Lateral diffusion of phospholipids in artificial cell membranes measured by single shallow NV centers

TL;DR

This study uses single shallow NV centers in diamond to measure the lateral diffusion of phospholipids in artificial cell membranes, revealing heterogeneities and the impact of diffusion models on results.

Contribution

It introduces a novel method for local NMR detection of molecular diffusion in membranes using single NV centers, highlighting the effects of model choice and substrate heterogeneity.

Findings

Diffusion coefficients vary among different NV centers.

A simple 2D diffusion model fits the data satisfactorily.

Local heterogeneities influence diffusion measurements.

Abstract

We measure diffusion of organic molecules located a few nanometers from the diamond surface. To study molecular diffusion, we perform local detection of nuclear magnetic resonance, based on single shallow Nitrogen-Vacancy (NV) centers in diamond. Specifically, we demonstrate measurements of translational diffusion coefficient of phospholipids in an artificial cell membrane by employing correlation spectroscopy. An analysis of correlation decay curves using different diffusion models shows, that a simple 2D diffusion model gives satisfactory diffusion coefficients, although the choice of the model affects the extracted numbers. We find significant differences among the diffusion coefficients measured by different single NV centers, which we attribute to local heterogeneities of the lipid layers, likely caused by the supporting diamond substrate.