Surface-initiated polymerization on unmodified inorganic semiconductor nanoparticles via surfactant-free aerosol-based synthesis toward core–shell nanohybrids with a tunable shell thickness
Surface-initiated polymerization on unmodified inorganic semiconductor nanoparticles via surfactant-free aerosol-based synthesis toward core–shell nanohybrids with a tunable shell thickness
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DOI：
10.1039/c7ta04985d
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发表时间：
2017-09
影响因子：
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通讯作者：
M. Shaban;Jalal Poostforooshan;A. Weber
中科院分区：
文献类型：
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作者：
M. Shaban;Jalal Poostforooshan;A. Weber
这里提出的工作描述了一种简便的方法，对各种无机半导体纳米粒子（ISNs），包括ZnO，TiO 2，和Fe 3 O 4与疏水性聚合物壳通过无表面活性剂的气溶胶为基础的合成方法的原位涂层。在这方面，新鲜的球形ZnO纳米粒子最初产生的火花放电，然后在气相中的烧结过程。然后，所得的ZnO纳米粒子表现出优异的性能，在光催化表面引发聚合的丙烯酸丁酯单体在连续气溶胶光聚合，在光反应器中的平均气溶胶停留时间为35秒。该方法基于单体蒸气在气态ISN表面周围的非均相冷凝，然后在UV光照射下“飞行”聚合。在这种一锅法合成中，ISN不仅充当无机核，而且同时能够在光激发时释放电荷载流子（电子-空穴对），这驱动其表面附近的自由基聚合。因此，不需要添加引发剂。为了进一步研究实验结果的基础和机理，采用三维时域有限差分（FDTD）方法模拟了ZnO纳米粒子在气相紫外光照射过程中的光学特性。此外，通过气溶胶光电子能谱（APE）评价了包覆效率，结果表明单体和聚合物包覆效率分别为99%和80%。然后，为了验证这种方法对涂层的通用性，不同种类的ISNs，如棒状ZnO，TiO 2 P25，和磁性Fe 3 O 4纳米粒子，被用作无机核和光引发剂。更重要的是，通过适当控制实验条件，可以很容易地在纳米尺度上调节聚合物壳层厚度。最后，成功的改变后，与聚合物壳封装的ISNs的表面疏水性证实了他们的偏好的有机溶剂。与传统的湿法相比，所提出的气溶胶光聚合过程是快速的，避免了在聚合之前对表面活性剂、共引发剂和ISN的表面改性的需要，并且连续地产生核-壳纳米结构。
The work presented here describes a facile approach toward the in situ coating of various inorganic semiconductor nanoparticles (ISNs) including ZnO, TiO2, and Fe3O4 with a hydrophobic polymer shell by a surfactant-free aerosol-based synthesis method. In this regard, fresh spherical ZnO nanoparticles were initially generated by spark discharge followed by a sintering process in the gas phase. Then, the resulting ZnO nanoparticles exhibit excellent performance in photocatalytic surface-initiated polymerization of the butyl acrylate monomer in the continuous aerosol-photopolymerization, within the average aerosol residence time of 35 s in the photoreactor. This method is based on heterogeneous condensation of monomer vapor around the surface of gas-borne ISNs, which is then polymerized “in flight” under UV light irradiation. In this one-pot synthesis, ISNs not only act as inorganic cores, but also at the same time are able to release charge carriers (electron–hole pairs) upon photoexcitation which drive the free radical polymerization near their surface. Therefore, no added initiator is required. To further investigate the basis and the mechanism of our experimental results, the optical properties of ZnO nanoparticles during the UV irradiation in the gas phase process were simulated by a three-dimensional finite difference time-domain (FDTD) method. Moreover, the coating efficiency was evaluated by aerosol photoemission (APE) and the results demonstrate that monomer and polymer coating efficiencies are 99% and 80%, respectively. Then, to verify the generality of this method toward coating, different kinds of ISNs, such as rod-like ZnO, TiO2 P25, and magnetic Fe3O4 nanoparticles, were used as inorganic cores and photoinitiators. More importantly, with proper control of the experimental conditions, the polymer shell thickness can be easily tuned at the nanoscale. Finally, the successful change in the surface hydrophobicity of ISNs after the encapsulation with the polymer shell was confirmed by their preference for an organic solvent. Compared with conventional wet methods, the presented aerosol-photopolymerization process is fast, avoids the need for surfactants, co-initiators and surface modification of ISNs before the polymerization and produces core–shell nanostructures continuously.