Cover Picture: Ann. Phys. 2'2018

In article number 1700256, Emanuele Verrelli and co‐workers propose that cluster beam deposition of sub‐2nm magic number Au clusters, Au20 and Au55, on flat surfaces reveals a rich evolution of the phenomena taking place at substrate level. New magic number clusters have been formed via coalescence of neighbouring clusters, such as Au561. Experimental and simulation results reveal that neighbouring clusters on the substrate coalesce only when the distance from their nearest neighbour cluster is below a critical mark of 0.5 nm

Electrical conductivity studies of anatase TiO2 with dominant highly reactive {0 0 1} facets

Nanostructured powders of titanium dioxide anatase nanoplates with dominant highly reactive {0 0 1} facets were fabricated using a solvothermal method. Two kinds of samples, as prepared and calcinated at 600 °C, were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrical conductivity in vacuum and in air. The dependence of the conductivity versus the inverse of temperature in the temperature range 150-440 K indicated the contribution of at least two conduction mechanisms in vacuum. The electron transport was controlled by partially depleted of charge carriers grains and adiabatic small polaron conduction in the high temperature regime and by Mott variable-range hopping (VRH) at lower temperatures. The environment was found from the experimental results to influence significantly the electrical conductivity values and its temperature dependence. A decrease with temperature in air is observed in the ranges 290-370 and 285-330 K for the as prepared and the calcinated sample respectively. Potential barriers caused by partial depletion of carriers at grain boundaries control the electrical conductivity behavior in air at high temperatures and VRH in the lower temperature regime

Solvothermal synthesis and photocatalytic performance of Mn4+-doped anatase nanoplates with exposed {001} facets

The photocatalytic activity of TiO2 and manganese doped TiO2 nanoplates with various manganese atomic percentages, in the range of 2-7%, was studied. The undoped and doped nanoplates with exposed {001} facets were produced by a solvothermal method. The crystal structure as well as the shape of the TiO2 and Mn4+/TiO2 anatase nanoparticles was determined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Both techniques revealed that the nanocrystals are in the form of plates. Moreover, the anisotropic peak broadening of the X-ray diffraction patterns was studied using the Rietveld refining method. Chemical analysis of the photocatalyst that was carried out with X-ray photoelectron spectroscopy (XPS) showed the presence of manganese ions in the TiO2 anatase matrix. The Density Functional Theory (DFT) calculations exhibited a decrease in the energy gap and an increase in the density of the electronic stated inside the gap for the doped TiO2. These observations were in agreement with the results of the UV-visible diffuse reflectance spectroscopy (DRS) that demonstrated an adsorption shift towards the visible region for the same samples. The photocatalytic activity of the synthesized catalysts was investigated by the photocatalytic oxidation of the gaseous nitric oxide (NO) and decomposition of the gaseous acetaldehyde (CH3CHO) under visible light irradiation. The optimal concentration of dopant that improves the photocatalytic activity of the nanoplates was determined. © 2014 Elsevier B.V

Effects of Precursor Concentration in Solvent and Nanomaterials Room Temperature Aging on the Growth Morphology and Surface Characteristics of Ni–NiO Nanocatalysts Produced by Dendrites Combustion during SCS

The morphology and surface characteristics of SCS(Solution Combustion Synthesis)-derived Ni−NiO nanocatalysts were studied. The ΤΕΜ results highlighted that the nanomaterial’s microstructure was modified by changing the reactants’ concentrations. The dendrites’ growth conditions were the main factors responsible for the observed changes in the nanomaterials’ crystallite size. Infrared camera measurements demonstrated a new type of combustion through dendrites. The XPS analysis revealed that the NiO structure resulted in the bridging of the oxygen structure that acted as an inhibitor of hydrogen adsorption on the catalytic surface and, consequently, the activity reduction. The RF-IGC indicated three different kinds of active sites with different energies of adsorption on the fresh catalyst and only one type on the aged catalyst. Aging of the nanomaterial was associated with changes in the microstructure of its surface by a gradual change in the chemical composition of the active centers

Modified magnetic core-shell mesoporous silica nano-formulations with encapsulated quercetin exhibit anti-amyloid and antioxidant activity

Targeted tissue drug delivery is a challenge in contemporary nanotechnologically driven therapeutic approaches, with the interplay interactions between nanohost and encapsulated drug shaping the ultimate properties of transport, release and efficacy of the drug at its destination. Prompted by the need to pursue the synthesis of such hybrid systems, a family of modified magnetic core-shell mesoporous silica nano-formulations was synthesized with encapsulated quercetin, a natural flavonoid with proven bioactivity. The new nanocarriers were produced via the sol-gel process, using tetraethoxysilane as a precursor and bearing a magnetic core of surface-modified monodispersed magnetite colloidal superparamagnetic nanoparticles, subsequently surface-modified with polyethylene glycol 3000 (PEG3k). The arising nano-formulations were evaluated for their textural and structural properties, exhibiting enhanced solubility and stability in physiological media, as evidenced by the loading capacity, entrapment efficiency results and in vitro release studies of their load. Guided by the increased bioavailability of quercetin in its encapsulated form, further evaluation of the biological activity of the magnetic as well as non-magnetic core-shell nanoparticles, pertaining to their anti-amyloid and antioxidant potential, revealed interference with the aggregation of β-amyloid peptide (Aβ) in Alzheimer’s disease, reduction of Aβ cellular toxicity and minimization of Aβ-induced Reactive Oxygen Species (ROS) generation. The data indicate that the biological properties of released quercetin are maintained in the presence of the host nanocarriers. Collectively, the findings suggest that the emerging hybrid nano-formulations can function as efficient nanocarriers of hydrophobic natural flavonoids in the development of multifunctional nanomaterials toward therapeutic applications

Surface morphology of low temperature grown GaAs on singular and vicinal substrates

Abstract The evolution of the surface morphology of epitaxial GaAs layers grown at low substrate temperatures (LT-GaAs) on singular and vicinal (001) GaAs substrates is studied by means of kinetic Monte-Carlo simulations. The simulation model includes the effects of Ehrlich-Schwoebel barriers at step-edges as well as anisotropic surface diffusion. We find that the surface morphology is dominated by a pattern of elongated growth mounds, which are organized into columns parallel to [1( 10]. The formation of this pattern is gradually suppressed on vicinal substrates as the misorientation angle increases. Simulated surface morphologies are compared to atomic force microscopy measurements on LT-GaAs epilayers grown on singular GaAs(001) substrates at different temperatures and good quantitative agreement is found. We propose to use vicinal substrates for LT-GaAs growth in order to overcome the known problem of epitaxial breakdown above a certain epitaxial thickness

Iron oxide nanoflowers encapsulated in thermosensitive fluorescent liposomes for hyperthermia treatment of lung adenocarcinoma

Magnetic hyperthermia (MHT) is in the spotlight of nanomedical research for the treatment of cancer employing magnetic iron oxide nanoparticles and their intrinsic capability for heat dissipation under an alternating magnetic field (AMF). Herein we focus on the synthesis of iron oxide nanoflowers (Nfs) of different sizes (15 and 35 nm) and coatings (bare, citrate, and Rhodamine B) while comparing their physicochemical and magnetothermal properties. We encapsulated colloidally stable citrate coated Nfs, of both sizes, in thermosensitive liposomes via extrusion, and RhB was loaded in the lipid bilayer. All formulations proved hemocompatible and cytocompatible. We found that 35 nm Nfs, at lower concentrations than 15 nm Nfs, served better as nanoheaters for magnetic hyperthermia applications. In vitro, magnetic hyperthermia results showed promising therapeutic and imaging potential for RhB loaded magnetoliposomes containing 35 nm Nfs against LLC and CULA cell lines of lung adenocarcinoma

Decoration of Carbon Nanotubes with CoO and Co Nanoparticles

Multiwall carbon nanotubes (MWNTs) decorated with CoO nanocrystals were synthesized by in-situ thermal decomposition of Co(acac)2 in oleyl amine under reflux conditions open in the air. The CoO/MWNTs composite material can be easily converted to metallic Co/MWNTs through annealing under reducing atmosphere (4%  H2) at 500°C without any significant sintering effect. The composite materials characterized by X-ray diffraction, transmission electron microscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy. The structural and morphological characterization shows that the CoO has cubic face (fcc) and the particles deposited uniformly on the external surface of the carbon nanotubes. In the annealed materials, the NMR shows that the fcc and hcp metallic Co phases coexist with a significant percentage of stacking faults. The magnetic measurements indicated that the CoO/MWNTs composite is largely composed of CoO nanoparticles with uncompensated surface spins. The fluctuations of spins persist in partially reduced CoO grains as shown by nuclear spin-lattice relaxation measurements

Photocatalytic H-2 evolution, CO2 reduction, and NOx oxidation by highly exfoliated g-C3N4

g-C3N4, with specific surface area up to 513 m(2)/g, was prepared via three successive thermal treatments at 550 degrees C in air with gradual precursor mass decrease. The obtained bulk and exfoliated (1ex, 2ex and 3ex) g-C3N4 were characterized and tested as photocatalysts for H-2 production, CO2 reduction and NOx oxidation. The exfoliated samples demonstrated graphene-like morphology with detached (2ex) and sponge-like framework (3ex) of layers. The surface area increased drastically from 20 m(2)/g (bulk) to 513 m(2)/g (3ex). The band gap (E-g) increased gradually from 2.70 to 3.04 eV. Superoxide radicals (O-center dot(2)-) were mainly formed under UV and visible light. In comparison to the bulk, the exfoliated g-C3N4 demonstrated significant increase in H-2 evolution (similar to 6 times), CO2 reduction (similar to 3 times) and NOx oxidation (similar to 4 times) under UV light. Despite the E-g widening, the photocatalytic performance of the exfoliated g-C3N4 under visible light was improved too. The results were related to the large surface area and low e(-)-h(+) recombination. The highly exfoliated g-C3N4 demonstrated selectivity towards H-2 evolution reactions.Web of Science1010art. no. 114

Solvothermal synthesis and photocatalytic performance of Mg2+-doped anatase nanocrystals with exposed {0 0 1} facets

The photocatalytic activity of TiO2 and magnesium doped TiO 2 nanocrystals in dopant range of 2-6.2 at%, was studied. The doped and undoped nanocrystals with exposed {0 0 1} crystal facets were synthesized by a solvothermal method. Several studies have shown that the (0 0 1) surface of the TiO2 anatase crystal is more reactive than the thermodynamically stable (1 0 1) surface. The crystal structure as well as the shape of the TiO2 and Mg2+/TiO2 anatase nanoparticles were determined using two different techniques, such as X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), which both lead to the agreeable conclusion that the nanocrystals are in the form of plates. Chemical analysis of the photocatalyst was carried out with X-ray photoelectron spectroscopy (XPS) and showed the presence of magnesium ions in the TiO 2 nanoplates. UV-vis diffuse reflectance spectroscopy (DRS) showed that there is an adsorption shift for doped TiO2 to visible light region. The photocalaytic efficiency of the synthesized catalysts was investigated by the photocatalytic oxidation of the gaseous nitric oxide (NO) and decomposition of the gaseous acetaldehyde (CH3CHO) under UV irradiation. It was demonstrated that the low Mg2+ doped catalysts exhibited higher photocatalytic activity than the pure TiO2. The optimal concentration of dopant that is beneficial for the photocatalytic activity was studied. © 2013 Elsevier B.V