Optical Absorption Band Research Articles

Spectroscopic studies, molecular structure optimization and investigation of structural and electrical properties of novel and biodegradable Chitosan-GO polymer nanocomposites

This article covers the molecular structure optimization and spectroscopic studies, such as Raman, UV–Vis absorption and FTIR, carried out for novel, biodegradable and biocompatible chitosan-graphene oxide (CS-GO) polymer nanocomposites (PNCs), which were synthesized by using simple blending technique followed by ultrasonification treatment. In addition, the structural and electrical properties have also been investigated. Under molecular structure optimization, the structural geometry, electronic structure (HOMO and LUMO) and potential distribution have been computed. X-ray diffraction of PNCs reveals that the crystallized phase of GO dominates over the CS giving modification in crystallite size and presence of micro-strain. FTIR and Raman spectroscopic studies have been carried out to confirm the proper formation of PNCs and presence of functional group in the composites. The surface morphology has been studied with the help of FESEM to confirm proper dispersion of GO sheets. Optical absorption edge and band gap analyzed from UV–Vis analysis reveal the semiconducting nature of PNCs. In addition, the optical band gap is tuned by varying the content of GO in PNCs. This tuning in band gap has also been supported by XRD and computational results. The dielectric constant and dc conductivity are found increased with increasing content of GO in PNCs. Additionally, the I–V characteristics of PNCs shows Ohmic type conduction with rising in current due to incorporation of GO. In view of the results achieved, the usage of CS-GO PNC is suitable for future development of optical and Gas sensors and UV-detectors, and therefore, such composite may be proven as a potential and suitable candidate for the optoelectronic or electrical devices operating at high frequencies.

Spatially indirect excitons in black and blue phosphorene double layers

Monolayer black and blue phosphorenes possess electronic and optical properties that result in unique features when the two materials are stacked. We devise a low-strain van-der-Waals double layer and investigate its properties with ab initio many-body perturbation theory techniques. A type-II band alignment and optical absorption in the visible range are found. The study demonstrates that spatially indirect excitons with full charge separation can be obtained between two layers with the same elemental composition but different crystalline structure, proving the system interesting for further studies where dipolar excitons are important and for future opto-electronic applications.

Influence of high-energy local orbitals and electron-phonon interactions on the band gaps and optical absorption spectra of hexagonal boron nitride

We report ab initio band diagram and optical absorption spectra of hexagonal boron nitride ($h$-BN), focusing on unravelling how the completeness of the basis set for $GW$ calculations and electron-phonon interactions (EPIs) impact on them. The completeness of the basis set, an issue which was seldom discussed in previous optical spectra calculations of $h$-BN, is found crucial in providing converged quasiparticle band gaps. In the comparison among three different codes, we demonstrate that by including high-energy local orbitals in the all-electron linearized augmented plane waves based $GW$ calculations, the quasiparticle direct and fundamental indirect band gaps are widened by $\ensuremath{\sim}0.2$ eV, giving values of 6.81 eV and 6.25 eV, respectively at the $G{W}_{0}$ level. EPIs, on the other hand, reduce them to 6.62 eV and 6.03 eV respectively at 0 K, and 6.60 eV and 5.98 eV respectively at 300 K. With clamped crystal structure, the first peak of the absorption spectrum is at 6.07 eV, originating from the direct exciton contributed by electron transitions around $K$ in the Brillouin zone. After including the EPIs-renormalized quasiparticles in the Bethe-Salpeter equation, the exciton-phonon coupling shifts the first peak to 5.83 eV at 300 K, lower than the experimental value of $\ensuremath{\sim}6.00$ eV. This accuracy is acceptable to an ab initio description of excited states with no fitting parameter.

2D XBiSe3(X = As, Sb) monolayers with high anisotropic mobility and enhanced optical absorption in visible light region

Configurations and properties of 2D XBiSe3(X = As, Sb) monolayers are predicted by first-principles calculations. Dynamic and thermal stabilities are affirmed by phonon dispersion and ab initio molecular dynamics simulation, respectively. Bandgap and band edges, density of states, optical absorptions, and mobilities are calculated by using the obtained structures. Effects of strain engineering on the band structure and optical absorption are also explored. Results reveal that the AsBiSe3 and SbBiSe3 monolayers have indirect gaps of 1.2 eV (HSE06)/1.43 eV (GW) and 1.1 eV (HSE06)/1.32 eV (GW), respectively. The high electron (approximately 105 cm2V−1s−1) and hole (approximately 104 cm2V−1s−1) mobilities of the XBiSe3 monolayers are observed for zigzag and armchair directions, and obvious anisotropy is observed. The intense optical absorptions in the UV–visible light regions are identified for the two monolayers. Interestingly, the band edge of the AsBiSe3 monolayer can span the redox potential of water under −4% biaxial compressive strain, which implies that this monolayer can be used as a candidate material for photocatalytic water splitting to produce hydrogen. All the results support the assertion that the XBiSe3 monolayers have potential for application in the optoelectronic, photocatalytic, and photovoltaic fields.

Investigation of the Optical Spectra and Spin-Hamiltonian Parameters for Vanadyl in Zinc Phosphate Glass

The optical absorption spectra and spin-Hamiltonian parameters (g factors g||, g⊥, and hyperfine structure constants A||, A⊥ ) of vanadyl in zinc phosphate glass are investigated, using the high-order perturbation formulas for a 3d1 ion in tetragonally compressed octahedra. In the calculations, the required crystal-field parameters are estimated from the superposition model, and the optical absorption bands and spin-Hamiltonian parameters are linked with the tetragonal distortion (characterized by ΔR = R⊥ – R||, where R⊥ and R|| denote the bond lengths perpendicular and parallel to the C4 axis). Based on the calculations, the tetragonal distortion ΔR (≈1.795 A) was obtained, and negative signs of the hyperfine structure constants A|| and A⊥ are suggested.

Two-dimensional Bi2Se3 monolayer with high mobility and enhanced optical absorption in the UV–visible light region

Abstract To find new two-dimensional materials is continually paid too much attention because of the wonderful properties and potential adhibitions. In the present paper, we report a new Bi2Se3 monolayer based on the first-principles calculation. The geometrical configuration is optimized and the stabilities are affirmed by the phonon dispersion and the ab initio molecular dynamics simulation, respectively. The bandgap and band edges, density of state, optical properties, and mobilities are calculated and analyzed. The effects of strain engineering on the band structure and optical absorption are also explored. The results reveal that the Bi2Se3 monolayer possesses an indirect gap of 1.42 eV(HSE06)/1.96 eV(GW) and can be effectively tuned by the strain. The result of the electronic properties shows that the spatial charge separation of the photogenerated pair of electron and hole is obvious. The Bi2Se3 monolayer is predicted to possess a high electron and hole mobilities of 1.96 × 105(zigzag)/1.6 × 104(armchair) and 3.4 × 104(zigzag)/2.51 × 103(armchair) cm2V−1s−1, respectively. The high optical absorption is observed in the UV–visible light regions and could be affected by the strain. All the obtained results support that the Bi2Se3 monolayer is a prospective material for the optoelectronic, photocatalytic and photovoltaic applications.

Cu/Ce-co-Doped Silica Glass as Radioluminescent Material for Ionizing Radiation Dosimetry.

Optically activated glasses are essential to the development of new radiation detection systems. In this study, a bulk glassy rod co-doped with Cu and Ce ions, was prepared via the sol-gel technique and was drawn at about 2000 °C into a cylindrical capillary rod to evaluate its optical and radioluminescence properties. The sample showed optical absorption and photoluminescence (PL) bands attributed to Cu+ and Ce3+ ions. The presence of these two ions inside the host silica glass matrix was also confirmed using PL kinetics measurements. The X-ray dose rate was remotely monitored via the radioluminescence (RL) signal emitted by the Cu/Ce scintillating sensor. In order to transport the optical signal from the irradiation zone to the detection located in the instrumentation zone, an optical transport fiber was spliced to the sample under test. This RL signal exhibited a linear behavior regarding the dose rate in the range at least between 1.1 mGy(SiO2)/s and 34 Gy(SiO2)/s. In addition, a spectroscopic analysis of this RL signal at different dose rates revealed that the same energy levels attributed to Cu+ and Ce3+ ions are involved in both the RL mechanism and the PL phenomenon. Moreover, integrated intensities of the RL sub-bands related to both Cu+ and Ce3+ ions depend linearly on the dose rate at least in the investigated range from 102 mGy(SiO2)/s up to 4725 mGy(SiO2)/s. The presence of Ce3+ ions also reduces the formation of HC1 color centers after X-ray irradiation.

Quasiparticle energies and excitonic effects of chromium trichloride: From two dimensions to bulk

Layered van der Waals (vdW) magnetic materials have attracted significant research interest to date. In this work, we employ the first-principles many-body perturbation theory to calculate excited-state properties of a prototype vdW magnet, chromium trichloride (CrCl3), covering monolayer, bilayer, and bulk structures. Unlike usual non-magnetic vdW semiconductors, in which many-electron interactions and excited states are sensitive to dimensionality, many-electron interactions are always enhanced and dominate quasiparticle energies and optical responses of both two-dimensional and bulk CrCl3. The electron-hole (e-h) binding energy can reach 3 eV in monolayer and remains as high as 2 eV in bulk. Because of the cancellation effect between self-energy corrections and e-h binding energies, the lowest-energy exciton (optical gap) is almost not affected by the change of dimensionality. Besides, for the excitons with similar e-h binding energies, their dipole oscillator strength can differ by a few orders of magnitude.Our analysis shows that such a big difference is from a unique interference effect between complex exciton wavefunctions and interband transitions. Finally, we find that the interlayer stacking sequence and magnetic coupling barely change quasiparticle band gaps and optical absorption spectra of CrCl3. Our calculated low-energy exciton peak positions agree with available measurements. These findings give insight into the understanding of many-electron interactions and the interplay between magnetic orders and optical excitations in vdW magnetic materials.

Синтез и исследование структуры наноразмерного оксида меди (II), стабилизированного полиэтиленгликолем

We developed a method for synthesising polyethylene glycol-stabilized copper oxide nanoparticles via a sol-gel process, obtained samples and investigated their structure, morphology and properties. We used photon correlation spectroscopy to establish that the copper oxide nanoparticles feature a monomodal size distribution with the average hydrodynamic radius of a particle being approximately 50 nm irrespective of the stabiliser molar mass. We detected an optical absorption band at 290 nm in all samples. We established that copper oxide samples consist of aggregates formed out of spherical nanoparticles whose diameters lie in the range of 10 to 30 nm. Phase composition analysis of the copper oxide samples revealed that the samples consist of particles featuring a monoclinic structure. We simulated the process of polyethylene glycol interacting with the copper oxide. We show that the most energetically favourable interaction model includes bond formation between the neighbouring intramolecular etheric oxygen atoms and the copper atom

Laser induced formation of copper species over TiO2 nanotubes towards enhanced water splitting performance

We proposed fast and scalable route where the ordered TiO2 nanotubes coated with thin copper layers were annealed by the laser beam of 355 nm wavelength at different fluencies in the range of 15–120 mJ/cm2. As a result, copper species are integrated with the titania substrate and the formed material exhibits unique optical absorption bands in the visible range. Moreover, X-ray photoelectron spectroscopy analysis reveals the formation of Cu2O while the 4+ oxidation state of titanium is preserved. According to the electrochemical results, the material treated by laser exhibits outstanding photoelectrochemical activity comparing to the pristine titania or the one only covered by the thin copper film. In particular, when the fluence of 60 mJ/cm2 was used for the modification of the titania decorated with Cu film, the current density recorded in KOH electrolyte reaches nearly 4.5 mA/cm2 at +2.0 V vs. Ag/AgCl/0.1 M KCl upon visible light.

Effect of [MnO6] Octahedra to the Coloring Mechanism of (Li1-x Na x )2MnO3.

(Li1–xNax)2MnO3 (0 ≤ x ≤ 0.10) solid solutions were synthesized by a conventional solid-state reaction technique to investigate the relationship between the steric structure of the [MnO6] octahedra and coloration mechanisms. The color, optical properties, and crystal structure of the solid solutions were characterized. The (Li1–xNax)2MnO3 (0 ≤ x ≤ 0.10) solid solutions absorbed the visible light at wavelengths shorter than 550 nm and around 680 nm. The former and latter optical absorption bands were attributed to the spin-allowed (4A2g → 4T1g, 4T2g) and spin-forbidden (4A2g → 2Eg, 2T1g) d–d transitions of tetravalent manganese ions, respectively. The absorption band assigned to the 4A2g → 4T2g transition shifted toward longer wavelengths with the enlargement of the average [Mn(2)O6] bond distance by doping Na+. In contrast, the latter absorption bands did not shift but the absorption intensities increased due to the distortion of the [Mn(2)O6] octahedra. Consequently, the red color purity of the sample gradually increased with the increase in the Na+ concentration. Among the (Li1–xNax)2MnO3 (0 ≤ x ≤ 0.10) samples synthesized in this study, the highest red color purity was obtained in the (Li0.93Na0.07)2MnO3 (hue angle: h° = 39.1) sample. The results of this study provide important insights for the development of environment-friendly inorganic red pigments containing Mn4+ ions as a coloring source.

Bi1.9Mn0.1Te3 nanocrystal functionalized diamagnetic glasses: optical, luminescence, magnetic and Faraday rotation

Mn doped Bi2Te3 nanocrystal, both as topological insulator and diluted magnetic semiconductor, has gained significant interest due to its interesting magnetic performance roused by the sp-d exchange interaction and unique time-reversal symmetry protected surface states. In this paper, for the first time, Bi1.9Mn0.1Te3 nanocrystal doped diamagnetic TeO2–PbO–B2O3 glass was studied. Pure 50nm hexagonal Bi1.9Mn0.1Te3 nanocrystals were synthesized with a specific surface area of 64.28 m2/g using the optimized PEG as surfactant. Due to the complex spin-orbit interactions between sp band of Bi2Te3 and d band of Mn, the prepared Bi1.9Mn0.1Te3 displayed characteristic luminescence, A11g, E2g, A21g Raman modes, good photocatalytic (70.2%) and ferromagnetic/paramagnetic co-existence behavior.Bi1.9Mn0.1Te3 doped diamagnetic glasses were prepared by melting-quenching technique and the influence of different doping amount to glass structure and properties was evaluated through X-ray diffraction, Fourier transforms infrared, Raman, Ultraviolet-visible, photoluminescence spectra and Verdet constant measurement. The glasses structure and properties were doping amount dependent. X-ray diffraction, Fourier transforms infrared and Raman spectra revealed the evolution of structure units of TeO4, TeO3, BO3 etc under the modification of Bi1.9Mn0.1Te3. SEM revealed the homogeneity and growth of nanocrystals in matrix. X-ray photoelectron spectroscopy displayed the chemical states changes of Mn2p, Bi4f, Te3d and O1s under different doping amounts. Both the optical absorption band at 540nm and cutoff wavelength increased with the dopant amount. The luminescence in visible range revealed the tetrahedral coordination state of paramagnetic Mn ions which also influenced the magnetization and Faraday rotation accordingly. Experimental results showed that glass with 2%Bi1.9Mn0.1Te3 exhibited good optical, luminescence, magnetic, significant high Verdet constant (0.2522min/G.cm) and good thermal stability as well. Such good quality diamagnetic glass is attractive for magneto-optical devices applications in isolator and current transducer etc.

High-resolution laser spectroscopy of the linear SiC2Si molecule and its astrophysical implications

Small silicon-carbon clusters are important gas-phase constituents of stellar atmospheres, and are thought to play a role as potential seeds of the interstellar dusts formed in the envelopes of evolved carbon stars. Here we present the high-resolution optical spectra of the linear SiC2Si molecule (l-Si2C2) studied via laboratory experiments. The l-Si2C2 molecules are generated in a supersonically expanding planar plasma by discharging a silane-acetylene-argon gas mixture. The optical absorption spectra in the 5000−5300 Å region are recorded using sensitive pulsed cavity ring-down spectroscopy. In total, five optical absorption bands belonging to the $ \tilde{C} ^{3}\Sigma_{u} ^{-} $ – $ \tilde{X} ^{3}\Sigma_{g} ^{-} $ electronic transition system of l-Si2C2 are measured with fully resolved spin splitting fine structures in individual rotational transitions. Accurate spectroscopic constants for both $ \tilde{X} ^{3}\Sigma_{g} ^{-} $ and $ \tilde{C} ^{3}\Sigma_{u} ^{-} $ states of l-Si2C2, including the spin-spin interaction constants and spin-rotation interaction constants, are determined from the experimental spectra, which can be used to simulate these optical bands with different temperatures. Using the determined spectroscopic constants, optical spectra of l-Si2C2 simulated with different rotational excitation temperatures are compared to the stellar spectra of evolved carbon stars V Hya and IRAS 12311−23509, where the triatomic SiC2 are known to be abundant. Tentative assignments of the l-Si2C2 spectral features in the stellar spectra are discussed.

In situ reorganization of Bi3O4Br nanosheet on the Bi24O31Br10 ribbon structure for superior visible-light photocatalytic capability

In situ synthesized 2D/2D heterojunctions often exhibit a more homogeneous mixture and stronger interface interaction, thereby providing higher interfacial charge transfer and larger interface contact area compared with 0D/2D and 1D/2D heterojunctions. Herein, novel 2D/2D Bi24O31Br10/Bi3O4Br heterojunctions with a “nanosheet-on-ribbon” hierarchical structure were fabricated via in situ reorganization of original elements in a hydrothermal process, and this method was accomplished through the intervention of NH3·H2O. The Bi24O31Br10/Bi3O4Br heterojunctions exhibit outstanding visible light activity than pure Bi3O4Br and Bi24O31Br10, reaching photodegradation efficiency of 85% for sulfamethoxazole in 180 min and removal rate of 32.5% for NO in 30 min. Crystalline phases, optical absorption properties, morphologies, microstructures, and band structures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, differential reflectance spectroscopy, valence band X-ray photoemission spectroscopy, Mott–Schottky methods, density functional theory, photoluminescence spectroscopy, photocurrent analysis, and electrochemical impedance spectroscopy. The superior photocatalytic activity could be ascribed to the special structure and interface interaction between Bi3O4Br and Bi24O31Br10, thereby enhancing surface-active sites, prolonging light absorption, and promoting charge separation capability during the photocatalytic reaction. The formation mechanism of Bi24O31Br10/Bi3O4Br heterojunctions was proposed, and NH3•H2O was not only a pH adjuster but also a structure-controlling agent. This work provides a reference for in situ synthesis of multifunctional 2D/2D photocatalytic nanocomposites.

One kind of new Ti3+ luminous center in Ti:Al2O3 crystals

In the optical absorption spectra of Ti:Al2O3 crystal doped with higher concentration of titanium and annealed with hydrogen, in addition to the main absorption band of TiAl3+ (490 nm, 540 nm), a small absorption band of 390 nm and a concomitant small bump on the short-wave side of the 490 nm absorption band was often observed. In this study, an independent optical absorption center that also has doublet structured optical absorption bands at 388 and 460 nm was separated from the above spectra by means of spectral decomposition, and its polarization property and annealing effect are consistent with the main absorption band of TiAl3+. It was supposed to be another kind of Ti3+ center related to interstitial Ti3+ locating at the intrinsic vacant octahedral in the corundum structure. Moreover, this Ti3+ center also produced a wide emission band centered at 760 nm, with weaker intensity, which indicated that there were two kinds of Ti3+ luminous centers in Ti:Al2O3 crystal: one is TiAl3+ in the lattice site of A1, the other is Tii3+ in the interstitial site.

Biogenic synthesis of mesoporous N–S–C tri-doped TiO2 photocatalyst via ultrasonic-assisted derivatization of biotemplate from expired egg white protein

The development of sustainable photocatalysts and their efficient utilization of solar light is one of key topics for addressing the current and future environmental remediation concerns. Herein, we report an ultrasonic-assisted green synthesis of mesoporous titanium dioxide (m-TiO2) nanoparticles (NPs) using an egg white protein (EWP) biotemplate derived from expired eggs, hereafter referred to as EWP-TiO2 NPs. The EWP biotemplate played multiple roles, such as source of nonmetallic elements (N, S, and C), structure-directing agent, and self-solvent, consequently bestowing excellent features on TiO2 photocatalyst. X-ray Diffraction, BET surface area, and X-ray photoelectron spectroscopy analyses indicated that the synthesized NPs have anatase phase of m-TiO2 NPs with Tri-N-S-C doping. The spherical EWP-TiO2 NPs exhibited a substantial decrease of the particle size as compared to EWP-free analogue (so-called bare TiO2 NPs). The photocatalytic activities of as-prepared TiO2 samples were evaluated by degrading Rhodamine B under simulated solar light (100 mW/cm2). The EWP-TiO2 NPs exhibited the two-fold higher photocatalytic activity than that of bare TiO2, owing to enlarged surface area, red-shift in the optical absorption band, and efficient charge separation. The biotemplate derivatization is a very effective strategy for fabricating mesoporous semiconductor doped with nonmetallic elements.

MICROWAVE ASSISTED GREEN SYNTHESIS OF SILVER NANOPARTICLES USING COLEUS AMBOINICUS LEAF EXTRACT

Objective: Current study is aimed at the formulation of silver nanoparticles loaded with the extract of Coleus amboinicus leaf extract by microwave irradiation. A facile and green synthesis of silver nanoparticles by using a biological agent such as plant extracts with the aid of microwave irradiation is proposed as an economical and environmentally friendly approach alternative to chemical and physical methods.
 Methods: In order to fabricate silver nanoparticles by microwave irradiation, aqueous extract of leaves Coleus amboinicus (CA) were treated with aqueous silver nitrate solution and mixture was placed in the microwave oven for exposure to microwave. Optimizations of the process were carried out by varying the quantity of extract, silver nitrate concentration and duration of microwave irradiation. Formations of nanoparticles were confirmed by UV-visible spectroscopy observing for the presence of surface plasmon resonance (SPR) peak. Nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy.
 Results: Silver nanoparticle showed the SPR optical absorption band peak at 434 nm by UV-Visible spectrophotometer. Reaction mixture containing 2 mmol silver nitrate and 9 ml of extract subjected to microwave irradiation of 60 sec at a temperature of 60 °C was found to be optimised condition, which produced nanoparticles that were spherical in shape and had an average diameter of 15.685 nm.
 Conclusion: This research study opens an innovative design to progress our understanding of how silver nanoparticles behave can be optimized to improve their surface morphology, which is beneficial to improve its therapeutic effect.

Visible-light-driven photocatalytic degradation of rhodamine B in water by BiOClxI1-x solid solutions.

Bismuth oxyhalides (BiOXs, X = Cl, Br and I) are emerging photocatalytic materials with unique layered structure, flexible band structure and superior photocatalytic activity. The purpose of this study was to develop a facile alcoholysis route to prepare BiOClxI1-x nanosheet solid solutions at room temperature. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence emission spectroscopy (PL) and Brunauer-Emmett-Teller (BET) surface area analyzer were used to characterize the as-prepared photocatalysts. These results revealed that two-dimension BiOClxI1-x nanosheet solid solutions could be obtained with high percentage of {001} crystal facets exposed. Moreover, the formation of solid solution could regularly change the optical absorption thresholds and band gaps of BiOClxI1-x photocatalysts. The photocatalytic experiments indicated that BiOCl0.75I0.25 exhibited the highest photocatalytic performance for the degradation of Rhodamine B (RhB) under simulated sunlight irradiation and the photocatalytic process followed a pseudo-first-order kinetic equation. A possible mechanism of RhB photodegradation over BiOClxI1-x solid solutions was proposed based on the structural properties of BiOClxI1-x solid solutions and RhB photosensitization.

The first principle study and experimental of boron synergistic sulfur doping in diamond

In this paper, optical absorption spectrum, band structure and electrical structure of diamond doped with B,S are investigated by density functional theory (DFT).Comparing optical absorption spectra of diamond un-doped and doped with B, S, absorption band edge of type IIa and type Ib diamonds doped with B,S move toward long wavelength direction and there are an absorption coefficient at a wavelength greater than that at 400 nm. In addition, incorporation of B contribute to improvement of conductive properties of diamond doped with BS. At the same time, comparing density of state for diamond doped with B or B-S, it is found that S-3p, B-2s and B-2p contribute to conduction band. In summary, it can be considered that conductivity type of diamond with BS co-doped is n-type semiconductor, and with synergy of B, S is as a suitable shallow donor impurity in diamond. Furthermore, in order to confirm above calculation results, type IIa and type Ib large single crystal diamond doped with B, S are synthesized under FeNi-C system. The color change of diamond is consistent with results of diamond optical absorption spectrum in DFT. The electrical measurement results show that type IIa and type Ib diamond doped with B,S present n-type semiconductor characteristics. The incorporation of B contributes to the improvement of electrical properties of diamond doped with S.

Comparison of optical absorption and thermoluminescence in LiF:Mg, TI (TLD-100) following irradiation by high energy protons and 90Sr/90Y beta rays

The optical absorption (OA) energy spectrum and thermoluminescence (TL) glow curve characteristics of LiF:Mg, Ti (TLD-100) samples following 90Sr/90Y beta ray irradiation and high energy proton irradiation are compared for the first time. The beta ray irradiations were carried at room temperature at a dose rate in LiF of approximately 0.13 Gy min−1. Proton irradiations were carried out at energies of 20 MeV, 40 MeV and 58 MeV with initial stopping powers of 5.5, 3.2 and 2.3 keV μm−1 respectively. Proton escaping the TL detectors had average energies 55.9, 37.1, 14.4 MeV and the corresponding stopping power in LiF 2.43, 3.36, 7.19 keV μm−1 respectively. All proton irradiations were carried out at a dose of 1124 Gy in LiF and the beta irradiations at a dose of 970 Gy in LIF. The OA spectra were deconvoluted with Gaussian Peak Shapes using a commercial “Peak-Fit” non-linear curve fitting program from Jandel Scientific. The Gaussian bands are characterized by the two parameters of band energy and width. The glow curves were deconvoluted using the Ben Gurion University mixed-order kinetics program. In the analysis first-order kinetics glow peak shapes were employed. The major difference between the two spectra is in the optical density of the F band at 5.08 eV; 0.17 compared to an average value of 0.33 following beta and proton irradiation respectively. The relative intensity, protons to betas, of the other OA bands are remarkably similar within the experimental errors and indicate that the traps associated with these OA bands are not created by the irradiation. It is demonstrated that proton irradiation of LiF:Mg, Ti (TLD-100) creates F centers with 75% greater efficiency than 90Sr/90Y beta particles. This finding lends further support to the conclusion that track structure theory is unable to accurately predict proton relative efficiencies in LiF:Mg, Ti The results are also interpreted in the framework the spatially correlated trapping center/luminescent center model for composite peak 5 in LiF:Mg,Ti.