Fine-tuning the fluorescent properties of Li and Na intercalated C60 with hydrogen

In this work we demonstrate how hydrogen can be utilized to fine tune the emission gap of C60 through the formation of direct CH bonds in sodium and lithium intercalated systems (M6C60Hx). Upon hydrogenation, a shift in the emission spectrum to shorter wavelengths (higher energy) is observed relative to alkali metal free fulleranes (C60Hx) and pure C60. This is attributed to the higher degree of hydrogenation of C60 that can be achieved upon intercalation with alkali metals which increases the sp3 hybridization of the system (decreases conjugation). Quantum yields of the sodium and lithium intercalated fulleranes are 1.3% and 1.8% respectively which are similar to those of alkali metal free fulleranes (1.4%). We also show that polymethyl methacrylate (PMMA) can be infused with the metal intercalated fulleranes to produce a fluorescent polymer with excellent transparency over the visible spectrum. This could potentially lead to further use of these materials in luminescent down shifting applications.