title: Ferrocene and porphyrin monolayers on Si(100) surfaces: preparation and effect of linker length on electron transfer.
abstract: The missing link: Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.Ferrocene and porphyrin derivatives are anchored on Si(100) surfaces through either a short two-carbon or a long 11-carbon linker. The two tether lengths are obtained by using two different grafting procedures: a single-step hydrosilylation is used for the short linker, whereas for the long linker a multistep process involving a 1,3-dipolar cycloaddition is conducted, which affords ferrocene-triazole-(CH(2))(11)-Si or Zn(porphyrin)-triazole-(CH(2))(11)-Si links to the surface. The modified surfaces are characterized by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Cyclic voltammetry experiments show that the redox activity of the tethered ferrocene or porphyrin is maintained for both linker types. Microelectrode capacitor devices incorporating these modified Si(100) surfaces are designed, and their capacitance-voltage (C-V) and conductance-voltage (G-V) profiles are investigated. Capacitance and conductance peaks are observed, which indicates efficient charge transfer between the redox-active monolayers and the electrode surface. Slower electron transfer between the ferrocene or porphyrin monolayer and the electrode surface is observed for the longer linker, which suggests that by adjusting the linker length, the electrical properties of the device, such as charging and discharging kinetics and retention time, could be tuned.
authors.affiliation: Department of Micro Technologies for Biology and Healthcare, CEA-LETI, 17 rue des Martyrs, 38054 Grenoble, France.
authors.forename: Kai
authors.initials: K
authors.lastname: Huang
authors.forename: Florence
authors.initials: F
authors.lastname: Duclairoir
authors.forename: Tiziana
authors.initials: T
authors.lastname: Pro
authors.forename: Julien
authors.initials: J
authors.lastname: Buckley
authors.forename: Gilles
authors.initials: G
authors.lastname: Marchand
authors.forename: Eugénie
authors.initials: E
authors.lastname: Martinez
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Marchon
authors.forename: Barbara
authors.initials: B
authors.lastname: De Salvo
authors.forename: Guillaume
authors.initials: G
authors.lastname: Delapierre
authors.forename: Françoise
authors.initials: F
authors.lastname: Vinet
mesh_terms: D025802:Electric Capacitance; D004579:Electron Transport; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D008839:Microelectrodes; D010084:Oxidation-Reduction; D011166:Porphyrins / Q000737:chemistry*; D011199:Potentiometry; D012825:Silicon / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D005296:Ferrous Compounds; D000075163:Metallocenes; D011166:Porphyrins; C004998:ferrocene; D012825:Silicon