Green synthesis of time-stable palladium nanoparticles using microfluidic devices

A systematic comparison between batch and continuous systems was performed for the synthesis of palladium nanoparticles (PdNPs). An eco-friendly protocol was used in which glucose and starch were the reducer and capping agents, respectively. The material morphology, particle size distribution and catalytic activity for the reduction of 4-nitrophenol of both suspensions was studied in two states: (i) fresh and (ii) 7 months-stored. XRD, UV-vis, FTIR and TEM techniques were used for the material characterization. The catalytic results together with the characterization evidences lead to the conclusion that palladium nanoparticles obtained with the microreactor give rise to more stable suspensions with smaller size and narrower particle size distribution, as compared to the ones obtained with the batch system (continuous system: 4.40 +/- 1.68 nm vs batch method: 7.18 +/- 21.14 nm for the fresh samples). In addition, the TOF of the PdNPs prepared using the microfluidic system proved to be better than the resulted from the suspension prepared using the batch system (749 h(-1) and 505 h(-1), respectively). On the other hand, the higher stability of the material obtained in the microreactor could be confirmed, as the TOF value remained constant even after 7 months of storage in aqueous media (753 h(-1) for the microreactor vs 336 h(-1) for the batch set-up).