Molecular Mechanisms Underlying Detection Sensitivity in Nanoparticle-Assisted NMR Chemosensing

Nanoparticle-assisted nuclear magnetic resonance (NMR)chemosensingexploits monolayer-protected nanoparticles as supramolecular hoststo detect small molecules in complex mixtures via nuclear Overhausereffect experiments with detection limits down to the micromolar range.Still, the structure-sensitivity relationships at the basisof such detection limits are little understood. In this work, we integrateNMR spectroscopy and atomistic molecular dynamics simulations to examinethe covariates that affect the sensitivity of different NMR chemosensingexperiments [saturation transfer difference (STD), water STD, andhigh-power water-mediated STD]. Our results show that the intensityof the observed signals correlates with the number and duration ofthe spin-spin interactions between the analytes and the nanoparticlesand/or between the analytes and the nanoparticles' solvationmolecules. In turn, these parameters depend on the location and dynamicsof each analyte inside the monolayer. This insight will eventuallyfacilitate the tailoring of experimental and computational setupsto the analyte's chemistry, making NMR chemosensing an evenmore effective technique in practical use.