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Review
. 2019 Feb 2;9(2):192.
doi: 10.3390/nano9020192.

Optical Sensors Based on II-VI Quantum Dots

Anna Lesiak  1   2 , Kamila Drzozga  3 , Joanna Cabaj  4 , Mateusz Bański  5 , Karol Malecha  6 , Artur Podhorodecki  7
Affiliations
Review

Optical Sensors Based on II-VI Quantum Dots

Anna Lesiak et al. Nanomaterials (Basel). .

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: colloidal quantum dots; detection mechanisms; nanomaterials; sensors.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
(a) TEM image of hydrophilic CdSe quantum dots. Schematic structure of selected quantum dot after synthesis (a1), after surface functionalization (with examples of most typical functional groups) (a2) and after bioconjugation (with examples of most common biomolecules used for detection/targeting) (a3). (b,c) Digital images of CdSe quantum dots dispersed in water with and without laser excitation.
Figure 2
Figure 2
(a) Emission spectra from CdS QDs (left side) and PbS QDs (right side) with different size and chemical composition; (b) absorbance and emission spectra of CdSe/CdS quantum dots; (c) emission and absorption spectra of Rhodamine; (d) emission intensity vs illumination time for CdSe/CdS QDs and Rhodamine.
Figure 3
Figure 3
Signal processing characteristics for living organisms and sensor machines.
Figure 4
Figure 4
Three examples of the strategy of QDs-based optical sensors (strategy a—modification of substrate with QDs directed to detection of analyte, strategy b—modification of substrate for detection of analyte-QDs complex, strategy c—using the analyte labeled with appropriate fluorophore).
Figure 5
Figure 5
Examples of physico-chemical mechanisms used for analyte optical detection—emission bleaching (a), increase of emission (b), emission localization (c), nanostructures growth’s modification (d), emission change (e).
Figure 6
Figure 6
Examples of physico-chemical mechanisms responsible for quantum dots emission quenching—energy transfer from QD to analyte (a), charge transfer from analyte to QD (b), degradation of QD surface (c).
Figure 7
Figure 7
Different detection possibilities with use of nonradiative energy-transfer phenomena.
See this image and copyright information in PMC

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