Preconcentration of albumin on silica with attached groups of polyoxyethylated isooctyl phenol

The potencies of silica with attached groups of polyoxyethylated isooctyl phenol (SiO ₂ -TX) as an adsorbent for the solid phase extraction (SPE) preconcentration of bovine serum albumin (BSA) in urine are examined. SiO₂-TX is shown to effectively extract BSA (up to 96%) as an ion associate with cationic (at pH 8) and anionic (at pH 1.5) surfactants. The maximal capacity of SiO₂-TX to BSA makes 33 mg/g in the presence of octylpyridinium bromide, 27 mg/g in the presence of cetyltrymethylammonium bromide or sodium dodecylsulfate with the linearity range in Henri’s area up to 23 and 20 mg/g of SiO₂-TX, respectively; the distribution coefficients attain 1.8 × 10³ mL/g. BSA is eluted quantitatively with 1–4 mL of acetonitrile containing NaOH, which makes possible the use of adsorbent for the reaction of protein with trifluoroethanol (TFE) before its photometric determination by the Lowry method. The influence of accompanying urine components is studied, i.e., urea, glucose, Na⁺, K⁺, Mg²⁺, chlorides, and phosphates, on the efficiency BSA extraction from model aqueous solutions on SiO₂-TX. The detection limit for BSA makes 4 mg/L and the analytical range, from 12 to 140 mg/L.     

Gold, palladium and gold–palladium supported on silica catalysts prepared by sol–gel method: synthesis, characterization and catalytic behavior in the ethanol steam reforming

Noble-metal-based catalysts supported on silica (Au/SiO₂, Pd/SiO₂ and Au–Pd/SiO₂) were prepared by the sol–gel method and were evaluated in the steam reforming of ethanol for hydrogen production. The catalysts were characterized by N₂ physisorption (BET/BJH methods), X-ray diffraction, temperature programmed reduction analysis, H₂ chemisorption, atomic absorption spectrophotometry and Raman spectroscopy. The structural characterization of the Au- and Pd-containing catalysts after calcination showed that the solids are predominantly formed by Au⁰, Pd⁰ and PdO species and was observed that the metallic Pd dispersion diminished in the presence of Au⁰. The results revealed that the catalytic behavior could be influenced by the experimental conditions and the nature of the catalyst employed. The Pd/SiO₂ catalyst showed the best performance among the catalysts tested at the highest reaction temperature (600 °C) due to the more effective action of the metallic active phase, which covers a greater area in this sample. At this same reaction temperature, the Au–Pd/SiO₂ catalyst showed a significant deactivation, probably due to the lower Pd dispersion presented by this catalyst.     

Adsorption behaviors of strontium using macroporous silica based hexagonal tungsten oxide

A novel macroporous silica-based hexagonal tungsten oxide (h-WO₃/SiO₂) with exchangeable sodium cations located in hexagonal tunnel structure was synthesized by a facile hydrothermal treatment of sodium tungstate dihydrate with 1 mol/L HCl solution. Utilization of the h-WO₃/SiO₂ adsorbent to remove aqueous strontium was investigated under the condition of various pH values, contact time, the initial concentration of metal ions, salt ion concentration, and coexisting ions. According to the experimental data, Sr²⁺ adsorption equilibrium was achieved within 15 min in acidic solution, and the maximum removal capacity of Sr²⁺ occurred at pH 4. The kinetic adsorption of Sr²⁺ on h-WO₃/SiO₂ was controlled by pseudo second-order model, and the saturated adsorption of Sr²⁺ on h-WO₃/SiO₂ was better described by Langmuir and Redlich-Peterson isotherm models compared with the Freundlich isotherm model. The distribution coefficient of Sr²⁺ was more than 2000 cm³/g in the presence of Ca²⁺, Mg²⁺, La³⁺, and Eu³⁺, indicating that the h-WO₃/SiO₂ showed excellent selectivity towards Sr²⁺ in pH 4.     

A Facile method to Prepare Monodispersed CdS/SiO2 Composite Microspheres and Investigation on Their Photocatalytic Properties

This article presents a facile method to prepare CdS/SiO₂ composite microspheres and their good catalytic properties. In our method, monodispersed SiO₂ particles bearing amino groups (–NH₂) were synthesized at first and then used as carriers to load nanosized CdS particles to form CdS/SiO₂ composite microspheres. With the addition of CdAc₂ solution to the SiO₂ dispersion, Cd²⁺ was attracted to the surfaces of the SiO₂ particles through coordination interaction, and then thioacetamide was added to the dispersion. By heating, S^2? released and reacted with the Cd²⁺, CdS/SiO₂ composite microspheres were obtained accordingly. The photocatalytic properties of the as‐prepared composite microspheres were investigated as well. It was found that the composite microspheres have excellent photocatalytic activities for the degradation of dyes comparing with the commercial P‐25 TiO₂ catalysts. After using and recycling for three times, the photocatalytic performance still remained very well.     

Zur Dimorphie von Nd3Cl[SiO4]2

On the Dimorphism of Nd₃Cl[SiO₄]₂ On reacting NdCl₃, Nd₂O₃, and SiO₂ (molar ratio: 1 : 4 : 6) at 850 °C in evacuated silica tubes, pale violet, hydrolysis resistant neodymium(III) chloride ortho‐silicate Nd₃Cl[SiO₄]₂ can be obtained within seven days. If equimolar amounts of NaCl are added as flux, rod‐ or platelet‐shaped, transparent single crystals of two modifications accumulate simultaneously. The one with the higher density (A‐Nd₃Cl[SiO₄]₂) crystallizes monoclinically (C2/c, no. 15; a = 1416.6(1), b = 638.79(6), c = 872.21(9) pm, β = 98.403(7)°; V_m = 117.55 cm³/mol, Z = 4), whereas the one with the lower density (B‐Nd₃Cl[SiO₄]₂) exhibits orthorhombic symmetry (Pnma, no. 62; a = 709.36(7), b = 1815.7(2), c = 631.48(6) pm; V_m = 122.45 cm³/mol, Z = 4). Two crystallographically independent Nd³⁺ cations exist in each of both crystal structures, which in the A type are surrounded by nine (1 Cl^– + 8 O^2–) and ten (2 Cl^– + 8 O^2–), whilst those in the B type by only two times eight (1 Cl^– + 7 O^2– and 2 Cl^– + 6 O^2–) anions, respectively. Thereby all oxygen atoms of both forms represent members of discrete ortho‐silicate tetrahedra ([SiO₄]^4–). Although both crystal structures are built of alternating anionic double layers {(Nd1)₂[SiO₄]₂}^2– and cationic single layers {(Nd2)Cl}²⁺, there is a higher cross‐linkage of the building units in the A‐type lattice, where the cations are coordinated by three and four tetrahedra edges of ortho‐silicate anions, compared to only two times two of them in the B type. From this an about 4% higher density of Nd₃Cl[SiO₄]₂ results for the A‐type structure (D_x = 5.55 g/cm³) in comparison with B‐type Nd₃Cl[SiO₄]₂ (D_x = 5.33 g/cm³).     

Immobilization of glucose oxidase on rod-like and vesicle-like mesoporous silica for enhancing current responses of glucose biosensors

The use of rod-like and vesicle-like mesoporous SiO₂ particles for fabricating high performance glucose biosensors is reported. The distinctively high surface areas of mesoporous structures of SiO₂ rendered the adsorption of glucose oxidase (GOx) feasible. Both morphologies of SiO₂ enhanced the sensitivities of glucose biosensors, but by a factor of 36 for vesicle-like SiO₂ and 18 for rod-like SiO₂, respectively. The greater enhancement of vesicle-like SiO₂ can be accounted for by its higher specific surface area (509 m² g⁻¹) and larger total pore volume (1.49 cm³ g⁻¹). Interestingly, the current responses of GOx immobilized in interior channels of the mesoporous SiO₂ were enhanced much more than those of simple mixtures of GOx and the mesoporous SiO₂. This suggests that the enhancement of current responses arise not only from the high surface area of SiO₂ for high enzyme loading, but also from the improved enzyme activity upon its adsorption on mesoporous SiO₂. Also compared were the performances of glucose biosensors with GOx immobilized on mesoporous SiO₂ by physical adsorption and by covalent binding to 3-aminopropyltrimethoxysilane (APTMS) modified SiO₂ using glutaraldehyde as the cross-linker. The covalent binding approach resulted in higher enzyme loading but lower current sensitivity than with the physical adsorption.     

Etching Efficiency for Si and SiO2 by CF+x,F+, and C+ Ion Beams Extracted from CF4 Plasmas

Fluorocarbon (CF⁺ _x), fluorine (F⁺), and carbon (C⁺) ion beams with highcurrent density (50i<800 A/cm²) were irradiated to Si and SiO₂surfaces to investigate the influence of the ion species on the etchingefficiency. The ion beams were extracted from magnetized helicon-wave CF₄plasmas operated in pulsed modes. The CF⁺ ₃ beam had the largest etchingefficiency for Si at the same beam energy. When the same data weresummarized as a function of the momentum of the incident ion beam, thedifference in the etching efficiency became small, although the CF⁺ ₃ beamstill had a slightly larger etching efficiency. On the other hand, theetching efficiency for SiO₂ by the CF⁺ ₃ beam was larger than that by theother ion beams in the low-momentum region. In addition, in the low-momentumregion, the etching efficiency for SiO₂ by CF⁺ ₃ was larger than that forSi. These results suggest the high chemical reactivity of CF⁺ ₃ with SiO₂,leading to the high etching selectivity of SiO₂ over underlying Si in thefabrication of semiconductor devices.     

Synthesis and properties of magnetite-poly(aminopropylsiloxane) composites

A method is developed for the synthesis of nanosized Fe₃O₄-(SiO₂) _x [NH₂(CH₂)₃SiO_3/2] _y magnetic composites with varied SiO₂: NH₂(CH₂)₃SiO_3/2, weight/weight, ratios. The structure, texture, morphology, and magnetic properties of the obtained materials are studied by several physicochemical methods. It is shown that the composites represent systems of magnetite nanoparticles coated with poly(aminopropylsiloxane). The specific surface areas, pore volumes, and saturation magnetizations of the composites are in the ranges of 21–27 m²/g, 0.03–0.04 cm³/g, and 59–62 G cm³/g, respectively.     

Investigation on the effect of nanosilica towards corn starch–lithium perchlorate-based polymer electrolytes

Biodegradable corn starch–lithium perchlorate (LiClO₄)-based solid polymer electrolytes with addition of nano-sized fumed silica (SiO₂) were prepared by solution casting technique. Ionic conductivity at ambient temperature was measured by AC impedance spectroscopy. Upon addition of nano-sized SiO₂, the ionic conductivity at room temperature is increased. The optimum ionic conductivity value obtained was 1.23?×?10^?4?S?cm^?1 at 4?wt% SiO₂. This may be attributed to the low crystallinity of the polymer electrolytes resulting from the dispersed nanosilica particles. Fourier–transform infrared spectroscopy studies confirmed the complexation between corn starch, lithium perchlorate, and silica. The thermal properties of the prepared samples were investigated with differential scanning calorimetry and thermogravimetric analysis. The surface morphology of the polymer electrolytes confirmed the agglomeration of particles after excess dispersion of inorganic filler. This was proven in the scanning electron microscopy studies.     

Sol–gel preparation and white up-conversion luminescence in rare-earth doped PbF<Subscript>2</Subscript> nanocrystals dissolved in silica glass

89.5(SiO₂)10(PbF₂)0.5(REF₃) silicate glasses have been prepared using room temperature sol–gel processing of Si(OCH₂CH₃)₄, Pb(CH₃COO)₂·3H₂O, RE(CH₃COO)₃·nH₂O and trifluoroacetic acid as a fluorinating agent, where RE stands for rare-earth ions, such as Yb³⁺, Er³⁺, Ho³⁺, Tm³⁺, or combinations of those ions. On heat treatment of these glasses at about 300–400 °C, the rare-earth doped spherical PbF₂ nanocrystals precipitate within SiO₂ glass matrix providing transparent nano-structured glass–ceramics, while the diameter of the nanocrystals can be set in the range from 5 to 25 nm by varying time and temperature of the heat treatment. The structural and photoluminescence studies confirm the incorporation of rare-earth ions into the PbF₂ nanocrystals and white and tuneable colour up-conversion luminescence has been detected in case of Yb³⁺-Er³⁺-Tm³⁺ and Yb³⁺-Ho³⁺-Tm³⁺ co-doped nanocrystals by varying dopant ratio and pump power.     

Dimeres SiO2 Matrix-IR-Untersuchungen und ab initio SCF-Rechnungen

Molecular SiO₂, Matrix IR Investigations and Ab Inito SCF-Calculations Dimeric SiO₂ is formed in a matrix reaction between (SiO)₂ and O₂. Its structure can be deduced from the IR spectra of different ¹⁸O-substituted isotopomers. The observed frequency shifts (¹⁶O/¹⁸O and ²⁸Si/²⁹Si) are in accordance with those calculated by a normal coordinate analysis. The structure concluded from experimental data is also confirmed by quantum chemical calculations. With the help of these calculations the dimerisation energy 2SiO₂ ? (SiO₂)₂ is obtained: ?453 kJ mol^?1. The mechanism of formation of (SiO₂)₂ from (SiO)₂ and O₂ is discussed with respect to some similarities to the elementary process during oxidation of the surface of silicon wafers.     

Studies on solid-state polymer composite electrolyte of nano-silica/hyperbranched poly(amine-ester)

A new solid-state polymer composite electrolyte based on hypergrafted nano-silica (SiO₂-g-HBPAE)/hyperbranched poly (amine-ester) (HBPAE) doped with lithium perchlorate (LiClO₄) was studied in this paper. The N,N-diethylol-3-amine-2-methyl methylpropionate monomer was firstly synthesized by methyl methacrylate (MMA) and diethanolamine through Michael addition reaction and then self-condensed on the surface of nano-silica pretreated by 3-aminopropyltriethoxysilane (APTES) and MMA. The synthetic procedure of the monomers and SiO₂-g-HBPAE/HBPAE was traced by fluorescence spectra. The size and grafting ratio of SiO₂-g-HBPAE were characterized by transmission electron microscopy, static light scattering and thermogravimetric analysis. Incorporating SiO₂-g-HBPAE to HBPAE could not only decrease the glass transition temperature of polymer according to the differential scanning calorimetry characterization, but also increase the elastic and viscosity modules indicated by rheological measurement results. Electrochemical properties of SiO₂-g-HBPAE/HBPAE/LiClO₄ were also investigated. The conductivity of SiO₂-g-HBPAE/HBPAE with 50 wt% LiClO₄ reached 1.4?×?10^?5 S/cm at 30 °C and 10^?3 S/cm at 100 °C. The lithium-ion transference number of synthesized hyperbranched electrolyte can be up to 0.55.     

Organosilicon Amine Gels Based on 3-Aminopropyltriethoxysilane, Cobalt(II) or Chromium(III) Clorides, and Triethoxysilane

Organosilicon gels [Co(NH₂R²)₂Cl₂] and [Cr(NH₂R²)₃Cl₃], containing a diaminodichloride complex of cobalt(II) and triaminotrichloride complex of chromium(III) (R² = CH₂CH₂CH₂SiO(OEt)), were synthesized by the hydrolysis of complexes [Co(NH₂R¹)₂Cl₂] (I) and [Cr(NH₂R¹)₃Cl₃] (II) incorporating peripheral triethoxysilyl groups (R¹ = CH₂CH₂CH₂Si(OEt)₃). The coprecipitated [Co(NH₂R²)₂Cl₂] · 4NH₂R³, [Cr(NH₂R²)₃Cl₃] · 6NH₂R³, [Co(NH₂R²)₂Cl₂] · 2SiO₂, and [Cr(NH₂R²)₃Cl₃] ·xSiO₂ · (3 – x)SiHO_1.5 (R³ = CH₂CH₂CH₂SiO_1.5) gels were obtained by cohydrolysis of complexes I and II with 3-aminopropyltriethoxysilane or triethoxysilane. Interaction with SiH(OEt)₃ is accompanied by the decomposition of silicon hydride groups and the formation of tetraethoxysilane derivatives. The heating of dry gels in a flow of argon or oxygen to 600° results in the formation of amorphous silica having a specific surface area 2–467 m²/g and containing crystalline metals, their chlorides, oxides, silicates, or carbides.     

Kinetics and mechanism of dehydration of kaolinite,muscovite and talc analyzed thermogravimetrically by the third-law method

Summary The third-law method has been applied to determine the enthalpies, Δ_rH_T⁰, for dehydration reactions of kaolinite, muscovite and talc. The Δ_rH_T⁰values measured in the equimolar (in high vacuum) and isobaric (in the presence of water vapour) modes (980±15, 3710±39 and 2793±34 kJ mol^-1, for kaolinite, muscovite and talc, respectively) practically coincide if to take into account the strong self-cooling effect in vacuum. This fact strongly supports the mechanism of dissociative evaporation of these compounds in accordance with the reactions (primary stages): Al₂O₃·2SiO₂·2H₂O(s)→Al₂O₃(g)↓+2SiO₂(g)↓+2H₂O(g); K₂O·3Al₂O₃·6SiO₂·2H₂O(s) →K₂O(g)↓+3Al₂O₃(g)↓+6SiO₂(g)↓+2H₂O(g) and 3MgO·4SiO₂·H₂O(s) →3MgO(g)↓+4SiO₂(g)↓+H₂O(g). The values of the Eparameter deduced from these data for equimolar and isobaric modes of dehydration are as follows: 196 and 327 kJ mol^-1for kaolinite, 309 and 371 kJ mol^-1for muscovite and 349 and 399 kJ mol^-1for talc. These values are in agreement with quite a few early results reported in the literature in 1960s.     

Photoluminescence of terbium-containing sol-gel glasses

Glasses of the following composition: T glass SiO₂, TL glass SiO₂/ligand, T-Tb glass SiO₂/terbium complex were obtained by the method of acid catalyzed hydrolytic homo- and cocondensation of tetraethoxysilane (the source of SiO₂) with 3-(3-triethoxysilylpropyl)pentane-2,4-dione (the ligand) and terbium(III) tris[3-3-triethoxysilylpropyl)pentane-2,4-dionate] (terbium complex). The study of the fluorescence spectra showed that the cationic luminescence is achieved by the excitation of terbium-containing glasses at the absorption band of the ligand (λ_exc 275–280 nm). Energy transfer from the matrix (SiO₂) to the ligand and cation with the following emission of Tb³⁺ is possible on exciting the T-Tb glass by the light with the wavelength 360 nm. However, this method of generating terbium cation emission seems to be less efficient.     

Preparation of Thermosensitive Hollow Imprinted Microspheres via Combining Distillation Precipitation Polymerization and Thiol‐ene Click Chemistry

Hollow molecular imprinted polymer microspheres were prepared by distillation precipitation polymerization with (S)‐(+)‐ibuprofen (S‐IBF) as template molecule and acrylamide (AM) as functional monomer. Using the silicon dioxide (SiO₂, 180 nm) modified by 3‐(trimethoxysilyl)propyl methacrylate (MPS) as the template microspheres, the molecular imprinted shells were coated on successfully (SiO₂@MIPs). The thermosensitive SiO₂@MIPs‐PNIPAM core‐shell microspheres were subsequently prepared by grafting the PNIPAM chains (M_n=1.21×10⁴ g/mol, polydispersity index=1.30), which were prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization, on the surface of SiO₂@MIPs microspheres via the thiol‐ene click chemistry. The grafting density of PNIPAM brushes on the SiO₂@MIPs microspheres was about 0.18 chains/nm². After HF etching, the hollow imprinted microspheres were finally obtained. For thermosensitivity analysis, the phase transition temperatures of multifunctional nanoparticles were measured by DSL at 25°C and 45°C respectively, and the sizes of the microspheres changed by about 35 nm. The modified microspheres presented excellent controlled release property to S‐IBF, moreover about half amount of the adsorptions passed into acetonitrile‐water solution through the specific holes of imprinted shell at 25°C under vibration.     

Obtaining of Ni<Subscript>0.65</Subscript>Zn<Subscript>0.35</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites by thermal decomposition of complex compounds embedded in silica matrix

This article presents the results of our investigation on the obtaining of Ni_0.65Zn_0.35Fe₂O₄ ferrite nanoparticles embedded in a SiO₂ matrix using a modified sol–gel synthesis method, starting from tetraethylorthosilicate (TEOS), metal (Fe^III,Ni^II,Zn^II) nitrates and ethylene glycol (EG). This method consists in the formation of carboxylate type complexes, inside the silica matrix, used as forerunners for the ferrite/silica nanocomposites. We prepared gels with different compositions, in order to obtain, through a suitable thermal treatment, the nanocomposites (Ni_0.65Zn_0.35Fe₂O₄)_x–(SiO₂)_100–x (where x=10, 20, 30, 40, 50, 60 mass%). The synthesized gels were studied by differential thermal analysis (DTA), thermogravimetry (TG) and FTIR spectroscopy. The formation of Ni–Zn ferrite in the silica matrix and the behavior in an external magnetic field were studied by X-ray diffraction (XRD) and quasi-static magnetic measurements (50 Hz).     

Étude structurale de britholite au césium Sr7La2Cs(PO4)5(SiO4)F2

Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr₈LaCs(PO₄)₆F₂, Sr₇La₂Cs(PO₄)₅(SiO₄)F₂ and Sr₂La₇Cs(SiO₄)₆F₂, were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO₄)₂. The refinement by the Rietveld method allowed also to precise the distribution of La³⁺ and Cs⁺ ions between the two cationic sites of the apatite.     

Fabrication of Core-Shell Nanocolloids with Various Core Sizes to Promote Light Capture for Green Fuels

Core-shell nanocolloids with tailored physical and chemical merits hold attractive potential for energy-related applications. Herein, core-shell nanocolloids composed of zinc/copper sulfide (ZnS/CuS_x) shells and silica (SiO₂) cores were fabricated by a template-engaged synthetic method. Interestingly, the sizes of SiO₂ cores can be tuned by different sulfurization time. In virtue of the light scattering and reflection on the SiO₂ surface, the efficiencies of light capture by ZnS/Cu₂S shells were highly dependent on the SiO₂ sizes. The as-fabricated SiO₂@ZnS/Cu₂S with a core size of 205 nm exhibited the highest and broadest absorption within a light wavelength of 380–700 nm. In virtue of the structural and componential features of these nanocolloids, maximum photocatalytic hydrogen (H₂) production rates of 2968 and 1824 μmol h⁻¹ g⁻¹ under UV-vis and visible light have been delivered, respectively. This work may provide some evidence for the design and fabrication of core-shell nanomaterials to convert solar energy to green fuels.