Core–Shell Interface-Oriented Synthesis of Bowl-Structured Hollow Silica Nanospheres Using Self-Assembled ABC Triblock Copolymeric Micelles

Abstract

Hollow porous silica nanospheres (HSNs) are emerging classes of cutting-edge nanostructured materials. They have elicited much interest as carriers of active molecules delivery due to their amorphous chemical structure, non-toxic nature and biocompatibility. Structural development with hierarchical morphology is mostly required for obtaining the desired performance. In this context, large through-holes or pore openings on shells are desired so that the post-synthesis loading of active molecules HSNs via a simple immersion method can be facilitated. This study reports the synthesis of HSNs with large through-holes or pore openings on shells, which are subsequently termed bowl-structured hollow porous silica nanospheres (BHSNs). The synthesis of BHSNs was mediated by the core-shell interfaces of the core-shell-corona structured micelles obtained from a commercially available ABC triblock copolymer (polystyrene-b-poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PS-P2VP-PEO)). In this synthesis process, polymer@SiO2 composite structure was formed because of the deposition of silica (SiO2) on the micelles' core. The P2VP block played the significant role in: firstly, hydrolysis and condensation of the silica precursor i.e. tetraethylorthosilicate (TEOS); and secondly, maintaining the shell's growth. The 4 PS core of the micelles built the void spaces. Transmission electron microscopy (TEM) images revealed a spherical hollow structure with an average particle size of 41.87 ± 3.28 nm. The average diameter of void spaces was 21.71 ± 1.22 nm and shell thickness was 10.17 ± 1.68 nm. According to the TEM image analysis the average large pore was determined as 15.95 nm. Scanning electron microscopy (SEM) images further confirmed the presence of large single pores or openings in shells. These were formed due to the accumulated ethanol on PS core acting to prevent the growth of silica.

Hollow Porous Silica Nanosphere with Single Large Pore Opening for Pesticide Loading and Delivery

“…In our previous study, it was observed that BHSNs possess a shell thickness and inner void space of 10.17 ± 1.68 and 21.71 ± 1.22 nm, respectively (Figure 1a). 39 This study shows the shell thickness of imi@BHSNs is 11.18 ± 2.23 nm and the inner void space is 19.37 ± 4.80 nm (Figure 1b). These changes in dimension clearly reflect deposition of imidacloprid on the inner surfaces of BHSNs.…”

“…The detailed synthesis procedure and characterization of BHSNs have been reported in our previous study. 39 2.2. Loading of Pesticide onto BHSNs.…”

Confined-Space Pyrolysis of Polystyrene/Polyacrylonitrile for Nitrogen-Doped Hollow Mesoporous Carbon Spheres with High Supercapacitor Performance

“…Polystyrene (PS) spheres, which represent a typical polymer, has been always used as a sacrificial hard template for hollow structure, because of its excellent decomposition characteristics with no carbon residue and uniform particle size. The use of PS spheres as a hard template has been widely examined in preparation of hollow silica or metal oxide spheres. − PS spheres is also an effective hard template for HCS. , Typical uniform HCS materials with high dispersion are prepared by using resin as a shell and PS as a template. However, the HCS materials prepared via this method show an inert surface, which limits their performance, especially electrochemical performance …”

Complex Hollow Bowl‐Like Nanostructures: Synthesis, Application, and Perspective

“…Ravi Naidu's group reported a method synthesizing a bowl‐like hollow silica nanosphere using self‐assembled ABC triblock copolymeric micelles. [ 63 ] Initially, polystyrene‐ b ‐poly(2‐vinylpyridine)‐ b ‐poly(ethylene oxide) (PS‐P2VP‐PEO) triblock copolymer was added to dimethylformamide (DMF) with 10 wt% water under stirring until dissolved completely. Next, DMF was eliminated by dialysis against DI water.…”