Physical Properties of Nanostructured CdO Films from Alkaline Baths Containing Saccharin as Additive
Nanostructured cadmium oxide (CdO) films were fabricated on glass substrates from alkaline baths containing saccharin as an additive by a successive ionic layer adsorption and reaction (SILAR) method. The effects of saccharin concentration in the bath on the structural, morphological, and optical properties were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence, and Raman spectroscopy. The analyses showed that the surface morphologies, XRD peak intensities, Raman spectroscopy, and photoluminescence properties of CdO films changed with saccharin concentration. From the results, it can be said that morphological characteristic and optical properties of the films could be calibrated by adding various saccharin percentages in the growth bath.
OPTOELECTRONIC PROPERTIES OF EU- AND H-CODOPED CDO FILMS
Abstract Structural, electrical, and optical properties of lightly (0.8 wt%) Eu-doped CdO thin films post-annealed in hydrogen atmosphere for different durations (15 min, 30 min, and 45 min) were studied. The prepared films were characterised by X-ray fluorescence, X-ray diffraction, UV–VIS–NIR absorption–reflection spectroscopy. The result indicates that H2 annealing does not change the crystalline CdO structure of the films. The bandgap of the hydrogenated Eu-doped CdO films changes with H2-annealing time following the changing in the carrier concentration. These results were found to be in agreement with the available models of bandgap widening with narrowing. The electrical behaviours of hydrogenated and non-hydrogenated Eu-doped CdO films show that they are degenerate semiconductors with bandgap around 1.8 eV. The Eu-doping of CdO films enhances the electrical conduction and additional enhancement was obtained with H2 low-temperature pre-annealing. It was found that the greatest enhancement of the electrical conduction parameters occurs by annealing of CdO:Eu films in H2 atmosphere for 15–30 min when the conductivity increased by about 90% and the free-electrons concentration increased by about 212% relative to the non-hydrogenated CdO:Eu. From transparent conducting oxide point of view, Eu is sufficiently effective for CdO doping especially when including pre-annealing in H2 atmosphere.
Development of new analytical methods for the determination of caffeine content in aqueous solution of green coffee beans
BackgroundThis study was conducted to develop fast and cost effective methods for the determination of caffeine in green coffee beans. In the present work direct determination of caffeine in aqueous solution of green coffee bean was performed using FT-IR-ATR and fluorescence spectrophotometry. Caffeine was also directly determined in dimethylformamide solution using NIR spectroscopy with univariate calibration technique.ResultsThe percentage of caffeine for the same sample of green coffee beans was determined using the three newly developed methods. The caffeine content of the green coffee beans was found to be 1.52 ± 0.09 (% w/w) using FT-IR-ATR, 1.50 ± 0.14 (% w/w) using NIR and 1.50 ± 0.05 (% w/w) using fluorescence spectroscopy. The means of the three methods were compared by applying one way analysis of variance and at p = 0.05 significance level the means were not significantly different. The percentage of caffeine in the same sample of green coffee bean was also determined by using the literature reported UV/Vis spectrophotometric method for comparison and found to be 1.40 ± 0.02 (% w/w).ConclusionNew simple, rapid and inexpensive methods were developed for direct determination of caffeine content in aqueous solution of green coffee beans using FT-IR-ATR and fluorescence spectrophotometries. NIR spectrophotometry can also be used as alternative choice of caffeine determination using reduced amount of organic solvent (dimethylformamide) and univariate calibration technique. These analytical methods may therefore, be recommended for the rapid, simple, safe and cost effective determination of caffeine in green coffee beans.