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Experimental and computational analysis of mixing inside droplets for microfluidic fabrication of gold nanoparticles

Emulsions formed by mixing reactant streams inside microdroplets are efficient micro-scale reactors for synthesis of nano/micro- particles/crystals due to small quantities of reagents confined within each droplet and separation of droplet contents from the reactor walls. In this work, the synthesis of size-tuneable gold nanoparticles (AuNPs) within emulsion droplets generated in a three-phase glass capillary microfluidic device was investigated experimentally and numerically using computational fluid dynamics (CFD). AuNPs were produced by micromixing two aqueous streams, 1.15 mM HAuCl4 containing 1% polyvinylpyrrolidone capping agent and 20 mM ascorbic acid solutions, inside monodispersed droplets created by 3D counter-current flow focusing in a medium-chain triglyceride. The mean particle size of AuNPs was tuneable in the range between 26 and 56 nm and depended on the degree of premixing of the reactant streams shortly before droplet generation, and the mixing efficiency within droplets, which was controlled by hydrodynamic conditions within the microfluidic device. The CFD results were compared and validated against experimental observations and revealed the presence of a recirculation zone near the outer wall of the injection capillary tip. The mixing efficiency was higher at smaller droplet size causing a reduction in the particle size of the AuNPs.

Funding

EPSRC grant EP/HO29923/1

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Chemical Engineering

Published in

Industrial & Engineering Chemistry Research

Publisher

American Chemical Society

Version

AM (Accepted Manuscript)

Rights holder

© 2021 American Chemical Society

Publisher statement

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Industrial & Engineering Chemistry Research, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.iecr.1c01960

Acceptance date

06/09/2021

Publication date

2021-09-16

ISSN

0888-5885

eISSN

1520-5045

Language

en

Depositor

Dr Brahim Benyahia. Deposit date: 6 September 2021