Nanoscale Au-ZnO heterostructure developed by atomic layer deposition towards amperometric H2O2 detection

Nanoscale Au-ZnO heterostructures were fabricated on 4-in. SiO2/Si wafers by the atomic layer deposition (ALD) technique. Developed Au-ZnO heterostructures after post-deposition annealing at 250 degrees C were tested for amperometric hydrogen peroxide (H2O2) detection. The surface morphology and nanostructure of Au-ZnO heterostructures were examined by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. Additionally, the electrochemical behavior of Au-ZnO heterostructures towards H2O2 sensing under various conditions is assessed by chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that ALD-fabricated Au-ZnO heterostructures exhibited one of the highest sensitivities of 0.53 mu A mu M(-1)cm(-2), the widest linear H2O2 detection range of 1.0 mu M-120mM, a low limit of detection (LOD) of 0.78 mu M, excellent selectivity under the normal operation conditions, and great long-term stability. Utilization of the ALD deposition method opens up a unique opportunity for the improvement of the various capabilities of the devices based on Au-ZnO heterostructures for amperometric detection of different chemicals

Schottky nanocontacts on ZnO nanorod arrays

We report on fabrication and electrical characteristics of ZnO nanorod Schottky diode arrays. High quality ZnO nanorods were grown for the fabrication of the Schottky diodes using noncatalytic metalorganic vapor phase epitaxy and Au was evaporated on the tips of the vertically well-aligned ZnO nanorods. I-V characteristics of both bare ZnO and Au/ZnO heterostructure nanorod arrays were measured using current-sensing atomic force microscopy. Although both nanorods exhibited nonlinear and asymmetric I-V characteristic curves, Au/ZnO heterostructure nanorods demonstrated much improved electrical characteristics: the reverse-bias breakdown voltage was improved from -3 to -8 V by capping a Au layer on the nanorod tips. The origin of the enhanced electrical characteristics for the heterostructure nanorods is suggested. (C) 2003 American Institute of Physics.X11326sciescopu

GREEN DEKORASI Au/ZnO NANOKOMPOSIT MELALUI MEDIA EKSTRAK DAUN GAHARU (Aquilaria malaccenensis L.) DAN PENENTUAN NILAI SUN PROTECTION FACTOR

Tujuan penelitian ini adalah mensintesis nanokomposit Au/ZnO melalui media green synthesis dengan memanfaatkan ekstrak daun gaharu (Aquilaria malaccenensis L). Ekstrak daun gaharu berfungsi sebagai bioreduktor alami dan capping agent dalam pembentukan nanokomposit Au/ZnO. Kehadiran koloid Au pada permukaan ZnO dapat merubah nilai celah pita, struktur kristal, ukuran partikel, dan nilai sun protection factor (SPF) ZnO. Au/ZnO nanokomposit memiliki nilai celah pita sebesar 3,0 eV dan hasil karakterisasi X-ray diffraction (XRD) menunjukkan puncak kristalinitas pada 2: 33,6o; 35,1o; 36,3o; 46,6o; 54,7o; 59,7o; 64,3o; dan 66,2o dengan rata-rata ukuran kristalit sebesar 37 nm. Gugus fungsi yang terkandung dalam ekstrak daun gaharu adalah O-H (3300 cm-1) berfungsi sebagai bioreduktor ion Au3+ menjadi Au0, C=C (1620 cm-1), dan C-N (1350 cm-1) berfungsi sebagai sumber basa dalam pembentukan Zn(OH)2 menjadi ZnO. Vibrasi Au-Zn-O terlihat pada bilangan gelombang 498 cm-1. Nilai SPF pada Au/ZnO nanokomposit sebesar 18,28. Dari data karakterisasi menunjukkan bahwa media ekstrak daun gaharu dapat digunakan sebagai bioreduktor alami, sumber basa, dan capping agent dalam dekorasi Au pada permukaan ZnO (Au/ZnO) nanokomposit

Sonochemical Synthesis, Characterization, and Photocatalytic Performance Evaluation of Au/ZnO Nanocomposite for Methyl Orange Degradation

This study examines the impact of gold (Au) incorporation on zinc oxide (ZnO) nanoparticles. Both pure ZnO and Au/ZnO nanocomposite have been synthesized using a unique and environmentally friendly sonochemical approach. The as-synthesized Au/ZnO nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) spectroscopic techniques. Under UV-visible irradiation, the photocatalytic effectiveness of ZnO nanoparticles and Au/ZnO nanocomposites for the degradation of dye was examined. The results demonstrated that the nanocomposite has greater photocatalytic activity than ZnO nanoparticles. This is due to the effective electron transfer from ZnO to Au prolonging the lifetime of photogenerated holes, which play the most important role in the dye degradation process.&nbsp

Recombination dynamics in ZnO nanowires: Surfaces states versus mode quality factor

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 97, 133116 (2010) and may be found at https://doi.org/10.1063/1.3496444.In this work, we investigate the influence of finite size on the recombinations dynamics of ZnO nanowires. We demonstrate that diameter as well as length of nanowires determine the lifetime of the neutral donor bound excitons. Our findings suggest that while the length is mainly responsible for different mode quality factors of the cavity-like nanowires, the diameter determines the influence of surface states as alternative recombinations channels for the optical modes trapped in the nanocavity. In addition, comparing nanowires grown using different catalyst we show that the surfaces states strongly depend on each precursor characteristics.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeDFG, 53182490, EXC 314: Unifying Concepts in Catalysi

Study on Method of Doping Au Nanoparticles on ZnO Stratified Microstructure to Enhance Photocatalytic Ability and Antibacterial Activity

In this study, stratified microstructure gold/zinc oxide (Au/ZnO) composites were successfully prepared by the method of dispersing Au nanoparticles (Au NPs) on the surface of the hierarchical flower ZnO via HAuCl4 reduction in the presence of different reducing agents such as sodium citrate (SC), sodium borohydride (SB), sodium hydroxide and ethanol (SE), and Hg lamp 250W. Au-doped samples were named Au/ZnO-SC, Au/ZnO-SB, Au/ZnO-SE, and Au/ZnO-Hg lamp, respectively. Au/ZnO-SC and Au/ZnO-SB revealed the uniform distribution of Au nanoparticles on the ZnO substrate, meanwhile, Au nanoparticles were very densely distributed in Au/ZnO-SE and Au/ZnO-Hg lamp samples. The pure ZnO only showed an absorption peak in the ultraviolet (UV) region, Au/ZnO samples indicated additional absorption peaks in the visible light region (500-600 nm), which were characteristic of the surface plasmon resonance (SPR) effect of Au NPs in composites. Therefore, their bandgap energy was reduced compared to ZnO (3.202 eV), leading to increased photocatalytic efficiency under visible light irradiation. Among the doped samples, Au/ZnO-SC (with Au content as 5 wt%) had the largest surface area (26.23 m2/g) and the highest pore volume (0.263 cm3/g) and average pore width (33.2 nm). As a result, it showed the highest catalytic efficiency through complete degradation of tartrazine (TA) within 30 min with a reaction rate of 0.124 min−1 under Hg lamp 250 irradiation. In addition, both pure ZnO and Au/ZnO nanocomposites exhibited high antimicrobial activity in killing Escherichia coli (E. coli), and their enhancing effect of them was reliant on the weight ratio of Au on ZnO and the concentration of tested samples. These results indicated that Au/ZnO material has prominent potential for applications in water environment treatment. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Ultrasonic triggering of giant magnetocaloric effect in MnAs thin films

Mechanical control of magnetic properties in magnetostrictive thin films offers the unexplored opportunity to employ surface wave acoustics in such a way that acoustic triggers dynamic magnetic effects. The strain-induced modulation of the magnetic anisotropy can play the role of a high frequency varying effective magnetic field leading to ultrasonic tuning of electronic and magnetic properties of nanostructured materials, eventually integrated in semiconductor technology. Here, we report about the opportunity to employ surface acoustic waves to trigger magnetocaloric effect in MnAs(100nm)/GaAs(001) thin films. During the MnAs magnetostructural phase transition, in an interval range around room temperature (0{\deg}C - 60{\deg}C), ultrasonic waves (170 MHz) are strongly attenuated by the phase coexistence (up to 150 dB/cm). We show that the giant magnetocaloric effect of MnAs is responsible of the observed phenomenon. By a simple anelastic model we describe the temperature and the external magnetic field dependence of such a huge ultrasound attenuation. Strain-manipulation of the magnetocaloric effect could be a further interesting route for dynamic and static caloritronics and spintronics applications in semiconductor technology

Electron transport through Al-ZnO-Al: an {\it ab initio} calculation

The electron transport properties of ZnO nano-wires coupled by two aluminium electrodes were studied by {\it ab initio} method based on non-equilibrium Green's function approach and density functional theory. A clearly rectifying current-voltage characteristics was observed. It was found that the contact interfaces between Al-O and Al-Zn play important roles in the charge transport at low bias voltage and give very asymmetric I-V characteristics. When the bias voltage increases, the negative differential resistance occurs at negative bias voltage. The charge accumulation was calculated and its behavior was found to be well correlated with the I-V characteristics. We have also calculated the electrochemical capacitance which exhibits three plateaus at different bias voltages which may have potential device application.Comment: 10 pages, 6 figure

The Annealing Effects of ZnO Thin Films on Characteristic Parameters of Au/ZnO Schottky Contacts on n-Si

200 nm ZnO thin films have been grown on n type Silicon substrates by DC sputtering technique. One of the thin films has been annealed at 300 ºC for 45 minutes. The Au front contacts on ZnO thin films have been formed by evaporation of Au metal by means of shadow mask. It has been seen that the rectification ratio of Au/ZnO device obtained using annealed ZnO thin film is higher than the one obtained using unannealed ZnO thin film. The characteristic parameters of Au/ZnO junctions such as ideality factor, barrier height and series resistance obtained by current-voltage (I-V) measurements of the structures at room temperature and in dark have been compared with each others. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2490