Gel electrolytes based on lithium modified silica nano-particles

In this work lithium modified silica (Li-SiO₂) nano-particles were synthesized and used as a single ion lithium conductor source in gel electrolytes. It was found that Li-SiO₂ exhibited good compatibility with DMSO, DMA/EC (a mixture of N,N-dimethyl acetamide and ethylene carbonate) and the ionic liquid, N-methyl-N-propyl pyrrolidinium bis(trifluoromethylsulfonyl) amide ([C₃mpyr][NTf₂]). Several gel electrolytes based on Li-SiO₂ were obtained. These gel electrolytes were investigated by DSC, solid state NMR, conductivity measurements and cyclic voltammetry. Conductivities as high as 10⁻³ S/cm at room temperature were observed in these nano-particle gel electrolytes. The results of electrochemical tests showed that some of these materials were promising for using as lithium conductive electrolytes in electrochemical devices, with high lithium cycling efficiency evident.

Surface-appropriate lipophobicity - Application in isobutene oligomerization over Teflon-modified silica-supported 12-silicotungstic acid

A series of silica-supported 12-silicotungstic acid catalysts (H4SiW12O40, abbreviated as HSiW), modified with various loadings of Teflon (HSiW/SiO2-Teflon), were prepared by an impregnation method. The surface properties of the catalysts were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), BET, infrared (IR) spectroscopy, NH3-TPD and the Drop Shape Analysis (DSA). SEM results combined with energy-dispersive X-ray (EDX) measurements of HSiW/SiO2-Teflon revealed that F-compound (Teflon) is effectively coated on the catalyst surface. The contact angles for water and oil of 50 wt% HSiW/SiO2 and HSiW/SiO2-Teflon indicate that HSiW/SiO2-Teflon catalyst enhances not only the surface hydrophobicity but also the surface lipophobicity by means of the addition of Teflon. Silica-supported 12-silicotungstic acid modified with Teflon exhibits higher C-8(=) selectivity and longer lifetime than that of silica-supported 12-silicotungstic acid in isobutene oligomerization. Thus, surface-appropriate lipophobicity of catalysts may be effective for decreasing the interaction between coke precursors and the catalyst surface and for removing deposited coke more easily.

Luminescence and energy transfer of organically modified silica xerogels (OMSX) doped and undoped with Eu3+ and Tb3+

Organically modified silica xerogels (OMSX) and Eu3+ (Tb3+)-doped OMSX were prepared by the reaction of (3-aminopropyl) triethoxysilane (APS) with 3-isocyanatepropyltriethoxysilane (ICPTES) followed by the subsequent hydrolysis and condensation in the presence of Eu3+ (Tb3+) via sol-gel method, which were characterized by FT-IR, XRD, fluorescence excitation and emission spectra. The as-formed OMSX shows a strong blue emission with the maximum excitation and emission wavelength at 351 and 420 nm, respectively. Due to the spectral overlap between the emission band of OMSX and f-f absorption lines of Eu3+ and Tb3+ in the UV-blue region, an energy transfer was observed from OMSX host to Eu3+ and Tb3+ in OMSX/Eu3+ and OMSX/Tb3+, respectively. Excitation at 350-360 nm resulted in a very weak emission around 420 nm from OMSX host and strong emission of Eu3+ and Tb3+ in OMSX/Eu3+ and OMSX/Tb3+, respectively. The emission spectra of Eu3+ and Tb3+ consist of D-5(0)-F-7(J) (J = 0, 1, 2, 3, 4) and D-5(4)-F-7(J) (J = 6, 5, 4, 3), respectively. Furthermore, the predicted structure of OMSX/Eu3+ and OMSX/Tb3+ is presented.

A gas chromatographic analysis of light hydrocarbons on a column packed with modified silica gel

A one-meter long column packed with silica gel is used to separate light hydrocarbons. The silica gel has been modified with several kinds of gas chromatography stationary phases. Among these, PEG 2000 shows fairly good effect when using 80-100 meshes silica gel for the separation of mixture of methane, ethane, ethylene, acetylene, propane, propylene and n-, i-butane. The different behavior of silica gel between batch to batch is also found. When silica gel is coated with a small amount of Al2O3 prepared with sol-gel method, better resolution has been observed on a 2-meter column compared with the non-modified silica gel.

Studies on the use of nano zinc oxide and modified silica in NR, CR and SBR

Department of Applied Chemistry, Cochin University of Science and Technology

Lithium-functionalised silica nanoparticles for enhanced ionic conductivity in an organic ionic plastic crystal

Addition of silica nanoparticles functionalised with lithium propane sulfonate to the organic ionic plastic crystal N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([C₂mpyr][NTf₂]) results in a significant increase in ionic conductivity. Analysis of these nanocomposites by impedance spectroscopy, NMR, positron annihilation lifetime spectroscopy (PALS) and Raman spectroscopy suggests that this is the result of higher matrix mobility due to an increase in defect size and concentration. The effect of these functionalised nanoparticles is compared to that previously observed for unfunctionalised nanoparticles in the lithium-doped and pure plastic crystal.

Robust, self-healing superamphiphobic fabrics prepared by two-step coating of fluoro-containing polymer, fluoroalkyl silane, and modified silica nanoparticles

A robust, superamphiphobic fabric with a novel self-healing ability to autorepair from chemical damage is prepared by a two-step wet-chemistry coating technique using an easily available material system consisting of poly(vinylidene fluoride-co-hexafluoropropylene), fluoroalkyl silane, and modified silica nanoparticles. The coated fabrics can withstand at least 600 cycles of standard laundry and 8000 cycles of abrasion without apparently changing the superamphiphobicity. The coating is also very stable to strong acid/base, ozone, and boiling treatments. After being damaged chemically, the coating can restore its super liquid-repellent properties by a short-time heating treatment or room temperature ageing. This simple but novel and effective coating system may be useful for the development of robust protective clothing for various applications.

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range -0.2 to + 0.6 V versus Ag/AgCl (0.02 mol L-1 KNO3; V = 20 mV s(-1)) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, cleaning solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L-1 Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 mu g L-1 mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity. (c) 2006 Elsevier Ltd. All rights reserved.

4-amine-2-mercaptopyrimidine modified silica gel applied in Cd(II) and Pb(II) extraction from an aqueous medium

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Preconcentration and determination of Cu(II) in a fresh water sample using modified silica gel as a solid-phase extraction adsorbent

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Copper Hexacyanoferrate Formation on the Modified Silica Surface with DAB-Am-16 Dendrimer

The third generation (G-3) polypropylenimine hexadecaamine dendrimer (DAB-Am-16) was grafted onto the silica gel surface. The modified silica interacts easily with Cu(2+) and then with potassium ferrocyanide to form copper hexacyanoferrate. The modified silica was characterized by the following techniques: Nuclear Magnetic Resonance (NMR), FTIR spectroscopy, Energy Dispersive X-ray (EDX) and Cyclic Voltammetry. The modified silica containing copper hexacyanoferrate (CuHCFSD) was tested for a voltammetric determination of nitrite using a modified graphite paste electrode.

Synthesis, characterization, and application of modified silica in the removal and preconcentration of lead ions from natural river water

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)