Hydrolysis Of Silica Precursor Research Articles

Versatile hollow fluorescent metal-silica nanohybrids through a modified microemulsion synthesis route

Silica-metal nanohybrids are common materials for applications in biomedicine, catalysis or sensing. Also, hollow structures are of interest as they provide additional useful features. However, in these materials the control of the size and accessibility to the inner regions of the structure usually requires complex synthesis procedures. Here we report a simple colloidal procedure for synthesizing hollow silica-metal nanohybrids, driven by the diffusion of metal precursors through the porous silica shell and subsequent reduction in aqueous solutions. The formation of hollow nanoparticles is controlled by the colloidal conditions during synthesis, which affect the ripening of hollow nanoparticles in presence of organosilanes. The modification of the conditions during synthesis affected the growth of silica precursors in presence of fluorescein isothiocyanate (FITC). The limited access to water molecules during the hydrolysis of silica precursors is attributed to the hydrophobicity of organic fluorescent molecules linked to the condensing silica clusters at the initial stages of nanoparticle formation and to the limitation of water content in the microemulsion method used. Finally, the growth of metal nanoseeds at the core of hollow nanoparticles can be easily achieved though a simple method in aqueous environment. The pH and thermal conditions during the reduction process affect the formation of metal-silica nanohybrids and their structural features.

Synthesis and Catalytic Activity of Fe-MCM-41 Nanoparticles

Mesostructured Fe-MCM-41 nanoparticles have been hydrothermally prepared for the first time with assistance of binary surfactants (CTAB and F127). The formation of nanoparticles consists of two steps, that is, the hydrolysis of silica precursor via catalysis by an acidic ferric salt, followed by facile assembly into mesostructured nanocomposites with cationic micelles by addition of condensation catalyst. In the hydroxylation of phenol with aqueous H2O2, Fe-MCM-41-NP displayed higher activity than a Fe-MCM-41 sample with normal particle size (Fe-MCM-41-LP).

Hydrothermal synthesis of mesostructured aluminosilicate nanoparticles assisted by binary surfactants and finely controlled assembly process

Mesostructured aluminosilicate nanoparticles with narrow grain size distribution have been hydrothermally prepared for the first time with assistance of binary surfactants and separate hydrolysis and assembly of inorganic precursors. Compared to the sample assembled at room temperature, condensation degree and aluminum stability were greatly improved using hydrothermal treatment. The formation of nanoparticles consists of two steps, that is, the hydrolysis of silica precursor via catalysis by an acidic aluminum salt, followed by facile assembly into mesostructured nanocomposites with cationic micelles by addition of condensation catalyst. Simultaneously, nonionic polyethylene glycol (PEG-4000) present in this process would surround the formed nanoparticles through hydrogen-bonding interactions, thereby tailoring the grain size distribution and preventing aggregation and growth of inter-nanoparticles during the hydrothermal treatment process. The microstructure and chemical compositions of these products were thoroughly characterized by XRD, SEM, TEM, N 2 sorption and 27Al MAS NMR techniques.