A compact time-gated instrument for QDs with low excitation energy and millisecond fluorescence lifetime as signal reporters, and its detection application

Abstract

Recently, bright quantum dots (QDs) possessing low energy for excitation and long fluorescence lifetime in milliseconds have been reported. These QDs such as Mn doped I(II)-III-VI nanocrystals are promising for highly sensitive time-gated sensing applications with a portable or small benchtop “personal” instrument because their unique optical properties not only ensure a high signal-to-background ratio in time-gated fluorescence-intensity (TGFI) measurement but also significantly simplify the TGFI measurement instrument design criteria. In this work, following up the research progress on these QDs, we developed a compact TGFI measurement instrument with high sensitivity and cost-effectiveness for these QDs (more specifically Mn:AZIS/ZnS QDs) as signal reporters. We applied the instrument for sensitive detection of copper(ii) ions in highly autofluorescent rum (alcoholic beverage) in a fluorescence quenching assay utilizing these QDs for signal transduction. The results from this work suggest that this instrument together with bright QDs with low-energy for excitation and long fluorescence lifetimes should have potential to not only convert many regular (non-time-gated) QD-based fluorescence assays to time-gated assays for higher sensitivities or lower LODs, but also facilitate the development of highly sensitive assays for in-field or point-of-care testing.

Optical Properties of Mn-Doped CuGa(In)S-ZnS Nanocrystals (NCs): Effects of Host NC and Mn Concentration

“…The setup consisted of a 405 nm laser-excitation source (20 mW) and its circuit driver, a cuvette and its holder, a photosensor with a bandpass filter (607 ± 18 nm), and optical fibers for excitation-light delivery and emission-light collection [ 41 ]. The 405 nm laser diode was turned on/off through its circuit driver with repeated pulses at a 0.5 kHz rate with 40% duty cycle.…”

A Highly Sensitive Time-Gated Fluorescence Immunoassay Platform Using Mn-Doped AgZnInS/ZnS Nanocrystals as Signal Transducers

“…Figure 1A presents the small time-gated immunoassay platform integrating a time-gated optical detector and a microplate-based immunoassay using Mn:AgZnInS/ZnS NC probes as signal transducers. Compared to our previously reported instrument [ 20 ], we kept all electronics but redesigned the optical path for microwell-based detection. Figure 1B illustrates the design of the optical unit using a dichroic-filter ZT514rc (Chroma) to split excitation and emission light.…”

“…As shown in Figure 2D , the calibration curve established by the non-time-gated microplate reader (with 405 nm excitation) indicates a LOD at ~273 ng/ml. For the time-gated system, its electronics design/setting and the data processing of this platform are the same as what we reported [ 20 ]: the gain control voltage of PMT is at 1.080 V (a maximum value) to achieve the highest gain for the input light to current conversion, the laser diode is pulsed with 200 μs for excitation with a repetition rate of 1.024 kHz, and the delay time after laser-off is 50 μs, and the time period to pick up the signal (the detection window) is 100 μs. The calibration curve measured using this platform (with a 405 nm laser as excitation) is shown in Figure 2E and presents a LOD of ~354 pg/ml.…”

“…We have recently presented a compact time-gated fluorescence instrument using Mn:AgZnInS/ZnS NC-based probes as signal reporters and applied it for sensitive detection of copper(II) ions in highly autofluorescent rum (alcoholic beverage) [ 20 ]. Nevertheless, this system adopted a quartz cuvette with a volume of several milliliters as the sample holder and an optical path corresponding to such a cuvette.…”

Polymer dots and derived hybrid nanomaterials: A review

“…104,105 The PD-based fluorescent nanoprobes detect Fe 2þ , Fe 3þ , Cu 2þ , Zn 2þ and biomolecules. [106][107][108] The polymer dot based hybrid nanomaterials may overcome the challenges of traditional quantum dot sensors such as low sensitivity and low efficiency. Polymer dot based nanocomposites have also been exploited in electronic devices.…”