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CHARACTERIZATION AND ANTIBACTERIAL ACTIVITY OF ZnO NANOPARTICLES SYNTHESIZED BY CO PRECIPITATION METHOD
摘要： Objective: In the present study the antibacterial activity of zinc oxide (ZnO) nanoparticles was investigated against gram negative (Escherichia coli and Proteus vulgaris) and gram positive (Staphylococcus aureus and Streptococcus mutans) organisms. Methods: The synthesis of ZnO nanoparticles was carried out by co-precipitation method using zinc sulfate and sodium hydroxide as precursors. These nanoparticles were characterized by XRD (X-Ray Diffraction), FTIR (Fourier Transform Infrared Radiation), UV-Visible spectroscopy and SEM (Scanning Electron Microscope) with EDX (Energy Dispersive X-ray analysis). As well as antibacterial activity and minimum inhibitory concentration of the nanoparticles were carried out by agar well diffusion method and broth dilution method respectively against gram negative (Escherichia coli and Proteus vulgaris) and gram positive (Staphylococcus aureus and Streptococcus mutans) bacteria. Results: The average crystallite size of ZnO nanoparticles was found to be 35 nm by X-ray diffraction. The vibration bands at 450 and 603 cm-1 which were assigned for ZnO stretching vibration were observed in FTIR spectrum. The optical absorption band at 383 nm was obtained from UV-Visible spectrum. Spherical shape morphology was observed in SEM studies. The antibacterial assay clearly expressed that E. coli showed a maximum zone of inhibition (32±0.20 mm) followed by Proteus vulgaris (30±0.45 nm) at 50 mg/ml concentration of ZnO nanoparticles. Conclusion: Zinc oxide nanoparticles have exhibited good antibacterial activity with gram negative bacteria when compared to gram positive bacteria.
关键词： EDX,SEM,MIC,FTIR,UV-VISIBLE spectroscopy,XRD,ZnO nanoparticles
更新于2025-11-21 11:18:25
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Crystallographically oriented porous ZnO nanostructures with visible-blind photoresponse: controlling the growth and optical properties
摘要： We have grown catalyst-free crystallographically oriented porous ZnO nanostructures by pulsed laser deposition (PLD) method. The deposition was performed in two stages for each sample. In the first stage, self-seeding of ZnO was performed on the quartz substrate, and the angle of deposition (seeding-angle) was varied. Thus, the growth of seeds is different here. In the second stage, the deposition was performed at a glancing angle (at 85?) for the fixed duration of time to grow the nanostructures. These PLD-grown nanostructures acquire highly oriented wurtzite structure. We find that the seeding-angle during the first stage is the determining deposition parameter which influences the growth and other properties of these nanostructures in a controllable manner. The variation in seeding-angle systematically tunes the crystallographic orientation and porosity, which in turn influences the visible-blindness and ultraviolet (UV) photoresponse of these nanonetworks. Here we report the growth of completely defect-free crystallographically oriented nanostructures with necessary porosity for application in visible-blind UV photodetection.
关键词： Crystalline ZnO,catalyst-free ZnO,glancing angle deposition (GLAD),seeding,pulsed laser deposition (PLD),nanostructures
更新于2025-11-21 11:03:13
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Effect of ethanolamine passivation for ZnO nanoparticles in quantum dot light emitting diode structure
摘要： Aging effect of ZnO nanoparticles in quantum dot light-emitting diode (QD-LED) structure is studied. Coarsening of as-synthesized ZnO nanoparticles is observed in both solution and thin film structure, which potentially deteriorates device performance of QD-LED over time. Firstly, temperature effect on ZnO coarsening is investigated, and it reveals that ripening of ZnO nanoparticles is faster at higher temperature due to its diffusion controlled mechanism of nanoparticle coarsening. To observe aggregation of the ZnO in the film state, electron transporting part (ZnO/Al) of QD-LED structure was prepared. Current densities of the ZnO film and electron only device (QD/ZnO between two electrodes) are also measured. Resistance of the film increased as a function of aging time, which corresponds to optical microscopy observation of ZnO film. Aggregation of ZnO nanoparticles was directly measured by root-mean-square value in atomic force microscopy. Ethanolamine (EA) stabilizer is added in the ZnO solution to disperse the ZnO nanoparticles without aggregation. The effect of EA on the surface passivation of the ZnO was revealed by scanning electron micriscopy observation directly by suppressed pinhole formation. Finally, device lifetime was measured for QD-LED with EA stabilized ZnO to understand the effect of ZnO aging on long term QD-LED device operation.
关键词： ethanolamine,coarsening,ZnO,aging
更新于2025-11-21 11:03:13
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Origin of anisotropy and compositional dependence of phonon and electron transport in ZnO based natural superlattices and role of atomic layer interfaces
摘要： Reaction of ZnO with trivalent ions can form natural superlattice (SL) compounds, which possess unusual structural characteristics and strong anisotropic physical transport properties. In this work, by synthesizing strongly textured bulk polycrystals of pure SL phases and performing characterization and measurements for both in-plane and cross-sectional directions, we revealed the strongly crystal orientation dependent transport properties. The observed compositional or SL interface spacing dependent electrical conductivity is largely attributed to the overall doping of ZnO wurtzite regions. The atomic layer SL interfaces are phonon barriers, and the interfacial thermal (Kapitza) resistance depends on SL interface spacing. The transport direction perpendicular to these SL interfaces are electron-conductive paths with remarkably higher electron mobility. There are electron potential barriers associated with these atomic layer SL interfaces. The effective and absolute potential barrier heights are determined, which are proportional to the natural conduction band discontinuities. The current study provides new findings and knowledge about the role of SL interfaces in phonon and electron transport process in these ZnO based natural SLs. The present work can be useful and inspiring to design and modify complex layer-structured compounds, including synthetic superlattice systems, for a variety of applications where energy carriers transport is involved.
关键词： Interfaces,Superlattices,Electron potential barrier,Interfacial thermal (Kapitza) resistance,Thermal conductivity,ZnO
更新于2025-11-21 11:03:13
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One-step synthesis of hexylresorcinol calix[4]arene-capped ZnO–Ag nanocomposites for enhanced degradation of organic pollutants
摘要： In this study, hexylresorcinol calix[4]arene (HRCA) is introduced into the reaction system, and HRCA-capped ZnO–Ag nanocomposites are prepared via a simple one-step reflux method. HRCA is used not only as a reducing agent for deoxidizing Ag+ to Ag, but also as a protectant for wrapping around the microstructure of the formed ZnO–Ag. The prepared samples are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and water contact angle. The Ag nanoparticles and ZnO adhere to each other and HRCA molecules encapsulate on the surface of ZnO–Ag nanocomposites. HRCA-capped ZnO–Ag nanocomposites with different Ag contents are investigated for use in photodegradation of organic pollutants (rhodamine B (RhB) and levofloxacin hydrochloride). The sample with 10.20 mol% Ag, denoted as ZA3, exhibits the highest catalytic activity for photodegradation of RhB and levofloxacin hydrochloride. Moreover, ZA3 exhibits high stability during photodegradation of organic pollutants even after multiple reuses. The possible photocatalytic mechanism is discussed. We believe that ?O2– and h+ are the chief active species responsible for the photocatalytic activity of HRCA-capped ZnO–Ag nanocomposite system. HRCA-capped ZnO–Ag nanocomposite is expected to be an effective photocatalyst with potential application to sewage treatment under sunlight.
关键词： HRCA-capped ZnO–Ag,Photocatalysis,Resorcinol calix[4]arene,Ag seed
更新于2025-11-21 11:03:13
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Solvent Effects on the Interface and Film Integrity of Solution-Processed ZnO Electron Transfer Layers for Quantum Dot Light Emitting Diodes
摘要： Solution-processed ZnO nanoparticle thin film is widely used as the electron transport layers (ETLs) in quantum dot light emitting diodes (QLEDs). While the ZnO nanoparticles (NPs) synthesis process has been thoroughly optimized, very few studies have focused on exploring how the solvents for dispersing the NPs affect the film-forming process, which has profound effects on the film quality and functionality as ETLs. Herein, we present a comprehensive investigation on the impact of the dispersing agent on the materials and carrier transport properties of spin-coated ZnO NP thin films. The first four members of the alkanol family, which show considerably different viscosities and volatilities, were used in this study. ZnO NP thin films deposited with different alcohols were used as the ETLs of the QLED structure and the optoelectronic performances of the devices are compared. Alcohols with high viscosity are found to cause NP agglomerations which roughen the film surface and lead to significant leakage current. Nano-cracks in the ZnO NP film are observed when a highly volatile solvent is used due to the vigorous bursts of vapor during solvent evaporation. Our results show that proper solvent can improve the surface roughness and compactness of the solution-processed ZnO films and lead to a 30% difference in the current efficiency of QLEDs. The findings here clearly indicate the important roles of the dispersing agent in the formation of high-quality NP-based thin films, which can be an important guidance for achieving high performances in QLEDs as well as a variety of solution-based devices.
关键词： Interface,Solvent,QLEDs,Electron transport layer,ZnO
更新于2025-11-21 11:01:37
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Electrochemical synthesis of Zn: ZnO/Ni2P and efficient photocatalytic degradation of Auramine O in aqueous solution under multi-variable experimental design optimization
摘要： Present work is devoted to synthesis Zn: ZnO/Ni2P by electrochemical method and identification and properties investigation by various techniques such as SEM, EDS, XRD and DRS. The experimental results reveal have ability for degradation of Auramine O (AO) following estimation of correlation among response to (main effect and variables interactions) variable like irradiation time, nanocomposite mass, pH and initial AO concentrations by a central composite design (CCD). The optimum condition for the photo-degradation of AO by photocatalyst was 6.72, 61.66 min, 13.13 mg.L-1 and 0.014 g correspond to the pH, irradiation time, AO concentration and photocatalyst mass, respectively. At these optimum conditions, the AO photocatalytic degradation percentages with desirability of 0.94 was 95.47% using reasonable consumption of reagent. The quasi first-order kinetic model derived from Langmuir–Hinshelwood (L–H) efficiently represent real behavior of experimental data of correspond to under study system. The photocatalytic reaction, L–H rate constants and L–H adsorption constants for Zn: ZnO/Ni2P were 0.0375 min-1, 27.39 mg.min-1.L and 0.00048 L.mg-1, respectively.
关键词： photocatalytic degradation,Auremine O,electrochemical synthesis.,Zn: ZnO/Ni2P,response surface methodology
更新于2025-11-21 11:01:37
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Band gap engineered zinc oxide nanostructures <i>via</i> a sol–gel synthesis of solvent driven shape-controlled crystal growth
摘要： A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, low shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10?3 S cm?1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.
关键词： electrical conductivity,ZnO nanostructures,optical band gap,shape-controlled crystal growth,sol–gel synthesis
更新于2025-11-19 16:56:42
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Valorization of tire wastes to carbon quantum dots (P-CDs) and photocatalytic degradation enhancement of organic wastes using ZnO-CDs nanocomposites
摘要： Valorization of solid wastes for the production of valuable materials is of great importance for sustainable development. In this paper, removal for solid and liquid wastes via hydrothermal and catalytic degradation was reported. The first removal process is the hydrothermal conversion of solid waste, here solid wastes of tire, to phosphorous and nitrogen doped carbon nanodots (P-CDs). The second removal is the visible-NIR light driven photocatalytic degradation of liquid waste, here methylene blue (MB) solution, using P-CDs loaded on ZnO nanoparticles. Energy-efficient light emitting diode (LED) was used as a weak sufficient irradiation source. Photodegradation rate constants for ZnO-P-CDs were almost 10 times higher (0.08 h?1 for ZnO-P-CDs) comparing to pure ZnO (0.008 h?1), such enhancement is significant for a weak light source. Cyclic voltammetry and optical properties were used to find HOMO and LUMO of P-CDs. Based on the energy levels of ZnO and P-CDs, the catalytic enhancement was attributed to increasing the separation rate of photogenerated electrons and hole due to the transfer of electrons from the conduction bands of P-CDs to the conduction band of ZnO. Up-conversion photoluminescence of P-CDs is another reason for increasing the separation of excitons and harvesting the longer wavelength light. The proposed approach, solid and liquid waste removal via hydrothermal and catalytic degradation combined with weak LED light, would be a powerful approach in solid waste treatment and water purification technology, simultaneously.
关键词： Valorization,Tire wastes,Carbon quantum dots,Photocatalytic degradation,ZnO-P-CDs nanocomposites
更新于2025-11-19 16:56:42
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A systematic approach to ZnO nanoparticle-assisted electron transport bilayer for high efficiency and stable perovskite solar cells
摘要： Minimizing the interface loss of perovskite solar cells is critical to achieving high photovoltaic performance, and intensive research is underway on interfacial engineering in this regard. In this work, we introduce a ZnO nanoparticles (ZnO NPs) interlayer between phenyl-C61-butyric acid methyl ester (PCBM) and a metal electrode in order to reduce the interface loss due to charge recombination and device degradation, and also investigate the dependence of device performance on the thickness and morphology of the PCBM and PCBM/ZnO electron transport bilayer. After achieving optimized PCBM and ZnO thickness, the PCBM/ZnO bilayer-based devices reached an average power conversion efficiency of 15.63% (Max. 16.39%) with an open circuit voltage of 1.05 V, short circuit current density of 18.69 mA cm-2, and fill factor of 79.95%. In addition, hysteresis behavior and atmospheric stability are significantly improved by the incorporation of a PCBM/ZnO bilayer. Therefore, the implementation of a PCBM/ZnO electron transport bilayer is a promising approach toward achieving a high-efficiency PSC with stable power output (low J-V hysteresis) and durability.
关键词： ZnO nanoparticles,interfacial engineering,stable perovskite solar cells,interface loss,high-efficiency perovskite solar cells,electron transport bilayer
更新于2025-11-19 16:46:39