Optical Absorption Studies Research Articles

Third order nonlinear optical absorption studies of Cr3+ doped PbWO4 nanostructures

We report the synthesis of Cr3+ doped PbWO4 nanoparticles with different concentration of Cr3+ through chemical method. The structural, morphological and optical characterization was studied through X-ray diffraction (XRD), Raman, UV–Visible spectra, Photoluminescence, X-ray photo electron spectroscopy (XPS) and Transmission electron Microscopy (HR-TEM). The XRD patterns revealed the tetragonal phase of stolzite and the peaks are highly crystalline structure with no segregation of Cr3+. UV–Vis absorption spectra reveal that the shift of absorption band edge towards higher wavelength upon doping of Cr3+ions. The average particle size of the nanostructure as revealed by the TEM image lies around 47 nm. Third order nonlinearity of Cr3+ doped PbWO4 nanoparticles were analysed by the standard Z-scan technique using 532 nm Nd: YAG laser. The observed nonlinear absorption (NLA) and nonlinear refraction (NLR) behavior is caused by thermal nonlinear effects due to localized heating. Experimental results have demonstrated that an increase in optical nonlinearity occurs with higher Cr3+ concentrations. Based on the observed nonlinearity it is suggested that the synthesized nanostructures could be used in various optical device applications.

Theoretical study of phase-controlled optical absorption, gain and group index in double-quantum-dot molecule

Theoretical study of phase-controlled optical absorption, gain and group index in double-quantum-dot molecule

Preparation and characterization of NiFe2O4 thin films for supercapacitor applications

ABSTRACT Mesoporous NiFe2O4 thin films have been prepared by chemical spray pyrolysis. The films are characterized by XRD, FESEM, EDAX, UV-Visible spectroscopy, DC electrical resistivity and electrochemical measurements. XRD result shows the cubic crystal structure with Fd-3 m (227) space group. Crystallite size is found in the range of 14–21 nm. FESEM showed crack free, well defined, uniform, mesoporous spherical grain-like surface morphology. EDAX study confirmed nearly stoichiometric deposition. The optical absorption studies confirmed direct allowed type transition with bandgap in the range of 2.09–2.29 eV. The films showed room temperature electrical resistivity of 2.34 × 104 Ωcm. The NiFe2O4 thin film spray deposited at 450°C exhibited a specific capacitance of 591 Fg−1 at a scan rate of 5 mV·s−1 from CV and specific capacitance of 632 Fg−1 at a current density of 0.5 Ag−1 from GCD. These findings recommend a constructive route towards the preparation of NiFe2O4 electrodes for high-performance electrochemical supercapacitors.

Optical and spectroscopic studies of Dy3+ ions doped Alumino tungsten borate glasses for w-LEDs applications

Alumino tungsten borate (AlWB) glasses doped with dysprosium ions are prepared by melt-quenching method and characterized using spectroscopic techniques such as optical absorption, photoluminescence (PL), and decay spectral studies to comprehend the importance in photonic devices, visible solid state lasers, and other applications. The amorphous nature of the as-prepared glasses were confirmed by XRD studies. The oscillator strengths are measured by using absorption spectra are intern used to evaluate the Judd-Ofelt (Ω2, Ω4, and Ω6) parameters. The PL spectra of the as-prepared glasses manifested three significant emission bands at 483 nm (blue), 575 nm (yellow) and 664 nm (red), and their corresponding electronic transitions are identified from 4F9/2 to 6H15/2,6H13/2 and 6H11/2 respectively. Various radiative parameters such as branch ratio (βR), transition probability (AR), radiative lifetime (τR), effective bandwidth (Δλp), and stimulated emission cross-section (σse) have been calculated. The CIE Chromaticity coordinates evaluated from the emission spectra of Dy-doped AlWB glasses reveal white light emission. Quantum efficiency values are evaluated by correlating the radiative lifetime with the experimental lifetime values measured from the PL decay spectral features. The data acquired from the as-prepared glasses allows us to contemplate that, the titled glasses are suitable to fabricate photonic devices. such as white LED’s and lasers.

Magnetic, dielectric and nonlinear optical absorption studies of nickel–zinc ferrite with Mg2+ doping

Magnetic, dielectric and nonlinear optical absorption studies of nickel–zinc ferrite with Mg2+ doping

EPR and optical absorption of VO2+ doped tetramethylammonium tetrachloro-zincate

• EPR studies of VO 2+ ions in TMZ single crystals are done at room temperature. • EPR analysis indicates four magnetically equivalent VO 2+ sites. • The vanadyl ion is found to take up substitutional position. The principal g and A are determined. • The optical absorption study is also carried out. • By correlating EPR and optical data the nature of bonding in the crystal is discussed. Electron paramagnetic resonance (EPR) studies of VO 2+ ions in [N(CH 3 ) 4 ] 2 ZnCI 4 (TMZ) single crystals are done at room temperature. Four magnetically equivalent VO 2+ sites are observed from EPR analysis. VO 2+ ion substitutes at Zn 2+ site. The principal g and A tensors are determined from angular variation of the EPR spectra. The optical absorption study is also performed. Using EPR and optical data the nature of bonding in the crystal is discussed.

Extremely low thermal conductivity in BaSb2Se4: Synthesis, characterization, and DFT studies

We report the synthesis of black-colored crystals and a polycrystalline phase of BaSb2Se4 by high-temperature reaction of elements at 1173 ​K and 973 ​K, respectively. The X-ray diffraction studies show that it crystallizes in the monoclinic P21/c space group, and the structure is composed of one-dimensional stripes of ∞1[Sb2Se4]2− that are separated by the Ba2+ cations. The optical absorption study reveals the semiconducting nature (Eg ​= ​1.3(1) eV) of the polycrystalline BaSb2Se4 sample. A thermal conductivity (κ) study shows a gradual decrease of the κ-value from ∼0.39 ​W/mK to ∼0.29 ​W/mK on heating the polycrystalline sample from 300 ​K to 773 ​K. The DFT study of the electronic structure of BaSb2Se4 shows that the bandgap is indirect with a magnitude in the range of ∼1.0–1.6 ​eV depending on the choice of XC functional. The COHP analysis has been performed to investigate the relative strengths of chemical bonding between pertinent atoms in the BaSb2Se4 structure.

Effects of bromination on anthryl-capped DPP-based semiconductor materials: Improved electrical characteristics of organic field-effect transistors

Diketopyrrolopyrrole (DPP), typically flanked with thiophene rings as π-spacers, has been regarded as a promising electron-acceptor unit for constructing donor-acceptor-donor (D-A-D) type small molecule organic semiconductors. Exploring the relationships between its conjugation structure and semiconducting property is of great importance for both molecular design and device fabrication of such DPP materials. Herein we describe the synthesis, self-assembly, and transistor characteristics of two novel N- and N′− 2-octyldodecylated DPP derivatives which were modified with native anthracene (An) and brominated anthracene (Br-An) at 5-, 5′-position of the flanked thiophenes, respectively, namely An-DPP and Br-An-DPP. Attributing to the self-assembly behaviors, they exhibit enormous difference in hole transport characteristics on interdigitated-electrode based organic field-effect transistor (OFET) devices even though there is only two atoms’ discrepancy in accordance with their molecular structures. The characterization of OFETs with interdigitated-electrodes based on Br-An-DPP reveals p-channel operation with highest field-effect mobility of 0.2 cm2·V−1·s−1, which is 107 times higher than that of An-DPP (4.8 × 10−8 cm2·V−1·s−1), and with a threshold voltage of - 2.5 V. X-ray diffraction, atomic force microscopy, scanning electron microscopy, and optical absorption studies reveal the presence of crystalline films caused by bromination on anthracene-modified alkylated DPP (i.e., Br-An-DPP), while An-DPP exhibits completely amorphous phase.

Structural, optical and electrical properties of anhydrous GdCl3 doped PEO polymer electrolyte films

GdCl3 doped PEO polymer electrolyte films were prepared using solution casting technique. XRD patterns, FTIR spectra and optical absorption studies confirm an amorphous nature and the formation of the polymer electrolyte films. The ionic conductivity increases with the GdCl3 content and the maximum value at room temperature is about 1.8310-2 S/cm for 20 mol% GdCl3doped PEO film. This value is more than two orders of magnitude larger than the ionic conductivity of NASICON type Gd-doped solid electrolytes and other polymer electrolytes. The results suggest that the Gd3+ doped PEO polymer electrolyte films are good candidates for future electrochemical devices.

Lead-doped cubic tin sulfide thin films for solar cell applications

Cubic tin sulfide (SnS), an earth-abundant and non-toxic material, is a promising candidate for thin film solar cells. Lead(Pb)-doped (0.0–11.6 atomic percent (at.%)) cubic SnS thin films were prepared via chemical bath deposition to achieve improved structural, optical, and electrical properties. X-ray diffraction studies revealed that the films were polycrystalline and exhibited cubic crystal structure, decreased crystallite size, and increased lattice parameter, strain, and dislocation density on increasing Pb content. Field emission scanning electron microscopy images revealed increased grain size up to 2.5 at.% and decreased grain size beyond 2.5 at.% of Pb content. Optical absorption studies showed a decrease in the band gap from 1.73 to 1.64 eV upon increasing the Pb dopant concentration. Hall measurements revealed an increase in the hole mobility up to 2.5 at.% and decreased mobility beyond the 2.5 at.% of Pb dopant concentration. In conclusion, the prepared cubic SnS films have potential for application in solar cells because of the demonstrated reduced optical band gap and enhanced hole mobility resulting from Pb-doping.

Optical transmission quality and radiation shielding performance of TeO2+ZnO+La2O3 ternary glass system

The high mass density that often characterize TeO2-based glasses makes them potentially useful in radiation shielding applications. In this paper, three ternary glass types defined by the chemical formula: (90−x)TeO2- xZnO-3La2O3 for x= 35 (TZL-A1), 15 (TZL-A2), and 5 mol% (TZL-A3) were considered for optical and gamma radiation absorption study. The reflection loss (RLoss), metallization criterion (M), optical transmission (TOpt.), optical dielectric constant (εoptical), and static dielectric constant (εSta.) were the optical parameters estimated for the glasses. Also, gamma radiation shielding ability of the glasses were assessed through computation of mass attenuation coefficient μm for energies 0.015 − 15 MeV using FLUKA simulations and XCOM computation. The RLoss is 0.105, 0.117 and 0.121 for TZL-A1 – TZL-A3, respectively while TOpt. is 0.809, 0.791 and 0.784 in the same order. The metallization criterion (M) is 0.513, 0.488 and 0.478 for TZL-A1, TZL-A2 and TZL-A3, respectively. The optical dielectric constant (εoptical) of TZL-A glasses is 2.849, 3.149 and 3.272 while the static dielectric constant (εSta.) is 3.849, 4.149 and 4.272 for TZL-A1, TZL-A2 and TZL-A3, respectively. Also, The value of μm varies between 0.03309 and 47.90855 cm2/g, 0.03332 and 46.67536 cm2/g, and 0.0333 – 43.12055 cm2/g for decreasing ZnO content accordingly. Computed value of the Zeff falls between 22.74 and 49.74 for TZL-A1, 23.34–51.07 for TZL-A2 and 23.61–51.59 for TZL-A3. Other computed photon shielding quantities shows that higher TeO2 content improves the shielding ability of the glasses. The present glasses showed superiority compared to some existing and popular shields such as ordinary concrete, commercial RS-253 and RS-360 glass shields. These glasses thus present better alternative materials which could be used in the implementation of an efficient photon collimator or biological shields in laboratories, industries, and medicine where gamma radiation are adopted for diverse applications.

In2S3-Gr and In2S3-CNT nanocomposite thin films as gas sensors

The present work reports the response of the In2S3-Gr and In2S3-CNT nanocomposite thin film sensors in the presence of interfering vapours such as alcohols like ethanol and methanol, ketone like acetone and inorganic gas like ammonia. We also investigated the variation in gas sensing properties with change in thickness of the nanocomposite thin films. The structural, topological, compositional and optical analysis of samples are performed using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and UV–Vis-NIR spectroscopy. The lattice strain, the crystallite size and dislocation density of as-deposited films were obtained from XRD analysis. The thickness of the films and surface roughness are determined by AFM analysis. The XPS depth profile affirms the presence of In, S, C and O in all the samples. From optical absorption studies, bandgap was determined and this is compared with thickness of the films. As the thickness increases, the bandgap energy of the In2S3-Gr/In2S3-CNT nanocomposite thin film decreases from 2.52/2.75 eV to 2.05/2.42 eV. The gas sensing parameters such as sensitivity, response time and recovery time of all the samples are determined. From the experiment, it is obtained that the triple dip In2S3-Gr nanocomposite thin film with the highest root mean square roughness and the lowest bandgap energy shows the highest gas sensing efficiency and have better sensitivity to ethanol vapour.

Synthesis and characterization of arrested precipitation assembled Cu2Se thin films

Nanostructured thin films of copper selenide (Cu2Se) deposited by arrested precipitation technique (APT) with controlled release of ions at suitable pH=10.5. The deposited Cu2Se films were characterized for optical, structural, and morphological properties. Optical absorption study indicates that the band gap energy (2.26 eV) of material and shows visible radiation absorption. XRD shoe that APT is a favorable technique for the synthesis of pure nanocrystalline Cu2Se thin films with monoclinic crystal structure. An electrochemical impedance spectroscopy analysis confirms the charge transfer resistance. X-ray photoelectron spectroscopy reveals stoichiometry at valance state of Cu2Se.

Synthesis and characterization of arrested precipitation assembled Cu2Se thin films

Nanostructured thin films of copper selenide (Cu2Se) deposited by arrested precipitation technique (APT) with controlled release of ions at suitable pH=10.5. The deposited Cu2Se films were characterized for optical, structural, and morphological properties. Optical absorption study indicates that the band gap energy (2.26 eV) of material and shows visible radiation absorption. XRD shoe that APT is a favorable technique for the synthesis of pure nanocrystalline Cu2Se thin films with monoclinic crystal structure. An electrochemical impedance spectroscopy analysis confirms the charge transfer resistance. X-ray photoelectron spectroscopy reveals stoichiometry at valance state of Cu2Se.

Design, Synthesis, and Application in OFET of a Quinoxaline-Based D-A Conjugated Polymer.

A novel alternating donor–acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V−1 s−1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

Site‐Selective Functionalization of Sila‐Adamantane and Its Ensuing Optical Effects

AbstractThe first syntheses of functionalized sila‐adamantanes via site‐selective reactions are described. Mechanistic inquiry into the isomerization of sila‐adamantane revealed new approaches for installing halides at the 2‐position of the cluster. Meanwhile, isomerization via Lewis acid catalysts with non‐nucleophilic counteranions provided access to sila‐adamantane on the gram‐scale, enabling us to discover strategies for substituting its 1‐, 3‐, 5‐, and 7‐positions with identical or distinct functional groups. Optical absorbance and density functional theory studies show that σ‐withdrawing substituents at the 1‐position strongly perturb optical absorbance in sila‐adamantane, whereas substituents at the exocyclic and 2‐position are optically inert. As silicon diamondoids are atomically precise models for silicon nanocrystals, our findings suggest that passivation at tertiary surface sites carries an outsized impact on the optical properties of surface‐functionalized Si nanocrystals.

Site‐Selective Functionalization of Sila‐Adamantane and Its Ensuing Optical Effects

The first syntheses of functionalized sila-adamantanes via site-selective reactions are described. Mechanistic inquiry into the isomerization of sila-adamantane revealed new approaches for installing halides at the 2-position of the cluster. Meanwhile, isomerization via Lewis acid catalysts with non-nucleophilic counteranions provided access to sila-adamantane on the gram-scale, enabling us to discover strategies for substituting its 1-, 3-, 5-, and 7-positions with identical or distinct functional groups. Optical absorbance and density functional theory studies show that σ-withdrawing substituents at the 1-position strongly perturb optical absorbance in sila-adamantane, whereas substituents at the exocyclic and 2-position are optically inert. As silicon diamondoids are atomically precise models for silicon nanocrystals, our findings suggest that passivation at tertiary surface sites carries an outsized impact on the optical properties of surface-functionalized Si nanocrystals.

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.

Fluorescence intensity ratio technique and its reliability

The present article reports the optical absorption and upconversion (UC) studies of 1.0 mol% Er3+/2.0 mol% Yb3+ doped/codoped glasses prepared by melt-quenching technique. The elements present and the composition of the prepared glass have been confirmed from XPS and XRF analysis respectively. Judd-Ofelt intensity parameters have been calculated using the absorption spectrum which is further utilized to predict the nature of Er_O bond, the transition probabilities, branching ratios and radiative lifetimes. The CIE study shows non-colour tunable and highly pure green emission (94.2%). The temperature-dependent UC emission spectra of the 2.0 mol% Yb3+ sensitized glass have been recorded at three different pump power densities to establish a reliable FIR based temperature scale. Furthermore, the Arrhenius fitting of the temperature-dependent spectra reveals low thermal quenching of green luminescence in the codoped glass.

Structural, Optical and Electrical Conductivity Studies in Polycarbazole and its Metal Oxide Nano Composites

Polycarbazole (PCz) has been synthesized by chemical oxidation method using APS as an oxidizing agent and PCz/CuO and PCz/Fe2O3 nanocomposites by in situ polymerization method for different wt% of CuO and Fe2O3 at room temperature. XRD patterns confirmed crystalline nature of samples. FTIR indicated strong interaction between PCz and nano fillers. The morphological and optical absorption studies were carried out using SEM and UV–Vis respectively. Addition of CuO or Fe2O3 to PCz decreased its direct and indirect band gaps. However, band gap showed a small change with dopant contents up to 30%. Urbach energy decreased with the addition of dopants. But Urbach energy of the composites increased with increasing dopants content from 10 to 30%. DC conductivity of PCz and its nanocomposites has been measured by following two probe technique in the temperature range 300–423 K. The conductivity of both the nanocomposites is found to be less than the pure PCz and it is found to increase with wt% of CuO or Fe2O3 as the case may be. The activation energy has been determined by fitting Arrhenius expression to the dc conductivity data at high temperature. The activation energy of polycarbazole is determined to be less than that of the composites. In both the composites, activation energy decreased and conductivity increased with the increase of dopant content.