Mesoporous Organosilica Hollow Nanoparticles: Synthesis and Applications

Abstract

Hollow periodic mesoporous organosilicas (PMOs) with molecularly homogeneous organic functional groups in the inorganic pore walls are attracting more and more attention due to the high surface areas, tunable pore sizes, low densities, large cavities in the center, permeable thin shells, and versatile organic–inorganic hybrid frameworks, which make them promising in a variety of applications including adsorption, catalysis, drug delivery, and nanotheranostics. Herein, recent advances in the synthesis of hollow PMO nanoparticles with various organic moieties are summarized, and the mechanism and new insights of synthesis approaches, including hard‐core templating methods, liquid‐interface assembly methods, and the interfacial reassembly and transformation strategy are discussed in‐depth. Meanwhile, the design principles, properties, and synthetic strategies for some smart hollow architectures such as multishelled hollow PMOs, yolk–shell structured PMOs, and nonspherical hollow PMOs are discussed. Moreover, the typical applications of hollow PMO nanomaterials as nanoreactors for chemical transformations and nanoplatforms for biomedicine are summarized. Finally, the challenges and prospects for the future development of hollow PMOs are described.

Transformation of Stöber Silica Spheres to Hollow Nanocatalysts

“…Two types of etching agents (i. e., etchants), alkaline‐ and fluoride‐based, are usually employed for etching processes. The etching of silica with an alkaline (e. g., NaOH, Na 2 CO 3 , NaBH 4 , and ammonia) is a reversible process in a sense that it can also end up producing unexpected products due to the possible re‐nucleation of the dissolved silica with existing structure directing agents (SDAs) in solution . Sometimes, this reaction is carried out in hot water to intensify the etching effect.…”

“…Such and similar template‐mediated approaches for making hollow materials are often adopted because of their flexibility and versatility . Particularly, hard‐core templating or simply hard‐templating is rather effective for the design of elaborated hollow structures, especially yolk‐shell ones . Three main steps are involved in this procedure: (i) preparing a hard‐core material (e. g., Stöber silica sphere), (ii) coating a layer (or a shell) on the core surface, and (iii) complete removal of the core by etching or other methods such as calcination or solvent treatment.…”

“…Over the past decades, a great number of exquisitely organized reviews have been devoted to highlight the syntheses methods and applications of hollow nanomaterials derived from siliceous precursors, but to the best of our knowledge, exclusive reviews on the use of Stöber SiO 2 spheres for hollow nanocatalysts are scantily found or not found at all . In this minireview, therefore, we will summarize recent advancements which were gained in preparation of various hollow nanocatalysts using Stöber SiO 2 spheres.…”

Targeted and stimuli–responsive mesoporous silica nanoparticles for drug delivery and theranostic use

“…First ever MPSNPs applied in drug delivery was M41S (Teng et al, ). Based on structural dimensions, following three categories of M41S are well documented (Figure ; Feng et al, ).…”

Robust Synthesis of Gold‐Based Multishell Structures as Plasmonic Catalysts for Selective Hydrogenation of 4‐Nitrostyrene

“…As ar esult, the inward diffusion of BH 4 À is much faster than outward diffusion of Au species.T hese diffusion rate distinctions finally lead to formation of multishell structures. [22][23][24] UV/Vis-NIR spectra (Figure 3d)ofthree samples (S-PSSAu, S-PDSAu, and S-PTSAu) with same Au concentration were determined to investigate their light absorption property. Accompanied by the increasing shell number, increased lightharvesting is observed, which may be caused by the presence of additional incident light reflections in the structures with more shells.…”