title: Molecular diffusion and DNP enhancement in aqueous char suspensions.
abstract: The heterogeneous 1H dynamic nuclear polarization (DNP) effect is studied at low magnetic fields for a system consisting of several newly synthesized carbon chars suspended in water. By using Fourier Transform pulsed-field-gradient spin-echo NMR spectroscopy, several different self-diffusion coefficients have been observed in aqueous char suspensions, corresponding to regions of differing water mobility in the porous structure. Proton spin-lattice relaxation data generally confirm the results of molecular diffusion measurements. Through utilization of the Torrey model, the influence of "cage effects" on DNP enhancement in porous media is discussed. Results suggest that short-range nuclear-electronic interactions in pores have a dominant effect on DNP enhancement in char suspensions.
authors.affiliation: Illinois Research EPR Center, Department of Chemistry, Urbana, USA.
authors.forename: B M
authors.initials: BM
authors.lastname: Odintsov
authors.forename: R L
authors.initials: RL
authors.lastname: Belford
authors.forename: P J
authors.initials: PJ
authors.lastname: Ceroke
authors.forename: Z S
authors.initials: ZS
authors.lastname: Idiyatullin
authors.forename: R S
authors.initials: RS
authors.lastname: Kashaev
authors.forename: I V
authors.initials: IV
authors.lastname: Kuriashkin
authors.forename: V S
authors.initials: VS
authors.lastname: Rukhlov
authors.forename: A N
authors.initials: AN
authors.lastname: Temnikov
authors.forename: R B
authors.initials: RB
authors.lastname: Clarkson
mesh_terms: D000465:Algorithms; D002244:Carbon / Q000032:analysis*; D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy; D005583:Fourier Analysis; D005632:Fructose / Q000032:analysis / Q000737:chemistry; D006358:Hot Temperature; D006859:Hydrogen; D007089:Image Enhancement; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics; D010316:Particle Size; D016062:Porosity; D012815:Signal Processing, Computer-Assisted; D013213:Starch / Q000032:analysis / Q000737:chemistry; D013535:Suspensions; D014867:Water / Q000737:chemistry; D014934:Wood
chemical_list: D013535:Suspensions; D014867:Water; D005632:Fructose; D002244:Carbon; D006859:Hydrogen; D013213:Starch