Solid-phase reaction synthesis of mesostructured tungsten disulfide material with a high specific surface area

A mesostructured tungsten disulfide (WS₂) material was prepared through a solid-phase reaction utilizing ammonium tetrathiotungstate as the precursor and n-octadecylamine as the template. The as-synthesized WS₂ material was characterized by X-ray powder Diffraction (XRD), Low-temperature N₂ Adsorption (BET method), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The characterization results indicate that the WS₂ material has the typical mesopore structure (3.7 nm) with a high specific surface area (145.9 m²/g), and large pore volume (0.18 cm³/g). This approach is novel, green and convenient. The plausible mechanism for the formation of the mesostructured WS₂ material is discussed herein.     

Preparation of modified nano ZnO/polyester/TGIC powder coating nanocomposite and evaluation of its antibacterial activity

Powder coating nanocomposite with antibacterial properties is the aim of this study. For this purpose, nano zinc oxide was modified by vinyltrimethoxysilane (VTMS) and Triethoxy(methyl)silane (TEMS). Then various percentages of modified and non-modified nano ZnO (1, 3 and 5%), polyester resin and triglycidyl isocyanurate as a hardener were blended by twin screw extruder. Prepared polymer–matrix composite (PMC) was atomized and coated by electrostatic method on aluminum plates. Finally, samples were cured for 10 min at 200 °C. For investigating the thermal stabilities of modified nano particles, thermogravimetric analyses (TGA) were used. Antibacterial properties of coatings were investigated by gram negative bacteria Escherichia coli and gram positive Staphylococcus aureus. The results showed that the coatings demonstrate significant antibacterial activity by increasing amounts of ZnO nanoparticles (5%) when were modified by VTMS.     

Facile preparation of carbon coated magnetic Fe3O4 particles by a combined reduction/CVD process

In this work, we report a simple method for the preparation of magnetic carbon coated Fe₃O₄ particles by a single step combined reduction of Fe₂O₃ together with a Chemical Vapor Deposition process using methane. The temperature programmed reaction monitored by Mössbauer, X-ray Diffraction and Raman analyses showed that Fe₂O₃ is directly reduced by methane at temperatures between 600 and 900 °C to produce mainly Fe₃O₄ particles coated with up to 4 wt% of amorphous carbon. These magnetic materials can be separated into two fractions by simple dispersion in water, i.e., a settled material composed of large magnetic particles and a suspended material composed of nanoparticles with an average size of 100-200 nm as revealed by Scanning Electron Microscopy and High-resolution Transmission Electron Microscopy. Different uses for these materials, e.g., adsorbents, catalyst supports, rapid coagulation systems, are proposed.     

Facile and template-free preparation of α-MnO2 nanostructures and their enhanced adsorbability

In this paper, nanostructured MnO₂ materials were successfully prepared through a simple and template-free hydrothermal method. X-ray diffraction pattern indicates that the as-prepared nanomaterials are α-MnO₂. Transmission Electron Microscopy and Scanning Electron Microscopy images demonstrate that nanostructured rod-clusters α-MnO₂ could be evolved from the nanorods. Brunauer-Emmett-Teller (BET) surface area measurement was employed to characterize the surface property. Moreover, the as-obtained (α-MnO₂) nanomaterials could act as an efficient adsorbent to remove Congo Red and Methlylene Blue. More significantly, the nanomaterials are nontoxic and environmentally friendly via biological methylthiazolyldiphenyltetrazoliumbromide assay experiments. Its nontoxic and enhanced adsorbability properties guarantee their safe applications in environmental protection and industrial aspects.     

Effect of crystallite size of zinc oxide on the mechanical,thermal and flow properties of polypropylene/zinc oxide nanocomposites

ZnO nanoparticles were prepared using zinc chloride and sodium hydroxide in chitosan medium. Prepared ZnO (NZO) and commercial ZnO (CZO) was characterized by scanning electron microscopic and X-ray diffraction studies. PP/ZnO nanocomposites were prepared using 0–5 wt% of zinc oxide by melt mixing. It was then compression moulded into films. Transparency of the composite films were improved by reducing the crystallite size of ZnO. Melt flow index studies revealed that NZO increased the flow characteristics of PP while CZO decreased. X-ray diffraction studies indicated α-form of isotactic polypropylene. An increase in mechanical properties, dynamic mechanical properties and thermal stability of the composites were observed by the addition of ZnO. Uniform dispersion of the ZnO was observed in the scanning electron micrographs of the tensile fractured surface of composites.     

Structure and superparamagnetic behaviour of magnetite nanoparticles in cellulose beads

Superparamagnetic magnetite nanoparticles were obtained starting from a mixture of iron(II) and iron(III) solutions in a preset total iron concentration from 0.04 to 0.8 mol l⁻¹ with ammonia at 25 and 70 °C. The regeneration of cellulose from viscose produces micrometrical spherical cellulose beads in which synthetic magnetite were embedded. The characterization of cellulose-magnetite beads by X-ray diffraction, Scanning and Transmission Electron Microscopy and magnetic measurement is reported. X-ray diffraction patterns indicate that the higher is the total iron concentration and temperature the higher is the crystal size of the magnetite obtained. Transmission Electron Microscopy studies of cellulose-magnetite beads revealed the distribution of magnetite nanoparticles inside pores of hundred nanometers. Magnetite as well as the cellulose-magnetite composites exhibit superparamagnetic characteristics. Field cooling and zero field cooling magnetic susceptibility measurements confirm the superparamagnetic behaviour and the blocking temperature for the magnetite with a mean size of 12.5 nm, which is 200 K.     

载银锌4A沸石抗菌剂抗变色性能的研究

通过调整抗菌剂中银、锌离子的含量,研究了载银锌4A沸石抗菌剂的抗变色性能.利用ICPS测定了样品的银、锌含量,通过XRD、IR、TEM表征了抗菌剂的结构和形貌,并对其抗变色性能和抗菌性能进行了测试和分析.结果表明,减少ZLSZ抗菌剂中银离子(Ag )的含量,增加锌离子(Zn2 )的含量,抗菌剂样品的抗菌性能变化不大,而抗变色性能却大幅度提高.从抗菌剂的成本、抗菌性能和抗变色性能等方面综合考虑,载银锌4A沸石抗菌剂中,银含量为0.41wt%,锌含量为3.83wt%为宜.     

Antibacterial study of Mg(OH)2 nanoplatelets

It was reported previously that Mg(OH)₂ nanoplatelets are effective antibacterial agent [1]. This paper further studied the mechanism study of Mg(OH)₂ nanoplatelets against Escherichia coli. Both experimental results and SEM analysis indicated that the membrane of the bacterial cell was destroyed by the direct contact with the Mg(OH)₂ nanoplatelets, leading to the cell death. In addition, UV illumination could further improve the antibacterial efficiency of Mg(OH)₂ nanoplatelets. Compared with other nanoparticles, it was also found that Mg(OH)₂ nanoplatelets have higher antibacterial efficiency, implicating their great potential application in biological control.     

Microwave dielectric properties and microstructures of CuO- and ZnO-doped LaAlO3 ceramics

The microwave dielectric properties and the microstructures of 0.25 wt.% CuO-doped LaAlO₃ ceramics with ZnO additions have been investigated. The sintered LaAlO₃ ceramics are characterized by X-ray diffraction spectra and scanning electron microscopy (SEM). Tremendous reduction in sintering temperature can be achieved with the addition of sintering aids CuO and ZnO. The ceramic samples show that dielectric constants (ε_r) of 22−24 and Q×f values of 33,000−57,000 (at 9.7 GHz) can be obtained at low sintering temperatures 1340−1460°C. The temperature coefficient of resonant frequency varies from −24 to −48 ppm/°C. At the level of 0.25 wt.% CuO and 1 wt.% ZnO additions, LaAlO₃ ceramics possesses a dielectric constant (ε_r) of 23.4, a Q×f value of 57,000 (at 9.7 GHz) and a τ_f value of −38 ppm/°C at 1400°C for 2 h.     

Second Harmonic Generation induced by optical poling in new TeO2-Tl2O-ZnO glasses

New tellurite glasses with a large glass forming domain were elaborated within the TeO₂-Tl₂O-ZnO ternary system. The evolution of the glass transition (T_g) and onset crystallization (T₀) temperatures for such tellurite glasses was studied, in particular, as a function of the Tl₂O addition. A decrease of both T_g and T₀ temperatures was observed; the former being more affected. Structural modifications induced by the addition of the modifiers were studied by Raman spectroscopy. For a fixed ZnO concentration, the increase in the Tl₂O content leads to a destruction of the glass framework, characterized by the transformation of TeO₄ disphenoids into isolated TeO₃²⁻ trigonal pyramid-like ortho-groups. For a fixed Tl₂O concentration, the ZnO addition induces similar effects on the glass structure. The optical transmission of the ((80 − x)TeO₂-xTl₂O-20ZnO) (x = 10, 20 and 30 mol%) glasses was measured in the 300-2000 nm range. Their good transparency was evidenced and a clear reduction of the optical band-gap was noticed with the increase in the Tl₂O content. Finally, Second Harmonic Generation was unambiguously detected for each glass composition. The second order non-linearity amplitude is found to be increasing as a function of the Tl₂O concentration, in the tested range.     

Effect of synthesis conditions on the nanopowder properties of Ce0.9Zr0.1O2

In this work, the synthesis of nanocrystalline Ce_0.9Zr_0.1O₂ powders via the gel-combustion method, using different fuels, and following either stoichiometric or non-stoichiometric pH-controlled routes is investigated. The objective is to evaluate the effect of synthesis conditions on the textural and morphological properties, and the crystal structure of the synthesized materials. The solids were characterized by nitrogen physisorption, Scanning Electron Microscopy (SEM), X-ray powder diffraction (XPD), and Carbon-Hydrogen-Nitrogen Elemental Analysis (CHN).All the powders exhibited nanometric crystallite size, fluorite-type structure and negligible carbon content. Synthesis conditions strongly affect the average crystallite size, the degree of agglomeration, the specific surface area and the pore volume. Our results indicate that, by controlling the synthesis conditions it is possible to obtain solids with custom-made morphological properties.     

Influence of annealing on structural, morphological and optical properties of Cd x Zn1?x O nanopowder prepared by Co-precipitation method

Structural and optical properties of Cd _x Zn_1?x O (x = 0.0, 0.025, 0.050, 0.075, 0.1) nanopowder, synthesized by co-precipitation method have been investigated. The effect of annealing on the structural and morphological properties was studied using X-ray diffraction. The samples with x = 0.0 up to 0.075 exhibit wurtzite hexagonal phase, whereas, the sample with x = 0.1 shows two phases: wurtzite hexagonal ZnO and cubic CdO phase. This behavior is explained on the basis of solubility of CdO in ZnO. Energy Dispersive X-ray analysis (EDX) results revealed the existence of Cd, Zn, and O elements in the nanopowder. Transmission Electron Microscopy (TEM) images confirm that the particle size of the prepared samples is in nano range. The optical band gap values obtained from the absorption spectra show that absorption depends on Cd composition. By doping of ZnO with CdO, a red shift in the absorption edge was observed.     

Studies on the structural and optical properties of zinc oxide nanobushes and Co-doped ZnO self-aggregated nanorods synthesized by simple thermal decomposition route

Pure and Co-doped zinc oxide nanomaterials were prepared by a simple low temperature synthesis and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), diffused reflectance spectroscopy (DRS) and electron paramagnetic resonance (EPR) techniques. The results showed the formation of nanobushes that consists of several nanowires for pure ZnO and the nanorods formed by self-aggregation for Co-doped ZnO. The presence of Co²⁺ ions replacing some of the Zn²⁺ in the ZnO lattice was confirmed by EPR and DRS studies. The mechanism for the formation of self-aggregated and self-aligned ZnO rods after the incorporation of cobalt in the lattice by the building block units is discussed in this study. Morphological studies were carried out using SEM and HR-TEM, which supports the validity of the proposed mechanism for the formation of ZnO nanobushes and Co-doped ZnO nanorods. The synthesized nanomaterials were found to have good optoelectronic properties.     

Facile synthesis of highly branched jacks-like ZnO nanorods and their applications in dye-sensitized solar cells

Highly branched, jacks-like ZnO nanorods architecture were explored as a photoanode in dye-sensitized solar cells, and their photovoltaic performance was compared with that of branch-free ZnO nanorods photoanodes. The highly branched network and large pores of the jacks-like ZnO nanorods electrodes enhances the charge transport, and electrolyte penetration. Thus, the jacks-like ZnO nanorods DSSCs render a higher conversion efficiency of η = 1.82% (V_oc = 0.59 V, J_sc = 5.52 mA cm⁻²) than that of the branch-free ZnO nanorods electrodes (η = 1.08%, V_oc = 0.49 V, J_sc = 4.02 mA cm⁻²). The incident photon-to-current conversion efficiency measurements reveal that the jacks-like ZnO nanorods DSSCs exhibit higher internal quantum efficiency (∼59.1%) than do the branch-free ZnO nanorods DSSC (∼52.5%). The charge transfer resistances at the ZnO/dye/electrolyte interfaces investigated using electrochemical impedance spectroscopy showed that the jacks-like ZnO nanorods DSSC had high charge transfer resistance and a slightly longer electron lifetime, thus improving the solar-cell performance.     

Photoluminescence characteristics of ZnO clusters confined in the micropores of zeolite L

Sub-nanometric ZnO clusters were prepared in the micropores of zeolite L by the incipient wetness impregnation method. The X-ray patterns (XRD), transmission electron microscope (TEM), N₂ adsorption-desorption isotherms, UV-vis absorption spectra (UV-vis) and photoluminescence spectra (PL) were used to characterize the composite materials. The results indicate that a small amount of sub-nanometric ZnO clusters can be introduced into the channel of zeolite L, however, when the amount of ZnO loading exceeds 20 wt%, macrocrystalline ZnO appears on the external surface of zeolite L. Different from bulk ZnO materials, these sub-nanometric ZnO clusters exhibit their absorption onset below 255 nm and a blue luminescence band in the range of 404-422 nm. The temperature-dependent luminescence demonstrates that the amount of the ZnO loading significantly affects the exciton-phonon interaction between the ZnO clusters and the zeolite host. The ZnO clusters exhibit a picosecond scale emission lifetime at room temperature.     

Structure and photocatalytic activity of Ni-doped ZnO nanorods

The one-dimensional (1D) Zn_1−xNi_xO (x = 0, 0.02, 0.05, 0.10) nanorods have been synthesized by a simple hydrothermal method. New bands show at ∼130 cm⁻¹ in the Raman spectra of Ni-doped ZnO nanorods and their relative intensity depends on the doping concentration of nickel. The optical band gap of the ZnO nanorods have been tuned by Ni-doping, which is revealed by absorption spectra. The photocatalytic activity of Zn_1−xNi_xO was studied by comparing the degradation rate of rhodamine B (RB) under UV-light irradiation. It was found that Zn_0.95Ni_0.05O exhibited the highest photocatalytic degradation efficiency among the samples.     

Dielectric response and energy storage efficiency of low content TiO2-polymer matrix nanocomposites

TiO₂/epoxy nanocomposites were prepared at different filler concentrations varying from 3 to 12 phr (parts per hundred resin per weight). The dispersion of TiO₂ was examined by Scanning Electron Microscopy and proved to be adequate. Differential Scanning Calorimetry was implemented to determine the glass to rubber transition temperature of the polymer matrix. The dielectric analysis was performed via Broadband Dielectric Spectroscopy in a wide frequency and temperature range. Five different mechanisms were observed in the spectra of the examined composites which are identified, in terms of increasing temperature at constant frequency, as γ, β, Intermediate Dipolar Effect (IDE), α and Interfacial Polarization (IP) relaxation modes. The activation energies of all relaxation modes were calculated. Finally, the dielectric response of the TiO₂ nanocomposites compared to that of the TiO₂ microcomposites reveals that the former exhibit significantly higher energy storage efficiency even at lower TiO₂ concentration than the corresponding of the microcomposites.     

Preparation of polymer nanocomposites of core-shell structure via surface-initiated atom transfer radical polymerizations

Polymer nanocomposites of core-shell structure were prepared by grafting poly(tert-butyl acrylate) (Pt-BA) from SiO₂ nanoparticle via the surface-initiated polymerization (SIP) strategy. This new organic inorganic hybrid particle has been extensively characterized by XPS (X-ray Photoelectron Spectroscopy), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), and TGA (ThermoGravimetric Analysis).     

Electromechanical properties of PZT/P(VDF-TrFE) composite ink printed on a flexible organic substrate

The fabrication and electromechanical properties of composite inks consisting of 30–70 vol.% of piezoceramic PZT powder and piezoelectric co-polymer P(VDF-TrFE) are presented. Samples were stencil-printed on a commercial PET film and printable silver ink was used for the electrodes thus allowing a maximum process temperature of 130 °C. The relative permittivity at 1 kHz varied between 33 and 69 depending on poling and composite composition. The highest remanent polarization, up to 4.8 μC/cm², with 34 MV/m electric field and piezoelectric coefficient d₃₁ up to 17 pm/V, was obtained with a 50 vol.% PZT loading level. The mechanical and electrical results indicate that the developed composite ink enables fully printable and flexible sensor applications with an increased level of integration.     

Novel PEGylated pH-sensitive polymeric hollow microspheres

Novel PEGylated pH-sensitive poly[methacrylic acid-co-poly(ethylene glycol) methyl ether methacrylate] [P(MAA-co-PEGMA)] hollow microspheres were synthesized by a two-stage distillation precipitation polymerization. PMAA@P(MAA-co-PEGMA) core shell microspheres were synthesized by the second-stage polymerization of MAA and PEGMA, using the N,N′-methylenebisacrylamide (MBAAm) as crosslinker in the presence of non-crosslinked PMAA microspheres. The cavity was formed by selective removal of PMAA core in ethanol. The resulted PEGylated hollow microspheres were characterized with Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). The shrink and swelling behavior under different pH was studied by Dynamic Light Scattering (DLS).