Regulating Surface Faceting as a Kinetic Switch for Core-Shell Nanoparticle Crystallization Pathways.

Core-shell nanoparticles have unusual physical, chemical and biological properties. Until now, for the Ag and TiO2 combination, only Ag core and TiO2 shell nanoparticles have been practically demonstrated. In this investigation, novel TiO2@Ag core-shell (TiO2 core and Ag shell) nanoparticles were produced via ultrasonic vibration of Ag-TiO2 compound nanoparticles. A bulk Ti/Ag alloy plate was used to generate colloidal Ag-TiO2 compound nanoparticles via picosecond laser ablation in deionised water. The colloidal nanoparticles were then sonicated in an ultrasonic bath to generate TiO2@Ag core-shell nanoparticles. They were characterised using a UV-VIS spectrometer, transmission electron microscopy (TEM), high-angle annular dark-field-Scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The Ag-TiO2 compound and the TiO2@Ag core-shell nanoparticles were examined for their antibacterial activity against Escherichia coli (E. coli) JM109 strain bacteria and compared with those of Ag and TiO2 nanoparticles. The antibacterial activity of the core-shell nanoparticles was slightly better than that of the compound nanoparticles at the same concentration under standard laboratory light conditions and both were better than the TiO2 nanoparticles but not as good as the Ag nanoparticles.

The H2S is a toxic and malodorous gas produced from coal mine, natural gas manufacturing processes, and wastewater treatment plants. Due to increased environmental concern, there is an increasing demand for semiconductor gas sensors that are selective and responsive towards H2S gas.SnO2 has been known as a representative semiconductor gas sensing material because of chemical stability and high electron mobility. However SnO2 has a problem that H2S gas doesn’t detached after adsorbing on the surface on SnO2. To solve this problem, the use of noble metal catalysts has been suggested. Au nanoparticles (NPs) are reported to be a good catalyst for the H2S oxidation reaction. To investigate the effects of Au NPs on H2S adsorption and desorption, Au@SnO2 core-shell NPs were applied as a sensing material.In this study, Au@SnO2 core-shell NPs has been synthesized by microwave-assisted hydrothermal method. Au@SnO2 core-shell NPs were calcined at various temperatures (350°C ~ 550°C) to control the surface morphology and crystallinity of SnO2 shell, and their gas sensing property were investigated towards H2S gas (2 ppm to 100 ppm). Based on the results of the sensing test of Au@SnO2 core-shell NPs, we examined the effect of Au NPs on H2S adsorption and desorption.The Au@SnO2 core-shell structure NPs were successfully synthesized by microwave-assisted hydrothermal method, and the particle size was 26-30 nm and the shell thickness of SnO2 shell layer was 14-18 nm. The highest sensing responses of pure SnO2 and Au@SnO2 core-shell NPs showed at the working temperature of 200°C, the responses value to 100 ppm H2S gas were 4,748 and 517, respectively. The optimum working temperature for Au@SnO2 core-shell NPs for detecting H2S gas was at 300°C because the gas sensing response showed relatively high as compared to pure SnO2 and the recovery rate was the highest value. Moreover, the selectivity of H2S toward CO, CH4, C2H5OH gases appeared at this working temperature. The reason why Au@SnO2 core-shell NPs selectively reacted with H2S gas at 300°C was due to the catalytic activity of Au core for H2S oxidation reaction.Keywords: Au@SnO2, nanoparticle, semiconductor gas sensor, H2S gas, adsorption

In typical seed-mediated syntheses of metal nanocrystals, the shape of the nanocrystal is determined largely by the seed nucleation environment and subsequent growth environment (where "environment" refers to the chemical environment, including the surfactant and additives). In this approach, crystallinity is typically determined by the seeds, and surfaces are controlled by the environment(s). However, surface energies, and crystallinity, are both influenced by the choice of environment(s). This limits the permutations of crystallinity and surface facets that can be mixed and matched to generate new nanocrystal morphologies. Here, we control post-seed growth to deliberately incorporate twin planes during the growth stage to deliver new final morphologies, including twinned cubes and bipyramids from single-crystal seeds. The nature and number of twin planes, together with surfactant control of facet growth, define the final nanoparticle morphology. Moreover, by breaking symmetry, the twin planes introduce new facet orientations. This additional mechanism opens new routes for the synthesis of different morphologies and facet orientations.

High chemical and mechanical stability of cathode surface are the prerequisites enabling high‐performance rechargeable battery. Surface facet is among the surface properties that dictate surface stability and cycling performance, while its underlying mechanism remains elusive. Herein, it is reported that surface stability is closely related to the surface facet for a variety of layered cathodes. The investigation shows that surface structure of P2 layered cathode undergoes sequential transformation upon cycling, which results in severe surface degradation. This study finds that the surface facets perpendicular to the (002) planes experience severe cracking and corrosion, while other surface facets are much more stable. The surface stability difference mainly comes from a geometric effect on strain release, which determines the mechanical stability of surface. Chemically, transition metal condensation forms a passivation layer to effectively prevent the inward propagation of surface degradation. Therefore, the surface facets oblique to the layered‐planes are intrinsically more resistant to mechanical cracking and chemical corrosion, which is further verified as a common effect in several O3‐type layered cathodes. This work not only deepens the understanding of the mechanism how surface facet affects surface stability, but also validates surface facet regulation can be a promising strategy for optimizing battery materials.

Bimetallic core-shell nanoparticles (CSNPs) often exhibit excellent and tunable properties, depending on their composition, sizes, morphology, atomic arrangement, thickness, and sequence of both core and shell. In this study, the geometrical structure, thermodynamic stability, chemical activity, electronic and magnetic properties, and catalytic activity in the hydrogen evolution reaction (HER) of 13- and 55-atom Pd, Au NPs, and Pd-Au CSNPs were systematically investigated using density functional theory calculations. The results showed that Au atoms prefer to segregate to the surface-shell, while Pd atoms were inclined to aggregate in the core region for bimetallic Pd-Au CSNPs; therefore, Pd@Au CSNPs with an Au surface-shell were thermodynamically more favorable than both the monometallic Pd/Au NPs and the Au@Pd CSNPs with a Pd surface-shell. The Pd surface-shell of the Au@Pd CSNPs displayed a positive charge, while the Au surface-shell of the Au@Pd CSNPs exhibited a negative charge due to the charge transfer in the Pd-Au CSNPs, resulting in that the d-band center of Au@Pd with the Pd surface-shell showed larger shift toward the Fermi level and higher chemical activity. The Pd@Au CSNPs with the Au surface-shell showed similar d-band curves and d-band centers with monometallic Au NPs. All 13-atom Pd, Au NPs, and Pd-Au CSNPs were magnetic, while the 55-atom NPs were non-magnetic with symmetry partial density of states' curves except for Pd55. Changing the location of Pd and Au atoms in the Pd-Au CSNPs influenced their total magnetic moments. In addition, an opposite trend was found: small 13-atom NPs with a Pd surface-shell showed superior HER activity to the ones with an Au surface-shell, while large 55-atom NPs with an Au surface-shell possessed higher HER activity than the ones with a Pd surface-shell.

The aim of this study was to synthesize iron oxide/silica core-shell nanoparticles (NPs) loaded with Doxorubicin (Dox) as hyperthermia-controlled drug delivery vehicles for cancer treatment. Simple and core-shell nanoparticles were evaluated with respect to their performances in the magnetic hyperthermia tests. The chemical composition and the morphological features of the magnetic nanoparticles were investigated by X-ray photoelectron spectroscopy (XPS) and high-resolution scanning electron microscopy (HRSEM). Preliminary flow cytometry and enhanced darkfield hyperspectral microscopy analyses revealed the ability of Dox-loaded core-shell magnetic nanoparticles to be uptaken by A375 human melanoma cells.

As the development of manufacturing technology for electronic devices, propresses it is necessary to study manufacturing technologies for mass storage, low-volume, improved reliability, and low cost materials for electronic devices used in data communication. The noble metals are the most commonly used raw materials used in such manufacturing. However, the raw materials (Ag, Pt, etc.) are expensive and raise the manufacturing cost. So, there is a need to replace these materials with raw materials of low cost. Recently, the much-cheaper Cu has received attention in that it has the same properties as the noble metals. Cu has good physical and chemical properties. However, its anti-oxidation is weak. Therefore, to make up for this weak point, research has generally been conducted to find a method to coat copper with a noble metal. The coating, comprised of the noble metal, is strong against the oxidation of the Cu surface. In this study, we made Cu@Ag core-shell nanoparticles; these particles have the same level of electro-conductivity as Ag. These materials are expected to reduce the product cost of raw materials.

In this article, it is shown that the efficiency of an electrochemical aptasensing device is influenced by the use of different nanoparticles (NPs) such as gold nanoparticles (Au), silver nanoparticles (Ag), hollow gold nanospheres (HGN), hollow silver nanospheres (HSN), silver–gold core shell (Ag@Au), gold–silver core shell (Au@Ag), and silver–gold alloy nanoparticles (Ag/Au). Among these nanomaterials, Ag@Au core shell NPs are advantageous for aptasensing applications because the core improves the physical properties and the shell provides chemical stability and biocompatibility for the immobilization of aptamers. Self-assembly of the NPs on a cysteamine film at the surface of a carbon paste electrode is followed by the immobilization of thiolated aptamers at these nanoframes. The nanostructured (Ag@Au) aptadevice for Escherichia coli as a target shows four times better performance in comparison to the response obtained at an aptamer modified planar gold electrode. A comparison with other (core shell) NPs is performed by cyclic voltammetry and differential pulse voltammetry. Also, the selectivity of the aptasensor is investigated using other kinds of bacteria. The synthesized NPs and the morphology of the modified electrode are characterized by UV-Vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and electrochemical impedance spectroscopy.

Photocatalytic Degradation of Effluent water by CuO@Ag Core–shell Nanoparticles as Effective Catalyst under Irradiation of UV-light

Fabrication and characterization of protein-phenolic conjugate nanoparticles for co-delivery of curcumin and resveratrol

The bimetallic core–shell nanoparticles (CSNPs) exhibit superior stability, selectivity, and catalytic activity as well as display new functions owing to a lattice strain induced by the unique core-shell structures and synergistic effects of different metal components. These properties of bimetallic CSNPs can be tuned and expanded by varying the composition and atomic arrangement as well as their sizes, morphology, thickness, and sequence of both core and shell. In this study, the geometrical structure, thermodynamic stability, and electronic properties of 13- and 55-atom Cu, Pd nanoparticles (NPs), and Cu–Pd CSNPs were systematically investigated using density functional theory calculations. The results showed that Pd atoms prefer to segregate to the surface shell, while Cu atoms were inclined to aggregate in the core region for bimetallic Cu–Pd CSNPs; therefore, Cu@Pd CSNPs with a Pd surface-shell were thermodynamically more favourable than both the monometallic Cu/Pd NPs and the Pd@Cu CSNPs with a Cu surface-shell. The charge transfer increased from the Cu-core to the Pd-shell for the Cu@Pd CSNPs, while it decreased from the Pd-core to the Cu-shell for the Pd@Cu CSNPs. Opposite charge transfer in these CSNPs led to the Pd surface-shell that displays a negative charge, while the Cu surface-shell exhibits a positive charge.

Laser direct joining of carbon fiber reinforced thermoplastic (CFRTP) composite plate and titanium alloy plate with a thickness of 2 mm was performed with swing laser. Numerous air bubble of submillimeter size were observed inside the fusion zone of CFRTP and titanium alloy at the cross section of the joints. The air bubble characteristics were analyzed based on the morphology and size, while the formation mechanism of air bubble was further elucidated according to the nucleation mode, nucleation site and nucleation position. The results demonstrated that the nucleation modes of air bubble are substantially divided into homogeneous nucleation and heterogeneous nucleation, which is related to the nucleation sites. The nucleation mode presents a crucial factor influencing the position and morphology of air bubble. In addition, the air bubble characteristics are also determined by the clamp pressure and resin flow. The final morphology of air bubble is primarily represented by four typical types.

A stepwise generation of Cu2O, Cu2O@Cu core-shell and Cu nanoparticles (NPs) inside the alumina films has been accomplished. First, CuO–Al2O3 films were prepared on glass substrates by dip-coating method using alumina sol derived from partially acetylacetonate (acac) chelated aluminium-tri-sec-butoxide doped with copper(II) chloride, followed by heat-treatment at 450 °C in air. Heat-treatment of CuO–Al2O3 films at 450–500 °C in reducing atmosphere resulted in the formation of stable Cu2O NPs which can be subsequently converted to Cu2O@Cu core-shell NPs with tunable Cu-shell thickness, and followed by pure Cu NPs by further heat-treatment at 550–700 °C. UV–visible, transmission electron microscopy (TEM) and grazing incidence X-ray diffraction (GIXRD) studies of the films in different stages confirmed the generation of Cu2O, Cu2O@Cu core-shell and Cu NPs. It has been understood that the chemical structure and property of matrix alumina facilitated the stabilization of Cu2O NPs inside the films. As a result, the formation of Cu2O@Cu NPs can be achieved easily by controlled heat-treatment in reducing atmosphere. The catalytic properties of Cu2O, Cu2O@Cu and Cu NPs incorporated alumina films were studied by monitoring the degradation of an azo dye congo-red. All films showed very good catalytic activities; among these Cu2O NPs doped films showed excellent stability, reusability and high rate constant values.

Co-delivery of curcumin and piperine in zein-carrageenan core-shell nanoparticles: Formation, structure, stability and in vitro gastrointestinal digestion

8 - Core-shell oxide nanoparticles and their biomedical applications