Facile Precipitation Route Research Articles

Impedance Spectroscopy, Magnetic and Optical Analysis of Cadmium Tungstate Nanoparticles from Influence of Capping Agent Additives

Nano crystals of cadmium tungstate (CdWO4) were obtained by facile precipitation route by using cadmium sulfate octahydrate and sodium tungstate dihydrate. These nanoparticles were then coated using different capping agents such as glucose, polyvinyl alcohol (PVA), and valine and their effects on the particle size, band gap, morphology, and magnetic character were investigated by powder X-ray diffraction, UV-Visible, FESEM, TEM, and VSM analysis. Capping agents are used in the synthesis of nanoparticles since they facilitate the growth and aggregation of particles in a precise manner, by usually acting as a physical barrier which controls the flow of free electron to the catalyst, so that they can be utilized by the catalyst and sensors of nanoparticle. Impedance spectroscopic technique was carried out, which was very useful in separating the grain boundary resistance and grain boundary capacitance contributions. We discuss the utilization of capping agents and their effects, including surface, optical and intergranular potential barriers in this work.

Influence of capping agents additives on morphology of cadmium tungstate nanoparticles and study of their photocatalytic properties

In this investigation, a facile precipitation route has been developed for the preparation of cadmium tungstate (CdWO4) nanoparticles by using cadmium nitrate hexahydrate and sodium tungstate dehydrate as cadmium and vanadate precursor, respectively. The effect of different capping agents such as glycine, valine, and alanine on the morphology and particle size of the products has been investigated. Facile preparation and separation are important features of this route. This work has provided a general, simple, and effective method to control the composition and morphology of cadmium tungstate in aqueous solution, which will be important for inorganic synthesis methodology. The morphology and particle size of products were investigated by scanning electron microscopy images, X-ray diffraction patterns, ultraviolet–visible and electron dispersive X-ray spectroscopy spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cadmium tungstate were also examined by degradation of methyl orange dye as water contaminant.

Giant electrorheological fluids with ultrahigh electrorheological efficiency based on a micro/nano hybrid calcium titanyl oxalate composite

A novel micro/nanoparticle hybrid calcium titanyl oxalate electrorheological (ER) material composed of micron-sized spindly particles and nanometer-sized irregular particles was successfully fabricated. The giant ER fluid based on the composite exhibits enhanced not only yield stress but also low field-off viscosity, thereby resulting in an ultrahigh ER efficiency that greatly exceeds that of any existing giant ER (GER) material. The synergistic effect between the spindly microparticles and irregular nanoparticles discovered in this study suggests a promising method for solving the long-standing ER efficiency problems. Moreover, the one-step synthesis approach presented in this work can be readily expanded for mass production of other GER materials in practical applications. A material that can alternate between a low-viscosity fluid and a strong solid has been developed by researchers in China and the USA. Applying an electric field to an electrorheological fluid transforms it from a fluid to nearly solid state, and removing the field changes it back to a fluid; but the application of a small stress can irreversibly deform such materials. Yuchuan Cheng, Shengqian Ma and co-workers from the Ningbo Institute of Materials Technology & Engineering and the University of South Florida have used a simple one-step process to synthesize a composite electrorheological material that has a high yield strength. The composite contains spindly microparticles, which ensure a low viscosity when there is no electric field, and irregular nanoparticles, which enhance its yield strength. These two properties impart the composite with ultrahigh electrorheological efficiency. Hybrid calcium titanyl oxalate (HCTO) composite containing anisotropic spindly microparticles and irregular nanoparticles have been synthesized via a facile precipitation route under mild conditions for the first time. The hybrid particles act synergistically to enhance electrorheological (ER) activity and reduce field-off viscosity, thereby resulting in ER fluids with ultrahigh ER efficiency. The results presented thus provide a new strategy for improving the performance of ER fluids.

Electrochemical properties and characterization of various ZnO structures using a precipitation method

A simple and facile precipitation route and its electrochemical properties were investigated by controlling the shape of crystalline ZnO nanostructures such as rods, flowers, and porous flower structures. In this paper, the morphological variation in ZnO nanostructures was achieved by varying the reaction time and precursors in the precipitation method because the precursor and reaction time ratio is important in the morphological control of ZnO nanostructures. Zinc nitrate hexahydrate and zinc acetate dehydrate were used as precursors, and refluxed at 90°C with reductant for various reaction times. We then propose a growth mechanism of ZnO nanostructures on the basis of shape-control by the precipitation technique. Also, the electrochemical properties of the ZnO electrodes obtained from different precursors and reaction times were evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements.

Synthesis and characterization of robust Ag2S/Ag2WO4composite microrods with enhanced photocatalytic performance

Abstract

Transient Cataluminescence on Flowerlike MgO for Discrimination and Detection of Volatile Organic Compounds

Methodologies for simple and rapid identification of gas compounds are needed in the fields of environmental and security. Here, a new and simple method for the discrimination of gas compounds was designed through an interesting transient cataluminescence (TRCTL) phenomenon on the highly efficient MgO materials. The flowerlike MgO with high CTL activity was controllably synthesized via a facile and time-saving aqueous precipitation route and characterized by scanning electron microscopy, powder X-ray diffractometry, high-resolution transmission electron microscopy, and N2 adsorption measurements, etc. With flowerlike MgO working as the sensing material, the newly developed CTL gas sensor exhibited highly active, ultrafast, and characteristic responses toward many analytes; the TRCTL curves thus were obtained and 10 VOCs have been successfully identified. Parallel experimental results show that the controllable synthesis of flowerlike MgO can greatly enhance the discrimination capacities for VOCs. Further, the TRCTL of CHCl3 and C2H5OC2H5 were taken as typical examples to illustrate the possible sensing mechanism, which could contribute to explaining processes of catalytic oxidations. We expect this novel TRCTL concept will be of practical importance for applications including gas detection, gas discrimination, and research of chemical kinetics processes.

Enhancement of g-C3N4 nanosheets photocatalysis by synergistic interaction of ZnS microsphere and RGO inducing multistep charge transfer

The ternary nanocomposite of g-C3N4/reduced graphene oxide/ZnS (CN/RGO/ZS) has been prepared through a facile precipitation route for the first time. The as-prepared CN/RGO/ZS composite exhibit distinctly enhanced photocatalytic activities toward the degradation of Rhodamine B (about 97% after 60min) under visible light irradiation, which was about 1.04, 1.17 and 5.38 times higher than those of CN/RGO, CN/ZS and RGO/ZS. The enhanced photocatalytic performance of RGO/CN/ZS composite arises from the synergistic effects of three components: effective charge separation, multistep transfer between CN/ZS heterojunction and RGO nanosheets, and enhanced visible-light absorption. The relative mechanism has been investigated by active species trapping and ESR analysis. This work may provide useful insights to design and construction of CN-based ternary composite photocatalysts with enhanced photocatalytic activity.

Synthesis, characterization, and investigation magnetic and photocatalytic property of neodymium vanadate nanoparticles

This research reports a novel facile precipitation route for the synthesis of neodymium vanadate (NdVO4) nanoparticles with the aid of ammonium metavanadate, neodymium(III) nitrate and lucien as the starting reagents and water as the solvent. Moreover, lucien plays role as capping agent, reducing agent, and natural template in the synthesis of NdVO4 nanoparticles. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and ultraviolet–visible spectroscopy. The magnetic properties of as-prepared NdVO4 nanoparticles were also investigated with vibrating sample magnetometer. To evaluate the photocatalyst properties of nanocrystalline NdVO4, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.

Synthesis and characterization of β-Ag2Se and β-AgCuSe nanoparticles via facile precipitation route

β-Ag2Se and β-AgCuSe nanoparticles were synthesized using AgCl precursor instead of conventional AgNO3 by simple precipitation method. It was found that orthorhombic structures were obtained for both β-Ag2Se and β-AgCuSe nanoparticles. The result shows Ag2S as impurity while increasing the concentration of AgCl. Moreover, the microstructural images show polyhedral- and pebble-like particles. The band gap energy is increased for β-Ag2Se owing to small crystallite size. The AgCl precursor can effectively produce pure nanoparticles. Hence, it is interesting in terms of identification of potential precursor for synthesizing β-Ag2Se and β-AgCuSe nanoparticles.

Improved sodium-storage performance of stannous sulfide@reduced graphene oxide composite as high capacity anodes for sodium-ion batteries

Stannous sulfide@reduced graphene oxide (SnS@RGO) composite is successfully synthesized via a facile precipitation route. The structural and morphological characterizations reveal SnS@RGO composites are composed of SnS nanoparticles of the size 5–10 nm, which are uniformly anchored on the surface of RGO. The electrochemical measurements demonstrate the reversible capacity of the SnS@RGO composite – that includes contributions from the conversion reaction of SnS to Sn and NaxS and the alloying reaction of Sn to NaxSn. The SnS@RGO electrode exhibits a reversible capacity of 457 mAh g−1 at 20 mA g−1, superior cycling stability (94% capacity retention over 100 cycles at 100 mA g−1) and adequate rate performance. Compared to the neat SnS nanoparticles, the enhanced electrochemical performance of the SnS@RGO composite is primarily due to the incorporation of RGO as a highly conductive, flexible component as well as possessing a large available surface area, which provides desirable properties such as improved electronic contact between active materials, aggregation suppression of intermediate products, and alleviation of the volume change during sodiation and desodiation. Encouraging experimental results suggest that the SnS@RGO composite is a promising material to achieve a high-capacity and stable anode for NIBs.

Zirconia Nanostructures: Novel Facile Surfactant‐Free Preparation and Characterization

Zirconia nanostructures have been prepared via a facile precipitation route using Zirconium (IV) oxynitrate hydrate and tetraethylenepentamine (TEPA). Here, TEPA was used as novel precipitator to fabricate zirconia nanostructures. The influence of reaction time, dosage of TEPA, and solvent was also examined to control the shape and particle size. Results of this work indicate that these reaction parameters have important impact on the control of shape and grain size of the zirconia. To characterize the as‐synthesized nanostructures, techniques such as X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, energy dispersive X‐ray microanalysis (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT‐IR) spectroscopy, and photoluminescence (PL) spectroscopy were applied. In addition, the formation mechanism of zirconia nanostructures was discussed.

Facile synthesis of nickel–cobalt double hydroxide nanosheets with high rate capability for application in supercapacitor

In this work, nickel–cobalt double hydroxide nanosheets with high rate capability are prepared by a facile epoxide precipitation route. The synthetic procedure includes an oxidization step using ammonium persulfate as oxidant and a precipitation step using propylene oxide as precipitation agent. As shown in the results of electrochemical characterization, high specific capacitance of 2548 F g−1 for this material can be obtained at current density of 0.9 A g−1 in aqueous solution of 3 mol L−1 KOH. It is surprising to notice that the capacitance of material still remains 1587 F g−1 at high current density of 35.7 A g−1. These results demonstrate that the as-prepared nickel–cobalt double hydroxide nanosheets are promising electrode material for supercapacitor application as a primary power source.

Catalytic total oxidation of 1,2-dichloroethane over highly dispersed vanadia supported on CeO2 nanobelts

CeO2 nanobelts were synthesized via a facile aqueous-phase precipitation route under mild conditions (template-free and non-hydrothermal), and then the highly dispersed vanadia catalysts with a wide range of VOx loadings were prepared by a conventional incipient-wetness impregnation method. The target VOx/CeO2 catalysts were characterized in detail and used in catalytic combustion of 1,2-dichloroethane (DCE). The results revealed that the monolayer dispersed VOx (6.0%VOx/CeO2) exhibited the most outstanding initial and stable activities, however, the main product containing carbon was CO, not desired CO2. A reaction mechanism of DCE total oxidation was proposed based on the study of TPSR and in situ FTIR. The first step of this mechanism was considered to be a dissociative adsorption of CCl bonds on Lewis acid sites (such as Ce4+/3+, V5+/4+ or Ce3+–O2−–V5+) via Cl abstraction, and then the dissociated DCE can be oxidized directly to CO2 by surface active oxygen species over pure CeO2. Whereas, over VOx/CeO2 catalysts, the formation of intermediate acetaldehyde was a key step via CH bond activation and hydrogen transfer on VOx species, subsequently, partially oxidized to CO by the lattice oxygen of VOx.

Facile synthesis, electronic structure and photocatalytic activity of a novel Bi-based hydroxyl oxalate Bi(C2O4)OH

A novel Bi-based hydroxyl oxalate Bi(C2O4)OH has been successfully synthesized via a facile aqueous precipitation route, and its photocatalytic activity was investigated for the first time. The as-prepared Bi(C2O4)OH nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra. It possesses an indirect-transition optical band gap of 3.73eV. The electronic structure, density of states as well as light absorption of Bi(C2O4)OH were studied by the first principle calculations. The photocatalytic performance of the samples was determined by photodegradation of Rhodamine B (RhB) in aqueous solution. The results revealed that RhB can be effectively decomposed by Bi(C2O4)OH, and the sample with reactant molar ratio of 1:2 exhibits the highest photocatalytic activity. The active species trapping experiments over Bi(C2O4)OH indicated that the hydroxyl radicals (OH) are the most important active species in the process of RhB photodegradation.

ZnS microsphere/g-C3N4nanocomposite photo-catalyst with greatly enhanced visible light performance for hydrogen evolution: synthesis and synergistic mechanism study

In this work, ZnS microsphere/g-C3N4 nanocomposites with different ZnS contents were synthesized by a facile precipitation route and characterized by a variety of techniques. The TEM results confirmed that ZnS microspheres are deposited on the surface of g-C3N4 nanosheets with intimate contact in the nanocomposites. Such type-II heterostructures formed between ZnS and g-C3N4 can unexpectedly improve the photocatalytic H2-production rate of g-C3N4 under visible light, which reaches an optimal value of up to 194 μmol h−1 g−1 at the ZnS content of 50 wt%. The synergistic effect of ZnS and g-C3N4 was proposed to be responsible for the efficient separation of the photogenerated charge carriers and, consequently, the enhancement of the visible light photocatalytic H2 production activity of the nanocomposites. This work highlights that the integration of g-C3N4 and ZnS will be an opportunity to obtain a g-C3N4-based nanocomposite photocatalyst with enhanced photocatalytic H2 production activity, and we hope our work may be helpful for the construction of photocatalysts with efficient visible light H2-production activities.

A facile route for preparation of monodisperse nanoparticles of one-dimensional Fe(ii)-4-amino-1,2,4-triazole coordination polymers with hysteretic spin-crossover near room temperature

Monodisperse nanoparticles of one-dimensional Fe(II)-4-amino-1,2,4-triazole coordination polymers show hysteretic spin-crossover near room temperature.

Template-free and non-hydrothermal synthesis of CeO2nanosheets via a facile aqueous-phase precipitation route with catalytic oxidation properties

Petal and belt-like CeO2nanosheets are synthesized using an aqueous phase precipitation method under template-free and non-hydrothermal conditions and exhibit excellent catalytic oxidation performance.

Cobalt hexacyanoferrate/graphene nanocomposite – Application for the electrocatalytic oxidation and amperometric determination of captopril

A nanocomposite of cobalt hexacyanoferrate/reduced graphene oxide was synthesized by a facile precipitation route. The nanocomposite morphology was characterized by scanning electron microscopy. A nanocomposite-modified carbon paste electrode was then fabricated and its redox behavior was characterized. In the voltammograms of the modified electrode recorded in phosphate buffer solution, pH 7.4, two quasi-reversible redox transitions appeared related to the Co(II)/Co(III) and Fe(II)/Fe(III) transitions. The diffusion of the counter cation into the nanocomposite and the charge transfer kinetics across the electrode/electrolyte interface were studied. The modified electrode showed an efficient electrocatalytic activity toward the electrooxidation of captopril. In the presence of captopril, the anodic peak current of the Fe(II)/Fe(III) transition increased and the cathodic one decreased, while, the peak currents of the Co(II)/Co(III) transition remained almost constant. This indicates that captopril was oxidized on the modified electrode surface through a surface mediated electron transfer (an electrocatalytic reaction). The catalytic rate constant and the electron transfer coefficient for the electrooxidation process and the captopril diffusion coefficient were reported. A sensitive and time-saving amperometric method was developed for the analysis of captopril. Based on the developed method, captopril was determined with a detection limit of 0.331μM. The proposed amperometric method was also applied to the analysis of captopril in tablets.

Controllable synthesis of hollow/flower-like BiOI microspheres and highly efficient adsorption and photocatalytic activity

Hollow/flower-like BiOI microspheres have been prepared through a facile precipitation route in a water–ethanol mixed solution with the assistance of PVP and citric acid (CA) at low temperature (70 °C). The obtained products were characterized by a range of methods such as XRD, FESEM, TEM, UV-vis, DRS, PL and nitrogen sorption. A three-stage growth mechanism of such hierarchical hollow/flower-like microstructures has been proposed by observing the XRD analysis and FESEM of the intermediate products at different reaction times. Interestingly, the structure of BiOI from hollow to flower-like could be obtained by only adjusting the different amounts of reagents in the reaction system. The photocatalytic activities of the hollow/flower-like microspheres were evaluated by the degradation of RhB under visible-light irradiation, compared with the nanoplate sample and P25. Although the hollow BiOI microspheres had a higher specific surface area, the flower-like BiOI microspheres exhibited much higher adsorption and photocatalytic activities than the former. This controllable morphology method and particular properties of BiOI hierarchical microstructures could be used to synthesize bismuth-based semiconductors or other structure-controllable materials and to explore remarkable potential applications of their photocatalytic degradation ability.

Facile Synthesis of Nanocrystalline TiO2 Mesoporous Microspheres for Lithium-Ion Batteries

TiO2 mesoporous nanocrystalline microspheres assembled from uniform nanoparticles were synthesized by a facile and template-free hydrolytic precipitation route in normal solvent media. The phase structure, morphology, and pore nature were analyzed by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and BET measurements. The electrochemical properties were investigated by cyclic voltammetry, constant current discharge−charge tests, and electrochemical impedance techniques. Microspheres with diameters ranging from 0.2 to 1.0 μm were assembled by aggregation of nanosized TiO2 crystallites (∼8−15 nm) and yielded a typical type-IV BET isotherm curve with a surface area of ∼116.9 m2 g−1 and a pore size of ∼5.4 nm. A simplified model was proposed to demonstrate the nanoparticle packing modes to form the mesoporous structure. The initial discharge capacity reached 265 mAh g−1 at a rate of 0.06 C and 234 mAh g−1 at a rate of 0.12 C. The samples demonstrated high rate capacity of 175 mAh g−1 at 0.6 C and 151 mAh g−1 at 1.2 C even after 50 cycles, and the Coulombic efficiency was approximately 99%, indicating excellent cycling stability and reversibility. Details of the kinetic process of the nanocrystalline mesoporous microspheres electrode reaction from electrochemical impedance spectra provided further insights into the possible mechanisms responsible for the good reversibility and stability. These investigations indicate that TiO2 nanocrystalline mesoporous microspheres might be a promising anode material for high-energy density lithium-ion batteries.