Atomically Monodisperse Palladium Nanoparticles: Size, Composition and Atomic Structure Studies

金(Au)和银(Ag)纳米粒子是由数十到数百个原子组成的集合，在原子水平上对物质的操纵已经取得了重大进展。超小的Au和Ag纳米粒子是指那些直径小于3 nm，由小于500个原子组成的纳米粒子。这些纳米颗粒显示出明确的结构，当特定的有机分子(称为配体)连接到它们的表面时，就可以合成它们。然而，其他金属的纳米颗粒还没有被这一策略很好地研究，而且没有配体，它们的结构可能定义得很差。钯(Pd)纳米粒子正被考虑用于各种实际应用，如氢传感器和催化重要的化学反应，包括几个在可再生能源中有兴趣的应用。在这个项目中，密西西比大学的阿迈勒·达斯博士正在合成原子精确的钯纳米粒子，这些纳米粒子具有特定数量的金属原子和保护配体。达斯博士正在将他的研究与推广活动结合起来，包括一个高中生暑期研究项目，一个本科生研究项目，以及向当地和密西西比河三角洲的学校进行科学示范。在化学部大分子、超分子和纳米化学(MSN)计划的资助下，达斯博士正在合成原子单分散的钯超小纳米颗粒。用基质辅助激光解吸电离(MALDI)和电喷雾电离(ESI)质谱仪测定了金属原子数、硫酸盐配体和总的化学成分。用X射线结晶学研究了这些纳米粒子的原子结构。使用电化学、光谱和电子显微镜进行了进一步的表征。研究了配体对Pd纳米颗粒组成和结构的影响，并制备了Pd合金纳米颗粒来调整化学和物理性能。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Significant progress has been made in the atomic level manipulation of matter in the case of gold (Au) and silver (Ag) nanoparticles, assemblies of tens to hundreds of atoms. Ultra-small small Au and Ag nanoparticles are those with diameters less than 3 nm and are composed of less than 500 atoms. These nanoparticles display well-defined structures and can be synthesized when specific organic molecules (known as ligands) are tethered to their surfaces. However, nanoparticles of other metals have not been well studied by this strategy and without ligands, their structures can be poorly defined. Palladium (Pd) nanoparticles are under consideration for a variety of practical applications, such as hydrogen sensors and to catalyze important chemical reactions including several of interest for applications in renewable energy. In this project, Dr. Amal Dass of the University of Mississippi is synthesizing atomically precise Pd nanoparticles with specific numbers of metal atoms and protecting ligands. Dr. Dass is integrating his research with outreach activities including a high school student summer research program, an undergraduate research program and science demonstrations to local and Mississippi Delta schools. Funded by the Macromolecular, Supramolecular and Nanochemistry (MSN) program of the Division of Chemistry, Dr. Dass is synthesizing atomically monodisperse palladium ultra-small nanoparticles. Matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry are used to determine the numbers of metal atoms, the thiolate ligands, and overall chemical composition. Atomic structures of these nanoparticles are examined using X-ray crystallography. Further characterization is conducted using electrochemistry, optical spectroscopy, and electron microscopy. The effect of ligands on the composition and structure of Pd nanoparticles is investigated and Pd alloy nanoparticles are prepared to tune chemical and physical properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.