Governing factors for preparation of silver nanoparticles using droplet-based microfluidic device
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Governing factors for preparation of silver nanoparticles using droplet-based microfluidic device O. Kašpar 1 & A. H. Koyuncu 1 & A. Pittermannová 1 & P. Ulbrich 2 & V. Tokárová 1
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Droplet-based microfluidic devices are now more than ever used for the synthesis of nanoparticles with low polydispersity and well-defined properties suitable for various industrial applications. Very small reaction volumes (microlitre to femtolitre) and short diffusion lengths, provide superior mixing efficiency and heat transport. Both play the dominant role in case of ultra-fast chemical reactions triggered upon reactant mixing, e.g. preparation of colloidal silver by reduction of silver salt. The high sensitivity of these systems to process variables makes otherwise more straightforward batch-wise production prone to suffer from inconsistency and poor reproducibility, which has an adverse effect on the reliability of production and further particle utilisation. This work presents a rigorous description of microfluidic droplet formation, reactant mixing, and nanoparticle synthesis using CFD simulations and experimental methods. The reaction mixture inside of droplets was homogenized in less than 40 milliseconds, which has been confirmed by simulations. Silver nanoparticles produced by droplet-based microfluidic chip showed superior to batch-wise preparation in terms of both particle uniformity and polydispersity. Keywords Two-phase flow . Nanoparticles . Droplets . CFD simulation . Mixing efficiency
1 Introduction Nanoparticles (NPs) of various sizes (1 to 100 nm), shapes (e.g., spheres (Agnihotri et al. 2014), triangles (Chandran et al. 2006), rods (Dahl et al. 2007) or stars (Minati et al. 2014)) and materials have found their applications in a wide variety of different fields. Thanks to their high surface area to volume ratio and quantum effects NPs poses in contrast to bulk material unique properties dependant on their size, shape and surface chemistry (Albanese et al. 2012; Elahi et al. 2018; Mody et al. 2010). Among the most investigated materials can be listed iron oxide, gold and silver which have been tailored specifically for diagnostic and therapeutic purposes. Superparamagnetic iron particles have found their application in magnetic positioning and on-demand release of active ingredients upon exposure to an external stimulus such as * V. Tokárová [email protected] 1
Department of Chemical Engineering, University of Chemistry and Technology, Prague, Technická 3, Prague 166 28, Czechia
2
Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague, Technická 3, 166 28 Prague, Czechia
radiofrequency heating (Haša et al. 2018; Kovačík et al. 2013), or in combination with responsive polymers for magnetic drug targeting (Zhang et al. 2007). Gold NPs are commonly used in optics and imaging (Zhang et al. 2013), biosensors (Cottat et al. 2013), catalysis (Atta et al. 2018) or surfaceenhanced Raman scattering (Tal
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