Indirect Energy Band Gap Research Articles

Rare earth (Dy3+-ion) induced near white light emission in sodium-zinc-borate glasses

In this report, we present a detailed investigation of the structural, spectroscopic and luminescence features of Dy3+ ion incorporated sodium-zinc-borate glasses with glass composition, 20Na2O – 10ZnO - (70-x) B2O3 – x (Dy2O3), where, x = 0.1, 0.5, 1.0, and 2.0 mol % glasses prepared via traditional melt-quenching method. Various characterization techniques such as, DSC, UV–vis-NIR, Luminescence and time decay were used to thoroughly examine the prepared glasses. In order to evaluate the impact of Dy3+ incorporation, various physical parameters were estimated. The incorporation of Dy3+ into the host causes significant changes in various physical parameters, resulting in the creation of NBO's and the non-metallic nature of the glasses. Surprisingly, DSC profiles up to 1 mol% Dy3+ revealed two glass transition temperatures. Furthermore, optical absorption spectra disclose the presence of an intense peak that corresponds to a hyperfine transition, as well as other host-dependent transitions. To determine the radiative parameters and efficiency, Judd-Ofelt theoretical calculations were used. After performing a JO analysis, it was discovered that the JO parameters are in the following order; Ω2 > Ω4 > Ω6. The estimated JO parameters were compared to the JO parameters of Dy3+-ions doped with different hosts reported in the literature. Tauc's method was also used to determine the indirect energy band gap of the glasses. Excitation wavelengths ranging from 349 nm to 452 nm have been used in emission studies. When excited with a wavelength of 349 nm, the glass containing 0.5 mol percent Dy3+ showed intense emission, which corresponds to white light. Overall, Dy3+ incorporated sodium-zinc-borate glasses may be potential candidates for while light emission applications, according to the findings.

An imidazole ligated zinc(II) transition metal complex as a “turn-off” fluorescent sensor for the selective and sensitive detection of brilliant blue FCF

Synthetic colors play a significant role in the food industry and processing sector whereas food safety incidents caused by the illegal addition of colors have gotten more successive. In this study, a highly selective novel zinc incorporated imidazole based metal complex (ZL1) was developed from ligand 2-[(1H-imidazole-2-ylmethylene)-amino]-4-methyl-phenol (L1) in 1:2 (metal:ligand) molar ratio. It was characterized quantitatively using standard spectroscopic techniques. The vital fluorescence properties such as stokes shift, lifetime and quantum yield values were evaluated for the rapid and non-destructive detection of brilliant blue FCF (BB) by the inner filter effect where the emission spectra of ZL1 were overlapped with the absorption spectra of BB. In the presence of BB, a bright yellow colored solution of ZL1 with an emission at 570 nm was quenched with a peak shift observed at 540 nm. It also illustrated the lower detection limit of 2.67 × 10-8 M in the linear range of 1 × 10-6 M to 5 × 10-6 M under optimal conditions. To attain more idea about the properties of a compound, indirect optical band gap energies (Eg) were found using a tauc plot. Encouragingly, the non-toxic property of ZL1 towards myogenic cell line H9c2 was done using a cytotoxicity study and showed excellent photostability. The theoretical approach for geometry optimization, vibrational band assignments, frontier molecular orbitals, and absorption spectrum of the ZL1 were investigated by DFT/B3LYP/6–311 + G(d,p) methods. The theoretical ultraviolet and infrared spectrum of the complex was obtained in vacuum state. Also, the elucidation of the quenching mechanism of fluorescence sensing was proposed with the help of cyclic voltammetry studies. In addition, the practical application of ZL1 was applied to access the BB in food samples showing its potential in food quality control in the future.

(Invited) Light-Emitting Devices Based on Defect-Enhanced Group-IV Nanostructures

Combining Si-based integrated optics with Si-based microelectronics is crucial for next-generation applications ranging from data transfer on short distances to sensing and, potentially, to quantum cryptography at telecom wavelengths. However, Si's intrinsically poor light-emitting properties, i.e., its indirect energy bandgap, inhibit a straightforward implementation of telecom devices such as light-emitting diodes and lasers operating at room temperature.We argue that adding Ge heterostructures, nanostructures, intentionally-induced defects, and defects within nanostructures to the Si platform can be a viable way to overcome the limitations of Si as a light-emitting material [1]. Significant progress for light-emission from group-IV nanostructures can be achieved by intentionally incorporating extended point defects inside the QDs upon in-situ low-energy ion implantation [2],[3]. This work discusses the superior light-emission properties from such defect-enhanced quantum dots (DEQDs) and our present understanding of their structural formation and light-emission mechanisms [4], indicating that optically direct recombination paths play a role in room-temperature light emission.As compared to other group-IV systems with pronounced optical emission, contact doping and hence fabrication of electrically driven devices is relatively straightforward in this nanosystem since DEQDs are embedded into a defect-free Si matrix [5],[6]. We show that useful electrically driven devices, such as light-emitting diodes (LEDs), can be fabricated employing optically active DEQD material. These LEDs exhibit exceptional temperature stability of their light-emission properties even up to 100°C, unprecedented for purely group-IV-based optoelectronic devices [7]. We discuss the role of vital parameters, such as the temperature stability of the structural properties [8],[9], the scalability of the light-emission with the nanostructure density [6], and passivation schemes to further improve the optical properties [8],[10]. Additionally, we elaborate on schemes for advanced layouts for electrically-pumped devices.References[1 ] M. Brehm, Silicon Photonics IV, 67-103, Silicon Photonics IV: Innovative Frontiers, edited by David J. Lockwood and Lorenzo Pavesi, Springer series Topics in Applied Physics (2021).[2] M. Grydlik et al., ACS Photonics 3, 298–303 (2016).[3] M. Grydlik et al., Nano Lett. 16, 6802–6807 (2016).[4] F. Murphy-Armando et al., Phys. Rev. B 103, 085310 (2021).[5] M. Brehm and M. Grydlik, Nanotechnology 28, 392001 (2017).[6] H. Groiss et al., Semicond. Sci. Technol. 32, 02LT01 (2017).[7] P. Rauter et al., ACS Photonics 5, 431-438 (2018).[8] L. Spindlberger et al., Crystals 10, 351 (2020).[9] L. Spindlberger et al., Physica Status Solidi (a) 216, 1900307 (2019).[10] L. Spindlberger et al., Appl. Phys. Lett. 118, 083104 (2021).

Structural optimization of indium oxide thin film for gamma dosimetry applications

Structural optimization of Indium oxide (INO) thin films was carried out with different deposition parameters for gamma sensing applications. Indium oxide films had been deposited on glass substrates by spray pyrolysis technique for three different concentrations of precursor solution and two different substrate temperatures. XRD spectra confirm the polycrystallinity and cubic structure of INO with a dependency of preferred orientation on both substrate temperature and thickness of the thin film. Raman analysis was done to study the structural information and to obtain the phonon modes present in the thin films. Phonon modes corresponding to cubic In2O3 were detected in Raman spectra. The morphological study revealed the change of grain shape with the preferred orientation. EDAX spectra validate the presence of Indium and Oxygen in the film. 0.1 M sample deposited at 4500C showed higher transmittance of about 75%. Direct and indirect bandgap energy were estimated for which it increased with an increment in substrate temperature and also decreased with an increment in molar concentration. Urbach energy shows an inverse relation with bandgap energy. PL spectra exhibit blue emissions implying the presence of oxygen vacancies or lattice defects along with Near band edge (NBE) emission. The presence of In and O was quantified, and chemical states were identified using XPS measurements. Electrical measurements ensure the good conductivity of prepared films. Thermoluminescence studies were carried out to confirm the suitability of the prepared film for dosimetry applications.

Pyrazinamide photodegradation on NiWO4-palygorskite nanocomposites under polychromatic irradiation.

In this work, antibiotic pyrazinamide (PZA) photodegradation on palygorskite (Pal), NiWO4 crystals, and NiWO4-Pal (2, 6, and 10%) nanocomposites was evaluated under polychromatic irradiation. In the characterization of the samples, XRD patterns displayed good crystallinity for NiWO4 crystals and nanocomposites. In addition, the diffractograms were used in the Rietveld refinement for phase indexing, revealing a wolframite-type monoclinic structure with the space group P2/c. The active vibrational modes related to the characteristic groups of the samples were identified using Raman and FTIR spectroscopy. Photoluminescence (PL) spectra revealed that NiWO4 and NiWO4-Pal (2%) nanocomposite have the highest electron-hole pair recombination rate, and the contribution of the green component in the NiWO4-Pal (2%) nanocomposite indicates a greater contribution of deep energy levels to the PL profile. DRS in the UV-visible region indicated that NiWO4 crystals have indirect band-gap energy (Egap) 2.64 eV; NiWO4-Pal (2, 6, and 10%) nanocomposites have 2.62, 2.58, and 2.59 eV, respectively; and Pal has 2.83 eV. The catalytic tests showed that the NiWO4-Pal (2%) nanocomposite samples, under polychromatic radiation, exhibit greater efficiency in photodegradation at 110 min, with yield of 98.5%. The ROS tests indicated that the studied reactive species play a similar role in PZA photodegradation.

Tailoring the optical characteristics and band-gap of BG doped PMMA/FTO nanocomposite films for laser power attenuation: New approach

Herein a good adherent film of PMMA doped with the various ratio of BG-dye deposited on optically flat FTO-substrates by using a well-controlled spin coating process. The average crystallite size and microstrain were determined by X-ray diffraction pattern analysis and were found to be 21.7219 nm and 0.0016, respectively, with a significant change with the amount of BG-dye doping in the matrix of PMMA film. Both linear and nonlinear optical characteristics, as well as their related parameters, were measured using a UV–Vis–NIR spectrophotometer. As a result of doping BG-dye molecules into the host PMMA matrix system, optical absorption studies revealed significant changes in optical characteristics. BG-dye doped PMMA film revealed impressive absorption bands in the range of 350–750 nm, depending on the degree of doping of BG-dye into the PMMA film. Another distinguished property is the attenuation of the complete absorption in the range of 552–688 nm and observed as a cut-off-absorbance. The point of the art of this contribution is the various applications for optical limitation systems like Cut-off filters and other related optical devices due to the remarkable optical features. The BG-dye doping influenced all optical metrics, including the absorption band, absorption edge, and direct and/or indirect energy band gap. The direct energy gap's first region is in the range of 1.77–1.97 eV, whereas the second is in the range of 2.68–2.82 eV, and the third is in the range of 3.67–4.09 eV. The indirectly allowed transitions are divided into two regions, the first of which is in the 1.74–1.82 eV range and the second of which is in the 3.69–3.98 eV range. The appearance of extra energy levels is confirmed by fluctuations in the optical band gap, which are aided by the influence of dopant concentration of BG-dye dopant wt.%. The ratio of BG-dye into the PMMA film is promising for the optical respective of the green light for the cut-off filter as well as optoelectronic device applications.

DFT study of structural, mechanical, thermodynamic, electronic, and thermoelectric properties of new PdTiZ (Z = Ge and Pb) half Heusler compounds

AbstractA first principle investigation of structural, mechanical, thermodynamical, electronic, and thermoelectric properties of PdTiZ (Z = Ge and Pb) were carried out using the plane‐wave pseudopotential (PP‐PW) method. The exchange‐correlation between the electrons was considered with the generalized gradient approximation of Perdew‐Burke‐Ernzerhof (PBE‐GGA). The energy band structure of the sample materials shows that it is a semiconductor with indirect energy band gaps of 0.66 eV and 0.387 eV in PdTiGe and PdTiPb, respectively, with the density of states being mainly dominated by the p states of Z and d states of Ti atom in the vicinity of the Fermi energy level. The sample compounds were found to be mechanically and dynamically stable in their non‐magnetic cubic phase. PdTiGe was found to be harder and stiffer than PdTiPb. The thermodynamic study revealed that pressure has a negative effect on heat capacity, whereas Debye temperature increases with enhanced pressure in both the sample compounds. The thermoelectric properties of the sample compounds predicted that p‐type nature of the sample compounds possess better thermoelectric performance. The room temperature Seebeck coefficient (S) values were found to be 98.73 μV/K and 94.82 μV/K for PdTiGe and PdTiPb, respectively, whereas S values of 245.73 μV/K and 218.77 μV/K at 1200 K at n = 1021 cm−3. The lowest values of lattice thermal conductivity () of 2.28 W/m‐K and .98 W/m‐K were observed for PdTiGe and PdTiPb, respectively. The optimum dimensionless figure of merits of .66 (1200 K) and .64 (1000 K) were found for p‐type PdTiGe and PdTiPb, respectively, at optimum carrier concentration.

Effect of N doping on the Optical and Electrical properties of Thermal Spray pyrolysed ZnO Thin Films

Nitrogen doped ZnO (ZnO:N), thin films have been deposited on glass substrate at the temperature of 350ºC by low cost homemade thermal spray pyrolysis (TSP) technique at a normal environmental conditions. In this study the average reflectance, transmittance and absorbance were measured (20%), (35%), and (45%), respectively. Absorption coefficient is 3.5x104cm-1 for N doped ZnO. Direct bandgap energy varies from 3.08-2.99eV and indirect band gap energy varies from 2.86-2.67eV for N doped ZnO. XRD analysis shows the (002) plane is present of samples and the average grain size decrease with increasing N concentration. Surface morphology of N doped ZnO films is studied by Scanning Electron Microscopy (SEM). It is seen that hexagonal crystal grains few voids are present for N doped ZnO samples. The surface exhibits more or less uniform surface morphology with some clusters on the whole surface. Hall Effect study confirms that Nitrogen doped ZnO (ZnO:N), thin films using Vander pauws method were made at room temperature at a constant field of 9.75 KG. Experimentally (1, 2, 3, and 4) % N doped ZnO thin films have shown in negative Hall Constant (RH). Which exhibited n-type characteristics. Hall Constant (RH), and Hall concentration (n), increases with increasing N doping concentration. Initially Hall mobility (μH), increases linearly for (1-2) % N doping concentration then it decreases for the rest of the doping concentration. We also found that the resistivity (ρ) decreases and the conductivity (s) increases with increasing N doping concentration which exhibits the semiconducting nature.

Electronic, Optical, and Elastic Properties of CaFI Monolayer and Acoustic Phonon Dispersion at Hypersonic Frequencies Using Density Functional Theory and beyond with Random Phase Approximation and Bethe-Salpeter Equation.

The extraordinary properties of graphene have motivated us to investigate a novel 2D compound. In this framework, we study the structural, vibrational, electronic, optical, and elastic properties of a new two-dimensional CaFI monolayer, using DFT, GW, RPA, and BSE methodologies. The phonon dispersion curve of the CaFI monolayer exhibited no unstable phonon modes, confirming that this 2D sheet is dynamically stable. Our GW calculations show that the indirect bandgap energy value of CaFI is 6.52 eV. Interestingly, the bandgap rapidly decreased by improving the electric field value. Our BSE computations indicate that this monolayer becomes translucent when the incident light frequency exceeds the plasma frequency (6.50 eV). Also, we have computed the second and third elastic constants of CaFI by combining the DFT and RPA approaches with the homogeneous deformation method. Additionally, the longitudinal acoustic phonon dispersion of CaFI was studied. We have determined that the longitudinal acoustic wave velocity in our sheet is higher than the LA wave velocity of germanium measured using Brillouin or ultrasonic techniques.

Modifications of optical, structural, chemical and morphological properties of molybdenum disulfide (MoS2) sputtered thin films under high dose gamma radiation

Molybdenum disulfide (MoS2) is considered to be a promising member of Transition metal dichalcogenides (TMDCs) displays significant physical and chemical peculiarities that make it promising candidate for extensive applications in nano and micro optoelectronic device applications, energy harvesting and light and gas detection devices. In the present work, we illustrated the influence of gamma ray irradiation on optical, morphological, structural and electronic peculiarities of 2D MoS2 thin films. 2D MoS2 thin films were grown by DC sputtering technique. The synthesized thin films samples were exposed to gamma radiation with 1500 kGy dose. There are significant structural and morphological alterations occur in thin films of MoS2 after exposure to gamma irradiation. From the absorption spectra Urbach energy, indirect optical band gap energy, absorption edge, and extinction coefficient were calculated. Alterations that occur in optical, structural, morphological and electronic parameters after the exposure of gamma irradiation have been corresponding with radiation instigated compositional and structural defects. The peculiarities of virgin and gamma exposed MoS2 thin films with 1500 kGy gamma-ray dose from Co-60 source were studied by UV spectrophotometer, X-ray diffraction (XRD), Rutherford Backscattering Spectroscopy (RBS), X-Ray photoelectron spectroscopy (XPS), Photoluminescence (PL) spectroscopy, Atomic Force Microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR).

DC conductivity, optical properties and Judd-Ofelt evaluation of 20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag mixed ionic-electronic glasses

20Li2O-xBi2O3-(78-x)TeO2-1Er2O3-1Ag glass system was prepared by melt quenching, and its DC conductivity, optical and spectroscopic properties were investigated. Its amorphous nature was confirmed by x-ray diffraction analysis. Results showed that DC conductivity σdc initially increased at x < 7 mol% and then decreased to a minimum at x = 11 mol% Bi2O3. UV–vis–NIR absorption spectra indicated six transition bands centered at 1496, 979, 799, 653, 544, and 521 nm corresponding to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 4S3/2, and 2H11/2 Er3+ transitions, respectively. Analysis on optical absorption edge by Tauc’s plot revealed maximum in direct Eoptd(3.609 eV) and indirect optical energy bandgap Eopti(3.259 eV) at x = 11 mol%. Judd–Ofelt intensity parameter Ω2was calculated from optical absorption data to describe the intensity of electron transitions within the 4 f shells of Er3+ ions in the glasses. A minimum Ω2 was obtained at x = 11 mol%. The minimum values of σdc and Ω2 at x = 11 mol% are related to the presence of high bridging oxygen in the mixed ionic-electronic region that influences the symmetry of surrounding Er3+ ions.

Opto-electronic, thermodynamic and charge carriers transport properties of Ta2FeNiSn2 and Nb2FeNiSn2 double half-Heusler alloys

A computational research study of the structural, electronic, and optical characteristics of double half-Heusler alloys Ta2FeNiSn2 and Nb2FeNiSn2 is presented by performing ab initio calculations. The density functional theory framework employs the full-potential linearized augmented plane wave method to solve Kohn–Sham equation as implemented in the Wien2k code. The exchange-correlation potential is processed by using the local density approximation and the generalized gradient approximation–Perdew, Burke, and Ernzerhof approximations to calculate the total energy and other physical properties. The obtained results showed that both alloys possess high cohesive energies, where Nb2FeNiSn2 (7.213 eV atom−1) is more consistent than Ta2FeNiSn2 (6.249 eV atom−1), these remarkable results support the structural stability for both alloys. Also, the thermodynamic stability of both compounds was confirmed through calculating the formation energy as the obtained results were close to the results obtained in as well as given the Open Quantum Materials Database. Electronic characteristics and chemical bonding are illustrated and discussed by computing the electron charge density, density of states, and band structure. Both alloys show semiconductor behavior with (∼0.5 eV) indirect energy bandgap. Also, we have calculated and analyzed the complex dielectric function, absorption coefficient, as well as, reflectivity spectra for both compounds. The semi local Boltzmann transport theory has been employed to treat temperature effect on thermoelectric properties of Ta2FeNiSn2 and Nb2FeNiSn2 compounds where the obtained results appears that both compounds have high coefficient at the normal condition, and they also have a good power factor at the Fermi level, which emphasizes that the thermoelectric efficiency of the two compounds is good and does not require doping. Also, depending on quasi-harmonic model was used for estimating the heat capacity, the lattice thermal conductivity, the thermal expansion and the Debye temperature under the pressure effects.

Optical characteristics of Eu3+ doped alumino borophosphate glass containing Al3+, Zn2+, Li2+, Sr2+ and Ba2+ ions

Europium (Eu3+) doped alumino borophosphate glass (ABP) containing Al3+, Zn2+, Li2+, Sr2+, and Ba2+ was formed by melt quenching method. FT-IR spectroscopy in the range 400–4000 cm−1 was used to describe the vibrational spectrum of the glass sample in order to define the various structural units. The optical absorption spectra of the glass revealed two weak bands due to 7F0 → 5L6 and 7F0 → 5D2 transition of Eu3+ in the UV–Vis range. The direct and indirect band-gap energies were calculated using Tauc’s plot. The refractive index (n) of the prepared glass medium was measured to be decreases as the wavelength increases, and it is varying from 2.25 to 2.07 over the visible region. A photoluminescence spectrum was obtained on non-irradiated glass sample, and the spectra analysis indicated emission peaks (at 593 nm, 615 nm, 653 nm and 703 nm) attributable to the presence of Eu3+. The photo-luminescence decay profile of 5D0 → 7F2 (614 nm) of Eu3+ was also performed to investigate the effect of excitation wavelengths. The luminescence colours of the prepared glass sample were entirely fall on red region (x = 0.648 and y = 0.336) with the dominant wavelength 610 nm in the CIE 1931 chromaticity map. Using CIE chromaticity coordinates, the excitation purity (Pe), colour purity (Pcolour), colorimetric purity (Pcol) and Colour correlated temperature (CCT) were also evaluated. After irradiating the glass with γ-rays at a dosage of 2 kGy, the structural changes caused by the reduction of Eu3+ into Eu2+ ion in the glass matrix was examined using the EPR spectrum as well as its thermo-luminescence characteristics was also studied in the temperature range 300–650 K. The glow curve could be well defined as a superposition of five peaks in the temperature range, and the peaks were explained by second-order kinetics.

Nano Ferrite Incorporated Poly (Vinyl Pyrrolidone (PVP) /Poly (Vinyl Alcohol (PVA) Blend: Preparation and Investigation of Structural, Morphological and Optical Properties

In this paper, the ferrite Cux Ni1-x FeO3 when (x=0.1) has been prepared by the co-precipitation method and examined through the XRD -diffraction and confirming the face center cubic spinel phase (FCC) which attributed to the ferrite and found that these materials was Nano-scale. Then with different content of ferrite nanoparticle (1, 3and 5 wt.%) additive to the (PVP/PVA) polymer matrix to synthesis (PVP/PVA/ferrite) nanocomposite by using casting method and study the Fourier transformation infrared (FTIR), (FE-SEM) and UV-Vis. Spectrophotometer. The FTIR confirming that there is no interactions between (PVP/PVA) polymer matrix and ferrite nanoparticles for all the sample prepared. From FESEM, the uniform morphology dispersed of ferrite inside the PVP/PVA blend with spherically shaped nanoparticles and the average grain size increased with increasing of concentration of ferrite. The absorption, absorption coefficient, transmittance and indirect energy band gap has been investigate.

Tailoring the linear and nonlinear optical characteristics of PVA/PVP polymeric blend using Co0.9Cu0.1S nanoparticles for optical and photonic applications

In this work, the linear and nonlinear optical characteristics of polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) polymeric blend have been tailored via Co0.9Cu0.1S nanoparticles (CCS NPs) incorporation. Plain PVA/PVP polymeric blend and different (0.1, 0.5, 1.0, 5.0 and 10.0) wt% of Co0.9Cu0.1S NPs polymeric nanocomposites (PNCs) were prepared by solution casting technique. The samples' surface morphology, structures’ variation, linear and nonlinear optical characteristics were explored using scanning electron microscopy, Fourier transform infrared (FT-IR) and UV–Vis–NIR spectrophotometry respectively. The FT-IR spectra analysis exposes the successful interaction and complexation of the CCS NPs with the host blend structure. The UV–Vis–NIR spectra analysis shows that the direct and indirect optical energy bandgap (Eg) of the host blend decreases from 5.15 eV to 4.94 eV–3.86 eV and 3.05 eV (10.0 wt% of CCS PNC) respectively. The Urbach energy of the plain blend increases from 0.41 eV to 1.18 eV (10.0 wt% of CCS PNC), which reveals the increase of the defects density due to CCS NPs incorporation. Also, the refractive index (n), dielectric constants (real εr and imaginary εi), optical conductivity, linear optical susceptibility (χ(1)), third-order nonlinear optical susceptibility (χ(3)) and nonlinear refractive index (n2) of the PVA/PVP blend are greatly enhanced due to CCS incorporation. The enhancement in the linear and nonlinear optical performance of the plain PVA/PVP blend via Co0.9Cu0.1S NPs incorporation nominates their applications in various optical and photonic devices.

Study of the preparation and properties of polyvinyl chloride/nitrocellulose polymer blends

AbstractIn this study, we prepared Polyvinyl chloride (PVC)/Nitrocellulose (NC) polymer blend by the solution casting technique. The structural properties and decreased interplanar spacing and crystalline nature of the PVC/NC blends were confirmed by an XRD technique. Basic chemical fingerprint regions of PVC/NC blends were confirmed by the Fourier transform IR method. Optical properties correlated with a decreased direct and indirect bandgap energy of PVC/NC were estimated using UV–visible spectra. They exhibited a shift in the absorption spectra towards the longer wavelength region due to process of charge transfer in the blend system. An increased microporous nature of the blends was demonstrated by SEM. Based on the Maxwell–Wagner model the dielectric constant and relative loss were found to have a maximum in the low frequency region which may be contributed by the polar nature of NC. We confirmed the hydrophilic nature of the PVC/NC blends due to the presence of hydroxyl groups by the goniometer technique. The thermophysical properties of the blends were measured by Lee's disc method. NC loading in the blend system increased the thermal conductivity from 0.12 to 0.18 W/(m.K). The Shore A softness test of the blends exhibited an 18% increase. We quantified structure, bandgap, morphology, and dielectric, surface and thermal properties as a function of NC blending. This new emerging blend may be a remedy for various engineering applications. © 2022 Society of Industrial Chemistry.

Low-energy consumption CuSCN-based ultra-low-ppb level ozone sensor, operating at room temperature

Ozone (O3) is one of the main indoor as well as environmental air pollutant, thus its detection is of great importance. As a result, plenty of materials have been tested as O3 gas sensing elements, over the last fifty years. In this work, the gas sensing performance of Copper (I) Thiocyanate (CuSCN) powder against O3, is presented. The structure of CuSCN powder was polycrystalline as revealed by the X-Ray Diffraction technique, while by employing optical absorption measurement the direct and indirect energy band gaps were calculated and found to be 3.72 eV and 3.48 eV, respectively. CuSCN powder was tested against O3 at different concentrations, showing a low detection limit of 15 ppb with a response of 1.06, at room temperature (25 °C), applying a very low input voltage of 0.1 V. Moreover, the corresponding response and recovery times were 137.4 s and 111 s, respectively, while it can successfully distinguish the different ozone concentrations in less than 20 s. The above-mentioned values make CuSCN a possible candidate material for ultra-low O3 concentration detection, at room temperature, with low-energy consumption.

Modulation of the optoelectronic properties of polyimide (Kapton-H) films by gamma irradiation for laser attenuation and flexible space structures

polyimide (PI or Kapton-H) has proven its potential in the field of optoelectronic, nuclear technology and space industry due to its excellent electric insulation, transparency and flexibility. The present study focuses the effect of γ-irradiation (0, 25, 50 and 100 Mrd) on the structural, optical, AC electrical conductivity and dielectric properties of PI film samples. In the results, the crystallite size was shown to be increased from 37.77 to 73.42 Å in the X-ray diffraction XRD study. Certain variations in assignment bands like (O–H) stretching and carbonyl (CO) symmetric stretching were observed in FTIR spectrum. A shift in the absorption edge is observed in the UV–vis spectroscopy to higher wavelengths and consequently a decrease in both direct and indirect band gap energy Egopt. The calculated values of the refractive index n is also increased upon γ-irradiation. The parameters of Wemple - DiDomenico (WDD) are calculated for pristine and γ-irradiated film samples. The dependence of the dissipation factor tanδ and optical conductivity σopt are studied as a function of the photon energy (hν) at different γ-doses. Moreover, the 3rd order non-linear susceptibility χ(3) and non-linear index of refraction n2 were also studied. Optical limiting measurements indicate that irradiation of PI samples with high γ-dose (100 Mrd) highly attenuated the laser beams (532 and 632.8 nm) which may be useful for use in optoelectronic laser limiters and filters. The AC electrical conductivity σac, dielectric constant ε′ and dielectric loss ε″ are also investigated in the range of frequency (100 Hz - 1 MHz). The values of σAC are enhanced by irradiation with γ-rays and the behaviors of the frequency exponent s indicates that the AC conduction in PI samples is governed by the correlated barrier hopping (CBH) mechanism.

Structural and optical properties of Nb2O5 films prepared by dual ion assisted deposition

Nb2O5 films were deposited with dual ion assisted deposition (DIAD) on silicon and corning 7980 quartz substrates, to investigate the effects of ion bombardment on the structural and optical properties of the films deposited in large coating chamber. The structure and chemical composition studies have been carried out using XRD, AFM, and XPS technologies. When the annealing temperature of the films is between 773 K and 873 K, the crystallization starts and some of the hexagonal phase peaks appear. The surface roughness increases along with the increase of the anode current. XPS spectra suggested that the films were all Nb2O5 films. The optical properties such as transmittance, refractive index and optical band gap energy have been estimated for Nb2O5 films. The refractive index and surface roughness of the films deposited with DIAD increased as the anode current of the ion source increased. The estimated indirect optical band gap energy was found to be somewhere between 3.42 eV and 3.43 eV for all the amorphous microstructure films. The dispersion energy parameters for different thin films are obtained by Lorentzian oscillator model as well as a single term Sellmeier oscillator model, in the normal dispersion range. The calculated values of the lattice dielectric constant, N/m* and ωp were found to increase with the rising anode current of the ion source.

Structure and emission properties of Nd3+ doped oxyfluorophosphate glasses

The characterization of the phosphate glass system doped by the active ion Neodymium (Nd3+) has been carried out using the Melt-Quenching method. The composition of the phosphate glass is made according to the chemical formula 64P205-20Li20-15X-1Nd203 (X = CaF2 and TeO2). Testing of the physical properties of glass is carried out using the Archimedes method. Testing the structural properties of glass using X-Ray Diffraction (XRD) and Fourier-transformed infrared (FTIR). Testing the optical properties of the glass using a UV-Vis spectrophotometer. XRD results show the glass made has an amorphous structure. The FTIR results show that absorption bands occur in the area of 710-772 cm−1, 871-890 cm−1, 990-1020 cm−1,1074-1157 cm−1, and 1240-1255 cm−1. The results of physical testing showed that the glass density increased and the molar volume decreased with the addition of CaF2 and TeO2 compounds. The highest absorption spectrum is at the transition 4I9/2 → 4G5/2 + 2G7/2 at a wavelength of 582 nm. The lowest direct and indirect bandgap energies are owned by PLTNd (use TeO2) glass, namely 3.30 eV and 3.85 eV. The highest emission spectra are in the two emission band transitions 4F3/2 → 4I11/2 and 4F3/2 → 4I13/2 with wavelengths of 1063 nm and 1334 nm. The highest emission spectrum is produced by PLCNd (use CaF2) glass.