Analysis of sensitivity enhancement by dynamic nuclear polarization in solid-state NMR: a case study of functionalized mesoporous materials

TitleAnalysis of sensitivity enhancement by dynamic nuclear polarization in solid-state NMR: a case study of functionalized mesoporous materials
Publication TypeJournal Article
Year of Publication2013
AuthorsKobayashi T, Lafon O, Thankamony ASL, Slowing II, Kandel K, Carnevale D, Vitzthum V, Vezin H, Amoureux JP, Bodenhausen G, Pruski M
Journal TitlePhysical Chemistry Chemical Physics
Volume15
Pages5553-5562
Date Published04/21
Type of ArticleArticle
ISBN Number1463-9076
Accession NumberWOS:000316467800031
Keywordschemical-shift, LOW-TEMPERATURE, mas-nmr, proteins, relaxation, ROTATING SOLIDS, si-29 nmr, silica nanoparticles, spectroscopy, theoretical calculations
Abstract

We systematically studied the enhancement factor (per scan) and the sensitivity enhancement (per unit time) in C-13 and Si-29 cross-polarization magic angle spinning (CP-MAS) NMR boosted by dynamic nuclear polarization (DNP) of functionalized mesoporous silica nanoparticles (MSNs). Specifically, we separated contributions due to: (i) microwave irradiation, (ii) quenching by paramagnetic effects, (iii) the presence of frozen solvent, (iv) the temperature, as well as changes in (v) relaxation and (vi) cross-polarization behaviour. No line-broadening effects were observed for MSNs when lowering the temperature from 300 to 100 K. Notwithstanding a significant signal reduction due to quenching by TOTAPOL radicals, DNP-CP-MAS at 100 K provided global sensitivity enhancements of 23 and 45 for C-13 and Si-29, respectively, relative to standard CP-MAS measurements at room temperature. The effects of DNP were also ascertained by comparing with state-of-the-art two-dimensional heteronuclear H-1{C-13} and Si-29{H-1} correlation spectra, using, respectively, indirect detection or Carr-Purcell-Meiboom-Gill (CPMG) refocusing to boost signal acquisition. This study highlights opportunities for further improvements through the development of high-field DNP, better polarizing agents, and improved capabilities for low-temperature MAS.

URL<Go to ISI>://WOS:000316467800031
DOI10.1039/c3cp00039g