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A new photoactive thin film of layered double hydroxide (LDH) nanocrystals containing fluorescein dyes (LDH-F) has been developed by self-assembly of the LDH nanocrystals and well-controlled intercalation of the dyes in organic media. XRD results and absorption spectra confirmed the highly oriented interlayer arrangement of the dianionic form of the fluorescein dyes in the LDH interlayers, in which the dye molecules were electrostatically immobilized between the positively charged LDH layers with a monolayer packing structure. An intensity weighted average PL lifetime was estimated to be 1.45 ns and fluorescence lifetime imaging microscopy revealed that the individual LDH nanocrystals on the LDH-F film had largely similar lifetimes, which were ascribed to the uniform loading of fluorescein dyes onto the LDH matrix without photoluminescence quenching.

A highly effective way to produce an oxygen reduction electrocatalyst was developed through the self‐assembly of exfoliated single layers of cobalt hydroxide (Co(OH)2) and graphene oxide (GO). These 2D materials have complete contact with one another because of their physical flexibility and the electrostatic attraction between negatively charged GO and positively charged Co(OH)2 layers. The strong coupling induces transformation of the Co(OH)2 single layer into a discrete nanocrystal of spinel Co3O4 with an average size of 8 nm on reduced GO (RGO) during calcination, which could not be obtained with bulk‐layered cobalt hydroxide because of its rapid layer collapse. The ultrafine Co3O4/RGO hybrid exhibited not only comparable performance in the oxygen reduction reaction but also higher durability compared with the commercial 20 wt % Pt/C catalyst. [ABSTRACT FROM AUTHOR]

We have developed a simple and facile method to fabricate gold nanoparticles (Au NPs) deposited on thin films of layered double hydroxide (LDH) nanocrystals. The oriented thin film of LDH nanocrystals was employed for the preferential deposition of Au NPs by in situ growth of Au NPs on the monolayer thin film of LDH nanocrystals, which effectively provided a large and uniform active hydroxide surface for deposition of a dense monolayer of Au NPs. The reactive hydroxide groups and the positive potential of the LDH surfaces play an important role in the uniform growth of the Au NPs and in their stabilization against agglomeration. This LDH-supported Au NP catalyst exhibits superior catalytic efficiency and reusability without significant loss in conversion efficiency for the reduction of p-nitrophenol with NaBH4, maintaining more than 96 % catalytic conversion efficiency. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the preparation of copper–indium bimetallic nanoparticles through the borohydride reduction in an alcohol solution for application in ink-coating and sputtering target materials. Copper, indium metal and copper–indium intermetallic materials were synthesized by reacting CuCl2 and InCl3 with NaBH4 in 2-propanol (IPA) and tetraethylene glycol (TEG) at room temperature. The Cu–In samples contained Cu2In and CuIn phases with particle sizes of 10–100nm and 30–200nm in both the IPA and TEG solutions, respectively. The nanoparticulate Cu–In precursor layer was coated onto a soda-lime glass through spin-casting, where the Cu–In intermetallic phases of Cu2In and Cu11In9 were produced through heat treatment in Ar gas and a microstructured CuInSe2 layer was produced in a selenium atmosphere. Cu, In, Cu–In intermetallic nanoparticles and the films were characterized using powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analyses. [ABSTRACT FROM AUTHOR]

In this study, tantalum network nanoparticles are prepared from a Ta 2 O 5 + k Mg system via a liquid magnesium-controlled combustion reaction. Super-stoichiometric amounts of magnesium are used in the preparation of a reaction mixture to produce a liquid magnesium pool capable of lowering the combustion temperature and leading to the formation of Ta network structures. The heat transfer kinetics from the hot reaction zone of 'cold' Mg particles is determined using heat transfer-coupled fluid dynamics simulation software. The formation of network structures is characterized through SEM, TEM, XRD, and BET analysis techniques. The mechanism of network formation is explained based on solid particle collisions in liquid media. Our method is able to produce Ta network structures in which the size of individual particles ranges between 50 and 700 nm. [ABSTRACT FROM AUTHOR]

Abstract A lot of efforts being invested into producing efficient thermoelectric devices based on Bi 0.5 Sb 1.5 Te 3 materials for room temperature applications. Key research achievements of these efforts that incorporation of oxide nanoparticles into Bi 0.5 Sb 1.5 Te 3 materials exhibit higher thermoelectric performance in nano-composite form. Here, we prepared Bi 0.5 Sb 1.5 Te 3 nanocomposite incorporated with TeO 2 nanoparticles (NPs) by high energy ball milling and spark plasma sintering, where in-situ Sb 2 O 3 phase and triple functional interfaces were developed. The formation mechanism of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored by the thermodynamic calculations; microstructural features and material composition in the bulk samples were investigated using high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive X-ray spectroscopy (EDS). The formation of interfaces between in situ senarmontite Sb 2 O 3 nanophase and Bi 0.5 Sb 1.5 Te 3 matrix causes an enhanced Seebeck coefficient by ∼20% due to increase of carrier energy filtering and significant reduction of thermal conductivity by ∼77% ascribed to intensified phonon scattering or trapping at 350 K. As a result, an improved dimensionless figure of merit (ZT) of 1.07 at 350 K was achieved in a Bi 0.5 Sb 1.5 Te 3 /3 wt%TeO 2 composites. The proposed in-situ reaction and interface formation mechanisms are expected to open the possibility of further increases in ZT. Graphical abstract Image 1 Highlights • Formation of in-situ Sb 2 O 3 phase in the Bi 0.5 Sb 1.5 Te 3 /TeO 2 composites was explored. • Sb 2 O 3 phase is obtained by in-situ reaction of Sb with TeO 2 during milling and SPS. • The Seebeck coefficient was enhanced owing to increase of energy filtering effect. • Thermal conductivity was reduced (77%) due to phonon scattering at interfaces. [ABSTRACT FROM AUTHOR]

The exothermic reduction of oxides mixture (MoO 3 +2SiO 2 ) by magnesium in NaF melt enables the synthesis of nanocrystalline MoSi 2 powders in near-quantitative yields. The combustion wave with temperature of about 1000–1200 °C was recorded in highly diluted by NaF starting mixtures. The by-products of combustion reaction (NaF and MgO) were subsequently removed by leaching with acid and washing with water. The as-prepared MoSi 2 nanopowder composed of spherical and dendritic shape particles was consolidated using the spark plasma sintering method at 1200–1500 °C and 50 MPa for 10 min. The result was dense compacts (98.6% theoretical density) possessing submicron grains and exhibiting hardness of 8.74–12.92 GPa. [ABSTRACT FROM AUTHOR]

A simple surface modification strategy to generate lithophilic sites in carbon-coated Si nanoparticles significantly enhances the capacity as well as cycling stability. [Display omitted] • A simple surface treatment process generates lithophilic surface groups on carbon-coated Si nanoparticles. • The surface-functionalized electrode of Si-C-AT shows a higher diffusion coefficient than Si-C. • The Si-C-AT shows a reversible capacity of 1575 mA h g−1 after 200 cycles at a current rate of 0.5C. • Functional groups on the Si-C-AT assist in accumulating the lithium-ions in excess on the carbon surface. Silicon nanoparticles (Si NPs) are potential anode materials for next-generation lithium-ion batteries due to their natural abundance, low discharge potential, and high theoretical capacity. Carbon coating improves the capacity of the Si NPs, protects them from disintegration during the lithiation/delithiation process, and provides an additional conductive matrix. Surface modification as a tool leading to capacity enhancement in carbon-coated Si NPs has rarely been explored. It is a straightforward process that involves the surface functionalization of carbon-coated Si NPs (Si-C) with the oxidizing acidic mixture. The surface-treated Si-C functionalized with carboxyl and hydroxyl groups in excess on the carbon surface of Si-C NPs. As a result of surface modification, the acid-treated Si-C (Si-C-AT) displayed a higher reversible capacity of 1575 mA h g−1 after 200 cycles compared to the Si-C (1261 mA h g−1) and bare Si (961 mA h g−1). This high capacity of Si-C-AT is a cumulative outcome of the functional groups and the disordered structure of the carbon shell. The functional groups act as lithophilic sites, and the disordered carbon shell facilitates the insertion-desertion of lithium ions. The simple surface modification strategy proposed in the present study significantly enhances the cyclability of the Si-C-AT NPs and has great potential for application in carbon-coated materials for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A melt-assisted solid flame synthesis approach was applied to synthesize boron nanoparticles in argon gas and air atmospheres. For this purpose, we investigated the characteristics of a thermally induced combustion wave in B 2 O 3 + α Mg mixtures ( α = 1.0–1.5 mol) in argon and air atmospheres. Utilizing stoichiometrically insufficient amounts of magnesium ensured that a large portion of molten B 2 O 3 remained in the sample, which reduced the combustion parameters and favored the formation of boron nanoparticles. Under these conditions the combustion temperature and burning velocity were controlled in the range of 1300–1580 °C and 0.065–0.18 cm/s, respectively, and boron nanoparticles in a ∼20–200 nm size range were obtained. The characteristics of boron nanoparticles (morphology, purity, specific surface area, oxidation activity, etc.) were analyzed and a reaction pathway leading to boron nanoparticles synthesis was proposed. [ABSTRACT FROM AUTHOR]

The synthesis of AlN nanoparticles in non-isothermal high-temperature conditions was developed. The process involved Al 2 O 3 –Mg–NH 4 Cl mixtures preparation and combustion in nitrogen atmosphere. Temperature profiles in the combustion waves were recorded by thermocouples, and the values of combustion temperature and wave velocity were determined from the recorded profiles. The existence of two independed combustion regimes with maximum temperatures of about 850 °C and 1400–1600 °C were revealed based on concentrations of NH 4 Cl. AlN nanocrystals were obtained and investigated by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller surface area. AlN nanocrystals prepared under non-isothermal combustion process were comprised well distributed multi-faceted particles with an average size of 50–200 nm. The chemical reactions in the combustion wave were discussed and a possible thermochemical pathway for the synthesis of AlN nanoparticles was proposed. [ABSTRACT FROM AUTHOR]

Amorphous boron nanoparticles were synthesized by heating a B 2 O 3 + 3 Mg + k NaCl ( k is the number of moles of NaCl) exothermic mixture in a laboratory oven at 800 °C under argon flow. NaCl was used as inert material to decrease the maximum combustion temperature of the reaction mixture when it was self-ignited after the melting of Mg at 650 °C. The size of the boron nanoparticles extracted from the final product by acid leaching ranged between 30 and 300 nm for k values ranging from 1 to 5. Moreover, increasing the value of k from 1 to 5 resulted in an increase in the specific surface area of the nanoparticles from 40 to 74 m 2 g −1 . However, at k = 10, a decrease in the specific surface area to 47.56 m 2 g −1 was recorded due to incomplete reduction of B 2 O 3 . The ignition point of boron nanoparticles in air as estimated using a thermocouple was approximately 300 °C. Digital camera recording of the combustion process of boron nanoparticles in air revealed that the burning speed of the nanoparticles increased significantly from 0.3 to 15 cm/s when k increased from 1 to 5. [ABSTRACT FROM AUTHOR]

Tantalum nitride nanoparticles were produced from a (K2TaF7 +5NaN3) exothermic mixture under the combustion regime. The effects of the K2TaF7/NaN3 ratio and KF and NH4F concentrations on the combustion parameters, product composition, and size of the tantalum nitride particles were studied. Depending on the synthesis conditions, the combustion temperature was maintained in the 700–1200°C range, resulting in hexagonal ε-TaN, TaN0.8, and Ta2N phases. The dominant phases were TaN and TaN0.8 in the 1000–1200°C range, whereas only the Ta2N phase was present in the 700–100°C range. Pure-phase cubic tantalum nitride (δ-TaN) was produced with 4.0mol of NH4F at a combustion temperature of ~800°C. Under controlled reaction conditions, the size of the tantalum nitride particles was about 10–50nm. We also found that during the synthesis, the stainless steel tube located inside of the reaction mixture was partially coated with fine TaN crystals. The mechanism of the combustion process is discussed in regards to the experimental results. [ABSTRACT FROM AUTHOR]