Inorganic nanoparticles: Possible solution for different problems

Formation and Controlled Growth of Bismuth Titanate Phases into Mesoporous Silica Nanoparticles: An Efficient Self-Sealing Nanosystem for UV Filtering in Cosmetic Formulation. Biocompatible tailored zirconia mesoporous nanoparticles with high surface area for theranostic applications. Structural and photophysical properties of rare-earth complexes encapsulated into surface modified mesoporous silica nanoparticlesUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Small-angle scattering behavior of thread-like and film-like systems

A film-like or a thread-like system is a system such that one of its constituting homogeneous phases has a constant thickness $\delta$ or a constant normal section of largest diameter $\delta$. The stick probability function of this phase, in the limit $\delta \to 0$, naturally leads to the definition of the correlation function (CF) of a surface or a curve. This CF fairly approximates the generating stick probability function in the range of distances larger than $\delta$. The surface and the curve CFs respectively behave as $1/r$ and $1/r^2$ as $r \to 0$. In the two cases, this result implies that small-angle scattering intensities of the relevant samples respectively behave as $1/q^2$ and $1/q$ in an intermediate range of the scattering vector $q$ and as $1/q^4$ in the outermost one. One reports the analytic expressions of the pre-factors of these behaviors. It may happen that a sample looks thread-like at large scale resolution and film-like at smaller one. The surface and the curve CFs have explicitly been evaluated for some simple geometrical shapes. Besides, it is also reported the algebraic expression of the circular cylinder CF in terms of two elliptic integral functions, and it is shown that the limits of this CF, as the height or the radius of the cylinder approaches to zero, coincide with the CF of a disk or a linear segment, respectively.Comment: 37 pages, 18 figure

Thermochromic Narrow Band Gap Phosphors for Multimodal Optical Thermometry: The Case of Y³⁺-Stabilized beta-Bi₂O₃:Nd³⁺

The design and development of effective luminescent thermal sensors have been driving technological progress in many different fields ranging from catalysis to biology and microelectronics, to name a few. The ratiometric concept of using the ratio between two luminescent emissions of lanthanide-doped phosphors allows overcoming some limitations resulting from the single emission-based thermometers. A fundamental requirement for the development of effective luminescent thermometers relies on efficient luminescence output, which is not always accessible. Therefore, alternative methods to probe the temperature in a reliable and simple way are still a challenge. Despite the conventional limits of using narrow band gap materials as hosts for lanthanoid ions, a smart design allows for the development of unusual phosphors with appealing properties. By taking advantage of the narrow band gap of Bi₂O₃ polymorphs, here we demonstrate the potential of the tetragonal Y-stabilized β-Bi₂O₃:Y³⁺, Nd³⁺ system as a multimodal thermometer combining the conventional Boltzmann thermometry based on Nd³⁺ together with the thermochromism of the host. With the aim of testing this new concept, the temperature dependence of the reflectance spectra was investigated. Moreover, from the application point of view, the chromaticity variations of the material described by means of simple thermometric parameters such as the ratio a*/b* and the hue angle hab are demonstrated to be particularly promising and already implemented in software commonly used worldwide. The results suggest the potential of the strategy of combining narrow band gap semiconductors with lanthanoid ions to design reliable and multimodal thermal sensors, paving the way to a new family of thermochromic and luminescent thermal sensors

Preparation and Characterization of Mixed-Oxide Electrocatalysts Based on RuO₂ and IrO₂

The formation processes of RuO2/TiO2, IrO2/TiO2 and IrO2/ZrO2 film electrodes have been studied by combined thermoanalytical and mass-spectrometric methods. The obtained materials have been characterized by cyclic voltammetry (CV). The precursor path leading to mixed oxides for the first two groups of matetials, consists of several stages, including solvent desorption, oxidative cracking, combustion, noble-metal chloride decomposition. Minima of the temperature of chlorine release and organic combustion have been observed for precursor salt mixtures with intermediate-low noble-metal concentrations. The microstructural investigation, carried out by wide-angle X-ray scattering (WAXS) has shown that solid solutions are formed within quite wide composition ranges for TiO2-stabilized materials. For the IrO2/ZrO2 system, segregation of amorphous ZrO2 takes place for IrO2 concentrations ≤ 80 mol-%. For the TiO2-stabilized samples, the characterization by cyclic voltammetry has shown that maxima of charge-storage capacity are observed for those electrodes whose composition is in the range of minimum temperature for the precursor reaction. A dependence of the faradaic voltammetric charge on the carbon content of the electrode films, as determined by nuclear reaction analysis (NRA), has been shown. The experimental results have been explained hypothesizing that minima of pyrolysis temperature involve less favorable conditions for rearrangements in the reacting films, and, consequently, larger degree of defectivity. In the case of IrO2/ZrO2 electrodes, the segregation of the amorphous ZrO2 phase seems to be main reason for the maximum of charge-storage capacity observed at 80 mol-% of IrO2

Correction: Unexpected optical activity of cerium in Y2O3:Ce3+, Yb3+, Er3+ up and down-conversion system

Correction for 'Unexpected optical activity of cerium in Y2O3:Ce3+, Yb3+, Er3+ up and down-conversion system' by Riccardo Marin et al., Dalton Trans., 2013, 42, 16837–16845

Small angle scattering of a polydisperse system of interacting hard spheres: an analytical solution

Recently, general results obtained from the study of the autocorrelation functions of liquids were used for a more accurate analysis of the full small angle scattering pattern fi om mono and polydisperse systems with interparticle interaction. The effects of polidispersity and density, in close-packed systems of hard spheres (case 1) and hard spheres with permeable shell (case 2) with Schulz distribution of radii, were investigated by Mengoni [J. Chem. Phys. 87, 2560 (1987)] by a numerical integration of the intensity in the framework of the Born-Green kinetic theory for fluids. In this paper we generalize the case 1 reported by Mengoni to a system of spherical particles of radius r(i) with an interacting hard sphere potential of radius R(HSi)proportional to r(i) and analytically solve the equations for the intensity

OSCILLATORY DEVIATIONS FROM POROD'S LAW IN THE INTENSITIES SCATTERED BY SOME GLASSES.

The oscillatory deviations with respect to the Porod asymptote, observed in the small-angle X-ray intensities scattered by some selenium ruby glasses, are explained in terms of a finite discontinuity of the second-order derivative of the correlation function. The best fit of the intensity allows the value of the discontinuity to be determined as well as the point at which it occurs. The physical implications of these results are discussed

Preparation and Structural Characterization of Ultrafine Zirconia Powders

Factors concerning the stabilization of the tetragonal and cubic phases, metastable at room temperature, with respect to the monoclinic stable phase in ultrafine zirconia powders are studied. The importance of Na+ ions in the initial zirconia amorphous gel in obtaining a cubic phase has been confirmed. By an X‐ray diffraction study using a new peak profile fitting procedure, the amount of the crystalline phases and their microstructural properties (crystallite size and lattice distortions) have been obtained. Copyright © 1989, Wiley Blackwell. All rights reserve

Oscillations in the Porod plot and particle sizes in demixed glasses

A new theoretical approach, based on the oscillations sometimes observed in the Porod plot, has been used to estimate particle sizes in phase separated glasses. We have studied the demixing kinetics consequent upon appropriate isothermal heating of the glasses of the quaternary system SiO2-Li2O-TiO2-Al2O3 of the mol% compositions (70,25,2,3), (70,21,6,3), and (70,17,10,3). Glasses of the first composition did not yield appreciable x-ray intensities. Oscillations were observed in the scattered intensities of glasses of the second composition, the amplitudes increasing with the duration of heating. By using a theoretical expression which we recently developed we have easily determined the particle sizes and the degree of monodispersity