Two-Phase Diffusion Technique for the Preparation of Ultramacroporous/Mesoporous Silica Microspheres via Interface Hydrolysis, Diffusion, and Gelation of TEOS

Abstract

Honeycombed hierarchical ultramacroporous/mesoporous silica microspheres were prepared via the hydrolysis of TEOS in the oil-water interface, with subsequent diffusion and gelation in the acidic water-phase microdroplets with the assistance of a simple homemade microdevice. The diffusion of furfuryl alcohol (FA) also happened at a relatively high rate during the hydrolysis and diffusion of TEOS. Therefore, plenty of FA will be inside of the water microdroplets and form a decent number of polyfurfuryl alcohol (PFA) microparticles, thereby obtaining honeycombed hierarchical porosity silica microspheres with abundant ultramacroporous cavities and mesopores after calcination. It was found that the concentration of FA, residence time, and reaction temperature have significant effects on the porosity and pore size due to the influence on the diffusion rate and amount of FA in water-phase microdroplets. The honeycombed silica microspheres have obvious microscopic visible ultramacroporous cavities with the submicrometer cavity diameter as high as 85% porosity based on the rough overall volume of microsphere. N adsorption-desorption isotherms show that the honeycombed hierarchical porosity silica microspheres have a high surface area of 602 m g, a mesopore volume of 0.77 cm/g, and a mesopore porosity of 99.6% based on the total pore volume of N adsorption-desorption. On the basis of the experiment results, a rational formation process of the honeycombed hierarchical porosity silica microspheres was deduced.

General Method to Synthesize Highly Stable Nanoclusters via Pickering-Stabilized Microemulsions

“…Transmission electron microscopy (TEM) ( Figure 1 b) reveals that these nanospheres have a hollow center, unlike solid silica particles obtained from a regular TEOS hydrolysis process. 27 In agreement with the SEM result, the particle size of these nanospheres is around 40 nm, with a central cavity of about 15 nm. X-ray photoelectron spectroscopy (XPS) is used to probe the state of Au in the powder.…”

“…The powder consists of uniform nanospheres with a diameter of 39 ± 4 nm. Transmission electron microscopy (TEM) (Figure b) reveals that these nanospheres have a hollow center, unlike solid silica particles obtained from a regular TEOS hydrolysis process . In agreement with the SEM result, the particle size of these nanospheres is around 40 nm, with a central cavity of about 15 nm.…”

Controllable Inducing Preparation of Polymorphous Hundred-Micron Alumina Microspheres via Droplet-Based Two-Stage Microfluidic Solvent Extraction Technology

“…Simultaneously, based on microdroplet technology, the combination of a liquid dispensing into individual droplets followed by drop coalescence further refines the operation of sol droplets, effectively avoiding any blockages caused by sediments or viscous gels . Various inorganic microspheres, such as alumina, silica, zirconia, and polymethylsilsesquioxane (PSQ) microspheres, with highly controllable morphologies have been successfully prepared using microfluidic systems owing to the advantage of precise control of liquid drops in such systems. − Generally, in a microfluidic chip, the controllability of the flow field is considerably enhanced, making it possible to operate the droplet mass transfer and gel processes based on the flow field. , The characteristics of the microfluidic precision operation can be leveraged to regulate the contact between the extractant and sol droplets in the microchannel and the direction of extraction diffusion. Combining the microfluidic technology with the extraction and solidification technologies of the sol–gel process can significantly expand the application scope of these processes.…”