Nanoparticle silicalite-1 crystallization as monitored by nitrogen adsorption
Nanoparticle silicalite-1 crystallization as monitored by nitrogen adsorption
复制标题
通过氮气吸附监测纳米粒子silicalite-1结晶
DOI：
10.1016/j.micromeso.2009.12.028
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发表时间：
2010
影响因子：
5.2
通讯作者：
A. Erdem
中科院分区：
文献类型：
--
作者：
Begum Tokay;Oguz Karvan;A. Erdem
纳米Silicalite-1从透明溶液中结晶后，在77K下进行氮气吸附，并应用于不同时间收集的合成溶液中的产物。等温线数据用t图/BET、密度泛函理论(DFT)和Saito-Foley方法进行分析。产物的微孔、中孔/外面积和体积随时间的变化与最近的一项研究非常一致，该研究表明，在诱导时间之后发生的成核伴随着较小颗粒的聚集。在此合成阶段，当记录到纳米颗粒在溶液中的有效直径突然跳跃时，观察到外表面积急剧减少，同时固体产物的微孔面积显著增加。虽然DFT和Saito-Foley分析表明，固体产物中较早出现了少量的颗粒/区域，其孔径范围包括Silicalite-1的孔尺寸，但Saito-Foley中值直径随合成时间的变化提供了明确的证据，证明了这一“诱导时间”的重要性，在此之后颗粒可以以恒定的线性速度增长。77K下的氮气吸附是监测Silicalite-1纳米粒子成核和晶体生长的有用工具。
Nanoparticle silicalite-1 crystallization from clear solutions was followed by nitrogen adsorption at 77K, applied to the products collected from the synthesis solution at different times. Isotherm data were analyzed by t-plot/BET, density functional theory (DFT), and Saito–Foley methods. Variation in the micropore and mesopore/external areas and volumes of the products with time, were in strong agreement with a recent study, which indicated that nucleation that took place after an induction time, was accompanied by an aggregation of a population of smaller particles. A sharp decrease in external surface area was observed parallel to a significant increase in the micropore area of the solid product at this stage of synthesis, when a sudden jump in the effective diameter of the nanoparticles in solution was recorded. Although earlier appearance in the solid products, of small amounts of particles/regions with pore sizes in a range including the pore sizes of silicalite-1, was indicated by both the DFT and Saito–Foley analyses, variation of the Saito–Foley median diameter with synthesis time provided a clear evidence of the significance of this “induction time”, after which particles could grow at a constant linear rate. Nitrogen adsorption at 77K was shown to be a useful tool to monitor the nucleation and crystal growth of silicalite-1 nanoparticles.