; bai, Gang; Lu, Chao; Jia, Xinlei; Ding, Bangfu; Zhao, Jianhui; Zhou, Zhenyu

    2017-05-01

    In this study, we present a metal/Ba0.6Sr0.4TiO3/SiO2/Si (MBOS) structure for charge trapping memory, where the single Ba0.6Sr0.4TiO3 film acts as the blocking layer and charge trapping layer. This MBOS device structure demonstrates excellent charge trapping characteristics, a large memory window up to 8.4 V under an applied voltage of ±12 V, robust charge retention of only 4% charge loss after 1.08 × 104 s, fast switching rate, and great program/erase endurance. These attractive features are attributed to the high density of defect states in the Ba0.6Sr0.4TiO3 film and its inter-diffusion interface with SiO2. The properties of defect states in the Ba0.6Sr0.4TiO3 film are investigated through measurements of photoluminescence and photoluminescence excitation spectroscopy. The energy levels of these defect states are found to be distributed between 2.66 eV and 4.05 eV above the valence band. The inter-diffusion at the Ba0.6Sr0.4TiO3/SiO2 interface is observed by high-resolution transmission electron microscopy. More defect sites were created to obtain a better charge trapping capability and retention characteristics.

  15. Emission Mechanisms of Si Nanocrystals and Defects in SiO2 Materials

    Directory of Open Access Journals (Sweden)

    José Antonio Rodríguez

    2014-01-01

    Full Text Available Motivated by the necessity to have all silicon optoelectronic circuits, researchers around the world are working with light emitting silicon materials. Such materials are silicon dielectric compounds with silicon content altered, such as silicon oxide or nitride, enriched in different ways with Silicon. Silicon Rich Oxide or silicon dioxide enriched with silicon, and silicon rich nitride are without a doubt the most promising materials to reach this goal. Even though they are subjected to countless studies, the light emission phenomenon has not been completely clarified. So, a review of different proposals presented to understand the light emission phenomenon including emissions related to nanocrystals and to point defects in SiO2 is presented.

  16. Nitrogen Plasma Processing of SiO2/4H-SiC Interfaces

    Science.gov (United States)

    Modic, A.; Sharma, Y. K.; Xu, Y.; Liu, G.; Ahyi, A. C.; Williams, J. R.; Feldman, L. C.; Dhar, S.

    2014-04-01

    A nitrogen plasma annealing process for gate dielectric applications in 4H-SiC metal oxide semiconductor (MOS) technology has been investigated. This process results in substantially greater interfacial N coverage at the SiO2/4H-SiC interface and lower interface trap densities than the state-of-the-art nitric oxide (NO) annealing process. Despite these exciting results, the field-effect mobility of MOS field-effect transistors (MOSFETs) fabricated by use of this process is very similar to that of NO-annealed MOSFETs. These results emphasize the importance of understanding mobility-limiting mechanisms in addition to charge trapping in next-generation 4H-SiC MOSFETs.

  17. La cascarilla de arroz como fuente de SiO2

    OpenAIRE

    Claudia Andrea Arcos; Diego Macíaz Pinto; Jorge Enrique Rodríguez Páez

    2007-01-01

    La cascarilla de arroz calcinada presenta un alto contenido de sílice. Este trabajo estudió la naturaleza de la fracción orgánica donde se nuclean los complejos de sílice y las condiciones óptimas para la síntesis de SiO2. La cascarilla de arroz y la sílice se analizaron utilizando microscopía electrónica de barrido (MEB), difracción de rayos de X (DRX), infrarrojo con transformada de Fourier (FTIR) y análisis térmico diferencial (ATD). La cascarilla fue tratada con HCl para eliminar impureza...

  18. Effect of CaO/ SiO2 ratio on viscosity and structure of slag

    Directory of Open Access Journals (Sweden)

    L. Řeháčková

    2015-07-01

    Full Text Available The objective of this work is experimental determination of temperature dependences of viscosity of the molten CaO – Al2O3 - SiO2 system and assessment of impact of CaO/SiO2 ratio on viscosity and structure of this system. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. Viscosity was measured in a rotational mode during heating at the rate of 3,3 °C/min in the temperature interval from 1 673 to 1 873 K. Viscosity in the molten oxide system is determined by the internal structure. Exact clarification of the change of structure of the oxide system caused by the increased content of CaO was performed by Fourier transform infrared spectroscopy.

  19. Electrical properties of SiO2-based graphene under monochromatic visible light irradiation

    Science.gov (United States)

    Li, Xiangdi; Liu, Xianming; Cao, Xueying; Zhang, Peng; Lei, Xiaohua; Chen, Weimin

    2017-08-01

    The purpose of this study is to investigate the electrical properties of graphene transparent conductive film under visible light irradiation. Sample in the study is chemical vapor deposition (CVD) growth graphene on the surface of copper foils and then transferred to the SiO2 substrate. Three monochromatic visible lights with wavelength of 635nm, 520nm and 450nm representing red (R), green (G) and blue (B) lights are used as irradiation sources. Results show that the graphene resistances increase slowly under light irradiation with all the three different wavelengths, while decrease slowly after the light is switched off. Light irradiation with higher power density will induce larger relative resistance change. When graphene is irradiated at the same density, blue light irradiation may result in the largest resistance change.

  20. Ultrasonic-Assisted Synthesis of Two t-Butoxycarbonylamino Cephalosporin Intermediates on SiO2

    Directory of Open Access Journals (Sweden)

    Feng Xue

    2016-01-01

    Full Text Available Herein, we describe a facile and high efficient strategy for the synthesis of two forms of the 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-4-carboxylates using ultrasonic irradiation. By SiO2 as weak Lewis acid catalyst, 4-methoxybenzyl 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-carboxylate (Boc-ACLE and benzhydryl 7β-t-butoxycarbonylamino-3-chloromethyl-3-cephem-4-carboxylate (Boc-ACLH were successfully synthesized through the efficient protection of the N-t-butoxycarbonyl (N-Boc, and the reactions occurred at low temperature requiring short reaction times and exhibiting excellent isolated yields (96% and 96.2%, resp.. The advantages of this reaction route including the usage of economical reagents and mild reaction conditions and high isolated yield make the two significant t-butoxycarbonylamino cephalosporin intermediates possible in large-scale production.

  1. Infrared spectroscopic ellipsometry of micrometer-sized SiO2 line gratings

    Science.gov (United States)

    Walder, Cordula; Zellmeier, Matthias; Rappich, Jörg; Ketelsen, Helge; Hinrichs, Karsten

    2017-09-01

    For the design and process control of periodic nano-structured surfaces spectroscopic ellipsometry is already established in the UV-VIS spectral regime. The objective of this work is to show the feasibility of spectroscopic ellipsometry in the infrared, exemplarily, on micrometer-sized SiO2 line gratings grown on silicon wafers. The grating period ranges from 10 to about 34 μm. The IR-ellipsometric spectra of the gratings exhibit complex changes with structure variations. Especially in the spectral range of the oxide stretching modes, the presence of a Rayleigh singularity can lead to pronounced changes of the spectrum with the sample geometry. The IR-ellipsometric spectra of the gratings are well reproducible by calculations with the RCWA method (Rigorous Coupled Wave Analysis). Therefore, infrared spectroscopic ellipsometry allows the quantitative characterization and process control of micrometer-sized structures.

  2. A mechanism for Frenkel defect creation in amorphous SiO2 facilitated by electron injection.

    Science.gov (United States)

    Gao, David Z; El-Sayed, Al-Moatasem; Shluger, Alexander L

    2016-12-16

    Using density functional theory (DFT) calculations we demonstrate how electron injection can facilitate the creation of Frenkel defects in amorphous (a)-SiO2. The precursor sites composed of wide O-Si-O bond angles in amorphous SiO2 act as deep electron traps and can accommodate up to two extra electrons. Trapping of two electrons at these intrinsic sites results in weakening of a Si-O bond and creates an efficient bond breaking pathway for producing neutral O vacancies and [Formula: see text] interstitial ions characterized by low transition barriers. The low barriers for the migration of [Formula: see text] ions of about 0.2 eV facilitate the separation of created defects. This mechanism may have important implications for our understanding of dielectric breakdown and resistance switching in a-SiO2 based electronic and memory devices.

  3. Positive magnetoresistance in Co40Fe40B20/SiO2/Si heterostructure

    KAUST Repository

    Zhang, Y.

    2016-07-20

    Current-perpendicular-to-plane electronic transport properties and magnetoresistance of amorphous Co40Fe40B20/SiO2/Si heterostructures are investigated systematically. A backward diode-like rectifying behavior was observed due to the formation of a Schottky barrier between Co40Fe40B20 and Si. The junction resistance shows a metal-insulator transition with decreasing temperature in both the forward and reverse ranges. A large positive magnetoresistance (MR) of ∼2300% appears at 200 K. The positive MR can be attributed to the magnetic-field-controlled impact ionization process of carriers. MR shows a temperature-peak-type character under a constant bias current, which is related to the spin-dependent barrier in the Si near the interface. © CopyrightEPLA, 2016.

  4. Blue photoluminescence and local structure of Si nanostructures embedded in SiO2 matrices

    Science.gov (United States)

    Zhang, Qi; Bayliss, S. C.; Hutt, D. A.

    1995-04-01

    Strong and stable blue photoluminescence (PL), visible to the naked eye under 0.4 μW of 300 nm and 2.7 μW of 370 nm excitation, has been observed for samples of Si clusters embedded in SiO2 matrices, prepared by rf co-sputtering followed by N2 annealing at 800 °C. Si K-edge extended x-ray absorption fine structure (EXAFS) and near-edge x-ray absorption fine structure (NEXAFS) strongly suggest the existence of Si nanoclusters with crystalline cores in the efficient emitting material. The PL excitation dependence is explained by an increase in the conduction band density of states deep in the band, and the formation of a band tail.

  5. Effects of optical design modifications on thermal performance of a highly reflective HfO2/SiO2/TiO2 three material coating

    Science.gov (United States)

    Ocak, M.; Sert, C.; Okutucu-Özyurt, T.

    2018-02-01

    Effects of layer thickness modifications on laser induced temperature distribution inside three material, highly reflective thin film coatings are studied with numerical simulations. As a base design, a 21 layer coating composed of HfO2, SiO2 and TiO2 layers of quarter wave thickness is considered. First, the laser induced temperature distribution in this base design is obtained. Then the layer thicknesses of the base design are modified and the corresponding temperature distributions in four alternative non-quarter wave coatings are evaluated. The modified thicknesses are determined using an in-house code developed to shift the electric field intensity (EFI) peak from the first high/low layer interface towards the adjacent low index layer that has a higher thermal conductivity, hence, higher laser damage resistance. Meanwhile, the induced increase in the EFI peak is kept at a user defined upper limit. The laser endurance of the base and alternative designs are compared in terms of their estimated temperature distributions. The results indicated that both the peak temperature and the highest interface temperature are decreased by at least 32%, in non-dimensional form, when alternative designs are used instead of the base design. The total reflection of the base design is only decreased from 99.8% to at most 99.4% when alternative designs are used. The study is proved to be successful in improving the laser endurance of three material thin film coatings by lowering the peak and interface temperatures.

  6. PERANAN KATALIS TiO2/SiO2-MONTMORILLONIT PADA REAKSI KONVERSI SITRONELAL MENJADI ISOPULEGOL

    Directory of Open Access Journals (Sweden)

    Is Fatimah

    2012-01-01

    Full Text Available Catalytic conversion of citronellal to isopulegol over TiO2/SiO2-montmorillonite catalyst was studied for citronellal isolated from Cymbopogon leaf oil. The role of physico-chemical characteristics of montmorillonite and SiO2-montmorillonit catalyst on total conversion, activity and selectivity to produce isopulegol was studied. Activity test was conducted for citronellal cyclication for 4 hour. The total conversion, catalyst activity and catalyst selectivity to produce isopulegol were evaluated based on product composition obtained by GC-MS analysis. The experimental result showed that TiO2/SiO2-montmorillonite plays role in the increase of total conversion significantly from 87.80% over SiO2-montmorillonit and 85.38% over natural montmorillonite become 95.53%. Total conversion and selectivity of the catalyst to produce isopulegol increase could be related to Lewis acidity of TiO2/SiO2-montmorillonite, and also specific surface area enhancement. However, in the range of 1:1.25 to 1:5.0 catalyst to citronellal mass ratio, there was no influence on total conversion and selectivity to produce isopulegol. This may be caused by dominant influence of Lewis acidity compared to other physico-chemical characteristic of material. Kinetics study of the reaction showed that TiO2 dispersion on SiO2-montmorillonite almost doubles the reaction rate constant with the factor of 1.955. Konversi katalitik sitronelal menjadi isopulegol menggunakan katalis TiO2/SiO2-montmorillonit dipelajari terhadap sitronelal hasil isolasi minyak daun sereh. Peranan karakter fisikokimiawi material katalis montmorillonit alam dan SiO2-montmorillonit terhadap konversi total, aktivitas dan selektivitas dalam pembentukan isopulegol dipelajari. Uji aktivitas katalis dilakukan pada reaksi siklisasi sitronelal selama 4 jam. Konversi total, aktivitas katalis dan selektivitas terhadap isopulegol dihitung berdasar perubahan komposisi hasil reaksi yang ditentukan menggunakan GC-MS. Hasil penelitian menunjukkan bahwa katalis TiO2/SiO2-montmorillonit berperanan meningkatkan konversi total reaksi secara signifikan dari sebesar 87,80% pada penggunaan SiO2-montmorillonit dan 85,38% dengan menggunakan montmorillonit alam menjadi sebesar 95,53%. Peningkatan konversi total dan selektivitas terhadap isopulegol berkaitan dengan keasaman Lewis yang dimiliki oleh TiO2/SiO2-montmorillonit serta peningkatan luas permukaan spesifik material. Namun pada rentang perbandingan massa katalis terhadap sitronelal 1:1,25 hingga 1:5,0 tidak berpengaruh signifikan terhadap konversi total dan selektivitas produk isopulegol. Hal ini mungkin disebabkan peranan keasaman Lewis lebih dominan terhadap sifat-sifat fisikokimiawi material katalis. Studi kinetika reaksi menunjukkan bahwa dispersi TiO2 pada SiO2-montmorillonit meningkatkan konstanta laju reaksi dengan faktor sebesar 1,955. 

  7. Polysilicic acid gel method derived V2O5/SiO2 composite materials: Synthesis and characterization

    Science.gov (United States)

    Wang, Dawei; Zhou, Linzong; Feng, Xiaofei; Zhao, Ning; Yang, Bin

    2017-01-01

    The V2O5/SiO2 composite was prepared by a sol-gel method followed a sintering procedure. The low-cost Na2SiO3•9H2O was used as silicon source, while NH4VO3 was used as vanadium source. By adding NH4VO3 to Na2SiO3 solution and adjusting the mixture's pH with saturated (NH4)2SO4 solution the polysilicic acid gel was formed to give a homogeneous gel composite with VO3-well-distributed in it. The gel composite was dried at 100 °C to give the xerogel, then the xerogel was calcined in air to obtain the V2O5/SiO2 composite. The V2O5/SiO2 composites were characterized by SEM analysis, FT-IR spectroscopy and powder X-ray diffractions.

  8. Fiber-optic thermometry using thermal radiation from Tm end doped SiO2 fiber sensor.

    Science.gov (United States)

    Morita, Kentaro; Katsumata, Toru; Komuro, Shuji; Aizawa, Hiroaki

    2014-04-01

    Fiber-optic thermometry based on temperature dependence of thermal radiation from Tm(3+) ions was studied using Tm end doped SiO2 fiber sensor. Visible light radiation peaks due to f-f transition of Tm(3+) ion were clearly observed at λ = 690 and 790 nm from Tm end doped SiO2 fibers sensor at the temperature above 600 °C. Thermal radiation peaks are assigned with f-f transition of Tm(3+) ion, (1)D2-(3)H6, and (1)G4-(3)H6. Peak intensity of thermal radiation from Tm(3+) ion increases with temperature. Intensity ratio of thermal radiation peaks at λ = 690 nm against that at λ = 790 nm, I790/690, is suitable for the temperature measurement above 750 °C. Two-dimensional temperature distribution in a flame is successfully evaluated by Tm end doped SiO2 fiber sensor.

  9. Effect of SiO2 nanoparticles on the removal of natural organic matter (NOM) by coagulation.

    Science.gov (United States)

    Xue, Nan; Wang, Xue; Zhang, Furong; Wang, Yan; Chu, Yongbao; Zheng, Ying

    2016-06-01

    In order to evaluate effect of engineered nanoparticles on the removal of natural organic matter (NOM), ENPs water sample (WATERNP), and common water sample (WATERCOMMON) were prepared by mixing the SiO2 nanoparticles (SiO2 NPs, 50 nm) and common SiO2 particles (2 μm) with water from Xiaoqing River. The removal variation, NOM fractionation, flocs properties, and IR spectra were investigated after polyaluminum chloride (PAC) coagulation. The results revealed that although the removal efficiencies of turbidity and NOM from WATERNP were moderately lower than those from WATERCOMMON, the fluorescence intensities of soluble microbial byproduct-like, humic acid-like, and aromatic protein II in coagulated WATERNP were lower than that in coagulated raw water and WATERCOMMON. What's more, flocs of WATERNP showed the smallest size and highest fractal dimension as compared with other water samples, except for those obtained at B = 2.0.

  10. Silver nanoparticle deposition on inverse opal SiO2 films embedded in protective polypropylene micropits for SERS applications

    Science.gov (United States)

    Ammosova, Lena; Ankudze, Bright; Philip, Anish; Jiang, Yu; Pakkanen, Tuula T.; Pakkanen, Tapani A.

    2018-01-01

    Common methods to fabricate surface enhanced Raman scattering (SERS) substrates with controlled micro-nanohierarchy are often complex and expensive. In this study, we demonstrate a simple and cost effective method to fabricate SERS substrates with complex geometries. Microworking robot structuration is used to pattern a polypropylene (PP) substrate with micropits, facilitating protective microenvironment for brittle SiO2 inverse opal (IO) structure. Hierarchical SiO2 IO patterns were obtained using polystyrene (PS) spheres as a sacrificial template, and were selectively embedded into the hydrophilized PP micropits. The same microworking robot technique was subsequently used to deposit silver nanoparticle ink into the SiO2 IO cavities. The fabricated multi-level micro-nanohierarchy surface was studied to enhance Raman scattering of the 4-aminothiophenol (4-ATP) analyte molecule. The results show that the SERS performance of the micro-nanohierarchical substrate increases significantly the Raman scattering intensity compared to substrates with structured 2D surface geometries.

  11. Synthesis of suitable SiO2 nano particles as the core in core-shell nanostructured materials.

    Science.gov (United States)

    Ghahari, Mehdi; Aghababazadeh, Roya; Ebadzadeh, Touradj; Mirhabibi, Alireza; Brydson, Rik; Fabbri, Paola; Najafi, Farhod

    2011-06-01

    The effect of surfactant on the luminescent intensity of SiO2 @Y2O3:Eu3+ particles with a core shell structure is described. Core-shell particles are used in phosphor materials and employing spherical particles with a narrow size distribution is vital for the enhancement of luminescent properties. Three kinds of different surfactants were used to synthesis SiO2 nano particles via a sol gel process. The results demonstrated that comb polycarboxylic acid surfactant had a significant influence on the morphology and particle size distribution. Somehow, particles with 100 nm size and narrow size distribution were produced. These particles had relatively uniform packing, unlike particles produced with other surfactants or without surfactant which had irregular assembly. The photoluminescence intensity of SiO2 @Y2O3:Eu3+ particles that was synthesized by comb polycarboxylic acid surfactant was higher than those which were produced without surfactant.

  12. Electronic band gap reduction and intense luminescence in Co and Mn ion-implanted SiO2

    Science.gov (United States)

    Green, R. J.; Zatsepin, D. A.; St. Onge, D. J.; Kurmaev, E. Z.; Gavrilov, N. V.; Zatsepin, A. F.; Moewes, A.

    2014-03-01

    Cobalt and manganese ions are implanted into SiO2 over a wide range of concentrations. For low concentrations, the Co atoms occupy interstitial locations, coordinated with oxygen, while metallic Co clusters form at higher implantation concentrations. For all concentrations studied here, Mn ions remain in interstitial locations and do not cluster. Using resonant x-ray emission spectroscopy and Anderson impurity model calculations, we determine the strength of the covalent interaction between the interstitial ions and the SiO2 valence band, finding it comparable to Mn and Co monoxides. Further, we find an increasing reduction in the SiO2 electronic band gap for increasing implantation concentration, due primarily to the introduction of Mn- and Co-derived conduction band states. We also observe a strong increase in a band of x-ray stimulated luminescence at 2.75 eV after implantation, attributed to oxygen deficient centers formed during implantation.

  13. Synthesis and photolysis of NaYF4@SiO2@TiO2 core-shell nanocomposites

    Science.gov (United States)

    Shi, Guoyou; Mao, Yifu; Ren, Guozhong; Gong, Lunjun; Zhi, Zhugong

    2014-12-01

    Monodisperse β-NaYF4 nanocrystals were synthesized with oleic acid as capping ligands by solvothermal method, and then, SiO2 and TiO2 were coated successively. Intense ultraviolet light is emitted from NaYF4:Yb/Tm under the 980 nm laser and the intensity of ultraviolet light reduce dramatically after these nanocrystals were coated with SiO2 and TiO2 shells, which means NaYF4@SiO2@TiO2 core-shell nanocomposites can be used to realize the infared photocatalysis. Photocatalytic activity of these nanocomposites is demonstrated using methyl orange (MO) as a chemical probe under the 980 nm laser excitation.

  14. ACr2O4 /SiO2 (A = Zn, Cu, Cd) nanocomposites, their preparation and physical properties

    Science.gov (United States)

    Holec, Petr; Poltierova Vejpravova, Jana; Plocek, Jiri; Nemec, Ivan; Kitazawa, Hideaki; Niznansky, Daniel

    2011-10-01

    This article presents preparation and characterization of zinc, copper and cadmium chromites nanocrystals embedded in a silica matrix. The ZnCr2O4/SiO2, CuCr2O4/SiO2 and CdCr2O4/SiO2 samples were prepared by a conventional sol-gel method using HNO3 as an acid catalyst, formamide as a modifier, methanol as a solvent and TEOS. Final heat treatment of the nanocomposites was carried out at temperatures in the range of 900 - 1100°C. The resulting samples were characterized by X-ray diffraction, High Resolution Transmission Electron Microscopy, and magnetic measurements.

  15. Biotemplated Mesoporous TiO2/SiO2 Composite Derived from Aquatic Plant Leaves for Efficient Dye Degradation

    Directory of Open Access Journals (Sweden)

    Zhiying Yan

    2017-03-01

    Full Text Available The biotemplating technique is an environmental-protective high-efficiency new technology by which the resulting TiO2 may simultaneously attain the duplication of structure and self-doping elements from biotemplate materials, which is highly desirable for photocatalytic applications. In this paper, aquatic plant leaves—including reed, water hyacinth, and duckweed—were used as both templates and silicon precursors to successfully synthesize biomorphic TiO2/SiO2 composite with mesoporous structures. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption–desorption, and UV–visible diffuse reflectance spectra were applied to characterize the microstructures of the samples. The results show that all TiO2/SiO2 composites are mainly composed of an anatase phase with mesoporous structure and possess high specific surface area. Compared with commercial Degussa P25 TiO2, all TiO2/SiO2 samples display intensive light-harvesting efficiency, particularly in the visible light range. The activities were evaluated by using gentian violet as a target for photocatalytic degradation experiments under simulated solar irradiation. The TiO2/SiO2 samples templated by reed and water hyacinth leaves exhibit high activity, while the TiO2/SiO2 samples obtained from duckweed are inferior to P25 in the degradation of gentian violet. A synergistic effect of SiO2 incorporation and structural construction through biotemplating is proposed to be beneficial to photocatalytic activity.

  16. Zn-vapor diffused Er:Yb:LiNbO 3 channel waveguides fabricated by means of SiO 2 electron cyclotron resonance plasma deposition

    Science.gov (United States)

    Pernas, P. L.; Hernández, M. J.; Ruíz, E.; Cantelar, E.; Nevado, R.; Morant, C.; Lifante, G.; Cussó, F.

    2000-07-01

    We report here the fabrication method and operation of Zinc-vapor diffused channel waveguides on Erbium/Ytterbium (Er/Yb)-doped Lithium Niobate (LiNbO 3). electron cyclotron resonance (ECR) plasma deposition technique, UV photolithography and Reactive Ion Etching (RIE) are used to define an SiO 2 mask for pattern transfer. The whole process is performed at low temperatures eliminating typical LiO 2 out-diffusion problems and achieving low surface damage. The flexibility of the fabrication technology has been shown to be potentially applicable to integrated optics. EDAX measurements reveal good confinement and homogeneity of the diffused regions. Atomic Force Microscopy (AFM) surface characterization shows the swelling of the diffused areas, consistent with the topoepitaxial growth of a Zn xLi yNb zO w layer.

  17. Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

    DEFF Research Database (Denmark)

    Abel, Brett M.; Morgan, James M.; Mauro, John C.

    2013-01-01

    Despite the important role of strontium aluminosilicate glasses in various technologies, there is no available phase diagram for this ternary system in the ACerS-NIST Phase Equilibria Diagrams Database. Establishing the liquidus surface (liquidus temperature Tliq and primary devitrification phase...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...

  18. Flexible SiO2 cantilevers for torsional self-aligning micro scale four-point probes

    DEFF Research Database (Denmark)

    Kjær, Daniel; Gammelgaard, Lauge; Bøggild, Peter

    2007-01-01

    In order to successfully measure the conductivity of a sample with a four- point probe, good alignment of the electrodes to the sample is important to establish even contact pressure and contact areas of the electrodes. By incorporating a hinge in a microfabricated SiO2 mono- cantilever the abili...... by proper dimensioning and placement of the hinge. Furthermore, it is shown that polymeric macro scale cantilever models can provide a fast and reliable understanding of the mechanical deflection properties of microfabricated SiO2 cantilevers....

  19. Determination of CaCO 3 and SiO 2 content in the binders of historic lime mortars

    OpenAIRE

    Uğurlu Sağın, Elif; Böke, Hasan; Aras, Nadir; Yalçın, Şerife

    2012-01-01

    The binders of historic mortars composed of small grain sized silica (SiO 2) and carbonated lime (CaCO 3) are considered as the main part that give hydraulic character and high strength to the mortar. In this study, FTIR, SEM-EDS, LIBS and XRD spectroscopy were used to find out the weight ratios of CaCO 3 to SiO 2 in the binders of historic lime mortars. For this purpose, a series of pure calcium carbonate and silica mixture were prepared in ten combinations in varying ratios from 0.5 to 5. C...

  20. Facile preparation of polyethylenimine-tannins coated SiO2 hybrid materials for Cu2+ removal

    Science.gov (United States)

    Huang, Qiang; Liu, Meiying; Zhao, Jiao; Chen, Junyu; Zeng, Guangjian; Huang, Hongye; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2018-01-01

    Polyethylenimine-tannins coated SiO2 (SiO2@PEI-TA) hybrid materials have been prepared via a single-step multifunctional coating with polyethylenimine (PEI) and tannins (TA), and characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The as-prepared SiO2@PEI-TA composites were examined as adsorbents to remove the Cu2+ from aqueous solution. The effects of contact time, initial Cu2+ concentration, solution pH and temperature, on Cu2+ adsorption have been investigated. The results show that the adsorption of Cu2+ onto SiO2@PEI-TA is dependent on the contact time, Cu2+ concentration, pH and temperature. The SiO2@PEI-TA composites show a 2.4-fold increase in adsorption capacity, implying that the introduction of PEI-TA coating is in favor of the Cu2+ adsorption. Based on the analysis of kinetic data, the kinetics of Cu2+ adsorption is more accurately described by the pseudo-second-order model. The equilibrium data are analyzed by Langmuir and Freundlich isotherms. Results of isotherms show that the better agreement is Freundlich isotherm model with correlation coefficient of 0.9914, which suggests that the adsorption of Cu2+ onto SiO2@PEI-TA is mainly a heterogeneous adsorption process. Thermodynamic analyses show that the adsorption interaction is actually a spontaneous and endothermic chemical process, which might involve the chemical chelation between Cu2+ and functional groups (amine and carboxyl groups) on the surface of SiO2@PEI-TA. In addition, the Cu2+ ions could desorb from SiO2@PEI-TA by using acid solution and the adsorption efficiency remains at high level after five adsorption-desorption recycles. These results provide potential applications of these novel adsorbents for the removal of heavy metal Cu2+ from aqueous solution and also provide strong evidence to support the adsorption mechanism proposed in the study.

  1. Adsorption of alcohols on a two-dimensional SiO2 single crystal - Alcohol adsorption on silicatene

    Science.gov (United States)

    Nayakasinghe, M. T.; Sivapragasam, N.; Burghaus, U.

    2017-12-01

    The adsorption kinetics of alcohols (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol) was studied on monoatomic, two-dimensional SiO2 single crystals (silicatene) using thermal desorption spectroscopy (TDS). Silicatene was grown on Mo(1 1 2) at ultra-high vacuum. In contrast to Mo, the alcohols physisorb molecularly on the hydrophobic SiO2/Mo surface. Zero coverage binding energies vary from 46.5 to 65.5 kJ/mol and increase with molecular size. Silicatene was characterized by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and water TDS.

  2. Synthesis of SiO2-Coated Fe3O4 Nanoparticles Using Ultrasound and Its Application in DNA Extraction from Formalin-Fixed, Paraffin-Embedded Human Cancer Tissues

    Science.gov (United States)

    Hieu, Nguyen Minh; Nam, Nguyen Hoang; Huyen, Nguyen Thi; Van Anh, Nguyen Thi; Nghia, Phan Tuan; Khoa, Nguyen Ba; Toan, Nguyen Linh; Luong, Nguyen Hoang

    2017-06-01

    SiO2-coated Fe3O4 nanoparticles (Fe3O4@SiO2 NPs) were successfully synthesized using ultrasound in order to extract DNA from cancer tissues for application in diagnostics. The core 10.7-nm-diameter Fe3O4 nanoparticles were synthesized by co-precipitation of Fe3+ and Fe2+ as reaction substrates and NH4OH as precipitant, then coated with a thin layer of amorphous silica by a modified Stober method. Further SiO2 coating using alkaline hydrolysis of tetraethyl orthosilicate in ethanol and water mixture was accelerated in the presence of a 37-kHz ultrasound, resulting in the NPs having different sizes of 14.5 nm (version M1), 24.4 nm (version M2), and 34.9 nm (version M3) with saturation magnetization values of 50.2 emu/g, 18.6 emu/g, 10.3 emu/g, respectively. Among the three Fe3O4@SiO2 NPs versions, the M1 NPs allowed extraction of DNAs from 10 mg formalin-fixed and paraffin-embedded (FFPE) tissues of nasopharyngeal carcinoma patients with the highest recovery of about 100-500 ng/ μl and good purity (A260/A280: 1.8-1.9). The extracted DNAs could be used as templates for downstream amplification of 252-bp sequencing specifically for the Braf cancer biomarker gene using polymerase chain reaction (PCR), as well as detection of the pathogenic Epstein-Barr virus (EBV) and the human papilloma-virus (HPV) using real-time PCR. DNA extraction recoveries of both EBV and HPV using Fe3O4@SiO2 NPs M1 were significantly better that those using commercialized Fe3O4@SiO2 microbeads, as indicated by lower threshold cycles of all fluorescent signals including fluorescein amidite (FAM) dye representative for EBV infection, hexachlorofluorescein (HEX) dye representative for β-globin (internal control), and SYBR Green dye representative for HPV infection in tested clinical samples from patients with nasopharyngeal carcinoma (NPC).

  3. The influence of SiO2 Addition on 2MgO-Al2O3-3.3P2O5 Glass

    DEFF Research Database (Denmark)

    Larsen, P.H.; Poulsen, F.W.; Berg, Rolf W.

    1999-01-01

    2MgO-Al2O3-3.3P2O5 glasses with increasing amounts of SiO2 are considered for sealing applications in Solid Oxide Fuel Cells (SOFC). The change in chemical durability under SOFC anode conditions and the linear thermal expansion is measured as functions of the SiO2 concentration. Raman spectroscop...... analysis of the glasses reveals no sign of important changes in the glass structure upon SiO2 addition. Some increase in glass durability with SiO2 concentration is reported and its cause is discussed.......2MgO-Al2O3-3.3P2O5 glasses with increasing amounts of SiO2 are considered for sealing applications in Solid Oxide Fuel Cells (SOFC). The change in chemical durability under SOFC anode conditions and the linear thermal expansion is measured as functions of the SiO2 concentration. Raman spectroscopy...

  4. THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

    Directory of Open Access Journals (Sweden)

    В. Судавцова

    2012-04-01

    Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

  5. Acid-Base Properties Of Glass Substrate And SiO2 - Bi2O3 Thin-Film Systems Obtained On It

    Science.gov (United States)

    Mal'chik, A. G.; Litovkin, S. V.; Filonov, A. V.; Ulyanova, O. V.; Gromov, V. E.

    2017-01-01

    The article describes an experimental research as a result of which SiO2 - Bi2O3 films have been synthesized of film-forming solutions based on tetraethoxysilane and bismuth nitrate (III). Acid-base properties of a glass substrate and SiO2 - Bi2O3 films obtained on it have been studied. The dependency of physical and chemical properties of SiO2 - Bi2O3 composites on their percentage composition have been revealed.

  6. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    Science.gov (United States)

    Bahrami, A.; Pech-Canul, M. I.; Gutiérrez, C. A.; Soltani, N.

    2015-12-01

    A study of the wetting behavior of three substrate types (SiC, SiO2-derived RHA and SiC/SiO2-derived RHA) by two Al-Si-Mg alloys using the sessile drop method has been conducted, using amorphous and crystalline SiO2 in the experiment. Mostly, there is a transition from non-wetting to wetting contact angles, being the lowest θ values achieved with the alloy of high Mg content in contact with amorphous SiO2. The observed wetting behavior is attributed to the deposited Mg on the substrates. A strong diffusion of Si from the SiC/Amorphous RHA substrate into the metal drop explains the free Si segregated at the drop/substrate interface and drop surface. Although incorporation of both SiO2-derived RHA structures into the SiC powder compact substrates increases the contact angles in comparison with the SiC substrate alone, the still observed acute contact angles in RHA/SiC substrates make them promising for fabrication of composites with high volume fraction of reinforcement by the pressureless infiltration technique. The observed wetting characteristics, with decrease in surface tension and contact angles is explained by surface related phenomena. Based on contact angle changes, drop dimensions and surface tension values, as well as on the interfacial elemental mapping, and XRD analysis of substrates, some wetting and reaction pathways are proposed and discussed.

  7. PENGUJIAN AKTIVITAS KOMPOSIT Fe2O3-SiO2 SEBAGAI FOTOKATALIS PADA FOTODEGRADASI 4-KLOROFENOL (The Activity Test of Fe2O3-SiO2 Composite As Photocatalyst on 4-Chlorophenol Photodegradation

    Directory of Open Access Journals (Sweden)

    Eko Sri Kunarti

    2009-03-01

    Full Text Available ABSTRAK  Pada penelitian ini telah dilakukan pengujian aktivitas komposit Fe2O3-SiO2 sebagai fotokatalis pada fotodegradasi 4-klorofenol. Penelitian diawali dengan preparasi dan karakterisasi fotokatalis Fe2O3-SiO2. Preparasi dilakukan dengan metode sol-gel pada temperatur kamar menggunakan tetraetil ortosilikat (TEOS dan besi (III nitrat sebagai prekursor diikuti dengan perlakuan termal pada temperature 500 oC. Karakterisasi dilakukan dengan metode spektrometri inframerah, difraksi sinar-X dan spektrometri fluoresensi sinar-X. Uji aktivitas komposit untuk fotodegradasi 4-klorofenol dilakukan dalam reaktor tertutup yang dilengkapi dengan lampu UV. Pada uji ini telah dipelajari pengaruh waktu penyinaran dan pH larutan terhadap efektivitas fotodegradasi 4-klorofenol. Hasil penelitian menunjukkan bahwa komposit Fe2O3-SiO2 dapat dipreparasi dengan metode sol-gel pada temperatur kamar diikuti perlakuan termal. Komposit Fe2O3-SiO2 dapat meningkatkan efektivitas fotodegradasi 4-klorofenol dari 11,86 % menjadi 55,38 %. Efektivitas fotodegradasi 4- klorofenol dipengaruhi waktu penyinaran dan pH larutan yang semakin lama waktu penyinaran efektifitas fotodegradasi semakin tinggi, namun waktu penyinaran yang lebih lama dari 4 jam dapat menurunkan efektivitasnya. pH larutan memberikan pengaruh yang berbeda-beda pada efektivitas fotodegradasi 4-klorofenol.   ABSTRACT The activity test of Fe2O3-SiO2 composite as photocatalyst on 4-chlorophenol photodegradation has been studied. The research was initiated by preparation of Fe2O3-SiO2 photocatalyst and followed by characterization. The preparation was conducted by sol-gel method at room temperature using tetraethylorthosilicate (TEOS and iron (III nitrate as precursors followed by thermal treatment at a temperature of 500oC. The characterizations were performed by X-ray Diffraction (XRD, Infrared and X-ray Fluorescence Spectrophotometry. The photocatalytic activity test of composites for 4 chlorophenol degradation was carried out in a closed reactor equipped with UV light. In this test, the influences of irradiation time and 4-chlorophenol pH were studied.  Results showed that the composite could be prepared through sol-gel method. The Fe2O3-SiO2 composite could increase activity of 4-chlorophenol photodegradation from 11.86 % to 55.38 %. The photodegradation effectiveness was influenced by irradiating time and pH of solution. The pH of solution gave different 4-chlorophenol photodegradation effectiveness.

  8. Preparation of Nano-TiO2-Coated SiO2 Microsphere Composite Material and Evaluation of Its Self-Cleaning Property

    Directory of Open Access Journals (Sweden)

    Sijia Sun

    2017-11-01

    Full Text Available In order to improve the dispersion of nano-TiO2 particles and enhance its self-cleaning properties, including photocatalytic degradation of pollutants and surface hydrophilicity, we prepared nano-TiO2-coated SiO2 microsphere composite self-cleaning materials (SiO2–TiO2 by co-grinding SiO2 microspheres and TiO2 soliquid and calcining the ground product. The structure, morphology, and self-cleaning properties of the SiO2–TiO2 were characterized. The characterization results showed that the degradation efficiency of methyl orange by SiO2–TiO2 was 97%, which was significantly higher than that obtained by pure nano-TiO2. The minimum water contact angle of SiO2–TiO2 was 8°, indicating strong hydrophilicity and the good self-cleaning effect. The as-prepared SiO2–TiO2 was characterized by the nano-TiO2 particles uniformly coated on the SiO2 microspheres and distributed in the gap among the microspheres. The nano-TiO2 particles were in an anatase phase with the particle size of 15–20 nm. The nano-TiO2 particles were combined with SiO2 microspheres via the dehydroxylation of hydroxyl groups on their surfaces.

  9. Multifunctional, angle dependent antireflection, and hydrophilic properties of SiO2 inspired by nano-scale structures of cicada wings

    Science.gov (United States)

    Zada, Imran; Zhang, Wang; Sun, Peng; Imtiaz, Muhammad; Abbas, Waseem; Zhang, Di

    2017-10-01

    Inspired by the multifunctional properties of cicada wings, we have precisely replicated biomorphic SiO2 with antireflective structures (ARSs) using a simple, inexpensive, and highly effective sol-gel ultrasonic method. The biomorphic replica of SiO2 was directly achieved from a cicada template at high calcination. The biomorphic SiO2 not only inherited the ARS effectively but also exhibited the excellent angle dependent antireflective properties over a wide range of incident angles (10°-60°). The change in reflectance spectra (visible wavelength) of biomorphic SiO2 was observed from 0.3% to 3.3% with the increasing incident angles. The smooth surface of the SiO2 crystal without nanostructures showed a high reflection of 9.2% compared to the biomorphic SiO2 with ARS. These excellent antireflective properties of biomorphic SiO2 can be attributed to the nanoscale structures which introduce a gradient in the refractive index between air and the material surface via ARS. In the meantime, biomorphic SiO2 demonstrates high hydrophilic properties due to the existence of nanostructures on its surface. These multifunctional properties of biomorphic SiO2, angle dependent antireflective properties, and hydrophilicity with high thermal stability may have potential applications in solar cells and antifogging optical materials.

  10. Preparation of Nano-TiO2-Coated SiO2 Microsphere Composite Material and Evaluation of Its Self-Cleaning Property

    Science.gov (United States)

    Sun, Sijia; Deng, Tongrong; Ding, Hao; Chen, Ying; Chen, Wanting

    2017-01-01

    In order to improve the dispersion of nano-TiO2 particles and enhance its self-cleaning properties, including photocatalytic degradation of pollutants and surface hydrophilicity, we prepared nano-TiO2-coated SiO2 microsphere composite self-cleaning materials (SiO2–TiO2) by co-grinding SiO2 microspheres and TiO2 soliquid and calcining the ground product. The structure, morphology, and self-cleaning properties of the SiO2–TiO2 were characterized. The characterization results showed that the degradation efficiency of methyl orange by SiO2–TiO2 was 97%, which was significantly higher than that obtained by pure nano-TiO2. The minimum water contact angle of SiO2–TiO2 was 8°, indicating strong hydrophilicity and the good self-cleaning effect. The as-prepared SiO2–TiO2 was characterized by the nano-TiO2 particles uniformly coated on the SiO2 microspheres and distributed in the gap among the microspheres. The nano-TiO2 particles were in an anatase phase with the particle size of 15–20 nm. The nano-TiO2 particles were combined with SiO2 microspheres via the dehydroxylation of hydroxyl groups on their surfaces. PMID:29099774

  11. Homogeneous synthesis of SiO2@TiO2 nanocomposites with controllable shell thickness and their enhanced photocatalytic activity.

    Science.gov (United States)

    Yu, Yong; Zhang, Ming-Zhen; Chen, Jun; Zhao, Yuan-Di

    2013-01-28

    Here we report the use of sulfuric acid as a catalyst for the facile and homogeneous synthesis of core-shell SiO(2)@TiO(2) nanocomposites using simple apparatus, under ambient pressure and temperature. The resultant SiO(2)@TiO(2) exhibits an ideal core-shell structure with uniform nanoscale TiO(2) coverage. The shell thickness of SiO(2)@TiO(2) can be conveniently tuned through adjustment of the esterification reaction parameters. Moreover, SiO(2)@TiO(2) shows improved catalytic activity in the photodegradation of methyl orange.

  12. Nanocristales de silicio en matriz de SiO2 para aplicaciones fotónicas

    Directory of Open Access Journals (Sweden)

    Morante, J. R.

    2004-04-01

    Full Text Available We describe in this work the development of both materials and technology approaches that have allowed us to successfully produce efficient and reliable LEDs by using only CMOS processes. Si nanocrystals (Si-nc were synthesised in SiO2 by ion implantation plus annealing and display average diameters from 2.5 to 6 nm. Wide photoluminescence around 700-800 (red nm is present in all the samples. The most efficient structures have Si-ncs with average size of 3 nm and densities of 1019 cm-3. We have estimated band-gap energies, lifetimes (20-200 μs and absorption cross-sections (10-15-10-16 cm2 as a function of size and surface passivation. From highly luminescent Si-nc, LEDs consisting of MOS capacitors were fabricated. Stable red electroluminescence has been obtained at room temperature and the I-V characteristics prove that the current is related to a pure tunnelling process.En este trabajo describimos la tecnología y los materiales empleados en la fabricación de nanocristales de silicio (Si-nc para obtener dispositivos luminiscentes usando procesos compatibles con la tecnología CMOS. Los nanocristales de Silicio se sintetizaron a partir de una implantación iónica sobre SiO2 y un posterior recocido, consiguiendo una distribución de tamaños que varia desde 2.5 a 6 nm dependiendo de la dosis de implantación. Todas las muestras presentan una fotoluminiscencia ancha alrededor de 700-800 nm (rojo, que se desplaza fuertemente con el tamaño medio de los nanocristales. Las estructuras más eficientes presentan una tamaño promedio de 3 nm, con una densidad de 1019 cm-3. En cuanto a fotoluminiscencia, se ha hecho una estimación de las energías del gap, de las vidas medias (20-200 μs y las secciones eficaces de absorción (10-15-10-16 cm2 en función del tamaño y de la pasivación de la superficie de los nanocristales. En estructuras tipo MOS con Si-nc se obtuvo electroluminiscencia muy fuerte y estable a temperatura ambiente. Las curvas I-V muestran que la corriente es debida puramente a un mecanismo de efecto túnel.

  13. Structural and optical studies of BiFeO3@SiO2 core/shell nanoparticles

    Science.gov (United States)

    Nayak, S.; C, Mahender; Soam, Ankur; Nanda, J.

    2017-10-01

    Sol-gel synthesized bismuth ferrite (BiFeO3) nanoparticles (NPs) were encapsulated with SiO2 by the Stöber method. The structural and microstructural studies were carried out by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The XRD pattern revealed the coating of SiO2 on distorted rhombohedral (R3c) structured BiFeO3 (BFO). The particle size of BFO was estimated to be 100–120 nm. The inter-planar spacing between the (1 1 0) planes was found to be 0.28 nm. The coating of amorphous SiO2 shell on crystalline BFO was quite evident from the TEM micrographs. The presence of O–Si–O stretching vibration in FTIR spectra reconfirmed the coating of SiO2. The direct bandgap energy was calculated to be 2.02 eV for BFO and 2.12 eV for BFO@SiO2 (from UV–vis spectra). The optical absorption was observed to be higher for BFO@SiO2 than BFO. These NPs may be used as photoelectrodes in dye sensitized solar cell application.

  14. Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

    Science.gov (United States)

    Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

    2018-01-01

    Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 ( D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 ( D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 ( x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant ( ɛ r > 7.19) and extremely low moisture absorption (<0.02%) were obtained, resulting from the relatively high density of the composites. The ceramic particles served as barriers and improved the thermal stability of the PTFE polymer, retarding its decomposition. The temperature coefficient of dielectric constant ( τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

  15. Modification of Nafion membrane with biofunctional SiO2 nanofiber for proton exchange membrane fuel cells

    Science.gov (United States)

    Wang, Hang; Li, Xiaojie; Zhuang, Xupin; Cheng, Bowen; Wang, Wei; Kang, Weimin; Shi, Lei; Li, Hongjun

    2017-02-01

    Proton currents are an integral part of the most important energy-converting structures in biology. We prepared a new type of bioinspired Nafion (Bio-Nafion) membrane composited of biofunctional SiO2 (Bio-SiO2) nanofiber and Nafion matrix. SiO2 nanofibers were prepared by electrospinning silica sol prepared from tetraethyl orthosilicate. Meanwhile, Bio-SiO2 nanofibers were synthesized by immobilizing amino acids (cysteine, serine, lysine, and glycine) on SiO2 nanofibers, which acted as efficient proton-conducting pathways that involved numerous H+ transport sites. In our study, the SiO2 nanofibers biofunctionalized with cysteine were further oxidized, and the composite membranes were designated as Nafion-Cys, Nafion-Lys, Nafion-Ser, and Nafion-Gly, respectively. We then investigated the different polar groups (sbnd SO3H, sbnd OH, and sbnd NH2) of the amino acids that contributed to membrane properties of thermal stability, water uptake (WU), dimensional stability, proton conductivity, and methanol permeability. Nafion-Cys exhibited the highest proton conductivity of 0.2424 S/cm (80 °C). Nafion-Gly showed the lowest proton conductivity and WU because glycine contains the least number of hydrophilic groups among the amino acids. Overall, the introduction of Bio-SiO2 nanofiber to composite membranes significantly improved proton conductivity, dimensional stability, and methanol permeability.

  16. Novel nanofluidic chemical cells based on self-assembled solid-state SiO2 nanotubes

    Science.gov (United States)

    Zhu, Hao; Li, Haitao; Robertson, Joseph W. F.; Balijepalli, Arvind; Krylyuk, Sergiy; Davydov, Albert V.; Kasianowicz, John J.; Suehle, John S.; Li, Qiliang

    2017-10-01

    Novel nanofluidic chemical cells based on self-assembled solid-state SiO2 nanotubes on silicon-on-insulator (SOI) substrate have been successfully fabricated and characterized. The vertical SiO2 nanotubes with a smooth cavity are built from Si nanowires which were epitaxially grown on the SOI substrate. The nanotubes have rigid, dry-oxidized SiO2 walls with precisely controlled nanotube inner diameter, which is very attractive for chemical-/bio-sensing applications. No dispersion/aligning procedures were involved in the nanotube fabrication and integration by using this technology, enabling a clean and smooth chemical cell. Such a robust and well-controlled nanotube is an excellent case of developing functional nanomaterials by leveraging the strength of top-down lithography and the unique advantage of bottom-up growth. These solid, smooth, clean SiO2 nanotubes and nanofluidic devices are very encouraging and attractive in future bio-medical applications, such as single molecule sensing and DNA sequencing.

  17. Highly selective chemical mechanical polishing of Si3N4 over SiO2 using advanced silica abrasive

    Science.gov (United States)

    Bae, KiHo; Baek, Kye Hyun; Kim, JaeSeok; Kim, Hoyoung; Yoon, Bo Un; Kim, Jae Jeong

    2017-05-01

    Highly selective chemical mechanical polishing (CMP) of Si3N4 over SiO2 is achieved by using a modified silica abrasive. Controlling the removal rate of Si3N4/SiO2, chemical reaction is a dominant factor for ceria abrasive, but physical force such as repulsion/attraction is a primary one for silica abrasive. In order to maximize mechanical action in CMP process using silica slurry, we modified the surface charge of silica abrasive into having more negative charge, which resulting in -50 mV of zeta potential in a low pH (< 3.0) slurry. This strong negative zeta potential of the modified silica abrasive enables enhancing attractive forces to Si3N4 and repulsive forces to SiO2 in a low pH environment. In addition, a cocoon shape silica abrasive shows 3 times higher Si3N4 RR than a spherical shape one. Consequently, selectivity of Si3N4 over SiO2 reaches 95.0, which is significantly improved from 0.0167 in the conventional silica abrasive case. When this modified silicon abrasive and the optimum pH condition are applied, in-chip uniformity at various pattern densities of Si3N4 (0, 12, and 32%) turns out to be well controlled under 100 Å. This result is an acceptable level for our semiconductor device integration.

  18. Intermetallic GaPd2 Nanoparticles on SiO2 for Low-Pressure CO2 Hydrogenation to Methanol

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria; Sharafutdinov, Irek; Carvalho, Hudson W. P.

    2015-01-01

    A nanodispersed intermetallic GaPd2/SiO2 catalyst is prepared by simple impregnation of industrially relevant high-surface-area SiO2 with Pd and Ga nitrates, followed by drying, calcination, and reduction in hydrogen. The catalyst is tested for CO2 hydrogenation to methanol at ambient pressure......, revealing that the intrinsic activity of the GaPd2/SiO2 is higher than that of the conventional Cu/ZnO/Al2O3, while the production of the undesired CO is lower. A combination of complementary in situ and ex situ techniques are used to investigate the GaPd2/SiO2 catalyst. In situ X-ray diffraction...... of exactly the same catalyst area recorded at the different steps of activation and reaction procedure) show that nanoparticle size and dispersion are defined upon calcination with no significant changes observed after reduction and methanol synthesis. Similar conclusions can be drawn from electron...

  19. Microstructural evolution during high energy ball milling of Fe2O3-SiO2 powders

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Zhou, Y.X.; Mørup, Steen

    1996-01-01

    of 15 nm have formed and no reaction between alpha-Fe2O3 and SiO2 is found in the two types of milling containers. This demonstrates that the high energy mechanical milling technique is able to prepare a dispersion of ultrafine alpha-Fe2O3 particles. After extended milling in the open container all iron...

  20. In situ XANES study on TiO2-SiO2 aerogels and flame made materials

    DEFF Research Database (Denmark)

    Grunwaldt, J.D.; Beck, C.; Stark, W.

    2002-01-01

    The structures of TiO2-SiO2 based aerogels and flame made particles, used as epoxidation catalysts, are compared by X-ray absorption near edge structure (XANES) spectroscopy and in situ XANES during dehydration of the calcined catalyst samples. The results are interpreted in terms of the titanium...

  1. Covalent Incorporation of SiO2 Nanoparticles in CO2-Based Copolymers: Synthesis, Characterization, Morphology and Property Studies.

    Science.gov (United States)

    Tran, Thi Nga; Mai, Thanh Binh; Bach, Long Giang; Islam, Md Rafiqul; Gal, Yeong Soon; Lim, Kwon Taek

    2015-01-01

    A new strategy has been developed for covalent incorporation of SiO2 nanoparticles (N-'s) in the CO2-based copolymer, poly(propylene carbonate-co-propylene oxide) (poly(PC-co-PO)). The poly(PC-co-PO)-g-SiO2 nanocomposites was prepared by the combination of epoxy-CO2 ring-opening polymerization and the condensation reaction of chloride and hydroxyl groups of the polymer and the SiO2 surface. FT-IR and NMR were employed for the characterization of the copolymers as well as nanocomposites. A uniform and spherical core-shell structure of poly(PC-co-PO)-g-SiO2 nanocomposites was demonstrated from TEM and SEM images. An improved thermal property of the polymer matrix with incorporating SiO2 nanoparticles was revealed by TGA study. The grafting of poly(PC-co-PO) considerably prevented the aggregation and improved the dispersibility of SiO2 nanoparticles in toluene.

  2. Porous SiO2/HAp Coatings on Cp-Titanium Grade 1 Surfaces Produced by Electrophoretic Deposition

    Directory of Open Access Journals (Sweden)

    Moskalewicz T.

    2016-12-01

    Full Text Available Porous hydroxyapatite doped SiO2 coatings were electrophoretically deposited (EPD on commercially pure titanium. The influence of EPD parameters on coatings quality was investigated. Microstructural observation was done using transmission and scanning electron microscopy as well as X-ray diffractometry.

  3. Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

    Science.gov (United States)

    Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

    2017-10-01

    Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 (D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 (D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 (x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant (ɛ r > 7.19) and extremely low moisture absorption (polymer, retarding its decomposition. The temperature coefficient of dielectric constant (τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

  4. Synthesis, characterization and luminescence of europium perchlorate with MABA-Si complex and coating structure SiO2@Eu(MABA-Si) luminescence nanoparticles.

    Science.gov (United States)

    Fu, Zhi-Fang; Li, Wen-Xian; Bai, Juan; Bao, Jin-Rong; Cao, Xiao-Fang; Zheng, Yu-Shan

    2017-05-01

    This article reports a novel category of coating structure SiO 2 @Eu(MABA-Si) luminescence nanoparticles (NPs) consisting of a unique organic shell, composed of perchlorate europium(III) complex, and an inorganic core, composed of silica. The binary complex Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O was synthesized using HOOCC 6 H 4 N(CONH(CH 2 ) 3 Si(OCH 2 CH 3 ) 3 ) 2 (MABA-Si) and was used as a ligand. Furthermore, the as-prepared silica NPs were successfully coated with the -Si(OCH 2 CH 3 ) 3 group of MABA-Si to form Si-O-Si chemical bonds by means of the hydrolyzation of MABA-Si. The binary complexes were characterized by elemental analysis, molar conductivity and coordination titration analysis. The results indicated that the composition of the binary complex was Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O. Coating structure SiO 2 @Eu(MABA-Si) NPs were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and infrared (IR) spectra. Based on the SEM and TEM measurements, the diameter of core-SiO 2 particles was ~400 and 600 nm, and the thickness of the cladding layer Eu(MABA-Si) was ~20 nm. In the binary complex Eu(MABA-Si) 3 ·(ClO 4 ) 3 ·5H 2 O, the fluorescence spectra illustrated that the energy of the ligand MABA-Si transferred to the energy level for the excitation state of europium(III) ion. Coating structure SiO 2 @Eu(MABA-Si) NPs exhibited intense red luminescence compared with the binary complex. The fluorescence lifetime and fluorescence quantum efficiency of the binary complex and of the coating structure NPs were also calculated. The way in which the size of core-SiO 2 spheres influences the luminescence was also studied. Moreover, the luminescent mechanisms of the complex were studied and explained. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Volume labeling with Alexa Fluor dyes and surface functionalization of highly sensitive fluorescent silica (SiO2) nanoparticles

    Science.gov (United States)

    Wang, Wei; Nallathamby, Prakash D.; Foster, Carmen M.; Morrell-Falvey, Jennifer L.; Mortensen, Ninell P.; Doktycz, Mitchel J.; Gu, Baohua; Retterer, Scott T.

    2013-10-01

    A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or ``free'' surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface-modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems. Electronic supplementary information (ESI) available: Cell culture preparation for dose/response imaging experiments. See DOI: 10.1039/c3nr02639f

  6. Improving thermal insulation of TC4 using YSZ-based coating and SiO2 aerogel

    Directory of Open Access Journals (Sweden)

    Lei Jin

    2015-04-01

    Full Text Available In this paper, air plasmas spray (APS was used to prepare YSZ and Sc2O3–YSZ (ScYSZ coating in order to improve the thermal insulation ability of TC4 alloy. SiO2 aerogel was also synthesized and affixed on TC4 titanium alloy to inhabit thermal flow. The microstructures, phase compositions and thermal insulation performance of three coatings were analyzed in detail. The results of thermal diffusivity test by a laser flash method showed that the thermal diffusivities of YSZ, Sc2O3–YSZ and SiO2 aerogel are 0.553, 0.539 and 0.2097×10−6 m2/s, respectively. Then, the thermal insulation performances of three kinds of coating were investigated from 20 °C to 400 °C using high infrared radiation heat flux technology. The experimental results indicated that the corresponding temperature difference between the top TC4 alloy (400 °C and the bottom surface of YSZ is 41.5 °C for 0.6 mm thickness coating. For 1 mm thickness coating, the corresponding temperature difference between the top TC4 alloys (400 °C and the bottom surface of YSZ, ScYSZ, SiO2 aerogel three specimens is 54, 54.6 and 208 °C, respectively. The coating thickness and species were found to influence the heat insulation ability. In these materials, YSZ and ScYSZ exhibited a little difference for heat insulation behavior. However, SiO2 aerogel was the best one among them and it can be taken as protection material on TC4 alloys. In outer space, SiO2 aerogel can meet the need of thermal insulation of TC4 of high-speed aircraft.

  7. Study the Effect of SiO2 Based Flux on Dilution in Submerged Arc Welding

    Science.gov (United States)

    kumar, Aditya; Maheshwari, Sachin

    2017-08-01

    This paper highlights the method for prediction of dilution in submerged arc welding (SAW). The most important factors of weld bead geometry are governed by the weld dilution which controls the chemical and mechanical properties. Submerged arc welding process is used generally due to its very easy control of process variables, good penetration, high weld quality, and smooth finish. Machining parameters, with suitable weld quality can be achieved with the different composition of the flux in the weld. In the present study Si02-Al2O3-CaO flux system was used. In SiO2 based flux NiO, MnO, MgO were mixed in various proportions. The paper investigates the relationship between the process parameters like voltage, % of flux constituents and dilution with the help of Taguchi’s method. The experiments were designed according to Taguchi L9 orthogonal array, while varying the voltage at two different levels in addition to alloying elements. Then the optimal results conditions were verified by confirmatory experiments.

  8. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj

    2014-07-22

    A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

  9. Potassium ions in SiO2: electrets for silicon surface passivation

    Science.gov (United States)

    Bonilla, Ruy S.; Wilshaw, Peter R.

    2018-01-01

    This manuscript reports an experimental and theoretical study of the transport of potassium ions in thin silicon dioxide films. While alkali contamination was largely researched in the context of MOSFET instability, recent reports indicate that potassium ions can be embedded into oxide films to produce dielectric materials with permanent electric charge, also known as electrets. These electrets are integral to a number of applications, including the passivation of silicon surfaces for optoelectronic devices. In this work, electric field assisted migration of ions is used to rapidly drive K+ into SiO2 and produce effective passivation of silicon surfaces. Charge concentrations of up to ~5  ×  1012 e cm‑2 have been achieved. This charge was seen to be stable for over 1500 d, with decay time constants as high as 17 000 d, producing an effectively passivated oxide–silicon interface with SRV  <  7 cm s‑1, in 1 Ω cm n-type material. This level of charge stability and passivation effectiveness has not been previously reported. Overall, this is a new and promising methodology to enhance surface passivation for the industrial manufacture of silicon optoelectronic devices.

  10. Crystallization of a Li2O2SiO2 Glass under High Hydrostatic Pressures

    Science.gov (United States)

    Fuss, T.; Day, D. E.; Lesher, C. E.; Ray, C. S.

    2004-01-01

    The crystallization behavior of a Li2O.2SiO2 (LS2) glass subjected to a uniform hydrostatic pressure of 4.5 or 6 GPa was investigated between 550 and 800 C using XRD, IR, Raman, TEM, NMR, and DTA. The density of the glass subjected to 6 GPa was between 2.52 plus or minus 0.01 and 2.57 plus or minus 0.01 grams per cubic centimeters, depending upon the processing temperatures, and was higher than that of the stoichiometric LS2 crystals, 2.46 plus or minus 0.01 grams per cubic centimeter. Thus, crystallization in 6 GPa glass occurred in a condition of negative volume dilatation, deltaV = V(sub glass) - V(sub crystal), while that for the 4.5 GPa glass occurred in the condition deltaV greater than 0. For deltaV greater than 0, which also includes the control glass at ambient (one atmosphere) pressure, the glasses always crystallize Li2Si2O5 (orthorhombic, Ccc2) crystals, but for deltaV less than 0 (6 GPa), the glasses crystallize Li2SiO3 crystals with a slightly deformed structure. The crystal growth rate vs. temperature curve moved to higher temperature with increasing pressure, and was independent of the sign of deltaV. These results for the effect of hydrostatic pressure on the crystallization of LS2 glass were discussed from thermodynamic considerations.

  11. Enhanced functionalization of Mn2O3@SiO2 core-shell nanostructures

    Directory of Open Access Journals (Sweden)

    Vaidya Sonalika

    2011-01-01

    Full Text Available Abstract Core-shell nanostructures of Mn2O3@SiO2, Mn2O3@amino-functionalized silica, Mn2O3@vinyl-functionalized silica, and Mn2O3@allyl-functionalized silica were synthesized using the hydrolysis of the respective organosilane precursor over Mn2O3 nanoparticles dispersed using colloidal solutions of Tergitol and cyclohexane. The synthetic methodology used is an improvement over the commonly used post-grafting or co-condensation method as it ensures a high density of functional groups over the core-shell nanostructures. The high density of functional groups can be useful in immobilization of biomolecules and drugs and thus can be used in targeted drug delivery. The high density of functional groups can be used for extraction of elements present in trace amounts. These functionalized core-shell nanostructures were characterized using TEM, IR, and zeta potential studies. The zeta potential study shows that the hydrolysis of organosilane to form the shell results in more number of functional groups on it as compared to the shell formed using post-grafting method. The amino-functionalized core-shell nanostructures were used for the immobilization of glucose and L-methionine and were characterized by zeta potential studies.

  12. Ordered Ag nanocluster structures by vapor deposition on pre-patterned SiO2.

    Science.gov (United States)

    Numazawa, Satoshi; Ranjan, Mukesh; Heinig, Karl-Heinz; Facsko, Stefan; Smith, Roger

    2011-06-08

    Highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO(2) surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well separated. Computer modeling of the growth has been performed with a lattice-based kinetic Monte Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag adatoms and ≈1 nm square surface migration ranges of Ag adatoms. It is also shown that metal nucleations can trigger even on defect free surfaces. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.

  13. The thermoluminescence response of doped SiO2 optical fibres subjected to fast neutrons.

    Science.gov (United States)

    Hashim, S; Bradley, D A; Saripan, M I; Ramli, A T; Wagiran, H

    2010-01-01

    This paper describes a preliminary study of the thermoluminescence (TL) response of doped SiO(2) optical fibres subjected to (241)AmBe neutron irradiation. The TL materials, which comprise Al- and Ge-doped silica fibres, were exposed in close contact with the (241)AmBe source to obtain fast neutron interactions through use of measurements obtained with and without a Cd filter (the filter being made to entirely enclose the fibres). The neutron irradiations were performed for exposure times of 1-, 2-, 3-, 5- and 7-days in a neutron tank filled with water. In this study, use was also made of the Monte Carlo N-particle (MCNP) code version 5 (V5) to simulate the neutron irradiations experiment. It was found that the commercially available Ge-doped and Al-doped optical fibres show a linear dose response subjected to fast neutrons from (241)AmBe source up to seven days of irradiations. The simulation performed using MCNP5 also exhibits a similar pattern, albeit differing in sensitivity. The TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre, the total absorption cross section for Ge in both the fast and thermal neutrons region being some ten times greater than that of Al. Copyright 2009 Elsevier Ltd. All rights reserved.

  14. Growth of ultra-thin SiO2 by laser-induced oxidation

    Science.gov (United States)

    Kailath, Binsu J.; Das Gupta, Amitava; Das Gupta, Nandita; Singh, B. N.; Kukreja, L. M.

    2009-10-01

    Pulsed laser-induced oxidation (LIO) has been suggested as an emerging technique to grow SiO2 at room temperature. LIO of silicon in a mixture of oxygen and nitrogen under different proportions has been studied in detail. The effect of the partial pressure of oxygen and nitrogen gases on the quality as well as the thickness of the oxide grown has been studied. Also, the oxidation has been carried out in the presence of dc discharge inside the growth chamber and its effect on the oxide properties has been discussed. Higher values of ramped breakdown field strength, characteristic life-time and lower leakage current have been obtained for oxide grown in the presence of dc discharge. However, LIO without dc discharge offers a significant advantage in terms of the thickness of the oxide grown. The optimized LIO process has been used to grow ultra-thin (<1 nm) oxide on silicon with good control and the electrical characteristics of the resulting MIS structure have been studied in detail.

  15. Mechanism of quantum dot luminescence excitation within implanted SiO2:Si:C films.

    Science.gov (United States)

    Zatsepin, A F; Buntov, E A; Kortov, V S; Tetelbaum, D I; Mikhaylov, A N; Belov, A I

    2012-02-01

    Results of the investigation of photoluminescence (PL) mechanisms for silicon dioxide films implanted with ions of silicon (100 keV; 7 × 10(16) cm(-2)) and carbon (50 keV; 7 × 10(15)-1.5 × 10(17) cm(-2)) are presented. The spectral, kinetic and thermal activation properties of the quantum dots (Si, C and SiC) formed by a subsequent annealing were studied by means of time-resolved luminescence spectroscopy under selective synchrotron radiation excitation. Independent quantum dot PL excitation channels involving energy transfer from the SiO(2) matrix point defects and excitons were discovered. A resonant mechanism of the energy transfer from the matrix point defects (E' and ODC) is shown to provide the fastest PL decay of nanosecond order. The critical distances (6-9 nm) of energy transport between the bulk defects and nanoclusters were determined in terms of the Inokuti-Hirayama model. An exchange interaction mechanism is realized between the surface defects (E(s)'-centres) and the luminescent nanoparticles. The peculiarities of an anomalous PL temperature dependence are explained in terms of a nonradiative energy transfer from the matrix excitons. It is established that resonant transfer to the luminescence centre triplet state is realized in the case of self-trapped excitons. In contrast, the PL excitation via free excitons includes the stages of energy transfer to the singlet state, thermally activated singlet-triplet conversion and radiative recombination.

  16. Natural CaO-TiO2-SiO2 based ceramics

    Directory of Open Access Journals (Sweden)

    Jelena Pantić

    2011-06-01

    Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

  17. Nd3+-doped colloidal SiO2 composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

    Science.gov (United States)

    Liu, Tingting; Lei, Hong

    2017-08-01

    Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd3+-doped colloidal SiO2 composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd3+-doped colloidal SiO2 composite abrasives and the silica cores were coated by shells (which contains SiO2, Nd2Si2O7 and Nd(OH)3) via chemical bonds and hydrogen bonds in the Nd3+-doped colloidal SiO2 composite abrasives, which made the composite abrasives' core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd3+-doped colloidal SiO2 composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd3+-doped colloidal SiO2 composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO2, Nd2Si2O7 and Nd(OH)3) of Nd3+-doped colloidal SiO2 composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd3+-doped colloidal SiO2 composite abrasives exhibited lower surface roughness and higher material removal rate (MRR) than the pure colloidal SiO2 abrasives in the same polishing conditions, which was attributed to the solid-state chemical reactions between shells of Nd3+-doped colloidal SiO2 composite abrasives and sapphire.

  18. Improved performance of Bis-GMA/TEGDMA dental composites by net-like structures formed from SiO2 nanofiber fillers.

    Science.gov (United States)

    Wang, Xiaoyan; Cai, Qing; Zhang, Xuehui; Wei, Yan; Xu, Mingming; Yang, Xiaoping; Ma, Qi; Cheng, Yali; Deng, Xuliang

    2016-02-01

    The major objective of this study was to explore the effects of silicon dioxide (SiO2) nanofibers on the performance of 2, 2-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA)/tri-(ethyleneglycol) dimethacrylate (TEGDMA) dental composites. At first, the mechanical properties of Bis-GMA/TEGDMA (50/50, w/w) resins containing different contents of SiO2 nanofibers were evaluated to identify the appropriate composition to achieve the significant reinforcing effect. Secondly, optimized contents (5 or 10wt.%) of SiO2 nanofibers were mixed into resins together with SiO2 microparticles, which was 60wt.% of the resin. Controls for comparison were Bis-GMA/TEGDMA resins containing only SiO2 microparticles (60wt.%) or with additional SiO2 nanoparticles (5 or 10wt.%). Properties including abrasion, polymerization shrinkage and mechanical properties were evaluated to determine the contribution of SiO2 nanofibers. In comparison with SiO2 nanoparticles, SiO2 nanofibers improved the overall performance of Bis-GMA/TEGDMA composite resins, especially in improving abrasion resistance and decreasing polymerization shrinkage. The explanations were that one-dimensional SiO2 nanofibers were able to shield particular fillers from being abraded off, and able to form a kind of overlapped fibrous network to resist polymerization shrinkage. With these approaches, SiO2 nanofiber-containing Bis-GMA composite resins were envisioned a promising choice to achieve long-term durable restorations in clinical therapies. Copyright © 2015. Published by Elsevier B.V.

  19. Luminescence dependence of Pr3+ activated SiO2 nanophosphor on Pr3+ concentration, temperature, and ZnO incorporation

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-08-01

    Full Text Available Green-emitting ZnO nanoparticles were successfully embedded in Pr3+-doped SiO2 by a sol–gel method resulting in a red-emitting ZnO·SiO2:Pr3+ nanocomposite phosphor. The particle morphology and luminescent properties of SiO2:Pr3+ phosphor powders...

  20. SiC/C composites prepared from wood-based carbons by pulse current sintering with SiO2 : Electrical and thermal properties

    NARCIS (Netherlands)

    Fujisawa, M; Hata, T; Bronsveld, P; Castro, [No Value; Tanaka, F; Kikuchi, H; Furuno, T; Imamura, Y

    2004-01-01

    A powder mix of wood charcoal and SiO2 was sintered into a SiC/C composite. The heat treatment temperatures were 1400-1800 degreesC, the SiO2 concentration 0, 10, 30 and 50 wt.% with respect to the dry weight of wood charcoal. The microstructure, electrical resistance and thermal conductivity were

  1. Influence of Poly (Ethylene Glycol) and Oleylamine on the Formation of Nano to Micron Size Spherical SiO2 Particles

    Science.gov (United States)

    We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO2 particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO2 particles are controlled by adjusting the concentration...

  2. Dehydration of glucose to 5-hydroxymethylfurfural by a core-shell Fe3O4@SiO2-SO3H magnetic nanoparticle catalyst

    Science.gov (United States)

    This paper discusses the potential use of (Fe3O4@SiO2-SO3H) nanoparticle catalyst for the dehydration of glucose into 5-hydroxymethylfurfural (HMF). A magnetically recoverable (Fe3O4@SiO2-SO3H) nanoparticle catalyst was successfully prepared by supporting sulfonic acid groups (SO3H) on the surface o...

  3. Ethoxy and silsesquioxane derivatives of antimony as dopant precursors: unravelling the structure and thermal stability of surface species on SiO2.

    Science.gov (United States)

    Alphazan, T; Florian, P; Thieuleux, C

    2017-03-22

    We report here the controlled preparation of SiO2 supported Sb-(mono)layers and their thorough characterization by in situ IR, solid-state NMR and elemental analyses. This study allows for the molecular understanding of the surface Sb species derived from the grafting of ethoxy and polyhedral oligomeric silsesquioxane antimony derivatives as mono- or bi-podal Sb(iii) surface species depending on the number of surface SiOH groups. This result is different from what was observed with the phosphorus analogue (POSS-P) that yielded P(v) species. A monolayer coverage of Sb species onto silica was also obtained using both POSS-Sb and the [Sb(OEt)3]2 derivative with surface densities ranging from ∼0.3 Sb nm-2 to 1.8 Sb nm-2, respectively. It is noteworthy that under optimized conditions, a layer of antimony species or suboxides on silica was produced using POSS-Sb without significant Sb loss, highlighting the protective properties of the POSS cage. These results open new perspectives for the controlled and non-destructive Sb-doping (Molecular Layer Doping) of semiconductors dedicated to nano-device applications.

  4. Yolk-shell Fe(0)@SiO2 nanoparticles as nanoreactors for fenton-like catalytic reaction.

    Science.gov (United States)

    Liu, Chao; Li, Jiansheng; Qi, Junwen; Wang, Jing; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

    2014-08-13

    Yolk-shell nanoparticles (YSNs) with active metal cores have shown promising applications in nanoreactors with excellent catalytic performance. In this work, Fe(0)@SiO2 YSNs were synthesized by a sequential "two-solvents" impregnation-reduction approach. Specifically, FeSO4 aqueous solution was introduced into the preformed hollow mesoporous silica spheres (HMSS), dispersed in n-hexane, via a "two-solvent" impregnation way. Subsequently, aqueous solution of sodium borohydride (NaBH4) was introduced into the cavity of HMSS by the same way, leading to the formation of Fe core inside the HMSS through the reaction between Fe(2+) and NaBH4. The resulting Fe(0)@SiO2 YSNs possess distinctive structures, including active cores, accessible mesoporous channels, protective shells, and hollow cavities. To present the catalytic performance of YSNs nanoreactors, Fenton-like catalytic oxidation of phenol was chosen as the model catalysis reaction. In addition to the Fe(0)@SiO2 YSNs, two other materials were also applied to the catalytic system for comparison, including Fe@SiO2 composites with iron nanoparticles sticking on the outer shells of HMSS (Fe@SiO2-DI) and bare iron nanoparticles without HMSS (bare Fe(0)), respectively. The catalytic results show that Fe(0)@SiO2 YSNs exhibit higher catalytic rate toward phenol removal at 2-fold and 4-fold as compared to that of Fe@SiO2-DI and bare Fe(0), indicating the outstanding catalytic property of YSNs nanoreactors. To further clarify the relationship between catalytic properties and structural characteristics, the adsorption experiments of the three samples were also performed in the absence of H2O2. Other than catalytic results, Fe(0)@SiO2 YSNs show slightly higher adsorption efficiency than the other two samples, indicating the accessibility of nanoreactors. This result demonstrates that the removal of phenol in the oxidation system of Fe(0)@SiO2 YSNs may have contributed to the structure-enhanced effect of YSNs as nanoreactors.

  5. Distribution of D1 dislocation luminescence centers in Si+-implanted silicon and the photoluminescence model

    Directory of Open Access Journals (Sweden)

    Sergeyi N. Nagornykh

    2015-06-01

    Full Text Available Using step-by-step removal of silicon layers, in which dislocation-related photoluminescence is observed after Si+ (100 keV, 1·1015 cm−2 ion implantation followed by high-temperature annealing in a chlorine containing atmosphere, it has been found that a majority of dislocation-related centers of luminescence at ~1.5 μm (D1 line is localized at the depths of Si+ ion ranges. Cross-sectional electron microscopy shows that the dislocations introduced by the implantation treatment (implantation plus annealing penetrate to depths of ~1 μm. A phenomenological model of the D1-line dislocation-related luminescence is developed based on the assumption that the K-centers and modified A-centers located in the atmospheres of dislocations are responsible for this luminescence line. The temperature dependence of luminescence intensity calculated on the basis of the model fits well the experimental data for the D1 line.

  6. Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@SiO2/TiO2 for reusing of textile wastewater

    Directory of Open Access Journals (Sweden)

    Laleh Enayati Ahangar

    2016-01-01

    Full Text Available In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2 under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions. A large range of cationic, anionic and neutral dyes including: methyl orange, methylene blue, neutral red, bromocresol green and methyl red are used for treatment investigations. Neutral red and bromocresol green have good results in reusing treatment. The high surface area of nanocomposites improve the kinetic of wastewater treatment. In this method, by using the magnetic properties of Fe3O4 nanoparticles, TiO2-based photocatalyst could be separated and reused for 3 times. The efficiency of this method is respectively 100% and 65% for low concentration (10 ppm and high concentration (50 ppm of neutral red and bromocrosol green after 3 h treatment. The efficiency of treatment using the second used nanocomposite was 90% for 10 ppm of the same dyes.

  7. Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

    Directory of Open Access Journals (Sweden)

    Zhuk Sergey I.

    2017-01-01

    Full Text Available Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6, KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic voltammetry. Тhe electroreduction of Si(IV to metallic Si was observed as a single 4-electron wave under all considered conditions. The reactions of cathode reduction of silicon from fluoride and oxyfluoride complexes were suggested. It was shown that the process can be controlled by the preliminary transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current density on structure and morphology of silicon deposits obtained during galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.

  8. Highly sensitive and thermal stable CO gas sensor based on SnO2 modified by SiO2.

    Science.gov (United States)

    Zhan, Zili; Chen, Juling; Guan, Shaokang; Si, Lifen; Zhang, Pengshuai

    2013-02-01

    Effects of surface chemical modification with SiO2 on the thermal stability and CO gas-sensing properties of SnO2 were investigated. The SiO2 on the SnO2 surface effectively inhibits the nanocrystal growth of SnO2. The average size of modified SnO2 sintered at 600 degrees C is 5.8 nm. The gas sensitivity to CO was found to be markedly enhanced by the surface chemical modification. The CO gas as low as 5 ppm can be effectively detected by the modified SnO2-based sensors. At the same time, the modified SnO2-based sensor has excellent selectivity to CO, fast response and recovery properties.

  9. SiO2 Etching Yield Measurements by CF3 Ion Beam Injections Superposed with Light Irradiation

    Science.gov (United States)

    Ikuse, Kazumasa; Yoshimura, Satoru; Takizawa, Toshifumi; Karahashi, Kazuhiro; Kiuchi, Masato; Hamaguchi, Satoshi

    Etching yields of SiO2 by CF3 ion beam injections with or without simultaneous light irradiation have been measured by a low-energy mass-selected ion beam system. A Xe Lamp, an L2D2 lamp, an Ar ICP (inductively coupled plasma) or a VUV (Vacuum Ultraviolet) Lamp was used separately as the light source. The etching yield is the ratio of the number of incident ions to that of removed atoms. The obtained SiO2 etching yields by simultaneous irradiation of CF3 ions and photons from the light source were smaller than those by ion beam irradiation only. This difference in etching yields may be caused by modification of CFx polymer formation on the substrate surface during the beam etching process.

  10. Unconventional magnetization of Fe3O4 thin film grown on amorphous SiO2 substrate

    Directory of Open Access Journals (Sweden)

    Jia-Xin Yin

    2016-06-01

    Full Text Available High quality single crystal Fe3O4 thin films with (111 orientation had been prepared on amorphous SiO2 substrate by pulsed laser deposition. The magnetization properties of the films are found to be unconventional. The Verwey transition temperature derived from the magnetization jump is around 140K, which is higher than the bulk value and it can be slightly suppressed by out-plane magnetic field; the out-of-plane magnetization, which is unexpectedly higher than the in-plane value, is also significantly increased as compared with the bulk value. Our findings highlight the unusual magnetization of Fe3O4 thin film grown on the amorphous SiO2 substrate.

  11. The spectroscopic studies of glasses in the BPO 4(GaPO 4)-SiO 2 system

    Science.gov (United States)

    Adamczyk, A.

    2002-09-01

    FTIR spectroscopic structural studies of gel-derived glasses in BPO 4-SiO 2 and BPO 4(GaPO 4)-SiO 2 systems are presented. 10B isotope substitution, spectra subtraction procedure and B 3+→Ga 3+ substitution were applied to distinguish the bands, originating from B-O, P-O and Si-O bond vibrations. The spectra of borophosphosilicate glasses containing 10B isotope have also been presented. Changes in the band positions helped to assign bands due to the different B-O bonds vibrations. The spectra subtraction procedure, due to the lowering of intensity of bands assigned to Si-O bonds vibrations, enabled to observe bands at 966 and 1225 cm -1, due to broken Si-O - bridges and (PO 2) - terminal groups, respectively.

  12. Additivity of kinetic and potential energy contributions in modification of graphene supported on SiO2

    Science.gov (United States)

    Zhang, Xitong; Zhao, Shijun; Wang, Yuyu; Xue, Jianming

    2017-04-01

    The damage production induced by MeV highly charged ions (HCI) irradiations in graphene supported on a SiO2 substrate is investigated using molecular dynamics method. We get results in agreement with our recent experiments. We find that the electronic energy loss and potential energy deposition have similar effects on the defects creation in SiO2 substrate-supported graphene and both mechanisms of energy deposition seem to contribute in an additive way. The influences of the energy deposition depth and radius are studied. Only the energy deposited below the surface within 2.5 nm will induce the damage in graphene. Hence, the HCI can be a powerful tool to induce defects in graphene without causing deep damage of the substrate. When charge of incident Xeq+ is above 30, a nanopore is formed and the size of nanopore in graphene can be controlled by changing the incident charge state.

  13. Soft nanoimprint lithography on SiO2 sol-gel to elaborate sensitive substrates for SERS detection

    Directory of Open Access Journals (Sweden)

    Frédéric Hamouda

    2017-12-01

    Full Text Available This paper presents a new alternative fabrication of biochemical sensor based on surface enhanced Raman scattering (SERS by soft nanoimprint lithography (S-NIL on SiO2 sol-gel. Stabilization of the sol-gel film is obtained by annealing which simplifies the manufacturing of these biosensors and is compatible with mass production at low cost. This detector relies on a specific pattern of gold nanodisks on a thin gold film to obtain a better sensitivity of molecules’ detection. Characterizations of SERS devices were performed on a confocal Raman microspectrophotometer after a chemical functionalization. We report a lateral collapse effect on poly(diméthylsiloxane (PDMS stamp for specific nanostructure dimensions. This unintentional effect is used to evaluate S-NIL resolution in SiO2 sol-gel.

  14. High Temperature Stable Separator for Lithium Batteries Based on SiO2 and Hydroxypropyl Guar Gum

    Directory of Open Access Journals (Sweden)

    Diogo Vieira Carvalho

    2015-10-01

    Full Text Available A novel membrane based on silicon dioxide (SiO2 and hydroxypropyl guar gum (HPG as binder is presented and tested as a separator for lithium-ion batteries. The separator is made with renewable and low cost materials and an environmentally friendly manufacturing processing using only water as solvent. The separator offers superior wettability and high electrolyte uptake due to the optimized porosity and the good affinity of SiO2 and guar gum microstructure towards organic liquid electrolytes. Additionally, the separator shows high thermal stability and no dimensional-shrinkage at high temperatures due to the use of the ceramic filler and the thermally stable natural polymer. The electrochemical tests show the good electrochemical stability of the separator in a wide range of potential, as well as its outstanding cycle performance.

  15. Biocomposite of Cassava Starch Reinforced with Cellulose Pulp Fibers Modified with Deposition of Silica (SiO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Joabel Raabe

    2015-01-01

    Full Text Available Eucalyptus pulp cellulose fibers were modified by the sol-gel process for SiO2 superficial deposition and used as reinforcement of thermoplastic starch (TPS. Cassava starch, glycerol, and water were added at the proportion of 60/26/14, respectively. For composites, 5% and 10% (by weight of modified and unmodified pulp fibers were added before extrusion. The matrix and composites were submitted to thermal stability, tensile strength, moisture adsorption, and SEM analysis. Micrographs of the modified fibers revealed the presence of SiO2 nanoparticles on fiber surface. The addition of modified fibers improved tensile strength in 183% in relation to matrix, while moisture adsorption decreased 8.3%. Such improvements were even more effective with unmodified fibers addition. This result was mainly attributed to poor interaction between modified fibers and TPS matrix detected by SEM analysis.

  16. Highly efficient photoluminescence of SiO2 and Ce-SiO2 microfibres and microspheres.

    Science.gov (United States)

    Ruso, Juan M; Gravina, A Noel; D'Elía, Noelia L; Messina, Paula V

    2013-06-14

    Semiconductor nanocrystals and nanostructures have been extensively studied in the last few years due to their interesting optical and optoelectronic properties. Nevertheless, combining precise photoluminescence properties with controlled morphologies of SiO2 is a major hurdle for a broad range of basic research and technological applications. Here, we demonstrate that microemulsion droplet interfacial elasticity can be manipulated to induce definite morphologies associated with specific intrinsic and extrinsic photoluminescent defects in the silica matrix. Thus, under precise experimental conditions hollow crystalline and compact amorphous SiO2 spheres showing ultraviolet-photoluminescence and helicoidal fibrils of Ce-doped amorphous silica with violet-blue emissions are obtained. Overall, it is demonstrated that the combination of microemulsions and doping represents an easy strategy for the design of specific nanoscale structures with high efficiency photoluminescence. The detailed structural analysis provided in the present work is expected to be useful as accurate information on assessment of technological nanostructures.

  17. BF3.SiO2: an efficient catalyst for the synthesis of azo dyes at room temperature

    Directory of Open Access Journals (Sweden)

    Bi Bi Fatemeh Mirjalili

    2012-07-01

    Full Text Available A rapid one-pot method has been developed for the synthesis of azo dyes via ‎sequential diazotization–diazo coupling of aromatic amines with coupling agents at room ‎temperature in the presence of BF3.SiO2 as acidic catalyst. The obtained aryl diazonium salts bearing silica supported boron tri-flouride counter ion‎ was sufficiently stable to be kept at room ‎temperature in the dry state.‎

  18. Controlled spectral translucence of nanoporous SiO2/Al2O3 xerogel filled with ammonia and acetone

    Science.gov (United States)

    Petrova, T. M.; Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Glazkova, E. A.

    2017-05-01

    The near infrared transmission spectra of nanoporous SiO2/Al2O3 xerogel have been recorded for the first time in the process of filling of nanopores with ammonia and acetone molecules. It has been found that the physical adsorption of these gases results in a reversible increase in the translucence of xerogel samples at the frequencies of vibrational bands of surface OH groups.

  19. Volume Labeling with Alexa-Fluor Dyes and Surface Functionalization of Highly Sensitive Fluorescent SiO2 Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei [ORNL; Foster, Carmen M [ORNL; Morrell-Falvey, Jennifer L [ORNL; Nallathamby, Prakash D [ORNL; Mortensen, Ninell P [ORNL; Doktycz, Mitchel John [ORNL; Gu, Baohua [ORNL; Retterer, Scott T [ORNL; Gu, Baohua [ORNL

    2013-01-01

    A new synthesis approach is described that allows the direct incorporation of fluorescent labels into the volume or body of SiO2 nanoparticles. In this process, fluorescent Alexa Fluor dyes with different emission wavelengths were covalently incorporated into the SiO2 nanoparticles during their formation by the hydrolysis of tetraethoxysilane. The dye molecules were homogeneously distributed throughout the SiO2 nanoparticles. The quantum yields of the Alexa Fluor volume-labeled SiO2 nanoparticles were much higher than nanoparticles labeled using conventional organic dyes. The size of the resulting nanoparticles was controlled using microemulsion reaction media with sizes in the range of 20-100 nm and a polydispersity of <15%. In comparison with conventional surface tagged particles created by post-synthesis modification, this process maintains the physical and surface chemical properties that have the most pronounced effect on colloidal stability and interactions with their surroundings. These volume-labeled nanoparticles have proven to be extremely robust, showing excellent signal strength, negligible photobleaching, and minimal loss of functional organic components. The native or free surface of the volume-labeled particles can be altered to achieve a specific surface functionality without altering fluorescence. Their utility was demonstrated for visualizing the association of surface modified fluorescent particles with cultured macrophages. Differences in particle agglomeration and cell association were clearly associated with differences in observed nanoparticle toxicity. The capacity to maintain particle fluorescence while making significant changes to surface chemistry makes these particles extremely versatile and useful for studies of particle agglomeration, uptake, and transport in environmental and biological systems.

  20. Towards Scalable Binderless Electrodes: Carbon Coated Silicon Nanofiber Paper via Mg Reduction of Electrospun SiO2 Nanofibers

    OpenAIRE

    Favors, Zachary; Bay, Hamed Hosseini; Mutlu, Zafer; Ahmed, Kazi; Ionescu, Robert; Ye, Rachel; Ozkan, Mihrimah; Ozkan, Cengiz S.

    2015-01-01

    The need for more energy dense and scalable Li-ion battery electrodes has become increasingly pressing with the ushering in of more powerful portable electronics and electric vehicles (EVs) requiring substantially longer range capabilities. Herein, we report on the first synthesis of nano-silicon paper electrodes synthesized via magnesiothermic reduction of electrospun SiO2 nanofiber paper produced by an in situ acid catalyzed polymerization of tetraethyl orthosilicate (TEOS) in-flight. Free-...

  1. Apoptotic effect of α-Fe2O3 and SiO2 nanoparticles in human rhabdomyosarcoma cell line

    Science.gov (United States)

    Fatima, Mahvish; Fakhar-e-Alam, Muhammad; Atif, M.; Nadeem Shakoor, Muhammad; Afzal, Muhammad; Waseem, Muhammad; Hammad Aziz, Muhammad

    2014-12-01

    Nanotechnology provides the opportunity for the development of new materials in the nanometer size range, with many potential applications in biological sciences and clinical medicine. It has been reported that RD (muscle cancer cell line) is the most common soft tissue sarcoma in children originating from immature cells, comprising 2.9% of all malignancies in patients younger than 20 years old, with 350 cases diagnosed annually in the United States. Soft tissue is the most common target organ for nanoparticles after they gain significant entry into the target site through any of the possible routes. RD cell lines have been used as an experimental biological model in this article. A suitable environment was provided until 75% of RD cell confluence was reached. Prior to determination of toxicity of hematite (α-Fe2O3) and SiO2 nanoparticles, the sizes and shapes were confirmed using scanning electron microscopy (SEM), and the sizes were about 66 and 250 nm respectively. Moreover, 10-80 μg ml-1 of α-Fe2O3 and SiO2 nanoparticles dispersed in solution were labeled for each row of 96 well plates. The present study evaluates the suppression factor of the said particles, which leads to cell killing phenomena. After successful measurements in the above mentioned experiment, the author will be able to give the actual cause of cell killing effects. The given study has provided valuable insights into a feasible mechanism of apoptosis caused by α-Fe2O3 and SiO2 nanoparticles. An underlying promising mechanism of apoptosis due to α-Fe2O3 and SiO2 nanoparticle exposure should be further investigated at the in vivo level.

  2. Lead-gallium glasses and glass-ceramics doped with SiO2 for near infrared transmittance

    Science.gov (United States)

    Marczewska, Agnieszka; Środa, Marcin; Nocuń, Marek; Sulikowski, Bogdan

    2015-07-01

    Lead-gallium glasses, due to the absence of typical glass-forming components, are characterized by an increased tendency to crystallization. Despite this, they are interesting materials due to a shift of IR absorption edge up to 6-7 μm. The paper considers how the SiO2 dopant affects thermal stability and the UV-VIS and IR transmittance of lead-gallium glasses. The base lead-gallium glass (0.75PbO·0.25Ga2O3) was modified by the addition of 5, 10 and 15 mol% SiO2, respectively. DTA/DSC data showed that the glasses are characterized by the multi-stage crystallization, which is changed with the amount of silica doped. The XRD analysis confirmed that: (i) different forms of lead oxide crystallize after heat treatment of the glass, and (ii) the Ga2PbO4 phase is formed at higher temperatures. The silica admixture allowed inserting a few percent of BaF2 into the lead-gallium glass structure. It was found that a transparent glass-ceramic based on the lead-gallium glass with a low phonon barium fluoride phase can be obtained during the thermal treatment. The study of UV-VIS-IR transmittance shows that 10-15 mol% SiO2 in the lead-gallium glasses diminishes the absorption band in the range of 2.6-4 μm due to the presence of hydroxyl groups and simultaneously reduces transmittance in the range of 5-6.5 μm from 10 to 20%. Introduction of SiO2 to the glass results in the increase of transmittance in the shorter wavelength region and the UV-edge shift is observed. It was also confirmed that the BaF2 nanocrystallites exert no effect on the transmittance of the spectrum analyzed.

  3. Improved dielectric properties of CaCu3Ti4O12 films with a CaTiO3 interlayer on Pt/TiO2/SiO2/Si substrates prepared by pulsed laser deposition

    Science.gov (United States)

    Lee, Sung-Yun; Kim, Hui Eun; Jo, William; Kim, Young-Hwan; Yoo, Sang-Im

    2015-11-01

    We report the greatly improved dielectric properties of CaCu3Ti4O12 (CCTO) films with a 60 nm-thick CaTiO3 (CTO) interlayer on Pt/TiO2/SiO2/Si substrates. Both CCTO films and CTO interlayers were prepared by pulsed laser deposition (PLD). With increasing the thickness of CCTO from 200 nm to 1.3 μm, the dielectric constants ( ɛ r ) at 10 kHz in both CCTO single-layered and CCTO/CTO double-layered films increased from ˜260 to ˜6000 and from ˜630 to ˜3700, respectively. Compared with CCTO single-layered films, CCTO/CTO double-layered films irrespective of CCTO film thickness exhibited a remarkable decrease in their dielectric losses ( tanδ) (Poole-Frenkel conduction model. [Figure not available: see fulltext.

  4. Synthesis and Luminescence Properties of Yellow-emitting SiO2/Zn2SiO4: Mn Nanocomposite

    Directory of Open Access Journals (Sweden)

    Karim OMRI

    2014-05-01

    Full Text Available Yellow light emitting Mn2+-doped b-Zn2SiO4 phosphor nanoparticles embedded in SiO2 host matrix, were prepared by a simple solid-phase reaction under natural atmosphere at 1500 °C for 2 hours after the incorporation of manganese doped zinc oxide nanoparticles in silica using sol-gel method. The SiO2/Zn2SiO4:Mn nanocomposite was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM and photoluminescence (PL. The nanopowder was crystallized in triclinic b-Zn2SiO4 phase with a particles size varies between 70 nm and 84 nm. The SiO2/b-Zn2SiO4:Mn nanocomposite exhibited a broad yellow emission band at 575 nm under UV excitation light. The dependence of the intensity and energy position of the obtained PL band on measurement temperature and power excitation will be discussed.

  5. Fixed-bed adsorption separation of xylene isomers over sio2/silicallite-1 core-shell adsorbents

    KAUST Repository

    Khan, Easir A.

    2013-12-29

    SiO2/Silicalite-1 core-shell material has been demonstrated as potential shape selective adsorbent in gas phase separation of p-xylene from a mixture of p/o-xylene isomers. The core-shell composite comprised of large silica core and thin polycrystalline silicalite-1 shell which was synthesized via a self-assembly of silicalite-1 nanocrystals on core silica surface followed by a secondary seeded growth method. The core materials, SiO2 used in this study has mesoporosity with an average pore diameter of 60Å and hence offers no shape selectivity for xylene isomers. However, the shell, silicalite-1 contains rigid pore structures and preferentially adsorbs p-xylene from their isomers mixtures. A series of adsorption fixed bed breakthrough adsorption/desorption experiment was performed to obtain the equilibrium isotherms and adsorption isotherm parameters of xylene isomers. The equilibrium isotherms of xylene isomers follow the Langmuir\\'s model. A chromatographic adsorption model has been used to describe the fixed-bed breakthrough profiles of xylene isomers. The model has successfully predicted the responses of the binary mixtures of p/o-xylene isomers. The SiO2/silicalite-1 core-shell adsorbents have shown para-selectivity as high as 15. © Bangladesh Uni. of Engg. & Tech.

  6. Binary and Ternary Catalytic Systems for Olefin Metathesis Based on MoCl5/SiO2

    Science.gov (United States)

    Bykov, Victor I.; Belyaev, Boris A.; Butenko, Tamara A.; Finkelshtein, Eugene Sh.

    Kinetics of α-olefin metathesis in the presence of binary (MoCl5/ SiO2-Me4Sn) and ternary catalytic systems (MoCl5/SiO2-Me4Sn-ECl4, E = Si or Ge) was studied. Specifically, kinetics and reactivity of 1-decene, 1-octene, and 1-hexene in the metathesis reaction at 27°C and 50°C in the presence of MoCl5/ SiO2-SnMe4 were examined and evaluated in detail. It was shown that experimental data comply well with the simple kinetic equation for the rate of formation of symmetrical olefins with allowance for the reverse reaction and catalyst deactivation: r = left( {k_1 \\cdot c_α - k_{ - 1} \\cdot c_s } right) \\cdot e^{ - k_d \\cdot tilde n_{tot} } . The coefficients for this equation were determined, and it was shown that these α-olefins had practically the same reactivity. It was found that reactivation in the course of metathesis took place due to the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5-6% of the amount of Mo) and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The role of individual components of the catalytic systems was revealed.

  7. Effect of elastic region nanoparticle SiO2 jet polishing on the laser damage properties of fused silica

    Science.gov (United States)

    Song, Jialiang; Shi, Feng; Xiao, Qi; Yang, Ping

    2017-08-01

    To further improve the laser-induced damage threshold of fused silica elements after Hydrogen Fluoride (HF) acid dynamic acid etching, the effect of the nanoparticle SiO2 jet polishing on the surface quality and laser damage properties of fused silica was studied. On the fused silica surface after HF acid dynamic etching, different depths were polished with nanoparticle SiO2 jet, and their surface roughness were measured by In-situ detection. The photothermal absorption, laser damage threshold and surface contamination element concentration at different depths were measured. The experimental results show that the RMS value of the surface roughness of the surface is reduced from 1.440nm to 0.507nm, and surface contamination elements are removed. The laser damage threshold is improved by 10%. The results show that nanoparticle SiO2 jet polishing can remove surface damage and contamination after HF acid dynamic etching on the basis of elastic processing. Therefore, laser damage threshold can be improved.

  8. Energy state of InGaAs quantum dots on SiO2-patterned vicinal substrate

    Science.gov (United States)

    Kim, Hyo Jin; Mothohisa, Junichi; Fukui, Takashi

    2012-02-01

    The optical properties of In0.8Ga0.2As self-assembled quantum dots (SAQDs) grown on GaAs wire structures formed by utilizing SiO2-patterned exact and 5°-off (001) GaAs substrates have been studied with micro-photoluminescence (μ-PL). Single PL peak was occurred for In0.8Ga0.2As SAQDs grown on SiO2-patterned exact (001) GaAs, whereas double PL peaks were showed for SAQDs grown on 5°-off (001) GaAs substrates as the width of the opening windows increased. The power-dependent μ-PL spectra show that the first and second peaks of these double peaks were originated from the well-defined ground and excited state, respectively. These results demonstrated that In0.8Ga0.2As SAQDs selectively grown by utilizing SiO2-patterned 5°-off (001) GaAs substrates have well-defined zero-dimensional quantum states.

  9. Hierarchical Porous Structured SiO2/SnO2 Nanofibrous Membrane with Superb Flexibility for Molecular Filtration.

    Science.gov (United States)

    Shan, Haoru; Wang, Xueqin; Shi, Feihao; Yan, Jianhua; Yu, Jianyong; Ding, Bin

    2017-06-07

    The separation and purification of chemical molecules from organic media under harsh chemical environments are of vital importance in the fields of water treatment, biomedical engineering, and organic recycling. Herein, we report the preparation of a flexible SiO2/SnO2 nanofibrous membrane (SiO2/SnO2 NFM) with high surface area and hierarchical porous structure by selecting poly(vinyl butyral) as pore-forming agent and embedding crystalline phase into amorphous matrix without using surfactant as sacrificial template. Benefiting from the uniform micropore size on the fibers and negatively charged properties, the membranes exhibit a precise selectivity toward molecules based on electrostatic interaction and size exclusion, which could separate organic molecule mixtures with the same electrostatic charges and different molecular sizes with a high efficiency of more than 97%. Furthermore, the highly tortuous open-porous structures and high porosity give rise to a high permeate flux of 288 000 L m-2 h-1. In addition, the membrane also displays excellent stability and can be reused for ten consecutive filtration-regeneration cycles. The integration of high filtration efficiency, large permeate flux, good reutilization, and easy to industrialization provides the SiO2/SnO2 NFM for potential applications in practical molecular purification and separation science.

  10. Defect induced phonon scattering for tuning the lattice thermal conductivity of SiO2 thin films

    Directory of Open Access Journals (Sweden)

    Sen Cao

    2017-01-01

    Full Text Available In this work, the thermal properties of nanoscale SiO2 thin films have been systematically investigated with respect to the thickness, crystal orientations and the void defects using non-equilibrium molecular-dynamics (NEMD simulation. Size effect for the lattice thermal conductivity of nanoscale SiO2 thin films was observed. Additionally, SiO2 thin films with [001] oriented exhibited greater thermal conductivity compared with other crystal orientations which was discussed in terms of phonon density of states (PDOS. Furthermore, the porosity of void defects was introduced to quantify the influence of defects for thermal conductivity. Results exhibited that the thermal conductivity degraded with the increase of porosity. Two thermal conductivity suppression mechanisms, namely, void defects induced material loss interdicting heat conduction and phonon scattering enhanced by the boundary of defects, were proposed. Then, a further simulation was deployed to find that the effect of boundary scattering of defects was dominant in thermal conductivity degradation compared with material loss mechanism. The conclusion suggests that the thermal conductivity could be configured via regulating the distribution of PDOS directly associated with void defects.

  11. In Vitro Cytotoxicity of Mesoporous SiO2@Eu(OH3 Core-Shell Nanospheres in MCF-7

    Directory of Open Access Journals (Sweden)

    M. Atif

    2016-01-01

    Full Text Available Initially, the sample was synthesized by a modified sol-gel process. Morphological analysis of growth SiO2@Eu(OH3 was confirmed by applying field emission transmission electron microscopy (high and low resolution FETEM. The images confirmed the average diameter of mesoporous SiO2@Eu(OH3 core-shell nanospheres (~392–400 nm with a silica core of ~230 nm in diameter and a shell composed of europium hydroxide ~162 nm (thickness. Moreover, an absorption band at 280 nm was confirmed which initiates from the europium hydroxide. The photoluminescence spectrum of the nanosphere was also recorded at ambient temperature under the excitation of 3.82 eV. Cytotoxic studies in vitro were performed by applying MTT, NR assays, and morphological analysis. Morphological changes and % loss in cellular viability was assessed in human breast cancer cells (MCF-7 labeled with mesoporous SiO2@Eu(OH3 core-shell nanospheres at different concentrations ranging from 10 µg/mL to 200 µg/mL. Current study demonstrates the quite rational strategy which might be useful in future clinical approach/applications.

  12. Multifunctional Fe3O4@SiO2-Au Satellite Structured SERS Probe for Charge Selective Detection of Food Dyes.

    Science.gov (United States)

    Sun, Zhenli; Du, Jingjing; Yan, Li; Chen, Shu; Yang, Zhilin; Jing, Chuanyong

    2016-02-10

    Nanofabrication of multifunctional surface-enhanced Raman scattering (SERS) substrates is strongly desirable but currently remains a challenge. The motivation of this study was to design such a substrate, a versatile core-satellite Fe3O4@SiO2-Au (FA) hetero-nanostructure, and demonstrate its use for charge-selective detection of food dye molecules as an exemplary application. Our experimental results and three-dimensional finite difference time domain (FDTD) simulation suggest that tuning the Au nanoparticle (NP) gap to sub-10 nm, which could be readily accomplished, substantially enhanced the Raman signals. Further layer-by-layer deposition of a charged polyelectrolyte on this magnetic SERS substrate induced active adsorption and selective detection of food dye molecules of opposite charge on the substrates. Molecular dynamics (MD) simulations suggest that the selective SERS enhancement could be attributed to the high affinity and close contact (within a 20 Å range) between the substrate and molecules. Density function theory (DFT) calculations confirm the charge transfer from food dye molecules to Au NPs via the polyelectrolytes. This multifunctional SERS platform provides easy separation and selective detection of charged molecules from complex chemical mixtures.

  13. Highly selective fluorescent chemosensor for Zn2+ derived from inorganic-organic hybrid magnetic core/shell Fe3O4@SiO2 nanoparticles.

    Science.gov (United States)

    Wang, Yujiao; Peng, Xiaohong; Shi, Jinmin; Tang, Xiaoliang; Jiang, Jie; Liu, Weisheng

    2012-01-25

    Magnetic nanoparticles with attractive optical properties have been proposed for applications in such areas as separation and magnetic resonance imaging. In this paper, a simple and novel fluorescent sensor of Zn2+ was designed with 3,5-di-tert-butyl-2-hydroxybenzaldehyde [DTH] covalently grafted onto the surface of magnetic core/shell Fe3O4@SiO2 nanoparticles [NPs] (DTH-Fe3O4@SiO2 NPs) using the silanol hydrolysis approach. The DTH-Fe3O4@SiO2 inorganic-organic hybrid material was characterized by transmission electron microscopy, dynamic light scattering, X-ray power diffraction, diffuse reflectance infrared Fourier transform, UV-visible absorption and emission spectrometry. The compound DTH exhibited fluorescence response towards Zn2+ and Mg2+ ions, but the DTH-Fe3O4@SiO2 NPs only effectively recognized Zn2+ ion by significant fluorescent enhancement in the presence of various ions, which is due to the restriction of the N-C rotation of DTH-Fe3O4@SiO2 NPs and the formation of the rigid plane with conjugation when the DTH-Fe3O4@SiO2 is coordinated with Zn2+. Moreover, this DTH-Fe3O4@SiO2 fluorescent chemosensor also displayed superparamagnetic properties, and thus, it can be recycled by magnetic attraction.

  14. Synthesis and microwave absorption enhancement of graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures.

    Science.gov (United States)

    Wang, Lei; Huang, Ying; Sun, Xu; Huang, Haijian; Liu, Panbo; Zong, Meng; Wang, Yan

    2014-03-21

    Hierarchical structures of graphene@Fe3O4@SiO2@NiO nanosheets were prepared by combining the versatile sol-gel process with a hydrothermal reaction. Graphene@Fe3O4 composites were first synthesized by the reduction reaction between FeCl3 and diethylene glycol (DEG) in the presence of GO. Then, graphene@Fe3O4 was coated with SiO2 to obtain graphene@Fe3O4@SiO2. Finally, NiO nanosheets were grown perpendicularly on the surface of graphene@Fe3O4@SiO2 and graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures were formed. Moreover, the microwave absorption properties of both graphene@Fe3O4 and graphene@Fe3O4@SiO2@NiO nanosheets were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrate that graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4, which probably originate from the unique hierarchical structure with a large surface area and high porosity.

  15. Crystallization, crystal structure, and isothermal melt crystallization kinetics of novel polyamide 6/SiO2 nanocomposites prepared using the sol-gel technique.

    Science.gov (United States)

    Rafique, Fatima Zohra; Vasanthan, Nadarajah

    2014-08-07

    Polyamide 6/SiO2 (PA6/SiO2) nanocomposites with varying amounts of SiO2 were prepared by using a novel sol-gel technique. These nanocomposites were formed in situ by hydrolysis and through the condensation of tetraethoxysilane (TEOS) using formic acid with a small amount of water as the solvent for PA6. Observations of TGA showed that the thermal stability of PA6 nanocomposite was significantly improved compared to that of neat PA6. Microstructure development during the thermally induced crystallization of PA6/SiO2 nanocomposites was investigated with a combination of differential scanning calorimetry (DSC), FTIR spectroscopy, scanning electron microscopy (SEM), and AFM. FTIR spectroscopy was used to determine the crystal form of these nanocomposites, and it was concluded that SiO2 nanoparticles have the γ-nucleating effect. The crystallinity of nanocomposites decreased with increasing TEOS loading as compared to that for neat PA6. SEM showed a very fine dispersion of nanoscale silica whereas SEM and Zetasizer proved the silica particle size was about 100-200 nm. The isothermal crystallization kinetics of these nanocomposites with increasing SiO2 content were investigated, and it was shown that the amount of SiO2 plays a significant role in crystallization kinetics.

  16. Preparation of transparent fluorocarbon/TiO2-SiO2 composite coating with improved self-cleaning performance and anti-aging property

    Science.gov (United States)

    Zhou, Jianping; Tan, Zhongyuan; Liu, Zhilei; Jing, Mengmeng; Liu, Wenjie; Fu, Wanli

    2017-02-01

    This work reports a facile method to fabricate transparent self-cleaning fluorocarbon coatings filled by semicrystalline colloidal particles of TiO2-SiO2 composite oxide presenting a particle size ranging from 6 to 10 nm. Anatase-TiO2 crystallites were successfully obtained after microwave heating treatment of the TiO2-SiO2 colloidal particles as confirmed by XRD, TEM and FTIR measurements. The fluorocarbon/TiO2-SiO2 composite coatings exhibited a superior hydrophilicity and an improved photocatalytic activity in contrast to the TiO2-filled coatings. In particular, a water contact angle (WCA) value of 4.5° and a decolorization ratio relative to methyl orange as high as 96.0% were achieved for the composite coatings containing 1.5 wt% of TiO2-SiO2 colloidal particles. The results of the anti-soiling experiments indicated that the fluorocarbon/TiO2-SiO2 composite coatings exhibited a prominent self-cleaning performance, while the accelerated aging experiments revealed that the fluorocarbon/TiO2-SiO2 composite coatings were highly stable toward UV irradiation when compared to the TiO2-filled fluorocarbon coatings. These findings indicated that the fluorocarbon/TiO2-SiO2 composite coatings could be a very attractive solution for many practical areas, especially for outdoor applications.

  17. A novel one-step synthesis of Gd3+-incorporated mesoporous SiO2 nanoparticles for use as an efficient MRI contrast agent.

    Science.gov (United States)

    Shao, Yuan-Zhi; Liu, Li-Zhi; Song, Shu-qin; Cao, Ri-hui; Liu, Huan; Cui, Chun-yan; Li, Xing; Bie, Meng-Jie; Li, Li

    2011-01-01

    Molecular imaging has generated a demand for more sensitive contrast agents for magnetic resonance (MR) imaging. We synthesized, by a novel one-step method, Gd(3+) incorporated mesoporous SiO(2) nanoparticles, Gd(2)O(3)@SiO(2), for use as an efficient contrast agent. The prepared nanoparticles were also coated with poly(lactic-co-glycolic acid) (PLGA). The size, morphology, composition and Brunauer-Emmett-Teller specific surface area of the nanoparticles were evaluated. The Gd(2)O(3)@SiO(2) nanoparticles possess intragranular network morphology with a uniform size distribution and an average size of approximately 20-40 nm. The PLGA-coated nanoparticles were spherical or near-spherical in shape with a diameter of approximately 120 nm, a smooth surface, and neither aggregation nor adhesion tendencies. No free Gd ions were detected to dissociate from Gd(2)O(3)@SiO(2) even up to the limit (energy. Both Gd(2)O(3)@SiO(2) and PLGA-coated Gd(2)O(3)@SiO(2) samples have a larger T(1) relaxivitiy than commercial gadolinium diethylene triaminepentaacetate (Gd-DTPA). In vitro and in vivo MR images using the Gd(2)O(3)@SiO(2) nanoparticles were observed with a 1.5 T clinical MR scanner and compared with the images using Gd-DTPA. The Gd(2)O(3)@SiO(2) nanoparticles display a better magnetic property than commercial Gd-DTPA. In vivo MR imaging demonstrated that the nanoparticles were mainly distributed in the liver. Strong enhancement was also detected in nasopharyngeal carcinoma CNE-2 xenografted tumors. The Gd(2)O(3)@SiO(2) nanoparticles are not only potential candidates for highly efficient contrast agents for MR imaging, but also might be developed into potent targeted probes for in vivo molecular imaging of cancer. Copyright © 2010 John Wiley & Sons, Ltd.

  18. Improving antiproliferative effect of the anticancer drug cytarabine on human promyelocytic leukemia cells by coating on Fe3O4@SiO2 nanoparticles.

    Science.gov (United States)

    Shahabadi, Nahid; Falsafi, Monireh; Mansouri, Kamran

    2016-05-01

    In this study, Fe3O4@SiO2-cytarabine magnetic nanoparticles (MNPs) were prepared via chemical coprecipitation reaction and coating silica on the surface of Fe3O4 MNPs by Stöber method via sol-gel process. The surface of Fe3O4@SiO2 MNPs was modified by an anticancer drug, cytarabine. The structural properties of the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Zetasizer analyzer, and transmission electron microscopy (TEM). The results indicated that the crystalline phase of iron oxide NPs was magnetite (Fe3O4) and the average sizes of Fe3O4@SiO2-cytarabine MNPs were about 23 nm. Also, the surface characterization of Fe3O4@SiO2-cytarabine MNPs by FT-IR showed that successful coating of Fe3O4 NPs with SiO2 and binding of cytarabine drug onto the surface of Fe3O4@SiO2 MNPs were through the hydroxyl groups of the drug. The in vitro cytotoxic activity of Fe3O4@SiO2-cytarabine MNPs was investigated against cancer cell line (HL60) in comparison with cytarabine using MTT colorimetric assay. The obtained results showed that the effect of Fe3O4@SiO2-cytarabine magnetic nanoparticles on the cell lines were about two orders of magnitude higher than that of cytarabine. Furthermore, in vitro DNA binding studies were investigated by UV-vis, circular dichroism, and fluorescence spectroscopy. The results for DNA binding illustrated that DNA aggregated on Fe3O4@SiO2-cytarabine MNPs via groove binding. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

    Science.gov (United States)

    Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

    2017-06-01

    We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

  20. Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values.

    Science.gov (United States)

    Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

    2017-06-02

    We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

  1. High Photocatalytic Activity of Fe3O4-SiO2-TiO2 Functional Particles with Core-Shell Structure

    OpenAIRE

    Chenyang Xue; Qiang Zhang; Junyang Li; Xiujian Chou; Wendong Zhang; Hua Ye; Zhanfeng Cui; Dobson, Peter J.

    2013-01-01

    This paper describes a novel method of synthesizing Fe3O4-SiO2-TiO2 functional nanoparticles with the core-shell structure. The Fe3O4 cores which were mainly superparamagnetic were synthesized through a novel carbon reduction method. The Fe3O4 cores were then modified with SiO2 and finally encapsulated with TiO2 by the sol-gel method. The results of characterizations showed that the encapsulated 700 nm Fe3O4-SiO2-TiO2 particles have a relatively uniform size distribution, an anatase TiO2 she...

  2. Formyl-peptide Receptor Agonists and Amorphous SiO2-NPs Synergistically and Selectively Increase the Inflammatory Responses of Human Monocytes and PMNs

    Directory of Open Access Journals (Sweden)

    Regina Tavano

    2016-02-01

    ligands, but not toward FPR2-specific ones. Conversely, the chemotaxis of monocytes toward FPR2-specific peptides was inhibited by SiO2-NPs. NADPH-oxidase activation triggered by FPR1- and FPR2-specific ligands in both cell types was not altered by SiO2-NPs. Microbial and tissue danger signals sensed by FPRs selectively amplified the functional responses of monocytes and PMNS to SiO2-NPs, and should be carefully considered in the assessment of the risk associated with nanoparticle exposure.

  3. Effect of SiO$_{2}$ passivating layer in segmented silicon planar detectors on the detector response

    CERN Document Server

    Verbitskaya, Elena; Eremin, Vladimir; Golubkov, S; Konkov, K; Roe, Shaun; Ruggiero, G; Sidorov, A; Weilhammer, Peter

    2004-01-01

    Silicon detectors with a fine segmentation (micropixel and microstrip) are the main type of detectors used in the inner trackers of LHC experiments. Due to the high luminosity of the LHC machines they are required to have a fast response to fit the short shaping time of 25 ns and to be radiation hard. Evaluation of silicon microstrip detectors developed for the ATLAS silicon tracker and carried out under collaboration of CERN and PTI has shown the reversal of the pulse polarity in the detector response to short- range radiation. Since the negative signal is of about 30% of the normal positive one, the effect strongly reduces the charge collection efficiency in irradiated detectors. The investigation presents the consideration on the origin of a negative response in Si microstrip detectors and the experimental proof of the model. The study of the effect has been carried out using "baby" strip detectors with a special design: each strip has a window in a metallization, which covers the p/sup +/ implant. The sca...

  4. Effect of the substitution of La2O3 for CaO on the bioactivity of 2.5CaO.2SiO2 glass.

    Science.gov (United States)

    Fresa, R; Costantini, A; Buri, A; Branda, F

    1996-10-01

    Glasses of the following composition were prepared: (2.5-x)CaO.x/3La2O3.2SiO2 (0 < or = x < or = 1). Their behavior when soaked in a simulated body fluid (SBF) was studied by means of electron microscopy (EM) equipped with an energy-dispersive system (EDS) for elemental analysis, IR spectroscopy, and x-ray diffraction. All the studied glasses react with SBF by forming a calcium phosphate layer. This layer appears to be increasingly thinner with increasing amounts of La2O3 substituted. The experimental results are in good agreement with mechanisms reported in the literature. Moreover they suggest that lanthanum oxide is retained in the layer below the phosphate. After 6 days of soaking, crystalline hydroxyapatite is formed in the case of La2O3 free glass.

  5. Photoacoustic emission from Au nanoparticles arrayed on thermal insulation layer.

    Science.gov (United States)

    Namura, Kyoko; Suzuki, Motofumi; Nakajima, Kaoru; Kimura, Kenji

    2013-04-08

    Efficient photoacoustic emission from Au nanoparticles on a porous SiO(2) layer was investigated experimentally and theoretically. The Au nanoparticle arrays/porous SiO(2)/SiO(2)/Ag mirror sandwiches, namely, local plasmon resonators, were prepared by dynamic oblique deposition (DOD). Photoacoustic measurements were performed on the local plasmon resonators, whose optical absorption was varied from 0.03 (3%) to 0.95 by varying the thickness of the dielectric SiO(2) layer. The sample with high absorption (0.95) emitted a sound that was eight times stronger than that emitted by graphite (0.94) and three times stronger than that emitted by the sample without the porous SiO(2) layer (0.93). The contribution of the porous SiO(2) layer to the efficient photoacoustic emission was analyzed by means of a numerical method based on a one-dimensional heat transfer model. The result suggested that the low thermal conductivity of the underlying porous layer reduces the amount of heat escaping from the substrate and contributes to the efficient photoacoustic emission from Au nanoparticle arrays. Because both the thermal conductivity and the spatial distribution of the heat generation can be controlled by DOD, the local plasmon resonators produced by DOD are suitable for the spatio-temporal modulation of the local temperature.

  6. Encapsulation of superparamagnetic Fe 3 O 4 @SiO 2 core/shell nanoparticles in MnO 2 microflowers with high surface areas

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yu-Gang; Truong, Tu T.; Liu, Yu-Zi; Hu, Yong-Xing

    2015-02-01

    Microflowers made of interconnected MnO2 nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO4 with aqueous HCl at elevated temperatures in the presence of superparamagnetic Fe3O4@SiO2 core-shell nanoparticles. Due to the chemical compatibility between SiO2 and MnO2, the heterogeneous reaction leads to the spontaneous encapsulation of the Fe3O4@SiO2 core-shell nanoparticles in the MnO2 microflowers. The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO2 nanosheets and superparamagnetism originated from the Fe3O4@SiO2 core-shell nanoparticles, which are beneficial for applications requiring both high surface area and magnetic separation. (C) 2014 Yu-Gang Sun.

  7. The relation between residual stress, interfacial structure and the joint property in the SiO2f/SiO2-Nb joints

    OpenAIRE

    Ma, Qiang; Li, Zhuo Ran; Yang, Lai Shan; Lin, Jing Huang; Ba, Jin; Wang, Ze Yu; Qi, Jun Lei; Feng, Ji Cai

    2017-01-01

    In order to achieve a high-quality joint between SiO2f/SiO2 and metals, it is necessary to address the poor wettability of SiO2f/SiO2 and the high residual stress in SiO2f/SiO2-Nb joint. Here, we simultaneously realize good wettability and low residual stress in SiO2f/SiO2-Nb joint by combined method of HF etching treatment and Finite Element Analysis (FEA). After etching treatment, the wettability of E-SiO2f/SiO2 was improved, and the residual stress in the joint was decreased. In order to b...

  8. Activation of stress-related signalling pathway in human cells upon SiO2 nanoparticles exposure as an early indicator of cytotoxicity

    LENUS (Irish Health Repository)

    Mohamed, Bashir M

    2011-07-29

    Abstract Background Nanomaterials such as SiO2 nanoparticles (SiO2NP) are finding increasing applications in the biomedical and biotechnological fields such as disease diagnostics, imaging, drug delivery, food, cosmetics and biosensors development. Thus, a mechanistic and systematic evaluation of the potential biological and toxic effects of SiO2NP becomes crucial in order to assess their complete safe applicability limits. Results In this study, human monocytic leukemia cell line THP-1 and human alveolar epithelial cell line A549 were exposed to a range of amorphous SiO2NP of various sizes and concentrations (0.01, 0.1 and 0.5 mg\\/ml). Key biological indicators of cellular functions including cell population density, cellular morphology, membrane permeability, lysosomal mass\\/pH and activation of transcription factor-2 (ATF-2) were evaluated utilizing quantitative high content screening (HCS) approach and biochemical techniques. Despite the use of extremely high nanoparticle concentrations, our findings showed a low degree of cytotoxicity within the panel of SiO2NP investigated. However, at these concentrations, we observed the onset of stress-related cellular response induced by SiO2NP. Interestingly, cells exposed to alumina-coated SiO2NP showed low level, and in some cases complete absence, of stress response and this was consistent up to the highest dose of 0.5 mg\\/ml. Conclusions The present study demonstrates and highlights the importance of subtle biological changes downstream of primary membrane and endocytosis-associated phenomena resulting from high dose SiO2NP exposure. Increased activation of transcription factors, such as ATF-2, was quantitatively assessed as a function of i) human cell line specific stress-response, ii) SiO2NP size and iii) concentration. Despite the low level of cytotoxicity detected for the amorphous SiO2NP investigated, these findings prompt an in-depth focus for future SiO2NP-cell\\/tissue investigations based on the combined analysis of more subtle signalling pathways associated with accumulation mechanisms, which is essential for establishing the bio-safety of existing and new nanomaterials.

  9. Marrying the mussel inspired chemistry and Kabachnik-Fields reaction for preparation of SiO2 polymer composites and enhancement removal of methylene blue

    Science.gov (United States)

    Huang, Qiang; Liu, Meiying; Chen, Junyu; Wan, Qing; Tian, Jianwen; Huang, Long; Jiang, Ruming; Deng, Fengjie; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-11-01

    The removal of organic dyes using functionalization SiO2 composites (denoted as SiO2-PDA-CSH) were prepared via a facile method that combined with mussel inspired chemistry and Kabachnik-Fields (KF) reaction. The size and surface morphology, chemical structure, thermal stability, surface charging property, and elemental composition were evaluated by means of transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), zeta potential, and X-ray photoelectron spectroscopy (XPS), respectively. The results demonstrated that the organic functional groups can be successfully introduced onto the surface of SiO2 microspheres through the combination of mussel inspired chemistry and KF reaction. The removal of cationic dye methylene blue (MB) by the raw SiO2 and SiO2-PDA-CSH composites was examined and compared using a series of batch adsorption experiments. The results suggested that SiO2-PDA-CSH composites had a 3-fold increase in the adsorption capacity towards MB than that of pure SiO2 microspheres and the adsorption process was dependent on the solution pH. According to the adsorption kinetics, the adsorption of MB onto SiO2-PDA-CSH composites was well described by pseudo-second-order kinetic model. The equilibrium data were fitted with Langmuir and Freundlich isotherm models with R2 = 0.9981 and R2 = 0.9982, respectively. The maximum adsorption capacity from Langmuir isotherm was found to be 688.85 mg/g. The adsorption thermodynamics was also investigated in detailed. The parameters revealed that the adsorption process was spontaneous and endothermic in nature. The adsorption mechanism might be the synergistic action of physical adsorption of SiO2-PDA-CSH particles and electrostatic interaction between the MB and functional groups on the surface of SiO2-PDA-CSH composites, including sulfydryl, amino, aromatic moieties, and phosphate groups. Taken together, we developed a novel and facile strategy for the surface modification of SiO2 to achieve high adsorption towards MB based on the mussel inspired chemistry and multicomponent KF reaction. More importantly, this strategy could be easily extended for fabrication of many other high efficient adsorbents due to the universality of mussel inspired chemistry and various multicomponent reactions based on amino groups. Therefore, this work will open a new avenue and direction for the environmental applications of mussel inspired chemistry.

  10. Transport and abatement of fluorescent silica nanoparticle (SiO2 NP) in granular filtration: effect of porous media and ionic strength

    Science.gov (United States)

    Zeng, Chao; Shadman, Farhang; Sierra-Alvarez, Reyes

    2017-03-01

    The extensive production and application of engineered silica nanoparticles (SiO2 NPs) will inevitably lead to their release into the environment. Granular media filtration, a widely used process in water and wastewater treatment plants, has the potential for NP abatement. In this work, laboratory-scale column experiments were performed to study the transport and retention of SiO2 NPs on three widely used porous materials, i.e., sand, anthracite, and granular activated carbon (GAC). Synthetic fluorescent core-shell SiO2 NPs (83 nm) were used to facilitate NP detection. Sand showed very low capacity for SiO2 filtration as this material had a surface with limited surface area and a high concentration of negative charge. Also, we found that the stability and transport of SiO2 NP were strongly dependent on the ionic strength of the solution. Increasing ionic strength led to NP agglomeration and facilitated SiO2 NP retention, while low ionic strength resulted in release of captured NPs from the sand bed. Compared to sand, anthracite and GAC showed higher affinity for SiO2 NP capture. The superior capacity of GAC was primarily due to its porous structure and high surface area. A process model was developed to simulate NP capture in the packed bed columns and determine fundamental filtration parameters. This model provided an excellent fit to the experimental data. Taken together, the results obtained indicate that GAC is an interesting material for SiO2 NP filtration.

  11. The influence of Pr3+ co-doping on the photoluminescence and cathodoluminescence properties of SiO2:Eu3+/Tb3+

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-07-01

    Full Text Available Tb3+-Pr3+, and Eu3+-Pr3+ ion pairs co-doped in a SiO2 matrix were prepared by a sol-gel method. Co-doping of Eu3+ and Tb3+ ions with Pr3+ in SiO2 resulted in the quenching of Eu3+ and Tb3+ emissions with increasing Pr3+ concentrations. The quenching...

  12. Biogenic Hierarchical TiO2/SiO2 Derived from Rice Husk and Enhanced Photocatalytic Properties for Dye Degradation

    Science.gov (United States)

    Yang, Dalong; Fan, Tongxiang; Zhou, Han; Ding, Jian; Zhang, Di

    2011-01-01

    Background Rice husk, an agricultural bioresource, is utilized as a non-metallic bio-precursor to synthesize biogenic hierarchical TiO2/SiO2 (BH-TiO2/SiO2) and the products are applied to dye degradation. Methodology/Principal Findings The as-prepared BH-TiO2/SiO2 samples are characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), nitrogen-adsorption measurement, UV-vis spectroscopy and electronic paramagnetic resonance (EPR). The results show that BH-TiO2/SiO2 possesses both anatase and rutile phases with amorphous SiO2 as background, which contains mesopore structure, and nitrogen derived from original rice husk is self-doped into the lattice. Besides, the light-harvesting within the visible-light range of BH-TiO2/SiO2 has been enhanced. Moreover, the catalytic activity of BH-TiO2/SiO2 has been proven by EPR, and both the photocatalytic activity and stability of BH-TiO2/SiO2 are improved as well, which has been illustrated by cycled degradation of methylene blue dye under irradiation. Conclusions/Significance This work provides a good way to combine natural hierarchical porous structure with synthetic material chemistry based on available biomass in the vast natural environment for the sustainable development of human society, and extends potentials of biomass in applications such as photocatalysts, sunlight splitting water and so forth. PMID:21931853

  13. Silver nanoparticles embedded mesoporous SiO2 nanosphere: an effective anticandidal agent against Candida albicans 077

    Science.gov (United States)

    Qasim, M.; Singh, Braj R.; Naqvi, A. H.; Paik, P.; Das, D.

    2015-07-01

    Candida albicans is a diploid fungus that causes common infections such as denture stomatitis, thrush, urinary tract infections, etc. Immunocompromised patients can become severely infected by this fungus. Development of an effective anticandidal agent against this pathogenic fungus, therefore, will be very useful for practical application. In this work, Ag-embedded mesoporous silica nanoparticles (mSiO2@AgNPs) have successfully been synthesized and their anticandidal activities against C. albicans have been studied. The mSiO2@AgNPs nanoparticles (d ˜ 400 nm) were designed using pre-synthesized Ag nanoparticles and tetraethyl orthosilicate (TEOS) as a precursor for SiO2 in the presence of cetyltrimethyl ammonium bromide (CTAB) as an easily removable soft template. A simple, cost-effective, and environmentally friendly approach has been adopted to synthesize silver (Ag) nanoparticles using silver nitrate and leaf extract of Azadirachta indica. The mesopores, with size-equivalent diameter of the micelles (d = 4-6 nm), were generated on the SiO2 surface by calcination after removal of the CTAB template. The morphology and surface structure of mSiO2@AgNPs were characterized through x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), particle size analysis (PSA), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) and high-resolution transmission electron microscopy (HRTEM). The HRTEM micrograph reveals the well-ordered mesoporous structure of the SiO2 sphere. The antifungal activities of mSiO2@AgNPs on the C. albicans cell have been studied through microscopy and are seen to increase with increasing dose of mSiO2@AgNPs, suggesting mSiO2@AgNPs to be a potential antifungal agent for C. albicans 077.

  14. A comparison of the human and mouse protein corona profiles of functionalized SiO2nanocarriers.

    Science.gov (United States)

    Solorio-Rodríguez, A; Escamilla-Rivera, V; Uribe-Ramírez, M; Chagolla, A; Winkler, R; García-Cuellar, C M; De Vizcaya-Ruiz, A

    2017-09-21

    Nanoparticles are a promising cancer therapy for their use as drug carriers given their versatile functionalization with polyethylene glycol and proteins that can be recognized by overexpressed receptors in tumor cells. However, it has been suggested that in biological fluids, proteins cover nanoparticles, which gives the proteins a biological identity that could be responsible for unexpected biological responses: the so-called protein corona. A relevant biological event that is usually ignored in protein-corona formation is the interspecies differences in protein binding, which can be involved in the discrepancies observed in preclinical studies and the nanoparticle safety and efficiency. Hence, the aim of this study was to determine the differences between human and mouse plasma protein corona profiles in an active therapy model using silicon dioxide nanoparticles (SiO 2 nanoparticles) functionalized with polyethylene glycol and transferrin. Functionalized SiO 2 nanoparticles were made with a primary particle size of 25 nm and a transferrin content of 50 μg mg -1 of nanoparticles and were PEGylated with a cross-linker. The proteomic analysis by nanoliquid chromatography tandem-mass spectrometry (nanoLC-MS/MS) showed interspecies differences. The most abundant proteins found in the human protein corona profile were immunoglobulins, actin cytoplasmic 1, hemoglobin subunit beta, serotransferrin, ficolin-3, complement C3, and apolipoprotein A-1. Meanwhile, the mouse protein corona adsorbed the serine protease inhibitor A3K, serotransferrin, alpha-1-antitrypsin 1-2, hemoglobin subunit beta, and fibrinogen gamma and beta chains. These protein-corona profile differences in the functionalized SiO 2 nanoparticles indicate that biological responses observed in in vivo models could not be translated to clinical use and must be considered in the interpretation of preclinical trials in order to design more efficient and safer nanomedicines.

  15. One-pot preparation of N,N′-alkylidene bisamide derivatives catalyzed by silica supported polyphosphoric acid (SiO2-PPA

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Mohammad Shafiee

    2014-04-01

    Full Text Available Silica supported polyphosphoric acid (SiO2-PPA as an efficient heterogeneous catalyst was found to be effective for the one-pot three-component condensation reaction of phenyl acetylene/1-hexyne, aromatic aldehyde and benzamide/acetamide to produce a series of N,N′-alkylidene bisamides. The desired products were obtained in good to high yields. The assistance of alkynes has been confirmed by using thin layer chromatographic (TLC studies. All the reactions were done at 100 °C using 0.025 g of catalyst. The developed method is valid for either substituted aldehyde, thus it constitutes a general synthetic method for these kinds of compounds. In all the cases aromatic aldehydes containing electron-withdrawing groups gave shorter time than that with electron-donating groups. Additionally, the reaction of butyraldehyde with benzamide failed to have any product in the presence of phenyl acetylene but with 1-hexyne the product was formed in moderate yield.

  16. Structural and electrical characterization of NbO2 vertical devices grown on TiN coated SiO2/Si substrate

    Science.gov (United States)

    Joshi, Toyanath; Borisov, Pavel; Lederman, David

    Due to its relatively high MIT temperature (1081 K) and current-controlled negative differential resistance, NbO2 is a robust candidate for memory devices and electrical switching applications. In this work, we present in-depth analysis of NbO2 thin film vertical devices grown on TiN coated SiO2/Si substrates using pulsed laser deposition (PLD). Two of the films grown in 1 mTorr and 10 mTorr O2/Ar (~7% O2) mixed growth pressures were studied. The formation of NbO2 phase was confirmed by Grazing Incidence X-ray Diffractometry (GIXRD), X-ray Photoelectron Spectroscopy (XPS) and current vs. voltage measurements. A probe station tip (tip size ~2 μm) or conductive AFM tip was used as a top and TiN bottom layer was used as a bottom contact. Device conductivity showed film thickness and contact size dependence. Current pulse measurements, performed in response to applied triangular voltage pulses, showed a non-linear threshold switching behavior for voltage pulse durations of ~100 ns and above. Self-sustained current oscillations were analyzed in terms of defect density presented in the film. Supported by FAME (sponsored by MARCO and DARPA, Contract 2013-MA-2382), WV Higher Education Policy Commission Grant (HEPC.dsr.12.29), and WVU SRF. We also thank S. Kramer from Micron for providing the TiN-coated Si substrates.

  17. Enhanced energy density and thermostability in polyimide nanocomposites containing core-shell structured BaTiO3@SiO2 nanofibers

    Science.gov (United States)

    Wang, Junchuan; Long, Yunchen; Sun, Ying; Zhang, Xueqin; Yang, Hong; Lin, Baoping

    2017-12-01

    High energy density polymer nanocomposites with high-temperature resistance are quite desirable for film capacitors and many other power electronics. In this study, polyimide-based (PI) nanocomposite films containing the core-shell structured barium titanate@silicon dioxide (BT@SiO2) nanofibers have been successfully synthesized by the solution casting method. In the BT@SiO2/PI nanocomposite films, the dielectric permittivity as well as the breakdown strength increase significantly. The SiO2 shell layers with moderate dielectric permittivity could effectively mitigate the local field concentration induced by the large mismatch between the dielectric permittivity of BT and PI, which contributes to the enhancement of the breakdown strength of the PI nanocomposite films. As a result, the PI nanocomposite film filled with 3 vol% BT@SiO2 nanofibers exhibits a maximal energy density of 2.31 J cm-3 under the field of 346 kV/mm, which is 62% over the pristine PI (1.42 J cm-3 at 308 kV/mm) and about 200% greater than the best commercial polymer, i.e. biaxially oriented polypropylenes (BOPP) (≈1.2 J cm-3). The thermogravimetric analysis results indicate that the BT@SiO2/PI nanocomposite films have good thermal stability below 500 °C.

  18. Synthesis and structure of nanomaterials in the system K2O-Nb2O5-SiO2

    OpenAIRE

    Georgi Chernev; Bisserka Samuneva; Isabel M. Miranda Salvado; Paula Vilarinho; Aiying Wu

    2009-01-01

    The aim of the present work is synthesis of ferroelectric nanomaterials, in the K2O-Nb2O5-SiO2 system via solgel method and studying the processes of formation and structure of the synthesized ferroelectric nanomaterials. The structure of synthesized materials has been studied by means of the following methods: EDS, XRD, FT-IR, SEM and AFM. The results obtained showed that the structure of the investigated compositions does not depend on the niobium content and all the samples keep their amor...

  19. Preparation and Photocatalytic Activity of Magnetic Fe3O4/SiO2/TiO2 Composites

    Directory of Open Access Journals (Sweden)

    Rijing Wang

    2012-01-01

    Full Text Available A simple sol-gel method was used to prepare magnetic Fe3O4/SiO2/TiO2 composites with core-shell structure. Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD, field emission scanning electron microscopy (FE-SEM, and transmission electron microscopy (TEM have been applied to investigate the structure and morphology of the resultant composites. The obtained composites showed excellent magnetism and higher photodegradation ability than pure TiO2. The photocatalytic mechanism was also discussed. The magnetic composites should be extended to various potential applications, such as photodegradation, catalysis, separation, and purification processes.

  20. Insulin adsorption on crystalline SiO2: Comparison between polar and nonpolar surfaces using accelerated molecular-dynamics simulations

    Science.gov (United States)

    Nejad, Marjan A.; Mücksch, Christian; Urbassek, Herbert M.

    2017-02-01

    Adsorption of insulin on polar and nonpolar surfaces of crystalline SiO2 (cristobalite and α -quartz) is studied using molecular dynamics simulation. Acceleration techniques are used in order to sample adsorption phase space efficiently and to identify realistic adsorption conformations. We find major differences between the polar and nonpolar surfaces. Electrostatic interactions govern the adsorption on polar surfaces and can be described by the alignment of the protein dipole with the surface dipole; hence spreading of the protein on the surface is irrelevant. On nonpolar surfaces, on the other hand, van-der-Waals interaction dominates, inducing surface spreading of the protein.

  1. Highly transparent and UV-resistant superhydrophobic SiO2-coated ZnO nanorod arrays

    KAUST Repository

    Gao, Yangqin

    2014-02-26

    Highly transparent and UV-resistant superhydrophobic arrays of SiO 2-coated ZnO nanorods are prepared in a sequence of low-temperature (<150 C) steps on both glass and thin sheets of PET (2 × 2 in. 2), and the superhydrophobic nanocomposite is shown to have minimal impact on solar cell device performance under AM1.5G illumination. Flexible plastics can serve as front cell and backing materials in the manufacture of flexible displays and solar cells. © 2014 American Chemical Society.

  2. Study on spectroscopic properties and effects of tungsten ions in 2Bi2O3-3GeO2/SiO2 glasses.

    Science.gov (United States)

    Yu, Pingsheng; Su, Liangbi; Cheng, Junhua; Zhang, Xia; Xu, Jun

    2017-04-01

    The 2Bi2O3-3GeO2/SiO2 glass samples have been prepared by the conventional melt quenching technique. XRD patterns, absorption spectra, excitation-emission spectra and Raman measurements were utilized to characterize the synthesized glasses. When substitute SiO2 for GeO2, the 0.4Bi2O3-(0.4-0.1)GeO2-(0.2-0.5)SiO2 glasses exhibit strong emission centered at about 475nm (under 300nm excitation), and the decay constants are within the scope of 20-40ns. W doping into 2Bi2O3-3SiO2 glass could increase the emission intensity of 470nm, and the W-doped 2Bi2O3-3SiO2 glass has shown another emission at about 433nm with much shorter decay time (near 10ns). The 2Bi2O3-3GeO2/SiO2 glass system could be the possible candidate for scintillator in high energy physics applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Preparation of SiO2 Nanotubes with Controllable Inner/Outer Diameter and Length Using Hydrothermally Grown ZnO Nanowires as Templates

    Science.gov (United States)

    Kuo, Der-Ming; Wang, Shui-Jinn; Uang, Kai-Ming; Chen, Tron-Min; Tsai, Wei-Chih; Hsu, Wen-I.; Lee, Wei-Chi; Wang, Pei-Ren; Tseng, Chih-Ren

    2010-04-01

    Through the deposition of a thin SiO2 film to sheathe hydrothermally grown (HTG) ZnO nanowires (ZnO-NWs), unveiling their top portion, and then selectively removing ZnO-NWs by wet chemical etching, SiO2 nanotubes (SiO2-NTs) with controllable inner/outer diameters and lengths were fabricated. The prepared SiO2-NTs with average inner/outer diameters and lengths of approximately 200/300 nm and 1.5 µm, respectively, exhibited a superior transmittance of 92% in the visible light spectrum. The surface roughened process using SiO2-NTs on vertical-structure GaN light-emitting diodes (VLEDs) showed additional light output improvement of about 11.6% at 350 mA and 10% at 750 mA, compared with those of VLEDs with ZnO-NWs, suggesting the effectiveness and promising applications of the proposed SiO2-NTs in optics and optoelectronics devices.

  4. Effects of rare earth ions (Tb, Ce, Eu, Dy) on the thermoluminescence characteristics of sol-gel derived and γ-irradiated SiO2 nanoparticles.

    Science.gov (United States)

    Bajpai, Namrata; Tiwari, Ashish; Khan, S A; Kher, R S; Bramhe, Namita; Dhoble, S J

    2014-09-01

    Highly pure SiO2 and SiO2 :RE nanoparticles were synthesized by the sol-gel method. The morphological, structural and optical properties of the nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD results indicate that all the samples studied were free from impurities. SEM/TEM results indicate that the samples were well dispersed. Surface characterization of the nanocrystals by Fourier transform infrared spectroscopy has been carried out and the structure of surface-bound SiO2 based on spectral analysis is proposed. Thermoluminescence (TL) characteristics were investigated to study the influence of rare earth dopants (Tb, Ce, Eu, Dy) on SiO2 matrix subjected to 0.5 kG (1 h) γ-irradiation. Among these rare earth elements, Eu(3+) was found to be the most efficient dopant for SiO2 showing maximum thermoluminescence intensity. SiO2 :Eu0.5 seems to be a promising candidate for use as a TL dosimeter. Copyright © 2013 John Wiley & Sons, Ltd.

  5. Well-organized meso-macroporous TiO2/SiO2 film derived from amphiphilic rubbery comb copolymer.

    Science.gov (United States)

    Jeon, Harim; Lee, Chang Soo; Patel, Rajkumar; Kim, Jong Hak

    2015-04-15

    We report the facile synthesis of a well-organized meso-macroporous TiO2/SiO2 thin film with high porosity and good interconnectivity from a binary mixture (i.e., titania precursor and polymer template). Our process is based on self-assembly of the amphiphilic rubbery comb copolymer, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM) with titanium tetraisopropoxide (TTIP). SiO2 is self-provided by thermal oxidation of PDMS chains during calcination under air. The selective, preferential interaction between TTIP and the hydrophilic POEM chains was responsible for the formation of well-organized TiO2/SiO2 films, as supported by transmission electron microscopy, scanning electron microscopy, X-ray photospectroscopy, and X-ray diffraction analyses. We investigated in detail the effect of precursor content, solvent type, and polymer concentration on thin film morphology. Photodegradation of methyl orange by the well-organized meso-macroporous TiO2/SiO2 film was greater than that of a dense TiO2 film prepared without PDMS-g-POEM as well as a SiO2-etched TiO2 film. These results indicate that the well-organized structure and SiO2 doping of the TiO2 film play a pivotal role in enhancing its photocatalytic properties.

  6. Behaviors in Ethylene Polymerization of MgCl2-SiO2/TiCl4/THF Ziegler-Natta Catalysts with Differently Treated SiO2

    Directory of Open Access Journals (Sweden)

    Nichapat Senso

    2011-01-01

    Full Text Available The present research focuses on investigation of the catalytic behaviors of MgCl2-SiO2/TiCl4/THF Ziegler-Natta (ZN catalysts with fumed SiO2 variously treated with silane compounds. The non-treated silica (NTS and other silicas treated with dimethylsilicone fluid (TSDMSF, dimethyldichlorosilane (TSDMDCS, and hexamethyl-disilazane (TSHMDS were employed. It was found that the Cat-TSDMDCS and Cat-TSHMDS exhibited remarkably high activity, even with a similar bulk Ti content as the others. Thus, the more powerful technique of XPS analysis was used to determine the Ti content at the catalyst surface. It was evident that the surface concentrations of Ti could play important role on the catalyst activity. As the result, the increased activity is proportional to the surface concentration of Ti. It was mentioned that the change in surface concentration of Ti with different treated silica can be attributed to the effect of silane spacer group and steric hindrance. The distribution of Ti on the external surface can be also proven by means of EDX mapping, which matched the results obtained by XPS analysis. The treated silica also resulted in narrower molecular weight distribution (MWD due to the more uniform active sites produced. There was no significant change in polymer morphology upon treatment of the silica.

  7. Influence of alumina coating on characteristics and effects of SiO2 nanoparticles in algal growth inhibition assays at various pH and organic matter contents.

    Science.gov (United States)

    Van Hoecke, Karen; De Schamphelaere, Karel A C; Ramirez-Garcia, Sonia; Van der Meeren, Paul; Smagghe, Guy; Janssen, Colin R

    2011-08-01

    Silica nanoparticles (NPs) belong to the industrially most important NP types. In a previous study it was shown that amorphous SiO(2) NPs of 12.5 and 27.0 nm are stable in algal growth inhibition assays and that their ecotoxic effects are related to NP surface area. Here, it was hypothesized and demonstrated that an alumina coating completely alters the particle-particle, particle-test medium and particle-algae interactions of SiO(2) NPs. Therefore, stability and surface characteristics, dissolution, nutrient adsorption and effects on algal growth rate of both alumina coated SiO(2) NPs and bare SiO(2) NPs in OECD algal test medium as a function of pH (6.0-8.6) and natural organic matter (NOM) contents (0-12 mg C/l) were investigated. Alumina coated SiO(2) NPs aggregated in all media and adsorbed phosphate depending on pH and NOM concentration. On the other hand, no aggregation or nutrient adsorption was observed for the bare SiO(2) NPs. Due to their positive surface charge, alumina coated SiO(2) NPs agglomerated with Pseudokirchneriella subcapitata. Consequently, algal cell density measurements based on cell counts were unreliable and hence fluorescent detection of extracted chlorophyll was the preferred method. Alumina coated SiO(2) NPs showed lower toxicity than bare SiO(2) NPs at concentrations ≥46 mg/l, except at pH 6.0. At low concentrations, no clear pH effect was observed for alumina coated SiO(2) NPs, while at higher concentrations phosphate deficiency could have contributed to the higher toxicity of those particles at pH 6.0-6.8 compared to higher pH values. Bare SiO(2) NPs were not toxic at pH 6.0 up to 220 mg/l. Addition of NOM decreased toxicity of both particles. For SiO(2) NPs the 48 h 20% effect concentration of 21.8 mg/l increased 2.6-21 fold and a linear relationship was observed between NOM concentration and effective concentrations. No effect was observed for alumina coated SiO(2) NPs in presence of NOM up to 1000 mg/l. All experiments point out that the alumina coating completely altered NP interactions. Due to the difference in surface composition the SiO(2) NPs, which had the smallest surface area, were more toxic to the alga than the alumina coated SiO(2) NPs. Hence, surface modification can dominate the effect of surface area on toxicity. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Modification of the SiO2/Si interface by pulsed fibre laser radiation*

    Science.gov (United States)

    Skvortsov, A. M.; Veiko, V. P.; Huynh, C. T.; Polyakov, D. S.; Tamper, A. M.

    2017-07-01

    We report a detailed study of structural modification of the silicon–silica interface under the effect of laser pulses at a wavelength of 1.07 μm. A thermal oxide layer on the silicon surface has been shown to have a significant effect on the defect formation process and surface microstructuring because of the complex stress state of such a structure.

  9. Photocatalytic, Morphological and Structural Properties of the TiO2-SiO2-Ag Porous Structures Based System

    Directory of Open Access Journals (Sweden)

    Gábor Kovács

    2015-03-01

    Full Text Available TiO2-SiO2-based nanocomposites with highly porous structures are gaining ever increasing attention due to their specific properties and large variability of synthesis pathways together with wide information on the impact of the synthesis on the activity of the catalyst. This thereby offers an alternative approach to traditional/commercially available photocatalysts. In our work TiO2-SiO2 based aerogels were obtained and modified with various amount of Ag nanoparticles, using different synthesis pathways. In the first instance their photocatalytic activity was examined in detail, by observing major differences toward salicylic acid and correlating them with their morphological and structural properties (investigating their mesoporous character, band-gap values, crystallinity grade etc.. Applying different techniques such as diffuse reflectance spectroscopy (DRS, X-ray diffraction measurements (XRD, transmission electron microscopy (TEM, Raman- and X-ray photoelectron spectroscopy (XPS the nanoparticles and their composite morphological and structural details were successfully evaluated. Major differences were observed in the activity towards salicylic acid.

  10. Magnetite (Fe3O4 Nanoparticle Synthesis using Silica (SiO2 Template and Magnetic Properties Characterisation

    Directory of Open Access Journals (Sweden)

    Suryani Taib

    2015-12-01

    Full Text Available Nanoparticles of magnetite (Fe3O4 have been successfully synthesized by coprecipitation method by mixing FeSO4.7H2O and FeCl3.6H2O with the addition of 10% NH4OH as kopresipitan. Then, functionalized Fe3O4  concentration variation silica (SiO2 5%, 10%, 15%, 20%, 30% and 50%. Particle size and magnetic properties of Fe3O4 nanoparticles were tested by X-Ray Diffraction (XRD and Vibrating Sample Magnetometer (VSM. XRD results showed the addition of silica is not found new phases when added SiO2that serves as a template. The particle size of Fe3O4 nanoparticles obtained 14.23 nm, while the Fe3O4nanoparticles with the addition of a concentration of 5% and 20% respectively SiO215.45 nm and 16.37 nm. VSM results show the value of saturation magnetization and remanent magnetization decreased as more silica concentration, and increased coercivity field. Test Results of Fourier Transform Infra Red (FTIR obtained new peaks which indicate that the functionalization process Fe3O4 with silica has been successfully carried out.

  11. Properties of Cathodoluminescence for Cryogenic Applications of SiO2-based Space Observatory Optics and Coatings

    Science.gov (United States)

    Evans, Amberly; Dennison, J.R.; Wilson, Gregory; Dekany, Justin; Bowers Charles W.; Meloy, Robert; Heaney, James B.

    2013-01-01

    Disordered thin film SiO2SiOx coatings undergoing electron-beam bombardment exhibit cathodoluminescence, which can produce deleterious stray background light in cryogenic space-based astronomical observatories exposed to high-energy electron fluxes from space plasmas. As future observatory missions push the envelope into more extreme environments and more complex and sensitive detection, a fundamental understanding of the dependencies of this cathodoluminescence becomes critical to meet performance objectives of these advanced space-based observatories. Measurements of absolute radiance and emission spectra as functions of incident electron energy, flux, and power typical of space environments are presented for thin (60-200 nm) SiO2SiOx optical coatings on reflective metal substrates over a range of sample temperatures (40-400 K) and emission wavelengths (260-5000 nm). Luminescent intensity and peak wavelengths of four distinct bands were observed in UVVISNIR emission spectra, ranging from 300 nm to 1000 nm. A simple model is proposed that describes the dependence of cathodoluminescence on irradiation time, incident flux and energy, sample thickness, and temperature.

  12. Multifunctional superparamagnetic fe3O4@SiO2 core/shell nanoparticles: design and application for cell imaging.

    Science.gov (United States)

    Zhao, Xueling; Zhao, Hongli; Yuan, Huihui; Lan, Minbo

    2014-02-01

    Highly biocompatible sub-50-nm monodisperse superparamagnetic Fe3O4@SiO2 core/shell nanoparticles with luminescent silica shells were synthesized by a w/o-microemulsion technique. And then these nanoparticles were coated with the covalently bonded biocompatible polymer poly(ethylene glycol) (PEG) and modified with the biological cancer targeting ligand folic acid (FA). After characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transformed infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), UV-vis, fluorescence spectroscopy and confocal laser scanning microscopy (CLSM), we confirmed that Fe3O4@SiO2 (FITC)-PEG-FA nanocomposites (SMNPs-FA) could be efficiently taken up by HeLa cancer cells and KB cells which are of over-expression of folate receptors. The multifunctional nanomaterials exhibited superparamagnetic, monodisperse, highly biocompatible, intensively fluorescent and capable of recognizing and binding cells that overexpress folate receptors, which would be useful for targeting cell imaging and provide an excellent platform for further development of an efficient cancer therapy.

  13. HIDRODENITROGENACION DE CARBAZOL SOBRE CATALIZADORES NiMo/Al2O3-SiO2(x

    Directory of Open Access Journals (Sweden)

    Felipe Sánchez-Minero

    2012-01-01

    Full Text Available En este trabajo se estudió la velocidad de reacción del carbazol sobre catalizadores NiMo soportados sobre Al2O3 modificada superficialmente con SiO2 (0 y 10 % en peso de SiO2 en el soporte. Los catalizadores fueron evaluados en un reactor intermitente a cuatro temperaturas (287, 300, 312 y 325oC, presión de 4.0 MPa y relación molar hidrogeno/carbazol de 2400. A partir de los resultados experimentales se realizó un estudio cinético utilizando ecuaciones del tipo Langmuir-Hinshelwood (L-H. Luego, los parámetros cinéticos fueron estimados mediante la minimización de Powell (programa Scientist de MicroMath. Los resultados muestran que el catalizador con sílice (NiMo-SAC 10 alcanza una mayor actividad para la HDN de carbazol debido a que presenta un mayor número de sitios activos (valor de A, así como una menor fuerza de adsorción entre el reactante y la superficie catalítica (valor de KN, lo cual posiblemente favorece una mejor regeneración de sitios activos.

  14. Plasma-treated Ce/TiO2-SiO2catalyst for the NH3-SCR of NOx.

    Science.gov (United States)

    Chen, Kaige; Chen, Ruoyu; Cang, Hui; Mao, Airong; Tang, Zhe; Xu, Qi

    2017-06-19

    Ce/TiO 2 -SiO 2 catalysts with different Ti/Si molar ratios are prepared by the incipient impregnation method and their NH 3 -SCR activities are evaluated at 100-500°C on a fixed reactor. The Ce/TiO 2 -SiO 2 (3/1) catalyst, modified by non-thermal plasma (NTP) treatment and then activated by thermal treatment at 500°C for 4 h, exhibits best performance. Comprehensive deNO x performance of the catalyst is evidently improved and its efficiency reaches up to 99.21% at 350°C. NO conversion efficiency of the treated catalyst doped with K remains about 90.23% at 300°C and the catalyst also shows improved activity at lower temperatures. Various characterization methods show that the activity enhancement is correlated only with NTP treatment, as it increases the number of Ce 3+ species, which generates more chemisorbed oxygen, leads to improved dispersion of Brønsted and Lewis acidic sites and finally has an inherent etching effect.

  15. A VUV photoionization measurement and ab-initio calculation of the ionization energy of gas phase SiO2

    Energy Technology Data Exchange (ETDEWEB)

    Kostko, Oleg; Ahmed, Musahid; Metz, Ricardo B.

    2008-12-05

    In this work we report on the detection and vacuum-ultraviolet (VUV) photoionization of gas phase SiO2 generated in situ via laser ablation of silicon in a CO2 molecular beam. The resulting species are investigated by single photon ionization with tunable VUV synchrotron radiation and mass analyzed using reflectron mass spectrometry. Photoionization efficiency (PIE) curves are recorded for SiO and SiO2 and ionization energy estimates are revealed from such measurements. A state-to-state ionizationenergy of 12.60 (+-0.05) eV is recorded by fitting two prominent peaks in the PIE curve for the following process: 1SUM O-Si-O --> 2PRODg [O-Si-O]+. Electronic structure calculations aid in the interpretation of the photoionization process and allow for identification of the symmetric stretch of 2PRODg [O-Si-O]+ which is observed in the PIE spectrum to be 0.11 eV (890 cm-1) above the ground state of the cation and agrees with the 892 cm-1 symmetric stretch frequency calculated at the CCSD(T)/aug-cc-pVTZ level.

  16. Sodium ions at defect sites at SiO2/Si interfaces as determined by X-ray photoelectron spectroscopy

    Science.gov (United States)

    Grunthaner, F. J.; Masserjian, J.

    1975-01-01

    X-ray photoelectron spectroscopy (XPS) is described in its application as a probe for studying defects such as sodium in SiO2 films. A general description is given of key experimental methods in XPS. Techniques are described for applying and monitoring a fixed bias at the surface of the oxide during the XPS measurement. These methods are shown to be capable of detecting extremely small Na and Cu concentrations in undoped samples (less than 10 to the 11th power per cu cm). In deliberately Na-doped samples, five spectral peaks are distinctly observed and related to different defect states at the vacuum/SiO2 and SiO2/Si interfaces. By applying a bias-temperature stress during the XPS measurements, these peaks change in relative intensity and can be related to the motion of the Na(+) ions between different states occurring at the two interfaces. An attempt is made to correlate the observations with previously reported models.

  17. Remotely triggered release of small molecules from LaB6@SiO2-loaded polycaprolactone microneedles.

    Science.gov (United States)

    Chen, Mei-Chin; Wang, Kuan-Wen; Chen, Dong-Hwang; Ling, Ming-Hung; Liu, Chih-Ying

    2015-02-01

    We established near-infrared (NIR)-light-triggered transdermal delivery systems by encapsulating NIR absorbers, silica-coated lanthanum hexaboride (LaB6@SiO2) nanostructures and the cargo molecule to be released in biodegradable polycaprolactone (PCL) microneedles. Acting as a local heat source when exposed to an NIR laser, these nanostructures cause a phase transition of the microneedles, thereby increasing the mobility of the polymer chains and triggering drug release from the microneedles. On IR thermal images, the light-triggered melting behavior of the LaB6@SiO2-loaded microneedles was observed. By adjusting the irradiation time and the laser on/off cycles, the amount of molecules released was controlled accurately. Drug release was switched on and off for at least three cycles, and a consistent dose was delivered in each cycle with high reproducibility. The designed microneedles were remotely triggered by laser irradiation for the controlled release of a chemotherapeutic drug, doxorubicin hydrochloride, in vivo. This system would enable dosages to be adjusted accurately to achieve a desired effect, feature a low off-state drug leakage to minimize basal effects and can increase the flexibility of pharmacotherapy performed to treat various medical conditions. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Revisitation of the frictional properties of SiO2 as the LFM (lateral force microscopy) reference

    Science.gov (United States)

    Kim, Sung Hyun; Kim, Suenne

    2015-03-01

    Recently, experimental studies concerning frictional properties at the nanoscale using AFM(atomic force microscopy), specifically with LFM, are made on various kinds of materials including noble 2D graphene sheets and 1D nanotubes. The LFM technique requires calibration assuredly and therefore choosing a stable substrate as a reference is of importance. SiO2 is often used as the standard to calibrate LFM data obtained from a material of interest. However, according to our observation, the friction of cleansed SiO2 substrate can change gradually by long-time continuous LFM scanning. The friction increases up to about 1.5 times (50%) in comparison to the initial state while minute topographical difference, at the Å level, is detected. The friction depends on the number of scanning events, and the change follows an inverse exponential function, F(t) = A(1-exp[-Bt]) +F(0), where F is friction, t means time when continuous measurements are made, and A, B, F(0) are constants. Here, friction shift accompanied by z-scanner movement has been observed concurrently and corrected for the long time AFM measurements. In this regard, proper correction for the LFM shift induced by the z-scanner drift will also be introduced. This research was supported by Basic Science Research Program through NRF of Korea funded by the ministry of Education (2014R1A1A2056555).

  19. Effective role of CaO/P2O5 ratio on SiO2-CaO-P2O5 glass system

    Directory of Open Access Journals (Sweden)

    P. Kiran

    2017-05-01

    Full Text Available In the present work, the effect of the CaO/P2O5 ratio on the composition of sol-gel synthesized 58SiO2-(19 − xP2O5–(23 + xCaO (x = 0, 5, 10 and 15 mol% glass samples was studied. Further, the effect of NBO/BO ratio on hydroxy carbonated apatite layer (HCA forming ability based on dissolution behavior in simulated body fluid (SBF solution was also investigated. CaO/P2O5 ratios of synthesized glass samples were 1.2, 2, 3.6, and 9.5, respectively. NBO/BO ratios were obtained using Raman spectroscopic analysis as 0.58, 1.20, 1.46, and 1.78, respectively. All samples were soaked in the SBF solution for 7 days. The calculated weight losses of these samples were 58%, 64%, 83%, and 89% for corresponding NBO/BO ratios. The increase in CaO/P2O5 ratio increases the NBO/BO ratios. However, the increase in NBO/BO ratio increases HCA forming ability of SBF treated samples. The HCA crystalline layer formation was confirmed through X-ray Diffraction (XRD, Transmission Electron Microscopy (TEM, Scanning Electron Microscopy (SEM, Raman and Infrared spectroscopic analysis. Higher CaO/P2O5 ratio favors the increase in HCA formation for SBF treated calcium phospho silicate glasses.

  20. A chemiluminescence biosensor based on the adsorption recognition function between Fe3O4@SiO2@GO polymers and DNA for ultrasensitive detection of DNA

    Science.gov (United States)

    Sun, Yuanling; Li, Jianbo; Wang, Yanhui; Ding, Chaofan; Lin, Yanna; Sun, Weiyan; Luo, Chuannan

    2017-05-01

    In this work, a chemiluminescence (CL) biosensor was prepared for ultrasensitive determination of deoxyribonucleic acid (DNA) based on the adsorption recognition function between core-shell Fe3O4@SiO2 - graphene oxide (Fe3O4@SiO2@GO) polymers and DNA. The Fe3O4@SiO2@GO polymers were composed by GO and magnetite nanoparticles. And the core-shell polymers were confirmed by Scanning Electron Microscope (SEM), X-Ray Powder Diffraction (XRD) and Fourier Transform Infrared (FTIR). Then Fe3O4@SiO2@GO was modified by DNA. Based on the principle of complementary base, Fe3O4@SiO2@GO-DNA was introduced to the CL system and the selectivity, sensitivity of DNA detection was significantly improved. The adsorption properties of Fe3O4@SiO2@GO to DNA were researched through the adsorption equilibrium, adsorption kinetic and thermodynamics. Under optimized CL conditions, DNA could be assayed with the linear concentration range of 5.0 × 10- 12-2.5 × 10- 11 mol/L. The detection limit was 1.7 × 10- 12 mol/L (3δ) and the relative standard deviation (RSD) was 3.1%. The biosensor was finally used for the determination of DNA in laboratory samples and recoveries ranged from 99% to 103%. The satisfactory results revealed the potential application of Fe3O4@SiO2@GO-DNA-CL biosensor in the diagnosis and the treatment of human genetic diseases.

  1. A Nonvolatile MOSFET Memory Device Based on Mobile Protons in SiO(2) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Vanheusden, K.; Warren, W.L.; Devine, R.A.B.; Fleetwood, D.M.; Draper, B.L.; Schwank, J.R.

    1999-03-02

    It is shown how mobile H{sup +} ions can be generated thermally inside the oxide layer of Si/SiO{sub 2}/Si structures. The technique involves only standard silicon processing steps: the nonvolatile field effect transistor (NVFET) is based on a standard MOSFET with thermally grown SiO{sub 2} capped with a poly-silicon layer. The capped thermal oxide receives an anneal at {approximately}1100 C that enables the incorporation of the mobile protons into the gate oxide. The introduction of the protons is achieved by a subsequent 500-800 C anneal in a hydrogen-containing ambient, such as forming gas (N{sub 2}:H{sub 2} 95:5). The mobile protons are stable and entrapped inside the oxide layer, and unlike alkali ions, their space-charge distribution can be controlled and rapidly rearranged at room temperature by an applied electric field. Using this principle, a standard MOS transistor can be converted into a nonvolatile memory transistor that can be switched between normally on and normally off. Switching speed, retention, endurance, and radiation tolerance data are presented showing that this non-volatile memory technology can be competitive with existing Si-based non-volatile memory technologies such as the floating gate technologies (e.g. Flash memory).

  2. Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 Systems

    Science.gov (United States)

    Kang, Youn-Bae; Jung, In-Ho

    2017-06-01

    A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2SiO4-Mn2SiO4) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3-FeSiO3) and braunite (Mn7SiO_{12} with excess Mn2O3) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3O4) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.

  3. Concentration, chemical bonding, and etching behavior of P and N at the SiO2/SiC(0001) interface

    Science.gov (United States)

    Xu, Y.; Xu, C.; Liu, G.; Lee, H. D.; Shubeita, S. M.; Jiao, C.; Modic, A.; Ahyi, A. C.; Sharma, Y.; Wan, A.; Williams, J. R.; Gustafsson, T.; Dhar, S.; Garfunkel, E. L.; Feldman, L. C.

    2015-12-01

    Phosphorous and nitrogen are electrically active species at the SiO2/SiC interface in SiC MOSFETs. We compare the concentration, chemical bonding, and etching behavior of P and N at the SiO2/SiC(0001) interface using photoemission, ion scattering, and secondary ion mass spectrometry. Both interfacial P and N are found to be resistant to buffered HF solution etching at the SiO2/SiC(0001) interface while both are completely removed from the SiO2/Si interface. The medium energy ion scattering results of etched phosphosilicate glass/SiC not only provide an accurate coverage but also indicate that both the passivating nitrogen and phosphorus are confined to within 0.5 nm of the interface. Angle resolved photoemission shows that P and N are likely situated in different chemical environments at the interface. We conclude that N is primarily bound to Si atoms at the interface while P is primarily bound to O and possibly to Si or C. Different interface passivating element coverages and bonding configurations on different SiC crystal faces are also discussed. The study provides insights into the mechanisms by which P and N passivate the SiO2/SiC(0001) interface and hence improve the performance of SiC MOSFETs.

  4. An Investigation on the Tribological Performances of the SiO2/MoS2 Hybrid Nanofluids for Magnesium Alloy-Steel Contacts.

    Science.gov (United States)

    Xie, Hongmei; Jiang, Bin; Liu, Bo; Wang, Qinghang; Xu, Junyao; Pan, Fusheng

    2016-12-01

    Hybrid nano-materials offer potential scope for an increasing numerous novel applications when engineered to deliver availably functional properties. In the present study, the SiO2/MoS2 hybrid nanoparticles with different mass ratios were employed as lubricant additives in the base oil, and their tribological properties were evaluated using a reciprocating ball-on-plate tribometer for magnesium alloy-steel contacts. The results demonstrate that the SiO2/MoS2 hybrid nanoparticles exhibit superior lubrication performances than individual nano-SiO2 or nano-MoS2 even in high load and diverse velocity cases. The optimal SiO2/MoS2 mixing ratio and the concentration of SiO2/MoS2 hybrid nanoparticles in the base oil are 0.25:0.75 and 1.00-1.25 wt%, respectively. The excellent lubrication properties of the SiO2/MoS2 hybrid nanoparticles are attributed to the physical synergistic lubricating actions of nano-SiO2 and nano-MoS2 during the rubbing process.

  5. Origin of the n -type and p -type conductivity of MoS 2 monolayers on a SiO 2 substrate

    KAUST Repository

    Dolui, Kapildeb

    2013-04-02

    Ab initio density functional theory calculations are performed to study the electronic properties of a MoS2 monolayer deposited over a SiO 2 substrate in the presence of interface impurities and defects. When MoS2 is placed on a defect-free substrate, the oxide plays an insignificant role since the conduction band top and the valence band minimum of MoS2 are located approximately in the middle of the SiO2 band gap. However, if Na impurities and O dangling bonds are introduced at the SiO2 surface, these lead to localized states, which modulate the conductivity of the MoS2 monolayer from n- to p-type. Our results show that the conductive properties of MoS2 deposited on SiO 2 are mainly determined by the detailed structure of the MoS 2/SiO2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS2-based devices. © 2013 American Physical Society.

  6. Sulfhydryl-Modified Fe3O4@SiO2 Core/Shell Nanocomposite: Synthesis and Toxicity Assessment in Vitro.

    Science.gov (United States)

    Guo, Xueyi; Mao, Fangfang; Wang, Weijia; Yang, Ying; Bai, Zhiming

    2015-07-15

    The objectives of this study are to prepare sulfhydryl-modified Fe3O4@SiO2 core/shell magnetic nanocomposites, assess their toxicity in vitro, and explore their potential application in the biomedical fields. Fe3O4 nanoparticles synthesized by facile solvothermal method were coated with SiO2 via the Stöber method and further modified by the meso-2,3-dimercaptosuccinic acid (DMSA) to prepare Fe3O4@SiO2@DMSA nanoparticles. The morphology, structure, functional groups, surface charge, and magnetic susceptibility of the nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, zeta potential analysis, dynamic laser scattering, and vibrating sample magnetometer. Cytotoxicity tests and hemolysis assay were also carried out. Experimental results show that the toxicity of sulfhydryl-modified Fe3O4@SiO2 core/shell nanoparticles in mouse fibroblast (L-929) cell lines is between grade 0 and grade 1, and the material lacks hemolytic activity, indicating good biocompatibility of this Fe3O4@SiO2@DMSA nanocomposite, which is suitable for further application in biochemical fields.

  7. A new approach to the drug release kinetics of a discrete system: SiO2 system obtained by ultrasonic dry spraying.

    Science.gov (United States)

    Jokanović, V; Čolović, B; Dutour Sikirić, M; Trajković, V

    2013-01-01

    Mesoporous silica materials have already proved to be non-toxic and biocompatible, and also to have large pore volume and very high specific surface area suitable for loading of small molecules. Having this in mind and the fact that silicon dioxide (SiO(2)) powders can be so designed to obtain particle structures organized at multi levels, SiO(2) was chosen as a potential carrier for metronidazole, an antibiotic drug. SiO(2) powder was synthesized in two stages: first silica sol was prepared by hydrothermal synthesis and second the sol was converted into powder by dry spraying with simultaneous incorporation of the antibiotic into its structure. Scanning and transmission electron microscopy study revealed very complex structure and sub-structure of SiO(2) particles. Cell viability tests were used for estimation of cytotoxicity of so synthesized SiO(2). The drug release data showed that the system can provide drug release for a long time. Also, the device behavior is fully predictable, according to our theoretical model of multilevel structure design, and gives many opportunities for model investigations of drug release and its kinetics. The pore sizes and their distribution were observed as a limiting factor of drug release kinetics. Therefore, as the pore sizes are given as a set of discrete values, the kinetics of drug release might also be given as a set of corresponding discrete values. Copyright © 2012 Elsevier B.V. All rights reserved.

  8. Characterization of remote O2-plasma-enhanced CVD SiO2/GaN(0001) structure using photoemission measurements

    Science.gov (United States)

    Truyen, Nguyen Xuan; Ohta, Akio; Makihara, Katsunori; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2018-01-01

    The control of chemical composition and bonding features at a SiO2/GaN interface is a key to realizing high-performance GaN power devices. In this study, an ∼5.2-nm-thick SiO2 film has been deposited on an epitaxial GaN(0001) surface by remote O2-plasma-enhanced chemical vapor deposition (O2-RPCVD) using SiH4 and Ar/O2 mixture gases at a substrate temperature of 500 °C. The depth profile of chemical structures and electronic defects of the O2-RPCVD SiO2/GaN structures has been evaluated from a combination of SiO2 thinning examined by X-ray photoelectron spectroscopy (XPS) and the total photoelectron yield spectroscopy (PYS) measurements. As a highlight, we found that O2-RPCVD is effective for fabricating an abrupt SiO2/GaN interface.

  9. One-Step Synthesis of Hierarchical Micro-Mesoporous SiO2/Reduced Graphene Oxide Nanocomposites for Adsorption of Aqueous Cr(VI

    Directory of Open Access Journals (Sweden)

    Guiyun Yi

    2017-01-01

    Full Text Available A novel micro-mesostructured SiO2/reduced graphene oxide (RGO nanocomposite was successfully synthesized by means of simple one-step hydrothermal method under acidic conditions using tetraethoxysilane (TEOS and graphene oxide (GO as the raw material. The nanocomposites were characterized by TEM, XRD, FT-IR, TG-DSC, and N2 adsorption-desorption. The results showed that GO was partially reduced to RGO without adding any reducing agent and SiO2 nanoparticles (ca. 10 nm were uniformly anchored on the surface of RGO. The optimized composite contained 75 wt.% SiO2 and possessed hierarchical micro-mesoporous structure with surface area of 676 m2/g. The adsorption performance of synthesized SiO2/RGO samples was investigated by removal efficiency of Cr(VI ions in wastewater. The Cr(VI adsorption reached equilibrium in 30 min and 98.8% Cr(VI adsorption efficiency was achieved at pH = 2 at 35°C. Stability tests showed that SiO2 nanoparticles effectively prevented RGO from the restacking. The mechanisms of composite formation and for Cr(VI adsorption were suggested.

  10. Structure and crystallization of SiO2 and B2O3 doped lithium disilicate glasses from theory and experiment.

    Science.gov (United States)

    Erlebach, Andreas; Thieme, Katrin; Sierka, Marek; Rüssel, Christian

    2017-09-27

    Solid solutions of SiO2 and B2O3 in Li2O·2SiO2 are synthesized and characterized for the first time. Their structure and crystallization mechanisms are investigated employing a combination of simulations at the density functional theory level and experiments on the crystallization of SiO2 and B2O3 doped lithium disilicate glasses. The remarkable agreement of calculated and experimentally determined cell parameters reveals the preferential, kinetically controlled incorporation of [SiO4] and [BO4] at the Li+ lattice sites of the Li2O·2SiO2 crystal structure. While the addition of SiO2 increases the glass viscosity resulting in lower crystal growth velocities, glasses containing B2O3 show a reduction of both viscosities and crystal growth velocities. These observations could be rationalized by a change of the chemical composition of the glass matrix surrounding the precipitated crystal phase during the course of crystallization, which leads to a deceleration of the attachment of building units required for further crystal growth at the liquid-crystal interface.

  11. Facile Synthesis of SiO2@C Nanoparticles Anchored on MWNT as High-Performance Anode Materials for Li-ion Batteries.

    Science.gov (United States)

    Zhao, Yan; Liu, Zhengjun; Zhang, Yongguang; Mentbayeva, Almagul; Wang, Xin; Maximov, M Yu; Liu, Baoxi; Bakenov, Zhumabay; Yin, Fuxing

    2017-12-01

    Carbon-coated silica nanoparticles anchored on multi-walled carbon nanotubes (SiO2@C/MWNT composite) were synthesized via a simple and facile sol-gel method followed by heat treatment. Scanning and transmission electron microscopy (SEM and TEM) studies confirmed densely anchoring the carbon-coated SiO2 nanoparticles onto a flexible MWNT conductive network, which facilitated fast electron and lithium-ion transport and improved structural stability of the composite. As prepared, ternary composite anode showed superior cyclability and rate capability compared to a carbon-coated silica counterpart without MWNT (SiO2@C). The SiO2@C/MWNT composite exhibited a high reversible discharge capacity of 744 mAh g-1 at the second discharge cycle conducted at a current density of 100 mA g-1 as well as an excellent rate capability, delivering a capacity of 475 mAh g-1 even at 1000 mA g-1. This enhanced electrochemical performance of SiO2@C/MWNT ternary composite anode was associated with its unique core-shell and networking structure and a strong mutual synergistic effect among the individual components.

  12. Hierarchical core-shell SiO2@PDA@BiOBr microspheres with enhanced visible-light-driven photocatalytic performance.

    Science.gov (United States)

    Zhu, Shuai-Ru; Qi, Qi; Zhao, Wen-Na; Wu, Meng-Ke; Fang, Yuan; Tao, Kai; Yi, Fei-Yan; Han, Lei

    2017-08-29

    To explore catalysts combining highly accessible specific surface areas with low recombination of the photo-induced electron-hole pairs, a novel SiO2@PDA@BiOBr composite photocatalyst with a hierarchical core-shell structure was prepared by a facile solvothermal method. The catalyst shows a superior performance on photodegradation of Rhodamine B under visible light irradiation, especially for SiO2@PDA-2@BiOBr with the reactant kinetics constant (k = 0.0487 min-1). The enhanced photocatalytic performance of SiO2@PDA-2@BiOBr was ascribed to the decreased band-gap, higher surface area, and effectively photo-generated electron-hole pairs by the introduction of polydopamine (PDA). In addition, the photocatalytic degradation is initiated by ˙O2- derived from dye photosensitization and h+ from the BiOBr. Cyclic experiments also indicate that the SiO2@PDA-2@BiOBr is reusable during the photodegradation process. The hierarchical core-shell SiO2@PDA@BiOBr photocatalyst will provide a theoretical model for the development of physical chemistry and structural properties of BiOBr-based composites to enhance the photocatalytic performances.

  13. Spontaneous dissociation of Co2(CO8 and autocatalytic growth of Co on SiO2: A combined experimental and theoretical investigation

    Directory of Open Access Journals (Sweden)

    Kaliappan Muthukumar

    2012-07-01

    Full Text Available We present experimental results and theoretical simulations of the adsorption behavior of the metal–organic precursor Co2(CO8 on SiO2 surfaces after application of two different pretreatment steps, namely by air plasma cleaning or a focused electron beam pre-irradiation. We observe a spontaneous dissociation of the precursor molecules as well as autodeposition of cobalt on the pretreated SiO2 surfaces. We also find that the differences in metal content and relative stability of these deposits depend on the pretreatment conditions of the substrate. Transport measurements of these deposits are also presented. We are led to assume that the degree of passivation of the SiO2 surface by hydroxyl groups is an important controlling factor in the dissociation process. Our calculations of various slab settings, using dispersion-corrected density functional theory, support this assumption. We observe physisorption of the precursor molecule on a fully hydroxylated SiO2 surface (untreated surface and chemisorption on a partially hydroxylated SiO2 surface (pretreated surface with a spontaneous dissociation of the precursor molecule. In view of these calculations, we discuss the origin of this dissociation and the subsequent autocatalysis.

  14. Facile Synthesis of SiO2@C Nanoparticles Anchored on MWNT as High-Performance Anode Materials for Li-ion Batteries

    Science.gov (United States)

    Zhao, Yan; Liu, Zhengjun; Zhang, Yongguang; Mentbayeva, Almagul; Wang, Xin; Maximov, M. Yu.; Liu, Baoxi; Bakenov, Zhumabay; Yin, Fuxing

    2017-07-01

    Carbon-coated silica nanoparticles anchored on multi-walled carbon nanotubes (SiO2@C/MWNT composite) were synthesized via a simple and facile sol-gel method followed by heat treatment. Scanning and transmission electron microscopy (SEM and TEM) studies confirmed densely anchoring the carbon-coated SiO2 nanoparticles onto a flexible MWNT conductive network, which facilitated fast electron and lithium-ion transport and improved structural stability of the composite. As prepared, ternary composite anode showed superior cyclability and rate capability compared to a carbon-coated silica counterpart without MWNT (SiO2@C). The SiO2@C/MWNT composite exhibited a high reversible discharge capacity of 744 mAh g-1 at the second discharge cycle conducted at a current density of 100 mA g-1 as well as an excellent rate capability, delivering a capacity of 475 mAh g-1 even at 1000 mA g-1. This enhanced electrochemical performance of SiO2@C/MWNT ternary composite anode was associated with its unique core-shell and networking structure and a strong mutual synergistic effect among the individual components.

  15. Morphology and FT-IR analysis of anti-pollution flashover coatings with adding nano SiO2 particles

    Science.gov (United States)

    Guo, Kai; Du, Yishu; Wu, Yaping; Mi, Xuchun; Li, Xingeng; Chen, Suhong

    2017-12-01

    By adding nano SiO2 particles, an enhanced K-PRTV anti-pollution flashover coating had been prepared. Optical profile meter (GT-K), atomic force microscopy (AFM), infrared spectrometer (FT-IR) and EDS characterization were carried out on the coating surface analysis. Those results has been use to optimize the further design and platform of the enhanced K-PRTV pollution flash coating experiment. It is also to improve the plan formulation, formulation optimization and preparation of the hydrophobic modified K-PRTV which is based on anti-pollution coating experiment. More importantly, the anti-pollution flashover K-PRTV coating with super hydrophobic modified is the great significance for K-PRTV coating.

  16. Linear and nonlinear intraband optical properties of ZnO quantum dots embedded in SiO2 matrix

    Directory of Open Access Journals (Sweden)

    Deepti Maikhuri

    2012-03-01

    Full Text Available In this work we investigate some optical properties of semiconductor ZnO spherical quantum dot embedded in an amorphous SiO2 dielectric matrix. Using the framework of effective mass approximation, we have studied intraband S-P, and P-D transitions in a singly charged spherical ZnO quantum dot. The optical properties are investigated in terms of the linear and nonlinear photoabsorption coefficient, the change in refractive index, and the third order nonlinear susceptibility and oscillator strengths. Using the parabolic confinement potential of electron in the dot these parameters are studied with the variation of the dot size, and the energy and intensity of incident radiation. The photoionization cross sections are also obtained for the different dot radii from the initial ground state of the dot. It is found that dot size, confinement potential, and incident radiation intensity affects intraband optical properties of the dot significantly.

  17. Adhesion of Y2O3-Al2O3-SiO2 coatings to typical aerospace substrates

    Energy Technology Data Exchange (ETDEWEB)

    Marraco-Borderas, C.; Nistal, A.; Garcia, E.; Sainz, M.A.; Martin de la Escalera, F.; Essa, Y.; Miranzo, P.

    2016-07-01

    High performance lightweight materials are required in the aerospace industry. Silicon carbide, carbon fiber reinforced carbon and slicon carbide composites comply with those requirements but they suffer from oxidation at the high temperature of the service conditions. One of the more effective approaches to prevent this problem is the use of protecting ceramic coatings, where the good adhesion between substrates and coatings are paramount to guarantee the optimal protection performance. In the present work, the adhesion between those substrates and glass coatings of the Y2O3-Al2O3-SiO2 system processed by oxyacetylene flame spraying is analyzed. Increasing load scratch tests are employed for determining the failure type, maximum load and their relation with the elastic and mechanical properties of the coatings. The results points to the good adhesion of the coatings to silicon carbide and carbon fibre reinforced silicon carbide while the carbon fiber reinforced carbon is not a suitable material to be coated. (Author)

  18. Preparation of CoFe2O4/SiO2 Nanocomposites at Low Temperatures Using Short Chain Diols

    Directory of Open Access Journals (Sweden)

    Thomas Dippong

    2017-01-01

    Full Text Available The preparation of 70% CoFe2O4/30% SiO2 (wt% nanocomposites by sol-gel method using three short chain diols (1,2-ethanediol, 1,3-propanediol, and 1,4-butanediol as chelators was studied. The Fourier transformed infrared spectra and X-ray diffraction patterns were used to confirm the formation of nanocomposites. The X-ray diffraction analysis showed that the chain length of the carboxylates embedded in the silica matrix influences the formation of crystallized cobalt ferrite as single phase at low temperatures. The influence of the methylene groups number in the precursors and annealing temperature on the nanocrystallite size was revealed. The stability of the obtained compounds was determined by calculation of thermodynamic parameters.

  19. Thermal Annealing Effect on Optical Properties of Binary TiO2-SiO2 Sol-Gel Coatings

    Directory of Open Access Journals (Sweden)

    Xiaodong Wang

    2012-12-01

    Full Text Available TiO2-SiO2 binary coatings were deposited by a sol-gel dip-coating method using tetrabutyl titanate and tetraethyl orthosilicate as precursors. The structure and chemical composition of the coatings annealed at different temperatures were analyzed by Raman spectroscopy and Fourier Transform Infrared (FTIR spectroscopy. The refractive indices of the coatings were calculated from the measured transmittance and reflectance spectra. An increase in refractive index with the high temperature thermal annealing process was observed. The Raman and FTIR results indicate that the refractive index variation is due to changes in the removal of the organic component, phase separation and the crystal structure of the binary coatings.

  20. Transparent cobalt doped MgO -Ga2O3-SiO2 nano-glass-ceramic composites

    Science.gov (United States)

    Duan, X. L.; Yuan, D. R.; Yu, F. P.; Wang, L. H.

    2006-10-01

    Transparent cobalt doped MgO -Ga2O3-SiO2 nano-glass-ceramic composites were prepared from Si, Ga, Mg, and Co molecular precursors by a sol-gel method. X-ray diffraction patterns and transmission electron microscopy showed that the resulting material is composed of an amorphous silicate network that encloses nanocrystalline MgGa2O4 particles. Analysis of the absorption and luminescence properties indicates that Co ions are, at least partially, trapped in the crystalline phase and located in tetrahedral sites in MgGa2O4 nanocrystals. The absorption section was calculated to be 1.15×10-19cm2.

  1. Synthesis and structure of nanomaterials in the system K2O-Nb2O5-SiO2

    Directory of Open Access Journals (Sweden)

    Georgi Chernev

    2009-06-01

    Full Text Available The aim of the present work is synthesis of ferroelectric nanomaterials, in the K2O-Nb2O5-SiO2 system via solgel method and studying the processes of formation and structure of the synthesized ferroelectric nanomaterials. The structure of synthesized materials has been studied by means of the following methods: EDS, XRD, FT-IR, SEM and AFM. The results obtained showed that the structure of the investigated compositions does not depend on the niobium content and all the samples keep their amorphous nature at room temperature. The surface structure shows random distribution of different kinds of aggregates with dimensions about 200–500 nm. The presence of a hybrid nanostructure with well-defi ned nanounits having special geometry is clearly observed.

  2. X-ray photoelectron spectroscopy study of the chemical structure of thermally nitrided SiO2

    Science.gov (United States)

    Vasquez, R. P.; Hecht, M. H.; Grunthaner, F. J.; Naiman, M. L.

    1984-01-01

    X-ray photoelectron spectroscopy has been used to study the composition of 100-A thermally grown SiO2 films that have been thermally nitrided in ammonia. The SiO(x)N(y)/Si interface was studied both by chemical depth profiling of the oxynitride and by removal of the Si substrate with XeF2. It is found that N is distributed throughout the film, but with the concentration higher at the surface and in a region centered 25 A from the film/substrate interface. The interface region itself is found to be oxygen-rich relative to the rest of the film. Possible models which can explain these results are discussed.

  3. Removal of Hazardous Pollutants from Wastewaters: Applications of TiO2-SiO2 Mixed Oxide Materials

    Directory of Open Access Journals (Sweden)

    Shivatharsiny Rasalingam

    2014-01-01

    Full Text Available The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2 binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

  4. The blue photoluminescence and nanostructure of Si and C clusters embedded in SiO 2 matrices

    Science.gov (United States)

    Zhang, Q.; Bayliss, S. C.; Al-Ajili, A.; Hutt, D. A.; Harris, P.

    1995-05-01

    Carbon and silicon clustered films have been prepared by rf sputtering using a SiO2 target on which were placed lumps of C or Si, respectively, followed by annealing at 800°C or 600°C for 20-30 min in a N2 atmosphere. Information about the nanostructure of the films has been determined from photoluminescence (PL) and extended X-ray absorption fine structure (EXAFS). Blue PL from these films has been observed and reported for the first time, with peak wavelengths in the range from 420-500 nm, when excited by 260, 300 and 370 nm light produced by the tuneable synchrotron at DRAL Daresbury. The blue PL is visible to the naked eye when illuminated by ∼ 2.7 μW UV beam.

  5. TPO characterization of ethanol reduced Pd nanoparticles supported on SiO$_{2}$

    CERN Document Server

    Horváth, A; Sarkany, A; Guczi, L

    2002-01-01

    Silica-supported Pd catalysts were prepared at 298-353 K from Pd(II) chloride or Pd(II) acetate in suspension of SiO/sub 2/ and ethanol- water or ethanol-toluene mixtures, respectively. Reduction of Pd ions diffusing from liquid phase was ensured in an ethanol-rich adsorption layer covering the SiO/sub 2/ particles. Temperature-programmed oxidation (TPO) measurements were performed to characterize the organic impurities retained by solid phase. Vapour phase reduction /adsorption experiments with ethanol confirmed that under the reported reduction conditions, the Pd nanoparticles decompose ethanol and the CO formed remains chemisorbed on the Pd sites. Upon contacting the samples with air during the drying process to eliminate the solvent, the CO molecules are immediately removed from Pd sites by O/sub 2/, and thereby, a significant fraction (22-34%) of Pd sites becomes accessible for catalytic reactions. (33 refs).

  6. Fibrinogen enhances the inflammatory response of alveolar macrophages to TiO2, SiO2 and carbon nanomaterials.

    Science.gov (United States)

    Marucco, Arianna; Gazzano, Elena; Ghigo, Dario; Enrico, Emanuele; Fenoglio, Ivana

    2016-01-01

    Many studies have shown that the composition of the protein corona dramatically affects the response of cells to nanomaterials (NMs). However, the role of each single protein is still largely unknown. Fibrinogen (FG), one of the most abundant plasma proteins, is believed to mediate foreign-body reactions. Since this protein is absent in cell media used in in vitro toxicological tests the possible FG-mediated effects have not yet been assessed. Here, the effect of FG on the toxicity of three different kinds of inorganic NMs (carbon, SiO2 and TiO2) on alveolar macrophages has been investigated. A set of integrated techniques (UV-vis spectroscopy, dynamic light scattering and sodium dodecyl sulphate-polyacrylamide gel electrophoresis) have been used to study the strength and the kinetics of interaction of FG with the NMs. The inflammatory response of alveolar macrophages (MH-S) exposed to the three NMs associated with FG has also been investigated. We found that FG significantly enhances the cytotoxicity (lactate dehydrogenase leakage) and the inflammatory response (increase in nitric oxide (NO) concentration and NO synthase activation) induced by SiO2, carbon and TiO2 NMs on alveolar macrophages. This effect appears related to the amount of FG interacting with the NMs. In the case of carbon NMs, the activation of fibrinolysis, likely related to the exposure of cryptic sites of FG, was also observed after 24 h. These findings underline the critical role played by FG in the toxic response to NMs.

  7. Study of ceramic pigments from the ZrO2 – SiO2- Fe2O3 system

    Directory of Open Access Journals (Sweden)

    Vassilev, S.

    2003-08-01

    Full Text Available In order to obtain high temperature ceramic pigments using colorless stable crystal carcasses turns out to be quite suitable in the case of ZrSiO4 and their coloring by introducing different chromophores. In the paper presented experiments have been carried out on synthesis of zircon pigments from the ZrO2-SiO2-Fe2O3 system. The technology of solid phase sintering have been applied for their obtaining. X -ray phase analysis, ESR and Moessbauer spectroscopy have been used to define the phase composition and to checked the Fe ions valency state above the optimal temperature of synthesis. In most pigments the basic phase is obtained at even 900 - 1000 ºC. The best pigments have been added to white faience glaze.La obtención de pigmentos cerámicos de alta temperatura a partir de cristales estables incoloros, puede ser muy viable en el caso del ZrSiO4 y su posterior coloración con diferentes cromóforos. En este artículo se han desarrollado pigmentos de zircón basados en el sistema ZrO2-SiO2-Fe2O3, utilizando la tecnología de sinterización en fase sólida. La composición de las fases se ha efectuado mediante análisis por DRX, ESR y Espectroscopía Moessbauer, comprobándose la valencia de los iones Fe a la temperatura óptima de sinterización. En la mayoría de los pigmentos la fase básica se obtiene en el intervalo 900-1000ºC Los mejores pigmentos se han añadido a un esmalte blanco de loza.

  8. Study of spontaneous and induced absorption in amorphous Ta2O5 and SiO2 dielectric thin films

    Science.gov (United States)

    Markosyan, A. S.; Route, R.; Fejer, M. M.; Patel, D.; Menoni, C.

    2013-04-01

    Tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2) are common high-index and low-index materials used in dielectric optical coatings for high average-power lasers since high-density sputtered oxide films with absorption losses at near- and mid-infrared wavelengths of less than 1 ppm can be obtained. These oxides have been chosen to investigate the spontaneous and optically induced absorption at λ0 = 1064 nm that occurs due to simultaneous illumination at shorter wavelengths. The effect is measured using the photothermal common-path interferometric technique. This technique is capable of detecting sub-ppm levels of optical absorption and tracking its changes at a given wavelength when a second laser beam is also incident on a thin film oxide sample. In this work, dual beam experiments are employed to assess changes in the optical absorption at λ0 = 1064 nm in ion beam sputtered Ta2O5 and SiO2 thin films deposited on fused silica substrates, with stimulating illumination λ1 ranging from λ1 = 266 nm to λ1 = 780 nm. The power and wavelength of the stimulating radiation were found to affect the optical absorption at λ0 = 1064 nm. Furthermore, the relaxation dynamics of the induced infrared absorption was found to be wavelength dependent and is thought to be associated with various electron traps existing in the forbidden gap that depend essentially on the film's preparation conditions. The significantly greater effect observed in Ta2O5 at λ1 = 266 nm is attributed to band-to-band transitions.

  9. Dopant concentration and thermoluminescence (TL) properties of tailor-made Ge-doped SiO2 fibres

    Science.gov (United States)

    Zahaimi, Nurul Arina; Ooi Abdullah, Mohd Haris Ridzuan; Zin, Hafiz; Abdul Rahman, Ahmad Lutfi; Hashim, Suhairul; Saripan, Mohd Iqbal; Paul, Mukul Chandra; Bradley, D. A.; Abdul Rahman, Ahmad Taufek

    2014-11-01

    Study focuses on characterisation of diverse concentrations of Ge-doped SiO2 fibre as a potential thermoluminescence (TL) system for radiotherapy dosimetry. Irradiations were made using a linear accelerator providing 6 MV and 10 MV photon beams. Investigation has been done on various doped core diameter Ge-doped SiO2 glass fibres such as commercial telecommunication fibres of 8 μm and 9 μm (CorActive High Tech, Canada), tailor-made fibres of 23 and 50 μm produced by the Central Glass and Ceramic Research Institute Kolkata, and tailor-made fibres of 11 μm produced by the University of Malaya Photonics Research Centre. The fibres have been characterised for TL sensitivity, reproducibility, dose- and energy-dependence. The area under the TL glow curve increases with increasing core diameter. For repeat irradiations at a fixed dose the dosimeter produces a flat response better than 4% (1SD) of the mean of the TL distribution. Minimal TL signal fading was found, less than 0.5% per day post irradiation. Linearity of TL has been observed with a correlation coefficient (r2) of better than 0.980 (at 95% confidence level). For particular dopant concentrations, the least square fits show the change in TL yield, in counts per second per unit mass, obtained from 50 μm core diameter fibres irradiated at 6 MV of photon to be 8 times greater than that of 8 μm core diameter fibre. With respect to energy response, the TL yield at 10 MV decreases by~5% compared to that at 6 MV, primarily due to the lower mass energy absorption coefficient at higher photon energy. These early results indicate that selectively screened fibres can be developed into a promising TL system, offering high spatial resolution capability and, with this, verification of complex radiotherapy dose distributions.

  10. Nanosecond microscopy of capacitance at SiO2/4H-SiC interfaces by time-resolved scanning nonlinear dielectric microscopy

    Science.gov (United States)

    Yamagishi, Y.; Cho, Y.

    2017-10-01

    The time-resolved measurement of capacitance is a powerful method in the evaluation of defects in semiconductors, carrier dynamics in quantum dots, and photo-induced dynamics in photovoltaic materials. In this study, we demonstrate time-resolved capacitance measurements at the nanoscale using scanning nonlinear dielectric microscopy. We detected the capacitance transient of SiO2/4H-SiC interfaces triggered by the application of a 3 ns pulse, showing the high temporal resolution of the developed method. We exemplified the method with the evaluation of the density and activation energy of defects at SiO2/4H-SiC interfaces that verified the quantitative capability and high sensitivity of the method. Two-dimensional mapping of the interface states showed nanoscale inhomogeneous contrasts, implying that the physical origin of the defects at SiO2/4H-SiC interfaces is microscopically clustered.

  11. The effects of colloidal SiO2 and inhibitor on the solid deposit formation in geothermal water of low hardness

    Directory of Open Access Journals (Sweden)

    Stanković Novica J.

    2011-01-01

    Full Text Available Low solubility of SiO2 and its occurrence in geothermal waters in the form of ionic, colloidal and suspended state are the main cause of the solid deposit occurrence. Certain chemical types of silica, under the influence of Fe2+, Al3+, F−, OH- ions and other micro-constituents, and due to significantly decreased solubility of SiO2, stimulate nucleation, particle growth and solid deposit formation. The aim of this paper is to inhibit the process of nucleation and solid deposit formation by adding originally designed inhibitor in the form of an emulsion, when the total concentration of the present and added colloidal SiO2 is beyond the solubility limit (120 mg/dm3. By turbidimetric, SEM, EDS and XRD analysis, the processes of solid deposit formation were investigated in Vranjska Banja (Serbia spa geothermal water source (water hardness of 4ºdH, and theoretical and practical conclusions were made.

  12. Heat treatment of Na2O-CaO-P2O5-SiO2 bioactive glasses: densification processes and postsintering bioactivity.

    Science.gov (United States)

    Sola, A; Bellucci, D; Raucci, M G; Zeppetelli, S; Ambrosio, L; Cannillo, V

    2012-02-01

    Because of their excellent bioactivity, bioactive glasses are increasingly diffused to produce biomedical devices for bone prostheses, to face the dysfunctions that may be caused by traumatic events, diseases, or even natural aging. However, several processing routes, such as the production of scaffolds or the deposition of coatings, include a thermal treatment to apply or sinter the glass. The exposure to high temperature may induce a devetrification phenomenon, altering the properties and, in particular, the bioactivity of the glass. The present contribution offers an overview of the thermal behavior and properties of two glasses belonging to the Na2O-CaO-P2O5-SiO2 system, to be compared to the standard 45S5 Bioglass(®). The basic goal is to understand the effect of both the original composition and the thermal treatment on the performance of the sintered glasses. The new glasses, the one (BG_Na) with a high content of Na2O, the other (BG_Ca) with a high content of CaO, were fully characterized and sintering tests were performed to define the most interesting firing cycles. The sintered samples, treated at 880°C and 800°C respectively, were investigated from a microstructural point of view and their mechanical properties were compared to those of the bulk (not sintered) glass counterparts. The effect of sintering was especially striking on the BG_Ca material, whose Vickers hardness increased from 598.9 ± 46.7 HV to 1053.4 ± 35.0 HV. The in vitro tests confirmed the ability of the glasses, both in bulk and sintered form, of generating a hydroxyapatite surface layer when immersed in a simulated body fluid. More accurate biological tests performed on the sintered glasses proved the high bioactivity of the CaO-rich composition even after a heat treatment. Copyright © 2011 Wiley Periodicals, Inc.

  13. SiO2 and CaF2 Behavior During Shielded Metal Arc Welding and Their Effect on Slag Detachability of the CaO-CaF2-SiO2 Type ENiCrFe-7-Covered Electrode

    Science.gov (United States)

    Wang, Huang; Qin, Renyao; He, Guo

    2016-09-01

    The metallurgical behavior during shielded metal arc welding (SMAW) and the slag detachability of the CaO-CaF2-SiO2 type ENiCrFe-7-covered electrodes was investigated. The results indicated that the slag detachability could be improved as the SiO2 in the flux coatings decreased. When the SiO2 in the flux coating was 10.9 pct, about 28.3 pct CaF2 resulted in the best slag detachability. The CaF2 and SiO2 in the flux coating interacted during SMAW to form gaseous SiF4 to be evacuated. In the reactions, one SiO2 consumed two CaF2, leading to the reduction of the ratio of CaF2/SiO2. After comparing the slag compositions, the best slag detachability was obtained at CaO:CaF2:SiO2 = 1.7:1.8:1, but the worst slag detachability appeared at CaO:CaF2:SiO2 = 1.3:0.9:1. The XRD analysis revealed that the oxides and fluorides in the slags preferred to gather together to form cuspidine and other complex phases. If the CaF2 was dominant in the slags, they intended to form homogenous porous microstructures that were relatively strong and would most likely detach from the weld metal in blocks, exhibiting good slag detachability. If the cuspidine phase was dominant, the slags exhibited a `rock strata'-like microstructure in the intergranular area. Such microstructure was very fragile and could be broken into fine powders that were easily embedded in the weld ripples, leading to slag adhesions. This work provides the researcher with a wealth of information and data, which will also be beneficial to the welding material producers and users.

  14. Nano SiO2 and MgO improve the properties of porous β-TCP scaffolds via advanced manufacturing technology.

    Science.gov (United States)

    Gao, Chengde; Wei, Pingpin; Feng, Pei; Xiao, Tao; Shuai, Cijun; Peng, Shuping

    2015-03-25

    Nano SiO2 and MgO particles were incorporated into β-tricalcium phosphate (β-TCP) scaffolds to improve the mechanical and biological properties. The porous cylindrical β-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped β-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from β-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (β-TCP) to 5.74 ± 0.62 MPa (β-TCP/SiO2), 9.02 ± 0.55 MPa (β-TCP/MgO) and 10.43 ± 0.28 MPa (β-TCP/SiO2/MgO), respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of β-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of β-TCP scaffold.

  15. Long-term water absorption and thickness swelling and determine their characteristics in wood flour/polypropylene/Nano SiO2 nanocomposite

    Directory of Open Access Journals (Sweden)

    Saeed Ismaeilimoghadam

    2016-09-01

    Full Text Available The objective of this study was to investigate the effect of nano SiO2 on long-term water absorption and thickness swelling, humidity coefficient diffusion and thickness swelling rate of wood plastic composite. For this purpose, 60% wood flour, 40% polypropylene, 2 per hundred compound (phc MAPP in internal mixer (HAAKE were mixed. Nano SiO2 with 0, 1, 3 and 5 (phc ratios as a reinforcing was used too. Finally test samples were fabricated by using the injection molding machine. Then long-term water absorption and thickness swelling for 1848 hours according to the ASTM standard on the samples were measured. Humidity coefficient diffusion and thickness swelling rate for closer look long-term water absorption and thickness swelling behavior in wood plastic nanocomposite were calculated too. For ensure to the formation of hydrogen bonds between hydroxyl grope of SiO2 nanoparticles with hydroxyl grope of wood flour form Fourier transform infrared (FTIR spectroscopy tests was used. The results showed that water absorption behavior of nanocomposite is according to Fick's law, in addition with increasing to SiO2 nanoparticles, long-term water absorption and thickness swelling and humidity coefficient diffusion in wood plastic nanocomposite decreased. The results of infrared spectroscopy showed that hydrogen bond between the nano SiO2 and wood flour confirmed. Statistical analysis showed that after 1848 hours of immersion, nano SiO2 showed a significant effect at a confidence level of 99% on water absorption and thickness swelling, so the sample with 5% silica nanoparticles was chosen as the best treatment.

  16. Photo-thermal characteristics of water-based Fe3O4@SiO2 nanofluid for solar-thermal applications

    Science.gov (United States)

    Khashan, Saud; Dagher, Sawsan; Omari, Salahaddin Al; Tit, Nacir; Elnajjar, Emad; Mathew, Bobby; Hilal-Alnaqbi, Ali

    2017-05-01

    This work proposes and demonstrates the novel idea of using Fe3O4@SiO2 core/shell structure nanoparticles (NPs) to improve the solar thermal conversion efficiency. Magnetite (Fe3O4) NPs are synthesized by controlled co-precipitation method. Fe3O4@SiO2 NPs are prepared based on sol-gel approach, then characterized. Water-based Fe3O4@SiO2 nanofluid is prepared and usedto illustrate the photo-thermal conversion characteristics of a solar collector under solar simulator. The temperature rise characteristics of the nanofluids are investigated at different heights of the solar collector, for duration of 300 min, under a solar intensity of 1000 W m-2. The experimental results show that Fe3O4@SiO2 NPs have a core/shell structure with spherical morphology and size of about 400 nm. Fe3O4@SiO2/H2O nanofluid enhances the photo-thermal conversion efficiency compared with base fluid and Fe3O4/H2O nanofluid, since the silica coating improves both the thermodynamic stability of the nanofluid and the light absorption effectiveness of the NPs. At a concentration of 1 mg/1 ml of Fe3O4@SiO2/H2O, and with the utilization of kerosene into the solar collector, and exposure for radiation for 5 min, the photo-thermal conversion efficiency has shown an enhancement at the bottom of the collector of about 32.9% compared to the base fluid.

  17. Bioactivity, pre-osteoblastic cell responses, and osteoconductivity evaluations of the electrospun non-woven SiO2-CaO gel fabrics.

    Science.gov (United States)

    Seol, Yang-Jo; Kim, Kyoung-Hwa; Kang, Young Mi; Kim, In Ae; Rhee, Sang-Hoon

    2009-08-01

    The evaluations of the fibers characteristics, bioactivity, pre-osteoblastic cell responses, and osteoconductivity of the non-woven SiO(2)-CaO gel fabric made by electrospinning method was carried out. Silica gels with four different calcium contents were prepared by condensation following hydrolysis of tetraethyl orthosilicate under acidic conditions. The molar ratios of Ca to Si prepared ranged from 0 to 0.15. SiO(2)-CaO gel fabrics were heat-treated at 300 degrees C for 3 h after spinning under an electric field of 2 kV/cm. As the Ca to Si ratio increased, the diameter of electrospun SiO(2)-CaO gel fibers increased because the viscosity of the SiO(2)-CaO gel solution increased. The apatite-forming ability of heat-treated, non-woven SiO(2)-CaO gel fabric was evaluated in simulated body fluid and tended to increase with an increasing Ca to Si molar ratio. However, proliferation and differentiation tended to decrease with an increasing Ca to Si molar ratio. The sample which had the Ca to Si ratio as 0.10 showed good osteoconductivity in vivo in the calvarial defect New Zealand white rabbit model compared to that had the Ca to Si ratio as 0 and empty defect. These results strongly suggest that non-woven SiO(2)-CaO gel fabric made by the electrospinning method has potential for application as a bone grafting material.

  18. Nanoscale Phase-Separated Structure in Core-Shell Nanoparticles of SiO2-Si1-xGexO2 Glass Revealed by Electron Microscopy.

    Science.gov (United States)

    Kubo, Yugo; Yonezawa, Kazuhiro

    2017-09-05

    SiO2-based optical fibers are indispensable components of modern information communication technologies. It has recently become increasingly important to establish a technique for visualizing the nanoscale phase-separated structure inside SiO2-GeO2 glass nanoparticles during the manufacturing of SiO2-GeO2 fibers. This is because the rapidly increasing price of Ge has made it necessary to improve the Ge yield by clarifying the detailed mechanism of Ge diffusion into SiO2. However, direct observation of the internal nanostructure of glass particles has been extremely difficult, mainly due to electrostatic charging and the damage induced by electron and X-ray irradiation. In the present study, we used state-of-the-art scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray spectroscopy (EDX) to examine cross-sectional samples of SiO2-GeO2 particles embedded in an epoxy resin, which were fabricated using a broad Ar ion beam and a focused Ga ion beam. These advanced techniques enabled us to observe the internal phase-separated structure of the nanoparticles. We have for the first time clearly determined the SiO2-Si1-xGexO2 core-shell structure of such particles, the element distribution, the degree of crystallinity, and the quantitative chemical composition of microscopic regions, and we discuss the formation mechanism for the observed structure. The proposed imaging protocol is highly promising for studying the internal structure of various core-shell nanoparticles, which affects their catalytic, optical, and electronic properties.

  19. Nano SiO2 and MgO Improve the Properties of Porous β-TCP Scaffolds via Advanced Manufacturing Technology

    Directory of Open Access Journals (Sweden)

    Chengde Gao

    2015-03-01

    Full Text Available Nano SiO2 and MgO particles were incorporated into β-tricalcium phosphate (β-TCP scaffolds to improve the mechanical and biological properties. The porous cylindrical β-TCP scaffolds doped with 0.5 wt % SiO2, 1.0 wt % MgO, 0.5 wt % SiO2 + 1.0 wt % MgO were fabricated via selective laser sintering respectively and undoped β-TCP scaffold was also prepared as control. The phase composition and mechanical strength of the scaffolds were evaluated. X-ray diffraction analysis indicated that the phase transformation from β-TCP to α-TCP was inhibited after the addition of MgO. The compressive strength of scaffold was improved from 3.12 ± 0.36 MPa (β-TCP to 5.74 ± 0.62 MPa (β-TCP/SiO2, 9.02 ± 0.55 MPa (β-TCP/MgO and 10.43 ± 0.28 MPa (β-TCP/SiO2/MgO, respectively. The weight loss and apatite-forming ability of the scaffolds were evaluated by soaking them in simulated body fluid. The results demonstrated that both SiO2 and MgO dopings slowed down the degradation rate and improved the bioactivity of β-TCP scaffolds. In vitro cell culture studies indicated that SiO2 and MgO dopings facilitated cell attachment and proliferation. Combined addition of SiO2 and MgO were found optimal in enhancing both the mechanical and biological properties of β-TCP scaffold.

  20. Optimizing Preparation of Micron SiO2-based Phase Change and Humidity Controlling Composites with Uniform Particle Size Distribution Based on RBF Neural Network

    Directory of Open Access Journals (Sweden)

    ZHANG Hao

    2017-08-01

    Full Text Available With SiO2 as the carrier, decanoic acid-palmitic acid as a phase change material,the micron SiO2-based phase change and humidity controlling composite materials were prepared by sol-gel method. The scheme was optimized by uniform design in a combination with RBF neural network to optimizing preparation of micron SiO2-based phase change and humidity controlling composite materials. The performance of micron SiO2-based phase change and humidity controlling composite materials with optimal uniform particle size distribution were tested and characterized. The results show that RBF neural network has the best approximation effect, when spread is 0.5; optimization technology parameters are solution pH value 4.27, amount of deionized water (mole ratio between deionized water and tetraethyl orthosilicate is 8.58, amount of absolute alcohol (mole ratio between absolute alcohol and tetraethyl orthosilicate is 4.83 and ultrasonic wave power is 316W; micron SiO2-based phase change and humidity controlling composite materials with optimal uniform particle size distribution' d10 is 383.51nm, d50 is 511.63nm and d90 is 658.76nm, measured value of d90-d10 is 275.25nm, the measured value and the predicted value are in good agreement (relative error is -2.64%; micron SiO2-based phase change and humidity controlling composite materials with optimal uniform particle size distribution' equilibrium moisture content in the relative humidity of 40%-60% is 0.0925-0.1493g/g, phase transition temperature is 20.02-23.45℃ and phase change enthalpy is 54.06-60.78J/g.

  1. UV-Triggered Self-Healing of a Single Robust SiO2 Microcapsule Based on Cationic Polymerization for Potential Application in Aerospace Coatings.

    Science.gov (United States)

    Guo, Wanchun; Jia, Yin; Tian, Kesong; Xu, Zhaopeng; Jiao, Jiao; Li, Ruifei; Wu, Yuehao; Cao, Ling; Wang, Haiyan

    2016-08-17

    UV-triggered self-healing of single microcapsules has been a good candidate to enhance the life of polymer-based aerospace coatings because of its rapid healing process and healing chemistry based on an accurate stoichiometric ratio. However, free radical photoinitiators used in single microcapsules commonly suffer from possible deactivation due to the presence of oxygen in the space environment. Moreover, entrapment of polymeric microcapsules into coatings often involves elevated temperature or a strong solvent, probably leading to swelling or degradation of polymer shell, and ultimately the loss of active healing species into the host matrix. We herein describe the first single robust SiO2 microcapsule self-healing system based on UV-triggered cationic polymerization for potential application in aerospace coatings. On the basis of the similarity of solubility parameters of the active healing species and the SiO2 precursor, the epoxy resin and cationic photoinitiator are successfully encapsulated into a single SiO2 microcapsule via a combined interfacial/in situ polymerization. The single SiO2 microcapsule shows solvent resistance and thermal stability, especially a strong resistance for thermal cycling in a simulated space environment. In addition, the up to 89% curing efficiency of the epoxy resin in 30 min, and the obvious filling of scratches in the epoxy matrix demonstrate the excellent UV-induced healing performance of SiO2 microcapsules, attributed to a high load of healing species within the capsule (up to 87 wt %) and healing chemistry based on an accurate stoichiometric ratio of the photoinitiator and epoxy resin at 9/100. More importantly, healing chemistry based on a UV-triggered cationic polymerization mechanism is not sensitive to oxygen, extremely facilitating future embedment of this single SiO2 microcapsule in spacecraft coatings to achieve self-healing in a space environment with abundant UV radiation and oxygen.

  2. A compressible mesoporous SiO2 sponge supported by a carbon nanotube network.

    Science.gov (United States)

    Yang, Yanbing; Shi, Enzheng; Li, Peixu; Wu, Dehai; Wu, Shiting; Shang, Yuanyuan; Xu, Wenjing; Cao, Anyuan; Yuan, Quan

    2014-04-07

    Applications of mesoporous silica (m-SiO2) have suffered from its fragility (monolithic m-SiO2 easily collapses under compression) and limited internal molecular exchange through small channels. Previously reported hierarchical porous m-SiO2 structures containing interconnected macropores could improve adsorption properties, but they were still intrinsically fragile without sufficient mechanical strength to sustain deformation. Here, we embed a three-dimensional carbon nanotube (CNT) skeleton into m-SiO2 to fabricate bulk, robust sponges that can be compressed to large strains (60% volume reduction) repeatedly in both air and water. This is done by directly casting a uniform m-SiO2 layer with tunable thickness onto the surface of CNTs while maintaining the original network and open porous structure, resulting in a core-shell CNT@m-SiO2 hybrid sponge. By pumping fluid through the CNT@m-SiO2 sponges under cyclic compression, the adsorption rate and efficiency of dye molecules can be significantly enhanced due to the mesoporous coating on CNTs and enhanced fluid exchange throughout internal pores. The CNT@m-SiO2 sponges may be used as robust and flexible adsorption media, and chemical and biological sensors with high performance.

  3. COMPOSITE MATERIALS BASED ON CEMENT BINDERS MODIFIED WITH SiO2 NANOADDITIVES

    Directory of Open Access Journals (Sweden)

    B. M. Khroustalev

    2017-01-01

    Full Text Available Development of nanotechnologies allows to solve a number of problems of construction materials science: increase in strength, durability, abrasion and corrosion resistance that determines operational reliability of building constructions. Generally it is achieved due to nanoparticles that modify the structure and properties of the existing materials or products and are entered into their volume or on a surface layer. It’s theoretically and experimentally proved that the modified water has the bigger activity owing to the change of the ionic composition influencing the рН size and other parameters. As nanoparticles have a high level of surface energy, they show the increased tendency to agglomeration, meanwhile the size of agglomerates can reach several micrometers. In this regard an urgent task is to equally distribute and disaggregate the nanoparticles in the volume of tempering water. The experiments on studying of influence of the nanoparticles of silica distributed in volume of liquid by means of ultrasonic processing on characteristics of cement and sand solution and heavy concrete have been conducted. Nanoadditive influence on density, speed of strength development, final strength under compression of materials on the basis of cement depending on nanoadditive mass percent has been established.

  4. Synthesis, Characterization and Cytotoxicity of Novel Multifunctional Fe3O4@SiO2@GdVO4:Dy3+ Core-Shell Nanocomposite as a Drug Carrier

    Directory of Open Access Journals (Sweden)

    Bo Li

    2016-03-01

    Full Text Available In this study, multifunctional Fe3O4@SiO2@GdVO4:Dy3+ nanocomposites were successfully synthesized via a two-step method. Their structure, luminescence and magnetic properties were characterized by X-ray diffraction (XRD, scanning electronic microscope (SEM, transmission electron microscopy (TEM, photoluminescence (PL spectra and vibrating sample magnetometer (VSM. The results indicated that the as-prepared multifunctional composites displayed a well-defined core-shell structure. The composites show spherical morphology with a size distribution of around 360 nm. Additionally, the composites exhibit high saturation magnetization (20.40 emu/g and excellent luminescence properties. The inner Fe3O4 cores and the outer GdVO4:Dy3+ layers endow the composites with good responsive magnetic properties and strong fluorescent properties, which endow the nanoparticles with great potential applications in drug delivery, magnetic resonance imaging, and marking and separating of cells in vitro.

  5. A Fluorescent Sensor for Zinc Detection and Removal Based on Core-Shell Functionalized Fe3O4@SiO2 Nanoparticles

    OpenAIRE

    Xu, Yaohui; Zhou, Yang; Ma, Wenhui; Wang, Shixing

    2013-01-01

    The magnetic Fe3O4@SiO2 nanoparticles (NPs) functionalized with 8-chloroacetylaminoquinoline as a fluorescent sensor for detection and removal of Zn2+ have been synthesized. The core-shell structures of the nanoparticles and chemical composition have been confirmed by TEM, XRD, FTIR, and XPS techniques. The addition of functionalized Fe3O4@SiO2 NPs into the acetonitrile solution of Zn2+ had an effect of visual color change as well as significant fluorescent enhancement. High-saturated magneti...

  6. Gas separation using Knudsen and surface diffusion II: Effects of surface modification of epoxy/porous SiO2 composite

    OpenAIRE

    Isobe, Toshihiro; Nishimura, Masaki; Takada, Yasuhiro; Matsushita, Sachiko; Honda, Sawao; Iwamoto, Yuji; Nakajima, Akira

    2014-01-01

    Epoxy/porous SiO2 composites were prepared with the pore surface modified using various silane coupling agents. The N2 adsorption and desorption isotherm shows that the porous SiO2 used for raw materials has sufficiently high pore volume. Their pore sizes, calculated using Barrett–Joyner–Halenda method as less than 20 nm was markedly smaller than the mean free path of the gases used for this study. The respective degrees of gas selectivity CO2/N2, CH4/N2, and O2/N2 were measured. Results show...

  7. The influence of the cooling rate of a 2PbO . SiO2 melt on the constitution of silicate anions

    OpenAIRE

    Götz, J; Hoebbel, Dagobert; Wieker, Wolfgang

    1980-01-01

    The kinetics of crystallization in a 2Pbo · SiO2 melt have been investigated. A TTT-diagram was constructed, which describes the kinetic parameters for the formation of crystalline phases in the system. By means of silicate anion analysis the relationship between the cooling rates of the melt and the structure of silicate units in solid 2PbO · SiO2 has been studied. Substantial differences in the thermal treatment of the melt lead to alterations of the silicate anion constitution, which cause...

  8. Improvement of light output power of InGaN/GaN light-emitting diode by lateral epitaxial overgrowth using pyramidal-shaped SiO(2).

    Science.gov (United States)

    Cho, Chu-Young; Lee, Jin-Bock; Lee, Sang-Jun; Han, Sang-Heon; Park, Tae-Young; Kim, Je Won; Kim, Yong Chun; Park, Seong-Ju

    2010-01-18

    We report on the improvement of light output power of InGaN/GaN blue light-emitting diodes (LEDs) by lateral epitaxial overgrowth (LEO) of GaN using a pyramidal-shaped SiO(2) mask. The light output power was increased by 80% at 20 mA of injection current compared with that of conventional LEDs without LEO structures. This improvement is attributed to an increased internal quantum efficiency by a significant reduction in threading dislocation and by an enhancement of light extraction efficiency by pyramidal-shaped SiO(2) LEO mask.

  9. Interaction of aluminum projectiles with quartz sand in impact experiments: Formation of khatyrkite (CuAl2) and reduction of SiO2 to Si

    Science.gov (United States)

    Hamann, Christopher; Stöffler, Dieter; Reimold, Wolf Uwe

    2016-11-01

    We analyzed the interaction of spherical, 6.36-mm-diameter, Cu-bearing aluminum projectiles with quartz sand targets in hypervelocity impact experiments performed at NASA Ames Vertical Gun Range. Impact velocities and inferred peak shock pressures varied between 5.9 and 6.5 km/s and ∼41 and 48 GPa, respectively. Shocked particles (;impact melt particles;) coated with thin crusts of molten projectile material were recovered from the floors of the ca. 33-cm-diameter craters and the respective ejecta blankets. Through petrographic and chemical (optical microscopy, FE-EMPA, SEM-EDX, and XRF) analysis we show that these particles have a layered structure manifested in distinct layers of decreasing shock metamorphism. These can be characterized by the following physical and chemical reactions and alteration products: (i) complete melting and subsequent recrystallization of the projectile, forming a distinct crystallization texture in the fused metal crust; (ii) projectile-target mixing, involving a redox reaction between Cu-bearing Al alloy und SiO2, leading to formation of khatyrkite (CuAl2), Al2O3 melt, euhedral silicon crystals, and spherical droplets of silicon; (iii) melting of quartz to lechatelierite and formation of planar deformation features in relic quartz grains; and (iv) shock lithification of quartz grains with fracturing of grains, grain-boundary melting, planar deformation features, and complete loss of porosity. To our knowledge, this is the first report of khatyrkite formed experimentally in hypervelocity impact experiments. These results have implications for the understanding of a similar redox reaction between Al-Cu metal and siliceous impact melt recently postulated for the Khatyrka CV3 carbonaceous chondrite. Moreover, these results bear on the processes that lead to layers of regolith on the surfaces of planetary bodies without atmospheres, such as asteroids in the main belt (e.g., 4 Vesta), and on the Moon. Specifically, impacts of mm

  10. Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

    Directory of Open Access Journals (Sweden)

    Jingbin Yang

    2017-06-01

    Full Text Available C-A-S-H (CaO-Al2O3-SiO2-H2O and N-A-S-H (Na2O-Al2O3-SiO2-H2O have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials.

  11. A combined interfacial and in-situ polymerization strategy to construct well-defined core-shell epoxy-containing SiO2-based microcapsules with high encapsulation loading, super thermal stability and nonpolar solvent tolerance

    OpenAIRE

    Yin Jia; Haiyan Wang; Kesong Tian; Ruifei Li; Zhaopeng Xu; Jiao Jiao; Ling Cao; Yuehao Wu

    2016-01-01

    SiO2-based microcapsules containing hydrophobic molecules exhibited potential applications such as extrinsic self-healing, drug delivery, due to outstanding thermal and chemical stability of SiO2. However, to construct SiO2-based microcapsules with both high encapsulation loading and long-term structural stability is still a troublesome issue, limiting their further utilization. We herein design a single-batch route, a combined interfacial and in-situ polymerization strategy, to fabricate epo...

  12. Three-dimensional SiO2@Fe3O4 core/shell nanorod array/graphene architecture: synthesis and electromagnetic absorption properties

    Science.gov (United States)

    Ren, Yulan; Zhu, Chunling; Zhang, Shen; Li, Chunyan; Chen, Yujin; Gao, Peng; Yang, Piaoping; Ouyang, Qiuyun

    2013-11-01

    We developed a new strategy, i.e., a seed-assisted method, to fabricate a three-dimensional (3D) SiO2@Fe3O4 core/shell nanorod array/graphene architecture. The fabrication processes involved deposition of β-FeOOH seeds on the graphene surfaces in the ferric nitrate aqueous solution, subsequent growth of β-FeOOH nanorod arrays on the graphene surfaces in the ferric chloride aqueous solution under hydrothermal conditions, deposition of SiO2 coating on the surfaces of β-FeOOH nanorods, and final formation of the 3D architecture by a thermal treatment process. Scanning electron microscopy and transmission electron microscopy measurements showed that the SiO2@Fe3O4 core/shell nanorods with a length and diameter of about 60 and 25 nm, respectively, were almost grown perpendicularly on both side surfaces of graphene sheets. The measured electromagnetic parameters showed that the 3D architecture exhibited excellent electromagnetic wave absorption properties, i.e., more than 99% of electromagnetic wave energy could be attenuated by the 3D architecture with an addition amount of only 20 wt% in the paraffin matrix. In addition, the growth mechanism of the 3D architecture was proposed, and thus, the strategy presented here could be used as a typical method to synthesize other 3D magnetic graphene nanostructures for extending their application areas.We developed a new strategy, i.e., a seed-assisted method, to fabricate a three-dimensional (3D) SiO2@Fe3O4 core/shell nanorod array/graphene architecture. The fabrication processes involved deposition of β-FeOOH seeds on the graphene surfaces in the ferric nitrate aqueous solution, subsequent growth of β-FeOOH nanorod arrays on the graphene surfaces in the ferric chloride aqueous solution under hydrothermal conditions, deposition of SiO2 coating on the surfaces of β-FeOOH nanorods, and final formation of the 3D architecture by a thermal treatment process. Scanning electron microscopy and transmission electron microscopy measurements showed that the SiO2@Fe3O4 core/shell nanorods with a length and diameter of about 60 and 25 nm, respectively, were almost grown perpendicularly on both side surfaces of graphene sheets. The measured electromagnetic parameters showed that the 3D architecture exhibited excellent electromagnetic wave absorption properties, i.e., more than 99% of electromagnetic wave energy could be attenuated by the 3D architecture with an addition amount of only 20 wt% in the paraffin matrix. In addition, the growth mechanism of the 3D architecture was proposed, and thus, the strategy presented here could be used as a typical method to synthesize other 3D magnetic graphene nanostructures for extending their application areas. Electronic supplementary information (ESI) available: The detailed synthesis process, structural characterization, and electromagnetic measurements for the 3D SiO2@Fe3O4 core/shell nanorod array/G architecture. HAAD-STEM and EDX analyses for 3D SiO2@β-FeOOH core/shell nanorod array/G and SiO2@Fe3O4 core/shell nanorod array/G architectures, XPS and SEM image of XRD patterns of 3D SiO2@Fe3O4 core/shell nanorod array/G architecture, SEM images of the product obtained without SiO2 coating, the reflection losses of the pure Fe3O4 nanorods and the tangent losses of the 3D architecture and the pure Fe3O4 nanorods, and the reflection losses of 3D architecture with low loading amounts of Fe3O4. See DOI: 10.1039/c3nr04058e

  13. Antireflection Coatings for Strongly Curved Glass Lenses by Atomic Layer Deposition

    OpenAIRE

    Kristin Pfeiffer; Ulrike Schulz; Andreas Tünnermann; Adriana Szeghalmi

    2017-01-01

    Antireflection (AR) coatings are indispensable in numerous optical applications and are increasingly demanded on highly curved optical components. In this work, optical thin films of SiO2, Al2O3, TiO2 and Ta2O5 were prepared by atomic layer deposition (ALD), which is based on self-limiting surface reactions leading to a uniform film thickness on arbitrarily shaped surfaces. Al2O3/TiO2/SiO2 and Al2O3/Ta2O5/SiO2 AR coatings were successfully applied in the 400–750 nm and 400–700 nm spectral ran...

  14. Evolution of silica coating layer on titanium surface and the effect on the bond strength between titanium and porcelain

    Science.gov (United States)

    Wang, Aili; Ge, Chaoqun; Yin, Hengbo; Gao, Yu; Jiang, Tao; Xia, Chunlin; Wu, Gang; Wu, Zhanao

    2013-07-01

    SiO2 coating layers were uniformly anchored at the surfaces of sandblasted/pre-oxidized commercially pure titanium (CP-Ti) substrates by the chemical deposition method using Na2SiO3 as the SiO2 precursor at the pH values of 8-10 with the Na2SiO3 concentrations of 0.05-0.5 mol/L. The SiO2 coating layers were composed of small-sized SiO2 nanoparticles with the average particle sizes ranging from 18.0 to 20.5 nm. After firing porcelain (Ti-22) on SiO2-coated sandblasted/pre-oxidized CP-Ti substrates, the bond strengths of CP-Ti and porcelain ranged from 33.56 to 40.43 MPa, which were detected by the three-point flexure bend test method. In the absence of SiO2 interlayer, the bond strength of sandblasted/pre-oxidized CP-Ti and porcelain was 25.6 MPa. The bond strengths in the presence of SiO2 interlayer were higher than that in the absence of SiO2 interlayer. On the other hand, when the CP-Ti substrates were only treated by hydrochloric acid pickling, the bond strengths of SiO2-coated acid-pickled CP-Ti and porcelain ranged from 12.99 to 16.59 MPa. The chemical interaction between the SiO2 interlayers and the oxidized CP-Ti surfaces probably played an important role in increasing the bond strength of CP-Ti and porcelain.

  15. Growth of rutile TiO2 nanorods in Ti and Cu ion sequentially implanted SiO2 and the involved mechanisms

    Science.gov (United States)

    Mu, Xiaoyu; Liu, Xiaoyu; Wang, Xiaohu; Dai, Haitao; Liu, Changlong

    2018-01-01

    TiO2 in nanoscale exhibits unique physicochemical and optoelectronic properties and has attracted much more interest of the researchers. In this work, TiO2 nanostructures are synthesized in amorphous SiO2 slices by implanting Ti ions, or sequentially implanting Ti and Cu ions combined with annealing at high temperature. The morphology, structure, spatial distribution and optical properties of the formed nanostructures have been investigated in detail. Our results clearly show that the thermal growth of TiO2 nanostructures in SiO2 substrate is significantly enhanced by presence of post Cu ion implantation, which depends strongly on the applied Cu ion fluence, as well as the annealing atmosphere. Due to the formation of Cu2O in the substrate, rutile TiO2 nanorods of large size have been well fabricated in the Ti and Cu sequentially implanted SiO2 after annealing in N2 atmosphere, in which Cu2O plays a role as a catalyst. Moreover, the sample with well-fabricated TiO2 nanorods exhibits a narrowed band gap, an enhanced optical absorption in visible region, and catalase-/peroxidase-like catalytic characteristics. Our findings provide an effective route to fabricate functional TiO2 nanorods in SiO2 via ion implantation.

  16. HClO4-SiO2 as a new, highly efficient, inexpensive and reusable catalyst for N-tert-butoxycarbonylation of amines.

    Science.gov (United States)

    Chakraborti, Asit K; Chankeshwara, Sunay V

    2006-07-21

    Perchloric acid adsorbed on silica-gel (HClO4-SiO2) was found to be a new, highly efficient, inexpensive and reusable catalyst for chemoselective N-tert-butoxycarbonylation of amines at room temperature and under solvent-free conditions.

  17. Synthesis and Characterization of CeO2-SiO2 Nanoparticles by Microwave-Assisted Irradiation Method for Photocatalytic Oxidation of Methylene Blue Dye

    Directory of Open Access Journals (Sweden)

    R. M. Mohamed

    2012-01-01

    Full Text Available CeO2-SiO2 nanoparticles were synthesized for the first time by a facile microwave-assisted irradiation process. The effect of irradiation time of microwave was studied. The materials were characterized by N2 adsorption, XRD, UV-vis/DR, and TEM. All solids showed mesoporous textures with high surface areas, relatively small pore size diameters, and large pore volume. The X-ray diffraction results indicated that the as-synthesized nanoparticles exhibited cubic CeO2 without impurities and amorphous silica. The transmission electron microscopy (TEM images revealed that the particle size of CeO2-SiO2 nanoparticles, which were prepared by microwave method for 30 min irradiation times, was around 8 nm. The photocatalytic activities were evaluated by the decomposition of methylene blue dye under UV light irradiations. The results showed that the irradiation under the microwave produced CeO2-SiO2 nanoparticles, which have the best crystallinity under a shorter irradiation time. This indicates that the introduction of the microwave really can save energy and time with faster kinetics of crystallization. The sample prepared by 30 min microwave irradiation time exhibited the highest photocatalytic activity. The photocatalytic activity of CeO2-SiO2 nanoparticles, which were prepared by 30 min irradiation times was found to have better performance than commercial reference P25.

  18. Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

    Data.gov (United States)

    U.S. Environmental Protection Agency — The data set is a matrix of cellular biochemical (metabolites) in HepG2 cells treated with various metal oxide nanomaterials composed of CeO2, SiO2 and CuO. This...

  19. Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

    Science.gov (United States)

    Abstract Background To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for 3 days to five different CeO2 (either 30 or 100 μg/ml), 3 SiO2 based (30 μg/ml) or 1 CuO (3 μg/ml) nanomaterials with dry primary particle sizes r...

  20. Hierarchical core/shell Fe3O4@SiO2@γ-AlOOH@Au micro/nanoflowers for protein immobilization.

    Science.gov (United States)

    Xuan, Shouhu; Wang, Feng; Gong, Xinglong; Kong, Siu-Kai; Yu, Jimmy C; Leung, Ken Cham-Fai

    2011-03-07

    A facile synthesis of monodispersed microparticles composed of superparamagnetic Fe(3)O(4) cores, SiO(2) shell, hierarchical γ-AlOOH periphery with Au nanoparticles is reported. These particles are found to be useful for protein immobilization and bear resemblance to daisy flowers, and are hereafter termed "nanoflowers".

  1. Core/shell Fe3O4 @SiO2 nanoparticles modified with PAH as a vector for EGFP plasmid DNA delivery into HeLa cells.

    Science.gov (United States)

    Shi, Mengran; Liu, Yiyao; Xu, Mingming; Yang, Hong; Wu, Chunhui; Miyoshi, Hirokazu

    2011-11-10

    Novel stable core/shell Fe(3)O(4)@SiO(2)/PAH nanoparticles are synthesized using 15 nm Fe(3)O(4) as the template that is modified with PAH. The resulting nanoparticles can absorb plasmid DNA to mediate gene transfer in cultured HeLa cells. An electrophoretic assay suggests that the Fe(3)O(4)@SiO(2)/PAH nanoparticles protect the plasmid DNA from serum and DNase I degradation. A cell viability assay shows that the Fe(3)O(4)@SiO(2)/PAH nanoparticles exhibit a low cytotoxicity toward endothelial cells. Qualitative analysis of transfection in HeLa cells by nanoparticles carrying a plasmid DNA encoding EGFP demonstrates a fairly high expression level, even in the presence of serum. Thus, Fe(3)O(4)@SiO(2)/PAH nanoparticles are biocompatible and suitable for nonviral delivery, and may find applications in cancer therapy. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Ionic liquid coated magnetic core/shell Fe3O4@SiO2 nanoparticles for the separation/analysis of linuron in food samples.

    Science.gov (United States)

    Chen, Jieping; Zhu, Xiashi

    2015-02-25

    Three hydrophobic ionic liquids (ILs) including 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM]PF6), 1-hexyl-3-methyl-imidazole hexafluorophosphate ([HMIM]PF6), and 1-octyl-3-methylimidazole hexafluoro-phosphate ([OMIM]PF6) coated Fe3O4@SiO2 nanoparticles with core-shell structure to prepare magnetic solid phase extraction agent (Fe3O4@SiO2@ILs) and establish a new method of magnetic solid phase extraction (MSPE) coupled with UV spectrometry for separation/analysis of linuron. The results showed that linuron was adsorbed rapidly by Fe3O4@SiO2@[OMIM]PF6 and eluanted by ethanol. Under the optimal conditions, preconcentration factor of the proposed method was 10-fold. The linear range, detection limit, correlation coefficient (R) and relative standard deviation (RSD) were found to be 0.04-20.00 μg mL(-1), 5.0 ng mL(-1), 0.9993 and 2.8% (n=3, c=4.00 μg mL(-1)), respectively. The Fe3O4@SiO2 nanoparticles could be used repeatedly for 10 times. This proposed method has been successfully applied to the determination of linuron in food samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Fabrication of Fe3O4/SiO2 core/shell nanoparticles attached to graphene oxide and its use as an adsorbent.

    Science.gov (United States)

    Yao, Yunjin; Miao, Shiding; Yu, Shaoming; Ma, Li Ping; Sun, Hongqi; Wang, Shaobin

    2012-08-01

    Amino-functionalized Fe(3)O(4)/SiO(2) core/shell nanoparticles were synthesized by reacting Fe(3)O(4) nanoparticles with tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane to introduce amino groups on the surface. The amino groups on the Fe(3)O(4)/SiO(2) were reacted with the carboxylic groups of graphene oxide (GO) with the aid of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinnimide to form Fe(3)O(4)/SiO(2)GO nanoparticles. The structural, surface, and magnetic characteristics of the material were investigated by scanning and transmission electron microscopy, energy-dispersive X-ray spectrometry, powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Adsorption equilibrium and kinetics of methylene blue on the Fe(3)O(4)/SiO(2)GO were studied in a batch system. The maximum adsorption capacities were found to be 97.0, 102.6, and 111.1 mg g(-1) at 25, 45, and 60°C, respectively. A second-order kinetic equation could best describe the sorption kinetics. Thermodynamic parameters indicated that the adsorption of methylene blue onto the material was thermodynamically feasible and could occur spontaneously. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Physics of Trap Generation and Electrical Breakdown in Ultra-thin SiO2 and SiON Gate Dielectric Materials

    NARCIS (Netherlands)

    Nicollian, Paul Edward

    2007-01-01

    This work spans nearly a decade of industrial research in the reliability physics of deeply scaled SiO2 and SiON gate dielectrics. In this work, we will present our following original contributions to the field: • Below 5V stress, the dominant mechanism for stressed induced leakage current in the

  5. Effect of contact angle, zeta potential and particles size on the in vitro studies of Al2O3 and SiO2 nanoparticles.

    Science.gov (United States)

    Karunakaran, Gopalu; Suriyaprabha, Rangaraj; Rajendran, Venkatachalam; Kannan, Narayanasamy

    2015-02-01

    Currently, nanometal oxides find their role in different biological applications such as tissue engineering, implant and bone replacement materials. Owing to the increased use of nanoparticles, it is necessary to understand their release and toxicity in the biological system. In this regard, three independent studies such as in vitro cytotoxicity, antioxidant activity and biocompatibility of nano- and micrometal oxide particles such as alumina (Al2O3) and silica (SiO2) are evaluated. It is evident from cell viability study that nanoAl2O3 and SiO2 particles are less toxic when compared with microAl2O3 and SiO2 to NIH 3T3 cell lines up to 200 µg/ml. Antioxidant properties of micro- and nanoAl2O3 in terms of radical scavenging percentage for micro- and nanoAl2O3 are 59.1% and 72.1%, respectively, at 100 mg. Similarly, the radical scavenging percentage of nano- and bulk SiO2 are 81.0% and 67.2%, respectively. The present study reveals that the cellular behaviour, interaction and biocompatibility of metal oxides differ with dose, particle size, contact angle and zeta potential. The present study opens up a new strategy to analyse in vitro nanotoxicity.

  6. High Photocatalytic Activity of Fe3O4-SiO2-TiO2 Functional Particles with Core-Shell Structure

    Directory of Open Access Journals (Sweden)

    Chenyang Xue

    2013-01-01

    Full Text Available This paper describes a novel method of synthesizing Fe3O4-SiO2-TiO2 functional nanoparticles with the core-shell structure. The Fe3O4 cores which were mainly superparamagnetic were synthesized through a novel carbon reduction method. The Fe3O4 cores were then modified with SiO2 and finally encapsulated with TiO2 by the sol-gel method. The results of characterizations showed that the encapsulated 700 nm Fe3O4-SiO2-TiO2 particles have a relatively uniform size distribution, an anatase TiO2 shell, and suitable magnetic properties for allowing collection in a magnetic field. These magnetic properties, large area, relative high saturation intensity, and low retentive magnetism make the particles have high dispersibility in suspension and yet enable them to be recovered well using magnetic fields. The functionality of these particles was tested by measuring the photocatalytic activity of the decolouring of methyl orange (MO and methylene blue (MB under ultraviolet light and sunlight. The results showed that the introduction of the Fe3O4-SiO2-TiO2 functional nanoparticles significantly increased the decoloration rate so that an MO solution at a concentration of 10 mg/L could be decoloured completely within 180 minutes. The particles were recovered after utilization, washing, and drying and the primary recovery ratio was 87.5%.

  7. Stress reduction and structural properties of Ta2O5/SiO2 mixture films produced by ion-beam sputtering

    Science.gov (United States)

    Pu, Yunti; Qiao, Zhao; Wang, Gang; Qiu, Fuming; Ma, Ping; Wang, Siyu

    2016-10-01

    Ta2O5/SiO2 mixture films with different composition ratios deposited by ion-beam sputtering were investigated. The different refractive indexes with different composition ratios were measured by Spectroscopic Ellipsometry. The relations between residual stress and structural properties were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the high compressive stress observed in SiO2 films (n=1.65-2.0, Ref. λ=500nm) was reduced significantly by mixing a properly amount of Ta2O5 (σTa2O5=-234MPa<σSiO2=-510MPa). Through analyzing microstructure properties and optical properties of Ta2O5/SiO2 mixture films, we found that the residual compressive stress was only related with the intrinsic stress σintr and the extrinsic stress σext. A model of stress evolution has been proposed to illustrate the mechanism of stress reduction . The reduction of compressive stress was due to less lattice mismatch and more vacancies. Moreover, the scanning electron microscopy (SEM) result showed that the surface quality of SiO2 film was improved by mixing a relatively amount of Ta2O5 (n=1.85, Ref. λ=500nm).

  8. Gas separation using Knudsen and surface diffusion II: Effects of surface modification of epoxy/porous SiO2 composite

    Directory of Open Access Journals (Sweden)

    Toshihiro Isobe

    2014-09-01

    Full Text Available Epoxy/porous SiO2 composites were prepared with the pore surface modified using various silane coupling agents. The N2 adsorption and desorption isotherm shows that the porous SiO2 used for raw materials has sufficiently high pore volume. Their pore sizes, calculated using Barrett–Joyner–Halenda method as less than 20 nm was markedly smaller than the mean free path of the gases used for this study. The respective degrees of gas selectivity CO2/N2, CH4/N2, and O2/N2 were measured. Results show that the epoxy/porous SiO2 composite surface-modified by APTES only exhibits CO2/N2 gas selectivity at a lower pressure drop. It originates in the affinity between amino group of the APTES and CO2 gas. The epoxy/porous SiO2 composite treated by APTES also shows gas separation capability. The 80% N2/20% CO2 mix gas was converted into 68.2% N2/31.8% CO2 gas after gas separation tests at 25 °C. The gas separation capability was maintained at high temperatures. The 80% N2/20% CO2 mix gas was converted into 70.8% N2/29.2% CO2 gas at 100 °C.

  9. Luminescent properties and quenching effects of Pr3+ co-doping in SiO2:Tb3+/Eu3+ nanophosphors

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2014-02-01

    Full Text Available Luminescence properties of Pr(sup3+) single doped SiO2 and Pr(sup3+) co-doped SiO(sub2):Tb(sup3+)/Eu(sup3+) nanophosphors synthesized using sol–gel method were investigated. X-ray diffraction (XRD), and scanning electron microscope (SEM) were used...

  10. Space Weathering of Silicates Simulated by Successive Laser Irradiation: In Situ Reflectance Measurements of Fo90, Fo99+, and Sio2

    Science.gov (United States)

    Loeffler, M. J.; Dukes, C. A.; Christoffersen, R.; Baragiola, R. A.

    2016-01-01

    Pulsed-laser irradiation causes the visible-near-infrared spectral slope of olivine (Fo90 and Fo99+) and SiO2 to increase (redden), while the olivine samples darken and the SiO2 samples brighten slightly. XPS analysis shows that irradiation of Fo90 produces metallic Fe. Analytical SEM and TEM measurements confirm that reddening in the Fo90 olivine samples correlates with the production of nanophase metallic Fe (npFe0) grains, 2050 nm in size. The reddening observed in the SiO2 sample is consistent with the formation of SiO or other SiOx species that absorb in the visible. The weak spectral brightening induced by laser irradiation of SiO2 is consistent with a change in surface topography of the sample. The darkening observed in the olivine samples is likely caused by the formation of larger npFe0 particles, such as the 100400 nm diameter npFe0 identified during our TEM analysis of Fo90 samples. The Fo90 reflectance spectra are qualitatively similar to those in previous experiments suggesting that in all cases formation of npFe0 is causing the spectral alteration. Finally, we find that the accumulation of successive laserpulses cause continued sample darkening in the Vis-NIR, which suggests that repeated surface impacts are an efficient way to darken airless body surfaces.

  11. Effect of doped SiO2 and calcinations temperature on phase transformation of TiO2 photocatalyst prepared by sol-gel method

    Directory of Open Access Journals (Sweden)

    Sutham Niyomwas

    2008-05-01

    Full Text Available The purpose of this research was to study the effect of calcinations temperature and SiO2 addition on phase transformation,crystallite size, and photocatalytic activity of SiO2/TiO2 thin films by using indigo carmine as an indicator. Thecomposite particles were prepared by sol-gel method via calcinations at a temperature range of 300-700oC for 2 h, and thecomposite thin films were prepared by means of spin coating. The microstructure and crystallite size of pure TiO2 and SiO2/TiO2 composite powders were characterized by using XRD, SEM and DTA. It was found that anatase structures wereformed at a calcinations temperature range of 300-600oC and mixed phases of anatase and rutile were observed at a temperatureof 700oC. Crystallite size of pure TiO2 tends to increase with an increase in calcinations temperature. Doped SiO2in the TiO2 has an effect on crystal phases and crystallite size of the composite powders and thin films, resulting in thechange of the photocatalytic activity of TiO2.

  12. SiO2/ZnO Composite Hollow Sub-Micron Fibers: Fabrication from Facile Single Capillary Electrospinning and Their Photoluminescence Properties.

    Science.gov (United States)

    Song, Guanying; Li, Zhenjiang; Li, Kaihua; Zhang, Lina; Meng, Alan

    2017-02-24

    In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS), polyvinylpyrrolidone (PVP) and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) spectra indicated that the asprepared composite hollow fibers consisted of amorphous SiO2 and hexagonal wurtzite ZnO. The products revealed uniform tubular structure with outer diameters of 400-500 nm and wall thickness of 50-60 nm. The gases generated and the directional escaped mechanism was proposed to illustrate the formation of SiO2/ZnO composite hollow sub-micron fibers. Furthermore, a broad blue emission band was observed in the photoluminescence (PL) of SiO2/ZnO composite hollow sub-micron fibers, exhibiting great potential applications as blue light-emitting candidate materials.

  13. Preparation and characterization of chain-like and peanut-like Fe3O4@SiO2 core-shell structure.

    Science.gov (United States)

    Shi, Haowei; Huang, Yan; Cheng, Chao; Ji, Guoyuan; Yang, Yuxiang; Yuan, Hongming

    2013-10-01

    The size- and shape-controlled Fe3O4@SiO2 nanocomposites were successfully synthesized via the sol-gel method. The results showed that the size, shape, and property of the products were directly influenced by the amount of TEOS, and the concentration of water-based magnetic fluid in the coating process. The morphology and properties of the products were characterized by TEM, SEM, X-ray powder diffraction, IR and EDS. The Fe3O4@SiO2 composites with easily-controlled size arranged from 58 to 835 nm could be synthesized by adjusting the experimental parameters. When TEOS amount is 1 mL and the concentration of magnetic fluid were 30.0 and 10.0 mg/mL respectively, chain-like and peanuts-like well-dispersed Fe3O4@SiO2 particles with clear core-shell structure were obtained. These size- and shape-controlled Fe3O4@SiO2 composites may have potential application in the field of targeted drug delivery and MRI contrast agent.

  14. SiO2/ZnO Composite Hollow Sub-Micron Fibers: Fabrication from Facile Single Capillary Electrospinning and Their Photoluminescence Properties

    Directory of Open Access Journals (Sweden)

    Guanying Song

    2017-02-01

    Full Text Available In this work, SiO2/ZnO composite hollow sub-micron fibers were fabricated by a facile single capillary electrospinning technique followed by calcination, using tetraethyl orthosilicate (TEOS, polyvinylpyrrolidone (PVP and ZnO nanoparticles as raw materials. The characterization results of the scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD and Fourier transform infrared spectroscopy (FT-IR spectra indicated that the asprepared composite hollow fibers consisted of amorphous SiO2 and hexagonal wurtzite ZnO. The products revealed uniform tubular structure with outer diameters of 400–500 nm and wall thickness of 50–60 nm. The gases generated and the directional escaped mechanism was proposed to illustrate the formation of SiO2/ZnO composite hollow sub-micron fibers. Furthermore, a broad blue emission band was observed in the photoluminescence (PL of SiO2/ZnO composite hollow sub-micron fibers, exhibiting great potential applications as blue light-emitting candidate materials.

  15. The relation between residual stress, interfacial structure and the joint property in the SiO2f/SiO2-Nb joints.

    Science.gov (United States)

    Ma, Qiang; Li, Zhuo Ran; Yang, Lai Shan; Lin, Jing Huang; Ba, Jin; Wang, Ze Yu; Qi, Jun Lei; Feng, Ji Cai

    2017-06-23

    In order to achieve a high-quality joint between SiO2f/SiO2 and metals, it is necessary to address the poor wettability of SiO2f/SiO2 and the high residual stress in SiO2f/SiO2-Nb joint. Here, we simultaneously realize good wettability and low residual stress in SiO2f/SiO2-Nb joint by combined method of HF etching treatment and Finite Element Analysis (FEA). After etching treatment, the wettability of E-SiO2f/SiO2 was improved, and the residual stress in the joint was decreased. In order to better control the quality of joints, efforts were made to understand the relationship between surface structure of E-SiO2f/SiO2 and residual stress in joint using FEA. Based on the direction of FEA results, a relationship between residual stress, surface structure and joint property in the brazed joints were investigated by experiments. As well the FEA and the brazing test results both realized the high-quality joint of E-SiO2f/SiO2-Nb and the shear strength of the joint reached 61.9 MPa.

  16. Effects of Ce3+ concentration, beam voltage and current on the cathodoluminescence intensity of SiO2: Pr3+–Ce3+ nanophosphor

    CSIR Research Space (South Africa)

    Mhlongo, GH

    2011-02-01

    Full Text Available SiO2:Pr3+–Ce3+ phosphor powders were successfully prepared using a sol–gel process. The concentration of Pr3+ was fixed at 0.2 mol% while that of Ce3+ was varied in the range of 0.2–2 mol%. High resolution transmission electron microscopy (HRTEM...

  17. Study of SiGe oxidation kinetics for preferential SiO2 formation under a low O2 pressure condition

    Science.gov (United States)

    Song, Woojin; Toriumi, Akira

    2017-11-01

    We have studied the oxidation kinetics of SiGe as parameters of O2 pressure and temperature. This paper first discusses the SiGe oxidation experimentally and thermodynamically. It was found that Si was predominantly oxidized in the Si0.5Ge0.5 oxidation under lower O2 pressures. This fact is thermodynamically reasonable, but the Ge remaining after Si oxidation may be a big concern in terms of SiGe gate stacks, because it should form defects at the interface or inside the SiO2 film. Therefore, it is critically important to understand how the Ge atoms behave after the SiO2 formation. Second, the GeO2/Si reaction, which might be a key part to well controlled SiGe gate stacks in the preferential SiO2 formation, is discussed. Two kinds of metallic Ge formation kinetics at the SiGe interface in the annealing of GeO2/Si are conjectured: One is the metallic Ge diffusion into the Si substrate and the other is the Ge precipitation at the interface, which should be avoided for improving the SiGe interface properties. The experimental results indicate that the former case is made possible by annealing under the low O2 pressure condition in a very thin SiO2 formation region.

  18. Effective surface modification of MnFe2O4@SiO2@PMIDA magnetic nanoparticles for rapid and high-density antibody immobilization

    Science.gov (United States)

    Rashid, Zahra; Soleimani, Masoud; Ghahremanzadeh, Ramin; Vossoughi, Manouchehr; Esmaeili, Elaheh

    2017-12-01

    The present study is aimed at the synthesis of MnFe2O4@SiO2@PMIDA in terms of highly efficient sensing platform for anti-prostate specific membrane antigen (PSMA) immobilization. Superparamagnetic manganese ferrite nanoparticles were synthesized following co-precipitation method and then SiO2 shell was coated on the magnetic core with tetraethyl orthosilicate (TEOS) through a silanization reaction to prevent oxidation, agglomeration and, increase the density of OH groups on the surface of MnFe2O4. Subsequently, MnFe2O4@SiO2@PMIDA obtained as a result of the reaction between N-(phosphonomethyl)iminodiacetic acid (PMIDA) and MnFe2O4@SiO2. The reactive carboxyl groups on the surface of magnetic nanoparticles can efficiently conjugate to a monoclonal antibody, specific to PSMA, which was confirmed by enzyme-linked immune sorbent assay (ELISA). Thus, this kind of functionalized magnetic nanoparticles is promising to be utilized in the improvement of ELISA-based biosensors and also will be effective in a variety of biomedical applications such as cell separation, diagnosis, and monitoring of human diseases.

  19. Fast dynamics of 1.5 μm photoluminescence in Er-doped SiO2 sensitized with Si nanocrystals

    NARCIS (Netherlands)

    Timmerman, D.; Saeed, S.; Gregorkiewicz, T.

    2011-01-01

    In order to investigate origin of fast photoluminescence at 1.5 μm reported to appear in Er-doped SiO2 sensitized with silicon nanocrystals, time-resolved photoluminescence measurements were compared between high temperature annealed Er-doped and Er-free samples. We confirm that this fast

  20. Facile preparation of magnetic mesoporous MnFe2O4@SiO2-CTAB composites for Cr(VI) adsorption and reduction.

    Science.gov (United States)

    Li, Na; Fu, Fenglian; Lu, Jianwei; Ding, Zecong; Tang, Bing; Pang, Jiabin

    2017-01-01

    Chromium-contaminated water is regarded as one of the biggest threats to human health. In this study, a novel magnetic mesoporous MnFe2O4@SiO2-CTAB composite was prepared by a facile one-step modification method and applied to remove Cr(VI). X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area, and vibrating sample magnetometer were used to characterize MnFe2O4@SiO2-CTAB composites. The morphology analysis showed that the composites displayed a core-shell structure. The outer shell was mesoporous silica with CTAB and the core was MnFe2O4 nanoparticles, which ensured the easy separation by an external magnetic field. The performance of MnFe2O4@SiO2-CTAB composites in Cr(VI) removal was far better than that of bare MnFe2O4 nanoparticles. There were two reasons for the effective removal of Cr(VI) by MnFe2O4@SiO2-CTAB composites: (1) mesoporous silica shell with abundant CTA(+) significantly enhanced the Cr(VI) adsorption capacity of the composites; (2) a portion of Cr(VI) was reduced to less toxic Cr(III) by MnFe2O4, followed by Cr(III) immobilized on MnFe2O4@SiO2-CTAB composites, which had been demonstrated by X-ray photoelectron spectroscopy results. The adsorption of Cr(VI) onto MnFe2O4@SiO2-CTAB followed the Freundlich isotherm model and pseudo-second-order model. Tests on the regeneration and reuse of the composites were performed. The removal efficiency of Cr(VI) still retained 92.4% in the sixth cycle. MnFe2O4@SiO2-CTAB composites exhibited a great potential for the removal of Cr(VI) from water. Copyright © 2016 Elsevier Ltd. All rights reserved.