Controlled Co-precipitation Method Research Articles

Facile synthesis of cryogenically controlled cobalt-nickel-based Prussian blue analogues for high-performance symmetric supercapacitors

Cobalt hexacyanoferrate (CoHCF) with high energy density as a potentially useful electrode for energy storage systems still suffers from inferior rate capability and low cycling performance due to high-spin nitrogen-coordinated Co ions. While nickel hexacyanoferrate (NiHCF) with low energy density can exhibit great cycling stability due to the electrochemical inertness of Ni. Herein, we have developed a series of cobalt nickel hexacyanoferrate (CoNiHCF) via a facile cryogenically controlled co-precipitation method. We explored the Co/Ni molar ratio and synthesis temperature on the effects of the specific capacitance in detail. As supercapacitor cathode, the Co0.7Ni0.3HCF with the Co/Ni molar ratio of 0.7:0.3 synthesized at 0 °C can exhibit a high specific capacitance of 406 F g−1 at 1 A·g−1 with capacitance retention of 81.89 % after 5000 cycles. The exceptional electrochemical performance is ascribed to the upgraded conductivity resulting from the coexistence of bimetallic components, the low particle size caused by the moderate introduction of Ni, the low interstitial water content, and the synergistic effect between Co and Ni. Moreover, the symmetric supercapacitor (SSC) of Co0.7Ni0.3HCF//Co0.7Ni0.3HCF can provide a high energy density of 72.96 W h kg−1 and 40.96 W h kg−1 at specific powers of 2876 W kg−1 and 28,577 W kg−1, respectively with a capacitance retention of 74.83 % after 4000 cycles.

Electrochemical capacitance and cubic-rhombohedral phase transition of sodium intercalated ferrimagnetic manganese hexacyanoferrate based open framework material

We report a synthesis of a highly crystalline, sodium intercalated manganese hexacyanoferrate open framework structure based on Prussian blue analogues with chemical stiochiometry of Na2xMn[Fe(CN)6]2(x+1)/3·zH2O (x = 0, 0.5, and 1) using controlled co-precipitation method. The effect of Na intercalation on structural properties, electrochemical performance along with magnetic ordering are prersnted. The formation of uniformly cube shaped sodium‑manganese hexacyanoferrate is evident from field-emission scanning electron microscopy. Infra-red spectroscopy shows presence of characteristic absorption peaks of MnII-C ≡ N-FeIII bonds, confirm the formation of manganese hexacyanoferrate. The Rietveld refinement of x-ray data reveals that the compounds are crystallized in Fm3m cubic symmetry up to x = 0.5, whereas, excess Na intercalation (x = 1) leads to a R-3 mH, rhombohedral symmetry. The dc magnetization measurements show ferrimagnetic nature of these compounds. The magnetic transition temperature increases with Na intercalation and was found to be ∼11, 12.5, and 13.4 K for x = 0, 0.5, and 1. The Mössbauer spectroscopy study confirms low and intermediate spin states of both Fe+2 and Fe+3 ions in the studied compounds, consistence with their magnetic properties. The electrochemical performance of the compounds with Na intercalation in terms of charging-discharging are studied using cyclic voltammetry. The compounds show capacitance values of 182.6 F/g at 10 A/g, 117.5 F/g at 6A/g, and 110.1 F/g at 2.8 A/g for x = 0, 0.5, and 1, respectively, suggesting their suitability as electrochemical capacitors.

Photocatalytic mineralization of phenol by Sn-modified calcites

Calcium-based photocatalysts represent an economic and available alternative for the photodegradation of distinct pollutants such as pesticides, pigments, colorants, and drugs, among others. In the following paper, the morphological, structural, optical, and textural properties of a series of materials based on calcium carbonate (calcite) modified with Tin and their evaluation in phenol photodegradation were studied. The synthesized materials were characterized by several techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), N2 adsorption–desorption at 196 °C, Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS). The characterization information indicated that a portion of Sn4+ was incorporated into calcite structure and the rest crystallized as SnO2. The effect of tin incorporation was also evidenced by the calculated bandgap values whereas the tin amount increased the values got close to SnO2 value. Neither the bare sample SnO2 nor CaCO3 presented photoactivity for phenol mineralization. Nevertheless, it was demonstrated that the modified calcites presented a photocatalytic activity comparable to P25-TiO2, carrying out phenol mineralization in 3 h. Tin-modified calcite compounds were obtained by a controlled coprecipitation method. The photocatalytic evaluations presented a photocatalytic activity comparable to P25-TiO2, which was assigned to tin presence in a low-value material such as calcite.

Synthesis, characterization and photo-catalytic activity of magnetic CoFe2O4 nanoparticles prepared by temperature controlled co-precipitation method

Cobalt ferrite (CoFe2O4) nano-particles were synthesized by temperature controlled co-precipitation method using cobalt chloride and iron chloride as the precursor materials. CoFe2O4 nanoparticles as prepared were annealed at 500 °C for 4 hrs and then subjected to structural and microstructural characterization. The structural characterization of CoFe2O4 nanoparticles was done by X-ray diffraction (XRD). Microstructural, morphological and energy dispersive X-ray analysis (EDX) studies reveals grain size, surface morphology and elemental composition of the CoFe2O4 nanoparticles. The crystallite size was estimated by Scherrer’s formula for as prepared and annealed nanoparticles. The variation of crystallite size with annealing temperature was explored. The particle size, inter-planar distance, phase and Miller indices were estimated by high resolution transmission electron microscopy (HRTEM) and correlated with XRD results. The photo-catalytic activity of as prepared and annealed CoFe2O4 nanoparticles was studied for the degradation of methylene blue (MB) dye under visible light irradiation and the results are compared.

Structural and photocatalytic degradation studies of rice straw based MgO nanocomposite

The present study is focused on the comparison of structural and photocatalytic degradation activities of nanocomposite of MgO formed with rice straw, a biopolymer. For comparison, counter parts were also synthesized. Nanoparticles of magnesium oxide were synthesized through controlled co-precipitation method in presence of citric acid. Structural characterizations of all the synthesized samples were carried out using XRD. Comparison of XRD of metal oxide with JCPDS confirmed that the formed metal oxide was MgO. Photocatalytic degradation of organic dyes Congo Red, an acidic dye and Methylene Blue, a basic dye was done.

Synthesis of Magnetic Ferrite Nanoparticles with High Hyperthermia Performance via a Controlled Co-Precipitation Method.

Magnetic nanoparticles (MNPs) that exhibit high specific loss power (SLP) at lower metal content are highly desirable for hyperthermia applications. The conventional co-precipitation process has been widely employed for the synthesis of magnetic nanoparticles. However, their hyperthermia performance is often insufficient, which is considered as the main challenge to the development of practicable cancer treatments. In particular, ferrite MNPs have unique properties, such as a strong magnetocrystalline anisotropy, high coercivity, and moderate saturation magnetization, however their hyperthermia performance needs to be further improved. In this study, cobalt ferrite (CoFe2O4) and zinc cobalt ferrite nanoparticles (ZnCoFe2O4) were prepared to achieve high SLP values by modifying the conventional co-precipitation method. Our modified method, which allows for precursor material compositions (molar ratio of Fe+3:Fe+2:Co+2/Zn+2 of 3:2:1), is a simple, environmentally friendly, and low temperature process carried out in air at a maximum temperature of 60 °C, without the need for oxidizing or coating agents. The particles produced were characterized using multiple techniques, such as X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV–Vis spectroscopy), and a vibrating sample magnetometer (VSM). SLP values of the prepared nanoparticles were carefully evaluated as a function of time, magnetic field strength (30, 40, and 50 kA m−1), and the viscosity of the medium (water and glycerol), and compared to commercial magnetic nanoparticle materials under the same conditions. The cytotoxicity of the prepared nanoparticles by in vitro culture with NIH-3T3 fibroblasts exhibited good cytocompatibility up to 0.5 mg/mL. The safety limit of magnetic field parameters for SLP was tested. It did not exceed the 5 × 109 Am−1 s−1 threshold. A saturation temperature of 45 °C could be achieved. These nanoparticles, with minimal metal content, can ideally be used for in vivo hyperthermia applications, such as cancer treatments.

A non-enzymatic electrochemical sensor based on ZrO2: Cu(I) nanosphere modified carbon paste electrode for electro-catalytic oxidative detection of glucose in raw Citrus aurantium var. sinensis

In this work, a sensitive and stable ZrO2-Cu(I) nanosphere mesoporous material modified non-enzymatic glucose sensor has been developed through simple, low cost chemistry.ZrO2-Cu(I) material was obtained by controlled co-precipitation method under ultra dilution conditions. Cyclic voltammetric tests were performed in order to evaluate the electrocatalytic activity ZrO2-Cu(I) modified electrode. The modified electrode showed high sensitivity, wide linear range and very low detection limit of 0.25 mM, this indicates that the modified sensor is competent with that reported earlier. Spherical morphology of the active material, alkaline environment and presence of +1 copper have significantly enhanced the electro-catalytic oxidation of glucose on carbon paste platform. Also, the fabricated electrode showed excellent anti-interference nature. Electro-catalytic oxidation of glucose was demonstrated in real raw unpurified orange juice, this shows the selective electrocatalytic activity of the ZrO2-Cu(I) nanosphere material towards glucose even in the presence of interferrants.

Structural, Optical and Photocatalytic Degradation Studies of Polymer Based Fe2o3 Nanocomposite

The present study is focused on the comparison of structural and optical properties of nanocomposite of Fe2O3 formed with both rice straw, a biopolymer and polyindole, a conducting polymer. For comparison, counter parts were also synthesized. Nanoparticles of iron oxide were synthesized through controlled co-precipitation method in presence of citric acid. Structural characterizations of all the synthesized samples were carried out using XRD. Comparison of XRD of metal oxide with JCPDS confirmed that the formed metal oxide was Fe2O3. Optical studies of all the samples were carried out using UV/Vis spectroscopy. From band gap calculation it was seen that all of them except polyindole showed subgaps. Also these samples were employed as photocatalyst in the photocatalytic degration study of organic acidic dye Congo Red. Results suggested that the nanocomposites prepared in the present study are promising photocatalysts. Also an increase in degradation efficiency was observed in the case of nanocomposites when compared to their counterparts.

Adsorption of diazinon from aqueous solutions by magnetic guar gum-montmorillonite

Abstract According to the considerable toxic impacts of diazinon on the human health and environment, removal of that is very essential. Magnetic nanomaterials are highly used due to their distinguished features which can be controlled by an external magnetic field. The magnetic guar gum and magnetic guar gum-montmorillonite was synthesized via a controlled coprecipitation method to obtain uniform and high efficient nanocomposite for diazinon removal. The effect of pH, contact time and initial diazinon concentration on the removal of diazinon was examined. The adsorbent morphology and chemical composition were evaluated using SEM and FTIR. The size distribution of Fe3O4-guar gum and Fe3O4-guar gum-montmorillonite was from 56 to 92 nm and 70 to 128 nm respectively. Kinetic studies were checked by pseudo-first order, pseudo-second order and Elovich models. The adsorption behavior of diazinon was matched by the pseudo-second order kinetic model (R2˃0.99). Langmuir, Freundlich, Temkin and Elovich isotherm models were checked by adsorption equilibrium data and Langmuir model indicated the best consistency with the experimental results and the maximum adsorption capacity are 47.17 and 80.00 mg g − 1 for the magnetic guar gum and magnetic guar gum-montmorillonite, respectively. Based on the results, magnetic guar gum-montmorillonite nanoadsorbent has high ability to diazinon removal from aqueous solution.

Excellent product selectivity towards 2-phenyl-acetaldehyde and styrene oxide using manganese oxide and cobalt oxide NPs for the selective oxidation of styrene

MnOx and Co3O4 nanoparticles (NPs) were synthesized using the temperature controlled co-precipitation method and were immobilized on the mesoporous metal oxide supports that were synthesized using the inverse surfactant micelle method. The synthesized catalysts were characterized using TEM, SEM, pXRD, N2-sorption, XPS, and H2-TPR. From TEM the well-dispersed metal oxide NPs were observed and the interaction of the NPs with the support was confirmed with H2-TPR. These metal oxide NPs and immobilized metal oxide NPs were employed in the selective oxidation of styrene using tert-butyl hydrogen peroxide (TBHP) as an oxidant. Higher selectivity towards styrene oxide was obtained using Co3O4 NPs. MnOx NPs gave higher selectivity towards 2-phenyl-acetaldehyde while the immobilized metal oxide NPs gave a mixture of products. The catalytic activities of the compared catalysts followed the following decreasing order of MnOx NPs (646.9 h−1) > Co3O4 NPs (338.1 h−1) > Co-MnO2_350 (54.1 h−1) > Mn-Co3O4_350 (44.1 h−1) ˃ MnO2_350 (35.8 h−1) > Co3O4_350 (21.3 h−1) after 8 h of reaction. The catalytic activities and selectivity profiles under various reaction conditions such as solvent type, catalyst amount, styrene to TBHP ratio and temperature are discussed. The catalytic recyclability of immobilized metal oxide NPs on mesoporous metal oxides showed that they are stable, and the structure of the catalyst was retained.

Photoluminescence studies of Cd0.8−xPbxZn0.2S semiconductor compounds

The present study involves synthesis of bulk polycrystalline samples of Cd0.8−xPbxZn0.2S through low cost controlled Co-precipitation method. The synthesized compounds were characterized with respect to their crystal structure, particle size and photoluminescence properties using X-ray diffraction (XRD), and PL spectroscopy respectively. XRD results revealed that both cubic and Hexagonal phases are present in the compounds. PL studies indicated the photosensitive character of the compounds. Blue shift in the peak position in PL spectra with increase in concentration of Pb indicates the increase in the energy gap. PL spectra confirmed the formation of defect levels in the forbidden energy gap and the transition is thought to occur from donor levels to acceptor levels.

Superparamagnetic behavior of nanosized ZnFe2O4

Herein, we have reported the structural, microstructural, magnetic and hyperfine properties of nanosized (∼ 20 nm) ZnFe2O4 synthesized by flow rate controlled coprecipitation method. The PXRD and HRTEM study demonstrate that the sample is nanosized, single phase spinel oxide which crystallizes in space group. The sample exhibits superparamagnetic relaxation above blocking temperature (∼ 25 K). The saturation magnetizations of the sample are 4, 20 and 28 emu g-1 at 300, 100 and 10 K, respectively and the sample exhibits no hysteresis at 300 and 100 K.

Experimental and theoretical study to explain the morphology of CaMoO4 crystals

CaMoO4 crystals were prepared by a controlled co-precipitation method and processed in a domestic microwave-assisted hydrothermal system with two different surfactants (ethyl 4-dimethylaminobenzoate and 1,2,4,5-benzenetetracarboxylic dianhydride). The corresponding structures were characterized by X-ray diffraction and Rietveld refinement techniques, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, and photoluminescence measurements. Field emission scanning electron microscopy was used to investigate the morphology of the as-synthesized aggregates. The structure, the surface stability of the (001), (112), (100), (110), (101), and (111) surfaces of CaMoO4, and their morphological transformations were investigated through systematic first-principles calculations within the density functional theory method at the B3LYP level. Analysis of the surface structures showed that the electronic properties were associated with the presence of undercoordinated [CaOx] (x = 5 and 6) and [MoOy] (y = 4 and 3) clusters. The relative surfaces energies were tuned to predict a complete map of the morphologies available through a Wulff construction approach. The results reveal that the experimental and theoretical morphologies obtained coincide when the surface energies of the (001) and (101) surfaces increase, while the surface energy of the (100) facet decreases simultaneously. The results provide a comprehensive catalog of the morphologies most likely to be present under realistic conditions, and will serve as a starting point for future studies on the surface chemistry of CaMoO4 crystals.

Tuning the Morphological, Optical, and Antimicrobial Properties of α-Ag2WO4 Microcrystals Using Different Solvents

New and effective antimicrobial agents are constantly being evaluated to address the increased prevalence of bacterial and fungal infections and the emerging drug resistance. In this work, α-Ag2WO4 microcrystals were synthesized by the controlled co-precipitation method at 90°C for 10 min in different solvents (water, alcoholic solution, and ammoniacal solution). The X-ray diffraction patterns of the newly synthesized α-Ag2WO4 microcrystals were well indexed to the orthorhombic structure. Two morphologies were observed by field-emission scanning electron microscopy, microrods in alcoholic solution and flower-like structures in water and ammoniacal solution. The synthesized α-Ag2WO4 microcrystals had fungistatic and fungicidal activity against Candida albicans, and bacteriostatic and bactericidal activity against Escherichia coli and methicillin-resistant Staphylococcus aureus. The antibacterial performance of α-Ag2WO4 samples as a function of their structural and morphological features was discussed.

Optimization of CdO nanoparticles by Zr4+ doping for better photocatalytic activity

Chemically controlled co-precipitation method has been adopted for the fabrication of pure and different wt% Zr doped CdO photocatalysts. Conventionally, the crystallite size and crystalline phase of CdO are in the midst of the parameters involved in the control of the photocatalytic activity. Aiming utterly at the size effect that modifies other attributes which are important to assess the photocatalytic activity of nanometric CdO, it was explored to synthesize CdO nanoparticles with controlled size, highly comparable morphology and analogous phase. The crystal structure and the crystallite size were estimated from the X-ray diffraction patterns and were confirmed through transmission electron microscope. The degree of crystallinity varied on Zr doping and the calculated crystallite sizes were in the range of 16–81 nm. The dopant ion Zr4+ have been detected through X-ray photoelectron spectroscopy (XPS) analysis signifying the dopant to substitute for cadmium (Cd2+) in the lattice of CdO. Particle size dependent optical band gaps calculated in the range 2.02–2.57 eV informed the viability of the materials to initiate photocatalytic reaction in the visible light region. Lesser recombination rate of the generated electrons and holes under light irradiation produced low intense photoluminescence peaks that displayed the appropriateness as photocatalysts. Zr4+ doping resulted in the enhancement of photocatalytic activity, evaluated by monitoring the degradation of methylene blue solution. 0.5 wt% Zr doped CdO nanoarticles calcined at 400 °C exhibited the highest photocatalytic activity with better percentage of color abatement (80.95%). The pseudo-first-order reaction rate became faster on Zr doping such that the rate constant is ~ 0.4–0.5 h−1 for Zr doped CdO while that for pure CdO is ~ 0.3 h−1.

Morphology controlled Co-precipitation method for nano structured transparent MgAl2O4

Abstract MgAl2O4 spinel nano powders with various morphologies were synthesized with ammonium aluminum carbonate hydroxide by carbonate precipitation. The powders with rod, corn, and spherical morphologies were synthesized, varying the concentration of ammonium ions, by growth and aggregation of nano precipitates. The powders with spherical morphology formed spinel phase at a lower calcination temperature than those with other shapes. The morphology provided a superb sinterability due to improved particle packing. Although the synthetic conditions resulted in a composition slightly off the stoichiometric composition with Mg loss, this provided a proper condition for inhibiting grain growth. Finally, Mg-spinel which was obtained from spherical particles and fabricated by spark plasma sintering (SPS) showed much improved transparency with an average grain size of ~200 nm (RIT and TFT are 55.92% and 63.75% at 550 nm 75.35% and 78.91% at 1500 nm, respectively) than those from other shaped particles.

Structure and optical properties of Fe3O4 nanoparticles synthesized by co-precipitation method with different organic modifiers

Synthesis and modification of magnetite nanoparticles were carried out by co-precipitation method. The influence of different organic modifiers on structure and optical properties of Fe3O4 nanoparticles has been studied in detail. The X-ray diffraction method, transmission electron microscopy, Fourier transform infrared spectroscopy and UV–visible spectroscopy were used to determine crystallite size, structure, morphology and optical band-gap energy. The magnetite nanoparticles with different crystallite size at range of 2.9–12.2nm were obtained by the modified controlled chemical co-precipitation method. The results showed that the Fe3O4 nanoparticles synthesized in solution containing tartaric acid were the smallest and had the highest value of optical band-gap energy (3.01eV). The use of dextrin allowed obtaining nanocomposite, in which magnetite nanoparticles were dispersed in polysaccharide matrix. It was confirmed that with the decrease in the crystallite size the value of the optical band-gap energy increases, which is related to quantum phenomena. Additionally, shift of characteristic peaks from FeO bond in Fourier transform infrared spectra were observed, what is also associated with change of the nanoparticles size.

Photo-thermal characteristics of water-based Fe3O4@SiO2 nanofluid for solar-thermal applications

This work proposes and demonstrates the novel idea of using Fe3O4@SiO2 core/shell structure nanoparticles (NPs) to improve the solar thermal conversion efficiency. Magnetite (Fe3O4) NPs are synthesized by controlled co-precipitation method. Fe3O4@SiO2 NPs are prepared based on sol–gel approach, then characterized. Water-based Fe3O4@SiO2 nanofluid is prepared and usedto illustrate the photo-thermal conversion characteristics of a solar collector under solar simulator. The temperature rise characteristics of the nanofluids are investigated at different heights of the solar collector, for duration of 300 min, under a solar intensity of 1000 W m−2. The experimental results show that Fe3O4@SiO2 NPs have a core/shell structure with spherical morphology and size of about 400 nm. Fe3O4@SiO2/H2O nanofluid enhances the photo-thermal conversion efficiency compared with base fluid and Fe3O4/H2O nanofluid, since the silica coating improves both the thermodynamic stability of the nanofluid and the light absorption effectiveness of the NPs. At a concentration of 1 mg/1 ml of Fe3O4@SiO2/H2O, and with the utilization of kerosene into the solar collector, and exposure for radiation for 5 min, the photo-thermal conversion efficiency has shown an enhancement at the bottom of the collector of about 32.9% compared to the base fluid.

Synthesis of cobalt ferrite nanoparticles by constant pH co-precipitation and their high catalytic activity in CO oxidation

A series of cobalt ferrite samples were synthesized from a metal nitrate solution at constant pH between 9 and 12 by the controlled co-precipitation method without any surfactant.

Highly selective doped Pt[sbnd]MgO nano-sheets for renewable hydrogen production from APR of glycerol

A series of M-doped PtMgO (M = Pd, Ir, Re, Ru, Rh and Cr) sheet-shaped nano-catalysts were synthesized by the controlled co-precipitation method. The effects of M-doping on both the physicochemical and the chemisorption characteristics of PtMgO catalysts were examined. The performance of the catalysts for the aqueous phase reforming (APR) of glycerol was also investigated. The APR activity of PtMMgO catalysts depended on the type of the M dopant used. The APR activity varied in the following order: Rh > Pd > Cr > Ir > undoped ≈ Ru > Re, with the Rh-promoted catalyst having an activity of about one order of magnitude higher than the Re-promoted catalyst at 250 °C. It was found that M-promotion had a significant effect on the reducibility of the PtMgO catalysts thus affecting their APR activity.