Particle Size Distribution of Graphene Quantum Dots

Graphene quantum dots (GQDs) are nanoscale crystals purely made of carbon atoms that have low toxicity, very stable, and efficient photoluminescent (PL) properties. Compared with other types of quantum dots, the superior thermal, electrical, and mechanical properties of GQDs have made them ideal candidates for state-of-the-art applications such as light-emitting diodes, bioimaging markers, fluorescent polymers, batteries, etc. Most of the unique properties of GQDs are diameter dependent, particularly the PL and other optical properties. Current synthesis protocols always produce GQDs of certain diameter distribution. We investigate the nature of the diameter distribution to better understand its influence specifically on the PL. We extracted the particle size distribution of GQDs from several publications and analyzed the distribution using MATLAB.  Our analysis confirmed that the majority of the size distribution follows a log-normal behavior. This is attributed to limitations in synthesizing smaller GQDs than their larger counterparts, leaving a tapering tail on the larger particle side (right side of the distribution). The fitting parameters obtained from the log-normal distribution are used for further work on the influence of the diameter distribution on the PL.