3D hierarchical MnO2 aerogels with superhydrophobicity for selective oil–water separation

Inorganic nanowire aerogel with low density, high specific surface area and high porosity has received increasing attention in the field of materials physics and chemistry because of not only the unique structural and physical features of metallic oxide but also low cost, environmental friendliness and earth abundant of precursor materials. In this work, MnO₂ nanowire aerogels (MNA) with ultralow density, and stable 3D hierarchical structures was successfully fabricated by freeze‐drying processes using MnO₂ nanowire as building blocks. The length of MnO₂ nanowires exceeds 100 μm, making it easier to cross‐link and self‐assemble into a 3D network of aerogels, and the acid and alkali resistance of MnO₂ enables it to adapt to extreme environments. Simultaneously, the monodispersed MnO₂ nanowire was prepared by the hydrothermal method, followed by acid treatment. To obtain superhydrophobic properties and achieve selective oil adsorption, the surfaces of nanowire aerogels were grafted the hydrophobic groups with low surface energy via vapor deposition. It is indicated that the obtained 3D hierarchical MNA show both superhydrophobic and super‐lipophilic properties simultaneously with a high‐water contact angle of 156°  ±  2° and an oil contact angle of 0°. And the MNA exhibited a high oil adsorption capacity of 85–140 g/g, thereby indicating its potential applications in oil/water separation. More importantly, the resulting MNA can be recycled ten cycles without loss of oil absorption capacity (more than 120 g/g). The results presented in this work demonstrate that the as‐prepared nanowire aerogel may find applications in chemical separation and environmental remediation for large‐scale absorption of oils from water.     

Self-assembled 3D flowerlike hierarchical Fe3O4@Bi2O3 core-shell architectures and their enhanced photocatalytic activity under visible light

Three‐dimensional (3D) flowerlike hierarchical Fe₃O₄@Bi₂O₃ core–shell architectures were synthesized by a simple and direct solvothermal route without any linker shell. The results indicated that the size of the 3D flowerlike hierarchical microspheres was about 420 nm and the shell was composed of several nanosheets with a thickness of 4–10 nm and a width of 100–140 nm. The saturation magnetization of the superparamagnetic composite microspheres was about 41 emu g^?1 at room temperature. Moreover, the Fe₃O₄@Bi₂O₃ composite microspheres showed much higher (7–10 times) photocatalytic activity than commercial Bi₂O₃ particles under visible‐light irradiation. The possible formation mechanism was proposed for Ostwald ripening and the self‐assembled process. This novel composite material may have potential applications in water treatment, degradation of dye pollutants, and environmental cleaning, for example.     

Hierarchical assemblies of Si3N4 nanostructures

In the present work, for the first time, we report the growth of hierarchical assemblies of Si₃N₄ nanostructures via catalyst-assisted pyrolysis of a polymeric precursor on the Si substrates. The synthesized products were characterized by using field emission scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. It is found that the size of the catalytic droplet plays a critical role on the formation of hierarchical assemblies of Si₃N₄ nanostructures rather than common single nanowire. A mechanism based on the Vapor–Liquid–Solid (VLS) process was proposed for the assembly of hierarchical Si₃N₄ nanostructures.     

Hydrothermal synthesis and photocatalytic property of porous CuO hollow microspheres via PS latex as templates

Porous copper oxide (CuO) hollow microspheres have been fabricated through a simple hydrothermal method using PS latex as templates. The as-obtained samples were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). The influences of the mole ratio of Ethylenediamine (C₂H₈N₂) and copper acetate (Cu(Ac)₂·H₂O), hydrothermal temperature and time on the size and morphologies of the final products have been investigated. The possible formation mechanism of porous CuO hollow microspheres has been proposed and the specific surface area of the hollow microspheres with 81.71 m²/g is measured by BET method. The band gap value calculated from a UV–vis absorption spectrum of porous CuO hollow microspheres is 2.71 eV. The as-synthesized product exhibits high photocatalytic activity during the photodegradation of an organic dyestuff, rhodamine B (RhB), under UV-light illumination.     

A facile and green synthesis route to C@LaCO3OH core-shell microspheres using colloidal carbonaceous spheres as template and its by-products as carbon source

C@LaCO₃OH core-shell microspheres have been synthesized by a hydrothermal method using colloidal carbonaceous spheres (CCSs) as template and its by-products as reactant without any other precipitating agent added in the reaction system. The FT-IR and XRD results indicated the successful formation of the well-crystallized LaCO₃OH shell with hexagonal crystal structure on the CCSs’ surface. The morphology and qualitative elemental chemical analysis were characterized by SEM, TEM, and EDS. The effects of co-solvent on the crystallinity of the LaCO₃OH shell were also studied. In addition, PL result showed one emission band centered at 421 nm (λ_ex = 365 nm) of the C@LaCO₃OH microspheres. The UV–visible spectrum was also employed to investigate the optical property of the products. Further, a possible formation mechanism of the core-shell structure was proposed.     

Influence of redox behavior of copper ions on dielectric and spectroscopic properties of Li2O–MoO3–B2O3: CuO glass system

Li₂O–MoO₃–B₂O₃ glasses mixed with different concentrations of CuO (ranging from 0 to 1.2 mol%) were prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Optical absorption, luminescence, ESR, IR and dielectric properties (viz., dielectric constant ?′, loss tan δ and a.c. conductivity σ_ac, over a wide range of frequency and temperature) of these glass materials have been investigated. The results of differential scanning calorimetric studies suggest that the glass forming ability is higher for the glasses containing CuO beyond 0.6 mol%. The analysis of results of the dielectric properties has revealed that the glasses possess high insulating strength when the concentration of CuO is >0.6 mol%. The variation of a.c. conductivity with the concentration of CuO passes through a maximum at 0.6 mol%. In the high-temperature region, the a.c. conduction seems to be connected with the mixed conduction viz., electronic conduction and ionic conduction. The optical absorption spectra of these glasses exhibited bands due to Cu⁺ ions in the UV region in addition to the conventional band due to Cu²⁺ ions in the visible region. The ESR spectral studies have indicated that there is a gradual adoption of Cu²⁺ ions from ionic environment to covalent environment as the concentration of CuO increases beyond 0.6 mol% in the glass matrix. The luminescence spectra excited at 271 nm have exhibited an intense yellow emission band centered at about 550 nm and a relatively broad blue emission band at about 450 nm; these bands have been attributed to the ³D₁ → ¹S₀ transition of isolated Cu⁺ ions and ³D₁ → ¹S₀ transition of (Cu⁺)₂ pairs, respectively. The quantitative analysis of the results of all these studies has indicated that as the concentration of CuO is increased beyond 0.6 mol% in the glass matrix, a part of Cu²⁺ ions have been reduced to Cu⁺ ions that have influenced the physical properties of these glasses to a substantial extent.     

Simultaneous growth of rutile TiO2 as 1D/3D nanorod/nanoflower on FTO in one-step process enhances electrochemical response of photoanode in DSSC

Simultaneous growth of 1D/3D-nanorod/nanoflower like structures of TiO₂ on fluorine doped tin oxide (FTO) glass substrates has been achieved in one-step hydrothermal process. X-ray diffraction (XRD) pattern confirms the formation of rutile phase whereas enhanced light scattering in 1D/3D nanorod/nanoflower TiO₂ photoanode was observed at longer wavelengths of 600–750 nm. Dye sensitized solar cell (DSSC) prepared with 1D/3D-nanorod/nanoflower structures had about 90% increases in efficiency as compared to 1D nanorod like structure. Thus, simultaneous assembly of TiO₂ as 1D/3D-nanorod/nanoflower like structure without significant change in their surface oxidation states (Ti^3 + and Ti^4 +) had better capabilities for light harvesting and efficient electron transportation for improving electrochemical responses of photo-electrode in DSSC to achieve higher sensitivity.     

Synthesis,crystal structure and optical properties of a new beryllium borate,CsBe4(BO3)3

A novel beryllium borate CsBe₄(BO₃)₃ has been grown in crystals by high-temperature flux method using spontaneous nucleation technique for the first time. The crystal structure of this compound was determined by single crystal X-ray diffraction analysis. It crystallizes in the orthorhombic space group Pnma with lattice parameters a = 8.3914(5) Å, b = 13.3674(7) Å, c = 6.4391(3) Å, Z = 4, V = 722.28(7) Å³. The crystal takes the same structure type as Rb analog based on the units of BO₃ triangles and BeO₄ tetrahedrons, displaying a three-dimensional tunnel structure with Cs atoms filling in the cages. The IR spectrum confirms the presence of BO₃ groups and the UV–vis–IR diffuse reflectance spectrum exhibits this compound has a short UV cut-off edge below 200 nm. Band structures and density of states were calculated.     

Facile solution-phase synthesis of γ-Mn3O4 hierarchical structures

Background  

A lot of effort has been focused on the integration of nanorods/nanowire as building blocks into three-dimensional (3D) complex superstructures. But, the development of simple and effective methods for creating novel assemblies of self-supported patterns of hierarchical architectures to designed materials using a suitable chemical method is important to technology and remains an attractive, but elusive goal.     

A facile route to the fabrication of morphology-controlled Sb2O3 nanostructures

We report in this paper a facile hydrothermal route for the preparation of Sb₂O₃ nanoribbons assembly with different aspect ratio and Sb₂O₃ polyhedral nanoparticles. Study indicates that the ratio of water and ethanol affects the morphology, size and crystal phase of Sb₂O₃ assembly building blocks. In a mixed alcohol and water solution, the orthorhombic Sb₂O₃ nanoribbons with a length of ～4 μm and a width of 400 nm were assembled into rod-like structures, while a length of ～3 μm and a width of 300 nm Sb₂O₃ nanoribbons were assembled into quadrangle structures with the increase of the water ratio. In the absolute alcohol solution, the cubic Sb₂O₃ particles with polyhedral morphology were formed. PL spectra indicate that the morphology strongly affects the luminescence property. The possible formation mechanisms involving the surfactant-assisted self-assembly and the confined growth were also proposed for the formation of the bundled nanoribbons and polyhedral granules, respectively.     

Electrochemical hydrogen evolution over MoO3 nanowires produced by microwave-assisted hydrothermal reaction

Molybdenum trioxide (MoO₃) nanowire with unprecedentedly high aspect ratios (>200) and good crystallinity was prepared via decomposition of (NH₄)₆Mo₇O₂₄·4H₂O under a microwave-assisted hydrothermal (MH) process. The nanowire was orthorhombic MoO₃ with 50 nm in diameter and 10–12 μm in length. The conventional hydrothermal (CH) reaction required higher temperature and longer reaction times to produce one-dimensional MoO₃, yet its quality was lower. In the electrochemical hydrogen evolution reaction in a H₂SO₄ solution, MoO₃ nanowire from MH process showed much higher electrocatalytic activity than MoO₃ prepared from CH method and commercial bulk MoO₃ particles. The facile vectorial electron transport along the nanowire axis was considered to be responsible for the excellent electrocatalytic activity of the MH–MoO₃ nanowire.     

Synthesis and characterization of CuO nanoparticles utilizing waste fish scale and exploitation of XRD peak profile analysis for approximating the structural parameters

In this research, we strived to utilize waste fish scale (labeo rohita) for synthesizing CuO nano-particles (CuO NPs), which gained much attention due to its distinctive properties and versatile applications. Upon the heat treatment, the collagen content of the fish scale got transformed into gelatin which in turn converted the precursor material into CuO NPs. The X-Ray diffraction (XRD) analysis confirmed the formation of CuO NPs and revealed the structure to be of monoclinic lattice. The structural parameters i.e. crystallite size, lattice parameters, microstrain, dislocation density was evaluated for the synthesized CuO NPs using the XRD data. Scherrer’s Method (SM), Scherrer Equation Average Method (SEAM), Linear Straight Line Method (LSLM), Straight Line Passing the Origin Method (SLPOM), Monshi Scherrer Method (MSM), Williamson-Hall Method (WHM), Size-Strain Plot Method (SSPM), Halder-Wagner Method (HWM) was exploited for the estimation of crystallite size. According to the calculations, the crystallite size was found to be 87 nm, 41 nm, 1980 nm, 62 nm, 66 nm, 28 nm, 13 nm, 13 nm respectively and the dislocation density was found to be 1.32 × 10^-4, 5.95 × 10^-4, 0.002 × 10^-4, 2.60 × 10^-4, 2.29 × 10^-4, 12.75 × 10^-4, 59.17 × 10^-4 and 59.17 × 10^-4 respectively. UV–Vis absorption analysis also confirmed the formation of CuO NPs based on the absorption peak at 262 nm (λ_max) and Tauc Plot method was used to calculate the optical band gap which was 3.84 eV. Functional group, especially the Cu-O bonding was confirmed by the Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) data. Field Emission Scanning Electron Microscopy (FESEM) showed three different shapes of CuO NPs which was also confirmed by Transmission Electron Microscopy (TEM). Particle size was determined based on FESEM and TEM image using imageJ software and also by the Dynamic Light Scattering (DLS) technique. Thermal analysis showed a four stage weight loss in case of Thermogravimetric (TGA) analysis and three conversion steps was observed in Differential Scanning Calorimetric (DSC) analysis. Such synthesis pathway is evidently green and facile for synthesizing CuO NPs with potentiality of various applications and also utilization of waste fish scale is a perquisite.     

Synthesis,characterization and kinetic computations of fullerene (C60)–CuO on the mechanism decomposition of ammonium perchlorate

CuO, C₆₀–CuO, and Al/C₆₀–CuO nanostructures were synthesized and characterized by scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FTIR). differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA) measurements were performed to study the influence of these additives on ammonium percolate (AP) thermal decomposition. From the comparison of DSC and TGA plots, the catalytic effect of CuO and C₆₀–CuO has been clearly noticed in which the lower temperature decomposition of AP was decreased from 331 °C to 315 °C, 310 °C, and 303 °C (in the presence of CuO, C₆₀–CuO, and Al/C₆₀–CuO, respectively) and the HTD was dropped from 430 °C (pure AP) to 352 °C, 335 °C, and 317 °C (for the compounds AP/CuO, AP/C₆₀–CuO, and AP/Al/C₆₀–CuO, respectively). The kinetics of the samples were investigated by isoconversional models and compared with an iterative procedure. The results of pure AP indicated a complex decomposition process involving three decomposition steps with specific reaction mechanism. The nanocatalysts incorporated in the AP have clearly affected its decomposition process in which the reaction mechanism and the number of stages were changed.     

Synthesis,crystal structure and properties of a new congruently melting compound,K3ZnB5O10

A new compound, K₃ZnB₅O₁₀, has been synthesized by solid-state reaction. It crystallizes in the monoclinic system, space group P2₁/n with unit–cell parameters a = 7.6391(5) Å, b = 19.2304(13) Å, c = 7.6905(5) Å, β = 116.698(4)° and Z = 4. The structure of the compound is solved by the direct methods and refined to R1 = 0.0286 and wR2 = 0.0600. K₃ZnB₅O₁₀ contains a two-dimensional ZnB₅O₁₀ layer, which forms by connecting isolated double ring [B₅O₁₀] groups and ZnO₄ tetrahedra. The K atoms filling in the interlayer and intralayer link the layers together. Functional groups presented in the sample were identified by FTIR spectrum. UV–vis–NIR diffuse reflectance spectrum exhibits ultraviolet cutoff edge is about 190 nm. The DSC analysis proves that K₃ZnB₅O₁₀ is a congruently melting compound.     

Synthesis of Fe3O4/CuO/ZnO/RGO and its catalytic degradation of dye wastewater using dielectric barrier discharge plasma

The design of an efficient and green dye degradation technology is of great significance to mitigate water pollution as well as ecological damage. Fe₃O₄/CuO/ZnO/RGO was prepared by solvothermal synthesis and homogeneous precipitation. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), and vibrating-sample magnetometry (VSM) were used to characterize the samples, to explore the morphology and structural composition of the composites. To enhance the degradation efficiency, a dielectric barrier discharge (DBD)–Fe₃O₄/CuO/ZnO/RGO co-catalytic system was created based on the DBD plasma technology. Response surface methodology analysis results demonstrate that the degradation effect of DBD–Fe₃O₄/CuO/ZnO/RGO is optimal and the decolorization rate is 95.06 % when the solution pH is 3, conductivity is 0.5 mS/cm, the input voltage is 90 V, and Fe₃O₄/CuO/ZnO/RGO concentration is 0.18 g/L. Therefore, this study offers a novel method for dye degradation and confirms the viability of a DBD–Fe₃O₄/CuO/ZnO/RGO synergistic catalytic system.     

Controlled synthesis of CuO nanostructures by a simple solution route

A simple solution route has been developed to prepare nanostructured CuO with Cu(NO₃)₂·3H₂O and NaOH as starting materials. CuO nanoribbons or nanorods and their assemblies into hierarchical structures have been synthesized, respectively, by controlling the molar ratio of NaOH to Cu(NO₃)₂, reaction temperature and the concentration of the starting NaOH solution. Experiments demonstrate that the molar ratio of NaOH to Cu(NO₃)₂ is an important parameter which may decide whether CuO exists in nanoribbons (nanorods) or assemblies into hierarchical structures. Whether Cu(NO₃)₂ is dissolved in ethanol or water also influences the formation of monodispersed CuO nanoribbons (nanorods). The growth mechanism of these nanostructures is discussed. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy (HRTEM) and their optical absorption spectra were also studied.     

Biosynthesis,characterization, biological and photo catalytic investigations of Elsholtzia blanda and chitosan mediated copper oxide nanoparticles

Bio synthesis of nanoparticles using plant parts has gained considerable attention, given the fact that the method is green, environment friendly, cheaper, simple and involves no hazardous substances. The present study involves the green synthesis of copper oxide nanoparticles (CuO NPs) using chitosan and the aqueous leaf extract of Elsholtzia blanda, an aromatic medicinal herb. The synthesized E.blanda-chitosan mediated copper oxide nanoparticles (CPCE) and E. blanda mediated copper oxide nanoparticles (PCE) were subjected to different characterization techniques, Ultraviolet–visible (UV–Vis), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX), High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED). The absorbance peaks in UV–Vis spectroscopy at 286 nm and 278 nm for CPCE and PCE respectively indicated the formation of nanoparticles. TEM and SEM employed for studying the surface morphology showed rod-like and spherical morphology bearing average size of 47.71 nm for CPCE and 36.07 nm for PCE. The antibacterial activities of the prepared nanoparticles were tested against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Salmonella typhi by agar well diffusion method. The results indicate that CuO NPs possess effective antibacterial potential against all tested bacteria with a maximum zone of inhibition of 18 mm for Enterococcus faecalis. Antioxidant studies revealed the highest DPPH scavenging activity of 89% at 25 μg/mL concentration of the nanoparticles. The percentage of the photo catalytic degradation of Congo red was found to be 95% after 10 h.     

Syntheses,characterization and nonlinear optical properties of sodium–scandium carbonate Na5Sc(CO3)4·2H2O

A novel nonlinear optical (NLO) material Na₅Sc(CO₃)₄·2H₂O has been synthesized under a subcritical hydrothermal condition. The structure is determined by single-crystal X-ray diffraction and further characterized by TG analyses and UV–vis–NIR diffuse reflectance spectrum. It crystallizes in the tetragonal space group P-421c, with a = b = 7.4622(6) Å, C = 11.5928(15) Å. The Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that Na₅Sc(CO₃)₄·2H₂O was a phase-matchable material, and its measured SHG coefficient was about 1.8 times as large as that of d₃₆ (KDP). The results from the UV–vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges of Na₅Sc(CO₃)₄·2H₂O is about 220 nm, suggesting that this crystal is a promising UV nonlinear optical (NLO) materials.     

Fabrication of Hierarchically Structured MOF‐Co3O4 on Well‐aligned CuO Nanowire with an Enhanced Electrocatalytic Property

Engineering appropriate shape and size of three‐dimensional inorganic nanostructures materials is of one the main critical problems in pursuing high‐performance electrode materials. Herein, we fabricate a metal‐organic framework derived cobalt oxide (Co₃O₄) are grown on copper oxide nanowire (CuO NWs) supported on the surface of 3D copper foam substrate. The highly aligned CuO NWs were prepared by using electrochemical anodization of copper foam in ambient temperature and followed by MOF Co₃O₄ was grown via a simple in situ solution deposition then consequent calcination process. The obtained binder‐free 3D CuO NWs@Co₃O₄ nanostructures were further characterized by using X‐ray diffraction, X‐ray photoelectron spectroscopy, field‐emission scanning electron microscopy, and transmission electron microscopy. Furthermore, electrochemical sensing of glucose was studied by using Cyclic Voltammetry, and chronoamperometry techniques. Interestingly, 3D CuO NWs@Co₃O₄ electrode exhibits excellent performance for the oxidation of glucose compared with individual entities. The proposed sensor shows wide linear ranges from 0.5 μM to 0.1 mM with the sensitivity of 6082 μA/μM and the lowest detection limit (LOD) of 0.23 μM was observed with the signal to noise ratio, (S/N) of 3. The superior catalytic oxidation of glucose mainly is endorsed by the excellent electrical conductivity and synergistic effect of the Co₃O₄ and CuO NWs.     

Synthesis of Co3O4 nanostructures using a solvothermal approach

The controlled synthesis of Co₃O₄ nanostructures with morphologies of micro-spheres, nanobelts, and nanoplates was successfully achieved by a simple solvothermal method. Various comparison experiments showed that several experimental parameters, such as the reaction temperature and the concentration of NH₃·H₂O, play important roles in the morphological control of Co₃O₄ nanostructures. A lower temperature and a lower concentration of NH₃·H₂O favor spherical products with a diameter of 1–1.5 μm, whereas a higher temperature and a higher concentration of NH₃·H₂O generally lead to the formation of nanobelts with a width of 20–150 nm. In addition, Co₃O₄ hexagonal nanoplates with an edge length of about 200–300 nm are also obtained by adding surfactant CTAB. A rational mechanism is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products.