Papers by Keyword: Absorption Spectra

Abstract: This study provides accounts of the bonding character, electronic structure, and optical properties of the cellulose–polyaniline hybrid complex using principles of quantum mechanics. The calculations revealed cellulose and polyaniline binding energy per unit ranged from -0.52 eV to -0.68 eV. The electron localization function of the complex revealed that there was no value at the interface but deformed basins, indicating a physisorption type of interaction. The highest occupied molecular orbitals and lowest molecular orbitals are mainly dominated by the polyaniline, with minor hybridization of the orbitals of the cellulose in all configurations. These results indicate that the bonding between cellulose and polyaniline is characterized as an unshared electron interaction. Generally, the density of states of the cellulose and polyaniline complex can be considered a superposition of the states of isolated subsystems—the bandgap of the complex ranges from 2.30 eV to 2.87 eV. The lowest bandgap is observed when the prototype polyaniline is placed near the cellulose hydroxy and hydroxymethyl group. Further, the optical absorption spectra are calculated using time-dependent density functional theory. The results indicate that the prominent peak of the prototype polyaniline at 3.59 eV (345.36 nm) is suppressed at the complex. Meanwhile, in the higher energy region, the optical absorption spectra can be considered a superposition of the absorption spectra of the isolated constituents. The results presented here provide new information on the cellulose–polyaniline complex's bonding mechanism and give the resulting electronic–optical properties. The results will be helpful in the development of innovative biomaterials, fibers, and multifunctional composites based on cellulose and polyaniline.

Abstract: Colloidal solutions of copper (I) oxide, Cu₂O, were obtained by pulsed laser ablation of metallic copper target in distilled water using fundamental harmonic of Nd:YAG laser (1064 nm, 7 ns, 20 Hz). Nanocolloids obtained were applied to cotton fabric. Nanoparticles composition and structure were studied by UV-Vis and Raman spectroscopy, transmission and scanning electron microscopy, and XRD. Antibacterial activity of Cu₂O nanoparticles on cotton fabric to E.coli bacteria was demonstrated in comparison with zinc oxide nanoparticles.

Abstract: In the article we present a unique analytical tool for the characterization of conjugated polymers – SEC-DAD (Size Exclusion Chromatography – Diode Array Detector). The chromatographic separation is performed in a conventional SEC mode which provides narrow molecular-weight fractions of the analyzed polymer. The uniqueness of the SEC-DAD combination comes out with the utilization of DAD for the monitoring the absorption characteristics of particular fractions along the molecular weight distribution. If applied in the characterization of the conjugated polymers, SEC-DAD helps to reveal the dependencies of (i) the extent of conjugation and (ii) covalent and configuration structure of the polymer on the molecular weight.

Abstract: Single crystalline high quality α-Mn₂O₃ nanorods and sea-urchins assembled with pen-type nanoneedles have been successfully synthesized by template-free hydrothermal route. The variation in hydrothermal temperature has affected the morphology of the α-Mn₂O₃ sea-urchin assembled with the nanoneedles noticeably. The influence of temperature change on the thickness, crystallinity, surface morphology and optical properties of α-Mn₂O₃ has been characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), Raman Spectroscopy (RS) and UV-visible Spectroscopy. The results showed that in our experimental conditions, single crystalline nanorods of the α-Mn₂O₃ were obtained at a low temperature of 180 °C, while single crystalline sea-urchin assembled with pen-type nanoneedles were obtained by increasing the temperature to 280 °C. Nanorods and sea-urchin assembled with pen-type nanoneedles obtained had the well defined morphology and crystalline quality. The sea-urchin synthesized at 280 °C exhibited more than 90% absorption in UV-visible spectrum.

Abstract: Modifying the optical properties of rare earth doped phosphate glasses in a tunable fashion via the embedment of magnetic nanoparticles (NPs) is challenging for magneto-optic devices. Glasses with compositions (69-x)P₂O₅-30ZnO-1Er₂O₃-(x)Fe₃O₄, where x = 0 to 1.5 mol% are prepared by conventional melt quenching method. The Fe₃O₄ NPs concentration dependent density, molar volume, refractive index and optical properties are determined. Density and molar volume shows strong correlation with structural alteration in the presence of NPs. The XRD spectra confirm the disordered nature of the glass and TEM micrograph display the presence of spherical NPs with average size ~26 nm. The optical band gap and Urbach energy calculated from the room temperature absorption spectra recorded in the range of 350-1700 nm reveal significant improvement. The density and refractive index increases and the molar volume decreases with the increase of Fe₃O₄ contents. The energy band gap for direct and indirect transitions varies in the range of 4.47-3.64 eV and 4.27-3.53 eV, respectively. The Urbach energy increases from 0.15 to 0.19 eV as the NPs concentration increases from 0 to 1.5 mol%.

Abstract: A new Diels-Alder Adduct of C₆₀ with 1,1’-biindene (CB) has been synthesized. The Langmuir trough study of this new fullerene derivative indicates that floating film could form monomolecular thick film at the air/water interface at lower concentration, and can be well transferred the floating mixed CB and arachidic acid film onto substrates using the Langmuir-Blodgett (LB) technique. In the case of the mixed film, high quality films with thickness of up to 50 layers could be readily built up. The absorption variation with film thickness at 255nm was measured, indicating good LB deposition up to 50 layers.

Abstract: As the third generation solar cells, quantum dot sensitized solar cells (QDSSC) has received wide attention from researchers because of its high theoretical energy conversion efficiency and low production costs. The preparation of CdS quantum dots for TiO₂ inverse opal based QDSSC by successive ionic layer absorption and reaction (SILAR) was investigated. The optimized number of SILAR cycle and ionic reaction time was obtained by the analysis of absorption spectra.

Abstract: Ho³⁺ doped zinc bismuth borate glasses of the composition 10ZnO : 30Bi₂O₃ : (60-x)B₂O₃ : xHo₂O₃ (where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol%) were fabricated by conventional melt quenching technique. In order to understand the role of Ho₂O₃ in these glasses, the density, molar volume and optical spectra were investigated. The molar volume decreases with an increase in Ho₂O₃ content, which is attributed to the structure becomes more compacted. The absorption spectra of Ho³⁺ doped in zinc bismuth borate glass correspond to several bands, which are assigned from the ground state, ⁵I₈ to ⁵G₅ (420 nm), ⁵G₆ + ⁵F₁ (451 nm), ⁵F₂ + ⁵F₄ (538 nm), ⁵F₅ (643 nm) and ⁵I₅ (1152 nm). Moreover, the optical basicities were also theoretically determined.

Abstract: Gallium Arsenide (GaAs) because of having unique characteristics like direct band gap, higher electron mobility and saturated electron velocity etcetera, has wide applications specifically in optoelectronic devices. In this research work we present a comprehensive density functional theory (DFT) based first principles study of optical properties of GaAs. Exchange correlation functional (XC) play a key role in the DFT investigations. A comparative study of the optical properties is presented based upon local density approximation (LDA) by Perdew and wang, Perdew-Burke-Ernzerhof parameterized generalized gradient approximation (GGA-PBE), Wu-Cohen parameterized GGA (GGA-WC) and Engel and Vosko proposed GGA (GGA-EV). Computations in this study have been performed by full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) approach designed within DFT as realized in the computational code WIEN2k. Our investigations, for the optical properties of GaAs with mentioned XC potentials, cover detailed analysis of dielectric functions, absorption coefficient α (ω), energy loss functions, reflectivity R(ω), refractive index n (ω) and extinction coefficient k (ω). The analysis shows that the optical parameters calculated with GGA-PBE are comparatively reasonable and closer to the experimental results. Keywords: Density functional theory, local density approximation, gradient and other corrections, APW calculations, Dielectric function, absorption and reflection spectra PACS: 71.15.Mb, 71.15.Ap, 77.22.Ch, 78.40.Pg

Abstract: The dosimetry characteristic of Rhizophora Apiculata dye solutions with and without 2, 3, 5 - triphenyltetrazolium chloride (TTC) salt to low dose of gamma irradiation up to 100Gy were investigated spectrometrically. The maximum absorbance was peaking at wavelength of 664nm characteristics of red colour. The dose responses at 664nm wavelength were found decreased with increase of gamma irradiation leading to colour bleaching of the dye solution. The dose sensitivity value of dye solution with TTC lower compared to dye solution without TTC. The colour stability of dyes solutions also have been investigated, the absorbance spectra found no significant change after stored in a dark room at room temperature for 2 weeks.