Characterization and X-ray peak broadening analysis in PZT nanoparticles prepared by modified sol–gel method

Lead zirconate titanate nanoparticles (PZT-NPs) were synthesized by a modified sol–gel method and were calcinated at temperatures of 600, 650 and 700 °C. Fourier transform infrared (FTIR), powder X-ray diffraction (XRD) and thermal analysis (TGA/DTA), indicate that single-phase perovskite PZT-NPs are obtained after heat treatment at a temperature of 650 °C. The TEM results obtained from the PZT-NPs confirm that the morphology of the PZT nanoparticles is spherical, with an average diameter size of 17 nm. We also investigated the crystallite development in the nanostructured PZT by X-ray peak broadening analysis. The individual contribution of many small crystallite sizes and lattice strains to the peak broadening in the PZT nanoparticles prepared at different temperatures were studied using Williamson–Hall (W–H) analysis in the range of 2θ = 15–80°.     

Vitis labruska skin extract assisted green synthesis of ZnO super structures for multifunctional applications

The formation of unique morphologies of zinc oxide (ZnO) super structured frameworks were reported via a simple and eco-friendly route employing Vitis labruska fruit Black Grape Skin (BGS) extract as a fuel. XRD, FTIR, UV–vis, PL, SEM and TEM studies are performed to analyse the formation and characterization of ZnO. XRD confirmed the crystalline nature of the material with hexagonal Wurtzite structure having average crystallite size of ~50 nm. FTIR spectrum shows a band at 532 cm⁻¹ due to the vibrational mode of Zn-O bending. The band gap of the ZnO was found to be 3.26 eV. SEM images confirm the formation of different morphologies like Mysore pak (a popular Indian dessert), canine teeth, hollow pyramids and gems were obtained by varying the weight of BGS. These superstructures were obtained due to the interaction of Zn²⁺ with BGS extract. TEM images clearly shows lattice spacing of 0.29 nm corresponding to the (002) plane of ZnO. Photoluminescence (PL) spectrum shows strong yellow light emission upon excitation at 320 nm due to the Zn-O defects. Synthesized ZnO nanoparticles (Nps) exhibited good photocatalytic activity for the degradation of Methylene blue (MB) dye. The photocatalytic activity was due to the production of OH˙ radicals during photo irradiation on ZnO Nps. ZnO Nps also exhibited superior antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria. Further, ZnO Nps were also used in the development of novel electrochemical sensing platform towards the electrochemical detection of hydrazine as a model system at very low concentrations having a detection limit of 0.3 µM.     

Influence of the pH on the ZnO nanoparticle growth in supercritical water: Experimental and simulation approaches

In order to improve the knowledge on the nucleation and the growth mechanisms of metal oxides nanoparticles produced in supercritical water domain, ZnO was used as a “model” material. A continuous process of hydrothermal synthesis was employed to synthesize ZnO nanopowders (T = 410 °C and P = 305 bar) from Zn(NO₃)₂ and KOH solutions with different values of [KOH]/[Zn(II)] ratio from 0 to 8 in order to investigate the pH effect on the growth of ZnO nanocrystallite in terms of size and morphology. The samples were characterized by X-Ray Diffraction and Transmission Electronic Microscopy. ZnO crystal was considered as a cylindrical crystallite with a diameter D and height H. Especially, the aspect ratio D/H was already used to observe the change of ZnO nanoparticle shape correlated with TEM observations and results from a CFD simulation model. A schematic synoptic of the ZnO growth in supercritical domain is also presented.     

Structural and optical characterization of Zn0.95−xMg0.05AlxO nanoparticles

The structural and optical properties of ZnO nanoparticles doped simultaneously with Mg and Al were investigated. XRD results revealed the hexagonal wurtzite crystalline structure of ZnO. The FE-SEM study confirmed the formation of nano-sized homogeneous grains whose sizes decreased monotonously with increasing doping concentrations of Mg and Al. The absorption spectra showed that band gap increased from 3.20 to 3.31 eV with Mg doping. As the Al concentration changed from x=0.01 to x=0.06 mol% at constant Mg concentration the band gap observed to be decreased. Particle sizes estimated from effective mass approximation using absorption data and these values are in good agreement with the crystallite sizes calculated from XRD data. Raman spectra of ZnO showed a characteristic peak at 436 cm⁻¹ correspond to a non-polar optical phonon E₂ (high). With increase of the Al doping concentrations, E₂ (high) phonon frequency shifted to 439 cm⁻¹ from to 436 cm⁻¹. The origin of E₂ (high) peak shift in ZnO nanoparticles is attributed to optical phonon confinement effects or the presence of intrinsic defects on the nanoparticles. PL spectra indicated that with increase of Al co-doping along with Mg into ZnO, intensity of the peak positioned at 395 nm was initially increased at x=0 and then decreased with increase of the Al concentrations from x=0.01 to x=0.06 mol%.     

Garcinia xanthochymus mediated green synthesis of ZnO nanoparticles: Photoluminescence,photocatalytic and antioxidant activity studies

Green synthesis of multifunctional zinc oxide nanoparticles (ZnO Nps) was achieved employing water extract of Garcinia xanthochymus by solution combustion synthesis. The structure and morphology were determined by XRD, UV–visible and scanning electron microscopy studies. The ZnO Nps were evaluated for photoluminescence (PL), photocatalytic and antioxidant properties. The water extract was found to comprise significantly high amounts of polyphenols and flavonoids. Powder XRD studies indicate the formation of pure wurtzite structure with absorption maximum of 370 nm corresponding to band gap energy of 3.33 eV. SEM studies reveal the formation of spongy cave like structures. The PL spectra exhibited 4 emission edges at 397, 436, 556 and 651 nm upon excitation at 325 nm because of oxygen deficiencies and zinc interstitials. Nps exhibit remarkable photodegradation of methylene blue (MB) in presence of UV and sun light. They exhibit antioxidant activity by inhibiting the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Therefore, the study reveals an efficient, ecofriendly and simple method for the green synthesis of multifunctional ZnO Nps.     

Structural and electrical properties of ZnO:Ag core-shell nanoparticles synthesized by a polymer precursor method

Monodispersed core-shell type ZnO:Ag nanoparticles were synthesized by a polymer precursor method and their structural and electrical properties were reported in detail. The synthesis technique involves a sol-gel type chemical reaction between aqueous solutions of poly-vinyl alcohol (PVA), sucrose and Zn²⁺ salt. The Zn²⁺-PVA-sucrose polymer precursor powders so obtained after the reaction was further explored for the synthesis of ZnO:Ag nanoparticles. The key part of the work lies in the use of polymer coated ZnO nanoparticles as templates to obtain the ZnO core-Ag shell type nanostructures. Structural and spectroscopic analyses of the derived samples were performed with X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the ZnO:Ag nanoparticles consist of distinct peaks corresponding to the hexagonal wurtzite type (space group P63mc) crystal structure of ZnO along with the typical peaks of face centered cubic crystal structure of metallic silver. EDS and XPS analyses confirmed the chemical composition and surface structure of the core-shell nanoparticles. Microstructural analysis revealed the monodispersed platelet shaped ZnO nanoparticles with a thin layer of Ag coating on the surface. UV–visible diffuse reflectance studies revealed the effects of Ag coating on the optical properties of the samples. Detail analysis of the dielectric properties of the samples were performed as a function of frequency (1 Hz to 10 MHz) and temperature (300–528 K) to investigate the electrical conduction mechanism in the samples.     

Heteroepitaxial ZnO/sapphire (0 0 0 1) structure prepared by sol–gel process

ZnO thin films were grown on sapphire (0 0 0 1) substrates by sol–gel process and their structural and optical properties were characterized in detail. High-quality texture was obtained by using precursor solution of zinc acetate and ethanolamine in 2-methoxyethanol, pyrolyzed at 300 °C, then heated at 500 °C, and finally annealed at 750 °C. Highly c-axis oriented ZnO films were confirmed by X-ray θ–2θ scan. A relatively high transmittance in the visible spectra range and clear absorption edge of the film were observed. Epitaxial relationship between ZnO and sapphire and photoluminescence of the film were examined by using a X-ray pole-figure analysis and He–Cd laser. Near-band-edge emission with a deep-level emission was observed.     

Hydrothermal processing and in situ surface modification of metal oxide nanomaterials

In situ surface modification of TiO₂ and ZnO metal oxide particles has been carried out under hydrothermal conditions within a wide range of temperature and pressure (T = 150–400 °C; P = up to 20 MPa). The influence of the surfactant and selective doping with active metal ions on the crystal size, morphology, and photocatalytic activity of TiO₂ and ZnO particles has been carried out. A systematic characterization of the product has been carried out using powder XRD, FTIR, TGA, SEM/TEM, and UV–vis spectroscopy. Similarly the photocatalytic activity in these metal oxides varies with the size, shape and dopant metals.     

Green synthesis of Ag/ZnO nanohybrid using sodium alginate gelation method

Mesoporous Ag/ZnO nanohybrid material has been successfully synthesized using simple and green route via sodium alginate media. The as-synthetized nanomaterial was structurally characterized using various techniques such as X-ray powder diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and N₂ adsorption-desorption measurements (BET). The Ag/ZnO nanoparticles were quasi-spherical, crystalline with a size ranging from 40 to 50 nm. In addition, characterization results confirmed that calcined Ag/ZnO nanomaterial sample was stable and mainly consisting of both hexagonal ZnO and cubic silver nanoparticles.     

In situ UV–vis and EXAFS studies of ZnO quantum-sized nanocrystals and Zn-HDS formations from sol–gel route

We have pointed out that, zinc-based particles obtained from zinc acetate sol–gel route is a mixture of quantum-sized ZnO nanoparticles, zinc acetate, and zinc hydroxide double salt (Zn-HDS). Aiming the knowledge of the mechanisms involved in the formation of ZnO and Zn-HDS phases, the thermohydrolysis of ethanolic zinc acetate solutions induced by lithium hydroxide ([LiOH]/[Zn²⁺] = 0.1) or water ([H₂O]/[Zn²⁺] = 0.05) addition was investigated at different isothermal temperatures (40, 50, 60 and 70 °C) by in situ measurements of turbidity, UV–vis absorption spectra and extended X-ray absorption fine structures (EXAFS). Only the growth of ZnO nanoparticles was observed in sol prepared with LiOH, while a two-step process was observed in that prepared with water addition, leading the fast growth of Zn-HDS and the formation of ZnO nanoparticles at advanced stage. A mechanism of dissolution/reprecipitation governed by the water/ethanol proportion is proposed to account for relative amount of ZnO.     

Macroporous gibbsite foams prepared from particle-stabilized emulsions using corn starch and agar as binders

Corn starch and agar were used independently as a water-uptake binder in combination with anionic sodium dodecul sulfate (SDS) which modifies the hydrophobicity of cationic gibbsite platelets for preparation of air-in-water (a/w) gibbsite foams via a simple mechanical frothing. Contact-angle (θ) measurements revealed that the apparent θ decreased from partially hydrophobic (θ ～ 62°) to more hydrophilic (θ ～ 47°) when the corn starch was first added, leading to foams with a reduced stability. As the concentration of corn starch reached above ～8 vol.%, θ returned back to greater than 60°, rendering then a stable foam. On the other hand, θ was found to decrease from 57° to 50° when the agar concentration increased above a mere 0.16 vol.%. This gave rise to a pronounced drainage and coalescence of the foam, and a further increase of the agar concentration only led to a quick disappearance of the a/w bubbles. By tailoring the binder concentration, macroporous gibbsite foams were produced from the air- or freeze-dried wet foams, which typically consisted of packing void cells over a cell-size distribution of 50–400 μm, a porosity ranging from 77% to 86%, and a three-point (green) rupture strength of up to 240 kPa.     

Antibacterial and photocatalytic behaviour of green synthesis of Zn0.95Ag0.05O nanoparticles using herbal medicine extract

The present work aimed to synthesize Zn_0.95Ag_0.05O (ZnAgO) nanoparticles using rosemary leaf extracts as a green chemistry method. The characterization of Ag-doped ZnO nanoparticles was performed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and ultraviolet–visible spectrophotometry (UV–visible). The XRD, FTIR, and UV–visible spectra confirmed the formation of the presence of hexagonal ZnAgO nanoparticles. FESEM micrograph shows that the nanoparticles have been distributed homogeneously and uniformly. The morphology of ZnAgO nanoparticles is quasi-spherical configuration. Also, the mean particle size is in the range of 22–40 nm. The photocatalytic degradation of methylene blue in the presence of Ag-doped ZnO nanoparticles is nearly 98.5% after exposing 100 min. The ultraviolet lamp was used as the light source for photocatalyst degradation. The disc diffusion method was chosen to study the antibacterial activity of as-synthesized ZnAgO nanoparticles. Antibacterial activity of Zn_0.95Ag_0.05O nanoparticles against Staphylococcus aureus and Escherichia coli revealed that the as-synthesized ZnAgO nanoparticles were efficient in inhibition of bacterial growth.     

Effect of Mg doping on photoluminescence of ZnO/MCM-41 nanocomposite

In this paper, photoluminescence (PL) behavior of Mg_xZn_1?xO/MCM-41 nanocomposite (where x = 0.05, 0.15, 0.25 and 0.30) is reported. Samples were characterized with small angle X-ray diffraction (SAXRD), wide angle XRD, BET (Brunauer–Emmet–Teller) surface area and pore size analyzer, field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HR-TEM) and PL spectrometer. The structure of MCM-41 was confirmed from both SAXRD and BET results. A broad PL band positioned at around 393 nm has been exhibited by ZnO/MCM-41 nanocomposite. With Mg doping, intensity of this PL band decreased for x = 0.05 and 0.15 and above this there was gradual enhancement in intensity. It was found that the intensity of the PL band, strongly depends on the particle size of ZnO. The increase in particle size along with MgO phase separation for x = 0.30 was proved by HR-TEM analysis. Interestingly, the differences in particle sizes at different concentrations of Mg did not account for shift in the PL band. A twofold enhancement in the intensity of PL band when x = 0.30 compared to bare ZnO/MCM-41 nanocomposite was observed. It is attributed for the increase in particle size which preserves the energy saved by passivation of ZnO nanoparticles and the other one is formation of heterojunction structures between ZnO and MgO. It was also evident from these results that there is increase in oxygen vacancies of ZnO crystallites with increase in particle size.     

Structural,optical and photocatalytic properties of hafnium doped zinc oxide nanophotocatalyst

A series of novel hafnium (Hf) doped ZnO nanophotocatalyst were synthesized using a simple sol–gel method with a doping content of up to 6 mol%. The structure, morphology and optical characteristics of the photocatalysts were characterized by XRD, SEM, TEM, FTIR, XPS, DRS and PL spectroscopy. The successful synthesis and chemical composition of pure and doped ZnO photocatalysts were confirmed by XRD and XPS. DRS confirmed that the spectral responses of the photocatalysts were shifted towards the visible light region and showed a reduction in band gap energy from 3.26 to 3.17 eV. Fluorescence emission spectra indicated that doped ZnO samples possess better charge separation capability than pure ZnO. The photocatalytic activity of Hf-doped ZnO was evaluated by the methylene blue (MB) degradation in aqueous solution under sunlight irradiation. Parameters such as irradiation time and doping content were found effective on the photoactivity of pure ZnO and Hf-doped ZnO. The photocatalysis experiments demonstrated that 2 mol% Hf-ZnO exhibited higher photocatalytic activity as compared to ZnO, ZnO commercial and other hafnium doped ZnO photocatalysts and also revealed that MB was effectively degraded by more than 85% within 120 min. The enhanced photoactivity might be attributed to effective charge separation and enhanced visible light absorption. It was concluded that the presence of hafnium within ZnO lattice could enhance the photocatalytic oxidation over pure ZnO.     

Synthesis and structural properties of GaN particles from GaO2H powders

Gallium nitride(GaN) powders have been synthesized by nitriding gallium oxyhydroxide (GaO₂H) powders in the flow of NH₃ gas at a nitridation temperature of 950 °C for 35 min. X-ray powder diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra reveal that simple heat treatment of GaO₂H in the flow of NH₃ leads to the formation of hexagonl GaN with lattice constants a = 3.191 Å, and c = 5.192 Å at 950 °C through intermediate conversion of β-Ga₂O₃. X-ray photo-electron spectroscopy (XPS) confirms the formation of bonding between Ga and N, and yields that the surface stoichiometry of Ga : N approximates 1 : 1. Transmission electron microscopy (TEM) image indicates that GaN particle is a single crystal, and its morphology is ruleless.     

Hydrothermal synthesis of dumbbell-shaped ZnO microstructures

Dumbbell-shaped ZnO microstructures have been successfully synthesized by a facile hydrothermal method using only Zn(NO₃)₂·6H₂O and NH₃·H₂O as raw materials at 150 °C for 10 h. The results from X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) show that the prepared ZnO samples exhibit dumbbell-shaped morphology and hexagonal wurtzite structure. The length of ZnO dumbbells is about 5–20 μm, the diameters of the two ends and the middle part are about 1–5 μm and 0.5–3 μm, respectively. The dumbbell-shaped ZnO microstructures may be formed by self-assembly of ZnO nanorods with 1–5 μm in length and 100–200 nm in diameter. The photoluminescence (PL) spectrum of dumbbell-shaped ZnO microstructures at room temperature shows three emission peaks at about 362, 384 and 485 nm.     

Synchrotron X-ray diffraction study on a single nanowire of PX-phase lead titanate

Synchrotron X-ray diffraction (XRD) measurements of Pb–Ti–O fine acicular crystals (nanowires) of the so-called PX-phase have been performed. The θ–2θ patterns of the nanowires dispersed on substrates with two different geometries indicated that the PX-phase Pb–Ti–O nanowire has [1 1 0] along its short axis and [0 0 1] along its longitudinal axis. Using a focused micro-X-ray beam, we first demonstrated the XRD analysis of a single nanowire of PX-phase Pb–Ti–O. Bragg reflections from the same single nanowire with scattering vectors at two different angles suggested its tetragonal unit cell having the rather large a-axis lattice constant.     

Enhanced nonlinear optical and optical limiting properties of graphene/ZnO hybrid organic glasses

Graphene/ZnO (G/ZnO) composites were synthesized for the first time by a wet chemical method. X-ray diffraction and transmission electron microscopy analyses demonstrated that ZnO nanoparticles with an average diameter of about 5 nm uniformly covered the graphene surfaces. G/ZnO composites were dispersed in methyl methacrylate (MMA), polymerized at 75 °C for 30–35 min, and finally, dried at 45 °C for 10 h, to afford G/ZnO/PMMA organic glasses. UV–visible spectra showed that the band gaps of the G/ZnO/PMMA organic glasses were about 3.54 eV, larger than that of bulk ZnO because of the small size effect of ZnO nanoparticles. The nonlinear optical (NLO) and optical limiting (OL) properties of the G/ZnO/PMMA organic glasses were investigated by a modified Z-scan technique. The total NLO coefficient α₂ of the G/ZnO/PMMA organic glass was as high as 1530 cm/GW, which was approximately 5.6 and 7.8 times larger than those of G/PMMA and ZnO/PMMA organic glasses. The enhanced NLO properties of the G/ZnO/PMMA organic glasses led to excellent OL performance, which was attributed to the positive synergistic effects between graphene and ZnO.     

Kinetics of magnetite nanoparticles formation in a one step low temperature hydrothermal process

In the present study, a one step hydrothermal process was employed to synthesize magnetite nanoparticles using oleic acid as surfactant agent at 140 °C. Effects of reaction time and alkalinity were studied on particles size and morphology. By changing these parameters, some monodisperse spherical nanoparticles with mean particle size between 2.71 and 13.88 nm were synthesized and characterized via TEM, XRD, VSM, TGA and FT-IR techniques. Assuming the Avrami behavior of particles formation, a kinetics equation was proposed for the transformation rate at 140 °C. Using some simplifying assumptions, nucleation and growth rates were calculated for the hydrothermal formation of magnetite nanoparticles at 140 °C.     

Pulsed-laser deposited amorphous-like PZT thin-films: Microstructure and optical properties

Amorphous lead–zirconate–titanate (Pb_0.97Nd_0.02(Zr_0.55Ti_0.45)O₃, PNZT) thin-films were grown on single-crystal MgO(1 0 0) substrates at room temperature by pulsed laser deposition (PLD). Part of PNZT films was left as-deposited amorphous and others were post-annealed at temperatures from 100 to 400 °C. X-ray diffraction (XRD) and scanning probe microscopy (SPM) were used to characterize the microstructure. Optical properties were analyzed using spectrophotometry at UV–vis–NIR and prism-coupler method at 633 nm wavelengths. Initially, films were amorphous with a broad XRD peak around 2θ ≈ 29.7°. As the post-annealing temperature increased above 250 °C, the amorphous peak started to shift towards lower 2θ-angles and got narrower indicating of decreasing interatomic spacing and possible glass transformation. At the same time, the transmittance at all wavelengths increased remarkably, although no crystal structure was detected by XRD. Also, sharp optical TE₀ modes with full-width half-maximum (FWHM) values of Δβ ≈ 0.00067 could be coupled into these films.