Transient response to perturbations in flow synthesis of citrate capped gold nanoparticles

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-08, Vol.470, p.143890, Article 143890
• Main Authors: Bari, Atul H., Shukla, Neerja, Gavriilidis, Asterios, Kulkarni, Amol A.
• Format: Article
• Language: English
• Subjects: Continuous flow synthesis; Gold nanoparticles; Particle size; Segmented flow; Unsteady behavior
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2023.143890

•This is the first ever report on response to transient perturbations in flow synthesis of Au NP.•Experimentally obtained kinetics were used for developing mathematical model for predicting dynamics.•Inline UV–vis spectra helped monitor the real time response to perturbations in temperature and flow rate.•A small change in process variables for short duration needed significantly long time to reach a steady new particle size.•The effect of temperature variation was seen to have the slowest effect on reaching a new steady state. This work reports the transient behavior of continuous flow synthesis of gold nanoparticles (Au NPs) when subjected to perturbations in operating conditions using controlled experiments. The intricacies are captured through a detailed mathematical model. Reversed Turkevich protocol was used for synthesis of Au NPs. The synthesis was first studied in batch mode to investigate the reaction kinetics and reproducibility of the process. The optimal set of operating conditions viz., residence time, flow rate, temperature was then used for flow synthesis in a 2 m, 1/16″ Polytetrafluoroethylene (PTFE) reactor with micromixer. Reactor clogging was avoided by using segmented flow. Inline UV measurement was used for real time monitoring of the process. Transient experiments were performed by abruptly changing the operating conditions. A mathematical model was found to be accurate in predicting the transient behavior of the exit precursor concentration and the particle size for unsteady state synthesis. Even a small change in process variables for short duration was found to disturb the quality of Au NPs for a significantly longer duration. Of the three operating parameters, the effect of temperature variation was seen to have a prolonged effect where the system remained in unsteady state for long time.