Silicon Nanochemistry

研究的重点是新型硅纳米晶。我们的灵感来自于我们新发现的将多分散的纳米硅晶体分离成1-5 nm范围内的单分散组分的能力，这使得首次能够测量和评估纳米硅晶体的尺寸依赖的化学、物理和生物特性。我们提议的未来研究将通过四个主要主题在这些重大进展的基础上扩展和丰富。第一个重点是合成一类氧化还原活性官能团与纳米晶表面化学连接的新型硅纳米晶。这将使得可以通过化学和/或电化学手段微调硅纳米晶体的表面电荷，从而微调其电学和光学性质。原型NCSI：R将由氧化还原活性官能团R组成，通过与烯烃或炔烃的硅氢化反应共价连接到氢化物封端的纳米晶硅前驱体NCSI：H的表面。通过化学或电化学控制NCSI芯层表面R基氧化的数量和程度(p，q)，可以将被覆盖的硅纳米晶转变为NCSI：(1-p)R.pRq，其中R将选自茂金属Cp2M，M=V，Cr，Mn，Fe，Co，Ni，配位化合物RuBipy，芳烃Ar和富勒烯C60。该项目的主要目标是演示硅纳米晶体的电学和光学性质的氧化还原调谐。第二个重点是合成不含表面有机物、具有可控表面电荷和胶体稳定性的“裸”硅纳米晶，这将提供无与伦比的途径，获得不受表面有机物阻碍的硅芯的化学和物理性质。在本项目中，将以氢化物或氯化物封端的前体NCSI：H或NCSI：CL为原料，用HBF4·Et2O、BH3·THF和AgPF6等试剂分别合成电荷稳定的[NCSI+][BF4-]、[NCSI+][BH4-]和[NCSI+][PF6-]。第三个重点是利用射频等离子体激发SiH4-PH3和SiH4-B2H6混合气体以及HF/H2O/FeCl3对n和p掺杂硅片的刻蚀来合成和表征掺杂形式的纳米硅，该项目的目标是确定B和P掺杂在NCSI中的掺杂浓度和空间位置，测量n和p掺杂的NCSI薄膜以及具有NCSI p-n结的薄膜的电荷传输、光学和光电性能，从而潜在地实现新一代NCSI器件。第四个是建立在胶体稳定的纳米晶体“硅墨水”用于制造可打印的多色光电设备的设想用途的基础上的。其目的是了解如何定制纳米硅晶体的尺寸和表面以控制其在极性和非极性溶剂中的溶解度，增强其电荷传输性能，微调其波长，并在可见光谱范围内最大限度地提高其光致发光和电致发光效率，以优化多色硅发光二极管(SiLED)的稳定性和性能。

The focus of the research centers on new classes of silicon nanocrystals. The inspiration stems from our newfound ability to separate ensembles of poly-dispersed silicon nanocrystals into mono-dispersed fractions in the range of 1-5 nm, which has enabled the first recorded measurement and evaluation of the size-dependent chemical, physical and biological properties of silicon nanocrystals. Our proposed future research will expand and enrich upon these significant advances through four main themes. The first focuses on the synthesis of a novel class of silicon nanocrystals with redox active functional groups chemically tethered to the nanocrystal surface. This will enable the surface charge and hence electrical and optical properties of the silicon nanocrystals to be fine-tuned by chemical and/or electrochemical means. The archetype ncSi:R will be comprised of a redox active functional group R covalently attached to the surface of a hydride-terminated nanocrystalline silicon precursor ncSi:H via hydrosilation with an alkene or alkyne. Through chemical or electrochemical control of the number and extent of oxidation (p,q) of the capping R groups on the surface of the ncSi core the capped silicon nanocrystals can be transformed to ncSi:(1-p)R.pRq, where R will be chosen from metallocenes Cp2M, M = V, Cr, Mn, Fe, Co, Ni, coordination compounds RuBipy, aromatics Ar and fullerenes C60. The primary goal of this project is to demonstrate redox tuning of the electrical and optical properties of silicon nanocrystals. The second focuses on the synthesis of ‘naked’ silicon nanocrystals, devoid of surface organics, with controlled surface charge and colloid-stability, which will provide unparalleled access to the chemical and physical properties of the silicon core unimpeded by surface organics. In this project the archetypes [ncSi+]]X-] will be synthesized from the hydride or chloride capped precursors ncSi:H or ncSi:Cl using reagents, such as HBF4.Et2O, BH3.THF and AgPF6 to form charge-stabilized [ncSi+][BF4-], [ncSi+][BH4-] and [ncSi+][PF6-], respectively. The third focuses on the synthesis and characterization of doped forms of nanosilicon using radio-frequency plasma excitation of SiH4-PH3 and SiH4-B2H6 gaseous mixtures as well as HF/H2O/FeCl3 etching of n- and p-doped Si wafers, the goal of the project being determination of the dopant concentration and spatial location of B and P dopants in the ncSi, measurement of charge transport, optical and optoelectronic properties of n- and p-doped ncSi films as well as films with ncSi p-n junctions, potentially enabling new generation ncSi devices. The fourth is founded upon the envisioned utility of colloidally-stable nanocrystal ‘silicon inks’ for the fabrication of printable multicolor optoelectronic devices. The objective is to learn how to tailor the sizes and surfaces of silicon nanocrystals to control their solubility in polar and non-polar solvents, enhance their electrical charge transport properties, fine-tune their wavelength, and maximize their photoluminescence and electroluminescence efficiency across the visible spectral range, to optimize the stability and performance of multicolor silicon light emitting diodes, SiLEDs.