Solvent Relaxation NMR as a Tool to Study Particle Dispersions in Non-Aqueous Systems

Abstract

The determination of the NMR spin–spin relaxation rate of water in (purely) aqueous particulate dispersions has been shown to be a convenient and facile experimental approach to probing the composition of near particle surface structures. Here, a systematic study has been undertaken of both non-aqueous and mixed aqueous–non-aqueous solvent particulate dispersions to explore the universality of the solvent relaxation technique. As in the aqueous case, a linear relationship between the surface area present and the solvent relaxation rate is observed, confirming the rapid exchange of the solvent molecules between the surface and the bulk and thereby illustrating the viability of the experimental methodology to study such systems. Crucially, the surface enhancement effect was considerably weaker in non-aqueous systems compared with aqueous dispersions and reflects a potential limitation of the wider deployment of this experimental methodology.

Keywords

• NMR spin–spin relaxation time
• specific relaxation rate
• average relaxation rate
• solvent composition
• solvent polarity