Interface-Engineered Graphene Oxide for Controlled Nanoparticle Organisation and Tunable Plasmonic Response

Graphene oxide (GO) surface chemistry influences nanoparticle organisation and optical response, yet these relationships remain poorly integrated across experimental and computational length scales. Here, two GO materials with contrasting surface oxygen contents, GO10 and GO30, were examined before and after PEG–NH2 treatment and incorporation of Ag- and Cu-containing particles using spectroscopy, microscopy, thermal analysis, molecular dynamics (MD) and finite-difference time-domain (FDTD) modelling. Higher surface oxygen content and PEG–NH2 treatment were associated with greater apparent PEG-associated loading, smaller particle populations and reduced nanoparticle aggregation and apparent contact, with Cu D50 decreasing from 22.5 to 7.8 nm. MD simulations showed more favourable interfacial interactions following PEG modification, with contact-area-normalised interaction-energy descriptors supporting stronger interactions at the modified interface. FDTD simulations revealed strong size- and separation-dependent responses, including LSPR redshifts of 96.25 nm for Ag and 61.25 nm for Cu across 10–100 nm. Experiment-informed assemblies exhibited higher resonance quality but weaker extreme hotspots as close particle contacts were reduced across the model series, indicating a trade-off between junction-driven enhancement and a less hotspot-dominated, more spectrally defined response. Overall, the results establish a multiscale structure–property framework linking GO interface chemistry, nanoparticle organisation and predicted electromagnetic response.