Fluorescence based sensors are attractive owing to its ultra-sensitivity and ability to detect the analyte of interest with high specificity. Many metal ions although play vital role in ample number of biological events, few are highly toxic and even fatal.^1,2 Hence, the field of metal ion detection using fluorescence spectroscopic technique has received tremendous attention in recent years.³ Among the fluorophores used for the metal ion detection, semiconductor based quantum dots such as CdTe, CdSe and CdS quantum dots have been exploited extensively for sensor applications on account of their bright and tuneable luminescence and ease of preparation.^4,5

The present report focuses on the fluorescence based detection of Hg²⁺ ions using green-yellow emitting CdTe quantum dots, which perform as both signalling and analyte specific material. A complete characterization of CdTe quantum dots and CdTe-Hg²⁺ is carried out to confirm the formation of quantum dots and to understand the quenching mechanism. Here the emission of quantum dots is quenched by the addition of Hg²⁺, hypothesized to be due to the electron transfer mechanism. The sensor responds to Hg²⁺ in the linear range of 12 to 40 μM with a limit of detection 2 μM. Further, an easy visual detection strategy for Hg²⁺ is also established by dropcasting CdTe quantum dots over a glass plate.

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