Probing single polymeric nanoparticles via impact voltammetry

由于纳米材料在研究和工业中的广泛应用，在过去的二十年里，纳米材料在技术上具有重要的意义。2014年，全球纳米材料市场价值34亿美元，预计到2020年将达到118亿美元，复合年增长率为23.1%。此外，到2020年，全球纳米技术产业将增长到758亿美元。其中，聚合物纳米颗粒(NPs)因其在药物输送、太阳能电池、生物传感器和腐蚀涂层等方面的广泛应用而引起人们的特别关注。虽然溶解的分子和离子的电化学已经得到了广泛的研究，但单个纳米颗粒的电化学仍然很大程度上还没有被探索。由于纳米粒子的浓度低、分子结构范围广、凝聚性、非均质性以及存在于复杂的基质中，可靠的检测是一个巨大的挑战。然而，出于对环境和人类健康的担忧，迫切需要对NPs进行表征。聚合物纳米粒子通常是通过系综方法进行研究的。然而，由于电荷转移和质量传输过程是重叠的，因此只能估计，因此监测这种系综中的充放电过程是复杂的。此外，这种方法可能会产生误导，因为颗粒会聚集在电极上，因此只有一小部分是活性的。在这里，我将展示最近发展起来的纳米撞击方法将如何用于研究单一聚合物-纳米粒子的充电和掺杂。纳米撞击是一种有效的方法，已经被证明在纳米粒子的动力学和热力学研究中非常有前途。该方法能够准确、快速地测定NPs的大小、浓度和组成。该项目旨在表征导电聚合物(例如PANI、PPy)的单个NPs。这些测量将提供诸如掺杂产额、掺杂效应和掺杂的可逆性等重要信息，这些信息是其他光谱方法难以获得的。通过将纳米撞击与独立的尺寸数据联系起来，人们可以探索是否整个粒子都被掺杂了，或者是制造了一种核壳结构。不同颗粒大小的筛选使我们能够确定可以完全掺杂的最大颗粒尺寸。为了更好地理解界面上的电化学反应，以及研究这些单个纳米粒子的动力学和生长机理。应研究掺杂参数的变化及其对聚合物行为的影响。应将纳米撞击数据与DLS等其他技术进行比较。这一理解预计将对新兴应用程序产生重大影响。

Due to their diversity of applications in research and industry, nanomaterials have had a great technological importance in the last two decades. The global nanomaterials market is valued at $3.4 billion in 2014, and is expected to reach $11.8 billion by 2020, showing a compound annual growth rate of 23.1%. Furthermore, the global nanotechnology industry will grow to reach $75.8 Billion by 2020. Among them, polymer nanoparticles (NPs) attract a special interest due to their wide use in drug delivery, solar cells, biosensors and corrosion coatings. Although the electrochemistry of dissolved molecules and ions has been intensively studied, the electrochemistry of single nanoparticles remains largely unexplored. Reliable detection of NPs is a significant challenge due to their low concentration, large range of molecular structures of organic ones, agglomeration, heterogeneous character and presence in complex matrices. However, there is an urgent need from environmental and human health concerns for NPs characterization. Polymeric-NPs have typically been studied via the ensemble method. However, monitoring charge/discharge processes in such ensemble is complex since charge transfer and mass transport processes are overlapping and thus can only be estimated. In addition, this method can be misleading since particles agglomerate on the electrode so that only a fraction of them is active. Here, I will show how the recently developed nanoimpact method will be used to study the charging and doping of single polymer-NPs.Nanoimpacts is an efficient method which has been shown to be very promising for the study of kinetics and thermodynamics of NPs. This method enables precise and fast determination of size, concentration and composition of NPs. This project aims to characterize individual NPs of conducting polymers (e.g. PANI, PPy). Important information such as doping yield, dopant effect and reversibility of doping will be provided by these measurements, which are difficult to obtain by other spectroscopic methods. By linking the nanoimpact with independent sizing data, one can explore if the entire particle is doped or a sort of core-shell structure is made. Screening of different particle sizes allows us to identify the largest particle size which can be fully doped. We also aim at a better understanding of the electrochemical reactions at interface, as well as the study of kinetics and growth mechanism of these single NPs. Variation of the doping parameters and its influence on the behavior of the polymer shall be investigated. Comparison of the nanoimpact data with other techniques like DLS shall be carried out. This understanding is expected to have a significant impact on emerging applications.