Nanoparticle-Assisted NMR Spectroscopy: Enhanced Detection of Analytes by Water-Mediated Saturation Transfer

Nanoparticle-assisted “NMR chemosensing” is an experimental protocol that exploits the selective recognition abilities of nanoparticle receptors to detect and identify small molecules in complex mixtures by nuclear Overhauser effect magnetization transfer. Although the intrinsic sensitivity of the first reported protocols was modest, we have now found that water spins in long-lived association at the nanoparticle monolayer constitute an alternative source of magnetization that can deliver a remarkable boost of sensitivity, especially when combined with saturation transfer experiments. The approach is general and can be applied to analyte–nanoreceptor systems of different compositions. In this work, we provide an account of the new method and we propose a generalized procedure based on a joint water–nanoparticle saturation to further upgrade the sensitivity, which ultimately endows selective analyte detection down to the micromolar range on standard instrumentation.