A new method is described to prepare strongly bonded, compact monolayer films of alkyl- or arylphosphonates on the native oxide surface of Si (SiO(2)/Si). This method is illustrated for octadecyl- and alpha-quarterthiophene-2-phosphonates. For both cases, AFM shows comprehensive coverage of the SiO(2)/Si surface. The thickness of the continuous film of 4TP/SiO(2)/Si was measured both by AFM and by X-ray reflectivity to be ca. 18 A. Direct gravimetric analysis shows surface coverage by alpha-quarterthiophene-2-phosphonate to be about 0.66 nmol/cm(2), which corresponds to molecular packing in the film close to that of crystalline alpha-quarterthiophene. Coverage by octadecylphosphonate was ca. 0.90 nmol/cm(2), corresponding to a cross-sectional area of about 18.5 A(2)/molecule, consistent with close-packed alkyl chains.

A new method is described for surface modification of ITO with an electroactive organic monolayer. This procedure was done to enhance hole injection in an electronic device and involves sequential formation of a monolayer of a pi-conjugated organic semiconductor on the indium tin oxide (ITO) surface followed by doping with a strong electron acceptor. The semiconductor monolayer is covalently bound to the ITO, which ensures strong adhesion and interface stability; reduction of the hole injection barrier in these devices is accomplished by formation of a charge-transfer complex by doping within the monolayer. This gives rise to very high current densities in simple single layer devices and double layer light emitting devices compared to those with untreated ITO anodes.

Experimental SectionGeneral. Aminopropyl(triethoxy)silane (1) (Gelest), 3-maleimidopropionic acid N-hydroxysuccinimide ester (3) (Aldrich, 99%), and RGDC (American Peptide) were used as received. Acetonitrile was distilled from CaH2.Titanium(III) Dihydrogen Orthophosphate on Ti-6Al-4V (TiP). Disks of Ti-6Al-4V ELI ( 3 /8 in. diameter) were sanded first with 240 grit and then 600 grit silicon carbide paper, rinsed, and sonicated successively with methylene chloride, methyl ethyl ketone, and methanol, dried, and stored in an oven at 200 °C. The disks were placed in a solution of aqueous phosphoric acid (1.4 M) as previously described for pure Ti. 16 TiP was identified as the sole surface species present, by X-ray diffraction analysis.Attachment of RGD to Ti-6Al-4V ELI via the TiP Interface. Disks of Ti-6Al-4V ELI coated with TiP were placed in a Teflon well, treated with a solution of 1 (10 mM in THF), and then solvent rinsed with sonication to give surface-bound 2 (IR: νCH 2 ) 2925, 2860 cm -1 ; residual νOH ) 3200 cm -1 ; νNH 2 group ) 1575 cm -1 9 ). The disks were then placed in solutions of 3 (5 mM in acetonitrile) for 18 h at room temperature. The disks were removed from solution, solvent evaporated, and analyzed by IR. They were then rinsed in acetonitrile with sonication and dried in vacuo (0.1 Torr) to give surface-bound 4 (IR: νCO(asymm) ) 1709 cm -1 ; absorbance intensity ≈0.1% vs ≈0.003% for the adduct prepared by direct silanization of the native oxide 9 ). A solution of RGDC (5 mM) was prepared in 5 mL of purified water (Millipore), with the pH adjusted to 6.5 using 0.1 M NaOH. Disks of 4 were left in the stirred solution of the peptide at room temperature for 24 h to give surface bound RGDC (5). They were then removed, dried, and analyzed by IR. The disks were then rinsed with water, dried, subjected to tape peel testing, and reanalyzed by IR (for 5, νCO ) 1700, 1650, 1560 (shoulder) cm -1 9 ).Attachment of RGD to Ti-6Al-4V ELI via an 11-Hydroxyundecylphosphonate Interface. Disks of Ti-6Al-4V were placed in a Teflon well and covered with a solution of

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