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 their optical properties continues to present significant technical challenge. 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 a photoluminescent quantum yield (PLQY) of 50.8% under optimized conditions (18 cm MPB filled with 2.0 mm glass beads, 0.2 mL min⁻¹ 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 enhanced flow rate (0.2 mL min⁻¹vs. 40 μL min⁻¹). Production capacity analysis revealed 6-fold and 2.67-fold increases in CdS:Ag⁺ doped-QD output compared to the batch flask method and the 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.