Carbon-coated ZnFe2O4 spheres with sizes of ~110–180 nm anchored on graphene nanosheets (ZF@C/G) are successfully prepared and applied as anode materials for lithium ion batteries (LIBs). The obtained ZF@C/G presents an initial discharge capacity of 1235 mAh g?1 and maintains a reversible capacity of 775 mAh g?1 after 150 cycles at a current density of 500 mA g?1. After being tested at 2 A g?1 for 700 cycles, the capacity still retains 617 mAh g?1. The enhanced electrochemical performances can be attributed to the synergetic role of graphene and uniform carbon coating (~3–6 nm), which can inhibit the volume expansion, prevent the pulverization/aggregation upon prolonged cycling, and facilitate the electron transfer between carbon-coated ZnFe2O4 spheres. The electrochemical results suggest that the synthesized ZF@C/G nanostructures are promising electrode materials for high-performance lithium ion batteries.
Layered zinc-based metal-organic framework ([Zn(4,4′-bpy)(tfbdc)(H2O)2], Zn-LMOF) nanosheets were synthesized by a facile hydrothermal method (4,4′-bpy = 4,4′-bipyridine, H2tfbdc = tetrafluoroterephthalic acid). The materials were characterized by IR spectrum, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, transmission electron microscope (TEM), scanning electron microscope (SEM), and the Brunauer–Emmett–Teller (BET) surface. When the Zn-LMOF nanosheets with the thickness of about 24 ± 8 nm were used as an anode material of lithium-ion batteries, not only the Zn-LMOF electrode shows a high reversible capacity, retaining 623 mAh g?1 after 100 cycles at a current density of 50 mA g?1 but also exhibits an excellent cyclic stability and a higher rate performance.
Graphical abstract Zinc-based layered metal-organic framework ([Zn(4,4′-bpy)(tfbdc)(H2O)2], Zn-LMOF) nanosheets have been synthesized, displaying a high capacity as anode materials for lithium-ion batteries.
Zirconia nanoparticles (ZrO2 NPs) have been extensively used in teeth and bone implants and thus get a chance to interact with the physiological system. The current study investigated the oral administration of various concentrations of ZrO2 NPs synthesized by the hydrothermal method (0.25 to 5.0 mg L?1) on Drosophila physiology and behaviour. The size of the currently studied nanoparticle varies from 10 to 12 nm. ZrO2 NPs accumulated within the gut in a concentration-dependent manner and generate reactive oxygen species (ROS) only at 2.5 and 5.0 mg L?1 concentrations. ROS was detected by nitroblue tetrazolium (NBT) assay and 2′,7′-dichlorofluorescein (H2DCF) staining. The ROS toxicity alters the larval gut structure as revealed by DAPI staining. The NP stress of larvae affects the Drosophila development by distressing pupa count and varying the phenotypic changes in sensory organs (eye, thorax bristle, wings). Besides phenotypic changes, flawed climbing behaviour against gravity was seen in ZrO2 NP-treated flies. All together, for the first time, we have reported that a ROS-mediated ZrO2 NP toxicity alters neuronal development and functioning using Drosophila as a model organism.
A novel nano-size MnxOy/clinoptilolite catalyst of high activity for propane-SCR reaction of NOx at low temperatures has been synthesized by a hydrothermal method in a temperature range of 80–180 °C. The optimum synthesis temperature resulting in maximum NOx conversion was 150 °C. An optimum manganese oxide loading of 0.2 wt.% results in the best catalytic behavior (71% NOx conversion). All catalysts exhibited an optimal propane-SCR reaction temperature of 200 °C. The optimum catalyst produces no detectable CO (GHSV 27,000 h) at 200 °C. Manganese in the optimum catalyst exists as Mn2+ (37.8%), Mn3+ (14.2%), and Mn4+ (48%).
Graphical abstract Flake-like manganese oxide nanostructures (indicated by an arrow in the TEM picture) next to the clinoptilolite zeolite sheet-like crystals result in a promising low-temperature propane-selective catalytic reduction of NOx.
Addition reaction between C60 and ethylenediamine occurred at room temperature in an ambient condition. C60-ethylenediamine adduct particles were prepared by mixing toluene solutions of C60 and ethyelenediamine. Average diameter of the C60-ethylenediamine adduct particles was changed non-linearly according to the reaction time, which were observed using transmission electron microscopy. Early stage of the reaction, the diameter of the adduct particles was changed from about 250 to about 430 nm. Then, the size of the adduct particles was converged to about 300 nm. During this addition reaction, the crystalline sizes of adduct particles were constant about 2–3 nm, regardless of the sizes of the adduct particles, which were determined by X-ray diffraction measurement.
Ternary composites of BiFeO3/graphene nanoplatelet (GNP)/epoxy composites were synthesized and its electromagnetic and microwave absorbing properties were studied; the main absorbing mechanism was illustrated. The phase, microstructure, and microwave absorbing properties were characterized by X-ray diffraction, scanning electron microscope, and vector network analyzer. The results indicated that the BiFeO3 was successfully synthesized and the GNP was uniformly distributed in the composites, and the complex permittivity of BiFeO3/GNP/epoxy composites increased with increasing the GNP content due to the interface polarization and conductance loss. The minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm when the GNP content was 2 wt%, and also the absorbing properties of (BiFeO3+GNP)/epoxy composites can be tailored by the GNP content and composite thickness, which may be used as a kind of absorbing materials with good absorbing performance and low density.
Graphical abstract The reflection loss curves and the simulated matching thickness of GNP-BiFeO3-epoxy composites with 2 wt% GNP content. As can be seen, the minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm, and also the quarter-wavelength matching theory can be used to illustrate the good absorbing properties of GNP-BiFeO3-epoxy composites.
In this paper, the green synthesis of fluorescent carbon dots (CDs) via one-step hydrothermal treatment of cornstalk was investigated. This approach is facile, economical, and effective. The obtained CDs with an average diameter of 5.2 nm possess many excellent properties such as emitting blue fluorescence under UV light (365 nm), high monodispersity, good stability, excellent water dispersibility, and absolute quantum yield of 7.6%. Then, these CDs were used as sensing probes for the detection of Fe2+ and H2O2 with detection limits as low as 0.18 and 0.21 μM, respectively. This sensing platform shows advantages such as high selectivity, good precision, rapid operation, and avoiding the precipitation of iron oxyhydroxides.
Ruthenium/reduced graphene oxide nanocomposites (Ru/rGO NCs) were synthesized via an electrostatic self-assembly approach. Polyvinylpyrrolidone (PVP) stabilized and positively charged metallic ruthenium nanoclusters about 1.2 nm were synthesized and uniformly loaded onto negatively charged graphene oxide (GO) sheets via strong electrostatic interactions. The as-prepared Ru/rGO NCs exhibited superior performance in catalytic hydrolysis of sodium borohydride (NaBH4) to generate H2. The hydrogen generation rate was up to 14.87 L H2 min?1 gcat?1 at 318 K with relatively low activation energy of 38.12 kJ mol?1. Kinetics study confirmed that the hydrolysis of NaBH4 was first order with respect to concentration of catalysts. Besides, the conversion of NaBH4 remained at 97% and catalytic activity retained more than 70% after 5 reaction cycles at room temperature. These results suggested that the Ru/rGO NCs have a promising prospect in the field of clean energy.
In the synthesis of nanostructures by pulsed laser deposition (PLD), a crucial role is played by the environmental deposition pressure and the substrate temperature. Due to the high temperature of nanoparticles (NPs) at landing, other factors may determine the structure of the resulting aggregates. Here, Au and TiO2 nanostructures are obtained by non-thermal fs-PLD in ambient conditions. On Si(100), only TiO2 NPs form fractals with areas up to ~ 1 × 106 nm2, while on quartz Au NPs also form fractals with areas up to ~ 5 × 103 nm2, a much smaller size with respect to the TiO2 case. The aggregation is described by a simple diffusive model, taking into account isotropic diffusion of the NPs, allowing quantitative simulations of the NPs and fractal area. The results highlight the key role of substrate thermal conductivity in determining the formation of fractals.
A new simple chemical method for synthesis of nanocrystalline bismuth telluride (Bi2Te3) has been developed by microwave assisted reduction of homogeneous tartrate complexes of bismuth and tellurium metal ions with hydrazine. The reaction is performed at pH 10. The nano-crystallites have rhombohedral phase identified by XRD. The size distribution of nanoparticle is narrow and it ranges between 50 to 70 nm. FESEM shows that the fine powders are composed of small crystallites. The TEM micrographs show mostly deformed spherical particles and the lattice fringes are found to be 0.137 nm. Energy dispersive X-ray spectroscopy (EDX) analysis shows the atomic composition ratio between bismuth and tellurium is 2:3. Thermoelectric properties of the materials are studied after sintering by spark plasma sintering method (SPS). The grain size of the material after sintering is in the nanometer range. The material shows enhanced Seebeck coefficient and electrical conductivity value at 300 K. The figure of merit is found to be 1.18 at 300 K.
Novel feather duster-like nickel sulfide (NiS) @ molybdenum sulfide (MoS2) with hierarchical array structure is synthesized via a simple one-step hydrothermal method, in which a major structure of rod-like NiS in the center and a secondary structure of MoS2 nanosheets with a thickness of about 15–55 nm on the surface. The feather duster-like NiS@MoS2 is employed as the counter electrode (CE) material for the dye-sensitized solar cell (DSSC), which exhibits superior electrocatalytic activity due to its feather duster-like hierarchical array structure can not only support the fast electron transfer and electrolyte diffusion channels, but also can provide high specific surface area (238.19 m2 g?1) with abundant active catalytic sites and large electron injection efficiency from CE to electrolyte. The DSSC based on the NiS@MoS2 CE achieves a competitive photoelectric conversion efficiency of 8.58%, which is higher than that of the NiS (7.13%), MoS2 (7.33%), and Pt (8.16%) CEs under the same conditions.
Graphical abstract Novel feather duster-like NiS@MoS2 hierarchical structure array with superior electrocatalytic activity was fabricated by a simple one-step hydrothermal method.
Catalytic systems designated for preferential oxidation of CO in the presence of H2 are prepared by ball milling of Cu and CeO2, a simple and cheap one-step process to synthesize such catalysts. It is found that after 60 min of milling, a mixture of 8 wt.% Cu–CeO2 powders exhibits CO conversion of 96% and CO selectivity of about 65% at 438 K. Two active oxygen states, which are not observed in case of pure CeO2, were detected in the nanocomposite lattice and attributed to the presence of Cu in surface sites as well as in subsurface bulk sites. Correspondingly, oxidation of CO to CO2 was found to occur in a two-stage process with Tmax ≈ 395/460 K, and oxidation of H2 to H2O likewise in a two-stage process with Tmax ≈ 465/490 K. The milled powder consists of CeO2 crystallites sized 8–10 nm agglomerated to somewhat larger aggregates, with Cu dispersed on the surface of the CeO2 crystallites, and to a lesser extent present as Cu2O.
The paper deals with the processes of photoburning and dark recovery of the photoluminescence (PL) yield of a “core-shell”-type hybrid nanoparticles Si/SiOx (npSi/SiOx) after exposure to laser light with a wavelength of 405 nm and power density of 0.05–1 W/cm2. The PL of npSi/SiOx occurs after excitation of nanocrystalline Si core and subsequent energy transfer to the luminescent oxygen-deficient centers (ODC) in the SiOx shell of a nanoparticle. These photoburning effects linearly depend on the power density of the exciting laser light, and the dynamics of the photoburning of PL is significantly non-exponential: the burning rate strongly drops during the exposure. The stop of laser exposure of npSi/SiOx is accompanied by a slow dark recovery of the quantum efficiency of PL up to its initial level. We have demonstrated the possibility of controlling the photosensibility of npSi/SiOx through changing the electron affinity of the environment. We have also proposed a physical mechanism that explains the observed photoburning and subsequent dark recovery of npSi/SiOx PL based on the existence of “traps” for electrons residing in the SiOx shell, where the electrons come as a result of tunneling from the excited ODC. The limiting time for this process is the lifetime of PL of ODC ranging from 10?5 to 10?4 s. The drop of the burning rate during exposure is caused by a strong difference in tunneling probabilities for different pairs of “ODC-trap”. The dark back tunneling of an electron from a trap to the original ODC occurs significantly (7–10 orders of magnitude) slower than the direct tunneling due to higher energy barrier.
Graphical abstract Dark recovery of photoluminescence efficiency of Si nanoparticles following laser burning in three surrounding media differing in electron affinity
This study describes the synthesis method of water-soluble, low-toxicity, photostable highly luminescent probes based on I–III–VI2 type semiconductor quantum dots (QDs) and the possibility of tumor targeting in living animals. Cd-free high-quality CuInS2/ZnS core/shell QDs were synthesized, and their surfaces were reacted with mercaptoundecanoic acid for aqueous phase transfer followed by reaction with glycol-chitosan; lastly, Arg-Gly-Asp (RGD) integrin-binding peptide was covalently attached for in vivo tumor targeting. Dowtherm A, a highly viscous heat-transfer organic fluid, was used to control semiconductor crystal growth at high temperature (>230 °C) during organic synthesis. The structural and optical properties of the resulting CuInS2/ZnS QDs were investigated. The average diameters of CuInS2 and CuInS2/ZnS QDs were 3.0 and 3.7 nm, respectively. Cell toxicity and in vivo tumor targetability in RR1022 cancer cell-xenografted mice were further evaluated using cRGDyk-tagged glycol-chitosan-coated CuInS2/ZnS QDs. Glycol-chitosan-coated MUA-QDs displayed a Z-average diameter of 203.8 ± 7.67 nm in water by dynamic light scattering.
The paper presents the synthesis, characterization, and in vitro cytotoxicity tests of Fe3O4 magnetic nanoclusters coated with ethylenediaminetetraacetic acid disodium salt (EDTA). Electron microscopy analysis (SEM) evidences that magnetite nanoparticles are closely packed into the clusters stabilized with EDTA with well-defined near spherical shapes and sizes in the range 100–200 nm. From XRD measurements, we determined the mean size of the crystallites inside the magnetic cluster about 36 nm. The saturation magnetization determined for the magnetic clusters stabilized with EDTA has high value, about 81.7 emu/g at 300 K. X-ray photoelectron spectroscopy has been used to determine both the elemental and chemical structure of the magnetic cluster surface. In vitro studies have shown that the magnetic clusters at low doses did not induce toxicity on human umbilical vein endothelial cells or lesions of the cell membrane. In contrast, at high doses, the magnetic clusters increased the lipid peroxidation and reduced the leakage of a cytoplasmic enzyme, lactate dehydrogenase (LDH), in parallel with increasing the antioxidant defense.
BaWO4 nanoparticles were successfully used as the photocatalysts in the degradation of methylthioninium chloride (MTC) dye at different pH levels of aqueous solution. Pure phase of barium tungstate (BaWO4) nanoparticles was synthesized by modified molten salt process at 500 °C for 6 h. Structural and morphological characterizations of BaWO4 nanoparticles (average particle size of ~40 nm) were studied in details using powder x-ray diffraction (XRD), FTIR, Raman, energy-dispersive, electron microscopic, and x-ray photoelectron spectroscopy (XPS) techniques. Direct band gap energy of BaWO4 nanoparticles was found to be ~3.06 eV from the UV–visible absorption spectroscopy followed by Tauc’s model. Photocatalytic properties of the nanoparticles were also investigated systematically for the degradation of MTC dye solution in various mediums. BaWO4 nanoparticles claim the significant enhancement of the photocatalytic degradation of aqueous MTC dye to non-hazardous inorganic constitutes under alkaline, neutral, and acidic mediums.
Asymmetric capacitor based on TiO2 with the size range from 90 to 410 nm and mesoporous MnO2 (ca. 200–380 nm) electrodes has been successfully constructed and characterized in LiClO4 aqueous electrolyte. The samples of both metal oxides were fully characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and so on. The electrochemical capacitive performances of both electrode materials were evaluated by cyclic voltammetry and galvanostatic charge-discharge in 1 mol/L LiClO4 with a working voltage of 2.0 V. The discharge profile of the asymmetric capacitor exhibited an excellent capacitive behavior and good cycling stability after 2000 cycles. Moreover, the TiO2//MnO2 asymmetric capacitor possesses both higher energy density and power density (7.7 Wh/kg, 762.5 W/kg) than that of Maxsorb//Maxsorb symmetrical capacitor (7.0 Wh/kg, 400.0 W/kg).
Graphical abstract A novel asymmetric capacitor based on TiO2 and mesoporous MnO2 electrodes has been successfully constructed and characterized in LiClO4 aqueous electrolyte.
Ligand-free palladium nanoparticles supported on multi-walled carbon nanotubes (Pd/MWCNT) were prepared by the supercritical carbon dioxide (scCO2) deposition method using a novel scCO2-soluble Pd organometallic complex as a precursor. The precursor with the perfluoroalkyl chain group was synthesized and identified by microanalytic methods. The deposition was carried out at the temperature of 363.15 K and pressure of 27.6 MPa CO2. The prepared metallic nanoparticles were obtained with an average size of 2 nm. Pd/MWCNT was utilized as a heterogeneous catalyst in Suzuki cross-coupling reaction. The nanocatalyst was found very effective in Suzuki reaction and it could also be recovered easily from the reaction media and reused over several cycles without significant loss of catalytic activity under mild conditions.
Graphical Abstract Pd/MWCNT was prepared by the scCO2 deposition method using a new synthesized perfluroalkylated vic-dioxime Pd complex as the precursor. The prepared nanoparticle was very effective as catalyst and reusable for Suzuki cross coupling reaction under mild conditions.
The Br-doped hollow TiO2 photocatalysts were prepared by a simple hydrothermal process on the carbon sphere template following with calcination at 400 °C. The structure and properties of photocatalysts were characterized by X-ray diffraction, Raman spectrum, scanning electron microscope, transmission electron microscopy, N2 desorption–adsorption, UV–Vis spectroscopy, and X-ray photoelectron spectroscopy. The TiO2 hollow spheres are in diameter of 500 nm with shell thickness of 50 nm. The shell is composed of small anatase nanoparticles with size of about 10 nm. The TiO2 hollow spheres exhibit high crystalline and high surface area of 89.208 m2/g. With increasing content of Br doping, the band gap of TiO2 hollow spheres decreased from 2.85 to 1.75 eV. The formation of impurity band in the band gap would narrow the band gap and result in the red shift of absorption edge from 395 to 517 nm, which further enhances the photocatalytic activity. The appropriate Br doping improves the photocatlytic activity significantly. The TiO2 hollow spheres with 1.55% Br doping (0.5Br-TiO2) exhibit the highest photocatalytic activity under full light. More than 98% of RhB, MO, and MB can be photodegraded using 0.5Br-TiO2 with concentration of 10 mg/L in 40, 30, and 30 min, respectively. The degradation rate of Br-doped photocatalysts was 40% faster than undoped ones.
Bismuth ferrite, Fenton-like catalysts have been successfully synthesized via simple hydrothermal methods without any templates. Through changing the molar ratio of Bi/Fe, the two main phases BiFeO3 and Bi25FeO40 can be synthesized under different temperatures. Furthermore, different morphologies of the BiFeO3 phase can be adjusted by changing different concentrations of HNO3 and NaOH which were used to dissolve the reactants and adjust the pH values in the prepared process. When the concentration of HNO3/NaOH was 8/12 M, some uniform cylindrical bodies with equal height (1 μm) and width (0.6 μm) were obtained, which have not been reported before. The uniform structures exhibited better activities in the photoassisted Fenton-like oxidation process for the degradation of rhodamine B (RhB) under visible light irradiation (420 nm < λ < 800 nm). Through the detection of the degradation mechanism, it showed that the concerted effect of the catalysts and H2O2 can increase the generation of the charge carriers and accelerate the photogenerated charge transfer between the catalysts and dyes. The BiFeO3 samples also showed magnetic properties at room temperature, which may have potential applications in multiferroic or magnetoelectric sensors and devices.
