Quantification of initial steps of nucleation and growth of silica nanoparticles: An in-situ SAXS and DLS study
Quantification of initial steps of nucleation and growth of silica nanoparticles: An in-situ SAXS and DLS study
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DOI：
10.1016/j.gca.2009.06.002
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发表时间：
2009-09-15
影响因子：
5
通讯作者：
Benning, Liane G.
中科院分区：
文献类型：
--
作者：
Tobler, Dominique J.;Shaw, Sam;Benning, Liane G.
对二氧化硅聚合和二氧化硅纳米颗粒形成的初始步骤进行了现场和实时研究。实验在接近中性pH（7-8）的溶液中进行，初始二氧化硅浓度为640和1600 ppm ([SiO2])，离子强度（IS）为0.02、0.05、0.11和0.22 m。通过中和高pH二氧化硅溶液（pH 12至7）诱导聚合反应，并通过单硅酸浓度随时间的随时间损耗来监测聚合反应。利用基于时间分辨同步加速器的小角度x射线散射（SAXS）和常规动态光散射（DLS）结合扫描和（冷冻）透射电子显微镜（SEM/cryo- tem），原位观察了二氧化硅纳米颗粒的成核和生长（即粒径随时间的变化）。测定了临界核直径（1.4 ~ 2 nm）， SAXS和DLS结果表明，在3℃以上，颗粒直径增加到8 nm左右。SEM和TEM显微照片验证了SAXS和DLS数据，并证实了形成的二氧化硅纳米颗粒的球形和水合结构。分形分析（即分形维数D-m近似于2.2）表明，形成的颗粒是开放的、聚合的、低密度的结构。对于二氧化硅纳米颗粒的成核和生长，提出了三个阶段的生长过程：(1)均匀和瞬时的二氧化硅纳米颗粒成核；(2)三维的，表面控制的一级反应动力学的颗粒生长；(3)奥斯特瓦尔德成熟和颗粒聚集。2009爱思唯尔有限公司版权所有。
The initial steps of silica polymerization and silica nanoparticle formation have been studied in-situ and in real-time. The experiments were carried out in near neutral pH (7-8) solutions with initial silica concentrations of 640 and 1600 ppm ([SiO2]) and ionic strengths (IS) of 0.02, 0.05, 0.11 and 0.22 M. The polymerization reactions were induced by neutralizing a high pH silica solution (from pH 12 to 7) and monitored by the time-dependent depletion in monosilicic acid concentration over time. The accompanied nucleation and growth of silica nanoparticles (i.e., change in particle size over time) was followed in-situ using time-resolved synchrotron-based Small Angle X-ray Scattering (SAXS) and conventional Dynamic Light Scattering (DLS) combined with scanning and (cryo)-transmission electron microscopy (SEM/cryo-TEM).The critical nucleus diameter was quantified (1.4-2 nm) and results from SAXS and DLS showed that over 3 It the particle diameter increased to a final size of similar to 8 nm. SEM and TEM photomicrographs verified the SAXS and DLS data and confirmed the spherical and hydrous structure of the forming silica nanoparticles. Furthermore, fractal analysis (i.e., fractal dimension, D-m similar to 2.2) indicated that the formed particles consisted of open, polymeric, low-density structures.For the nucleation and growth of silica nanoparticles a 3-stage growth process is proposed: (1) homogeneous and instantaneous nucleation of silica nanoparticles, (2) 3-D, surface-controlled particle growth following 1st order reaction kinetics and (3) Ostwald ripening and particle aggregation. (C) 2009 Elsevier Ltd. All rights reserved.