Enhanced LSCF oxygen deficiency through hydrothermal synthesis

High-performance perovskites are promising materials for diverse renewable energy technologies. Besides design characteristics, the devices performance depends on the material synthesis, since the processes occurring during synthesis may produce different structures and properties. In this work, the perovskite La_0.1Sr_0.9Co_0.9Fe_0.1O_3-δ (LSCF1991) was synthesized by different methods, and the phase composition and oxygen deficiency were assessed and discussed. We show that it is possible to increase oxygen deficiency by promoting oxygen release during crystallization within hydrothermal synthesis, producing a remarkable improvement of ?δ ~0.2 in comparison with the citrate method. The single phase LSCF1991 powder was characterized, shaped by different routes and sintered to demonstrate the stability and suitability to manufacture electrochemical devices.     

Low-temperature synthesis of CdWO4 nanorods via a hydrothermal method

Cadmium tungstate (CdWO₄) nanorods were successfully synthesized via a hydrothermal process and characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and photoluminescent spectra techniques (PL). A pure monoclinic phase of well-crystallized CdWO₄ nanorods, with lengths of 250–400 nm and widths of 30–60 nm, could be readily synthesized at as low temperature as 70 °C.The CdWO₄ nanorods showed a PL emissions peak at 435 nm.     

Morphology-controlled synthesis and characterization of bismuth sulfide crystallites via a hydrothermal method

Bismuth sulfide (Bi₂S₃) crystallites with various morphologies have been successfully synthesized via a hydrothermal process assisted by KOH mineralizer. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that the mineralizer played a key role in the crystallization and morphology-controlled synthesis of Bi₂S₃ crystallites. The room temperature photoluminescence spectra (PL) showed that uniform rod-shape morphology resulted in better luminescence.     

Large-scale synthesis of highly emissive and photostable CuInS2/ZnS nanocrystals through hybrid flow reactor

We report a high-yield, low-cost synthesis route to colloidal CuInS₂/ZnS (CIS/ZnS) nanocrystals (NCs) with Cu vacancies in the crystal lattice. Yellow-emitting CIS/ZnS core/shell NCs of high luminescence were facilely synthesized via a stepwise, consecutive hybrid flow reactor approach. It is based on serial combination of a batch-type mixer and a flow-type furnace. In this reactor, the flow rate of the solutions was typically 1 mL/min, 100 times larger than that of conventional microfluidic reactors. This method can produce gram quantities of material with a chemical yield in excess of 90% with minimal solvent waste. This is a noninjection-based approach in 1-dodecanethiol (DDT) with excellent synthetic reproducibility and large-scale capability. The optical features and structure of the obtained CIS/ZnS NCs have been characterized by UV–vis and fluorescence spectroscopies, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM). The resulting CIS/ZnS NCs in chloroform exhibit quantum yield (QY) of 61.4% with photoemission peaking at 561 nm and full width at half maximum (FWHM) of 92 nm. The as-synthesized CIS/ZnS NCs were proven to have excellent photostability. The synthesized CIS/ZnS NCs can be a promising fluorescent probe for biological imaging and color converting material for light-emitting diode due to Cd-free constituents.     

Low-temperature synthesis of ZnNb2O6 powders via hydrothermal method

ZnNb₂O₆ powder was successfully synthesized via hydrothermal method with Nb₂O₅ and Zn(NO₃)₂·6H₂O as raw materials and cyclohexane as solvent. Phase composition, morphology, and chemical composition were determined via a combination of XRD, SEM, TEM and EDS techniques. The effects of synthesis temperature and reaction time on phase composition and particle morphology were investigated in this paper. The results showed that fine ZnNb₂O₆ powders could be obtained at a hydrothermal temperature of 190 °C or above under different reaction time.     

Low-temperature synthesis of Bi2Fe4O9 nanoparticles via a hydrothermal method

Bi₂Fe₄O₉ (BFO) nanoparticles were successfully synthesized by a hydrothermal method at a temperature as low as 100 °C. The as-prepared powders, characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM) and physical property measurement system (PPMS), exhibited a pure BFO phase about 100 nm size with uniform sheet-like shape and exhibited an AF order at room temperature. It was found that high alkali concentration and alkali ion Na⁺ played a key role in the formation of BFO nanoparticles at a low temperature of 100 °C.     

ZnS nanoparticles prepared via simple reflux and hydrothermal method: Optical and photocatalytic properties

In this research, zinc sulfide nanoparticles (NPs) with various morphologies such as spherical, flower-like, microspheres decorated with nanoparticles and nanorods were synthesized by two distinct, simple and efficient methods. These approaches include reflux and hydrothermal methods. Zinc nitrate hexahydrate (${\mathrm{Zn}({\mathrm{NO}}_3)}_2$).6H₂O were used as Zn source and thioacetamide (TAA) was used as S source. The effects of TAA to zinc ion mole ratio were investigated on the morphology, particle size, optical and photocatalytic properties of ZnS nanocrystals. In hydrothermal synthesis with increasing Zn²⁺:TAA mole ratio from 1:1 to 1:2 dendrite-like nanocrystals changed to semi-spherical nanoparticles with average particle size 50–60?nm, with different effect as photocatalysts. But any change at morphology were didn’t observed with changing Zn²⁺:TAA mole ratio from 1:1 to 1:30 in the reflux method. In the reflux method with increasing in Zn²⁺:TAA mole ratio, dispersed semi-sphere nanoparticles were observed. The synthesized nanocrystals were characterized by infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. XRD analysis and FESEM images show that the size of synthesized ZnS NPs is in the range of 15–25?nm. UV–vis spectra showed that by increasing the amount of sulfur source and increasing the reaction time, ${\lambda }_{\mathit{max}}$ shifted towards lower wavelengths, and the band gap was in the range of ~ 3.9–4.8?eV for all of the samples. Also, photoluminescence (PL) analysis showed by increasing particle size and degree of agglomeration, emission intensity (${\mathrm{\lambda }}_{\mathrm{em}}$) decreased. The photocatalytic activity of the as-prepared samples has been compared for the photocatalyst degradation of reactive blue 21. The sample with low Pl intensity has higher photocatalyst efficiency.     

Synthesis and characterization of wurtzite ZnS nanoplates through simple solvothermal method with a novel approach

A thio Schiff-base-assisted solvothermal process has been developed to synthesize zinc sulfide (ZnS) nanoplates via the reaction between a metal salt, Zn(NO₃)₂·6H₂O and thio Schiff-base of 2-(benzylidene amino) benzenethiol (C₁₃H₁₁NS) as a new precursor. XRD, TEM, SEAD, UV–vis spectroscopy, TG-DTA and FT-IR spectra were employed to characterize the obtained product. The results of this paper indicate that the shape and size of zinc sulfide nanoplates can be controlled systematically by setting certain reaction parameters, such as the reaction temperature and duration and type of solvent. Zinc sulfide nanoplates with different morphology and size have been successfully prepared.     

Fabrication of polymer/ZnS nanoparticle composites by matrix-mediated synthesis

Zinc sulfide nanoparticles are obtained as primary particles in a polymer matrix by a matrix-mediated synthesis. Two types of matrix polymer are synthesized via the copolymerization of hydrophobic, cation-exchange, and cross-linking monomers. The ZnS nanoparticles are affected by the composition of the matrix polymer, and especially by its hydrophobicity. In a low-hydrophobicity copolymer matrix, aggregates of ZnS nanoparticles are observed in the matrix using transmission electron microscopy (TEM) and X-ray diffraction (XRD). In a high-hydrophobicity cation-exchange copolymer matrix, primary particles of ZnS with 2–5 nm diameters are observed in the matrix by TEM. However, the ZnS pattern is not distinguishable in XRD measurements because the particle sizes are too small to diffract X-rays.     

水热一步法合成SO2-4/Zr-PHTS及其催化性能

在低酸度硫酸体系中,以P123 (EO20PO70EO20)为模板剂水热法一步合成硫酸化锆掺杂PHTS固体酸催化剂(SO2-4/Zr-PHTS),利用XRD、TEM、N2吸附脱附以及NH3-TPD、Py-FTIR等手段对其进行表征.结果表明,SO2-4/Zr-PHTS具有有序的六方相介孔结构,具有以L酸为主的弱、中强度的酸性中心;随着硅锆摩尔比的增加,其酸量逐渐减少,比表面积逐渐增加,孔容、孔径无显著变化.SO2-4/Zr-PHTS在催化四氢呋喃聚合中表现出良好的反应性能,推测固体酸的表面酸性和孔结构决定着催化四氢呋喃聚合的反应性能.     

The rapid synthesis of nanostructured orthorhombic KNbO3 particles by a microwave-assisted hydrothermal method and their characterization

We studied the molar ratio effects of niobium and potassium precursors on the structure and morphology of potassium niobate powders prepared via microwave-assisted hydrothermal synthesis (MaHS). KNbO₃ nanostructures in the form of nanotowers and nanocubes were obtained at reduced synthesis times (30–240 min). The products were characterized via XRD, Raman spectroscopy, SEM, and TEM; band gap calculations used diffuse reflectance data. The results indicate that KNbO₃ nanostructures were obtained with crystallite sizes ranging from 33 to 52 nm. An orthorhombic crystalline structure was formed from the increase of KOH at a molar ratio Nb₂O₅:KOH (1:8 to 1:16 M). The band-gap of 3.1–3.3 eV has potential use in photodegradation applications.     

磷石膏水热合成硫酸钙晶须的研究

本文针对磷石膏的溶解特性,利用水热合成技术制备硫酸钙晶须,并讨论了料浆质量分数、反应温度、搅拌速度、反应时间对硫酸钙晶须生长过程的影响,从而探讨其生长机理,为磷石膏水热合成硫酸钙晶须实现工业化生产提供了理论基础.     

Easy synthesis of ordered mesoporous carbon containing nickel nanoparticles by a low temperature hydrothermal method

Ordered mesoporous carbons (OMCs) with embedded metallic nickel (Ni) nanoparticles have been directly synthesized by a simple and low temperature (50 °C) hydrothermal method. The synthesis involved the use of a triblock copolymer Pluronic F127 as the mesostructure directing agent, resorcinol (R) and formaldehyde (F) as carbon precursors, and Ni(NO₃)₂·6H₂O as nickel source. It consisted in the self-assembly of F127, Ni²⁺ salt and RF polymer in an acidic medium and further carbonization, where the Ni²⁺ was captured by the network of F127/RF and further reduced into metallic Ni nanoparticles. The resultant Ni/carbon materials were characterised by X-ray diffraction, thermogravimetric analysis, transmission electron microscopy and nitrogen sorption. Ni/carbon materials with a highly ordered mesostructure were obtained using equal moles of resorcinol and formaldehyde molar ratio (R/F = 1/1), whereas an excess amount of formaldehyde (R/F = 1/2) was found to not form an ordered carbon structure. The results showed that nickel particles, with sizes of ∼10–50 nm, were homogeneously dispersed in the carbon matrices, while the pore mesostructure remained intact. The homogeneous Ni/carbon composites synthesized by this easy hydrothermal route have been demonstrated to be effective molecular adsorbents for magnetic separation.     

In situ synthesis and characterization of ZnS/epoxy nanocomposites via gas‐liquid state reaction method

In this article, the ZnS/epoxy nanocomposites were successfully prepared by the reaction of zinc acetate and H₂S gas via a simple step. Epoxy resin acted as the matrix for the formation of ZnS nanoparticles (10–20 nm) in the reaction system and kept them from agglomerating. The structure, composition, and mechanical properties of the resultant products were successfully investigated by powder X‐ray diffraction, transmission electron microscope, field emission scanning electron microscope, energy dispersive X‐ray fluorescence, and universal testing machine. Meanwhile, by employing differential scanning calorimetry (DSC) we had studied, under nonisothermal condition, the kinetic analysis of the cure reaction which was performed using two classic models: Kissinger and Flynn‐Wall‐Ozawa. The activation energy of curing reaction was 74.63 kJ/mol and 77.57 kJ/mol, respectively, by Kissinger's and Flynn‐Wall‐Ozawa's methods. The possible mechanism of preparation of ZnS/epoxy composites was discussed in this article. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

水热一步法合成SO42-/Zr-PHTS及其催化性能

在低酸度硫酸体系中,以P123(EO₂₀PO₇₀EO₂₀)为模板剂水热法一步合成硫酸化锆掺杂PHTS固体酸催化剂(SO₄^2-/Zr-PHTS),利用XRD、TEM、N₂吸附-脱附以及NH₃-TPD、Py-FTIR等手段对其进行表征。结果表明,SO₄^2-/Zr-PHTS具有有序的六方相介孔结构,具有以L酸为主的弱、中强度的酸性中心;随着硅锆摩尔比的增加,其酸量逐渐减少,比表面积逐渐增加,孔容、孔径无显著变化。SO₄^2-/Zr-PHTS在催化四氢呋喃聚合中表现出良好的反应性能,推测固体酸的表面酸性和孔结构决定着催化四氢呋喃聚合的反应性能。     

The synthesis of NiS,ZnS and SrS through solid-gas reaction of sulfidizing gas mixture

In this study, the sulfidizations of NiO, ZnO, SrNO₃ and SrCO₃ were investigated by using solid-gas reactions under sulfidizing gas mixture, which contains the gas mixture of carbonyl sulfide (COS), carbon disulfide (CS₂) and sulfur (S₂).

The powder crystalline forms of nickel sulfide (NiS), zinc sulfide (ZnS) and strontium sulfide (SrS) were prepared purely by solid-gas reaction technique. The product crystalline phases were characterized by the X-Ray Diffraction (XRD) technique. XRD data of the NiS, ZnS and SrS were in good agreement with the Joint Committee for Powder Diffraction Systems (JCPDS) card numbers, 2-1280, 12-688 and 8-489 in series. The crystalline grain sizes of samples were estimated by using Debye Scherrer formula. The grain sizes of the products are in the range of nano sizes.

In light of this study, it could be proposed that the compounds, NiS, ZnS and SrS could be prepared purely through sulfidizing gas mixture by solid-gas reactions under cooling of a nitrogen atmosphere.     

Size and morphology-controlled synthesis of mesoporous hydroxyapatite nanocrystals by microwave-assisted hydrothermal method

We report the rapid microwave-assisted hydrothermal synthesis of mesoporous hydroxyapatite (HAp) nanocrystals with controlled size, morphology, and surface area using various organic modifiers as regulators. The products were analyzed for their crystalline nature, phase purity, morphology, particle size and pore size distribution. Results indicated that ascorbic acid, cetyltrimethyl ammonium bromide (CTAB) and polyvinylpyrrolidone (PVP) play an important role to obtain needle like, rod like and fiber like mesoporous HAp nanocrystals with different specific surface area by controlling growth habit of HAp along c-axis. In addition, the prepared samples were B-type carbonated HAp similar to bone minerals. Therefore, the present approach can be a promising way to obtain precursor for making tissue engineering scaffolds, drug/protein delivery carriers and bone fillers with tunable characteristics.     

Enhanced performance of LiFePO4 through hydrothermal synthesis coupled with carbon coating and cupric ion doping

A hydrothermal reaction has been adopted to synthesize pure LiFePO₄ first, which was then modified with carbon coating and cupric ion (Cu²⁺) doping simultaneously through a post-heat treatment. X-ray diffraction patterns, transmission electron microscopy and scanning electron microscopy images along with energy dispersive spectroscopy mappings have verified the homogeneous existence of coated carbon and doped Cu²⁺ in LiFePO₄ particles with phospho-olivine structure and an average size of 400 nm. The electrochemical performances of the material have been studied by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The carbon-coated and Cu²⁺-doped LiFePO₄ sample (LFCu5/C) exhibited an enhanced electronic conductivity of 2.05 × 10⁻³ S cm⁻¹, a specific discharge capacity of 158 mAh g⁻¹ at 50 mA g⁻¹, a capacity retention of 96.4% after 50 cycles, a decreased charge transfer resistance of 79.4 Ω and superior electrode reaction reversibility. The present synthesis route is promising in making the hydrothermal method more practical for preparation of the LiFePO₄ material and enhancement of electrochemical properties.     

水热法合成SAPO-34分子筛的影响因素

水热法是制备SAPO-34分子筛最常用的方法之一,分子筛的纯度、结晶度受合成因素影响较多。详述了原料及合成条件中各因素对水热法制备SAPO-34分子筛的影响。     

One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates

Quantum dots (QDs) are luminescent semiconductor nanocrystals with great prospective for use in biomedical and environmental applications. Nonetheless, eliminating the potential cytotoxicity of the QDs made with heavy metals is still a challenge facing the research community. Thus, the aim of this work was to develop a novel facile route for synthesising biocompatible QDs employing carbohydrate ligands in aqueous colloidal chemistry with optical properties tuned by pH. The synthesis of ZnS QDs capped by chitosan was performed using a single-step aqueous colloidal process at room temperature. The nanobioconjugates were extensively characterised by several techniques, and the results demonstrated that the average size of ZnS nanocrystals and their fluorescent properties were influenced by the pH during the synthesis. Hence, novel ''cadmium-free’ biofunctionalised systems based on ZnS QDs capped by chitosan were successfully developed exhibiting luminescent activity that may be used in a large number of possible applications, such as probes in biology, medicine and pharmacy.