Abstract: Synthesis of stable hybrid iridium@graphene nanomaterials in the ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIm][BF 4 ] through microwave irradiation (MWI) or electron-beam (e-beam) irradiation (IBA Rhodotron accelerator) induced decomposition of Ir 4 (CO) 12 in the presence of graphene provides an easy method for the generation of small iridium nanoparticles with size distributions of 1.0 ± 0.4 and 2.7 ± 0.7 nm by MWI reactions with 90 and 60 min decomposition time, respectively, and of 3.6 ± 1.0 nm for e-beam irradiation synthesis. Graphene was derived by thermal reduction of graphite oxide (TRGO). Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) showed the formation of Ir nanoparticles which are evenly distributed on the TRGO sheets. Ir@TRGO proved to be a highly active (∼10 000 mol cyclohexane x(mol Ir) −1 x h −1 for benzene hydrogenation) and selective heterogeneous catalyst for the industrially relevant hydrogenation of benzene or cyclohexene to cyclohexane under mild conditions (100 °C, 10 bar H 2 ) with quantitative conversion. The catalyst could be re-used over 10 consecutive hydrogenation reactions with similar activities. A brief correlation between activity and particle size points to an optimal diameter or surface regime for the catalytic activity with iridium particles of 3.6 ± 1.0 nm on TRGO giving here the highest activity in benzene hydrogenation.

Abstract: Ruthenium nanoparticles (Ru-NPs) can be deposited on thermally reduced graphite oxide (TRGO) in propylene carbonate (PC). Propylene carbonate is a biodegradable and non-toxic solvent. Synthesis of Ru-NPs and deposition on TRGO were achieved by decomposition of ruthenium dodecacarbonyl, Ru 3 (CO) 12 , by microwave irradiation. Ru@graphene nanomaterials were identified and characterized by high resolution transmission electron microscopy (TEM, HR-TEM), energy-dispersive X-ray diffraction (EDX), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) with a small diameter and size distribution of 7 ± 4 nm Ru-NPs on TRGO. These Ru@graphene nanomaterials are active catalysts for the solvent-free hydrogenation of benzene to cyclohexane under mild conditions (100 °C, 10 bar) with activities of 34,000 ( mol cyclohexane ) ⋅ ( mol Ru ) − 1 ⋅ h − 1 and over 90% conversion in at least ten consecutive runs.

Abstract: The synthesis, morphological characterization, and colloidal properties of Hematite nanoparticles (hemNP) with different sizes and shapes were presented. To prepare hemNP we used hydrothermal synthesis with different combinations of reaction conditions. Various characterization techniques involving XRD, TEM, AFM and DLS were employed to describe the dependence of the hemNP size, charge and morphology on different synthesis conditions. Spheroidal Hematite nanoparticles from 20 to 60 nm were obtained by varying the rate of addition of iron precursor solutions and the aging time (Δt) at ca. 100∘C. The transformation from Ferrihydrite to Hematite (α-Fe2O3) started with a burst nucleation of nanosized crystallites, followed by a first-order kinetic growth of primary grains up to a final threshold size of ca 30 nm. Colloidal behavior was also checked at pH 4 and 7, finding interparticle aggregation at circumneutral pH only for hemNP obtained for Δt<2 h. Electrophoretic ζ potential measurements yield positive values at pH 4 and negative at pH 7. The shifts in (IEP) at lower values depended on the adsorption of appreciable counterions on the particle surface and reduced at pH 7 the charge–charge repulsion, whereas the attractive forces became predominant. The results confirmed that the particle size of the Hematite nanoparticle critically affected their colloidal behavior with significant consequences for sorption and aggregation processes. Particularly for low particle sizes of the order of 10–20 nm, the surface charge and surface reactivity also could differ in important ways compared to 40–60 nm size particles.

Abstract: Ce x Fe 1 − x O 2 / Ce x Zr 1 − x O 2 ( x : 0 , 0.25, 0.5, 0.75, 1) prepared by coprecipitation method were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), N 2 adsorption at −196 °C, Fourier transform Infra Red (FT-IR) spectroscopy, Fourier Transform Raman spectroscopy and thermal analysis (TG-DTA). XRD and TEM analyses reveal the presence of nanoparticles in all oxides beyond solid solution limit. The reduction in lattice parameter values of Ce–Zr/Fe mixed oxides compared to ceria can be attributed to the compositional changes along with particle growth since the ionic radius of Fe/Zr is smaller than that of Ce. Changes in the solid solution structure from cubic fluorite occur as a result of the crystallite growth of Fe 2 O 3 /ZrO 2 particles on increased Fe/Zr content. Lattice strain measured by Williamson–Hall plot indicates an increase in lattice strain as a result of incorporation of Fe/Zr ions into the ceria lattice. The BET surface area and pore volume of synthesized composites are in the range of 30–10 m 2 / g and 0.004–0.01 cm 3 / g . Raman analysis reveals that iron incorporated ceria lattice have increased oxygen vacancy formation and gradual shrinkage of the unit cell. FT-IR spectra reveal the characteristic Ce–O stretching and crystalline water absorption of synthesized nanoparticles. Thermal analysis data shows these oxides to be thermally stable.

Abstract: A new synthetic route to water-soluble ultra-small CdSe quantum dots (QDs) is proposed based on using a mixed complex of Cd(II) with ammonia and mercaptoacetate (MA) anions as a stabilizer and Na 3 SeO 3 as a stable and non-volatile selenium precursor that can be reduced in situ to Se 2− by MA. The method is facile, reproducible and allows gram-scale production of CdSe QDs in the form of powders, uniform and smooth films and concentrated solutions with a CdSe content up to 20 m%. At a molar MA/Cd(II) ratio of 2.25 the ultra-small CdSe QDs are characterized by an average size of around 2 nm and a narrow size distribution, as well as by a stability towards oxidation by ambient oxygen and under light illumination. A combined Raman and XPS study shows that the stability of the CdSe QDs arises from a thin layer of CdS on the QD surface formed during the post-synthesis thermal treatment. An increase in a MA/Cd(II) ratio to 4.00 results in the formation of a species that by its spectral characteristic resembles earlier reported “magic-size” (CdSe) 19 clusters. Upon heating this species transforms into CdSe QDs with a broadened size distribution.

Abstract: Three-fold increase in the efficiencies of inverted bottom-emission organic light emitting diodes (IBOLEDs) is achieved with triangular-shaped zinc oxide nanoparticles (ZnO NPs) synthesized in methanol. ZnO nanoparticles with a diameter ranging from 5 to 10 nm are deposited by a solution process and used as an electron injecting layer (EIL). Influences of the process conditions on device performances such as concentration, annealing temperature and solvents are investigated. IBOLEDs are fabricated with ITO/ZnO NPs/polymer/V 2 O 5 /Al layout where poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is used as an active layer. The highest brightness and luminous efficiency reaching 1340 cd m −2 and 0.65 cd A −1 are achieved with 2.5% wt triangular-shaped ZnO NPs synthesized in methanol. On the other hand, performances of the devices fabricated with ZnO NPs synthesized in isopropanol (IPA) and ethanol were 723 cd m −2 /0.22 cd A −1 and 67 cd m −2 /0.011 cd A −1 , respectively. Through this work, it is found that for the performances of the devices, shape effect is more important than the size.

Abstract: Remediation of chemicals such as pesticides in contaminated surface water and ground water is a major global concern because of the increased public awareness of the health risks and environmental risks of such chemicals. For use as a pesticide remediation system, we herein report a scalable, high-yield three-dimensional mesocage collector of micrometric aluminosilica particles with a large cavity of 7.0-nm pocket-like pores and a regular entrance pore. Analysis of the geometrical features of the mesocage collector cavities (MCC) revealed that they had several key characteristics, such as suitable guest accommodation, intermolecular forces, and electrostatic and non-electrostatic interactions. The MCC took up large quantities of pesticides onto the framework surfaces and into the hierarchical pocket-like pores, and the pesticides could subsequently be efficiently recovered from the MCCs, which could then be reused. We used the MCCs to recover pesticides from contaminated tap water and lake water samples, and our results indicate that the MCCs are a potentially effective tool for reducing the environmental burden due to contaminated water.

Abstract: Spectroscopic and microscopic measurements show that 10,12-pentacosadiynoic acid is able to densely adsorb on the surface of silver nanoparticles by properly selecting the synthesis procedure. Its subsequent polymerization by UV irradiation under controlled photochemical conditions produces the blue form of poly(pentacosa-10,12-diynoic acid). The resulting nanohybrids are very stable in aqueous suspension and exhibit a bilayered, core–shell architecture. We propose a model of the polyPCDA self-assembled on silver nanoparticles and we evaluate the surface coverage density.

Abstract: Based on (dimethylamino)ethyldiselenide, (diethylamino)ethyldiselenide and (dimethylamino)propyldiselenide six different bis(dialkylamino)alkylselenolates with zinc and cadmium were decomposed by microwave irradiation in the ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoridoborate ([BMIm][BF 4 ]) to give the respective metal selenide nanoparticles. In comparison to common methods like the hot injection method attention was paid how variations of the ligand system and different decomposition times affect the nanoparticle synthesis with respect to size, shape, crystallinity and crystal phase. The decomposition of the single-source zinc and cadmium precursors in the fluorous IL led mostly to spherical, crystalline and only slightly agglomerated nanoparticles. No formation of ZnF 2 or CdF 2 was observed which is different from the known dual-source synthesis. In case of the zinc precursors, hexagonal and cubic ZnSe with a particle diameter between 4–7 nm were obtained, whereas in case of the cadmium precursors hexagonal CdSe with an average particle diameter of 10–19 nm were prepared. An increase in decomposition time from 5 to 15 min at 250 °C mostly led to similar results concerning the particle size and crystal phase which is different from the hot injection method, thereby suggesting that the IL has a decisive role for nanocrystal growth and stabilization. No further stabilizing agents were necessary to reproducibly prepare ZnSe or CdSe particles with an average diameter below 10 or 20 nm, respectively. All dispersions of the metal selenide nanoparticles in [BMIm][BF 4 ] were characterized by high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (PXRD).

Abstract: Carbon nanomaterials have gained tremendous importance in nanoscience owing to their excellent properties and versatile applications. However, the major concern in using carbon nanomaterial is that they are costly to synthesize and use harmful precursors throughout their synthesis. Therefore, alternative means for the production of carbon nanomaterials using safer and greener sources are being currently investigated. In this viewpoint, camphor has demonstrated potential for the synthesis of new carbon nanomaterials with excellent physico-chemical property and biocompatibility. However the research on camphor based nanomaterials has not received much attention in the scientific community. Apart from traditional carbon nanomaterials like carbon nanotube, graphene and fullerene, camphor has the potential to synthesize new materials like carbon nanoparticles, nano-onions and carbon dots using simpler techniques for potential industrial applications. The present review focuses on the recent developments on camphor based carbon nanomaterials, their latent applications and future prospects.

Abstract: The effect of hydrothermal treatment conditions on the formation, morphology, crystal growth, and photoluminescence of columbite-type ZnNb 2 O 6 nanocrystals having rose-like morphology that were directly formed from aqueous precursor solutions of ZnSO 4 and NbCl 5 in the presence of aqueous ammonia was investigated. The crystallization of ZnNb 2 O 6 nanocrystals was observed at 210 °C, but the hydrothermal treatment at 240 °C for 5 h under weakly basic condition around pH=8.4 was necessary for the sufficient crystallite growth of columbite-type ZnNb 2 O 6 phase. On the other hand, the solid product formed at 240 ° C from the precursor solution at pH=9.0 was almost amorphous. The observation by means of the transmission electron microscopy, selected area diffraction, and energy dispersive X-ray spectrometry showed that the ZnNb 2 O 6 particles with the morphology like flower or rose consisted of arrayed nanosized-sheets having crystallite size of 11 nm. The ZnNb 2 O 6 particles grew from about 1 to 4 μ m accompanying crystal growth with morphological change into rose-like shape via the solution and precipitation mechanism as hydrothermal holding time at 240 °C increased from 5 to 72 h. The as-prepared ZnNb 2 O 6 nanocrystals showed a broad-band emission in the UV-blue region centered at 420 nm (and peaked at 360 nm) under excitation at 276 nm.

Abstract: The photoluminescent (PL) properties of colloidal semiconductor nanoparticles (NPs) can be strongly affected by coupling of the organic moieties on their surfaces. A deeper understanding of various factors governing the actual PL emission of Cadmium sulfide (CdS) NPs is important to utilize the same in functional devices. In present work, a comparative investigation on surfactant-structure dependent PL emission of CdS NPs prepared by a convenient chemical precipitation method has been described. By varying the surfactant (stabilizer) species on NP’s surface, the PL emission of CdS NPs varies significantly under similar conditions. Additionally, the effect of photoactivation using normal daylight and UV-light has also been studied on PL of CdS NPs. Photo-dissolution of CdS NPs under both normal as well as UV-light has produced smaller NPs. The PL emission performance of the NPs has also been improved manifold after photoactivation which has been explained in the terms of changing surface states.

Abstract: Sol–gel processing and heat-treatment were used to obtain nanopowders with tetragonal phase of undoped zirconia reinforced with well-dispersed multi-walled carbon nanotube (MWCNTs), having contents between 1 and 5 wt.%. Amorphous nanopowders treated at 500 ° C crystallized in the tetragonal phase of zirconia with an average crystallite size of 25 nm. The nanocomposites containing 3 wt.% of MWCNTs reached 98% of the theoretical density, with an increase in hardness of about 15%, and a fracture toughness about 110% higher compared to the values obtained for pure zirconia compacted at the same conditions. The novelty in our study is the production of zirconia/MWCNTs nanocomposites with enhanced mechanical properties by compaction of nanopowders under high-pressure at moderate temperature.

Abstract: Fast and simple methods with high sensitivity and selectivity for H 2 O 2 assessment are important in biological and medical fields. In this study, we explored the effect of nano-object hemeproteins (denoted as N-HP) with various bio-functionalities on the electrochemical sensing performance of working electrodes toward H 2 O 2 molecules by affecting interfacial electron transport and surface properties of N-HP. We successfully constructed three enzyme-free H 2 O 2 sensors by coating a three-dimensional open-pore nickel (3D-Ni) foam electrode with similar concentrations of three different N-HP namely, hemoglobin (Hb; 68.000 kDa, 7.0 nm), myoglobin (Mb, 16,950 kDa, 4.0 nm), and cytochrome c (Cyt.c, 12,327 kDa, 3.0 nm). The N-HP-modified Ni foam can be directly used as electrodes, thereby simplifying the electrode fabrication process and offering advantages, such as enhanced electrode–electrolyte contact area and minimum diffusion resistance. N-HP can function as redox mediators for shuttling electrons on the electrode–electrolyte interface and for engaging sufficient electro-active species exposed on the surface of the Ni foam for Faradaic redox reactions. The electrocatalytic activities of the Ni foam electrodes modified with different N-HP (i.e., Hb, Mb, and Cyt.c) in the selective oxidation of H 2 O 2 were investigated. Among the N-HP-modified Ni foam electrodes, Cyt.c modified Ni foam electrode showed the highest sensitivity with reduced hysteresis between cathodic and anodic sweep and low detection limit ( 0.20 μ M , with signal to noise ratio of 3). This diversity in sensing performance originates from the versatility of the heme group with different bio-functionalities, different sizes and interactions at the surface of the immobilized Ni foam substrate. In addition, the N-HP-modified Ni foam electrodes exhibited no effects on major interferences, such as ascorbic, uric acids, dopamine, L-Cysteine (L. Cyst), vitamin A, L-glutathione. Hence, these electrodes can be applied in analyzing biological systems, such as lemon juice. Immobilization of different N-HP with different bio-functionalities and sizes onto Ni foam electrodes may facilitate the design and fabrication of novel biosensors.

Abstract: Fil: Lloret, Paulina. Instituto Nacional de Tecnologia Industrial. Procesos Superficiales; Argentina

Abstract: The influence of the crystal structure on the physical properties of monoclinic ZrO 2 nanocrystals is investigated by an annealing treatment. Monoclinic ZrO 2 nanocrystals with diameters of approximately 20 nm are synthesized by a hydrothermal method using subcritical water. The nanocrystals have chemisorbed water molecules, hydroxides and nitro groups on their surfaces. The crystallographic structures are reformed by annealing the nanocrystals at 800 °C for 5 h. This treatment causes the crystallite sizes to increase, the crystal lattice to shrink and some of the molecules chemisorbed on the surfaces to be lost. The annealing treatment leads to there being fewer lattice defects, and to the modification of surface characteristics of the nanocrystals. The treatment also changes the optical absorption characteristics of the nanocrystals. The magnetic moments caused by lattice defects are identified.