Single-component and mixed ferrocene-terminated alkyl monolayers covalently bound to Si(111) surfaces.
Self-assembled ferrocene monolayers covalently bound to monocrystalline Si(111) surfaces have been prepared from the attachment of an amine-substituted ferrocene derivative to a pre-assembled acid-terminated alkyl monolayer using carbodiimide coupling. This derivatization strategy yielded nanometer-scale clean, densely packed monolayers, with the ferrocene units being more than 20 A from the semiconductor surface. The amount of immobilized electroactive units could be varied in the range 2 x 10(-11) to approximately 3.5 x 10(-10) mol cm(-2) by diluting the ferrocene-terminated chains by inert n-decyl chains. The highest coverage obtained for the single-component monolayer corresponded to 0.25-0.27 bound ferrocene per surface silicon atom. The electrochemical characteristics of the mixed n-decyl/ferrocene-terminated monolayers were found to not depend significantly on the surface coverage of ferrocene units. The reversible one-electron wave of the ferrocene/ferrocenium couple was observed at E degrees ' = 0.50 +/- 0.01 V vs SCE, and the rate constant of electron transfer kapp was about 50 s(-1).
Grande Unité Sciences Chimiques de Rennes, UMR CNRS 6226, Matière Condensée et Systèmes Electroactifs MaCSE, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France. fabre@univ-rennes1.fr
Bruno
B
Fabre
Fanny
F
Hauquier
D000478:Alkylation; D004563:Electrochemistry; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D018625:Microscopy, Atomic Force; D015394:Molecular Structure; D012825:Silicon / Q000737:chemistry*
D005296:Ferrous Compounds; D000075163:Metallocenes; C004998:ferrocene; D012825:Silicon