http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/285 2026-04-07T07:14:44Z 2026-04-07T07:14:44Z Islam, Md. Nazrul http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/4782 2026-03-02T05:48:00Z 2026-03-02T00:00:00Z

Particle Phase Organic Compounds in the Atmospheric Particulate Matter at Urban and Rural Areas in Bangladesh Islam, Md. Nazrul Particle Phase Organic Compounds (PPOCs) are significant organic fraction of atmospheric suspended particulate matter. They comprise of harmful chemicals which have adverse effects on human health. There is very limited research regarding the source, seasonal variation and health impact of PPOCs in Bangladesh. The objectives of this study are to measure the 16 PPOCs at four different locations with seasonal variation, correlation coefficient, source identification with positive matrix factorization (PMF), influence of wind direction with backward air mass trajectory analysis by HYSPLIT and potential health risk assessment. In this study, suspended particulate matter samples have collected on quartz filters with a low volume sampler (Model: 700) at four locations in Bangladesh (Dhaka, Rajshahi, Narayangonj and Bhola) for one year at each location between January, 2016 and February, 2020. Concentration of 16 organic compounds (Naphthalene, Anthracene, Diazinon, Deltamethrin, Pyrabenzoxime, Pyrazosulfuran, Prophenophos, Butachlor, Propiconazole, Cymoxanil, Cypermethrin, Lamdacyhalothrin, Dimethoate, Chlorpyriphos, Carbofuran, and Metalaxyl) were determined with a Gas Chromatography-Mass Spectrometry (GC-MS). The total average PPOCs concentration was 11.60 ± 0.1 μgm-³ in Dhaka, 8.69± 0.3 μgm-³ in Rajshahi, 11.84±0.4 μgm-³ in Narayangonj and 7.22± 0.2 μgm-³ in Bhola. These concentrations were 2 to 18 times higher during winter season than that of monsoon season. The PPOCs concentration was similar between Dhaka and Narayangonj and it was 32% higher than Rajshahi and Bhola. Source apportionment by Positive Matrix Factorization (PMF) revealed five sources of PPOCs - diesel exhaust, biomass burning, industrial emission, gasoline exhaust, and other sources. Industrial emission was predominant in urban areas whereas biomass burning was the major pollution vi source in rural areas. Backward air mass trajectory analysis by Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) indicated that during winter more than half of the period wind (60%) comes entirely from the Indo- Gangetic Plain (IGP) region originating from Africa. In monsoon, half of the wind (50%) comes entirely from the Indian Ocean through the Bay of Bengal. According to the health risk assessment study, 16 PPOCs had a Hazard Index (HI) value of 30.19, indicating a serious non-carcinogenic effect. The largest contributor to the hazard index (32%) was dimethoate. One in 340 people had a chance of getting cancer in their lifetime. The average lifetime cancer risk value (2.9410-3) was higher than the US Environmental Protection Agency's (USEPA) recommended threshold (110- 4). Naphthalene was found to pose the highest carcinogenic risk. As particulate phase organic compounds are mostly emitted from anthropogenic sources and pose severe health threat, so public awareness should be raised and more detailed research should be conducted in local and regional level. This thesis is submitted for the degree of Doctor of Philosophy.

2026-03-02T00:00:00Z Foisal, A.B. M. http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/4677 2025-07-07T04:47:31Z 2025-07-07T00:00:00Z

Development and Fabrication of Conductive Metallic Thin Films on Polyether Ether Ketone Monofilament in Wet Chemical Method Foisal, A.B. M. The aim of this work is to develop and fabricate conductive metallic silver thin films on polyether ether ketone (PEEK) monofilament surface. It was coated with silver particles using wet chemical method after being treated with low-pressure glow discharge plasma of gases like air, nitrogen, oxygen, etc. at a definite condition of plasma parameters. The wet chemical method was based on the use of metallic salt silver nitrate (AgNO3) and ammonium hydroxide (NH4OH), which are well-suited to form a silver diamine complex and tetra ethylene pentamine (TEPA) used as an adhesion promoter. Catalytic silver was used to coat the modified monofilaments and after chemical reduction, the cationic silver transforms into metallic silver particles on the filament surface. The concentration of AgNO3 and reducing agent are varied at different stages of wet chemical method. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) analysis were used to observe the morphology of the silver particles and characterize the elemental analysis of the silver coated filaments respectively. The silver particle size was determined by ImageJ software. The atomic force microscopy (AFM) was used to monitor the surface roughness of the plasma treated and silver coated filament. The oxygen/carbon (O/C) ratio on the plasma treated surface was determined by x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) pattern was used to find out the crystallite size of the PEEK and silver particles. The thermogravimatric analysis (TGA) is performed to find out the thermal stability and silver percentages present on silver coated monofilaments. Electrochemical impedance spectroscopy (EIS) analyzer was used to determine the electrical resistance on dependency of frequency through the silver coated PEEK monofilaments and alternating current (AC) conductivity is measured. To find out how the modification affects the mechanical properties of plasma-modified and silver-coated PEEK monofilaments, universal strength tester was used. The coated monofilaments were also integrated into textile to investigate the capability of resisting the friction during sewing of silver coated monofilaments into the cotton woven plain fabric. PEEK monofilament surfaces have been rough due to low-pressure glow discharge air, N2, and O2 plasma treatment. The roughness of plasma treated monofilaments is higher than the unmodified surface as well as the O/C ratio is increased on the plasma treated surfaces of the monofilaments. Both exhibit synergistic effect on plasma modified surface for adhesion of metallic silver particles. The particles are distributed on plasma modified surface homogeneously and covered the surface as thin films. The roughness of the plasma modified surface has been reduced after deposition and dispersion of silver particles on the modified surface. The characteristic diffraction peaks of PEEK are not remarkably altered by covering the surface with silver nanoparticles. The breaking force and elongation of plasma treated and silver coated monofilament are not significantly changed in comparison with the normal monofilament. The thermal decomposition of normal PEEK and plasma modified-silver coated PEEK both exhibit above 500 °C which indicates thermal behavior has not been remarkably changed. In terms of electrical properties, AC conductivity was increased with the increment of silver percentages on plasma modified-silver coated surface. The increment of silver wt. (%) on the surface of the plasma modified PEEK monofilament has remarkably changed and turned it from insulating to conductive behavior. The electrical conductivity of silver thin film coated monofilament increases with the increase of concentration of AgNO3 and the silver contents (wt.%) on the surface of plasma modified PEEK monofilament. A pronounced non-linear dependence of electrical conductivity is observed on the silver coated PEEK monofilament. The surface morphology, roughness, particles distribution, elemental composition and apparent silver content (wt.%) of O2 plasma modified-silver thin film coated PEEK monofilament intensely influences the electrical conductivity over air and N2 plasma modified-silver coated PEEK monofilaments. Finally, silver thin film coated PEEK monofilament has been integrated into woven fabric to observe resistance of friction between coated filament and fabric during sewing manually. The electrical resistance was measured after integration into textile. The electrical resistance remains stable within range, which indicates that the silver coated monofilament can be integrated into textile and used as conductive threads for smart textiles. This thesis is submitted for the degree of Doctor of Philosophy.

2025-07-07T00:00:00Z Ahmed, Akhtar Uddin http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/3983 2025-03-19T04:41:11Z 2025-03-19T00:00:00Z

Innovation of building materials from Indigenous sources of Bangladesh and studies of their Physio-Chemical properties Ahmed, Akhtar Uddin This thesis is submitted for the degree of Doctor of Philosophy.

2025-03-19T00:00:00Z sen, Ashis ratan http://reposit.library.du.ac.bd:8080/xmlui/xmlui/handle/123456789/3982 2025-03-19T04:39:11Z 2025-03-19T00:00:00Z

Studies on vulcanized rubber and rubber products sen, Ashis ratan This thesis is submitted for the degree of Doctor of Philosophy.

2025-03-19T00:00:00Z