Direct dynamic nuclear polarization targeting catalytically active (27)Al sites.
Phys Chem Chem Phys
; 17(38): 25449-54, 2015 Oct 14.
Article
in En
| MEDLINE
| ID: mdl-26365719
ABSTRACT
Here we present a systematic study of direct (27)Al Dynamic Nuclear Polarization (DNP) as induced by three different mono-radical probes with side groups of varying charge states. By employing 4-amino TEMPO that adsorbs to negatively charged surface sites of Al-SBA-15, we achieve a (27)Al signal enhancement factor of â¼13 compared to a signal enhancement factor of â¼3-4 from mono-radicals that do not adsorb as strongly to the surfaces of Al-SBA-15, here 4-carboxy- and 4-hydroxy-TEMPO. By performing Electron Spin Echo Envelope Modulation (ESEEM) experiments and continuous wave (cw) Electron Paramagnetic Resonance (EPR) lineshape analysis using various nitroxide probes imbibed in Al-SBA-15, we find that direct (27)Al DNP enhancements achieved with different spin probes can be attributed to proximity and local concentration of the spin probes to aluminum on the surface of mesoporous alumina-silica.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Phys Chem Chem Phys
Journal subject:
BIOFISICA
/
QUIMICA
Year:
2015
Document type:
Article
Affiliation country:
Estados Unidos