Monitoring Temporal Evolution of Silicate Species during Hydrolysis and Condensation of Silicates Using Mass Spectrometry

• Published in: Journal of the American Chemical Society Vol. 128; no. 13; pp. 4310 - 4317
• Main Authors: Pelster, Stefan A, Schrader, Wolfgang, Schüth, Ferdi
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 05.04.2006
• Subjects: Chemistry; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Reactivity and mechanisms; Crystal growth; Hydrolysis; Condensation reaction; Silicon Organic compounds; Reaction mechanism; Crystal nucleation; Aqueous solution; Experimental study; Tandem reaction; Mass spectrometry; Electrospray; Organic silicate
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja057423r

The first stages of solid-state formation from solution can be crucial in determining the properties of the resulting solids. We are trying to approach prenucleation reactions of silicates from an aqueous solution containing tetraalkylammoniumhydroxides (TAAOH) and tetraalkoxysilanes (TAOS) by analyzing hydrolysis and condensation using electrospray mass spectrometry (ESI MS). Time-resolved measurements were performed using different reactor systems to show the stepwise hydrolysis of the silanes and subsequent condensation of silicate monomers via oligomers to form larger units. We approached the precipitation point by varying the pH and the concentrations of the reactants. The results show the evolution of different silicate species occurring during condensation. No defined molecular entities were identified at pH values close to precipitation, which suggests that under the conditions used, solids are probably not formed from defined building blocks.