Unified Charge-Transfer Diagram for Molecules Adsorbed on Graphene: A van Arkel–Ketelaar–Inspired Framework for Teaching Doping Phenomena

Understanding charge transfer between molecular adsorbates and graphene is a recurring topic in courses on physical chemistry, materials science, and nanoscience.However, students are often exposed to case-specific energy level diagrams that hinder comparative reasoning and obscure the conceptual connection between molecular electronic structure and doping behavior.In this work, we introduce a unified charge transfer diagram that maps molecular adsorbates in a two-dimensional space defined by global chemical descriptors-namely, the average frontier orbital energy and the HOMO-LUMO gap.