Tauc Relation Research Articles

Preparation and characterizations of Erbium(III)-Tris(8-hydroxyquinolinato) nanostructured films for possible use in gas sensor

In this paper, Erbium(III)-Tris(8-hydroxyquinolinato) (Erq3), with the empirical formula: C27H18ErN3O3, has been introduced as a photoelectronic performance sensor of a promised candidate film with high sensitivity to NO2 gas. The present film was prepared by the thermal vacuum process, and the structure and composition of Erq3were investigated by the analysis of XRD-pattern, FTIR-spectra, and AFM technique. A polycrystalline with a single peak (at the centered Bragg’s angle, 2θ = 11.40°) has been observed for the Erq3 film. AFM images indicate that the film surface is composed of distributed plateaus. The absorption spectrum showed three absorption bands at 265 nm corresponding to f-π* transitions, while the peaks at 330 and 375 nm are attributed to the π-π* transitions. The band gap energy was evaluated by Tauc relation, while the electronic transition was indirect. The response time, recovery time, and sensitivity at the operating temperature of 348 K were 1.46 s, 14.2 s, and 20%, respectively. A comparison of sensor parameters with other relative materials was also reported.

Effect of annealing temperature on the structural, thermoluminescent, and optical properties of naturally present salt from Lluta region of Peru

The effect of annealing temperature on the structural, thermoluminescence, and optical properties of the thermally treated naturally occurring salt from Lluta were studied. Samples were submitted to different annealing temperatures from 300 to 700 °C for 30 min. X-ray diffraction analysis of all samples was performed. The predominant crystalline phase found in the Lluta salt sample is NaCl, with minor phases (CaSO4 and Na). TL technique has been used to characterize and determine the dosimetric properties. After the thermal annealing process of samples, an increase in the TL response of up to 80 times the TL intensity of the natural sample is observed. A promising dosimetric high-temperature peak was found for the sample with an annealing temperature of 400 °C for 30 min. Besides, activation energy, frequency factor, and peak position have been determined by E-Tstop, Tm-Tstop, and deconvolution methods. The UV–Vis optical absorption of Lluta salt sample subjected to several annealing temperatures was investigated. The optical energy gap Eg was calculated using the Tauc relation and the relation between the variation of the optical band gap and the density of thermoluminescent traps was analyzed.

MBE grown preferentially oriented CdMgO alloy on m- and c-plane sapphire substrates

Unlike other II-VI semiconductors, CdO-based transparent oxide has great potential application for the fabrication of many optoelectronic devices. In this work, we study the growth of CdxMg1-xO alloys on m- and on c-plane sapphire substrates in Cd-rich to Mg-rich conditions using the plasma-assisted molecular beam epitaxy method. A structural and morphological study of CdMgO random alloys was carried out using X-ray diffraction and Atomic Force Microscope (AFM) techniques whereas composition analysis was done by Energy-dispersive X-ray (EDX) spectroscopy method. The optical properties of thin films were investigated by UV–Vis spectroscopy at room temperature. X-ray analysis confirmed the presence of cubic rock salt structure with <111> CdMgO crystallographic orientation on c-plane sapphire and <110> CdMgO preferential orientation on m-plane sapphire. The surface roughness was measured by the AFM. From the absorption curve, the optical bandgaps were determined using Tauc relation and it was found that the bandgap of films is influenced by the incorporation of Mg2+ ions into the CdO lattice. Bowing parameter was calculated for both samples on m- and c-sapphires.

Oxygen irradiation induced modification on the linear and nonlinear optical behavior of flexible MC/PANI/Ag polymeric nanocomposite films

• Irradiated of flexible MC/PANI/Ag nanocomposite films using homemade cold cathode ion source. • Studying the effect of oxygen irradiation on the structural and functional groups of MC/PANI/Ag composite films. • Improving the linear and nonlinear optical behavior of the irradiated MC/PANI/Ag for optoelectronics applications. In the present work, flexible polymeric composite films composed of polyaniline (PANI), silver nanoparticles (AgNPs), and methylcellulose (MC) are synthesized using solution cast preparation method for applied in optoelectronic devices. Subsequently, the MC/PANI/Ag films have been irradiated using broad beam homemade cold cathode ion source with oxygen fluence 8 × 10 17 , 16 × 10 17 , and 24 × 10 17 ions·cm −2 . The synergistic effects of oxygen irradiation on the structure, functional groups and optical properties of MC/PANI/Ag composite films are investigated using X-ray diffraction (XRD), Fourier transforms infrared (FT-IR) and UV–Vis spectroscopy, respectively. The optical band gap and Urbach energy of un-irradiated and irradiated MC/PANI/Ag films were calculated using Tauc's relation. Furthermore, the linear optical parameters such as refractive index, dielectric constant, extinction coefficient, and dielectric loss are determined. Moreover, the Wemple and Di-Domenico model was used to compute the dispersion properties of the studied films. The non-linear optical susceptibility and non-linear refractive index of the un-irradiated and irradiated films were also evaluated. As a consequence, ion-induced structural and optical changes in MC/PANI/Ag composite films, which would clear the way for using irradiated MC/PANI/Ag flexible nanocomposite films for a range of applications, particularly optoelectronic devices.

Effect of plant extracts on structural & morphological features of CuO nano structured material

Cupper oxide (CuO) nano structured material has been synthesized by using eco-friendly simple solution method using plant leaf extracts(Mangifera indica, Carica papaya and Azadirachta indica) as a reducing agent. The obtained material is subjected to calcination at 500 °C for further studies. Powder X-ray diffraction (PXRD) and Fourier transmittance Infrared spectroscopy (FTIR) was performed for the structural confirmation of the calcined CuO samples.The CuO prepared by using Mangifera indica, Carica papaya and Azadirachta indica leaf extracts exhibited flake shape, irregular and spherical structures respectively in scanning electron microscope (SEM) micrographs.In addition, the UV-Visible absorption spectrum was recorded and the energy gap determined by using Tauc relation was 3.5, 3.75 and 3.9eV for Mangifera indica, Carica papaya and Azadirachta indica respectively.

Optical and dielectric studies for the determination of gap states of the ‘polypyrrole’

The polypyrrole is a conducting polymer prepared by chemical route. The diffuse reflectance measured in the wavelength range (300–2500 nm) permitted the calculation of the refractive index (n), extinction coefficient (k), dissipation factor (tan δ) and relaxation time (τ). The optical band gap (E g) was evaluated from the dielectric and conductivity properties, and its value (1.01 eV) was confirmed by using the Tauc relation.

X-rays/gamma rays radiation shielding properties of Barium–Nickel–Iron oxide nanocomposite synthesized via low temperature solution combustion method

In the present communication, for the first time Ba–Fe–Ni oxide nanocomposite (BFNONC) was synthesized by using solution combustion method and calcined at 500oC. The synthesized sample was characterized using the techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transmission infrared spectroscopy (FTIR) and UV–Visible spectrophotometer to determine phase purity, functional group, surface morphology, structural analysis and energy band gap. The presence of diffraction peaks corresponding to BaO, Fe2O3 and NiO clearly confirms the formation of BFNONC. The average crystallite size was found to be 30 nm. The direct energy band gap determined by using Wood and Tauc's relation was found to be 2.1 eV. Further, the X-ray/gamma ray shielding properties of BFNONC in the energy range 0.081–1.332 MeV using NaI (Tl) detector and multi channel analyser (MCA) were measured. The measured shielding parameters are compared with the theory. Above 356 keV energy of X-ray/gamma ray, the measured shielding parameters agrees well with the theory, whereas slight deviation is observed below 356 keV. This deviation is mainly due to the influence of atomic/crystallite size of the BFNONC. This BFNONC finds an application as a shielding material in radiation shielding.

Synthesis and Characterizations of CH3NH3PbI3 : ZnS Microrods for Optoelectronic Applications

Organometallic perovskite is one of the potential materials in the various optoelectronic research fields. This study demonstrates the synthesis of CH3NH3PbI3 : ZnS microrods via one-step spin coating for optoelectronic applications. Incorporation of ZnS in the perovskite material caused bandgap variation in the visible wavelength range. Structural and chemical properties have been observed using X-ray diffraction, scanning electron microscope, and Fourier transform infrared spectroscopy. The optical and electrical properties were studied via UV-Vis spectroscopy and impedance analyzer. The addition of ZnS caused to increase the optical absorption coefficient from ∼104 cm−1 to ∼105 cm−1. The bandgaps of the thin films were calculated using the Tauc relation and electrical method, obtained in the range 1.51 eV–1.64 eV, suitable for various optoelectronic applications.

New insight in photocatalytic degradation of textile dyes over CeO2/Ce2S3 composite

Cerium oxide, sulfide and composites of cerium sulfide-cerium oxide were prepared by co-precipitation technique. The fabricated samples were characterized by XRD. The photocatalytic degradation of synthesized samples was made to check their catalytic performance. The results of photocatalytic activity verified that 94% degradation of the rhodamine B dye took place in presence of catalyst (composite of cerium oxide/sulfide) and UV–visible irradiation, whereas in catalyst absence, percentage degradation of rhodamine B dye was less than 15% at the end of 120 min. The composite of cerium oxide/sulfide showed greater photo degradation (94%) with rhodamine B dye under UV irradiation than cerium oxide (80%) and cerium sulfide (71%). Percentage degradation of composite materials was greater due to the band gap because photo catalysis depends upon the band gap energy. Band gap energy for composite of cerium oxide/sulfide may be calculated by Tauc relationship. Photo degradation reaction obeyed the rules of pseudo-first-order kinetic reaction.

Impact of Mg2+ substitution on structural, magnetic and optical properties of Cu-Cd ferrites

The Mg2+ doped MgxCu0.5-xCd0.5Fe2O4 [x = 0.0 to 0.5, Δx = 0.1] ferrites were produced utilising an oxalate precipitant and a co-precipitation technique. Fourier Transform Infrared spectroscopy (FT-IR) and Thermogravimetry (TG) were used to characterise the produced oxalate precursor powders. The structural, magnetic, and optical properties of prepared final ferrites were investigated using X-ray diffraction (XRD), FT-IR, Vibrating Sample Magnetometer (VSM), and UV–Vis Diffuse Reflectance Spectroscopy (UV–Vis DRS) techniques. The development of cubic spinel ferrite structure was confirmed by XRD signals. XRD data was used to calculate various characteristics such as crystallite size, theoretical and experimental lattice constants, unit cell volume, and X-ray density. With increasing Mg2+ doping, the values against lattice parameter (both experimental and theoretical) and unit cell volume show a rising trend, whereas the values against X-ray density show a decreasing trend. Ionic radii (rA and rB), bond lengths (A-O and B-O), hopping lengths (LA and LB) and anion-anion distance (dtet, shared doct and unshared doct) are also reported. FT-IR spectra of synthesized ferrite powders revealed two distinct bands in the ranges of 555 to 579 cm−1 and 414 to 476 cm−1, revealing ferrite's typical features. The FT-IR data was also used to calculate force constants and Debye temperatures for produced ferrite powders, and the results were consistent with the literature. VSM is also used to investigate the magnetic behaviour of synthesized ferrites. Finally, all samples' absorption spectra and energy band gaps are investigated using UV–Vis DRS. Using Tauc's relation, the optical band gaps of Mg-Cu-Cd ferrites samples were computed.

Development of spinel magnesium aluminate by modified solid state process and its characterization

Spinel magnesium aluminate synthesis by modified solid state process using AR grade oxide precursors in stoichometric (1:1) ratio was used after mild activation carried by agate-mortar pestle in dry condition. Thermal analyses were carried off for the mixed activated powder to determine the zone for phase formation (spinelization) which plays a pivotal role for annealing temperature selection. Followed by phase transition studied from thermal analyses, heat treatment of powders (annealing/sintering) in air was carried at various temperatures of 900˚C, 1050˚C and 1150˚C for variable durations. Phase development was confirmed after XRD analyses while FTIR determine the bonding of compound as well as required M−O coordinations for the required phase formation. Morphological analyses of annealed powders by SEM, FESEM represent dense agglomerates with fine particulates of spherical to hexagonal shape, irregular polygon with negligible interconnected porosity. Electronic transition of the compound developed was studied by UV–VIS followed by band gap estimation using Tauc relation. Band gap of the compound evolved was noted to be varying with temperature and soaking period.

Effect of solvent on fluorescence and absorption spectra of fluorescent coumarin derivative: Estimation of ground and excited state dipole moments

Solvent effect on fluorescence and absorption spectra of fluorescent coumarin derivative viz, 4-[(5-amino-1,3,4-thiadiazol-2-thio)methyl]–2H-benzo[h]chromen2-one(4ATMBC) has been studied in different solvents at room temperature. The shifts in the position, intensities and shapes of the absorption and fluorescence bands have been observed. The ground and excited state dipole moment of the fluorescent molecule have been calculated from Solvatochromic shift method. The excited-state dipole moments were estimated from Lippert, Bakhshiev and Kawski-Chamma–Viallet equations by using the variation of the Stokes' shift with the solvent dielectric constant and refractive index. The Reichardt‘s microscopic solvent polarity parameter has been used to calculate change in dipole moment. It was found that the excited-state dipole moments were higher than those of the ground-state dipole moment. The large increase in dipole moment in the excited state is due to more polar excited state than in the ground state. The ratio of ground and excited state dipole moments is used to know the solubility of the fluorophore in different solvents. Further, we have calculated angle between the ground and excited state dipole moments which is found to be zero. This shows that ground and excited state dipole moments are parallel. Energy band gap values of different solvents were calculated using Tauc relation. Kamlet-Taft and Catalan methods were used to have the information of non-specific solute–solvent interactions and hydrogen bonding interactions.

Termal Buharlaştırma ile Üretilen Cu2-xSe İnce Filmlerin Yapısal, Morfolojik ve Optik Özellikleri Üzerine Araştırma

In this work, the influence of post-annealing on the structural, morphological, and optical properties of copper selenide thin films deposited on glass substrate by thermal evaporation was investigated in detail. The post-annealing process at different ambient temperatures in a nitrogen atmosphere was applied to thin films deposited at room temperature. The X-ray diffraction (XRD) patterns showed the presence of cubic Cu2-xSe phase, and it was observed that the crystallinity improves with increasing annealing temperature. In addition, it was deduced that the average crystallite size increased with the annealing temperature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the surface morphology of thin films. It was seen that all samples have compact and densely packed surface morphology and grains on the surface become larger. Surface roughness increased from 11nm to 53 nm as the annealing temperature increased. On the other hand, the optical properties of as-deposited and annealed thin films were investigated by utilizing a UV-Visible spectrophotometer. The direct bandgap energies of as-deposited and annealed samples were estimated to be 2.34 eV, 2.31 eV, and 2.29 eV by using the well-known Tauc relation, respectively. The direct bandgap energy of thin films was also calculated using the derivative spectroscopy technique.

Facile green synthesis of Molybdenum oxide nanoparticles using Centella Asiatica plant: Its photocatalytic and electrochemical lead sensor applications

The molybdenum oxide nanoparticles (MoO3 NPs) have been successfully synthesized via green combustion method using Centella asiatica plant powder. The powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopic (FTIR), scanning electron microscopic (SEM) and diffuse reflectance spectroscopic (DRS) techniques were used to characterize the MoO3 nanoparticles. The PXRD patterns of the sample revealed pure hexagonal phase. The Scherrer's method was employed to find the crystallite size of the synthesized material and the result obtained was confirmed by the TEM analysis. The optical energy band gap value (Eg) of the sample was calculated using the Tauc relation, and it was found to be around 3.41 ​eV. The photocatalytic degradation of MoO3 NPs on Direct Green (DG) and Navy Blue (NB) dye was evaluated under UV light irradiation. The electrochemical study of prepared electrode with graphite powder in 0.1 ​M KOH electrolyte solution displayed superior redox potential output as intended by cyclic voltammetric and amperometric studies, where the material was employed for its sensing abilities such as a highly toxic metal like lead.

Photocatalytic degradation of methyl orange by cadmium oxide nanoparticles synthesized by the sol-gel method

Cadmium oxide (CdO) nanoparticles were synthesized successfully by use of the sol-gel reaction route using ethanol, in order to study their structural, optical, morphological and photocatalytic properties. A variety of techniques were used to characterize the CdO nanoparticles,including, XRD, UV–visible absorption spectroscopy,Scanning Electron Microscope (SEM) with energy dispersive X-ray Analysis (EDAX) and transmission electron microscopy (TEM). The resultant CdO nanoparticles were tested as a photocatalyst for the degradation of methyl orange (MO) under visible light.The results show that cadmium oxide nanoparticles were synthesized using a single phase through sol- gel method, with a crystal structure corresponding to a cubic system as confirmed by the XRD pattern. The surface morphology and chemical composition of the nanoparticles revealed a spherical morphology which lacked impurities. The band gap of the samples was calculated using the Tauc relationship; the energy band gap (Eg) was seen to increase with particle-size reduction. Photocatalytic degradation of methyl orange (MO) dye was tested under visible light exposure, with the best results being seen within 45 min; we conclude therefore that cadmium oxide nanoparticles are more effective photocatalysts at this nanoscale when synthesized by sol- gel method.

Synthesis and Characterization of MgO Thin Films Obtained by Spray Technique for Optoelectronic Applications

Magnesium oxide (MgO) thin films with different magnesium concentrations ([Mg2+] = 0.05, 0.1, 0.15 and 0.2 mol·L−1) in a spray solution have been successfully grown using a spray pyrolysis technique. X-ray diffraction (XRD), Maud software, FTIR spectroscopy, a confocal microscope, Wien2k software, spectrophotometry and a Photoluminescence spectrometer were used to investigate the structural, morphological and optical properties. XRD analysis revealed a better crystalline quality of the MgO thin layer synthesized with [Mg2+] = 0.15 mol·L−1, which crystallized into a face-centered cubic structure along the preferred orientation (200) lattice plan. The enhancement of the crystalline quality for the MgO thin film ([Mg2+] = 0.15 mol·L−1) was obtained, which was accompanied by an increment of 94.3 nm of the crystallite size. No secondary phase was detected and the purity phase of the MgO thin film was confirmed using Maud software. From the transmission spectra results, high transparent and antireflective properties of the MgO thin film were observed, with an average transmission value of about 91.48% in the visible range, which can be used as an optical window or buffer layer in solar cell applications. The films also have a high reflectance value in the IR range, which indicates that the highly reflective surface will prevent an increase in surface temperature under solar irradiation, which could be beneficial in solar cell applications. A direct band gap type was estimated using the Tauc relation which is close to the experimental value of 4.0 eV for optimal growth. The MgO material was tested for the degradation of methylene blue (MB), which reached a high photodegradation rate of about 83% after 180 min under sunlight illumination. These experimental trends open a new door for promising the removal of water contaminants for photocatalysis application.

Investigation of the opto-magnetic properties of Co doped ZnO nanoparticles and thin films for spintronics

Zn1-xCoxO (0≤x≤0.10) nanocrystalline compounds with different compositions were prepared by ball milling, and thin films of these compounds were prepared by electron evaporation method. XRD patterns are used to study the structural properties of these films. All films showed a hexagonal wurtzite structure. Using XRD patterns, calculate crystallite. The optical constants n and k of the Zn1-xCoxO nanocrystalline film are calculated in the range of 300-2500 nm based on K-K method. As Co is more doped, the refractive index also shows an increase. According to the Tauc relationship, the optical energy gap of the Zn1-xCoxO film is calculated, which proves to be a direct transition.

Improvement of the optical characteristics of PVA/PVP blend with different concentrations of SnS2/Fe

AbstractPolyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP; weight 7:3) polymer blends doped with different ratios (1 wt%, 3 wt%, 5 wt%, and 10 wt%) from nano SnS2/Fe are developed using casting and thermolysis procedures. Rietveld analysis showed that Fe is incorporated into the SnS2 lattice forming a single hexagonal phase with an average crystallite size of 6 nm along [00l] direction and 15 nm along [h00] direction. X‐ray diffraction together with Fourier transform infrared data is used to examine the homogeneity distribution of the nanofiller over the blend matrix. The effect of doping on the absorbance, transmittance, extinction coefficient, refractive index, direct and indirect optical band gaps, and other dispersion parameters of the blend is studied in detail. The nature of electronic transitions in the different blends was determined using Tauc's relation and the dielectric loss parameter. As the weight concentrations of SnS2/Fe dopants increased, the nonlinear optical parameters are increased relative to the undoped PVA/PVP polymer blend. The influence of the different excitation wavelengths and the amount of nanofillers on the fluorescence spectra from different blends are also investigated.

X-ray / gamma ray radiation shielding properties of α-Bi2O3 synthesized by low temperature solution combustion method

In the present communication, pure and stable α-Bismuth Oxide (Bi2O3) nanoparticles (NPs) were synthesized by low temperature solution combustion method using urea as a fuel and calcined at 500oC. The synthesized sample was characterized by using powder X-ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), Energy dispersive X-ray analysis (EDAX), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and UV–Visible absorption spectroscopy. The PXRD pattern confirms the formation of mono-clinic, stable and low temperature phase α-Bi2O3. The direct optical energy band gap was estimated by using Wood and Tauc's relation which was found to be 2.81 eV. The characterized sample was studied for X-ray/gamma ray shielding properties in the energy range 0.081–1.332 MeV using NaI (Tl) detector and multi channel analyzer (MCA). The measured shielding parameters agrees well with the theory, whereas, slight deviation up to 20% is observed below 356 keV. This deviation is mainly due to the influence of atomic size of the target medium. Furthermore an accurate theory is necessary to explain the interaction of X-ray/gamma ray with the NPs.The present work opens new window to use this facile, economical, efficient, low temperature method to synthesize nanomaterials for X-ray/gamma ray shielding purpose.

Significant and systematic impact of yttrium doping on physical properties of nickel oxide nanoparticles for optoelectronics applications

The structural, optical, and dielectric properties of pure NiO and yttrium (Y) doped NiO (Y: NiO) were studied in the present article for optoelectronic application. The pristine and different concentrations of 1.0, 2.5, 5.0, 7.5, and 10 wt.% doped Y: NiO nanoparticles (NPs) were synthesized by flash combustion route. X-ray diffraction patterns (XRD), Raman spectroscopy and scanning electron microscopy (SEM) images were used to study the structural properties of as-prepared nanoparticles. The average crystallite sizes (29.8–6.7 nm) and grains size (159.2–17.9 nm) were found to be decreased with an increase in Y contents. The dislocation density (1.12–21.75 × 10−3 1/nm2), lattice strain (2.79–12.46 × 10−3) and surface area (29.48–131.13 cm2/g) were increased on increasing Y contents. Direct optical band gaps of prepared samples were estimated using the Tauc's relation in the range of 3.52–3.37 eV. Photoluminescent spectra of prepared samples exhibit spectra at 355 nm, 451–482 nm, and 493 nm emission bands, which confirm the existence of oxygen and nickel vacancies. The improvement in the dielectric constant (143), dielectric loss (1233), and loss tangent (8.67) were observed for 5.0 wt.% Y doped NiO from the dielectric analysis of the samples. The electrical conductivities of Y: NiO NPs were also improved compared to pure NiO NPs. The improvement in the optical and dielectric properties of NiO in the substitution of yttrium (Y) can be used for optoelectronics applications.