Abstract
Core-shell nanoparticles are promising candidates for theranostic drugs, as they combine different intrinsic properties with a small size and large surface area. However, their controlled synthesis, or the screening and optimization of synthesis conditions are often difficult and labor intensive. Through the precise control over mass and heat transfer, and automatization possibilities, microfluidic devices could be a solution to this problem in a lab scale synthesis. Here, we demonstrate a microfluidic, capillary, droplet reactor for the multi-step synthesis of iron oxide/gold core-shell nanoparticles. Through the integration of a transmission measurement at the outlet of the reactor, synthesis results can be monitored in a real-time manner. This allowed for the implementation of an optimization algorithm. Starting from three separate initial guesses, the algorithm converged to the same synthesis conditions in less than 30 minutes for each initial guess. These conditions resulted in diameter for the iron oxide core of 5.8 ± 1.4 nm, a thickness for the gold shell of 3.5 ± 0.6 nm, and a total diameter of the core-shell particles of 13.1 ± 2.5 nm. Finally, applications of the iron oxide/gold core-shell nanoparticles were demonstrated for Surface Enhanced Raman Spectroscopy (SERS), photothermal therapy, and magnetic resonance imaging (MRI).
Highlights
Core-shell nanoparticles are promising candidates for theranostic drugs, as they combine different intrinsic properties with a small size and large surface area
Extending from our previous work on the synthesis of iron oxide nanoparticles in capillary reactors, here we show the synthesis of iron oxide/gold core-shell nanoparticles in a capillary, droplet reactor
After an initial incubation of the droplets for the formation of iron oxide nanoparticles, a gold precursor solution was injected into the droplets in three separate steps, each followed by an incubation period
Summary
Core-shell nanoparticles are promising candidates for theranostic drugs, as they combine different intrinsic properties with a small size and large surface area Their controlled synthesis, or the screening and optimization of synthesis conditions are often difficult and labor intensive. Microfluidic reactors that automatically screen, optimize, or monitor reaction conditions became a valuable tool, as they can be used as an inexpensive method for developing larger reactors[28] An example of this can be seen of the microfluidic synthesis of lipid nanoparticles including an online fluorescent measurement controlling the particle quality using a feedback mechanism[29]. The entire setup can be assembled for less than $100, allowing it to be used for initial screening experiments To our knowledge, this is the first demonstration of an automated optimization of a multi-step core-shell nanoparticle synthesis in a capillary droplet reactor
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