Mn-doped ZnO Nanoparticles Research Articles

Protic Ionic Liquid Assisted Synthesis, Structural, Optical and Magnetic Properties of Mn-Doped ZnO Nanoparticles

Protic Ionic Liquid Assisted Synthesis, Structural, Optical and Magnetic Properties of Mn-Doped ZnO Nanoparticles

Correlation between structural, optical and magnetic properties of Mn-doped ZnO

We have investigated the structural, optical and magnetic properties of Mn-doped ZnO nanoparticles with different doping concentrations (0, 2, 4 and 6 %) synthesised by sol–gel method. Lattice parameters, cell volume, atomic packing fraction, crystallite size and confirmation of hexagonal wurtzite crystal structure have been studied by X-ray diffraction data. Surface morphology as well as grain size and the presence of all the elements have been confirmed by scanning electron microscope and energy-dispersive X-ray spectroscopy, respectively. The decrease in lattice parameters ratio (c/a) with Mn concentration indicates lattice distortion with the incorporation of Mn2+ ions at Zn2+ site of ZnO structure, which has been confirmed by Raman analysis. It has been observed that microstructure defects induced some extra Raman vibration modes. Ultraviolet–visible analysis shows that absorption edge lies in visible region, and encroachment in visible region increases, while energy band gap decreases with the increase in Mn concentrations. We have recorded FTIR spectra at room temperature to study the vibrational bands present in Zn1−x Mn x O samples. The magnetic study of samples indicates ferromagnetic behaviour at room temperature. The magnetic properties increases with doping concentration due to small lattice distortion and defects.

Ferroic behavior induced by oxygen vacancies in Mn-doped ZnO compounds

Mn-doped ZnO nanoparticles were successfully synthesized through the sol–gel technique. X-ray diffraction results showed that Mn doping did not disturb the hexagonal wurtzite structure of ZnO and no secondary phases were identified. Raman studies indicated the presence of defects in the form of oxygen vacancy clusters created due to Mn doping. Ferromagnetic-like curves were determined at room temperature for the sample with low doping (2% Mn). The results indicate that the observed ferromagnetism at room temperature can essentially be attributed to interactions mediated by magnetic impurities throughout the large number of oxygen vacancies created by Mn ions.

Synthesis, structural and optical properties of Mn doped ZnO nanoparticles and their antibacterial application

In the present investigation, MnxZn1-xO (x = 0.05, 0.075 and 0.1%) nanoparticles have been synthesized by simple precipitation method. Their structural, morphological and optical properties were examined by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Differential scanning calorimetry (DSC) and UV-Visible spectroscopy. The Powder X-ray diffraction studies confirmed that the manganese doped ZnO have a single phase nature with hexagonal wurtzite structure and Mn successfully incorporated into the lattice position of Zn in ZnO lattice. The FESEM and HRTEM images are coincided with each other for aggregation of particles in nature. The elemental analysis of doped samples has been evaluated by EDX. The antibacterial activity of Mn doped ZnO nanoparticles has also been examined.

Diverse Spectroscopic Studies and First-Principles Investigations of the Zinc Vacancy Mediated Ferromagnetism in Mn-Doped ZnO Nanoparticles

A systematic study on the room temperature ferromagnetism (RTFM) in undoped and Mn-doped ZnO nanoparticles (NPs) prepared by the coprecipitation method has been reported. The neutral and singly ionized zinc vacancy defects exhibited in the results of photoluminescence (PL), micro-Raman spectroscopy, and electron paramagnetic resonance (EPR) studies are found to be of ferromagnetic origin in bare ZnO, and it has been confirmed that Mn2+ ions substitutionally enter at Zn2+ sites in wurtzite ZnO. The results of positron annihilation and coincidence Doppler broadening measurements corroborate the Zn vacancies and their clusters. It is observed that in Mn:ZnO, the magnetic ordering is changed from ferro- to paramagnetic because of interacting adjacent Mn–Mn ions. The higher saturation magnetization of 565 × 10–3 emu/g is explained by a quasi indirect exchange mechanism based on the interaction of bound magnetic polarons formed by the Zn vacancies (VZn) and nearby Mn ions. Further, first principle calculations ...

Correlation between oxygen vacancies and dopant concentration in Mn-doped ZnO nanoparticles synthesized by co-precipitation technique

Zn1-xMnxO nanoparticles with different Mn concentration (0.01–0.1) were synthesized by co-precipitation technique. The structural, optical and magnetic properties of Zn1-xMnxO nanoparticles were investigated. The Zn1-xMnxO nanoparticles keep wurtzite structure without any impurity phase until the Mn concentration reaches 0.1. The magnetic measurements show ferromagnetism of Zn1-xMnxO nanoparticles is improved with increase of the Mn concentration (x = 0.01–0.08). The optimal doping concentrations for enhancement in ferromagnetism of Zn1-xMnxO nanoparticles is 0.08. The reduction in ferromagnetism of Zn0.9Mn0.1O is caused by coexistence of the Mn3+ and Mn2+ ions, which can form antiferromagnetic interaction. Results of UV-vis absorption spectra indicate that the bandgap and carrier concentration increase gradually with increasing Mn concentration, which can be explained by Burstein-Moss shift. Singly charged oxygen vacancies in the Zn1-xMnxO were analyzed according to the visible photoluminescence spectra results. Experiment results reveal that the singly charged oxygen vacancies and surrounding Mn2+ ions form bound magnetic polarons model, which is responsible for the origin of ferromagnetism in Mn-doped ZnO nanoparticles.

Porous Mn-doped ZnO nanoparticles for enhanced solar and visible light photocatalysis

Porous Mn-doped ZnO (ZnO:Mn) nanoparticles with an average diameter of ca. 21nm were prepared by a simple and cheap solvothermal process involving no templates, post-synthetic annealing or etching. The particles produced were characterized by XRD, Raman spectroscopy, SEM, TEM, XPS, diffuse reflectance spectroscopy and BET surface area measurements and the effects of Mn2+-doping on the structural, optical and photocatalytic properties of ZnO particles were investigated. The particles doped with 3mol% Mn2+ were found to exhibit the highest catalytic activity toward the photodegradation of the Orange II dye under solar light irradiation. Our results demonstrate that Mn2+-doping shifts the optical absorption to the visible region, increases the specific surface area of the photocatalyst and reduces the recombination of electron-hole pairs. The influence of various operational parameters (amount of catalyst, concentration of dye and pH) on the photodegradation and the photocatalytic mechanism were studied. Finally, we demonstrated that the ZnO:Mn photocatalyst is stable and can be easily recycled up to ten times without any significant decrease in photocatalytic activity.

Structural, Optical and Room Temperature Magnetic Study of Mn-Doped ZnO Nanoparticles

Undoped and Mn-doped ZnO nanoparticles (Zn[Formula: see text]MnxO), with nominal weight percentages [Formula: see text], have been synthesized by co-precipitation technique. The synthesized nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR). From XRD analysis, the compound ZnMnO3is formed for [Formula: see text] with cubic structure ([Formula: see text][Formula: see text]Å) and its concentration increases with x. Moreover, XRD analysis reveals the wurtzite hexagonal crystal structure for ZnO. The lattice parameters (a and c) of Zn[Formula: see text]MnxO are calculated and they increase with the doping concentration of Mn as a consequence of the larger ionic size of Mn[Formula: see text] ions compared to Zn[Formula: see text] ions. The crystallite size is calculated for all the samples using Debye–Scherrer’s method (SSM), Williamson–Hall methods (UDM, USDM and UDEDM) and Size-Strain Plot method (SSP), and the results are in good agreement with TEM. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra that shows a peak shift between undoped and doped ZnO. The energy bandgap [Formula: see text] is calculated for different concentrations of Mn [Formula: see text] by using the UV-visible optical spectroscopy, between 300[Formula: see text]nm and 800[Formula: see text]nm, showing a noticeable drop in [Formula: see text] with x. At room temperature, the magnetization of the samples reveals the intrinsic ferromagnetic (FM) behavior of undoped ZnO, ferromagnetic behavior of ZnxMn[Formula: see text]O [Formula: see text] and the co-existence of ferromagnetic and paramagnetic behavior for ZnxMn[Formula: see text]O [Formula: see text]. This ferromagnetism is decreased for the doped samples as a consequence of antiferromagnetic coupling between Mn ions. The two samples correspond to [Formula: see text] and [Formula: see text], tend to be superparamagnetic because of the formation of single domain particles as a consequence of small particle size. [Formula: see text] shows an optimum value of Mn concentration for maximum saturation magnetization and the best ferromagnetic nature.

Influence of Lithium doping on the correlated ferromagnetic ordering and red shift of band gap in weakly Mn-doped ZnO nanoparticles

Manganese and Lithium co-doped ZnO nanoparticles were synthesized by a simple wet chemical method. In this study we report the influence of lithium on room temperature ferromagnetic ordering of Mn-doped ZnO nanoparticles. The influence of defect chemistry on the exchange interaction between localized magnetic moments of Mn2+ ions and free charge carriers responsible for room temperature ferromagnetism has been studied in detail. The study also reveals a strong correlation between enhanced ferromagnetic ordering and red shift of optical band gap in (Li, Mn) co-doped ZnO nanoparticles.

Systematic approach on the fabrication of Mn doped ZnO semiconducting nanoparticles by mixture of fuel approach for antibacterial applications

Undoped and Mn-doped ZnO nanoparticles were synthesized by sol–gel auto combustion method with precursors such as Zinc and Manganese nitrates with the assistance of Ammonium acetate and Urea as fuel by increasing the manganese concentration in zinc oxide and their structural, morphological, optical, magnetic and antibacterial properties were studied by XRD, field emission scanning electron microscope, transmission electron microscope, photoluminescence, fourier transform infrared spectroscope and vibrating sample magnetometer (VSM). In this article magnetic property and antibacterial activity were estimated at Mn (X = 0.05, 0.15 and 0.25 wt%) doping level in ZnO. Pseudomonas aeruginosa is a Gram negative, great metabolic diversity (soil, water and atmosphere) bacteria and also in its role as an opportunistic human pathogen, plant pathogen, soil bacterium, which may affect the spintronics and biomedical devices. The magnetization curves obtained using VSM show a sign of paramagnetism when the Mn doping level is 0.05 and 0.15 wt% and a behavior of ferromagnetism was observed at 0.25 wt% due the secondary phase Mn3+ and Mn4+ interactions, these interaction not only enhance the magnetic property, but also exhibits good antibacterial efficiency. So there is an immense importance for the fabrication of spintronic and biomedical devices with antibacterial activity to the sustainable technologies.

Synthesis and Characterization of ZnO and Mn-Doped ZnO Nanoparticles

Synthesis and Characterization of ZnO and Mn-Doped ZnO Nanoparticles

Effect of doping on structural, physical, morphological and optical properties of Zn1−xMnxO nano-particles

The effect of Mn doping on the structural physical, morphological and optical properties of Zn1−xMnxO nanoparticles prepared by novel co-precipitation route. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. Broad peaks observed in XRD patterns indicates that all samples were nanocrystalline with hexagonal phase. Studied lattice parameters and volume of unit cell as a function of Mn content. The crystalline size, lattice strain, stress and strain energy density of Mn doped ZnO nanoparticles were determined from XRD patterns using W–H three models. The results obtained yields strain, stress and strain energy density increases with increasing Mn content and crystalline size decrease. Among the developed models, UEDM model was observed to be the best fit for co-precipitation route. The transmission electron microscopy (TEM) result confirms that mean particle size of Zn1−xMnxO nanoparticles were about 20–27nm. The optical study shows the decrease in optical energy band gap with Mn doping and confirm that Mn2+ ions substituting in ZnO materials. The u parameter and bond length of Mn doped ZnO nanoparticles were also investigated in this paper.

Synthesis and characterization of Mn-doped ZnO diluted magnetic semiconductors

In the present work undoped and Mn doped ZnO nanoparticles (ZnO:Mn), diluted magnetic semiconductors, were successfully synthesized by the sol–gel method at room temperature. The morphology of ZnO nanoparticles constituted by flower-like structures with hexagonal morphologies that changed significantly after the incorporation of Mn. Rietveld refinements results showed that Mn ions are successfully doped into ZnO matrix without altering its wurtzite phase. Meanwhile, Raman spectroscopy analyses confirm the wurtzite structure of undoped ZnO and ZnO:Mn nanoparticles. The lattice parameters increase with increasing Mn content due to the large ionic radius of Mn2+ compared to that of Zn2+. Electron spin resonance measurements were performed to gain information about oxidation state and site occupancy of the magnetic Mn ions in the ZnO lattice. Moreover, UV–vis absorption spectra have been utilized to calculate the optical band gap of the undoped ZnO and ZnO:Mn nanoparticles before and after different γ-irradiation doses. The band gap of ZnO:Mn (2%) is 2.62eV which is noticeably smaller than the 3.26eV of undoped ZnO. The thermal decomposition properties of the prepared nanoparticle samples were also studied using simultaneous Thermogravimetric analysis in temperature range from 30 to 500°C.

The Influence of Montmorillonite Incorporation in Mn-Doped ZnO Nanoparticles for Photocatalytic Degradation of Organic Dyes

The present study compares the photocatalytic decolorization ability of bare Mn-doped ZnO and montmorillonite modified Mn-doped ZnO nanoparticles towards aqueous solution of organic dyes (methylene blue and malachite green) under UV light irradiation. Both photocatalysts were synthesized using co-precipitation method and characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier-transform infrared absorption, electron spin resonance, and diffuse reflectance spectroscopy. Comparison of degradation efficiency demonstrated that montmorillonite modified Mn-doped ZnO nanoparticles exhibited higher activity than bare Mn-doped ZnO nanoparticles.

Ensemble effect of intrinsic defects and Mn ions on the enhancement of third order nonlinearity of ZnO nanoparticles

Mn doped ZnO nanoparticles were synthesized by the chemical co-precipitation method and XRD confirms the hexagonal structure of nanoparticles with good crystallinity. From TEM analysis, the average crystallite size of the nanoparticles is evaluated as 7–13 nm. All the prepared nanoparticles exhibit reverse saturable absorption in open aperture Z-scan measurements. The experimental data best fits for two-photon absorption along with saturable absorption and the obtained β values are found to be in the range of 0.3–0.5 × 10−10 m W−1. The enhancement of β upon increasing Mn concentration is attributed to the increase of absorption due to defect states created by Mn doping. EPR and PL measurements provide evidence of the presence of zinc vacancy defects. The self-defocusing nonlinearity exhibited in Mn doped ZnO nanoparticles at 532 nm indicates the reverse saturable absorption (RSA) based optical limiting behavior.

Efficient and green oxidative degradation of methylene blue using Mn-doped ZnO nanoparticles (Zn1−xMnxO)

Mn-doped ZnO nanoparticles, Zn1−xMnxO, were synthesised by a polyethylene glycol (PEG) sol–gel method and the physicochemical properties of compounds were characterised by atomic absorption spectroscopy (AAS), energy-dispersive X-ray analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The catalytic degradation of an organic dye, methylene blue (MB), in the presence of Zn1−xMnxO as the catalyst and hydrogen peroxide (H2O2) as the oxidant at room temperature in water has been studied. Effects of oxidant, catalyst amount, catalyst composition, pH value of the solution and an OH-radical scavenging agent on the degree of the decomposition of MB dye were also studied.

Mn-Doping Effects on Structure and Magnetic Properties of ZnO Nanoparticles

Magnetic properties of Mn-doped ZnO nanoparticles, synthesized by the co-precipitation method, have been studied. The presence of a single crystalline phase identified as the wurtzite structure was determined by X-ray diffraction measurements in all the samples. Additional Bragg reflections associated to manganese oxides phases have been found in the 10 mol\(\%\) Mn-doped ZnO sample which are more evident after calcinating at high temperatures. Magnetization measurements reveal a paramagnetic behavior with antiferromagnetic interactions becoming weaker as the Mn concentration is increased. For the 10 mol\(\%\) Mn-doped ZnO sample the coexistence of a paramagnetic and a ferromagnetic phase has been determined. The latter phase was associated with the presence of Mn\(_3\)O\(_4\) compound which is in agreement with the structural results.

Enhancing visible light responsive photocatalytic activity by decorating Mn-doped ZnO nanoparticles on graphene

Novel visible-light-responsive Mn-doped ZnO/Graphene nanocomposite photocatalysts were synthesized using a facile single step solvothermal method. A range of techniques including X-Ray diffraction (XRD), a high resolution transmission electron microscope (HR-TEM), a transmission electron microscope (TEM), a scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) surface area analyzer and X-ray photoelectron spectroscopy (XPS) were employed to characterize the as-prepared composites. UV–visible diffuse reflectance spectroscopy (DRS) was used to study the optical properties, which confirmed that the spectral responses of the nanocomposite catalysts were gradually extended to the visible-light region as Mn dosage increased. Fluorescence emission spectra verified that Mn-doped ZnO/Graphene nanocomposites possess enhanced charge separation capability compared to ZnO/Graphene, Mn-doped ZnO and pure ZnO. The photocatalytic activity was investigated by following the degradation of methylene blue (MB), a model dye under visible light irradiation. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The results demonstrated that Mn-doped ZnO/Graphene nanocomposites efficiently bleached out the MB, showing an impressive photocatalytic enhancement over Mn-doped ZnO and pure ZnO samples. The enhanced activity of composite photocatalysts can be attributed to large adsorption by the dyes, enhanced visible light absorption and efficient charge separation and fast transfer processes.

Transition-metal-doped ZnO nanoparticles: Synthesis, characterization and photocatalytic activity under UV light

ZnO nanoparticles doped with transition metals (Mn and Co) were prepared by a co-precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-rays, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy and diffuse reflectance spectroscopy. The photocatalytic activities of the transition-metal-doped ZnO nanoparticles were evaluated in the degradation of methyl orange under UV irradiation. ZnO nanoparticles doped with 12at.% of Mn and Co ions exhibited the maximum photodegradation efficiency. The experiment also demonstrated that the photodegradation efficiency of Mn-doped ZnO nanoparticles was higher than that of Co-doped ZnO nanoparticles. These results indicate that charge trapping states due to the doping were the decisive factor rather than the average particle size and energy gap. Moreover the effect of pH values on the degradation efficiency was discussed in the photocatalytic experiments using 12at.% Mn- and Co-doped ZnO nanoparticles.

Natural Zeolite Incorporated in Zinc Oxide Nanoparticles Doped with Manganese for Degradation of Organic Dye in Water under UV Light Irradiation

In this study, the photocatalytic degradation of methylene blue has been investigated using natural zeolite modified Mn-doped ZnO nanoparticles synthesized by co-precipitation method. Comparison of degradation efficiency demonstrated that natural zeolite modifiedMn-doped ZnO exhibited higher activity than bare Mn-doped ZnO.