Synthesis of Pt Double-Walled Nanoframes with Well-Defined and Controllable Facets

In this paper, we demonstrate the synthesis of morphologically complex nanoframes wherein a mixture of frames and thin solid planes, which we refer to as walled-nanoframes, are present in a single particle. By applying multiple chemical steps including shape evolution of Au nanocrystals and controlling chemical potential of solution for selective deposition, we successfully designed a variety of Pt nanoframes including Pt cuboctahedral nanoframes and Pt single-walled nanoframes. The rationale for on-demand chemical steps with well-faceted Au overgrowth allowed for the synthesis of double-walled nanoframes where two Pt single-walled nanoframes are concentrically overlapped in a single entity with a clearly discernible gap between the two nanoframes. Given the coexistence of an open structure of nanoframe and thin plates within one entity, the double-walled nanoframes showed a dramatic increase in catalytic activity toward the methanol oxidation reaction, acting as high-surface area, carbon-free, and volume-compact nanocatalysts.

Can an InChI for Nano Address the Need for a Simplified Representation of Complex Nanomaterials across Experimental and Nanoinformatics Studies?

Chemoinformatics has developed efficient ways of representing chemical structures for small molecules as simple text strings, simplified molecular-input line-entry system (SMILES) and the IUPAC International Chemical Identifier (InChI), which are machine-readable. In particular, InChIs have been extended to encode formalized representations of mixtures and reactions, and work is ongoing to represent polymers and other macromolecules in this way. The next frontier is encoding the multi-component structures of nanomaterials (NMs) in a machine-readable format to enable linking of datasets for nanoinformatics and regulatory applications. A workshop organized by the H2020 research infrastructure NanoCommons and the nanoinformatics project NanoSolveIT analyzed issues involved in developing an InChI for NMs (NInChI). The layers needed to capture NM structures include but are not limited to: core composition (possibly multi-layered); surface topography; surface coatings or functionalization; doping with other chemicals; and representation of impurities. NM distributions (size, shape, composition, surface properties, etc.), types of chemical linkages connecting surface functionalization and coating molecules to the core, and various crystallographic forms exhibited by NMs also need to be considered. Six case studies were conducted to elucidate requirements for unambiguous description of NMs. The suggested NInChI layers are intended to stimulate further analysis that will lead to the first version of a "nano" extension to the InChI standard.

An optical Bragg scattering readout for simultaneous detection of all low-order mechanical modes of gallium nitride nanowires in nanowire arrays

We report the use of optical Bragg scattering and homodyne interferometry to simultaneously measure all the first order cantilever-mode mechanical resonance frequencies and quality factors (Q) of gallium nitride nanowires (GaN NWs) in 100 NW periodic selected-area growth arrays. Hexagonal 2D arrays of 100 GaN NWs with pitch spacings of 350-1100 nm were designed and prepared to allow optical Bragg scattering. The NWs studied have diameters ranging from 100-300 nm, lengths from 3-10 μm, resonance frequencies between 1-10 MHz, and Q-values near 10,000 at 300 K. The system can passively detect the thermally induced Brownian mechanical motion of the NWs and can study driven NW motion, enabling the simultaneous monitoring of hundreds of mechanical resonators in a 10-100 μm² area with a single optical beam. The read-out system allows large arrays of NWs to be characterized and applied as e.g. spatially resolved temperature and mass sensors.

Complex Nanostructures from Materials based on Metal-Organic Frameworks for Electrochemical Energy Storage and Conversion

Metal-organic frameworks (MOFs) have drawn tremendous attention because of their abundant diversity in structure and composition. Recently, there has been growing research interest in deriving advanced nanomaterials with complex architectures and tailored chemical compositions from MOF-based precursors for electrochemical energy storage and conversion. Here, a comprehensive overview of the synthesis and energy-related applications of complex nanostructures derived from MOF-based precursors is provided. After a brief summary of synthetic methods of MOF-based templates and their conversion to desirable nanostructures, delicate designs and preparation of complex architectures from MOFs or their composites are described in detail, including porous structures, single-shelled hollow structures, and multishelled hollow structures, as well as other unusual complex structures. Afterward, their applications are discussed as electrode materials or catalysts for lithium-ion batteries, hybrid supercapacitors, water-splitting devices, and fuel cells. Lastly, the research challenges and possible development directions of complex nanostructures derived from MOF-based-templates for electrochemical energy storage and conversion applications are outlined.