Probing molecular dynamics at the nanoscale via an individual paramagnetic centre

Abstract

We demonstrate a protocol using individual nitrogen-vacancy centres in diamond to observe the time evolution of proton spins from organic molecules located a few nanometres from the diamond surface. The protocol records temporal correlations among the interacting protons, and thus is sensitive to the local dynamics via its impact on the nuclear spin relaxation and interaction with the nitrogen vacancy. We gather information on the nanoscale rotational and translational diffusion dynamics by analysing the time dependence of the nuclear magnetic resonance signal. Applying this technique to liquid and solid samples, we find evidence that liquid samples form a semi-solid layer of 1.5-nm thickness on the surface of diamond, where translational diffusion is suppressed while rotational diffusion remains present. Extensions of the present technique could be exploited to highlight the chemical composition of molecules tethered to the diamond surface or to investigate thermally or chemically activated dynamical processes such as molecular folding.

Single spin magnetic resonance

“…In the other extreme case, wherein T C 's length is longer by one target nuclear spin half Larmor period, the phases are opposite and the correlation would be negative. This would lead to a periodic oscillation, limited by the NV's relaxation time, T 1 , with possible decay due to interactions of the nuclei with neighboring nuclei or with surface dipoles [51]. A display of this technique has been initially demonstrated on 13 C spins [45] and 1 H spins [52], and more recently as a tool to probe molecular dynamics [51] (see Fig.…”

“…This would lead to a periodic oscillation, limited by the NV's relaxation time, T 1 , with possible decay due to interactions of the nuclei with neighboring nuclei or with surface dipoles [51]. A display of this technique has been initially demonstrated on 13 C spins [45] and 1 H spins [52], and more recently as a tool to probe molecular dynamics [51] (see Fig. 7d) and achieve chemical contrast, and nuclei hyperfine couplings [53].…”

Delayed entanglement echo for individual control of a large number of nuclear spins

“…For example, the signals from the target nuclear spins which has weaker coupling can be damaged by those with stronger coupling, regardless of the potential high spectral resolution. As a consequence reported results using the ENDOR techniques18232627 provide high spectral resolution but do not demonstrate any increase in the number of detectable nuclear spins by sensor electrons comparing with the achieved numbers by standard DD techniques614. Note that individual addressing of nuclear spins and the implementation of quantum gates on them are more demanding than nuclear-spin detection, but essential in quantum information processing and thorough characterization of nuclear spins.…”

A quantum spectrum analyzer enhanced by a nuclear spin memory

“…Correlation spectroscopy has been applied to both generic ac magnetic fields and to nuclear spin detection, and spectral resolutions of a few 100 Hz have been demonstrated. [20][21][22] Despite these impressive advances, there is a strong motivation to further extend the spectral resolution. For example, many proposed nanoscale NMR experiments [9][10][11] require discrimination of fine spectral features, often in the few-Hz range.…”