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The N-doped porous carbon (NC) has been regarded as one of the promising support materials for nanoparticles (NPs) catalyst due to its inherent virtues such as porosity, large surface areas, and heteroatom incorporation. In this work, Fe/NC-800 hybrid was facilely prepared by uniform dispersion of in situ formed FeNPs onto NC-800 from carbonization of ZIF-8 at 800 °C for the first time. The optimized Fe/NC-800 catalyst was characterized by TEM, XPS and XRD. Compared with sole FeNPs and NC-800, the Fe/NC-800 catalyst exhibited an enhanced oxidase-like activity that could oxidize the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to the heavy blue without extra oxidants such as H 2 O 2 . The possible reason for the enhanced oxidase-like activity of the Fe/NC-800 was discussed on the basis of the experiments of radical scavengers, indicating the importance of superoxide (O 2 •- ) and singlet ( 1 O 2 ) in colorimetric reaction between TMB and Fe/NC-800 hybrid. Furthermore, the oxidase-like activity of Fe/NC-800 was significantly inhibited by dopamine (DA), leading to blue color fading. On this basis, a sensitive and selective colorimetric sensor was fabricated for the quantitative analysis of DA with a linear range of 0.01–40 μM and a low detection limit of 10 nM. The proposed colorimetric method was successfully applied to determine DA in human serum and injection samples, suggesting a promising application in biological analysis. [ABSTRACT FROM AUTHOR]

XRD and TEM characterisation evidenced the formation of well-dispersed CdS nanoparticles inside a phosphate glass matrix. Optical absorption and time-resolved photoluminescence study were carried out on the prepared glass samples. Optical absorption revealed the fast character of the growth of CdS nanoparticles in this medium. Photoluminescence spectra showed only one large band with a maximum at almost 740 nm, which was associated to transitions between energy levels within the bandgap of the CdS nanoparticles. From the steady state and time-resolved measurements, it was suggested that the emission comes mainly from sulfur vacancies inside the nanocrystals and on its surface, which act as deep traps for the photogenerated electrons. The creation of such vacancies was attributed to the loss of sulfur during the glass preparation as evidenced from a chemical analysis using energy dispersive X-ray spectrometry. These traps may be also induced by the fast growth of CdS nanocrystals in this matrix or laser exposure during PL measurements. These CdS-doped glasses with an intense absorption in the UV–Vis region and a large emission band with long lifetime and a large Stokes-shift are adequate for luminescent solar concentrators, photocatalytic applications and solid-state lasers. [ABSTRACT FROM AUTHOR]

Dynamic light scattering (DLS) is one of the most adapted methods to measure the size of nanoparticles, as referred to the hydrodynamic radii (Rh). However, the Rh represents only that of three-dimensional spherical nanoparticles. In the present research, the size of two-dimensional (2D) nanoparticles of yttrium oxide (Y2O3) and zirconium phosphate (ZrP) was evaluated through comparing their hydrodynamic diameters via DLS with lateral sizes obtained using scanning and transmission electron microscopy. We demonstrate that the hydrodynamic radii are correlated with the lateral sizes of both square and circle shaped 2D nanoparticles. Two proportional coefficients, i.e., correcting factors, are proposed for the Brownian motion status of 2D nanoparticles. The correction is possible by simplifying the calculation of integrals in the case of small thickness approximation. The correcting factor has great significance for investigating the translational diffusion behavior of 2D nanoparticles in a liquid and in effective and low-cost measurement in terms of size and morphology of shape-specific nanoparticles. [ABSTRACT FROM AUTHOR]

Characterization of core–shell type nanoparticles in 3D by transmission electron microscopy (TEM) can be very challenging. Especially when both heavy and light elements coexist within the same nanostructure, artifacts in the 3D reconstruction are often present. A representative example would be a particle comprising an anisotropic metallic (Au) nanoparticle coated with a (mesoporous) silica shell. To obtain a reliable 3D characterization of such an object, a dose-efficient strategy is proposed to simultaneously acquire high-angle annular dark-field scanning TEM and annular dark-field tilt series for tomography. The 3D reconstruction is further improved by applying an advanced masking and interpolation approach to the acquired data. This new methodology enables us to obtain high-quality reconstructions from which also quantitative information can be extracted. This approach is broadly applicable to investigate hybrid core–shell materials. [ABSTRACT FROM AUTHOR]

Soluting rare earth atoms Tb or Dy into body centered cubic (BCC) Fe-Ga through rapid cooling significantly enhances the magnetostriction due to strong localized magnetocrystalline anisotropy. Origin of the local strong anisotropy, however, awaits comprehensive microstructural investigation. In this letter, formation of tetragonal nanoparticles with c/a~0.979 has been found in the giant magnetostrictive ribbons Fe82.89Ga16.88Tb0.23 due to local symmetry breaking of the BCC lattice using high resolution transmission electronic microscopy. First principal calculations suggest that random replacement of Tb atoms for Fe or Ga in the ordered DO3 superlattice is beneficial in the formation of such tetragonal symmetry. Exchange couplings between the nearest Tb-Fe or Tb-Tb pairs of the tetragonal nanoparticles might generate strong localized magnetocrystalline anisotropy, leading to extraordinary magnetostriction enhancement. [ABSTRACT FROM AUTHOR]

Recent advancements in metal-enhanced fluorescence (MEF) suggest that it can be a promising tool for detecting molecules at very low concentrations when a fluorophore is fixed near the surface of metal nanoparticles. We report a simple method for aggregating multiple gold nanoparticles (GNPs) on Rhodamine B (RhB)-doped silica nanoparticles (SiNPs) utilizing dithiocarbamate (DTC) chemistry to produce MEF in solution. Dye was covalently incorporated into the growing silica framework via co-condensation of a 3-aminopropyltriethoxysilane (APTES) coupled RhB precursor using the Stöber method. Electron microscopy imaging revealed that these mainly non-spherical particles were relatively large (80 nm on average) and not well defined. Spherical core-shell particles were prepared by physisorbing a layer of RhB around a small spherical silica particle (13 nm) before condensing an outer layer of silica onto the surface. The core-shell method produced nanospheres (~30 nm) that were well defined and monodispersed. Both dye-doped SiNPs were functionalized with pendant amines that readily reacted with carbon disulfide (CS) under basic conditions to produce DTC ligands that have exhibited a high affinity for gold surfaces. GNPs were produced via citrate reduction method and the resulting 13 nm gold nanospheres were then recoated with an ether-terminated alkanethiol to provide stability in ethanol. Fluorescent enhancement was observed when excess GNPs were added to DTC coated dye-doped SiNPs to form nanoparticle aggregates. Optimization of this system gave a fluorescence brightness enhancement of over 200 fold. Samples that gave fluorescence enhancement were characterized through Transmission Emission Micrograph (TEM) to reveal a pattern of multiple aggregation of GNPs on the dye-doped SiNPs. [ABSTRACT FROM AUTHOR]

Spheric and anisotropic gold nanoparticles (GNPs) such as rods, stars or nanoprism prepared using hexadecyltrimethyl ammonium bromide (CTAB) as the stabilising agent have received a great deal of interest in the last years. The literature procedures exploited lead to GNPs in aqueous solution. We herein describe a fast, efficient, and cheap method to transfer particles of different shapes from water into toluene solution via ligand exchange (CTAB to dodecanethiol), which was mediated by acetone as a cosolvent. Absorption spectra and TEM-pictures before and after the transfer revealed that the particles survived the transfer intact and without change in shape. [ABSTRACT FROM AUTHOR]

The synthesis, spectroscopic characterisation, and thermal studies of pyridyl adducts of Zn(II) and Cd(II) complexes of N-ethyl-N-phenyl dithiocarbamate, represented as [ZnL2py] and [CdL2py2], are reported. Single-crystal X-ray structural analysis of the Zn compound showed that it is five-coordinate with four sulphurs from dithiocarbamate and one nitrogen from pyridine in a distorted square pyramidal geometry. The thermogravimetric studies indicate that the zinc and cadmium compounds undergo fast weight loss, and the temperature at maximum rate of decomposition is at 277 °C and 265 °C respectively, to give the metal (Zn or Cd) sulphide residues. These compounds were used as single molecule precursors to produce nanocrystalline MS (M = Zn, Cd) after thermolysis in hexadecylamine. The morphological and optical properties of the resulting MS nanocrystallites were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis absorption and photoluminescence (PL) spectroscopy, and powdered X-ray diffraction (XRD). By varying the growth time, the temporal evolution of the optical properties and morphology of the nanocrystals were investigated. [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]

The synthesis of shape and size-controlled free gold nanoparticles (AuNPs) was achieved by wet chemical methods. The UV-vis spectroscopy measurements and transmission electron microscopy characterizations confirmed the fine distribution in size and shape of the AuNPs. The zeta potential measurements permitted the evaluation of the stability of the AuNPs suspension. For the first time, the shape dependence on the electrocatalytic activity of these NPs is thoroughly investigated. The underpotential deposition (UPD) of lead reveals that their crystallographic facets are affected by their shape and growth process. Moreover, the glucose oxidation reaction strongly depends on the shape of AuNPs. Indeed, the gold nanocuboids (GNCs) and the spherical gold nanoparticles (GNSs) are significantly more active than the gold nanorods (GNRs) followed by the polyhedrons (GNPs). The oxidation process occurs at low potential for GNCs whereas the current densities are slightly higher for GNSs electrodes. Most importantly, the control of the shape and structure of nanomaterials is of high technological interest because of the strong correlation between these parameters and their optical, electrical and electrocatalytic properties. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanoparticles have been used in a wide-ranging of applications such as transparent UV protection, light emitting diodes, sensors and photovoltaic cells. Many applications of ZnO nanoparticles could be improved by changing the particle size, shape and morphology. Therefore, studying the mechanism of shape evolution is crucial for size and shape controlled synthesis of nanocrystaline ZnO particles. As an alternative to sophisticated techniques such as transmission electron microscopy (TEM) and X-ray powder diffraction (XRD), commonly used for studying nanoparticles evolution, we herein employed UV/Vis spectroscopy for monitoring the evolution process of the ZnO nanocrystals coupled with chemometric methods for analyzing overlapped and complex spectral data. The evolutionary UV-Visible absorbance data of ZnO nanoparticles through particle formation via precipitation methods in various solution conditions were analyzed using factor analysis, evolving factor analysis, and multivariate curve resolution-alternative least-squares analysis. Depending on chemical routs, three or four chemical factors that attributed to the ZnO nanoparticles of different size were detected and the concentration profiles and pure spectra of the particles were resolved. The interpretation of the evolution profiles of the detected ZnO nanoparticles were achieved by Ostwald ripening mechanism. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

La0.7Sr0.3MnO3 (LSMO) nanoparticles with a size of ∼23 nm have been prepared by a combustion method and functionalized with polyvinylpyrrolidone (PVP) for their possible application in magnetic fluid hyperthermia (MFH). Uncoated and PVP-coated samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy and vibrating sample magnetometer studies. Magnetic measurements of both coated and uncoated particles reveal the superparamagnetic nature at room temperature. Colloidal stability has been measured in terms of zeta potential. The resulting PVP-coated particles form a stable suspension in phosphate buffer saline (PBS) and double distilled water (DDW) and possess a narrow hydrodynamic size distribution. The induction heating studies of these nanoparticles at different alternating magnetic fields (167.6, 251.4 and 335.2 Oe) were carried out by dispersing nanoparticles in DDW and PBS. These PVP-coated LSMO NPs exhibit a higher specific absorption rate in PBS than in DDW. The results suggest that combustion-synthesized LSMO nanoparticles coated with PVP can be used as potential heating agents in MFH. [ABSTRACT FROM AUTHOR]

The heteroaggregation rates of negatively charged multiwalled carbon nanotubes (CNTs) and positively charged hematite nanoparticles (HemNPs) were obtained over a broad range of nanoparticle distributions using time-resolved dynamic light scattering (DLS). Binary systems comprising CNTs and HemNPs were prepared using low ionic strength solutions to minimize the concurrent occurrence of homoaggregation. To elucidate the mechanisms of heteroaggregation: the structures of CNT-HemNP aggregates were observed using cryogenic transmission electron microscopy (cryo-TEM). An initial increase in the CNT concentration, while keeping the HemNP concentration constant: resulted in a corresponding increase in the rate of heteroaggregation: which occurred through the bridging of HemNPs by CNT strands. At the optimal CNT/HemNP mass concentration ratio (CNT/HemNP ratio) of 0.0316, the heteroaggregation rate reached 3.3 times of the HernNP homoaggregation rate in the diffusion-limited regime. Increasing the CNT/HemNP ratio above the optimal value, however, led to a dramatic decrease in the growth rate of heteroaggregates, likely through a blocking mechanism. In the presence of humic acid, the trends in the variation of the heteroaggregation rate with CNT/HemNP ratio were similar to that in the absence of humic acid. However, as the humic acid concentration was increased, the maximum aggregate growth rate decreased due to the lessening in the available suthce of the HemNPs that CNTs can attach to through favorable electrostatic interaction. [ABSTRACT FROM AUTHOR]

The physicochemical properties of nanoparticles and biomaterials exert influences over their interactions with cells and consequently play an important role when introduced into any given system. Characterisation of these said materials is a detailed and, above all, a cross-disciplinary relationship of physical, chemical, mechanical, surface,in vitroandin vivomulti-integrated research topics. The biocompatibility of a functional structure with desired properties is affected by the biomaterials’ structural characteristics and building block pathways. Moreover, the sensitivity, depth of field, resolution and dimension of a given material also make structural analysis of a nano-biomaterial particularly challenging to characterise. In this paper, we discuss the use of biomaterial characterisation techniques (fluorescent and optical) to characterise structural aspects of biomaterials, with the aim of improving both the understanding and relationship between a biomaterials’ structure and its functionality. [ABSTRACT FROM AUTHOR]