Morphology control of zinc oxide films via polysaccharide-mediated, low temperature, chemical bath deposition

In this study we present a three-step process for the low-temperature chemical bath deposition of crystalline ZnO films on glass substrates. The process consists of a seeding step followed by two chemical bath deposition steps. In the second step (the first of the two bath deposition steps), a natural polysaccharide, namely hyaluronic acid, is used to manipulate the morphology of the films. Previous experiments revealed a strong influence of this polysaccharide on the formation of zinc oxide crystallites. The present work aims to transfer this gained knowledge to the formation of zinc oxide films. The influence of hyaluronic acid and the time of its addition on the morphology of the resulting ZnO film were investigated. By meticulous adjustment of the parameters in this step, the film morphology can be tailored to provide an optimal growth platform for the third step (a subsequent chemical bath deposition step). In this step, the film is covered by a dense layer of ZnO. This optimized procedure leads to ZnO films with a very high electrical conductivity, opening up interesting possibilities for applications of such films. The films were characterized by means of electron microscopy, X-ray diffraction and measurements of the electrical conductivity.BMB

Interaction of differently functionalized fluorescent silica nanoparticles with neural stem- and tissue-type cells.

Abstract Engineered amorphous silica nanoparticles (SiO2 NPs), due to simple and low cost production, are increasingly used in commercial products and produced on an industrial scale. Despite the potential benefits, there is a concern that exposure to certain types of SiO2 NPs may lead to adverse health effects. As some NPs can cross the blood--brain barrier and may, in addition, reach the central nervous system through the nasal epithelium, this study addresses the responses of different neural tissue-type cells including neural stem cells, neurons, astrocytes and microglia cells to increasing doses of 50 nm fluorescent core/shell SiO2 NPs with different [-NH2, -SH and polyvinylpyrrolidone (PVP)] surface chemistry. The SiO2 NPs are characterized using a variety of physicochemical methods. Assays of cytotoxicity and cellular metabolism indicates that SiO2 NPs cause cell death only at high particle doses, except PVP-coated SiO2 NPs which do not harm cells even at very high concentrations. All SiO2 NPs, except those coated with PVP, form large agglomerates in physiological solutions and adsorb a variety of proteins. Except PVP-NPs, all SiO2 NPs adhere strongly to cell surfaces, but internalization differs depending on neural cell type. Neural stem cells and astrocytes internalize plain SiO2, SiO2-NH2 and SiO2-SH NPs, while neurons do not take up any NPs. The data indicates that the PVP coat, by lowering the particle-biomolecular component interactions, reduces the biological effects of SiO2 NPs on the investigated neural cells

Transport of light in amorphous photonic materials

Amorphous photonic materials based on dense assemblies of high refractive index spherical particles are presented. Light transmission through these photonic glasses shows a nontrivial wavelength dependence. The transmission spectra can be quantitatively reproduced by modeling the optical properties starting from their building blocks. Our results emphasize the relevance of including short range order correlations and an appropriate effective refractive index in the analysis of light transmission through amorphous photonic materials

Preparation and Characterization of Hollow Spheres of Rutile

Hollow spherical particles of rutile were obtained by coating colloidal polystyrene beads with a titanium oxide hydrate layer and subsequently calcining at elevated temperatures under an oxygen atmosphere. In order to investigate the optimum conditions for the preparation of these hollow beads the maximum temperature and heating rate were systematically varied. The dimensions of the voids and the shell thickness of the hollow beads can be tailored by the size of the polystyrene beads and the thickness of the inorganic layer, respectively

Altered characteristics of silica nanoparticles in bovine and human serum: the importance of nanomaterial characterization prior to its toxicological evaluation

This is an open access article distributed under the terms of the Creative Commons Attribution License.[Background]: Many toxicological studies on silica nanoparticles (NPs) have been reported, however, the literature often shows various conclusions concerning the same material. This is mainly due to a lack of sufficient NPs characterization as synthesized as well as in operando. Many characteristics of NPs may be affected by the chemistry of their surroundings and the presence of inorganic and biological moieties. Consequently, understanding the behavior of NPs at the time of toxicological assay may play a crucial role in the interpretation of its results. The present study examines changes in properties of differently functionalized fluorescent 50 nm silica NPs in a variety of environments and assesses their ability to absorb proteins from cell culture medium containing either bovine or human serum. [Methods]: The colloidal stability depending on surface functionalization of NPs, their concentration and time of exposure was investigated in water, standard biological buffers, and cell culture media by dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Interactions of the particles with biological media were investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) in bovine and human serum, and extracted proteins were assessed using matrix-assisted laser desorption/ionization-time of flight technique (MALDI-TOF). [Results]: It was recognized that all of the studied silica NPs tended to agglomerate after relatively short time in buffers and biological media. The agglomeration depended not only on the NPs functionalization but also on their concentration and the incubation time. Agglomeration was much diminished in a medium containing serum. The protein corona formation depended on time and functionalization of NP, and varied significantly in different types of serum. [Conclusions]: Surface charge, ionic strength and biological molecules alter the properties of silica NPs and potentially affect their biological effects. The NPs surface in bovine serum and in human serum varies significantly, and it changes with incubation time. Consequently, the human serum, rather than the animal serum, should be used while conducting in vitro or in vivo studies concerning humans. Moreover, there is a need to pre-incubate NPs in the serum to control the composition of the bio-nano-composite that would be present in the human body. © 2013 Izak-Nau et al.; licensee BioMed Central Ltd.This study was supported by the EU 7th Framework Programme, Marie Curie Actions, Network for Initial Training NanoTOES (PITN-GA-2010-264506),Peer Reviewe

Synthesis and Characterization of Hollow and Non-Hollow Monodisperse Colloidal TiO2 Particles

Monodisperse spherical hollow and non-hollow titania particles of variable sizes are produced in a sol–gel synthesis from Ti(EtO)4 in ethanol. Hollow spherical particles of rutile were obtained by coating colloidal polystyrene beads with a titanium oxide hydrate layer and subsequently calcination at elevated temperatures in oxygen atmosphere. The non-hollow titania particles were produced in the presence of salt or polymer solution. The influence of different salt ions or polymer molecules on the size and on the size distribution of the non-hollow particles was investigated. Nitrogen absorption measurements revealed that the addition of polymers yields porous titania colloids

Silver particles tailoring of shapes and sizes

Dispersions of colloidal silver have been prepared by the reduction of silver nitrate, with different reductants in the presence of various stabilising agents. Aging these dispersions at room temperature for 2 h yielded particles with average sizes ranging from 1 nm up to 6 μm and with various shapes like spheres, plates, needles or leafs. Reducing and stabilising agents were found to control the final particle sizes and shapes. The diversity of morphologies of the silver particles were studied by using electron microscopy. Thermogravimetry, powder X-ray diffraction (XRD) and UV/VIS spectroscopy were carried out for further characterisation

Synthesis and characterisation of porous and non-porous monodisperse TiO2 and ZrO2 particles

Monodisperse spherical titania and zirconia particles of variable sizes are produced in a sol–gel synthesis from metal tetraalkoxides in alcohol with addition of a salt or a polymer solution. The influence of various precursor concentrations and the addition of different salt ions or polymer molecules on the size and on the size distribution of the final particles was investigated. The particles were characterised by electron microscopy, thermogravimetry, X-ray diffraction and electrophoresis. Nitrogen absorption measurements revealed that in the case of titania the addition of polymers yielded porous titania colloids

Influence of additives on size and porosity in the synthesis of uniform TiO2 Nanoparticles

Monodisperse spherical titania particles of variable sizes are produced in a sol-gel synthesis from Ti(EtO)4 in ethanol with addition of a salt or a polymer solution. The influence of different salt ions or polymer molecules on the size and on the size distribution of the final particles was investigated. The amorphous hydrous titania particles were characterized by electron microscopy, thermogravimetry, 1H-MAS-NMR and X-ray absorption spectroscopy and electrophoresis. Nitrogen absorption measurements revealed that the addition of polymers yields hollow and porous titania colloids

Synthesis of monodisperse magnetic methacrylate polymer particles

Monodisperse magnetic polymer colloids have been synthesized via a three-step procedure and evidence for the formation of homogeneously distributed magnetite particles in the polymer matrix is presented (see Figure). Owing to their magnetic behavior and uniform particle size, these colloids are perfect candidates for the fabrication of photonic bandgap materials