Highly Ordered Mesoporous Silica Films with Perpendicular Mesochannels by a Simple Stöber‐Solution Growth Approach

Abstract

Surfactant-templated synthesis [1,2] has been a focus of materials science, because it provides a unique means to prepare a variety of ordered mesostructured materials with high surface areas and large, uniform pores. These materials have shown great promise for applications in physics, chemistry, and biology. [3][4][5][6][7][8][9] Different morphologies of mesoporous materials, such as spheres, films, monoliths, rods, and fibers, can all be controllably synthesized. [10,11] Among these, mesoporous thin films have attracted significant attention owing to their unique structures and functions. [12][13][14][15] Previously, ordered mesoporous silica films have been synthesized by selfassembly of silica precursors with surfactant templates at air-water [16] or water-oil interfaces, [17] or by using the evaporation-induced self-assembly (EISA) approach.[18] As the surfactant micelles tend to orient parallel to substrates to reduce the surface energy at interfaces, the mesochannels obtained are always oriented parallel to the film surfaces. [3,[19][20][21] Continuous mesoporous films with perpendicularly aligned channels have recently been prepared by guiding the self-assembly of block copolymers or gemini surfactants with organosilica. [22][23][24][25] However, the thermal and mechanical stability of the films are low, as the pore walls consist of polymers and organosilica. Substrate-templating growth strategies for controlling mesopore orientation based on pp or hydrophilic-hydrophobic interactions have been reported. [26][27][28][29][30] However, these methods require special substrates, such as pyrolytic graphite, anodic alumina with conical holes, or block polymer modified glass, and the alignment of the mesophases at their interface is generally of mixed orientation. Furthermore, perpendicular mesochannels have also been prepared by magnetic-field or electrochemically assisted methods. [31,32] However, these methods often require special equipment and complex processes, and the obtained films have poor regularity and low levels of mesochannel alignment. To date, the synthesis of films with mesopore channels perpendicular to a substrate is still a major challenge.The Stçber approach is a facile and effective method for the synthesis of uniform mesoporous silica nanospheres by a self-assembly process using silica precursors with surfactant templates in an aqueous ethanol solution.[33] The ordered mesochannels in these mesoporous silica nanospheres are often oriented radially to the particle surfaces, [34][35][36] which is an ideal pore arrangement for applications such as catalysis and selective adsorption. Herein, we demonstrate a simple Stçber-solution growth method for the synthesis of mesoporous silica thin films with continuous 2D-ordered mesochannels perpendicular to the substrate. This is accomplished by immersing the substrate into a Stçber solution containing cetyltrimethylammonium bromide (CTAB), tetraethoxysilane (TEOS), ethanol, and ammonia. Moreover, a new type of sandwichlike mesoporous silica film, w...

Facile Synthesis of Yolk-Shell-Structured Triple-Hybridized Periodic Mesoporous Organosilica Nanoparticles for Biomedicine

“…Nitrogen sorption isotherms of the triple-hybridized PMOs show a type IV curve with a large hysteresis loop in the relative pressure range ( p / p 0 ) of 0.5-1.0 (Figure 2 c), suggesting a typical mesopore structure. [ 48,49 ] The specifi c surface area and pore volume of the triple-hybridized PMOs were calculated to be 320 m 2 g -1 and 0.59 cm 3 g -1 , respectively. The pore size calculated based on the nonlocal density functional theory (NLDFT) method reveals the triple-hybridized PMOs have a uniform mesopore size of about 2.5 nm (Figure 2 d).…”

Fabrication of graphene nanoplatelets-supported SiOx-disordered carbon composite and its application in lithium-ion batteries

“…With the help of aqueous ammonia, the resulting negatively charged oligomeric silicate species approach the micelle surface through electrostatic interaction. Additionally, the presence of ammonia also can facilitate the formation hydrogen bonds between the CTAB micelles and silicate oligomers [34]. These absorbed oligomeric silicate species polymerize each other to form polymer.…”

Facile Synthesis of Yolk–Shell Structured Inorganic–Organic Hybrid Spheres with Ordered Radial Mesochannels

“…The assembly and cross-linking processes of two silica-based precursors with CTAB surfactant are similar to the preparation of pure mesoporous silica materials by using only TEOS as a silica source and CTAB as a structure-directing agent in ethanol aqueous solution. [ 49,50 ] Owing to the gradual hydrolysis of TEOS and BTSE, Si-OC 2 H 5 groups should exist in the as-made mesostructured hybrid spheres. When the as-made hybrid spheres are mixed with water, the silicate-CTAB composites with low condensation degree are easily attacked by water molecules and dissolved, [ 43,51 ] resulting in defects in the interiors.…”