Structure Of ZnO Research Articles

Synthesis of ZnO co-doped with Er and Co: Effect of the dopants on the structural, optical properties and yellow eosin photocatalytic response

In the present work, the sol-gel method was used to synthesize the Zn1-x-yErxCoyO system with different cations concentrations. The effect of dopant cations on the morphological, structural, and optical properties of particles, as well as their photocatalytic degradation of Yellow Eosin (YE) dye under UV irradiation, was investigated. X-ray diffraction (XRD) indicated excellent crystallinity of Wurtzite-like ZnO structures. Fourier Transform Infrared Spectroscopy showed characteristic absorption bands of ZnO. In addition, the dopant with different ions caused a decrease in the band gap energy compared to pure ZnO (3.16 eV), which is likely due to the defect levels formation. At higher Er3+ concentrations, the materials showed a slight reduction in the band gap (3.10 eV). However, for the samples with the highest Co2+ concentration, a lower band gap (3.0 eV) was observed, indicating that higher Co2+ concentrations favor the ZnO lattice distortion. In photocatalytic tests, the degradation rate of YE (∼48.7 %) was achieved using the ZEC23 sample (2 % of Er3+ and 3 % of Co2+), which is associated with the greater surface area found for this material. In a scavenger study, there was an increase in the rate of dye degradation (66.81 %) using ZEC23 when using an electron (e–) inhibitor reagent. In the presence of MetOH, a degradation rate of 44.0 % was observed, suggesting that the •OH radicals play a key role in the YE degradation.

Combustion synthesis and characterization of visible-light-driven La/Al co-doped ZnO nanoparticles used for wastewater treatment

Visible-light-driven LaxAl0.03-xZn0.97O (x = 0.01, 0.015 and 0.02) nanoparticles were synthesized by tartaric acid-assisted combustion method. Both ZnO and La/Al co-doped ZnO samples were indexed to the pure hexagonal wurtzite ZnO structure and were composed of nanoparticles with particle size ranges of 100-150 nm and 20-50 nm, respectively. The photocatalytic activities of ZnO and LaxAl0.03-xZn0.97O (x = 0.01, 0.015 and 0.02) nanoparticles were monitored through the degradation of methylene blue (MB) under visible light irradiation. The La0.02Al0.01Zn0.97O nanoparticles have the highest photocatalytic activity in degrading of MB under visible light irradiation because the La/Al co-dopant played the role in creating shallow energy level under the conduction band of ZnO.

Synthesis of Pure and Manganese Doped Zinc Oxide Nanoparticles by a Solution Growth Technique: Structural and Optical Investigation

Pure and manganese doped zinc oxide nanoparticles have been successfully synthesized over the composition range, Zn1-xMnxO (0<x<0.5), by a solution growth process. The effect of Mn doping on the structure, morphology and optical properties were investigated by several techniques. X-Ray diffraction studies confirmed the formation of a single-phase polycrystalline hexagonal wurtzite structure of ZnO within the range, 0 < x < 0.3. No Mn related secondary phases were detected, within this range, which could be attributed to the fact that the dopant atoms had been well incorporated into the ZnO crystal lattice. For Zn1-xMnxO (x = 0.5), several low intensity peaks belonging to remnants of Manganese acetate were observed in the diffractogram, establishing a solubility limit for the synthesis technique used. The variation of d-spacing with Mn percent doping showed a very good agreement with Vergard’s law within the range (0<x<0.25). EDAX analysis of the nanoparticles was consistent with the formation of Mn doped ZnO. The optical band gap of the ZnO nanoparticles decreased linearly with increasing Mn percent doping, suggesting the possibility of tuning the band gap of ZnO by doping with Mn.

Biogenic ZnO/CuO/Fe2O3 Nanocomposite: A Groundbreaking Approach for Enhanced Degradation Capabilities and Reusability in Dye Removal Applications

We present the successful synthesis of a biogenic ZnO/CuO/Fe2O3 nanocomposite using an aqueous leaf extract of Ocimum Basilicum L. The confirmation of biosynthesis was achieved through UV–Visible spectrophotometry (UV–Vis), which provided evidence of ZnO/CuO/Fe2O3 NC formation. Scanning Electron Microscopy further confirmed the nanoscale size of the NC, measuring at 65 nm. X-Ray Diffraction analysis revealed a hexagonal structure for ZnO and a monoclinic structure for CuO. The successful synthesis of the environmentally friendly ZnO/CuO/Fe2O3 NC was further verified using Fourier transformed infrared (FT-IR) spectroscopy, which identified the functional groups present in the composite. Notably, the ZnO/CuO/Fe2O3 NC demonstrated exceptional degradation capabilities for toluidine blue (TB), p-toluidine (PT), and m-Toluidine (MT), with degradation rates of 99%, 99.1%, and 99.7%, respectively, within a reaction time of 120 min. The reaction kinetics followed a pseudo-first order model, with rate constant (k) values of 0.0314 min−1 and 0.0189 min−1 for TB and PT, respectively. This high rate of dye degradation can be attributed to the low band gap of the NC, which was determined to be 1.44 eV for the indirect bandgap. Furthermore, the nanocomposite exhibited excellent degradation reusability, maintaining a high degradation rate in each cycle.

Multifaceted applications of chitosan-L-ornithine modified ZnO nanoparticles: Antibacterial, antioxidant, and anticancer potentials

Developing polymeric inorganic nanoparticle-based nanomedicines has significantly advanced antibacterial and anticancer treatments. These innovative agents have attracted significant attention due to their unique physicochemical properties and promising efficacy in targeting bacteria and cancer cells. The primary objective of this study is to investigate the synthesis of chitosan and l-ornithine-supported zinc oxide nanoparticles (ZnCsLO NPs) to assess their biological effects. The X-ray diffraction (XRD) pattern confirmed the synthesis of ZnO and ZnCsLO NPs, with wurtzite hexagonal structure. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed nano-flake and polygonal structures for ZnO and ZnCsLO NPs, respectively. Fourier transform infrared (FTIR) spectroscopy of ZnO and ZnCsLO NPs revealed characteristic peaks such as ZnO, chitosan, and l-ornithine molecules. The photoluminescence (PL) spectra of ZnO and ZnCsLO NPs displayed green emission peaks at 519 nm and 527 nm respectively, attributed to oxygen vacancies and inherent defects. The antibacterial activity was tested against various Gram-positive and Gram-negative bacterial strains using the well diffusion method. The ZnCsLO NPs exhibited higher antibacterial activity than ZnO NPs. In terms of antioxidant activity, ZnCsLO NPs exhibited the highest scavenging activity compared to ZnO NPs against DPPH. The anticancer activity of ZnO and ZnCsLO NPs was tested against the breast cancer cell line MDA-MB-231, where ZnCsLO NPs exhibited higher anticancer activity than ZnO NPs. Toxicity studies of ZnCsLO NPs on human fibroblast L929 showed less harmful effect on healthy cells compared to ZnO. Based on the findings of this research, there is a strong indication that ZnCsLO NPs hold great potential as a nanomaterial well-suited for advanced biomedical industrial applications.

Modification of PVDF hollow fiber membrane with ZnO structure via hydrothermal for enhanced antifouling property in membrane distillation

This study aims to provide a close insight into the possibilities and constraints associated with the development of ZnO structures on polyvinylidene fluoride (PVDF) hollow fiber membranes using the hydrothermal method to enhance membrane surface roughness for improved fouling resistance in membrane distillation (MD). Due to the flexible nature of polymeric hollow fiber membranes, there is a considerable risk of the ZnO structure detaching from the membrane surface when the membrane is bent. To address this issue, the hydrothermal duration was varied between 4 and 16 h to optimize the ZnO structure for high integrity, followed by fluorination. The results reveal that the membrane treated with hydrothermal for 8 h exhibits stable coating integrity, imparting the membrane with the highest contact angles with various liquids. This membrane demonstrates a flux of 4.0 kg/m2h and excellent salt rejection (>99.9 %) in direct contact MD (DCMD) when treating a 35 g/L saline solution. Additionally, the membrane exhibits outstanding antifouling performance with minimal flux reduction over 24 h when treating a saline solution containing humic acid. However, the upscaling of the hydrothermal approach may pose challenges due to the difficulty in maintaining the consistency of ZnO structure formation.

Facile Synthesis of Ni-Doped ZnO Nanoparticles Using Cashew Gum: Investigation of the Structural, Optical, and Photocatalytic Properties

This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol–gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples’ optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature.

SYNTHESIS AND CHARACTERIZATION OF Al-DOPED ZnO THIN FILMS AS ANTI-REFLECTION COATINGS FOR SOLAR CELL APPLICATIONS

In this work, we have synthesized ZnO:Al thin films by pulsed laser deposition technique and investigated their microstructural and optical properties. The XRD study confirmed a polycrystalline structure of wurtzite ZnO in all films. Further, Al doping has improved the crystallinity and decreased the crystal size and volume of the unit cell. The surface morphology was homogeneous with nanoscopic crystals clustered to form granular nanoparticles. The optical properties significantly improved by increasing the Al doping concentration. The produced thin films are excellent candidates for use as an anti-reflection layer in solar cells due to their outstanding properties.

Heterogeneous Structures Consisting of Rod-like ZnO Interspersed with Ce2S3 Nanoparticles for Photo-Sensitive Supercapacitors with Enhanced Capacitive Performance.

Photosensitive supercapacitors incorporate light-sensitive materials on capacitive electrodes, enabling solar energy conversion and storage in one device. In this study, heterogeneous structures of rod-shaped ZnO decorated with Ce2S3 nanoparticles on nickel foam (ZnO@Ce2S3/NF) are synthesized using a two-step hydrothermal method as photosensitive supercapacitor electrodes for capacitance enhancement under visible light. The formation of ZnO@Ce2S3 heterogeneous structures is confirmed using various structural characterization techniques. The area-specific capacitance of the ZnO@Ce2S3/NF composite electrode increased from 1738.1 to 1844.0mFcm-2 after illumination under a current density of 5 mAcm-2, which is 2.4 and 2.8 times higher than that of ZnO and Ce2S3 electrodes under similar conditions, respectively, indicating the remarkable light-induced capacitance enhancement performance. The ZnO@Ce2S3/NF electrode also exhibits a higher photocurrent and photovoltage than the two single electrodes, demonstrating its excellent photosensitivity. The improved capacitance performance and photosensitivity under illumination are attributed to the well-constructed energy-level structure, which stimulates the flow of photogenerated electrons from the outer circuit and the involvement of photogenerated holes in the resulting surface-controlled capacitance. In addition, the assembled ZnO@Ce2S3/NF-based hybrid supercapacitor exhibits a great energy density of 145.0 mWhcm-2 under illumination. This study provides a novel strategy for the development of high-performance solar energy conversion/storage devices.

Improved performance of AZO/Ag/AZO transparent conductive films by inserting an ultrathin Ti layer

Multilayer thin films of titanium-embedded Al-doped ZnO/Ag/Al-doped ZnO (AZO/Ag/AZO) structures have been designed and deposited onto polyethylene terephthalate (PET) substrates to develop an indium-free transparent flexible electrode. The effect of Ti layer on the morphological, structural, optical and electrical properties of multilayer thin films was investigated. The insertion of ultra-thin Ti layers enhances the near-infrared transmittance of AZO/Ag/AZO thin films, widens the spectral transmission window of AZO/Ag/AZO thin films, and improves the conductivity and surface roughness of AZO/Ag/AZO thin films. As the Ag thickness increases from 8 nm to 12 nm, the sheet resistance of the AZO/Ti/Ag/AZO thin film decreases from 16.22 Ω sq-1 to 7.17 Ω sq-1. AZO/Ti/Ag/AZO with an Ag thickness of 8 nm exhibits excellent optoelectronic properties with an average transmittance of 80.3 % and 61.7 % in the wavelength range of 400–1100 nm and 400–2000 nm, as well as a sheet resistance of 16.22 Ω Sq-1. It is demonstrated that AZO/Ti/Ag/AZO multilayer flexible films have great potential in various fields.

Role of CeO₂ and calcination temperature on the structural and optical properties of (ZnO) ₁-x/ (CeO₂)ₓ nanocomposites in the UV–visible region

This study explores the optical properties of (ZnO)1-x/(CeO2)x nanocomposites within the UV–visible range (250–1000 nm). Two sets of samples were synthesized using a gelatin-based sol-gel method. The first set comprises (ZnO)1-x/(CeO2)x, where x values are 0.0 (pure ZnO), 0.03 (ZCe3), 0.05 (ZCe5), and 0.01 (ZCe10) that calcined at 600 °C for 2 h. The second set consists of (ZnO)0·97/(CeO2)0.03 samples, which were obtained at varying temperatures denoted as ZCe3-700, ZCe3-800, ZCe3-900, and ZCe3-1000 °C. X-ray diffraction (XRD) analysis was employed to investigate the structure of the prepared nanocomposites under different conditions. The XRD patterns revealed a hexagonal lattice structure for ZnO and a cubic lattice structure for CeO₂, confirming that ZnO and CeO₂ nanocrystals grew independently. The crystalline size of the samples was determined using the Size Strain Plot (SSP) method. Reflectance data acquired through UV–visible spectroscopy were utilized to calculate the band-gap value, which was subsequently analyzed using the Kramer-Kronig method. The results indicate that, although there is negligible variation in the band gap values among samples prepared with different combinations and temperatures, these parameters influence n(ω) and k(ω). These findings suggest that ZnO/CeO₂ nanocomposites hold promise for optoelectronic applications, and the optical properties can be fine-tuned by controlling the aspect ratio of ZnO and CeO₂.

Study of structural, optical and electrical properties of Nickel doped ZnO (Ni–ZnO) nanorods grown by chemical bath deposition

To investigate the effect of Nickel on ZnO thin films, doped ZnO (Ni–ZnO) thin films were synthesized using chemical bath deposition on seed layers which were first grown using the conventional spray pyrolysis method. Structural, optical and electrical properties were studied at different doping levels of Ni (0, 2, 4, 6, 8 %). All samples exhibited a highly defined (002) peak indicating a strong hexagonal crystal structure orientation. The samples showed a red shift at E2L and E2H Raman modes indicative of structural alterations. The undoped, 2 % and 4 % Ni doping levels showed lower mean roughness values compared to the 6 % and 8 % Ni doping. The Introduction of Ni into the ZnO structure appears to reduce the grain size from 167 nm to the lowest 79 nm at 2 % Ni concentration. Optical and electrical properties showed that the introduction of Ni as a dopant led to improved transmittance of up 70 % within the visible range and reduced resistivity from 3.590*10−3 (Ωcm) at undoped ZnO to 0.616*10−3 (Ωcm) 2 % Ni doped ZnO concentration.

Negative temperature co-efficient of resistance behaviour of Cr doped ZnO nanoceramics

Here, High Energy Ball Milling (HEBM) is used to prepare Cr doped ZnO (Zn1-xCrxO, x = 0–0.04) nanoceramics and their electrical behaviour is studied in detail. The X-ray diffraction suggests a hexagonal wurtzite structure. The Rietveld refinement XRD pattern of the sample calcined at 900 °C suggests that up to 4 at% of Cr can be doped into the ZnO structure. After sintering, the growth in the particle size was observed for Cr doped ZnO samples. The complex impedance behaviour of samples suggests a decrease in resistance with temperature. This shows the Negative Temperature Coefficient of Resistance (NTCR) characteristic of the Cr doped ZnO sample in the studied temperature range (300–500 °C). At higher temperature, the electrical relaxation behaviour is of the non-Debye type as observed from the relaxation time distribution. The equivalent electrical circuit of ZnO and Cr doped ZnO ceramic samples are a parallel arrangement of bulk capacitance (Cb) and bulk resistance (Rb).

CeO2-ZnO nano composites: Dual-functionality for enhanced photocatalysis and biomedical applications

In present study, we employed a simple and cost-effective chemical precipitation method to synthesize CeO2:ZnO nanocomposites with various Ce:Zn molar ratios. The X-ray diffraction pattern confirms the formation of a cubic structure of CeO2 and a hexagonal wurtzite structure of ZnO in the Ce:Zn nanocomposites. Structural parameters were determined through a Rietveld refinement process using the X-ray diffraction pattern. The elemental composition of the synthesized compounds were assessed using energy-dispersive X-ray spectroscopy (EDX). Raman spectroscopy revealed the presence of the F2g vibrational mode corresponding to CeO2 NPs as well as the E2 mode corresponding to ZnO NPs. Transmission electron microscopy shows the lateral dimensions of both CeO2 and ZnO nanoparticles in the prepared composites. Photoluminescence (PL) spectra were analysed to examine the defects present in the samples. Absorption spectra were recorded in the wavelength range of 325–1100 nm using UV–Vis spectroscopy. The photocatalytic activity of the synthesized samples was studied for the degradation of methylene blue (MB) under UV light irradiation. Among all prepared composites, the Ce: Zn (1:3) nanocomposite showed the highest photodegradation activity (95 %) against the methylene blue (MB) dye. We also examined in detail the anticancer potential of the Ce:Zn composites against human lung carcinoma cells (A549).

Preparation, Characterization, Photochromic Properties, and Mechanism of PMoA/ZnO/PVP Composite Film.

A novel photochromic heteropolyacid-based composite film consisting of phosphomolybdic acid (PMoA), ZnO, and polyvinylpyrrolidone (PVP) was fabricated by a sol-gel process. The microstructure and photochromic properties of the PMoA/ZnO/PVP were characterized via Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible spectroscopy (UV-Vis). The FTIR spectra showed that the basic structures of ZnO and PVP, and the Keggin structure of PMoA in the PMoA/ZnO/PVP composite film, had not been destroyed during the preparation. The TEM images demonstrated that ZnO presented a rod-like structure, while PMoA was spherical, and many PMoA balls adhered to the surface of the ZnO rods. The XPS spectra of Mo 3d indicated that the valency of Mo atoms in the PMoA/ZnO/PVP was changed by visible light exposure. After visible light irradiation, the PMoA/ZnO/PVP varied from slight yellow to blue, while undergoing an opposite color change upon heating. The discoloration mechanism of the PMoA/ZnO/PVP was consistent with the photoelectron transfer mechanism.

Oxidation of Zinc Microparticles by Microwave Plasma to Form Effective Solar-Sensitive Photocatalysts

The presented work studies the processes of synthesis of ZnO microstructures using atmospheric-pressure microwave nitrogen plasma and investigates their photocatalytic activity in the processes of degradation of 2,4-dinitrophenol and the antibiotic ciprofloxacin when irradiated with sunlight. The work proposes an effective method for formation of photosensitive ZnO powders. Due to the features of plasma treatment in the open atmosphere of zinc metal microparticles, ZnO structures are formed with sizes from hundreds of nanometers to several micrometers with various micromorphologies. The lattice parameters of ZnO structures are characteristic of a hexagonal unit with a = 3.258 Å and c = 5.21 Å, volume 47.95 Å3. The size of the crystallites is 48 nm. The plasma treatment was performed by means of a 2.45-GHz plasmatron at a power input of 1 kW in nitrogen flow at a rate of 1–10 L/min. Zn microparticles were injected into the microwave plasma at a mass rate of 20 g/min. High photoactivity was demonstrated (rate constants 0.036 min−1 and 0.051 min−1) of synthesized ZnO structures during photo-degradation of 2,4-dinitrophenol and ciprofloxacin, respectively, when exposed to solar radiation. Photo-active structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds. Structures of ZnO synthesized using microwave plasma can find application in processes of mineralization of toxic organic compounds, and also in scintillation detectors, phosphors.

Effect of synthesis process steps on the structure and photocatalytic performance of ZnO–TiO2 composites

ZnO–TiO2 composites (Z@T and T@Z) were prepared by two processes. Z@T was to prepare ZnO particles first, and then TiO2 particles were prepared on the surface of ZnO; T@Z, in contrast, was to prepare TiO2 first and then ZnO. The samples were characterized by TG-DSC, XRD, SEM, EDS, UV–Vis, and PL spectra to explore the effects of synthesis process on the thermal effect, crystal structure, surface composition, energy band gap, recombination rate of photogenerated carriers, and photocatalytic performance of samples calcined at different temperatures. T@Z composites have an excellent crystal structure and effectively inhibit the recombination of photogenerated carriers. The T@Z prepared at 600 °C exhibited higher photocatalytic performance of methyl orange than that of ZnO, TiO2, and Z@T composites under UV light irradiation, which was about twice as large as that of Z@T calcined at 600 °C mainly due to the fact that T@Z composites possess rod and rice-like morphologies, high light absorption capability and low recombination rate of photogenerated carriers.

Interfacial polymerisation and functionalization of Cu-doped ZnO/polyaniline nanocomposites for optoelectronic application

Copper-doped zinc oxide (5 % and 15 % Cu-doped ZnO) nanoparticles have been synthesised and incorporated into the polyaniline (PANI) matrix in an in-situ interfacial polymerisation of aniline with ammonium persulphate (APS) to obtain solution processable PANI/5 % and 15 % Cu-doped ZnO nanocomposites, without the aid of surfactants. The samples were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDX), and Four-point probe method. The XRD patterns of the nanoparticles revealed that they possess hexagonal wurtzite crystal structure of ZnO with slight shift of the diffraction peaks to higher 2θ values, and their estimated crystallite sizes were 27.165 and 32.450 nm, respectively. The estimated optical bandgaps of the nanoparticles decreased with Cu doping (3.09 and 2.85 eV at 5 and 15 % Cu doping, respectively) when compared with the standard value of pure ZnO (3.30 eV), consistent with the redshift in the absorption wavelength observed in the UV–Vis absorption spectra. In contrast to the significant reduction observed in the bandgaps of the nanoparticles, marginal changes were observed in the optical bandgaps of the PANI/Cu-doped ZnO nanocomposites with increasing nanoparticles loading ranging from 2.29 eV to 2.46 eV. The FTIR of the nanocomposite depicted the same characteristic peaks of PANI but were slightly shifted to higher wavenumbers attributed to the interaction between PANI and the nanoparticle, while the XRD patterns of the nanocomposites revealed the orthorhombic crystal structure of PANI and weak diffraction peaks of the nanoparticles. From the SEM/EDX, the observed elemental composition of the nanocomposite confirmed the presence of the nanoparticles within the PANI matrix. The electrical measurement revealed that the PANI/Cu-doped ZnO nanocomposites exhibited enhanced electrical conductivity, which reached maximum values at specific nanoparticles loadings. The obtained results and the solution processability of these nanocomposites make them suitable for applications in optoelectronics.

Femtosecond laser-induced production of ZnO@Ag nanocomposites for an improvement in photocatalytic efficiency in the degradation of organic pollutants

Green synthesis based nanoparticle production methods and water purification techniques were carried out using pulsed laser ablation and photocatalysis degradation techniques. The femtosecond laser ablation based ZnO and Ag nanoparticles were produced with different concentration ratios such as 2.0 wt%, 4.0 wt%, 6.0 wt%, 8.0 wt% and 10.0 wt% in ultra pure water to photocatalytic degradation of methylene blue dye contaminant. Following the production of nanoparticle and photocatalysis applications, FTIR, XRD and linear absorption spectra were recorded. HRTEM and FE-SEM microscopy was carried out to determine size and shape performance of nanoparticles. The crystal peak density of ZnO and its crystal size were decreased by doping Ag into ZnO nanoparticles. LSPR peak was formed due to plasmonic properties of Ag nanoparticles in ZnO. As Ag content is increased in ZnO, it has been observed that band gap of ZnO@Ag structure is decreased. The morphological structure of ZnO is partially composed of homogeneous particle mergers while ZnO@Ag can be formed from the growth of small particles on AgO clusters. The photocatalytic activity of composite photocatalysts was systematically investigated as a function of amount of Ag nanoparticles in samples. Experimental results showed that the optimal composite was Ag-ZnO composite containing 6.0 wt% Ag. This composite photocatalyst exhibited a 68.62% higher rate constant value in the degradation of methylene blue (MB) dye molecules under visible light compared to pure ZnO nanoparticles. The improved photocatalytic performance compared to pure ZnO nanoparticles was attributed to some increase in light absorption performance, more efficient charge separation due to the gradual band structure between plasmonic Ag nanoparticles and semiconductor ZnO nanoparticles. In addition, active radicals taking role in the degradation mechanism of MB were revealed by scavenger chemical experiments.

Defect analysis and microstructural characterization of zinc-substituted cadmium oxide nanocrystallites by positron annihilation and supplementary methods

Pure and zinc-doped cadmium oxide nanocrystallites of sizes in the range 25 nm to 16 nm are synthesized by adopting a chemical precipitation method and by varying the doping concentration from 0.0 to 0.25. The decrease in nanocrystallite sizes with increasing substitution is expected from the smaller ionic radii of Zn2+. But more revealing is the interfacial defects formation at higher concentration of doping, which is attributed to the dissimilar crystalline structure of ZnO and CdO. X-ray diffraction patterns show well defined peaks and additional characterisation is done through transmission electron microscopy. The optical band gap measurements indicate the dominance of substitution-induced disorder over the confinement of excitons, leading to a decrease in the band gap energies. The results of positron annihilation studies confirm the cancellation of the existing vacancy type defects in the initial stage, followed by the substitution. Photoluminescence spectra reveal the distinct peaks of optical plasmonic excitations and the defect population in the bandgap and the intensity variations agreed with that of the defect related positron annihilation lifetime intensity. The segregation of ZnO phase leading to the formation of interfacial boundaries is found as a strong deterrent against the success of continued substitution.