Papers by Keyword: UV-Visible

Abstract: Starch-based biodegradable films of polybutylene adipate co-terephthalate (PBAT) have been prepared by the solution casting method. The effect of heating at two different temperatures (80 and 110°C) on the mechanical, optical and morphological properties of these films has been evaluated. The two temperatures were selected based on the crystallization and melting temperatures of PBAT. The blend of PBAT with thermoplastic starch has been prepared by melt mixing technique using two roll mills and then the solution casting method has been followed to prepare the films. Apart from curing at room temperature, the films have been cured at 80°C and 110°C. The tensile strength of the films increased by 110% and 252% for films heated to 80°C and 110°C, respectively. As revealed from spectroscopic analysis, the heating of films has no significant effect on the absorption of light by the films in the UV-visible region. The bonding characteristics of the films have been evaluated using Fourier transform infrared (FTIR) spectroscopy. The lowest water absorption and vapour permeability have been obtained in films cured at 80°C.

Abstract: In the present investigation, Y³⁺ doped (5 wt. %, 10 wt. %, and 12 wt. %) cerium sesquisulfides (Ce₂S₃) nanoparticles (NPS) were synthesized by a simple chemical precipitation method. Thin films of Y³⁺:Ce₂S₃ NPs achieved on ITO (indium tin oxide) substrate. XRD (X-ray diffraction) patterns were used to estimate the size of the NPS, morphology index, texture coefficient, and lattice constants. The crystallite size was found to be in the range of 18-34 nm. UV-visible spectral studies were carried out in order to understand optical absorptivity, and optical band (E_g) of the as-synthesized nanostructures (NS). It has been observed that the red shift in the optical absorptivity and E_g value varies between 3.45 eV to 2.59 eV. Morphology and the presence of Y⁺³ were investigated by scanning electron microscope (SEM) and energy dispersive X-ray studies (EDX). However, agglomerated spherical-shaped NPs and homogeneous dispersion of Y³⁺ were observed in EDX analysis. Chemical constituents and nature of the doped NS were examined by X-ray photoelectron spectroscopy (XPS), and binding energies matched with Y 3d_3/2, Y 3d_5/2, Ce 3d_3/2, Ce 3d_5/2, O1s, C1s peaks. Y³⁺: Ce₂S₃ (12 wt. %) NS subjected for dielectric property studies in the frequency range of 10 Hz-10 MHz at room temperature (RT). High dielectric permittivity (Ɛ), and very low dielectric loss (tan δ) were observed at low frequency for 12 wt. % Y³⁺:Ce₂S₃ NS as compared with other doped NS. The as-synthesized NS can be used for high dielectric permittivity, low dielectric loss, and capacitor-related applications.

Abstract: In the current study, the density function theory (DFT) is used to investigate the chemical adsorption strength of NO₂ gas molecule. The relaxation structure, molecular orbital energy, energy gap and adsorption energy are calculated at ground state. The time dependent DFT (TD-DFT) used to simulate excitation provides UV-Visible spectrum. There was a perpendicular geometrical orientation of the gas molecule around the surface and an adsorption distance of 2.58 Å. The adsorption distance shows the chemical reaction between the gas molecule and the surface. The result of adsorption energy indicates that the gas molecule that closed to the surface has high interaction and it decreases gradually when gas molecule goes further from the graphene nano-ribbon surface. The UV-Visible measurement indicates that the system interaction with gas molecule has red shifting in electromagnetic radiation. The final result concludes that graphene nano-ribbon has high reactivity for NO₂ gas molecule. The theoretical calculations provide the ability to design optical sensor which has useful applications in an environmental monitoring.

Abstract: In this study, Zinc oxide (ZnO) undoped and Lanthanum doped (ZnO: La) thin films were deposited on 400°C heated glass using spray pyrolysis technique with moving nozzle. The components (Zn (CH₃COO)2, 2H₂O) and (LaCl₃, 7H₂O) were used as sources to produce ZnO thin film and doped Lanthanum, respectively. Effects of dopant on the optical and structural properties of undoped and 0, 2 and 4 wt. % Lanthanum doped ZnO thin films were studied. Optical transmittance spectra of the films showed high transparency of about 98% in visible region. The optical gap for ZnO and 0, 2 and 4 wt. % La doped ZnO thin films were found to be in 3.25-3.28 [eV] range. The X-ray diffraction showed that the thin films have hexagonal wurtzite structure with a strong (002) as preferred orientation, whereas the crystalline size was ranged in 15.89-33.45 nm. The ZnO thin films are promising to be used a light emitting diodes, gas sensor and UV detectors applications.

Abstract: In this paper, the influence of immersion time on the structural and optical properties of SnO2 thin films was investigated. A series of samples was deposited by Sol-Gel dip coating method onto glass substrates. The number of layers was fixed at 03, but the immersion time was varied between 01 to 10 minutes. The samples [(3 layers) - SnO2 / glass] were submitted to thermal treatments in air at 500°C during 2h. The specimens are characterized by Raman spectroscopy and UV-Visible spectroscopy. Raman spectroscopy show that the thin films of SnO2 obtained at 06 and 10 minutes of immersion time, are crystallizes in rutile phase. The obtained results of optical analysis showed that the SnO2 thin films are transparent (77-85%) in the visible region and the values of the optical band gap varied from 3.81eV and 3.86 eV.

Abstract: Silver nanoprisms, a kind of silver nanoparticles (NPs) synthesized by chemical reduction in water phase and treated with the light irradiation, have special optical properties and can be used as optoelectronic materials. However the hydrophilic property of silver nanoprisms suppresses their applications. In this study, thiols were used to modify the surface of the silver nanoprism to enhance its hydrophobicity. The ultraviolet-visible spectrometry (UV-Visible) was used to explore the surface properties of the NPs. Experimental results showed that the addition of a long chain thiol (pure 1-undecanthiol) to the water solution of silver nanoprisms gave a red shift in the absorption spectra in comparing with that of original silver nanoprisms colloid. It is due to the absorption of the thiol to surfaces of the NPs. The absorption of the long chain thiols can turn the hydrophilic surface to be hydrophobic. The NPs treated with the cracking rubber oil had the similar results. It is believed that the cracking rubber oil can be a feasible agent to enhance the surface hydrophobicity of silver nanoprisms.

Abstract: An investigation has been done to study the influence of the Fe and Al doping concentration on the optical properties of zinc oxide thin films. A spray pyrolysis system was used to obtain ZnO:M films doped with Iron and Aluminum, using zinc acetate dihydrate, hydrated iron chlorate and hydrated aluminum chlorate, respectively. The temperature and the concentration were fixed at 450°C and 0.1mol/L, respectively. Our thin films deposed on glass substrate. UV-VIS spectrophotometer has been used for the layers characterization. The optical transmittance spectra showed that the 2% Al dopand improves the optical transmittance in the visible that the Fe dopand. Zinc oxide thin films is the n type semiconductor with direct optical band gap varied between 3.219-3.346eV for obtain the films in photovoltaic application. But the urbach energy of ZnO thin films undoped and doped by Iron and Aluminum is varied between 101– 202 meV.

Abstract: CuAlO₂ microcrystallites were synthesized by Sol-gel method at 1200°C with Cu (CH₃COO)₂·H₂O, Al (NO₃)₃·9H₂O and ethylene glycol as raw materials. The phase composition,morphology,and optical properties of CuAlO₂ microcrystallites were chatacterized by X-ray diffraction, Scanning electron microscope,Photoluminescence and UV-visible spectroscopy respectively. The results of XRD show that CuAlO₂ with delafossite crystal structure is obtained. The defect emission were observed through PL spectrum test. It can be concluded that Cu-vacancy may be the possible reason of the observed activated p-type conductivity of CuAlO₂. Can be found three characterized peak (λ₁=290nm, λ₂=410nm, λ₃=430 nm) on the spectra.

Abstract: We have These films were irradiated with 85 MeV C-ions at the fluences of 1 x 10¹¹ and 1 x 10¹² ions/cm². Changes in the optical, structural, dielectric, magnetic and thermal properties of (PMMA)/Ni nanocomposites of different concentrations of nickel nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of UVvisible spectroscopy, X-ray diffraction, impedance gain phase analyzer, SQUID and differential scanning calorimetry. Optical properties like band gap were estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength range 200-800 nm. It was found that the band gap value shifted to lower energy on doping with metal nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to the scissioning of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Surface morphology of the pristine and irradiated films was studied by scanning electron microscopy (SEM). The breakage of chemical bonds resulted in an increase of free radicals, unsaturation etc. as revealed from FTIR analysis. The dielectric properties were observed to enhance with an increase in metal compound concentration as well as with irradiation dose. This may be due to metal/polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. Zero-Field-Cooled (ZFC)/Field-Cooled (FC) magnetization and magnetic hysteresis measurements were performed using a superconducting quantum interference device (SQUID) magnetometer from temperatures ranging from 5 K to 300 K, to investigate the magnetic properties of nanocomposites. The changes in topography of surfaces were also observed upon irradiation.

Abstract: High energy ion beam induced modifications in polymeric materials is of great interest from the point of view of characterization and development of various structures and filters. Due to potential use of conducting polymers in light weight rechargeable batteries, magnetic storage media, optical computers, molecular electronics, biological and thermal sensors, the impact of swift heavy ions for the changes in electrical, structural and optical properties of polymers is desirable. The high energy ion beam irradiation of polymer is a sensitive technique to enhance its electrical conductivity, structural, mechanical and optical properties. Recent progress in the radiation effects of ion beams on conducting polymers are reviewed briefly. Our recent work on the radiation effects of ion beams on conductive polymers is described. The electrical, structural and optical properties of irradiated films were analyzed using V-I, X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV-Visible spectroscopy and Fourier transform infrared spectroscopy methods.