Jet-mixing reactor for the production of monodisperse silver nanoparticles using a reduced amount of capping agent

Commonly used batch reactors for nanomaterial synthesis can be difficult to scale since rapid particle nucleation and growth require efficient mixing to produce monodisperse particle size distributions (PSD). Monodisperse particles can be synthesized through efficiently mixing the reactants in the liquid phase using a jet-mixing reactor. Using common synthesis precursors and concentrations, the jet-mixing reactor produces silver nanoparticles with a diameter of 5 +/- 2 nm, as characterized by TEM, and a monomodal surface plasmon resonance (SPR) in the UV-vis spectrum. In comparison, a batch synthesis using the same concentrations of reactants produces nanoparticles with a diameter of 9 +/- 4 nm and a bimodal SPR, indicating that jet-mixing produces a more monodisperse particle size distribution than batch synthesis. For the jet-mixing synthesis, the concentration of the capping agent can be reduced to a value of 0.05 mM while retaining a narrow full-width of half-maximum (FWHM) of the SPR spectrum. Interestingly, decreasing the capping agent quantity from the standard concentration of 0.2 mM to 0.05 mM decreases the FWHM of the SPR, corresponding to a more monodisperse PSD at lower capping agent concentration. This result is attributed to the increased stabilization at lower ion concentrations in the solution. For low capping agent concentrations, additional experiments adding small amounts of sodium nitrate support this observation. Overall, the jet-mixing reactor represents a viable system for the continuous production of size-controlled silver nanoparticles with reduced amounts of capping agent.