Alkynyl ligands-induced growth of ultrathin nanowires arrays.

Ligands are almost essential in the synthesis of nanostructures. In this work, we introduce the alkynyl ligands into the synthesis of ultrathin gold (Au) nanowires arrays. The strong binding affinity of the alkynyl ligands enables one-dimensional (1D) growth via the active surface growth mechanism. The scope of the ligand generality was systematically investigated, and the alkynyl ligand-induced nanowire growth processes were compared and contrasted with those involving thiolated ligands. While strong ligands are usually difficult to dissociate from the nanostructure surface and therefore problematic for post-synthetic processing, the alkynyl ligands are readily dissociable, making the alkynyl ligand-stabilized Au nanowires potentially more modifiable and applicable. As a demonstration, direct palladium (Pd) deposition on the Au nanowires was successfully carried out without any ligand exchange process.

Template-less Synthesis of Coded Au Nanowires.

Morphological coding of nanostructures represents a capability in rapid modulation of structural features and most importantly, the transcription of information into nanoscale. Exploiting the regioselectivity in the template-less electrochemical synthesis of ultrathin Au nanowires, we show that rapid alternation of applied potential would cause corresponding change in the width of the emerging nanowire segments. By understanding the growth kinetics, a strong correlation between the nanowire morphologies and the deposition potential is established and applied in emulating the Morse code.

Noble metal nanowire arrays as an ethanol oxidation electrocatalyst.

Vertically aligned noble metal nanowire arrays were grown on conductive electrodes based on a solution growth method. They show significant improvement of electrocatalytic activity in ethanol oxidation, from a re-deposited sample of the same detached nanowires. The unusual morphology provides open diffusion channels and direct charge transport pathways, in addition to the high electrochemically active surface from the ultrathin nanowires. Our best nanowire arrays exhibited much enhanced electrocatalytic activity, achieving a 38.0 fold increase in specific activity over that of commercial catalysts for ethanol electrooxidation. The structural design provides a new direction to enhance the electrocatalytic activity and reduce the size of electrodes for miniaturization of portable electrochemical devices.

Precise Dimerization of Hollow Fullerene Compartments.

Controlled docking, merging, and welding of hollow structures at the nanoscale are essential in constructing sophisticated hollow systems in ways similar to plumbing and biosystems. To this end, regioselectivity is an important milestone demanding new tools. We bring the steric effect, a powerful regioselective method in organic reactions, to the nanoscale. By tuning the exposed liquid area of Janus nanobowls, the sterics of the merging m-xylene liquid template can be precisely modulated, giving high-purity dimers (93.6%) and tetramers (80.6%) in one step. The shape uniformity of the nanobowls, the precise percentage of the exposed liquid, and, most importantly, the error correction in merging liquid domains are the critical factors leading to the precise regioselectivity. We believe that the development of a new regioselective tool and the understanding in docking and welding hollow structures would expand the horizon of nanoscience, opening new possibilities for designing sophisticated nanosystems.

Controllable syngas production on gold nanowires/nickel foam electrode in non-aqueous system.

A hierarchical electrode is prepared with Au nanowires grown on nickel foam. With large specific active surface area, it is used for producing syngas (H2/CO) with controllable ratio, through electrochemical process in DMF. The synthetic innovation lies in the use of 3-cyanopropyltriethoxysilane, to achieve the adsorption of appropriate amount of Au seeds for the one-dimensional growth of ultrathin Au nanowires (d ≈ 5 nm). With the nanowires forest on the three-dimensional porous nickel foam substrate, syngas is produced by electro-catalysis with high overall Faradic efficiency and tunable H2/CO ratios. This synthetic strategy opens a facile way to synthesize the hierarchical nanostructured materials, and broaden the choice of the catalysts for electrochemical applications.

The Synthesis of Hollow/Porous Cu2O Nanoparticles by Ion-Pairing Behavior Control.

Owing to the properties of low density, large surface areas, excellent loading capacity, high permeability, and interstitial hollow spaces, hollow nanostructures have been widely applied in many important research fields, such as catalysis, drug-controlled release, confined synthesis, optics and electronics, and energy storage. This work provided a simple platform for hollow Cu2O nanostructure synthesis based on the surfactant controlling methodology, which is under the supposed mechanism of ion-pairing behavior at the initial nucleation stage. Thus here, we explore our system in two different directions: (1) we get different types of hollow Cu2O nanoparticles by controlling the surfactant concentration during the synthesis step in colloids, which is critical to the novel structure design and potential application in many different areas and (2) we explore the method to Cu2O hollow particle synthesis to test the hypothesis of the ion-pairing behavior during the initial nucleation by tuning the solvent ratio, cation concentration (such as NH4NO3 addition amount difference in the synthetic step), and selective etching. By tuning the synthetic conditions as well as designing control experiments, we hope to provide a solid understanding of the crystal growth mechanism. Our improved understanding in similar systems (both Cu2O and ZnO systems) will make it easier for interpreting nanostructure formation in new discoveries and, more importantly, in rationally designing various complex nanostructures based on a bottom-up strategy.

Transformable masks for colloidal nanosynthesis.

Synthetic skills are the prerequisite and foundation for the modern chemical and pharmaceutical industry. The same is true for nanotechnology, whose development has been hindered by the sluggish advance of its synthetic toolbox, i.e., the emerging field of nanosynthesis. Unlike organic chemistry, where the variety of functional groups provides numerous handles for designing chemical selectivity, colloidal particles have only facets and ligands. Such handles are similar in reactivity to each other, limited in type, symmetrically positioned, and difficult to control. In this work, we demonstrate the use of polymer shells as adjustable masks for nanosynthesis, where the different modes of shell transformation allow unconventional designs beyond facet control. In contrast to ligands, which bind dynamically and individually, the polymer masks are firmly attached as sizeable patches but at the same time are easy to manipulate, allowing versatile and multi-step functionalization of colloidal particles at selective locations.

Facile and controlled fabrication of functional gold nanoparticle-coated polystyrene composite particle.

Gold nanoparticles-coated polystyrene (AuNPs-coated PS) composite particles with raspberry-like morphology are successfully prepared with the aid of a unique thermodynamically driving effect. It is of considerable interest that the AuNPs generate and self-assemble with raw, ordinary PS microspheres that preexist in the oxidation-reduction systems. The synthesized AuNPs-coated PS composite particles have been extensively characterized using scanning electron microscope, transmission electron microscope, and UV-Vis-NIR spectroscopy. The results indicate that the morphology of the resultant composite particles is governed by simply changing the amount and type of reductants and the concentration of PS microspheres. The AuNPs-coated PS composite particles also exhibit the good surface-enhanced Raman scattering and catalytic performances.