Rajarshi Roy, Jénnifer Gómez, Souvik Bhattacharjee, Nilesh Mazumder, Subhajit Saha, Lenka Zajíčková
Temperature dependent photoluminescence characteristics in amino-functionalized graphene quantum dots
Carbon 247 (2026) 120979
Graphene quantum dots (GQDs) have attracted significant attention in the last decade due to its superior tunable luminescence in diverse fields of research including opto-electronics, bio-imaging, drug delivery and catalysis. However, probing the luminescence at low temperatures in such quantum dots has been mostly elusive thus far which provides pivotal information about the bandgap and the nature of electron-phonon interactions widely important for opto-electronic applications. In this work, we establish the temperature dependence of the excitonic bandgap renormalization and electron-phonon coupling in amino-functionalized GQDs of 5–7 nm diameter from the photoluminescence measurements across 76.5–303.1 K by model fitting using different well known theoretical frameworks (Varshni, Vina and Pässler models). We have shown that the defect related emission from the hybridized interstate energy level explicitly due to amino-functionalization as a result of n–π transition violates the relationship associated with the excitonic bandgap renormalization and thereby fails to obey the Varshni model and other associated frameworks (Vina, Pässler). Finally, the amino-GQDs showcase distinctive excitonic bandgap shrinkage anomaly and the electron-phonon coupling resulting from the extent of the optical phonon dispersions and phonon damping due to disorder deduced from the fitted model parameters.
You can also contact one of the authors: gomez.perez@ceitec.muni.cz, lenkaz@physics.muni.cz