Ultraviolet-light-induced electron transfer between chlorine anions and graphene

Abstract Outer-shell electrons of singly-charged anions are allowed to be detached by absorbing photons with appropriate energy that is larger than the corresponding atomic electron affinity. In an anion-graphene system, these escaped electrons face the possibility of travelling to graphene through the electron-exchanged path that originates from the anion-graphene orbital overlapping. Using electrical measurements, we observe that the hole concentration of gold-chloride-functionalized graphene decreases upon ultraviolet-light impingements, yet by contrast it persists under visible lights. Then we identify the governing mechanism in which chlorine anions are neutralized to gaseous molecules, thus donating electrons to graphene, subsequently elevating the Fermi level, and lowering the electrical conductivity in graphene. This mechanism is validated by field-effect-transistor-based Dirac-point-shift measurements that reveal Fermi-level and carrier-mobility variations of graphene. Raman statistical analyses and X-ray photoelectron spectroscopy measurements are employed to further confirm this electron-transfer-related process. Our study can be applied to designs of anion-graphene-embedded devices for sensing as well as energy harvesting.