Polyhydrogenated Graphene - Excited State Dynamics in Photo- and Electroactive 2D-Domains

TL;DR

This study investigates the excited state dynamics and photoluminescence properties of hydrogenated graphene, revealing size-dependent band gap emissions and charge transfer interactions with perylenediimides that stabilize dispersions.

Contribution

It provides a comprehensive characterization of hydrogenated graphene's structure and spectroscopy, and explores its excited state behavior and hybrid interactions with electron acceptors.

Findings

Graphene islands of 1.1 to 1.75 nm diameter exhibit band gap photoluminescence between 450 and 800 nm.

Hydrogenated graphene forms stable dispersions with PDI via π-stacking and charge transfer.

Photoexcited charge separated states have a lifetime of approximately 300 ps.

Abstract

Understanding the phenomenon of intense photoluminescence in carbon materials such as hydrogenated graphene, graphene nanoribbons, etc. is at the forefront of investigations. In this study, six different types of hydrogenated graphene (phG) produced from different starting materials, were fully characterized in terms of structure and spectroscopy. Comprehensive photoluminescence lifetime analyses of phGs were conducted by combining time-correlated single-photon counting spectroscopy with steady-state fluorescence spectroscopy and femtosecond transient absorption spectroscopy. The conclusion drawn from these assays is that graphene islands with diameters in the range from 1.1 to 1.75 nm reveal band gap photoluminescence between 450 and 800 nm. As a complement, phGs were implemented in hybrids with water-soluble electron accepting perylenediimides (PDI). By virtue of mutual {\pi}-stacking and charge transfer interactions with graphene islands, PDIs assisted in stabilizing aqueous dispersion of phG. Implicit in these ground state interactions is the formation of 300 ps lived charge separated states once photoexcited.