Homogeneous Precipitation Process Research Articles

Optical Properties of Heterostructured ZnO/NiO Nanocomposites Synthesized via Facile Precipitation Process

The semiconductor zinc oxide/nickel oxide (ZnO/NiO) heterostructured nanocomposites have been successfully synthesized via facile and eco-friendly homogeneous precipitation process with ethanol and water as solvents. The prepared nanocomposites were studied by means of structural and optical characteristics by using X-ray diffraction, ultraviolet visible absorption and photoluminescence emission spectro-scopies. The peaks in the XRD pattern attributed to the hexagonal wurtzite structure of ZnO and face-centered cubic structure of NiO, as a result the XRD analysis further confirmed that the solvents play a powerful role in size of the crystallite of the synthesized nanocomposites. Strong UV absorption may be seen in UV-vis absorbance spectra and samples of ZnO/NiO nanocomposite materials had greater energy gap (Eg) values than those of pure NiO and ZnO materials. The synthesized materials have demonstrated high photoluminescence emission in UV-blue region in the range of 241-498 nm, it might be a valuable source for future display applications. According to the aforementioned finding, the ZnO/NiO nanocomposites showed significant promise and were a viable material for optoelectronic devices.

Citrate-Assisted One-Pot Hydrothermal Preparation of Carbonated Hydroxyapatite Microspheres

Carbonated hydroxyapatite (CHA) microspheres have aroused wide concern in biofields because of their excellent biological and surface properties. However, the facile preparation of CHA microspheres from organic compounds, especially the microstructural transformation during synthesis, has been rarely reported. In this work, CHA microspheres with an average diameter of 2.528 μm and a BET surface area of 51.0658 m2/g were synthesized via a one-pot hydrothermal method at 180 °C for 10 h by using calcium chloride, diammonium hydrogen phosphate, urea, and trisodium citrate (TSC) with a molar ratio of TSC to Ca of 1:2. The effects of hydrothermal treatment temperature and molar ratio of TSC to Ca on the morphology of the products were investigated. As a chelating agent, TSC is crucial to the formation of CHA microspheres during the hydrothermal homogeneous precipitation process. A possible mechanism of the microstructural transformation from bundle to dumbbell, dumbbell ball, and finally, microspheres regulated by TSC and urea was proposed. The CHA microspheres can be used as effective drug carriers for biomedical applications.

Carboxylate functionalized NaDy(MoO4)2 nanoparticles with tunable size and shape as high magnetic field MRI contrast agents

Uniform sodium-dysprosium double molybdate (NaDy(MoO4)2) nanoparticles having different morphologies (spheres and ellipsoids) and tunable size have been synthesized for the first time in literature. The procedure is based on a homogeneous precipitation process at moderated temperatures (≤220 °C) from solutions containing appropriated precursors dissolved in ethylene glycol-water mixtures, in the absence (spheres) or the presence (ellipsoids) of tartrate anions. The effects of the morphological characteristics (size and shape) of the nanoparticles on the magnetic relaxivity at high field (9.4 T) have been evaluated finding that the latter magnitude was higher for the spheres than for the ellipsoids, indicating their better suitability as contrast agents for high-field magnetic resonance imaging. Such nanoparticles have been successfully coated with polymers bearing carboxylate functional groups through a layer-by-layer process, which improves the colloidal stability of the nanoparticles in physiological media. It has been also found that the coating layer had no significant effects on the nanoparticles relaxivity and that such coated nanoparticles exhibited a high biocompatibility and a high chemical stability. In summary, we have developed NaDy(MoO4)2 based bioprobes which meet the required criteria for their use as contrast agents for high-field magnetic resonance imaging.

Usage of Yb(OH)CO3 Nanoparticles-based Computed Tomography Image in the Prediction Model of Lung Biopsy Pneumothorax.

This study aimed to explore the application of Yb(OH)CO3 nanoparticles in the prediction model of computed tomography (CT) contrast lung biopsy pneumothorax (LBP) by synthesizing a new type of Yb(OH)CO3 nanoparticles, which provides a basis for clinical application. Yb(OH)CO3 nanoparticles were prepared by a homogeneous precipitation process based on urea, and the samples were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Methyl thiazolyl tetrazolium (MTT) assay was adopted in vitro cytotoxicity test, optical density (OD) value was measured with a microplate reader at a wavelength of 570 nm, the cell viability was analyzed, and the cytomorphological changes were observed with an optical microscope. Besides, 40 selected patients with CT-guided percutaneous needling biopsy (PTNB) were rolled into a control group and an observation group. A pneumothorax prediction model was constructed under the support vector machine (SVM) model. The accuracy, sensitivity, and specificity of SVM for pneumothorax prediction were 88.7%, 71.3%, and 100%, respectively; while those of CT imaging with Yb(OH)CO3 nanoparticles were 96.7%, 84.3%, and 100%, respectively. Mean squared errors (MESs) of Yb(OH)CO3 nanoparticles-based CT contrast agent and conventional contrast agent were 14,532 and 7,021, respectively, and mutual information (MI) was 0.1232 and 0.2354, respectively, so the difference between the two groups was significant (P < 0.05). In summary, Yb(OH)CO3 nanoparticles-based CT contrast agents showed good histocompatibility and low toxicity, and the Yb(OH)CO3 nanoparticles-based CT images showed high accuracy in the prediction of LBP.

Synthesis, characterization and formation mechanism of pompon-like Lu2O2SO4: Eu3+ phosphors via a facile homogeneous precipitation method followed by calcination

A series of Eu3+ doped pompon-like Lu2O2SO4 phosphors with diameter of ~800 nm have been synthesized by commercial available lutetium oxide (Lu2O3), nitric acid (HNO3), europium nitrate (Eu(NO3)3·6H2O), urea (CO(NH2)2), ammonium sulfate ((NH4)2SO4) and ammonia (NH3·H2O) as the starting materials via a facile homogeneous precipitation method followed by a subsequent calcination process. The as-prepared products were well characterized by X-ray powder diffraction (XRD), thermogravimetry and differential scanning calorimeter (TG-DSC), flourier transform infrared spectra (FT-IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra. Studies have shown that the molar ratio of Lu3+:(NH4)2SO4:CO(NH2)2 is very important in the homogeneous precipitation process, and the optimal ratio is selected as 1:25:50. In the subsequent calcination process, the effect of calcination temperature on the target product was studied and the optimal calcination condition is the calcination temperature of 800 °C for 2 h in air. And the morphology mechanism of the pompon-like Lu2O2SO4 is explored, detailed investigation showed the formation of pompon structure is accompanied by two different growth mechanisms. According to PL spectra, under 396 nm ultraviolet (UV) light excitation, the strongest emission peak for the Lu2O2SO4:x%Eu3+ phosphors located at 620 nm, which corresponds to the typical 5D0-7F2 transition of Eu3+ ions. The optimal doping concentration of Eu3+ ions in the Lu2O2SO4 host lattice is 6.0%, whose average lifetime τ and color correlation temperature (CCT) are calculated to be 39.558 μs and 1915 K, respectively.

Efficient Imine Formation by Oxidative Coupling at Low Temperature Catalyzed by High-Surface-Area Mesoporous CeO2 with Exceptional Redox Property.

High-surface-area mesoporous CeO2 (hsmCeO2 ) was prepared by a facile organic-template-induced homogeneous precipitation process and showed excellent catalytic activity in imine synthesis in the absence of base from primary alcohols and amines in air atmosphere at low temperature. For comparison, ordinary CeO2 and hsmCeO2 after different thermal treatments were also investigated. XRD, N2 physisorption, UV-Raman, H2 temperature-programmed reduction, O2 temperature-programmed desorption, EPR spectroscopy, and X-ray photoelectron spectroscopy were used to unravel the structural and redox properties. The hsmCeO2 calcined at 400 °C shows the highest specific surface area (158 m2 g-1 ), the highest fraction of surface coordinatively unsaturated Ce3+ ions (18.2 %), and the highest concentration of reactive oxygen vacancies (2.4×1015 spins g-1 ). In the model reaction of oxidative coupling of benzyl alcohol and aniline, such an exceptional redox property of the hsmCeO2 catalyst can boost benzylideneaniline formation (2.75 and 5.55 mmol h-1 based on >99 % yield at 60 and 80 °C, respectively) in air with no base additives. It can also work effectively at a temperature of 30 °C and in gram-scale synthesis. These are among the best results for all benchmark ceria catalysts in the literature. Moreover, the hsmCeO2 catalyst shows a wide scope towards primary alcohols and amines with good to excellent yield of imines. The influence of reaction parameters, the reusability of the catalyst, and the reaction mechanism were investigated.

Utilization of Zinc Oxide Nanopowder for Photocatalytic Removal of Pb++ Ions from Aqueous Wastewater.

Nanometer-sized zinc oxide powders were prepared with a "solution-combustion method (SCM)." This method used zinc oxide nanopowder as a semiconductor oxide catalyst to initiate light-induced redox reactivity in the presence of 150 ppm aqueous lead-ethylenediaminetetraacetic acid solution (Pb-EDTA) for photocatalysis under UV illumination. Removal rates of lead ions in the aqueous Pb-EDTA solution using SCM ZnO powder were compared with those of two other titanium dioxide photocatalysts, P-25 TiO₂-powder (Degussa) and rutile TiO₂ powder, prepared via a homogeneous precipitation process at low temperature (HPPLT). Using SCM ZnO nanopowder, complete removal of lead ions from the aqueous Pb-EDTA solution was observed within 25 min after UV irradiation. However, HPPLT TiO₂ powder and P25 TiO₂ powder took almost 45 and 65 minutes to completely remove the lead ions, respectively. Thus, lead ions removal efficiency of SCM ZnO nanopowder is at least twice higher than the efficiency of the other two titanium dioxide photocatalysts investigated.

Influence of hydrothermal treatment on structural property of NiZrAl mixed-metal oxides and on catalytic steam reforming of glycerol for hydrogen production

NiZrAl layered double hydroxides (LDH) precursors were synthesized by co-precipitation and homogeneous precipitation processes. The introduction of hydrothermal treatment into crystallization showed its significant influences on structure of LDH as well as mixed-metal oxides after thermal decomposition. The characterization results showed that the catalysts prepared by hydrothermal synthesis involved bigger pore diameter of ca. 13.5 nm and wider pore size distribution of 2–60 nm, and hydrothermal treatment was helpful to enhance the reduction of NiO species weakly interacted with support and to enhance the interaction among the metal oxides. Although the Ni dispersion, the surface area as well as the ability of anti-sintering were evidently improved, the ability of coke resistance decreased by 2 times for samples prepared by co-precipitation and by nearly 10 times for the ones prepared by homogeneous precipitation due to the enlarged pores. The maximum value of conversion to gaseous products (96.5%) and minimum deposited coke (36 mgc/gcat.) were achieved on NiZrAl-u sample.

Monodispersed spherical Y2O3 and Y2O3:Eu3+ particles synthesized from modified homogeneous urea precipitation process

Monodispersed spherical Y2O3 powders are of great scientific interests as well as practical and technological applications. Here, the present study reports a modified homogeneous urea precipitation process to achieve monodispersed spherical Y2O3 powders using polyvinyl pyrrolidone(PVP-K30) as surface active agent. Owing to that of controlling the decomposition of urea and nucleation of metal ions with PVP-K30 as surface active agent during the precipitation process, the as-obtained precipitate precursor are monodispersed sphere with uniform particle size in a high Y3+ concentration about 0.5 M, which led to the formation uniform spherical Y2O3 particles after the calcining process at 800 °C for 2 h. The optical performance of spherical Y2O3: Eu3+ was also studied, which displayed strong red emission peak at 613 nm ascribed to 5D0–7F2 forced electric dipole transition of Eu3+. All these critical characteristics suggest that the as-obtained Y2O3 powders hold promising applications in bioimaging, solid-state lighting, display devices and functional ceramics.

Controllable fabrication of graphitic nanocarbon encapsulating FexNiy hybrids for efficient splitting of water

The hybridized electrocatalysts constituted by binary 3d transition nanoparticles with a varied ratio of Fe to Ni were successfully synthesized through a two-step fabrication procedure, a homogeneous precipitation process, and a successive graphitization process. A superior oxygen evolution reaction (OER) efficiency with a yielded remarkable low overpotential of ∼0.26 V and a Tafel slope of ∼56 mV/decade is achieved for the heterostructured Fe1Ni2 nanoparticles coated by graphitic nanocarbon in a 1 mol/L KOH solution. The influencing factors for synthesizing the electrocatalysts, such as the graphitization temperature, the content of iron and the thickness of the carbon shells are also carefully investigated, and improved electrocatalytic efficiency is achieved with appropriate fabrication parameters for the hybridized catalysts. It is considered that the synergistic effect of the defects and electrochemical conductivity of the graphitic carbon shells shows great influences on the electrocatalytic activity. In addition, the detailed electrochemically active surface area and the electrochemical impedance suggest that the FexNiy hybrids coated by graphitic nanocarbon have improved the mass transport and electron transfer rate, resulting in an enhanced electrocatalytic water splitting efficiency. This work opens up a new way to fabricate promising oxygen-evolving catalysts with high-efficiency and low-cost.

Effect of “Magnetized Water” on Size of Nickel Oxide Nanoparticles and their Catalytic Properties in Co2 Reforming of Methane

It was shown that the particle size of NiO nanoparticles has been controlled through the homogeneous precipitation process by using “magnetized water” which, according to the authors, is due to a change in the surface tension and viscosity of water under the influence of a magnetic field. The textural properties, shape, recovery behavior, and size distribution of NiO nanoparticles were determined using BET, XRD, TPR, and TEM methods. The effect of NiO particle size on the catalytic reaction of carbon dioxide reforming of methane into synthesis gas was studied. The CO2 and CH4 conversions and the yield of CO and H2 products possess higher values for the treated NiO sample.

Ternary structural assembly of BiOCl/TiO2/clinoptilolite composite: Study of coupled mechanism and photocatalytic performance

Novel BiOCl/TiO2/clinoptilolite composite was prepared via a homogeneous precipitation and calcination-crystallization process in this study. Through structural design and spatial assembly, the ternary composite based on clinoptilolite layer as well as the TiO2 nano particles and BiOCl nano sheets was successfully synthesized. The prepared composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), N2 isothermal adsorption-desorption test and electrochemical measurement, respectively. Compared with bare photocatalysts (i.e. TiO2 and BiOCl), the composite exhibited enhanced photoactivity under visible light irradiation towards rhodamine B (RhB). Based on the pseudo-first-order kinetic constants, the photocatalytic performance of BiOCl/TiO2/clinoptilolite composite is around 48 and 11 times higher than that of pure TiO2 and BiOCl, respectively. The enhanced photocatalytic properties of the composite should be attributed to the improved adsorption ability and the formation of the n-p heterojunction between BiOCl and TiO2, which is beneficial to establish the rapid adsorption-desorption system and promote the efficient separation of the photogenerated electron-hole pairs. The excellent visible-light-driven performance makes the BiOCl/TiO2/clinoptilolite composite possible to be utilized in the field of industrial wastewater treatment.

Hydroxyapatite Coating of Volcanic Glass Microballoons by a Homogeneous Precipitation Process

Hydroxyapatite Coating of Volcanic Glass Microballoons by a Homogeneous Precipitation Process

Synthesis, functionalization and properties of uniform europium-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)2, X = Mo,W) probes for luminescent and X-ray computed tomography bioimaging

A one-pot simple procedure for the synthesis of uniform, ellipsoidal Eu3+-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)2, X = W, Mo) nanophosphors, functionalized with carboxylate groups, is described. The method is based on a homogeneous precipitation process at 120 °C from appropriate Na+, Ln3+ and tungstate or molybdate precursors dissolved in ethylene glycol/water mixtures containing polyacrylic acid. A comparative study of the luminescent properties of both luminescent materials as a function of the Eu3+ doping level has been performed to find the optimum nanophosphor, whose efficiency as X-ray computed tomography contrast agent is also evaluated and compared with that of a commercial probe. Finally, the cell viability and colloidal stability in physiological pH medium of the optimum samples have also been studied to assess their suitability for biomedical applications.

Controllable synthesis and luminescence property of spherical Lu(OH)CO3:Ln3+/LuBO3:Ln3+ (Ln = Eu, Tb) nanoparticles

Lu(OH)CO3:Ln3+/LuBO3:Ln3+ (Ln = Eu, Tb) nanospheres have been synthesized by the soft chemistry route. This synthesis process does not require the addition of any organic solvents and surfactant. The whole process consists of homogeneous precipitation and hydrothermal process. First, uniform spherical Lu(OH)CO3:Ln3+ (Ln = Eu, Tb) nanoparticles with the sizes of 70 nm were obtained by the classic urea-based homogeneous precipitation. Then, with the above Lu(OH)CO3:Ln3+ (Ln = Eu, Tb) nanosphere as the precursor, the composites of Lu(OH)CO3:Ln3+/LuBO3:Ln3+ (Ln = Eu, Tb) nanospheres formed by the simple hydrothermal process. The phases, morphologies, as well as the luminescence properties of as-prepared samples were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and photoluminescence. Under a short wavelength excitation, the down-conversion Eu3+ and Tb3+-doped LuBO3 samples were investigated and explained.

Research and simulation of hydrated alumina homogeneous precipitation and its application to obtain a carrier for catalysts in the petrochemical industry

The results of studies of the process of hydrated alumina homogeneous precipitation were presented in this work. The variants of this process are considered. The most convenient embodiment of this process is the precipitation of hydrated alumina from its salts with the use of auxiliary substances, such as urea. Urea hydrolysis allows a homogeneous precipitation process under the most mild conditions. It is shown that the process of hydrolytic precipitation in the aluminum salt-urea system proceeds according to the dissociative mechanism SN1. This article analyzes the regularities of precipitation of solid colloidal particles of hydrated metal oxides on the surface of various substrates. Two models of this process are proposed. The proposed α-model is a process of continuous nucleation of interaction centers, at random points of a free surface throughout the process. The proposed β-model provides for the instantaneous nucleation of these centers when they are randomly distributed over the entire surface of the substrate. Based on the proposed models, the average values of the following values are calculated: the thickness of the gel film; its roughness and specific surface area. The calculations carried out in the article showed that these parameters are universal functions of the degree of filling of the surface and do not depend on the specific model of the mechanism of the process. Studies have been conducted on the use of homogeneously precipitated aluminum hydroxide as a binder in the preparation of porous materials. The resulting materials have a developed specific surface area and porosity.

Core-shell type Tourmaline@ZnO composites equipped with carbon dots for high efficiency photocatalyst

Here we report that a novel type of Tourmaline@ZnO core-shell composite equipped with carbon dots (CDs) as multi-band light active sensitizer has been successfully designed and efficiently ultilized as the superior photocatalyst towards the degradation of methyl orange (MO) under Xenon lamp at room temperature. The bare ZnO, CDs/ZnO, Tourmaline@ZnO and CDs/Tourmaline@ZnO were systemically synthesized following the facile homogeneous precipitation process and characterized in detail by XRD, FTIR, FESEM, HRTEM, UV-Vis, PL, PC and EIS investigations in succession. Bare ZnO displays as 3-dimensional hierarchical nano-flowers with large specific surface area reaching up to 62.049 m2/g by BET measurement, while the other composite products confirm the core-shell structures with CDs inlaying on ZnO layer surfaces. The photocatalytic activities of the polynary hybridations obtain effective enhancements compared to pure ZnO, the ternary system (CDs/Tourmaline@ZnO) deserves more attention for achieving the maximum (91.25%). It should been the synergistic effect on the highly efficient catalysis performances exerting by the presence of CDs modifier and the Tourmaline core, which make ZnO matrix receive more photo-generated electrons and broaden the visible light response originated from CDs, and synchronously hinder the recombination of electrons-hole pairs by the spontaneous polarization and surface electric field of Tourmaline.

Large-scale synthesis of SnS/carbon nanotube composites with enhanced reversible lithium-ion storage

SnS in situ hybridized with carbon nanotubes has been achieved via a facile homogeneous precipitation process. The structure and morphology of the as-prepared SnS/carbon nanotube composites have been characterized by X-ray diffraction and transmission electron microscopy. Results indicate that SnS nanoparticles are uniformly dispersed on the surface of carbon nanotubes. The lithium-ion storage properties of the materials are investigated by cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy. It demonstrates that SnS/carbon nanotube composites exhibit better electrochemical performance as compared to single SnS and carbon nanotubes. The enhanced reversible lithium storage could be ascribed to the synergistic effect of SnS and carbon nanotubes.

Single-step synthesis of Er3+ and Yb3+ ions doped molybdate/Gd2O3 core–shell nanoparticles for biomedical imaging

Nanostructures as color-tunable luminescent markers have become major, promising tools for bioimaging and biosensing. In this paper separated molybdate/Gd2O3 doped rare earth ions (erbium, Er3+ and ytterbium, Yb3+) core–shell nanoparticles (NPs), were fabricated by a one-step homogeneous precipitation process. Emission properties were studied by cathodo- and photoluminescence. Scanning electron and transmission electron microscopes were used to visualize and determine the size and shape of the NPs. Spherical NPs were obtained. Their core–shell structures were confirmed by x-ray diffraction and energy-dispersive x-ray spectroscopy measurements. We postulated that the molybdate rich core is formed due to high segregation coefficient of the Mo ion during the precipitation. The calcination process resulted in crystallization of δ/ξ (core/shell) NP doped Er and Yb ions, where δ—gadolinium molybdates and ξ—molybdates or gadolinium oxide. We confirmed two different upconversion mechanisms. In the presence of molybdenum ions, in the core of the NPs, Yb3+– (∣2F7/2, 3T2〉) dimers were formed. As a result of a two 980 nm photon absorption by the dimer, we observed enhanced green luminescence in the upconversion process. However, for the shell formed by the Gd2O3:Er, Yb NPs (without the Mo ions), the typical energy transfer upconversion takes place, which results in red luminescence. We demonstrated that the NPs were transported into cytosol of the HeLa and astrocytes cells by endocytosis. The core–shell NPs are sensitive sensors for the environment prevailing inside (shorter luminescence decay) and outside (longer luminescence decay) of the tested cells. The toxicity of the NPs was examined using MTT assay.

A new method for preparing mono-dispersed nanoparticles using magnetized water

We studied the use of magnetized water on the size of the nanoparticles. Magnetized water found to reduce the diameter of the nanoparticles during a homogeneous precipitation process, which is a combination of nucleation and nuclei growth processes. We found that the modified water, which demonstrated different physical properties especially on the surface tension and viscosity, significantly influenced the both processes. Therefore, the nucleation process was initially prolonged in the homogeneous precipitation process due to the lower critical size of nucleus and higher rate of nucleation, and consequently formed smaller particles and a larger number of particles. Furthermore, the growth rate of nanoparticles was hindered owing to the higher viscosity of the water and restriction in the mass transport process. As a result, the precipitated particles with the magnetized water were eventually structured smaller particle diameter compared to the bulk. The presented method in here indicated a low cost, straightforward, and feasible technique for industrial application. In addition, this method could open a new promising perspective on nanomaterial synthesis in order to facilitate the production of monodispersed nanoparticles. Molecular dynamic confirmed that surface tension decreased as the external magnetic field was applied. Moreover, the density profile illustrated that the average number of hydrogen atoms is greater than oxygen atoms.