*Review* **Optical Sensors Based on II-VI Quantum Dots**

#### **Anna Lesiak 1,2, Kamila Drzozga 1, Joanna Cabaj 1,\*, Mateusz Ba ´nski 2, Karol Malecha 3 and Artur Podhorodecki 2,\***


Received: 30 December 2018; Accepted: 28 January 2019; Published: 2 February 2019

**Abstract:** Fundamentals of quantum dots (QDs) sensing phenomena show the predominance of these fluorophores over standard organic dyes, mainly because of their unique optical properties such as sharp and tunable emission spectra, high emission quantum yield and broad absorption. Moreover, they also indicate no photo bleaching and can be also grown as no blinking emitters. Due to these properties, QDs may be used e.g., for multiplex testing of the analyte by simultaneously detecting multiple or very weak signals. Physico-chemical mechanisms used for analyte detection, like analyte stimulated QDs aggregation, nonradiative Förster resonance energy transfer (FRET) exhibit a number of QDs, which can be applied in sensors. Quantum dots-based sensors find use in the detection of ions, organic compounds (e.g., proteins, sugars, volatile substances) as well as bacteria and viruses.

**Keywords:** nanomaterials; colloidal quantum dots; sensors; detection mechanisms
