Impacts of annealing on structural and photophysical properties of zinc phthalocyanine adsorbed on graphene

TL;DR

This study investigates how annealing affects the structural and photophysical properties of zinc phthalocyanine monolayers on graphene, revealing a phase transition and enhanced reactivity post-annealing.

Contribution

It demonstrates a combined microscopy and spectroscopy approach to analyze annealing-induced phase changes in ZnPc on graphene, highlighting new insights into molecular transitions.

Findings

Annealing induces a planar-square to shuttlecock phase transition.

Post-annealing, Zn atoms show improved reactivity with reactants.

Confinement within a 2D matrix allows detailed analysis of phase change.

Abstract

We report the demonstration and analysis by combined scanning-tunneling-microscopy and optical microspectroscopy of a 2D phase change experienced by a self-assembled zinc phthalocyanine (ZnPc) monolayer adsorbed on graphene. To probe the intrinsic properties of individual ZnPc molecules, they are spatially confined within the pores of a self-assembled 2D matrix. This confinement allows us to track a phase change induced by annealing, which we discuss in terms of a planar-square to shuttlecock molecular transition. We show that after annealing of the adsorbed ZnPc, the exposition of Zn atoms to reactants in a supernatant solution is improved, for example, for metal-ligand formation towards 3D self-assembly.