Ultrasensitive Picomolar Detection of Aqueous Acids in Microscale Fluorescent Droplets

Wang, Hui; Wei, Zixiang; Vagin, Sergei I.; Zhang, Xuehua; Rieger, Bernhard; Meldrum, A.

doi:10.1021/acssensors.1c02076

Cited by 8 publications

(13 citation statements)

References 51 publications

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“…From the bulk solution sensing data (Figure 3), one would thus expect an improvement in the LoD by about the same factor, so the droplet LoD might be expected to be 46 μM/1053 = 43 nM for DNT. The fact that we observe a value about 1,000 times lower than this suggests an enhanced droplet partitioning effect, 40 an idea consistent with a recent report. 42 This could possibly be owing to the formation of NA complexes with the associated GQDs or to an interface-related partition enhancement.…”

Section: ■ Results and Discussionsupporting

confidence: 93%

“…This means that it is easier to perform an analysis insofar as every droplet will change in more-or-less the same fashion, although potentially at different rates. 40 To verify the droplet-sensing performance, an aqueous solution of 1 nM DNT (or alternatively NB) was pumped over the droplets. This low concentration was chosen because of the expectation that the droplets might respond much better than the bulk solutions, as the NA compound should be partitioned into the hydrophobic droplets.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…One advantage of the fluorescent droplet method, in comparison to previous colorimetric droplet-sensing results, is that the color analysis of the droplets is less affected by the droplet thickness. This means that it is easier to perform an analysis insofar as every droplet will change in more-or-less the same fashion, although potentially at different rates …”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Graphene Quantum Dot Bearing Liquid Droplets for Ultrasensitive Fluorescence-Based Detection of Nitroaromatics

Wang

Firouzi-Haji

Aghajamali

et al. 2022

ACS Appl. Nano Mater.

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Sensing and detecting nitroaromatics (NAs) are essential for environmental, health, and safety reasons. Graphene quantum dots (GQDs) respond to the presence of NAs by a well-understood fluorescence quenching mechanism. However, despite the relative simplicity of fluorescence-based sensing, the limit of detection (LoD) can compare unfavorably with other methods. Here, we show that the LoD for sensors based on GQDs can be lowered by orders of magnitude using a droplet-based analyte partitioning effect. While previous efforts have attempted to improve the intrinsic GQD sensitivity via surface functionalization and size control, we show that a major improvement can be attained by changing from a bulk solution to droplet-based sensing of 2,4-dinitrotoluene and nitrobenzene. Moreover, the method is compatible with sensing from an aqueous solvent and has broader implications for many fluorescence-quenching-based sensing strategies that could benefit from partition-related enhancements.

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Section: ■ Results and Discussionsupporting

confidence: 93%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Graphene Quantum Dot Bearing Liquid Droplets for Ultrasensitive Fluorescence-Based Detection of Nitroaromatics

Wang

Firouzi-Haji

Aghajamali

et al. 2022

ACS Appl. Nano Mater.

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“…Zeng et al proposed a device to control convective mixing: Solvent exchange. ,− Solvent exchange is an effective approach to control the volume, composition, and size distribution of the final surface nanodroplets …”

Section: Droplet Formation and Asphaltene Precipitation By Solvent Ex...mentioning

confidence: 99%

Review of Microscale Dynamics of Dilution-Induced Asphaltene Precipitation under Controlled Mixing Conditions

2022

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As the most complex and heaviest component in bitumen, asphaltene precipitation induced by solvent dilution is important in oil sands extraction to remove solids and water from bitumen froth through dilution by paraffinic solvents. This review will compare asphaltene precipitation to dilution-induced solvent shifting in aqueous systems via the ouzo effect. We attempt to highlight similarities and differences in the evolution of nanodroplets and effects from solvent mixing conditions and point out mutual experimental techniques and modeling approaches for the research of both asphaltene precipitation and nanodroplet formation. The review will start from basic concepts in both asphaltene precipitation and the ouzo effect, then move on to the effects of solvent mixing on asphaltene precipitation in bulk. After that, we will introduce advances in microfluidic systems combined with cutting-edge experimental and simulation tools for asphaltene precipitation induced under controlled mixing with solvents and a droplet formation. Such comparison will inspire more in-depth understanding and control of asphaltene precipitation and the ouzo effect in aqueous systems.

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“…The mechanism is similar to what was reported in the latest work on acid-base reactions, and is the reason why the droplet sensing can achieve very high sensitivity. 43,44…”

Section: Growing Microbubbles In Reacting Surface Dropletmentioning

confidence: 99%

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

Li¹,

Zeng²,

Zhang³

2022

Preprint

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Chemical reactions in small droplets are extensively explored to accelerate the discovery of new materials, increase efficiency and specificity in catalytic biphasic conversion and in high throughput analytic. In this work, we investigate the local rate of gas-evolution reaction within femtoliter droplets immobilized on a solid surface. The growth rate of hydrogen microbubbles (≥ 500 nm in radius) produced from the reaction was measured online by high-resolution confocal microscopic images. The growth rate of bubbles was faster in smaller droplets, and of bubbles near the three-phase boundary in the same droplet. The results were consistent for both pure and binary reacting droplets and on substrates of different wettability. Our theoretical analysis based on diffusion, chemical reaction and bubble growth in a steady state predicted that the concentration of the reactant diffusing from the surrounding depended on the droplet size and the bubble location inside the droplet, in good agreement with experimental results. Our results reveal that the reaction rate may be spatially non-uniform in the reacting microdroplets. The findings may have implications for formulating chemical properties and uses of these droplets.

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Ultrasensitive Picomolar Detection of Aqueous Acids in Microscale Fluorescent Droplets

Cited by 8 publications

References 51 publications

Graphene Quantum Dot Bearing Liquid Droplets for Ultrasensitive Fluorescence-Based Detection of Nitroaromatics

Graphene Quantum Dot Bearing Liquid Droplets for Ultrasensitive Fluorescence-Based Detection of Nitroaromatics

Review of Microscale Dynamics of Dilution-Induced Asphaltene Precipitation under Controlled Mixing Conditions

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

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