Tauc Plot Method Research Articles

The Mechanism of the Formation of Binary Compounds Between Zn and S Impurity Atoms in Si Crystal Lattice

The paper presents the results of an experimental study of surface morphology, elemental composition, electrophysical and optical properties of Si samples earlier doped with impurity atoms of Zn and S. The results of the study revealed a sufficient concentration of Zn and S elements on Si surface after diffusion (3.1% and 2.6% by weight, respectively). After additional thermal treatment at different temperatures, i.e., at 850°C and 875°C, the samples of I group have regained their initial parameters. However, it’s noteworthy that the mobility of charge carriers in group I samples was comparatively lower than that in group II samples allegedly under the influence of Zn and S binary molecules. After additional heat treatment of all samples at a temperature of 875°C, the authors have studied optical absorption coefficients. And their band gap energies were determined using the Tauc Plot method. According to the results of the study, the optical band gaps in group II and III samples were 1.12 eV, whereas the band gap energy in group I samples after additional thermal treatment at a temperature of 875 °C turned out to be 1.31 eV. Having theoretically calculated the band gap by applying Vegard’s law, the authors suggested that the new structure must be of Si0.92ZnS0.08 - type.

The Fabrication of Halogen-Doped FeWO4 Heterostructure Anchored over Graphene Oxide Nanosheets for the Sunlight-Driven Photocatalytic Degradation of Methylene Blue Dye.

Rapid industrialization and urbanization are the two significant issues causing environmental pollution. The polluted water from various industries contains refractory organic materials such as dyes. Heterogeneous photocatalysis using semiconductor metal oxides is an effective remediation technique for wastewater treatment. In this research, we used a co-precipitation-assisted hydrothermal method to synthesize a novel I-FeWO4/GO sunlight-active nanocomposite. Introducing dopant reductive iodine species improved the catalytic activity of FeWO4/GO. I- ions improved the catalytic performance of H2O2 by doping into FeWO4/GO composite. Due to I- doping and the introduction of graphene as a support medium, enhanced charge separation and transfer were observed, which is crucial for efficient heterogeneous surface reactions. Various techniques, like FTIR, SEM-EDX, XRD, and UV-Vis spectroscopy, were used to characterize composites. The Tauc plot method was used to calculate pristine and iodine-doped FeWO4/GO bandgap. Iodine doping reduced the bandgap from 2.8 eV to 2.6 eV. The degradation of methylene blue (MB) was evaluated by optimizing various parameters like catalyst concentration, oxidant dose, pH, and time. The optimum conditions for photocatalysts where maximum degradation occurred were pH = 7 for both FeWO4/GO and I-FeWO4/GO; oxidant dose = 9 mM and 7 mM for FeWO4/GO and I-FeWO4/GO; and catalyst concentration = 30 mg and 35 mg/100 mL for FeWO4/GO and I-FeWO4/GO; the optimum time was 120 min. Under these optimum conditions, FeWO4/GO and I-FeWO4/GO showed 92.0% and 97.0% degradation of MB dye.

Synthesis and Characterization of Hydrothermal Synthesized Ultra-Red CdS1−x Se x Pigment

Ultra-red pigment is in urgent need to enrich the colour range as well as to improve the quality of ceramic product. In this study, ultra-red CdS1−x Se x pigments (CP) were synthesized through hydrothermal technique. The effects of S/Se ratio on the structural and optical properties of CPs were investigated. CPs were characterized by XRD, ICP, SEM and UV-vis techniques. The colorimetric parameters of CPs were measured as also their band-gaps were estimated based on Tauc plot method. Furthermore, detailed formation mechanism of CdS1−x Se x has been elucidated. The results demonstrate that different compositions of CdS1−x Se x can be facilely obtained by adjusting the R value (starting S/Se molar ratio); when R is equal to 0.67 and 0.83, the prepared samples are CdS0.75Se0.25, when R is equal to 1.00, 1.17 and 1.33, the prepared samples are CdS0.571Se0.429. It is found that excessive S2− plays critical role in CdS1−x Se x formation. CP prepared with R=1.00 owns L*=44.69, a*=49.93, b*=22.66, implying an excellent red colour, which indicates potential use as an ultra-red ceramic pigment.

Co(II)-TiO2/Ti Thin Film as Antibacterial Photocatalysts Escherichia Coli Under Visible Light Ilumination

A thin layer of TiO2 doped with Cobalt (II) immobilized on the surface of a titanium foil (Co(II)-TiO2/Ti) has been synthesized from a titanium foil (Ti) as a TiO2 precursor as well as a thin layer matrix and CoCl2.6H2O as a source of Co(II) on variations of 0.5%, 1% and 2%. Synthesis was carried out by anodizing method using ethylene glycol electrolyte solution with the addition of NH4F and followed by calcination treatment at 450ºC for 3 hours. The obtained Co(II)-TiO2 /Ti thin films were characterized using Fourier-transform infrared (FT-IR) spectroscopy, Diffuse Reflectance UV-Vis (DRSUV-Vis) and X-ray diffraction (XRD) methods. Doping Co(II) variations of 0.5%, 1.0% dan 2.0% in the TiO2 structure causes a shift in the vibrational absorption peak of Ti-O (460.99 cm-1) towards a smaller wave number of 459.06 cm-1 respectively ; 453.27 cm-1 and 451.34 cm-1. This is supported by the results of the DRUV-Vis analysis using the tauc plot method, which shows a decrease in the band gap energy of TiO2 (3.24 eV) to 2.57 eV, 2.47 eV and 2.28 eV. Based on XRD analysis, it is known that the Co(II)-TiO2/Ti photocatalyst has anatase phase with a crystal size of 15-17 nm. The photocatalytic activity of Co(II)-TiO2/Ti under visible light illumination was evaluated for inhibition of Escherichia coli bacterial growth. Co(II)-TiO2/Ti photocatalyst at 2.0% Co(II) concentration had the best inhibition (43.2%) compared to 0.5% and 1.0% Co(II) concentrations, respectively 18% inhibition and 27%.

To Study the Cadmium Sulphide Thin Films Synthesis by Simple Spin Coating Method for Energy Application

The paper examines the properties of CdS thin film, which is used for window material of solar cells and optical devices. The cadmium sulfide (CdS) thin film was prepared by sol-gel method on glass and ITO substrate. Prepared thin film dried in a vacuum oven at 70℃. Thin film and powder of CdS characterized for structural, optical, and electrical properties by X-ray Diffractometer (XRD), UV-Visible spectrometer, and Keithley spectrometer. The average crystallite sizes, microstrain, and dislocation density of the samples were calculated by the Debye Scherrer formula. The optical band gap of CdS calculated by the Tauc-plot method and obtained 2.40 and 2.41eV for powder and film. The absorption wavelength of CdS is suddenly decreased near 280nm and becomes flat in the higher wavelength region. The FTIR spectrometer is used to identification of unknown materials and bond formation. The bond formation, imperfections, and impurities were observed by the PL spectrometer. Keithley spectrometer is used for I-V characteristics and calculates electrical resistivity by Ohms law.

Limitations of the Tauc Plot Method

AbstractThe Tauc plot is a method originally developed to derive the optical gap of amorphous semiconductors such as amorphous germanium or silicon. By measuring the absorption coefficient α(hν) and plotting versus photon energy hν, a value for the optical gap (Tauc gap) is determined. In this way non‐direct optical transitions between approximately parabolic bands can be examined. In the last decades, a modification of this method for (poly‐) crystalline semiconductors has become popular to study direct and indirect interband transitions. For this purpose, (ahν)n (n = , 2) is plotted against hν to determine a value of the electronic bandgap. Due to the ease of performing UV–vis measurements, this method has nowadays become a standard to analyze various (poly‐) crystalline solids, regardless of their different electronic structure. Although this leads partially to widely varying values of the respective bandgap of nominally identical materials, there is still no study that critically questions which peculiarities in the electronic structure prevent a use of the Tauc plot for (poly‐) crystalline solids and to which material classes this applies. This study aims to close this gap by discussing the Tauc plot and its limiting factors for exemplary (poly‐) crystalline solids with different electronic structures.

Hazardous radiation protective glasses for medical and research laboratories

In the current study, the bismuth oxide (Bi2O3) content was inter-substituted with gadolinium oxide (Gd2O3) in sodium borate glass. Glass sample density and molar volume values show a reverse trend. The optical transparent radiation shielding glasses are more commonly used materials in hospitals or any hazardous radiation working environments, the glasses used in this work are more emphasized on their superior transmittance and acceptable for shielding materials for commercial purposes. The optical band gap value was calculated using the Tauc plot and absorption fitting method. Radiation shielding parameters like mass attenuation co-efficient, effective atomic number, effective electron density, equivalent atomic number, lead equivalent thickness, half value layer, tenth value layer, Geometric-Progression fitting parameters like (b, c, a, XK, and d), γ-ray build-up factor, and exposure build-up factor have all been evaluated. In the current work, photoluminescence studies for Gd3+ ions were investigated and discussed.

Exploring the structural, optical, and magnetic properties of Ni-doped ZnO nanoparticles synthesized via microwave irradiation

Nickel-doped zinc-oxide nanoparticles are synthesized by the solvothermal method at different doping concentrations (x = 0.02, 0.04, 0.06, and 0.08). The structural properties of undoped and nickel-doped zinc oxide nanoparticles are carried out. X-ray diffraction analysis confirms the hexagonal wurtzite structure (belonging to the space group p63mc) and optical properties are analyzed through UV–visible, Fourier-transformed infrared, and hotoluminescence. Energy bandgap values are found using the Tauc plot method. The Lande splitting factor is calculated using EPR analysis. Magnetic properties of the sample are measured using a vibrating sample magnetometer at room temperature. It is observed that their behavior changes from paramagnetic to superparamagnetic structure with an increase in their doping values. In the large saturation magnetization, it is very suitable for magnetic storage device applications.

Structural phase transition driven dielectric and optical properties with reduction in band gap in Sr2+ modified BaTiO3 ceramics

Ferroelectric materials with crystal symmetry transition from single phase to multiphase coexistence exhibit anomalous photosensitive properties. The optical properties (optical band gap and photosensitive) found on non-centrosymmetric and centrosymmetric systems achieved research interest because of their interesting behavior. In this regard, the lead-free polycrystalline Ba1−x Sr x TiO3 (BSTO, 0 ) has been synthesized to explore its crystal structure, dielectric, light absorption, and photocurrent sensing properties for various applications. Both experimental and theoretical studies on BSTO (0 ceramics confirm the crystal symmetry transition with the reduction of band gap as compared to pristine BaTiO3. This crystal symmetry transition plays an important role in varying the various physical properties as it involves the transition from the polar phase to the non-polar phase. The optical band gap has been estimated experimentally by the Tauc plot method and found that there is a small variation of energy band gap from 3.615 eV to 3.212 eV with Sr substitution. The highest dielectric constant was found to be 5327 at lower frequency on Ba0.76Sr0.24TiO3 after that for further increase in Sr concentration the dielectric constant decreases because of the introduction of the non-polar phase. A strong correlation between crystal structure and physical properties (dielectric, optical, etc.) has been observed. The photocurrent of the samples is significant which reveals that the sample is influenced by the photons. In a nutshell, the present study deepens the understanding of the correlation between crystal structure and various physical properties of BSTO and, hence provides an idea of required design parameters to construct a ferroelectric system for better photosensitive nature suitable for device applications.

Electrochromic and optical properties of Al2O3 doped WO3 layer deposited by thermionic vacuum arc technique

WO3 is a promising active material for electrochromic application. In this study, 5% Al2O3 doped WO3 layers were investigated. The thickness of the deposited material was measured as 132 nm and the refractive index at 550 nm wavelength was measured as 1.92. The band gap energy of the doped material was calculated by the Tauc-Plot method and it was found as 3.95 eV. Electrochromic (EC) measurements of the material were obtained in the voltage range of −0.6 V to +0.6 V. The intercalated/de-intercalated charge amounts into the material were calculated as 0.40 mC and 0.14 mC, respectively. It was observed that colored time was 14 s and bleaching time was determined as 20 s. The material was performed to a 300-cycle test. That is, 5% Al2O3 doped WO3 layers is promising material for the EC application.

Synthesis and Characterisation of SrAl2O4: Eu3+ Orange-Red Emitting Nanoparticles.

The current study involves the synthesis and characterisation of europium doped strontium aluminate nanophosphors using the solid-state reaction method with varying concentrations of europium. The existence of the SrAl2O4 phase in all samples was verified using X-ray diffraction and FTIR analysis. The lattice parameters as well as phase fractions were determined using Rietveld refinement. Surface morphology was studied using field emission scanning electron microscope. Using the Tauc plot method acquired from the diffuse reflectance spectra, the band gaps of the samples were determined and it was found that the doped samples possess lower band gaps compared to the host. Our findings demonstrate that these nanophosphors exhibiting bright orange-red emission under UV excitation with quantum efficiency 70.68%, can be applied for display and fluorescence imaging.

Sol-gel synthesis, characterization of ZnO thin films on different substrates, and bandgap calculation by the Tauc plot method

The sol-gel spin coating method was used for the preparation of the Zinc Oxide which was coated over polymer, transparent, and glass translucent substrates and characterized with the help of a UV-Vis Spectroscope. The wavelength bandgap of those samples was found to be 296nm, 310.5nm, and 330nm respectively. The actual band gap of ZnO is 388nm. Similarly, their optical bandgap energy calculated by the Tauc Plot method were 3.641eV, 3.385eV, and 3.495 eV respectively. The transparent polymer slide has the lowest wavelength bandgap and the translucent glass slide has the highest. Further, the bandgap’s value differs from its actual value to the difference in the absorption process due to the presence of the substrate. These results suggest that the choice of substrate can significantly impact the optical properties and performance of the zinc oxide thin film. This result can be applied in developing and optimizing zinc oxide thin films for various purposes, such as in solar cells, sensors, and optoelectronics. By carefully selecting the substrate, it may be possible to tailor the bandgap energy and other optical properties of the thin film to better suit the specific application.

Structural, optical, and thermal investigation of SnO2 nanoparticles incorporated PANI nanofibers as an emissive layer material

Nowadays, polyaniline (PANI) based nanocomposites have emerged as a boon that has opened a new door for researchers working in a wide range of applications, including optoelectronic devices, electrochromic devices, batteries, medicinal materials, and imaging devices. Pure PANI and PANI/SnO2 nanocomposites were synthesized via chemical oxidative polymerization using FeCl3 as an oxidative agent. FESEM analysis reveals a spherical aggregated structure of SnO2 nanoparticles on the surface of PANI nanofibers. Particle sizes of 15% PS nanocomposite are estimated to be 12–23 nm through HR-TEM. XPS has been employed to find out the chemical oxidation states of the optimized nanocomposites. Direct optical band gaps and optical conductivities of nanocomposites were calculated via Tauc's plot method through UV–Visible spectroscopy. Thermogravimetric study shows the thermal stability is enhanced for the 15% PS nanocomposite. The PL intensity of the PANI can be tuned by varying the concentrations of SnO2 nanoparticles. The highest PL intensity is observed for 15% PS nanocomposite. Color purity is estimated at ∼91.6% for blue emission color. Enhanced PL intensity and thermal stability are insisted that 15% PS nanocomposite might be used as an emissive material in polymer-based blue light-emitting diodes application.

The Correlation between Dye absorption Wavelength and Illumination Wavelength on DSSC Performance

This study examines the effect of the wavelength of light illuminated on DSSC on the absorption wavelength and gap dye energy. The dye used was sea lettuce anthocyanin from Sanur Beach, Bali. As much as 20 grams of dried sea lettuce powder was dissolved in 80 mL of 96% ethanol and 6% HCl. After 24 hours of immersion, it was filtered with Whatman 41 paper. The filtrate was characterized using a UV-Vis-NIR spectrophotometer so that the absorption wavelengths of the anthocyanin dye were 272.5 nm, 417 nm, and 653.5 nm. The gap energy was calculated using the Tauc Plot method, and the result was 2.826 eV. The dye was applied to make DSSC using the sandwich method, which was then irradiated with white, red, and purple LEDs with respective wavelengths of 400–700 nm (with peaks at 439.67 nm and 550.29 nm), 629.04 nm and 425.38 nm and variations in intensity values, namely 1000 lux, 2000 lux, and 3000 lux. Illumination using purple LEDs produces the maximum current and highest efficiency compared to white and red, namely 1.33 mA, 1.57 mA, and 1.83 mA for 1000 lux, 2000 lux, and 3000 lux, respectively, and the efficiency is 0.0039 for 1000 lux. The purple color has a wavelength close to and intersects with the absorbance wavelength of the dye and has energy (2.918 eV) greater than the gap energy of the sea lettuce dye.

Investigation of boron-doped graphene oxide anchored with copper sulphide flowers as visible light active photocatalyst for methylene blue degradation

The non-biodegradable nature of waste emitted from the agriculture and industrial sector contaminates freshwater reserves. Fabrication of highly effective and low-cost heterogeneous photocatalysts is crucial for sustainable wastewater treatment. The present research study aims to construct a novel photocatalyst using a facile ultrasonication-assisted hydrothermal method. Metal sulphides and doped carbon support materials work well to fabricate hybrid sunlight active systems that efficiently harness green energy and are eco-friendly. Boron-doped graphene oxide-supported copper sulphide nanocomposite was synthesized hydrothermally and was assessed for sunlight-assisted photocatalytic degradation of methylene blue dye. BGO/CuS was characterized through various techniques such as SEM–EDS, XRD, XPS, FTIR, BET, PL, and UV–Vis DRS spectroscopy. The bandgap of BGO-CuS was found to be 2.51 eV as evaluated through the tauc plot method. The enhanced dye degradation was obtained at optimum conditions of pH = 8, catalyst concentration (20 mg/100 mL for BGO-CuS), oxidant dose (10 mM for BGO-CuS), and optimum time of irradiation was 60 min. The novel boron-doped nanocomposite effectively degraded methylene blue up to 95% under sunlight. Holes and hydroxyl radicals were the key reactive species. Response surface methodology was used to analyze the interaction among several interacting parameters to remove dye methylene blue effectively.

Plant Based Synthesis of ZnO Nanoparticles and Characterization by UV-Vis Spectroscopy

In the modern fast changing world, as the green and environment friendly methods are much required and preferred over conventional toxic methods, plant based nano synthesis plays a vital role in future developments of nanotechnology. In this research article, we discussed on the synthesis and characterization of Zinc Oxide nanoparticles by green synthesis method utilizing the leaves of Ocimum Tenuiflorum as reducing agent for Zn salt. ZnO NPs prepared by such a technique exhibit superior antibacterial efficacy against a range of bacteria compared to ZnO NPs produced through chemical methods, without developing resistance to antibiotics. Further the prepared ZnO NPs were characterized by UV-Vis spectroscopy technique and the bandgap of particles was calculated by Tauc Plot method.

The Optical Energy Gap of the Semiconducting Intrinsic Layer for Organic Solar Cell Applications

The optical energy gap of the semiconducting intrinsic layer plays a crucial role in determining the increase in efficiency. The carbon-based biomass can be a choice for the silicon used as solar cell material. Here, we proposed the best biomass that can be used as a semiconductor component in solar cell applications. Coconut shells as bio-waste and palmyra sap, which are available in most areas of Indonesia, can be the best candidates to be considered. The XRD measurement showed both organic materials have an amorphous phase. The coconut shells sample has two peaks that are identical to graphene peaks, therefore this material is called graphenic-like carbon (GC). Furthermore, from the UV-visible spectroscopy, it was shown that both materials have a high transmittance of more than 95%, which indicates that they have transparent properties. Also, the Tauc plot method gives information about the optical energy gap of coconut shell charcoal (GC) and palmyra sap (a:C) which are 2.67 and 1.83 eV, respectively. From this result, palmyra sap becomes promising material to be applied as an intrinsic layer for semiconducting components in solar cell applications.Keywords: Amorphous phase, Coconut shells charcoal, Optical energy gap, Palmyra sugar.

The development of program for calculating the band gap energy of semiconductor material based on UV-Vis spectrum using delphi 7.0

The optical properties of semiconductor material are the important information for its application in solar cell. One of the parameter which influence the material optical properties is the band gap energy. The value of band gap energy can be obtained from experimental data of UV-Vis absorbance spectrum by doing three steps, i.e. curve smoothing, baseline arrangement data value and the calculation of the band gap energy using Tauc plot method embedded in the Origin software. Conventionally, these three processes are done sequentially. In this research, we developed the program for calculating the band gap energy which differ from the one usually used. In this program all the processes for curve smoothing, baseline arrangement data value and the calculation of the band gap energy are done simultaneously. For input data, we used the experimental UV-Vis absorbance spectrum of ZnO, TiO2 sensitized-Dye and Dye-N719 materials. The calculated band energy obtained by our program are 3.19 eV, 2.14 eV and 1.73 eV for ZnO, TiO2+Dye N719and Dye-N719 materials, respectively. These results are almost the same to the one obtained by conventional method i.e. 3.20 eV for ZnO, 2.10 eV for TiO2 based Dye-sensitized and 1.60 eV for Dye-N719. We also found that our program for calculating the band gap energy is more easily, user friendly and more efficient compared to the conventional method.

A New Combination Method of N-doped TiO2 Nanoparticles Synthesis for Heavy Metal Ions Cr(VI) Photoreduction Applications

Through a combination of biosynthetic and hydrothermal methods, N-doped TiO2 photocatalyst has been successfully synthesized using various concentrations of ammonia as a nitrogen source, namely 10% w/w (NTO10), 20% w/w (NTO20), 35% w/w (NTO35), and 50% w/w (NTO50). The synthesis of TiO2 was conducted using Aloe vera (L) Burm F. rind extract as a natural capping agent via the biosynthetic method, followed by a nitrogen doping process via the hydrothermal method. The X-ray Diffraction (XRD) analysis revealed that all phases were anatase. According to the results of the UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS) analysis using the Tauc-Plot method, all N-doped TiO2 samples showed a decrease in the energy gap compared to the TO sample. This indicates that the doping of TiO2 using nitrogen has been successfully doped into TiO2. The photocatalytic activity of N-doped TiO2 was evaluated for the photoreduction of the Cr(VI) model pollutant using a 24-watt LED lamp as a visible light source for 120 minutes. The results indicate that the NTO35 is the best-prepared N-doped TiO2, which showed a reduced rate for the Cr (VI) model pollutant of 50.88%, or two times greater than that of undoped TiO2.

Synthesis and characterization of tris(5,7-diphenyl-8-quinolinolato) aluminum(III), gallium(III), and indium(III) complexes: Effect of metal ions on the structural, photoluminescence, thermal and electrochemical properties

The 5,7-diphenyl-8-hydroxyquinoline (5,7-Phq) organic ligand was successfully synthesized via Suzuki cross-coupling reaction followed by synthesis of the novel organometallic complexes tris(5,7-diphenyl-8-quinolinolato) metal(III) [M(5,7-Phq)3; M = Al, Ga, or In]. All synthesized M(5,7-Phq)3 complexes were characterized using various analytical techniques. The molecular structure of In(5,7-Phq)3 was confirmed using single-crystal X-ray crystallography, which indicates that the three 5,7-Phq ligands are arranged in a meridional configuration around the central metal In3+ ion, and the complex is distorted from ideal octahedral geometry. There are no significant differences in the UV–visible absorption spectra of the complexes in the tetrahydrofuran (THF) solution and they are all red-shifted compared to that of the parent Mq3 (M = Al3+, Ga3+, In3+) compounds. The broad absorption band at around 417 nm is assignable to the π-π* transition. The synthesized M(5,7-Phq)3 complexes in the solution and in the solid-state show red-shifted emission compared to that of the parent unsubstituted compounds. The decrease in the solution and the solid-state emission efficiency and intensity from Al to In complexes is attributed to the heavy atom effect. Despite the electrochemical band gap energies (Egec) of the complexes determined from cyclic voltammetry being in good agreement with those reported for the unsubstituted complexes, the optical band gap energies (Egopt) determined from the Tauc plot method are smaller. The results of the fluorescence decay of the M(5,7-Phq)3 complexes both in CHCl3 solution and in solid state at 298 K show that the decays fit a bi-exponential model with two lifetimes (τ1 and τ2). The average values of fluorescence lifetimes of the complexes in CHCl3 are significantly greater than those of the complexes in the solid state.