AVS 46th International Symposium
    Biomaterial Interfaces Group Wednesday Sessions
       Session BI-WeP

Paper BI-WeP1
Self-Assembly of Tetraphenylporphyrin Monolayers on Gold Substrates

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: A.L. Bramblett, University of Washington
Authors: A.L. Bramblett, University of Washington
M.S. Boeckl, University of Washington
T. Sasaki, University of Washington
B.D. Ratner, University of Washington
J.W. Rogers, Jr., University of Washington
Correspondent: Click to Email
The development of the next generation of medical implants involves attaching appropriate biorecognition molecules in the proper orientation and concentration on the surface of an implant, to prevent the cellular activation that leads to the foreign body response, and implant encapsulation. Porphyrin molecules are ideal for the development of a uniform monolayer, with controlled, optimal spacing of biorecognition groups. Self-assembled porphyrin monolayers on gold surfaces have been demonstrated with three custom synthesized alkylthiol substituted tetraphenylporphyrin molecules. Several techniques including x-ray photoelectron spectroscopy (XPS), ultraviolet/visible absorption spectroscopy (UV/Vis), scanning tunneling microscopy (STM), and grazing-angle infrared spectroscopy (GAIR) have been used to characterize the monolayers. XPS binding energy shifts in the S(2p) spectra reveal that the porphyrins are chemisorbed to the surface through a sulfur-gold bond.@footnote 1@ A red shift without a significant blue shift of the Soret band in the UV/Vis absorption spectra demonstrates that the porphyrin molecules are aligned on the gold surface in a side-by-side orientation.@footnote 2@ GAIR with a polarized light source, indicates that the porphyrin rings are oriented parallel to the gold surface. Round STM features, approximately 2 nm in diameter, correspond closely to the diameter of tetraphenylporphyrin (1.8 nm), and are distributed relatively evenly over the surface. Finally, XPS and UV/Vis coverage calculations show approximately monolayer coverage. Taken together, this data indicates the formation of self-assembled porphyrin monolayers. @FootnoteText@ @footnote 1@ Castner, D.; Hinds, K.; Grainger, D. W. Langmuir 1996, 12, 5083-5086. @footnote 2@ Osuka, A.; Maruyama, K. J. Am. Chem. Soc. 1988, 110, 4454-4456.