Dendrimers make more sense

Branching molecules detect the presence of metals. Click on picture to enlarge view

Italian and German researchers have increased the sensitivity to cobalt ions of a fluorescent monodansyl compound by thirty-two times by converting it into a branching, dendrimeric form. The discovery could lead to the development of new highly sensitive detectors for a variety of important metal ions.

Vincenzo Balzani and his colleagues at the University of Bologna working with Fritz Vögtle's team at the University of Bonn realised that molecules that glow can be quickly switched off by attaching a metal ion. This is the basis of fluorescent sensors in which the presence of a metal quenches the fluorescent glow of an organic molecule. The degree of quenching indicates the amount of metal ion present.

	Vincenzo Balzani, a glowing report on dendrimers

The Italian-German team has now built a branching polymer, known as a dendrimer, which incorporates a receptor unit that can "catch" metal ions in solution and a fluorescent unit whose glowing properties change in response.

Fritz Vögtle, branching out in science with dendrimers

The fourth-generation dendrimer created by the team is based on a monodansyl building block and can detect cobalt ions at concentrations as low as 4.6 x 10^-6 molar. They point out, however, that an observable response is obtained at a tenth this concentration.

According to the team the well-defined and fully programmable structures of dendrimers make them promising species for sensors. They point out that the ability to daisy chain the dendrimers adds the possibility of signal amplification which boosts the sensor's power.

Reference:
Chem. Commun, 2000, 853^*.

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