Metal Clusters, Metal Nanostructures, Semiconductor Nanocrystals, Single-Ion Magnets

我的研究项目旨在了解和优化金属簇的催化性能，金属纳米结构和半导体纳米晶体的光电性能，以及掺杂金簇单离子磁体的操作性能。 i）如何优化金属簇合物对乙醇氧化的催化性能？乙醇是可再生的，可生物降解的，富含氢气，可以氧化合成各种有价值的化学品。我们研究了无载体钴金属簇在零开尔文下催化乙醇氧化的第一步的能力。我们发现，铜簇是更好的催化剂比银或金催化剂，阴离子簇是更好的比中性簇，和单一的M原子是更好的催化剂比M2，M3，和M4。这些结果将指导我们在有限温度下对负载金属团簇的进一步研究。ii）我们如何优化金属纳米结构和半导体纳米晶体的光电性能？对于金属纳米结构，我们将关注金，因为它相对不活泼，可以采用许多（局部）稳定的几何形状。我们的重点是金棒结构，因为它们可以用作纳米结构器件中的电连接器。半导体纳米晶体用于光伏器件。在吸收光子时，形成电子-空穴对并且可以产生电流。它们也用于显示设备，其中发生相反的过程。由于量子限制，较小的光子晶体具有较大的带隙，这使得更好地利用较高能量的光子。在实验条件下，这些物质通常富含镉（并且带正电荷），并且必须使用带负电荷的X型配体（例如Cd 16 Se 10 Cl 12和Cd 59 Se 50（CH 3COO）18）进行钝化。受实验研究的启发，我们将研究用银原子掺杂小的CdSe纳米晶体对电荷迁移率的影响。此外，我们还将研究掺杂高自旋原子如Mn、Fe或Co的CdSe纳米晶体的磁性。iii）我们如何优化新型单离子磁体的磁性？单分子磁体（SMM）具有用作量子信息处理设备中的量子比特（qubit）的潜力。SMM通常具有通过氧或氮桥接原子彼此连接的6至12个高自旋原子。我们的主要目标是深入了解SMM的一个子集，称为单离子磁体（西姆斯），通常由一个配体保护的高自旋原子，被困在一个固定的SIM-SIM距离的晶格。如果金簇掺杂有高自旋原子如Mn、Fe、Co，则由于Au的较大电负性，高自旋原子将具有正电荷。因此，这些物种是一种新型的“自立式”SIM，可以排列在具有最佳SIM-SIM距离的表面上。这可能导致具有独特功能的量子位。

My research program seeks to understand and optimize the catalytic properties of metal clusters, the optoelectronic properties of the metal nanostructures and semiconductor nanocrystals, and the operational properties of doped gold cluster single-ion magnets. i) How can we optimize the catalytic properties of metal clusters for ethanol oxidation? Ethanol is renewable, biodegradable, hydrogen rich and can be oxidized to synthesize a wide range of valuable chemicals. We examined the ability of unsupported coinage metal clusters to catalyze the first step of ethanol oxidation at zero Kelvin. We found that copper clusters were better catalysts than silver or gold catalysts and that anionic clusters are better than neutral clusters, and that single M atoms are better catalysts than M2, M3, and M4. These results will guide our future studies of supported metal clusters at finite temperature. ii) How can we optimize the optoelectronic properties of metal nanostructures and semiconductor nanocrystals? For metal nanostructures we will focus on gold since it is relatively unreactive and can adopt many (locally) stable geometries. Our focus is on gold rod structures because they could be used as electrical connectors in nanostructured devices. Semiconductor nanocrystals are used in photovoltaic devices. Upon absorption of a photon, an electron-hole pair is formed and an electrical current can be generated. They are also used in display devices in which the reverse process takes place. Due to quantum confinement, a smaller nanocrystal has a larger band gap, which makes better use of higher energy photons. Under experimental conditions these species are typically cadmium rich (and positively charged) and must be passivated using negatively charged X-type ligands e.g. Cd16Se10Cl12 and Cd59Se50(CH3COO)18. Motivated by experimental studies, we will examine the effect on charge mobility of doping small CdSe nanocrystals with silver atoms. Also, we will examine the magnetic properties of CdSe nanocrystals doped with a high-spin atom such as Mn, Fe, or Co. iii) How can we optimize the magnetic properties of novel single-ion magnets? Single molecule magnets (SMMs) have potential for use as quantum bits (qubits) in quantum information processing devices. SMMs typically have six to twelve high-spin atoms connected to one another via oxygen or nitrogen bridging atoms. Our primary objective is to gain insight into a subset of SMMs called single ion magnets (SIMs) which are usually comprised of a ligand-protected high-spin atom that is trapped in a crystal lattice with fixed SIM-SIM distances. If a gold cluster is doped with a high-spin atom such as Mn, Fe, Co then, due to the greater electronegativity of Au, the high-spin atom will have a positive charge. These species are therefore a novel type of "free standing" SIM that could be arrayed on a surface with optimum SIM-SIM distances. This could result in a qubit with unique functionality.