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Despite remarkable progress, colloidal synthesis of metal nanocrystal is still far away from reaching the goal for robust, reproducible, and scalable production. Even with the adoption of seed-mediated growth, the synthesis can still be complicated by issues such as self-nucleation, galvanic replacement, stochastic symmetry reduction, and unwanted compositional variation. All these issues can be addressed by switching to steady-state synthesis characterized by a slow, constant, and tightly controlled reduction rate. Steady-state synthesis can be achieved by adding one reactant dropwise while using the other reactant in large excess, but this method is not suitable for scale-up production in a continuous flow reactor. There is a pressing need to develop alternative methods capable of establishing the steady-state kinetics characteristic of dropwise addition while introducing both reactants by one-shot injection. In this Perspective, we discuss a number of methods that allow for both one-shot injection and steady-state synthesis. 

Abstract This work investigates the kinetics and mechanistic details involved in the synthesis of phenolic resin beads when formaldehyde is added in one‐shot or dropwise to react with an excess amount of 3‐aminophenol. In one‐shot synthesis, the sharp rise in formaldehyde concentration, [F], to a high level leads to a rapid kinetics that triggers simultaneous substitution, condensation, and polymerization reactions for the formation of homogeneous, fully‐cross‐linked beads that cannot be etched by acetone. Conversely, dropwise synthesis, characterized by a significantly lower [F] in the early stage, results in the formation of low‐substitution monomers, which then polymerize into heterogeneous beads consisting of a cross‐linked shell and an etchable core. With dropwise addition, it can precisely control the level of [F] in the reaction mixture to obtain resin beads with tunable diameters. After etching away the lightly‐crosslinked core, the beads can be carbonized to obtain hollow carbon beads sought for applications in catalysis and energy storage.