Hexagonal Wurtzite Structure Of ZnO Research Articles

Fabrication and characterization of B/Sn-doped ZnO nanoparticles via mechanochemical method for photocatalytic degradation of rhodamine B

Undoped and B/Sn-doped ZnO nanoparticles are successfully produced by a simple mechanochemical method, and are characterized by XRD, FTIR, EDX, SEM, XPS and BET techniques. The XRD studies reveal that the prepared nanoparticles possess the hexagonal wurtzite structure of ZnO. The presence of various functional groups (–OH, –CH, Zn–O) are observed by FTIR. It is clear from EDX analysis that B, Sn, Zn and O elements are present in the nanoparticles. SEM images confirm the relatively smooth surface of B/Sn-doped ZnO nanoparticles. XPS results indicate that B and Sn are successfully doped into ZnO matrix. The photocatalytic performances of undoped and B/Sn-doped ZnO nanoparticles are investigated for the degradation of aqueous solution of Rhodamine B (RhB) dye in natural sunlight irradiation. The photocatalytic degradation of RhB dye in 1 h with B/Sn-doped ZnO nanoparticle is about 70.2%, which is significantly enhanced compared with the undoped ZnO (51.8%).

Highly conducting and transparent low-E window films with high figure of merit values based on RF sputtered Al and In co-doped ZnO

In this work, we have studied the correlation between the electrical, optical and plasma properties of RF sputtered 1 at.% Al and In co-doped ZnO (AIZO) thin films with thickness 210–1590 nm in a comprehensive manner. The lattice strain of the hexagonal wurtzite ZnO structure decreases as the film thickness increases. The lowest resistivity of 8.9 × 10−4 Ω-cm is obtained for the 930 nm thick film with an electron concentration and mobility values of 3.96 × 1020 cm−3 and 17.7 cm2/Vs respectively. Optical transmission value is ~85%–90% in the range 400–700 nm for all the films. Most notably the figure of merit value of 2.65 × 10−2 Ω−1 for the 930 nm thick film is the highest among all the reports on AIZO films till date. High transparency in the visible region as well as higher reflectivity in the NIR region (with a plasma frequency of 8.2 × 1014 Hz) indicates its promising application in the low-E window.

ZnO as photocatalyst: An approach to waste water treatment

ZnO nanorods having uniform size have been synthesized using hydrothermal method. Different standard analytical techniques were employed to investigate the microscopic structure and optical properties of the prepared sample. The formation of the hexagonal wurtzite structure of ZnO was established by XRD and SEM analyses. UV-visible spectra of the as-synthesized ZnO show absorption band edge in UV region at 373 nm, corresponding to which the calculated band gap of ZnO nanorods is found to be 3.4 eV. Photodegradation of methylene blue (MB) using ZnO as photocatalyst have also been studied. Experiments revealed that ZnO nanorods with high aspect ratio can degrade 65% of initial concentration of MB in only 50 min.

Tuning of CO gas sensing performance of spray pyrolyzed ZnO thin films by electron beam irradiation

Electron beam induced effects on the sensing performance of spray-coated ZnO thin films for carbon monoxide (CO) detection are reported. The optical transmittance of pristine film was around 80% and decreased upon e-beam treatment. XRD studies confirmed the hexagonal wurtzite structure of ZnO. Carbon monoxide (CO) sensing measurements performed at 300 °C revealed that irradiated ZnO films exhibited enhanced response and recovery time compared to pristine film. The 5 kGy irradiated film displayed improved sensing performance with respect to response and recovery time towards the CO concentrations tested. It showed a quick response time of 43 s and a recovery time of 77 s towards the lowest detected CO gas limit of 2 ppm. The response time of 10 kGy irradiated film was 5 s towards 2 ppm. The 5 kGy irradiated ZnO sensor exhibited an excellent response of 1.39 and 2.63 towards 2 ppm and 5 ppm of CO gas respectively. The observed enhancement in both response and recovery times as well as response of the sensor is ascribed to the oxygen vacancies present in the film which is evident from the photoluminescence studies and also due to large number of grain boundaries.

Superior sunlight photocatalytic of N/La codoped ZnO nanostructures synthesized using different chelating agents

N/La codoped ZnO exhibited high sunlight activity, good reusability and rapid photodegradation for Congo red, malachite green and methylene blue dyes. Pure and N/La codoped ZnO were synthesized by sol gel using different chelating agents. All XRD patterns are fully indexed to hexagonal wurtzite structure of ZnO. The XRD peak shift and the increases in unit cell volume confirm the effective incorporation of N/La ions into ZnO. N/La blend extended the absorption ability of ZnO nanostructures to visible light region. Pure and N/La codoped ZnO synthesized by citric acid showed homogenous spherical nanoparticles distribution. Oxalic acid induced the formation of nanosheets and fine nanoparticles in N/La codoped ZnO. The adsorption capacity of pure and N/La codoped ZnO powders toward CR, MG and MB was less than 8%. The degradation of CR, MG and MB dyes under sunlight without catalyst is very weak. N/La codoped ZnO nanostructures exhibited superior sunlight photocatalytic activity for organic dyes degradation. N/La codoped ZnO–C and N/La codoped ZnO–O samples displayed remarkable photodegradation activities within 92–97% for CR, MG and MB in 60 min. N/La codoped ZnO–C showed a perfect photostability and reusability for four cycles. N and La enhance the charge carriers’ separation and the visible light absorption in ZnO which increase the photocatalytic activity.

Visible-Light Driven Photocatalytic and Antibacterial Assessment of Ag/ZnO/Cellulose Nanocomposite

Ag/ZnO/cellulose nanocomposites were synthesised through in-situ solution casting method, which offers a good adhesion and dispersity of nanostructured materials. SEM analysis revealed formation of nanodiscs-like structures for ZnO while nanospheres and hierarchical nanosheets were observed for Ag and cellulose, respectively. XRD analysis pointed to the monoclinic type-1 phase of cellulose. Peaks corresponding to typical hexagonal wurtzite structure of ZnO and face-centredcubic Ag structure were also identified. Photodecomposition of aqueous methylene blue (MB) under direct sunlight irradiation was monitored to study the photocatalytic activity of the nanocomposite. About 92% of MB dye was photodegraded in the presence of Ag/ZnO/cellulose nanocomposite. The influence of Ag+ ions on the photocatalytic efficiency of ZnO is discussed. The antibacterial efficiency of the synthesised samples was investigated against two Gram positive pathogenic bacteria species: Staphylococcus aureus and a spore forming Bacillus subtilis as well as a Gram-negative Escherichia coli. The prepared nanocomposite exhibited strong activity against the growth of all the bacterial species though in different quantified measures.

Structural and Optical Performance of The doped ZnO Nano-thin Films by (CSP)

In this study, were investigated structural, optical properties and morphological ofZnO and Te-doped ZnO Nano-thin films deposited by Chemical spray pyrolysis(CSP) method. The structural properties of films were studied as pure and Te dopant ZnO at concentration 2 and 4%. The films were characterized by XRD to study the structure of films. It was observed that the hexagonal wurtzite structure of ZnO for all samples. The films exhibited wurtzite (102) preferential growth in pure and the dopant ratios. Grain size values calculated fromScherrer’s formula of the films were varied in range of (79-113) nm. The band gap energy values were calculated respectively for undoped ZnO and 2% 4% Te doped ZnO samples.

Thin Film Transistors p-type Depletion Mode based on Nickel-doped Zinc Oxide

In this work, Nickel-doped Zinc oxide (Ni:ZnO) thin film transistors (TFTs) p-type depletion mode were fabricated with different channel lengths. Channel lengths for TFTs were 50 μm, 70 μm and 100 μm. Ni:ZnO thin films deposited by hydrothermal technique The X-ray Diffraction (XRD) was used to examine the structural analytic of the prepared thin films. The diffraction peaks of prepared Ni:ZnO thin films are fairly matching with the hexagonal wurtzite ZnO structure with the preferred orientation (002) plane. The Scanning Electron Microscopy (SEM) with Atomic Force Microscopy (AFM) were used to characterize the surface morphologies of the fabricated thin films and study them. The SEM images confirm nanorods nanostructures. Hall Effect measurements reveal that the fabricated thin film is p-type. The characterization of Ni:ZnO TFTs p-type depletion mode was investigated by transfer (IDS–VGS) characteristics. The threshold voltage (VTh), subthreshold-swing (S.S), the on-off current ratio (ION/OFF) and the mobility carrier (saturation regime) were calculated. The 50μm Ni:ZnO TFT shows better performance based on device carrier mobility and highest ION/OFF ratio.

Enhanced structural, optical and morphological properties of ZnO thin film using green chemical approach

In this work, ZnO thin film is fabricated by a green chemical approach using Uncaria gambir leaf extract on a glass substrate. The hexagonal wurtzite structure of ZnO does not change with the use of extracts. While ZnO fabricated without extract does not show preferred orientation, the ZnO prepared with extract shows c-axis orientation. The crystallite size is also significantly reduced from 41 nm to 32 nm. The visible transmittance increases from 71% to 76%, while the bandgap energy increases from 3.66 eV to 3.70 eV. The intensity of infrared transmission of ZnO with extract is lower than ZnO without extract because of the smaller crystallite size. The surface morphology of the film with extract is smoother, flatter, more homogeneous, and has smaller grain sizes, and uniform distribution.

Sensing layer combination of vertically aligned ZnO nanorods and graphene oxide for ultrahigh sensitivity IDE capacitive humidity sensor

An interdigitated electrode (IDE) capacitive humidity sensor fabricated on a silicon substrate was used to investigate sensing materials, which proved to be an ultrahigh‐sensitivity humidity sensor. A sensing layer combination (SLC) between vertically aligned ZnO nanorods and optimal graphene oxide (GO) was prepared on the device and was tested as a humidity sensor. X‐ray diffractometry (XRD) exhibited crystallized wurtzite structure of ZnO nanorods and transmission electron microscope (TEM) shown perfectly indexed hexagonal wurtzite ZnO structure dots position correspondence. A scanning electron microscope (SEM) was used to analyze ZnO nanorods/GO morphologies. Furthermore, Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS) clearly exhibited GO presence and hydrophilic functional groups (carboxyl, epoxy, and hydroxyl), respectively. The SLC prominently demonstrated ultrahigh sensitivity (up to 196.95% or 1.97 times from commercial sensor; HS1101, Humirel) and linear responses behavior with 0.96 for coefficient of determination. The device sensitivity obviously improved as steps of 40, 50, 60, 70, 80, and 90% RH at values of 1.09, 1.41, 1.51, 1.65, 1.80, and 1.91 times, respectively. The device also exhibited fast response (25 s) and short recovery times (17 s). Its hysteresis (6.58%) manifestly improved to 1.84 times. Moreover, repeatability and long‐term ability of the device demonstrated high accuracy (range ±0.37pF) and durability. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Biosynthesis, structural, photoluminescence and photocatalytic performance of Mn/Mg dual doped ZnO nanostructures using Ocimum tenuiflorum leaf extract

Here, pure ZnO, Zn0.98Mn0.02O and Zn0.96Mn0.02Mg0.02O nanostructures using aqueous leaf extract of Ocimum tenuiflorum were reported. XRD patterns revealed that no secondary phase was noticed and ZnO hexagonal wurtzite structure was not altered by Mn/Mg simultaneous doping. Mg co-doping with Zn0.98Mn0.02O considerably decreased the crystallite size from 46 to 34 nm due to ionic size difference. The superior absorbance and tuning of energy gap by Mn/Mg substitution is useful for opto-electronic applications. The presence of Mn and Mg in Zn-Mn-Mg-O network was confirmed by IR analysis. The effective charge separation, enhanced optical absorbance in the visible range, increased surface area and the generation of more defect related states were responsible for the noticed highest photocatalytic activity in Mn/Mg doped ZnO.

Enhancement of optical and electrical properties of spray pyrolysed ZnO thin films obtained from nitrate chemical by Al-Sn co-doping

Un-doped, Al-doped, and Sn-Al co-doped ZnO thin films have been successfully synthesized by Spray Pyrolysis method. Zinc Nitrate (Zn(NO3)2), Tin Chloride (SnCl2) and Aluminum Nitrate (Al(NO3)3) were used as starting chemicals at different compositions. Films depositions were carried out on glass substrates at 350 °C. The X-ray diffraction confirmed that the Al-Sn co-doping did not change the ZnO Hexagonal Wurtzite structure. The obtained un-doped ZnO films were highly oriented along the preferential (002) crystallographic plane while the Sn- Al co-doped ZnO films were disoriented with slight loss of crystallinity. The optical measurement showed an increase of the average transmittance from 65 % to 81 % and the band gap energy (Eg) from 3.23 to 3.30 eV. The electrical conductivity has increased with the Al-Sn co-doping concentration to reach the value of 0.335 (Ω.cm)−1.

Developing Conductive Highly Ordered Zinc Oxide Nanorods by Acetylacetonate-Assisted Growth.

Highly ordered vertically grown zinc oxide nanorods (ZnO NRs) were synthesized on ZnO-coated SiO2/Si substrate using zinc acetylacetonate hydrate as a precursor via a simple hydrothermal method at 85 °C. We used 0.05 M of ZnO solution to facilitate the growth of ZnO NRs and the immersion time was varied from 0.5 to 4 h. The atomic force microscopy revealed the surface roughness of ZnO seed layer used to grow the ZnO NRs. The morphology of vertically grown ZnO NRs was observed by field emission scanning electron microscopy. X-ray diffraction examination and transmission electron microscopy confirmed that the structure of highly ordered ZnO NRs was crystalline with a strong (002) peak corresponded to ZnO hexagonal wurtzite structure. The growth of highly ordered ZnO NRs was favorable due to the continuous supply of Zn2+ ions and chelating agents properties obtained from the acetylacetonate-derived precursor during the synthesis. Two-point probe current–voltage measurement and UV–vis spectroscopy of the ZnO NRs indicated a resistivity and optical bandgap value of 0.44 Ω.cm and 3.35 eV, respectively. The photoluminescence spectrum showed a broad peak centered at 623 nm in the visible region corresponded to the oxygen vacancies from the ZnO NRs. This study demonstrates that acetylacetonate-derived precursors can be used for the production of ZnO NRs-based devices with a potential application in biosensors.

Zn0.9Ce0.05M0.05O (M = Er, Y, V) nanocrystals: Structural and energy bandgap engineering of ZnO for enhancing photocatalytic and antibacterial activity

Novel photocatalytic and antibacterial material Zn0.9Ce0.05M0.05O (M = Er, Y, V) nanocrystals were synthesized via a facile co-precipitation technique and characterized by different analytical techniques. XRD confirmed the incorporation of Ce, Er, Y, and V, that without modifying the basic ZnO hexagonal wurtzite structure affects strongly structural properties. The Scherrer, W–H, and SSP methods were used to calculate different microstructural parameters using XRD data. The optical energy bandgap was found to be decreased in all co-doped samples (3.14–2.82 eV) calculated from UV–vis spectra by employing different methods. The effect of dopants ions on the optical properties of ZnO was also studied in detail. The FTIR spectrum inveterate the existence of Zn–O, and Zn-M–O (M = Ce, Er, Y, V) vibrational mode that further confirmed the incorporation of dopants ions. The photocatalytic performance of the grown products was evaluated under sunlight illumination against methylene blue (MB) dye. The antibacterial activity was performed against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa bacteria. The co-doped nanocrystals have shown enhanced photocatalytic and antibacterial activity as compared to Ce-doped ZnO but the Ce–V co-doped ZnO shown the highest activity. The influence of different operational parameters such as the amount of catalyst, the concentration of dye, and pH of the solution on photocatalytic activity of Ce–V co-doped ZnO nanocrystal was also studied and discussed in detail. The radical trapping experiments were also performed to identify the active species involved in photodegradation reaction. The recyclability test exhibited that Ce–V co-doped ZnO catalyst has high stability and can be reused up to the 6th cycles. Furthermore, a possible photocatalytic mechanism was also proposed for the photodegradation of MB dye.

Localized surface plasmon resonance of Cu-doped ZnO nanostructures and the material’s integration in dye sensitized solar cells (DSSCs) enabling high open-circuit potentials

Herein, we report one step co-precipitation method of synthesis of ZnO and Cu-doped ZnO nanostructures with distinct amount (1, 3 and 5 mol %) of copper. All the synthesized samples are characterized by X-ray powder diffraction, Field emission scanning and Transmission emission microscopy. The optical properties of the samples were evaluated by UV-visible spectroscopy and photoluminescence studies. The presence of Cu atoms in the ZnO matrix enhances a broad spectral absorption upto near-IR region. Suppressed E2high phonon modes are observed in Cu-doped samples through Raman scattering measurements, which furnishes evidence for effective Cu-doping in ZnO crystal lattice. Un-doped and Cu-doped ZnO samples were integrated in Dye sensitized solar cells (DSSCs) as photoanode materials. The device performance and interface charge transfer properties were evaluated through photocurrentdensity-photovoltage measurements and electrochemical impedance spectroscopy respectively. It is noted that the incorporation of Cu2+ into the hexagonal wurtzite structure of ZnO considerably elevates the Fermi levels towards the conduction band edge which is the root cause for high open-circuit potentials of DSSCs integrated with Cu-doped ZnO photoanodes.

Synthesis and photocatalytic study of Zn0.90Co0.10O and Zn0.90Co0.05M0.05O (M = Ca, Ba, Cr, Pb) nanocrystals: structural, optical and electrical investigations

Novel Zn0.90Co0.10O and Zn0.90Co0.05M0.05O (M=Ca, Ba, Cr, Pb) nanocrystals were synthesized by co-precipitation method and studied its structural, optical and electrical properties along with their photocatalytic activity. The XRD confirmed that Ca, Ba, Cr, and Pb have been incorporated without modifying ZnO hexagonal wurtzite structure. The microstructural parameters were calculated using Scherrer, W–H, and SSP methods. FTIR confirmed the existence of Zn–O vibrational modes. UV–vis spectra used to calculate the energy bandgap by using Tauc’s plot, Energy equation, Vegard’s law, and Derivative method. Optical parameters such as Urbach energy, refractive index, dielectric constant, extinction coefficient and optical conductivity were also studied. The IV measurements demonstrated that electrical conductivity was increased significantly by co-doping. The photocatalytic activity for the decolorization of methylene blue (MB) and methyl orange (MO) dyes under sunlight revealed the highest degradation efficiency for co-doped nanocrystals against MB as compared to MO in 100min illumination. The grown nanocrystals are propitious sunlight driven photocatalyst to eradicate organic toxins.

Hydrophilic and Superhydrophilic Self-Cleaning Coatings by Morphologically Varying ZnO Microstructures for Photovoltaic and Glazing Applications.

Transparent, superhydrophilic materials are indispensable for their self-cleaning function, which has become an increasingly popular research topic, particularly in photovoltaic (PV) applications. Here, we report hydrophilic and superhydrophilic ZnO by varying the morphology for use as a self-cleaning coating for PV applications. Three different ZnO microstructures, such as ZnO nanorods (R-ZnO), ZnO microflowers (F-ZnO), and ZnO microspheres (M-ZnO), were developed by hydrothermal methods. The surface morphology by using X-ray diffraction (XRD), wettability behavior by using water contact angle (WCA) measurements, structural and optical properties by using photoluminescence (PL), Raman, and UV–vis spectrophotometry, and defect estimation by using X-ray photoelectron spectroscopy (XPS) of the ZnO nanostructured films were systematically investigated. XRD confirmed the formation of the hexagonal wurtzite structure of ZnO. The average crystallite sizes of prepared R-ZnO, F-ZnO, and M-ZnO were found to be 28.95, 11.19, and 41.5 nm, respectively. The band gap values of ZnO nanostructures were calculated from the UV–vis absorption spectrum and found to be 3.6, 3.3, and 3.1 eV for R-ZnO, F-ZnO, and M-ZnO, respectively. The WCAs for R-ZnO and F-ZnO were 20.2 and 11.19°, respectively, while M-ZnO behaved like a superhydrophilic material having a WCA of 2.8°.

Study on the Photocatalytic Activity of Metal Oxide Nanoparticles towards the Degradation of Some Organic Dyes

The present study involves the successful synthesis of zinc oxide and tin oxide nanoparticles by green and chemical co-precipitation methods respectively. The synthesized samples were characterized by X-ray diffraction (XRD) and UV-visible absorption techniques. XRD analysis confirms the formation of hexagonal wurtzite structure of ZnO and pure cassiterite rutile tetragonal phase of SnO2. UV-visible spectroscopic study confirms the absorption of UV light by samples. The photocatalytic activities of both samples on Methylene blue (MB) and Malachite green (MG) dyes were analyzed and their corresponding kinetic modelings were studied. It is observed that SnO2 shows better degradation activity compared to ZnO.

Natural dyes as photo-sensitizer in solar cells

The objective of this research is to employ the natural dyes in dye-sensitized solar cell (DSSC). On account of eco-friendly, renewable, and non-hazardous properties of natural dyes over silicon, a semiconductor, photo-sensitizer in conventional solar cells, cyclohexane extract of Terminalia alata, a natural dye, was employed as photo-sensitizer. The photoanodes ZnO and 5% Al-doped ZnO for DSSCs were developed by spray pyrolysis. The X-ray diffraction (XRD) has shown hexagonal wurtzite structure of ZnO with lattice constants a = 3.2487 Å and b = 5.1518 Å having particle size 25.85 nm for ZnO and 33.17 nm for Al-doped ZnO. The DSSC properties such as solar conversion efficiency (η), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) were found to be 0.31%, 2.10 mA/cm2, 0.73V, and 45% for ZnO photoanode and 0.37%, 2.25mA/cm2, 0.70 V, and 52.10% for 5% Al-doped photoanode respectively.
 BIBECHANA 17 (2020) 27-32

OPTICAL AND STRUCTURAL PERFORMANCE OF NANOSTRUCTURED Te THIN FILMS BY (CSP) WITH VARIOUS THICKNESSES

In this study, were investigated structural, optical properties and morphological of Te Nano-thin films with different thicknesses by Chemical spray pyrolysis (CSP) method. The structural properties of the films were studied as a Te dopant at 150-450 thicknesses. The films were characterized by XRD to study film structure. It was observed that the hexagonal wurtzite structure of ZnO for all samples. The films exhibited wurtzite (102) preferential growth in different thicknesses. Grain size values calculated from Scherrer’s formula, were varied in range of (96-84) nm. The band gap energy values were calculated respectively for Te thickness samples