Tetragonal Copper Research Articles

Structural and electrochemical characterization of tetragonal copper ferrite nanoparticles

Structural and electrochemical characterization of tetragonal copper ferrite nanoparticles

SÍNTESE, CARACTERIZAÇÃO, ATIVIDADE ANTIMICROBIANA DE NANOPARTÍCULAS DE FERRITA DE COBRE E SUA INCORPORAÇÃO EM CIMENTO DE IONÔMERO DE VIDRO

SYNTHESIS, CHARACTERIZATION, ANTIMICROBIAL ACTIVITY OF COPPER FERRITE NANOPARTICLES AND THEIR INCORPORATION IN GLASS IONOMER CEMENT. Pure cubic copper ferrite (c-CuFe2O4), cerium-doped cubic copper ferrite (c-CuCeFe2O4) and pure tetragonal copper ferrite (t-CuFe2O4) nanoparticles were synthesized from the proteic sol-gel method, and characterized by X-ray diffraction, Rietveld method, FT-IR spectroscopy, and field emission scanning electron microscope. The antibacterial activity of the particles was tested in vitro against pathogenic Gram-positive, Gram-negative bacteria. Thus, it has been observed that the nanoparticles are capable of inhibiting the growth of such microorganisms. The nanoparticles were incorporated into glass ionomer cement, followed by Vickers microhardness evaluation. It is concluded that the cubic copper ferrite showed the best antimicrobial result, being the most suitable for market studies (industrial and biomedical).

Reaction time influence on copper tin sulfide micro flowers for enhanced electrochemical hydrogen evolution reaction (HER) performance

Herein, we report the effective way to optimize the copper tin sulfide (Cu2SnS3) micro flowers via a simple hydrothermal method using different reaction times, which could enhance the fabricated electrocatalyst in electrochemical water splitting applications. The prepared Cu2SnS3 was identified by X-ray diffraction (XRD) analysis, which demonstrated the formation of triclinic phase Cu2SnS3 with a=0.664, b=1.151 and c=1.993 nm, respectively. Phase confirmation was further analyzed by using Raman and Fourier-transform infrared (FTIR) spectroscopy, which also demonstrated pure tetragonal copper tin sulfide (CTS) phase. The morphology of the copper tin sulfide (CTS) materials was explored with the help of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies, which confirmed crystalline nature of triclinic copper tin sulfide (CTS) 3D hierarchical micro flowers. The prepared electrocatalyst was further characterized employing Energy-dispersive (EDX) and X-ray (XPS) spectroscopy. It exhibited chemical composition of Cu2p, Sn3d, and S2p in stoichiometric ratio with an atomic percentage of Cu, Sn, and S being 37.5, 40.7, and 21.7%, respectively. CTS-16 h exhibited 151 mV to afford 10 mA/cm2 and 139 mV/dec Tafel slope value, which was demonstrated by electrochemical characterizations. Moreover, the efficient electrocatalyst of CTS-16 h exhibited 131.5 cm2 electrochemical active surface area, while the other catalysts such as CTS-4 h, CTS-8 h and CTS-24 h were 49.25, 67.5, and 107.5 cm2 respectively. The CTS-16 h electrode shows excellent stability towards long-term CA test for one day with 94% retention. Therefore, the overall result suggests that the synthesized material provided a new approach for the noble metal catalysts substitute, and it is a potential material for clean energy systems.

Low temperature and high magnetic field Mössbauer study of CuFe2O4 synthesized by sol–gel auto-combustion method

Copper ferrite samples were prepared by sol–gel auto-combustion method and annealed from 400 to 800 °C. The structure and morphology of the samples was analyzed by x-ray diffraction and scanning electron microscopy techniques. An In-field Mössbauer spectroscopic analysis was carried out at a temperature of 5 K without and with 5 T magnetic field. A cubic phase with spinel ferrite structure was observed for the as prepared sample and the sample annealed at 400 °C. Further, a tetragonal copper ferrite phase along with CuO and α-Fe2O3 as secondary phases was identified for 500, 600, 700 and 800 °C annealed samples. The estimated average crystallite size was found to be in the range of 27–43 nm. The grain growth and the agglomerated morphology were observed due to annealing at higher temperatures. The Mössbauer analysis reveals that isomer shift values 0.347–0.534 mm/s, shows the random variation. S1 sextet (A-site) has a higher hyperfine field than S2 sextet (B-site). The larger variation of quadrupole shift for the observed sextets shows that crystal structure has lattice distortions. S1 sextet has a lower relative absorption area than S2 sextet, while the S3 sextet (α-Fe2O3) has an increasing relative absorption area as the annealing temperature rises. Inversion parameter values were found in the range of 0.51–0.88 at 5 K and 0.66–0.95 at 5 K–5 T. The partial inverse and random spinel nature of prepared samples was observed. The estimated weight percentage of the copper ferrite samples clearly indicates an increase in the α-Fe2O3 and CuO impurity phases. The evolution of structural phases and their impact on the cation distribution in copper ferrite were studied by Mössabuer spectra taken at low temperature and high magnetic field.

Structural and elastic properties of tetragonal nano-structured copper ferrite

Abstract The surge of interest in ferrimagnetic materials over the years has been driven by their fascinating multifunctional properties. The elastic properties of these materials are a subject of much interest and vital importance due to their wide range of technological and industrial applications. In the present work, the structural and elastic properties of tetragonal copper ferrite (CuFe2O4) nanoparticles synthesized by a citrate assisted sol-gel auto combustion technique have been investigated. The nanocrystalline powder of copper ferrite was characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and UV–Visible spectroscopic techniques. The X-ray diffraction pattern revealed pure spinel structure of copper ferrite nanoparticles with Jahn–Teller tetragonal distortion. The band gap of copper ferrite nanoparticles was found to be 3.14 ± 0.03 eV using the diffuse reflectance spectra. The values of elastic moduli (Young’s modulus (E) = 186.3 ± 0.5 GPa, bulk modulus (B) = 124.1 ± 0.3 GPa, and rigidity modulus (G) = 74.4 ± 0.2 GPa) and Debye temperature (θ D = 500.5 ± 0.5 K) suggest that the synthesized nano-structured copper ferrite is a promising candidate for high temperature and high pressure applications.

Structural and electromagnetic characterization of yttrium doped copper ferrite

In this study, Yttrium doped Copper ferrites (CuFe2-xYxO4;x=0.1,0.2,0.3,0.4,0.5) are synthesized through sol–gel auto combustion technique. X-ray diffraction and scanning electron microscope is employed to carry out structural and morphological study of as prepared samples. The XRD patterns show formation of stable tetragonal copper ferrite with and without doping. Tetragonal structure transformation is achieved with high sintering temperature. Vibrational modes were further examined through Raman and FTIR spectra and affirm formation of tetragonal structure with MO bonding. Electromagnetic response of the powdered samples was investigated in microwave region from 1 to 15 GHz. The decrease in real permittivity from 5 to 3 (F/m) as well as in real permeability from 2.5 to 1.75 (H/m) by increasing Y3+ content is observed. This trend directly correlates with degree of crystallinity. The low values of dielectric and magnetic loss tangent make them highly suitable for low loss applications.

Tetragonal transition metal selenide for hydrogen evolution

Hydrogen evolution reaction (HER) plays an important role in energy conversion through water splitting to produce hydrogen. Considering the large surface/volume ratio, exploration of two-dimensional materials with high-efficient basal plane has attracted a great enthusiasm in designing electrocatalysts. Herein, tetragonal copper selenide (CuSe) was identified as a promising candidate toward HER by density functional theory calculations. The low exfoliation energy Eexf of 41.47 meV/Å2 ensures the exfoliation of CuSe monolayer along [001] direction, which allows the exposure of the basal plane. More importantly, the pristine CuSe monolayer without any treatment delivers relatively good activity, as reflected by the small thermodynamic barrier of 0.3 eV. Furthermore, CuSe possesses good electron conductivity, which makes it beneficial to the electron transfer during electrocatalysis. Therefore, these results indicate that CuSe acts as a promising material for the next-generation HER catalysis with the high basal utilization.

A single step synthesis by mechanical alloying and characterization of nanostructured Fe2B of high magnetic moment

This paper delineates a single-step production method of nanostructured diiron boride (Fe2B) and its structural, magnetic and magnetothermal properties. Structurally Fe2B resembles the tetragonal copper aluminide, CuAl2. The samples of nanostructured Fe2B were synthesized by milling Fe and B powders without any pre-treatment. Single phase Fe2B nanoparticles were successfully produced with the crystallite sizes of 68 and 46 nm after milling the powders for 10 h and 20 h, respectively. The saturation magnetization of the samples was found to decrease with increased milling time indicating that the surface spin disorder plays a crucial role in the magnetic properties. The highest saturation magnetization (Ms) of 141 emu/g with low coercivity (Hc) of 48 Oe was obtained for the 10 h milled sample of Fe2B, whereas the 20 h milled sample exhibited Ms and Hc as 129 emu/g and 149 Oe. This paper also presents a detailed information on the total and atom projected densities of state functions as well as the magnetic moment contribution of the individual atoms of Fe and B in Fe2B explaining the strong room temperature ferromagnetic properties contributed by the large number of unpaired 3 d electrons in Fe. The magnetothermal properties of the as-made Fe2B nanocrystals of high magnetic moment were investigated by measuring the rise in temperature as a function of time in the presence of AC magnetic fields. The magnetic Fe2B nanocrystals show significant thermal response with the high specific absorption rate of 172 W/g, demonstrating the advantages of using Fe2B nanocrystals for the application in magnetic fluid therapy for hyperthermia.

Pragmatically designed tetragonal copper ferrite super-architectures as advanced multifunctional electrodes for solid-state supercapacitors and overall water splitting

Stabilization of tetragonal copper ferrite super-architectures has been proposed for the fabrication of high-performance supercapacitor and water splitting electrodes. The reaction parameters are optimized to keep the tetragonal phase intact (with high yield per batch ~ 7.5 g) in order to have better ions intercalation/de-intercalation processes and longer cycling stability, according to Jahn-Teller distortion theory. The developed porous layered architectures are mesoporous with large specific surface area available for ionic interactions. The redox additive insertion in the electrolyte raises the specific capacity to ~ 450 mAh g−1 (~2490F g−1) from the fabricated electrode. The physical mechanism involved behind the electrochemical performance in presence of redox additives is elaborately discussed to gain insight into the charge storage characteristics. The fabricated asymmetric solid-state supercapacitor exhibits broad potential window (~1.8 V) with excellent energy (128 Wh kg−1) cum power traits, and a long-lasting stable performance for > 10000 cycles. For water splitting, the super-architectures based electrode displays promisingly lower OER/HER (~298/103 mV) overpotentials with excellent stability over longer durations (>30 h). The fabricated symmetric device with the alkaline electrolyte is highly stable with cell voltage of 1.62 V, which being an oxide material is excellent and superior to various oxides/chalcogenides based high-grade materials.

Influence of the Synthesis Route in Obtaining the Cubic or Tetragonal Copper Ferrite Phases.

In this work, magnetic copper ferrite nanoparticles are synthesized by polymer-assisted sol-gel and coprecipitation methods. The obtained purity and particle size reach values of 96% and 94 nm, respectively. Evident differences in the crystal structure have been found in the synthesized nanoparticles. A tetragonal structure is formed by the sol-gel method, while the cubic form is obtained when the coprecipitation approach is used. This work provides experimental evidence of the formation of both phases by using the same reactants and thermal conditions and only modifying the technical procedure. The formation and stability of each phase are analyzed by temperature-dependent measurements, and the observed crystal structure differences are used to propose a potential fundamental explanation to our observations based on differences in the cations' distribution and Jahn-Teller distortion. Moreover, different copper ferrite purities and particle sizes are found when using each of the methods. The spherical shape of the particles and their tendency to sinter, forming micrometric clusters, are observed by electron microscopy. Finally, the divergence in magnetization between the samples prepared by each method supports our argument about the different cations' distribution and opens the door to a wide range of different technological applications for these materials.

Direct-coated Cu2SnS3 films from molecular solution inks for solar photovoltaics

Cu-based solution/ink coated sulphides have gained tremendous interest in last few years for low-cost solar cells. In this paper, pure copper tin sulphide films have been directly-coated from two different types of molecular solution inks developed with ethylene glycol and ethylene glycol - isopropyl alcohol mixture. Structural, compositional and microstructural properties of direct-coated films were studied and compared. The formation of pure tetragonal copper tin sulphide is confirmed by X-ray diffraction and Raman spectroscopy analysis. Overall it is found that films deposited from ethylene glycol - isopropyl alcohol mixture (glycoholic ink) are comparatively smoother and denser. An X-ray photoelectron study confirms the presence of Cu+ state in the films. The films are photoconducting and show p-type conduction. In general, microstructure of the films was found to depend upon type of solvents.

RETRACTED ARTICLE: Structural, optical and magnetic properties of CuFe2O4 nanoparticles

The manuscript presents structural, optical and magnetic properties of CuFe2O4 nanoparticles obtained employing a simple co-precipitation method in aqueous solution. Influence of ferric chloride concentration on the structural, optical and magnetic properties of CuFe2O4 nanoparticles was investigated. XRD results clearly revealed the spinel tetragonal copper ferrite structures. The observed characteristic Raman E1g, F2g and A1g phonon mode of vibrations revealed the tetragonal copper ferrite structures. The observed PL results explored inverse spinel copper ferrite emission peaks in the range of visible region. IR result revealed the metal oxygen intrinsic vibrations of octahedral and tetrahedral sites in the spinel copper ferrite structure. SEM analysis clearly revealed the spherical shape morphology particles sizes are in the nano scale range. VSM studies clearly revealed that copper ferrite exhibit weak ferromagnetic behaviour. It was found that the ferric chloride concentration added to copper chloride precursor in the ratio of 1:1, 1:2 and 1:3 during the synthesis process played a significant role in structural and magnetic properties of the obtained product.

Magnetically induced ferroelectricity in Bi2CuO4

The tetragonal copper oxide ${\mathrm{Bi}}_{2}{\mathrm{CuO}}_{4}$ has an unusual crystal structure with a three-dimensional network of well separated ${\mathrm{CuO}}_{4}$ plaquettes. The spin structure of ${\mathrm{Bi}}_{2}{\mathrm{CuO}}_{4}$ in the magnetically ordered state below ${T}_{\text{N}}\ensuremath{\sim}43$ K remains controversial. Here we present the results of detailed studies of specific heat, magnetic, and dielectric properties of ${\mathrm{Bi}}_{2}{\mathrm{CuO}}_{4}$ single crystals grown by the floating zone technique, combined with the polarized neutron scattering and high-resolution x-ray measurements. Down to 3.5 K our polarized neutron scattering measurements reveal ordered magnetic Cu moments which are aligned within the $ab$ plane. Below the onset of the long range antiferromagnetic ordering we observe an electric polarization induced by an applied magnetic field, which indicates inversion symmetry breaking by the ordered state of Cu spins. For the magnetic field applied perpendicular to the tetragonal axis, the spin-induced ferroelectricity is explained in terms of the linear magnetoelectric effect that occurs in a metastable magnetic state. A relatively small electric polarization induced by the field parallel to the tetragonal axis may indicate a more complex magnetic ordering in ${\mathrm{Bi}}_{2}{\mathrm{CuO}}_{4}$.

Phase transition of tetragonal copper sulfide Cu2S at low temperatures

The low-temperature behavior of tetragonal copper sulfide, ${\mathrm{Cu}}_{2}\mathrm{S}$, was investigated by powder and single-crystal x-ray diffraction, calorimetry, electrical resistance measurements, and ambient temperature optical absorption spectroscopy. The experiments were complemented by density-functional-theory-based calculations. High-quality, polycrystalline samples and single crystals of tetragonal copper sulfide were synthesized at 5 GPa and 700 K in a large volume multianvil press. Tetragonal ${\mathrm{Cu}}_{2}\mathrm{S}$ undergoes a temperature-induced phase transition to an orthorhombic structure at around 202 K with a hysteresis of $\ifmmode\pm\else\textpm\fi{}21$ K, an enthalpy of reaction of 1.3(2) $\mathrm{kJ}\phantom{\rule{0.16em}{0ex}}{\mathrm{mol}}^{\ensuremath{-}1}$, and an entropy of reaction of 6.5(2) $\mathrm{J}\phantom{\rule{0.16em}{0ex}}{\mathrm{mol}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$. The temperature dependence of the heat capacity at the transition temperature indicates that the transition from the tetragonal to the low-temperature polymorph is not a single process. The structure of the low-temperature polymorph at 100 K was solved in space group $Pna{2}_{1}$. The structure is based on a slightly distorted cubic close packing of sulfur with copper in threefold coordination similar to the structure of tetragonal copper sulfide. The electrical resistance changes several orders of magnitude at the transition following the temperature hysteresis. The activation energy of the conductivity for the tetragonal phase and the low-temperature polymorph are 0.15(2) and 0.22(1) eV, respectively. The direct band gap of the tetragonal polymorph is found to be 1.04(2) eV with the absorption spectrum following Urbach's law. The activation energies and the band gaps of both phases are discussed with respect to the results of the calculated electronic band structures.

Study of thermal, structural and impedance characteristics of nanocrystalline copper chromite synthesized via hydrothermal process

Nanocrystalline copper chromite (CuCr2O4) spinel oxide was prepared by hydrothermal method. X-ray diffraction results showed that single-phase tetragonal copper chromite was obtained after calcination at 800 °C for 4 h. This phase was also confirmed by Rietveld refinement study with lattice parameters of a = b = 6.0336 A, c = 7.8265 A and space group of I-4 2D. Thermogravimetric analysis showed an overall mass loss of about 24 %. This was due to evaporation of adsorbed water and decomposition of chromium and copper hydroxides to form copper chromite (CuCr2O4). Differential scanning calorimetric analysis indicated the commencement of crystallization at 417 °C. Thermal study revealed that CuCr2O4 was thermally stable above 800 °C. FESEM revealed that the grain size of CuCr2O4 increased with increase in sintering temperature, and well-defined fine octahedron-like crystals of CuCr2O4 were obtained after sintering at 1050 °C for 4 h. Impedance spectroscopy was performed and an equivalent circuit model (R 1 Q 1) (R 2 Q 2) was fitted to explain two electroactive regions associated with grains and grain boundaries in CuCr2O4 oxide material. Frequency-dependent conductivity and dielectric constant of the material showed increasing and decreasing trends, respectively.

Structural, magnetic and gas sensing properties of nanosized copper ferrite powder synthesized by sol gel combustion technique

Stoichiometric nano sized copper ferrite particles were synthesized by sol gel combustion technique. They were then calcined at various temperatures ranging from 300–800°C and were either furnace cooled or quenched in liquid nitrogen. A high magnetisation value of 48.2emu/g signifying the cubic phase of copper ferrite, was obtained for sample quenched to liquid nitrogen temperature from 800°C. The ethanol sensing response of the samples was studied and a maximum of 86% response was obtained for 500ppm ethanol in the case of a furnace cooled sample calcined at 800°C. The chemical sensing is seen to be correlated with the c/a ratio and is best in the case of tetragonal copper ferrite.

Investigations of the EPR g factors for tetragonal copper site in Sr2Ca2Cu3Ox

The electron paramagnetic resonance (EPR) [Formula: see text] factors are quantitatively investigated for tetragonal [Formula: see text] site in [Formula: see text] by utilizing the perturbation formulas of the [Formula: see text] factors for a tetragonally elongated octahedral [Formula: see text] cluster from the cluster approach. The anisotropy of the [Formula: see text] factors is discussed from the local tetragonal elongation of this five-fold coordinated copper site. The present EPR analysis for this precursor of Hg-1223 superconductors can be useful to the understandings of the relationships between the local structure (significant elongation of the copper site) and the intense Cu–O orbital hybridization and hence the high [Formula: see text] of the Hg-1223 systems.

Nanorod Formation of Copper Indium (di) Selenide Nanorod Synthesize by Solvothermal Route

The compound belongs to I-III-VI2 group are promising material as an effective light-absorbing materials. Now a day, ternary chalcopyrite semiconductors, especially copper based I-III-VI2 semiconductors have attracted many investigators. They have several desirable features as absorbers in the thin film solar cells. In present work, copper indium (di) selenide have been prepared via solvothermal route. Several methods have been reported to prepare CuInSe2 nanostructures by solution route. In present work, tetragonal chalcopyrite copper indium (di) selenide nanorods has been synthesized by solvothermal method using ethylene diamine as a solvent. Structural analysis had been done by X-ray diffraction (XRD). The surface morphology of the as-grown nanorod has been studied using scanning electron microscopy. The bandgap of as grown nanorods is obtained from UV-Vis spectrum which will applicable to the solar cell devices.

Fabrication, characterization, and magnetic properties of copper ferrite nanoparticles prepared by a simple, thermal-treatment method

Tetragonal copper ferrite nanoparticles were fabricated by a thermal-treatment method by using a solution that contained poly(vinyl alcohol) (PVA) as a capping agent and Cu and Fe nitrates as alternative sources of metal. Heat treatment was conducted at temperatures between 673 and 823K, and final products had different crystallite sizes ranging from 11 to 42nm. The influence of calcination temperature on the degree of crystallinity, morphology, microstructure, and phase composition was investigated by different characterization techniques, i.e., X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), and Fourier transform infrared (FT-IR) spectroscopy, respectively. The compositions of the samples were determined by energy dispersion X-ray analysis (EDXA), which revealed the presence of Cu, Fe, and O in the samples. The formed nanoparticles exhibited ferromagnetic behavior with unpaired electrons spins, which was confirmed by using a vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) spectroscopy.

An Anionic, Tetragonal Copper(II) Superoxide Complex

Insight into copper-oxygen species proposed as intermediates in oxidation catalysis is provided by the identification of a Cu(II)-superoxide complex supported by a sterically hindered, pyridinedicarboxamide ligand. A tetragonal, end-on superoxide structure is proposed based on DFT calculations and UV-vis, NMR, EPR, and resonance Raman spectroscopy. The complex yields a trans-1,2-peroxodicopper(II) species upon reaction with [(tmpa)Cu(CH(3)CN)]OTf and, unlike other known Cu(II)-superoxide complexes, acts as a base rather than an electrophilic (H-atom abstracting) reagent in reactions with phenols.