Sol Particles Research Articles

Preparation of Phosphor Fine Particles for Mercury-Free Lamps by Using Liquid-Phase Synthesis Method

The liquid-phase synthesis method for preparing phosphor (Y2O3: Eu) fine particles, which was expected in the application for mercury-free fluorescent lamps, was investigated. The monodispersed sols as the precursor of phosphor fine particles were first synthesized by the co-precipitation method under different conditions in the aqueous-phase. The colloidal particles of precursor sols were spherical and almost uniform. The particle sizes of the sols were under 1 μm, and the size distributions were sufficiently narrow. The metal element ratio of the sol particles could be controlled by adjusting the initial concentration of the synthesis solution. The as-prepared precursor sols were converted into well crystalline phosphor particles by heat-treatment over approximately 600°C. The phosphor particles showed emission spectra with a remarkable emission line of Eu3+ activator, and the emission intensity was sensitively influenced by the concentration of Eu3+ in the precursor solution. A morphological feature as the monodisperse of the phosphor particles remained after the heat-treatment.

A New Preparation Method of Bimodal Catalyst Support and Its Application in Fischer–Tropsch Synthesis

The silica-based supports that contained distinct bimodal structure were prepared by incipient-wetness impregnation of silica or zirconia sols into the large pores of silica gel. The pore-size distributions of the obtained supports proved that two kinds of pores coexisted according to the bimodal structure. For these bimodal supports, the increased specific surface area and decreased pore volume indicated that the particles of silica or zirconia sols had entered the large pores of the silica gel. The obtained supports were applied in liquid-phase Fischer–Tropsch synthesis (FTS) after cobalt had been loaded. The catalytic properties of these catalysts exhibited increased activity and decreased selectivities of CH4 and CO2 due to the spatial promotional effect of the bimodal pore structure and chemical effects of the porous zirconia inside the large pores of the original silica gel.

A sol particle homogeneous immunoassay for measuring serum cystatin C

Objectives: We have developed a sol particle immunoassay (SPIA) for measuring serum cystatin C, an endogenous marker of glomerular filtration rate (GFR). Design and methods: We used colloidal gold particles coated with anti-cystatin C antibodies. Results: The assay was linear in the range 0.2 to 8 mg/L and showed good correlation between theoretical and obtained values. The within and between-day coefficients of variation (CV) varied from 1.1 to 1.6% and 0.4 to 1.0%, respectively. Analytical recovery was 95.7 to 103.7%. No interference could be detected from bilirubin (up to 200 mg/L), hemoglobin (up to 3 g/L), chyle (up to 5000 FTU), rheumatoid factor (up to 1000 IU/mL) or anticoagulants. Serum samples ( n = 101), from which turbidity had been removed, were measured either with our assay or with Dako Cystatin C PET kits, using a Model 7070 Hitachi automatic clinical analyzer. Comparing these two methods, the calculated linear regression equation and the correlation coefficient were y = 0.986 x −0.153 and r = 0.995, respectively. Conclusions: Our new SPIA assay is a fully automated, homogeneous immunoassay that can readily be used in conjunction with various commercial analyzers that are currently available. The assay is sensitive, precise and suitable for clinical use and appears to offer advantages over other GFR markers such as creatinine.

The complexes of macromolecules and metal nanoparticles: pseudo‐template synthesis and behavior

AbstractMetal sols composed of metal nanoparticles (1 ‐ 10 nm in diameter) protected with polymer molecules may be regarded as dispersions of polymer‐metal complexes formed due to cooperative non‐covalent (e.g., hydrophobic, coulombic) interaction of polymer chains with the surface of metal nanoparticles. The sols are commonly prepared by reducing of metal ions in solutions of appropriate polymers.The interactions between macromolecules and nanoparticles are reversible. In the case of long polymer chains and minute particles, the equilibrium constant of the reaction exponentially depends on the surface area of the particle. The probability of mutual “recognition” (complex formation) of growing particle and a macromolecule rapidly increases from practically zero to practically unity in narrow interval of the particle's diameters. The recognition is followed with the shadowing of the particles and the stop of their growths. Such kind of processes was termed “pseudo‐template”. In frame of the concept of pseudo‐template processes can be estimated: (1) the conditions at which sol particles of desirable size can be prepared, (2) the influence of temperature, polymer concentration, nanoparticles size, and other conditions on the stability of polymer ‐ particle complex having been prepared, and (3) the conditions at which stable sol does not exist and can not be prepared at all.The interactions between metal nanoparticles and macromolecules are highly selective regard to the structure of polymer chains. The property can be effectively used for the control the size characteristics of metal nanoparticles (in course of their formation) and the stability of metal sols.The selectivity provides high conversions in catalytic chemical modification reactions in which a macromolecule is the substrate and a component of the catalyst in the same time. As an example, the hydrolysis of lactame groups in monomer unites of poly(N‐vinyl pyrrolidone) catalyzed with copper sols is discussed.

알루미나-지르코니아 복합체의 제조공정 및 미세구조에 미치는 폴리머 첨가의 영향

Two-component ceramic (alumina-zirconia) composites were fabricated by a soft-solution process in which polyethylene glycol (PEG) was used as a polymeric carrier. Metal salts and PEG were dissolved in ethyl alcohol without any precipitation in 1:1 volume ratio of alumina and zirconia. In the non-aqueous system, the flammable solvent made explosive, exothermic reaction during drying process. The reaction resulted in formation of volume expanded, porous precursor powders by a vigorous decomposition of organic components in the precursor sol. The PEG content affected the grain size of sintered composites as well as the morphology of precursor powders. The difference of microstructure in sintered composite was attribute to the solubility and homogeneity of metal cations in precursor sol. At the optimum amount of the PEG polymer, the metal ions were dispersed effectively in solution and a homogeneous polymeric network was formed. It made less agglomerated particles in the precursor sol and affected on uniform grain size in sintered composite.

Making spherical zirconia particles from inorganic zirconium aqueous sols

Spherical zirconia particles were formed by coagulation of colloidal particles in zirconium aqueous sols followed by calcination. The zirconium sols were derived from zirconium oxychloride aqueous solutions by adjusting their pH values. The coagulation that resulted from reduction of dielectric permittivity of the sol medium was caused by the addition of propanol in the sols. The size of the spherical zirconia particles varied with the concentration of zirconium in the sols.

Electrochemical redox reaction at silicate based electrode–silicate based electrolyte interface

The electrochemical redox reactions of ferrocene or ferrocenedimethanol were studied at silicate based electrode–silicate based electrolyte interface. The electrode was prepared from methyltrimethoxysilane sol and graphite particles. The electrolyte consists of silicate matrix obtained from tetramethoxysilane with embedded redox probe and salt solution in propylene carbonate or water. It was prepared with electrodes immersed before gelation occurred. Stable slow scan peak shaped voltammograms were obtained after tens of days elapsed after gel formation. Their shape depends on whether electrode is immersed in liquid electrolyte, sol and gel. For organic solvent based gels the weak dependence of the magnitude of the peak current on time elapsed after gelation, whereas for aqueous based system its substantial decrease is observed. On the results of potential step experiments some features typical for spherical diffusion as well as these indicating penetration of the electrode matrix by organic solvent were observed.

Visible-light responsive cerium ion modified titania sol and nanocrystallites for X-3B dye photodegradation

The cerium ion (Ce4+) modified titania sol and nanocrystallites were prepared by chemical coprecipitation–peptization and hydrothermal synthesis methods, respectively. XRD patterns show that Ce4+-TiO2 sol particles had anatase semicrystalline structure. And the calcined Ce4+-TiO2 powder was composed of predominant anatase titania and crystalline cerium titanate (11.18wt.% CexTi(1−x)O2). AFM micrograph shows that ultrafine particles were well dispersed in sol system and average particle size was about 10nm. Ce4+-TiO2 nanocrystallites have grown into 70nm in mean size. The difference in calculated particle size (2.41nm for sol particle and 4.53nm for crystallite) by XRD Scherrer’s formula was mainly due to aggregation effect of nanoparticles. The experimental results exhibit that Ce4+-TiO2 sol and nanocrystallites can effectively photodegrade reactive brilliant red dye (X-3B) with the dye/Ce4+-TiO2/visible-light reaction system. Moreover, photocatalytic reaction also can carry out in hydrosol reaction system as well as in suspension reaction system. And Ce4+-TiO2 sol has shown higher efficiency than nanocrystallites in respect of photocatalytic activity. Meanwhile, dye photodegradation mechanisms involving photolysis, photocatalysis, photosensitized photocatalysis and interband photocatalysis were proposed regarding different photocatalytic reaction system.

Photocatalysis of neodymium ion modified TiO 2 sol under visible light irradiation

Nd 3+ ion modified TiO 2 sol was prepared by chemical coprecipitation–peptization method. The sol particles were well distributed in colloid system and mean size was 10 nm by AFM analysis. Direct conversion of Nd 3+–TiO 2 sol particles from amorphous to semicrystalline phase was achieved at 62 °C and pH 1.0 with 12 h peptizing process. Photocatalytic reactivity of Nd 3+–TiO 2 sol was evaluated by photodegradation of phenol in solution under visible light irradiation. It was found that concentration decreased from initial 100 mg l −1 phenol to final 5.29 mg l −1 phenol and 75.2 mg l −1 phenol derivatives after 2 h photocatalysis This result indicates that Nd 3+–TiO 2 nanocolloids exhibited photocatalytic activity in the visible range. Meanwhile, total organic carbon (TOC) value declined from initial 37.1 mg l −1 to final 29.3 mg l −1, which indicates the weak capability of photomineralization, but the power of selective photocatalysis. The reaction mechanism of Nd 3+–TiO 2 sol photocatalysis was proposed as the process of self-sensitization and sub-bandgap overlapping.

Surface Polymerization of Hydrophilic Methacrylates from Ultrafine Silica Sols in Protic Media at Ambient Temperature: A Novel Approach to Surface Functionalization Using a Polyelectrolytic Macroinitiator

A convenient one‐pot synthesis of polymer‐grafted nano‐sized silica particles using atom transfer radical polymerization (see Figure) is described. Physical adsorption of a cationic macroinitiator allows polymerization of a range of hydrophilic methacrylates. A high degree of coverage of the silica sol particles by the grafted polymer chains was indicated.

Production of rare-earth orthoferrite ceramic fibres by aqueous sol-gel blow spinning process

Rare-earth orthoferrite, LnFeO3 (Ln=La, Sm, Gd, Dy, Er and Yb) ceramic fibres were produced by aqueous sol-gel blow spinning process at low-temperatures. Stable, charge stabilised, colloidal precursor sols of orthoferrites were prepared by room temperature processing of inexpensive and commercially available metal salts. The average diameter (Zav) of the colloidal sol particles was in the range 4–7 nm and had a narrow size distribution. The sols were concentrated, combined with spinning aids, and processed further to a viscous ‘spinning solution’. The gel fibres of about 6 mm diameter were blow spun, collected as random fibres, dried and heated to increasingly higher temperatures at a rate of 50 C/h. The gel fibres converted to flexible ceramic fibres, and single-phase perovskite structure crystallised directly for all the LnFeO3 (Ln=La, Sm, Gd, Dy, Er and Yb ) fibres on heating them to 700 C. The ceramic fibres had mean diameter of about 3–4 mm, and consisted of randomly oriented submicron sized grains. # 2003 Elsevier Ltd. All rights reserved.

Zinc ions and zinc sulfide particles in sol–gel zirconium phosphate synthesis, thermal behavior and X-ray characterization

Zinc ions can be exchanged in sol–gel zirconium phosphate by using the batch or hydrothermal method. The zinc materials obtained that undergo thermal treatment after complete dehydration, can rehydrate fully or partially depending on whether half or all the zinc ions are exchanged. At high temperature syntherization is evident. By flowing sulfide acid over the zinc forms, zinc sulfide particles are formed and their amount depends on the length of time of the gas flow and on the state of hydration of the original material. This is not the case in the half exchanged zinc zirconium phosphate material. The decomposition temperature of the ZnS particles depends on their position in the exchanger: whether on the surface or between the layers of the host matrix. The XRD patterns of the materials obtained are similar to those of the sol–gel zirconium phosphate. The presence of ZnS particles is evident.

EPR spectroscopic investigation of the sol–gel transition in modified tetraethylorthosilicate gels

Cu 2+ ions are used to follow the sol–gel transition in amino-modified TEOS mixtures. In contrast to unmodified TEOS gels, fixation of the spin probe (Cu 2+) to the sol particle surface takes place and changes in mobility are detectable. Furthermore, we find changes in the coordination sphere of the copper ions and a temporary loss of EPR intensity. By using a simple kinetic model it is possible to estimate the rate constants of the condensation and syneresis processes.

Photocatalytic activity and recycle application of titanium dioxide sol for X-3B photodegradation

Abstract In this paper, TiO 2 sol was prepared by chemical coprecipitation–peptization method. XRD pattern shows that TiO 2 sol particles without calcination treatment had anatase crystal structure. The particle size distribution (PSD) analysis shows that TiO 2 sol particles had narrow distribution characterization with a mean size of 21 nm, which was in good agreement with analytical result by AFM (25 nm). A novel hydrosol reaction system was applied to process X-3B photodegradation reaction under visible light illumination. The results demonstrate that TiO 2 sol nanoparticles have better interfacial adsorption capability and higher photoactivity than P25 TiO 2 in suspension system, which was ascribed to the characteristics of better dispersion, less aggregation of composite TiO 2 sol nanoparticles in the aqueous medium. By adjusting the pH value of hydrosol system, TiO 2 sol nanoparticles can be effectively separated from X-3B/TiO 2 hydrosol reaction system and dispersed again into aqueous solution to form sol system. This TiO 2 sol photocatalyst can be applied to recycle use for many times while keeping high photoactivity on X-3B degradation reaction.

Complexation of poly(vinylidene fluoride):LiPF6 solid polymer electrolyte with enhanced ion conduction in ‘wet’ form

Poly(vinylidene fluoride) (PVDF):LiPF6 complex membranes as ‘solid’ and ‘wet’ polymer electrolytes are evaluated. X-ray diffraction (XRD) and differential scanning calorimetric (DSC) studies show a decrease in crystalline size and crystallinity of the polymer PVDF with increasing LiPF6 concentration. Although PVDF is not an ionomer, acid–base complexation between the PVDF polymer at fluorine sites and the Li ions of the LiPF6 salt is evident from X-ray photoelectron spectroscopy (XPS) spectra. Such interaction is responsible for the reduction in both PVDF crystallinity and sol particle size during solid film formation. As evident from scanning electron micrographs, smaller spherical domains in the dry film are found with increasing lithium salt. Impedance (ac) measurements suggested the ionic conductivity of PVDF:LiPH6 film increases with increasing lithium salt. By comparison, PVDF:LiPH6 solid polymer electrolyte (SPE) wetted with Ethylene carbonate/propylene carbonate (EC/PC) shows less dependence of conductivity on salt concentration with a shallow maximum at about 15 wt.% salt. The average value is comparable with that of the solvent-free film at 20 wt.% LiPF6. This result suggests the existence of dual conduction mechanisms in ‘wet’ SPE via the amorphous PVDF matrix and the EC/PC solution trapped in the swollen region of the PVDF porous network.

Preparation and characterization of polypyrrole–silica colloidal nanocomposites in water–methanol mixtures

The effect of methanol cosolvent on the synthesis of polypyrrole–silica colloidal nanocomposites using ultrafine silica sols in combination with both FeCl 3 and APS oxidants has been investigated. Two protocols were evaluated: the addition of methanol to an aqueous silica sol and the addition of water to a methanolic silica sol. The latter protocol proved to be more robust, since it allowed colloidally stable dispersions to be prepared at higher methanol content (up to 50 vol% using the APS oxidant). This allowed greater control over the particle size of the nanocomposite particles. In general, the spectroscopic data, the particle size range, silica contents and electrical conductivities of these nanocomposites were similar to those reported earlier for purely aqueous formulations. Polypyrrole contents ranged from 49 to 71% by mass and particle diameters varied from around 160 to 360 nm. In terms of colloid stability, the APS oxidant was preferred for nanocomposite syntheses in the presence of methanol. However, the FeCl 3 oxidant generally gave higher conductivities and narrower size distributions under comparable conditions. HF etching experiments combined with transmission electron microscopy studies indicated that, to a first approximation, these nanocomposite particles had core–shell morphologies, with a hydrophobic polypyrrole core and a hydrophilic silica shell that compose approximately one monolayer of silica sol particles. Finally, aqueous electrophoresis measurements suggested that the polypyrrole–silica nanocomposites were silica-rich and that the methanolic silica sol was more hydrophobic (lower surface charge density) than the aqueous silica sol.

Emulsion Combustion and Flame Spray Synthesis of Zinc Oxide/Silica Particles

Two flame spray methods, emulsion combustion method (ECM) and flame spray pyrolysis (FSP), were compared for synthesis of pure and mixed SiO2 and ZnO nanoparticles. The effect of silicon precursor was investigated using liquid hexamethyldisiloxane (HMDSO) or SiO2 sol, while for ZnO zinc acetate (ZA) was used. Gas phase reaction took place when using HMDSO as Si precursor, forming nanoparticles, whereas the SiO2 sol used as Si source was not evaporated in the flame, creating large aggregates of the sol particles (e.g. 1 μm). The FSP of ZA produced ZnO homogeneous nanoparticles. Lower flame temperatures in ECM than in FSP resulted in mixed gas and liquid phase reaction, forming ZnO particles with inhomogeneous sizes. The FSP of HMDSO and ZA led to intimate gas-phase mixing of Zn and Si, suppressing each other's particle growth, forming nanoparticles of 19 nm in BET-equivalent average primary particle diameter. Nucleation of ZnO and SiO2 occurred independently by ECM of HMDSO and ZA as well as by FSP of the SiO2 sol and ZA, creating a ZnO and SiO2 mixture. The reaction of ZnO with SiO2 was likely to be enhanced by ECM of the SiO2 sol and ZA where both Zn and Si species were not evaporated completely, resulting in ZnO, β-willemite and Zn1.7SiO4 mixed phase.

Vibrational spectroscopic studies of mesna and dimesna

Raman, and infrared spectra of mesna and dimesna have been collected in the present spectroscopic studies. Based on the group frequencies, relative intensities and Raman depolarization measurements, some vibrational assignments have been suggested. For both mesna and dimesna, at least two rotational conformers have been identified. Adsorption behavior was investigated from the recorded surface-enhanced Raman scattering (SERS) spectra. It was found that both mesna and dimesna adsorbed as thiolate on silver sol particles with the cleavage of the SH bond in mesna and the SS bond in dimesna. For the adsorbed thiolate, two conformers existed in the adsorption state.

Role of binder in the synthesis of titania membrane

The synthesis of titania membrane through sol-gel route involves hydrolysis of alkoxide peptization of hydrous oxide of titanium to obtain a sol, adjustment of the sol viscosity by including a binder and filtration of the viscous sol through a microporous support, gelation and sintering to desired temperature. The binder plays an important role in that it not only helps in adjustment of sol viscosity but also helps in binding the sol particle with porous support. Here a comparative study on the role of different binders, viz. polyvinyl alcohol, polyethyleneimine, polyacrylamide, effect of their viscosity and surface tension effect on the morphology of the titania membrane is presented. The results show that among the three binders studied polyvinyl alcohol gave rise to membranes of desired characteristics when the sol viscosity was 0.08 pa.s.

Structural evolution of SiO2–ZrO2 nano-sol intercalated clays upon pillaring reactionElectronic supplementary information (ESI) available: BJH pore size distribution and k3-weighted EXAFS spectra of the SiO2–ZrO2 sol-pillared clay at different calcination temperatures. See http://www.rsc.org/suppdata/jm/b2/b208929g/

A two-dimensional layered nanohybrid with a high specific surface area has been prepared by ion exchange reactions between the sodium ions in montmorillonite and the positively charged Zr-coated SiO2 sol particles. The basal spacing increases from 12.5 A to 26 A upon intercalation due to the insertion of a SiO2–ZrO2 nano-sol into the interlayer space of montmorillonite. Upon calcining at 300 °C, it transforms into a porous nanohybrid with a basal spacing of 22.6 A. The N2 adsorption–desorption isotherms were characterized as being of type IV according to the BDDT classification, indicating the existence of a large number of micro- and mesopores. From its hysteresis curves, one can classify the nanohybrid as being of the H3 type with slit-shaped pores by the IUPAC classification. The estimated BET specific surface area and average micropore size are about 358 m2 g−1 and 12 A, respectively, with the latter value is similar to the gallery height of the sample indicating that the SiO2–ZrO2 sol particles are intercalated to form a monolayer. The local structural evolution of the Zr species in SiO2–ZrO2 sol particle has been investigated systematically by X-ray absorption spectroscopy at the Zr K-edge with respect to the calcination temperature. The EXAFS spectroscopic results confirm that the surface of the nano-sized SiO2 sol particles is coated with the Zr species.