Nanometre scale chemical heterogeneity has been revealed in a phosphosilicate gel by 31P spin exchange. Monomeric phosphorus was found near to phosphorus singly cross-linked with phosphorus. Phosphorus doubly cross-linked with phosphorus was found to be remote from both other types of phosphorus species. Radiofrequency driven magnetisation exchange through 31P-31P dipolar coupling was rather ineffective, even with recoupling times of up to 30 ms, demonstrating the weak 31P-31P dipolar coupling and the effect of residual 1H-31P dipolar coupling. Effective 31P spin exchange was possible in the laboratory frame through the 1H spin interactions, when mixing times from 100 ms to 2 s were used
Chemical heterogeneity in phosphosilicate gels by NMR magnetisation exchange / Clayden, N. J.; Esposito, S.; Aronne, A.. - In: JOURNAL OF THE CHEMICAL SOCIETY. DALTON TRANSACTIONS. - ISSN 1472-7773. - 13(2001), pp. 2003-2008. [10.1039/b100474n]
Titolo: | Chemical heterogeneity in phosphosilicate gels by NMR magnetisation exchange | |
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Data di pubblicazione: | 2001 | |
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Digital Object Identifier (DOI): | http://dx.doi.org/10.1039/b100474n | |
Appare nelle tipologie: | 1.1 Articolo in rivista |
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http://hdl.handle.net/11583/2872190