Assisted Co-precipitation Route Research Articles

Oxygen vacancies mediated changes in ferromagnetic, optical, Photoluminescent and electronic structure properties of Ho-doped CeO2 nanoparticles

The undoped CeO2 and Ce1-xHoxO2 (x = 0.03, 0.05 and 0.07) nanoparticles prepared using microwave assisted co-precipitation route are investigated using X-Ray Diffraction (XRD), UV–Vis–NIR, Raman, photoluminescence, X-ray Photoelectron Spectroscopy (XPS) and SQUID-VSM magnetometer. The XRD validates the inclusion of Ho3+ at the Ce3+/Ce4+ site while maintaining the crystal structure with development of defects and oxygen vacancies with expansion of the CeO2 nanolattice. The composition of the elements with desired stoichiometry is confirmed by Energy Dispersive X-ray spectra analysis. The absorption spectroscopy analysis reports the Urbach energy along with refractive index increases with Ho3+ doping and the optical band gap is decreased indicating red shift. All the nanoparticles are subjected to PL investigations to ascertain the oxygen vacancy and defect structure of nanoparticles. Raman active modes at ∼500 - 630 cm−1 verifies the existence of oxygen vacancies (Vo)., which are seen to rise with concentration of Ho-doping in the CeO2 lattice. When Ce4+ transforms into Ce3+, oxygen vacancies are generated in the lattice to maintain the charge neutrality, as can be seen by the Ce-3d, O-1s, and Ho-4d core level XPS spectra. To demonstrate that Ho3+ doping favours ferromagnetic ordering in the CeO2 lattice, the magnetic properties using the Bound Magnetic Polaron model and F centre exchange mechanism are discussed. The development of various complexes that involve host and doped cations are mediated by Vo suggests the existence of F0, F+, and F2+ centres. The weak ferromagnetic behaviour in Ho3+-doped CeO2 nanoparticles reinforce the relationship between Vo to explain the observed magnetic properties of nanoparticles.

Structural and optical properties of chromium oxide in CuCr2O4-δnanostructured materials

Nano-composites of Chromium Oxide (Cr2O3) incorporated CuO have been prepared by microwave assisted co-precipitation route using sodium hydroxide (NaOH) as a precipitating agent and then characterized under techniques such as Diffraction by X-Rays (XRD), UV–Visible, IR spectroscopy (FTIR), Field Emission Scanning Electron Microscopy and High Resolution Transmission Electron Microscopy. Diffractometric study explores that the formed nano-composites are crystalline in nature and their dimensions lies in nano-region i.e. 21 nm to 46 nm. The shape and size of the calcined composites samples has been analysed via FESEM and HRTEM images. The outcomes of Tauc plot confirmed the formation of nano-composites as well as semiconducting nature of samples with optical band gap 2.6 eV to 3.4 eV.

Tailoring the Physicochemical Properties of Mg Promoted Catalysts via One Pot Non-ionic Surfactant Assisted Co-precipitation Route for CO2 Co-feeding Syngas to Methanol

Tailoring the Physicochemical Properties of Mg Promoted Catalysts via One Pot Non-ionic Surfactant Assisted Co-precipitation Route for CO2 Co-feeding Syngas to Methanol

Synthesis of iron oxide nanoparticles for hyperthermia application: effect of ultrasonic irradiation assisted co-precipitation route

In this research, maghemite (γ-Fe2O3) and magnetite (Fe3O4) nanoparticles (NPs) were synthesised by co-precipitation route with the aid of ultrasonic irradiation. The morphology, crystallite size, particle size, and structural analysis of magnetic NPs were investigated by transmission electron microscope (TEM) and X-ray diffraction (XRD). Thermal properties of magnetic NPs were also investigated by specific loss power (SLP) measurements. The X-ray diffraction patterns determined the formation of maghemite and magnetite phases. The results obtained from the TEM analysis indicated that the mean particle size of maghemite and magnetite NPs was 20 ± 0.2 nm and 22 ± 0.3 nm, respectively. Moreover, the crystallite size was calculated by modified Scherrer method. Vibration sample magnetometer (VSM) was used to evaluate magnetic behaviour of the synthesised NPs. The magnetic saturation for both γ-Fe2O3 and Fe3O4 was 44 emu g−1 and 55 emu g−1, and coercivity field was 2 Oe and 70 Oe, respectively. The SLP values for synthesised NPs were significant, and the temperature of these magnetic NPs reached 44 °C–47 °C within 10 min in the existence of an external magnetic field with an intensity of about 6 kA/m. This temperature range seems to be appropriate for hyperthermia application and destruction of cancerous cells. In addition, the size of these magnetic NPs was less than 50 nm, which facilitates better penetration of these NPs into the cancerous tumours.

Influence of PVP surfactant on the morphology and properties of ZnO micro/nanoflowers for dye mixtures and textile wastewater degradation

Flower-like ZnO micro/nanostructures were successfully prepared using a polyvinylpyrrolidone (PVP)-assisted co-precipitation route and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy. Smaller sizes of ZnO micro/nanoflowers were synthesized with different amounts of PVP as surfactant. Possible morphology evolution and formation mechanism of the flower-like micro/nanostructures were postulated. Concentrations of PVP in the reaction mixtures served as key role for morphology-controlled synthesis of ZnO as PVP can assist the oriented crystal growth during the synthesis. The as-synthesized ZnO samples prepared at 12.5 mg/mL PVP displayed higher photoactivity for the simultaneous degradation of methyl orange and methyl green mixtures. The photocatalytic tests also indicated that process parameters such as the initial dye concentration and solution pH exerted their individual influences on the dye mixtures degradation. Under determined experimental conditions, 94.1% chemical oxygen demand (COD) removal of dye mixtures was attained after 240 min of reaction. The ZnO photocatalytic degradation of real textile wastewater was then evaluated and a lower COD removal efficiency (∼75%) was observed at similar treatment duration. Other real textile wastewater quality parameters of biochemical oxygen demand (BOD5), turbidity, total suspended solid (TSS), colour, ammoniacal nitrogen (NH3-N) and pH were also investigated.

Transparent sub-mircon Gd2Zr2O7 ceramic prepared by spark plasma sintering using nanocrystalline powders

In this work, transparent sub-mircon Gd2Zr2O7 (GZO) ceramic was successfully sintered for the first time by spark plasma sintering (SPS) using nanocrystalline powders synthesized via a solvothermal assisted co-precipitation route. With the aids of fast heating and cooling rate and high pressure, the GZO transparent sample with an average grain size of about 205nm was obtained at 1400°C for 5min. The maximum transmittance of about 70% was achieved at a wavelength of 2000nm.

Li doping induced physico-chemical modulations in Cd ferrite (CdLixFe(2−x)O4−x) synthesized using aqueous ammonia assisted co-precipitation route

Ammonium hydroxide as a co-precipitating agent has been used in nanofabrication of pure and Li doped Cd ferrites (CdLixFe(2−x)O(4−x);x = 0.0–0.5) using wet chemical route. Various spectroscopic investigations viz. simultaneous thermal analysis (STA), powder X-ray diffraction (XRD), infrared (FT-IR), elemental analysis (ICAP), electron microscopy (SEM, TEM), magnetic measurements (VSM) and Mӧssbauer technique have been employed to ascertain the modulations in structural, magnetic and other microstructural parameters of as-obtained ferrite, thus, establish the formation of single phasic, nanocrystalline, magnetically ordered alloys with novel physico-chemical properties. An increase in Li+ concentration from x = 0.0 to 0.3 inculcates a reduction in the particle size thereby improving electro-magnetic parameters of the doped ferrites. Overall, concentration of the dopant along with the chemical method employed for the synthesis control the size of as-obtained particles and site status within the ferrite lattice structure.

Engendering 0-D to 1-D PbCrO4 nanostructures and their visible light enabled photocatalytic H2S splitting

Nanorods (3214 μmol h−1) exhibited better photocatalytic H2S splitting than spherical nanoparticles (2054 μmol h−1) via a conventional and ultrasonication assisted co-precipitation route.

Methanol steam reforming behavior of copper impregnated over CeO2–ZrO2 derived from a surfactant assisted coprecipitation route

A series of ceria-zirconia solid solutions has been prepared by a surfactant assisted coprecipitation method. After impregnation of copper, their activities have been assessed for methanol steam reforming. The results indicate that the compositions with 10 and 15 at.% loading of copper on Ce0.6Zr0.4O2 exhibit maximum catalytic efficiency. Detailed structural analyses reveal high degree of copper dispersion on the ceria-zirconia matrix. In situ XPS studies confirm reduction of surface CuO species with concomitant lowering of Cu-surface atomic composition and increase of carbon. These evidences point to the formation of large aggregates of copper covered with coke that is suggested to be responsible for on stream activity loss. On regeneration, these aggregates break into a mixture of oxidized (Cu2+) and reduced (Cu0 and Cu+) copper species showing similar activity to the as prepared catalysts. In general, we have attributed catalytic activity to different proportions of copper components in the various forms of these catalysts.

Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

Spinel‐layered composites, where a high‐voltage spinel is incorporated in a layered lithium‐rich (Li‐rich) cathode material with a nominal composition x{0.6Li2MnO3 · 0.4[LiCo0.333Mn0.333Ni0.333]O2} · (1 – x) Li[Ni0.5Mn1.5]O4 (x = 0, 0.3, 0.5, 0.7, 1) are synthesized via a hydroxide assisted coprecipitation route to generate high‐energy, high‐power cathode materials for Li‐ion batteries. X‐ray diffraction patterns and the cyclic voltammetry investigations confirm the presence of both the parent components in the composites. The electrochemical investigations performed within a wide potential window show an increased structural stability of the spinel component when incorporated into the composite environment. All the composite materials exhibit initial discharge capacities >200 mAh g–1. The compositions with x = 0.5 and 0.7 show excellent cycling stability among the investigated materials. Moreover, the first cycle Coulombic efficiency achieve a dramatic improvement with the incorporation of the spinel component. More notably, the composite materials with increased spinel component exhibit superior rate capability compared with the parent Li‐rich material especially together with the highest capacity retention for x = 0.5 composition, making this as the optimal high‐energy high‐power material. The mechanisms involved in the symbiotic relationship of the spinel and layered Li‐rich components in the above composites are discussed.

Facile synthesis of carbon nanotubes supported NiO nanocomposite and its high performance as lithium-ion battery anode

NiO nanocrystals anchored on carbon nanotubes (CNTs) were fabricated via a polyvinylpyrrolidone assisted co-precipitation route. At a current density of 100mAg−1, the composite anode delivers an initial reversible capacity of 962mAhg−1 and retains the capacity to 601mAhg−1 after 50 cycles. In contrast, the reversible capacity of the pure NiO particles faded to 380mAhg−1 immediately and then gradually decreased to 278mAhg−1 after 50 cycles. The significantly improved electrochemical performance of the NiO/CNT nanocomposite is attributed to the formation of conductive networks by CNTs, and large surface areas of NiO nanoparticles grown on CNTs which stabilizes these nanoparticles against agglomeration and reduces the diffusion length for lithium-ions. The present results indicate that NiO/CNT nanocomposite has potential applications in lithium-ion battery anodes.

Structural, microstructure and magnetic properties of strontium hexaferrite particles synthesised by modified coprecipitation method

Strontium hexaferrite (SrFe12O19) particles were synthesised using the modified chemical coprecipitation method. The results indicated that a single strontium hexaferrite phase formed at low annealing temperature 800°C in the presence of surfactant or by oxalic acid addition. Sonochemical assisted coprecipitation route improved the formation of well crystalline strontium hexaferrite phase with Fe3+/Sr2+ molar ratios of 9·23 and 8 annealed at 1000°C for 2 h. The crystallite size of the produced powders increased with increasing annealing temperature. The crystallite size of the formed powders was in the range between 67 and 125 nm. The microstructures of the formed particles appeared as a hexagonal platelet-like structure. Moreover, the addition of surfactant exhibited a uniform homogeneous hexagonal platelet-like structure. The formed ultrafine pure SrFe12O19 powders have good magnetic saturations (44·6–73·6 emu g−1) and wide intrinsic coercivities (692–5612 Oe).

Facile polymer-assisted synthesis of LiNi0.5Mn1.5O4 with a hierarchical micro–nano structure and high rate capability

We report the facile preparation of spinel type LiNi0.5Mn1.5O4 with hierarchical micro–nano structures (LNMO-HMs) and their application as cathode materials for rechargeable lithium-ion batteries. The LNMO-HMs, which were synthesized through a poly(ethylene glycol) (PEG)-assisted co-precipitation route, have a particle size of 5–10 μm, which are composed of nano-particles with a size of about 200 nm. The effect of PEG on the phase purity and morphology of the LNMO products was studied. It was found that as the molecular weight of PEG increased, the lithium nickel oxide impurity decreased at first and then increased slightly. The average size of the nano-particles also showed a similar trend of first a decrease and then an increase, while the secondary micro-particles were enlarged with longer PEG chains. Raman mapping technology proved that the P4332 phase and the Fd3m phase LNMO coexist in the as-prepared samples, but the latter is the mainstay. When applied as cathode materials for lithium-ion batteries, PEG4000-assisted LNMO-HMs showed a remarkably high rate capability and cycling stability. The deliverable discharge capacity exceeded 120 mAh g−1 at 40 C current rate and the capacity retention approached 89% after 150 cycles at 5 C current rate, showing the potential in the application of high rate discharge.