Direct Crystallization of Layered Silicates on the Surface of Amorphous Silica

Abstract

We overview the entire surface coverage of amorphous silica with layered silicates (smectite-like) using the direct crystallization technique under hydrothermal conditions. Various shapes (e. g., microspheres, fibers, microcapsules) have been available as the silica substrates, which involve partial dissolution triggered by the hydrolysis of urea for supplying a source of the layered silicates. Other sources (e. g., Li , Mg , Al ) have been supplied from aqueous solutions, participating the heterogeneous nucleation of the layered silicates. Because of partial dissolution of the silica substrates, the original shape has been preserved after the hydrothermal reactions. Cation exchange reactions, usually observed for conventional smectite systems, occurred by replacing the interlayer cations in the silicates with metal (a rare-earth ion) and organic (a quaternary long-chain alkylammonium, methylene blue, and a tris-chelated complex) cations. We have discussed the mechanism of the crystallization and displayed some applications of the hybrids (e. g., chiral discrimination, filtering, and magnetic recovery).

Monodisperse Clay Microballs for Tuning the Pseudogaps by Adsorption in Amorphous Photonic Structures

“…The transmission electron microscopy (TEM) image of A1 (Figure 1a) shows the silica spheres evenly covered with Hect crystals while maintaining the original spherical shape. The average particle size of A1 (193 nm) recorded by TEM was slightly smaller than the pristine silica (194 nm), because of partial dissolution of silica during the hydrothermal reactions [20] . However, the size distribution was homogeneous with only a slight deviation (the relative standard deviation (RSD) was approximately 2 %).…”

“…The average particle size of A1 (193 nm) recorded by TEM was slightly smaller than the pristine silica (194 nm), because of partial dissolution of silica during the hydrothermal reactions. [20] However, the size distribution was homogeneous with only a slight deviation (the relative standard deviation (RSD) was approximately 2 %). Irrespective of the initial size of the silica spheres, the overall homogeneous coverage of Hect was achieved as indicated by the RSD values of within 5 % ( Table 1).…”

“…The spherical clay particles were prepared using an in situ crystallization technique, [20,21] in which the clay component (Hect) was firmly immobilized on monodisperse spherical colloidal silica (silica@Hect: Scheme 1). The spherical silica particles were hydrothermally reacted with LiF and MgCl 2 with a molar Li : Mg:Si ratio of 0.84 : 0.69 : 8.0 in the presence of urea (the preparation procedure and the XRD patterns ( Figure S1) are enclosed in Supporting Information).…”

Cobalt silicate: critical synthetic conditions affect its electrochemical properties for energy storage and conversion

“…These hollow spheres are formed by the cobalt silicate nanosheets like in the previous report. 48 Under the action of hydroxide in the solution, the silica on the surface enters the solution phase and binds with the metal ions in the solution. The resulting nano-flake silicate is then reattached to the surface of the template (silica sphere).…”

Hydrated Silicate Layer Formation on Mica-Type Crystals

“…Reactions that occur at hetero-interfaces have recently attracted interest, from both scientific and practical viewpoints, because they frequently provided unexpectedly useful crystalline/anisotropic solids. Designing inorganic nanosheets with highly anisotropic shapes and thicknesses of less than 1 nm typically fascinates researchers, especially those in the field of materials chemistry, owing to their varied electrical and surface tailorabilities. , In particular, metal oxides, including SiO 2 , Al 2 O 3 , and CuO, have known surfaces available for the architectural growth of inorganic nanosheets including those of cation- − and anion-exchangeable fine crystals through heterogeneous nucleation reactions (or so-called in situ crystallization). Specifically, mica surfaces have been classed as highly crystalline layered aluminosilicates, which have received much attention recently as platforms for growing inorganic nanosheets for potential applications as catalytic supports or flexible optoelectronic devices.…”