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Kumada, Takayuki; Noda, Yohei; Ishikawa, Norito
Journal of Magnetic Resonance, 218, p.59 - 65, 2012/05
Times Cited Count：6 Percentile：34.81(Biochemical Research Methods)We compared dynamic nuclear polarization (DNP) behavior of electron-beam irradiated polyethylene (e-PE) with that of TEMPO-doped polystyrene (T-PS). Although both T-PS had a sharp maximum in nuclear polarization at the concentration of free radicals of 2
10
spins cm
, that of e-PE depend much less. Growth and decay rates of polarization of e-PE linearly increased with increasing the radical concentration, whereas those rates of T-PS increased with square of radical concentration. We concluded that, not a pair of unspecified radicals accidentally located nearby, but a pair of alkyl radicals produced by the dissociation of C-H bond by an electron irradiation and the subsequent hydrogen abstraction reaction play an important role on DNP of e-PE.
Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi
Journal of Magnetic Resonance, 201(2), p.115 - 120, 2009/12
Times Cited Count：7 Percentile：36.49(Biochemical Research Methods)We have carried out a dynamic nuclear polarization (DNP) study of proton spins of UV-irradiated solid butanol containing phenol. By the aid of butyl free radicals produced by the photolysis, the butanol sample was dynamically polarized up to the polarization of 1.4% at 1.5 K and 1.2 T. Unlike persistent free radicals such as nitroxy and trityl free radicals commonly used for DNP, the butyl free radicals immediately decay by melting. We propose that free radicals produced by UV-photolysis are applicable to the DNP-enhanced hyperpolarized liquid-state NMR.
