A MPB intensified tube microreactor system for continuous synthesis of Ag+ doped CdS quantum dots

Recent advances in microreactor technology have established these systems as promising platforms for colloidal nanocrystal synthesis. Nevertheless, the continuous production of high-quality doped quantum dots (QDs) with precise control over optical properties continues to present significant technical challenges. This study introduces a micropacked bed (MPB) intensified tube microreactor system for the efficient and continuous synthesis of Ag+ doped CdS QDs (CdS:Ag+ doped-QDs). Through systematic optimization of reaction parameters, the MPB system achieved photoluminescent quantum yield (PLQY) of 50.8% under optimized conditions (18 cm MPB filled with 2.0 mm glass beads, 0.2 mL/min flow rate, and 70 °C reaction temperature), and the yield increased to 64.6%. These results represent significant improvements over the traditional batch flask method (40% PLQY, 43.01% yield) and the microreactor method (43% PLQY, 48.41% yield). The developed MPB system demonstrates multiple operational advantages: reaction duration reduced to 30 minutes, simplified fluidic architecture requiring only two pumps (vs. three in conventional systems), and enhancement in flow rate (0.2 mL/min vs. 40 μL/min). Production capacity analysis revealed 6-fold and 2.67-fold increases in CdS:Ag+ doped-QDs output compared to batch flask method and microreactor method, respectively, per unit time. This continuous flow strategy establishes a viable pathway for industrial-scale synthesis of doped quantum dots with enhanced process efficiency and material quality.