Amino-Induced 2D Cu-Based Metal-Organic Framework as an Efficient Heterogeneous Catalyst for Aerobic Oxidation of Olefins.

With the assistance of hydrogen bonds of the o-amino group, we have successfully tuned a coordination structure from a metal-organic polyhedron (MOP) to a two-dimensional (2D) metal-organic framework (MOF). The amino group forms hydrogen bonds with the two vicinal carboxylic groups, and induces the ligand to coordinate with copper ions to form the 2D structure. The obtained 2D Cu-based MOF (Cu-AIA) has been applied as an efficient heterogeneous catalyst in the aerobic epoxidation of olefins by using air as oxygen source.

Synthesis of Palladium Nanoscale Octahedra through a One-Pot, Dual-Reductant Route and Kinetic Analysis.

Shape-controlled synthesis of colloidal metal nanocrystals has traditionally relied on the use of an approach that involves the reduction of a metal precursor by a single reductant. Once the concentration of atoms surpasses supersaturation, they will undergo homogeneous nucleation to generate nuclei and then seeds, followed by further growth into nanocrystals. In general, it is a grand challenge to optimize such an approach because the kinetic requirement for nucleation tends to be drastically different from what is needed to guide the growth process.

Toward a Quantitative Understanding of the Reduction Pathways of a Salt Precursor in the Synthesis of Metal Nanocrystals.

Despite the pivotal role played by the reduction of a salt precursor in the synthesis of metal nanocrystals, it is still unclear how the precursor is reduced. The precursor can be reduced to an atom in the solution phase, followed by its deposition onto the surface of a growing nanocrystal. Alternatively, the precursor can adsorb onto the surface of a growing nanocrystal, followed by reduction through an autocatalytic process.

Shape-controlled synthesis of CO-free Pd nanocrystals with the use of formic acid as a reducing agent.

This paper reports the use of formic acid as a reducing agent for the shape-controlled synthesis of Pd nanocrystals with no chemisorption of CO on the surface, as confirmed by attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy.

Synthesis and Characterization of Pt-Ag Alloy Nanocages with Enhanced Activity and Durability toward Oxygen Reduction.

Engineering the elemental composition of metal nanocrystals offers an effective strategy for the development of catalysts or electrocatalysts with greatly enhanced activity. Herein, we report the synthesis of Pt-Ag alloy nanocages with an outer edge length of 18 nm and a wall thickness of about 3 nm. Such nanocages with a composition of PtAg could be readily prepared in one step through the galvanic replacement reaction between Ag nanocubes and a Pt(II) precursor.

Quantitative Analysis of the Reduction Kinetics Responsible for the One-Pot Synthesis of Pd-Pt Bimetallic Nanocrystals with Different Structures.

We report a quantitative understanding of the reduction kinetics responsible for the formation of Pd-Pt bimetallic nanocrystals with two distinctive structures. The syntheses involve the use of KBr to manipulate the reaction kinetics by influencing the redox potentials of metal precursor ions via ligand exchange. In the absence of KBr, the ratio between the initial reduction rates of PdCl4(2-) and PtCl4(2-) was about 10.

Coating Pt-Ni Octahedra with Ultrathin Pt Shells to Enhance the Durability without Compromising the Activity toward Oxygen Reduction.

We describe a new strategy to enhance the catalytic durability of Pt-Ni octahedral nanocrystals in the oxygen reduction reaction (ORR) by conformally depositing an ultrathin Pt shell on the surface. The Pt-Ni octahedra were synthesized according to a protocol reported previously and then employed directly as seeds for the conformal deposition of ultrathin Pt shells by introducing a Pt precursor dropwise at 200 °C. The amount of Pt precursor was adjusted relative to the number of Pt-Ni octahedra involved to obtain Pt-Ni@Pt1.

Pd@Pt Core-Shell Concave Decahedra: A Class of Catalysts for the Oxygen Reduction Reaction with Enhanced Activity and Durability.

We report a facile synthesis of multiply twinned Pd@Pt core-shell concave decahedra by controlling the deposition of Pt on preformed Pd decahedral seeds. The Pt atoms are initially deposited on the vertices of a decahedral seed, followed by surface diffusion to other regions along the edges/ridges and then across the faces. Different from the coating of a Pd icosahedral seed, the Pt atoms prefer to stay at the vertices and edges/ridges of a decahedral seed even when the deposition is conducted at 200 °C, naturally generating a core-shell structure covered by concave facets.

Organic-inorganic interface-induced multi-fluorescence of MgO nanocrystal clusters and their applications in cellular imaging.

Surface functionalization of inorganic nanomaterials through chemical binding of organic ligands on the surface unsaturated atoms, forming unique organic-inorganic interfaces, is a powerful approach for creating special functions for inorganic nanomaterials. Herein, we report the synthesis of hierarchical MgO nanocrystal clusters (NCs) with an organic-inorganic interface induced multi-fluorescence and their application as new alternative labels for cellular imaging. The synthetic method was established by a dissolution and regrowth process with the assistance of carboxylic acid, in which the as-prepared MgO NCs were modified with carboxylic groups at the coordinatively unsaturated atoms of the surface.

Rational design of oriented assembly of gold nanospheres with nanorods by biotin-streptavidin connectors.

Through the different functionalities on Au nanosphere (AuNSs) and Au nanorod (AuNRs) surfaces, we successfully control AuNSs attachment onto either the end or side surface of anisotropic AuNRs via bio-recognition, and then consciously construct side-by-side or end-to-end assembly nanostructures. This study provides a feasible approach to organize nanoparticles with different morphologies into controllable assembly geometries, which can potentially benefit the construction of future nanodevices.