Properties of novel gel particles with projections and preparations of composite particles with gold nanoparticles

Mono-dispersed gel particles with projections were prepared by dispersion polymerization with ethyleneglycol dimethacrylate and a polyethyleneglycol (PEG) block macro azo initiator in H₂O/ethanol solutions. The effects of molecular weight of PEG blocks and polymerization conditions on the morphology and some properties were examined for the gel particles. The diameters and the extent of coagulation were different with the polymerization conditions. Relatively large specific areas and large swelling ratio with H₂O were obtained, and these values were related with the polymerization conditions. By mixing the gel particles with gold nanoparticles in solutions, composite particles were formed, which were composed of gold nanoparticles adsorbed on the gel particles. Interaction between gold nanoparticles and reactive azo groups remained in the gel particles concerned for the formation of the composite particles.     

T型混合反应器内共沉淀法制备吡啶硫酮铜

在T型混合反应器内通过喷射共沉淀方法合成了吡啶硫酮铜(CPT).利用扫描电镜和小角度光散射实验手段研究了分散液中吡啶硫酮铜的形貌和大小。通过喷射共沉淀方法获得的初级吡啶硫酮铜颗粒为棒状, 在分散液中这些棒状颗粒易发生团聚, 形成分形维数为2.1的团聚体。用平均回转半径(R_g)表征分散液中团聚体的平均大小, 考察了反应温度和反应物化学计量比(吡啶硫酮钠/硫酸铜)对团聚体大小的影响, 随着反应温度的降低, 团聚体的回转半径逐渐减小;过量的吡啶硫酮钠也有利于降低团聚体的大小, 当吡啶硫酮钠过量量达到~25%时, 进一步增大吡啶硫酮钠的过量量, 团聚体的回转半径不再发生明显变化。     

T型混合反应器内共沉淀法制备吡啶硫酮铜

在T型混合反应器内通过喷射共沉淀方法合成了吡啶硫酮铜(CPT)。利用扫描电镜和小角度光散射实验手段研究了分散液中吡啶硫酮铜的形貌和大小。通过喷射共沉淀方法获得的初级吡啶硫酮铜颗粒为棒状,在分散液中这些棒状颗粒易发生团聚,形成分形维数为2.1的团聚体。用平均回转半径()表征分散液中团聚体的平均大小,考察了反应温度和反应物化学计量比(吡啶硫酮钠/硫酸铜)对团聚体大小的影响,随着反应温度的降低,团聚体的回转半径逐渐减小;过量的吡啶硫酮钠也有利于降低团聚体的大小,当吡啶硫酮钠过量量达到~25%时,进一步增大吡啶硫酮钠的过量量,团聚体的回转半径不再发生明显变化。     

Silica‐supported metallocenes: effect of the preparation procedure on the morphology of polyethylene particles

Polyethylene (PE) particles are produced by a catalyst prepared by contacting a (C₄H₉Cp)₂ZrCl₂/MAO pre‐mixing solution with SiO₂ support. These particles have a large granular size and very few fine particles compared with those derived from a catalyst prepared by adsorption of (C₄H₉Cp)₂ZrCl₂ onto methylaluminoxane modified SiO₂. The amount of Al in the pre‐mixing catalyst has an important effect on its activity and the PE particle size distribution. The optimal concentration is about 30 wt.‐%. The PE particles produced using a pre‐mixing catalyst consist of globules with randomly oriented fiber structure on the surface, whereas those produced using adsorption catalysts have worm‐like fibrils protruding from the PE globule surface.     

A study by voltammetry and the photocurrent response method of copper electrode behavior in acidic and alkaline solutions containing chloride ions

The electrochemical behavior of Cu electrodes in Cl⁻ solutions was studied in a wide range of pH. The results were compared with those obtained in solutions containing F⁻, Br⁻, I⁻ and So²⁻₄ ions at pH 8.5, and discussed in terms of the competitive formation of Cu₂O and CuCl films on the Cu surface and the influence of CuCl on the properties of Cu₂O. At pH 8.5 or higher, Cu₂O was formed first, whereas at pH 5.7 or lower the Cu₂O film was formed on the Cu surface under the CuCl layer which was formed initially. It is believed that the Cu₂O films doped with Cl⁻ ions exhibited poor protective properties against Cu corrosion.     

Control of Semiconductor Particle Size in Sol-Gel Thin Films

Thin silica and silica-titania films containing CdS and PbS quantum size particles were obtained by separate preparation of the matrix and the colloidal sols and successive mixing. Sulfide particles were obtained by reaction of metal acetates with thioacetamide and control of particle size was achieved by surface capping agents. Powders and thin films deposited on soda-lime slides were prepared and characterized by XRD. Absorption spectra were recorded on films. The nonlinear refractive index was measured by anm-line technique on a CdS-doped sample. The nonlinear effect was found to be reversible and an ₂ value of −3 10⁻⁹ cm²/kW was measured.     

The chemical passivation of copper in ammonia solutions containing chlorine ions

It was shown that the CuCl layers deposited on copper chemically and electrochemically from copper-ammonia solutions were different. The layer formed chemically was loose, and that formed on the anode, dense. During multilayer copper passivation, the chemically deposited CuCl layer interfered with the formation of electrochemical CuCl and Cu₂O layers.     

Preparation and characterization of calcium phosphate–albumin colloidal particles by high ultrasonic irradiation

Using high intensity ultrasonic irradiation, we prepared calcium phosphate–albumin colloidal particles from aqueous solutions of Ca(H₂PO₄)₂ and Ca(OH)₂ in the presence of bovine serum albumin (BSA). The effect of concentration of BSA (2–5 g/L) properties of the colloidal particles was studied at constant temperature. The effect of a resting period on the size distribution of the colloidal particles was also investigated. Morphology, phase composition, average diameter, size distribution and zeta potential were obtained by transmission electron microscopy, X-ray diffraction, particle size determination by PCS and electrokinetic measurements.     

Synthesis of Barium Sulfate Nanoparticles in Water-in-Oil Microemulsion Systems

Micellar solutions of poly(ethylene glycol) octylphenyl ether and n-hexyl alcohol in cyclohexane were used to study the formation of water-in-oil microemulsion system and to synthesize barium sulfate nanoparticles. Barium sulfate particles (the average diameter is 10 nm) were obtained by mixing two microemulsion systems containing Ba²⁺and SO^2– ₄ions. It was shown that the sizes of BaSO₄particles measured by the dynamic light scattering and electron microscopy are in good agreement with each other.     

Spectroscopic,crystallographic and photochemical properties of atrans-cinnamonitrile — Copper(I) chloride adduct

Summary The first copper(I) complex oftrans-cinnamonitrile,trans- (PhCHCHCN)₃ · CuCl, has been prepared. Its infrared and Raman spectra indicate that bonding of the ligands to the metal occursvia the nitrogen atoms and that coordination induces a slight strengthening of the CN bond and weakening of the C=C bond. Single crystals of the compound and the isostructural bromide have been obtained, and the structure of the latter determined by x-ray methods. A photochemical study, performed on CuCl solutions in pure nitrile or in cinnamonitrile diluted in MeOH have shown the photoassistance of thetrans-cis nitrile isomerization by thetrans- (PhCHCHCN)₃ · CuCl complex. The quantum yields of this isomerization were compared.     

Physico-chemical Properties of the Molten CuCl–CuCl<Subscript>2</Subscript> System: Experiment,Thermodynamics and Molecular Dynamics Simulations

The molten CuCl–CuCl₂ system was studied by means of the maximum bubble pressure method, thermodynamics and molecular dynamics simulations at temperatures of 835, 866, 905 and 943 K. The equilibrium constant of CuCl₂ decomposition has been determined with thermodynamic simulation. The density and molar volume of the CuCl–CuCl₂ system were established as a function of composition. Some evidence of ideality of CuCl–CuCl₂ solutions was observed. The molar volumes of pure liquid CuCl₂ are equal to 44.64, 46.23, 46.55 and 46.81 cm³·mol^?1 at 835, 866, 905 and 943 K, correspondingly. Radial distribution functions, coordination numbers, self-diffusion coefficients and trajectories of motion were obtained by molecular dynamics simulation. For this reason a new pair potential for Cu²⁺–Cl^? pair has been designed. The coordination number of Cu²⁺ by Cl^? is about 4. This value corresponds to literature data with regards to this coordination. The self-diffusion coefficients are close to diffusion coefficients measured in molten salts solutions.     

Thermochemische Untersuchungen an Mischungen einiger Lanthanoidchloride mit CuCl,AgCl und TlCl

Thermochemical Investigations on Mixtures of Some Lanthanoide Halides with CuCl, AgCl, and TlCl The phase diagrams CuCl/LaCl₃ (GdCl₃, YbCl₃), AgCl/LaCl₃ (GdCl₃, YbCl₃) and TlCl/LaCl₃ (GdCl₃, YbCl₃) were determined by difference thermal analysis. The systems with CuCl resp. AgCl as component are eutectic, however in mixtures with YbCl₃ the compounds Cu₃YbCl₆ and Ag₃YbCl₆, resp., which decompose peritectically, were observed. The systems with thallous chloride contain several compounds, namely TlLn₂Cl₇ (TlCl/GdCl₃ resp. YbCl₃), Tl₂LnCl₅ (TlCl/LaCl₃ resp. GdCl₃) and Tl₃LnCl₆ (TlCl/GdCl₃ resp. YbCl₃). The enthalpies of mixing of liquid mixtures of AgCl/LaCl₃ and AgCl/YbCl₃ were measured calorimetrically at 1173 K. On comparing the alkali chloride–lanthanoide chloride systems with the MCl systems presented in this paper some differences were observed. The M⁺ ions with d¹⁰ configuration decrease the tendency to form ternary halides in the MCl? LnCl₃ systems, the enthalpies of mixing are also much less exothermic than those of the comparable NaCl + LnCl₃ mixtures. The Tl⁺ ion with d¹⁰ s² configuration on the other hand behaves like an alkali cation of comparable size.     

Influence of SDS on particle size and adhesion of precipitating calcium carbonate

The effect of different amounts of sodium dodecyl sulfate (SDS) and time of their addition to the system on the properties of calcium carbonate precipitated from aqueous solutions of CaCl₂ and Na₂CO₃ were studied. From statistical evaluation it was found that average number of the particles deposited on glass surface and, average and total surface area they occupy depend on the amount of the surfactant and time of its addition. Only if the surfactant was added to the system just after the CaCl₂ and Na₂CO₃ solutions mixing up, a decrease of these parameters took place, the greatest in the presence of 0.42 μmol of SDS. On the contrary, if SDS solution was added after 3 min, it caused an increase of the average and total surface area occupied by the CaCO₃ particles, while the average number of particles changed only within standard deviation. From the obtained results it may be concluded that SDS can affect both nucleation and crystal growth of CaCO₃, but its nature depends on the surfactant amount and time of its addition to the system.     

Some considerations of coherency in topoenergetic terms

The spatial coherency of composite structures is discussed in topoenergetic terms by considering mixing experiments on water and aqueous solutions with HRMC. Two series of experiments are presented: on normal and shaken successively diluted aqueous solutions of Na₃PO₄· 12H₂O with methanol as structure developer, and on the solubility behaviour in water of a narrow size fraction of KCl crystals irradiated at 546 nm for different time multiples of 5 seconds. The amplitude of relative standard deviation of the integral mixing energy as a function of mixing time shows the contribution of different elementary processes by revealing the specific spectrum of the composite structure in water and aqueous solutions.The series of experiments denoted as A were hosted by the Interdisciplinary Research Center (Fundeni Hospital, Bucharest) and with the kind help of biologist Liliana Pislaru, physicist Emil Toroiman and technician Tatiana Culea, who contributed with careful weighings and irradiation of KCl samples.     

The formation of Pt-Ru alloy nanoparticles in a carbon matrix under IR pyrolysis conditions

Nanosized Pt-Ru alloy and Pt₁₃Ru₂₇ intermetallic compound particles dispersed in a carbon matrix were obtained for the first time directly during the preparation of the composite. The alloying of the Pt and Ru particles occurred at IR pyrolysis intensities corresponding to temperatures above 700°C over the whole homogeneity range of solid solutions based on platinum. Metallic nanoparticles were round-shaped (the mean size 6–8 nm) and had a narrow particle-size distribution.     

Early stages of particle formation in precipitation reactions-quinacridone and boehmite as generic examples

For many products, such as nanoparticulate systems, particle formation by precipitation is an essential procedural step. To learn more about the processes involved in precipitation, we investigated particle formation during precipitation reactions by means of online and offline methods. As model systems we chose the catalyst boehmite and the organic pigment quinacridone. The reactants were mixed in a mixing device and led into a reaction tube. At the end of the tube, a free jet of the suspension was produced. By varying the length of the reaction tube the time between mixing the reactants and the moment of observation was varied. Thus a time resolution down to 10 ms from the beginning of the reaction was obtained. Small-angle X-ray scattering on the free jet yielded online information about the structural inhomogeneities within the reacting systems. Transmission electron microscopy patterns obtained from quenched samples, which were taken by shooting copper grids through the free jet into liquid nitrogen, provided complementary information about structural features. Immediately after mixture an emulsion-like structure develops indicating that classical nucleation theory does not apply in the present systems. This finding can be explained by assuming instantaneous reaction at the interfaces of the two reactants that meet in the mixing device. From this preliminary state primary particles form with a size in the nanometer range. The observations can be rationalized by considering the underlying hydrodynamics of turbulent mixing of the reactants.     

In situ detection of monovalent copper in aerosols by photoemission

Summary In situ information on nanoparticle surface chemistry and modes of particle growth is obtained in gas suspension by the technique of photoelectric charging of particles (PCP) which depends on the surface chemical compositon as well as the electronic structure of the particles via the spectral dependence of the photoelectric yield. With CuCl particles, photoelectric charging is about 100 times more efficient compared to other divalent transition metal compounds. Therefore, particles containing monovalent Cu can be detected with extremely high sensitivity of below 10 ng/m³. In atmospheric aerosols emitted from volcanoes, the relation of solid state oxidation/reduction in Fe_1–xCu_xCl₂ resulting in monovalent Cu for x<0.4 is important. As an example of the PCP technique this relation is monitored in laboratory generated aerosols. The nanoparticles are also precipitated onto a substrate where their surface chemical composition is analyzed by XPS which is important for the interpretation of the results obtained by photoelectric charging.     

Ordering of Ionic Solutes in Dilute Solutions through Attraction of Similarly Charged Solutes—A Change of Paradigm in Colloid and Polymer Chemistry

EXAFS measurements indicate the presence of a quasi lattice-like ordering of simple ions in dilute solutions. Small-angle X-ray scattering (SAXS) measurements on dilute aqueous solutions of synthetic macroions, polynucleotides, and proteins show a single broad peak; a binary mixture of synthetic macroions of different molecular weight gives a new scattering curve that is entirely different from the composite curve of the constituents before mixing. This would indicate that the macroions are distributed in a fairly regular way in the solution. The intermacroion spacing (2D_exp) obtained by the Bragg equation is found to be smaller than the average spacing (2D₀) calculated from the polymer concentration. Furthermore, the 2D_exp value decreases with increasing number of charges per macroion. This finding is confirmed by studies on model systems, e. g. on monodisperse ionic latex particles, which are large enough (diameter: about 3000 Å) to be seen under the ultramicroscope. It follows, from the inequality relation 2D_exp<2D₀, that there is an attraction between ionic species of like-charge. This conclusion contradicts prevailing views in colloid chemistry; it has been pointed out that such a behavior can be explained in terms of a new theory, in which counterions between the macroions or ionic latex particles play a decisive role.     

PREPARATION OF CaCO3 PARTICLES IN WATER POOL IN NONAQUEOUS NONIONIC SURFACTANT SOLUTIONS

ABSTRACT

CaCO₃ particles were prepared by bubbling of CO₂ into the systems consisting of polyoxyethylene(6) nonylphenyl ether/aqueous Ca(OH) ₂/cyclohexane. Spherical particles were formed in any systems, but those size distribution depended on the solubility behavior of aqueous Ca(OH) ₂ in surfactant solutions, i.e., monodisperse particles were formed in colorless solution, whereas in blue translucent solution they became bimodal. Such change was also observed for the size of reversed micelles. This suggested that the formation of CaCO₃ particles were related with that of micelles. On the other hand, the particles obtained were consisted of calcite, vaterite and aragonite. Those fraction differed also from the solubility behavior of aqueous Ca(OH) ₂. Both the vaterite and aragonite were transformed into calcite and those rate constants were order of 10^?6 sec^?1.     

Colloidal stability of PVC primary particles in vinyl chloride

The electrostatic contribution to the colloidal stability of PVC primary particles (R=0.15 m) dispersed in vinyl chloride, was calculated using models based on the Coulombic interactions and the DLVO theory. The calculations were based on: a) the particle charge as obtained from literature data on the electrophoretic mobility of PVC primary particles in VCM and b) on estimates of the Debye length as obtained from measurements of the electrical conductivity of VCM and of solutions of Bu₄NBF₄ in VCM.The calculations showed that particle stability would decrease with particle size (experimentally-observed behaviour), only if the particle charge increased with size at a lower rate than in proportion to particle radius.The calculations also suggest that particle growth may be governed by a competitive growth mechanism of electrostatic origin. Particle growth is assumed to occur by absorption of many small, weakly charged basic particles from the monomer phase. According to the calculations, the electrostatic interaction between primary and basic particles may be such that the growth of the smaller primary particles is favoured over that of the larger ones.