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Dhaka, Bangladesh
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Doha M.H.,University of Dhaka | Alam M.J.,University of Dhaka | Rabeya J.,University of Dhaka | Siddiquee K.A.M.H.,University of Dhaka | And 6 more authors.
Optik | Year: 2015

Zinc sulfide (ZnS) thin films are deposited onto both bare and ITO coated glass by low-cost and simple aqueous chemical bath deposition (CBD) method for using it in thin film solar cells. The optimized growth conditions are chosen for deposition of ZnS thin films by investigating photo-electrochemical (PEC), optical, structural and morphological properties of both as-deposited and annealed films. PEC measurements of the films show n-type electrical conductivity. Optical measurements show that the films have higher transmittance and lower absorbance above 700 nm. The band gap of the films lies in the range 3.67-3.68 eV for bare glass substrates and 3.62-3.65 eV for ITO coated conducting glass substrates. From the X-ray diffraction (XRD) study, as-deposited films are found to be polycrystalline with (1 1 1) and (2 2 0) preferential orientations of the cubic structure. The XRD results show that the average crystallite size is estimated to 40.41 nm for as-deposited films and 50.59 nm for annealed films deposited on to bare glass substrates. For ITO coated conducting glass substrates it is estimated to 43.23 nm for as-deposited films and to 53.32 nm for annealed films. The XRD results also show that lattice constant of ZnS is observed to 0.5626-0.5671 nm. From Scanning Electron Microscopy (SEM) study it is found that the films appeared dense crack-free surfaces with regular granular shaped grains. Comparing the results of the deposited ZnS thin films on bare and ITO coated glass substrates, it is observed that the properties of the deposited films are not substrate dependent. © 2015 Elsevier GmbH. All rights reserved.


Rahman M.M.,University of Rajshahi | Khan M.K.R.,University of Rajshahi | Islam M.R.,University of Rajshahi | Halim M.A.,University of Rajshahi | And 4 more authors.
Journal of Materials Science and Technology | Year: 2012

The nano-structural Al-doped ZnO thin films of different morphologies deposited on glass substrate were successfully fabricated at substrate temperature of 350 °C by an inexpensive spray pyrolysis method. The structural, electrical, optical and photoluminescence properties were investigated. X-ray diffraction study revealed the crystalline wurtzite (hexagonal) structure of the films with nano-grains. Scanning electron microscopy (SEM) micrographs indicated the formation of a large variety of nano-structures during film growth. The spectral absorption of the films occurred at the absorption edge of ∼410 nm. In the present study, the optical band gap energy 3.28 eV of ZnO decreased gradually to 3.05 eV for 4 mol% of Al doping. The deep level activation energy decreased and carrier concentrations increased substantially with increasing doping. Exciting with the energy 3.543 eV (λ=350 nm), a narrow and a broad characteristic photoluminescence peaks that correspond to the near band edge (NBE) and deep level emissions (DLE), respectively emerged. © 2012 The Chinese Society for Metals.


Aminul Islam M.,University of Rajshahi | Gafur M.A.,BCSIR | Saidul Islam M.,University of Rajshahi
Science of Sintering | Year: 2015

A good understanding about the properties of La/Nd doped Bismuth Titanate (BIT) ceramics at high temperature is very important as the new materials being developed based on the BIT. Pure BIT, La doped (BLT), Nd doped (BNT) and La and Nd co-doped BIT (BLNT) powders were synthesized by solid state reaction method. Prepared powders were calcined at different temperatures and structural properties measured by XRD. For pure BIT better crystal quality was obtained at 750°C and for both BLT and BNT better result obtained at 800°C. Calcined powders were formed into pellets and sintered at different temperatures and its dielectric properties were characterized. Optimum sintering temperature for both BLT and BNT showed was 850°C and La and Nd co-doped bismuth titanate (BLNT) revealed optimum sintering temperature of 950°C. Therefore, optimum sintering temperature of bismuth titanate was increased due to La and Nd doping. © 2015, International Institute for the Science of Sintering (IISS). All rights reserved.


Rahman M.M.,University of Rajshahi | Islam M.B.,BCSIR | Biswas M.,University of Rajshahi | Khurshid Alam A.H.M.,University of Rajshahi
BMC Research Notes | Year: 2015

Background: In humans, many diseases are associated with the accumulation of free radicals. Antioxidants can scavenge free radicals and minimize their impact. Therefore, the search for naturally occurring antioxidants of plant origin is imperative. Here, we aimed to investigate the antioxidant and free radical scavenging properties of methanolic extracts from Tabebuia pallida (T. pallida) stem bark (TPSB), root bark (TPRB), leaves (TPL), and flowers (TPF). Methods: The antioxidant and free radical scavenging activity were determined by several standard methods using spectrophotomer. Total phenolic and flavonoid contents were estimated using Folin-Ciocalteu reagent and aluminum chloride colorimetric assay methods, respectively. Results: Among the extracts, TPL showed the highest total antioxidant capacity followed by TPRB, TPF, and TPSB. Based on DPPH and hydroxyl radical scavenging activity, TPL showed strong scavenging activity (91.05 ± 1.10 and 62.00 ± 0.57) with IC50 of 9.20 ± 0.28 and 46.00 ± 2.84 μg/mL, respectively when compared with standard BHT (IC50 of 7.00 ± 0.25 μg/mL) and CA (75.00 ± 0.14 μg/mL). These results suggest that TPL had the highest radical scavenging activity among the extractives that closely resembled the standard's. In lipid peroxidation inhibition assay, TPL exhibited the most potent inhibitory activity (83.18 ± 2.12 %) with IC50 of 12.00 ± 2.12 μg/mL, which closely resembled standard CA (IC50 of 10.50 ± 0.28 μg/mL). Also, the reducing capacity on ferrous ion was in the following order: TPL > TPRB > TF > TPSB. The phenolic and flavonoid contents of TPL were higher than other extractives. A positive correlation (p value <0.001) was observed between phenolic content and free radical (DPPH· and ·OH) scavenging efficiencies and lipid peroxidation inhibition activity. Conclusion: Methanolic extract of T. pallida leaf is a potential source of natural antioxidants and serves as an effective free radical scavenger and/or inhibitor. Hence, T. pallida might be a good plant-based pharmaceutical product for several diseases caused by free radicals. © 2015 Rahman et al.


Muhlbach H.P.,University of Hamburg | Tantau H.,University of Hamburg | Stubbe A.,University of Hamburg | Palm D.,University of Hamburg | And 6 more authors.
Plant Tissue Culture and Biotechnology | Year: 2014

Dieback of sissoo (Dalbergia sissoo Roxb.) is a devastating plant disease, whose causative biotic agents were not yet identified unequivocally. Our previous studies revealed that bacteria belonging to the genus Pseudomonas were associated with dieback-affected sissoo trees. To study the bacterial community associated with dieback-affected sissoo trees, DNA based approaches were used in the present work. Sequencing almost the complete 16S rRNA gene of 33 selected Pseudomonas isolates allowed them to be grouped into two main clusters only. The major group consisted of 19 isolates related to P. oryzihabitans, while in the minor one ten isolates related to P. putida were found together with very few other pseudomonads. Almost the same clustering was obtained a with the independent grouping methods of amplified ribosomal DNA restriction analysis (ARDRA). These results strongly indicate that mainly bacteria strains related to Pseudomonas oryzihabitans were associated with dieback-affected Dalbergia sissoo trees. Immuno-histological studies with thin-sections of sissoo roots using Pseudomonas-specific antibodies showed that bacteria had invaded the root parenchyma. © 2014, Bangladesh Association for Plant Tissue. All rights reserved.


Khan M.K.R.,University of Rajshahi | Rahman M.A.,University of Rajshahi | Shahjahan M.,University of Rajshahi | Shahjahan M.,University of Toyama | And 4 more authors.
Current Applied Physics | Year: 2010

CdO and Al-doped CdO nano-crystalline thin films have been prepared on glass at 300 °C substrate temperature by spray pyrolysis. The films are highly crystalline with grain size (18-32 nm) and found to be cubic structure with lattice constant averaged to 0.46877 nm. Al-doping increased the optical transmission of the film substantially. Direct band gap energy of CdO is 2.49 eV which decreased with increasing Al-doping. The refractive index and dielectric constant varies with photon energy and concentration of Al as well. The conductivity of un-doped CdO film shows metallic behavior at lower temperature region. This behavior dies out completely with doping of Al and exhibits semiconducting behavior for whole measured temperature range. Un-doped and Al-doped CdO is an n-type semiconductor having carrier concentration is of the order of ∼1021 cm-3, confirmed by Hall voltage and thermo-power measurements. © 2009 Elsevier B.V. All rights reserved.


PubMed | BCSIR and University of Rajshahi
Type: | Journal: BMC research notes | Year: 2015

In humans, many diseases are associated with the accumulation of free radicals. Antioxidants can scavenge free radicals and minimize their impact. Therefore, the search for naturally occurring antioxidants of plant origin is imperative. Here, we aimed to investigate the antioxidant and free radical scavenging properties of methanolic extracts from Tabebuia pallida (T. pallida) stem bark (TPSB), root bark (TPRB), leaves (TPL), and flowers (TPF).The antioxidant and free radical scavenging activity were determined by several standard methods using spectrophotomer. Total phenolic and flavonoid contents were estimated using Folin-Ciocalteu reagent and aluminum chloride colorimetric assay methods, respectively.Among the extracts, TPL showed the highest total antioxidant capacity followed by TPRB, TPF, and TPSB. Based on DPPH and hydroxyl radical scavenging activity, TPL showed strong scavenging activity (91.05 1.10 and 62.00 0.57) with IC50 of 9.20 0.28 and 46.00 2.84 g/mL, respectively when compared with standard BHT (IC50 of 7.00 0.25 g/mL) and CA (75.00 0.14 g/mL). These results suggest that TPL had the highest radical scavenging activity among the extractives that closely resembled the standards. In lipid peroxidation inhibition assay, TPL exhibited the most potent inhibitory activity (83.18 2.12 %) with IC50 of 12.00 2.12 g/mL, which closely resembled standard CA (IC50 of 10.50 0.28 g/mL). Also, the reducing capacity on ferrous ion was in the following order: TPL > TPRB > TF > TPSB. The phenolic and flavonoid contents of TPL were higher than other extractives. A positive correlation (p value <0.001) was observed between phenolic content and free radical (DPPH() and ()OH) scavenging efficiencies and lipid peroxidation inhibition activity.Methanolic extract of T. pallida leaf is a potential source of natural antioxidants and serves as an effective free radical scavenger and/or inhibitor. Hence, T. pallida might be a good plant-based pharmaceutical product for several diseases caused by free radicals.

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