Schindler T, Schmiele M, Schmutzler T, Kassar T, Segets D, Peukert W, Radulescu A, Kriele A, Gilles R, Unruh T
Chair of Crystallography and Structural Physics, Friedrich-Alexander-Universät Erlangen-Nürnberg , Staudtstraße 3, 91058 Erlangen, Germany.
Institute of Particle Technology, Friedrich-Alexander-Universät Erlangen-Nürnberg , Cauerstraße 4, 91058 Erlangen, Germany.
Langmuir. 2015 Sep 22;31(37):10130-6. doi: 10.1021/acs.langmuir.5b02198. Epub 2015 Sep 10.
ZnO nanoparticles (NPs) have great potential for their use in, e.g., thin film solar cells due to their electro-optical properties adjustable on the nanoscale. Therefore, the production of well-defined NPs is of major interest. For a targeted production process, the knowledge of the stabilization layer of the NPs during and after their formation is of particular importance. For the study of the stabilizer layer of ZnO NPs prepared in a wet chemical synthesis from zinc acetate, only ex situ studies have been performed so far. An acetate layer bound to the surface of the dried NPs was found; however, an in situ study which addresses the stabilizing layer surrounding the NPs in a native dispersion was missing. By the combination of small angle scattering with neutrons and X-rays (SANS and SAXS) for the same sample, we are now able to observe the acetate shell in situ for the first time. In addition, the changes of this shell could be followed during the ripening process for different temperatures. With increasing size of the ZnO core (d(core)) the surrounding shell (d(shell)) becomes larger, and the acetate concentration within the shell is reduced. For all samples, the shell thickness was found to be larger than the maximum extension of an acetate molecule with acetate concentrations within the shell below 50 vol %. Thus, there is not a monolayer of acetate molecules that covers the NPs but rather a swollen shell of acetate ions. This shell is assumed to hinder the growth of the NPs to larger macrostructures. In addition, we found that the partition coefficient μ between acetate in the shell surrounding the NPs and the total amount of acetate in the solution is about 10% which is in good agreement with ex situ data determined by thermogravimetric analysis.
由于其纳米级可调节的电光特性，氧化锌纳米颗粒（NPs）在例如薄膜太阳能电池等领域具有巨大的应用潜力。因此，制备明确的纳米颗粒备受关注。对于有针对性的生产过程，了解纳米颗粒形成过程中和形成后的稳定层尤为重要。到目前为止，对于通过湿化学合成由醋酸锌制备的氧化锌纳米颗粒的稳定剂层的研究，仅进行了非原位研究。发现干燥的纳米颗粒表面结合有一层醋酸盐层；然而，缺少针对天然分散体中纳米颗粒周围稳定层的原位研究。通过对同一样品结合小角中子散射和小角X射线散射（SANS和SAXS），我们现在首次能够原位观察醋酸盐壳层。此外，在不同温度的熟化过程中可以跟踪该壳层的变化。随着氧化锌核（d（core））尺寸的增加，周围的壳层（d（shell））变大，壳层内的醋酸盐浓度降低。对于所有样品，发现壳层厚度大于醋酸盐分子的最大伸展长度，壳层内醋酸盐浓度低于50体积％。因此，覆盖纳米颗粒的不是单层醋酸盐分子，而是醋酸根离子的溶胀壳层。该壳层被认为会阻碍纳米颗粒生长为更大的宏观结构。此外，我们发现纳米颗粒周围壳层中的醋酸盐与溶液中醋酸盐总量之间的分配系数μ约为10％，这与通过热重分析确定的非原位数据非常吻合。
