Band Gap Of ZnO Nanoparticles Research Articles

Green synthesis and characterization of silver doped ZnO particles

Green Synthesis is a chemical-free, economic, efficient, eco-friendly, and less time-consuming technique for the production of various nanoparticles. In the present study, green synthesized silver doped ZnO particles are synthesized. Silver nanoparticles are synthesized using Neem leaves and Silver salt (Silver Nitrate, AgNo3). Leaves extract act as a reducing agent for this synthesis. EDAX confirms the formation of Ag nanoparticles and ZnO particles. ZnO nanoparticles were successfully synthesized by the co-precipitation method, zinc acetate dehydrate and sodium hydroxide was used as precursor material. The green synthesized Ag nanoparticles are doped with ZnO. The synthesized particles were then characterized through XRD and UV–Vis spectrophotometry. The values of interplanar spacing and lattice parameters obtained were consistent with its standard values. The band gap of ZnO nanoparticles got reduced with doping Ag nanoparticles.

Comparative Study of the Effects of Growth Temperature, Annealing Temperature, and Calcination Temperature on the Size and Bandgap of ZnO Nanoparticles

Comparative Study of the Effects of Growth Temperature, Annealing Temperature, and Calcination Temperature on the Size and Bandgap of ZnO Nanoparticles

Eco-friendly Green Synthesis of stable ZnO nanoparticles using citrus limon: X-Ray Diffraction Analysis and Optical Properties

Eco-friendly stable ZnO nanoparticles (NPs) were synthesized by sol-gel method using citrus limon as a chelating agent. The structural analysis and optical properties of ZnO NPs annealed in air ambient at different temperatures ranging from 600 to 900 °C are reported. A detailed x-ray diffraction (XRD) analysis of ZnO NPs has been discussed. Morphological and optical properties of the NPs were investigated using Field Emission Scanning Electron Microscopy (FE-SEM), XRD, Diffuse Reflectance Spectroscopy (DRS), Photoluminescence (PL), Fourier Transform Infrared spectroscopy (FTIR) and Raman Spectroscopy techniques. The FE-SEM reveals that the average particle size of ZnO NPs increased from 62 to 77 nm due to agglomeration of particles or Ostwald ripening which usually happens at high temperature. Physical and microstructural properties such as crystallite size, strain, stress and dislocation density of ZnO NPs were obtained from XRD spectra studies and compared the estimated parameters by various models. It is observed that, the crystallite size increased after annealing and the strain present in NPs is due to defects. Kubelka-Munk function is used to obtain bandgap of NPs from DRS spectra. A slight decrease in the bandgap of ZnO NPs is due to the increase in particle size. PL spectra reveals that the emission around 402 nm near the UV region is attributed to the near band edge emission (NBE) and emission peaks in a visible region is due to the transition of electrons from traps in bandgap to the valence band.

Green synthesis of multilayer Graphene/ZnO nanocomposite for photocatalytic applications

Green synthesis of nanostructures is an alternative method to physical and conventional chemical methods, which is cost-effective and environmentally friendly. This study focuses on the synthesis of nanostructured multilayer graphene and zinc oxide nanocomposites from natural extracts and their utilization for photodegradation of brilliant black (BB) under solar light irradiation. The fabricated ZnO and graphene nanostructures were used to fabricate multilayer graphene/zinc oxide (MLG/ZnO) nanocomposites, with different ratios of MLG to ZnO (1:1, 1:2, 1:3) through ex-situ casting of the two materials. Various characterization techniques such as XRD, SEM, HR-TEM, EDS, BET, UV-Vis, and Raman were used to study the physico-chemical properties of the synthesized materials. The XRD profiles and Raman spectra exhibited predominant features of MLG and the characteristic wurtzite structure of ZnO in the nanocomposites. The UV-Vis absorbance spectra analysis revealed that combining MLG and ZnO reduced the energy band gap of ZnO nanoparticles, consequently improving the light absorption of the ZnO in the visible range. The overall percentage photodegradation of BB under sunlight by MLG, ZnO, MLG/ZnO_1, MLG/ZnO_2 and MLG/ZnO_3 were found to be 7%, 63%, 39%, 81% and 93%, respectively. Scavenger experiments confirmed that holes played a significant role in the photodegradation of BB followed by superoxide radicals and hydroxyl radicals being the least. The results of this study showed that MLG/ZnO nanocomposite can be adopted for beneficial application in the removal of pollutants from water using natural solar light irradiation.

Serrated hexagonal ZnO Nanoparticles: Synthesis and its characterization

ZnO nanoparticles with serrated hexagonal morphology were synthesised via hydrothermal route. XRD plot affirms the ZnO nanoparticles are formed. FTIR was performed to study the various vibrational modes of the synthesised ZnO nanoparticles. UV–VIS spectra was recorded to calculate the energy band gap of ZnO nanoparticles. Electrochemical studies were performed via Electrochemical Impedance Spectroscopy and Cyclic voltammetry techniques that shows the synthesised nanoparticles are appropriate for the application in Dye-sensitized solar cells.

Antifungal Activity of Iron-gold and Cobalt-gold co-doped ZnO Nanoparticles

Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O nanoparticles (NPs) have been synthesized via poly ethylene glycol assisted route. The average crystallite size of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were estimated from X-ray diffraction results and the values are 31.38 nm and 36.14 nm respectively. The UV absorption spectra confirmed the formation of the NPs with the characteristic peaks at 374 and 366 nm respectively. This spectral observation indicates that the band gap of ZnO nanoparticles decreases by doping iron/gold and cobalt/gold nanoparticles. The morphology and elemental composition of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were investigated. The antifungal activity of synthesized Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O NPs were found against four postharvest pathogenic fungi like Aspergillus niger, Aspergillus flavus, Rhizopus microsporus and Pencillium sp. The doping of iron and gold in ZnO nanoparticles enhances the zone of inhibition for the fungal pathogens compared to pure ZnO nanoparticles. Antifungal activity of Zn0.98Fe0.01Au0.01O and Zn0.98Co0.01Au0.01O nanoparticles were higher when compared with standard antibiotic mycostatin whose zone of inhibition is 18 mm against Aspergillus niger, Aspergillus flavus, Rhizopus microsporus and Pencillium sp.

Photocatalytic degradation of Rhodamine B (RhB) dye in waste water and enzymatic inhibition study using cauliflower shaped ZnO nanoparticles synthesized by a novel One-pot green synthesis method

The ZnO nanoparticles (NPs) are considered to be one of the inexpensive and very important bioactive materials widely used in drug delivery, as a photo-catalyst material, antibacterial, bioimaging, anticancer, anti-inflammation, wound healing, and diabetes treatment. Therefore, we have prepared ZnO NPs using Alchemilla vulgaris (Lady’s mantle) leaves and investigated their anti-enzymatic properties. Phases of the ZnO NPs were determined from X-Ray diffraction (XRD) spectra. The shape and size of the green synthesized NPs were investigated by scanning electron microscopy (SEM) and it confirms the cauliflower shape with an average size of 120 nm. But the beads inside the cauliflower shape are 20 nm in size. The prepared ZnO NPs show the cumulative median particle size of 550 nm. The thermogravimetric (TG) and differential thermal analysis (DTA) were performed at different heating rates to study the percentage of weight loss, and activation energy. The activation energy was calculated to be 4.98 kJ/moles using Kissinger method. We also studied the enzyme inhibition effect of ZnO NPs containing biologically active groups on important metabolic enzymes like butyrylcholinesterase(BChE), acetylcholinesterase (AChE) and α-glycosidase (α-Gly) enzymes. The bandgap of ZnO NPs was also studied by UV–Vis spectroscopy via Tauc's method and it was determined to be 3.27 eV. The photocatalytic property of the ZnO NPs was executed against rhodamine B (RhB) under the illumination of an AM 1.5 solar simulator.

Giant ferromagnetism in Li doped ZnO nanoparticles at room temperature

Wide band gap diluted magnetic semiconductor nanomaterials with improved magnetic and semiconducting properties have achieved great importance in spintronic technology since last decades. Synthesis of a good quality of magnetic semiconductor at room temperature is still a challenge for material scientist. Herein, we report synthesis of Li doped ZnO nanoparticles (NPs) using chemical precipitation method at room temperature with improved magnetic and semiconducting properties. Structure and phase of ZnO NPs have been confirmed by XRD pattern. Optical band gap of ZnO NPs have been tuned in the range of 3.10–3.34 eV using different percentage of Li doping. Maximum optical band gap in ZnO NPs was found 3.34 eV in ZnOLi-1 sample. It has been found that specific Li doping percentage can enhance magnetic property of ZnO NPs at room temperature. The coercivity of ZnO NPs has been tuned in the range of 317–1570 Oe by Li doping. Saturation magnetization and coercivity have been found maximum 0.055 emu/gm and 1570 Oe in ZnOLi-1 NPs respectively. In this work we have observed that ZnOLi-1 NPs show maximum optical band gap and coercivity. Thus we achieved wide band gap diluted magnetic semiconductor with enhance optical and ferromagnetic property at room temperature in terms of Li doped ZnO NPs.

Comparison of Ag and Zr substitution on the structural and optical behaviour of ZnO nanoparticles

Silver (Ag) and zirconium (Zr) doped ZnO (Ag-doped ZnO and Zr-doped ZnO) nanostructures were prepared utilizing the co-precipitation method, and the physical properties of all prepared samples were characterized utilizing X-ray diffractions, energy dispersive X-ray, and UV-Vis spectroscopy. Ag-doped ZnO and Zr-doped ZnO exhibit the hexagonal wurtzite structure, and the elemental analysis shows that the Ag and Zr concentrations on the samples were 3 atomic percent (at.%). The grain sizes of both samples were examined using Williamson-Hall plots with three different approaches using the uniform deformation model. The band gap energy of the prepared samples investigated using Kubelka-Munk analysis showed a red-shift to a lower energy compared to the band gap of ZnO nanoparticles, and the Zr-doped ZnO shows the lowest band gap energy. The red-shift of the band gap energy from Ag-doped ZnO and Zr-doped ZnO is probably due to the decreased grain size of both samples.

Characterization and Photoactivity of Cotton Loaded with ZnO NPs

In this work, ZnO NPs were prepared by a simple co-precipitation technique. Cotton fibers loaded with ZnO NPs were prepared also. X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectrophotometer have been used to characterize the prepared samples. The photocatalytic properties of the cotton loaded with ZnO (C-ZnO) and ZnO NPs, were studied under sunlight irradiation and lamp illumination as a function on time. The results showed that X-ray diffraction of ZnO NPs has a single-phase wurtzite structure with an average particle size of 29 nm. The morphology on the surface of ZnO NPs has a spherical shape. The optical band gap of ZnO nanoparticles was 3.37 eV. The photocatalytic confirms that C-ZnO exhibited higher photocatalytic activities than ZnO NPs.

Catalytic induced morpholical transformation of porous ZnO to ZnO nanorods by Sn(IV) and their effect on photocatalytic reduction of methylene blue and DFT calculations.

In this work, a new method for the preparation of ZnO hexagonal nanocrystals by using Sn(IV) as a catalyst was established, which resulted in tranformation of Porous to nanorod-like structures of ZnO. X-ray diffraction (XRD), Energy Dispersion X-ray analysis (EDX), and FT-IR measurements showed that all ZnO nanostructures were of hexagonal phase structure. Transmission electron microscopy (TEM) and scanning electron microscopic (FESEM) studies revealed that morphology of porous-like ZnO (100-200 nm) was converted into nanorod-like (length ~2 μm, diameter ~80 nm) structures upon addition of Sn(IV) as a catalyst. Spectroscopic studies demonstrated that the Zinc(II) compound yields high-quality porous ZnO which upon addition of Sn(IV) catalyst changes into crystalline hexagonal nanorods. The band gap of ZnO nanoparticles calculated employing UV spectrum was found to be 3.31 eV. Moreover, the photocatalytic degradation of methylene blue (MB) under UV light irradiation was performed, which confirmed higher photodegradation of hexagonal ZnO than porous ZnO nanostructures. Furthermore, DFT/TDDFT calculations of MB dye and the expected photodegradation product were also assessed, which were consistent with the kinetic studies. Additionally, zeta potential of the ZnO nanoparticles was measured in the dispersion medium of SDS surfactant which supported high stability of particles are in solution.

Investigation on the g-C3N4 encapsulated ZnO nanorods heterojunction coupled with GO for effective photocatalytic activity under visible light irradiation

The present work reports on a novel ternary nanocomposite of ZnO rods encapsulated by graphitic like carbon nitride (g-C3N4) and coupled with graphene oxide (GO) prepared by ultrasonication assisted hydrothermal method which provides enhanced photocatalytic activity and stability. Field emission scanning electron microscopy analysis showed that the surface morphology of ZnO, g-C3N4 (prepared by heating method) and the GO contains nanorods structures, sheet like structures and sheets with porous structures respectively. Formation of rod like structures of ZnO and thin sheet like structures of g-C3N4 were observed from transmission electron microscopy analysis. Transmission electron microscopy analysis of g-C3N4 (6 wt%)/ZnO nanocomposites showed that ZnO nanorods are encapsulated by the thin sheets of g-C3N4 and g-C3N4(6 wt%)/ZnO/GO (30 mg) ternary nanocomposites contains porous structures of GO. The optical band gap of ZnO nanoparticles was shifted from 3.08 eV to 2.85 eV for g-C3N4(6 wt%)/ZnO/GO(30 mg) ternary nanocomposites. Under visible light irradiation the ZnO nanorods and g-C3N4 (6 wt%)/ZnO showed photodegradation efficiency of ∼21% and 90% respectively for 120 min whereas g-C3N4 (6 wt%)/ZnO/GO(30 mg) showed about 99% photodegradation efficiency in a time period of 14 min. The recycle process carried out for g-C3N4(6 wt%)/ZnO/GO(30 mg) composites up to five cycles showed 91.5% of photodegradation in the fifth cycle for a time period of 14 min. Total Organic Carbon (TOC) analysis shows removal of carbon content 83% in 28 min. The Gas Chromatography-Mass Spectroscopy analysis shows the intermediate products of 1,2 benzenedicarboxylic acid and phthalic acid during the RhB dye photodegradation process. The radical trapping experiment reveals that the photo-induced holes (h+) are one of the main reactive species involved in the degradation of the RhB.

E. tirucalli plant latex mediated green combustion synthesis of ZnO nanoparticles: Structure, photoluminescence and photo-catalytic activities

Abstract ZnO nanoparticles were synthesized using esterases contained E. tirucalli plant latex as a fuel. The structural, morphological and spectroscopic studies of the as-synthesized ZnO nanoparticles were analyzed using powder X-ray Diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), UV–Visible absorption and photoluminescence (PL) spectroscopy. The structural parameters were refined by the Rietveld refinement method using PXRD data and confirmed that the prepared compound is pure hexagonal wurtzite structure with space group P63mc (No. 186). The average crystallite size was estimated by Scherrer's and W H plots and found to be in the range 17–23 and 20–26 nm respectively. The band gap of ZnO nanoparticles was estimated using Wood–Tauc relation and found to be in the range of 3.10–3.25 eV. PL studies revealed that a broad yellow emission peak appeared at 570 nm upon 380 nm excitation peaks. Photocatalytic degradation of Methylene blue (MB) dye was studied under UV irradiations. 5.5 ml of 5% esterases contained E. tirucalli plant latex used for the synthesis of ZnO shows 96% of degradation (5 × 10−5 M MB at pH 12). The prepared ZnO nanoparticles find application in optical and photo-catalytic degradations.

Structural and optical properties of pure and copper doped zinc oxide nanoparticles

Abstract Pure and copper-doped zinc oxide nanoparticles (NPs) have been synthesized via chemical co-precipitation method where hydrazine is used as reducing agent and aqueous extract of Euphorbia milii plant as capping agent. Main objectives of the reported work are to investigate the effect of copper doping on crystal structure of ZnO nanoparticles; to study the effect of copper doping on optical band gap of ZnO nanoparticles and photoluminescence (PL) study of pure and copper-doped ZnO nanoparticles. To achieve the aforementioned objectives, XRD and SEM tests were performed for the identification and confirmation of crystal structure and morphology of the prepared samples. From XRD data the average grain size for pure ZnO was observed to be 24.62 nm which was first decreased to 18.95 nm for 5 wt% Cu-doped sample and then it was found to increase up to 37.80 nm as the Cu doping was increased to 7 wt%. Optical band gap of pure and Cu-doped ZnO nanoparticles was calculated from diffuse reflectance spectroscopy (DRS) spectra and was found to decrease from 3.13 eV to 2.94 eV as the amount of Cu increases up to 7 wt%. In photoluminescence study, PL technique was used and enhanced visible spectrum was observed. For further characterization FT-IR and EDX tests were also carried out.

A simple, one-pot, low temperature and pressure route for the synthesis of RGO/ZnO nanocomposite and investigating its photocatalytic activity

A simple, low temperature and pressure, catalyst-free reflux method was reported for the synthesis of reduced graphene oxide (RGO)/ZnO nanocomposite (NC). Formation of ZnO Nanoparticles (NPs) on the surface of Graphene oxide (GO) sheets was led to reduction of GO and fabricating RGO/ZnO NC. The photoluminescence (PL) analysis showed two broad and intense peaks in PL spectra of ZnO and RGO/ZnO samples which are assigned to the electronic transition from zinc interstitial levels (IZn) to Zinc vacancy levels (VZn) and from conduction band to the oxygen vacancy levels (VO), respectively. Broad and intense peaks in PL spectra of ZnO NPs synthesized by our method makes many photogenerated e-h pairs in trap levels due to large number of trap levels. Hybridizing ZnO NPs with GO considerably improve photocatalytic activity of samples due to transferring these electrons to GO sheets and preventing e-h recombination. XRD and FT-IR analyses confirmed that the as-obtained NC is in the form of RGO/ZnO instead of GO/ZnO. Synthesizing NCs by this route largely enhanced photocatalytic activity of NCs, because this synthesis route generates many trap state energy levels such as VO, VZn and IZn subband energy levels in the band gap of ZnO NPs. These numerous trap states -compared to that of RGO/ZnO NCs obtained by other methods- play an important role in the photocatalytic performance of synthesized NCs by enhancing the visible light absorption due to the resulting ZnO band gap narrowing.

Optical and Electrical Characteristics of n-ZnSmO/p-Si Heterojunction Diodes

Sm doped ZnO nanoparticles were synthesized by a simple wet chemical route. The obtained nanomaterials were studied for their structural, morphological and optical properties. The average crystalline size of the ZnO nanomaterials were enhanced from 50nm to 70nm for the Sm doping concentration. The morphological properties were elucidated with the aid of SEM images, in which the ZnO nanoparticle size of about 60–100nm were enhanced to micron size for Sm dopants. The optical absorbance spectrum indicated the enhanced photons absorption of the nanoparticles in both UV and visible region with red shift in the characteristic excitonic absorption band edge. The band gap of ZnO nanoparticles (3.31eV) had narrowed to 2.84eV for the doping of Sm3+ ions in the lattices of Zn-O, since the charge transformation between the 4f electronic level of Sm3+ ions and conduction band of ZnO. The obtained pn junction structures (n-ZnSmO/p-Si) have also showed the enhanced electrical conductivity for ZnSmO specimens, due to the contribution 4f rich electrons of Sm3+ ions. Further the various device parameters were calculated and their interpretations with the material properties were also discussed in detail.

Facile synthesis of ZnO nanoparticles for the photocatalytic degradation of methylene blue

ZnO nanoparticle photocatalysts with a grain size range of 20–100 nm were prepared via a simple sol–gel method and characterized by X-ray powder diffractometry, scanning electron microscopy, gas adsorption, photoluminescence, UV-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. As-synthesized ZnO samples were highly crystallized with hexagonal wurtzite structure, and the grain size was between 20 and 100 nm and increased with the annealing temperature. It was found that the band gap of ZnO nanoparticles narrowed to visible light region, i.e., ~ 2.69 eV, which increased with the calcining temperature. The sample with a high concentration of oxygen vacancy exhibits excellent photocatalytic activity toward methylene blue (MB) degradation under solar light irradiation, at which the highest photodegradation with a react constant k value of 0.12 min−1 was achieved. In addition, MB solution was decomposed within 30 min, and after 9 cycles, the catalyst maintains more than 95% photodegradation. Moreover, the intermediate process experiment demonstrated that •O2 − and h+ are the main active intermediate species during the photocatalytic processes.

Magnetic Properties of Chromium-Doped ZnO

Cr-doped ZnO was synthesized by using a low-temperature co-precipitation technique producing Zn1−x Cr x O nanoparticles. The effects of the Cr concentration (0, 0.03, 0.05, and 0.07) on the structural, optical, and magnetic properties of ZnO were investigated by first-principles calculations, X-ray diffraction, scanning electron microscope, the optical spectroscopy (UV–Vis), and magnetization measurements. The results show that Cr atoms are substituted for Zn ions successfully. The Cr ions exhibited + 3 valence state other than + 2 valence state, which is supported by the fact of high-spin configurations of Cr ions in the first-principle calculations. X-ray diffraction confirms that the samples have a single-phase wurtzite structure with the main crystal size decreases with increasing dopant concentration. This decrease occurs due to the small ionic radius of Cr ions in compared to Zn ions. The morphology on the surface shows further that the samples had a spherical shape with an average particle size of 75 nm. The optical band gap of ZnO nanoparticles varies with Cr doping, which is attributed to the s-d and p interaction. Introducing Cr into ZnO induces a strong magnetic moment. The estimated that the effective magnetic moment is very close to the magnetic moment obtained from total energy calculations.

Size and Shape Tailoring of ZnO Nanoparticles

ZnO nanoparticles were successfully synthesized via the co-precipitation method using zinc nitrate and sodium hydroxide as raw materials. Size and shape of ZnO nanoparticles were well controlled by varying the ratio of sodium hydroxide solutions (0.5-0.9 mole) and the synthesized temperatures (65, 75 and 85 °C). ZnO nanoparticles exhibited a high degree crystallinity with wurtzite hexagonal structure for all conditions carried out using SEM, XRD, EDS and Raman. It was clearly observed that both sodium hydroxide solution and synthesized temperatures strongly affected on the size and shape of ZnO nanoparticles. The smallest ZnO nanoparticle was observed to be 47 nm with 0.7 mole of sodium hydroxide solution at 75 °C. Uniformed ZnO nanoparticles were obtained at synthesized temperatures above 65 °C. Optical properties of ZnO nanoparticles were also studied and carried out as absorbance spectra. In addition, optical energy band gap of ZnO nanoparticles was in the range of 3.24-3.35 eV.

A Simple Up-Scalable Thermal Treatment Method for Synthesis of ZnO Nanoparticles

A simple thermal treatment method, utilizing only zinc nitrate, polyvinyl pyrrolidone (PVP), and deionized water, was used to synthesize ZnO nanoparticles, and their characteristics were investigated by various techniques. The TGA measurement demonstrated that the bulk of the capping agent PVP can be removed at temperatures higher than 500 °C and is consistent with the absence of the majority of PVP absorption peaks in the FT-IR spectra. The formation of almost pure ZnO nanoparticles was established by the presence of single absorption peak in the FT-IR spectra due to being only Zn–O bonds at calcination temperatures of 500 °C and above. The TEM images revealed that the nanoparticles have a spherical shape and the particle size increased from 60.1–83.1 nm with an increase in calcination temperatures from 500–600 °C. The XRD diffraction patterns indicated that the particles are of a wurzite lattice structure. The optical properties were determined by UV-Vis spectrophotometer, and it was found that the band gap of ZnO nanoparticles decreased from 3.249–3.239 eV with an increase in calcination temperature from 500–600 °C.