title: Using supramolecular binding motifs to provide precise control over the ratio and distribution of species in multiple component films grafted on surfaces: demonstration using electrochemical assembly from aryl diazonium salts.
abstract: Supramolecular interactions between two surface modification species are explored to control the ratio and distribution of these species on the resultant surface. A binary mixture of aryl diazonium salts bearing oppositely charged para-substituents (either -SO3(-) or -N(+)(Me)3), which also reduce at different potentials, has been examined on glassy carbon surfaces using cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Striking features were observed: (1) the two aryl diazonium salts in the mixed solution undergo reductive adsorption at the same potential which is distinctively less negative than the potential required for the reduction of either of the two aryl diazonium salts alone; (2) the surface ratio of the two phenyl derivatives is consistently 1:1 regardless of the ratio of the two aryl diazonium salts in the modification solutions. Homogeneous distribution of the two oppositely charged phenyl species on the modified surface has also been suggested by XPS survey spectra. Diffusion coefficient measurements by DOSY NMR and DFT based computation have indicated the association of the two aryl diazonium species in the solution, which has led to changes in the molecular orbital energies of the two species. This study highlights the potential of using intermolecular interactions to control the assembly of multicomponent thin layers.
authors.affiliation: School of Chemistry and Australian Centre for NanoMedicine, The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Alicia L
authors.initials: AL
authors.lastname: Gui
authors.forename: Hon Man
authors.initials: HM
authors.lastname: Yau
authors.forename: Donald S
authors.initials: DS
authors.lastname: Thomas
authors.forename: Muthukumar
authors.initials: M
authors.lastname: Chockalingam
authors.forename: Jason B
authors.initials: JB
authors.lastname: Harper
authors.forename: J Justin
authors.initials: JJ
authors.lastname: Gooding
mesh_terms: D003979:Diazonium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D055664:Electrochemical Techniques; D046911:Macromolecular Substances / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011789:Quantum Theory; D012492:Salts / Q000138:chemical synthesis / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003979:Diazonium Compounds; D046911:Macromolecular Substances; D012492:Salts