Usefulness of Mesoporous Silica as a Template for the Preparation of Bundles of Bi Nanowires with Precisely Controlled Diameter Below 10 nm

Pore shape-reflecting morphosynthesis of lithium niobium oxide via mixed chloride flux growth in the presence of mesoporous silica

A new synthesis method, "chloride flux growth in the rigid nanospace of mesoporous silica", was developed to obtain lithium niobium oxide anisotropic nanoparticles. The morphologies reflect the pore size and shape of the used mesoporous silicas. This method has great potential for synthesizing size-tuned anisotropic nanoparticles of other complex metal oxides.

Size-Controlled Synthesis of Anatase in a Mesoporous Silica, SBA-15

The preparation of anatase in the cylindrical mesopore of SBA-15 (pore size of 8 nm) was done by the impregnation of tetraisopropyl orthotitanate and its subsequent crystallization. The impregnation was done without a solvent. Hydrolysis and condensation were promoted by the HCl vapor to encapsulate a larger amount of titanium oxo species in the mesopore and to suppress the desorption of the titanium oxo species during crystallization to anatase. After the reaction, the shape of the N₂ adsorption isotherm changed significantly, indicating the decrease of the Brunauer-Emmett-Teller surface area from 743 to 283 m²/g and of the pore volume from 1.27 to 0.26 cm³/g, respectively. After the crystallization to anatase, the TiO₂ content in the product was estimated to be 62 mass %, filling 30% of the pore volume of SBA-15. The homogeneous distribution of titanium in the SBA-15 sample was confirmed by elemental mapping based on scanning electron microscopy/energy-dispersive X-ray spectrometry. The crystal size of the anatase was determined to be ca. 8.1 nm, which is consistent with the pore size of the used SBA-15 (8.0 nm, derived from the Barrett-Joyner-Halenda analysis of the nitrogen adsorption isotherm). The zeta potential measurements showed the absence of anatase as isolated particles or on the surface of SBA-15 particles. All of these characterizations confirmed the successful size-controlled synthesis of anatase in the mesopore of SBA-15.

Mesoporous Silica Thin Membranes with Large Vertical Mesochannels for Nanosize-Based Separation

Membrane separation technologies are of great interest in industrial processes such as water purification, gas separation, and materials synthesis. However, commercial filtration membranes have broad pore size distributions, leading to poor size cutoff properties. In this work, mesoporous silica thin membranes with uniform and large vertical mesochannels are synthesized via a simple biphase stratification growth method, which possess an intact structure over centimeter size, ultrathin thickness (≤50 nm), high surface areas (up to 1420 m² g^-1 ), and tunable pore sizes from ≈2.8 to 11.8 nm by adjusting the micelle parameters. The nanofilter devices based on the free-standing mesoporous silica thin membranes show excellent performances in separating differently sized gold nanoparticles (>91.8%) and proteins (>93.1%) due to the uniform pore channels. This work paves a promising way to develop new membranes with well-defined pore diameters for highly efficient nanosize-based separation at the macroscale.