Variation Of Band Gap Energy Research Articles

Solution-combustion synthesis of AgCo3O4/FeMn-O multiphase composite for high-performance asymmetric supercapacitor

A multiphase composite system AgCo3O4/FeMn-O was synthesized using an easy and low-cost solution combustion method for supercapacitor application. The multiphase composite system consisting of Co3O4, α-MnO2, and Mn5O8 was identified by X-ray diffraction analysis. The phases were observed as settled on each other in the form of large spherical and hair-like formations in morphological images obtained from scanning electron microscopy. UV-VIS spectroscopy supported the results of variation of band gap energies of Co3O4, α-MnO2, and Mn5O8 due to Ag and Fe. Based on Raman spectroscopy, characteristic modes of Co3O4, α-MnO2, and Mn5O8 were observed. In electrochemical analysis, the cyclic voltammetry (CV) confirmed the intercalation type-pseudocapacitive nature of the prepared composites. Galvanostatic charge-discharge (GCD) analysis showed the highest specific capacitance of 904 F/g obtained from one of the composites at 1 A/g current density. The supercapacitor device was fabricated and showed remarkable cyclic stability of 89 % even after 5000 GCD cycles along with 11.5 Wh/kg energy density and 522 W/kg power density. The good electrochemical performance was attributed to the multiple redox reactions occurred in the bulk of electrode material. Hence, the solution combustion method provides an easy and cost-effective approach to synthesize metal-oxide composites for supercapacitor applications.

Unveiling the influence of dopants on structural, defect chemistry, morphological and optical characteristics of NiO nanostructures

Abstract In this paper, undoped and doped (Fe, Co and Fe-Co) nickel oxide (NiO) nanostructures have been synthesized using co-precipitation method. Prepared samples were characterized for the structural, compositional, morphological and optical properties using x-ray diffraction, scanning electron microscopy (SEM), Energy dispersive spectrocopy (EDS), UV-visible spectroscopy and photoluminescence spectroscopy. Structural analysis confirmed the single cubic phase formation of undoped and doped samples. Defect chemistry showed that Fe-Co co-doped NiO possesses a lower density of defects than other samples. SEM results revealed the agglomeration of particles. EDS results confirmed the presence of Ni, O, Fe and Co in the respective undoped and doped samples. Optical analysis revealed the band edge shifts with the incorporation of dopants in the NiO crystal lattice confirmed the variation of band gap energy. Emission peaks were observed in the UV and visible regions. The Incorporation of dopants in the crystal lattice causes variation of emission centers. Surface oxygen vacancies and imperfections significantly impact the emission characteristics of NiO. Variable spectral response of NiO with dopant incorporation has potential for optoelectronic applications.

Substitution of an isovalent Te-ion in SnSe thin films for tuning optoelectrical properties

In present work, SnSe1-xTex thin films with varying Te concentrations were deposited on glass substrate through thermal evaporation technique. SnSe1-xTex thin films were characterized using X-ray diffraction (XRD), atomic force microcopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis NIR spectroscopy and room-temperature hall measurements technique. XRD patterns revealed that all the samples had a polycrystalline orthorhombic structure. Additionally, a low level of Te impurity improved the crystalline quality of the SnSe thin films. AFM images showed a noticeable alteration in the surface structure of the SnSe thin films caused by Te doping. UV–Vis NIR spectroscopy was employed to assess the optical characteristics of SnSe1-xTex thin films, revealing a variation in the optical band gap energy (Eg) between 1.75 and 1.89 eV, attributed to Te doping. The Hall effect measurement revealed n-type conductivity, and the carrier concentration decreased as the Te dopant concentration increased, corresponding to a decrease in antisite SnSe defects. The experimental findings suggest that adding a moderate amount of Te is a beneficial method for enhancing the optical and electrical properties of SnSe films. Furthermore, the Schottky device parameters of the Ag/SnSe1-xTex/Al:ZnO structure were established by analyzing the temperature-dependent Current-Voltage (I–V-T) characteristics through the thermionic emission current transport mechanism.

Unraveling the role of Cu2+ induced Jahn-Teller distortion and electron occupation alternation in modulating electronic and optical properties of CuxFe1-xFe2O4

In recent years, attractive Fe3O4 and transition metal-doped Fe3O4 magnetic ferrites have received increasing attention due to their wide range of applications in catalyst carriers. The doping of Cu in Fe3O4 can tune optical and electrical properties. Due to the arrangement of the valence electrons of the Cu atoms, the distortion of Jahn-Teller (J-T) is very easy to occur. It needs to be studied that the physical mechanism of J-T distortion and energy band gap variation with Cu concentration. In this study, the electronic structure and optical properties of the CuxFe1-xFe2O4 (x = 0–1) defect system have been calculated based on the density-functional theory using the hybrid functional method. Two distinct types of J-T distortion, compression distortion and elongation distortion, have been present in our calculations. Furthermore, projected density of states (PDOS) has verified that the electron arrangement of compressed Cu2+ is (t2g)6 (dx2−y2)2 (dz2)1, then the electron arrangement of elongated Cu2+ is (t2g)6 (dz2)2 (dx2−y2)1. The doped Cu lowers the position of conduction band minimum (CBM), so the energy gap decreases with increasing of Cu concentration (0 < x < 1). When x = 1, the FeOct2+ is completely replaced by CuOct2+ and the valence band maximum (VBM) levels are provided by the doped Cu atom, then the energy gap is maximum. The elongated Cu2+ results in the CBM localized around the doped Cu, and increase the absorption intensity of visible light. It shows that the doped Cu atom system in the visible region of the absorption intensity increases and the absorption of light range is more extensive. Our findings demonstrate that distinct J-T distortions induced by Cu can efficiently modulate the electronic and optical properties of CuxFe1-xFe2O4. Cu doping changes the light absorption and extinction coefficients of Fe3O4. This provides a theoretical basis for the application of CuxFe1-xFe2O4 in wave absorption. At x = 0.5, the absorption coefficient of Cu-doped Fe3O4 is increased by 1.8 times. Because of its magnetic properties, it is easy to separate the catalyst. The application in catalyst support engineering has far-reaching research significance. This study is groundbreaking as it provides a detailed explanation at the electronic level for the physical mechanism of Jahn-Teller distortion in Cu2+. It is useful to investigate defect-induced light absorption and energy band engineering at the microscopic level.

Optical Properties of Gd2O3 with Silver doped Zinc Borate Glasses

Glasses with chemical composition ZnO-B2O3-Gd2O3-Ag2O were prepared using melt quenching method. The synthesized glass was characterized using X-ray diffraction method. The densities of these glasses were measured using the Archimedes method, and the corresponding molar volumes were calculated using the corresponding formula. Absorption spectra were recorded using a UV-visible spectrometer. The energy bandgap was investigated using the Tauc’s diagram. The variation of band gap energy in relation to Gd2O3 concentration has been discussed. Study the structure and functional groups of the prepared samples were studied using FTIR spectra. Emission and excitation spectra were recorded using a luminescence spectrometer. Photoluminescence spectra provides stable blue light emission in rich in Gd2+ ions glass, Color coordination has also been decided using CIE chromaticity diagram and showing that blue emission was observed in all samples with slightly different positions.

Highly sensitive sensing of CO and HF gases by monolayer CuCl.

Using a first-principles approach, the adsorption characteristics of CO and HF on a CuCl monolayer (ML) are studied with Grimme-scheme DFT-D2 for accurate description of the long-range (van der Waals) interactions. According to our study, CO gas molecules undergo chemisorption and HF gas molecules show a physisorption phenomenon on the CuCl monolayer. The adsorption energy for CO is -1.80 eV, which is quite a large negative value compared to that on other previously studied substrates, like InN (-0.223 eV), phosphorene (0.325 eV), Janus Te2Se (-0.171 eV), graphene (P-graphene, -0.12 eV, B-graphene, -0.14 eV, N-graphene, -0.1 eV) and monolayer ZnS (-0.96 eV), as well as pristine hBN (0.21 eV) and Ti-doped hBN (1.66 eV). Meanwhile, for HF, the adsorption energy value is -0.31 eV (greater than that of Ti-doped hBN, 0.27 eV). For CO, the large value of the diffusion energy barrier (DEB = 1.26 eV) during its movement between two optimal sites indicates that clustering can be prevented if many molecules of CO are adsorbed on the CuCl ML. For HF, the value of the DEB (0.082 eV) implies that the adsorption phenomenon may happen quite easily upon the CuCl ML. The transfer of charge according to Bader charge analysis and the variation in the work function depend only on the properties of the elements involved, i.e., their nature, rather than the local binding environment. The work function and band-gap energy variation of the CuCl ML (before and after adsorption) show high sensitivity and selectivity of CO and HF binding with the CuCl monolayer. HF molecules give a more rapid recovery time of 1.09 × 10-7 s compared to that of CO molecules at a room temperature (RT) of 300 K, which indicates that the necessary adsorption and reusability of the CuCl ML for HF can be accomplished effectively at RT. Significant changes in the conductivity are observed due to the CO adsorption at various temperatures, as compared to adsorption of HF, which suggests the possibility of a modification in the conductivity of the CuCl ML.

CuS/Cellulose acetate nanofiber composite: A study on adsorption and photocatalytic activity for water remediation

This paper addresses the pressing concern of environmental deterioration by investigating innovative solutions for tackling water pollution in aquatic ecosystems. Various hazardous pollutants, such as dyes, pharmaceuticals, heavy metals, and pesticides, pose significant threats to both the environment and human health. To combat these issues, in this work we explored the synthesis of composite nanofibers using copper sulfide (CuS) nanoparticles and cellulose acetate (AC) polymer matrix through a gas-liquid sulfurization process. The resulting nanocomposites were used to fabricate nanofibers by the electrospinning technique. The morphological analyses revealed a transition from ribbon-like structures to cylindrical forms as nanoparticle concentration was increased. Chemical analysis confirmed the presence of CuS nanoparticles within the composite nanofibers. XRD studies indicated a covellite crystal structure of the CuS nanoparticles. TGA analysis revealed a coordination complex formation between nanoparticles and dimethylformamide. Optical properties showed variations in band gap energies, from 1.76 to 1.9 eV, as nanoparticle concentration changed. Photocatalysis studies demonstrated that the composite nanofibers exhibited enhanced adsorption and degradation of methylene blue dye under solar irradiation. Overall, this study contributes to understanding the potential application of CuS/AC composite nanofibers for environmental remediation.

Structural, dielectric and electronic properties of Ba1-xSrxZr0.3Ti0.7O3 (x = 0.0, 0.1, 0.2, 0.24, 0.27, 0.3) ceramics: Combined experimental and ab-initio study

Ba1-xSrxZr0.3Ti0.7O3 (x = 0.0, 0.1, 0.2, 0.24, 0.27 and 0.3) materials were synthesized using conventional solid state reaction route. Structural properties were investigated using X-ray diffraction analysis. All the samples reveal single phase structure. The dielectric properties of all the samples were investigated at different temperatures of 100 K to 300 K, and at different frequencies of 1 kHz to 500 kHz. The diffusivity rises with increase in Sr divalent cation concentration. It is seemed that with increase in Sr2+ concentration the transition temperature reduces for all compositions. This may because of the introduction of Sr2+ by replacing Ba2+ since Sr+2 has smaller ionic radius than Ba+2. Moreover, the dielectric constant maxima for Ba1-xSrxTi0.7Zr0.3O3 increases up to x = 0.24 and then further increment in Sr content up to x = 0.3, the maxima of dielectric constant shows decrease. Moreover, charge conduction mechanism and optical response of Ba1-xSrxZe0.3Ti0.7O3 (x = 0.0, 0.1, 0.2, 0.3) has been calculated theoretically by using CASTEP. Herein, the calculated density of states (DOS) and three dimensional integrated charge density reveal that concentration of Sr in Ba1-xSrxZe0.3Ti0.7O3 (x = 0.1, 0.2, 0.3) causes variation in energy band gap. As regards optical response of Ba1-xSrxTi0.7Zr0.3O3, with x = 0.3 the high frequency absorption decreases to minimal value in accordance to experimental findings.

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.

Effect of precursors on ZnO nanoparticles to enhance the level-III ridge details of LFPs and anti-counterfeiting applications

Comparative analysis for the combustion-based synthesis of zinc oxide nanoparticles (NPs) utilizing various precursors of zinc was reported. l-ascorbic acid extraction was used as a fuel for the combustion process. The sizes, morphologies, structural details and purity of samples were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometry (XRD). XRD pattern matches with the standard JCPDS card of ZnO with good crystallite size. The average crystallite size of the NPs was confirmed the nano-regime. Variations in morphological structures and the energy band gap variation with the change in precursors was reported. Using a powder-dusting technique, on separate surfaces, level-III features of the fingerprints produced by these NPs without any background noise. The suggested powder composition was easy to make and effective for producing latent finger prints on a variety of dry and wet surfaces. In the area of counterfeit prevention, the fluorescent ink has several potential applications. Invisible security ink was developed for anti-counterfeiting applications based on the UV fluorescence feature of ZnO NPs. The fluorescent invisible security ink for screen printing was evaluated and proved to be stable on a variety of microporous papers. The new strategy adopted here lowers the cost of ink by using rare earth free ZnO NPs.

Optical characteristics of Mg-based (Mg/Co & Mg/Mn) TF for hydrogen storage applications

This study has proposed and analyzed the role of hydrogen gas on optical characteristics of Mg-based Mg/Co and Mg/Mn bilayer structures. Thermal evaporation at a pressure of 10-5 torr was used to prepare these Thin Films (TF), which were then effectively deposited onto glass substrates. To obtain homogenous structure, prepared TF were vacuum annealed at 573 K. Hydrogen gas was injected into the chamber at various pressures (10, 20 & 30 psi) to observe how hydrogenation influenced TF. Using a Hitachi-330 spectrophotometer, the UV–Vis transmission spectra were recorded in visible range of wavelength (300–800 nm). TF' optical transmission was reduced, and it was revealed that the energy band gap increased as hydrogen pressure increased. It implies that hydrogen absorption in TF can be used to tailor the energy band gap. An optical micrograph of a hydrogenated TF that has been annealed reveals a dark black state. The variation in energy band gap due to hydrogen and increasing value of the film resistance are evidence for the phase shifts caused on by hydrogenation from metal to semiconductor.

Defect-Induced Phase Transformations in CuO Thin Films by Ag Ion Implantation and Their Gas-Sensing Applications

The present study is aimed to modify the structural, optical, and morphological properties of CuO thin films with Ag ion implantation toward their potential applications. Fabrication of thin films of CuO was carried out using a thermal evaporation technique on silicon (Si) substrate; post implantation was done with 30 keV Ag ions with varying fluences from 1 × 1014 to 1 × 1016 ions/cm2. The pristine and implanted samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and diffused reflectance spectroscopy (DRS). SRIM simulation was also carried out to understand the range and other effects. XRD measurements confirmed the formation of the CuO phase for pristine samples, and with the increase in ion fluence, the chemical composition changed from pure CuO to Cu2O + CuO and then to Cu2O + Cu at higher ion fluences. These experimental results from Raman spectroscopy were also consistent with the XRD analysis, which also showed the presence of mixed phases of CuO, Cu2O, and Cu. Results from AFM showed that the value of average roughness increased due to more defects. DRS results revealed the variation in band-gap energy for pristine and implanted samples from 1.96 to 1.71 eV. Density functional theory (DFT) simulations confirmed that Ag ion implantation causes the reduction of CuO surface into Cu2O and Cu. We found that Ag ion implantation-induced defects lead to the mixed phases of CuO, Cu2O, and Cu, which can help in the selective sensing of ethanol and acetone, demonstrating this as a useful technique and having potential applications in energy conversions, and gas and biomolecule sensing.

Characterization of pristine bismuth manganite thin films deposited on glass substrates by spray pyrolysis technique

The multiferroic Bismuth Manganite (BiMnO3) material which has wide application in memory device. The effect of solute and annealing temperature on spray pyrolyzed pure phase BiMnO3 was studied in detail. The deposited thin films showed the polycrystalline nature with bismuth oxide and manganese oxide impurity phases. The salt considered for the manganese source has effect on obtaining bismuth manganite phase and the annealing temperature has effect on the crystalline nature of the film. The needle like surface morphology was noticed from the deposits. The variation of energy band gap noticed with used solutes and annealing temperature due to change in chemical reaction during deposition and crystallinity respectively. The least energy band gap of 1.81 eV was observed by optimizing the deposition parameters. The blue emission and different defect related peaks are observed in photoluminescence. This work helps in developing prominent material for optoelectronic application.

First principle study of electronic and optical properties of WS2(1-x)Se2x obtained by isoelectronic Se substitution on S-site of monolayer WS2

Two-dimensional semiconducting transition metal dichalcogenides have recently grabbed attention among the researchers, due to their extraordinary electrical, optical and thermal properties. Also, they have shown their suitability for application in digital electronics, photovoltaic cells, Thermoelectric generators and so on. Still, it is desired to precisely control the material properties to expand their scope of application and revamp the device performance. The substitutional doping technique is one of the widely explored processes, which is conventionally used to modulate the material properties. In the present work, the substitutional doping of selenium at the sulfur site within the WS2 sheet, is used indigenously to improve the electrical and optical response of the material. In doing so, electrical and optical properties of such doped materials are studied by employing density functional theory and linearized Boltzmann transport equation by considering the relaxation time approximation. The study has shown an almost linear variation of electronic band gap energy with the doping percentages. Also, the electron and hole mobility were found to be tailored due to the doping. Notably, hole mobility has shown a noticeable improvement at or near 60 percent of selenium doping. In the last section of the current work, the optical properties are extracted for the doped structures. The WS2 monolayer has shown the highest absorption peak near 3 eV. But for the doped materials, absorption peaks are relatively smaller and left shifted in the energy axis due to their low band gap energies.

CORRELATION BETWEEN ELECTRICAL AND OPTICAL PROPERTIES OF DOPED SILICON NANOCRYSTALS

We propose through this work a correlation method leading to a determination of a semi-empirical relationship between optical and electrical properties in terms of refractive index and dark conductivity of doped silicon nanocrystals based on experimental data published in literature. First, an analytical model relating the conductivity and bandgap of doped silicon nanocrystals was derived. Using an empirical expression relating the refractive index to the bandgap energy, we correlated the electrical and optical parameters of N-type nanocrystalline silicon with a semi-empirical expression. The semi-empirical relationship was found to account correctly for the experimental results and yield a reasonably good agreement in an interval of the bandgap energy variation of N-type silicon nanocrystal films. The values of the fitting parameters were calculated for the N-type silicon nanocrystal films having their bandgap energy between 1. 7 eV and 2.2 eV.

Effect of sulphate ions on the physical and optical properties of zinc phosphate glasses containing Sm3+ ions

Lithium based zinc-phosphate containing Sm2O3 glasses of the system (5-x) Li2SO4 − 20Li2O − 45P2O5 − 30ZnO - xSm2O3, (where x = 0, 0.1, 0.5, 1, 2 and 3 mol%) were prepared by melt quenching technique. The amorphous nature of the prepared glasses is ascertained by X-ray diffraction. The density and molar volume are found to vary non-linearly with Sm2O3 content. The addition of modifier oxides such as Li2O to P2O5 glass would break P-O-P bonds and resulting in the creation of non-bridging oxygen’s. The creation of non-bridging oxygen atoms makes the structure less rigid and would leads to the formation of weaker phosphate structural entities. This would lead to the formation of voids between the phosphate groups. The addition of alkali and samarium content in the phosphate glasses is accountable for the collective number of the non– bonded oxygens and this may cause a non-linear variation in the volume of the network structure which in turn lead to non-linear variation in the density. The optical spectrum consists of a characteristic Ultraviolet absorption bands of Sm3+ ions in the range 200–400 nm and other strong bands at 940 nm and 1100 nm which are considered to originate from the transitions of ground state to the different excited states. The optical band gap energies were determined from both ultraviolet band edges and Tauc’s plots. The band gap energy varies non-linearly with Sm2O3 content. The non-linear variation in density, molar volume and band gap energy discloses the intermediate-range structure composed of PO4and ZnO4tetrahedra and are discussed in view of the polymeric chain of phosphate network structure.

First-Principles Insight into a B4C3 Monolayer as a Promising Biosensor for Exhaled Breath Analysis.

Nanomaterial-based room temperature gas sensors are used as a screening tool for diagnosing various diseases through breath analysis. The stable planar structure of boron carbide (B4C3) is utilized as a base material for adsorption of human breath exhaled VOCs, namely formaldehyde, methanol, acetone, toluene along, with interfering gases of carbon dioxide and water. The adsorption energy, charge density, density of states, energy band gap variation, recovery time, sensitivity, and work function of adsorbed molecules on pristine B4C3 are analyzed by density functional theory. The computed adsorption energies of VOC are in the range of − 0.176 to − 0.238 eV, and a larger interaction distance validate the physisorption behavior of these VOCs biomarkers on pristine boron carbide monolayer. Minute changes are determined from the electronic band structure of all adsorbed systems conserving the semiconducting nature of the B4C3 monolayer. The band gap variation upon adsorption of VOCs and interfering gases is examined between 0.05 and 0.52%. The 13.63 × 10–9 s recovery time of methanol is slower among VOCs, and 0.556 × 10–9 s of carbon dioxide (CO2) is faster for desorption. The results reveal that boron carbide can be utilized as a biosensor at room temperature for the analysis of exhaled VOCs from human breath.Graphical abstract

Interrelation of micro-strain, energy band gap and PL intensity in Ce doped ZnS quantum structures

Three-dimensional (3-D) quantum structures (QSs) of ZnS and Cerium (Ce) doped ZnS were synthesized via chemically affordable sol-gel process. Influence of Ce doping and thus induced micro-strain on the structural, morphological, and optical characteristics was explored. XRD confirmed the formation of single-phase zinc blende ZnS. Estimated average crystal size corresponding to highest intensity XRD peak (111) varied within 1.65–4.65 nm which are comparable with Bohr radius of ZnS. Due to the size mismatch between Ce and Zn, micro-strain and vacancies were found to be developed in host matrix of ZnS. Thermodynamic calculations validated an expansion and contraction in lattice parameter due to Ce doping. FTIR spectra confirmed the presence of different functional groups related to Zn and S. Photoluminescence (PL) emissions observed at 420, 461, 509 and 560 nm are related to the defect states such as interstitial sulfur, zinc interstitial, sulfur vacancies and zinc vacancies respectively. Rise of another emission peak in doped ZnS at 600 nm was due to 5d → 4f energy level transitions in Ce3+ ions. Evolved micro-strain profile, PL intensity and energy band gap variation were analogous to each other with respect to doping concentration. Microscopic images confirmed the structural transformation to cuboidal shaped ZnS QSs with increase in doping concentration. EDX and XPS supported the elemental analysis along with oxidation states of the available elements such as Zn, S and Ce.

Effect of Ni2+ substitution on magnetic, optical and electrical properties of SrFe2O4

Citrate gel combustion method is used for the synthesis of Ni2+ substituted strontium ferrite Sr1-xNixFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8). The characterization of synthesized material is done by different techniques. Fourier transform Infra-red (FT-IR) spectra revealed the inverse spinel structure and showed slight shift in spectrum. X-ray diffraction (XRD) patterns demonstrated the orthorhombic phase of spinel formation with trace of secondary phase impurity of SrCO3. Scanning electron microscopy (SEM) images showed agglomeration of particles. The effect of Ni2+ substitution in SrFe2O4 on structural, magnetic, optical and direct current (DC) electrical resistivity properties are investigated. Room temperature vibrating sample magnetometer (VSM) studies indicated increase in trend of saturation magnetization (Ms) and remanence magnetization (Mr) with increase in content of Ni2+ ion. The squareness ratio (SQR) Mr/Ms for SrFe2O4 is found to be 0.5752, while for remaining samples it is found to be less than 0.5 which demonstrated multi domain to single domain transition. Variation of band gap energy with Ni2+ substitution is reported with the help of ultra-violet diffuse reflectance spectra (UV-DRS). Temperature dependent DC electrical resistivity by two probe method measurement obeyed Arrhenius equation and revealed the typical semiconducting behavior of the samples. The change in slope of line observed in resistivity due to ferrimagnetic to paramagnetic transition in all samples attributed strong exchange interaction between the outer and inner electrons. Activation energy (Ea) for ferri and paramagnetic region is calculated. For ferrimagnetic region the Ea is found to increase with increasing Ni2+ content while, in paramagnetic region for Ni2+ substituted samples the Ea is found to be greater than 0.2 eV which inferred the hopping motion of small polarons are responsible for conductivity. The complex impedance spectra revealed the information about conduction mechanism.

The gas-sensing mechanism of Pt3 cluster doped SnS2 monolayer for SF6 decomposition: A DFT study

In this study, Pt3-cluster-doped SnS2 was first proposed as the adsorption and sensing materials of typical SF6 decomposed gases (SO2, SOF2, SO2F2 and H2S). Based the density functional theory, the possible application of Pt3-SnS2 as gas sensor or absorbents for the SF6 decomposed gas is discussed through the analysis of the density of states, adsorption energy, charge transfer and the frontier molecular orbital. These results illustrate that the doping of Pt metal clusters can greatly improve the response of pure SnS2 monolayer to the characteristic decomposition gas of sulfur hexafluoride (SF6). The excessive high adsorption energy indicates a strong chemical interaction of the Pt3-SnS2 monolayer with SO2 (−2.800 eV) and H2S (−3.346 eV) molecules, which suggests that Pt3-SnS2 is a potential ideal candidate for gas adsorbent. Moreover, the large variation of band gap and appropriate adsorption energy show that Pt3-SnS2 has the promising to be a candidate gas sensor material for the SOF2 (−1.060 eV), and SO2F2 (−0.904 eV). This study also provides guidance for further study of the SnS2 monolayer doped by transition metal clusters.