Egyptian Blue/gold nanocomposite supramarbles, a platform for IR emission enhancement

Abstract

Nanotechnology manufacturing requires a unique skillset and access to that technology is not yet within the reach of many small businesses and startups. What if a specialty product could be offered as pellets or marbles, and this new platform enabled uniform nano-coatings readily handled by off the shelf standard manufacturing technologies? The platform – a supramarble (SM) – introduced in this work is a crosslinked polymer core with a coating (or corona) of hydrophobic micro- and nanoparticles. A photoactive 2-D nanoparticulate pigment, Egyptian Blue (EB) has gained tremendous popularity in sensing applications recently due to its intense near-infrared emission at ∼900 nm. Gold nanoparticles (AuNPs) have been reported to modify the spontaneous emission of other adjacent fluorophores in a remarkable way. By combining near-infrared emitting EB microparticles and AuNP decorated fumed silica (Au-FS) NPs as the corona of an SM, significant (4-fold) fluorescence enhancement is demonstrated in this work. A maximum in fluorescent intensity was shown at 70 wt% EB and 30 wt% Au-FS composite coating. The 4-fold enhancement was attributed to AuNPs’ generation of a localized electric field synergistically interacting with the fluorescent emission of EB. The influence of Au-FS on the original, intrinsic fluorescent emission wavelength of EB (∼900 nm) was also investigated.