Comparison of Overhauser DNP at 0.34 and 3.4 T with Frémy’s Salt

Abstract

Dynamic nuclear polarization (DNP) is investigated in the liquid state using a model system of Frémy’s salt dissolved in water. Nuclear magnetic resonance signal enhancements at 0.34 and 3.4 T of the bulk water protons are recorded as a function of the irradiation time and the polarizer concentration. The build-up rates are consistent with the T1n of the observed water protons at room temperature (for 9 GHz/0.34 T) and for about 50 ± 10 °C at 94 GHz/3.4 T. At 94 GHz/3.4 T, we observe in our setup a maximal enhancement of −50 at 25 mM polarizer concentration. The use of Frémy’s salt allows the determination of the saturation factors at 94 GHz by pulsed ELDOR experiments. The results are well consistent with the Overhauser DNP mechanism and indicate that higher enhancements at this intermediate frequency require higher sample temperatures.

Photo-induced radical polarization and liquid-state dynamic nuclear polarization using fullerene nitroxide derivatives

“…Importantly, it follows expected kinetics according to T 1n that is on the time scale of seconds. 33 Our DNP results appear to be consistent with the previous report of a photo-induced 1 H-NMR DNP signal up to À4 of water in a mixture of Rose-Bengal and TEMPO. 16 As compared to our enhancements, the reported larger negative enhancement is consistent with the completely emissive (negative) transient polarization of TEMPO mixed with Rose-Bengal.…”

One-thousand-fold enhancement of high field liquid nuclear magnetic resonance signals at room temperature

“…The K x for CHCl 3 and CCl 4 were determined to be 2.9±0.8*10 9 s -1 M -1 and 2.5±0.8*10 9 s -1 M -1 , respectively. The theoretical expressions for s 1 (irradiated) and s 2 for the twoline EPR spectrum of 15 N-TEMPONE were reported previously, 3,4 and depend on microwave field strength B 1 , T 2e , the concentration dependent Heisenberg exchange rate  ex = cK x as well as the transition probabilities 2w e = 1/T 1e and the probability for internal nitrogen relaxation 2w n :…”

Optimization and prediction of the electron–nuclear dipolar and scalar interaction in1H and13C liquid state dynamic nuclear polarization

“…[6][7][8][9][10] Liquid state Overhauser effect DNP has been applied for signal enhancement of ow imaging [11][12][13][14] as well as the characterization of local water dynamics in biological systems. [15][16][17][18][19][20][21] More recently, 1 H liquid state DNP measurements of water [22][23][24][25][26] and small organic molecules [27][28][29] at higher magnetic elds have been reported. However, liquid state DNP experiments also provide an excellent approach for understanding and predicting intermolecular solution interactions.…”