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Diethylaminoethanethiol
Chemical warfare agents are toxic chemical substances used by terrorists with the intention to kill, injure or incapacitate their perceived enemies. Under the provisions of the Chemical Weapons Convection [343], such agents are regarded as the “poor man’s atomic bomb because of the low cost and the low technology required to develop them [343]. It is known that about 70 different chemicals have been used or stockpiled as chemical weapon agents during the 20th and 21st century. Notable of these agents are the so-called V-type (i.e., VE, VG, VM and VX) nerve agents [343,344].
The V-type nerve agents are considered more dangerous because they are more persistent, do not easily evaporate into a gas, and therefore present primarily a contact hazard to man. One of the main thiol hydrolysis products (Equation 1.32) of the V-type nerve agents is the 2-diethylaminoethanethiol (DEAET) [344]. 2-diethylaminoethanethiol (DEAET) is a thiol compound, a well known degradation product of the V-type nerve agent [343-345].
Since, DEAET is more stable in the aqueous environment than its parent Russian analogue of the V-type nerve agent, called R-VX (i.e.,O-isobutyl-S-(2-diethylaminoethyl)methylphosphonothioate), it
serves as one of the excellent models for electrochemical detection and interrogation of the behaviour of the R-VX nerve agent or thiol compounds at electrode surface. Although several methods including chromatography, mass spectrometry and electrochemistry are common for the detection of thiols, the use of such analytical methods for the detection of the hydrolysis products of V-type nerve agents is still hugely unexplored. Few reports involving electrophoresis [346,347] and electrochemical techniques [28,106,107,348] have emerged for the detection of DEAET. Some of the reported techniques are fraught with some notable drawbacks such as the employment of unstable enzyme materials, time-consuming electrode preparation involving chemical pretreatments
and derivatizations. Also, electrochemical oxidation of thiols at conventional electrodes occurs at very high potential, thus the need for chemically modified electrodes cannot be overemphasised. Therefore, this study explored the detection of DEAET on CNT-metal nanocomposite platform. The study also represent the first time the catalytic behaviour of this nanocomposite on EPPG electrode will be investigated. To the best of my knowledge, there has been no report on the use of electrodes
modified with nickel nanoparticle-decorated carbon nanotubes for the detection of degradation products of V-type nerve agents.
Indeed, compared to transition metals, nickel is not a popular redox-mediator in electroanalysis. But it was observed previously that surface-confined nickel micropowder (ca. 17 – 60 mm range) immobilized on basal plane pyrolytic graphite electrode showed good electrocatalytic response towards DEAET.
Nitrite
Nitrite ion is important as it is commonly used as an additive in some foods [349]. Other uses include color fixative and preservation in meats, manufacturing diazo dyes, in the textile industry, photography, manufacture of rubber chemicals, fertilizers in agriculture [350] and medicinal agents (used as a vasodilator [351], bronchodilator [352], intestinal relaxant [353]. It can be formed as a result of the degradation of some fertilizers and corrosion inhibitor [354]. Nitrite is one of the major components of waste water from nuclear power production [355] and is involved in the bacterial process known as the nitrogen cycle [356]. It also plays important physiological roles in the form of NO, for example, as an intra- and messenger, a neurotransmitter, and an immune system mediator [349]. Nitrite promotes corrosion when dissolved in water and is also classified as an environmentally hazardous species because of its toxicity [357]. The ions can interact with amines to form carcinogenic nitrosamines [358].
Due to the importance of nitrite in the environmental sciences and in food chemistry, a large number of analytical methods have been used to determine nitrite ions, including spectrophotometry [359-362], chromatography [363] and electrochemical methods [364-366] in recent years but with some shortcomings such as interference by other ions and complicated sample pre-treatment process, unsuitability for on-site monitoring and inability for detoxification. Electrochemical methods offer useful alternative since they allow a faster and precise analysis [59,367,368]. In order to tackle this problems, devices which are simple, inexpensive, stable and having the potential for the detoxification of these molecules are highly in demand. Electrochemical devices fall into this category, therefore electrocatalytic oxidation of nitrite on CNT/M or CNT/MO EPPGE modified electrode is reported in this study for the first time.
SECTION A
CHAPTER ONE
Introduction
1.1 General Overview of Thesis: Problem Statement
1.2 Overview of Electrochemistry
1.3 Voltammetric Techniques
1.4 Electrochemical Impedance Spectroscopy (EIS)
1.5 Chemically Modified Electrodes
1.6 Nanoscience in Electrochemistry
1.7 Langmuir Isotherm Adsorption Theory
1.8 Microscopy and Spectroscopy Techniques
1.9 Overview of Analytes Used As Analytical Probe
REFERENCES
CHAPTER TWO
Experimental
2.1 Materials and Reagents
2.2 Equipment and Procedure
2.3 Electrode Modification and Pretreatments
2.4 Electron Transport Experimental Procedure
2.5 Electrocatalytic and Electroanalysis Experiment Procedure
2.6 Electrochemical supercapacitive procedure
REFERENCES
SECTION B
RESULT AND DISCUSSION
CHAPTER THREE
Insights Into the Electro-oxidation of Hydrazine at Single-Walled Carbon Nanotube – Modified Edge- Plane Pyrolytic Graphite Electrode Electrodecorated with Metal and Metal Oxide Films
3.1 Comparative FESEM images and Electron-Dispersive X-rays.
3.2 Comparative Redox Chemistry of modified EPPGEs in Aqueous Solution
3.3 Comparative electrocatalytic oxidation of hydrazine
3.4 Electrochemical impedimetric studies
3.5 Effect of varying scan rates
3.6 Chronoamperometric investigations
REFERENCES
CHAPTER FOUR
Electron Transfer Behaviour of Single-Walled Carbon Nanotubes Electro-Decorated with Nickel and Nickel Oxide Layers and Its Electrocatalysis Towards Diethylaminoethanethiol (DEAET): An Adsorption-Controlled Electrode Process
4.1 FTIR, SEM images and EDX characterisation
4.2 Comparative redox chemistry in aqueous solution
4.3 Comparative Electron Transport Properties
4.4 Electrochemical response of the Ni-modified electrodes towards DEAET oxidation.
4.5 Comparative electrochemical response to DEAET at different Ni deposition time
4.6 Electroanalysis of DEAET
REFERENCES
CHAPTER FIVE
Electron Tranport and Electrocatalytic Properties of MWCNT/Nickel Nanocomposite: Hydrazine and Diethylaminoethanethiol as Analytical Probes
5.1 Comparative TEM, XRD and EDX spectra
5.2 Comparative Electrochemical characterization
5.3 Comparative electrocatalytic properties: DEAET and Hydrazine as analytical probe.
5.4 Effect of varying scan rates
5.6 Electroanalysis of DEAET and Hydrazine
REFERENCES
CHAPTER SIX
Probing the Electrochemical Behaviour of SWCNTCobalt Nanoparticles and Their Electrocatalytic Activities Towards the Detection of Nitrite in Acidic and Physiological pH Conditions
6.1 Comparative FESEM, AFM images EDX spectra
6.2 Comparative Electrochemical characterization
6.3 Comparative electron transport properties
6.4 Electrocatalytic oxidation of Nitrite in neutral and acidic pH
6.5 Electrochemical impedance studies
6.6 Effect of varying scan rate
6.7 Electroanalysis of nitrite at neutral and acidic pH
REFERENCES
CHAPTER SEVEN
Electrocatalytic Detection of Dopamine at Single- Walled Carbon Nanotubes-Iron (iii) Oxide Nanoparticles Platform
7.1 Characterisation with FESEM, AFM, EDX and XPS
7.2 Electrocatalytic detection of dopamine: Voltammetric and Impedimetric properties
7.3 Effect of varying potential scan rates
7.4 Analytical Application
7.5 Interference study
7.6 Real sample analysis: Dopamine drug
REFERENCES
CHAPTER EIGHT
Electrocatalytic Properties of Prussian Blue Nanoparticles Supported on Poly(m- Aminobenzenesulfonic Acid) – Funtionalized Single-Walled Carbon Nanotubes Toward the Detection of Dopamine
8.1 Comparative TEM and AFM images and UV-vis spectra
8.2 Cyclic voltammetric characterisation of the electrodes
8.3 Electrocatalytic oxidation of dopamine
8.4 Effect of varying scan rate
8.5 Electroanalysis using square wave voltammetry (SWV), chronoamperometric (CA) and Linear Sweep Voltammetry (LSV)
8.6 Detection of DA in the presence of AA (Interference study)
8.7 Real sample analysis: Dopamine drug
REFERENCES
CHAPTER NINE
Electrocatalytic Oxidation of Diethylaminoethanethiol, Hydrazine and Nitrite at Single-Walled Carbon Nanotubes Modified with Prussian Blue Nanoparticles
9.1 Microscopic and spectroscopic characterisation
9.2 Electrochemical characterization
9.3 Electrocatalytic oxidation properties
9.4 Concentration studies and proposed mechanism
REFERENCES
CHAPTER TEN
Supercapacitive Behaviour of Single-Walled/Multi- Walled Carbon Nanotubes-Metal (Ni, Fe, Co) Oxide Nanocomposites in Acidic and Neutral pH Conditions
10.1 Comparative EDX, XPS and FESEM
10.2 Comparative cyclic voltammetric experiments
10.3 Comparative galvanostatic charge / discharge experiments
10.4 Electrochemical impedance studies
References
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
RECOMMENDATIONS
