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. 2020 Mar 4;59(9):3730-3735.
doi: 10.1021/acs.iecr.9b04230. Epub 2019 Nov 5.

On-demand Milifluidic Synthesis of Quantum Dots in Digital Droplet Reactors

Craig Richard  1   2 , Rachel McGee  1 , Aditya Goenka  3 , Prabuddha Mukherjee  1 , Rohit Bhargava  1   2   4   5
Affiliations

On-demand Milifluidic Synthesis of Quantum Dots in Digital Droplet Reactors

Craig Richard et al. Ind Eng Chem Res. .

Abstract

Colloidal quantum dots (QDs) offer dramatic potential due to their size-dependent optical properties. Lack of facile synthesis methods for precise and reproducible size and composition, however, present an extant barrier to their widespread use. Here we report the use of droplet microfluidics for the simple and highly reproducible synthesis of cadmium sulfide (CdS) and cadmium selenide (CdSe) QDs without the use of harsh solvents and in ambient conditions. Our approach uses a liquid-liquid barrier between two immiscible liquids to generate a digital droplet reactor. This reaction droplet is easily controlled and manipulated and offers enhanced mixing when coupled to a helical mixer, resulting in a significant reduction in size distribution compared to benchtop procedures. Furthermore, QD characteristics have modeled and predicted based on the parameters of the microfluidic device. We believe this method overcomes the current manufacturing challenges with synthesizing nanostructures, which is required for the next generation of nanosensors.

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Figures

Figure 1:
Figure 1:
Schematic representation of the droplet reactor microfluidic device. Flow was visualized in the devices by replacing the metal and chalcogen precursors with water soluble dyes. The inset are images obtained during each of the conditions. The righthand schematic is an image based on those observations. (Case 1 and Case 2) Images of the formation of droplets as different flow rates. (Case 1) Demonstrates the merging of droplets at low flow rate value. Droplets merge within the junction of the device. (Case 2) Demonstrates the merging of droplets at a selected high flow rate. A train of unmixed droplets emerge from the junction that later merge.
Figure 2
Figure 2
(a) Absorbance spectra of synthesized CdS and CdSe QDs (b) Raman spectra of synthesized CdS and CdSe QDs (c) representative TEM images synthesized CdS QDs(d) representative TEM images synthesized CdSe QDs
See this image and copyright information in PMC

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