Luminescent CdTe nanocrystals as ion probes and pH sensors in aqueous solutions

CdTe nanocrystals capped by short-chain thiol molecules can easily be prepared in aqueous solution, possess a single narrow emission band and can potentially be used as luminescence sensors and ions probes. We report the effect of pH and various ions, including physiology important cations such as calcium(II), manganese(II) and iron(III), on the luminescence intensity of CdTe nanocrystals capped by thioglycolic acid. Quenching of luminescence of CdTe nanocrystals by Ag(I)-cations points out their use in cellular studies as fluorescent labels and quenching agents, respectively. Micromolar amounts of Hg2+ ions caused quenching of the emission of CdTe nanocrystals, while at increasing Hg2+ concentration alloyed CdxHg1−xTe nanocrystals were formed, followed by appearance of a near-infrared luminescence band. Luminescence of both bare CdTe nanocrystals and CdTe nanocrystals embedded into polymer microcapsules was found to be pH sensitive within the pH range of 4–6.