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(Fe(Htrz)2(trz))(BF4) nanoparticle production in a milli-scale segmented flow crystalliser

corresponding

KAREN ROBERTSON1*, PIERRE-BAPTISTE FLANDRIN1, HELENA J. SHEPHERD2, CHICK C. WILSON1
*Corresponding author
1. Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
2. School of Physical Sciences, University of Kent,Canterbury, Kent, CT2 7NH, United Kingdom

Abstract

Microfluidics has become well established as the benchmark method of nanoparticle production but the need for special equipment and the challenge of scale-up can make it prohibitive for many laboratories. In contrast, the larger scale millifluidics methodology provides a platform for controlled nanoparticle production in a simple set-up without risk of blockages, increasing the volume of material produced while continuing to offer control over particle attributes. Nanoparticle size can have a profound effect on the properties exhibited, in the case of spin-crossover materials the size of nanoparticles can have a direct correspondence with the hysteresis of magnetic susceptibility vs temperature. Nanoparticle synthesis of the spin-crossover coordination polymer (Fe(Htrz)2(trz))(BF4) (Htrz = 1,2,4-1H-triazole) has hitherto been reported through batch methods alone. Here we present the first flow synthesis of (Fe(Htrz)2(trz))(BF4) in a milli-scale segmented flow crystalliser (the Kinetically Regulated Automated Input Crystalliser, KRAIC).


INTRODUCTION
One of the most well exploited areas of flow chemistry is nanoparticle production. Due to the inherent property/size relationship (1) of nanoparticles it is vital to synthesise them with careful control over particle morphology and dispersity. Most nanoparticles are synthesised through either reactive or anti-solvent crystallisation, which relies upon homogeneity of initial mixing conditions for homogeneity of product, which is particularly difficult to achieve in batch conditions. Microfluidic devices have been successfully used to synthesise a range of nanoparticles with a very narrow particle size distribution (PSD) (2-4) The intense mixing conditions imparted by micromixers, enables control over the nucleation, growth and quenching of nanoparticl