Morphology conserving aminopropyl functionalization of hollow silica nanospheres in toluene

Abstract Inorganic nanostructures containing cavities of monodisperse diameter distribution find applications in e.g. catalysis, adsorption and drug delivery. One of their possible synthesis routes is the template assisted core-shell synthesis. We synthesized hollow silica spheres around polystyrene cores by the sol-gel method. The polystyrene template was removed by heat treatment leaving behind a hollow spherical shell structure. The surface of the spheres was then modified by adding aminopropyl groups. Here we present the first experimental evidence that toluene is a suitable alternative functionalization medium for the resulting thin shells, and report the comprehensive characterization of the amino-functionalized hollow silica spheres based on scanning electron microscopy, transmission electron microscopy, N2 adsorption, FT-IR spectroscopy, Raman spectroscopy and electrokinetic potential measurement. Both the presence of the amino groups and the preservation of the hollow spherical morphology were unambiguously proven. The introduction of the amine functionality adds amphoteric character to the shell as shown by the zeta potential vs. pH function. Unlike pristine silica particles, amino-functionalized nanosphere aqueous sols can be stable at both acidic and basic conditions

The formation kinetic of mechanochemical synthesized perovskites

In this study, we aimed to achieve mechanochemical perovskite synthesis and to quantify the energy used during milling (Eb - impact energy and Ecum - cumulative energy) and to describe the relationship between them. For mechanochemical treatment a Fritsch Pulverisette-6 type planetary ball mill was used. As a model compound the widely used barium-titanate (BaTiO3) was chosen, which was produced by the reaction of barium-oxide (BaO) and titanate-dioxide (TiO2). The aim was to track the formation of BaTiO3 and to determine the minimum milling energies required for its production. Three important parameters were considered for the calculation of energy values: the material of the milling vials and balls, the number of balls and the speed of rotation. The transformation was tracked by X-ray diffraction (XRD) measurement, and the applied energy was determined using the Burgio-Rojac energy model. Our goal was to draw conclusions that can be used to predetermine optimal milling parameters in the production of other perovskite structured materials. The hypothesis was verified by the mechanochemical synthesis of zinc-titanate (ZnTiO3) which was produced by the reaction of zinc-oxide (ZnO) and TiO2

Optimization of layering technique and secondary structure analysis during the formulation of nanoparticles containing lysozyme by quality by design approach

In our study, core-shell nanoparticles containing lysozyme were formulated with precipitation and layering self-assembly. Factorial design (DoE) was applied by setting the process parameters during the preparation with Quality by Design (QbD) approach. The factors were the concentration of lysozyme and sodium alginate, and pH. Our aim was to understand the effect of process parameters through the determination of mathematical equations, based on which the optimization parameters can be predicted under different process parameters. The optimization parameters were encapsulation efficiency, particle size, enzyme activity and the amount of α-helix structure. The nanoparticles were analysed with transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopy. Based on our results, we found that pH was the most important factor and pH 10 was recommended during the formulation. Enzyme activity and α-helix content correlated with each other very well, and particle size and encapsulation efficiency also showed very good correlation with each other. The results of the α-helix content of FTIR and CD measurements were very similar for the precipitated lysozyme due to the solid state of lysozyme. The mixing time had the best influence on the encapsulation efficiency and the particle size, which leads to the conclusion that a mixing time of 1 h is recommended. The novelty in our study is the presentation of a mathematical model with which the secondary structure of the protein and other optimization parameters can be controlled in the future during development of nanoparticle based on the process parameters