Solid‐state lead‐207 NMR of lead(II) nitrate: Localized heating effects at high magic angle spinning speeds
Solid‐state lead‐207 NMR of lead(II) nitrate: Localized heating effects at high magic angle spinning speeds
复制标题
硝酸铅的固态铅-207 NMR：高魔角旋转速度下的局部加热效应
DOI：
10.1002/mrc.1260331005
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发表时间：
1995
影响因子：
2
通讯作者：
R. Wasylishen
中科院分区：
文献类型：
--
作者：
L. van Gorkom;J. Hook;Michael B. Logan;J. Hanna;R. Wasylishen
发现硝酸铅(II)的固体核磁共振谱对温度变化高度敏感。Pb207的化学位移与温度呈线性关系，斜率为0.70±0.02ppm K−1，即温度升高导致化学位移向更高的频率变化。这个斜率在静态固体平行实验的实验误差范围内，为0.72±0.06ppm K−1。在较高的魔角旋转速度和环境探测温度下，由于局域加热效应，Pb207信号分裂成几个分量。这些效应在由部分稳定的氧化锆制成的转子中比由氮化硅制成的转子更明显，并归因于氧化锆陶瓷较差的导热性能。在氧化锆转子中，硝酸铅(II)样品内部存在离散的热区，在12 kHz的MAS速度下，这些热区相差5K。铅-207硝酸铅(II)信号对温度变化的响应表明，它可用于校准固体核磁共振探针。
Solid‐state Pb‐207 NMR spectra of lead(II) nitrate were found to be highly sensitive to variations in temperature. The Pb‐207 chemical shift exhibits a linear dependence on temperature with a positive slope of 0.70 ± 0.02 ppm K−1, i.e. increases in temperature cause a change in chemical shift to higher frequency. This slope is within experimental error of the value obtained from parallel experiments on the static solid, 0.72 ± 0.06 ppm K−1. At higher magic angle spinning (MAS) speeds and ambient probe temperature, the Pb‐207 signal splits into several components owing to localized heating effects. These effects are more pronounced in rotors made from partially stabilized zirconia than those made from silicon nitride and are attributed to the poorer thermoconductive properties of the zirconia ceramic. In the zirconia rotors, discrete thermal regions within the lead(II) nitrate sample were located and differ by 5 K at 12 kHz MAS speeds. The response of the Pb‐207 lead(II) nitrate signal to temperature variation suggests that it could be used for calibrating solid‐state NMR probes.