Nov.5, Modification of Monolayers and Their Applications State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Chinese Academy of Sciences Chemically Modified Electrodes (CMEs)

Nov.5, 2003 Contents History and Development of CMEs Classification of CMEs Orientated Monolayer & Classification of Kaleidoscopic SAMs Several Examples

Nov.5, Early of 1970’s, F.C. Anson (CalTech), theory of chemical adsorption and adlayer structure , R.F. Lane (Hawaii) & A.T. Hubbard (Cincinnati), olefin derivatives at Pt surface , L.L. Miller (Colorado State), asymmetric reagent for preparing chiral electrode, electrosynthesis of optical rotation substance, electrode-selective reaction. 4. R.W. Murray (North Carolina), Covalent modification, metal oxide (SnO 2 ) + silicane - monolayer modification. 5.T. Kuwana (Ohio State), Cyanourea Acyl Chloride/Graphite Early Studies on CMEs

Nov.5, 2003 Classification of CMEs Chemically Modified Electrodes (CMEs) Monolayer Multilayer Composite & Others Polymer Thin Film Vapor Deposition Adsorption Irreversible Adsorption Underpotential Deposition (UPD) LB & SA Films Covalent Bonding Carbon Series Metal Oxide & Semiconductors By Chemical Synthesis Simply by Physical/ Chemical Adsorption MonomerPolymer Electrochemical Polymerization Chemical Polymerization Plasma PolymerizationRadiation Polymerization DippingDropping Rotating Electrodeposition

Nov.5, 2003 Merit: Function & Structure - tunable & controllable Applications: Electrosynthesis & Electrocatalysis ChemiSensors & Biosensors Electroanalysis & Electrochemical Detection Electrolyzing, Electroplating & Fuel Cell T he understanding of the interrelationship between the molecular structure of amphiphiles and their organization on different surfaces is a fundamental problem. The packing and orientation of such molecules affect the surface chemistry of the monolayer, and play an important role in the phenomena of boundary lubrication, corrosion inhibition, adhesion, and catalysis.

Nov.5, 2003 Orientated Monolayer Origin of the oil-on-water and LB film, 1. Aristotle - spread oil droplets on a water surface and used the behavior of the film to foretell the future , Benjamin Franklin, the first preparation of LB film, and show the thickness of the oil layer is a few nanometers , Agnes Pockels, the first monolayers at the water-air interface , Rayleigh, Devaus, and Hardy, the nature of these layers, and the amphiphilic structure , Langmuir, the first systematic study of monolayers of amphiphilic molecules at the water-air interface , Blodgett, the first study on a deposition of multilayers of long chain carboxylic acid onto a solid substrate. Deposition of a monolayer from the water-air interface to a vertical plate.

Nov.5, 2003 Classical SAM literatures, 1. Bigelow, W.C.; Pickett,D.L.; Zisman, W.A. J. Colloid Interface Sci. 1946, 1, Zisman, W.A. Adv. Chem. Ser. 1964, 43, Sagiv, J. J. Am. Chem. Soc. 1980, 102, 92. Several typical examples of organic monolayers Self-Assembled Monolayers Organosilicon/Hydroxylated surfaces (SiO 2 /Si, Al 2 O 3 /Al, Glass, etc.) Alkanethiols/Au, Ag, Cu Dialkyl sulfides, dialkyl disulfides/Au Alcohols, amines, pyridines/Au, Pt Carboxylic acids/Al 2 O 3, Ag (acid-base interaction --> salt) Self-assembled monolayers are molecular assemblies that are formed spontaneously by the immersion of an appropriate substrate into a solution of an active surfactant in an organic solvent.

Nov.5, 2003 Surface-active headgroup Interchain van der waals and electrostatic interactions Surface group Alkyl, or derivatized- alkyl group Chemisorption Surface A schematic view of the forces in a self-assembled monolayer Electroactive Groups in SAMs Ferrocene Viologen Quinone Porphyrin Bioactive Molecules in SAMs Electroactive Biomolecules in SAMs Inorganic composites and particles in SAMs Polymers in SAMs Self-Assembled Monolayers

Nov.5, 2003 Extended SAM Systems Small Organic Molecules -Classical SAMs Inorganic Ions/AtomsMetal Atoms UPD of Ag, Cu, Ni, Pb, etc. I - /I S 2- /S ca.1- SCN - NSC - Charged negatively, or positively Neutral Tail group Conjugated ChainNon-conjugated CN - Bulk Chain Different Headgroups, eg. -SH, Pyridyl, etc. Headgroup (unconventional SAM systems)