2017
DOI: 10.1039/c7cp06073d
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Photo-induced radical polarization and liquid-state dynamic nuclear polarization using fullerene nitroxide derivatives

Abstract: We report on radical polarization and optically-driven liquid DNP using nitroxide radicals functionalized by photoexcitable fullerene derivatives. Pulse laser excitation of the fullerene moiety leads to transient nitroxide radical polarization that is one order of magnitude larger than that at the Boltzmann equilibrium. The life time of the radical polarization increases with the size of the fullerene derivative and is correlated with the electronic spin-lattice relaxation time T. Overhauser NMR signal enhance… Show more

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Cited by 30 publications
(39 citation statements)
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“…The scope for maintaining enhancements using a pulsed laser to produce much lower duty cycle trains of pulses has been discussed elsewhere and remains a target for future experimental investigation. 23 As noted elsewhere the build-up time for the optical enhancement is expected to be governed by the nuclear relaxation time T 1n , 23,37 values for which are given in Table 2. While one might therefore expect maximal polarization to be achieved with illumination for B5T 1n , corresponding to 3.5-7.0 s in the present case, illumination longer than 4 s reduced the enhancement obtained.…”
Section: Nuclear Polarizationmentioning
confidence: 85%
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“…The scope for maintaining enhancements using a pulsed laser to produce much lower duty cycle trains of pulses has been discussed elsewhere and remains a target for future experimental investigation. 23 As noted elsewhere the build-up time for the optical enhancement is expected to be governed by the nuclear relaxation time T 1n , 23,37 values for which are given in Table 2. While one might therefore expect maximal polarization to be achieved with illumination for B5T 1n , corresponding to 3.5-7.0 s in the present case, illumination longer than 4 s reduced the enhancement obtained.…”
Section: Nuclear Polarizationmentioning
confidence: 85%
“…This is likely the result of unwanted heating effects when using a high power illumination source, similar to observations of Liu et al who noted polarization build up at twice the expected rate. 37 Laser induced heating was particularly problematic in the most viscous solvent mixture when using the highest illumination power of 2.0 W, with data showing poor reproducibility under these conditions. For this reason only data recorded with illumination powers of up to 1.5 W are presented for samples containing 30% glycerol by volume.…”
Section: Nuclear Polarizationmentioning
confidence: 99%
“…To extend the scope of high‐resolution NMR spectroscopic investigations in photocatalysis with stable radicals, a combined NMR and UV/Vis spectroscopic tool would be ideal 10. However, reaction profiles of photocatalytic processes featuring longer reaction times of up to several hours or even days impose severe challenges for separated setups.…”
mentioning
confidence: 99%
“…To extend the scope of high‐resolution NMR spectroscopic investigations in photocatalysis with stable radicals, a combined NMR and UV/Vis spectroscopic tool would be ideal . However, reaction profiles of photocatalytic processes featuring longer reaction times of up to several hours or even days impose severe challenges for separated setups.…”
Section: Figurementioning
confidence: 99%