UV Vis Optical Absorption Spectra Research Articles

Synergistic effect of WO3 on structural, physical, optical, and dielectric characteristics of multicomponent borate glasses for optoelectronic applications

This study demonstrates the promising potential of WO3-doped calcium lithium silicate borate glasses as a multifunctional material with adjustable characteristics for a range of current technological purposes. The melt quenching technique was used for the manufacture of calcium lithium silicate borate glass samples doped with WO3 with a chemical composition of (50-x)B2O3+10SiO2+15CaO+25Li2O + xWO3, where x = 0, 1, 2, 3, and 5 mol%. Raman spectroscopy and UV optical absorption methods were used to investigate the spectroscopic characteristics of glass samples. The dielectric characteristics of the produced glass samples were investigated by broadband dielectric spectroscopy (BDS) measurements. The extremely short-range ordering structural matrices revealed by X-ray diffraction have validated the amorphous nature. The Raman spectra of the calcium lithium silicate borate glass exhibit considerable differences from those of glasses containing WO3. The prepared glass samples exhibited an obvious relationship between the replacement of WO3 and their density and molar volume. As a result of a modification in the structure, the values of packing density (Vp) and oxygen packing density (OPD) decrease as the molar concentration of WO3 increases. The inclusion of WO3 increased the optical absorbance of the synthesized glasses, as demonstrated by UV–Vis optical absorption spectra. According to the dielectric characteristics, the dielectric loss and dielectric constant decrease with frequency, while the AC electrical conductivity exhibits a progressive increase.

Effect of zirconium oxide nanoparticles on thermal, optical, and radiation shielding properties of Bi2O3-B2O3-MnO2 glasses

This study has explored the DSC, UV–Vis absorption spectroscopy, gamma ray and neutron shielding properties of Bi2O3-B2O3-MnO2: ZrO2 glasses. It demonstrates a unique approach to photon shielding analysis using JENDL/PD-2016 photonuclear data and employs a validated spherical neutron model for neutron shielding. Five transparent glasses were prepared with the chemical composition (in mol%) of 29Bi2O3-70B2O3-(1-x)MnO2: xZrO2, and labeled as MZ0.00 (for x = 0), MZ0.25 (for x = 0.25), MZ0.50 (for x = 0.5), MZ0.75 (for x = 0.75) and MZ1.00 (for x = 1). The glass ceramic nature of the samples has been characterized by DTA thermograms. The glass forming ability parameters (Kgl, S & H) were found to be highest for the sample MZ1.00. The UV–Visible optical absorption spectra have been interpreted, and hence the cut-off wavelength (λcut-off) and optical band gap (Eo) were evaluated. The absorption spectra have revealed the co-existence of manganese ions in three stable valence states Mn4+, Mn3+ and Mn2+ in the samples. When ZrO2 nanoparticles were added in the composition up to x = 0.50 mol%, the red shift in the cut-off wavelength (λcut-off) with gradual shrinkage in optical band gap (Eo) has been observed. Also, the linear and non-linear optical parameters viz., refractive index (no), non-linear refractive index (n2), linear optical susceptibility (χ(1)) and non-linear optical susceptibility (χ(3)) have been evaluated. These parameters showcased that B-O, Bi-O, Mn-O, Zr-O, etc. bonds could be strengthened by subsequent reduction of polarization of the trivalent ions (B3+ ions, Bi3+ ions and Mn3+ ions) in the glass system at higher concentrations of ZrO2. Photoatomic and photonuclear attenuation studies portrayed that the sample MZ0.50 has the lowest photon shielding capability. The fast neutron effective removal cross section (ΣR) was observed to be the highest for the sample MZ1.00. Thus, these glasses can be used to design the thermally stable transparent glasses, tunable optical elements, and radiation shielding materials.

Structural and optical properties of polyvinyl alcohol/copper oxide (PVA/CuO) nanocomposites

In the present investigation, pristine polyvinyl alcohol (PVA) and copper oxide (CuO) incorporated nanocomposite films have been fabricated via simple solution cast technique. The structural and optical properties of the prepared films were studied in detail. Various concentrations of CuO NPs (0.1–0.4 wt %) incorporated in the PVA film were prepared. The X-ray diffraction (XRD) profiles indicate the presence of CuO nanoparticles (NPs) in PVA film. XRD results indicate that, the CuO NPs were successfully incorporated into the PVA host matrix with no additional impurity peaks. The obtained CuO NPs belong to the monoclinic phase as confirmed by the XRD results. The peak observed at 2θ = 19.4° evident for the formation of semi crystalline PVA polymer. The average crystallite size of the prepared NPs was observed to be ∼0.52 nm. The vibrational bands present in the prepared films were confirmed by the Fourier transform infra-red spectroscopy (FTIR) plots. The presence of the NPs in the films was further investigated with the help of Raman spectra. UV–visible optical absorption spectra was recorded to evaluate the band gap values of the prepared films. The band gap value for pristine PVA was found to be 5.35 eV and it decreases with increase of CuO NPs concnetration owing to the change in the electronic structure of the pure PVA. The dielectric properties were also evaluated and it was found that, with increase in the CuO NPs concentration the dielectric constant also increases owing to the increase in density of states leading to the formation of polarization. The optical conductivity of the prepared nanocomposites increases with increase in the NPs concentration due to the formation of the charge transfer complex. The obtained results reveal that, the addition of CuO NPs reduces the optical band gap of the PVA polymer films.

WS2–TiO2 hetero-photocatalysts for efficient hydrogen evolution via plasmon-induced resonance energy transfer

Lowering the cost and increasing the efficiency of photocatalysts for hydrogen (H2) evolution remain challenging, especially with eco-friendly materials. With these goals in mind, in this study we adopted tungsten disulfide (WS2) nanosheets, a nonmetallic surface plasmon resonance (SPR) material covering P25 TiO2, for plasmon-induced resonance energy transfer (PIRET) to improve the photocarrier response of H2 evolution. Under simulated solar light irradiation, the optimized 2.4W heterostructure provided a durable and outstanding H2 evolution rate (321 μmol g−1 h−1) that was approximately 55.3 times higher than that of TiO2. Raman spectra revealed the presence of dipole–dipole interactions within the WS2–TiO2 heterostructure, while UV–Vis optical absorption spectra indicated that the WS2 absorption range overlaid the band gap of TiO2. Under irradiation with light, the SPR of the WS2 nanosheets underwent near-field dipole-dipole coupling with the excitons of TiO2 to increase the number of excitons and inhibit charge recombination. This study suggests the possibility of using nonmetallic SPR materials for efficient solar energy conversion.

Structural features and optical-luminescent properties of the Pb-containing germanate and silicate oxyfluoride glasses

The XRD, IR transmission, EPR, optical absorption, luminescence spectra and decay kinetics in new un-doped 0.5PbO–0.3GeO2–0.2AlF3 and 0.53PbO–0.226SiO2–0.244AlF3 glasses were investigated. The XRD patterns were analysed in order to obtain the radial distribution functions and define the average interatomic distances and coordination numbers in the network of investigated glasses. The IR transmission, EPR, and UV–vis optical absorption spectra of the studied glasses were interpreted. Optical band gap and Urbach energy were obtained from analysis of the fundamental absorption edge. Under UV photoexcitation the 0.5PbO–0.3GeO2–0.2AlF3 and 0.53PbO–0.226SiO2–0.244AlF3 glasses demonstrate broad emission band at 493 nm and 499 nm, respectively. Fast (band-to-band recombination) and slow (recombination with a contribution of defects levels) mechanisms of intrinsic luminescence have been proposed from a detailed analysis of luminescence spectra and decay kinetics curves. The CIE chromaticity diagram shows a variation in emission colour of studied glasses with the change in their composition.

Band gap determination by Tauc’s, ASF and DASF methods of alkaline earth modified lithium borate glasses co-doped with transition metal ions

In the current manuscript the inorganic glassy system with composition 15Li2O-25RO-59B2O3-0.7CuO-0.3Fe2O3 (R = Ca/Sr/Ba) have been synthesized through classical melt-quench method and investigated by XRD, and optical absorption techniques. The X-ray diffraction images of the synthesized glassy materials substantiated the inorganic glassy structure. The UV–Visible optical absorption spectra of the synthesized glassy materials were recorded with in the wavelength range 300 to 900 nm. The Tauc’s, ASF and DASF methods were employed to ascertain the optical and Urbach energies of the prepared glass system. The effect of alkaline earths on the optical absorption was discussed.

Development of novel flexible photodetectors based on 0.5PVA/0.5PVP/Fe:NiO nanocomposite system with enhanced optoelectronic properties

Ordinary casting technique has been used to fabricate the intrinsic films of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) polymer blend matrix incorporated with dissimilar weight percent contents of Fe:NiO nanocomposite (NC). X-ray diffraction (XRD) and infrared (IR) spectroscopy has been implemented to analyze NC structure of these films. Significant interaction and tuning of PVA/PVP blend matrix due to Fe:NiO NC is detected. XRD pattern reflects the structural modification and partial crystalline nature of the pristine blend matrix. The corresponding peaks of Fourier transform IR identifies the vibrational group of the synthesized samples. Atomic force microscope images indicate that a change in the Fe:NiO concentration in a pristine blend leads to an increase in the roughness and clusters. Numerous optical factors such as E g (transition band gap), refractive index (n), and E ed (absorption edge) of pure blend and blend films with different concentrations of Fe:NiO were assessed via UV–Vis optical absorption spectra. As we increased the doping concentration in pristine blends, the value of E g goes to decrease. The dispersion (E d) and oscillator (E o) energies were calculated from Wemple and Di. Domenico of a single oscillator. Although, optical susceptibilities and nonlinear refractive index were enhanced by doping with Fe:NiO NC. The change in doping content leads to modifications in the optical limiting. The photocurrent density–voltage properties of the present polymers were studied at different values of white light intensity. It was found that the photoconductivity of the PVA/PVP blend is 1.03275 × 10−8 (Ω cm)−1, while NC films varied in the range (1.03–10.6954) × 10−8 (Ω cm)−1 at 8600 lux. In addition, the photosensitivity increased from 13.82 to 24.08. The recombination process was found monomolecular process for pure and doped polymers. The present films assume the possibility of their uses in optical and photo-electric devices.

Studies on Electrical Energy Storage Density in Lead-Free Ferroelectric Ba1-x SrxTiO3 (x = 0.1, 0.3, and 0.7) Capacitors

Structure, phonon, and energy storage density were studied in Sr2+-substituted lead-free ferroelectric Ba1-x SrxTiO3 (BSTx) (x = 0.1, 0.3, and 0.7) samples, prepared using solid state reaction techniques, utilizing X-ray diffraction, Raman, and ferroelectric polarization measurement techniques. The system is tetragonal for x = 0.1 with large c/a ratio at room temperature. The tetragonal anisotropy decreases with increasing x, and becoming cubic for x > 0.3. All these structural properties change due to change in the c/a ratio upon rising temperature. Temperature dependent phonon spectroscopic results (80-500 K) indicate reduction in tetragonal to cubic phase transition temperature upon increasing x due to reduction in tetragonal anisotropy (c/a). Overdamping of ~90 cm-1 E-soft phonon mode and a dramatic decrease in the intensity of ~160 cm-1 A-mode were observed at around the tetragonal ferroelectric to cubic paraelectric phase. Using UV-Vis optical absorption spectra, the optical band gaps of these compounds were calculated as 1.73, 1.7, and 1.68 eV as a function of increasing the dopant concentration (x). The energy storage densities of these electrically polled BSTx capacitors were estimated using the polarization hysteresis loops. For x = 0.7, a large energy storage density (Ure) of 20 Joule/cm3 with the efficiency of 57 % was estimated at applied electrical field of 88 kV/cm. Close to Tc large dielectric constant and high energy density values of BSTx capacitors indicate its possible application in high energy storage and pulse power devices. These results will be presented in detail at the meeting.

Introducing the novel composite photocatalysts to boost the performance of hydrogen (H2) production

Endeavor has been made in this work to develop a supported Si photocatalyst to efficiently split water into hydrogen under irradiation with visible light. Hydrothermal and solid phase reaction method were used to synthesize of Si/CNTs photocatalysts and characterized by using UV–visible optical absorption spectra (UV–Vis), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Scanning electron microscope (SEM) and etc. By examining their properties, it was found that the two types of surface dangling bonds existed on the surface of CNTs which greatly impacts on reaction efficiency. The generation of hydrogen (H2) onto supported Si catalyst may take place on hydroxyl and hydrogen bond with Si. The bandgap estimated from the reflection spectra was 2.2 eV for Si/CNTs photocatalyst. The highest generation of H2 of Si/CNTs was observed as 648 μmol h−1 which is greater than pristine Si without adding any hole-scavengers. The outcomes demonstrated that CNTs had a significant impact on photocatalytic water splitting activity because of high conductivity on remarkable net-like 2D structure. No apparent decrease in H2 production was detected after three successive runs representing the stability of the catalyst. Surface functions hold to achieve high efficiency in such a photocatalytic framework.

Effect of radiative energy transfer and direct excitation on the up-conversion and down-shifting emission properties of Er3+-doped Zn3(VO4)2

Er3+-doped Zn3(VO4)2 samples were synthetized by solid-state reaction process at 800 °C. The doping level was varied from 1.0 to 4.0 mol%. All samples were analyzed by different techniques such as X-ray diffraction, Raman spectroscopy, optical absorption and photoluminescent spectroscopy. X-ray diffraction patterns revealed a majority presence of Zn3(VO4)2, with residues of Zn2V2O7, Zn4V2O9, ZnO, and ErVO4. Raman spectroscopy displayed vibrational modes associated with the Zn3(VO4)2 compound. Additionally, vibrational modes with lower intensity related to Zn2V2O7 and ErVO4 compounds were also present, in concordance with X-ray diffraction patterns. UV–Vis optical absorption spectra showed four bands located at 2.23, 2.37, 2.53 and 2.74 eV which are due to the Er3+: 4S3/2, 2H11/2, 4F7/2 and 4F5/2 electronic transitions, respectively. The band gap energy (Eg) values were found around 2.75 eV. The visible down-shifting emission spectra of the Zn3(VO4)2 sample upon 350 nm excitation, revealed a broadband from 400 to 800 nm due to the VO43− tetrahedron. In presence of Er3+, the emission band exhibited sinks, which match well with absorption of the Er3+: 4F7/2, 2H11/2, 4S3/2 and 4F9/2 levels, indicating the existence of radiative energy transfer from the host to Er3+. This energy transfer gave rise to the NIR Er3+: 4I13/2 → 4I15/2 emission. Non-radiative energy transfer was ruled out by the no shortening of the decay time profiles. The up-conversion emission spectra recorded upon 980 nm diode laser excitation, showed the characteristics Er3+ emission bands in the green and red region, which linearly grow with the Er3+ content. Such process is dominated by an excited state absorption mechanism. The NIR down-shifting emission spectra upon 980 nm excitation, displayed the NIR Er3+ emission band attributed to the Er3+:4I13/2 → 4I15/2 transition. The Stark splitting exhibited by the NIR emission attained upon direct and indirect excitations, revealed the existence of two Er3+ sites, which are activated depending on the excitation mechanism.

Influence of Na2O addition on the alkali borochromate glasses: structure and ligand field

Trivalent chromium is a very common ion used for coloring in the industry of glass. As glasses are melted under high oxidizing circumstances, hexavalent chromium Cr(VI) can be fixed and found in certain advertising applications of UV-protection receptacles. Melt quenching technique is employed to prepare oxide glasses with a general formula xNa2O–(30 − x) Li2O–10K2O–10ZnO–49.7B2O3–0.3Cr2O3 (where x = 0, 5, 10 and 15 mol%). The amorphous nature of the samples is confirmed using X-ray diffraction. The optical absorption spectra have been recorded, and the resulting data were used for the ligand field theory analysis, from which the crystal-field energy (10Dq), Racah parameters (B and C) and nephelauxetic function (h) were evaluated. The variations in the optical bandgap and the band tail with Na2O content have been discussed in relation to the glass structure. FTIR of these glasses revealed that the borate network is affected by the replacement of Na2O by Li2O content. It showed also reduction in N4 with increasing Na2O. This result indicates the increase of non-bridging oxygens (NBOs) which in turn reduces the rigidity of the glass matrix and opens up the structure. The density and the molar volume (VM) measurements were also employed to investigate the structure. These measurements show a linear increase as Na2O content increases. This can be attributed to the differences in the ionic radii of sodium and lithium ions, being larger for sodium. UV–Visible optical absorption spectra show three characteristics bands around ~ 588, 435 and 360 nm which are assigned to the transitions 4A2g → 4T2g, 4A2g → 4T1g and 4A2g → 2A1g, respectively. Racah parameters (B and C) show an opposite behavior. The obtained ratio (10Dq/B) reveals a strong ligand field around chromium ions. Also, the nephelauxetic parameter of the ligand shows the same 10Dq behavior. The increase of chromium ions in the trivalent state shows that it acts as modifiers, yielding the higher concentration of NBOs in the glass matrix and confirming the FTIR and optical results. Electron spin resonance spectroscopy was measured and studied to confirm the existence of Cr3+ and Cr6+.

Microstructure, dynamics and optical properties of metal-doped imidazolium-based ionic liquids

In this paper we study the complexation of Al3+ and several transition metals (Cr3+, Fe3+, Mn2+, Ni2+) in the ionic liquid 1-butyl-3-methylimidazolium thiocyanate. New insights into the structure, single-particle dynamics and electronic properties (optical absorption spectra) of these bulk mixtures are provided by molecular dynamics and density functional theory calculations, and our results are successfully compared with available experimental data. Our theoretical results reveal the existence of a bridging coordination mode between neighboring metal-ligand complexes in the polar nanoregions, and a scarce influence of the apolar nanoregions in the single-particle dynamics of the species in the mixture. Moreover, most part of the relevant features of the UV–Vis optical absorption spectra of these systems is properly explained by our density functional theory calculations for isolated complexes in the gas phase, evidencing that ionic liquid cations play only a limited role in the complex electronic properties.

Synthesis of Polyaniline/Scarlet 3R as a Conductive Polymer.

Polyaniline (PANI) was prepared in the presence of the acidic dye scarlet 3R. Color tuning was performed on PANI through doping–dedoping processes and by changing the solvent used during the optical absorption spectroscopic measurements. The chemical structure of the resulting polymer–dye composite was analyzed using infrared absorption spectroscopy, and it showed the occurrence of secondary doping in m-cresol. The shape of the UV–Vis optical absorption spectra for the composite solution is dependent on the types of organic solvents used during the analysis, which was influenced by the conformation of PANI and the ionic interactions between PANI and scarlet 3R.

Steady state charge conduction through solution processed liquid crystalline lanthanide bisphthalocyanine films

In-plane electrical characteristics of non-peripherally octyl(C[Formula: see text]H[Formula: see text]- and hexyl(C[Formula: see text]H[Formula: see text]-substituted liquid crystalline (LC) double decker lanthanide bisphthalocyanine (LnPc[Formula: see text] complexes with central metal ions lutetium (Lu), and gadolinium (Gd) have been measured in thin film formulations on interdigitated gold (Au) electrodes for the applied voltage ([Formula: see text] range of [Formula: see text]. The conduction mechanism is found to be Ohmic within the bias of [Formula: see text] while the bulk limited Poole–Frenkel mechanism is responsible for the higher bias. The compounds show individual characteristics depending on the central metal ions, substituent chain lengths and their mesophases. Values of 67.55 [Formula: see text]cm[Formula: see text] and 42.31 [Formula: see text]cm[Formula: see text] have been obtained for room temperature in-plane Ohmic conductivity of as-deposited octyl lutetium (C[Formula: see text]LuPc[Formula: see text] and hexyl gadolinium (C[Formula: see text]GdPc[Formula: see text] films, respectively while C[Formula: see text]GdPc[Formula: see text] films exhibit nearly two orders of magnitude smaller conductivity. On annealing at 80[Formula: see text]C, Ohmic conductivities of C[Formula: see text]LuPc[Formula: see text] and C[Formula: see text]GdPc[Formula: see text] are found to have increased but the conductivity of C[Formula: see text]GdPc[Formula: see text] decreased by more than one order of magnitude to 1.5 [Formula: see text]cm[Formula: see text]. For physical interpretation of the charge transport behavior of these three molecules, their UV-vis optical absorption spectra in the solution and in as-deposited and annealed solid phases and atomic force microscopy study have been performed. It is believed that both orientation and positional reorganizations are responsible, depending upon the size of the central ion and side chain length.

Fluorosubstituted lead phthalocyanines: Crystal structure, spectral and sensing properties

In this work, we synthesized and investigated tetra- (PbPcF4) and hexadecafluorinated (PbPcF16) lead phthalocyanines. Their single crystal structures were refined for the first time. PbPcF4 crystallizes in stacks with all molecules facing in one direction identically to the monoclinic PbPc polymorph in the tetragonal space group I4, while PbPcF16 crystallizes in the triclinic P-1 space group. Moreover, the effect of fluorosubstitution on the structural features of thin films grown by organic molecular beam deposition (OMBD), vibrational and UV–visible optical absorption spectra is discussed. Apart from this, the chemiresistive sensor response of PbPcFx (x = 0, 4, 16) films to ammonia (1–5 ppm) in dependence on fluorination degree is also studied. It was shown that the sensor response to ammonia decreases in the order of PbPcF4 > PbPcF16 > PbPc. The nature of interaction between PbPcFx and ammonia molecules was studied using DFT calculations.

Optical, thermal and microstructural studies of epoxy-CoSO4.7H2O hybrid material

Organic–inorganic polymer hybrid films of epoxy polymer were prepared, using Cobaltous sulfate heptahydrate (CoSO4.7H2O) as a filler component, by physical blending method. UV–Vis optical absorption spectra were analyzed to determine optical band gaps (Eg) of the hybrid material. FTIR studies revealed the interaction of inorganic component with molecules of the polymer matrix. Glass transition temperature (Tg) and degradation temperature were determined by DSC. TG analysis showed the improvement in thermal stability of prepared hybrid films. XRD patterns revealed the amorphous nature of the pure epoxy polymer. Additional sharp peaks were seen for higher filler levels (FLs), indicating self formed nanostructures in the material, which was also evident from SEM analysis.

Size-dependent structural phase transitions and their correlation with photoluminescence and optical absorption behavior of annealed Zn0.45Cd0.55S quantum dots

In this paper, we investigate the effect of thermally induced structural phase transitions on the photoluminescence (PL) and optical absorption behaviour of Zn0.45Cd0.55S nanoparticles (NPs). Analysis of X-ray diffraction (XRD) patterns and high-resolution electron microscope (HRTEM) images reveal that the as-synthesized sample possesses zinc-blende-type cubic structure. In addition, at annealing temperature (Ta) 400 °C, the cubic structure transforms completely into the wurtzite-type hexagonal structure. Furthermore, the second phase transition of the as-synthesized sample has observed at 700 °C, where the cubic structure has transformed into mixed polycrystalline phases of hexagonal ZnO, cubic CdO, monoclinic CdSO3, and orthorhombic ZnSO4 structures. These new phases have also confirmed from the analysis of Raman and FTIR spectra. Analysis of UV–visible optical absorption spectra demonstrates that Increasing Ta results in the decrease of optical band gap due the improvement in crystallinity accompanied by the increase in the particle size. The PL emission bands at an excitation energy of 3.818 eV exhibit redshift and a decrease in the intensity with increasing Ta up to 500 °C. Meanwhile, further increase in Ta up to 700 °C results in the enhancement of green emission intensity. On the other hand, PL emission spectra at 3.354 eV and Ta 700 °C, reveal a dramatic increase in the emission intensity nearly by one-order of magnitude with respect to its value of the as-synthesized sample. This behaviour is ascribed to the incorporation of oxygen-related defects via thermal annealing in air, which act as additive radiative centers. Also, we have interpreted the observed spectral blue shift of PL emission spectrum with increasing excitation energy.

2-(4-Ethoxy phenyl)-4-phenyl quinoline organic phosphor for solution processed blue organic light-emitting diodes.

This paper reports the synthesis and characterization of 2-(4-ethoxyphenyl)-4-phenyl quinoline (OEt-DPQ) organic phosphor using an acid-catalyzed Friedlander reaction and the preparation of blended thin films by molecularly doping OEt-DPQ in poly(methyl methacrylate) (PMMA) at different wt%. The molecular structure of the synthesized phosphor was confirmed by Fourier transform infra-red (FTIR) spectroscopy and nuclear magnetic resonance spectra (NMR). Surface morphology and percent composition of the elements were assessed by scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX). The thermal stability and melting point of OEt-DPQ and thin films were probed by thermo-gravimetric analysis (TGA)/differential thermal analysis (DTA) and were found to be 80°C and 113.6°C, respectively. UV-visible optical absorption spectra of OEt-DPQ in the solid state and blended films produced absorption bands in the range 260-340nm, while photoluminescence (PL) spectra of OEt-DPQ in the solid state and blended thin films demonstrated blue emission that was registered at 432nm when excited at 363-369nm. However, solvated OEt-DPQ in chloroform, tetrahydrofuran or dichloromethane showed a blue shift of 31-43nm. Optical absorption and emission parameters such as molar extinction coefficient (ε), energy gap (Eg ), transmittance (T), reflectance (R), refractive index (n), oscillator energy (E0 ) and oscillator strength (f), quantum yield (φf ), oscillator energy (E0 ), dispersion energy (Ed ), Commission Internationale de l'Éclairage (CIE) co-ordinates and energy yield fluorescence (EF ) were calculated to assess the phosphor's suitability as a blue emissive material for opto-electronic applications such as organic light-emitting diodes (OLEDs), flexible displays and solid-state lighting technology.

Defects induced in cerium dioxide single crystals by electron irradiation

Micro-Raman spectroscopy, X-band electron paramagnetic resonance (EPR) spectroscopy, and UV-visible optical absorption spectroscopy were used to study the damage production in cerium dioxide (CeO2) single crystals by electron irradiation for three energies (1.0, 1.4, and 2.5 MeV). The Raman-active T2g peak was left unchanged after 2.5-MeV electron irradiation at a high fluence. This shows that no structural modifications occurred for the cubic fluorite structure. UV-visible optical absorption spectra exhibited a characteristic sub band-gap tail for 1.4-MeV and 2.5-MeV energies, but not for 1.0 MeV. Narrow EPR lines were recorded near liquid-helium temperature after 2.5-MeV electron irradiation; whereas no such signal was found for the virgin un-irradiated crystal or after 1.0-MeV irradiation for the same fluence. The angular variation of these lines in the {111} plane revealed a weak g-factor anisotropy assigned to Ce3+ ions (with the 4f1 configuration) in a high-symmetry local environment. It is concluded that Ce3+ ions may be produced by a reduction resulting from the displacement damage process. However, no evidence of F+ or F0 center or hole center formation due to irradiation was found from the present EPR and optical absorption spectra.

Synthesis, Adsorptive, and Photocatalytic Properties of Carbon Nanotubes/TiO2 Nanocomposite Photocatalysts

The carbon nanotubes/TiO2 (CNTs/TiO2) composite photocatalysts composed of TiO2 nanoparticles and multiwalled carbon nanotubes (CNTs) were prepared by a facile hydrothermal method. The photocatalysts were characterized by a range of analytical techniques including X-ray powder diffraction, field emission scanning electron microscope, thermal gravimetric analysis and UV–Vis optical absorption spectra, etc. The amount of TiO2 nanoparticles growing on CNTs could be tuned by adjusting the dosage of precursor in the reaction solution. Both the adsorptivity and photocatalytic activities of pure CNTs, pure TiO2, and the CNTs/TiO2 nanocomposites were tested by the removal of methylene blue from water in dark and under a simulated sunlight, respectively. By comparison, the improved photocatalytic activity of the CNTs/TiO2 nanocomposite is mainly due to that the CNTs can disperse the active component of TiO2 nanoparticles, provide a larger the specific surface area, as well as act as an electron sink to accelerate the separation of the photogenerated charges.