Tag Archives: Shahriar Kabir

Radiation Physics and Chemistry

Mohammed Mizanur Rahman
Applied Chemistry and Chemical Engineering
University of Dhaka
Shahriar Kabir
Applied Chemistry and Chemical Engineering
University of Dhaka
Taslim Ur Rashid
Applied Chemistry and Chemical Engineering
University of Dhaka

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define cialis moment In the present study we have synthesized chitosan from waste prawns hell via g-irradiation of chitin and subsequent alkaline treatment. The detailed experimental studies demonstrated that nonirradiated chitin deacetylated by 40% NaOH solution showed 72% degree of deacetylation(DD), however 50k Gy irradiated chitin, deacetylated by 20% NaOH demonstrated 81.5% DD. Chitosanin solid state as obtained from g-irradiation of chitin was further irradiated by different doses(2–100kGy) of gamma irradiation and the effects of irradiation on the molecular weight, the rmo-mechanical by differential scanning calorimetry(DSC) and thermogravimetric analysis (TGA), and antimicrobial properties were evaluated with respect to nonirradiated chitosan sample. Gamma irradiation of chitosan with a dose of 100kGy caused a decrease in average molecular weight from1.9_105 to 6.5_104 Da  and thus increased its solubility in water. Nonirradiated and g-irradiated chitosan at concentration 1% (w/w) in water were prepared and used to evaluate of its potentiality for growth stimulation of Malabar spinach. The chitosan solution was sprayed on the specimen plants and neighboring soil where germinations were taken place and various plant growth parameters such as plan th eight, number of leaves, leaf areas, dry and wet weight of the plants and roots were investigated. The details study revealed that application of 30 k Gyirradiated chitosan yielded 60% higher growth of the Malabar spinach than that obtained from Nonirradiated chitosan. The data are consistent with preliminary results from field experiments and unambiguously confirms that a minor amount of chitosan has a pro found effect on the growth and development of Malabar spinach. 

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A new approach for the preparation of chitosan from γ -irradiation of prawn shell: effects of radiation on the characteristics of chitosan

Taslim Ur Rashid,
Mohammed Mizanur Rahman,
Shahriar Kabir,
Chitosan is a biodegradable polymer composed of randomly distributed β-(1,4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit). It is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimps) and the cell walls of fungi. In the work reported, we
developed a facile technique for the preparation of chitosan by irradiating prawn shell at various intensities from 2 to 50 kGy. It was observed that γ -irradiation of prawn shell increased the degree of deacetylation (DD) of chitin at a relatively low alkali concentration during the deacetylation process. Among the various irradiation doses applied to prawn shell, a dose of 50 kGy and 4 h heating in 50% NaOH solution yielded 84.56% DDwhile the chitosan obtained from non-irradiated prawn shell with the same reaction conditions had only 74.70% DD. In order to evaluate the effect of γ -irradiation on the various physicochemical, thermomechanical and morphological properties, the chitosan samples were again irradiated (2–100 kGy) with γ -radiation. Molecular weight, DD, thermal properties with differential scanning calorimetry and thermogravimetric analysis, particle morphology by scanning electron microscopy, water binding capacity (WBC), fat binding capacity (FBC) and antimicrobial activity were determined and the effects of various γ -radiation doses were assessed. The DD, WBC, FBC and antimicrobial activity of the chitosan were found to improve on irradiation. It was obvious that irradiation caused a decrease of molecular weight from 187 128 to 64 972 gmol−1 after applying a radiation dose of 100 kGy which occurred due to the chain scission of chitosan molecules at glycosidic linkages. The decrease of molecular weight increased the water solubility of the chitosan, the extent of which was explored for biomedical applications.
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