Spectrophotometric titration of bimetallic metal cation binding in polyamido(amine) dendrimer templates

Katherine A. Marvin, Justin A. Johnson, Stacia E. Rodenbusch, Lucy Gong, David A. Vanden Bout, Keith J. Stevenson

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Spectrophotometric titration and a binding isotherm were used to accurately assess the loading capacity of generation four polyamido(amine) (PAMAM) dendrimer templates with terminal alcohol groups (G4-OH). Preparation of bimetallic G4-OH dendrimer-encapsulated metal nanoclusters (DENs) necessitates knowledge of the precise metal-ion binding capacity. The binding of metal ions such as Pt2+ and Pd2+ has proven difficult to assess via UV-vis spectroscopy because the absorbance shifts associated with metal-ion binding within the dendrimer template are masked by the absorbance of the PAMAM dendrimer itself. In contrast, the binding of Cu2+ to G4-OH PAMAM dendrimer results in a strong, distinct absorption band at 300 nm, making UV-vis spectrophotometric titration with copper straightforward. Here we use copper binding as a means to assess the number of binding sites remaining within the PAMAM G4-OH dendrimer after the complexation of a specified molar excess of Pd2+ or Pt2+. In addition, we use a binding isotherm to mathematically estimate the loading capacity of the dendrimer in each case. The loading capacities for M2+ in the G4-OH dendrimer were found to be ∼16 for copper alone, ∼21 for copper combined with palladium, and ∼25 for copper combined with platinum.

Original languageEnglish
Pages (from-to)5154-5158
Number of pages5
JournalAnalytical Chemistry
Volume84
Issue number11
DOIs
Publication statusPublished - 5 Jun 2012
Externally publishedYes

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