Effect of rapid cooling time on optical absorption and band gap energy of TiO2 nanoparticles

In this paper, TiO₂ nanoparticles were synthesized via sol–gel method by using of TiCl₄ as a precursor in the ethanol solution. The structure and the morphology of TiO₂ nanoparticles were characterized by X-ray diffraction and scanning electron microscopy. We have studied the optical properties by using of UV–Vis spectroscopy. The results show that the calcination temperature is an important factor in size of nanoparticles, the morphology of powders and the band gap energy of TiO₂ nanoparticles. Also, rapid cooling time of samples is an important factor to decrease band gap energies, considerably. The calculated band gap of the TiO₂ nanoparticles is in range of 2.39–3.50 eV.     

Synthesis and study of the structure,magnetic, optical and methane gas sensing properties of cobalt doped zinc oxide microstructures

Undoped and Cobalt (Co) doped zinc oxide (ZnO & CZx) nanoparticles were synthesized by Solvothermal method. The samples were studied by X-Ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), UV–Vis spectroscopy and Scanning and Transmission Electron Microscopy (SEM & TEM). Moreover the gas sensing properties of the nanoparticles for methane gas took place. Purity of the samples and Co concentration was investigated by EDS and ICP spectroscopy respectively. XRD results described the hexagonal wurtzite structure for all the samples in which crystallinity and the crystallites size decreased with increase of Co doping level. Using UV–Vis spectroscopy the band gap energy was evaluated and redshift of band gap energy was observed by increasing of Co concentration. SEM images demonstrated that nanoparticles were agglomerated with increase of Co doping level. TEM images revealed the nanoparticles size in the range 11–44 nm. Methane sensing properties was enhanced after Co doping of the ZnO nanoparticles for Co concentration up to 4%.     

Investigations on structural, optical and electrochemical properties of blue luminescence SnO2 nanoparticles

A simple solution approach has been developed to synthesis SnO₂ nanoparticles using polyethylene glycol as stabilizer. X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), UV–Vis absorption spectroscopy, photoluminescence (PL) emission spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the nanoparticles. XRD, HR-TEM and AFM indicate that the SnO₂ nanoparticles correspond to tetragonal crystal structure with size ranges below Bohr’s exciton radius. UV–Vis absorption spectrum showed band gap exhibiting a 1.3 eV shift from that of bulk SnO₂ structures. The blue emission owing to transition of an electron from conduction band to deeply trapped hole in SnO₂ nanoparticles was analyzed using PL spectroscopy. The charge transfer capability had been investigated using CV and EIS in different electrolytes. A detailed exploration on confinement effect that occurred in SnO₂ nanoparticles, mechanism behind visible emission and electron transfer mechanism in different electrolyte was discussed.     

Bi2S3 nanoparticles by facile chemical synthesis: Role of pH on growth and physical properties

In this work, we have synthesized Bi₂S₃ nanoparticles (NPs) by facile chemical precipitation method. The reaction conditions were optimized in order to obtain high yield in a short time. The nanoparticles were synthesized at different pH values ranging from 0.5 to 1.6 and the effect of pH on the growth was investigated. XRD, Raman spectroscopy, SEM, HRTEM, XPS - UV–Vis spectroscopy, and Seebeck were used for the characterization of the nanoparticles. The XRD patterns and Raman analysis revealed the formation of orthorhombic Bismuthunite without any impurity phases. The crystal size of the samples was found to decrease with the increase in pH. SEM images showed that NPs synthesized at pH lower than 1.2 are nanorods and tend to agglomerate as microspheres. At pH 1.6, morphology changes from nano-rods to nano-flakes, and from micro-spheres to micro stems decorated with nano-branches. A possible growth mechanism for the observed pH dependent morphological change is discussed. The estimated band gap energy is in the range of 1.35–1.42?eV. The thermoelectric measurements showed n-type conductivity and high Seebeck coefficients for Bi₂S₃ NPs.     

Opto-electronic and antibacterial activity investigations of mono-dispersed nanostructure copper oxide prepared by a novel method: reduction of reactive oxygen species (ROS)

A novel approach for synthesis of copper oxide nanoparticles is reported by separation of nucleation and growth. The nano-material was characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy, transmission electron microscopy, atomic force microscopy, and Brunauer–Emmett–Teller analyses. Optical analysis of mono-dispersed nanostructure copper oxide by UV–Vis diffused reflectance spectroscopy showed the band gap value of 1.47 eV with a blue-shift in the optical band gap due to quantum confinement effect. The dynamic light scattering and zeta potential results showed fairly narrow size distribution and colloidal stability. The results showed that nano-particles were mono-dispersed spheres of 8 nm with no aggregation. Cell viability of treated murine fibroblast cell line (L-929) treated by different concentrations of nanoparticles showed significant viability up to 96% at concentrations 15 and 30 μg ml^?1. The nanoparticles exhibited outstanding and stable antibacterial activity against Staphylococcus aureus ATCC 6538 at 30 µg ml^?1. The viability and reactive oxygen species (ROS) generation in the L-929 cell line indicated that the nanoparticles were not toxic at the concentrations which were effective on bacteria. ROS analysis using DCFH-DA probe on L-929 were exposed to 7.5–60 μg ml^?1 of copper oxide nanoparticles in 6 h revealed ROS generation was decreased dramatically compare to the untreated cells and positive control.     

Synthesis and characterization of solar photoactive TiO2 nanoparticles with enhanced structural and optical properties

The structural, morphological, and optical properties of the sol–gel derived TiO₂ nanoparticles at different pH and calcination temperature were investigated in the present study. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), UV–Visible(Vis) spectroscopy, energy dispersive studies (EDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoluminescence (PL) spectroscopy, BET surface area analysis, and Barrett-Joyner-Halenda (BJH) pore size distribution and pore volume analysis were used to characterize the prepared TiO₂ photocatalyst. The range of crystallite size and band gap of the synthesized TiO₂ samples were in the range of 20–80?nm and 2.5–3.2?eV respectively. The photocatalytic performance of prepared TiO₂ photocatalysts was evaluated by photodegradation of Methylene Blue (MB) solution under simulated solar irradiation. Results illustrate that the synthesized TiO₂ exhibits visible light activity at higher calcination temperature. Crystallinity and surface area plays a vital role in the overall performance of the prepared TiO₂ photocatalyst.     

Effect of carbon nanotubes support on band gap energy of MgO nanoparticles

In this study, the effect of carbon nanotube supports (CNT) on the morphology and band gap of MgO nanoparticles was studied. The synthesis of MgO nanoparticles on the surface of CNT supports was carried out by direct precipitation method and using magnesium nitrate in aqueous solutions containing CNT. The prepared samples were characterized using X-ray diffraction. The optical properties of the nanoparticles were studied using UV–Vis spectrometer. The results indicated that the presence of CNTs decrease the average size of the MgO nanoparticles. Also the use of CNTs as support has reduced the band gap energy of MgO nanoparticles, considerably.     

Shed light on submerged DC arc discharge synthesis of low band gap gray Zn/ZnO nanoparticles: Formation and gradual oxidation mechanism

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical agent. Electric discharge current was set to 20, 50, 100 and 150?A during synthesis. Estimated values of plasma excitation energies were 2.41, 2.66, 2.86 and 3.04?eV and diameter size of nanoparticles were 63, 42, 37 and 29?nm for these applied currents respectively. Synthesized nanoparticles were dark gray as prepared and became more transparent gradually getting white color finally. XRD and UV–vis results revealed that the oxidation process was time dependent. The colloidal nanoparticles composed of two metal and metal-oxide phase and white crystalline ZnO was achieved after complete oxidation process. These results provided a flexible and versatile method to synthesize metal oxide nanoparticles with controlled composition.     

Hydrothermal synthesis of nickel iron oxide nano-composite and application as magnetically separable photocatalyst for degradation of Solar Blue G dye

In this research, nickel iron oxide nano-composite was effectively prepared via a simple hydrothermal route in an autoclave at 180?°C. The phase formation and opto-elctronic properties of nano-composite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectra (UV–Vis DRS) and vibrating sample magnetometer (VSM) techniques. The VSM reults showed magnetization value of 38.25 emu/g. FTIR and XRD results confirmed the formation of cubic NiFe₂O₄ and rhombohedral Fe₂O₃ phases. The results of FESEM and EDAX studies indicate the formation of nickel iron oxide nano-composite with size of 7–10 nm. UV–Visible diffuse reflectance spectra experimental results showed transition energies of 1.66, 2.5 and 3.7 eV. Additionally, the prepared nickel iron oxide nano-composite were used as photocatalyst for for degradation Solar Blue G dye and the results showed good activity and recyclable by applying an appropriate magnetic field. The reuse of the prepared nickel iron oxide nano-composite for removal of Solar Blue G dye water pollutants was attained in five cycles with an average efficiency of 81%.     

Synthesis of nano-structured lanthanum tungstates photocatalysts

Nano-particles of lanthanum tungstate were prepared through an optimized chemical precipitation reaction using the aqueous solutions of the ingredients. The optimization of the procedure was performed based on performing the so-called Taguchi robust design. The effects of various conditions influencing the size of the produced particles were evaluated using an orthogonal array. The optimally prepared lanthanum tungstate particles were found to be about 31 nm in diameter. The chemical and physical properties of the products were studied through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy, UV–Vis and Fluorescence. Also the band gap energy of the produced nanoparticles was assessed through UV–Vis diffuse reflectance spectroscopy. The optimally prepared nano-structures were evaluated as photocatalysts in the pho-degradation of methylene blue.     

The use of biodegradable polymers for the stabilization of copper nanoparticles synthesized by chemical reduction method

Copper nanoparticles were synthesized by a convenient and rapid chemical reduction method in ambient condition using \(\hbox {Cu}(\hbox {NO}_{3})_{2}{\cdot } 3\hbox {H}_{2}\hbox {O}\) as a precursor, hydrazine hydrate as reducing agent and deionized water as solvent. The product was characterized by X-ray diffraction (XRD) patterns, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. However, agglomerated copper nanoparticles were obtained by this chemical reduction method. Hence, the effects of three polymers of polyvinyl pyrrolidone, polyethylene glycol (PEG) and starch as stabilizers on the size and size distribution of Cu nanoparticles were investigated. According to the results, smallest copper nanoparticles (30–50 nm) with a narrow size distribution were obtained using PEG as the stabilizing polymer. Zero-valent copper nanoparticles with high purity were obtained by this method and there was no peak related to the oxidized impurities such as CuO and \(\hbox {Cu}_{2}\hbox {O}\) in the XRD and UV–Vis studies, both in the presence and in the absence of stabilizer. On the other hand, by this method, zero-valent copper nanoparticles were obtained in the absence of any anti-oxidant agent and any inert gas flow. The effects of synthesis parameters including initial concentration of precursor, polymer concentration and the reaction temperature on the size and size distribution of copper nanoparticles were investigated using the UV–Vis analysis to determine the optimum synthesis conditions.     

Effect of deposition time on structural, optical and photoluminescence properties of Cd0.9Zn0.1S thin films by chemical bath deposition method

The present work investigates the effect of deposition times on the structural, optical and photoluminescence properties of Cd_0.9Zn_0.1S thin films deposited on glass substrate by chemical bath deposition method. The deposition time was varied from 30 to 90 min. The deposited films were uniform and adherent to the glass substrates and amorphous in nature. Structural, optical and photoluminescence properties of Cd_0.9Zn_0.1S thin films were studied through X-ray diffraction, energy dispersive X-ray, scanning electron microscopy, UV–Vis absorption, fourier transform infra red spectroscopy and photoluminescence spectroscopy. The average crystal size was increased from ~1.3 to 2.5 nm with increase in deposition times. The absorption of the films was increased and the absorption peak shifted to lower wavelength side when deposition time increases. The increased energy gap from 2.4 to 2.49 eV with deposition time was due to quantum size effect and better crystallization. The presence of functional groups and chemical bonding were confirmed by FTIR. PL spectra showed two well distinct and strong bands; blue band around 407–415 nm and green band around 537–541 nm due to size effect.     

Sunset yellow dyed triglycine sulfate single crystals: enhanced thermal,mechanical, optical and di-/piezo-/ferro-/pyro-electric properties

Single crystals of pure and sunset yellow (SSY) dye doped (0.05 mol%) triglycine sulphate (TGS) were grown by slow evaporation solution technique with the vision to improve the properties of pure TGS crystal. The external morphology of TGS crystal was deduced from its internal crystal structure by using two of the well established models, namely Bravais–Friedel–Donnay–Harker model (B–F–D–H) and Hartman–Perdok (H–P) periodic-bound chain (PBC) vectors model. The selective nature of sunset yellow dye to selectively stain the particular growth sectors of TGS crystal was studied. The structural analysis of both the crystals was carried out using powder XRD and FTIR studies. UV–Vis–NIR spectroscopy was carried out on both pure and SSY dyed TGS crystals to study their linear optical properties and various optical parameters namely optical band gap, refractive index, extinction coefficient and optical conductivity were determined. The thermal stability, melting point, ferro- to para-electric transition temperature, piezoelectric charge coefficient, ferroelectricity and mechanical hardness got enhanced as an effect of SSY dye doping in TGS matrix. The piezoelectric conversion efficiency (d₂₂) got enhanced from ~?56 pm/V for pure TGS single crystal to ~?85 pm/V for SSY doped TGS single crystal. The true-remanent polarization was determined for dyed TGS crystal using ‘Remanent Hysteresis Task’ which showed the presence of very small contributions of non-switchable components. ‘Time-Dependent Compensated (TDC)’ hysteresis task revealed the absence of resistive leakage in SSY-Doped TGS crystal. The pyroelectric coefficient got enhanced from ~?761 µCm^?2/°C for pure TGS single crystal to ~?850 µCm^?2/°C for SSY doped TGS single crystal. Comparative optical, mechanical, dielectric, piezoelectric, ferroelectric and pyroelectric studies provide useful scientific information of an important class of TGS crystals and suggest SSY-Doped TGS crystal as a better alternative than pure TGS crystal for various opto-electronics and ferroelectric devices applications.     

Eco-friendly synthesis of large band gap ZnO nanoparticles by trisodium citrate: investigation of annealing effect on structural and optical properties

In this study, large band gap zinc oxide nanoparticles (ZnO-NPs) were prepared by a facile, cost-effective, and eco-friendly co-precipitation method in aqueous solutions. Trisodium citrate was employed as a green and bio-safe complexing agent for zinc ions without using ammonia and/or any organic solution. The annealing effect on crystal structure, morphology, particle size, composition, UV absorption, and fluorescence (FL) properties of the synthesized ZnO-NPs was evaluated using various techniques. The UV–Visible absorption spectra of the ZnO-NPs showed a strong absorption peak in the UV-C region with a wide band gap energy of 4.2–4.4 eV. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images demonstrated fine spherical particles with approximate diameters of 20–50 nm. The average hydrodynamic diameter and zeta potential values of the as-prepared and the annealed ZnO-NPs in deionized water were 28.2 nm, ? 32.4 mV, 38.9 nm, and ? 16.1 mV, respectively. The FL and UV–Visible results illustrated that the annealing could considerably influence the emission and absorption spectra of the samples in the UV region. The FL and EDX results revealed that the annealing affects the composition, defect points, and states population in the crystal structure of the ZnO-NPs. Practical experiments of exposing the samples to UV radiation and the FL measurements indicated that the ZnO-NPs were sensitive to the excitation wavelengths, therefore, they have potential application in fabricating various types of UV sensors and filters (blockers), as well as photocatalytic activities.

     

Synthesis and Characterization of Pure Single Phase BiFeO3 Nanoparticles by the Glyoxylate Precursor Method

Perovskite-type BiFeO ₃ nanoparticles have been synthesized by thermal decomposition of glyoxylate precursor. The effects of different thermal decomposition temperatures (300–600 °C) on the phase evolution, morphology, and physical properties were investigated by thermal analysis, infrared spectroscopy, X-ray diffraction, electron microscopy, vibrating sample magnetometry, and UV–Vis spectroscopy methods. The high purity bismuth ferrite nanoparticles synthesized at 600 °C showed the weak ferromagnetism behavior, due to the size confinement effect. Furthermore, the BiFeO ₃ nanoparticles also exhibited strong absorption in the visible region with the lowest band gap of about 2.08 eV.     

Novel synthesis of interconnected nanocubic PbS thin films by facile aqueous chemical route

In the present investigation, we have successfully synthesized lead sulfide (PbS) thin films by using simple, cost effective and facile aqueous chemical route. The effect of deposition time on optical, structural and morphological properties of PbS thin films were investigated by using UV–Vis–NIR absorption spectroscopy, X-ray diffraction (XRD), photoluminescence, field emission scanning electron microscopy (FESEM), high-resolution-transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The optical band gap energy was varied in the range of 0.96–1.56 eV. The XRD patterns revealed the formation of pure cubic crystal structure. FESEM micrographs demonstrated the conversion of morphology from pyramidal to interconnected nanocubic. HRTEM and selected area electron diffraction (SAED) pattern illustrated that nanoparticles are compact, well interconnected and single crystalline in nature. EDS spectrum confirms that deposited PbS thin films are in good stoichiometry.     

Tuning of optical,thermal and antimicrobial capabilities of CdS nanoparticles with incorporated Mn prepared by chemical method

Cadmium sulfide (CdS) nanoparticles with different amounts of incorporated Manganese (Mn: 10, 15 and 20 mol%) has been prepared by chemical method. In optical properties the UV–Vis–NIR absorption spectra of all samples showed blue shift compared with the bulk CdS and decrease in band gap with Mn concentration. The presence of functional groups was identified by fourier transform infrared spectroscopy. It confirmed presence of metal sulfur bonding and weak interaction between anions (S^2?) and cations (Mn²⁺). The Photoluminescence spectra showed two emission peaks at 397 and 541 nm corresponding to the electron-hole recombination of CdS and surface trap induced emission respectively. In thermal properties thermogravimetric curve indicated increase in weight loss with Mn incorporation suggesting that pure CdS nanoparticles are thermally more stable than Mn incorporated CdS nanoparticles. The antimicrobial activities of Mn incorporated CdS were studied against Gram-positive and Gram-negative bacteria as test microorganisms using agar plating-spot inoculation method.     

Quantum confinement effect of CdS nanoparticles dispersed within PVP/PVA nanocomposites

Nanocomposite films of CdS nanoparticles within PVP/PVA blend were prepared. The prepared films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Ultraviolet–visible spectroscopy (UV–vis), transmission electron microscopy (TEM) and photoluminescence (PL) spectra. The amount of Cd⁺ used strongly influenced the size of the CdS nanoparticles, which was confirmed by XRD, UV–vis absorption spectra, PL emission spectra and TEM images. Smaller sized CdS nanoparticles were formed in higher content of cadmium. The results of XRD indicate that CdS nanoparticles were formed with hexagonal phase in the polymeric matrix. PL and UV–vis spectra reveal that nanocomposite films shows quantum confinement effect. Optical band gap and particle size were calculated and is in agreement with the results obtained from TEM data. The direct energy band gap was increased up to 2.86 eV.     

Synthesis, structural and optical properties of Ni-doped ZnO micro-spheres

Ni doped ZnO nanoparticles were synthesized by a simple chemical method at low temperature with Ni:Zn atomic ratio from 0 to 5 %. The synthesis process is based on the hydrolysis of zinc acetate dihydrate and nickel acetate tetrahydrate followed by heat treatment at 65 °C under refluxing using methanol as a solvent. X-ray diffraction analysis reveals that the Ni-doped ZnO crystallizes in a wurtzite structure with crystal size of 4–11 nm. These nanocrystals self-aggregated themselves into hollow spheres of size of 600–170 nm. High resolution transmission electron microscopy image shows that each sphere is made up of numerous nanoparticles of average diameter 4 nm. The XRD patterns, Scanning electron microscopy and transmission electron microscopy micrographs of doping of Ni in ZnO are confirmed the formation of micro-spheres. Furthermore, the UV–vis. spectra and photoluminescence spectra of the Ni-doped ZnO nanoparticles were also investigated. The band gap of the nanoparticles can be tuned in the range of 3.55–3.36 eV by the use of the dopants. The observed red shift in the band gap from UV–visible analysis and near band edge UV emission with Ni doping may be considered to be related to the incorporation of Ni ions into the Zn site of the ZnO lattice.     

An investigation on the properties of SnO2 nanoparticles synthesized using two different methods

Tin oxide SnO₂ nanoparticles have been synthesized using chemical co-precipitation and solvothermal methods. The structures and morphologies of SnO₂ prepared using both routes were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier infrared absorption spectroscopy (FT-IR), UV–Vis Spectroscopy and BET specific surface area. The XRD patterns showed the presence of the tetragonal structure in the nanometric range and both crystallinity as well as crystal size increased with the increasing in temperature. The size of the produced tin dioxide nanoparticles was from 6.2 to 10.6 nm by solvothermal route while it was from 9.3 to 16.2 nm for nanoparticles by co-precipitation pathway. Furthermore, TEM results showed that the sizes of SnO₂ particles in all powders were tetragonal like structure and the grain size was increased with temperature. FT-IR spectra revealed that intensity of the transverse optical mode of Sn–O stretching vibration was increased with the sintering temperature while the bending vibration of O–Sn–O showed a blue shift. The optical band gap was shifted to a lower energy with increasing temperature due to the improvement of the crystallinity and the value was varied from 2.9 to 4.25 eV. The specific surface area of the as-made SnO₂ in comparison with such calcined samples decreased with increasing the calcination temperature due to the changes in the sample particle size and in the sample crystal phases.