Mesopore-Free Hollow Silica Particles with Controllable Diameter and Shell Thickness via Additive-Free Synthesis

Abstract

Mesopore-free hollow silica particles with a spherical shape, smooth surface, and controllable diameter (from 80 to 300 nm) and shell thickness (from 2 to 25 nm) were successfully prepared using an additive-free synthesis method. Different from other hollow particle developments, a mesopore-free shell was produced because of the absence of additive. Although common reports pointed out the importance of the additional additive in pasting and growing silica on the surface of a template, here we preferred to exploit the effect of the template charge in gaining the silica coating process. To form the silica, basic amino acid (i.e., lysine) was used as a catalyst to replace ammonia or hydrazine, which is harmless and able to control the silica growth and produce hollow particles with smooth surfaces. Control of the particle diameter was drastically achieved by altering the size of the template. The flexibility of the process in controlling the shell thickness was predominantly attained by varying the compositions of the reactants (i.e., silica source and catalyst). The present mesopore-free hollow particles could be efficiently used for various applications, especially for thermal insulator and optical devices because of their tendency not to adsorb large molecules, as confirmed by adsorption analysis.

Semi-crystalline diblock copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization of stearyl methacrylate

“…Lysine (1.4 mg/mL) was also added to facilitate silica deposition. 45 TEM images of the resulting hybrid PDMA 55 -PSMA 93 vesicles are shown in Figure 7b, where a uniform layer of silica is clearly visible on the particle surface. Unlike the precursor vesicles, these silica-clad vesicles required no TEM staining since the relatively high density of the inorganic over layer confers sufficient electron contrast.…”

Mesopore-free silica shell with nanometer-scale thickness-controllable on cationic polystyrene core

“…Surfactant-free cationic PS particles with various sizes (ranged from 80 to 300 nm) were used as a model of core material. PS particles are spherical, monodisperse, and size-and charge-controllable, which can be effective to support the investigation of electrostatic attraction between the core material and the negatively charged silica without any additives [23,26]. Different from other silica coating reports, mesopore-free shell was produced due to the absence of additive in the silica coating process, in which to the best of our knowledge, this type of shell was the first in the core-shell particle developments.…”

“…Different from other PS particles, our synthesized PS had a positive zeta charge. Due to this positive zeta charge, these PS particles exhibited a potential way for assisting the formation of various inorganic hollow particles (prepared using either a spray-drying [23] or a liquid-phase synthesis method [26]). …”

“…Different from other silica coating reports, mesopore-free shell was produced due to the absence of additive in the silica coating process, in which to the best of our knowledge, this type of shell was the first in the core-shell particle developments. Mesopore-free structure is important because this structure can increase the shell strength and avoid the penetration of larger molecules into or out of the particles [26]. For forming the silica, basic amino acid (i.e., lysine) was used as a catalyst, replacing ammonia or hydrazine.…”

Influence of morphology of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

“…3(b) and 3(c). The hollow spheres were prepared using a PS template method as described previous study [39,[44][45][46]. In this method, silica-alumina composite primary particles were prepared using a sol-gel method, and the primary particles were deposited on the surface of PS template particles to form composite shells [44,[47][48][49].…”