Semiconductor Nanocrystals, Gold Nanostructures, Toxic Metals in the Environment

在计算方面，我的研究项目旨在建立模型，从而了解(i)半导体纳米晶体，（ii）金纳米结构，以及（iii）环境中的有毒金属的特性。在理论方面，我的研究计划寻求(i)检查量子势作为反应性和键合的度量，（ii）获得动能的精确表达式，这是电子密度的直接函数。对于基态计算，我们主要使用密度泛函理论（DFT）的Kohn-Sham公式，包括梯度校正泛函和混合泛函。对于激发态计算，我们主要使用具有远程修正泛函的时变密度泛函理论（TD-DFT）。对于有限温度计算，我们主要使用Born-Oppenheimer分子动力学（BOMD）。

On the computational side, my research program seeks to model and thereby understand the properties of (i) semiconductor nanocrystals, (ii) gold nanostructures, and (iii) toxic metals in the environment. On the theoretical side, my research program seeks to (i) examine the quantum potential as a measure of reactivity and bonding and (ii) obtain an accurate expression for the kinetic energy that is a direct functional of the electron density. For ground state calculations we primarily use the Kohn-Sham formulation of density functional theory (DFT) with both gradient-corrected and hybrid functionals. For excited state calculations we primarily use time-dependent density functional theory (TD-DFT) with long-range corrected functionals. For finite temperature calculations we primarily use Born-Oppenheimer molecular dynamics (BOMD). Ligand-passivated semiconductor nanocrystals (NCs), also called quantum dots, have applications in many areas including photovoltaic devices. Upon adsorption of a photon with energy greater than the band gap, an electron-hole pair is formed and, if it can be separated, an electric current can be generated. Due to quantum confinement, a smaller NC has a larger band gap which can make better use of higher energy photons. Our current focus is on CdSe nanocrystals and related structures in which Se is replaced by Te or Cd is replaced by Cu2. Gold nanostructures have properties which are very different from those of the bulk metal. We established the stability of helical gold nanorods (both bare and with adsorbed molecules) and compared them to alternative compact and cage structures. Our current focus is on the optoelectronic properties of helical gold nanorods and their chiral applications as catalysts and biosensors. For toxic metals in the environment, our current focus is on arsenic. Arsenic exists in both inorganic and organic forms that can be interconverted by biogeochemical processes. Less is known about the organic forms and the ways in which they bind to inorganic soil particles.