Nano

Hierarchical self-assembling of materials represents one of the most appealing subjects in nanoscience, since bottom-up strategies allow for tailor-made synthesis of functional structures in commodities as well as in living systems. Herein we show that nanorings of ca. 10nm silica nanoparticles without any inorganic metal oxide or organic participant are able to spontaneously self-assemble presenting sophisticated forms and hierarchy. It was observed that after synthesis, silica nanoparticles are chaotically distributed but during storage at ambient conditions they spontaneously form self-assembled aggregates with multiplicity of morphologies when a small amount of water is added in the environment. Detailed description of the morphology of such structures by high resolution transmission electron microscope (HRTEM) is presented together with a discussion about the role of water during their spontaneous formation.

We performed a combined experimental and theoretical study of the conjugates obtained from single-walled carbon nanotubes and anticancer antibiotic doxorubicin (DOX). Atomic force microscopy (AFM) imaging at lower magnification revealed, extended regions of single-walled carbon nanotubes (SWNT_S) fully covered with DOX adsorbed molecules, along with some bare parts without the adsorbed drug, thus suggesting that the DOX adsorption is a cooperative process. Ambient atmosphere scanning tunneling microscopy (STM) at higher resolutions found that individual SWNTs-DOX conjugates exhibit a periodic texture, whose most important morphological feature is alternating depressions and protrusions along the nanotube. Based on the images and profiles measured, we suggest that doxorubicin molecules self-assemble on SWNTs sidewall according to a helical pattern, in which their tetracyclic fragments are turned with respect to the nanotube axis by about 50${}^{\circ }$. To provide an additional insight into the structure of noncovalent SWNTs-DOX conjugates, we employed density functional theory (DFT) calculations with three long-range corrected functionals: M05-2X, wB97X-D and LCBLYP, of which M05-2X yielded the most realistic results in terms of geometries and energies.

In this report, an inorganic salt assisted micro-emulsion method was reported for the preparation of mono-disperse CaWO₄ microspheres with hierarchical structures. The as-obtained microspheres are composed of tiny nanorods, which have been proved by the field emission scanning electronic microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) observations. The formation of these hierarchical mono-disperse microspheres is considered to be the synergistic effect of both surfactant and the inorganic salt. Based on the time-dependent experiments, a probable formation mechanism based on surface adsorption and oriented attachment has been proposed. The photoluminescence properties of the microspheres were investigated. The generality of this synthetic method for other metal tungstates were also carefully investigated, which indicates that the morphologies of the final product not only depend on the synthetic conditions, but also depend on the growth habit of the materials.

Here we reported the synthesis of nanoporous carbide-derived carbons (CDCs) from a new precursor, titanium tin carbides (Ti₂SnC), via chlorination at 400–1100${}^{\circ }$C. At low chlorination temperature (400–500${}^{\circ }$C), as-synthesized CDCs mainly consisted of amorphous carbon and chlorides. As the chlorination temperature increased up to 600${}^{\circ }$C, chlorides disappeared, and the main composition of CDCs was amorphous carbon. At high chlorination temperature, there was a trend of graphitization. The microstructure of CDCs was observed and characterized by scanning electron microscopy and transmission electron microscopy. Some graphite-like sheet structures in CDCs were found. Specific surface area (SSA) and pore volume of CDCs increased with chlorination temperature, except an abnormal decrease of the CDC chlorinated at 900${}^{\circ }$C. CDC chlorinated at 1100${}^{\circ }$C had the largest SSA, 1580m²/g. In order to apply these materials as novel hydrogen/methane storage media in the area of energy efficient transport, gas adsorption properties of CDCs were measured. For CDC chlorinated at 1100${}^{\circ }$C, pore volume uptakes are $\sim 206$cm³/g at 60 bar (25${}^{\circ }$C) for methane, and $\sim 442$cm³/g at 35 bar ($-196^{\circ }$C) for hydrogen, respectively. It was suggested that CDCs from Ti₂SnC are promising materials for hydrogen/methane adsorptive storage.

In this paper, the co-precipitation method was used to synthesize pure and Ag-doped LiF crystals and the effect of crystalline cube sizes and Ag concentration on the thermoluminescent (TL) response is reported. The synthesized materials were characterized by scanning electron microscopy and their morphology and size distributions were determined. Crystal sizes were found to be strongly dependent on the ethanol:water ratio, varying from 4.1$\mu$m to 150nm for pure LiF crystals. For Ag-doped samples, the best ethanol:water ratio was found to be 9:1, giving crystals from 0.50$\mu$m to 1.21$\mu$m. A single cubic crystalline phase was determined by XRD for all synthesized samples. The photoluminescence spectra as well as UV-Vis absorbance were also analyzed. The TL response to X-ray irradiation was studied for an exposition of 43R. Two effects were observed in the TL response. The first concerns with a significant dependence of the TL intensity on the size of the crystals, being larger for the smallest crystals for pure LiF, and second, for Ag-doped samples the TL intensity augmented almost linearly with the Ag concentration.

Undoped and Mn-doped ZnO nanoparticles (Zn${}_{1-x}$Mn_xO), with nominal weight percentages $(0.00\le x\le 0.10)$, have been synthesized by co-precipitation technique. The synthesized nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR). From XRD analysis, the compound ZnMnO₃ is formed for $x\ge 0.05$ with cubic structure ($a=8.3694$Å) and its concentration increases with x. Moreover, XRD analysis reveals the wurtzite hexagonal crystal structure for ZnO. The lattice parameters (a and c) of Zn${}_{1-x}$Mn_xO are calculated and they increase with the doping concentration of Mn as a consequence of the larger ionic size of Mn${}^{2+}$ ions compared to Zn${}^{2+}$ ions. The crystallite size is calculated for all the samples using Debye–Scherrer’s method (SSM), Williamson–Hall methods (UDM, USDM and UDEDM) and Size-Strain Plot method (SSP), and the results are in good agreement with TEM. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra that shows a peak shift between undoped and doped ZnO. The energy bandgap $(E_g)$ is calculated for different concentrations of Mn $(0.00\le x\le 0.10)$ by using the UV-visible optical spectroscopy, between 300nm and 800nm, showing a noticeable drop in $E_g$ with x. At room temperature, the magnetization of the samples reveals the intrinsic ferromagnetic (FM) behavior of undoped ZnO, ferromagnetic behavior of Zn_xMn${}_{1-x}$O $(0.01\le x\le 0.03)$ and the co-existence of ferromagnetic and paramagnetic behavior for Zn_xMn${}_{1-x}$O $(0.05\le x\le 0.10)$. This ferromagnetism is decreased for the doped samples as a consequence of antiferromagnetic coupling between Mn ions. The two samples correspond to $x=0.01$ and $x=0.10$, tend to be superparamagnetic because of the formation of single domain particles as a consequence of small particle size. $x=0.03$ shows an optimum value of Mn concentration for maximum saturation magnetization and the best ferromagnetic nature.

In this study, we use the atomic-scale finite element method to investigate the vibrational behavior of the armchair- and zigzag-structured nanoporous graphene layers with simply supported-free-simply supported-free (SFSF) and clamped-free-free-free (CFFF) boundary conditions. The fundamental frequencies computed for the graphene layers without pores are compared with the results of previous studies. We observe very good correspondence of our results with that of the other studies in all the considered cases. For the armchair- and zigzag-structured nanoporous graphenes with SFSF and CFFF boundary conditions, the frequencies decrease with increasing porosity. When the positions of the pores are symmetric with respect to the center of the graphene, the frequency of the zigzag nanoporous graphene is higher than that of the armchair one. To the best of our knowledge, this is first study investigating the relation between the vibrational behavior and porosity of nanoporous graphene layers, which is essential for tuning the material/structural design and exploring new applications for nanoporous graphenes.

This study designs Ni–Mg bimetallic catalysts for preparation of multi-walled carbon nanotubes (MWCNTs) from polypropylene (PP). The study further investigates the influence of Mg content on the catalytic activity of Ni catalyst. It is found that bimetallic Ni–Mg catalysts have higher reduction temperature, smaller Ni particle size and improved stability. Consequently, the addition of Mg not only enhances the yield of MWCNTs, but simultaneously improves the morphology and graphitization of MWCNTs. The activities of the bimetallic Ni–Mg catalysts are dependent on their composition. Among the different Ni–Mg bimetallic catalysts ration, Ni–Mg catalyst shows the highest activity when the ratio of Ni/Mg is 9/1. Moreover, the obtained MWCNTs presents smooth surface with highest graphitization degree. With our bimetallic Ni–Al catalyst, it is promising to achieve mass production of MWCNTs by using waste polymers as feedstock.

A novel conducting copolymer based on amidoxime groups, polypyrrole and graphene oxide was synthesized by in situ copolymerization by usin g two monomers. The monomer, amidoxime-pyrrole, was synthesized by amidoximation of 1-(2-cyanoethyl) pyrrole. The other monomer, GO-pyrrole, was prepared via esterification between –COOH of GO and –NH₂ of 1-(3-aminopropyl) pyrrole. The conductive ability of the copolymer was based on conductive $\pi$-conjugated system of polypyrrole backbone. The copolymer was able to be used as an effective sorption material for the preconcentration and recovery of uranium. The maximum of adsorption capacity for uranyl ion is as high as 149.57mg/g.

Silver nanoparticles (Ag NPs) were synthesized by one-step process in the presence of kollicoat as capping, reducing and stabilizing mediator. The synthesized NPs were characterized by using FTIR, TEM, DLS, XRD, EDS and UV-Vis spectroscopy. The resulting Ag NPs had an incomparable colloidal stability against the salt addition and change of pH. The effect of different synthesis parameters and the catalytic property of the NPs were examined.

In this work, Ni-doped ZnO/Al composites were prepared by a facile chemical co-precipitation method. The morphology and structure of the as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the flake-like Al powders were successfully coated by Ni-doped ZnO nanoparticles with slight aggregation and Ni${}^{2+}$ was successfully doped into the crystal lattice of ZnO. Moreover, the effects of ZnO concentration and doped Ni concentration on the infrared emissivity of ZnO/Al composites at the waveband range of 8–14$\mu$m were studied. The results showed that the ZnO/Al composites exhibited the lowest infrared emissivity of 0.34 with 50wt.% ZnO concentration. Meanwhile, the electromagnetic parameters and microwave absorbing properties of Ni-doped ZnO/Al composites in the frequency range of 2–18GHz were explored. Significantly, 12mol.% Ni-doped ZnO/Al composites presented the lowest infrared emissivity of 0.37 and the maximum reflection loss reached $-$32.5dB at 13.6GHz with a thickness of 4.5mm. The excellent microwave absorbing properties could be attributed to the good impedance match, crystal lattice defects and interfacial polarization. It was believed that the Ni-doped ZnO/Al composites could be used as potential infrared-microwave compatible stealth materials.

One-dimensional (1D) CuO/In₂O₃ heterostructured nanofibers with the diameter of about 300 nm were successfully prepared through combining a facile single-capillary electrospinning with sintering process, and investigated by thermogravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) techniques, etc. The photocatalytic activities were examined by degrading methylene blue (MB) under 500W xenon lamp, halogen lamp and mercury lamp irradiation, respectively. The heterostructured nanofibers exhibited a higher photocatalytic activity than P25-TiO₂ under 500W xenon lamp irradiation due to the enhanced absorption for visible light and the efficient electron–hole separation and transportation. The single CuO microfibers and In₂O₃ nanofibers were also prepared as the control groups by the same method.