| Popis: |
The magnetic-field dependence of the water-proton spin-lattice relaxation rate 1/ T 1 is reported for aqueous colloidal silica suspensions as a function of temperature, particle size, silica concentration, and isotopical proton dilution. At low concentrations, it is found that T 1 is essentially determined by a coupling of solvent protons with nonexchangeable protons situated near the colloid surface. Comparison of NMRD and photon correlation spectroscopy measurements indicates that interparticle interactions increase the NMR relaxation rates at low frequencies. Finally, it is also shown that, in contrast to protein solutions, there is no evident link between the NMRD inflection frequency and the correlation time of the rotational Brownian motion of the colloidal particles. |
Full Text from ScienceDirect