eV For ZnO Research Articles

An investigation of n-type semiconductors based on optical and photoluminescence of pure and Al doped Pr:123 compound

With ZnO comparison, we report here an investigation of n-type semiconductors in terms of optical and photoluminescence (PL) analysis based on PrBa2Cu3-3xAl3xOy (AlPr:123) compound with (0.00 ≤ x ≤ 1.00). The structure is tetragonal of the samples with x ≤ 0.30 and changes to orthorhombic for x > 0.30, whereas it is wurtizite (hexagonal) for ZnO. As x increases to 1.00, the grain size is decreased, while the crystallite size and porosity are increased, but they are comparable with those obtained for ZnO. The Debye temperature, Young’s modulus and energy gap are drastically decreased by increasing x until reach to their maximum values of 623.14 K, 952 GPa and 3.45 eV for x = 1.00 (650.39 K, 17 GPa and 3.28 eV for ZnO). The x = 0.05 has increased the carrier density to 8.06 × 10 19 (cm−3), which is about 8-times higher than of ZnO (1.07 × 10 19 (cm −3). The highest value of q-factor (3.5 × 10 5) is obtained for x = 0.00, which is about 10-tims higher than of ZnO (3 × 10 4). As x increases above 0.30, the optical conductivity is significantly increased to be greater than that of ZnO. The PL intensity of the visible emission peaks was gradually increases against x until becomes higher than that of ZnO when x = 1.00. A slight UV shift is obtained for x ≤ 0.30 samples, but it changed to blue for x ≥ 0.60, which is typically similar to ZnO. As compared to ZnO, the present samples are strongly recommended for plastic deformation, solar cell, light emission, super-capacitor and high-power operation. To the best of our knowledge, the present work has never been done elsewhere.

Enhanced Photocatalysis via Inverse Opal Structures: Synthesis and Characterization of TiO2/ZnO and ZnO/TiO2 Composites Using Plasma-Enhanced ALD

Inverse opals (IO) based functional materials show potential in photocatalysis due to their unique light interaction properties. This study presents a low-temperature plasma-enhanced atomic layer deposition (PEALD) method for synthesizing TiO2, ZnO, and composite IOs using a polystyrene nanoparticle-based opal template. We comprehensively characterized the obtained materials using SEM-EDX, TSEM, TG, FTIR, XRD, Raman, ellipsometry, photoluminescence (PL), and UV-Visible spectroscopy. SEM analysis confirmed the successful formation of PEALD IOs with a periodically ordered structure, enabling conformal coating while preserving their original architecture. XRD and Raman analysis also confirmed that the IOs consisted of anatase for TiO2 and hexagonal wurtzite for ZnO. UV-Vis reflectance spectroscopy revealed strong UV absorption and modified photonic bandgaps (PBGs) for all materials. The bare and composite IOs exhibited PBGs in the visible region, suggesting that the arising "slow photon" effect might enhance photocatalysis. This study explored the photocatalytic degradation of 4-Nitrophenol (4-NP) and Rhodamine 6G (Rh6G) using pristine and composite IO photocatalysts under UV and visible light irradiation. Pristine TiO2 and ZnO IOs demonstrated superior performance for 4-NP degradation under UV light. This can be attributed to two key factors: their highly ordered macroporous structure (with a large surface area for efficient dye adsorption, and their band gaps (3.0 eV for TiO2 and 3.2 eV for ZnO) that enable strong absorption of UV light photons for effective pollutant degradation. Conversely, composite IOs (TiO2/ZnO and ZnO/TiO2) displayed higher activity for both test molecules under visible light due to a synergistic effect between bandgap harmonization and the PBG effect.

Sr-doped ZnO thin film on a silicon substrate (100) grown by sol-gel method: Structural and optical study

In the current study, Sr-doped ZnO thin films were fabricated through a sol-gel route on a silicon substrate (100). The structural, optical, and morphological studies were examined through XRD, UV–vis, PL spectroscopy, and SEM. The crystalline superiority is enhanced through increasing Sr content while the optical bandgap is reduced because of lattice distortion and the production of active imperfections in ZnO, which may be the reason for bandgap tailing. The grain sizes observed are 53, 54, and 60 nm for ZnO, ZnSr1%, and ZnSr2%. Microstructural and strain were explored through Scherrer, W–H, and SSP methods. Furthermore, peak broadening was investigated using these methods. UV–Vis spectroscopy was employed to investigate the band gap of all grown thin films, which are 3.37, 3.28, and 3.20 eV of ZnO, ZnSr1% and ZnSr2%. The optical study was carried out to investigate the band gap, including different parameters such as Absorbance (A), transmittance (T), absorption coefficient (α), band gap (Eg) using different methods, band gap by derivative method, urbach energy (Eu), skin depth (δ), optical density (OD), refractive index (n), extinction coefficient (k), optical conductivity (σopt), dielectric constants (εr, εi), and Tan (α) were also explored. PL spectroscopy was used to study the defects in grown thin films. SEM was employed to examine the morphology of all fabricated thin films. ZnO thin film is widely studied for optoelectronics applications.

Influence of (Co+Al) co−doping on structural, micro-structural, optical and electrical properties of nanostructured zinc oxide

This study investigates the effect of (Co + Al) co−doping on the physical properties of the ZnO nanoparticles, synthesized via the simple co−precipitation method. X−ray diffraction (XRD) analysis revealed a hexagonal structure for all samples, with a formation of Al2O3 phase in both Zn0.98Co0.01Al0.01O and Zn0.94Co0.01Al0.05O nanoparticles. The crystallite size increased from 26.5 nm for ZnO to 16.6 nm for Zn0.94Co0.01Al0.05O nanoparticles. Scanning electron microscopy (SEM) technique showed a notable alteration in the morphology of ZnO upon the incorporation of Al. A transition from spherical nanoparticles in ZnO and Co doped ZnO to irregular, dendritic-like structures in (Co + Al) co−doped nanoparticles is observed. Transmission electron microscopy (TEM) substantiated the presence of the Al2O3 phase in the co−doped samples. Raman and FTIR spectroscopy confirmed the incorporation of Co and Al into the ZnO lattice through the presence of Co–O–Co and Al–O bonds. Optical characterization indicated a decrease in the band gap energy from 3.18 eV in ZnO to 2.84 eV in Zn0.94Co0.01Al0.05O nanoparticles. Electrical conductivity measurements revealed an increase from 1.2 × 10−4 Ω−1 cm−1 to 1.8 × 10−3 Ω−1 cm−1 as the Al content increased from 0 % to 5 % at the frequency of 103 Hz and the temperature of 423K. Likewise, dielectric constant raised from 775 in ZnO to 5455 in Zn0.94Co0.01Al0.05O nanoparticles at the temperature 423K. These results highlight the potential of (Co + Al) co−doped ZnO nanoparticles for advanced optoelectronic applications.

Sustainable green synthesis and characterization of nanocomposites for synergistic photocatalytic degradation of Reactive Orange 16 in textile wastewater using CuO@A-TiO2/Ro-TiO2

This paper explores the photocatalytic degradation of Reactive Orange 16 (RO16) dye in textile wastewater employing a novel CuO@A-TiO2/Ro-TiO2 nanocomposite. The nanocomposite was synthesized via a hydrothermal technique, resulting in a monoclinic phase of leaf-shaped CuO loaded on a hexagonal wurtzite structure of rod-shaped ZnO, as confirmed by FE-SEM and XRD analyses. Optical experiments revealed band gap energies of 1.99 eV for CuO, 2.19 eV for ZnO, and 3.34 eV for the CuO@A-TiO2/Ro-TiO2 nanocomposite. Photocatalytic degradation experiments showcased complete elimination of a 100 mg/L RO16 solution (150 mL) after 120 min of UV light illumination and 100 min of sunlight illumination, emphasizing the nanocomposite's efficiency under both light sources. The study further delves into the application of the CuO@A-TiO2/Ro-TiO2 nanocomposite for the degradation of actual textile wastewater samples under sunlight irradiation. The results underscore the nanocomposite's remarkable efficacy in treating RO16 in textile wastewater, positioning it as a promising candidate for sustainable and efficient wastewater treatment applications. This research contributes valuable insights into the development of advanced photocatalytic materials for textile dye degradation in wastewater treatment.

Study the characterization of ZnO and AZO films prepared by spray pyrolysis and the effect of annealing temperature

Spray-pyrolysis was used to successfully create ZnO and AZO (Al-doped ZnO) thin films on glass substrates at various annealing temperatures. Structure, morphology, and optical characteristics were investigated in relation to doping and annealing temperature using analytical techniques such as FTIR, UV–Vis spectroscopy, XRD, and FE-SEM. The films' singular-phase polycrystalline hexagonal Würtzite structure was revealed by XRD data, and the crystallographic plane for both AZO and ZnO was (0 0 2). Crystallite sizes are increased by raising the annealing temperature and adding Al-doping, which enhances surface morphology. where the diameters of the AZO crystallites expanded from 23.3 to 33.3 nm, whereas the ZnO crystallites grew from 27.8 to 28.5 nm. Scanning electron microscopy's morphology reveals that the surface particles' tiny, round shapes have changed to spherical clusters that resemble cauliflowers with increasing annealing temperatures. Notably, the ZnO film has a high transmittance, whereas the AZO film has a relatively low transmittance. Furthermore, at an annealing temperature of 400 °C, all films show notable absorbance, with the highest absorption seen at 400 and 413 nm for ZnO and AZO, respectively. The bandgap values at various annealing temperatures vary from 3.22 to 3.23 eV and 3.08–3.12 eV for ZnO and AZO, respectively. As the annealing temperature rose, the phenomena showed a drop in value.

Enhanced photocatalytic activity of FeSO4 in a ZnO photocatalyst with H2O2 for dye degradation

In this study, the photocatalytic degradation efficiency of ZnO synthesized by a hydrothermal method and iron-supported ZnO catalysts by an impregnation method, dried (D) and calcined (C), was evaluated, through the degradation of methylene blue (MB) and methyl orange (MO) molecules under UV irradiation. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, and UVvisible diffuse reflectance spectroscopy (DRS). XRD showed that FeSO4 is supported on ZnO, and the XPS study revealed higher concentrations of hydroxyl groups and Fe3+ for the dried catalyst. The bandgap energies were 3.24, 3.23, and 3.19 eV for ZnO, Fe/ZnO D and Fe/ZnO C, respectively. The results revealed that Fe/ZnO D with H2O2 exhibited a higher photocatalytic degradation efficiency than ZnO, achieving 97% and 99% degradation for MB and MO at 10 min, which implies that the integrated iron in ZnO serves as an electron-hole separator. In addition, the catalyst has a larger BET specific area, the presence of hydroxyl groups and sulfate ions on the surface of the catalyst with holes forms hydroxyl radicals (•OH), and the presence of Fe3+ on the surface catalyst with H2O2 produces more •OH radicals. •OH radicals are the major oxidation species in this process, which promotes the degradation of dyes. The photocatalytic dye degradation efficiency was also evaluated for various catalyst doses, dye concentrations and solution pH values. Moreover, the stability of the catalyst over repeated cycles of dye treatment was demonstrated.

Investigations on the enhanced anti-microbial activity of one step synthesized ZnO, WO3, and rGO nano particles and fabrication of rGO nano electrode for EMG biomedical application

Abstract The proposed study aims to synthesize ZnO, WO3, and rGO nano particles (NPs) using simple and effective chemical reduction technique and to investigate its biomedical applications. According to the XRD results, synthesized NPs had hexagonal, monoclinic, and cubic crystal forms. The FESEM micro image shows sheet-like structure for rGO NPs, an algal crystal structure for ZnO, and a bulk cluster formation for WO3 NPs. The value of band gap was found to be 5.75, 5.37 and 3.01 eV for ZnO, WO3, and rGO NPs respectively. The presence of diverse functional groups in the produced NPs was verified using Fourier-transform infrared spectroscopy. Investigations against different microorganisms indicated an augmentation in the antibacterial activity for ZnO and WO3 NPs. Electrodes coated with rGO NP were made and discovered to be effective in collecting human biomedical data more effectively. The performance of rGO NP coated electrodes was compared using a development board for electromyography analysis along with an android application for monitoring purposes. The quality of the signal, the ratio between the signal and the background noise, as well as the level of impedance between the electrode and the skin was observed to be better than conventional electrodes.

Improved photocatalytic activity for degradation of methylene blue dye using ZnO NPs

We present a plant-mediated green synthesized bare ZnO and Ni–ZnO NPs (nanoparticles) employing soursop leaf extract. The plant extract was treated with 0.1 M of Zn (NO3)2·6H2O The ZnO NPs have a wurtzite structure, according to XRD measurements. The mean size of the ZnO and Ni–ZnO NPs was examined to be 47.64 and 48.18 nm using an X-ray diffraction (XRD) pattern. The UV–visible spectrum displays absorbance maxima at 335 and 340 nm, which corresponds to an energy band gap of 3.28 and 3.24 eV for ZnO and Ni–ZnO NPs. Morphology studies show that the NPs are very permeable. The PL spectra of NPs revealed extremely intriguing blue, green, and red emissions following excitation at 391, 491 and 545 nm for ZnO and Ni–ZnO NPs, respectively. When exposed to UV light, the NPs exhibit photocatalytic efficacy for the reduction of methylene blue (MB) dye.

Green combustion synthesis of multifunctional inorganic ZnO: Co2+ (1–11 mol%) nanoparticles: Electrochemical and photocatalytic applications

Aloe Barbadensis Miller (Aloe vera) gel fuel-assisted facile combustion synthesized novel ZnO:Co2+ nanoparticles were analysed for its multifunctional applications such as supercapacitors, sensors, and photocatalytic dye degradation. The PXRD pattern of ZnO was matched with DFT-based computational XRD pattern. The morphology of the prepared nanomaterial was tested using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) techniques. Band gaps were estimated using the Kubelka-Munk function (K-M function) using diffuse reflectance spectra (DRS). The band gap was found to be a minimum ̴ 1.90 eV for ZnO: Co2+ (7 mol%) nanoparticles. Electrochemical properties of ZnO: Co2+ (1–11 mol%) nanoparticles based modified carbon paste electrodes were studied in KCl electrolyte using cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS) and Galvanostatic charge–discharge (GCD). Enhanced and optimized electrochemical performance in terms of specific capacitance was observed for ZnO: Co2+ (7 mol%) electrodes for supercapacitor application. EIS shows minimum ESR value of 72 Ω and GCD shows ̴ 99 % cyclic stability over 1550 cycles for ZnO: Co2+ (7 mol%) electrode. Effect of low band gap on electrochemical properties were established and found that low band gap leads to high performance in electrochemical activities. Sensitive detection of paracetamol and glucose (1––7 mM concentration) was carried out using the ZnO: Co2+ (7 mol%) electrode, for electrochemical sensor application. Photocatalytic degradation of methylene blue (MB) & acid orange-8 (AO-8) dyes was carried out using ZnO: Co2+ (7 mol%) photocatalyst under sunlight including scavenging examinations. Under sunlight, 92.45 % of MB and 98.29 % of AO-8 dyes were degraded in 120 min. Overall, this paper reports, multifunctional applications (EDLC, Sensor and Photocatalysis) of toxic free green combustion synthesized ZnO: Co2+ (1–11 mol%) nanoparticles.

The electronic and optical properties of InSe/ZnO van der Waals heterojunction:First principles study

The efficient, simple and low-cost photocatalysts has become a hot topic in the field of photocatalysis, ZnO has attracted the attention of researchers due to its high photocatalytic efficiency. Although, the broad band gap of around 3.4 eV in ZnO greatly limits its optical absorption efficiency. Based on this, two types of InSe/ZnO heterojunction models with different configurations are constructed, their electronic and optical properties are studied through first principles calculations. The results indicate that the II InSe/ZnO heterojunction has a band gap of 1.84 eV, which compensates for the shortcomings of ZnO monolayer broad band gap absorption of visible light and the difficulty of InSe monolayer in participating in water splitting oxidation reactions. The construction of heterojunctions using InSe and ZnO significantly improves the light absorption efficiency, especially in the visible spectral region, compared to ZnO monolayers, accelerating the generation and migration efficiency of photo generated electrons, thereby improving the catalytic efficiency of ZnO.

Photovoltaic ZnO/SnSx heterostructures obtained by “electrochemical deposition-successive ionic layer adsorption and reaction” approach

In this work, ZnO/SnS/indium tin oxide (ITO)/glass functional heterostructures have been developed using a combined approach of electrodeposition of a SnSx layer and successive ionic layer adsorption and reaction (SILAR) of the ZnO layer. The high-quality 400 nm-thick orthorhombic SnS0.9–0.95 films were formed on the ITO substrates with a thickness of 130 nm and an electrical conductivity of less than 40 Ω/□. Chemical deposition of ZnO thin films by the SILAR method allowed to deposit hexagonal films with a thickness of about 200 nm. The morphology, elemental and phase composition of the films were characterized by Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The band gap (1.4 eV for SnSx and 3.3 eV for ZnO), as well as the high light absorption coefficient of SnSx films (1–2) × 104 cm–1 were determined. The obtained ZnO/SnSx/ITO heterostructures formed by the electrodeposition–SILAR cycle showed a photoEMF value of 198 mV. These properties make ZnO/SnS heterostructure promising for low-cost solar cells based on affordable materials.

Effect of reduced graphene oxide on the structural and optical properties of ZnO nanoparticles

The co-precipitation method was used to synthesize ZnO nanoparticles (NPs). Then, graphene oxide (GO) sheets which were reduced during the reaction process to become (rGO), were embellished with ZnO NPs. The impact of rGO on the structure and morphology of ZnO was investigated using XRD, FTIR, TEM, and SEM techniques. Investigating the optical characteristics was done using UV–vis spectroscopy. ZnO exhibits a hexagonal phase, as proved by XRD. The average crystallite size reduced from 22 to 18 nm after being anchored on rGO sheets. TEM and SEM testify to the presence of ZnO in nanoscales with quasi-spherical shapes, which dispersed homogeneously along the GO sheets. The optical bandgap was increased from 2.57 eV to 3.17 eV for ZnO and ZnO-rGO, respectively. Based on the obtained optical bandgap, the refractive index of ZnO and ZnO-rGO nanocomposite was theoretically determined using different models such as Moss and Ravindra models. ZnO-rGO nanocomposite's ability to change optical characteristics makes it a superior nominee for optoelectronic applications.

The development of program for calculating the band gap energy of semiconductor material based on UV-Vis spectrum using delphi 7.0

The optical properties of semiconductor material are the important information for its application in solar cell. One of the parameter which influence the material optical properties is the band gap energy. The value of band gap energy can be obtained from experimental data of UV-Vis absorbance spectrum by doing three steps, i.e. curve smoothing, baseline arrangement data value and the calculation of the band gap energy using Tauc plot method embedded in the Origin software. Conventionally, these three processes are done sequentially. In this research, we developed the program for calculating the band gap energy which differ from the one usually used. In this program all the processes for curve smoothing, baseline arrangement data value and the calculation of the band gap energy are done simultaneously. For input data, we used the experimental UV-Vis absorbance spectrum of ZnO, TiO2 sensitized-Dye and Dye-N719 materials. The calculated band energy obtained by our program are 3.19 eV, 2.14 eV and 1.73 eV for ZnO, TiO2+Dye N719and Dye-N719 materials, respectively. These results are almost the same to the one obtained by conventional method i.e. 3.20 eV for ZnO, 2.10 eV for TiO2 based Dye-sensitized and 1.60 eV for Dye-N719. We also found that our program for calculating the band gap energy is more easily, user friendly and more efficient compared to the conventional method.

Preparation and characterisation of pure and Ni doped ZnO nanorods

ABSTRACT One-dimensional pure and Ni-doped zinc oxide nanorods (NRs) were prepared by chemical bath technique. Some physical properties like optical, morphological and structural were examined for prepared NRs. The result of X-ray diffraction XRD was exposed that the crystal structure was hexagonal for both pure and Ni-doped NRs where there is no change in the crystal system but some small shifting in diffraction angle appeared. The chemical composition and the presence of Ni atoms in the ZnO were approved by EDX test. Additionally, morphology investigation of the scanning electron microscopy (SEM) is conducted and showed that the shape of prepared materials was NRs. A red shift in the absorption spectrum and band gap happened after doping with Ni where the energy gap dropped from 3.72 for ZnO to 3.5 eV for ZnO:Ni.

Investigation of structural, morphological, optical, elemental, and anticancer property of pure ZnO and PbO: ZnO nanocomposites prepared by flame synthesis method

In this work, Pure ZnO nanoparticles and a nanocomposite of PbO: ZnO were prepared by the flame synthesis method, and was analyzed for structural, morphological, optical, elemental, and biocompatibility studies. The structural analysis revealed a hexagonal structure for ZnO and an Orthorhombic structure for PbO: ZnO nanocomposite. Scanning electron microscopy (SEM) image showed a Nano-Sponge-like surface morphology for PbO: ZnO nanocomposite and energy dispersive spectra (EDS) confirmed the absence of undesired impurities. Transmission electron microscopy (TEM) image showed a particle size of ∼50 nm for ZnO and ∼20 nm for PbO: ZnO. Using Tauc plot the optical band gap was found to be 3.2 eV for ZnO and 2.9 eV for PbO: ZnO. Anticancer studies confirm the excellent cytotoxicity activity of both compounds. PbO: ZnO nanocomposite has demonstrated the highest cytotoxicity against the tumorigenic HEK 293 cell line with the lowest IC50 value of 13.04 μM. Our study shows that the prepared PbO: ZnO nanocomposite has a huge potential in cancer therapy.

Modified sol-gel technique for the synthesis of pure MgO and ZnO nanoparticles to study structural and optical properties for optoelectronic applications

Pure MgO and ZnO nanoparticles were synthesized using the modified sol–gel technique at optimized calcination temperatures of 200 °C and 300 °C for 2 h. The structural and optical properties were characterized using X, -ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–VIS spectroscopy, Energy dispersive X-ray spectroscopy (EDAX), and scanning electron microscopy (SEM). The XRD analysis confirms that MgO and ZnO are in cubic and hexagonal Wurtzite phase and are in nanosize, with major diffraction peaks of MgO at (200), (220), and for ZnO nanoparticles at (100), (002), and (101), respectively. The average crystallite size of MgO and ZnO nanoparticles was calculated by using the Debye-Scherrer formula, which is found to be 16 nm for MgO and 20 nm for ZnO NP’s. Particle sizes of 30 to 50 nm for MgO and 40 to 80 nm for ZnO nanoparticles were confirmed by SEM results. From UV–Visible spectroscopy, the excitation wavelengths of MgO and ZnO were 322 nm and 375 nm, respectively. The optical band gap is found to be 5.4 eV for MgO and 5.2 eV for ZnO, which is determined using the Tauc Plot equation. These results are suitable for advanced optoelectronic and photonic applications.

Effect of Annealing on the Structural and Optical Properties of ZnO/ITO and AZO/ITO Thin Films Prepared by Sol-Gel Spin Coating

This paper aims to investigate the effect of annealing on the structural and optical properties of ZnO/ITO and AZO/ITO thin films. In the preparation of ZnO and AZO films, zinc acetate dehydrate (Zn(CH3COO)2.2H2O), ethanol, diethanolamine (DEA), and AlCl3 were used as a starting material, solvent, stabilizer, and dopant sources, respectively. Both ZnO and AZO films were fabricated on ITO (indium tin oxide) substrates using the spin coating technique at room temperature with a rotating speed of 3,000 rpm in 30 s. The films were heated at various temperatures in the temperature range of 400 - 600 °C for 60 min. The crystallite size of the film is calculated using Debye-Scherrer and Williamson-Hall Methods. Based on the UDM results, the crystallite size of ZnO/ITO and AZO/ITO films increases after annealing in comparison with the films before annealing. From the optical UV-Vis measurements, there was an increase in the transmittance value of the samples after annealing. The transmittance value of ZnO/ITO and AZO/ITO films increases from 40 % before annealing to approximately 80 and 90 %, respectively after annealing. The increase in the transmittance valued in both ZnO/ITO and AZO/ITO after annealing is mainly due to an improvement in the crystalline phase of these films. The band gap energy of ZnO and AZO films is reduced with increasing annealing temperatures, from 3.26 eV before annealing to 3.19 eV for ZnO and 3.23 eV for AZO films after annealing at 600 °C.
 HIGHLIGHTS
 
 The sol-gel spin coating method was used to study the effect of annealing on the structural and optical properties of ZnO/ITO and AZO/ITO films
 The transmittance valued in both ZnO/ITO and AZO/ITO after annealing increase as a result of an improvement in the crystalline phase of these films
 Reducing the amorphous phase and the increase of the crystallite size of the films are the main reason for narrowing the band gap energy of the ZnO/ITO and AZO/ITO films

Photoelectrical and thermal sensing measurement of spin coated ZnO and ZnO-RGO thin film

This research reported the synthesis of ZnO and ZnO-RGO as well as their photo sensing and thermal sensing properties. This is with a view to reducing the electron hole recombination in ZnO and improving the sensing properties. ZnO and ZnO-RGO were synthesized by the hydrothermal method and spin coated on glass to obtain the thin film. The SEM micrograph of ZnO-RGO showed mini ZnO nanorods decorated and formed on the RGO sheet. The adherence of the nanorods were improved as the loading mass of GO increased in the hybrid. Though ZnO and ZnO-RGO had comparable thermal sensing response of 2.8 and 3.1 respectively at 573 K, ZnO-RGO showed improved electrical conductivity as temperature increased. ZnO sensors logged a negative temperature coefficient (NTC) value of 0.00236/K and a sensitivity value of 0.0139 Ω/K while ZnO-RGO had a NTC value of 0.00248/K (which is higher than values obtained in literature for silver and palladium based graphene hybrids) and a sensitivity value of 0.00769 Ω/K. A value of 0.0561eV was obtained for the activation energy of ZnO sensor while 0.0615eV was obtained for ZnO-RGO. For the photo sensing, incorporation of GO into ZnO decreased the band gap at peak wavelength of ZnO-RGO to 2.48 eV from 3.1 eV for ZnO and improved the photoconductivity to the order of 106 Ω. This research has confirmed that incorporating GO in ZnO increased the activation energy of ZnO-RGO thermistor, and consequently increased the thermal sensing response thus resulting in improved thermal and photo sensing properties of ZnO. With an improved NTC, sensor response and activation energy, ZnO-RGO can replace Pd based RGO and Ag nanoparticles based RGO as thermistors.

Coupling ZnO with CuO for efficient organic pollutant removal.

Fabrication of heterojunction semiconductors for the photodegradation of toxic organic dyes under sunlight exposure has earned significant recognition from researchers nowadays. On that account, we have synthesized and explored a comparative photodegradation study of ZnO/CuO nanocomposite with ZnO and CuO nanoparticles. ZnO and CuO nanoparticles have been synthesized by biosynthesis methods usingFicus benghalensisleaf extract. As-synthesized ZnO and CuO nanoparticles have been further utilized for the synthesis of ZnO/CuO nanocomposite by the mortar pestle crushing/milling method. Both biosynthesis methods and mortar pestle crushing/milling methods are simple, low-cost, and environmentally friendly. Structural, optical, and morphological analysis of all the synthesized nanomaterials havebeen doneby powder X-ray diffraction (PXRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM),Brunauer-Emmett-Teller (BET),field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy.PXRD data reveal that synthesized ZnO nanoparticles are in the hexagonal wurtzite phase, CuO nanoparticles in the monoclinic phase, and ZnO/CuO nanocomposite in the hexagonal wurtzite as well as in monoclinic phase. FE-SEM and TEM images of ZnO/CuO nanocomposite reveal the nanorod-shaped morphology along with micro-sized and nano-sized flakes. The BET analysis shows the surface areas 18.128 m2/g for ZnO nanoparticles, 16.653 m2/g for CuO nanoparticles, and 19.580 m2/g for ZnO/CuO nanocomposite, respectively. Theenergyband gap values of ZnO/CuO nanocomposite are obtained 3.13eV for ZnO and 2.76eV for CuO, respectively. The photocatalytic behaviors of all the synthesized nanomaterialsareexamined against aqueous dye solutions of methylene blue (MB), rhodamine B (RhB), and methyl orange (MO) under sunlight irradiation. The results reveal that the photocatalytic degradation efficiency of ZnO/CuO nanocompositehasbeen found higher than with ZnO and CuO nanoparticles for all the dyes. Also, all the synthesized nanomaterialsindicatehigher photocatalytic degradation efficiency for methylene blue dye among allthreedyes. The kinetics of photodegradation of all the dye solutions has also been investigated in the presence of ZnO, CuO, and ZnO/CuO photocatalysts separately. The results exhibit that rate constant values for all the dyes are higher with ZnO/CuOnanocompositethan with ZnO and CuOnanoparticles.ZnO/CuO nanocomposite demonstrates degradation efficiency for MB dye99.13%, for RhB80.21%, and for MO67.22%after 180min of sunlight exposure.ZnO/CuO nanocomposite and ZnO and CuO nanoparticles also show thebestreusability and stability up to three cycles for photocatalytic degradation of MB dyes amongall the dyes.Therefore, green synthesized ZnO/CuO nanocomposite could be used asan efficientphotocatalyst for the degradation of various toxic dyes.The mineralization of different dyes using ZnO/CuO nanocomposite has been examined by FTIR analysis. Furthermore, the mineralizationof MB dye has been done by total organic carbon (TOC)measurements.