Unraveling the Growth Mechanism of Silica Particles in the Stober Method: In Situ Seeded Growth Model
Unraveling the Growth Mechanism of Silica Particles in the Stober Method: In Situ Seeded Growth Model
复制标题
揭示 Stober 法中二氧化硅颗粒的生长机制：原位晶种生长模型
DOI：
10.1021/acs.langmuir.7b01140
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发表时间：
2017-06-13
期刊：
影响因子：
3.9
通讯作者：
Yang, Wensheng
中科院分区：
文献类型：
--
作者：
Han, Yandong;Lu, Ziyang;Yang, Wensheng
在这项工作中，我们研究了氨催化的原硅酸乙酯（TEOS）的水解和随后的缩合之间的动力学平衡的生长中的二氧化硅颗粒的Stiiber方法。我们的研究结果表明，在初始阶段，反应是由TEOS水解形成硅烷醇单体，这是表示为路径I，是负责通过缩合相邻的硅烷醇单体和衍生的SiO2网络簇的小二氧化硅颗粒的成核和生长。之后，通过将新形成的硅烷醇单体缩合到先前形成的二氧化硅颗粒上来控制反应，这表示为途径II，并且是二氧化硅颗粒尺寸增大的原因。当TEOS水解被显著促进时，无论是在高氨浓度（>= 0.95 M）下还是在LiOH作为第二催化剂的存在下在低氨浓度下，途径I和II的时间分离使得Stober方法使人想起原位接种生长。这种知识的进步使我们不仅能够将文献中最流行的仅聚集和单体加成模型调和成一个一致的框架来解释Stober过程，而且还能够生长尺寸在15-230 nm范围内的单分散二氧化硅颗粒，该颗粒在LiOH的帮助下通过氨浓度简单但精确地调节。
In this work, we investigated the kinetic balance between ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) and subsequent condensation over the growth of silica particles in the Stiiber method. Our results reveal that, at the initial stage, the reaction is dictated by TEOS hydrolysis to form silanol Monomers, which is denoted as pathway I and is responsible for nucleation and growth of small silica particles via condensation of neighboring silanol monomers and siloxarie network clusters derived thereafter. Afterward, the reaction is dictated by condensation of newly formed silanol monomers onto the earlier formed silica particles, which is denoted as pathway II and is responsible for the enlargement in size of silica particles. When TEOS hydrolysis is significantly promoted, either at high ammonia concentration (>= 0.95 M) or at low ammonia concentration in the presence of LiOH as secondary catalyst, temporal separation of pathways I and II makes the Stober method reminiscent of in situ seeded growth. This knowledge advance enables us not only to reconcile the most prevailing aggregation only and monomer-addition models in literature into one consistent framework to interpret the Stober process but also to grow monodisperse silica particles with sizes in the range 15-230 nm simply but precisely regulated by the ammonia concentration with the aid of LiOH.