Cr-doped ZnO Nanoparticles Research Articles

Role of Fe and Cr doped ZnO nanoparticles for electrocatalytic oxygen evolution reaction

Developing highly efficient catalysts for oxygen evolution reactions using abundant earth-rich and non-precious metals poses a critical and indispensable challenge. In this study, Fe: 1, 3, and 5% and Cr: 2% doped ZnO nanoparticles (NPs) were synthesized by employing a simple solution combustion method (SCM) for oxygen evaluation reaction (OER). Using a variety of methods, the synthesized transition metal-doped metal oxides were thoroughly examined. The electrochemical behavior of the Fe and Cr-doped ZnO electrodes in an alkaline solution was investigated through LSV, EIS, CV, and CA. The electrochemical studies showed that ZnO/Cr/Fe:5 (η = 305 mV and Tafel slop = 46 mV/dec) demonstrates significant oxygen evolution reaction (OER) activity under alkaline conditions. All prepared samples exhibit good stabilities for up to 10 h.

Green mediated approach to investigate the optical, structural, photocatalytic, magnetic and dielectric properties of Cr3+ doped ZnO nanoparticles for energy applications

Herein, the influence of Cr3+ dopant on the structural, morphological, optical, photocatalytic, dielectric and magnetic properties of ZnO was investigated for various applications. Pure ZnO and Cr3+ doped ZnO nanoparticles were synthesised by green mediated approach. The synthesised nanoparticles examined by using XRD, SEM, EDX, FTIR, PL, UV–Vis spectroscopy, dielectric and magnetic analysis. XRD confirmed the wurtizte hexagonal structure of synthesised samples and also revealed that the Cr didn't alter the structure of host ZnO. The FTIR analysis revealed the presence of Cr ions in ZnO structures. Doping of Cr ions improved the optical absorbance of ZnO and the optical band gap showed the blue shift with increasing concentration of Cr. The synthesised Cr doped nanoparticles show the outstanding photocatalytic efficiency under solar irradiation against MG pollutant dye. The dielectric constant (ε) improves and dielectric loss (tan (δ)) reduces at lower frequencies with increasing content of Cr. The AC conductivity for doped nanoparticles showed the increasing trend, especially for 4.5 % Cr doped ZnO nanoparticles. The ferromagnetic behavior at room temperature of Cr doped ZnO nanoparticles confirmed by VSM. The obtained results from all investigations make the Cr doped ZnO samples a potential choice for various applications such as, spin based electronic devices and energy storage devices.

Insights into the compositional and temperature-mediated magnetic characteristics of chromium-doped ZnO nanoparticles

This study explores the influence of chromium content and temperature on the magnetic characteristics of ZnO synthesized via the cost-effective coprecipitation approach. The host ZnO structure is not significantly changed by chromium doping, even at 5 wt.% of chromium concentration, according to x-ray diffraction studies. The Zn–O characteristic stretching vibration band at 480 cm−1 and the other functional group attached to the Cr-doped ZnO nanoparticles are confirmed by Fourier-transform infrared (FTIR) spectroscopy studies. Diffuse reflectance spectroscopy analysis shows the interaction between chromium ions and ZnO causes bandgap narrowing, and the observed optical bandgap values fall as chromium content increases in the host ZnO matrix. Point defects such as zinc interstitial, zinc vacancy, and oxygen vacancy that exist in the Cr-doped ZnO nanoparticles are inveterate through photoluminescence spectroscopy. Vibrating sample magnetometry investigations reveal weak ferromagnetic behavior at low applied fields and diamagnetic signatures dominating at high applied fields in the Cr-doped ZnO nanoparticles at 300 K. The magnetic characteristics are also tunable in terms of temperatures, which opens new avenues for fabricating dilute magnetic semiconductors with various applications.

Synthesis, characterization and properties of Cr-doped ZnO nanoparticles via a facile solvothermal route

Cr-doped ZnO ([Formula: see text]–0.08) nanoparticles are synthesized using the microwave solvothermal irradiation technique. The final product is calcinated at 450∘C and the nanostructure of the material is investigated using various techniques. In structural studies, XRD analysis shows that the hexagonal wurtzite structure of ZnO is present in the standard JCPDS card. FESEM spectrum reveals the hexagonal shape of the synthesized samples and EDS provides information on the qualitative composition of the nanoparticles. Optical absorbance images show exciton peaks in the UV region, which can be attributed to Cr incorporation into the ZnO lattice, and the optical energy bandgap values are calculated using the tauc plot method. Photoluminescence (PL) emission spectra are measured using PL spectroscopy. Interestingly, vibrating sample magnetometry (VSM) reveals enhancements in the magnetic properties in M–H loops and it is widely used for biological applications like antibacterial activity.

Bio-inspired benign synthesis of Cr doped ZnO nanoparticles towards electrochemical detection of Bovine Serum Albumin

In this study, we aimed to synthesize monodisperse chromium-doped zinc oxide (Cr-ZnO) nanoparticles (NPs) through green synthesis for the construction of a highly sensitive electrochemical biosensor for BSA detection. Characterization techniques such as X-ray diffraction, FTIR spectroscopy, UV-Vis absorption, and photoluminescence studies confirmed the structural, chemical, and optical properties of the synthesized NPs. FESEM and EDS analysis revealed a spherical nodular morphology with a cauliflower-shaped structure. Nano-bio interaction studies between Cr-ZnO NPs and BSA were conducted using UV-Vis absorption and PL measurements, indicating fluorescence quenching due to complex formation. The synthesized NPs were utilized as electrode material for an electrochemical sensor, demonstrating sensitivity and selectivity in detecting BSA concentrations within the range of 1.5 nM to 48 nM. The sensor's response was linear, showing a decrease in anodic peak current response from 5.08 µA to 3.48 µA for different BSA concentrations. Remarkably, the optical interaction results mirrored the electrochemical findings, emphasizing the consistency between the two methods. The linear response of the electrochemical sensor, coupled with its optical interactions, suggests the versatility and reliability of the synthesized NPs for biosensing applications. With a simple setup requiring minimal samples, the electrochemical sensor offers an inexpensive, rapid, and sensitive screening method for BSA. These findings underscore the potential of the synthesized NPs as a promising electrochemical surface for biosensors, with implications for diagnostic and therapeutic applications, particularly in the context of cattle-related research.

Cr doped ZnO nanoparticles as photocatalyst for the degradation of methylene blue dye

Herein, pristine and Cr doped ZnO nanoparticles (NPs) were synthesized using hydrothermal method and were used as a photocatalyst for the degradation of methylene blue (MB) dye under natural sunlight. Rietveld refinement of the X-ray Diffraction (XRD) pattern confirmed the hexagonal wurtzite structure whereas the presence of elements along with their orbitals was verified from the XPS survey spectra. Field Emission Scanning Electron Microscopy (FE-SEM) images show a distorted rod-like morphology. Among the prepared nanostructure, Zn0.98Cr0.02O NPs possess the lowest bandgap energy due to the presence of optically active sub-levels within the bandgap region. The photoluminescent (PL) spectra were taken with 325 nm as the excitation wavelength with emission peaks in the visible region. The enhanced photocatalytic dye degradation efficiency demonstrated by Zn0.98Cr0.02O under visible light was attributed to the presence of defects in lattice, leads to the reduction electron-hole recombination rate. These features make the prepared nanoparticles as an excellent candidate for applications relating to a number of environmental issues.

Thermo-mechanical and opto-electrical study of Cr-doped-ZnO-based polyvinyl chloride nanocomposites

Polymer nanocomposites exhibit unique physical properties inaccessible from their individual constituents, which are tunable through the type of the polymer matrix, the type and size of the incorporated nanoparticles, and the doping level, and therefore, can be utilized in a wide range of potential applications. Here, we report the fabrication of pure Polyvinyl chloride (PVC) and PVC-based nanocomposites containing different loadings of pure and Cr-doped ZnO nanoparticles, using solvent casting method. Scanning electron microscopy images of the obtained nanocomposite films confirmed the successful incorporation of nanoparticles within the PVC matrix, with higher dispersion quality for the Cr-doped ZnO samples. The prepared nanocomposite samples were found to possess higher thermo-mechanical stability, compared to pure PVC, resulting from the strong interaction between the nanoparticles and polymeric chains, as inferred from their thermogravimetric and dynamic mechanical analysis (TGA and DMA) profiles. Specifically, the temperatures corresponding to the onset and 50% weight loss as well as the glass transition temperature are increased by ~ 88, ~ 34, and ~ 16 °C, respectively, after loading selected amounts of the nanoparticles. In addition to the thermo-mechanical stability, the nanocomposites revealed potentially relevant dielectric response, where the dielectric permittivity exhibits remarkable enhancement, by 400%, compared to pristine PVC. The optical transmission of the PVC is strongly suppressed over the entire visible spectral regime, upon loading the nanoparticles, and its optical band gap (~ 4.1 eV) is red shifted toward the value of pristine ZnO nanoparticles (~ 3.3 eV), while the distinct Cr3+ and Cr6+ optical transitions are preserved for the nanocomposites. The obtained thermo-mechanical stability, required for working devices, together with the here reported improvements in the dielectric response for the nanocomposite samples may alter the typical applications of PVC polymers from being insulating materials to be utilized in energy storage and capacitors manufacture, while the preserved optical properties of the incorporated nanoparticles render these nanocomposites suitable candidates for optoelectronic devices.

Chromium doped ZnO nanoparticles for energy storage, gas and humidity sensing and spin based electronic devices applications

This work was suggested to study the impact of Cr ions doping on the structural, optical, electrical and magnetic behavior of ZnO nanoparticles (NPs). The Zn1-xCrxO (with 0 ≤ x ≤ 0.14 wt %) samples were fabricated by the co-precipitation technique. The obtained samples were characterized by the X-ray diffraction (XRD) technique, (FTIR) spectroscopy, UV–vis spectrophotometer, Ac measurements and Vibrating Sample Magnetometer (VSM). As a key results of all the mentioned above tools we can be summarized them as following; XRD patterns showed the presence of wurtzite (hexagonal) crystal structure with secondary phase formation in all doped samples. Also, it was found that as Cr ions were increased the particle size showed gradually decreasing in the samples that doped with Cr ions content of (0.06 and 0.1 wt %), while at 0.14 Cr content a slight increase was observed. The FTIR spectroscopy spectra showed the existence of chromium ions in the structure of ZnO nanoparticles. UV–vis spectra showed a red shift in the centers of the absorption bands. The energy band gab was found to be increased from 3.84 to 4.02 eV with increasing Cr content. The dielectric parameters such as, dielectric constant ({varepsilon }^{^{prime}}) and dielectric loss (mathrm{tan}delta), were investigated as a function of frequency and Cr doping content. The results showed increasing values of {varepsilon }^{^{prime}} at lower frequencies especially with high Cr doping content, whereas mathrm{tan}delta gives a higher value for the blank sample at a lower frequencies and decreased as the doping of Cr concentration increased. The ac conductivity (σac) for Cr doping samples showed increasing values, especially the sample of 0.14 wt % Cr concentration. In addition, the Cr doped ZnO nanoparticles exhibited a ferromagnetic behavior at room temperature. All the results obtained from the different techniques were considered promising for different applications i.e. energy storage devices, gas and humidity sensing and spin based electronic devices applications.

Efficient removal of organic dyes by Cr-doped ZnO nanoparticles

Efficient removal of organic dyes by Cr-doped ZnO nanoparticles

Modulation of structural, morphological and electrical charge transport property of Cr-doped ZnO nanomaterials prepared by chemical process

The present work reports the synthesis of undoped ZnO and Cr-doped ZnO nanomaterials by co-precipitation and hydrothermal methods. Crystallographic information of Cr-doped ZnO nanomaterials has been estimated by Rietveld analysis using MAUD. UV–visible absorption measurement concludes the significant reduction of band gap energy and the presence of strong s-d, p-d spin-exchange interaction in all co-precipitated nanoparticles as compared to the hydrothermally prepared rod-like structures. The dielectric response study of undoped and Cr-doped ZnO nanomaterials shows significant enhancement of the dielectric constant of the rod-like structures in comparison to the sphere-like nanoparticles. Impedance spectroscopy has been studied and the Nyquist plot or Cole-Cole plots of all the undoped and Cr-doped ZnO nanoparticles and nanorods have been constructed to understand the individual contributions of electrical responses of the grains and grain boundaries and the conducting nature of the nanomaterials.

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

Environmentally benign and economical bio-fabrication of ZnO and Cr-doped ZnO nanoparticles using leaf extract of Citrus reticulata for biological activities

Environmentally safe and economical bio-fabrication of nanoparticles using plant extracts plays a vital role in nanotechnology. The present study focuses on green fabrication of ZnO and Cr-doped ZnO nanoparticles (NPs) using leaf extract of C. reticulata as both stabilizing and reducing agents. Characterization through X-ray diffraction (XRD) revealed crystalline nature of wurtzite ZnO having hexagonal structure with lattice parameters a = 3.25 Å, b = 3.25 Å and c =5.21 Å. Using XRD data, the average crystallite size of ZnO and Cr-doped ZnO NPs was found to be 19.6 and 24.3 nm, respectively. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) confirmed synthesis of ZnO NPs and doping of Cr, while a spheroid like morphology was observed for the NPs. Fourier transform infrared (FT-IR) spectroscopy confirmed presence of various functional groups along with the metallic bonds of zinc and chromiumC. Thermo-gravimetric analysis (TGA) revealed that Cr-doped ZnO-NPs were more thermally stable than pure ZnO. Biological activities of NPs indicated that both ZnO and Cr-doped ZnO-NPs had strong free radical scavenging potential. Moreover, a remarkable antibacterial activity was exhibited by Cr-doped ZnO against E. coli, S. aureus, K. pneumonia and P. aeruginosa with zone of inhibition of 22.4 ± 1.98, 15.5 ± 0.78, 10.2 ± 0.55 and 7.5 ± 1.55 mm, respectively. Significant hemolytic activity was also evident using Cr-doped ZnO-NPs. The higher pharmacological activity of Cr-doped ZnO-NPs than un-doped ZnO is attributed to the excessive production of reactive oxygen species and high penetration power of doped NPs.

Fabrication of Cr–ZnO photocatalyst by starch-assisted sol–gel method for photodegradation of congo red under visible light

In this work, a sol–gel method has been employed to fabricate Cr-doped ZnO nanoparticles (NPs) in the presence of starch at different annealing temperatures. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and Fourier transforms infrared spectroscopy (FTIR). All samples were defined as hexagonal wurtzite ZnO with particle sizes equal to 26, 22, and 31 nm for pure ZnO, Cr-doped ZnO at 500 °C and 700 °C, respectively. The Cr-doped ZnO photocatalyst at 500 °C shifted the band gap energy of ZnO from 3.16 to 3.09 eV. The nanomaterials' photocatalytic activity was tested through the photodegradation of congo red (CR) under visible light illumination. The results demonstrated that the Cr-doped ZnO annealed at 500 °C is an excellent photocatalyst with enhanced degradation competence towards CR dye by virtue of its reduced size and lower band gap energy. The kinetics of the photodegradation fitted the pseudo-first-order model while the mechanistic investigations revealed the great impact of h+ and ·OH on the degradation process. The starch-stabilized chromium-doped ZnO shows a high photocatalytic activity towards CR, indicating their possible environmental remediation application.

Substantial effect of Cr doping on the antimicrobial activity of ZnO nanoparticles prepared by ultrasonication process

This study was involved to investigate the effect of Cr incorporation on various physic-chemical properties of ZnO nanopowder that including structural, morphological, optical and antibacterial. The synthesized powder reveals wurtzite hexagonal structure with decreased crystallite size from X-ray diffraction analysis. The scanning electron microscope (SEM) result confirmed that the formation of hexagonal shaped particles was observed on Cr doped ZnO nanoparticles. The presence of vibration band in the range of 450–600 cm−1 was confirm, the successful formation of Zn-O bond in bare and Cr doped ZnO nanoparticles. The decreased reflectance and red shift in the UV–vis diffused reflectance spectra was confirmed the decreased band gap energy. The antibacterial investigation of the nanopowder reveals, the higher zone of inhibition, membrane damage and intracellular alterations were observed against K. pneumoniae and C. albicans compared with other microorganisms. Thus, the result was suggested that the Cr doped ZnO nanoparticle as a promising candidate material for the development of new antibiotics against various bacteria.

High performance Cr doped ZnO by UV for NH3 gas sensor

In this work, Cr doped ZnO nanoparticles were synthesized by a hydrothermal method. Ammonia gas (NH3) sensing was tested under UV illumination at room temperature. The irradiation returned the sensor after detecting the NH3 molecules back to their initial states. More importantly, it created the electrons needed to ionize the oxygen molecules absorbed on the surface of the Cr:ZnO nanoparticles. This increase is necessary for the creation of more active surface sites which are necessary for the detection of the NH3 molecular in air. It was found that the increase in the output of doped ZnO nanoparticles sensor is due both to the Cr doping and to the UV irradiation. For a NH3 concentration of 50 ppm, the increase in the signal was 9 %. The results showed that the irradiated Cr doped ZnO nanoparticles have a higher sensitivity for detecting the presence of NH3 gas at room temperature than the undoped and unirradiated ZnO nanoparticles.

Investigation of photocatalytic behavior of undoped ZnO and Cr-doped ZnO nanoparticles for the degradation of dye

Nanosized ZnO and Cr-doped ZnO nanoparticles (NPs) were prepared by co-precipitation method, which were employed as photocatalysts for the degradation of murexide dye in aqueous media. The nanoparticles were characterized by FTIR, SEM, XRD and TGA. The morphological study illustrated that both ZnO and Cr-doped ZnO NPs are irregular round shaped. The XRD results presented that the crystallite size of undoped ZnO and Cr-doped ZnO were 30.07 and 28.14 nm, respectively. The band gap of undoped ZnO and Cr-doped ZnO were 3.4 and 3 eV, respectively. The precursor decomposition to ZnO after annealing at ∼500 °C was confirmed by TGA. The photodegradation study presented that the Cr-doped ZnO and undoped ZnO NPs degraded about 92 and 89% dye within 100 min, respectively. The effect of different parameters like dye initial concentration, contact time, pH and temperature on the photocatalytic degradation of dye was studied. The activity of recovered catalyst was also studied.

Effect of Cr Doping on Visible-Light-Driven Photocatalytic Activity of ZnO Nanoparticles

Visible–light response semiconductors have been recognized by many researchers as powerful photocatalysts due to their efficient utilization of solar energy. Herein, Cr-doped ZnO nanoparticles (Cr-ZnO NPs) with different Cr atomic percentages were synthesized via a facile sol–gel route and systematically investigated with respect to the photocatalytic degradation of recalcitrant organic contaminants under visible–light conditions. The crystal structure and morphology of materials were characterized by x-ray diffraction patterns and transmission electron microscopy. X-ray photoelectron spectroscopy was employed to confirm the presence of Cr3+ ions successfully incorporated into the ZnO lattice. UV–Vis diffuse reflectance spectroscopy and photoluminescence spectra revealed that Cr doping remarkably increased the absorption of ZnO NPs and charge carrier separation, resulting in improved photocatalytic degradation efficiency. In addition, a trapping experiment was conducted to identify the involvement of reactive radicals in the photocatalysis process, suggesting that photogenerated electrons play a predominant role in photocatalytic degradation of Cr-ZnO NPs.

Investigation on Photocatalytic Removal of NO under Visible Light over Cr-Doped ZnO Nanoparticles.

Removal of nitrogen oxide pollution has attracted much attention, and photocatalysis is considered as an effective method to treat polluted gas. Currently, modified semiconductors with approximate band gap are used as visible-light-driven photocatalysts. Herein, this is the first investigation of photocatalytic removal of NO under visible light over Cr-doped ZnO nanoparticles (Cr–ZnO NPs). Furthermore, the trapping species experiment and electron spin resonance measurement were conducted to identify the primary reactive factor of the photocatalytic reaction. In this study, Cr–ZnO NPs were synthesized by the sol–gel method with a narrow band gap, enhanced NO photocatalytic degradation performance, low NO2 conversion yield, and high stability under visible light.

Mechanism of enhanced photocatalytic activity of Cr-doped ZnO nanoparticles revealed by photoluminescence emission and electron spin resonance

In this work, we successfully synthesized Cr3+ doped ZnO nanoparticles using a sol-gel method, and elucidated how Cr3+ dopant is critical for enhancing photocatalytic activity. The nature of the point defect analyzed by electron spin resonance (ESR), and photoluminescence (PL) emission revealed the role of the Cr3+ dopant. When introducing Cr3+ ions in ZnO, the PL emission intensity decreased, indicating a reduction of the radiative recombination rate due to the heterojunction formation between the dopant and the host. The Cr3+ doped ZnO nanostructures showed that the typical ESR signal with g-factor value ∼1.96 was completely passivated, indicating the diffusion of electrons near the conduction band into the dopant ions. The doped Cr3+ ion acts as an electron trap in the ZnO crystal described as The mechanism for enhancing the photocatalytic activity of heterogeneous ZnO:Cr3+ was proposed in respect of point defect evolution through the manner of Cr3+ doping. As a result, the photocatalytic efficiency investigated by measuring methylene blue degradation under 210 min of direct sunlight irradiation reached 93.5% for 1 at % Cr3+ doped ZnO, which was significantly improved compared to 59.8% of the pure ZnO.

Variations of energy band gap and magnetic properties upon quantum confinement effects on the Cr doped ZnO nanoparticles

In this paper, Cr doped ZnO nanoparticles with different at % ratio (0, 2, 4, 6, 8, 10) (NPs) were synthesized with a precipitation method in ethanol. The synthesized nanoparticles have been analyzed using thermogravimetric analysis (TGA), x-ray diffraction (XRD), Energy dispersive x-ray spectroscopy (EDXS), transmission electron microscope (TEM), UV–vis spectrometer and Vibrating sample magnetometer (VSM) measurements. The XRD studies showed that the phase singularity of ZnO wurtizte hexagonal type structure. The surface morphology investigations by TEM confirmed the reduction of the particle size with increasing Cr content estimated from Williamson-Hall analysis of the diffraction peaks. The analysis of the UV–vis spectra of Cr doped NPs reveals that the wavelength of the absorption maxima λmax blue shifted to lower wavelength with increases the Cr content indicating the decrease in the particle size and recommends the increasing of energy gap with Cr content into ZnO semiconducting NPs. The observed increase of the energy band gap of Cr-doped ZnO nanoparticles caused by the decrease in the particle size with Cr concentration is attributed to the quantum confinement effect. The magnetization measurements showed room temperature ferromagnetism for all synthesized nanoparticles which can be attributed to the carrier-mediated exchange interaction improved by intrinsic defects.