Stepwise self-assembly of ordered supramolecular assemblies based on coordination chemistry.
Ultrathin multilayers based on transition metal complexes have been prepared by successive deposition and self-assembly. Dendrimer layers were deposited onto SiO2 wafers by alternately immersing the substrate into a solution of terpyridyl (tpy)-pendant poly(amido amine) (PAMAM) dendrimers (dend-n-tpy; n = 8, 16) dissolved in CH2Cl2, followed by the interfacial coordination reaction with cobalt (Co2+) from aqueous solution. The films derived from this simple assembly method have been characterized by electrochemical methods, synchrotron-based X-ray reflectivity (XRR), and X-ray fluorescence (XRF) recorded under grazing incidence. XRR analysis revealed a linear thickness dependence with an increase of 9.9 +/- 0.5 angstroms and 10.8 +/- 0.4 angstroms per growth cycle for both dend-8-tpy and dend-16-tpy, respectively, indicative of a layer-by-layer (LbL) growth of single dendrimer/Co2+ layers. XRF and electrochemical results showed that the amount of Co2+ increases linearly as more layers are deposited, and that the Co2+ concentration (mol/L) in dend-8-tpy/Co2+ films decays slowly as the number of growth cycles (l) increases. Moreover, a preliminary kinetics analysis indicated that the growth of a dendrimer layer in a deposition cycle is a self-limiting process.
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
Daniel R
DR
Blasini
Samuel
S
Flores-Torres
Detlef-M
DM
Smilgies
Héctor D
HD
Abruña
D050091:Dendrimers / Q000737:chemistry; D004563:Electrochemistry; D046911:Macromolecular Substances / Q000737:chemistry*; D011073:Polyamines / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission; D017356:Synchrotrons
D050091:Dendrimers; D046911:Macromolecular Substances; C104700:PAMAM Starburst; D011073:Polyamines