Continuous flow synthesis of small silver nanoparticles involving hydrogen as the reducing agent

Two narrow-channel reactor designs have been developed and used in conjunction with gas-liquid segmented flow in order to intensify reactions and to effect synthesis under continuous flow conditions, incorporating single pass and recirculating capability, under high pressure and temperature. Silver nanoparticles approximately 3-5 nm in diameter are accessible with the average size depending on the reaction temperature and polyphosphate concentration, with smaller and more monodisperse nanoparticles produced at low polyphosphate concentrations and low temperatures. The use of continuous flow conditions leads to the possibility of simple scale-up to commercial production.