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Electrochemical Characterization of Some Electroactive Nucleophilic Substitution Reactions
No full textThis thesis submitted in partial fulfillment of the requirements for the degree of
Master of Philosophy (M.Phil) in Chemistry.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 149-154).The substitution reaction of Catechol in presence of Imidazole, L-Arginine and L-Serine have been studied by cyclic voltammetry, controlled potential coulometry and differential pulse voltammetry techniques using Glassy carbon (GC), Gold (Au) and Platinum (Pt) electrodes. The voltammetric studies have been carried out by varying the composition of Catechol, Imidazole, L-Arginine and L-Serine in the buffer solution of different pH, different electrodes and scan rate.
Pure Imidazole, L-Arginine and L-Serine are electro-inactive whereas pure Catechol is electro-active. In the second scan of potential, a new anodic peak appears at the lower potential and the oxidation and reduction peak shifted with respect of pure catechol after addition of Imidazole, L- Arginine and L-Serine in catechol solution. At the same time the anodic and cathodic peak current decreases significantly compared with the pure catechol that indicates the participation of reaction of o-benzoquinone with Imidazole, L-Arginine and L-Serine. The reaction products generated from the reaction of catechol in presence of Imidazole, L-Arginine and L-Serine are assumed to be 4-(1H-imidazol-1-yl)cyclohexa- 3,5-diene-1,2-dione- 2-amino-4-(1-(3,4-dioxocyclo hexa-1,5-dien-1-yl)guanidino)-4- oxobutanoic acid and 3-hydroxy-2-((3-hydroxy-4-oxocyclohexa-2,5-dien-1- ylidene)amine)propanoic acid respectively that undergo electron transfer at more negative potentials than the Catechol. The electro –synthesized products generated from Catechol with Imidazole, L-Arginine and L-Serine were isolated. The formation of Catechol-nucleophile adducts are also confirmed by FTIR spectra.
The pH effect of catechol in presence of Imidazole, L-Arginine and L-Serine has been investigated in different pH from 3 to 11. From the experiment it has been observed that almost no new anodic peak appeared after repetitive cycling at pH 3-5 (acidic media) and pH 9-11 (basic media). At pH 7, the o-benzoquinone undergoes nucleophilic attack by the amines that is reflected from voltammetric new anodic peak, A0 appeared after repetitive cycling. The slopes of the peak potential, Ep vs pH plot has determined graphically as the anodic peaks of Catechol-Imidazole (60 mV/pH), Catechol-Arginine (56mV/pH) and Catechol-Serine (61.5 mV/pH) at 0.1V/s.Md. Rabiul IslamMaster of Philosophy (M.Phil) in Chemistr
Investigation of the Electrochemical Behavior of Catechol in Presence of Glycine, Aspartic acid and Glutamic acid
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, July 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 156-161)To monitor the electrochemical behavior of Catechol in presence of Glycine, L-Aspartic
acid and L-Glutamic acid; cyclic voltammetry (CV), differential pulse voltammetry
(DPV), controlled potential coulometry (CPC) and chronoamperometry (CA) techniques
have been employed. A wide range of concentration (10mM to 150mM) of nucleophiles
(Glycine, L-Aspartic acid and L-Glutamic acid), various pH media (5 to11), different
electrodes ((Glassy carbon (GC), Gold (Au) and Platinum (P)) and successive scan rate
(0.05 V/s to 0.5 V/s) have been used to find out the favorable condition.
Catechol is an electroactive substance which shows a pair of redox peak whereas
Glycine, L-Aspartic acid and L-Glutamic acid are electroinactive, hence it shows no
anodic and cathodic peak in the potential range (-0.6 to 0.9 V) of investigation.
By the addition of above nucleophiles in Catechol solution arises a new peak at lower
potential, the corresponding redox peak shifts and peak current intensity of Catechol
decreases with respect to the pure Catechol that indicates the participation of 1,4-Michael addition reaction of o-benzoquinone with mentioned nucleophiles. The formation of adducts from the reaction of Catechol with Glycine, L-Aspartic acid and L-Glutamic acid are assumed to be 2-((3,4-dihydroxyphenyl)amino)acetic acid, 2-((3,4-dihydroxy phenyl)amino)succinic acid and 2-((3,4-dihydroxyphenyl)amino)pentanedioic acid severally that go through electron transfer at more negative potentials than the Catechol. The influence of pH of Catechol in presence of Glycine, L-Aspartic acid and L-Glutamic acid has been studied by varying pH from 5 to 11. It is seen that at pH 3, 5, 9 and 11 no new anodic peak appears after repetitive cycling. In the neutral media (pH 7), the o-benzoquinone undergoes nucleophilic attack by the above nucleophiles that
voltammetric new anodic peak A0 appears after repetitive cycling. The slopes of the peak
potential was determined graphically from Ep vs pH plot as the anodic peaks of Catecholglycine adducts (27 mV/pH) proceeded via one step 2e−/2H+ process, Catechol-aspartic acid adducts (50 mV/pH) and Catechol-glutamic acid adducts (69 mV/pH) via two step 1e−/1H+ process.
The reaction is strongly influenced by the different pH media as well as various
compositions of nucleophiles. These reactions have been carried out wide range of
concentration of nucleophiles. The optimum conditions for the formation of adducts such
as Catechol-glycine (pH-7, Concentration 70 mM, GC electrode and Scan rate 0.1 V/s),
Catechol-aspartic acid (pH-7, Concentration 70 mM, GC electrode and Scan rate 0.1 V/s)
and Catechol-glutamic acid (pH-7, Concentration 30 mM, GC electrode and Scan rate
0.1 V/s) system are observed.
The effect of scan rates has been investigated on cyclic voltammogram of Catechol in
presence of above nucleophile. The anodic and cathodic peak current increases
proportionally with increasing square root of scan rates. This linear relationship indicates the reaction is controlled by diffusion process. The current function, Ip/v1/2 decreases exponentially with increases scan rate which determine the reaction is controlled by ECE mechanism. The electro-synthesized adducts generated from the controlled potential coulometry of Catechol with Glycine, L-Aspartic acid and L-Glutamic acid was isolated and the generated adducts supported by FTIR spectra.Md. Nazim UddinMaster of Science in Chemistr
Installation of Simple Water Treatment Unit at Cyclone-Aila Affected Koyra Region and Assessment of DALYs Lost due to Diarrhoea
No full textThis thesis is submitted to the Department of Civil Engineering of Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering, November, 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 65-73)The South-western coastal region of Bangladesh is composed of Satkhira, Khulna, Bagerhat and parts of Jessore districts. On 25 May 2009, the „Cyclone Aila‟ occured into the south-western coastal region where Khulna and Satkhira districts were severely affected. Aila devastated all the drinking water sources and caused destruction of sanitation facilities. In this context, till recent time, many people are compelled to drink such polluted water without any sort of purification and consequently suffer from water borne diseases such as diarrhea, cholera, allergy, and skin disease. Diarrhoeal disease is one of the leading causes of morbidity and mortality in developing
countries, especially among children under the age of five. However, water borne diseases can be reduced by improving water quality and preventing casual use of other unimproved sources of water. For instance, simple filtration and disinfection of water at the household level dramatically improves the microbial quality of water, and reduces the risk of diarrheal disease at low cost. Scarcity of safe drinking water is a great phenomenon in Koyra and Kaligonj coastal region. The Disable Adjusted Life Years (DALYs) is a time-based measure that combines years of life lost due to premature mortality and years of life lost due to time lived in health states less than ideal health. DALY is an indicator of Burden of Disease (BoD) in a population. This study aims at investigating the existing drinking water quality, sanitation and hygiene practices in
“Cyclone Aila” affected areas and installation of simple household water treatment unit and awareness development for improved sanitation and hygiene practices and finally assessment of improvement in DALYs lost with the adopted intervention. In the study areas, microbiological water qualities in various sources were found to be varied in the range of 8-360 N/100mL as Faecal Coliform. Field survey on toilet facilities in the study area identified that there were 61.64% simple pit latrines, 29.06% pour flush latrines and remaining 9.31% inhabitants had no toilet facilities in Koyra and Kaligonj coastal region. At the commencement of this study, it was found that 8.26% population had been using soap, 13.74% using ash and remains percent using others materials such as soil and only water for hand washing after defecation. However, an awareness development campaign on hygiene practice was undertaken in this research work and with this initiative the use of soap and ash for hand washing after defecation was found to be
increased slightly to 12.26% and 16.84%, respectively and about 44% use of soil as hand washing after defecation. In the study area, total disable adjusted life years (DALY) was found to be 0.042 for three months before the installation of water treatment unit. A simple water treatment unit or household filter was developed and installed at five locations of the study area. The efficiency of bacteria removal through these filter units were found to be around 98%. In this case, total disable adjusted life years (DALY) was found to be decreased significantly to 0.01 for three months‟ time period after the satisfactory efficiency of water treatment units as well as consciousness development about improved sanitation and hygiene practices. Overall, improvement in DALYs lost was found to be 74.1% with facilitating safe drinking water, improved sanitation and hygiene practices.Md. Farid MunnafMaster of Science in Civil Engineerin
A Case Study of the Solution of Laminar Convective Boundary Layer Flow around a Vertical Slender Body with Transpirations
No full textThis thesis is submitted to the Department of Mathematics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Mathematics, January 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 50-55).In this thesis, a case of the similarity solution of laminar convective boundary layer flow around a vertical slender body with transpirations has been investigated. Firstly, the governing boundary layer partial differential equations have been made dimensionless and then simplified by using Boussinesq approximation Secondly, similarity transformations are introduced on the basis of detailed analysis in order to transform the simplified coupled partial differential equations into a set of ordinary differential equations. In the present thesis one of the important similarity case, out of four cases has been studied. Under the considered case, the transformed complete similarity equations are solved numerically by using computer software MATLAB. Further the flow phenomena have been characterized with the help of obtained flow controlling parameters such as suction/blowing parameter, buoyancy parameter, Prandtl number, body-radius parameter and other driving parameter. Finally, the effects of these involved parameters on the velocity and temperature fields are presented graphically. It is observed that a small suction or blowing played a significant role on the patterns of' flow and temperature fields.S. Md. Abdur RazzakMaster of Science in Mathematic
Effect of Grain Size and Phase Constitution on the Magnetic Properties of Fe-X-Nb-Si-B [X = Cu, Au & Ag] Alloys
No full textThis thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy in Physics, November, 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 113-123).Amorphous FINEMET type alloy nominal composition of Fe73.5X1Nb3Si13.5B9
[ X = Cu, Au and Ag] has prepared by melt spinning technique. The samples are
initially prepared in the amorphous state in the form of thin ribbons by rapid
quenching technique at wheel speed of 25m/s in an Ar atmosphere. The ribbon has
been annealed in a controlled way in temperature range 450o – 800oC for 30 minutes.
The kinetics of crystallization amorphous FINEMET type alloys were investigated by
the use of differential thermal analysis (DTA) and X-ray diffraction (XRD)
techniques. DTA runs for these three samples show the existence of two exothermic
peaks one for α-Fe(Si) and other for Fe2B phase. The crystallization of each phase
has occurred over a wide range of peak temperatures and the primary crystallization
like α-Fe(Si) phase temperature shift higher temperature as the replace Ag>Au>Cu
concentration. DTA experiment and from the obtain data activation energy of primary
crystallization α-Fe(Si) phase are varies 2.18 - 4.37eV and secondary crystallization
products Fe2B phase is 3.62 - 4.45 eV. Amorphosity of the ribbon and
nanocrystalline state has been evaluated by XRD. The primary crystallization phase
shifts to higher annealed temperature with Cu replacement Au or Ag implying the
enhancement of thermal stability of amorphous alloys against crystallization. All the
three samples has been annealed in the temperature range 6000C -8000C for 30
minutes and taken under XRD experiment in order to study the effect of structural
parameters such as lattice parameter, grain size and silicon content of the
nanocrystalline α-Fe(Si) grain. In optimizing annealing condition the grain size has
been obtained in the range of 14 - 20nm for Cu, 13 - 25nm for Au and 09 - 30nm for
Ag. Saturation magnetization Ms increase in order with condition Ag > Cu > Au in
these experimental samples. The reduction curie temperature (Tc) with substitution of
Cu by Au or Ag in order Ag < Au < Cu may attributed to this simultaneous
weakening of strength of exchange interaction between the magnetic moments. This is
because the amorphous matrix is depleted Fe and relative amount of Nb in the
amorphous matrix increases Cu replace Au or Ag which weakness the exchange
interaction resulting in reduction of Tc.A. K. M. AsaduzzamanMaster of Philosophy in Physic
Physico-Chemical Properties of Some Alcohols in SDS-Acetonitrile Containing Ternary Systems
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, November, 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 157-165)The critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS) in 80%
acetonitrile + 20% water was determined from the conductance and viscosity
measurement. They shows a sharp break in their values where micelle starts to form. The estimated CMC of SDS was found to be 0.02 mol. L-1. Densities and viscosities of ternary mixtures of Ethanol + (80% acetonitrile + 20% water + 0.02M SDS), n-Propanol + (80% acetonitrile + 20% water + 0.02M SDS), iso-Propanol +(80% acetonitrile + 20% water + 0.02M SDS),n-Butanol + (80% acetonitrile + 20% water + 0.02M SDS), iso-Butanol + (80% acetonitrile + 20% water + 0.02M SDS), n-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) and iso-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) have been studied over the entire range of composition (0 ˂ X2 ˂ 1) at 98.15-323.15K with an interval of 5K. In pure state the density of alcohol has been found to be in the order of: n-Pentanol > Ethanol > n-Butanol > n-Propanol and iso-Pentanol > iso-Butanol > iso-Propanol The values of densities of Alkanols + (80% acetonitrile + 20% water + 0.02M SDS) at equimole fraction solvent systems has been found to be
n-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) > Ethanol + (80% acetonitrile
+ 20% water + 0.02M SDS) > n-Butanol + (80% acetonitrile + 20% water + 0.02M SDS)
> n-Propanol + (80% acetonitrile + 20% water + 0.02M SDS) and iso-Pentanol + (80% acetonitrile + 20% water + 0.02M SDS) > iso-Butanol + (80% acetonitrile + 20% water + 0.02M SDS) > iso-Propanol + (80% acetonitrile + 20% water + 0.02M SDS) The value of the density of alcohols in 80% acetonitrile + 20% water + 0.02M SDS increases with increasing of composition of the alcohols. The densities of all alcohols increase with carbon number which may be depend on the molecular weight of alcohols
and structural formula. The densities decrease regularly with increasing of temperature.
This is due to the thermal agitation and hence the dipole-dipole interaction or the
dissociation of H-bonding are occurred.
The excess molar volumes, VE were calculated from the densities of the mixtures at
different temperatures. The values of VE for all the systems are negative over the entire
range of composition, showing minima at ~ 0.5 mole fraction of Ethanol, ~ 0.8 mole
fraction of n-Propanol, ~ 0.8 mole fraction of iso-Propanol, ~ 0.7-0.8 mole fraction of n-
Butanol, ~ 0.8 mole fraction of iso-Butanol, ~ 0.7 mole fraction of n-Pentanol, ~ 0.7 mole
fraction of iso-Pentanol.
The increasing of VE with carbon chain length of alcohols may be related to increase of the
size of alcohols. The values of VE for the studied alcohols increase with increase of
temperature. The observed values of VE for the mixtures have been explained in terms of
physical, chemical and geometrical contributions.
The viscosity coefficients, ɳ of all the above mixtures at all the different temperatures have
also been determined. The viscosities increase initially slowly up to ~ 0.8 mole fraction of
Ethanol, n-Propanol, iso-Propanol, n-Butanol, iso-Butanol, n-Pentanol and iso-Pentanol in
80% acetonitrile + 20% Water + 0.02M SDS systems and later on, the viscosities increases
sharply until the pure alcohol is reached specially at lower temperature. In the pure state
the viscosity of the alcohols has been found to be in the order of
n-Pentanol > n-Butanol > n-Propanol > Ethanol
and
iso-Pentanol > iso-Butanol > iso-Propanol
and
iso-Pentanol > n-Pentanol and iso-Butanol > n-Butanol and iso-Propanol > n-Propanol
These are a marked decrease in the viscosity with the increase of temperature for all the
studied alcohols. This ascribed that the alcohol solutions are less stable at higher
temperature. The increasing of viscosity with carbon number of alcohols ascribed that the solution resistance increase with the increase of carbon chain length. The linear
dependence of lnɳ against 1/T shows for the all studied alcohols. The branched chain
isomers are less stable than linear chain isomers at higher temperature.
The excess viscosities, ηE values are found to be negative, indicating that the (80%
acetonitrile + 20% water + 0.02M SDS) solutions of alcohols are non-ideal. Excess
viscosities are negative at all the temperature over the entire range of composition for all
the systems with minima occurring between 0.7-0.8 mole fraction of Ethanol, n-Propanol,
iso-Propanol, n-Butanol, iso-Butanol, n-Pentanol and iso-Pentanol. The negative excess
viscosities, ηE of the systems indicate that the dissociation of component through
dispersion force or steric hindrance. The position of minima virtually does not change
remarkably with the variation of temperature.
The negative VE, negative ηE and negative for the systems indicate the segmental
inclusion of Acetonitrile in the interstices of polymolecular alkanols aggregate; these will
be fewer surfaces available for friction that may results in a reduction of viscosity. For
long chain or branched chain alkanols, maximum geometrical for the steric hindrance are
occurred.
The thermodynamic parameters such as free energy (ΔG#), enthalpy (ΔH#) and entropy
(ΔS#) change of activation for the viscous flow for these systems were examined for the
entire range of composition. The free energy (ΔG#) were found to be positive in magnitude
indicating that the kinetic species involved in forming cavities or holes in the liquid
medium is giving by the work required in forming the hole against surface tension of the
solution. The excess properties (VE, ηE, ΔG#E) data have been fitted by the least square
method to the four parameter Redlich-kister equation and the values of the parameter ai and
standard deviation have been reported.Biswajit Kumar DasMaster of Science in Chemistr
Temperature Induced Anomalous Exciton Localization in InGaN/GaN and GaN/AlInN Multiple Quantum Wells
No full textThis thesis is submitted to the Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Electrical and Electronic Engineering, August 2016.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 61-67).InGaN and AlInN alloys including their relevant Quantum Well (QW) structures have
attracted intensive research interest due to their potential applications in numerous
optoelectronic devices. However, the emission mechanism in such QWs is still unveiled
incompletely. The physical origin of spontaneous emission in InGaN/GaN or GaN/AlInN
QWs is attributed to the recombination of localized excitons. The localization of exciton
occurs due to the formation of Indium-rich clustering and abrupt interfaces between well and
barrier layers. Conversely, the InGaN/GaN QWs can be grown without Indium-rich
clustering and abrupt interfaces. Thus a detail understanding is essential to link the intricate
structure of InGaN/GaN and GaN/AlInN QWs with their secretive optical behaviors.
In this dissertation, the details of exciton localization dynamics in InGaN/GaN and
GaN/AlInN multiple quantum wells (MQWs) have been reported using Monte Carlo
simulation of exciton hopping for a wide range of temperature of 10K to 300K. The
calculated photoluminescence (PL) peak energy position of both of MQWs shows unusual
behavior (redshift-blueshift-redshift) with the increase in temperature. The PL line width also
exhibits W-shaped temperature dependent inhomogeneity. It is found that the phononinduced
lifetime variation of excitons have the remarkable effects on the PL peak position
and line-widths in both of MQWs. The blue-shift of PL peak position is observed at high
temperature in the MQWs with well and barrier thicknesses near the critical values,
indicating the dominancy of two dimensional excitonic kinetics for the entire range of
temperature.
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Significantly, different temperature dependences for PL line-widths were perceived
for the GaN/AlInN MQWs with different barrier heights. The MQWs having barrier height
near to the lattice matched QW structure of GaN/AlInN showed the smaller band potential
profile fluctuation. These results could be important to understand the emission properties of
InGaN and AlInN MQWs optoelectronic devices.Md. Soyaeb HasanMaster of Science in Electrical and Electronic Engineerin