Investigation of hydrogen induced fluorescence in C and its potential use in luminescence down shifting applications.

Herein the photophysical properties of hydrogenated fullerenes (fulleranes) synthesized by direct hydrogenation utilizing hydrogen pressure (100 bar) and elevated temperatures (350 °C) are compared to the fulleranes CH and CH synthesized by amine reduction and the Birch reduction, respectively. Through spectroscopic measurements and density functional theory (DFT) calculations of the HOMO-LUMO gaps of CH (0 ≤ x ≤ 60), we show that hydrogenation significantly affects the electronic structure of C by decreasing conjugation and increasing sp hybridization. This results in a blue shift of the emission maximum as the number of hydrogen atoms attached to C increases. Correlations in the emission spectra of CH produced by direct hydrogenation and by chemical methods also support the hypothesis of the formation of CH and CH during direct hydrogenation with emission maxima of 435 and 550 nm respectively. We also demonstrate that photophysical tunability, stability, and solubility of CH in a variety of organic solvents make them easily adaptable for application as luminescent down-shifters in heads-up displays, light-emitting diodes, and luminescent solar concentrators. The utilizization of carbon based materials in these applications can potentially offer advantages over commonly utilized transition metal based quantum dot chromophores. We therefore propose that the controlled modification of C provides an excellent platform for evaluating how individual chemical and structural changes affect the photophysical properties of a well-defined carbon nanostructure.