State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, and Laboratory of Advanced Materials, Fudan University , 220 Handan Road, Shanghai 200433, China.
German Institute for Polymers (DKI) , Schlossgartenstrasse 6, D-64289 Darmstadt, Germany.
Langmuir. 2017 Mar 7;33(9):2235-2247. doi: 10.1021/acs.langmuir.6b04069. Epub 2017 Feb 21.
We present a general, convenient, and efficient synthetic concept for the coating of colloidal particles with a silica (SiO) shell of well-defined and precisely controlled morphology and porosity. Monodisperse submicroscopic polystyrene (PS) particles were synthesized via two-stage emulsifier-free emulsion polymerization and subsequent swelling polymerization, enabling selective particle surface modification by the incorporation of ionic (methacrylic acid, MAA) or nonionic (hydroxyethyl methacrylate, HEMA or methacrylamide, MAAm) comonomers, which could be proven by zeta potential measurements as well as by determining the three-phase contact angle of the colloidal particles adsorbed at the air-water and n-decane-water interface. The functionalized particles could be directly coated with silica shells of variable thickness, porosity, and controlled surface roughness in a seeded sol-gel process from tetraethoxysilane (TEOS), leading to hybrid PS@silica particles with morphologies ranging from core-shell (CS) to raspberry-type architectures. The experimental results demonstrated that the silica coating could be precisely tailored by the type of surface functionalization, which strongly influences the surface properties of the colloidal particles and thus the morphology of the final silica shell. Furthermore, the PS cores could be easily removed by thermal treatment, yielding extremely uniform hollow silica particles, while maintaining their initial shell architecture. These particles are highly stable against irreversible aggregation and could be readily dried, purified, and redispersed in various solvents. Herein we show a first example of coating semiconducting CdSe/ZnS nanocrystals with smooth and spherical silica shells by applying the presented method that are expected to be suitable systems for applications as markers in biology and life science by using fluorescence microscopy methods, which are also briefly discussed.
我们提出了一种通用、方便、高效的胶体颗粒表面涂覆二氧化硅（SiO）壳的方法，该方法具有明确的和精确控制的形态和孔隙率。通过两步无乳化剂乳液聚合和随后的溶胀聚合合成了单分散亚微米级聚苯乙烯（PS）颗粒，通过引入离子（甲基丙烯酸，MAA）或非离子（羟乙基甲基丙烯酸酯，HEMA 或甲基丙烯酰胺，MAAm）共聚单体，可以对其进行选择性的颗粒表面改性，这可以通过动电位测量以及测定胶体颗粒在空气-水和正癸烷-水界面上的三相接触角来证明。功能化的颗粒可以直接在种子溶胶-凝胶过程中用正硅酸乙酯（TEOS）涂覆具有不同厚度、孔隙率和控制表面粗糙度的二氧化硅壳，从而得到从核壳（CS）到覆盆子型结构的形态各异的 PS@二氧化硅杂化颗粒。实验结果表明，通过表面功能化的类型可以精确地调整二氧化硅涂层，这强烈影响胶体颗粒的表面性质，从而影响最终二氧化硅壳的形态。此外，PS 核可以通过热处理很容易地去除，从而得到非常均匀的空心二氧化硅颗粒，同时保持其初始壳结构。这些颗粒具有很高的稳定性，不易发生不可逆聚集，并且可以很容易地干燥、纯化并在各种溶剂中重新分散。在此，我们展示了应用所提出的方法涂覆半导体 CdSe/ZnS 纳米晶体的光滑球形二氧化硅壳的第一个例子，预计这些纳米晶体将作为生物和生命科学中的标记物应用的合适体系，我们还简要讨论了荧光显微镜方法的应用。
