Further development in solid-state NMR of half-integer quadrupolar nuclei

QD Chemistry

Sasaki, Akiko ; Lennon, David

University:University of Glasgow

Department:School of Chemistry

关键词: Solid-state, NMR.;   

Others  :  http://theses.gla.ac.uk/7153/1/2016sasakiphd.pdf

来源: University of Glasgow

【 摘 要 】

Half-integer quadrupolar nuclei constitute more than 70% of the NMRactivenuclei in the Periodic Table. Owing to the presence of anisotropicquadrupolar broadening, high-resolution methods are often required forcomplete spectral analysis of solid-state NMR spectra of half-integerquadrupolar nuclei. The DOR and DAS techniques require specialist probeswhilst the MQMAS and STMAS methods are two-dimensional correlationexperiments performed under MAS conditions. The MQMAS experiment hasbeen widely used in materials investigations, whereas the STMAS counterpartis ideal for the study of NMR-insensitive nuclei. This thesis is mainly concerned with the satellite transitions of halfintegerquadrupolar nuclei. Firstly, sensitivity enhancement schemes for theSTMAS method are proposed and investigated both theoretically andexperimentally using 23Na and 87Rb NMR of simple inorganic compounds, andthe applicability and limiting factors of the novel methods are discussed. Arecent addition to the aforementioned high-resolution techniques is theSTARTMAS experiment. Further development of the STARTMAS approach isdescribed, with respect to the spectral analysis, sensitivity enhancement, andimplementation under fast MAS conditions, using 23Na, 87Rb and 69/71Ga NMRat B0 = 9.4 and 20.0 T.A potential area of interest in which the intrinsic sensitivity advantage ofthe STMAS method can be exploited is the natural abundance 33S solid-stateNMR. In the latter half of this thesis, ettringite, a cementitious mineral, isemployed to demonstrate the feasibility of high-resolution 33S STMAS NMR atB0 = 9.4 and 20.0 T, with particular emphasis on the implementation of 33SSTMAS experiments all performed at the natural abundance levels of the 33Snucleus. Additional investigations are then proposed and performed using 1H-33S CP-MAS NMR experiments to probe the presence of dynamics in ettringite.Recently, quantum mechanical calculations of solid-state NMR parameters havegained popularity, aiding experimentalists to predict and interpret solid-stateNMR spectra. Further investigations of first-principles calculations of solidstate33S NMR parameters are also presented in this thesis, to support thepresence of dynamics around the S nuclei in ettringite.