Microflow reactor synthesis of palladium nanoparticles stabilized with poly(benzyl ether) dendron ligands

Abstract

A simple glass capillary microflow reactor system has been applied for the synthesis of palladium nanoparticles by thermal decomposition of palladium acetate (Pd(OAc)2) in diphenyl ether in the presence of poly(benzyl ether) dendron ligands (PBED Gn- NH2, n = 1-3) as a stabilizer. Effect of hydrodynamic parameters (capillary diameter, linear flow rate, volume flow rate, and reaction temperature) and concentrations (precursor and stabilizer) on the par- ticle size was investigated. The particle size can be controlled by varying linear flow rate and temperature as well as ligand/precursor concentration ratio. Vol- ume flow rate does not affect the particle size when the linear flow rate is held constant for different capillary diameters (150-320 lm). Unlike batch sys- tems, in this microreactor system, smaller particles are produced at low ligand concentrations when the molar ratio of the ligand to metal precursor ranged from 1 to 5. As another characteristic of the microreactor synthe- sis, the concentration of the Pd precursor can be increased (up to 27 mM) with maintaining a constant particle size (3.1 ± 0.2 nm) and a good monodisper- sity, while in the batch system a significant increase and broadening in the particle size are observed with increasing precursor concentration.