Dendritic Ternary Alloy Nanocrystals for Enhanced Electrocatalytic Oxidation Reactions

Engineering the morphology and composition of multimetallic nanocrystals composed of noble and 3d transition metals has been of great interest due to its high potential to the development of high-performance catalytic materials for energy and sustainability. In the present work, we developed a facile aqueous approach for the formation of homogeneous ternary alloy nanocrystals with a dendritic shape, Pt–Pd–Cu nanodendrites, of which synthesis is hard to be achieved because of synthetic difficulties. Proper choice of stabilizer and fine control over the amount of stabilizer and reductant allowed the successful formation of Pt–Pd–Cu nanodendrites with controlled sizes and compositions. The prepared ternary alloy nanodendrites exhibited considerably improved electrocatalytic performance toward methanol and ethanol oxidation reactions compared to their binary alloy counterparts and commercial Pt and Pd catalysts, as well as to previously reported Pt- and Pd-based nanocatalysts because of synergism between their morphological and compositional characteristics. We anticipate that the present approach will be helpful to develop efficient electrocatalysis systems for practical applications

Universal Sulfide-Assisted Synthesis of M–Ag Heterodimers (M = Pd, Au, Pt) as Efficient Platforms for Fabricating Metal–Semiconductor Heteronanostructures

We report a universal sulfide-assisted synthesis strategy to prepare dumbbell-like M–Ag heterodimers (M = Pd, Au, Pt). Sulfide ions can give fine control over the reaction kinetics of Ag precursors, resulting in the anisotropic overgrowth of Ag to realize the dumbbell-like heterodimers irrespective of the surface facets or components of the M domain. The M–Ag heterodimers were facilely transformed to M–Ag₂S heterodimers via a simple sulfidation reaction. This study provides a versatile approach to realizing not only metal–metal heterodimers but also semiconductor–metal heterodimers and will pave the way for designing heteronanostructures with unprecedented morphologies and functions

Multimetallic Alloy Nanotubes with Nanoporous Framework

One-dimensional nanotubes (NTs) that consist of multiple metallic components are promising platforms for potential applications, whereas only a few synthetic methods of multimetallic NTs have been reported to date. In the present work, we developed a general synthesis route for the production of uniform multicomponent one-dimensional tubular nanostructures with various combinations of Pt, Pd, and Ag by using ZnO nanowires (NWs) as sacrificial templates. The ZnO NWs serve not only as physical templates but also as nucleation sites for the reduction of metal precursors, and thereby several metal precursors could be reduced simultaneously to produce multimetallic NTs. By using this approach, Pt–Pd, Pt–Ag, and Pd–Ag binary alloy NTs, and even Pt–Pd–Ag ternary alloy NTs could be successfully prepared. The prepared Pt–Pd binary alloy NTs exhibited improved electrocatalytic activity and stability toward ethanol oxidation due to their characteristic tubular morphology with well-interconnected nanoporous framework and synergism between two constituent metals. Furthermore, our approach can facilitate the fabrication of patterned multimetallic NT arrays on solid and flexible substrates with strong mechanical robustness. The present templating method does not require any extra steps to remove templates or additional surfactants which are often required to control the shape of nanostructures. This strategy offers a convenient, versatile, low-cost, and highly valuable approach to the fabrication of multimetallic nanostructures with various components and compositions

Charting Microbial Phenotypes in Multiplex Nanoliter Batch Bioreactors

High-throughput growth phenotyping is receiving great attention for establishing the genotype–phenotype map of sequenced organisms owing to the ready availability of complete genome sequences. To date, microbial growth phenotypes have been investigated mostly by the conventional method of batch cultivation using test tubes, Erlenmeyer flasks, or the recently available microwell plates. However, the current batch cultivation methods are time- and labor-intensive and often fail to consider sophisticated environmental changes. The implementation of batch cultures at the nanoliter scale has been difficult because of the quick evaporation of the culture medium inside the reactors. Here, we report a microfluidic system that allows independent cell cultures in evaporation-free multiplex nanoliter reactors under different culture conditions to assess the behavior of cells. The design allows three experimental replicates for each of eight culture environments in a single run. We demonstrate the versatility of the device by performing growth curve experiments with <i>Escherichia coli</i> and microbiological assays of antibiotics against the opportunistic pathogen <i>Pseudomonas aeruginosa</i>. Our study highlights that the microfluidic system can effectively replace the traditional batch culture methods with nanoliter volumes of bacterial cultivations, and it may be therefore promising for high-throughput growth phenotyping as well as for single-cell analyses