Band Gap Of Zinc Oxide Research Articles

Engineering the Integration of Titanium and Nickel into Zinc Oxide Nanocomposites through Nanolayered Structures and Nanohybrids to Design Effective Photocatalysts for Purifying Water from Industrial Pollutants

Water pollution is one of the main challenges currently facing scientists around the world because of the rapid growth in industrial activities. On this basis, 2D nanolayered and nanohybrid structures, which are based on a ternary system of nickel–titanium–zinc, are considered favorable sources for designing effective nanocomposites for the photocatalytic degradation of industrial pollutants in a short period of time. These nanocomposites were designed by modifying two-dimensional nanolayers to produce a three-dimensional porous structure of multi-doped Ni/Ti-ZnO nanocomposites. Additionally, another additive was produced by constructing nanohybrids of nickel–titanium–zinc combined with a series of hydrocarbons (n-capric acid, myristic acid, stearic acid, suberic acid, and sebacic acid). Energy-dispersive X-ray spectrometry, X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermal analyses confirmed the growth of the nanolayered and nanohybrid materials in addition to the production of nanocomposites. The positive role of the dopants (nickel and titanium) in producing an effective photocatalyst was observed through a significant narrowing of the band gap of zinc oxide to 3.05–3.10 eV. Additionally, the high photocatalytic activity of this nanocomposite enabled the complete removal of colored dye from water after 25 min of UV radiation. In conclusion, this study proposes an unconventional approach for designing new optical nanocomposites for purifying water. Additionally, it suggests a novel supporting method for designing new kinds of nanohybrids based on multi-metals and organic acids.

Green synthesis and studies on citrus medica leaf extract-mediated Au–ZnO nanocomposites: A sustainable approach for efficient photocatalytic degradation of rhodamine B dye in aqueous media

Abstract Incorporating narrow band gap oxide semiconductors and metals into zinc oxide (ZnO) nanostructures broadens the range of light sensitivity to include visible wavelengths. In this study, the photocatalytic degradation of rhodamine B (RhB) dye was studied as a model for environmental pollution in aqueous media. This study describes the use of photodegradation catalysts, including gold (Au), ZnO, and Au–ZnO nanocomposites (prepared in ratios of 90:10 and 95:5) using the extract of Citrus medica leaves. X-ray diffraction (XRD) findings have shown that ZnO nanoparticles (NPs) have a hexagonal wurtzite structure. Field emission-scanning electron microscopy findings have depicted that ZnO NPs have diverse shapes, including spherical, quasi-spherical, hexagonal, and anisotropic, with some clumping. Au exhibits consistent spherical shapes and sizes with even distribution. Au–ZnO (90:10) shows quasi-spherical NPs with interconnected spherical Au, forming a porous and uneven surface. Au–ZnO (95:5) has spherical gold nanoparticles (Au NPs) dispersed on a textured ZnO surface, with some clustering and size variation as evident from the transmission electron microscopy, atomic force microscopy, and diffuse reflectance UV-visible spectroscopy analysis. The characterization results have demonstrated the uniform distribution of Au across the ZnO lattice. Additionally, the XRD patterns confirmed the hexagonal wurtzite structure of ZnO. Furthermore, energy-dispersive analysis of X-ray (EDX)-mapping verified the inclusion of zinc, oxygen, and Au in the hybrid Au–ZnO nanocomposites and their effective distribution. The topological analysis revealed a rough surface for the generated nanostructures. By comparing the results of various techniques, EDX analysis using atomic and weight ratios confirmed the presence of oxygen and Au in the nanocomposite. Additionally, the surface area analysis (BET) test has reported that the adsorption and desorption of nitrogen follow a Type III isotherm. The presence of an H3-type hysteresis loop further confirms the mesoporous nature of the composites, which reports the presence of wedge-shaped pores. The Au–ZnO (90:10) nanocomposite exhibits a higher surface roughness compared to other composites. In addition, this UV-visible diffuse reflectance spectroscopy has enumerated the band gaps of various nanomaterials using UV-visible spectroscopy. Moreover, the analysis has unveiled that combining ZnO with Au NPs (doping) improved the photocatalytic performance of ZnO. This improvement is attributed to the formation of additional energy levels within the ZnO band gap due to the presence of Au ions. Experimental investigation of the breakdown of RhB dye under visible light irradiation revealed superior photocatalytic activity for the Au–ZnO (90:10) nanocomposite compared to both Au–ZnO (95:5) and pure ZnO and Au counterparts. Multiple experiments confirmed the effective photodegradation and removal of RhB dye from the aqueous medium using the nanocatalyst under visible light irradiation. Under optimal conditions (1.0 g·L−1 photocatalyst, 10 ppm RhB, and pH 10), 99% photodegradation efficiency was reached within 50 min of irradiation. Investigation of reactive species revealed that the increased effectiveness of photodegradation in Au–ZnO (90:10) stems from the presence of photogenerated holes and hydroxyl radicals. The study also analyzed the reaction kinetics and order, and the reusability of the best photocatalyst Au–ZnO (90:10)) was confirmed through five consecutive cycles, demonstrating its sustained effectiveness in photodegradation. These findings highlight the potential of Au–ZnO (90:10) nanocomposite as a promising material for photocatalytic degradation of organic dyes.

Environmental-related applications of ZnO nanopowders: Photocatalytic activity and photoluminescence response to ethanol

Zinc oxide (ZnO) and copper-doped zinc oxide (ZnO:Cu) nanopowders were synthesized via solvothermal methods using methanol and hexamethylenetetramine (HMTA). Undoped ZnO nanopowders underwent calcination in O2-rich and H2-rich atmospheres at 600 °C. Samples were studied by scanning electron microscopy, Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), and Raman, photoluminescence (PL) and UV–vis absorbance spectroscopies. The doping and calcinations led to a reduction of the optical bandgap of the nanopowders, while their structure remained hexagonal wurtzite with some changes in lattice parameters and average nanoparticle sizes. The Cu2+ doping led to a BET surface area and violet PL component increase. Samples were also examined for environmental related applications, namely as photocatalyzers for dye degradation and as ethanol optical sensors. For photocatalytic activity in methylene blue degradation under UV, H2-rich calcined powders excelled, with a rate constant of −0.076 min−1, surpassing −0.057 min−1 (ZnO:Cu), −0.056 min−1 (O2-rich calcination), and −0.041 min−1 (as-grown ZnO). We propose that this improvement can be attributed to the formation of ZnO/Zn interfaces stemming from the reduction of surface interstitial zinc by H2 during calcination, in addition to the observed reduction of the ZnO bandgap. The doped nanopowders PL also showed excellent response when exposed to ethanol vapor.

Zn12O12 Cluster‐Based Materials with Enhancing Visible Light Absorption by Doping Alkaline Earth Metal Atoms: A First‐Principles Prediction

Zinc oxide (ZnO) is a promising semiconductor material in the field of photocatalysis due to its excellent electronic and optical properties. Due to its wide bandgap, ZnO cannot absorb visible light, which limits its photocatalytic performance. The current research is mainly to reduce the bandgap of wurtzite ZnO by doping different atoms, so as to enhance its visible light absorption, but the effect is limited. Under the framework of first‐principles calculation, three alkaline earth metal elements, Be, Mg, and Ca, are selected to dope the low‐energy sites in the cavities of Zn12O12 cluster‐assembled material (SOD type) with single and double atoms, respectively (equivalent to the doping concentration of 8.3% and 16.7%) using a combination of geometric optimization and molecular dynamics, and a stable new semiconductor material with direct bandgap less than 1 eV is obtained, which has excellent light absorption properties in the visible region. In addition, the reason for the bandgap reduction of doped materials is revealed by analyzing the energy band structures and the density of states. This work provides a new idea for the development of new photocatalytic material based on ZnO.

Synthesis of Metal (Ni) Doped Metal Oxide (ZnO) Heteronanostructures and Investigation of Their Morphological-Optical Properties

In this study, different volumes of Nickel (Ni) doped Zinc oxide (ZnO) thin films were deposited on FTO by hydrothermal method. The films were characterized by SEM, EDS, and UV-Vis Spectroscopy. When the SEM images were examined, the nanostructures showed different morphological features as the amount of doped (v) nickel-ZnO increased in comparison to undoped nickel-ZnO. Furthermore, it was demonstrated that the obtained film surface has a homogeneous distribution. EDS spectra showed the increase in Ni by volume and its presence in the film composition. The UV-Vis Spectroscopy results showed that Ni doping can change the transmittance and band gap values from 2.94 to 3.38, and thus the ZnO band gap can be adjusted by Ni doping. As a result of the findings, ZnO-NiO thin films are promising candidates for both high-performance hetero nanostructures and practical applications.

Comparative studies of “3d” transition metals (Co, Mn, Ni) doped ZnO nanoparticles for visible light degradation of methylene blue

The development of efficient visible-light photocatalysts is highly desired for a clean and sustainable environment. Herein, we report the fabrication and functionalization of zinc oxide (ZnO) nanostructures for the degradation of organic pollutants, one of the key components of environmental pollution. Pure and “3d” transition metal ions doped ZnO (Zn1−xMxO, where M = Mn, Ni, Co with varying doping concentration x = 1 % and 7 %) were synthesized by co-precipitation method and their structural, electronic, morphological, and optical properties were investigated in detail. The powder X-ray diffraction (XRD) pattern of pure and Zn1−xMxO nanostructures confirmed the hexagonal wurtzite phase (p63mc) with an average crystallite size of around 22–27 nm. The energy dispersive x-ray (EDX) analysis confirmed the presence of metal dopants in ZnO. The morphology of synthesized nanostructures was found to be spherical. The band gap of ZnO was considerably narrowed from 3.15 to 1.8 eV through doping, indicating extension towards visible light absorption. Photoluminescence (PL) emission spectra of doped ZnO revealed a low recombination rate of electrons (e-) and holes (h+) and various possible defect states within the bandgap. Furthermore, electron spin resonance showed the presence of Mn2+ centers. Optimized metal-doped zinc oxide revealed higher photocatalytic activity, during degradation of methylene blue model dye under visible light.

Coalescing ZnO and graphene oxide to form ZnO@graphene oxide nanohybrid for healthcare applications

Nanohybrids with less toxicity and excellent antibacterial activity have fascinated researchers across the globe in the recent past. In the present work, zinc [email protected] oxide ([email protected]) nanohybrid along with zinc oxide (ZnO) were fabricated via the co-precipitation method. The structural and morphological features reveal the homogeneity in the dispersion of ZnO particles on the graphene oxide with less agglomeration. The band gap of ZnO decorated on the GO is found to be 3.18 eV while that of pristine ZnO is 3.21 eV. By using the disc diffusion method, the antibacterial efficacies of ZnO and [email protected] nanohybrid were gauged against the bacterial species Escherichia coli and Staphylococcus aureus. The enhancement in the antibacterial efficacy of the [email protected] nanohybrid reflects its advanced bio-compatibility compared to ZnO. The results reported herein focus the prominence of the nanohybrid based on the semiconductor hybridized with the carbonaceous materials in the development of effective bactericidal agents.

Novel photo and bio-active greyish-black cotton fabric through air- and nitrogen- carbonized zinc-based MOF for developing durable functional textiles

This study explores the potential of using the carbonization of Zn-based metal-organic frameworks (Zn-MOF-5) under N2 and air to modify zinc oxide (ZnO) nanoparticle for the production of various photo and bio-active greyish-black cotton fabrics. The MOF-derived ZnO under N2 demonstrated a significantly higher specific surface area (259 m2g−1) compared to ZnO (12 m2g−1) and MOF-derived ZnO under air (41.6 m2 g−1). The products were characterized using various techniques, including FTIR, XRD, XPS, FE-SEM, TEM, HRTEM, TGA, DLS, and EDS. The tensile strength and dye degradation properties of the treated fabrics were also investigated. The results indicate that the high dye degradation capability of MOF-derived ZnO under N2 is likely due to the lower ZnO band gap energy and improvement in electron-hole pair stability. Additionally, the antibacterial activities of the treated fabrics against Staphylococcus and Pseudomonas aeruginosa were investigated. The cytotoxicity of the fabrics was studied on human fibroblast cell lines using an MTT assay. The study findings demonstrate that the cotton fabric covered with carbonized Zn-MOF under N2 is human-cell compatible while showing high antibacterial activities and stability against washing, highlighting its potential for use in developing functional textiles with enhanced properties.

Optical and Structural Properties of 2D ZnO Nanosheets Synthesized Using Simple Chemical Solution Route

In the present paper, two-dimensional (2D) Zinc oxide (ZnO) nanosheets were prepared through a simple, single-step chemical solution method followed by annealing treatment without any surfactant, template or catalyst. The prepared ZnO nanosheets were characterized for their structural and optical properties by different techniques such as XRD, SEM with EDS, RAMAN, FTIR, UV-Visible and photoluminescence (PL) spectroscopy. The X-ray diffraction (XRD) spectra display sharp and highly intense peaks corresponding to the (101) plane, confirming the wurtzite crystal structure of ZnO. Scanning electron microscopy (SEM) images confirm the sheet-like structure of ZnO nanosheets with a thickness of approximately 23 nm. The elemental composition has been estimated through the Energy dispersive spectroscopy (EDS) technique. The basic reaction mechanism is discussed in detail. The stretching vibrations of Zn and O bonding were observed from FTIR spectra. The optical properties and optical bandgap have been obtained by UV-Visible and PL spectroscopy. The optical bandgap of ZnO is 3.20 eV from UV-Visible spectroscopy via Tauc’s plot. PL measurement confirming oxygen deficiency in ZnO nanosheets. These results of prepared ZnO nanosheets are expected to perform well in various applications such as photodetectors, sensors and in optoelectronic devices.

UV Sensor Based on Surface Acoustic Waves in ZnO/Fused Silica.

Zinc oxide (ZnO) thin films have been grown by radio frequency sputtering technique on fused silica substrates. Optical and morphological characteristics of as-grown ZnO samples were measured by various techniques; an X-ray diffraction spectrum showed that the films exhibited hexagonal wurtzite structure and were c-axis-oriented normal to the substrate surface. Scanning electron microscopy images showed the dense columnar structure of the ZnO layers, and light absorption measurements allowed us to estimate the penetration depth of the optical radiation in the 200 to 480 nm wavelength range and the ZnO band-gap. ZnO layers were used as a basic material for surface acoustic wave (SAW) delay lines consisting of two Al interdigitated transducers (IDTs) photolithographically implemented on the surface of the piezoelectric layer. The Rayleigh wave propagation characteristics were tested in darkness and under incident UV light illumination from the top surface of the ZnO layer and from the fused silica/ZnO interface. The sensor response, i.e., the wave velocity shift due to the acoustoelectric interaction between the photogenerated charge carriers and the electric potential associated with the acoustic wave, was measured for different UV power densities. The reversibility and repeatability of the sensor responses were assessed. The time response of the UV sensor showed a rise time and a recovery time of about 10 and 13 s, respectively, and a sensitivity of about 318 and 341 ppm/(mW/cm2) for top and bottom illumination, respectively. The ZnO/fused silica-based SAW UV sensors can be interrogated across the fused silica substrate thanks to its optical transparency in the UV range. The backlighting interrogation can find applications in harsh environments, as it prevents the sensing photoconductive layer from aggressive environmental effects or from any damage caused by cleaning the surface from dust which could deteriorate the sensor's performance. Moreover, since the SAW sensors, by their operating principle, are suitable for wireless reading via radio signals, the ZnO/fused-silica-based sensors have the potential to be the first choice for UV sensing in harsh environments.

Effect of feedstock solution concentration on the spectroscopic and electrical transport properties of thermal plasma synthesized ZnO nanoparticles

The structural, optical, spectroscopic, and electrical transport properties of zinc oxide (ZnO) nanoparticles prepared using the solution precursor plasma spray (SPPS) technique were investigated for different feedstock solution concentrations such as 1-mol and 4-mol. Rietveld refined powder X-ray diffraction and Raman spectra reveal that the prepared ZnO crystallizes in a hexagonal wurtzite structure with no secondary phase. The crystallite sizes for 1-mol and 4-mol samples are 27.5 nm and 31.3 nm, respectively. Analysis of UV–vis spectra shows that ZnO's band gap has increased from 3.19 eV to 3.23 eV as the mole concentration has increased. The spherical nature and nano size of the ZnO are confirmed by the pictures obtained using field emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). The presence of elements zinc and oxygen in the Zn2+ and O2− ionic states are revealed by X-ray photoelectron spectroscopy (XPS). Electrical study demonstrates that the initial mole concentration of ZnO powder affected both its electrical conductivity and dielectric constant. The activation energy value of electrical conductivity for 1-mol and 4-mol is 0.661 eV and 0.552 eV, respectively. The impedance analysis shows the electrode effect for the 1-mol sample whereas it is not observed for the 4-mol sample, which is further confirmed by modulus analysis. The presence of defect in the 1-mol sample results in a lower conductivity (3.68 × 10−12 S/cm at 1 Hz) than the 4-mol sample. The comprehensive analysis confirms that the structural, spectroscopic and electrical properties of the ZnO nanoparticle can be tunable to meet demand by changing the feedstock mole concentration in the SPPS process.

Investigation of optical properties of zinc oxide nanofilms deposited by electrodeposition technique

Zinc oxide (ZnO) nanofilms were synthesized by electrochemical deposition from a simple aqueous zinc chloride onto indium tin oxide (ITO) substrate. Chronoamperometry experiments were performed to deposit nanofilms at the cathodic potential −1.0 V and time 5000 s at 70°C. Diffraction measurements of x-ray showed the hexagonal wurtzite structure of the as-grown nanofilms and the preferred orientation was along the (002) axis. A well-defined ZnO morphology was generated under −1.0 V for 1000 s on ITO glass. Atomic force microscopy observations explored the effect of electrode coating technique on the microscale ZnO nanofilms. The optical constants and thickness of nanofilms were determined with high precision using spectroscopic ellipsometry. The measurements of photoluminescence demonstrated two emission peaks; the first of which was related to excitonic emissions at about 392 nm, referring to the band gap of ZnO, and the second was related to oxygen vacancies ionized singly at about 490 nm.

Effect of Repeated Contact to Food Simulants on the Chemical and Functional Properties of Nano ZnO Composited LDPE Films for Reusable Food Packaging

The effect of repeated contact with food simulants on the properties and functionality of zinc oxide (ZnO) in nanocomposite films was investigated to examine possible safety hazards from the point of view of long-term use as food packaging. Low-density polyethylene (LDPE) embedded with 5 wt% nano-ZnO was immersed in distilled water, 50% ethanol, 4% acetic acid, and n-heptane. The cycle of immersion-rinse-dry was repeated up to 40 times for same sample under constant condition. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), field emission-scanning electron microscopy (FE-SEM), and UV-Vis spectroscopy analyses were performed to identify the changes in the chemical and functional properties of the nanocomposite film. Acetic acid had the greatest impact on the LDPE-ZnO nanocomposite films, while other food simulants caused little change. A new carboxylate bond was formed by the reaction of ZnO with acetic acid, as evidenced by the FTIR spectra. In addition, XRD and XAS confirmed the phase changes of nano-ZnO into zinc salts such as zinc hydroxy acetate or zinc acetate dihydrate. Furthermore, the light barrier property of the nanocomposite film drastically decreased, owing to the change in the bandgap of ZnO and film morphology.

Morphological and optical properties of Nb-doped ZnO nanoparticles

Niobium (Nb) was successfully doped into zinc oxide (ZnO) thin film via a modified sol–gel spin coating technique. Zinc acetate, diethanolamine, and isopropyl were used as starting material, stabilizer, and solvent, respectively. Energy Dispersive X-ray Spectroscopy (EDX) analysis shows the presence of Niobium of 1.01 at. %. on ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) shows the thin film composed of nanoparticles. The estimation size of particles slightly reduced from 44.15 nm for undoped ZnO nanoparticles to 35.77 nm after the introduction of the niobium dopant. The roughness of Nb-doped ZnO thin films was lower as compared to undoped films based on atomic force microscopy (AFM) analysis. The optical properties were investigated using UV–vis and the results had shown that both samples exhibit good transmittance in visible range. In addition, the absorption edge was red-shifted after being doped with niobium. The estimated optical band gap of Nb-doped ZnO reduced to 3.27 eV from 3.30 eV for undoped ZnO nanoparticles.

Precursor mediated and defect engineered ZnO nanostructures using thermal chemical vapor deposition for green light emission

We used thermal chemical vapour deposition to synthesize zinc oxide nanostructured thin films on n-type silicon substrate using zinc oxide (ZnO) and zinc chloride (ZnCl2) powder precursors in conjunction with bulk graphite powder. The synthesized ZnO nanostructured thin films structures are polycrystalline with a relatively enhanced c-axis orientation for ZnO powder precursor with respect to that of ZnCl2 precursor. The scanning electron microscopic analysis substantiate the higher c-axis orientation of ZnO nanostructures, grown using ZnO powder precursor. The photoluminescence (PL) and UV–Vis measurements suggest the presence of zinc vacancies, causing the green emission from both nanostructured thin films. The measured bandgap of ZnO nanostructured thin film using ZnO powder precursor is slightly higher than that of ZnCl2 powder precursor. The capacitance-voltage and Mott-Schottky measurements showed the n-type characteristics with 6.3 × 1016 cm−3 and 2.7 × 1015 cm−3 carrier densities for ZnO nanostructured thin films prepared using ZnO and ZnCl2 precursors, respectively. The current-voltage measurements showed relatively lower current for ZnO nanostructured thin films, synthesized using ZnCl2 precursor, signifying the presence of zinc vacancies trap sites and is also consistent with Mott-Schottky measurements, showing lower carrier concentrations with respect to that of ZnO precursor derived ZnO nanostructured thin films. Thus, controlled Zn vacancies in ZnO nanostructured thin films may lead to the efficient green light emitters, useful for green light colour emission applications.

Optical and surface properties of Gd-doped ZnO thin films deposited by thermionic vacuum arc deposition technology

In this paper, Zinc oxide (ZnO) was doped with Gadolinium (Gd) and it was deposited onto the glass and silicon substrates by thermionic vacuum arc (TVA) method to examine its morphological, compositional, and optical properties. The results show that the substrates strongly affect the morphological structures of the thin films. According to the obtained information, the surface roughness was found to be 38 nm and 6 nm for silicon and glass respectively. The images showed that the surface onto the glass had more symmetry and more regular grains. The optical properties of the nano composite on the glass substrate were analyzed with an optical interferometer and UV–Vis spectrophotometer. Absorbance, transparency, and refractive index of the thin film were obtained. It also had a relatively high refractive index. Furthermore, it was found that the band gap of ZnO decreased. The band gap of the deposited thin film was found 3.3 eV.

Machine-learning-aided DFT-1/2 calculations for bandgaps of zinc oxide thin films

Using the Density Functional Theory (DFT) -1/2 method, the electronic structure and bandgap of zinc oxide (ZnO) are calculated, providing the initial data sets for machine learning based on the genetic-algorithm-based artificial neural networks (GANNs) model. The predicted bandgaps from the well-trained GANNs model are close to (less than 5%) the calculated ones from the DFT-1/2 method along cutoff radius = 2.4 for Oxygen and cutoff radius = 1.2 for Zinc, agreeing with the experimental data. Our results show that combining the DFT-1/2 method with GANNs is an efficient way to correct the band gap of Zinc Oxide in DFT simulation.

Nitrogen-doped carbon-ZnO heterojunction derived from ZIF-8: a photocatalytic antibacterial strategy for scaffold

Antibacterial property is urgently needed in scaffold-induced bone regeneration. Zinc oxide (ZnO) as a photocatalyst enables to produce photoexcited electron-hole pairs to catalyze reactive oxygen species (ROS) generation, which triggers the peroxidation and consequently apoptosis of bacteria. However, the fast recombination of electron-hole pairs and the wide band gap of ZnO restrict the full play of its antibacterial property. Herein, a nitrogen-doped carbon-ZnO (NC-ZnO) heterojunction derived from metal organic frameworks was synthesized by direct carbonization. On one hand, the N-doped C in NC-ZnO acted as electron acceptors to trap photoexcited electrons in conduction band of ZnO, which improved the separation efficiency of electron-hole pairs. On the other hand, the N-doped C with high absorption coefficient enabled NC-ZnO to possess a relatively narrow band gap and wide light absorption range compared with ZnO. The obtained NC-ZnO heterojunction was then introduced into poly-l-lactic acid (PLLA) scaffold to construct a photodynamic antibacterial platform. The results showed that NC-ZnO endowed the scaffold with excellent photocatalytic activity and greatly stimulated the production of ROS. The antibacterial tests suggested that the PLLA/NC-ZnO scaffold possessed robust antibacterial activities with 99.9% antibacterial efficiency toward Escherichia coli, which was increased by 113.9% compared with PLLA/ZnO scaffold.

Sensing Performance of a ZnO-based Ammonia Sensor

Monitoring and remediation of toxic and flammable gases have become a critical task for the development of a clean society. Among various types of metal oxide semiconductors (MOS), zinc oxide (ZnO) is considered a potential material for gas sensing application because of its high sensitivity, easy synthesis, and high thermal stability behaviours. This research aimed to gain an in-depth understanding of the sensing task of a very stable and porous thin film of spin coated ZnO for detecting toxic ammonia vapour at room temperature. As-prepared ZnO films were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) analyses. XRD and SEM results revealed the polycrystalline wurtzite ZnO phase with grainy surface morphology. Optical calculations quantify the direct band gap of ZnO as 3.2 eV. The sensitivity measurements showed a good response ratio of 38.5 ± 0.6 with an exposure of 400 ppm of ammonia vapour. The results on sensitivity measurement of several cycles illustrated its stability and sensing performance better than other reported similar works. These findings will be useful to develop a low cost and efficient room temperature MOS gas sensor that can efficiently detect extremely low concentrations as 20 ppm of ammonia vapour which is below the Occupational Safety and Health Administration (OSHA) recommended value.

Effect of Mn doping on the structural, optical, magnetic properties, and antibacterial activity of ZnO nanospheres

This work investigates the systematic study of the structural, optical, magnetic, and antibacterial properties of Mn-doped ZnO. Zinc oxide (ZnO) and Mn2+ doped zinc oxide (ZnMnO) nanoparticles (NPs), were prepared through the co-precipitation method. The X-ray diffraction studies confirmed that the synthesized nanoparticles did not modify the crystal structure upon Mn doping. However, the microstructural parameters were changed considerably upon the increase of the concentration of Mn dopant. The HRTEM images showed that the ZnO NPs exhibit nanospheres-like morphology, and a reduction in the average particle size from 41 nm to 33 nm was observed upon Mn2+ doping. The elemental composition of Zn, Mn, and O atoms were identified by EDAX spectra. The Zn–O stretching bands were observed at around 550 cm−1 in the FTIR spectra and the zinc and oxygen vacancies defects were confirmed by PL spectra. The estimated band gap of ZnO was 2.95 eV and increased to 3.14 eV for ZnMnO3. In addition, the Mn-doped ZnO NPs showed a more significant antibacterial effect than the pure ZnO NPs. The ZnO and Mn-doped ZnO NPs showed significant changes in the M-H loop where the diamagnetic behavior of ZnO changes to a weak ferromagnetic nature when doped with Mn ions. Graphical abstract