Ring and Volcano Structures Formed by a Metal Dipyrromethene Complex

Abstract

Department of Chemistry, University of British Columbia, 2329 West Mall Vancouver BC Canada V6T 1Z4Received January 31, 2014, Accepted February 18, 2014Dichloromethane liquid droplets containing a cobalt dipyrromethene trimer deposited on a graphite surfacewere found to form coffee ring, toroid ring, or volcano dot structures due to the redistribution of the soluteduring solvent evaporation. The shapes and size distributions of the ring structures depended on the dryingtemperature. The shape differences were attributed to the fact that the solvent evaporation rate controlled theself-assembly process that yielded the coffee stain and pinhole structures.Key Words : Dipyrromethene, AFM, Coffee-ring, Toroid ring, EvaporationIntroductionThe deposition of a molecular solution onto a solid surfacesets in motion a complex interplay of interactions that affectthe morphology and pattern of the resulting film. Obtainingsolid morphologies with unusual shapes is important to thesearch for new nanoscale material properties and for creatinginterfaces for emerging applications, such as the productionof templates that order adsorbates or growing crystals, thecreation of self-healing surfaces, and the preparation ofsurfaces with tailored properties.