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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. 

We report a versatile method based on seed-mediated growth for the facile synthesis of trimetallic Pd@PtxAu1−x core-shell nanocubes. By simply varying the feeding ratio between the Pt(II) and Au(III) precursors, the atomic ratio of Pt to Au in the shell and thereby the ensemble state of Pt atoms on the surface can be tuned to control the binding configuration of O2 molecules. Specifically, discrete Pt atoms on the surface promote the adsorption of O2 molecules in the Pauling configuration to enhance the catalytic selectivity of the nanoparticles toward H2O2 via the two-electron oxygen reduction reaction, with the Pd@Pt0.025Au0.975 nanocubes showing selectivity as high as 91% at 0.45 VRHE. This work offers a viable means to augment the electrocatalytic performance of alloy nanocrystals by controlling their surface compositions. 

Surface-enhanced Raman scattering was used to resolve the chemical species, including chloride ions, on the surface of Ag nanocrystals in their original reaction solution, avoiding changes to the surface while eliminating possible artifacts. 

Abstract Biological effectors play critical roles in augmenting the repair of cartilage injuries, but it remains a challenge to control their release in a programmable, stepwise fashion. Herein, a hybrid system consisting of polydopamine (PDA) nanobottles embedded in a hydrogel matrix to manage the release of biological effectors for use in cartilage repair is reported. Specifically, a homing effector is load in the hydrogel matrix, together with the encapsulation of a cartilage effector in PDA nanobottles filled with phase‐change material. In action, the homing effector is quickly released from the hydrogel in the initial step to recruit stem cells from the surroundings. Owing to the antioxidation effect of PDA, the recruited cells are shielded from reactive oxygen species. The cartilage effector is then slowly released from the nanobottles to promote chondrogenic differentiation, facilitating cartilage repair. Altogether, this strategy encompassing recruitment, protection, and differentiation of stem cells offers a viable route to tissue repair or regeneration through stem cell therapy.