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Conjugating Luminescent CdTe Quantum Dots with Biomolecules

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journal contribution
posted on 20.11.2008, 00:00 by Christina Gerhards, Christian Schulz-Drost, Vito Sgobba, Dirk M. Guldi
Newly prepared CdTe quantum dots (QD) bearing shells of water solubility providing capping agents (i.e., thioglycolic acid (TGA) and 2-(dimethylamino)ethanethiol hydrochloride (DMAET) were subjected to electrostatic assays with several proteins (i.e., cytochrome c (cyt c) and human serum albumin (HSA)). In particular, we employed absorption, emission, transient absorption and time-resolved emission spectroscopic means to test their response to light. Only for negatively capped QDs spectroscopic and kinetic evidence were gathered that corroborate the successful bioconjugation of QDs with cyt c to yield QDcyt c bioconjugates. In fact, photoexcitation of QDcyt c leads to a fast deactivation of the QD band gap emission and of the QD excited state. Notably, these interactions depend on the size of the QDs. Repulsive forces, on the other hand, are operative between the positively capped QDs and cyt c, hampering any bioconjugation.