3D-printed microfluidic device for the synthesis of silver and gold nanoparticles

For the first time, a 3D-printed microfluidic device based on fused deposition modeling was created using poly(lactic acid) as the 3D-printed part on top of a poly(methyl methacrylate) slide, allowing the creation of transparent microfluidic channels and used on the continuous-flow synthesis of silver and gold nanoparticles. In order to reduce fouling inside the microchannels, the device was optimized to use a segmented flow of mineral oil. The synthesized nanoparticles were characterized by UV–Visible spectroscopy and scanning and transmission electron microscopy. Silver nanoparticles were synthesized using different concentrations of sodium borohydride and flow rates of reactants (30 and 120 μL min−1) at 20 °C, with sizes ranging from 5 ± 2 nm to 8 ± 3 nm and verified to be stable for at least three weeks. Subsequently, the silver nanoparticles were applied on measurement of gallic acid using a modified carbon paste electrode. Gold nanoparticles were synthesized at 90 °C varying the concentration of trisodium citrate and flow rates of reactants (40 and 100 μL min−1), yielding sizes from 20 ± 9 to 34 ± 12 nm and verified to be stable for at least three weeks. Afterwards, the gold nanoparticles were employed in surfaced enhanced Raman scattering using crystal violet as model molecule.