Tribo-induced photoluminescent behavior of graphene and YSZ:Er/graphene composite films.

In the present work, a novel method was developed to study the evolving surface state of graphene film as it is subject to friction, characterized by photoluminescence properties. We prepared the graphene film (GF) and YSZ:Er (Er-Y co-doped ZrO)/graphene composite films (ZGCF). The Raman spectra and photoluminescence properties of the GF and ZGCF were characterized before and after the sliding friction. A remarkable phenomenon was observed that after friction the GF generated a more pronounced luminescence response than it had prior, apparently due to graphene quantum dots which were found in the wear debris of the GF. Furthermore, the introduction of graphene into YSZ:Er nanoparticles (NPs) resulted in an unmistakable red-shift on the main luminescence bands of ZGCF after the applied friction. This is explained by the formation of considerable graphene scrolls in the wear debris of ZGCF due to the interaction of the graphene and the YSZ:Er NPs. It can be concluded that changes to the configuration of graphene greatly influence the tribo-induced photoluminescence response. Our findings justify further investigation into the composition and morphology of worn surfaces in order to better understand how photoluminescence relates to frictional effects. In addition, this work proposes the fabrication of graphene quantum dots and nanoscale scrolls as a new potential application of the tribo-induced photoluminescence study.