Visible-Light-Driven Room Temperature NO2 Gas Sensor Based on Localized Surface Plasmon Resonance: The Case of Gold Nanoparticle Decorated Zinc Oxide Nanorods (ZnO NRs)

In this work, nitrogen dioxide (NO2) gas sensors based on zinc oxide nanorods (ZnO NRs) decorated with gold nanoparticles (Au NPs) working under visible-light illumination with different wavelengths at room temperature are presented. The contribution of localized surface plasmon resonant (LSPR) by Au NPs attached to the ZnO NRs is demonstrated. According to our results, the presence of LSPR not only extends the functionality of ZnO NRs towards longer wavelengths (green light) but also increases the response at shorter wavelengths (blue light) by providing new inter-band gap energetic states. Finally, the sensing mechanism based on LSPR Au NPs is proposed.

SYNTHESIS AND STUDY OF GAS-SENSITIVE NANOSTRUCTURES OF THE Zn-Sn-O SYSTEM

Наностержни оксида цинка синтезированы гидротермальным методом. Проведена обработка полученных образцов в водно-спиртовом растворе станната калия и мочевины при 170°С в течение 30 и 60 минут. В результате получены наноструктуры Zn - Sn - O. Химический состав поверхности образцов ZnO и Zn - Sn - O исследован с помощью рентгеновской фотоэлектронной спектроскопии. Проанализирована их чувствительность к парам изопропилового спирта (1000 мд) при температурах 120 °С, 180°С, 250 °С. Показано перераспределение электронной плотности при формировании композитных наноструктур Zn - Sn - O, проявляющееся в химическом сдвиге пиков O1s и Zn2p. Это свидетельствует о перестроении химических связей при замещении атомов цинка оловом. Обнаружено, что чувствительность композитных структур к парам изопропилового спирта значительно превышает чувствительность ZnO во всем исследуемом температурном диапазоне. Улучшение газочувствительных свойств связано с наличием в образцах системы Zn - Sn - O поверхностных центров различного типа, принимающих участие в адсорбции и окислении изопропилового спирта. Zinc oxide nanorods were synthesized by the hydrothermal method. The obtained samples were processed in an aqueous-alcohol solution of potassium stannate and urea at 170 °C during different times. As a result, Zn - Sn - O nanostructures were obtained. The surface chemical composition of ZnO and Zn - Sn - O was studied using the X-ray photoelectron spectroscopy. Its sensitivity to vapors of isopropyl alcohol (1000 ppm) at 120 °C, 180 °C, 250 °C was analyzed. The electron density redistribution during the Zn - Sn - O composite nanostructures formation manifests itself in the chemical shift of the O1s and Zn2p peaks. It confirm the rearrangement of chemical bonds when zinc atoms are replaced by tin ones. It was found that the sensitivity of composite structures to isopropyl alcohol vapors significantly exceeds that of ZnO in the entire temperature range under study. The improvement of gas-sensitive properties is associated with the presence of various types of surface centers in the Zn - Sn - O samples that participate in the adsorption and oxidation of isopropyl alcohol.

Ionization Radiation Shielding Effectiveness of Lead Acetate, Lead Nitrate, and Bismuth Nitrate-Doped Zinc Oxide Nanorods Thin Films: A Comparative Evaluation

The fabrication of Nano-based shielding materials is an advancing research area in material sciences and nanotechnology. Although bulky lead-based products remain the primary choice for radiation protection, environmental disadvantages and high toxicity limit their potentials, necessitating less costly, compatible, eco-friendly, and light-weight alternatives. The theme of the presented investigation is to compare the ionization radiation shielding potentialities of the lead acetate (LA), lead nitrate (LN), and bismuth nitrate (BN)-doped zinc oxide nanorods-based thin films (ZONRs-TFs) produced via the chemical bath deposition (CBD) technique. The impact of the selected materials’ doping content on morphological and structural properties of ZONRs-TF was investigated. The X-ray diffractometer (XRD) analyses of both undoped and doped TFs revealed the existence of hexagonal quartzite crystal structures. The composition analysis by energy dispersive (EDX) detected the corrected elemental compositions of the deposited films. Field emission scanning electronic microscope (FESEM) images of the TFs showed highly porous and irregular surface morphologies of the randomly aligned NRs with cracks and voids. The undoped and 2 wt.% BN-doped TFs showed the smallest and largest grain size of 10.44 nm and 38.98 nm, respectively. The linear attenuation coefficient (µ) values of all the optimally doped ZONRs-TFs measured against the X-ray photon irradiation disclosed their excrement shielding potency. The measured µ values of the ZONRs-TFs displayed the trend of 1 wt.% LA-doped TF > 1 wt.% LN-doped TF > 3 wt.% BN-doped TF > undoped TFs). The values of μ of the ZONRs-TFs can be customized by adjusting the doping contents, which in turn controls the thickness and morphology of the TFs. In short, the proposed new types of the LA-, LN- and BN-doped ZONRs-TFs may contribute towards the development of the prospective ionization radiation shielding materials.

X-ray Photoelectron Spectroscopy of Surface Layers of Faceted Zinc Oxide Nanorods

The control of the nanomaterials surface’s hydrophilic properties is of interest for various applications, including optics, photocatalysis, and spintronics. In this work, techniques for designing the defective structure of the surface layers of faceted zinc oxide nanorods during sacrificial doping with iodine by hydrothermal synthesis were considered. The features of the chemical composition of the surface of the obtained layers were studied using X-ray photoelectron spectroscopy (XPS). It was found that peaks corresponding to the binding energy of iodine were not observed in the X-ray photoelectron spectra. An additional peak with a binding energy of 531.8 eV, corresponding to the oxygen of OH groups, was observed in the O 1s level spectrum for zinc oxide nanorods doped with iodine. During the heat treatment of the synthesized layers, iodine evaporates, which leads to a change in the surface composition and an increase in the oxygen content of the surface hydroxyl groups. A model has been proposed to explain the experimental results. It has been established that XPS techniques are effective for analyzing the defective surface structure of functional layers based on faceted zinc oxide nanorods.

Prediction of Surface Plasmon Resonsnce and More Accurate Representation of Absorption Features Both Below and Above the Bandgap in ZnO Nanorods array – Au Heterostructures

Well-oriented zinc oxide nanorods (ZnO NRs) arrays have been grown by low temperature chemical bath deposition on seeded substrates. A gold thin film has obliquely been deposited by DC magnetron sputtering on the ZnO NRs array. The structure, mophology/ chemical identity, vibrational identity have been studied by X-ray diffraction (XRD), field effect- scanning electron microscope/ energy dispersive X-ray spectroscopy (FE-SEM/EDX) and Raman spectroscopy, respectively. The FCC structure of Au is formed on vertically oriented ZnO NRs-array. The wavelength dependent photocurrent of ZnO NRs array-Au heteronanostructure (HNS) was evaluated by photogain response under red, green and blue laser illuminations. Surface plasmon excitation activates selective response to green laser exposure. An analytical dispersion formalism has been constructed to fit experimental absorption spectrum over wide spectrum range and to extract precise bandgap energy, subband tailing, dielectric constant and carrier effective mass. The proposed model exploits the Frouhi–Bloomer (FB) parameterization and Gaussian oscillator dispersion to the complex dielectric function for Au decorated ZnO NRs array. Sharp variation in the optical absorption around the bandgap edge and the absorption behavior beyond the bandgap edge are covered as well. It is surprising that the surface plasmon resonance (SPR) is included without new formalism. The new model has been satisfactorily tested on CuO optical absorption.

Additive Production of a Material Based on an Acrylic Polymer with a Nanoscale Layer of Zno Nanorods Deposited Using a Direct Current Magnetron Discharge: Morphology, Photoconversion Properties, and Biosafety

On the basis of a direct current magnetron, a technology has been developed for producing nanoscale-oriented nanorods from zinc oxide on an acrylic polymer. The technology makes it possible to achieve different filling of the surface with zinc oxide nanorods. The nanorods is partially fused into the polymer; the cross section of the nanorods is rather close to an elongated ellipse. It is shown that, with intense abrasion, no delamination of the nanorods from the acrylic polymer is observed. The zinc oxide nanorods abrades together with the acrylic polymer. Zinc oxide nanorods luminesces with the wavelength most preferable for the process of photosynthesis in higher plants. It was shown that plants grown under the obtained material grow faster and gain biomass faster than the control group. In addition, it was found that on surfaces containing zinc oxide nanorods, a more intense formation of such reactive oxygen species as hydrogen peroxide and hydroxyl radical is observed. Intensive formation of long-lived, active forms of the protein is observed on the zinc oxide coating. The formation of 8-oxoguanine in DNA in vitro on a zinc oxide coating was shown using ELISA method. It was found that the multiplication of microorganisms on the developed material is significantly hampered. At the same time, eukaryotic cells of animals grow and develop without hindrance. Thus, the material we have obtained can be used in photonics (photoconversion material for greenhouses, housings for LEDs), and it is also an affordable and non-toxic nanomaterial for creating antibacterial coatings.