Synthesis of Anisotropic Silica Nanoparticles

Anisotropic silica nanoparticles (AISNPs) are appealing for various applications due to their greater effective surface area and increased active sites compared to isotropic silica nanoparticles (ISNPs).Herein,we employed a sol-gel method to synthesize AISNPs utilizing the mixture of ethylenediamine (EDA);1,3-diaminopropane (1,3-DAP) as both structure-directing agents and catalysts.With increasing EDA:1,3-DAP molar ratio,the samples transitioned from isotropic spherical particles to anisotropic particles with increasing sizes.The synthesis of AISNP with a particle size of ca.40 nm,average circularity (e) of 0.83,fitting ellipse aspect ratio (ar) of 1.18 and percentage of deformed particles of 83.3% was achieved with a molar ratio of EDA:1,3-DAP=7:3.It is speculated that the close proximity of EDA's amine groups facilitates their adsorption on the same primary particle through electrostatic interaction,inhibiting primary particle connections and resulting in spherical seeds that grow into small isotropic particles;the long-distance amine groups of 1,3-DAP connect adjacent particles anisotropically due to the steric hindrance,leading to large anisotropic particles;the mixtures with different EDA/1,3-DAP molar ratios result in different morphologies and sizes by their cooperative effect.

Formation of Lamellar Mesostructured Crystalline Silica by Self-assembly of CTAB

Controlling organic-inorganic liquid crystal structures to form lamellar mesostructured crystalline silica nanosheets(LCS) was achieved by using the simple cationic surfactant cetyl trimethyl ammonium bromide(CTAB). The organic-inorganic interaction under the condtions of a high surfactant concentration and suitable synthesis temperature played an important role in the construction of mesostructured crystalline silica.

Mesoporous Silica Microspheres Composited with SBA-15s for Resonance Frequency Reduction in a Miniature Loudspeaker

Microspheres composited with mesoporous SBA-15 particles and silica were investigated as fillers in miniature loudspeakers to study the factors influencing the resonance frequency offsets(RFOs).Mesoporous silica microspheres(MSMs)were prepared by self-assembling SBA-15 mesoporous silica in a microemulsion synthesis system.The formation process involved the fabrication of a stable O/W microemulsion of tetrabutyl orthosili-cate(TBOS)and hexadecyltrimethylammonium bromide(C16TAB)and encapsulation of SBA-15s.The RFO increased and then decreased with increasing particle size(in the length range of 0.7—5.5 μm and in the width range of 0.2—0.45 μm),increased with increasing pore size(in the range of 7.0—9.4 nm)of SBA-15s,and increased with decreasing particle size(105—900 μm)of MSMs.