# The Antifouling Mechanism and Efficacy of Graphene Nanomaterials in Composite Coatings against Marine Diatoms

## TL;DR

This study explores how graphene nanomaterials in composite coatings prevent marine diatoms from sticking, finding that physical disruption rather than chemical toxicity is the main mechanism.

## Contribution

The study reveals that graphene's antifouling effect in composites is primarily physical, through membrane disruption, rather than chemical toxicity.

## Key findings

- Graphene-based coatings significantly reduce diatom adhesion compared to pure epoxy.
- Cell death is mainly caused by contact-mediated phospholipid damage, not oxidative stress.
- Graphene shows higher cell mortality than graphene oxide, emphasizing mechanical disruption.

## Abstract

The urgent need for
sustainable antifouling solutions in marine
environments has intensified the search for alternatives to toxic
biocides. One promising approach involves embedding graphene nanomaterials
into polymer composites. While graphene’s antifouling properties
have been extensively studied in solution, its mechanisms within solid
composites remain unclearparticularly whether its effects
are primarily chemical, such as oxidative stress, or physical, such
as mechanical disruption. This study investigates the antifouling
mechanisms of native, unmodified graphene and graphene oxide embedded
in epoxy composite coatings targeting marine diatoms under laboratory
conditions. Both graphene-based coatings significantly outperformed
pure epoxy in reducing diatom adhesion in flow-through systems, using
both monocultures and mixed algal cultures, with efficacy increasing
alongside filler concentration. A comprehensive suite of characterizationsincluding
surface energy analysis, reactive oxygen species (ROS) measurements,
and scanning and transmission electron microscopywas employed
to elucidate the mode of action. Unlike commercial antifouling coatings,
the high surface energy of these composites rules out fouling release
as the dominant mechanism. ROS measurements indicated minimal oxidative
stress, suggesting that chemical toxicity is not the primary driver.
Microscopy revealed membrane disruption as the main cause of cell
death, primarily through contact-mediated phospholipid damage. Furthermore,
cellular assays showed higher cell mortality on graphene-containing
surfaces compared with those with graphene oxide, reinforcing the
role of mechanical disruption. Overall, these findings demonstrate
that graphene nanomaterials confer antifouling activity primarily
through direct contact interactions, highlighting their potential
for durable, nontoxic marine coatings. However, to fully leverage
the biocidal properties of graphene and graphene oxide, efficient
removal of dead foulants remains a critical challenge.