Au Hollow Nanospheres Research Articles

Hgn@ZnS Yolk@Shell Nanocrystals for Solar Hydrogen Production

Design of metal/semiconductor heterostructures has become a topic of great interest in recent years due to the combined interaction between the two components that allows them to show synergistic properties and functionalities. Yolk@shell nanocrystals composed of metal and semiconductor components represent a new family of heterostructures. These structures comprise a core, mobile particle surrounded by a hollow, permeable shell, which can be employed as a robust nanoreactor for catalytic applications. In comparison with the similar counterpart, core@shell nanocrystals, yolk@shell nanocrystal have superior features, such as homogeneous reaction environment, accelerated mass transfer dynamics and incremental surface active sites. In this work, a novel hollow Au nanospheres (HGN)@ZnS yolk@shell nanocrystal have been prepared and employed as photocatalysts for hydrogen production. The samples were synthesized by conducting ion exchange reactions on HGN@Cu2O core@shell nanocrystal template, which involved a Kirkendall anion exchange process and a kinetically controlled cation exchange reaction. The microstructures, electronic interactions, band alignment and interfacial charge dynamics of the resultant HGN@ZnS were characterized. The effects of HGN as a charge separation enhancer and a plasmonic sensitizer on the photocatalytic performance of hydrogen production were explored. The results revealed the great promise of HGN@ZnS as highly efficient photocatalysts for solar hydrogen production.

SERS biosensors for ultrasensitive detection of multiple biomarkers expressed in cancer cells

The design and fabrication of multifunctional surface-enhanced Raman scattering (SERS) nanotags are key issues in their application to biological imaging of cells and tissues. In this study, highly sensitive, reproducible and long-term stable SERS nanotags were developed for the identification of localized distribution of multiple protein biomarkers expressed on breast cancer cells. To enhance the surface electromagnetic fields of Raman reporter molecules, Ag-encapsulated Au (Ag-Au) hollow nanospheres were synthesized. Strong Raman signal enhancement effects could be achieved by positioning Raman reporter molecules in nanogaps between the Au hollow nanospheres and silver shell. In addition, the signal was also enhanced due to the localization of surface electromagnetic fields through the pinholes on the surface of Au hollow nanospheres. To maintain the long-term stability of the Au hollow-Ag core/shell nanospheres, their surface was coated with a polyethylene glycol (PEG) layer. The biocompatibility of PEGylated Ag-Au hollow nanospheres was investigated using the premix water soluble tetrazolium salt (WST-1) cell viability test. These SERS nanotags also enabled a high-resolution multiplexed live cell imaging. Our proposed SERS imaging technique using the new SERS nanotags provides a new platform for fast and accurate classification of different phenotypes of breast cancer cells.

Plasmonic Particles – Now Tailored to Your Needs

Plasmonic Particles – Now Tailored to Your Needs

Nanowire networks and hollow nanospheres of Ag–Au bimetallic alloys at room temperature

Due to their physicochemical properties, metallic nanoalloys have potential applications in biomedicine, electrocatalysis and electrochemical sensors, among many other fields. New alternative procedures have emerged in order to reduce production costs and the use of toxic substances. In this study we present a novel low-toxicity synthesis method for the fabrication of nanowire networks (NWNs) and Ag–Au hollow nanospheres. The synthesis process is performed at room temperature without any sophisticated equipment, such as special cameras or furnaces, etc. Transmission electron microscopy showed that the NWNs contain random alloys with a diameter of between 10–13 nm. The radius for the hollow nanospheres is approximately located between 70–130 nm. The absorption bands in the UV–vis spectrum associated with the surface plasmon in Ag–Au bimetallic nanoparticles are highlighted at 385 nm for the NWNs and 643 nm for the hollow nanospheres. The study was performed with low-toxicity substances, such as rongalite, ascorbic acid and sucrose, and showed high efficiency for the fabrication of these types of nanostructures, as well as good stability for long periods of time.

Highly efficient Au hollow nanosphere catalyzed chemo-selective oxidation of alcohols

Micelles of poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-PVP-PEO) with core–shell–corona structures have been used as a scaffold for the fabrication of gold (Au) hollow nanospheres of particle size 26±2nm using HAuCl4 and NaBH4 as metal precursor and reducing agent, respectively. The PS core acts as a template for hollow void, the PVP shell serves as reaction sites for inorganic precursors, and PEO corona stabilizes the composite particles. Under acidic conditions, the PVP shell domain becomes positively charged pyridinum-species that electrostatically interacts with negatively charged AuCl4− ions. On reduction of these composite particles and subsequent solvent extraction leads to the formation of Au hollow nanospheres. Various analytical tools such as powder X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric analyses (TG/DTA), dynamic light scattering of (DLS) have been employed to characterize the polymeric micelles and hollow nanoparticles. The TEM and XRD studies confirmed the formation of highly crystalline Au hollow nanospheres. The Au hollow nanosphere/H2O2 system efficiently catalyzes the chemoselective oxidation of allylic-type unsaturated alcohols into aldehydes and ketones under mild liquid-phase conditions. The versatility of present catalytic system for the oxidation of other substrates like aliphatic-, acylic-, aromatic-, and heteroaromatic alcohols to their respective keto compounds has also been reported.

Au hollow nanospheres on graphene support as catalyst for sodium borohydride electrooxidation

Abstract The Au hollow nanospheres on graphene support (HNAu/G) are prepared by galvanic replacement reaction between sacrificial cobalt nanoparticles and AuCl4− ions. The reaction is conducted at room temperature in aqueous solution. The prepared HNAu/G is used as the anode electrocatalyst for sodium borohydride electrooxidation. The physical and electrochemical properties of as-prepared electrocatalyst are investigated by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), chronoamperometry (CA), and chronopotentiometry (CP). The results show that Au hollow nanospheres on graphene support are coreless with the size of about 18 nm. The Au hollow nanospheres on graphene support exhibit an enhanced electrocatalytic performance for borohydride electrooxidation compared with the solid Au nanoparticles on graphene support (NAu/G).

Au/Pd core-shell nanoparticles with varied hollow Au cores for enhanced formic acid oxidation

A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, and electrochemical measurements. When the concentration of the Au solution was decreased, grain size of the polycrystalline hollow Au nanospheres was reduced, and the structures became highly porous. After the Pd shell formed on these Au nanospheres, the morphology and structure of the Au/Pd nanoparticles varied and hence significantly affected the catalytic properties. The Au/Pd nanoparticles synthesized with reduced Au concentrations showed higher formic acid oxidation activity (0.93 mA cm-2 at 0.3 V) than the commercial Pd black (0.85 mA cm-2 at 0.3 V), suggesting a promising candidate as fuel cell catalysts. In addition, the Au/Pd nanoparticles displayed lower CO-stripping potential, improved stability, and higher durability compared to the Pd black due to their unique core-shell structures tuned by Au core morphologies.

Au/Pd core–shell nanoparticles for enhanced electrocatalytic activity and durability

Unique Au/Pd core–shell nanoparticles were synthesized via galvanic replacement of Cu by Pd on hollow Au nano-spheres. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The Au/Pd nanoparticles exhibit superior formic acid oxidation (FAO) performance, lower CO-stripping potential, and long-term durability and stability compared to commercial Pd black due to enhanced electronic coupling between the Au core and Pd shell, which is confirmed by XPS results.

Synthesis of highly active and stable Au–PtCu core–shell nanoparticles for oxygen reduction reaction

Au-PtCu core-shell nanoparticles were successfully synthesized via galvanic replacement of Cu by Pt on hollow Au nano-spheres. Characterizations of the nanoparticles were conducted by X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrochemical measurements. Results indicate 2-2.5 times higher specific activity and mass activity of the Au-PtCu catalysts than commercial Pt black and Pt/C in oxygen reduction reaction (ORR), measured in a rotating disk electrode system. Besides, thinner PtCu coating (25 nm thick, deposition time of 20 min) on the hollow Au nano-spheres demonstrated a pronounced CO oxidation peak shift (by 0.13 V) and long-term durability probably due to the unique core-shell structure and strong electronic coupling between the Au core and the PtCu shell.

A versatile approach for the fabrication of Au hollow nanoparticles based on poly(styrene-co-2-aminoethyl methacrylate) template

The hollow Au nanospheres were successfully prepared by the template method. The poly(styrene-co-2-aminoethyl methacrylate hydrochloride) (P(St-co-AEMH)) nanoparticles synthesized by the emulsion polymerization were used as the templates. After coating by Au colloidal nanoparticles and the formation of Au shells, the interior templates were etched out by sulfuric acid, leading to the formation of Au hollow nanospheres. The structure and morphology of the nanoparticles and hollow nanospheres were carefully investigated by the fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), wide-angle X-ray diffractometer (WAXD), and thermal gravimetric analysis (TGA) techniques.

Novel Hybrid Electrocatalyst with Enhanced Performance in Alkaline Media: Hollow Au/Pd Core/Shell Nanostructures with a Raspberry Surface

In this paper, a hollow Au/Pd core/shell nanostructure with a raspberry surface was developed for methanol, ethanol, and formic acid oxidation in alkaline media. The results showed that it possessed better electrocatalyst performance than hollow Au nanospheres or Pd nanoparticles. The nanostructure was fabricated via a two-step method. Hollow Au nanospheres were first synthesized by a galvanic replacement reaction, and then they were coated with a layer of Pd grains. Several characterizations such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to investigate the prepared nanostructures. The intensive studies of fuel cells encouraged us to examine the electrocatalytic properties of the prepared nanostructures, and that alkaline media could supply a more active environment than acidic electrolyte in previous reports inspired us to operate the experiments in alkaline media. According to the results, this hollow Au/Pd core/shell nanostructure with a raspberry surface possesses excellent electrocatalytic properties and can be further used in direct alcohol/formic acid fuel cells (DAFCs or DFAFCs), sensors, and catalysts.

Carbon-Supported Au Hollow Nanospheres as Anode Catalysts for Direct Borohydride−Hydrogen Peroxide Fuel Cells

Carbon-Supported Au Hollow Nanospheres as Anode Catalysts for Direct Borohydride−Hydrogen Peroxide Fuel Cells

Investigation of carbon-supported Au hollow nanospheres as electrocatalyst for electrooxidation of sodium borohydride

A carbon-supported Au hollow nanospheres composite electrocatalyst was prepared in aqueous solution with Co nanoparticles as sacrificial templates at room temperature. The electrocatalyst was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersion X-ray (EDX) spectra and electrochemical tests. The results showed that carbon-supported Au hollow nanospheres were porous, and composed of discrete Au nanoparticles with the crystallite size of about 6 nm. For comparison, the electrocatalytic performances of both carbon-supported Au hollow nanospheres and carbon-supported Au solid nanoparticles on borohydride electrooxidation in fuel cells were investigated by cyclic voltammetry, chronoamperometry, and chronopotentiometry. The fundamental electrochemical test results indicated that the electrocatalytic activity of carbon-supported Au hollow nanospheres is much better than that of carbon-supported Au solid nanoparticles.