A scalable synthesis of ternary nanocatalysts for a high-efficiency electrooxidation catalysis by microfluidics

Kinetically Controlled Nucleation Enabled by Tunable Microfluidic Mixing for the Synthesis of Dendritic Au@Pt Core/Shell Nanomaterials

The nucleation stage plays a decisive role in determining nanocrystal morphology and properties; hence, the ability to regulate nucleation is critical for achieving high-level control. Herein, glass microfluidic chips with S-shaped mixing units are designed for the synthesis of Au@Pt core/shell materials. The use of hydrodynamics to tune the nucleation kinetics is explored by varying the number of mixing units. Dendritic Au@Pt core/shell nanomaterials are controllably synthesized and a formation mechanism is proposed. As-synthesized Au@Pt exhibited excellent ethanol oxidation activity under alkaline conditions (8.4 times that of commercial Pt/C). This approach is also successfully applied to the synthesize of Au@Pd core/shell nanomaterials, thus demonstrating its generality.

Spontaneous Phase Segregation Enabling Clogging Aversion in Continuous Flow Microfluidic Synthesis of Nanocrystals Supported on Reduced Graphene Oxide

Eliminating clogging in capillary tube reactors is critical but challenging for enabling continuous-flow microfluidic synthesis of nanoparticles. Creating immiscible segments in a microfluidic flow is a promising approach to maintaining a continuous flow in the microfluidic channel because the segments with low surface energy do not adsorb onto the internal wall of the microchannel. Herein we report the spontaneous self-agglomeration of reduced graphene oxide (rGO) nanosheets in polyol flow, which arises because the reduction of graphene oxide (GO) nanosheets by hot polyol changes the nanosheets from hydrophilic to hydrophobic. The agglomerated rGO nanosheets form immiscible solid segments in the polyol flow, realizing the liquid-solid segmented flow to enable clogging aversion in continuous-flow microfluidic synthesis. Simultaneous reduction of precursor species in hot polyol deposits nanocrystals uniformly dispersed on the rGO nanosheets even without surfactant. Cuprous oxide (Cu₂O) nanocubes of varying edge lengths and ultrafine metal nanoparticles of platinum (Pt) and palladium (Pd) dispersed on rGO nanosheets have been continuously synthesized using the liquid-solid segmented flow microfluidic method, shedding light on the promise of microfluidic reactors in synthesizing functional nanomaterials.

A Review of Microfluidic Experimental Designs for Nanoparticle Synthesis

Microfluidics is defined as emerging science and technology based on precisely manipulating fluids through miniaturized devices with micro-scale channels and chambers. Such microfluidic systems can be used for numerous applications, including reactions, separations, or detection of various compounds. Therefore, due to their potential as microreactors, a particular research focus was noted in exploring various microchannel configurations for on-chip chemical syntheses of materials with tailored properties. Given the significant number of studies in the field, this paper aims to review the recently developed microfluidic devices based on their geometry particularities, starting from a brief presentation of nanoparticle synthesis and mixing within microchannels, further moving to a more detailed discussion of different chip configurations with potential use in nanomaterial fabrication.

Continuous-flow syntheses of alloy nanoparticles

Alloy nanoparticles (NPs), including core-shell, segregated and solid-solution types, show a variety of attractive properties such as catalytic and optical properties and are used in a wide range of applications. Precise control and good reproducibility in the syntheses of alloy NPs are highly demanded because these properties are tunable by controlling alloy structures, compositions, particle sizes, and so on. To improve the efficiency and reproducibility of their syntheses, continuous-flow syntheses with various types of reactors have recently been developed instead of the current mainstream approach, batch syntheses. In this review, we focus on the continuous-flow syntheses of alloy NPs and first overview the flow syntheses of NPs, especially of alloy NPs. Subsequently, the details of flow reactors and their chemistry to synthesize core-shell, segregated, solid-solution types of alloy NPs, and high-entropy alloy NPs are introduced. Finally, the challenges and future perspectives in this field are discussed.