Nemoto Takahiro, Sakai Toshio, Okada Tomohiko
Department of Materials Chemistry, Faculty of Engineering, Shinshu University 4-17-1, Wakasato Nagano 380-8553 Japan
Research Initiative for Supra-Materials, Shinshu University 4-17-1, Wakasato Nagano 380-8553 Japan.
RSC Adv. 2021 Jun 29;11(37):22921-22928. doi: 10.1039/d1ra03384k. eCollection 2021 Jun 25.
This study investigates the regulation of the size of 100 nm hollow-sphere silica particles using surfactant-free water-in-oil (W/O) emulsion. First, water droplets were dispersed in soybean oil sequential ultrasound irradiation (28 kHz → 200 kHz → 950 kHz). A precursor of hollow silica particles was prepared using hydrolysis and polymerization of methylsilyl trichloride into a stable W/O emulsion. The final structure/morphology of the silica particles was influenced by the volume ratio of water/soybean oil, the cycle number of the sequential ultrasound irradiation, and the amount of organosilane added to the emulsion. The emulsion was stabilized by Ostwald ripening, as the size distribution at 5/10 (water/oil = v/v) was a bimodal split between a water droplet size of a few μm and some with a size of a few tens of nm. The most appropriate cycle number was 3 in this system. Further cycling to 5 resulted in a broad and bimodal size distribution of the final particles due to rapid coalescence of water droplets. Subsequent hydrolysis of methylsilyl trichloride consumed water with diminishing large droplets, forming fine and unimodal (0.12 ± 0.02 μm) hollow silica particles. Very fine and uniform-sized hollow particles (0.08 ± 0.01 μm) were successfully produced by decreasing the volume ratio to 1/10 (water/oil) because of a transparent stable emulsion as a homogeneous template of the hollow structures.
本研究利用无表面活性剂的油包水（W/O）乳液研究了100纳米空心球形二氧化硅颗粒尺寸的调控。首先，通过顺序超声辐照（28千赫→200千赫→950千赫）将水滴分散在大豆油中。利用甲基三氯硅烷的水解和聚合反应，在稳定的W/O乳液中制备了空心二氧化硅颗粒的前驱体。二氧化硅颗粒的最终结构/形态受水/大豆油的体积比、顺序超声辐照的循环次数以及添加到乳液中的有机硅烷量的影响。乳液通过奥斯特瓦尔德熟化得以稳定，因为在5/10（水/油 = 体积比）时的尺寸分布是在几微米的水滴尺寸和几十纳米尺寸之间的双峰分裂。在该体系中最合适的循环次数是3次。进一步循环至5次会导致最终颗粒的尺寸分布变宽且呈双峰，这是由于水滴的快速聚结。随后甲基三氯硅烷的水解消耗了水，大液滴减少，形成了细小且单峰（0.12±0.02微米）的空心二氧化硅颗粒。通过将体积比降至1/10（水/油），成功制备出了非常细小且尺寸均匀的空心颗粒（0.08±0.01微米），这是因为形成了透明稳定的乳液，作为空心结构的均匀模板。
