Safo I A, Werheid M, Dosche C, Oezaslan M
Physical Chemistry, Carl von Ossietzky University of Oldenburg 26129 Oldenburg Germany
Institute of Technical Chemistry, Technical University of Braunschweig 38106 Braunschweig Germany
Nanoscale Adv. 2019 Jun 24;1(8):3095-3106. doi: 10.1039/c9na00186g. eCollection 2019 Aug 6.
In this work, we have investigated the specific role of PVP and Ag ions in the formation of platinum nanocubes (NCs) in polyol synthesis. Various characterization techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to unravel the effects of PVP and Ag ion concentrations on the monodispersity and particle size of the obtained Pt NCs. Very interestingly, we have already fabricated Pt NCs with similar monodispersity and particle size using only 0.4 M PVP (absence of Ag ions). Furthermore, the dispersity of the Pt NCs strongly depends on the initial PVP concentration. This observation underscores the important role of PVP during the NC formation processes by controlling the relative growth rates along the <100> direction with respect to those of the <111>. Time-resolved experiments show that the formation and growth of Pt NCs are much faster in the absence of Ag ions than with Ag ions, which can be explained by the enhanced growth rate along the <100> direction or/and the suppression of the growth rate along the <111>. Electronic interactions between the chemisorbed pyrrolidone ring of the PVP and Pt surface are revealed from the XPS and FTIR data, showing a negative shift of the binding energy of N 1s and a red shift of the Pt-CO vibration band. From our experimental results, we propose extended formation and growth mechanisms based on PVP as the main structure-directing agent. Our model indicates that the aliphatic chains of PVP forming a multi-layer shell influence the mass transport of precursor ions to the initial Pt seed to control the growth rate of Pt NCs with exposed {100} planes. Altogether, we provide a simple, efficient and resource-friendly synthetic guideline for the preparation of nano-sized Pt NCs with high monodispersity and high purity.
在本工作中，我们研究了聚乙烯吡咯烷酮（PVP）和银离子在多元醇合成法制备铂纳米立方体（NCs）过程中的具体作用。采用了多种表征技术，如透射电子显微镜（TEM）、傅里叶变换红外（FTIR）光谱和X射线光电子能谱（XPS），以揭示PVP和银离子浓度对所得铂纳米立方体的单分散性和粒径的影响。非常有趣的是，我们仅使用0.4 M PVP（无银离子）就已经制备出了具有相似单分散性和粒径的铂纳米立方体。此外，铂纳米立方体的分散性强烈依赖于初始PVP浓度。这一观察结果强调了PVP在纳米立方体形成过程中通过控制沿<100>方向相对于<111>方向的相对生长速率所起的重要作用。时间分辨实验表明，在没有银离子的情况下，铂纳米立方体的形成和生长比有银离子时要快得多，这可以通过沿<100>方向生长速率的提高或/和沿<111>方向生长速率的抑制来解释。XPS和FTIR数据揭示了PVP化学吸附的吡咯烷酮环与铂表面之间的电子相互作用，表现为N 1s结合能的负移和Pt-CO振动带的红移。根据我们的实验结果，我们提出了基于PVP作为主要结构导向剂的扩展形成和生长机制。我们的模型表明，形成多层壳的PVP脂肪链影响前驱体离子向初始铂种子的质量传输，以控制具有暴露{100}面的铂纳米立方体的生长速率。总之，我们为制备具有高单分散性和高纯度的纳米级铂纳米立方体提供了一种简单、高效且资源友好的合成指导。
