Chemisorption of Water on the Surface of Silicon Microparticles Measured by Dynamic Nuclear Polarization Enhanced NMR
Chemisorption of Water on the Surface of Silicon Microparticles Measured by Dynamic Nuclear Polarization Enhanced NMR
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动态核极化增强核磁共振测量硅微粒表面水的化学吸附
DOI：
10.1021/acs.jpcc.6b11065
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Ramanathan, Chandrasekhar
中科院分区：
文献类型：
--
作者：
Guy, Mallory L.;van Schooten, Kipp J.;Zhu, Lihuang;Ramanathan, Chandrasekhar
我们在液氦温度下使用动态核极化（DNP）增强核磁共振（NMR）直接检测附着在硅微粒表面的氢。多晶硅粉末 (1–5 μm) 干燥样品的质子核磁共振谱显示出明显窄的洛伦兹形共振，宽度为 6.2 kHz，表明附着在硅表面的质子分布非常稀疏。这些质子位于硅表面的几个原子单层内。与同一场的室温 NMR 信号相比，整体信号增强了 4150，从而能够对低表面积 (0.26–1.3 m2/g) 颗粒的表面质子进行高灵敏度 NMR 检测。当颗粒悬浮在含有 80% H2O 和 20% D2O 的溶剂中时，观察到窄峰的强度随着时间的推移而增强，表明稀疏表面质子层的生长。然而，当颗粒悬浮在含有 20% H2O 和 80% D2O 的溶剂中时，由于表面质子与溶液中氘之间的交换，观察到狭窄的结合质子峰收缩。随着溶剂的相对质子浓度增加，这种降低伴随着冷冻溶剂峰强度的伴随增长。当颗粒悬浮在有机溶剂己烷中时，质子核磁共振谱随时间保持不变。这些结果与已知的水在硅表面上的化学吸附导致氢化物和羟基物质的形成一致。因此，低温 DNP NMR 可用作水环境中硅表面腐蚀的无损探针。这对于在此类环境中使用硅微机电系统（MEMS）和生物MEMS设备、硅微米和纳米粒子磁共振成像（MRI）成像剂以及使用纳米硅在燃料电池中分解水来说非常重要。
We use dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) at liquid helium temperatures to directly detect hydrogen attached to the surface of silicon microparticles. The proton NMR spectrum from a dry sample of polycrystalline silicon powder (1–5 μm) shows a distinctively narrow Lorentzian-shaped resonance with a width of 6.2 kHz, indicative of a very sparse distribution of protons attached to the silicon surface. These protons are within a few atomic monolayers of the silicon surface. The high-sensitivity NMR detection of surface protons from low surface area (0.26–1.3 m2/g) particles is enabled by an overall signal enhancement of 4150 over the room-temperature NMR signal at the same field. When the particles were suspended in a solvent with 80% H2O and 20% D2O, the narrow peak was observed to grow in intensity over time, indicating growth of the sparse surface proton layer. However, when the particles were suspended in a solvent with 20% H2O and 80% D2O, the narrow bound proton peak was observed to shrink due to exchange between the surface protons and the deuterium in solution. This decrease was accompanied by a concomitant growth in the intensity of the frozen solvent peak, as the relative proton concentration of the solvent increased. When the particles were suspended in the organic solvent hexane, the proton NMR spectra remained unchanged over time. These results are consistent with the known chemisorption of water on the silicon surface resulting in the formation of hydride and hydroxyl species. Low-temperature DNP NMR can thus be used as a nondestructive probe of surface corrosion for silicon in aqueous environments. This is important in the context of using silicon microelectromechanical systems (MEMS) and bioMEMS devices in such environments, for silicon micro- and nanoparticle magnetic resonance imaging (MRI) imaging agents, and the use of nanosilicon for splitting water in fuel cells.
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DOI：
10.1039/c003685b
发表时间：
2010-06-14
期刊：
Physical chemistry chemical physics : PCCP
影响因子：
--
作者：
Rosay M;Tometich L;Pawsey S;Bader R;Schauwecker R;Blank M;Borchard PM;Cauffman SR;Felch KL;Weber RT;Temkin RJ;Griffin RG;Maas WE
通讯作者：
Maas WE
影响因子：
18.1
作者：
D. Haneman
通讯作者：
D. Haneman
在溶解 DNP 设置中低成本实施 EPR 检测。
影响因子：
2.2
作者：
J. Granwehr;J. Leggett;W. Köckenberger
通讯作者：
W. Köckenberger
核磁共振氢谱 (1H1NMR) ina-Si
DOI：
--
发表时间：
1982
期刊：
影响因子：
--
作者：
W. Carlos;P. Taylor
通讯作者：
P. Taylor
非晶 Si:H 薄膜中与氢相关的无序模式
DOI：
--
发表时间：
1980
期刊：
影响因子：
--
作者：
W. Carlos;P. Taylor
通讯作者：
P. Taylor