Nanoparticles In Ethanol Research Articles

Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media

We studied the effects of the surrounding liquid environment on the size and optical properties of silver nanoparticles prepared by laser ablation by a pulsed Nd:YAG laser operated at 1064 nm. The silver targets used were kept in acetone, water and ethanol. TEM observations and optical extinction were employed for characterization of particle size, shape and optical properties, respectively. Nano silver in acetone showed a narrow size distribution with a mean size of 5 nm and the colloidal solution was stable. In deionised water a rather narrow size distribution with a mean size of 13 nm was observed and nanoparticles were precipitated slowly after about two weeks. In ethanol, a broadening in size distribution and optical extinction spectra was observed. Silver nanoparticles in ethanol with a mean size of 22 nm were completely precipitated after 48 h. In acetone, deionised water and ethanol, the wavelengths of maximum optical extinction are 399, 405 and 411 nm respectively, which is attributed to increasing the size of the nanoparticles. Growth, aggregation and precipitation mechanisms were related to the dipole moment of the surrounding molecules in order to clarify the difference in size, optical properties and stability of the nanoparticles.

Preparation and properties of amorphous titania-coated zinc oxide nanoparticles

Amorphous TiO 2-coated ZnO nanoparticles were prepared by the solvothermal synthesis of ZnO nanoparticles in ethanol and the followed by sol–gel coating of TiO 2 nanolayer. The analyses of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the resultant ZnO nanoparticles were hexagonal with a wurtzite structure and a mean diameter of about 60 nm. Also, after TiO 2 coating, the TEM images clearly indicated the darker ZnO nanoparticles being surrounded by the lighter amorphous TiO 2 layers. The zeta potential analysis revealed the pH dependence of zeta potentials for ZnO nanoparticles shifted completely to that for TiO 2 nanoparticles after TiO 2 coating, confirming the formation of core-shell structure and suggesting the coating of TiO 2 was achieved via the adhesion of the hydrolyzed species Ti–O − to the positively charged surface of ZnO nanoparticles. Furthermore, the analyses of Fourier transform infrared (FTIR) and Raman spectra were also conducted to confirm that amorphous TiO 2 were indeed coated on the surface of ZnO nanoparticles. In addition, the analyses of ultraviolet–visible (UV–VIS) and photoluminescence (PL) spectra revealed that the absorbance of amorphous TiO 2-coated ZnO nanoparticles at 375 nm gradually decreased with an increase in the Ti/Zn molar ratio and the time for TiO 2 coating, and the emission intensity of ZnO cores could be significantly enhanced by the amorphous TiO 2 shell.

Dispersion Stability of Ni Nanoparticles in Ethanol with Poly (1-Vinyl-2-Pyrrolidone)

The stability of nanosized Ni dispersions with varying concentrations of poly (1-vinyl-2- pyrrolidone) (PVP) was investigated by means of a visual inspection, transmission profile measured by Turbiscan, zeta potential, and transmission electron microscopy. For dispersions with PVP, the ζ potential values varied from positive charge to negative charge. For dispersion with a 0.04 weight percentage of PVP, the ζ potential value showed 31.71 mV, which was the highest value, and the flocculation of Ni nanoparticles was not observed. Stable dispersions of Ni nanoparticles were produced by electrostatic, steric interactions, and the formation of bridging aggregation.

Solvothermal synthesis of titania-zirconia composite

Nanocomposite particles of anatase-type titania (TiO2) and cubic/tetragonal zirconia were synthesized from hydrothermal processing of TiCl4 and ZrOCl2·8H2O or ZrCl4 alcohol solutions at 160–200 °C. It was found that the morphologies and composition of the composite particles were mainly controlled by the precursors and the sequence by which the precursors were added. The TiO2–ZrO2 composite particles with nanoscale uniformity can be obtained by solvothermal processing of TiCl4 or a ZrO2 precursor together with preformed ZrO2 or yttria stabilized zirconia (YSZ) nanoparticles in ethanol. A novel one-step and non-template method for preparing ZrO2–TiO2 core–shell structured composite particles with hollow interior was identified, and possible reaction mechanism was suggested.

Polyelectrolyte adsorption and rheological behavior of ITO nanoparticles in ethanol with ammonium polyacrylate as a surfactant

Polyelectrolyte adsorption and rheological behavior of ITO nanoparticles in ethanol with ammonium polyacrylate as a surfactant

Role of quantum-sized effects on the cathodic photocorrosion of ZnO nanoparticles in ethanol

Cathodic photocorrosion occurs upon stationary photoirradiation of ethanolic ZnO sols. The photocorrosion rate increases with decreasing particle size. This effect due to the appearance of quantum-sized effects in ZnO nanocrystals results from an increase in the reduction potential of the semiconductor upon irradiation, which may exceed the Fermi level for cathodic decomposition of zinc oxide nanoparticles.

Linear aggregation of gold nanoparticles in ethanol

Gold colloidal particles were found to spontaneously organize into linear aggregates in ethanol. The morphology of these aggregates was characterized with transmission electron microscope (TEM) and atomic force microscope (AFM), which revealed the quasi one-dimensional (1D) chain-like shape. Immobilization of these chains from solution onto substrate surface as well as the measurement of UV–visible extinction spectrum was performed to investigate the aggregation mechanism. The results presented the evidence for the existence of the nanoparticle chains in solution. Moreover, the kinetic aspects of the chain-like aggregation were detailed studied using UV–visible spectroscopy. It is believed that dipole–dipole interaction is the driving force of nanoparticle linear aggregation. This finding provides a novel strategy for the construction of quasi 1D structures, which are suitable for the fabrication of solid-state devices based on single-electron tunneling.

ZnS Nanoparticle Treatment to Enhance its Luminescence, Shape, and Stability

The luminescence, shape, and stability of ZnS nanoparticles in ethanol are enhanced by capping the surface with (3-mercaptopropyl)trimethoxy silane (MPS) or by treating the surface with SiO 2 . While MPS forms an exterior network to encapsulate the ZnS surface, SiO 2 surrounds ZnS nanoparticles to smoothen the surface. Both MPS and SiO 2 reform ZnS nanoparticles into more stable shapes and increase their luminescence, especially in the visible region. Thus both treatments are suggested to improve various properties of optoelectronically valuable ZnS nanoparticles.

FT-EPR Study of Photoinduced Electron Transfer at the Surface of TiO2 Nanoparticles

Photoinduced electron transfer at the surface of TiO2 nanoparticles in ethanol has been studied with Fourier transform EPR (FT-EPR). Measurements were performed on three systems: (1) a solution of coumarin 343 (C343) dye and methyl viologen (MV2+) in ethanol, (2) a colloidal solution of TiO2 in ethanol containing MV2+, and (3) a colloidal solution of TiO2 in ethanol containing both C343 and MV2+. In the C343/MV2+ system, pulsed-laser (355 nm) excitation of the dye results in MV2+ reduction. The rate constant of the photoinduced electron-transfer reaction, derived from the time profile of the FT-EPR spectrum of the MV+ radical, was found to be ∼ 5 × 109 M-1 s-1, consistent with a near diffusion controlled reaction. Bandgap excitation (308 nm) of the semiconductor particles in the TiO2/MV2+ system also gives rise to MV+ formation. In this case the FT-EPR signal growth can be described by a single exponential with rate constant kf = 0.41 × 106 s-1. The kinetics indicates that MV2+ reduction involves photogenerated electrons trapped on the TiO2 particles and is controlled by interfacial charge transfer rather than diffusive encounters of acceptor molecules with TiO2 particles. Dye-sensitized formation of MV+ radicals is observed as well following laser (355 nm) excitation of the C343/MV2+/TiO2 system. However, whereas the MV+ spectrum produced by the C343/MV2+ system reaches its maximum intensity around 100 ns after laser excitation, in the presence of TiO2 the maximum is found tens of microseconds after the laser pulse. The time profile of MV+ formation in this case follows first-order kinetics with a time dependent rate constant, kf = k0tα-1, where both k0 and α are a function of the degree of dye adsorption onto the TiO2 particles and the pH of the solution. In this system, the trapped electrons responsible for MV2+ reduction are generated by excitation of adsorbed dye molecules, which leads to electron injection into the conduction band of the semiconductor. Dye-sensitization of the TiO2 particles strongly increases the free radical yield. However, as the surface coverage by dye molecules approaches saturation level, the rate of electron transfer from semiconductor particles to acceptor molecules in solution is strongly attenuated.

Reduction and Stabilization of Silver Nanoparticles in Ethanol by Nonionic Surfactants

The reduction of Ag+ ions in ethanol when certain surfactants are also present in the solution is shown to take place, even in the total absence of light. The reduction process leads to dispersions of silver nanoparticles, which are stable for weeks, although they show a certain tendency to stick to glass walls. Several surfactants were tested, showing that there is a dependency on their nature and concentration. Nonionic ethoxylated surfactants proved to be the most effective of all the surfactants tested, the reduction then being due to the oxidation of oxyethylene groups. In any case, the yield is very low (around 1%). Colloidal stability is achieved by adsorption of surfactant molecules onto the particles, which permits easy transfer of the particles into nonpolar solvents. The reduction rate markedly depends in a first-order fashion on silver salt concentration and depends on temperature according to Arrhenius's law. The optical properties of the obtained colloids are influenced by the surfactant molecules attached to the particle surface.

Prostaglandins and gastric mucosal protection by esaprazole (E)

This study describes the development of α-bisabolol-loaded lipid-core nanocapsules (α-BLNC) and Cocoa-theospheres (α-BCT), aiming oral use for gastroprotection. α-Bisabolol was efficiently encapsulated in high drug loading (25%) in lipid-core nanocapsules and cocoa-theospheres. Laser diffraction analysis showed nanometric and unimodal distributions (mean diameters of 216 and 148 nm, respectively). The gastroprotective indexes in rats for the ethanol-induced ulcers were 0.11 (α-BCT), 0.68 (blank-CT), 0.29 (α-BLNC) and 0.37 (blank-LNC), while for the indomethacin-induced ulcer model, the results were 37.33 (α-BCT), 48.14 (blank-CT), 31.33 (α-BLNC) and 45.33 (blank-LNC). SEM analysis of the stomach mucosa showed more homogenous and cohesive coatings for α-BLNC and α-BCT treatments in comparison with the blank formulations. In histological evaluations, protection against the tissue damage and Periodic Acid-Schiff-positive increase were observed after the pretreatment with α-bisabolol nanoparticles in ethanol and indomethacin-induced ulcers. α-Bisabolol-loaded in cocoa-theospheres provided a gastroprotective effect absent in blank-cocoa-theospheres, while the drug-loaded lipid-core nanocapsules maintained the gastroprotective effect observed for blank lipid-core nanocapsules, which are per se antioxidant agents. The nanoencapsulation enabled a dose reduction of α-bisabolol. Moreover, lipid-core nanocapsules and cocoa-theospheres have mucoadhesive properties even though they present diverse supramolecular structures. Both lipid-core nanocapsules and cocoa-theospheres are promising platforms for the development of prophylactic formulations.