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Poster templateThe Mechanism of Photoreduction of Copper Ions Complexed to Amine-Terminated
S. F. Shuler, H. Wan, K. J. Smith, and S. C. Street
MINT Center and Department of Chemistry This project was supported by the MRSEC program & shared equipment from NSF-DMR-02-13985 Motivation
Probe Molecules for Investigating
Electron Paramagnetic Resonance Studies on G0 PAMAM
Cu2+ (H O) (complex A)
Cu2+-(N)-(NH) (complex B)
Dendrimers are highly branched, three-dimensional globular macromolecules that have distinct characteristics and properties.1 The chemical functionalities of poly(amidoamine) (PAMAM) or gII = 2.390
gII = 2.30
poly(propyleneimine) (PPI) dendrimers provide sites for metal cation coordination. Subsequent chemical reduction, usually with sodium borohydride, produces metallic-dendrimer nanocomposites. An alternative method for reducing metal ions has become known through employing UV photoreduction to the metal ion-dendrimercomplex without the need of additional reactants. Researchers stated the idea of photodecomposition of the dendrimer that yields carbonyl compounds that may induce reduction.2 mechanism of the photoreduction process has not been investigated In this study, we focus our attention on determining the source of electrons within the dendrimers that are used to reduce the metal Several molecules with amine functionalities were used to investigate (1) Tomaila, D. A.; Naylor, A. M.; Goddard, W. A. Angew Chem. Int. Ed. 1990, 29, 138-175.
the mechanism of the photoreduction process. However, only the 1- hydroxyurea molecule complexed with Cu2+ ions. TEM images (2) Esumi, K.; Suzuki, A.; Aihara, N.; Usui, K.; Torigoe, K. Langmuir 1998, 14, 3157-3159.
EPR results show the localized nitrogen environment changing upon revealed the metal-hydroxyurea complex did not produce any complexation with Cu2+ as a function of pH. Acidic conditions protonate nanoparticles after irradiation with UV light. coordination sites (e.g., tertiary and primary amines) and prevent Cu2+ from complexation. At neutral or slightly basic conditions, the terminal primaryamines may undergo protonation to a small extent, but the tertiary amines are Dendrimers as Functional Components
Cu & G4 PAMAM
Cu & G4 PAMAM (irradiated)
Results have shown that there are crucial Cu2+ & G4
criteria in the photoreduction process: (1) 60 hr irradiated
coordination and the number of amine sites N radical
are critical for particle formation; (2) tertiary and secondary amines contribute major roles in providing electrons for reducing Cu2+ from Wavelength (nm)
Cu & G5 PPI
Cu2+ & G5 PPI (irradiated)
EPR spectra (above) of a) Cu2+ with G0 dendrimer before irradiation
Cu2+ & G5
and b) Cu2+ with G0 dendrimer after 45 min irradiation in toluene at 77 Dendrimer
60 hr irradiated
K. Irradiation was conducted with a mercury lamp (λ Shelby Shuler
UV-vis spectra (right) of Cu2+ complexed with PAMAM and PPI
dendrimers. Reduction of Cu2+ is evident (PAMAM solution) with Dr. Shane Street
increasing slope, which strongly suggests aggregation among Cu email@example.com
atoms. Reduction of Cu2+ is not as evident (PPI solution) since the before and after irradiation appears similar. “G” is define as generation.
Center for Materials for Information Technology
The University of Alabama
an NSF Materials Research Science and Engineering Center
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