# Experimental Observations of Graphene at Phospholipid Monolayers

## TL;DR

This paper studies how graphene interacts with a phospholipid film at an air-water interface using experimental methods to measure particle movement.

## Contribution

The study experimentally quantifies graphene diffusivity at phospholipid monolayers and reveals its interaction mechanism.

## Key findings

- Graphene particles primarily interact with DPPC hydrocarbon tails.
- Measured diffusivities differ from theoretical predictions, indicating non-embedding behavior.
- DPPC surface concentration affects graphene particle movement.

## Abstract

Interactions between particles and phospholipids at fluid–fluid
interfaces play an important role in biological systems, nanotechnology,
and consumer products. Two-dimensional (2D) particles are atomically
thick particles whose interaction with phospholipid films is little
understood and challenging to study experimentally. In this work we
have quantified the diffusivity of graphene, a well-studied 2D particle,
at a phospholipid monolayer using experimental methods. Particle diffusivities
are used to identify how the graphene arranges in the phospholipid
film. Diffusion coefficients of graphene particles were calculated
from tracking their displacements at an air–water interface
covered with Dipalmitoylphosphatidylcholine (DPPC) phospholipids.
DPPC surface area concentration was varied, and diffusivities of the
particles were compared with model predictions to deduce whether the
particles were embedded within the phospholipid film or interacted
primarily with one side of the film. Discrepancies between experimentally
obtained diffusivities and theoretically predicted diffusivities suggest
that the graphene particles fabricated in this work interact primarily
with DPPC hydrocarbon tails rather than displacing DPPC molecules
to embed within the film.