A general phase-transfer protocol for metal ions and its application in nanocrystal synthesis. Nat. Mater. 8, 683

Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, Singapore 138669, Singapore.
Nature Materials (Impact Factor: 36.5). 08/2009; 8(8):683-9. DOI: 10.1038/nmat2490
Source: PubMed


Nanocrystals prepared in organic media can be easily self-assembled into close-packed hexagonal monolayers on solvent evaporation for various applications. However, they usually rely on the use of organometallic precursors that are soluble in organic solvents. Herein we report a general protocol to transfer metal ions from an aqueous solution to an organic medium, which involves mixing the aqueous solution of metal ions with an ethanolic solution of dodecylamine (DDA), and extracting the coordinating compounds formed between the metal ions and DDA into toluene. This approach could be applied towards transferring a wide variety of transition-metal ions with an efficiency of >95%, and enables the synthesis of a variety of metallic and semiconductor nanocrystals to be carried out in an organic medium using relatively inexpensive water-soluble metal salts as starting materials. This protocol could be easily extended to synthesize a variety of heterogeneous semiconductor/noble-metal hybrids and to nanocomposites with multiple functionalities.

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Available from: Edward H Sargent, Jun 12, 2015
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    • "Platinum (Pt) nanoparticles are catalytically active for the anodic reaction (methanol oxidation reaction, MOR) of the direct methanol fuel cell (DMFC)123. Hollowing platinum (Pt) nanoparticles with galvanic replacement or scarificial templates offers a promising approach to meet the high performance goals in electrocatalysis456789. For intance, Fan and co-workers developed a photocatalytic approach using densely packed optically active porpyrins to template the synthesis of well-defined hollow Pt nanostructures which were excellent catalyst for the methanol oxidation reaction (MOR)7. "
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    ABSTRACT: The integration of different components into a hybrid nanosystem for the utilization of the synergistic effects is an effective way to design the electrocatalysts. Herein, we demonstrate a hybrid strategy to enhance the electrocatalytic property of hollow structured Pt nanoparticles for methanol oxidation reaction. This strategy begins with the preparation of bimetallic Ag-Pt nanoparticles with a core-shell construction. Element sulfur is then added to transform the core-shell Ag-Pt nanostructures into hybrid nanodimers consisting of Ag2S nanocrystals and remaining Pt domains with intact hollow interiors (Ag2S-hPt). Finally, Au is deposited at the surface of the Ag2S domain in each hetero-dimer, resulting in the formation of ternary Ag2S-Au-hPt nanocomposites with solid-state interfaces. The ternary nanocomposites exhibit enhanced electrocatalytic property toward methanol oxidation due to the strong electronic coupling between Pt and other domains in the hybrid particles. The concept might be used toward the design and synthesis of other hetero-nanostructures with technological importance.
    Full-text · Article · Aug 2014 · Scientific Reports
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    • "contained within each NC, these nanoscale materials are generally represented by an exact chemical formula: Au m (SR) n where m and n are the numbers of Au atoms and thiolate ligands respectively [9]. Unlike traditional nanocrystals [10] having a size within the length scale of 3–100 nm, NCs exhibits discrete electronic structure and molecular-like behaviour. However, the successful biological applications of these thiolated NCs will require a better understanding of the NCs parameters that can potentially impact biological interactions and functions. "
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    ABSTRACT: Au nanoclusters (AuNCs) hold tremendous potential to be employed in a wide variety of biological applications. Despite the rapid development in the field of NCs synthesis, a comprehensive understanding of how cells interact with this class of ultra-small nanoparticles (<2 nm) having defined sizes and surface chemistry, remains poorly understood. In this study, we show that the choice of the surface ligand used to protect AuNCs can significantly perturb cellular uptake and intracellular redox signaling. A panel of monodisperse, atomically precise AuNCs with different core Au atom number (i.e., Au15, Au18 and Au25) protected with either mercaptopropionic acid (MPA) or glutathione (GSH) capping agent were synthesized and their effects on the generation of intracellular reactive oxygen species (ROS), cytotoxicity and genotoxicity of the NCs were assessed. Both mitochondrial superoxide anion (O2 ·−) and cytoplasmic ROS were found to be higher in cells exposed to MPA but not GSH capped AuNCs. The unregulated state of intracellular ROS is correlated to the amount of internalized AuNCs. Interestingly, MPA-AuNCs induction of ROS level did not lead to any detrimental cellular effects such as cell death or DNA damage. Instead, it was observed that the increase in redox status corresponded to higher cellular metabolism and proliferative capacity. Our study illustrates that surface chemistry of AuNCs plays a pivotal role in affecting the biological outcomes and the new insights gained will be useful to form the basis of defining specific design rules to enable rational engineering of ultra-small complex nanostructures for biological applications.
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    • "Finally, the as-prepared ternary Au@Ag2S-Pt nanocomposites were transferred from aqueous phase to toluene using an approach developed for the phase transfer of metal nanoparticles and ions3637. Phase transfer of the nanocomposites from aqueous phase to a non-polar organic medium was conducted since we experimentally found that the loading efficiency of the particles on XC-72C carbon supports from the organic medium (~99%) was much higher than that from the aqueous phase (~37%). "
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    ABSTRACT: Mastery over the structure of nanomaterials enables control of their properties to enhance their performance for a given application. Herein we demonstrate the design and fabrication of Pt-based nanomaterials with enhanced catalytic activity and superior selectivity toward the reactions in direct methanol fuel cells (DMFCs) upon the deep understanding of the mechanisms of these electrochemical reactions. In particular, the ternary Au@Ag2S-Pt nanocomposites display superior methanol oxidation reaction (MOR) selectivity due to the electronic coupling effect among different domains of the nanocomposites, while the cage-bell structured Pt-Ru nanoparticles exhibit excellent methanol tolerance for oxygen reduction reaction (ORR) at the cathode because of the differential diffusion of methanol and oxygen in the porous Ru shell of the cage-bell nanoparticles. The good catalytic selectivity of these Pt-based nanomaterials via structural construction enables a DMFC to be built without a proton exchange membrane between the fuel electrode and the oxygen electrode.
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