title: Porphyrins as Templates for Site-Selective Atomic Layer Deposition: Vapor Metalation and in Situ Monitoring of Island Growth.
abstract: Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth. Analytical fitting of in situ QCM mass uptake reveals island growth to be hemispherical with a convergence radius of 1.74 nm. This growth mode is confirmed with synchrotron grazing-incidence small-angle X-ray scattering (GISAXS) measurements. Finally, we extend this approach to other ALD chemistries to demonstrate the generality of this route to discrete metallo island materials.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Avila
authors.affiliation: Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Emery
authors.affiliation: Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pellin
authors.affiliation: Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Alex B F
authors.initials: AB
authors.lastname: Martinson
authors.affiliation: Faculty of Science, Department of Chemistry, King Abdulaziz University , Jeddah 21577, Saudi Arabia.
authors.forename: Omar K
authors.initials: OK
authors.lastname: Farha
authors.affiliation: Argonne National Laboratory , 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hupp
keywords: atomic layer deposition; grazing incident small angle scattering; island nucleation; manganese oxide; porphyrin; quartz crystal microbalance; vapor metalation