From a silane monomer to anisotropic buckled silica nanospheres: a polymer-mediated, solvent-free and one-pot synthesis

Abstract

The morphology of particles, along with other particle attributes, has been shown to affect the biological fate of particles administered into the body. Particles with collapsed surfaces or shells (dimpled, buckled or crumpled) can have different appearances, under the microscope, that resemble many things encountered in our daily life, such as apples/cherries, doughnuts, and bowls. Recent studies have demonstrated that they are not just particles with interesting geometries, but they can also be used as functional blocks for assembled complex materials. Since previous research focus has been on micron-sized particles and organic solvents were often used, it is of particular interest to synthesize the nanosized counterpart with a buckled surface using a purely aqueous method. Herein we report a facile method for rapid synthesis of buckled silica nanoparticles (SiNPs) based on S-nitrosothiol chemistry in a solvent-free reaction. 3-Mercaptopropyl trimethoxysilane (MPTMS) was used as a single silane source in a one-pot aqueous solution containing sodium nitrite and polyvinyl alcohol (PVA). Upon the addition of HCl, S-nitrosation and condensation of MPTMS occur simultaneously and the reaction system undergoes a rapid transition from a clear solution to a solution containing nanoparticles with a lag time controlled mainly by the amount of HCl added. The experimental parameters were systematically studied to determine the optimal concentration of each component. For a typical reaction, sub-100 nm nanoparticles can be produced in less than 1 h, and the best result can be obtained within 2 to 4 h. Remarkably, the nanoparticle exhibits buckled surface morphologies under TEM and SEM. The average size is about 60 nm in diameter. Moreover, the solid-state Si-NMR data show that T and T silicon species are rapidly evolved with slight dynamic changes over the reaction time. Further, PVA is shown to control the surface buckling as well as to stabilize the formed particles. The as-prepared SiNPs can be used as a nitric oxide (NO) carrier with the potential to release NO in an apparent zero-order manner. In conclusion, the study demonstrates the feasibility of employing an aqueous route for efficiently preparing SiNPs with multifarious surface cavities based on S-nitrosothiol chemistry.

Facile Fabrication of Lilium Pollen-like Organosilica Particles

“…6 Lo et al reported a series of anisotropic buckled silica nanoparticles, including apple-like, doughnut-like, and bowl-like nanoparticles, with mercaptopropyl trimethoxysilane as the only silane source. 20 Hao et al fabricated biomimic walnut kernellike and erythrocyte-like mesoporous silica nanoparticles with two surfactants. They further identified that these silica nanoparticles performed superiorly in cellular imaging and drug delivery.…”

“…Zhou et al fabricated golf ball-like organic–inorganic silica microspheres with a wrinkled surface . Lo et al reported a series of anisotropic buckled silica nanoparticles, including apple-like, doughnut-like, and bowl-like nanoparticles, with mercaptopropyl trimethoxysilane as the only silane source . Hao et al fabricated biomimic walnut kernel-like and erythrocyte-like mesoporous silica nanoparticles with two surfactants.…”

Bioinspired Approach to Silica Nanoparticle Synthesis Using Amine-Containing Block Copoly(vinyl ethers): Realizing Controlled Anisotropy

“…Lo et al obtained buckled bowl-like organosilica nanoparticles (50−60 nm in diameter) using 3-mercaptopropyl trimethoxysilane as a silane source in an aqueous solution containing poly(vinyl alcohol). 27 The buckled nanoparticles formed as a result of drying. Ma et al reported the synthesis of sub-10 nm silica nanoparticles bearing half-pores by using micelles of hexadecyltrimethylammonium hydroxide as templates.…”

“…Only a few reports demonstrated the preparation of single-hole nanoparticles smaller than 100 nm in diameter. Lo et al obtained buckled bowl-like organosilica nanoparticles (50–60 nm in diameter) using 3-mercaptopropyl trimethoxysilane as a silane source in an aqueous solution containing poly­(vinyl alcohol) . The buckled nanoparticles formed as a result of drying.…”

Kinetics of fluoride-catalysed synthesis of organosilica colloids in aqueous solutions of amphiphiles

“…[25][26][27][28][29][30][31] Previously, there have been several attempts to prepare organosilica particles in a solvent-free system, based mainly on acidic or basic routes. [32][33][34][35][36][37] Most recently, we have demonstrated a general "salt route" for efficiently synthesizing organosilica nanospheres in purely aqueous reaction systems containing common salts and common surfactants or polymers. 38 We demonstrated that under the mild reaction conditions (neutral pH, room temperature, no stirring), stable colloidal solutions containing organosilica nanoparticles (about 100 nm) could be produced within 24 h. 38 Fluoride ion (F À ) has been used as a catalyst to mediate the hydrolysis and condensation of silica precursors and form mesoporous or microporous solid materials.…”