Structural and Magnetic Properties of Co‒Mn Codoped ZnO Nanoparticles Obtained by Microwave Solvothermal Synthesis

Rapid Bio-Assisted Synthesis and Magnetic Behavior of Zinc Oxide/Carbon Nanoparticles

The biomimetic synthesis of a ZnO/C nanocomposite has been achieved using the egg white-assisted self-combustion method. The characterization of this composite has been carried out using different techniques, such as XRD, FTIR, Raman, SEM/EDS and TEM. A comparative study was conducted between ZnO in the form of this composite and pristine ZnO, which was prepared via the same procedures but without the egg white. The resulting ZnO had a hexagonal structure, similar to wurtzite, with a P63mc space group. When this egg white method was used to produce a ZnO-based material, a ZnO/C nanocomposite was developed, and the ZnO’s crystallite size was significantly decreased. The structural properties—including the unit cell volume, strain, atom displacement and dislocation density—of this ZnO crystal are increased as a result of the presence of a C atom. On the other hand, the length of the Zn–O bond is reduced by the presence of the C atom. Results derived from a combination of Raman, FTIR, and EDS demonstrate that the carbonaceous layers and ZnO nanoparticles were integrated with a close interfacial contact. The preparation method used here brought about obvious changes in the morphological and magnetic behaviors of the as-prepared materials. Using a small amount of egg white resulted in the transformation of the particle’s shape from a hexagonal cone-type structure to an ellipsoidal structure. Based on an analysis of diffuse reflectance, the ZnO and ZnO/C band gap values were revealed using UV–VIS spectra. ZnO and ZnO/C exhibit band gap energies of 3.09 and 2.60 eV, respectively. A phase transition from weakly ferromagnetic to completely diamagnetic magnetic was discovered.

Synthesis, Characteristics, and Effect of Zinc Oxide and Silver Nanoparticles on the In Vitro Regeneration and Biochemical Profile of Chrysanthemum Adventitious Shoots

Studies on nanoparticles' effects on plants are relevant for horticulture. This study aimed to test the influence of zinc oxide submicron particles (ZnO SMPs), zinc oxide nanoparticles (ZnO NPs), and zinc oxide nanoparticles combined with silver nanoparticles (ZnO+1%Ag NPs) applied at 100 and 500 mg·L^-1 on the regeneration and biochemical activity of adventitious shoots in Chrysanthemum × morifolium (Ramat.) Hemsl. 'UTP Burgundy Gold' and 'UTP Pinky Gold'. The original microwave solvothermal synthesis and characteristics of the ZnO samples were described. Internodes were cultured on the MS medium with 0.6 mg∙L^-1 6-benzylaminopurine (BAP) and 2 mg∙L^-1 indole-3-acetic acid (IAA). In 'UTP Burgundy Gold', the highest shoot regeneration efficiency was obtained for 100 mg·L^-1 ZnO SMPs and 500 mg·L^-1 ZnO NPs treatments (6.50 and 10.33 shoots per explant, respectively). These shoots had high or moderate chlorophyll and carotenoid contents. In 'UTP Pinky Gold', the highest shoot number was produced in the control (12.92), for 500 mg·L^-1 ZnO SMPs (12.08) and 500 mg·L^-1 ZnO NPs (10.42). These shoots had increased chlorophyll (a+b)-to-carotenoid ratios. In 'UTP Pinky Gold', the ZnO SMPs and ZnO NPs affected the anthocyanins biosynthesis, whereas ZnO + 1%Ag NPs decreased the phenolics accumulation. These results are important for the improvement of chrysanthemum micropropagation.

Structural, FTIR spectra and optical properties of pure and co-doped Zn1-x-y Fe x M y O ceramics with (M = Cu, Ni) for plastic deformation and optoelectronic applications

We report here a considered novel study on the structural, FTIR spectra and optical properties of pure and co-doped Zn0.90-x Fe0.1M x O with ((M = Cu, Ni and (x = 0.00, 0.10) and (0.00 < y < 0.20)) at different sintering temperatures T s (T s  = 850 °C for series I and 1000 °C series II). Although the ZnO wurtzite structure is conformed for all samples, some secondary lines with little intensity are formed. But the number of these lines is higher for series I than for series II. The (c/a) value and U-parameter are almost constant for all samples, while Zn-O bond length L is slightly increased. The porosity and crystallite size are decreased by Fe, and also for (Fe + Cu) samples, and their values for series I are lower than for series II. The residual stress is tensile for most samples. Interestingly, the Young's, rigid and bulk modulus, Poisson's ratio and Debye temperature, obtained from FTIR analysis, are increased by Fe addition with a further increase for Fe + Ni) samples for both series. A ductile nature is obtained for pure, Fe and (Fe + Cu) samples; whereas a brittle nature is approved for (Fe + Ni) samples. On the other hand, the energy gap (E g ), residual lattice dielectric constant (ε L ) and carrier density N are increased by Fe addition, followed by a further increase for (Fe + Cu) samples, while the vice is versa for the inter-atomic distance R. For example, E g was increased from 3.153 eV for pure ZnO to 3.974 eV for (Fe + Cu) samples (i.e., 0.821 eV more), while it was decreased to 2.851 eV for (Fe + Ni) samples (i.e., 0.302 eV less). A direct behavior is obtained between E g and both elastic modulus (Y, β), lattice and micro strains (ε L , ε m ), dislocation density (δ), residual stress (σ) and carrier density N, whereas a reverse behavior is obtained between E g and both crystallite size (D), porosity (PS) and inter-atomic distance (R) . These results are explained in terms of the generated blocked states of the conduction band as indicated by the Burstein Moss effect. These novel findings reveal that the co-doping has intense ZnO and moderate metal oxide modes in the ZnO matrix structure, which makes ZnO co-doped with (Fe + Cu) more suitable for gas sensors and optoelectronic devices. In contrast, ZnO co-doped with (Fe + Ni) samples is strongly recommended for altering plastic deformation. To our knowledge, the present investigation can be considered the first study and probably has never been discussed elsewhere, which highlights the present investigation.

Facile Chemical Synthesis of Doped ZnO Nanocrystals Exploiting Oleic Acid

Zinc oxide nanocrystals (ZnO-NCs) doped with transition metal elements or rare earth elements can be probed for magnetic resonance imaging to be used as a molecular imaging technique for accurate diagnosis of various diseases. Herein, we use Mn as a candidate of transition metal elements and Gd as a presenter of rare earth elements. We report an easy and fast coprecipitation method exploiting oleic acid to synthesize spherical-shaped, small-sized doped ZnO-NCs. We show the improved colloidal stability of oleate-stabilized doped ZnO-NCs compared to the doped ZnO-NCs synthesized by conventional sol-gel synthesis method, i.e., without a stabilizing agent, especially for the Mn dopant. We also analyze their structural, morphological, optical, and magnetic properties. We are able to characterize the persistence of the crystalline properties (wurtzite structure) of ZnO in the doped structure and exclude the formation of undesired oxides by doping elements. Importantly, we determine the room-temperature ferromagnetism of the doped ZnO-NCs. This oleate-stabilized coprecipitation method can be subjected as a standard procedure to synthesize doped and also co-doped ZnO-NCs with any transition metal elements or rare earth elements. In the future, oleate-stabilized Gd/Mn-doped ZnO-NCs can be exploited as magnetic resonance imaging (MRI) contrast agents and possibly increase the signal intensity on T1-weighted images or reduce the signal intensity on T2-weighted images.

A Review of Microwave Synthesis of Zinc Oxide Nanomaterials: Reactants, Process Parameters and Morphoslogies

Zinc oxide (ZnO) is a multifunctional material due to its exceptional physicochemical properties and broad usefulness. The special properties resulting from the reduction of the material size from the macro scale to the nano scale has made the application of ZnO nanomaterials (ZnO NMs) more popular in numerous consumer products. In recent years, particular attention has been drawn to the development of various methods of ZnO NMs synthesis, which above all meet the requirements of the green chemistry approach. The application of the microwave heating technology when obtaining ZnO NMs enables the development of new methods of syntheses, which are characterised by, among others, the possibility to control the properties, repeatability, reproducibility, short synthesis duration, low price, purity, and fulfilment of the eco-friendly approach criterion. The dynamic development of materials engineering is the reason why it is necessary to obtain ZnO NMs with strictly defined properties. The present review aims to discuss the state of the art regarding the microwave synthesis of undoped and doped ZnO NMs. The first part of the review presents the properties of ZnO and new applications of ZnO NMs. Subsequently, the properties of microwave heating are discussed and compared with conventional heating and areas of application are presented. The final part of the paper presents reactants, parameters of processes, and the morphology of products, with a division of the microwave synthesis of ZnO NMs into three primary groups, namely hydrothermal, solvothermal, and hybrid methods.