Sensitivity of Saturation Transfer Electron Spin Resonance Extended to Extremely Slow Mobility in Glassy Materials |
| |
Authors: | Ivon J van den Dries PAdrie de Jager Marcus A Hemminga |
| |
Institution: | aDepartment of Food Science, Food Physics Group, Wageningen Agricultural University, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands;bDepartment of Molecular Physics, Wageningen Agricultural University, P.O. Box 8128, 6700 ET, Wageningen, The Netherlands |
| |
Abstract: | A novel extension of the saturation transfer (ST) ESR technique that enables the determination of extremely long rotational correlation times of nitroxide spin labels up to values around 104s is proposed. The method is based on the observation that the integral of ST-ESR spectra is sensitive to the spin–lattice relaxation time of the electron of the spin label, which in turn is directly dependent upon the rotational correlation time. The method is applied to the spin label TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) in glycerol. From the known viscosity data and the related rotational correlation times of the TEMPOL spin label in glycerol, the rotational correlation times of unknown samples can be determined. The method is especially applicable to systems with a very high viscosity, such as glassy materials. The method is applied to a 20 wt% glucose–water mixture in the glassy state, giving a value for the highest limiting rotational correlation time of about 103s at a temperature of 45 K below the glass transition temperature of this system. This is an extension by six decades for the rotational correlation time, as compared to the current application of ST-ESR. |
| |
Keywords: | correlation time TEMPOL glycerol glucose |
本文献已被 ScienceDirect 等数据库收录! |
|