On the role of wall thickness in determining the plasmonic properties of silver-gold nanocages.

This work examines the roles played by wall thickness in determining the plasmonic properties of gold-silver (Ag-Au) nanocages. Ag-Au cages with different wall thicknesses, but the same void or outer size, shape, and elemental composition, were designed as a model platform. The experimental findings were understood with theoretical calculations. This study not only investigates the effect of wall thickness but also provides an effective knob to tailor the plasmonic properties of hollow nanostructures.

Morphology-Invariant Metallic Nanoparticles with Tunable Plasmonic Properties.

Current methods for tuning the plasmonic properties of metallic nanoparticles typically rely on alternating the morphology (i.e., size and/or shape) of nanoparticles. The variation of morphology of plasmonic nanoparticles oftentimes impairs their performance in certain applications. In this study, we report an effective approach based on the control of internal structure to engineer morphology-invariant nanoparticles with tunable plasmonic properties. Specifically, these nanoparticles were prepared through selective growth of Ag on the inner surfaces of preformed Ag-Au alloyed nanocages as the seeds to form Ag@(Ag-Au) shell@shell nanocages. Plasmonic properties of the Ag@(Ag-Au) nanocages can be conveniently and effectively tuned by varying the amount of Ag deposited on the inner surfaces, during which the overall morphology of the nanocages remains unchanged. To demonstrate the potential applications of the Ag@(Ag-Au) nanocages, they were applied to colorimetric sensing of human carcinoembryonic antigen (CEA) that achieved low detection limits. This work provides a meaningful concept to design and craft plasmonic nanoparticles.

Template Regeneration in Galvanic Replacement: A Route to Highly Diverse Hollow Nanostructures.

The ability to produce a diverse spectrum of hollow nanostructures is central to the advances in many current and emerging areas of technology. Herein, we report a general method to craft hollow nanostructures with highly tunable physical and chemical parameters. The key strategy is to regenerate the nanoscale sacrificial templates in a galvanic replacement reaction through site-selective overgrowth. As examples, we demonstrate the syntheses of nanocages and nanotubes made of silver, gold, palladium, and/or platinum with well-controlled wall thicknesses and elemental distributions. Using the nanocages of silver and gold as models, we demonstrate they possess intriguing plasmonic properties and offer superior performance in biosensing applications. This study provides a powerful platform to customize hollow nanostructures with desired properties and therefore is expected to enable a variety of fundamental studies and technologically important applications.

A general approach to multicomponent metal-decorated crumpled reduced graphene oxide nanocomposites using a flame-based process.

We introduce a general approach for synthesizing multicomponent metal-decorated crumpled reduced graphene oxide nanocomposites using a one-step, continuous flame-based process. Crumpled reduced graphene oxide balls (CGB) were produced from graphene oxide (GO) in a High Temperature Reducing Jet (HTRJ) reactor. Moreover, CGBs were simultaneously decorated with different transition metal nanoparticles, including cobalt (Co), nickel (Ni), iron (Fe), and palladium (Pd). Various metal alloy-decorated crumpled reduced graphene oxide balls (M-CGBs) including CoPd-, CoNi-, CoPdNi-, and CoNiFe-CGBs were successfully synthesized using a general recipe. The key advantage of the HTRJ system over common flame-based aerosol synthesis methods is the separation of flame and product formation zones, which allows production and/or reduction of nanomaterials that can be reduced by H2 in the presence of H2O. Nanomaterials are produced from aqueous precursors containing low-cost metal salts and dispersed GO. Electron microscopy and other characterization methods show the decoration of the CGBs with sub-4 nm diameter binary and ternary alloy, non-oxide transition metal nanoparticles of controlled compositions. The nanostructures made by this process can potentially be used as electrocatalysts for fuel cells, electrodes in batteries and supercapacitors, conductive inks for printed electronics, catalysts in wastewater treatment, and many other applications where a graphitized carbon-metal nanomaterial is needed.

An affinity-based aqueous two-phase mixed micellar system and its purification of Yeast 3',5'-bisphosphate nucleotidase.

Aqueous two-phase micellar system (ATPMS), as an alternative liquid-liquid extraction technique, has been extensively exploited for the precise separation or large-scale concentration of biomolecules. In this article, a novel affinity-based ATPMS composed of mixed micelles was constructed by introducing a Copper-chelated Triton X-114 (TX-Cu(II)) into an aqueous solution of hydrophobically modified ethylene oxide polymer (HM-EO). Phase diagram of the HM-EO/TX-Cu(II) system was measured, and the partitioning behavior of model proteins (YND, BSA, lysozyme) were studied by using this new system. The addition of HM-EO can result in formation of the micellar network in the micelle-rich phase, making the phase separation easier and stabler. In addition, the extractive performance of ATPMS was enhanced due to the existence of the mixed micelles composed by HM-EO and Cu(II)-chelated TX. It was found in the partitioning experiments that the hexahistidine-tagged Yeast 3',5'-bisphosphate nucleotidase (YND) was selectively extracted into the micelle-rich phase, while the histidine-poor proteins (BSA and lysozyme) remained in the micelle-poor phase. Finally, HM-EO/TX-Cu(II) was used directly to process the fermentation broth. The target protein, YND could be recovered from the cell lysate with a recovery yield of 49.23% and purification factor of 2.63. The results indicated that the new affinity-based HM-EO/TX-Cu(II) system had high partitioning performance which is promising for effectively separation of the histidine-tagged proteins.