Chemical Co-precipitation Route Research Articles

Top-down and bottom-up approaches to obtain magnetic nanoparticle of Fe3O4 compound: Pulsed laser deposition and chemical route

Our goal in this work was to prepare nanoparticles (NPs) of Fe3O4 using two approaches: top-down and bottom-up. In the former two wavelengths (1064 and 532 nm) were used in the pulsed laser deposition (PLD) technique to produce NPs from α-Fe bulk, with subsequent heat treatment to produce Fe3O4, and in the latter the NPs were produced by chemical co-precipitation route (CR).Transmission Electron Microscopy (TEM) revealed that the as-deposited NPs exhibit a spherical morphology with core/shell structure and with diameters of (8 ± 4) nm (1064 nm) and (16 ± 5) nm (λ = 532 nm) for PLD approach, while for the CR, diameters of 8.0 ± 0.3 and 18.0 ± 0.3 nm were obtained for pure and SiO2-coated samples, respectively. X-Ray diffraction technique with Rietveld method was used to quantify the phases of oxidized NPs, and the percentages obtained were: 58% of Fe3O4 and 42% of α-Fe (532 nm) and 85% of Fe3O4 and 15% of α-Fe (1064 nm). For the samples obtained by CR, no spurious phase was observed in the diffractograms, only a very broad peak of SiO2 was observed around 25°, which indicates that the NPs were coated with SiO2, and this layer is amorphous. From Rietveld refinement, we found that the SiO2-coated sample has the highest Fetet-O-Feoct bond angle, which indicates a greater magnetic coupling between Fe atoms for these samples. Measurements of AC magnetization in different frequencies were carried out for all NPs and a detailed analysis of the dependence of the χ′ peak with T(K) helped to find out the relaxation time of the sample coated with SiO2 is 8.7 × 10−6 s, while for the other samples it was on the order of 10−9 s. Based on the results, it was possible to conclude that the coated sample presents a super spin-glass behavior, while in the other samples a magnetic interaction between NPs and oriented ferromagnetic clusters may be present.

Temperature-dependent photoluminescence and optical thermometry performance in Ca3Bi(PO4)3:Er3+ phosphors

Single phase crystalline Er3+ doped Ca3Bi(PO4)3 (CBP:Er3+) phosphors were prepared using chemical co-precipitation route. The structural, optical, morphological and luminescent characteristics of the CBP:Er3+ phosphors for optical thermometry and optoelectronic applications were examined. The diffraction patterns of the samples were matched well with the standard data with single phase cubic structure and not changed after doping. The reflectance spectrum shows the various absorption peaks owing to Er3+ ions. The field emission scanning electron microscopy (FE-SEM) images disclose that the sample particles have asymmetric and spherical particles with some aggregation. Elemental analysis and mapping confirm the existence of various compositional elements. The PL spectra specifies that the phosphor can be effectively excited by near-ultraviolet (n-UV) LED, which was well-observed from n-UV excitation spectrum. As-prepared phosphor emits the visible emission at 523 (2H11/2 → 4I15/2), 552 (4S3/2 → 4I15/2) and 662 nm (4F9/2 → 4I15/2) under n-UV excitation (376 nm). The calculated color coordinates reveal the green color emission from the phosphor under 376 nm excitation with high color purity. PL variation and fluorescence intensity ratio from the thermally coupled 4S3/2 and 2H11/2 levels of Er3+ ions can be utilized to explore applications in optical thermometry and found the good temperature sensitivity in the range of 300–473 K. Hence, the mentioned structural and optical characteristics of the prepared CBP: xEr3+ phosphors will find fascinating applicability in optical thermometry, and other optoelectronic devices.

Synthesis, characterization, dielectric and magnetic properties of substituted Y-type hexaferrites

Fabrication of a series of zinc–strontium hexaferrites, Sr2Zn2−xMnxFe12−yHoyO22 (x = 0.0–1.0, y = 0.0–0.1) was carries out by chemical co-precipitation route with the aim to enhance the saturation magnetization and coercivity and decrease the resistivity to make the materials applicable for recording media of high-density applications. The synthesized hexaferrites were interpreted by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results of XRD investigation certify the single magnetoplumbite phase formed in hexaferrites with regular crystallite particle size in the 31–38 nm range. Magnetic and dielectric properties of the hexaferrites were also observed. The dielectric parameters (dielectric loss also its tan loss and dielectric constant) were measured at ambient temperature and in 1.0 MHz to 3.0 GHz frequency range. These parameters of Mn–Ho-substituted Zn–Sr hexaferrites showed constant trend with frequency up to a certain value after that resonance sort of behavior was observed. In all the hexaferrites dielectric parameters initially decrease with frequency then become almost constant followed by resonance type behavior. The dielectric parameters of the synthesized samples decrease with dopant content initially but then increase up to maximum dopant level. The saturation magnetization (Ms) and remanence (Mr) increase as the dopant content increases due to magnetic substituents. The squareness ratios of all the nanomaterials synthesized in the present studies is less than 0.5. The coercivity (Hc) decreases by the substitution of Mn and Ho.

An extremely sensitive carbon paste electrode modified with Prussian blue analogue (PbA @CPE) for the electrochemical determination of Tetramisole HCl anthelmintic drug as a food contaminant in beef cuts and infant formula milk powder

Tetramisole hydrochloride (TMS) - the drug of choice for ascariasis- is used as an anthelmintic. In this paper, both qualitative and quantitative determination of TMS in bulk, infant milk powder, and frozen cuts-up bovine meat samples were developed to provide consumersafety. In this paper, chemically modified carbon paste with Prussian blue analogue nanoparticles (PbA-NPs /CP) was developed for determination of TMS utilizing cylic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry methods. In this regard, Prussian blue analogue (PbA) was synthesized by the chemical co-precipitation route. XRD technique was used for crystal structure analysis indicating that the fabricated nanopowder belongs to a cubic structure with lattice constants a=b=c=10.176AThe grain size was estimated approximately equal 20 nm, and the dislocation density was 25×10-4nm-2. The molecular structure was analyzed using Raman spectroscopy, and the elements C, N, O, Co, Ni, Cr, Ir were recorded by EDX spectrum. SEM images showed the particles very fine in spherical shape. Transmittance and reflectance spectra have been measured through wavelength range from 200 nm to 900 nm.Energy gap (Eg) and refractive index (n) of the films were determined suggesting the strong optical absorption. Finally, this method was carried out at pH 4.0 within a linearity range (10.0 × 10−9–1.0 × 10−4) M and a minimum detection limit of 2.7 × 10−9M.

Molybdenum-doped iron oxide nanostructures synthesized via a chemical co-precipitation route for efficient dye degradation and antimicrobial performance: in silico molecular docking studies.

In this research, various concentrations of molybdenum (2, 4 and 6 wt%) doped Fe3O4 nanostructures (Mo-Fe3O4 NSs) were prepared via a co-precipitation technique. Various techniques were then used to investigate the optical, morphological and structural properties of the NSs in the presence of the dopant materials. X-ray diffraction (XRD) was used to investigate the crystalline nature of the prepared NSs and confirm the orthorhombic and tetragonal structure of Fe3O4, with a decrease in crystallinity and crystallite sizes of 36.11, 38.45, 25.74 and 24.38 nm with increasing concentration of Mo (2, 4 and 6%). Fourier-transform infrared (FTIR) spectroscopy analysis was carried out to examine the functional groups in the NSs. Structure, surface morphology and topography were examined via field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), which confirmed the fabrication of nanoparticles and nanorods and a floccule-like morphology with a higher doping concentration and the interlayer d-spacing was calculated using high-resolution (HR)TEM, the results of which were a good match to the XRD data. The presence of Mo, Fe and O in a lattice of Mo (2, 4 and 6%) doped Fe3O4 was confirmed by energy dispersive X-ray spectroscopy (EDS) analysis. The energy band gap (E g) was measured via the optical analysis of pure and doped samples, showing a decrease from 2.76 to 2.64 eV. The photoluminescence (PL) spectra exhibit a higher charge combination rate of electron-hole pairs with a higher concentration of doping. The NSs exhibited excellent catalytic activity (CA) in degrading methylene blue (MB) dye in a basic medium by around 86.25%. Additionally, the antimicrobial activity was tested against Escherichia coli (E. coli) bacteria. Pairs of electrons and holes are the fundamental basis for generating reactive oxygen species that kill bacteria. The significant inhibition zones were calculated against E. coli bacteria at around 3.45 mm compared to ciprofloxacin. In silico docking investigations of the Mo-Fe3O4 NSs for dihydropteroate synthase (DHPS, binding score: 6.16 kcal mol-1), dihydrofolate reductase (DHFR, binding score: 6.01 kcal mol-1), and β-ketoacyl-acyl carrier protein synthase III (FabH, binding score: 5.75 kcal mol-1) of E. coli show the suppression of the aforementioned enzymes as a potential mechanism besides their microbicidal assay.

Chemical and sweet basil leaf mediated synthesis of cerium oxide (CeO2) nanoparticles: Antibacterial action toward human pathogens

The current study explores the bacterial inactivation of CeO2 nanoparticles (NPs) synthesized via chemical co-precipitation (C-CeO2) and green synthesis (G-CeO2) route. In the green synthesis route, the sweet basil leaf extract is used as a reducing agent while CTAB acts as a surfactant in the chemical route. The structural, surface, and optical properties were studied by different physico-chemical techniques. X-ray diffraction pattern of CeO2 nanoparticles confirms face-centered cubic (FCC) crystal system. The crystallite size is reduced for the green synthesized CeO2 nanoparticles. The surface analysis reveals the formation of small-sized CeO2 nanoparticles with agglomeration. The antibacterial activity of C-CeO2 and G-CeO2 nanoparticles were analyzed against Staphylococcus aureus and Escherichia coli bacterial strains which showed their potential for bacterial cell death.

Facile low temperature synthesis of homogeneous CuS nanosheets: An effect of Ga loading on structural, optical, nonlinear and antimicrobial properties

Herein, we report the facile synthesis and characterization of gallium (Ga) doped copper sulfide (CuS) nanosheets (Ga:CuS NSs) via chemical co-precipitation (CCP) route. The phase was studied by XRD, Raman and XPS analyses. Furthermore, from applications point of view, the UV–Vis–NIR, Z-scan measurements, and antibacterial studies were performed on the prepared NSs. XRD/Raman analysis reveals hexagonal structure of NSs and the crystallite size was calculated in range of 6–13 nm. SEM images unveiled an increase in grains size with Ga contents. The band gap values of Ga:CuS NSs were calculated from diffuse reflectance spectra (DRS) using Kubelka-Munk (K-M) theory, which are found in the range of 2.2 – 2.4 eV. The nonlinear absorption coefficient (β) and nonlinear refractive index (n2) were found in range of 1.73 × 10−8 – 1.85 × 10−8 cm/W and 2.61 × 10−13 – 2.15 × 10−13 cm2/W, respectively. The antimicrobial findings showed that the tested Ga:CuS NSs are most effective against Gram positive bacteria. The outcomes spotlight the multifunctional nature of the prepared Ga:CuS NSs for a wide-range of applications.

Soft/hard ferrite nanocomposites: Evaluation of temperature dependent dielectric properties

Nanocomposites of cobalt ferrite (CoFe2O4) and strontium ferrite (SrFe12O19) were synthesized with various weight ratios 1:1, 1:2, 1:4, 1:8 and 1:16, by chemical co-precipitation route with higher content corresponding to SrFe12O19. Dual phase refinement employed for the prepared composites and confirms the presence of independent CoFe2O4 and SrFe12O19 phases. The increasing weight fraction of SrFe12O19 in the prepared composites is in accordance with its increasing weight ratio. An increase in compressive strain in the composites was attributed to larger ionic radius of Sr+2 ions. The electrical behavior in the composites was described by Cole-Cole plots at 250 °C from 20 Hz-106 Hz. An increase in impedance with increasing weight ratio of SrFe12O19 was observed, due to creation of effective scattering centers. Conductivity mechanism was explained by Overlapping large polaron tunneling (OLPT) model. A decrease in dielectric constant with increasing frequency is due to decreasing space charge polarization, due to inability of charge carriers to follow the varying ac field. Decreasing trend in dielectric loss for the prepared composites confirms their utility in microwave absorption applications.

Structural and tunable dielectric properties of cobalt ferrite-based nanocomposites

Nanocomposites C:S-1:4 comprising cobalt ferrite (CoFe2O4), strontium ferrite (SrFe12O19) and C:B-1:4 containing cobalt ferrite (CoFe2O4), barium ferrite (BaFe12O19) were synthesized in weight ratios of 1:4 by chemical co-precipitation route with higher content corresponding to SrFe12O19 and BaFe12O19. Rietveld refinement was employed to confirm the presence of independent CoFe2O4, SrFe12O19 and BaFe12O19 phases. The average crystallite size of CoFe2O4 and SrFe12O19 in C:S-1:4 was observed as 20 nm and 56 nm which depicts an increase as compared to individual components. The observed lattice strain in C:S-1:4 was 0.05% and 0.03% for CoFe2O4 and SrFe12O19. In C:B-1:4, the value of strain was 0.06% and 0.04% for CoFe2O4 and BaFe12O19. Increased lattice strain was observed in the prepared composites. Increase in impedance for the prepared composites was observed from measurements performed in the frequency range 20 –106 Hz. Conduction mechanism was explained by overlapping large polaron tunneling model. Dielectric loss measurements for the prepared composites were observed to decrease establishing their usage in microwave applications.

CuWO4: A promising multifunctional electrode material for energy storage as in redox active solid-state asymmetric supercapacitor and an electrocatalyst for energy conversion in methanol electro-oxidation

• CuWO 4 has been prepared by quick co-precipitation route within 20 min. • ASC device shows specific capacity of 103 mAh g −1 at 1 A g −1 . • ASC device shows retention of 119.4% of initial capacity after 5000 cycles. • ASC device exhibits energy density of 103 Wh kg −1 at power density of 0.95 kW kg −1 . • For methanol oxidation, the CuWO 4 electrode exhibits 38 mA cm −2 at 0.5 V. This article reports the formation the multifunctional CuWO 4 nanoparticles towards the application of gel electrolyte-based supercapacitor and methanol electro-oxidation. The CuWO 4 nanoparticles were synthesized by a quick chemical co-precipitation route within 20 min. The hydrated precursor was treated at 600 °C for 2 h to convert in to final CuWO 4 products. Structural features of the prepared CuWO 4 were investigated by means of X-ray diffraction, electron microscopies, Fourier transform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy. The CuWO 4 electrode exhibits the specific capacity of 415 mAh g −1 at a current density of 2 A g −1 in three electrode configurations in 1 M Na 2 SO 4 and 3 mM KI mixed electrolyte. The electrode shows retention of 86.1% of its initial specific capacity after 10,000 galvanostatic charge–discharge cycles at 30 A g −1 . An asymmetric solid-state device was assembled by sandwiching the PVA-Na 2 SO 4 and 3 mM KI gel electrolyte in between the CuWO 4 nanoparticle and activated carbon electrodes. The device shows the specific capacity of 103 mAh g −1 at a current density of 1 A g −1 and device shows the retention of 93.4% after 5000 galvanostatic charge–discharge cycles at 7 A g −1 . The hybrid device exhibits energy density of 103 Wh kg −1 at power density of 0.95 kW kg −1 . In electro-catalysis of methanol, the CuWO 4 electrode exhibits the high current density of 38 mA cm −2 at 0.5 V and onset potential achieved as 0.38 V in mixed solution of 1 M KOH and 0.5 M methanol.

Dye-sensitized solar cell performance and photocatalytic activity enhancement using binary zinc oxide-copper oxide nanocomposites prepared via co-precipitation route

Zinc oxide nanoparticles (ZnO NPs) and binary ZnO–CuO nanocomposites (ZnO–CuO NCs) were prepared through a simple chemical co-precipitation route. The influence of copper (Cu2+) ions concentration (0.03, 0.06, 0.09, and 0.12 M) on optical, morphological, structural, and elemental characteristics of the ZnO–CuO NCs was examined by appropriate characterization techniques. The visible light reactive CuO created absorption shift to red region that minimized band gap of the ZnO–CuO NCs. The concentration of Cu2+ ions produced appreciable impact on size of the ZnO–CuO NCs. The dye-sensitized solar cell (DSSC) constructed using ZnO–CuO NC photoanode with Cu2+ ions concentration of 0.06 M generated a conclusive solar to electrical energy transformation efficiency of 2.56%, which was a 2.2-times greater over the DSSC encompassed pristine photoanode of ZnO NPs. The electrochemical impedance spectroscopy analysis revealed the longer lifetime of the photogenerated electrons and reduction in the charge recombination rate in the ZnO(0.44)–Cu(0.06) NC photoanode based DSSC. Furthermore, the ZnO(0.44)–Cu(0.06) NC disclosed substantial photocatalytic activity towards methylene blue dye degradation that could be chiefly credited to its particles size induced visible light absorption property.

Structural and thermal properties of pure and chromium doped zinc oxide nanoparticles

Pure ZnO and Cr-doped ZnO nanoparticles have been synthesized via a facile chemical co-precipitation route and their structural, thermal characteristics were discussed systematically. In the experimental producer, the doping concentration has varied the range, 0.05–0.1 M, while calcined at 600 °C. The influence of Cr-doping on the physical characteristics of ZnO nanoparticles was investigated and addressed. As-prepared samples were analyzed via XRD, FTIR, TGA/DTA, BET, and ICP-MS. XRD analysis shows that ZnO and Cr doped ZnO nanoparticles with average particle sizes between 23 and 39 nm were successfully developed with hexagonal wurtzite structure. The FTIR spectroscopy analysis confirms the existence of chromium in the doped ZnO nanoparticles and the formation of ZnO. The TGA/DTA analysis shows that Cr–ZnO nanoparticles are more thermally stable than ZnO nanoparticles. Moreover, the dopant concentration has been analyzed via ICP-MS and showed a good agreement with the expected chromium concentration. The BET surface area measurement shows that 176.25 m2/g and 287.17 m2/g for un-doped ZnO, and 0.1 M Cr-doped ZnO nanoparticles, respectively. Hence, doping of Cr enhances the surface area and thermal stability. Thus, Cr–ZnO nanoparticles show good thermal stability, and high surface area, which is an excellent characteristices of nanomaterials.Graphic abstract

Structural and Magnetic Properties Study of Fe2O3/NiO/Ni2FeO4 Nanocomposites

In the current work, the nanocomposites that consist chiefly of three components—α-Fe2O3, NiO and Ni2FeO4, in two different ratios 2:2:1 (FNN-221) and 2:1:1 (FNN-211), respectively—were produced. The synthesis was done in two steps by following the chemical co-precipitation and mechanical ball-milling route. The presence of individual phase was identified from the XRD data without the detection of any additional impurities. The phase fraction of each component estimated from the profile fitting of XRD patterns were found to be 41.2%, 39.7%, 19.1% in FNN-221 sample and 49.5%, 26.4%, 24.1% for FNN-211 sample, respectively, which were consistent with the experimental values. The total magnetization at 300 K was obtained to be 13.41 emu/g and 10.95 emu/g for FNN-221 and FNN-211 samples, respectively. In FNN-211 compound the zero field coercivity (HC) expanded towards the higher field values thereby signifying the exchange bias behavior. Furthermore, the exchange bias field (Hex) for FNN-211 was obtained as 35.1 Oe.

Introducing magnetic properties in Fe-doped ZnO nanoparticles

Proper correlation among the microstructural, optical and magnetic responses of Fe-doped ZnO nanoparticles has been established in this work. All the Fe-doped ZnO nanoparticles (Zn1−xFexO: x = 0.00, 0.05, 0.10 and 0.15) were prepared using chemical co-precipitation route. Average crystallites size of 18 nm to 28 nm was estimated using Scherrer’s formula. Compressive microstrain was detected in pristine ZnO samples, which moved toward tensile regime upon introducing Fe ions of different weight percentages. Mean crystallites size obtained from Scherrer’s formula was found in almost exact match with the particle size estimated from HRTEM images. Nearly spherical ZnO nanoparticles were seen in HRTEM images and negligible agglomeration among particles was also observed. Direct optical band gaps were found in the range of 2.89–3.24 eV as estimated from Tauc plots. A decent ferromagnetic signature in non-magnetic ZnO nanoparticles was also introduced at room temperature with the doping of Fe ions.

Synthesis and Rheological Properties of Magnetic Chitosan Hydrogel

The aim of the present work is first to synthesis a magnetic chitosan hydrogel (chitosan ferrogel) using the blending method and second to study it rheological behavior. Magnetic components ( maghemite particles γ-Fe2O3 ) were synthesized via a simple chemical co-precipitation route also called Massart's procedure. Before being dispersed in chitosan network, γ-Fe2O3 particles were covered with a cationic polyelectrolyte (Polydiallyldimethylammonium chloride; PDADMAC) and the exact quantity required to cover the entire surface of maghemite particles was determined by Electrophoretic mobility. The successful functionalization of maghemite particles was confirmed by zeta potential measurement. The prepared ferrogel was gelified using glyoxal as crosslinking agent. The effect of continuous magnetic field on rheological properties of the elaborated ferrogel was studied, under controlled temperature before and after the gelation process, using a rotating rheometer fitted with a new magneto-rheological cell. Moreover the influence of iron oxide content on the gelation time of magnetic hydrogel was studied by comparing two ferrogels with different maghemite particles content. Flow and viscoelastic measurements showed that applying magnetic field facilitates the formation of a new structure (column-like arrangements), which was confirmed by in situ optical microscopic observation. Kinetic study was investigated by mechanical spectroscopy and demonstrates that the gelation time depends on both iron oxides content and magnetic field.

Influence of Ni2+ ions on the structural, morphological, photoluminescence, photo-catalytic and anti-bacterial studies of Cd0.9Zn0.1S nanostructures.

The present investigation reported the controlled synthesis of Cd0.9Zn0.1S and Cd0.89Zn0.1Ni0.01S nanostructures by simple chemical co-precipitation route. The XRD analysis confirmed the cubic structure of CdS on Zn doped CdS and Zn, Ni dual doped CdS without any secondary/impurity phases and no alteration in CdS cubic phase was noticed by Zn/Ni addition. The shrinkage of crystallite size from 69 to 43 Å and the variation in lattice constants and micro-strain were described by the addition of Ni and the defects associated with Ni2+ ions. Microstructural and optical studies of the prepared films were carried out using scanning electron microscope (SEM), UV-visible spectrometer and photoluminescence (PL) spectra. The enhanced optical absorbance in the visible wavelength and the reduced energy gap by Ni substitution showed that Cd0.89Zn0.1Ni0.01S nanostructures are useful to improve the efficiency of opto-electronic devices. The functional groups of Cd-S/Zn-Cd-S/Zn/Ni-Cd-S and their chemical bonding were verified by Fourier transform infrared (FTIR) studies. The elevated visible PL emissions such as blue and green emissions by Ni addition was explained by decreasing of crystallite size and generation of more defects. Zn, Ni dual doped CdS nanostructures are identified as the probable an efficient photo-catalyst for the degradation of methylene blue dye. The liberation of more charge carriers, better visible absorbance, improved surface to volume ratio and the creation of more defects are accountable for the current photo-catalytic activity in Zn/Ni doped CdS which exhibited better photo-catalytic stability after sex cycling process. The better bacterial killing ability is noticed in Ni doped Cd0.9Zn0.1S nanostructure which is due to the collective effect of lower particle/grain size and also higher ROS producing capacity.

Influence of defects on the structural, optical, photoluminescence and magnetic properties of Cr/Mn dual doped ZnO nanostructures

Cr (2%) doped ZnO and Cr, Mn (Cr = 2% and Mn = 2–4%) dual doped ZnO nanostructures were synthesized by chemical co-precipitation route. The hexagonal structure of Cr/Mn doped ZnO was not distorted by Mn doping and no secondary/impurity phases of Cr/Mn were detected in the XRD pattern. The reduced crystallite size at Mn = 2% is due to depression of growth rate and the dissimilarities between dopant and host ions and elevated crystallite size at 4% is accountable for the more defect sites in Zn-Cr-O lattice. The stable c/a ratio (~ 1.603) indicates that the hexagonal ZnO wurtzite structure of the synthesized composite is not affected by Mn substitution. The reduced crystallite size and the elevated UV–visible absorption at the higher wavelength side i.e., visible range at Mn = 2% recommended it for improved photocatalytic and efficient for solar cell applications. The broadening of energy gap at Mn = 2% is explained by Burstein-Moss (BM) band filling effect through energy level diagram. The presence of Zn-O-Cr/Mn bonding is confirmed by Fourier transform infra-red (FTIR) studies. The elevated PL emission and the intensity ratio between the green and blue emissions revealed the existence of more oxygen vacancies and oxygen related defect sites in Zn-Mn-Cr-O lattice. The exhibited room temperature ferromagnetism (RTFM) with strong magnetization in Cr, Mn doped ZnO is induced by both the oxygen vacancy mediated bound magnetic polarons (BMP) and the enhanced exchange coupling among the free electrons and local spin polarized electrons.

Investigation on microstructure, energy gap, photoluminescence and magnetic studies of Co and Cu in situ doped ZnO nanostructures

Co (3%)-doped ZnO and Co, Cu (Co = 3% and Cu = 2 to 4%) dual-doped ZnO nanostructures were prepared using chemical co-precipitation route. The structural analysis indicated no alteration in the structure of hexagonal ZnO and the absence of secondary/impurity phases induced by Co/Cu addition into ZnO. The reduction of crystallite size (≈ 25 nm) at Cu = 2% is due to the suppression of growth rate and the dissimilarities between Co2+/Cu2+ and Zn2+ ions, and the enhanced crystallite size (≈ 29 nm) at Cu = 4% is responsible for the more defect sites associated with interstitials and vacancies of Co2+ and Cu2+ in Zn–O lattice. The persistent c/a ratio (~ 1.602) signified the absence of structural modification by Co/Cu substitution for Zn. The decrease in optical absorption, increase in transmittance and the enhanced energy gap of ZnO by Co/Cu addition were discussed by consideration of dopants and the stimulated defect states. The continuous widening of energy gap (ΔEg ≈ 0.08 eV) with Cu substitution is clarified using Burstein–Moss (BM) band filling effect through energy-level diagram. The existence of Zn–O and Zn–Co/Cu–O bondings around ≈ 442–468 cm−1 was verified by Fourier transform infra-red analysis. The elevated intensity ratio between green and ultra-violet photoluminescence (IG/IUV) at higher Cu concentration, Cu = 4% (≈ 0.74), revealed the occurrence of higher number of defects, particularly oxygen-related defect states, in (Zn, Co, Cu)O lattice. The observed room temperature ferromagnetism (RTFM) in Co, Cu-doped ZnO nanostructures is discussed based on the oxygen vacancy-mediated bound magnetic polarons (BMP) and the exchange interaction between the free electrons and local spin-polarized electrons.

Fabrication and characterization of W-Ni nanocomposites via a facile chemical co-precipitation route

A novel method by combined chemical co-precipitation and hydrogen reduction was proposed in this work to synthesize nanopowders of W-10wt.%Ni. The morphology, microstructure and properties of the nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). It was found that the average grain size of NiW nanopowders were 18–40 nm. For evaluation of the thermal stability of the synthesized powders, further heat treatment under different temperatures were carried out, which demonstrated the addition of Ni influence the diffusion coefficient which leading to the variation of sintering structure. The form of NiW intermetallic compound inhibits the grain growth of nanopowder.

Synthesis and characterization of palladium nanoparticles by chemical and green methods: A comparative study on hepatic toxicity using zebrafish as an animal model

Nanoparticles synthesized by chemical methods are of a matter of concern, whereas, the green methods are said to be eco-friendly and environmentally safe. In this study, the toxicity of palladium nanoparticles (Pd NPs) synthesized through chemical co-precipitation and green route method using Annona squamosa seed kernels (As-Pd NPs) were evaluated using zebrafish as an animal model. The synthesized nanoparticles (NPs) were characterized using UV‐Visible spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS) and Zeta potential. Zebrafish (Danio rerio) were exposed to 0.4 ng/L of Pd NPs and As-Pd NPs for 96-h, further oxidative stress parameters and histological changes were evaluated. The superoxide dismutase (SOD), catalase (CAT) activity and the lipid peroxidation (LPO) levels were elevated in the Pd NPs groups. But in the As-Pd NPs group, the SOD activity showed a biphasic nature while the CAT activity gradually declined till the 96-h compared to the control and Pd NPs groups. The LPO levels in the As-Pd NPs groups showed a measurable increase till 72-h and sudden decline at the end of 96-h. Anomalies in the histological changes such as ruptured hepatocytes, sinusoidal congestion, vacuolation and accumulation of erythrocytes were observed in both the NPs treated groups but As-Pd NPs exhibited lesser lesions than the control and Pd NPs groups. However, our present study reveals the possible reliability of the nanoparticles and the mechanism of scavenging activity suggesting that the As-Pd NPs synthesized by green route are less toxic comparing to the chemically synthesized Pd NPs.