Abstract
Ultrathin layers of hexagonal boron nitride (h-BN) are used to fully encapsulate single perylene microcrystals. The morphology and chemical stability for samples prepared using different encapsulation methods are characterized using electron, optical, and atomic force microscopies. Only multilayer MBE-grown h-BN could fully protect the organic crystals from dissolution and sublimation. To determine the interaction of the two-dimensional material with the underlying organic chromophores, a polymer film with Lumogen Red dye molecules that act as energy donors was used to characterize the fluorescence quenching ability of the encapsulation layer. Encapsulation using wet-transfer method leads to h-BN layers that have an effective Forster quenching radius of 2.9 nm, as compared to 14.6 nm for graphene. Fluorescence quenching by h-BN can be completely avoided by using dry-transfer methods, suggesting that wet transfer leads to structural defects that act as energy acceptors. Both the type of h-BN and its method of transfer determine its ability to act as an inert coating and avoid fluorescence quenching. Encapsulation of organic molecular crystals using multilayer h-BN is feasible, but attention must be paid to preparation conditions and the nature of the h-BN sample.