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Hexagonal würtzite structure of ZnO. Elementary cell with parameters a = b = c and α = β = 90 • , γ = 120 • was marked.
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In this work, nanocrystalline powders of iron-doped zinc oxide ZnO (iron content 3, 5, and 10 at.%) were
prepared utilizing co-precipitation method. X-ray diffraction, scanning electron microscopy, and the Mössbauer
spectroscopy were used as complementary methods to investigate the structure and hyperfine interactions of the
material. It was found...
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... oxide can be observed in two crystalline forms, i.e., hexagonal würtzite ( Fig. 1) and cubic zinc blende, the former being most stable at ambient conditions. The bonding in ZnO is ionic (Zn 2+ -O 2− ). Hexagonal ZnO belongs to the family of wide band-gap semiconductors, having a band gap of about 3.3 eV at room temperature. Moreover, zinc oxide has piezoelectric and pyroelectric properties [10], hardness of 4.5 on ...
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... Our obtained c/a ratio in all samples is significantly smaller in comparison to an ideal stoichiometric wurtzite structure (c/a = 1.6330). This result may be an indication of the presence of oxygen and/or zinc vacancies in the ZnO lattice, which are formed to keep charge neutrality [43]. The presence of oxygen and zinc vacancies can be seen from the photoluminescence (PL) spectra of Fe-ZnO nanoparticles as shown in Figure 5 It was also observed that the peak position (101) of Fe doped ZnO samples prepared by both precipitation method and microwave method B shifted towards a lower diffraction angle when compared to the corresponding peak position in undoped ZnO. ...
Iron doped ZnO (Fe-ZnO) nanoparticles were synthesized using two techniques that are economical as well as scalable to yield tunable properties of nanoparticles for facilitating down conversion in an absorbing layer of a solar cell. To evaluate the suitability of Fe-ZnO nanoparticles prepared by two deposition methods, we present a comparison of optical, electrical, and structural properties of Fe-ZnO using several experimental techniques. Structural properties were analyzed using transmission electron microscopy and x-ray diffraction spectroscopy (XRD) with Rietveld analysis for extracting information on compositional variations with Fe doping. The chemical composition of nanoparticles was analyzed through X-ray photoelectron spectroscopy (XPS). The optical properties of nanoparticles were studied using photoluminescence and UV-Vis absorption spectroscopy. In addition, fluorescence lifetime measurement was also performed to study the changes in an exponential decay of lifetimes. The electrical transport properties of Fe-ZnO were analyzed by impedance spectroscopy. Our studies indicate that ethanol as a solvent in a microwave method would produce smaller nanoparticles up to the size of 11 nm. In contrast, the precipitation method produces secondary phases of Fe2O3 beyond 5% doping. In addition, our studies show that the optical and electrical properties of resulting Fe-ZnO nanoparticles depend on the particle sizes and the synthesis techniques used. These new results provide insight into the role of solvents in fabricating Fe-ZnO nanoparticles by precipitation and microwave methods for photovoltaic and other applications.
... At an optimal dose of 500 µg/mL, the time for complete disinfection for Fe/ZnO NPs was relatively shorter (i.e., 80 min) when compared to undoped ZnO (120 min) and TiO2 (180 min) as shown in Figure 38b (inset). By doping with Fe, Fe 3+ ions replaced Zn 2+ ions at tetrahedral sites of ZnO [307]. Under solar light irradiation, Fe 3+ ions acted as the hole and electron traps, thus promoting the ROS generation. ...
... At an optimal dose of 500 µg/mL, the time for complete disinfection for Fe/ZnO NPs was relatively shorter (i.e., 80 min) when compared to undoped ZnO (120 min) and TiO 2 (180 min) as shown in Figure 38b (inset). By doping with Fe, Fe 3+ ions replaced Zn 2+ ions at tetrahedral sites of ZnO [307]. Under solar light irradiation, Fe 3+ ions acted as the hole and electron traps, thus promoting the ROS generation. ...
This article reviews the recent developments in the synthesis, antibacterial activity, and visible-light photocatalytic bacterial inactivation of nano-zinc oxide. Polycrystalline wurtzite ZnO nanostructures with a hexagonal lattice having different shapes can be synthesized by means of vapor-, liquid-, and solid-phase processing techniques. Among these, ZnO hierarchical nanostructures prepared from the liquid phase route are commonly used for antimicrobial activity. In particular, plant extract-mediated biosynthesis is a single step process for preparing nano-ZnO without using surfactants and toxic chemicals. The phytochemical molecules of natural plant extracts are attractive agents for reducing and stabilizing zinc ions of zinc salt precursors to form green ZnO nanostructures. The peel extracts of certain citrus fruits like grapefruits, lemons and oranges, acting as excellent chelating agents for zinc ions. Furthermore, phytochemicals of the plant extracts capped on ZnO nanomaterials are very effective for killing various bacterial strains, leading to low minimum inhibitory concentration (MIC) values. Bioactive phytocompounds from green ZnO also inhibit hemolysis of Staphylococcus aureus infected red blood cells and inflammatory activity of mammalian immune system. In general, three mechanisms have been adopted to explain bactericidal activity of ZnO nanomaterials, including direct contact killing, reactive oxygen species (ROS) production, and released zinc ion inactivation. These toxic effects lead to the destruction of bacterial membrane, denaturation of enzyme, inhibition of cellular respiration and deoxyribonucleic acid replication, causing leakage of the cytoplasmic content and eventual cell death. Meanwhile, antimicrobial activity of doped and modified ZnO nanomaterials under visible light can be attributed to photogeneration of ROS on their surfaces. Thus particular attention is paid to the design and synthesis of visible light-activated ZnO photocatalysts with antibacterial properties.
A series of Zn[Formula: see text]Fe x O ([Formula: see text], 0.015, 0.045, 0.075) nanoparticles were synthesized using the solution co-precipitation method, and their structural and property characteristics were investigated. X-ray diffraction (XRD) analysis revealed that all Zn[Formula: see text]Fe x O samples exhibited a hexagonal wurtzite crystal structure with the P63mc space group. The introduction of Fe doping led to a slight lattice distortion in the samples. The morphology of the nanoparticles, including polydispersion and agglomeration, as well as the presence of the second phase ZnFe 2 O 4 , was examined by scanning electron microscope (SEM) and transmission electron microscope (TEM). UV–Vis diffuse reflectance spectroscopy demonstrated that the band gap of Zn[Formula: see text]Fe x O lies between 3.152 and 3.163[Formula: see text]eV. With the increase in Fe ion doping, the band gap shows a slight decreasing trend. Mössbauer spectroscopy revealed that iron ions in the nanoparticles existed in a trivalent state and exhibited two different configurations: One involved iron replacing zinc without creating a vacancy, while the other involved iron substituting zinc with a vacancy. The ferromagnetic nature of the Fe-doped samples can be attributed to the exchange interaction between two Fe[Formula: see text] ions mediated by the F-center mechanism.
Candidiasis is an infection caused by the fungus C. albicans . Ferrofluid Zn 0.2 Fe 2.8 O 4 /Ag is the best candidate to overcome the problem of infection caused by this fungus. In addition to the safe ingredients used, its ability to create ROS and maintain stability has the potential to be an excellent antifungal agent. The purpose of this study was to create a new ferrofluid with double surfactants for the antifungal C. albicans. Zn 0.2 Fe 2.8 O 4 /Ag ferrofluids were synthesized using a bottom-up method, starting from the synthesis of Zn 0.2 Fe 2.8 O 4 nanoparticles, Zn 0.2 Fe 2.8 O 4 /Ag nanocomposites, to the synthesis of Zn 0.2 Fe 2.8 O 4 /Ag ferrofluids. Zn 0.2 Fe 2.8 O 4 /Ag powder was characterized using XRD and SEM to determine the particle structure and morphology. Meanwhile, Zn 0.2 Fe 2.8 O 4 /Ag ferrofluids were characterized using FTIR and antifungal activity tests to determine the functional group and zone of inhibition against the growth of the fungus C. albicans . The results of the characterization analysis showed that Zn 0.2 Fe 2.8 O 4 /Ag nanoparticles had good crystallinity, with a crystallite size of Zn 0.2 Fe 2.8 O 4 /Ag of 11.32 nm and an Ag crystallite size of 7.00 nm. SEM characterization showed that Zn 0.2 Fe 2.8 O 4 /Ag nanoparticles had agglomeration with the average particle size distribution of 443 nm. The functional groups detected by FTIR confirmed the success of the ferrofluid synthesis Zn 0.2 Fe 2.8 O 4 /Ag where spinel functional groups, olefin groups, and functional groups S=O were formed. The results of the antifungal activity test showed that Zn 0.2 Fe 2.8 O 4 /Ag ferrofluids were relatively active as an antifungal agent, with a diameter of the C. albicans growth inhibition zone of 9.63 mm.
We synthesized Mg and Cu caged ZnO nanoparticles by considering polyvinyl alcohol (PVA), Poly vinylpyrrolidone (PVP) and biotin (BT) as organic stablizer by chemical co-precipitation route at room temperature. All the synthesized materials were characterized by X-ray diffraction (XRD), showed good crystallinity at low dimension with stabilized crystallite size. No uneanted phase formation was detected. High resolution transmission electron microscopy (HRTEM) images of crystallite planes of PVP caped Mg doped ZnO and PVA caped Cu doped ZnO suggesting that the prepared particles are mostly multi-domain crystallites. The average particles diameter in the case of PVP caped Mg doped ZnO and PVA caped Cu doped ZnO are around 50 nm and 38 nm respectively. The particle sizes are controlled by using different capping agents PVA, PVP and biotin. Photoluminescence spectroscopy (PL) shows another green wider emission band from 450 nm to 650 nm in the visible spectral range, apart from UV band, which has been frequently assigned to several intrinsic and extrinsic defects. The band gap of the doped ZnO nanoparticles was estimated from the UV-Vis absorption spectra. The energy gap estimated for all samples are found to be decreases due to the effect of the dopant, in comparison to the energy gap of bulk ZnO (3.37 eV). Raman spectra show several peaks characteristic to the defects of oxygen vacancies, Zn interstitials and vibrational modes in ZnO.
