P. Tripathi

Study of ZnO and Mg doped ZnO nanoparticles by sol-gel process

Nano-crystalline undoped and Mg doped ZnO (Mg-ZnO) nanoparticles with compositional formula MgxZn1-xO (x=0,1,3,5,7,10 and 12 %) were synthesized using sol-gel process. The XRD diffraction peaks match with the pattern of the standard hexagonal structure of ZnO that reveals the formation of hexagonal wurtzite structure in all samples. SEM images demonstrates clearly the formation of spherical ZnO nanoparticles, and change of the morphology of the nanoparticles with the concentration of the magnesium, which is in close agreement with that estimated by Scherer formula based on the XRD pattern. To investigate the doping effect on optical properties, the UV–VIS absorption spectra was obtained and the band gap of the samples calculated.

Plasmons and their damping in a doped semiconductor superlattice

The complex zeroes of dielectric response function of a doped GaAs superlattice are computed to study the frequencies and damping rates of oscillations in coupled electron-hole plasma. The real part of a complex zero describes the plasma frequency, whereas imaginary part of it yields the damping rate. Strong scattering of charge carriers from random impurity potentials in a doped GaAs superlattice gives rise to a large value of damping rate which causes over-damping of plasma oscillations of coupled electron-hole gas below qc, a critical value of wave vector component (q) along the plane of a layer of electrons (holes). The plasma oscillations which correspond to electrons gas enter into over-damped regime for the case of weak coupling between layers. Whereas, plasma oscillations which belong to hole gas go to over-damped regime of oscillations for both strong as well as weak coupling between layers. The damping rate shows strongq-dependence forq < qc, whereas it weakly depends onq forq ≥qc. The damping rate exhibits a sudden change atq =qc, indicating a transition from non-diffusive regime (where collective excitation can be excited) to diffusive regime (over-damped oscillations).

Structural and room temperature dielectric properties of ethylene glycol assisted pure and Al doped NiO nanoparticles

We have synthesized undoped and Al doped NiO nanoparticles with compositional formula Ni1-xAlxO (x=0 and 1%) using sol-gel method annealed at 700°C. The XRD diffraction peaks match with the pattern of the cubic structure of NiO that reveals the formation of hexagonal wurtzite structure in all samples. TEM image of undoped NiO demonstrates clearly the formation of spherical NiO nanoparticles, In addition, we have also discussed the effect of Al insertion in NiO lattice on dielectric properties such as dielectric constant, loss factor, AC conductivity and impedance Nyquist plot of our samples.We have synthesized undoped and Al doped NiO nanoparticles with compositional formula Ni1-xAlxO (x=0 and 1%) using sol-gel method annealed at 700°C. The XRD diffraction peaks match with the pattern of the cubic structure of NiO that reveals the formation of hexagonal wurtzite structure in all samples. TEM image of undoped NiO demonstrates clearly the formation of spherical NiO nanoparticles, In addition, we have also discussed the effect of Al insertion in NiO lattice on dielectric properties such as dielectric constant, loss factor, AC conductivity and impedance Nyquist plot of our samples.

Investigation of optical properties of nickel oxide nanostructures using photoluminescence and diffuse reflectance spectroscopy

Nickel oxide (NiO) nanoparticles with a crystal size of around 16.26 nm have been synthesized via sol-gel method. The synthesized precursor was calcined at 600 °C for 4 hours to obtain the nickel oxide nanoparticles. The XRD analysis result indicated that the calcined sample has a cubic structure without any impurity phases. The FTIR analysis result confirmed the formation of NiO. The NiO nanoparticle exhibited absorption band edge at 277.27 nm and the optical band gap have been estimated approximately 4.47 eV using diffuse reflectance spectroscopy and photoluminescence emission spectrum of our as-synthesized sample showed strong peak at 3.65 eV attributed to the band edge transition.Nickel oxide (NiO) nanoparticles with a crystal size of around 16.26 nm have been synthesized via sol-gel method. The synthesized precursor was calcined at 600 °C for 4 hours to obtain the nickel oxide nanoparticles. The XRD analysis result indicated that the calcined sample has a cubic structure without any impurity phases. The FTIR analysis result confirmed the formation of NiO. The NiO nanoparticle exhibited absorption band edge at 277.27 nm and the optical band gap have been estimated approximately 4.47 eV using diffuse reflectance spectroscopy and photoluminescence emission spectrum of our as-synthesized sample showed strong peak at 3.65 eV attributed to the band edge transition.

Frequency dependent dielectric properties of Sr doped NiO nanostructures

Ni1-xSrxO (x=0.0, 0.02) nanoparticles have been synthesized using sol-gel method calcined at temperature 600 °C. The XRD analysis result revealed that the calcined sample has a cubic structure with single phase structure. We have calculated crystallite size of samples using both Debye-Sherrer and William Hall (W-H) method which are found to be 19.69 nm, 22.39 nm and 28.50 nm, 33.27 nm, respectively. TEM image reveals the formation of spherical shaped particles. In addition, dielectric properties have been studied using LCR measurement and found that e′, e″ and tan δ are decreases with increase in frequency whereas ac conductivity increases with increase in frequency. This behavior may be explained using Maxwell–Wagner and Koop theory.Ni1-xSrxO (x=0.0, 0.02) nanoparticles have been synthesized using sol-gel method calcined at temperature 600 °C. The XRD analysis result revealed that the calcined sample has a cubic structure with single phase structure. We have calculated crystallite size of samples using both Debye-Sherrer and William Hall (W-H) method which are found to be 19.69 nm, 22.39 nm and 28.50 nm, 33.27 nm, respectively. TEM image reveals the formation of spherical shaped particles. In addition, dielectric properties have been studied using LCR measurement and found that e′, e″ and tan δ are decreases with increase in frequency whereas ac conductivity increases with increase in frequency. This behavior may be explained using Maxwell–Wagner and Koop theory.

Influence of Ag substitution on structural and dielectric properties of TiO2 nanoparticles

In this paper, we report the structural, electrical and dielectric properties of Ag-substituted TiO2 nanoparticles synthesized by sol-gel method. The X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles are pure and crystalline in nature and showing tetragonal anatase phase of TiO2. TEM micrograph shows that shapes of the nanoparticles are non-spherical. We have also studied the dielectric properties and in relation to it the dielectric constants, dielectric loss and A.C. conductivity have been studied as the function of frequency and composition of iron. The above theory may be explained by ‘Maxwell Wagner Model’.In this paper, we report the structural, electrical and dielectric properties of Ag-substituted TiO2 nanoparticles synthesized by sol-gel method. The X-ray diffraction (XRD) spectra revealed that the synthesized nanoparticles are pure and crystalline in nature and showing tetragonal anatase phase of TiO2. TEM micrograph shows that shapes of the nanoparticles are non-spherical. We have also studied the dielectric properties and in relation to it the dielectric constants, dielectric loss and A.C. conductivity have been studied as the function of frequency and composition of iron. The above theory may be explained by ‘Maxwell Wagner Model’.

Structural phase analysis, band gap tuning and thermal properties of TiO2/ZnO nanocomposite

The present work emphasizes the structural, optical and thermal properties of pure TiO2 and TiO2/ZnO nanocomposite. The samples were synthesized by sol–gel method and characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Ultraviolet-visible spectroscopy and Thermal gravimetric analysis (TGA). The XRD analysis shows that synthesized TiO2 nanoparticles consisted of only anatase phase and also it revealed the presence of both, TiO2 and ZnO phases in TiO2/ZnO nanocomposites. TEM analysis confirmed that the shapes of TiO2/ZnO nanocomposite are spherical (due to TiO2) and nanorods (due to ZnO) and EDS analysis confirmed that synthesized material has no impurity. Thermal gravimetric analysis (TGA) shows the weight loss of the nanoparticles which is found to take place up to 800°C, beyond this temperature no significant weight loss was observed. The band gap of pure TiO2 and TiO2/ZnO nanocomposite have been estimated from absorption peak a...

Polyethylene glycol (PEG) assisted size-controlled SnO2 nanoparticles by sol-gel process

Tetragonal phase tin oxide (SnO2) nanoparticles have been synthesized by sol–gel method using SnCl4.5H2O and polyethylene glycol (PEG) of different concentration. The phase, size and purity of the final products are characterized by X-ray diffraction (XRD). The morphology is confirmed by scanning electron microscopy (SEM) analysis. There exists relationship between the concentration of PEG and particle size of SnO2 nanoparticles. Increase in concentration of PEG caused the reduction of particle size of tin oxide nanoparticles. The results suggest that the concentration of PEG plays a significant role in determining the size of SnO2 nanoparticles synthesized via this method. The optical property of the product has been explored by Ultraviolet (UV-visible) and Fourier Transform Infrared (FTIR) spectroscopic techniques.

Influence of Fe ions on structural, optical and thermal properties of SnO2 nanoparticles

In the present work, Fe doped SnO2 nanoparticles with the composition Sn1-xFexO2 (x = 0, 0.02, 0.04 and 0.06) have been successfully synthesized using sol-gel auto combustion technique. The samples are characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), Ultraviolet (UV-Visible) absorption spectroscopy and thermal gravimetric analysis (TGA). The XRD study shows that all the samples have been found in tetragonal rutile structure without any extra phase and average crystallite size which lies in the range of 6-17 nm. The EDAX spectrum confirmed the doping of Fe ion into tin oxide nanomaterial. The optical band gap of doped SnO2 is found to decrease with increasing Fe ion concentration, which is due to the formation of donor energy levels in the actual band gap of SnO2.

The study and characteristics of ZnO/CdS nanocomposite and its application on nanoantibacterial activities

We have studied the structural and optical properties of ZnO/CdS nanocomposite and its application on nanoantibacterial activities. In this paper, we have used X-ray diffraction, Transmission electron microscope (TEM) and Energy dispersive X-ray spectroscopy (EDX) techniques in order to know about the structural and optical properties of synthesized ZnO/CdS nanocomposite. After TEM and EDX analysis it has been confirmed that the shape of this nanocomposite is hexagonal and it has no impurity. The optical absorption spectra of pure ZnO and ZnO/CdS nanocomposite have been presented by UV-Visible Spectrometer and the estimated band gap from absorption peak has been found to be 3.36 and 3.74 eV respectively. Antibacterial activity of ZnO/CdS nanocomposite was evaluated by using standard zone of inhibition (ZOI) microbiology assay. The synthesized ZnO/CdS showed promising antibacterial activity against Staphylococcus aureus in dose dependent manner.