Nano

In the present work, we synthesized a composite medium consisting of Ag nanorods embedded in Co${}_{0.05}$Ti${}_{0.95}$O₂ matrix (Ag/CTO) using the sol-gel method. We applied a uniform AC electric field at the beginning of gelation and during drying for manipulating Ag nanorods in the matrix.

The structure and morphology characterizations of Ag/CTO nanocomposites were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The permittivity and permeability behaviors of samples were investigated. Results showed that for the sample dried in the existence of the electric field, simultaneous negative permittivity and permeability were realized. These results imply the realization of double negative properties in this sample. Therefore, this work suggests that Ag/Co${}_{0.05}$Ti${}_{0.95}$O₂ nanocomposites can be introduced as a negative index metamaterials (NIMs).

Li₄Ti₅O₁₂–rutile TiO₂ (LTO–RTO) dual-phase nanocomposite anode materials show excellent electrochemical performance. However, the effects of molar ratio of Li/Ti and thermal treatment on electrochemical properties of the LTO–RTO composite have been rarely reported. In this work, LTO–RTO nanocomposites were prepared by sol-hydrothermal method with different Li/Ti molar ratios in raw materials and following calcinations at 600${}^{\circ }$C, 650${}^{\circ }$C and 700${}^{\circ }$C for the different holding time. The results indicate that with the decrease of Li/Ti molar ratio, the discharge capacity of the LTO–RTO nanocomposite increases at first and then decreases, and the optimal Li/Ti molar ratio is 4:4.77, which was obtained with calcination at 600${}^{\circ }$C for 10h. The effects of calcination temperature and holding time were further investigated. The result demonstrates that the thermal treatment has an obvious influence on the electrochemical performance due to the morphology change in the nanocomposite. The LTO–RTO nanocomposite calcinated at 650${}^{\circ }$C for 2h with a Li/Ti molar ratio of 4:4.77 in raw materials delivers excellent rate capability: the initial discharge capacity is 175.9, 176.3, 170.4, 167.5, 163.3 and 155.6mA h g${}^{-1}$ at the rate of 0.5, 1, 3, 5, 10 and 20${}^{\circ }$C (1 C$=$175 mA h g${}^{-1}$), respectively.

Geometrical structures of (ZnSe)_n, $n=3x$, ($x=$ 1–4) and (Mn_xZn${}_{2x}$Se${}_{3x})$, ($x=1-4)$ clusters were calculated using density functional theory (DFT). Optical/absorption spectra, Raman spectra, HOMO–LUMO gap energy and binding energy of each cluster were calculated. The calculated results show the red shift of the optical/absorption spectra band caused by the manganese atoms doped in ZnSe clusters, and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) gap energy value is decreased. Furthermore, we realized highly monodispersed manganese-doped zinc selenide quantum dots (Mn:ZnSe d-dots) experimentally by using a convenient route. The as-synthesized Mn:ZnSe d-dots were characterized by UV-Vis absorption, photoluminescence (PL), X-ray diffraction (XRD), TEM and HRTEM. The experimental results revealed that the as-prepared Mn:ZnSe d-dots with zinc-blende structure have an average size of about 3.9 nm.

BiOCl/SnS₂ core-shell heterojunction is prepared by a facile and economic hydrothermal method. The obtained BiOCl/SnS₂ heterojunction displays high photocatalytic activity in the degradation of Rhodamine B (RhB). The high performance is explained by the fast separation of the photoinduced electron–hole pairs promoted by the heterojunction. The cycle life of the heterojunction is also improved compared with individual BiOCl or SnS₂.

Ti${}^{3+}$ self-doped TiO₂ (TiO${}_{2-x}$)/N-doped carbon nanostructure composites were prepared via a facile one-step hydrothermal method to optimize the use of visible light and reduce recombination of photogenerated electrons and holes. The composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The amounts of carbon and nitrogen sources affect the morphology and photocatalytic performance. At low amounts of the sources, the N-doped carbon nanostructure is an amorphous film and is well-combined with TiO${}_{2-x}$ nanoparticles through surface carbon–oxygen groups. At high amounts of the sources, N-doped carbon quantum dots (NCQDs) were obtained, and carbon atoms could substitute for oxygen atoms in the TiO₂ lattice to form Ti–C structures, which are responsible for the high photocatalytic activity under visible light illumination. Transient photocurrent response and electrochemical impedance spectroscopy results indicate that the amorphous hybrid film becomes a trap for electrons and that NCQDs can accelerate electron transfer. The improved visible light photocatalytic property for the TiO${}_{2-x}$/NCQDs composite can be attributed to the enhancement of light absorption and inhibition of the photogenerated electron–hole recombination of anchored NCQDs.

The ZnCo₂O₄ nanorods and nanosheets were grown on nickel foam by a facile and effective hydrothermal method, respectively. The effect of the morphologies of the nanostructures on electrochemical performance was investigated. Importantly, ZnCo₂O₄ nanorod electrodes with a high specific surface area exhibited a higher specific capacitance of 2457.4 F g${}^{-1}$ at 2 A g${}^{-1}$ and remarkable cycling stability with capacitance retention of 97.7% after 1000 cycles, which are superior to those of ZnCo₂O₄ nanosheet electrodes. Such a result is well explained. The investigation on the electrochemical properties of these two nanostructures as electrodes confirmed that the morphology of active materials has an important impact on electrochemical properties.

BiOI/HZSM-5 composites were synthesized via a facile and environmentally-benign hydrothermal method. The crystalline structures and morphologies of the powder have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity of samples was tested for degradation of methylene blue (MB) and Rhodamine B (RhB) dye under simulated solar light irradiation. The degradation rate of MB and RhB by BiOI/HZSM-5 composite photocatalysts respective reach 99.6% and 98.6% under visible light irradiation, BiOI/HZSM-5 exhibited the highest photocatalytic performance when compared with pure BiOI.

In this study, Zn-doped Fe₃O₄ nanoparticles were successfully synthesized by a facile solvothermal method in the presence of sodium dodecyl sulfate (SDS). The morphology, magnetic properties and electromagnetic wave absorbing properties of these materials were characterized. Results showed that Zn${}^{2+}$ played a significant role in the formation of Zn-doped Fe₃O₄. With the protection of SDS, highly dispersed Fe₃O₄ nanoparticles were obtained. The nanoparticle size decreased after Zn${}^{2+}$ doping, and the dispersity deteriorated with increasing Zn${}^{2+}$ doping concentration. Zn-doped Fe₃O₄ exhibited excellent electromagnetic wave absorbing property, which resulted in magnetic loss and dielectric loss at an appropriate doping concentration. The minimum reflection loss (RL) was approximately $-27.2$dB at 16.9GHz. As the coating layer thickness increased to 4.0mm, the bandwidth was approximately 5.0GHz corresponding to RL below $-10$dB, which nearly covered the entire S band (2–4GHz) and C band (4–8GHz). The peak frequency of RL and the number of peaks matched the quarter-wave thickness criteria. It was believed that the Zn-doped Fe₃O₄ could be a potential electromagnetic wave absorbing material in S and C bands.

Nanostructured metal oxide-based resistive-type gas sensors are of high research interest. Chemical stability is the most critical issue due to the surface electron species and density. In the present paper, 2D-nanostructured WO₃ was prepared and characterized, and a WO₃-based sensor was fabricated and analyzed. The results showed that the synthesized WO₃ material exhibited nanosheet structure, and during hydrogen sensing testing, the current baseline shifted with various tendencies, even completely opposite directions under different operation temperatures. The chemistry analysis results indicated that water molecule and hydroxyl group were formed under low operation temperature but further oxidation occurred at higher temperatures. The adsorption of H₂ on oxygen terminated WO₃(0 0 1) surfaces by density functional theory (DFT) method indicated that a water molecule formed by adsorption of a hydrogen molecule at the O site with the most thermodynamically stable state, and two surface hydroxyl groups formed by dissociative adsorption with a thermodynamically less stable state. The water molecule and surface hydroxyl groups increased the conductivity of the WO₃ film while that was decreased as the oxidation occurred.

In the present study, the effect of particle concentration, particle diameter and temperature on the thermal conductivity and viscosity of Al₂O₃/water nanofluids was investigated experimentally using design of experiment approach (full factorial design). Variables were selected at two levels each: particle concentration (0.1–1%), particle diameter (20–40nm) and temperature (10–40${}^{\circ }$C). It was observed that the thermal conductivity of the Al₂O₃/water nanofluids increases with increasing concentration and temperature and decreases with increase in particle diameter, while viscosity increases with increasing particle diameter. Results showed that the interaction effect of concentration and temperature also has significant effect on the thermal conductivity of Al₂O₃/water nanofluids. For viscosity, the interaction of particle diameter and temperature was important. Utility concept was used to optimize the properties collectively for better heat transfer performance. The optimal combination for high thermal conductivity and low viscosity was obtained at higher level of particle concentration (1%), lower level of particle diameter (20nm) and higher level of temperature (40${}^{\circ }$C). At this condition the increment in thermal conductivity and viscosity compared to base fluid was 11.51% and 6.37%, respectively.

Thiol-functionalized three-dimensional (3D) mesoporous silica FDU-12 and SBA-15 with ordered pore were prepared. All the obtained materials were characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Mesoporous silica FDU-12 (Fm3m) materials with various unit cell sizes, multifaceted pore were convenient for the interaction of subject and object; the 2D SBA-15 mesoporous silica materials with short and order pore channel were better than the traditional SBA-15 mesoporous silica, in which the pore channel can be used fully. 3D mesoporous silica FDU-12 is used as a sensing material to reconstruct QCM sensors to enhance the stability and this material is an ideal material to deal with heavy metal ions in water.

In this study, flower-like Bi₂MoO₆/BiOI heterostructure photocatalysts were synthesized via an anion exchange method using BiOI as precursor. The composition of Bi₂MoO₆/BiOI can be easily controlled by adjusting the MoO${}_4^{2-}$/I${}^{-}$ molar ratio. Photocatalytic activity studies based on the degradation of Rhodamine B (RhB) show that Bi₂MoO₆/BiOI$=$50% photocatalyst exhibited the best performance under visible light excitation. The radical scavengers test demonstrated that holes was the main reactive species for the degradation of RhB, and$\cdot$O${}^{2-}$ also took part in the photodecomposition process. Photoelectrochemical measurement reveals that the Bi₂MoO₆/BiOI$=$50% exhibit enhanced carrier densities, charge separation and photocurrent compared with the original Bi₂MoO₆ and BiOI. Our results show that bismuth-based heterojunctions fabricated through the anion exchange method could be a cost-effective approach to improve the photocatalytic activity and photoelectrochemical performance of BiOI.