Cobalt Doped Zinc Oxide Nanoparticles Research Articles

Polyol synthesis of cobalt doped zinc oxide green nano-pigments: Colorimetry assessments and chemical synthesis parameters optimization

Cobalt-doped zinc oxide nanoparticles were synthesized as inorganic nano-pigments by the Polyol chemical preparation method, which is a simple and cost-effective method. Results showed that ethylene glycol (EG) should be utilized for synthesis of nanoparticles with smaller average crystallite size and better crystallinity. Other factors such as molar ratio of cobalt nitrate(Co(No3)2) to zinc acetate(Zn(Ac)2, reaction time, molar ratio of water and sodium hydroxide(NaOH) to the zinc acetate, surfactant and its molar ratio to the zinc were optimized via Taguchi design. The optimum sample was prepared under conditions such as the cobalt nitrate to zinc molar ratio of 0.01, reaction time of 5h, and Triton X100 (molar ratio of 0.2). X-Ray diffraction analysis demonstrated that average crystallite size of the optimum sample was 11 nm. FESEM revealed the uniformity of the powders having nearly a rod-like structure with low aspect ratios. Besides, the impacts of the effective synthesis factors on the colorimetric properties were optimized. Accordingly, the optimum sample revealed a green region with brightness of 58.89(L*), color purity (a* = −22.82), and color hue of 166.89(h°). Average crystallite size, amorphous phase percentage and colorimetric properties correlations have been investigated for the first time. Placement of more cobalt atoms in the ZnO structure raises the brightness coordinate and results more greenness in the color and increase of the crystal size does not directly affect the brightness coordinate.

Cubic engineering approached a novel needle-structured cobalt-doped zinc oxide interconnected with carbon nanofiber as a composite for the determination of toxic 4-nitrophenol in environmental water samples

It is essential for developing an effective and accurate method for analysis for detecting 4-nitrophenol (4-NP), as its harmful effect is one of the most frequent environmental concerns. In this work, the 4-NP was detected by the CNF/CZO nanocomposite. The cobalt-doped zinc oxide (CZO) was synthesized utilizing a simple hydrothermal technique and carbon nanofiber (CNF) was combined with cobalt-doped zinc oxide (CZO) to get CNF/CZO nanocomposite. The morphological and chemical characteristics of the CNF|CZO nanocomposite have been studied using several characterization techniques. The CZO nanoparticles have equal dispersion across the surface of the CNF and the nanocomposites were modified with a glassy carbon electrode (GCE), which is utilized as a working electrode for the electrochemical studies. Hence, the CNF|CZO the nanocomposite was confirmed using field emission scanning electron microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray analysis, X-ray Diffraction Analysis, and X-ray Photoelectron Spectroscopy, Fourier-transform infrared spectroscopy, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry research, and Differential Pulse Voltammetry studies were done. Hence, the GCE|CNF|CZO electrode displays a low detection limit of 0.2 μM, a wide linear response range of 0.01–520 µM, and a higher sensitivity of 0.0137 μA μM−1 cm−2. Further, the GCE|CNF|CZO electrode detected 4-NP in environmental water samples and also showed exceptional selectivity, repeatability, stability, and reproducibility. Hence, we conclude that GCE|CNF|CZO electrode exhibited good catalytic activity due to the inherent interaction between CNF and CZO providing an electron transfer network and high catalytic activity towards 4-NP detection.

Synthesis and characterization of cobalt doped zinc oxide nanoparticles and their application for catalytic reduction of methylene blue dye

The co-precipitation approach has been used in the current research work to synthesize cobalt-doped zinc oxide nanoparticles (ZnO NPs) employing zinc and cobalt nitrate hexahydrate as precursor salts. Ultraviolet-visible spectra and Fourier transform infrared were used to confirm that the manufacturing procedure was efficient and that the synthesized sample contained a range of unique binding sites. The catalytic efficacy of the prepared nanoparticles for the reduction of Methylene blue dye in the presence of NaBH4 as a reducing agent has been investigated. The concentration of methylene blue, the catalyst dose, and the concentration of sodium borohydride all play significant roles in the catalytic reduction of methylene blue (MB). The best result for the complete reduction of methylene blue was obtained in 14 min of reaction time. Catalytic reduction of methylene blue in the involvement of synthesized nanoparticles was found to be followed by the Langmuir-Hinshelwood mechanism. Concerning this process, the reduction reaction is affected by the quantity of methylene blue, catalyst, and sodium borohydride. This effective catalytic activity of Co-doped ZnO nanoparticles suggests that these NPs can work wonders as nano-catalysts for the reduction of hazardous dyes.

Hydrothermal-assisted synthesis of Co-doped ZnO nanoparticles catalyst for sodium borohydride dehydrogenation and photodegradation of organic pollutants in water

In recent years, studies on dye removal and hydrogen energy have gained momentum. However, these studies are still not in the desired position. Existing biological and physical methods for dye removal are quite inadequate. In hydrogen production, the efficiency is very low when a catalyst is not used. It is important to obtain inexpensive catalysts for both purposes. For this purpose, Cobalt doped Zinc oxide nanoparticles (Co-doped ZnO NPs) were synthesized using a one-pot flash combustion approach. The photocatalytic activity and hydrolysis process of the produced catalyst on NaBH4 were evaluated. The photocatalytic activity of Co-doped ZnO NPs was investigated for decolorization against certain dyes under sunlight irradiation. Co-doped ZnO NPs were analyzed for hydrogen production from NaBH4 hydrolysis. It has been determined that the nanomaterial has a superior catalytic activity with Turnover frequency (TOF) of 1682.3 min−1, 32.45 kJ/mol enthalpy (∆E),-158.4 J/mol.K entropy (∆S), and 34.94 kJ/mol activation energy (EA) obtained as a result of the hydrolysis reaction of Co-doped ZnO NPs. Their reusability was found to be 72.5% at the 4th cycle. The photocatalytic activity of the Co-doped ZnO NPs was found 81.22% (120 min) and 86.98% (90 min) against RhB and MB dyes, respectively. According to the results obtained, it has been seen that Co-doped ZnO NPs are reusable catalysts with high catalytic activity for hydrogen production as a clean energy source. At the same time, it was emphasized that a photocatalyst with high catalytic activity was obtained for wastewater treatment.

ZnO and cobalt decorated ZnO NPs: Synthesis, photocatalysis and antimicrobial applications

The rapid growth of pollutants, both biological and non-biological, puts environmental systems in jeopardy. In view of this, the current study demonstrates the synthesis of undoped and Cobalt-doped zinc oxide nanoparticles (Co doped ZnO NPs) via co-precipitation method. The confirmation of incorporation of the Co dopant into ZnO NPs was verified through various spectroscopic and microscopic techniques. UV-absorption spectra of cobalt-doped ZnO NPs revealed a red shift with change of absorption spectra from 356 nm to 377 nm as compared to undoped ZnO NPs. XRD studies inferred that the average crystallite size of 0.5% and 1% Co-doped ZnO powder was obtained to be ∼16 nm and 14 nm respectively. A drop in band gap value from 3.48 eV to 3.30 eV provided as substantive evidence of the successful integration of Co2+ ions inside the ZnO matrix. FESEM and HRTEM studies revealed that the obtained ZnO NPs are in narrow size distribution (15–20 nm) with a wurtzite crystal structure. The synthesized ZnO and Co–ZnO NPs showed excellent photocatalytic and antimicrobial potency towards reactive brown dye (RB-1) and two bacterial strains, respectively. 1% Co-doped ZnO demonstrated the maximum photocatalytic activity (∼95%), in contrast to 0.5% Co-doped ZnO and undoped ZnO. Thus, the findings of this work support the developed system has a dual role as the photocatalyst, and antibacterial agent for efficient environmental remediation.

Lead (II) adsorption from aqueous systems using visible light activated cobalt doped zinc oxide nanoparticles

In this study, co-precipitation method was used to produce cobalt doped zinc oxide (CoZnO) nanoparticles (NPs) by reacting zinc, cobalt and hydroxide (OH− ) in methanol at 60 °C and used as an adsorbent for the removal of lead (Pb) from aqueous systems. Co-ZnO NPs were characterized by X-ray diffraction (XRD) via X-ray Diffractometer (JDX-3532, JEOL, Japan), while Transmission electron microscopy (TEM) was carried out for the shape and size of the NPs. Results shows that Co-ZnO NPs was oval in shape within the size range between 40 to 60 nm. Moreover, the Pb(II) adsorption on Co-ZnO NPs surface was carried out with respect to time, optimum dose, different pH, light effects, filtration and sonication process. The result shows that Co-ZnO NPs can remove Pb(II) efficiently from aqueous systems in the presence of sunlight, optimum dose, neutral pH, and sonication process, while the same NPs could not show effective removal of Pb(II) with respect to darkness, tube light, low and high pH respectively. Using Co-ZnO NPs, Pb(II) can be reduced up to the permissible limit set by World health organization (WHO). CoZnO NPs work effectively in pH range of 5.8–7.2 so therefore, no need to adjust the pH of test solution for the activation of these NPs. The synthesized Co-ZnO NPs are eco-friendly and a capable adsorbent for the removal of Pb(II) from aqueous systems.

Photodegradation studies of pure and cobalt doped zinc oxide nanoparticles

ABSTRACT Pure and cobalt (Co)-doped zinc oxide (ZnO) nanoparticles were synthesised by co-precipitation method. Various characterisation studies such as powder X-ray diffraction, scanning electron microscope (SEM) and UV-visible spectra were carried out to investigate their structural and optical characteristics. The absorbance spectrum shows the red shift for the Co-doped ZnO nanoparticles and also decrease in their band gap due to increase in dopant concentration. The SEM analysis reveals that the pure ZnO has spherical-shaped morphology and Co-doped samples have hexagonal-shaped nanorods and nanoflowers. Photo catalytic activity of pure and Co-doped Zinc oxide was analysed using Malachite Green and Chrysodine Y dyes under UV irradiation, and it shows good photo catalytic behaviour.

Pongamia pinnata biodiesel production using cobalt doped ZnO nanoparticles—An analytical study

AbstractKaranja is second most popular non‐edible oil, in Indian sub‐continent, for Biodiesel production; with current plantation, almost 55,000 ton/year of oil can be extracted. Also, studies in past two decades have elucidated that use of heterogeneous solid catalyst has been commercially most viable, economical, produces almost pure biodiesel, easy to use, recycle and environment friendly. In this paper, we have used cobalt doped zinc oxide (CZO) nanoparticles for dual step esterification—transesterification processes, which has not been studied for Karanja oil, additionally, the detailed analytical study such as X‐ray diffraction, field emission scanning electron microscope, Brunauer–Emmett–Teller and energy‐dispersive analysis of X‐rays on catalyst unavailable in literature, has also been incorporated here. The CZO particles are synthesized using co‐precipitation method and yields particles of size ~75 nm, the reusability of catalyst is also included. The optimum process parameters where experimentally determined and compositional analysis of oil and biodiesel is done using Fourier transformed infrared. The economic and technical aspects of CZO synthesis, the benefits of easy separation of glycerol and reduced impurities in final product, make this process commercially more suitable for Karanja oil biodiesel synthesis, and study will promote use of CZO nanoparticles for other oil biodiesel production too. Result shows that under optimized condition of transesterification, 1:25 M ratio of oil:methanol, 0.3 wt% catalytic concentration, 70°C reaction temperature, 180 min time of reaction and 500 rpm of stirring speed fatty acid methyl ester (biodiesel) conversion was 98.5 ± 0.5%.

A study on improving the antibacterial properties of palygorskite by using cobalt-doped zinc oxide nanoparticles

Naturally rich and cheap palygorskite (Pal) is an excellent carrier for environmental protection. In present study, Co-doped ZnO nanoparticles (Co-ZnO) were prepared and decorated on acidified palygorskite by a simple sol-gel method to improve the antibacterial properties of palygorskite. Compared with bare Pal, Co-ZnO/Pal nanocomposites exhibited excellent antibacterial properties, with a minimum inhibitory concentration of 3 mg/mL. This is largely due to the large amount of superoxide anions (·O2−) and hydroxyl radicals (·OH) produced by Co-ZnO/Pal, and the morphology of palygorskite play an important physical piercing effect on the cell surface. This result opens up a new way for future functional clay materials.

Optimizing the structural, morphological and thermoelectric properties of zinc oxide by the modulation of cobalt doping concentration

A study is conducted to determine the effects of cobalt doping concentration on structural, morphological and thermoelectric properties of Zinc Oxide (ZnO). To test this hypothesis, cobalt doped zinc oxide nano-particles are prepared by hydrothermal method by modulating the Cobalt (Co) concentration from 0.1 to 0.5. The X-Ray Diffraction (XRD) and Raman data is suggested that crystallinity of grown samples is found to be decreased by increasing the concentration of Co atoms. The poor crystallinity of the sample having higher concentration of Co atoms is due to the emergence of secondary phases. The value of Seebeck coefficient is also improved with doping as indicated by the high Seebeck value (250 µV/°C) of Zn0.5Co0.5O. This enhancement of Seebeck coefficient is linked with the number of secondary phases. In contrast, electrical conductivity is reduced due to the generation of the impurity level close to the conduction band. In conclusion, at higher doping content, the overall power factor is enhanced with a slow increase in Seebeck coefficient and decrease in electrical conductivity by doping content.

Enhancement of photocatalytic activity of synthesized Cobalt doped Zinc Oxide nanoparticles under visible light irradiation

Abstract In the present work, pure Zinc Oxide (ZnO) and Cobalt (Co) doped ZnO nanoparticles with various dopant concentrations are synthesized by chemical precipitation method. All the synthesized samples are subjected to characterization by different instrumentation tools such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Ultra Violet–visible (UV–vis) absorption spectroscopy and Photoluminescence (PL) spectroscopy respectively. XRD results show the decrease in crystallite size of the synthesized samples with the increase of Co content. SEM image reveals that Co doping in ZnO results in change of the morphology of ZnO to nearly flower-like structures. The UV–vis absorption study shows that the energy band gap decreases as compared to pure ZnO with the increase of the content of Co dopant. PL spectra exhibit UV emission peak along with defect related visible emission. The intensity of visible emission reduces as the content of Co dopant increases. The photocatalytic activity of the synthesized samples is investigated for the degradation of Methylene Blue (MB) dye under visible light irradiation. The total organic carbon (TOC) analysis is done to evaluate the mineralization of the MB dye during photocatalytic process. Further, the effects of various parameters such as dopant concentration, catalyst dosage and initial concentration of the dye on the photocatalytic degradation process are extensively studied.

XRD structural studies on cobalt doped zinc oxide nanoparticles synthesized by coprecipitation method: Williamson-Hall and size-strain plot approaches

Cobalt doped Zinc Oxide (Zn1-xCoxO) (x = 0.03) nanoparticles have been synthesized by chemical co-precipitation method at room temperature and characterized by X-ray diffraction (XRD) study. The XRD pattern indicates that Co doped ZnO NPs are with hexagonal wurtzite geometry and diffraction peaks get shifted to higher angles which is the characteristic influence of dopant Co that has an ionic radius smaller than the host cation. The true values of lattice constants have been calculated using Nelson–Riley Function. Crystallite size calculated using Scherrer formula has been compared with that estimated by uniform deformation (UDM), uniform stress deformation (USDM) and uniform deformation energy density (UDEDM) models of Williamson – Hall method, and also by size-strain plot (SSP) method. The lattice strain has also been calculated. The surface morphology and elemental analysis of the product have been characterized by field emission scanning electron microscopy (FESEM) and energy dispersive (EDAX) spectra.

Photo-inactivation and efflux pump inhibition of methicillin resistant Staphylococcus aureus using thiolated cobalt doped ZnO nanoparticles

Multidrug resistance (MDR) in bacteria is a major concern these days. One of the reasons is the mutation in efflux pump that prevents the retention of antibiotics and drugs in the bacterial cell. The current work is a step to overcome MDR in bacteria via inhibition of efflux pump and further photoinhibition by thiolated chitosan coated cobalt doped zinc oxide nanoparticles (Co-ZnO) in visible light. Co-ZnO were synthesized in a size range of 40–60 nm. Antibacterial activity of the Co-ZnO against methicillin resistant Staphylococcus aureus (MRSA) was found 100% at a concentration of 10 μg/ml upon activation in sunlight for 15 min. Interestingly, it was found that cobalt as a dopant was able to increase the photodynamic and photothermal activity of Co-ZnO, as in dark conditions, there was only 3–5% of inhibition at 10 μg/ml of nanoparticle concentration. Upon excitation in light, these nanoparticles were able to generate reactive oxygen species (ROS) with a quantum yield of 0.23 ± 0.034. The nanoparticles were also generating heat, Because of the magnetic nature, thus helping in more killing. Thiolated chitosan further helped in blocking the efflux pump of MRSA. The current nanoparticles were also found biocompatible on human red blood cells (LD50 = 214 μg/ml). These data suggest that the MRSA killing ability was facilitated through efflux inhibition and oxidative stress upon excitation in visible light hence, were in accordance with previous findings.

Effect of cobalt doping on structural, thermo and photoluminescent properties of ZnO nanopowders

Nanocrystalline cobalt doped zinc oxide nanoparticles are synthesized by solution combustion method using sucrose as a fuel. The synthesized samples are characterized by XRD, SEM, FTIR, Micro-Raman, UV–Visible techniques. XRD studies confirm that both undoped and Co doped samples exhibit hexagonal wurtzite structure with crystallite size ~30nm for undoped ZnO and 25–18nm for Co doped ZnO samples. Both undoped and Co doped samples exhibit Raman peaks at 432, 502, 578, 681, 766, 865, 967 and 1175cm−1. Intensity of E2 (high) mode of ZnO appeared at 432cm−1 and decreases drastically with increase in cobalt concentration. Photoluminescence (PL) of all the samples shows violet emission peaks at 361, 398nm, blue emission peaks at 468,492nm and weak green emission peaks at 517 and 567nm. PL intensity is found to decrease with the increase in Co2+ doping. Thermoluminescence (TL) glow curves of Co doped ZnO nano crystalline phosphors are γ-irradiated in the dose range 0.1–5.0kGy. Prominent glow peaks at 412 and 575K are observed for all the exposed doses without changing its glow peak structure. TL intensity increases linearly with γ-dose up to 4kGy. The Kinetic parameters of TL glow are calculated by deconvolution technique. Activation energy and frequency factor are found to be 1.35eV and 2.10×1011s−1 respectively.

Study of structural, optical and magnetic properties of cobalt doped ZnO nanorods

Cobalt doped zinc oxide nanoparticles (NPs) and nanorods (NRs) were synthesized by a simple chemical method.

Structural, morphological and electroluminescence studies of Zno:Co nanophosphor

The nanoparticles of zinc oxide (ZnO) doped with various concentrations of cobalt (Co) were synthesized by chemical precipitation method in the presence of capping agent polyvinylpyrrolidone (PVP). The effect of doping concentration on structural and morphological properties has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Cell volume, bond length, texture coefficient, lattice constants and dislocation density are also studied. Here, we also compared the interplaner spacing and relative peak intensities from their standard values with different angles. Crystallite sizes have been calculated by Debye–Scherrer’s formula whose values are decreasing with increase in cobalt content up to 3 %. It has been seen that the growth orientation of the prepared ZnO nanorods was (101). The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure. The electroluminescence (EL) cells were prepared by placing pure and cobalt-doped ZnO nanoparticles between ITO-coated conducting glass plate and aluminium foil. Alternating voltage of various frequencies was applied, and EL brightness at different voltages was measured and corresponding current was also recorded. The voltage dependence of electroluminescence (EL) brightness of the ZnO:Co shows exponential increase. The linear voltage–current characteristic indicates ohmic nature. The EL brightness at a particular voltage is found to increase by increasing Co doping, but for higher percentage of Co the EL brightness is reduced. It is also seen that Co does not influence the threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

Synthesis and Magnetic Properties of Cobalt Doped Zinc Oxide Nanoparticles

Synthesis and Magnetic Properties of Cobalt Doped Zinc Oxide Nanoparticles

Effect of Co Doping on Structural and Optical Properties of Zinc Oxide Nanoparticles Synthesized by Sol-Gel Method

In the present work Pure and Cobalt (Co) doped Zinc Oxide (ZnO) Nanoparticles were synthesized by Sol-gel method. The effect of Co doping on structural and optical properties of Nanoparticles were investigated using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopic characterization techniques. The XRD spectrum revealed the formation of Wurtzite structure of ZnO. The structural properties of nanoparticles including particle size and lattice strain were calculated from XRD data. SEM shows the morphology of Nanoparticles. The presence of functional groups was analyzed from FTIR spectra. The properties of Cobalt doped zinc oxide nanoparticles prepared through simple cost effective, Sol-gel method can be used in optoelectronics and thermally stable devices.

Anti-microbial activity of cobalt doped zinc oxide nanoparticles: Targeting water borne bacteria

Zinc oxide (ZnO) nanoparticles were chemically synthesized with cobalt doping and characterized through UV–visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. Cobalt doped ZnO nanoparticles were found to be crystalline having a single phase as confirmed by XRD and SEM. It has been observed that the increase in the percentage of Co from 0% to 5% in ZnO, increases the crystallite size from 20.5 to 25.7nm and accordingly its band gap varies from 3.22 to 3.30eV. After treatment morphology of materials was changed from rod to spherical shaped. Further these nanomaterials were applied as a bactericidal agent to control water borne bacterial pathogen. Cobalt doping on zinc oxide and exposure of sunlight enhanced the antibacterial activity against water borne bacterial isolate at 50μg concentration. Interestingly, most effective bactericidal results were found against Escherichia coli and Vibrio cholerae.

Effect of Calcination on Properties of Cobalt Doped ZnO Nanoparticles

Diluted magnetic semiconductors are of great interest in spintronic applications due to the involvement of both spin and charge. We have investigated effect of calcination on structural and magnetic properties of cobalt doped zinc oxide nanoparticles prepared by sol-gel method. Cobalt doped ZnO nanoparticles are calcined at different temperatures ranging from 100°C to 500°C. X-ray diffraction analyses (XRD) and vibrating sample magnetometer (VSM) was used to characterize the calcined cobalt doped ZnO nanoparticles. XRD results confirm the formation of hexagonal wurtzite structure of the calcined cobalt doped ZnO. Decrease in crystallite size (34 to 27.7nm) is observed with increasing calcination temperature. Shrinkage in lattice parameters has been observed with calcination temperature. Ferromagnetic behavior was observed with increase in saturation magnetization till calcination temperature of 300°C.