AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP11
Covalent Attachment of Pt-Dendrimer Encapsulated Nanoparticles to 11-Mercaptoundecanoic Acid Thin Films

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Surface Science Poster Session
Presenter: D.A. Chen, University of South Carolina
Authors: T.J. Black, University of South Carolina
K.A. Perrine, University of South Carolina
Y. Gu, University of South Carolina
H.J. Ploehn, University of South Carolina
D.A. Chen, University of South Carolina
Correspondent: Click to Email
Polyamidoamine dendrimers represent a diverse tool for chemical and biological research due to their functionality and highly tunable properties. The work presented here takes advantage of the dendrimer's ability to act as a nanoscale template for controlling the size distribution of metal particles formed in solution. Specifically, amine-terminated, generation 4 polyamidoamine dendrimers (G4-NH@sub 2@) are treated with K@sub 2@PtCl@sub 4@ in a metal:dendrimer ratio of 40:1 to coordinate approximately 40 Pt@super 2+@ ions inside each dendrimer. Subsequent reduction with NaBH@sub 4@ is believed to form metallic Pt particles ~2 nm in diameter according to transmission electron microscopy studies. We have optimized a procedure that covalently links the dendrimer encapsulated nanoparticles onto a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) on Au(111) surfaces; this robust dendrimer film allows for various mechanical and chemical treatments that would not otherwise be possible. After the MUA monolayer is exposed to EDC (1-[3-(diethylamino)propyl]-3-ethylcarbodiimide hydrochloride) and an NHS (hydroxysuccinic acid)catalyst followed by treatment with the dendrimer solution, infrared reflection absorption spectroscopy (IRAS) experiments suggest that amide bonds are formed between the SAMs and the dendrimer by the disappearance of the carboxylic acid mode at 1722 cm@super -1@ from the MUA accompanied by the appearance of amide modes at 1670 cm@super -1@ and 1556 cm@super -1@. X-ray photoelectron spectroscopy also confirmed the presence of Pt-G4NH@sub 2@ on the SAMs since nitrogen and platinum signals were detected. The next step of this project will be to remove the dendrimer templates and SAM from the Au(111) surface by oxidation-reduction cycles, leaving behind the Pt nanoparticles. The ultimate goal of this work is to study the surface chemistry of the supported, well-characterized Pt particles in model catalytic reactions, such as CO oxidation.