Hydrothermal Synthetic Method Research Articles

P-type quaternary chalcogenides of Cu2ZnSn(S,Se)4 nanocrystals: Large-scale synthesis, bandgap engineering and their thermoelectric performances

Cu2ZnSn(S,Se)4 nanocrystals up to 10 grams per batch were acquired by a large-scale hydrothermal synthetic method. The bandgap engineering of Cu2ZnSn(S,Se)4 nanocrystals was achieved by controlling the ratios of sulfur and selenium atoms in the solid solution nanocrystals. The bandgaps of Cu2ZnSn(S,Se)4 nanocrystals were tuned approximately linearly from 1.29, 1.34, 1.39, 1.44 to 1.52 eV with the increase of sulfur and selenium atomic ratios. Finally, the thermoelectric properties of Cu2ZnSn(S,Se)4 nanocrystals with the various ratios of Se/(S+Se) (0, 0.25, 0.5, 0.75, 1) from 300 to 700 K are elaborated in detail, indicating that the thermal conductivity of Cu2ZnSn(S,Se)4 nanocrystals is lower than that of their bulk counterparts and other binary materials. Besides, the Seebeck coefficients and figure of merit for Cu2ZnSn(S,Se)4 nanocrystals (x = 0.25, 0.5, 0.75) is higher than those of Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals. It is indicated that transferring from bulk materials to the solid solution nanomaterials is an effective way to further enhance the TE performance of CZTS NCs.

A facile synthesis of a 3D high-index Au NCs@CuO supported on reduced graphene oxide for glucose sensing

A novel electrochemical sensor based on 3D reduced graphene oxide supported high-index Au NCs@CuO (RGO-Au NCs@CuO) for detection of glucose was reported in this work. A facile one-pot hydrothermal synthetic method was employed at room temperature with electrostatic self-assembly technology for the synthesis of reduced graphene oxide supported high-index Au nanocrystals. Morphology, structure and composition of RGO-Au NCs@CuO were characterized by various technologies including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Significantly, with the combination of large active surface area and high conductivity, electrocatalytic activity toward the oxidation of glucose was markedly enhanced. Under the best experimental conditions, the steady-state current response was linearly proportional to glucose concentration in the range from 0.1μM to 3mM with a low detection limit (30nM). Meanwhile, the sensor was of excellent selectivity and stability and successfully applied to the detection of glucose in human serum.

Stable ABTS Immobilized in the MIL-100(Fe) Metal-Organic Framework as an Efficient Mediator for Laccase-Catalyzed Decolorization.

The successful encapsulation of 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), a well-known laccase mediator, within a mesoporous metal-organic framework sample (i.e., MIL-100(Fe)) was achieved using a one-pot hydrothermal synthetic method. The as-prepared ABTS@MIL-100(Fe) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, nitrogen sorption, and cyclic voltammetry (CV). Our ABTS@MIL-100(Fe)-based electrode exhibited an excellent electrochemical response, indicating that MIL-100(Fe) provides an appropriate microenvironment for the immobilization and electroactivity of ABTS molecules. ABTS@MIL-100(Fe) was then evaluated as an immobilized laccase mediator for dye removal using indigo carmine (IC) as a model dye. Through the application of laccase in combination with a free (ABTS) or immobilized (ABTS@MIL-100(Fe)) mediator, decolorization yields of 95% and 94%, respectively, were obtained for IC after 50 min. In addition, following seven reuse cycles of ABTS@MIL-100(Fe) for dye treatment, a decolorization yield of 74% was obtained. Dye decolorization occurred through the breakdown of the chromophoric group by the Laccase/ABTS@MIL-100(Fe) system, and a catalytic mechanism was proposed. We therefore expect that the stability, reusability, and validity of ABTS@MIL-100(Fe) as a laccase mediator potentially render it a promising tool for dye removal, in addition to reducing the high running costs and potential toxicity associated with synthetic mediators.

Synthesis of zeolitic imidazolate framework-69 for adsorption separation of ethane and ethylene

The zeolitic imidazolate framework ZIF-69 with topology of GME has been synthesized successfully via a facile hydrothermal synthetic method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption measurements, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The ethane/ethylene separation potential was measured by single-component adsorption isotherms, and the selectivity was calculated based on the ideal adsorbed solution theory (IAST). SEM and TEM images confirmed that the as-synthesized seeds possessed a well-crystallized and uniform morphology, appearing as a flat hexagonal prism with double hexagonal pyramid heads. The obtained ZIF-69 exhibited a higher adsorption capacity of C2H6 over C2H4 at 100 kPa, and the C2H6/C2H4 adsorption selectivity was about 1.7 at below 100 kPa. The outcome would provide a new insight into the study on the effective separation of ethane/ethylene using different topological structures of ZIFs.

Superior acetone sensor based on single-crystalline α-Fe2O3 mesoporous nanospheres via [C12mim][BF4]-assistant synthesis

Ionic liquid 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C12mim][BF4]) assisted growth of single-crystalline α-Fe2O3 mesoporous nanospheres via hydrothermal synthetic method was investigated. The structure and morphology of the resultant products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption techniques. The results indicate that [C12min][BF4] plays an important role in microstructure and morphology controlled synthesis of the α-Fe2O3 nanostructures, which are self-assembled with the primary nanoparticles. The gas sensing properties of such single-crystalline α-Fe2O3 mesoporous nanospheres to some organic compounds such as methanol, ethanol, acetone benzene and methylbenzene were investigated. The sensors based on such mesoporous nanospheres, especially the nanospheres calcined at 300°C, exhibit excellent gas selectivity to acetone at working temperature of 170°C, which could be partially ascribed to appropriate amount of [C12mim][BF4] retention. They can detect acetone down to 0.1ppm with good anti-interefernce of ethanol and humidity, implying their potential application in the detection of breath acetone in type-Ι diabetic patients. The formation process and acetone sensing mechanism of such mesoporous nanospheres are also discussed in detail.

Uniformly grown PtCo-modified Co3O4 nanosheets as a highly efficient catalyst for sodium borohydride electrooxidation

A facile hydrothermal synthetic method, followed by in situ reduction and galvanic replacement processes, is used to prepare PtCo-modified Co3O4 nanosheets (PtCo/Co3O4 NSs) supported on Ni foam. The prepared nanomaterial is used as an electrocatalyst for NaBH4 oxidation in alkaline solution. The morphology and phase composition of PtCo/Co3O4 NSs are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of PtCo/Co3O4 NSs is investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in a standard three-electrode system. Current densities of 70 and 850 mA·cm–2 were obtained at–0.4 V for Co/Co3O4 and PtCo/Co3O4 NSs, respectively, in a solution containing 2 mol·L–1 NaOH and 0.2 mol·L–1 NaBH4. The use of a noble metal (Pt) greatly enhances the catalytic activity of the transition metal (Co) and Co3O4. Besides, both Co and Co3O4 exhibit good B–H bond breaking ability (in NaBH4), which leads to better electrocatalytic activity and stability of PtCo/Co3O4 NSs in NaBH4 electrooxidation compared to pure Pt. The results demonstrate that the as-prepared PtCo/Co3O4 NSs can be a promising electrocatalyst for borohydride oxidation.

Hydrothermal Synthesis and Crystal Structure of Novel Oxovanadium Coordination Polymer: [(VIVO)2(OH)2(C10H6(COO)2)

A novel coordination polymer [(VIVO)2(OH)2(C10H6(COO)2)]∞ based on vanadium(IV) and 2,6-naphthalenedicarboxylato ligand has been prepared by hydrothermal synthetic method. The compound was characterized by elemental analysis, thermogravimetric analysis, Fourier Transform infrared spectroscopy, room-temperature magnetic susceptibility measurement, manganometric titration, bond valance sum calculations (BVS), and single-crystal X-ray diffraction method. BVS calculations, manganometric titration, and room-temperature magnetic susceptibility measurement showed that the compound has paramagnetic property due to tetravalent vanadium ions. The single-crystal structure analysis of the compound illustrates a 2D metal organic framework structure. Coordination geometry of vanadium ions was a distorted square-pyramid (square-pyramidal coordination environment of oxygen atoms). The compound represents a novel 2D inorganic-organic coordination polymer involving vanadium(IV) and 2,6-naphthalenedicarboxylato ligand.

Structural Phase Transition Effect on Resistive Switching Behavior of MoS2 -Polyvinylpyrrolidone Nanocomposites Films for Flexible Memory Devices.

The 2H phase and 1T phase coexisting in the same molybdenum disulfide (MoS2 ) nanosheets can influence the electronic properties of the materials. The 1T phase of MoS2 is introduced into the 2H-MoS2 nanosheets by two-step hydrothermal synthetic methods. Two types of nonvolatile memory effects, namely write-once read-many times memory and rewritable memory effect, are observed in the flexible memory devices with the configuration of Al/1T@2H-MoS2 -polyvinylpyrrolidone (PVP)/indium tin oxide (ITO)/polyethylene terephthalate (PET) and Al/2H-MoS2 -PVP/ITO/PET, respectively. It is observed that structural phase transition in MoS2 nanosheets plays an important role on the resistive switching behaviors of the MoS2 -based device. It is hoped that our results can offer a general route for the preparation of various promising nanocomposites based on 2D nanosheets of layered transition metal dichalcogenides for fabricating the high performance and flexible nonvolatile memory devices through regulating the phase structure in the 2D nanosheets.

Surfactant-free Synthesis of CuO with Controllable Morphologies and Enhanced Photocatalytic Property

A green synthesis for nanoleave, nanosheet, spindle-like, rugby-like, dandelion-like and flower-like CuO nanostructures (from 2D to 3D) is successfully achieved through simply hydrothermal synthetic method without the assistance of surfactant. The morphology of CuO nanostructures can be easily tailored by adjusting the amount of ammonia and the source of copper. By designing a time varying experiment, it is verified that the flower- and dandelion-like CuO structures are synthesized by the self-assembly and Ostwald ripening mechanism. Structural and morphological evolutions are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectra. Additionally, the CuO nanostructures with different morphologies could serve as a potential photocatalyst on the photodecomposition of rhodamine B (RhB) aqueous solutions in the presence of H2O2 under visible light irradiation.

An Efficient Simple Hydrothermal Method to Synthesis FeS<sub>2</sub> Microspheres and their Optical Property

Pyrite (FeS2) is an important semiconductor material which shows various excellent optical and electrical properties and extensive applied prospect as a new-type, photoelectrical functional materials. In this study, a low cost and efficient simple hydrothermal two-step synthetic method was given to obtain FeS2 microspheres with 2-3 μm in diameter. The obtained products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet and visible spectrophotometer (UV-Vis). XRD showed that the synthetic sample consisted of two crystal structures of FeS2, pyrite and marcasite. SEM observation indicated that FeS2 microspheres were well crystallized and had good uniformity. UV-Vis spectrum had a strong optical absorption in the region of 200-400 nm wave length. The reaction temperature had an impact on the size of FeS2 microspheres. A possible mechanism for the size of the FeS2 microspheres generated at high temperature is smaller than that at low temperature is discussed.

Anatase nano-TiO2 with exposed curved surface for high photocatalytic activity

Anatase nano-TiO2 with exposed highly active curved surface was obtained via a simple hydrothermal route with the assistance of citric acid and HF. In this progress, exposed percentage of curved surface can been directly tuned by controlling the mole ratio of citric acid and HF. Such anatase nano-TiO2 with exposed curved surface shows a unique truncated biconic morphology and has large specific surface area. The nano-TiO2 shows higher photocatalytic activity than that of TiO2 nanosheets with exposed {001} facets which confirms the curved surface have higher activity than {001} facets. The higher photocatalytic activity of curved surface can be ascribed to the fact that some high index facets such as {112} and many crystal edges contained on the curved surface may have higher activity than {001} facets. A synergistic effect between curved and {001} facets is confirmed that nano-TiO2 with a optimal coexposed ratio between curved and {001} facets has higher photocatalytic activity than that of TiO2 with exposed curved or {001} facets. The optimal coexposed ratio is affected by degradation molecules. The present work demonstrates a explore of hydrothermal synthetic method for controlling preparation of nano-materials.

Microwave-assisted synthesis of titanium dioxide nanocrystalline for efficient dye-sensitized and perovskite solar cells

A rapid microwave-assisted hydrothermal synthetic method is reported for the fabrication of TiO2 nanoparticles. Their photovoltaic activities are performed in dye-sensitized and perovskite-based solar cells. Power conversion efficiencies using microwave-assisted synthesized TiO2 are relatively similar compared with those employed TiO2 nanoparticles made of conventional hydrothermal process. The reaction time that is typically 12h (literature value) was greatly reduced to only 25min using microwave-heating process for TiO2 nanoparticles formation, which provides an energy-saving and cost-effective method for making the building blocks of photoactive TiO2 nanocrystallines. The material properties of the microwave-synthesized TiO2 nanoparticles are characterized in details by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and photoluminescence emission spectra. An optimal dye-sensitized solar cell with impressive power conversion efficiency of 8.2% was achieved using microwave-synthesized nanoparticles in combination with commercial paste (CCIC HPW-400) as scattering layer. A mesoscopic perovskite-based solar cell employing microwave-assisted synthesized TiO2 nanoparticles obtained power conversion efficiency over 10%.

Biomolecule-assisted Hydrothermal Synthesis and Electrochemical Properties of Copper Sulfide Hollow Spheres

Abstract Copper sulfide (CuS) hollow spheres could be successfully synthesized in large quantities through a facile biomolecule-assisted hydrothermal synthetic method. The as-fabricated CuS hollow spheres showed specific capacitances and excellent cycling stability in supercapacitors.

Theoretical and experimental investigation into photoelectrocatalytic oxidation and reduction property of ZnFeTi mixed metal oxides

In this paper, we synthesized ZnFeTi layered double hydroxides (LDHs) by hydrothermal synthetic method at high temperature. The LDHs was further calcined by microwave to make ZnFeTi mixed metal oxides (MMO) with special particle size. In addition, the band gap of ZnFeTi-LDHs and MMO were calculated by DFT for the first time, which was in good agreement with the experimental result from UV–vis. MMO was finally dye sensitized and used as thin film electrode to test the photoelectrocatalytic performance for both p-chlorophenol oxidation degradation and CO2 reduction under visible light. The results showed that without the applied voltage, the p-chlorophenol degradation and CO2 reduction rates were not high; after the electric filed was introduced into the reaction, not only the degradation efficiency of p-chlorophenol was increased to 99.1% within 210min, but also the reactivity of CO2 reduction reaction was enhanced a lot. Furthermore, from the results of HPLC and UV–vis, we could conclude that p-chlorophenol was finally decomposed into small inorganic molecules going through 4-chloropyrocatechol and hydrochinone under the co-effect of hydroxide radicals and the photoelectrons. This result could be proved by frontier electron densities on atoms of p-chlorophenol calculated by DFT.

Preparation of New Multi-Component Nanometer Manganese Dioxide/Carbon for Air Electrode

Lithium air batteries have aroused a considerable concern all over the world owing to their outstanding performances. Especially, catalysts of the air electrode, as one of the most core components of lithium air batteries, have been most extensively studied in recent years. In this paper the nanometer manganese dioxide catalysts and their compounds with Super P, TNRGO and OMC were prepared successfully via hydrothermal synthetic method. Characterized by XRD, SEM and BET, most of them have regular shape, perfect dispersion and high specific surface area, especially SBETof MnO2/TNRGO/OMC of the three-component catalysts was up to 126.70m2/g. The air electrodes with nanoMn02/carbons catalysts have lower resistance, and better reversibility.

Synthesis and Crystal Structures of Copper(II) Complexes with Schiff Base Ligands

Schiff bases containing N, O/S donor atoms and their metal complexes have received considerable attention owing to their intriguing structural motifs and industrial, antifungal, and biological applications. Recently, dinuclear copper(II) complexes, [Cu2(L)2(CH3COO)](ClO4) (L = 2benzoylpyridine S-methyldithiocarbazate) and [Cu2L2(SO4)] (L = di-2-pyridyl ketone N(4),N(4)-(butane-1,4-diyl)thiosemicarbazone) in which sulfur atom from Schiff bases ligand together with acetate or sulfate oxygen atoms bridges the two copper(II) ions, respectively, were reported. Although many metal(II)-Schiff base complexes have been reported, dinuclear Cu(II) complexes consist of Schiff base and other the second ligand, especially, dinuclear complexes linked through the other second ligand except the solvent molecule or the counter anion of metal salt as starting material have been little published. In this context, we reported dinuclear Cu(II) complexes of an acetyl pyridine based dithiocarbamate or 4-phenyl-3-thiosemicarbazide with benzilic acid (H2BA) as second ligand. For metal ions, benzilic acid can provide a variety of chelating and/or bridging coordination modes displayed by the carboxylic or hydroxy groups. Many frameworks constructed by BA or HBA with transition metal ions or rare earth ions have been reported, mainly using hydrothermal synthetic method. In this study, we extended these systems to a dinuclear compound of copper(II)-benzilate with 2-acetylpyridine/2-benzoylpyridine based benzhydrazide (Scheme 1) in order to study the crystal structure as part of our longstanding interest in synthesizing and extending the dimensionality of coordination compounds with mixed N,O/S coordination spheres. The molecular structures of 1 and 2 were determined using single crystal X-ray diffraction techniques. The crystallographic data and refinement parameters are listed in Table 1. Selected bond parameters are listed in Table 2. The molecular structure of complex 1 contains dinuclear [Cu2 (apb)2(HBA)(ClO4)] in which two enolate oxygen atoms and bidentate bridging HBA anion bridge the two copper(II) centers and lattice water molecule (Fig. 1a). Each of the two copper atoms in [Cu2(apb)2(HBA)(ClO4)] has different coordination environments. Cu1 adopts a five-coordinate square-pyramidal (τ = 0.27, the geometric parameter τ = |β − α|/60, where β and α are the two largest angles around the central atom; τ = 0 and 1 for the perfect square pyramidal and trigonal bipyramidal geometries, respectively.) with a N2O3 donor. The pyridine nitrogen (N1), the azomethine nitrogen atom (N2) and the enolate oxygen atom (O1) together with the carboxyl oxygen atom (O(3)) from HBA ligand comprise the basal plane of the square-pyramid whereas the enolate oxygen atom (O2) of another ligand occupies the apical position. The maximum displacement of them from the coordination plane is 0.005 (4) A (N2). Cu1 atom displaces 0.022(1) A out of the plane. The behavior of apb results in the formation of two five-membered rings around Cu1 atom. Two planes [Cu1−N1−C5−C6−N2 and Cu1−N2−N3−C8−O1] are nearly planar with mean deviation of 0.048(5) and 0.018(4) A, respectively, the dihedral angle between them being 2.3(1)°. The environment around Cu2 atom can be best described as a distorted octahedral geometry in a N2O4 manner. One

Synthesis of g-C3N4/CaIn2S4 composites with enhanced photocatalytic activity under visible light irradiation.

A series of graphite-like g-C3N4 hybridized CaIn2S4 photocatalysts with different g-C3N4 contents were fabricated via a facile hydrothermal synthetic method. These as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Visible absorption spectra (UV-Vis) and Fourier transform infrared (FT-IR) spectra. Under visible light irradiation, the as-prepared g-C3N4/CaIn2S4 nanocomposites showed enhanced photocatalytic performance for rhodamine B (RhB) degradation. The sample with 5 wt% g-C3N4 hybridized CaIn2S4 exhibited the highest photocatalytic activity. The enhanced photocatalytic performance under visible light irradiation could be attributed to the high separation efficiency of the photogenerated electron-hole pairs. This work could provide a new insight into the fabrication of visible light driven photocatalysts with efficient and stable performance.

The first 3-connected SrSi2 -type 3D chiral framework constructed from {Ni6 PW9 } building units.

A novel 3-connected SrSi2 -type 3D chiral framework constructed from hexa-Ni(II) -cluster-substituted polyoxometalate (POM) units [Ni(enMe)2 ]3 [WO4 ]3 [Ni6 (enMe)3 (OH)3 PW9 O34 ]2 ⋅9H2 O (1) (enMe=1,2-diaminopropane) has been made from a hydrothermal synthetic method. This POM represents the first 3D framework based on {Ni6 PW9 } units and {WO4 } connectors.

Nanoscale anatase TiO2 with dominant {111} facets shows high photocatalytic activity

Abstract In this work, we report a novel synthesis of nanoscale anatase TiO 2 with dominant highly active {1 1 1} facets by a simple one-step hydrothermal route with the assistance of NH 4 F and HF. In this progress, the exposed crystal facets of TiO 2 can been directly tuned by controlling the mole ratio of NH 4 + and F − . When the mole ratio of NH 4 + and F − reach 1:2, nanoscale anatase TiO 2 with dominant {1 1 1} facets can be obtained. Nanoscale anatase TiO 2 with exposed {1 0 1} or {0 0 1} facets will be prepared when there is only ammonia or HF added respectively. Such nano-TiO 2 with exposed highly active {1 1 1} facets has large specific surface area and shows excellent photocatalytic activity: as much as 2–3 times than that of TiO 2 nanosheets with exposed {0 0 1} facets and commercial Degussa P25 which confirms the {1 1 1} facets have higher photocatalytic activity than {0 0 1} and {1 0 1} facets. The higher photocatalytic activity of {1 1 1} facets can be ascribed to the fact that all Ti and O atoms on the surface are unsaturated Ti 5c , Ti 3c and O 2c modes which produces a higher adsorption and degradation ability. The present work demonstrates a explore of hydrothermal synthetic method for controlling preparation of nano-materials.

Facile synthesis of hierarchical flower-like γ-AlOOH films via hydrothermal route on quartz surface

In this work, an interesting morphological evolution from single nanosheet to nanosheet assemblies and flower-like nanostructures boehmite (γ-AlOOH) on quartz surface was discovered via a facile hydrothermal synthetic method. The effects of hydrothermal temperature and time on the morphology and phase of the flower-like boehmite films were studied systematically. The formation mechanism of the flower-like boehmite had also been investigated. The flower-like γ-Al2O3 was prepared by calcining the hierarchical boehmite at 500°C for 2h, preserving the same morphology during the thermal transformation process. X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope (SEM), and transmission electron microscopy (TEM) were used to characterize the structure and morphology of the products.