Water‐Soluble Off–On Spin‐Labeled Quantum‐Dots Conjugate

Engineering quantum dots (QDs) with a paramagnetic nitroxide radical tail yields a weakly fluorescent spin-labeled QD conjugate. Quenching of the intrinsic fluorescence of the QDs results from electron transfer between the QDs and nitroxide radical. Interestingly, when the paramagnetic properties of the nitroxide moiety are eliminated, the quenched fluorescence of QDs is readily restored, making the spin-labeled QDs sensitive to a biological antioxidant, vitamin C (Vc; see figure). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2296/2008/smll200700788_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.