Pelster Stefan A, Schrader Wolfgang, Schüth Ferdi
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim, Germany.
J Am Chem Soc. 2006 Apr 5;128(13):4310-7. 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.
从溶液中形成固态的最初阶段对于确定所得固体的性质可能至关重要。我们试图通过使用电喷雾质谱法（ESI MS）分析水解和缩合反应，来研究从含有四烷基氢氧化铵（TAAOH）和四烷氧基硅烷（TAOS）的水溶液中发生的硅酸盐预成核反应。使用不同的反应器系统进行了时间分辨测量，以显示硅烷的逐步水解以及随后硅酸盐单体通过低聚物缩合形成更大单元的过程。我们通过改变pH值和反应物浓度来接近沉淀点。结果显示了缩合过程中不同硅酸盐物种的演变。在接近沉淀的pH值下未鉴定出明确的分子实体，这表明在所使用的条件下，固体可能不是由明确的结构单元形成的。
