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Abstract Based on a low-temperature route, monodispersed CoFe2O4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe2O4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe2O4 MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role.

Fe-doped LiNbO3 thin films were deposited on Si (111) substrates by RF magnetron sputtering technique. The X-ray absorption spectroscopy (XAS) at Fe K-edge revealed the incorporation of Fe ions into Nb sites in the LiNbO3 host lattice with Fe3+ and Fe2+ mixed-valent state. The local structural analysis also confirmed that oxygen vacancies are present in the nearest coordination shell of the Fe atoms. The SQUID results showed that all films exhibited room temperature ferromagnetism and the maximum magnetic moment was found when the Fe-doped concentration is 7 at%. The observed room temperature ferromagnetism of Fe-doped LiNbO3 films could be ascribed to the super-exchange interactions of pentahedral-pentahedral and pentahedral-octahedral Fe3+ ions mediated by the oxygen ions, as well as the double-exchange interactions based on the Fe2+-O2−-Fe3+ pairs. Our results demonstrated that the room temperature ferromagnetism can be activated in LiNbO3 ferroelectrics by introducing transition metal impurities. [ABSTRACT FROM AUTHOR]

Black 3D-TiO2 nanotube arrays are successfully fabricated on the Ti meshes through a facile electrochemical reduction method. The optimized black 3D-TiO2 nanotubes arrays yield a maximal photocurrent density of 1.6 mA/cm2 at 0.22 V vs. Ag/AgCl with Faradic efficiency of 100%, which is about four times larger than that of the pristine 3D-TiO2 NTAs (0.4 mA/cm2). Such boosted PEC water splitting activity primarily originates from the introduction of the oxygen vacancies, which results in the bandgap shrinkage of the 3D-TiO2 NTAs, boosting the utilization efficiency of visible light including the incident, reflected and/or refracted visible light captured by the 3D configuration. Moreover, the oxygen vacancies (Ti3+) can work as electron donors, which leads to the enhanced electronic conductivity and upward shift of the Fermi energy level, and thereby facilitating the transfer and separation of the photogenerated charge carrier at the semiconductor-electrolyte interface. This work offers a new opportunity to promote the PEC water splitting activity of TiO2-based photoelectrodes. [ABSTRACT FROM AUTHOR]

Temporal response is an important factor limiting the performance of two-dimensional (2D) material photodetectors. The deep trap states caused by intrinsic defects are the main factor to prolong the response time. In this work, it is demonstrated that the trap states in 2D molybdenum disulfide (MoS2) can be efficiently modulated by defect engineering through mild oxygen plasma treatment. The response time of the few-layer MoS2 photodetector is accelerated by 2–3 orders of magnitude, which is mainly attributed to the deep trap states that can be easily filled when O2 or oxygen ions are chemically bonded with MoS2 at sulfur vacancies (SV) sites. We characterized the defect engineering of plasma-exposed MoS2 by Raman, PL and electric properties. Under the optimal processing conditions of 30 W, 50 Pa and 30 s, we found 30-fold enhancements in photoluminescence (PL) intensity and a nearly 2-fold enhancement in carrier field-effect mobility, while the rise and fall response times reached 110 ms and 55 ms, respectively, at the illumination wavelength of 532 nm. This work would, therefore, offer a practical route to improve the performance of 2D dichalcogenide-based devices for future consideration in optoelectronics research. [ABSTRACT FROM AUTHOR]

Superparamagnetic ZnFe2O4/ZnS core–shell sub-microspheres were fabricated via a two-step forming method for recyclable photocatalytic degradation of bisphenol A (BPA) driven by visible light. The ZnFe2O4/ZnS nanocomposites display much higher photocatalytic efficiency as compared to that of the individual ZnFe2O4, which could remove about 97.7% of BPA in 135 min. The enhancement of photocatalytic activity is mainly attributed to the synergy effect of the energy band gap between ZnFe2O4 and ZnS, resulting in the enhanced visible light absorbance and separation efficiency of photo-generated electron–hole pairs. Specifically, the ZnFe2O4/ZnS nanocomposites can retain their stable photocatalytic activity toward BPA photodegradation for six successive cycles of reaction with rate constants of 0.0281–0.0272 min−1 under visible light irradiation. The highly recyclable and stable performance of ZnFe2O4/ZnS nanocomposites might benefit from its superparamagnetic, which nanocomposite could be rapidly separated from aqueous solution by an external magnetic field, and without agglomeration when magnetic field removed. Our work demonstrates a practical means for fabrication of superparamagnetic nanocomposite to improve the visible light photocatalytic activity and reusability of photocatalyst. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have been extensively applied to the electrode materials of supercapacitors for its intrinsic high capacitance, low electronegativity, low cost, and outstanding conductivity. However, the common vulcanization processes for preparing electrode materials of transition metal sulfides are generally time-consuming (nearly 10–24 h) and inseparable from high-temperature heat treatment (nearly 200–400 °C). In this paper, we introduce a rapid room temperature process with direct sulfuration (4 h) of precursors without additional preheating treatment steps to prepare the nail-like Cu2S nanoarrays with a partial interconnected structure on copper foam (Cu2S/Cu). As the electrode of supercapacitors, the Cu2S/Cu reveals good capacitance performance (1219 F g−1 at 5 mA cm−2) and outstanding cycling stability (92% retained after 5000 cycles at 30 mA cm−2). These superior electrochemical performances may be mainly due to the fact that the nail-like Cu2S nanoarrays with a partial interconnected structure will provide efficient transport pathways for both electrons and ions along the longitudinal axis of the one-dimensional nanostructure. [ABSTRACT FROM AUTHOR]

Abstract: Undoped and Mn-doped In2O3 films were prepared by radiofrequency magnetron sputtering technique. The effects of Mn doping on the structural and optical properties of as-prepared films were investigated using X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy. Mn doping can enhance the intensity of (222) peak in Mn-doped In2O3 thin film, indicating Mn dopant promotes preferred orientation of crystal growth along (222) plane. XPS analyses revealed that the doped Mn ions exist at + 2 oxidation states, substituting for the In3+ sites in the In2O3 lattice. UV-Vis measurements show that the optical band gap Eg decreases from 3.33 to 2.87 eV with Mn doping in In2O3, implying an increasing sp-d exchange interaction in the film. Our work demonstrates a practical means to manipulate the band gap energy of In2O3 thin film via Mn impurity doping, and significantly improves the photoelectrochemical activity.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Focusing on the Ni80Fe20 (Py)/Nd-Cu bilayers, the magnetization dynamic damping from spin pumping effect is investigated systematically by doping itinerant Cu in rear earth metal Nd. Various Ta/Py/Nd1-xCux/Ta/Si films with x = 0%, 16%, 38%, 46% and 58% are prepared by magnetron sputtering. For every content of Cu, the thickness of Nd-Cu layer is changed from 1 nm to 32 nm. The damping coefficient increases with increasing the thickness of Nd-Cu layer, which shows the trend of the spin pumping behavior. Also, with increasing Cu concentration in the Nd-Cu layer, the damping coefficient decreases, implying that the spin-orbit coupling in Nd-Cu layer is indeed cut down by high itinerant of Cu dopants. It is interesting that the spin diffusion length (λSD) in the Nd-Cu layer for different Cu dopants is not found to increase monotonously. [ABSTRACT FROM AUTHOR]

Abstract: Superparamagnetic Fe3O4 hollow microspheres with an average diameter of 240nm have been solvothermally synthesized where each of them is composed of primary nanoparticles with the size of 10–14nm. Based on electron microscopy technique, the morphological evolution with the reaction time is observed. Since the transformation from solid to hollow spheres was perceived, Ostwald ripening process is proposed to explain the formation of hollow microspheres. In particular, the magnetism investigation indicates that the as-prepared samples remain room-temperature superparamagnetic behavior with a high saturation magnetization (up to 83.5emu/g), which results from the separation of the primary magnetic nanoparticles. The excellent products may lead to many promising applications in enzyme immobilization, cancer therapies, and MRI contrast agents, and environment-friendly. [Copyright &y& Elsevier]

The search for above room temperature ferromagnetism in dilute magnetic semiconductors has been intense in recent year. Arrays of perpendicular ferromagnetic nanowire/rods have recently attracted considerable interest for their potential use in many areas of advanced nanotechnology. We report a simple low-temperature chemical vapor deposition (CVD) to create self-assembled comb-like Ni-/undoped ZnO nanostructure arrays. The phases, compositions, and physical properties of the studied samples were analyzed by different techniques, including high-resolution X-ray diffraction/photoelectron spectroscopy/transmission electron microscopy, photoluminescence, and MPMS. In particular, the Ni-doped ZnO nanocombs (NCs) with ferromagnetic and superparamagnetic properties have been observed whereas undoped ZnO NCs disappear. The corresponding ferromagnetic source mechanism is discussed, in which defects such as O vacancies would play an important role. [ABSTRACT FROM AUTHOR]

The core-shell structural Fe3O4/ZnS nanocomposites with controllable shell thickness were well-fabricated via seed-mediate growth method. Structural and morphological characterizations reveal the direct deposition of crystalline II-VI compound semiconductor ZnS shell layer on Fe3O4 particles. Spin dependent electrical transport is studied on Fe3O4/ZnS nanocomposites with different shell thickness, and a large magnetoresistance (MR) ratio is observed under the magnetic field of 1.0 T at room temperature and 100 K for the compacted sample by Fe3O4/ZnS nanocomposites, which is 50% larger than that of sample with pure Fe3O4 particles, indicating that the enhanced MR is contributed from the spin injection between Fe3O4 and ZnS layer. [ABSTRACT FROM AUTHOR]

A new combined system of ultrasound (US)/ H 2 O 2 /KI was presented in this study for the degradation of amoxicillin (AMX). Various parameters that influencing the degradation efficiency, such as ultrasonic power, pH value of the solution, concentrations of H 2 O 2 and KI, initial concentration of AMX were investigated. The maximum degradation efficiency of 84.1% in 60 min was obtained under the optimal conditions when the ultrasonic power was 195 W, the solution pH was 3.2, the concentrations of H 2 O 2 and KI were 120 and 2.4 mmol/L, respectively. Results also showed US/H 2 O 2 /KI system possessed better degradation efficiency compared with that by using the systems of US alone, H 2 O 2 , US/H 2 O 2 , US/KI and H 2 O 2 /KI. The degradation reaction of AMX should be a very complex process, and the corresponding degradation pathways may change at different concentrations or under different reaction conditions. The results indicate that the combined system of US/ H 2 O 2 /KI has great potential applications for the treatment of wastewater containing antibiotics with high concentrations.

We report the design, fabrication and characterization of novel TiO 2 nanotube photonic crystals with a crystalline core/disordered shell structure as well as substantial oxygen vacancies for photoelectrochemical (PEC) water splitting. The novel TiO 2 nanotube photonic crystals are fabricated by annealing of anodized TiO 2 nanotube photonic crystals in hydrogen atmosphere at various temperatures. The optimized novel TiO 2 nanotube photonic crystals produce a maximal photocurrent density of 2.2 mA cm -2 at 0.22 V versus Ag/AgCl, which is two times higher that of the TiO 2 nanotube photonic crystals annealed in air. Such significant PEC performance improvement can be ascribed to synergistic effects of the disordered surface layer and oxygen vacancies. The reduced band gap owing to the disordered surface layer and localized states induced by oxygen vacancies can enhance the efficient utilization of visible light. In addition, the disordered surface layer and substantial oxygen vacancies can promote the efficiency for separation and transport of the photogenerated carriers. This work may open up new opportunities for the design and construction of the high efficient and low-cost PEC water splitting system.