Absorption Bands In Ultraviolet Region Research Articles

Study of lead free double perovskites Na2XAgCl6 (X = Ga, In Tl) for solar cells and transport applications

The double perovskites are rich merchant to harvest energy from solar cells and thermoelectric generators to cover up its shortfall. Therefore, in this article, the electronic, optical, and thermoelectric characteristics of Na2XAgCl6 (X = Ga, In Tl) are briefly elaborated. The tolerance and octahedral factors are calculated for structural stability and formations energy for thermodynamically existence. The band structures are show the tuning of band gap from 2.57 eV to 1.30 eV by the changing cations from Ga to Tl. The density of states shows the p-d hybridization among X, Ag and Cl ions is responsible for decreasing band gap. The optical analysis in terms of dielectric constant, absorption and other dependent parameters illustrate broad absorption bands in ultraviolet region (Ga, In) and in visible region (Tl). The shifting of absorption zone to visible region increase their potential for solar cells. Thermoelectric calculations have been performed to evaluate the electrical conductivity, Seebeck coefficient, and thermal conductivity by BoltzTraP code. The large figure of merit and extremely small lattice thermal conductivity at room temperature also make them important for thermoelectric generators fabrication to harvest heat energy.

Photoacoustic spectroscopy as an approach to assess chemical modifications in edible oils

Photoacoustic spectroscopy was used to obtain optical properties of edible soybean, canola and olive oils as well to evaluate the oil modifications induced by thermal treatment. The normalized photoacoustic signal intensity and its phase were independently measured as a function of wavelength of the radiation source. The oil samples were heated up to the smoke point and then for additional 30 min in order to degrade them. After, the oil samples were cooled down and photoacoustic measurements were conducted in order to obtain the absorption spectra of samples at both degraded and non-degraded conditions. Comparisons between the two conditions indicate that the degraded oil samples exhibited widening of the absorption bands in ultraviolet region of the spectra, relative to the respective non-degraded sample. Also, the peaks of those absorption bands presented a red shift.

Photoacoustic Spectroscopy as an Approach to Assess Chemical Modifications in Edible Oils

Photoacoustic spectroscopy was used to obtain optical properties of edible soybean, canola and olive oils as well to evaluate the oil modifications induced by thermal treatment. The normalized photoacoustic signal intensity and its phase were independently measured as a function of wavelength of the radiation source. The oil samples were heated up to the smoke point and then for additional 30 min in order to degrade them. After, the oil samples were cooled down and photoacoustic measurements were conducted in order to obtain the absorption spectra of samples at both degraded and non-degraded conditions. Comparisons between the two conditions indicate that the degraded oil samples exhibited widening of the absorption bands in ultraviolet region of the spectra, relative to the respective non-degraded sample. Also, the peaks of those absorption bands presented a red shift.

Photoconducting hybrid perovskite containing carbazole moiety as the organic layer: Fabrication and characterization

PbCl 2-based thin films of perovskite structure with hole-transporting carbazole derivatives as the organic layer were successfully prepared by spin-coating from dimethylformamide solution containing stoichiometric amounts of organic and inorganic moieties. The crystal structure and optical property of the hybrid perovskite were characterized by Fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD), UV–vis absorption and photoluminescence (PL). FT-IR spectra confirmed the formation of organic–inorganic hybrid perovskite structure. UV–vis spectra of hybrid perovskite thin films exhibited a wide absorption band in ultraviolet region as well as a sharp peak at 330 nm characteristic of PbCl 2-based layered perovskite. X-ray diffraction profiles indicated that the layered structure was oriented parallel to the silica glass slide plane. Meanwhile, double-layer photoreceptors of the hybrid perovskite were also fabricated, which showed the enhancement of photoconductivity by carbazole chromophore.

A Study of the Absorption Spectra of Cerium in Glasses

The absorption bands of cerium in trivalent and tetravalent states in silicate and phosphate glasses, whose exact positions are still open to discussion, and the effects introduced by the change of composition and of melting condition were investigated.For the measurement of the absorption spectra of silicate glasses with poor ultraviolet transmission the thickness of the sample plates was reduced to 0.12-0.02mm by polishing.The results obtained are as follows: (1) In the silicate glass consisting of K2O, BaO, and SiO2, Ce3+ gives a sharp and weak absorption band at 320mμ, whereas Ce4+ gives a broad and strong absorption band in ultraviolet region below 350mμ. (2) In the phosphate glass consisting of K2O, BaO, Al2O3 and P2O5, Ce3+ gives three sharp and weak absorption bands at 294, 245, and 227mμ, whereas Ce4+ gives a broad and strong absorption band in ultraviolet region, as before.