Controlling Factors of the Particle Size of Spherical Silica Synthesized by Wet and Dry Processes

We clarified the controlling factors of the particle size of the amorphous silica synthesized by wet and dry processes. In the wet process using methyl-trimethoxy-silane as a starting monomer, the obtained particle size can be easily controlled by changing the reaction time appropriately. However, to obtain larger particles, a relatively long time is needed. After the condensation reaction was conducted for 50h, the silica particles (D50: 3μm) were synthesized by calcination at 550oC in air. To synthesize larger silica particles, we used silica-seed particles (8μm) to obtain very large spherical silica particles (D50: 20μm). Thus, although the wet process needs a relatively long reaction time, it is very useful for synthesizing spherical silica particles with a wide range of particle size. In the dry process, we used methyl-trimethoxy-silane (MTMS), tetra-ethoxy-silane (TEOS), and octamethyl-cyclotetrasiloxane (OMCTSO) as the starting materials. In this process, the size of the silica particles was dominated by the molecular structure of the monomer, in particular, the number of silicon atoms contained in the monomer and the bulkiness of the substituent group. The largest silica particles were synthesized from OMCTSO, which contains the largest number of silicon atoms.

Spherical Silica Functionalized by 2-Naphthalene Methanol Luminophores as a Phosphorescence Sensor

Photoluminescence is known to have huge potential for applications in studying biological systems. In that respect, phosphorescent dye molecules open the possibility to study the local slow solvent dynamics close to hard and soft surfaces and interfaces using the triplet state (TSD: triplet state solvation dynamics). However, for that purpose, probe molecules with efficient phosphorescence features are required with a fixed location on the surface. In this article, a potential TSD probe is presented in the form of a nanocomposite: we synthesize spherical silica particles with 2-naphthalene methanol molecules attached to the surface with a predefined surface density. The synthesis procedure is described in detail, and the obtained materials are characterized employing transmission electron microscopy imaging, Raman, and X-ray photoelectron spectroscopy. Finally, TSD experiments are carried out in order to confirm the phosphorescence properties of the obtained materials and the route to develop phosphorescent sensors at silica surfaces based on the presented results is discussed.

Combination of Selective Etching and Impregnation toward Hollow Mesoporous Bioactive Glass Nanoparticles

In this study, binary SiO2-CaO hollow mesoporous bioactive glass nanoparticles (HMBGNs) are prepared by combing selective etching and impregnation strategies. Spherical silica particles (SiO2 NPs) are used as hard cores to assemble cetyltrimethylammonium bromide (CTAB)/silica shells, which are later removed by selective etching to generate a hollow structure. After the removal of CTAB by calcination, the mesoporous shell of particles is formed. Calcium (Ca) is incorporated into the particles using impregnation by soaking the etched SiO2 NPs in calcium nitrate aqueous solution. The amount of incorporated Ca is tailorable by controlling the ratio of SiO2 NPs:calcium nitrate in the soaking solution. The produced HMBGNs are bioactive, as indicated by the rapid formation of hydroxyapatite on their surfaces after immersion in simulated body fluid. In a direct culture with MC3T3-E1 cells, HMBGNs were shown to exhibit concentration-dependent cytotoxicity and can stimulate osteogenic differentiation of MC3T3-E1 cells at concentrations of 1, 0.5, and 0.25 mg/mL. Our results indicate that the combination of selective etching and impregnation is a feasible approach to produce hierarchical HMBGNs. The produced hollow particles have potential in drug delivery and bone tissue regeneration applications, and should be further investigated in detailed in vitro and in vivo studies.

Facile Fabrication of Fluorine-Free Superhydrophobic Surfaces with SiO2 Monospheres

Recently, superhydrophobic surface on various type of substrates have attracted much attentions in electronics field. In this work, the classic Stöber method was used to prepare spherical silica particles with different particle sizes by adding different amounts of electrolyte (potassium chloride), giving rise to size distribution ranging from 300 nm to 2.55 yitm. Herein we constructed a micro-nano lotus-like structure in a facile way, achieving a superhydrophobic surface with using any Fluorine related chemicals. In the sense, the silica particles modified with HMDS were sprayed to prepare hydrophobic surface with contact angle up to 152.96° by increasing the frequency of sprays.

Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

GO@f-SiO2@Co is a heterogenous catalyst composed of spherical silica particles grafted on the surface of graphene oxide with ethylenediamine ligands and coordination with Co(ii). We assessed the activity of the catalyst for the synthesis of aminonaphthoquinones.

Темплатный метод синтеза монодисперсных наночастиц MoS-=SUB=-2-=/SUB=-

Monodisperse molybdenum disulfide nanoparticles were synthesized in mesopores of spherical silica particles (mSiO2) served as a template. First, the pores of mSiO2 particles were impregnated with the precursor (ammonium tetrathiomolybdate solution). Then, the reduction of the filler in thermodynamically equilibrium conditions in H2S/H2 atmosphere was carried out. The template material (a-SiO2) was selectively etched from the composite mSiO2/MoS2 particles with HF to obtain individual MoS2 nanoparticles. The mean size of MoS2 nanoparticles determined by microscopic methods was found to be 3.5 nm. According to dynamic light scattering data, the nanoparticles had low size scatter (18%).

Eco-friendly and facile synthesis of size-controlled spherical silica particles from rice husk

The valorization of inorganic silica components from rice husk has been considered an important research topic over the last few decades. However, owing to various problems, such as the difficulty...

Theory and experiment of chain length effects on the adsorption of polyelectrolytes onto spherical particles: the long and the short of it

We study here the role of polyelectrolyte chain length, that is number of repeat units (mers), in the competitive adsorption of a simple model polyanion onto 85 nm spherical silica particles capped with a model polycation.

Fabrication of permanent silver cement frit at the inlet of micro-columns: a significant progress toward realization of disposable micro-columns

The advent of disposable micro-columns will be a hope of workers of chromatography-related laboratories. A very critical and important requirement is the formation of affordable inlet frits. Welding a metal screen to a column inlet is not recommended because of the risk of damage to stationary phase. In this study, the Tollens probe (silver mirror reaction) was adopted to make affordable frits. Silver is reduced on the particle surface and in an empty space among the particles, forming a solid silver network structure at the column inlet area by injecting the reaction solution into the packed column at a depth of one third (10 cm) of the packed bed (0.5 mm × 300 mm). The silver cement structure was successfully formed, and the silver cement frit endured mobile phase flow well when C18 modified ground silica monolith particles were used to make the packed bed. The formation of the silver cement frit was not successful when the stationary phase based on conventional spherical silica particles was used. Negligible reduction of chromatographic performance by the silver cemented frit was observed. This study serves as the first step toward realization of disposable micro-columns.