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Hollow microparticles are important materials, offering a larger surface area and lower density than their solid counterparts. Furthermore, their inner void space can be exploited for the encapsulation and release of guest species in a variety of applications. Herein, we present phosphazene-based silica hollow microparticles prepared via a surfactant-free sol-gel process through self-assembly of the alkoxysilyl-containing polymer in water–ethanol solution. Solely, a silane-derived polyphosphazene was used as the precursor for the microparticle formation, without additional classical silica sources. These novel hollow silica-based microparticles were prepared without surfactant, using a designed amphiphilic polyphosphazene for the particle formation made by two components, a hydrophilic unit consisting of 3-mercaptopropyl(trimethoxysilane), and a hydrophobic unit (dodecanethiol) attached to the double bonds from the poly(allylamine)phosphazene backbone via a thiol-ene photoreaction. Due to these two functionalities, a "vesicle"-like self-assembled structure was formed in the reaction medium, which could be then utilized for the microparticle preparation. The influence of NaOH during the synthesis was shown to affect the size and the wall thickness of the microparticles. This effect may enhance the possibilities to tailor such microparticles for drug delivery purposes or for future controlled release of other substances, such as drugs, fragrances, or anticorrosive pigments. [ABSTRACT FROM AUTHOR]

Strategies for production and use of nanomaterials have rapidly moved towards safety and sustainability. Beyond these requirements, the novel routes must prove to be able to preserve and even improve the performance of the resulting nanomaterials. Increasing demand of high-performance nanomaterials is mostly related to electronic components, solar energy harvesting devices, pharmaceutical industries, biosensors, and photocatalysis. Among nanomaterials, Zinc oxide (ZnO) is of special interest, mainly due to its environmental compatibility and vast myriad of possibilities related to the tuning and the enhancement of ZnO properties. Doping plays a crucial role in this scenario. In this work we report and discuss the properties of undoped ZnO as well as lanthanide (Eu, Tb, and La)-doped ZnO nanoparticles obtained by using whey, a by-product of milk processing, as a chelating agent, without using citrate nor any other chelators. The route showed to be very effective and feasible for the affordable large-scale production of both pristine and doped ZnO nanoparticles in powder form. [ABSTRACT FROM AUTHOR]

The last few years of enhancing the design of hybrid mesoporous organosilica nanoparticles has allowed their degradation under specific pathologic conditions, which finally is showing a light in their potential use as drug delivery systems towards clinical trials. Nevertheless, the issue of controlling the degradation on-demand at cellular level still remains a major challenge, even if it has lately been addressed through the incorporation of degradable organo-bridged alkoxysilanes into the silica framework. On this basis, this mini review covers some of the most recent examples of different degradable organosilica nanomaterials with potential application in nanomedicine, from degradable non-porous to mesoporous organosilica nanoparticles (MONs), functionalized with responsive molecular gates, and also the very promising degradable periodic mesoporous organosilica materials (PMOs) only consisting of organosilica bridges. [ABSTRACT FROM AUTHOR]

Herein we present hybrid mesoporous silica nanomaterials (MSN) with visible light-sensitive ruthenium complexes acting as gates. Two different [Ru(bpy)2L1L2]2+ complexes were investigated by grafting [Ru(bpy)2(4AMP)2](PF6)2 (RC1) and [Ru(bpy)2(PPh3)Cl]Cl (RC2) via two or one ligands onto the surface of mesoporous silica nanoparticles (MSNs), to give MSN1-RC1 and MSN2-RC2, respectively. The pores were previously loaded with a common dye, safranin O, and release studies were conducted. The number and position of the ligands were shown to influence the photocages behavior and thus the release of the cargo. Release studies from MSN1-RC1 in acetonitrile showed that in the dark the amount of dye released was minimal after 300 min, whereas a significant increase was measured upon visible light irradiation (ca. 90%). While successful as a photochemically-controlled gated system, RC1 was restricted to organic solvents since it required cleavage of two ligands in order to be cleaved from the surface, and in water only one is cleaved. Release studies from the second nanomaterial MSN2-RC2, where the complex RC2 was bound to the MSN via only one ligand, showed stability under darkness and in aqueous solution up to 180 min and, rapid release of the dye when irradiated with visible light. Furthermore, this system was demonstrated to be reversible, since, upon heating to 80 °C, the system could effectively re-close the pores and re-open it again upon visible light irradiation. This work, thus, demonstrates the potential reversible gate mechanism of the ruthenium-gated nanomaterials upon visible light irradiation, and could be envisioned as a future design of photochemically-driven drug delivery nanosystems or on/off switches for nanorelease systems. [ABSTRACT FROM AUTHOR]

The natural occurrence of precious opals, consisting of highly organized silica particles, has prompted interest in the synthesis and formation of these structures. Previous research has shown that a highly organized photonic crystal (PhC) array is only possible when it is based on a low polydispersity index (PDI) sample of particles. In this study, a solvent-only variation method is used to synthesize different sizes of silica particles (SiPs) by following the traditional sol-gel Stöber approach. The controlled rate of the addition of the reagents promoted the homogeneity of the nucleation and growth of the spherical silica particles, which in turn yielded a low PDI. The opalescent PhC were obtained via self-assembly of these particles using a solvent evaporation method. Analysis of the spatial statistics, using Voronoi tessellations, pair correlation functions, and bond order analysis showed that the successfully formed arrays showed a high degree of quasi-hexagonal (hexatic) organization, with both global and local order. Highly organized PhC show potential for developing future materials with tunable structural reflective properties, such as solar cells, sensing materials, and coatings, among others. [ABSTRACT FROM AUTHOR]

Porous organosilica microparticles consisting of silane-derived cyclophosphazene bridges were synthesized by a surfactant-mediated sol-gel process. Starting from the substitution of hexachlorocyclotriphosphazene with allylamine, two different precursors were obtained by anchoring three or six alkoxysilane units, via a thiol-ene photoaddition reaction. In both cases, spherical, microparticles (size average of ca. 1000 nm) with large pores were obtained, confirmed by both, scanning and transmission electron microscopy. Particles synthesized using the partially functionalized precursor containing free vinyl groups were further functionalized with a thiol-containing molecule. While most other reported mesoporous organosilica particles are essentially hybrids with tetraethyl orthosilicate (TEOS), a unique feature of these particles is that structural control is achieved by exclusively using organosilane precursors. This allows an increase in the proportion of the co-components and could springboard these novel phosphorus-containing organosilica microparticles for different areas of technology. [ABSTRACT FROM AUTHOR]