Xiaoqing Huang

Freestanding palladium nanosheets with plasmonic and catalytic properties

Ultrathin metal films can exhibit quantum size and surface effects that give rise to unique physical and chemical properties. Metal films containing just a few layers of atoms can be fabricated on substrates using deposition techniques, but the production of freestanding ultrathin structures remains a significant challenge. Here we report the facile synthesis of freestanding hexagonal palladium nanosheets that are less than 10 atomic layers thick, using carbon monoxide as a surface confining agent. The as-prepared nanosheets are blue in colour and exhibit a well-defined but tunable surface plasmon resonance peak in the near-infrared region. The combination of photothermal stability and biocompatibility makes palladium nanosheets promising candidates for photothermal therapy. The nanosheets also exhibit electrocatalytic activity for the oxidation of formic acid that is 2.5 times greater than that of commercial palladium black catalyst.

Amine-Assisted Synthesis of Concave Polyhedral Platinum Nanocrystals Having {411} High-Index Facets

High-index surfaces of a face-centered cubic metal (e.g., Pd, Pt) have a high density of low-coordinated surface atoms and therefore possess enhanced catalysis activity in comparison with low-index faces. However, because of their high surface energy, the challenge of chemically preparing metal nanocrystals having high-index facets remains. We demonstrate in this work that introducing amines as the surface controller allows concave Pt nanocrystals having {411} high-index facets to be prepared through a facile wet-chemical route. The as-prepared Pt nanocrystals display a unique octapod morphology with {411} facets. The presence of high-index {411} exposed facets endows the concave Pt nanocrystals with excellent electrocatalytic activity in the oxidation of both formic acid and ethanol.

Simplifying the Creation of Hollow Metallic Nanostructures: One-Pot Synthesis of Hollow Palladium/Platinum Single-Crystalline Nanocubes†

Efficiency simplified: A synthetic strategy has been developed to prepare single-crystalline hollow Pd/Pt nanocubes (right, see picture; left: nanocubes). Compared to the solid Pd/Pt nanocubes of similar sizes, the hollow Pd/Pt nanocubes increase accessible surface area and therefore improve electrocatalytic activity in formic acid oxidation.

Controlled Formation of Concave Tetrahedral/Trigonal Bipyramidal Palladium Nanocrystals

Novel concave Pd nanocrystals with uniform diameter were successfully prepared in the presence of formaldehyde. While the outer surfaces of the as-prepared concave Pd nanocrystals are {111}, the faces concave toward the polyhedral center are high-surface-energy {110} faces. The degree of concavity and therefore the percentage of {110} of the nanocrystals are tunable by varying the amount of formaldehyde and the reaction temperature. Owing to the existence of active {110} facets, the electrocatalytic activity of the concave Pd nanocrystals displays dependency on their degree of concavity.

Core–Shell Pd@Au Nanoplates as Theranostic Agents for In-Vivo Photoacoustic Imaging, CT Imaging, and Photothermal Therapy

Uniform plasmonic Pd@Au core-shell bimetallic nanoplates are synthesized by seeded growth strategy. Surface modified with SH-PEG makes it good biocompatibility, prolonged blood circulation, and relatively high tumor accumulation. Enhanced tumor contrast effects can be obtained for in vivo photoacoustic/CT imaging after intravenous injection of Pd@Au-PEG. Moreover, efficient photothermal tumor ablation is achieved, guided by the imaging techniques. This work promises further exploration of the superiority of 2D nanostructures for in vivo biomedical applications.

An Assembly Route to Inorganic Catalytic Nanoreactors Containing Sub-10-nm Gold Nanoparticles with Anti-Aggregation Properties**

通讯作者地址: Zheng, NF (通讯作者), Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China n地址: n1. Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China n2. Xiamen Univ, Dept Chem, Xiamen 361005, Peoples R China n3. Univ Calif Santa Barbara, Dept Chem & Biochem, Santa Barbara, CA 93106 USA n电子邮件地址: nfzheng@xmu.edu.cn, stucky@chem.ucsb.edu

Enhancing the Photothermal Stability of Plasmonic Metal Nanoplates by a Core‐Shell Architecture

通讯作者地址: Zheng, NF (通讯作者),Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China n地址: n1. Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China n2. Xiamen Univ, Dept Chem, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China n电子邮件地址: nfzheng@xmu.edu.cn

Interfacial electronic effects control the reaction selectivity of platinum catalysts

Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

Etching Growth under Surface Confinement: An Effective Strategy To Prepare Mesocrystalline Pd Nanocorolla

An etching growth strategy was developed to prepare corolla-like Pd mesocrystals consisting of unidirectionally aligned, well-spaced, and connected ultrathin (1.8-nm-thick) Pd nanosheets. The combined use of CO and Fe(3+) is critical to the successful synthesis of the branched corolla-like Pd mesocrystals. While CO functions as the surface-confining agent to allow anisotropic growth of the 1.8-nm-thick Pd nanosheets as branches, Fe(3+) etches the Pd seeds at the early stage of the reaction to induce formation of the branched structure. Inheriting the unique properties of 1.8-nm-thick Pd nanosheets, the as-prepared Pd mesocrystals display well-defined surface plasmon resonance absorption in the near-infrared region, a high electrochemically active surface area, and a significant photothermal effect when irradiated with a near-infrared laser. Owing to the presence of internal voids and increased apparent thickness, the Pd mesocrystals also exhibit several features superior to those of single-domain Pd nanosheets, making them promising for electrocatalysis and cancer photothermal therapy applications.

Synthesis of magnetic, fluorescent and mesoporous core-shell-structured nanoparticles for imaging, targeting and photodynamic therapy

A synthetic method to prepare novel multifunctional core-shell-structured mesoporous silica nanoparticles for simultaneous magnetic resonance (MR) and fluorescence imaging, cell targeting and photosensitization treatment has been developed. Superparamagnetic magnetite nanoparticles and fluorescent dyes are co-encapsulated inside nonporous silica nanoparticles as the core to provide dual-imaging capabilities (MR and optical). The photosensitizer molecules, tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc), are covalently linked to the mesoporous silica shell and exhibit excellent photo-oxidation efficiency. The surface modification of the core-shell silica nanoparticles with folic acid enhances the delivery of photosensitizers to the targeting cancer cells that overexpress the folate receptor, and thereby decreases their toxicity to the surrounding normal tissues. These unique advantages make the prepared multifunctional core-shell silica nanoparticles promising for cancer diagnosis and therapy.