One-step hydrothermal microwave-assisted synthesis of LaFeO3 nanoparticles

Lanthanum orthoferrite (LaFeO₃) powders were synthesized via a highly efficient one-step hydrothermal microwave-assisted synthesis at relatively low temperatures of 240 °C and pressure of 60 bar. The use of microwave irradiation for heating during the synthesis intensifies the LaFeO₃ crystallization process leading to reduced synthesis duration at least 16 times as compared with conventional heating (3 versus 48 h).     

Controllable synthesis of ZnO nanostructures on the Si substrate by a hydrothermal route

In this paper, controllable synthesis of various ZnO nanostructures was achieved via a simple and cost-effective hydrothermal process on the Si substrate. The morphology evolution of the ZnO nanostructures was well monitored by tuning hydrothermal growth parameters, such as the seed layer, solution concentration, reaction temperature, and surfactant. X-ray diffraction and photoluminescence measurements reveal that crystal quality and optical properties crucially depend on the morphology of the ZnO nanostructures. The ease of synthesis and convenience to tune morphology and optical properties bring this approach great potential for nanoscale applications.     

Effect of substrate surface treatment on the hydrothermal synthesis of zinc oxide nanostructures

In this investigation, ZnO nanostructures were coated via hydrothermal process on glass substrate surfaces, which were treated by acidic and alkaline solutions. Furthermore, the ZnO structure was doped by different amounts of Al⁺³ ions to investigate the microstructural variation. Characteristics of the samples by XRD and SEM analyses confirmed the formation of different morphologies and various crystal sizes for the nanostructured ZnO on the substrates including nanoflower, nanorod, and nanopanel morphologies. Furthermore, XRD results showed that the Zn²⁺ concentration was a crucial factor in changing the grain size. EDS analysis confirmed the uniform distribution of Al dopant, while the FTIR spectra revealed the presence of Al–O and Zn–O stretching bonds in the coatings. The results confirmed that the sample, which was etched by fused NaOH had a uniform and compacted structure. Moreover, it was evident the proposed treatment and synthesis process was successful in the formation of uniform nanostructured ZnO film on the glass substrate without the requirement for seed layer deposition.     

One-step hydrothermal synthesis of N-doped TiO2/C nanocomposites with high visible light photocatalytic activity

N-doped TiO(2) nanoparticles modified with carbon (denoted N-TiO(2)/C) were successfully prepared by a facile one-pot hydrothermal treatment in the presence of L-lysine, which acts as a ligand to control the nanocrystal growth and as a source of nitrogen and carbon. As-prepared nanocomposites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) spectra, and N(2) adsorption-desorption analysis. The photocatalytic activities of the as-prepared photocatalysts were measured by the degradation of methyl orange (MO) under visible light irradiation at λ≥ 400 nm. The results show that N-TiO(2)/C nanocomposites increase absorption in the visible light region and exhibit a higher photocatalytic activity than pure TiO(2), commercial P25 and previously reported N-doped TiO(2) photocatalysts. We have demonstrated that the nitrogen was doped into the lattice and the carbon species were modified on the surface of the photocatalysts. N-doping narrows the band gap and C-modification enhances the visible light harvesting and accelerates the separation of the photo-generated electrons and holes. As a consequence, the photocatalytic activity is significantly improved. The molar ratio of L-lysine/TiCl(4) and the pH of the hydrothermal reaction solution are important factors affecting the photocatalytic activity of the N-TiO(2)/C; the optimum molar ratio of L-lysine/TiCl(4) is 8 and the optimum pH is ca. 4, at which the catalyst exhibits the highest reactivity. Our findings demonstrate that the as-obtained N-TiO(2)/C photocatalyst is a better and more promising candidate than well studied N-doped TiO(2) alternatives as visible light photocatalysts for potential applications in environmental purification.     

Microstructure and photocatalytic activity of electrospun carbon nanofibers decorated by TiO2 nanoparticles from hydrothermal reaction/blended spinning

Recently, carbon nanofibers@TiO₂ (CNFs@TiO₂) composites as photocatalysts for dye degradation have attracted intense attention. However, only few contributions had been made to investigate systematically the differences between the various preparation approaches and the influence of thermal treatment on the photocatalytic activity. In this work, the electrospun CNFs@TiO₂ composites which were prepared by hydrothermal reaction and blended spinning, respectively, have been fabricated via stabilization in air at 280 °C and then carbonization in N₂ at heat treatment temperature between 500 and 1100 °C. The composites which were prepared by hydrothermal reaction and blended spinning showed the outstanding photocatalytic activity at 900 °C and 1100 °C, respectively. And the photocatalytic activity of composites prepared by hydrothermal reaction was higher than that prepared by blended spinning, but reversibility of the composites showed a reverse trend. These results indicated that the effect of heat treatment temperature on the photocatalytic activity depended on the synergistic effect among the adsorptive property of CNFs, TiO₂ loading amount and anatase phase content in composites. Hence, combining the merits of hydrothermal reaction and blended spinning, a novel method for preparing CNFs@TiO₂ composites with high TiO₂ loading amount and strong interfacial interaction could be envisioned.     

Yb3+/Er3+ co-doped Gd2Te4O11 nanosheets with intrinsic polarity: One-step hydrothermal synthesis and upconverted optical temperature measuring ability

The digadolinium tellurite phosphors of Gd₂Te₄O₁₁(GTO):Yb³⁺/Er³⁺ have been successfully synthesized as upconversion luminescence (UCL) materials via one-step hydrothermal method. The crystal structure, morphology, and upconversion luminescence property were systematically characterize by XRD, SEM, and spectroscopy techniques. The Rietveld refinements of crystal structure were carried out on the XRD patterns and the feature of crystal structure was analyzed. Under the 980 nm NIR excitation, these materials showed very bright upconverted emissions. The concentrations of Yb³⁺ and Er³⁺ were optimized and the strongest upconverted emissions were achieved in the GTO:15%Yb³⁺/1%Er³⁺. The possible energy transfer mechanism of UCL was proposed based upon the analysis of power-dependent UCL and fluorescence kinetics. Furthermore, the fluorescence intensity ratio (FIR) derive from the two thermally coupled energy levels (²H_11/2 and ⁴S_3/2) of Er³⁺ was employed as indicator for temperature measurement. The maximum absolute sensitivity can be achieved to be 7.34 × 10^?3 K^?1 at 501 K. This material exhibited good reliability and repeatability in optical temperature measurement, which could be a novel promising candidate for noncontact temperature sensors.     

Low temperature polymer assisted hydrothermal synthesis of bismuth ferrite nanoparticles

BFO nanoparticles were successfully synthesized by a polymer assisted hydrothermal method at a temperature as low as 160 °C. The as-prepared powders, characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), exhibited a pure BFO phase about 10 nm size and uniform sphere-like shape. It was found that the added polymer played a key role in decreasing the growing speed of BFO nuclei and resulted in the formation of BFO nanoparticles.     

利用Sol-Gel法与水热合成法制备纳米TiO2及其光催化活性研究

以Sol-Gel法及水热合成方法制备了纳米TiO2,利用XRD进行了表征,以太阳光为光源,通过对亚甲基蓝溶液的降解反应,考察了两种方法所得样品的光催化活性。结果表明,利用水热合成法制备的锐钛矿型TiO2具有更小的粒径,而通过溶胶-凝胶制得的样品为混晶型TiO2,对亚甲基蓝降解具有较高的光催化活性。     

MXene (Ti3C2Tx) supported electrocatalysts for methanol and ethanol electrooxidation: A review

MXene is a growing class of two-dimensional layered material that has been showed promising application in various energy storage and conversion technologies, due to its unique electrical, mechanical, surface and electrocatalytic properties. One of the promising applications of MXene is, its definite role as durable catalyst support material, for fuel cell anodic/cathodic reactions. Very recently, MXene supported catalysts have been identified as potential and stable support for various Pt and non-Pt metals designed for cathodic oxygen reduction reaction and it has been proved as excellent material to enhance the oxygen reduction kinetics. This had motivated the researchers to explore MXene as catalyst support for anodic methanol/ethanol oxidation reactions. In this review, recent developments in experimental and theoretical research on MXene-based electrocatalysts for the methanol/ethanol oxidation reactions are examined and overviewed. After careful examination of the available literature, we presume that MXene supported electrocatalyst showed enhanced methanol/ethanol oxidation kinetics and therefore believed to have tremendous opportunities as durable catalyst support for alcohol fuel cells. However, researchers also consider several limitations and challenges that must be addressed for efficient application of MXenes as catalyst supports. Therefore, current research on MXenes with respect to the methanol/ethanol oxidation are discussed, with a focus on synthesis strategies, oxidation kinetics, and factors responsible for enhancing the electrocatalytic performance. Several strategies for the further development of efficient and durable MXene supported catalysts are also proposed.     

Two-dimensional (2D) Ti3C2Tx MXene nanosheets with superior adsorption behavior for phosphate and nitrate ions from the aqueous environment

With the advancement of modern industries and metropolitan areas, negative environmental impacts such as eutrophication have become serious issues obstructing the usage of water sources in many countries. In this study, two-dimensional (2D) MXene materials were employed for the adsorptive removal of phosphate and nitrate ions from waters. The adsorption parameters of the sorption system including reaction time, solution pH, background ions, and reusability, were evaluated in batch experiments. Material characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis, Brunauer–Emmett–Teller analysis, and high-resolution transmission electron microscopy were performed. The mechanism of removing phosphate and nitrate was clearly described by various kinds of interactions such as electrostatic interactions, and the complexation was significant to elucidate the adsorption mechanism. The adsorption data for phosphate and nitrate update was determined using different isotherms and kinetic models. Reusability and field studies on the MXenes were also conducted. The above findings demonstrate that 2D MXenes could act as promising adsorbents for the elimination of toxic ions from water/wastewater.     

Preparation of Li2TiO3 by hydrothermal synthesis and its structure evolution under high energy Ar+ irradiation

Ultrafine lithium titanate (Li₂TiO₃) powder was synthesized by hydrothermal method. The phase formation and transition condition among α, β, and γ-Li₂TiO₃ were discussed. XRD and ICP-AES showed the single α-phase was formed at 180 °C with 2 h hydrothermal reaction, and it transited into β-phase at 400 °C. SEM observation and EDS analysis confirmed the dissolution of TiO₂ and the formation of α-Li₂TiO₃ proceeded simultaneously with preferable growth direction of (-133) lattice. During the phase transition, the powder maintained the small crystallite, which facilitated the fabrication of Li₂TiO₃ bulk with small grain size. After the Ar⁺ irradiation, the surface region to the depth of 3 μm of Li₂TiO₃ ceramic was affected, where the decrease of crystallization and disturbance of short-range order were confirmed by GIXRD and Raman spectroscopy. In spite of the structure change at the surface area, the ceramic bulk maintained the same.     

Influence of anionic and non-ionic surfactants on the synthesis of core-shell Fe3O4@TiO2 nanocomposite synthesized by hydrothermal method

Magnetite spinel nanoparticles (Fe₃O₄) coated titanium dioxide has been prepared by the solvo-hydrothermal method for application in dye degradation and wastewater remediation. The core-shell Fe3O4@TiO2 nanoparticles have been synthesized using titanium butoxide (TBT) and ferric chloride as precursors. In this method, firstly, magnetite nanoparticles have been prepared through a solvothermal process using ethylene glycol as a solvent. Then, titanium butoxide was used as a precursor to synthesize Fe₃O₄@TiO₂ core-shell nanoparticles using the hydrothermal method. The surfactants that were added, in separate synthetic processes, were anionic oleic acid and Sodium Dodecyl sulfonate, and non-ionic Polyvinylpyrrolidone and Polyethylene glycol. The effects of the various surfactants on the fabrication of core-shell magnetic nanoparticles were studied. Various characterization methods have been established to examine the morphology and magnetization features of the nanostructured particles, such as XRD, FTIR, TEM, FESEM, UV-spectroscopy, and VSM, etc., which validated the formation of Titania coated magnetite nanoparticles. The TiO₂ shell formation drastically reduces the saturation magnetization of the magnetic nanoparticles. The Oleic acid as a surfactant produces the smallest nanoparticles. The PVP coating is best amongst these surfactants for the retention of saturation magnetization upon coating.     

Simple microwave synthesis of TiO2/NiS2 nanocomposite and TiO2/NiS2/Cu nanocomposite as an efficient visible driven photocatalyst

Approximately 47% of solar-terrestrial radiation is visible. It is a great achievement to produce a highly efficient visible driven photocatalyst. Here TiO₂/NiS₂/Cu nanocomposite was prepared as a highly active visible driven photocatalyst. TiO₂/NiS₂/Cu nanocomposite was prepared by microwave method. It degrades 92%, 86%, 87%, and 88% of Rhodamine B (RhB), Methyl orange (MO), Acid Black 1 (AB1), and Acid Brown 214 (AB214), respectively. Adding NiS₂ and Cu to TiO₂ dramatically increased the degradation efficiency from 17% for bare TiO₂ to 92% for TiO₂/NiS₂/Cu nanocomposite under visible light. As-prepared TiO₂/NiS₂/Cu nanocomposite was characterized by SEM, TEM, XRD, DRS, BET, and EDX.     

Synthesis and characteristics of carbon encapsulated magnetic nanoparticles produced by a hydrothermal reaction

A novel process to synthesize carbon encapsulated magnetic nanoparticles was developed by heating an aqueous glucose solution containing Fe@Au (Au coated Fe nanoparticles) or Ni nanoparticles at 160–180 °C for 2 h. In comparison with traditional methods, such a hydrothermal approach is not only simple but also able to provide functional groups such as –OH on the surface of carbon sphere. Only pure Fe nanoparticles did not favor the formation of carbon encapsulated magnetic nanoparticles due to the oxidation of Fe nanoparticles by H₂O during the reaction and their surfaces had to be coated by an Au shell in advance. The results of TEM, HRTEM, XRD, XPS and vibration sample magnetometer characterization show that uniform carbon spheres containing some embedded Fe@Au nanoparticles with a saturation of 14.6 emu/g are obtained and the size of a typical product is 200 nm. Carbon encapsulated Ni nanoparticles have been successfully prepared in the same way.     

Ti3C2Tx/Ni/TiO2复合粉体的制备及吸波性能研究

采用热处理的方法制备出二维层状Ti3C2Tx/Ni/TiO2复合粉体,并利用TG-DSC、SEM、XRD和XPS对样品进行表征分析,通过矢量网络分析仪测试样品的电磁参数并模拟计算不同涂层厚度下样品的反射损耗值(RL).结果表明:随着热处理温度的升高,样品中TiO2质量含量增加;当热处理温度为300℃时,在频率f=17....     

Sacrificial template synthesis of core-shell SrTiO3/TiO2 heterostructured microspheres photocatalyst

The core-shell SrTiO₃/TiO₂ heterostructure was obtained via a combined hydrothermal route and calcination treatment using amorphous spherical TiO₂ as both template and reactant. Adjusting the hydrothermal environments can control the morphology of the post-calcined sample when it is hydrothermally treated at 180 °C/3 h and 200 °C/6 h, respectively. Following the heat treatment at 700 °C/4 h, the obtained powder illustrates the core-shell heterostructure with a hierarchical surface, and the diameter of the microsphere is about 700 nm. This synthesizing route facilitates the formation of a concentration gradient of SrTiO₃ and TiO₂, and subsequently constructs a gradient energy level, which helps the samples exhibited an excellent de-colorize activity over the methylene blue. The possible formation mechanism of core-shell SrTiO₃/TiO₂ heterostructures was proposed to guide the further improvement of their photocatalytic activity.     

Controllable synthesis of Bi2S3 via a simple hydrothermal approach starting from an inorganic precursor

A hydrothermal method was used to fabricate Bi₂S₃ with different morphologies (nanoparticles, nanoflaked flowers and nanothorny columniform structures) using bismuth(III) monosalicylate [BiO(C₇H₅O₃)] and three kinds of sulfur sources [l-cysteine, thiourea and thioacetamide in water, respectively]. The influences of the reaction conditions are discussed and possible mechanism for the formation of different Bi₂S₃ nanostructures is proposed. The products were characterized by XRD, UV–vis, PL, FT-IR. Bismuth salicylate, which is known to be a complex, may play a critical role as a precursor and a template for the growth of linear bismuth sulfide nanorods.     

Effective removal of Cr(VI) and methyl orange from the aqueous environment using two-dimensional (2D) Ti3C2Tx MXene nanosheets

Industrial use of heavy metals and dyes critically depends on the effective handling of industrial effluents. Effective remediation of industrial effluents using various adsorbent materials has thus become critical. In this paper, we study two-dimensional MXenes as an adsorbent for removing Cr(VI) and methyl orange (MO) in waters. The physico-chemical performance of MXenes was studied using X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer?Emmett?Teller, scanning electron microscopy, high resolution-transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy techniques. The adsorption system, including influence of contact time, pH of solutions, co-ions, and desorption experiments were performed for effective Cr(VI) and MO removal. The Cr(VI) and MO removal rate of the MXenes was very fast, and the kinetic system was driven by pseudo-second-order kinetics. The sorption isotherm closely well-tailored with the Langmuir isotherm, and the maximum removal efficiencies were 104 and 94.8 mg/g for Cr(VI) and MO, respectively. The MXenes was successfully regenerated by 0.1 M NaOH aqueous solution and can be repeatedly recycled. The uptake of Cr(VI) and MO by the MXenes was mainly due to chemical adsorption, namely electrostatic adsorption, complexation, surface interactions, and ion exchange mechanisms. This investigation demonstrates the selectivity and feasibility of the MXenes as a real adsorbent for eliminating Cr(VI) and MO from the aqueous environment.     

Preparation and characterization of K0.5Bi0.5TiO3 particles synthesized by a stirring hydrothermal method

Nanoparticles of potassium bismuth titanate K_0.5Bi_0.5TiO₃ (KBT) with an average particle size of 38 nm were prepared using a stirring hydrothermal method. The pure KBT was obtained in 8 h reaction time instead of 24–48 h for conventional hydrothermal method. X-ray diffraction, Raman spectroscopy and TG analysis were used to check the proportion of hydroxyl group existing into the crude and the calcined KBT. A Hydroxyl group was found to affect the crystallite structure parameters and cell volume. When temperature increases from 25 to 1050 °C, the tetragonal structure presents a c/a ratio which decreases from 1.048 to 1.012. TG analysis and Raman vibration at high frequencies show that c/a is affected by hydroxyl group content below 750 °C and by potassium and bismuth vacancies above this temperature. The ceramic KBT showing a 300 nm size presents an improved ε_r=780 and a dielectric loss tan δ=0.062 at room temperature. Electric conductivity σ_ac was also lowered to 10⁻⁶ (Ω m)⁻¹ with an activation energy change at 673 K from 0.35 to 0.605 eV.