![]() Polytetrafluoroethylene (PTFE) tubing (1 mm inner diameter, VICI Jour) was used for all tubing, and ferrules and fittings made of polyether ether ketone (PEEK) (Upchurch) were used for all required connections in the experimental set-up. cm) was used for all aqueous solutions in all experiments.Basic blue 3 (C 20H 26ClN 3O, Sigma-Aldrich) was used for the evaluation of the liquid-liquid separation using the membrane separator. H 2O, Sigma-Aldrich), trisodium citrate (Na 3Ct: Na 3C 6H 5O 7♲H 2O, Fisher Scientific), Gold (III) chloride trihydrate (HAuCl 4∙3H 2O, Sigma-Aldrich) and n-heptane (≥ 99 %, CH 3(CH 2) 5CH 3, Sigma-Aldrich) and were of analytical grade.The reactants used in this work were citric acid (H 3Ct: C 6H 8O 7 An online UV-Vis spectrometer allows live monitoring of the quality of the synthesised nanoparticles and hence assessment of the stability and yield of the manufacturing process. A membrane separator is implemented for the separation and collection of the two phases in flow (the aqueous phase comprising the colloidal Au NPs and the organic phase). A two-phase flow system, using heptane as the continuous phase is used to prevent fouling on the reactor walls. The aim of this work is the targeted synthesis of 10–20 nm citrate-capped Au NPs. The throughput could potentially increase up to 5 g/day, followed by ultrafiltration and dialysis for sample purification. Operating at 95 oC with 5 min residence time, yielded monodisperse particles of ~ 15 nm in size. ![]() developed a segmented flow tubular reactor (SFTR) for the synthesis of citrate-capped spherical Au NPs. Two-phase flow using toluene as the continuous phase (the colloidal Au NPs were formed in the aqueous disperse phase) avoided fouling on the hydrophobic capillary walls, but absorption of the particles at the liquid-liquid interface was observed. Kulkarni and Sebastian Cabeza compared the toluene-water two-phase flow in a hydrophobic PTFE capillary reactor (inner diameter: 2.5 mm) and a hydrophilic microreactor (similar to Sebastian Cabeza et al. The air-water system provided the best internal recirculation in the aqueous slugs, improving the residence time distribution. The smallest particles were synthesised in the air-water system (2.8 ± 0.2 nm), while the silicon oil-water system resulted in a bimodal particle size distribution (7.8 ± 6.5 and 15.5 ± 3.1 nm). Due to the hydrophilicity of the silicon channels, water was the continuous phase. Wagner and Köhler used a continuous flow microreactor for the reduction of \(HAu\) for the synthesis of Au NPs (aqueous phase) in a silicon microreactor (channel depth x width: 400 μm x 400 μm) segmented by air, toluene or silicone oil. Single-phase micro- and milli-reactors have been investigated due to the rapid heat and mass transfer and minimising particle size distribution. In the past years, there have been several attempts for the translation of batch Au NPs syntheses towards continuous flow processing. These applications have also been driving the demand for translation from lab-scale synthesis to scalable production and for further downstream processing for appropriate functionalisation. This has led to the need for robust and sustainable manufacturing platforms for the delivery of high quality, uniform shape and monodisperse Au NPs. ![]() The unique properties of gold nanoparticles (Au NPs) have instigated research in their biomedical applications, drug delivery and antimicrobial applications. This study addresses the challenges for the translation of the synthesis from batch to flow and provides tools for the development of a continuous manufacturing platform for gold nanoparticles. Process yield increased at higher inlet flow rates (from 70 % to almost 100 %), due to lower residence time of the colloidal solution in the separator resulting in less fouling in the PTFE membrane. A hydrophobic membrane separator provided successful separation of the aqueous and organic phases and collection of colloidal Au NPs in flow. The synthesis was stable and reproducible over time for gold precursor concentration above 0.23 mM (after mixing), resulting in average particle size between 12 and 15 nm. Continuous syntheses for up to 2 h demonstrated its potential application for continuous manufacturing, while live quality control was established using online UV-Vis photospectrometry that monitored the particle size and process yield. The use of a two-phase flow system – using heptane as the continuous phase – prevented fouling on the reactor walls, while improving the residence time distribution. A continuous manufacturing platform was developed for the synthesis of aqueous colloidal 10–20 nm gold nanoparticles (Au NPs) in a flow reactor using chloroauric acid, sodium citrate and citric acid at 95 oC and 2.3 bar(a) pressure.
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