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Cerium doped zinc oxide (2 at. %) aerogels were synthesized in supercritical methanol and different supercritical mixture solvents (methanol-acetone and methanol-ethanol). The as-elaborated samples were analyzed without any additional heat or chemical treatments by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), optical absorption, photoluminescence (PL) and TGA techniques. The XRD results show that drying in solvents mixture enhances the crystalline quality and acts as a compression agent by exerting stress on the lattice parameters. SEM images demonstrate that the agglomeration rate of aerogel particles decreases when solvents mixture is used. TGA measurements showed the high purity of the samples. FTIR results showed a shift of Zn O bond indicating that supercritical solvent influences the number of Ce O Zn bonds at the surface of the crystallites. UV–vis characterization demonstrates that a band-to-band transition (3.34 eV) is observed only in the spectrum of the aerogel synthesized in supercritical acetone. The photoluminescence (PL) spectra exhibited different optical properties of the aerogels in violet-blue-green wavelengths region (350–530 nm). A blue-green emission located at 485 nm is observed only in methanol and acetone. The intensity of this band is sensitive to the supercritical organic solvent. [ABSTRACT FROM AUTHOR]

Magnetic core–shell nanoparticles (CSNs) have potential applications in spintronic devices, drug delivery systems, and magnetic random access memory. By use of our hydrothermal nano-phase epitaxy method, we have accomplished synthesis of novel, well-ordered α-Cr2O3@α-Mn0.35Cr1.65O2.94 inverted CSNs. XRD and TEM analyses show a core–shell structure with corundum phase throughout the core and shell with a minimal amount of interface defects. TEM-EDX and XPS data show Mn having the +2 oxidation state in the shell of the CSNs. Magnetization measurements at 5 K show a weak coercivity (HC) value of 8 Oe and an exchange bias field (HE) of 293 Oe. Ab initio calculations show that Mn incorporation in α-Cr2O3 results in narrowing of the energy band gap, substantiated by UV–Vis measurements, and half metallic behavior in case of Mn(III) substitution. Our calculations substantiate that Mn substitution in α-Cr2O3 results in a combination of antiferromagnetic and weak ferrimagnetic character of our CSNs. [ABSTRACT FROM PUBLISHER]

Two shapes of TiO2 nanomaterial will largely affect the catalytic activity. TiO2 nanoparticles (NPs) and TiO2 nanofibers (NFs) were used to investigate the effect of shape on catalytic activities and get the optimum shape of catalysis. Electrochemical behaviors of two modified electrodes by TiO2 nanomaterial were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. Various electrochemical parameters such as electrode surface area and electron-transfer rate constant were also studied and calculated in the aqueous solution. Results showed that the response of NF is better than NP for electrooxidation of hydroquinone (HQ). The different electrochemical response of TiO2 is related to the various morphological structures, so controlling the shape and structure of nanomaterial is very important factor which is because of the powerful correlation between these parameters and their optical, catalytic and electrical properties. [ABSTRACT FROM AUTHOR]

Mn and Fe-doped Co3O4 nanoparticles were prepared by a simple precipitation method. The synthesized particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UVVis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and vibrating sample magnetometer (VSM) techniques. XRD analysis showed the cubic structure of Co3O4. SEM and TEM images confirmed the formation of interconnected nanoparticles. Mn and Fe-doped Co3O4 showed broad absorption in the visible region compared to undoped sample and the band gap values are red shifted. Five Raman active modes were observed from the Raman spectra. FTIR spectra confirmed the spinel structure of Co3O4 and the doping of Mn and Fe shifts the vibrational modes to lower wave number region. The magnetic measurements confirmed that Fe-doped Co3O4 shows a little ferromagnetic behavior compared to undoped and Mn-doped Co3O4, which could be related to the uncompensated surface spins and the finite size effects. [ABSTRACT FROM AUTHOR]

A new liquid–liquid system, employing dimethyl sulfoxide and the mixture of oleyl amine and oleic acid as separate solvents, inorganic lead salt as lead source, and sulfide as sulfur source has been developed to synthesize PbS nanoparticles with a narrow size distribution. The process can be conducted under mild conditions. The obtained PbS nanoparticles exhibit high crystallinity and uniformity. The initial Pb/S molar ratio of precursor has great effect on the particle size and optical properties of product. Larger proportion of sulfur precursor, which results in the larger particle size, is more likely to restraint crystal nucleation, rather than promote crystal growth. [ABSTRACT FROM AUTHOR]

Sensitive and accurate characterization of nanoparticle size in aqueousmatrices at environmentally relevant concentrations is still challenging for current nano-analysis techniques. Single particle inductively coupled plasma mass spectrometry (spICP-MS) is an emerging method to characterize the size distribution of nanoparticles and determine their concentrations. Herein for the first time the K-means clustering algorithm is applied to signal processing of spICP-MS raw data. Compared with currently used data processing approaches, the K-means algorithm improved discrimination of particle signals from background signals and provides a sophisticated, statistically based method to quantitatively resolve different size groups contained within a nanoparticle suspension. In tests with commercial Au nanoparticles (AuNPs), spICP-MS with the K-means clustering algorithm can quantitatively discriminate secondary "impurity-size nanoparticles," present at fractions of less than 2% by mass, from primary-size nanoparticles with the minimum resolvable size difference between the primary and secondary nanoparticles at ~20 nm. AuNP mixtures in which 80 nm particles act as the "primary size group" and 20 nm, 50 nm, or 100 nm particles act as the "impurity size group" were analyzed by spICP-MS, which reliably measured percentages of secondary impurity-size nanoparticles that are consistent with the expected experimentally determined values. Compared with dynamic light scattering (DLS), spICP-MS has remarkably better particle size resolution capability. We also demonstrated the size measurement advantage of spICP-MS over DLS for commercial CeO2 nanoparticles that are commonly used in the semiconductor industry, where quality control of the nanoparticle size distribution is critical for the wafer polishing process. [ABSTRACT FROM AUTHOR]

Synthesis of nano CuZnO2 compound is carried out by thermal decomposition method. The crystalline phase of the material is characterized by XRD. The calculated unit cell constants are α = 3.1 Å and c = 3.4786 Å and are of tetragonal structure. The unit cell constants are different from wurtzite (hexagonal) which indicate that a nanocompound is formed. Further TEM images reveal that the metal ion is in tetragonal structure with oxygen ligands. The prepared CuZnO2 is then characterized for crystallite size analysis by employing transmission electron microscopy (TEM). The size is found to be 100 nm. Uniform bright rings are noticed in the TEMpicture suggesting that the nanocrystals have preferential instead of randomorientations. The selectedarea electron diffraction (SAED) pattern clearly indicates the formation of CuO-ZnO nanocompound. The nature of bonding is studied by electron paramagnetic resonance (EPR). The covalency character is about 0.74 and thus the compound is electrically less conductive. Optical absorption spectral studies suggest that Cu(II) is placed in tetragonal elongation crystal field. The spin-orbit coupling constant, λ, is calculated using the EPR and optical absorption spectral results suggest some covalent bond betweenmetal and ligand. Near infrared (NIR) spectra are due to hydroxyl and water fundamentals. [ABSTRACT FROM AUTHOR]

Nano- and microparticles have optical, structural, and chemical properties that differ from both their building blocks and the bulk materials themselves. These different physical and chemical properties are induced by the high surface-to-volume ratio. As a logical consequence, to understand the properties of nano- and microparticles, it is of fundamental importance to characterize the particle surfaces and their interactions with the surrounding medium. Recent developments of nonlinear light scattering techniques have resulted in a deeper insight of the underlying light-matter interactions. They have shed new light on the molecular mechanism of surface kinetics in solution, properties of interfacial water in contact with hydrophilic and hydrophobic particles and droplets, molecular orientation distribution of molecules at particle surfaces in solution, interfacial structure of surfactants at droplet interfaces, acid-base chemistry on particles in solution, and vesicle structure and transport properties. [ABSTRACT FROM AUTHOR]

Nanoparticles exhibiting zero backscattering but a large scattering cross section in the forward direction should play a key role as light diffracting elements in photonic devices like solar cells. Using Mie theory we address lossless dielectric spheres that were recently reported to possess a magnetodielectric response to the illuminating wave, and analyze their scattering cross section together with their zero-backwards scattering conditions. We show that there is an optimum particle refractive index (m = 2.47), which yields maximum forward scattering without backwards scattering of light. [ABSTRACT FROM AUTHOR]

Barium borate (β-BaB2O4) nanoparticles were prepared by a hydrothermal technique using barium chloride and boric acid as starting materials. Powder x-ray diffraction confirms the pure single phase formation of β-BaB2O4. Fourier transform infrared spectroscopy spectra shows the presence of BO3 units which extend themselves to form (B3O6)3− anionic groups in β-BaB2O4. Scanning electron microscopy imaging shows the two-dimensional undulating particle surface with particle size in the range of 45–170 nm. β-BaB2O4 has strong absorption in the UV region and it possesses a wide optical transmittance window (201 to 1100 nm). The optical band gap of the β-BaB2O4 nanoparticle is estimated to be 5.9 eV. In the photoluminescence spectra the presence of self trapped excitonic state (347 nm) was identified. The third order optical nonlinearity of the sample excited in two different pumping regimes, short pulse excitation (532 nm, 5 ns) and continuous wave laser (532 nm, 50 mW) was studied. The material shows limiting behavior due to two photon absorption in the pulsed laser regime and self defocusing in the continuous wave regime. [ABSTRACT FROM AUTHOR]