کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5406921 | 1393194 | 2009 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Practical comparison of sensitivity and resolution between STMAS and MQMAS for 27Al
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
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چکیده انگلیسی
An experimental comparison of sensitivity and resolution of satellite transition (ST) MAS and multiple quantum (MQ) MAS was performed for 27Al (I = 5/2) using several pulse sequences with a z-filter and SPAM, and two inorganic samples of kaolin (Al2Si2O5(OH)4) and glass (43.1CaO-12.5Al2O3-44.4SiO2). Six pulse sequences of STMAS (double-quantum filter-soft pulse added mixing = DQF-SPAM, double-quantum filter = DQF, double-quantum = DQ) and MQMAS (3QMAS-z-filter = 3Qz, 3QMAS-SPAM = 3Q-SPAM, 5QMAS-z-filter = 5Qz) are employed. All experiments have been conducted utilizing a static field of 16.4 T (700 MHz for 1H) and a rotor spinning frequency of 20 kHz. Dependence of S/N ratios as a function of radio frequency (r.f.) field strengths indicates that strong r.f. fields are essential to obtain a better S/N ratio in all experiments. High sensitivity is obtained in the following order: DQF-SPAM, DQF, DQ, 3QSPAM, and 3Qz, although the degree of sensitivity enhancement given by STMAS for glass is slightly smaller than that for kaolin. This might be due to the different excitation and conversion efficiencies of ST and MQ coherences as a function Cq values because quadrupolar interaction of the glass are widely distributed, or to motional broadening caused by framework flexibility in the structure of glass. With respect to resolution, the full widths at half maximum (FWHM) of F1 projections of DQF-STMAS and 3QMAS spectra for kaolin are found to be comparable, which agrees with a simulated result reported in a literature. For glass, the STMAS possess slightly wider line widths than 3QMAS. However, because such a difference in line widths of STMAS and 3QMAS spectra is substantially small, we have concluded that STMAS and 3QMAS have comparable resolution for crystalline and non-crystalline materials.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Magnetic Resonance - Volume 198, Issue 2, June 2009, Pages 228-235
Journal: Journal of Magnetic Resonance - Volume 198, Issue 2, June 2009, Pages 228-235
نویسندگان
Takafumi Takahashi, Koji Kanehashi, Yuichi Shimoikeda, Takahiro Nemoto, Koji Saito,