Ba-doped ZnO Research Articles

Probing the impact of Ba on properties of ZnO at the nanoscale: optical, dielectric and antibacterial activity evolution

The sol–gel dip coating technique was used to manufacture undoped and Barium doped zinc oxide thin films. Doping is extensively used to refine semiconductor properties. Without and with varying ratios of Ba 1–9 wt% dopant, ZnO thin films have been manufactured. The effect of Ba on the dielectric, structural, antibacterial, optical and morphological characteristics of ZnO was investigated. The optical properties demonstrate that the bandgap of the pure ZnO thin film is higher than that of Ba-doped ZnO films, which is beneficial for improving solar cell performance. According to the XRD data, all films of ZnO have hexagonal wurtzite structures According to XRD structural analysis; the incorporation of Ba lowers the crystallinity of ZnO thin films by reducing the crystallite size. The Ba doping changes the surface roughness and morphology. The hopping process defines the dielectric characteristics that follow Koop’s theory as well as the Maxwell–Wagner model. A lower dielectric constant makes it ideal for high-frequency devices. These films exhibit ferromagnetism. Barium-doped zinc oxide photocatalyst could successfully decompose methylene blue dye by making it suitable for wastewater treatment. Ba doping effectively kills both gram-negative and gram-positive bacteria. They have antimicrobial applications in the food industry and biomedicine.

Synthesis, structural, photoluminescence, ultraviolet blocking and antibacterial performances of Ba-doped ZnO nanostructures

In the current experimental work, pure ZnO and Ba-doped ZnO nanorods have been prepared by implementing a facile wet chemical technique. XRD study reveals the formation of the hexagonal wurtzite phase of pure ZnO and Ba-doped ZnO nanorods. Interestingly, Ba-doped ZnO nanorods show very good absorption in the UVA (93% at 351 nm), UVB (90% at 300 nm) and UVC (61% at 220 nm) regions. The obtained results of the UV–visible absorbance study validate in such a way that the Ba-doped ZnO nanorods could be a better bet to be utilized as a UV blocker for the next generation of UV shielding materials. The Photoluminescence spectrum of Ba-doped ZnO nanoparticles reveals widespread UV–Visible bands between 350 and 600 nm. Also, the zone of inhibition is found to be 15 nm for both bacterial strains S.aures and E.coli and implies excellent antibacterial activity. Interestingly, the outcome as observed in the zone of inhibition towards S. aureus and E. coli in the present study is found to be higher than many doped ZnO and Ba-doped metal oxide nanostructures. The observed experimental results via the aforementioned characterizations imply that the synthesized samples possess the potential ingredients required for the applications related to the field of health care.

Synthesis, Characterization, and Photocatalytic Property of Ba-Doped ZnO Nanoparticles Synthesized Using Facile Precipitation

This work represents a facile synthesis of ZnO and Ba-doped ZnO (BaZnO) for using as photocatalysts. ZnO and BaZnO are sub-micron particles and nanoparticles, respectively, with similar hexagonal wurtzite polycrystalline structures. Even the size of the lower particles and crystals of BaZnO, compared with ZnO, correspond to the improved specific surface area and dislocation density. The existence of surface chemical defects was detected for both ZnO and BaZnO. For use as photocatalysts, both ZnO and BaZnO were dispersed into a carbaryl solution activated with ultra-violet irradiation. The BaZnO had a higher degradation rate constant of 17.34 × 10−2 min−1 than ZnO (12.40 × 10−2 min−1), an improvement of 39.8%. The improvement is facilitated by the synergistic effects of high specific surface areas and defects caused by small particle sizes and high dislocation density, respectively. Therefore, it can be demonstrated that Ba is an effective dopant for modifying suitable BaZnO nanoparticles to enhance photocatalytic degradation of the toxic carbaryl insecticide.

Ba-doped ZnO nanorods: Efficient piezoelectric filler material for PDMS based flexible nanogenerator

We report the synthesis of pure and Ba-doped ZnO nanoparticles by chemical co-precipitation technique with the aim to study the viability of Ba-doped ZnO nanoparticles as piezoelectric fillers in composite piezoelectric nanogenerators. The influence of Ba-doping on the structural, ferroelectric and piezoelectric properties of ZnO has been investigated in detail. Structural study by powder XRD reveals the formation of single hexagonal wurtzite phase for both pure and Ba-doped ZnO nanoparticles. Hexagonal rod-like morphology has been observed for both the samples from field emission scanning electron microscopy. The ferroelectric properties of Ba–ZnO have also been investigated and the remnant polarization and coercive field was measured to be 0.049 μC/cm2 and 4.088 kV/cm. In addition, Ba–ZnO sample shows a typical butterfly curve and the average d33 value of 41.28 p.m./V. Owing to improved piezoelectric properties and reduced leakage current, Ba–ZnO nanorods were utilized for the fabrication of flexible PDMS polymer based nanogenerators. A series of nanogenerators were fabricated with different amounts of Ba–ZnO filler varied from 10 to 40 wt% to individuate the optimal nanofiller concentration. The device with 30 wt% of Ba–ZnO generated the maximum open-circuit output voltage of about 10.5 V upon perpendicular compression of 2 kgf. Thus, Ba–ZnO:PDMS based composite device can be explored for application in mechanical energy harvesting and driving portable electronics.

Adsorption Behavior of Congo Red onto Barium-Doped ZnO Nanoparticles: Correlation between Experimental Results and DFT Calculations.

Ba-loaded ZnO nanoparticles (Ba/ZnO) were obtained by the co-precipitation process and employed as a sorbent for Congo Red (C32H22N6Na2O6S2) dye (CR). Physicochemical parameters such as particle size, pH, and contact time were checked to characterize the adsorption process. The maximum adsorption capacity of Ba/ZnO NPs for CR (1614.26 mg/g) proves its potential utility in the elimination of CR dye from wastewater. The adsorption mechanism was studied via infrared spectroscopy and density functional theory calculations. The geometrical parameters and electronic properties of the CR-Ba/ZnO complex, particularly the interaction energy, the density of states, and the charge transfer, highlighted the Ba-ion mediation in the chemical bond formation between CR and the surface. The interaction between CR and Ba-doped ZnO has found to show strong chemisorption with charge transfer between the SO3- group and adsorbed Ba2+ ion on the surface.

Synthesis, characterization and anti-bacterial activity of Mg and Ba-doped ZnO Nanoparticles

Mg and Ba-doped zinc oxide nanoparticles were prepared by chemical precipitation method. The prepared nanoparticles were annealed at 700 °C. The Wurtzite geometry was confirmed in the X-ray diffraction. The crystallite size was found from the Debye-Scherer’s formula. The dopant Ba highly influences crystalline size than the dopant Mg. From Tauc’s plot, the band gap of the prepared samples was calculated and analyzed. The red shifted band gap was observed due to the metal dopant. From the charge carrier concentration, it was observed that the prepared nanoparticles were p-type in nature. The refractive index decreases as the metal dopant concentration increases. High metal doping concentration inhibits the growth of E. coli. Ba-doped zinc oxide nanoparticles have high anti-bacterial activity than Mg-doped nanoparticles.

Structural and Electrical Characterization of Ba/ZnO Nanoparticles Fabricated by Co-precipitation

Ba-doped ZnO nanostructures (0.8–4 mmol) were successfully fabricated by the co-precipitation method. X-ray diffraction analysis indicated that all samples exhibited a typical hexagonal wurtzite ZnO structure with the emergence of BaO phase. Moreover, the incorporation of Ba resulted in an increase of crystallite size and lattice parameter while microstrain decreases. The broadening of the Zn–O vibrational band and the redshift in Raman vibrational modes provided clear evidence of the incorporation of Ba within ZnO host lattice. Furthermore, Ba doping prompted an increase of the dielectric constant and ac conductivity (σac). Additionally, the subsequent decrease in tangent loss with increasing the applied field frequency was associated with the hopping frequency of electron that enhances the charge carriers’ mobility.

Photo-degradation of a mixture of dyes using Barium doped ZnO nanoparticles

The potential use of Barium (Ba) doped ZnO nanoparticles for the photo-degradation of a mixture of dyes that mimics natural effluents has been attempted. Undoped and Ba-doped ZnO nanoparticles were efficiently synthesized via co-precipitation method. The effect of Ba concentration on the structural, morphological, optical properties and photocatalytic activity of ZnO nanoparticles was probed. X-ray diffraction analysis disclosed the formation of hexagonal polycrystalline nanoparticles with ZnO wurtzite crystal structure having an average crystallite sizes ranging from 20 nm for pure ZnO up to 28 nm in diameter after adding different ratios of barium. The FE-SEM images revealed rod-like nanoflakes morphology for all of the samples with a clear influence of the presence of Ba impurities on the width of the rods. Mapping analysis showed even Ba distribution in the ZnO lattice. FTIR spectra manifested the presence of the characteristic absorption peak at 400–600 cm−1 of Zn–O stretching modes confirming the target nanoparticles synthesis. While the BET and BJH data analysis indicated increased specific surface area and reduced pore volume as a result of Ba intercalation. The incorporation of Ba into the ZnO matrix has shifted the 371 nm absorption band to 475 nm as observed in photoluminescence spectra for all samples. This red shift in the absorption was reflected in lowering the band energy enabling it to decolorize a dyes mixture under visible light illumination. Based on the aforesaid results, the Ba doping is responsible for the visible light driven photocatalytic activity of the composites.

Ethanol gas sensing improvement at high humidity levels and optical features using Ba-doped ZnO NPs

Undoped and barium (Ba)-doped zinc oxide nanoparticles (BZ NPs) were successfully synthesized as a gas sensor by sol-gel method at high humidity. The performance of hexagonal structure BZ NPs was investigated in sensing ethanol gas. The physical features of the BZ NPs samples such as microstructure, morphology, and photoluminescence (PL) were examined. The X-ray diffraction (XRD) pattern illustrated that the Ba-doping significantly affects grain size, and crystalline quality in the BZ NPs. Also, the effects of temperature changes, gas concentrations, gas type, and relative humidity (RH) on the gas sensing system were investigated. The obtained data showed the high ethanol selectivity over the different gases, such as methanol, benzene, formaldehyde, carbon monoxide, and acetone. The improvement of sensing parameters was ascribed to the accumulation of active area for oxygen adsorption and test gases on the surface of BZ NPs samples. By rising RH from 25 to 60%, the response was gradually increased from 15 to 44 for undoped and 6% BZ NPs, respectively. When increasing the RH from 60 to 88%, the response decreased gradually. Moreover, recovery time for 5 to 100 ppm gas concentrations increased from 44 to 75 s, respectively.

Room-temperature synthesis and optical properties of nanostructured Ba-Doped ZnO thin films

Abstract Zinc oxide films with and without barium-doping have been prepared by the SILAR technique at different concentrations (1 mol%, 3 mol%, 5 mol% and 7 mol%) of Ba content on glass slides. The effects of the concentration of barium doped zinc oxide (BaZnO) were characterized using x-ray difffractometry (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area electron diffraction (SAED) techniques, ultraviolet–visible spectroscopy and photoluminescence (PL) studies. The structural studies using XRD plots confirmed the polycrystalline nature of ZnO films. The Ba doped ZnO films deposited were found to have strong orientation at (002) lattice plane which exhibited polycrystalline hexagonal wurtzite structure. TEM and SAED results confirmed the morphological and structural properties of the films. The SEM showed that the grain size of the films increased as a result of increase in the concentration of barium doping. EDX results confirmed the elemental presence of the films. An increase in the Ba concentration showed a decrease in the optical band gap values between 3.41 eV and 3.19 eV. PL studies confirmed the presence of defects in the ZnO films.

Sol–gel synthesis of Ba‐doped ZnO nanoparticles and its use in varistor ceramics

Un-doped and Ba-doped ZnO nanoparticles (Zn1−x Bax O 0 wt% ≤ x ≤4 wt%) were prepared by the sol–gel method and annealed at 500°C for 4 h under air atmosphere. Several techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy and scanning electron microscopy were used to characterise the as-prepared samples. The samples exhibited hexagonal ZnO lattice structure and a secondary phase of BaO is evolved for the sample with x = 0.02 and 0.04. The calculated average crystalline size decreases from 38.27 to 33.74 nm for x = 0 to 0.02 then reaches 39.93 nm for x = 0.04 which is confirmed by TEM. The change in micro-strain and a small shift in XRD peaks reveal the substitution of Ba2+ ions into the ZnO lattice. Additionally, using Ba-doped ZnO powders via this sol–gel method after sintering in air at 1150°C for 2 h, the varistor possesses good electrical characteristics, with present nonlinear coefficient of ∼24.43 and breakdown voltage of ∼2487.27 V/cm.

Electronic structures and ferroelectric properties of Ba-doped ZnO

Wurtzite ZnO has long been considered to be a promising candidate material for photovoltaic application due to its high power conversion efficiency. More interestingly and very recently, some research results suggested that the ferroelectric property of the photovoltaic material introduced by chemical elements doping can promote its power conversion efficiency significantly. Therefore, in order to understand the effect of Ba doping on the electronic structure and the ferroelectric properties of ZnO and to reveal the potentially optoelectronic properties of Zn1-xBaxO, the energy band structure, the density of states, and the polarizability and the relative dielectric constant of the bulk Ba-doped ZnO supercell system, in which the Zn atoms are partly and uniformly substituted by the Ba atoms, are investigated by using the first-principles method based on the density functional theory and other physical theory. The norm-conserving pseudopotentials and the plane-wave basis set with a cut-off energy of 600 eV are used in the calculation. The generalized gradient approximation refined by Perdew and Zunger (GGA-PBE), the local density approximation (LDA) and the local density approximation added Hubbard energy (LDA+U) are employed for determining the exchange-correlation energy respectively. Brillouin zone is set to be within 4×4×5K point mesh generated by the Monkhorst-Pack scheme. The self-consistent convergence of total energy is at 2.0×10-6 eV/atom. Additionally, in order to obtain a stable and accurate calculation result, the cell structure is optimized prior to calculation. The calculated results suggest that the bulk Ba-doped ZnO semiconductor system is still a semiconductor with a direct wide band gap. The band gap of Zn1-xBaxO increases gradually with Ba atom doping percentage increasing from 12.5% to 87.5%. Consequently, the ferroelectric polarization properties and the dielectric properties of the bulk Ba-doped wurtzite ZnO materials are tailored by doping Ba atoms. It indicates that the polarizability of Zn1-xBaxO system increases with Ba doping atomic percentage increasing, especially, the polarizability reaches to a maximum when the atomic percentage of doping is 75%. Meanwhile, the relative dielectric constant inversely decreases with Ba atomic percentage increasing. This is attributed to the effective contribution of Ba atoms to the density of state at the bottom of the valence band. The diagonalized components of polarizability imply that there are possible micro-domains in the supercell while applying externally electric field to it. And the supercell presents a nearly isotropic polarizability macroscopically due to the strong interaction among the electric dipole moments existing in the different domains.

Sol-gel synthesis of Ba-doped ZnO nanoparticles with enhanced photocatalytic activity in degrading Rhodamine B under UV-A irradiation

In this work, Ba-doped ZnO (Ba/ZnO) nanoparticles were synthesized through a facile sol-gel approach without the use of surfactants. The impacts of Ba content and calcination temperature on the performance of Ba/ZnO nanoparticles as photocatalyst in degrading Rhodamine B (RhB) under UV-A light irradiation were investigated. The results of the study indicated performance of Ba/ZnO nanoparticles than bare ZnO nanoparticles. Maximum photocatalytic activity was achieved at 0.1% Ba doped ZnO at 400°C calcination temperature. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), nitrogen physisorption and Diffuse Reflectance Spectroscopy (DRS) techniques were used for investigating the structure and properties of Ba/ZnO nanoparticles. XRD pattern did not indicate any peaks regarding Ba phase in Ba/ZnO nanoparticles and a wurtzite crystal structure was observed. Also, mapping analysis revealed fair Ba distribution in ZnO lattice. Near spherical shape was observed in SEM image for Ba/ZnO nanoparticles and results of BET and BJH analysis indicated specific surface area of 109.81m2g−1 and pore volume of 0.424cm3g−1. DRS spectra indicated decrease in band-gap energy for 0.1% Ba doped ZnO in comparison with bare ZnO.

Effect of barium doping on the physical properties of zinc oxide nanoparticles elaborated via sonochemical synthesis method

The aim of this work is to study the effect of barium (Ba) doping on the optical, morphological and structural properties of ZnO nanoparticles. Undoped and Ba-doped ZnO have been successfully synthesized via sonochemical method using zinc nitrate, hexamethylenetetramine (HMT) and barium chloride as starting materials. The structural characterization by XRD and FTIR shows that ZnO nanoparticles are polycrystalline with a standard hexagonal ZnO wurtzite crystal structure. Decrease in lattice parameters from diffraction data shows the presence of Ba2+ in the ZnO crystal lattice. The morphology of the ZnO nanoparticles has been determined by scanning electron microscopy (SEM). Incorporation of Ba was confirmed from the elemental analysis using EDX. Optical analysis depicted that all samples exhibit an average optical transparency over 80%, in the visible range. Room-temperature photoluminescence (PL) spectra detected a strong ultraviolet emission at 330 nm and two weak emission bands were observed near 417 and 560 nm. Raman spectroscopy analysis of Ba-doped samples reveals the successful doping of Ba ions in the host ZnO.

Ba-doped ZnO nanostructure: X-ray line analysis and optical properties in visible and low frequency infrared

In this work, X-ray diffraction analysis and optical properties of pure and Ba-doped ZnO nanoparticles prepared by the precipitation method were investigated. X-ray analysis was employed to evaluate the micro structural parameters of ZnO nanoparticles in terms of crystallite sizes and lattice strain by the Williamson–Hall method. The average crystallite size of Ba-doped ZnO nanoparticles estimated by the Williamson–Hall method varied as the doping concentration increased. The effect of Ba doping on the photoluminescence (PL) emission spectrum of ZnO was also investigated. The temperature dependence of the PL emissions was also studied, and it was found that at low temperature, the samples show stronger emissions than those at room temperature in both UV and visible regions. As a final point, the FT–IR reflection spectrum along with Kramers–Kronig (K–K) method and classical dispersion theory was applied to obtain optical properties of the samples at low frequency infrared regime.

Effects of Ba doping on structural, morphological, optical, and photocatalytic properties of self-assembled ZnO nanospheres

A simple low-temperature co-precipitation method was employed to synthesize pure and Ba-doped self-assembled ZnO nanospheres. The presence of self-assembled nanosphere-like morphology, high crystallinity, uniform size distribution, and more defects were confirmed by X-ray diffraction, high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Photocatalytic degradation of 2,4,6-trichlorophenol, a potent endocrine-disrupting chemical in aqueous medium was investigated. The effects of Ba doping on the structure, morphology, absorption, emission, and photocatalytic activity of ZnO nanospheres were investigated systematically. Furthermore, the effects of different photocatalytic degradation reaction parameters were investigated. The resulting photocatalytic degradation activity of Ba-doped ZnO nanospheres shows superior efficiency compared to pure ZnO and commercial TiO2 (Degussa P-25). A simple co-precipitation method was developed to synthesize pure and Ba-doped ZnO self-assembled nanospheres. The prepared photocatalyst shows a novel morphology, high crystallinity, uniform size distribution, and more defects. Effect of Ba doping on the structural, optical and photocatalytic properties of ZnO nanospheres were investigated systematically.

Theoretical investigation of optical and structural properties of Ba-doped ZnO material

The doping process is a technique widely used for improving the properties of semiconductors. Through insertion of doping controlled amount is possible change drastically the electronic, optical and structural properties of a material. This work focuses on effects of Ba atoms insertion on wurtzite-ZnO structure at 12.5% amount. The results showed that the presence of Ba in low quantity cause increase in the lattice parameters and decrease in band- gap in relation to the ZnO material. In the percentage of 12.5%, the doping is noted as a potential alternative for application in opt-electronic devices, electronic devices, solar cells and photocatalytic process.

Comparative Investigation on the Photocatalytic Degradation of 2,4,6-Trichlorophenol Using Pure and M-Doped (M = Ba, Ce, Mg) ZnO Spherical Nanoparticles.

Pure and M-doped (Ba, Ce, Mg) ZnO spherical nanoparticles are synthesized by a simple low temperature co-precipitation method, and were characterized by X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), and high resolution transmission electron microscopy (HR-TEM). The XRD results showed the formation of single phase ZnO with wurtzite crystal structure and the electron microscopic studies supported the validity for the formation of pure and M-doped (Ba, Ce, Mg) ZnO spherical nanoparticles. Photocatalytic degradation (PCD) of 2,4,6-trichlorophenol, a potent endocrine disrupting chemical in aqueous medium was investigated by both pure and M-doped (Ba, Ce, Mg) ZnO spherical nanoparticles under UV-light irradiation. The influence of the metal dopants on the structure and photocatalytic (PC) activity of ZnO was investigated systematically. Furthermore, the effect of different parameters such as 2,4,6-trichlorophenol concentration, photocatalyst amount, pH and dopant wt% on the resulting PC activity was investigated. The kinetics of the photocatalytic degradation of 2,4,6-trichlorophenol was found to follow the pseudo-first order reaction, and it was established that Ba-doped ZnO is photocatalytically more active than the other photocatalysts.

High Tc ferroelectricity in Ba-doped ZnO nanoparticles

Effects of Ba doping on structural, optical and ferroelectric properties of ZnO nanoparticles prepared by a low cost thermal decomposition method are presented. The substitution of Ba on Zn sites of the wurtzite structure of ZnO was observed by X-ray diffraction. Some structural transformation in the morphology of nanostructure with Ba doping was observed. Redshift in band gap is observed in the UV–visible spectra after Ba doping, supported by photoluminescence spectra and showing enhanced defect states with Ba doping. In dielectric studies, high value of dielectric constant and transition temperature at (~330°C) were observed. High value of remnant polarization (1.01µCcm−2) and low value of coercive field (2.02kVcm−1) were also observed in ferroelectric studies which can be useful for potential applications.

A rapid method for phosphorus in iron and steel, modified from a method procedure by Dr. Thos. M. Drown

In this work, X-ray diffraction analysis and optical properties of pure and Ba-doped ZnO nanoparticles prepared by the precipitation method were investigated. X-ray analysis was employed to evaluate the micro structural parameters of ZnO nanoparticles in terms of crystallite sizes and lattice strain by the Williamson–Hall method. The average crystallite size of Ba-doped ZnO nanoparticles estimated by the Williamson–Hall method varied as the doping concentration increased. The effect of Ba doping on the photoluminescence (PL) emission spectrum of ZnO was also investigated. The temperature dependence of the PL emissions was also studied, and it was found that at low temperature, the samples show stronger emissions than those at room temperature in both UV and visible regions. As a final point, the FT–IR reflection spectrum along with Kramers–Kronig (K–K) method and classical dispersion theory was applied to obtain optical properties of the samples at low frequency infrared regime.