Gao Lei, Wang Enbo, Kang Zhenhui, Song Yanli, Mao Baodong, Xu Lin
Polyoxometalate Institute, Chemistry Department, Northeast Normal University, Changchun, Jilin, People's Republic of China 130024.
J Phys Chem B. 2005 Sep 8;109(35):16587-92. doi: 10.1021/jp051818f.
The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.
多金属氧酸盐（POM）化学领域在新化合物快速合成方面经历了前所未有的发展，但基于POM的功能材料和器件的发展却较为缓慢。与此同时，受层层组装方法引入的鼓舞，微胶囊领域的研究人员正在寻找用于构建功能胶囊器件的优质组分。在此，鉴于基于POM的微胶囊可能具有的多种特性，采用层层组装方法构建了各类POM-聚电解质复合微胶囊。显微镜观察表明，在阳离子聚电解质存在下，多金属氧酸盐在壳层上形成纳米颗粒。这些与聚电解质相连的纳米颗粒构成了壳层，并支撑微胶囊在干燥后不发生塌陷，这是一个与普通复合胶囊和聚电解质胶囊不同的有趣特性。利用傅里叶变换红外光谱（FTIR）、紫外可见吸收光谱和X射线光电子能谱（XPS）来研究微胶囊中POM的性质。所制备的微胶囊比聚电解质微胶囊表现出更高的热稳定性。此外，当POM组装到微胶囊中时，其功能得以保留。事实证明，带有具有氧化还原活性的POM的微胶囊能够提供还原环境，这可实现材料的原位合成，并且以具有光致发光的POM为组分的微胶囊也可具有光致发光特性，为开发功能胶囊器件提供了一条途径。这项工作可能为丰富多金属氧酸盐化学和胶囊领域提供一个契机。
