Synthesis and characterization of PbTe nanostructures in the presence of novel surfactants

For the first time, two novel surfactants base on the Schiff base compounds derived from 1,8-diamino-3,6-dioxaoctane, 2-hydroxyacetophenone, and salicylaldehyde were synthesized, characterized, and then used for the preparation of PbTe nanostructures. The surfactant synthesized by 1,8-diamino-3,6-dioxaoctane and 2-hydroxyacetophenone was marked as [(DaDo)-(2-HAP)]. Besides, the Schiff base derived from 1,8-diamino-3,6-dioxaoctane and salicylaldehyde was marked as [(DaDo)-(Sal)]. In addition, the effect of preparation parameters like reaction time and temperature in hydrothermal synthesis on the morphology of the PbTe nanostructures was tested in the presence of the surfactants. The products were analyzed with the aid of ¹H NMR, SEM, XRD, FT-IR, and EDS. Based on the FT-IR and ¹H NMR results, it was found that pure Schiff bases have been successfully synthesized by heating the starting reagents at 70 °C. According to the XRD results, it was found that pure cubic PbTe nanostructures have been obtained by this method.     

Hydrothermal synthesis, characterization, and influence factors of PbTe nanocrystals

In the present paper, we successfully prepared PbTe nanocrystals in a simple aqueous system via the hydrothermal route employing PbO, Te powders and N₂H₄·H₂O as the starting reactants at 150 °C for 14 h. Some factors affecting the morphologies of the PbTe nanocrystals, such as the reaction temperature, time, the amount of NaOH, sorts of reductants and Pb²⁺ ion sources, were systematically investigated. Experimental results indicated that, under keeping the other experimental conditions constant: raising the reaction temperature, the shapes of the as-obtained PbTe hardly changed, while decreasing the temperature, some PbTe dendrites were obtained; the short reaction time availed to obtain cubes with a hole in the center of each face; more amounts of NaOH were favorable to the formation of regular PbTe nanocuboids. When NaBH₄ was used as the reductant, a large amount of near spherical PbTe nanocrystals was produced; while NaH₂PO₂ was used, many PbTe crystals with hollow framework structures were obtained. When Pb(CH₃COO)₂ was used as the Pb²⁺ ion source, some dendrites made of many irregular particles were generated; while PbSO₄ was employed, many PbTe nanocuboids were produced. A possible formation mechanism of PbTe nanocrystals was proposed based on the experimental results.     

Sodium dodecyl benzene sulfonate-assisted synthesis through a hydrothermal reaction

The effects of the anionic surfactant on the morphology, size and crystallization of NiSe precipitated from NiCl₂·6H₂O and SeCl₄ in presence of hydrazine (N₂H₄·H₂O) as reductant were investigated. The products have been successfully synthesized in presence of sodium dodecyl benzene sulfonate (SDBS) as surfactant via an improved hydrothermal route. A variety of synthesis parameters, such as reaction time and temperature, capping agent and amount of reducing agent have a significant effect on the particle size, phase purity and morphology of the obtained products. The sample size became bigger with decreasing reaction temperature and increasing reaction time. In the presence of 2 ml hydrazine, the samples were found to be the mixture of Ni₃Se₂ and NiSe. With increasing the reaction time and amount of hydrazine a pure phase of hexagonal NiSe was obtained. X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) images indicate phase, particle size and morphology of the products. Chemical composition and purity of the products were characterized by X-ray energy dispersive spectroscopy (EDS). Photoluminescence (PL) was used to study the optical properties of NiSe samples.     

Electrochemical and thermodynamic studies to evaluate inhibition effect of 2-[(4-phenoxy-phenylimino)methyl]-phenol in 1 M HCl on mild steel

Inhibition of the corrosion of mild steel in 1.0 M HCl solution by a Schiff base compound named 2-[(4-phenoxy-phenylimino)methyl]-phenol (APS) was investigated at different temperatures (25–55 °C) using electrochemical measurements. The inhibition efficiency increased as APS concentration and temperature increased. It was found that adsorption for APS on mild steel complies with the Langmuir adsorption isotherm in all studied temperature. Thermodynamic parameters (ΔG_ads, ΔH_ads and ΔS_ads) for APS adsorption on mild steel were found out and discussed at each temperature. Time dependency of mild steel in 1.0 M HCl solution in the absence and presence of APS was also studied. The surface morphology of mild steel was examined via SEM analysis.     

System PbTe–CoSe2

Phase relations in the PbTe–CoSe₂ system were studied by physicochemical analysis. The system was found to contain an incongruently melting compound of composition PbCoSe₂Te. The lattice parameters, microhardness, and standard thermodynamic functions of PbCoSe₂Te were determined. At room temperature, the solubility of CoSe₂ in PbTe is 10 mol % and that of PbTe in CoSe₂ is 8 mol %.     

Preparation of barium strontium titanate using a modified polymeric precursor method

Barium strontium titanate with Ba/Sr ratio of 50/50 (BST5) was prepared using a modified polymeric precursor method. Unlike other methods, it proved to be cost effective since neither moisture sensitive nor costly starting materials were used for the preparation. The optimum preparation condition was established, and it was found that an annealing temperature of 600 °C with a dwell time of 20 h followed by a heat treatment at 800 °C with dwelling time of 4 h is enough to obtain well crystallized, phase pure fine powder of BST5. The oxide powder thus obtained was single phased, crystalline with cubic structure. The average lattice constant of the polycrystalline oxide was examined using XRD and it was determined to be 0.3950 nm (±0.0003 nm). The average crystallite size of the ceramic was found to be about 25–30 nm. The reaction pathway, temperature of decomposition of the precursor and the temperature of formation of the oxide was found using the data from the EGA-TGA-MS coupled instrument. TGA data showed about 75% of total weight loss over the entire heating process. The SEM studies showed that the grains were in micrometer size range, having high degree of agglomeration and irregular morphology. This process is interesting as it yields phase pure BST5 ceramic at a temperature of 800 °C devoid of secondary phases like (Ba,Sr)₂TiO₄.     

Catalytic hydrogenation of various organic substrates using a reusable polymer-anchored palladium(II) complex

A stable, reusable, and highly active catalyst for liquid phase hydrogenation reaction has been developed by reacting poly(3,6-diamino N-vinylcarbazole) with benzaldehyde to get polymer-anchored Schiff base which was then reacted with bis(benzonitrile)palladium(II)chloride [Pd(PhCN)₂Cl₂] to get the polymer-anchored complex. The complex was characterized by using scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis, atomic absorption spectroscopy (AAS), and spectrometric methods like diffuse reflectance spectra of solid (DRS) and Fourier transform infrared spectroscopy (FTIR). The catalytic performance of this catalyst was investigated in hydrogenation of various organic substrates under high-pressure condition. The results showed that the catalyst were highly efficient for hydrogenation reaction and gave excellent yields of products. At the same time, the catalyst was very stable and could be reused for more than five times without noticeable loss of its catalytic activity.     

Synthesis of molybdenum oxide hollow microspheres by ethanol and PEG assisting hydrothermal process

Molybdenum oxide hollow microspheres were successfully synthesized via a combination of a hydrothermal method with ethanol and PEG assisting technique. The as-obtained products were characterized by SEM, XRD. The SEM results showed that the sizes of molybdenum oxide hollow spheres were 1-2 μm, and the spherical shape of the hollow microsphere products remained almost unaltered after calcination at 500 °C for 2 h. The XRD results showed that a purity phase of α-MoO₃ could be obtained after calcination. It was also found that the reaction temperature played a key role in the formation of hollow microshphere structure.     

Preparation and growth mechanism of lead telluride nanocrystals by a modified molten composite-hydroxides method

PbTe nanocrystals were prepared by a modified molten composite-hydroxides method at 180 degrees C for different times, using Pb(NO3)2 and TeO2 as starting materials and KBH4 as a reductant. The nanocrystal structure and morphologies of the synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution TEM (HRTEM), respectively. The results showed that the reaction time has a significant influence on the size and shape of the as-prepared PbTe nanocrystals. As the reaction time increased, the as-prepared products were eventually transformed from nanomaterials (nanocubes, nanorods, and nanosheets) to microcrystals with different morphologies (microcubes, mciroprisms, and microplates). The formation mechanism of the PbTe was proposed, and a one-dimensional oriented attachment growth process combined with two-dimensional oriented attachment growth process was suggested for the growth of nanorods and nanosheets.     

Controlled synthesis and photoluminescence properties of hierarchical BaXO4 (X = Mo, W) nanostructures at room temperature

Controlled synthesis of hierarchical Barium molybdate (BaMoO₄) nanostructures with different morphologies, such as peanut-like, cube-like and flower-like, was successfully achieved in aqueous solution at room temperature. The obtained products were characterized by a scanning electron microscope (SEM) and an X-ray power diffractometer (XRD). The morphologies of the obtained products were found to be greatly dependent on reaction time, EDTA concentration and the [Ba²⁺]/[MoO₄²⁻] ratio. This controllable method could be readily extended to produce hierarchical Barium tungstate (BaWO₄) nanostructures with peanut-like, dumbbell-like, sphere-like and flower-like morphologies. The photoluminescence (PL) properties of the obtained BaMoO₄ and BaWO₄ nanostructures exhibited strong dependence on the morphologies and sizes, respectively.     

La0.5Sr0.5TiO3 nanopowders prepared by the hydrothermal method

La_0.5Sr_0.5TiO₃ nanopowders were prepared by the hydrothermal method. The influence of processing parameters, including KOH concentration, reaction temperature and reaction time on the obtained products were studied. The structure and morphology of the obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD results show that pure phase La_0.5Sr_0.5TiO₃ nanopowders can be successfully synthesized with 2 M KOH concentration at a low temperature of 220 °C for 24 h. In addition, the product has a plate-like shape with particle sizes in the range of 25–100 nm as estimated by TEM.     

Adsorption characteristics of activated carbon prepared from spent ground coffee

This paper reports results of a research project which attempts to produce low-cost activated carbon from agro-residue wastes. The ground coffee residue which is a by-product of coffee making was collected from coffee shops, prepared, and converted to activated carbon by a chemical activation method. The objective of this work is to investigate the effects of preparation conditions on properties of the activated carbon obtained. The preparation condition is defined by pyrolysis rate, concentration of ZnCl₂, impregnation time, and carbonization temperature. The pyrolysis rate was fixed at 10 °C min^?1 for 4 h with three concentrations of ZnCl₂ (5, 10, and 15 wt%), three durations of impregnation time (8, 12, and 24 h), and three carbonization temperatures (400, 450, and 500 °C). The morphology and specific surface area were, respectively, determined using SEM and BET techniques. It was found in this study that the activated carbon with the best properties was obtained at the preparation condition given by 15 wt% of ZnCl₂, impregnation time of 24 h, and 500 °C carbonization temperature. On average, the activated carbon had a pore diameter of 0.61 nm, specific surface area of 831 m² g^?1, and a total pore volume of 0.44 cm³ g^?1. It was also found that the adsorption isotherm of Cu (II) fitted well with Freundlich isotherm.     

Facile hydrothermal synthesis for size-controlled YVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> micro/nanosheets and its luminescence properties

Homogeneous and size-controlled YVO₄:Eu³⁺ micro/nanosheets were successfully synthesized on a large scale by using an ammonium oxalate (AO)-assisted hydrothermal route and post-calcination process. In this study, the shape and size of the as-prepared architectures can be changed effectively by controlling a series of experimental parameters, such as the precursor’s reaction temperature, hydrothermal reaction time and molar ratio of organic additive AO:Y³⁺. YVO₄:Eu³⁺ micro/nanosheets were synthesized with lengths ranging from 2000 to 400 nm and thicknesses ranging from 200 to 50 nm. When changing the precursor’s reaction temperature and reducing the hydrothermal reaction time to 2 h, the phase composition was transformed into Y₂O₃ instead of YVO₄. Functioning as a precipitant and shape modifier, AO exerted a dynamic effect by adjusting the growth rate of different facets under the various experimental conditions, resulting in the formation of different shapes and sizes of the final products. The correlative growth mechanism was analyzed in detail. Photoluminescence and Electroluminescence properties of the products exhibited a strong red emission focused on 618 nm under 275 nm ultraviolet excitation or direct current high-voltage field. Small sample sizes exhibited high EL intensity. The size-controlled products synthesized successfully via the hydrothermal method could provide a great opportunity for systematically evaluating their luminescence properties and accelerating the use of different types of applications in color display devices.     

A rapid route for the synthesis of submicron Se and Te rod-like crystals

Submicron Se and Te rod-like crystals were successfully synthesized via a rapid polyol process by refluxing Na₂EO₃ (ESe, Te) and (NH₃)₂S₂O₃ in ethylene glycol at 180 °C for 0.5 h under vigorous stirring. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and XPS procedures. Studies found that reaction time and temperature have great influences on the morphology of the final products.     

Parametric investigation on anhydrous sodium metaborate (NaBO2) synthesis from concentrated tincal

In this study, anhydrous sodium metaborate (NaBO₂), an industrial and technologically important boron compound, synthesis from concentrated tincal (CT) was carried out. Experiments with different temperature and time were performed in the parametric investigation to map out the reaction mechanism. Crystalline phase characterization of metaborates products indicates that anhydrous NaBO₂ synthesis from CT occurred at 400 °C with 5 h of reaction conditions. At the end of synthesis, the obtained anhydrous NaBO₂ product can be used in many fields without having the calcination step due to the advantages of this method.     

Facile synthesis and characterization of CdTiO<Subscript>3</Subscript> nanoparticles by Pechini sol–gel method

In this work, CdTiO₃ nanoparticles were synthesized through reaction between Cd(CH₃COO)₂.2H₂O, Ti(OC₄H₉)₄, trimesic acid as a new chelating agent and ethanol as solvent by Pechini sol–gel method. X-ray diffraction (XRD) patterns showed that CdTiO₃ nanostructures have rhombohedral structure with diameter of about 35.61 nm. The structure, morphology and size of CdTiO₃ nanoparticles were characterized by FT-IR, XRD, SEM and EDAX. The optical properties of the products were studied by DRS. Based on the results of experiments, it was found that temperature and time of calcination, pH and the solvent of reaction are important parameters for formation of CdTiO₃ nanoparticles. Utilizing trimesic acid (benzene-1,3,5-tricarboxylic acid) as a new chelating agent for preparation of CdTiO₃ nanostructures was initiative of this work.     

Hydrogenation of the intermetallic compound Zr2Ni

We have determined conditions for the preparation of hydride phases with the composition Zr₂NiH_～5 by reacting the intermetallic compound Zr₂Ni with hydrogen or ammonia and identified the products of the reaction between the intermetallic compound and ammonia in the temperature range 150–500°C in the presence of NH₄Cl as an activator. The results demonstrate that the use of ammonia at 500°C leads to decomposition of the intermetallic compound and formation of zirconium hydride, zirconium nitride, and metallic nickel.     

Solubility and formation of ternary Widmanstätten precipitates in PbTe in the pseudo-binary PbTe–Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> system

A unidirectional solidification experiment by Bridgman method has been performed for the Pb₁₄Bi_28.8Te_57.2 composition, which lies on the pseudo-binary PbTe–Bi₂Te₃ system, resulting in the formation of Widmanstätten precipitates of a ternary compound, most likely with the structure of PbBi₂Te₄ in the PbTe matrix. The formation of the precipitates is caused by the decrease of bismuth solubility in the PbTe phase with decreasing temperature. The PbTe-rich part of the PbTe–Bi₂Te₃ phase diagram was investigated from the compositional variations in the unidirectionally solidified sample and the diffusion couples. This proved that the solubility decreases with decreasing temperature: 15.6 ± 0.9 (583 °C) to \( 6. 2_{ - 1.7}^{ + 2.1} \) (450 °C) at.% Bi. The orientation relationship between the matrix and precipitates has been examined by electron backscatter diffraction technique; precipitation occurs on {111} habit planes in PbTe with orientation relationship (0001)_precipitate//{111}_PbTe and <11\( \overline{2} \)0>_precipitate//<110>_PbTe. The thermoelectric properties in PbTe with Widmanstätten precipitates as examined by the scanning Seebeck probe method is –46 ± 2 μVK^?1.     

3D navicular ceria micro/nanocomposite structure with multi-layered arrangement and its application in CO oxidation

In this work, novel three-dimensional (3D) navicular ceria micro/nanocomposite architecture with multi-layered structure was synthesized for the first time via solution reaction followed by a simple hydrothermal treatment in the presence of lysozyme. During the synthesis procedure, a 3D navicular ceria precursor (Ce₂O(CO₃)₂·H₂O) with multi-layered structure was obtained after hydrothermal treatment at 100 °C for 10 h. Ceria with the same morphology can be obtained after thermal decomposition of this Ce₂O(CO₃)₂·H₂O precursor. Structural properties of the products were characterized by XRD, TG-DTA, FT-IR, SEM, TEM, and N₂-sorption techniques. Then a possible layer-by-layer electrostatic self-assembled growth mechanism was proposed for the formation of this 3D navicular architecture based on the experimental results and detail analysis of the evolution process of ceria precursors. Furthermore, a mold reaction of the catalytic oxidation of CO was conducted on the as-obtained CeO₂ and gold supported catalyst, both showed excellent activity and durability for CO conversion.     

Glutaraldehyde as a crosslinking agent for collagen-based biomaterials

The formation of Schiff bases during crosslinking of dermal sheep collagen (DSC) with glutaraldehyde (GA), their stability and their reactivity towards GA was studied. All available free amine groups had reacted with GA to form a Schiff base within 5 min after the start of the reaction under the conditions studied (0.5% (w/w) GA). Before crosslinks are formed the hydrolysable Schiff bases initially present were stabilized by further reaction with GA molecules. An increase in shrinkage temperature (T _s) from 56°C for non-crosslinked DSC (N-DSC) to 78°C for GA crosslinked DSC (G-DSC) was achieved after crosslinking for 1 h. From the relationship between the free amine group content and the T _s during crosslinking it was concluded that higher GA concentrations and longer reaction times will result in the introduction of pendant-GA-related molecules rather than crosslinks. After 24 h crosslinking an average uptake of 3 GA molecules per reacted amine group was found. No increase in the tensile strength of the materials was observed after crosslinking, which may be a result of formation of crosslinks within the fibres rather than in between fibres. Aligning of the fibres by applying a pre-strain to the samples and subsequent crosslinking yielded materials with an increased tensile strength.