Investigation of the Reflectivity Spectrum of the a-Plane Oriented ZnO Epilayers Grown by Plasma-Assisted Molecular Beam Epitaxy from the Gaussian Distribution
Alioune Aidara Diouf,
Bassirou Lo,
Abel Sambou,
Oumar Sakho,
Aboubaker Chedikh Beye
Issue:
Volume 5, Issue 5, October 2017
Pages:
50-54
Received:
25 October 2017
Accepted:
3 November 2017
Published:
18 December 2017
Abstract: The Photoluminescence spectra at low temperature of the a-plane oriented ZnO grown on r-plane (011-2) sapphire substrates by plasma-assisted molecular beam epitaxy, showed experimentally three types of excitons A, B and C. In the reflectivity spectra, authors used a program based on the theory of the spatial resonance dispersion Hopfield model to fit the free excitons. The A and B free excitons were fitted together and the C exciton with the band gap. But these fits were not perfect in the transparency zone at low energy. This is mainly due to the fact that the A and B free excitons are closer and the C exciton is closer to the band gap but another reason is the value of the oscillator strength. In the present work, we present a method taking account the Gaussian distribution, to fit perfectly the excitons A, B and C using almost the same physical parameters than the theory of the spatial resonance dispersion Hopfield model.
Abstract: The Photoluminescence spectra at low temperature of the a-plane oriented ZnO grown on r-plane (011-2) sapphire substrates by plasma-assisted molecular beam epitaxy, showed experimentally three types of excitons A, B and C. In the reflectivity spectra, authors used a program based on the theory of the spatial resonance dispersion Hopfield model to f...
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Optical Photocatalytic Degradation of Methylene Blue Using Lignocellulose Modified TiO2
Yilkal Dessie Sintayehu,
Abebe Belay Gemeta,
Solomon Girmay Berehe
Issue:
Volume 5, Issue 5, October 2017
Pages:
55-58
Received:
8 February 2017
Accepted:
4 March 2017
Published:
19 December 2017
Abstract: This paper reports the photo-catalytic activity and stability of Lignocellulose/TiO2 nanoparticles (NPs) was evaluated through using the decomposition of methylene blue (MB) as a testing model reaction under visible light irradiation (λmax > 420nm). The modified (NPs) (pH = 6.94 - 6.97) photocatalyst material was dried for 24 hours at the temperature of 80°C and calcinated at 400°C for 2 hours through constant air flow. The degradation of MB was performed using 250 Watt xenon lamp within every 30 minute time interval followed by measuring the absorbance. The maximum characterstic absorption peak of MB solution was observed at (λmax ~ 664nm) and the absorbance of this peak approaches to a minimum value and the degradation efficiency become effective after illumination for 150 minute. Optimized parametric conditions like pH ≈ 6, initial concentration (Co= 6 ppm), time = 120 min and catalyst loading (160 mg) results were examined to improve the degradation efficiency (> 95%).
Abstract: This paper reports the photo-catalytic activity and stability of Lignocellulose/TiO2 nanoparticles (NPs) was evaluated through using the decomposition of methylene blue (MB) as a testing model reaction under visible light irradiation (λmax > 420nm). The modified (NPs) (pH = 6.94 - 6.97) photocatalyst material was dried for 24 hours at the temperatu...
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