title: Zinc porphyrin-driven assembly of gold nanofingers.
abstract: Nanofingers of gold covered by porphyrins are prepared by a combination of atomic manipulation and surface self-organization. A submonolayer of zinc(II) 5,10,15,20-tetrakis(4-tert-butylphenyl)-porphyrin (ZnTBPP) axially ligated to a self-assembled monolayer of 4-aminothiophenol (4-ATP) on Au(111) is prepared and studied using a combination of ultrahigh vacuum techniques. Under the electric field produced by the STM tip, the relatively weakly bound Au surface atoms along the discommensuration lines become mobile due to the strong bond to 4-ATP, while the tendency of the porphyrins towards self-assembly result in a collective motion of gold clusters. The clusters diffuse onto the surface following well-defined pathways along the [112] direction and then reach the step edges where they assembled, thus forming nanofingers. First-principles density functional theory calculations demonstrate the reduction of the binding energies between the surface gold clusters and the substrate induced by adsorption of thiols. Scanning tunneling microscopy images show assemblies across three adjacent discommensuration lines of the Au(111)-(22 x square root 3) reconstruction, which collectively diffuse along these lines to form islands nucleated at step edges.
authors.affiliation: National Nanotechnology Laboratory (CNR-INFM), Distretto Tecnologico ISUFI, Università degli studi di Lecce ,via Arnesano, 73100 Lecce, Italy. valentina.arima@unile.it
authors.forename: Valentina
authors.initials: V
authors.lastname: Arima
authors.forename: Robert I R
authors.initials: RI
authors.lastname: Blyth
authors.forename: Francesca
authors.initials: F
authors.lastname: Matino
authors.forename: Letizia
authors.initials: L
authors.lastname: Chiodo
authors.forename: Fabio
authors.initials: F
authors.lastname: Della Sala
authors.forename: Julie
authors.initials: J
authors.lastname: Thompson
authors.forename: Tom
authors.initials: T
authors.lastname: Regier
authors.forename: Roberta
authors.initials: R
authors.lastname: Del Sole
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mele
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vasapollo
authors.forename: Roberto
authors.initials: R
authors.lastname: Cingolani
authors.forename: Ross
authors.initials: R
authors.lastname: Rinaldi
mesh_terms: D003460:Crystallization / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D036103:Nanotechnology / Q000379:methods*; D043942:Nanotubes / Q000737:chemistry*; D010316:Particle Size; D011166:Porphyrins / Q000737:chemistry*; D013499:Surface Properties; D015032:Zinc / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D011166:Porphyrins; D006046:Gold; D015032:Zinc