Formation Mechanism and Size Control in One-Pot Synthesis of Mercapto-Silica Colloidal Spheres

Abstract

Mercapto-silica spheres with controllable size from ∼150 nm to ∼3.5 μm and narrow size distribution have been prepared in water using a one-pot synthesis, in which 3-mercaptopropyltrimethoxysilane (MPS) was used as the sole silica source and ammonia as the base catalyst. The hydrolysis of MPS at the early stage of the reaction produces amphiphilic silicate species which initiate the self-emulsification of the system and lead to the formation of oil-in-water emulsion droplets. Further hydrolysis and condensation promote the nucleation and growth of the mercapto-silica spheres inside the emulsion droplets. These mercapto-silica spheres are both structurally and functionally different from typical silica particles prepared from silicon alkoxides. Understanding the formation mechanism allows systematic tuning of the size of mercapto-silica spheres in a wide range by changing the amount of precursor, the concentration of ammonia, the amount of additional surfactants, and the reaction time. We find that Ostwald ripening may occur quickly if the spheres are kept in the reaction solution, resulting in significant broadening of the particle size distribution. In order to obtain uniform and stable samples, it is important to quench the growth of the mercapto-silica spheres by separating them from the original reaction mixture and then storing them in solvents that can prevent further ripening.

Total Synthesis and Structural Revision of (–)‐Protubonine A and (–)‐Protubonine B

“…Recently, organosilica nanoparticles comprising the sole organosilicate precursor were developed 21, 22. For example, thiolated nanoparticles have been made using MPTS as single organosilicate source 22, 23. Due to the absence of an inorganic silica source, the functional group content is much higher on the particle surface, allowing further surface grafting or sensitive analytical applications.…”

Thermoresponsive PNIPAM/silica nanoparticles by direct photopolymerization in aqueous media

“…The method (Scheme , top left) is particularly suitable for preparing thiol‐functionalized silica (silica‐SH) particles as (3‐mercaptopropyl)trimethoxysilane (MPTMS) is easily hydrolyzed into organosilanetriol by self‐hydrolysis. The size of thiol‐functionalized silica particles prepared by this method is usually larger (typically >1 µm but can be controlled to some extent) . In this work, larger silica‐SH particles with an diameter of ∼692 nm were prepared by this one‐step method [Fig.…”

Biofunctionalization of silica microspheres for protein separation

“…This drawback, fortunately, can be well overcome by directly applying organosilane precursors to produce organosilica [16]. For example, 3-mercaptopropyltrimethoxysilane (denoted as MPS) is often used to produce thiol-functionalized silica [17,18]. During the process, MPS is hydrolyzed at the early stage to produce amphiphilic silicate species which can initiate the self-emulsification of the reaction system to form oil-in-water emulsion droplets, and further hydrolysis-condensation taking place inside the emulsion droplets affords desired thiolfunctionalized silica.…”