Witter R, Hartmann P, Vogel J, Jäger C
Institute of Optics and Quantum Electronics, Friedrich Schiller University Jena, Germany.
Solid State Nucl Magn Reson. 1998 Dec;13(3):189-200. doi: 10.1016/s0926-2040(98)00088-5.
31P double quantum (DQ) NMR is used for improved studies of the structure of phosphate glasses. The common Qn notation of the network forming tetrahedral phosphate units with n bridging oxygen atoms is extended to Qn,jkl indicating the Q type of the bonded adjacent units by the additional superscripts j,k and l. It will be shown that: (i) Q1 units have different isotropic chemical shifts depending on whether they form diphosphate anions in the amorphous state (Q1,1) or end groups of chains (Q1,2) and (ii) that even Q2 units possess different isotropic chemical shifts such that in the DQ dimension Q2,11 can be distinguished from Q2,12 and middle groups of longer chains or rings (Q2,22). Based on this result the opportunity for measuring chain length distributions in the amorphous state is discussed and first results for binary calcium phosphate glasses are presented. The advantages and also the limitations of this novel approach will be discussed.
31P双量子（DQ）核磁共振用于改进对磷酸盐玻璃结构的研究。具有n个桥连氧原子的网络形成四面体磷酸盐单元的常见Qn表示法扩展为Qn,jkl，通过额外的上标j、k和l表示键合相邻单元的Q类型。结果表明：（i）Q1单元具有不同的各向同性化学位移，这取决于它们在非晶态下形成二磷酸阴离子（Q1,1）还是链端基（Q1,2）；（ii）即使是Q2单元也具有不同的各向同性化学位移，使得在DQ维度中Q2,11可以与Q2,12以及较长链或环的中间基团（Q2,22）区分开来。基于这一结果，讨论了测量非晶态下链长分布的机会，并给出了二元磷酸钙玻璃的初步结果。还将讨论这种新方法的优点和局限性。
