الفهرس 
General introductionOnly 14 pages are availabe for public view
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Abstract
- The thesis content can be portrayed briefly as five chapters:
Chapter (I): General introduction:
- This chapter contains a general introduction regarding the work done and includes two parts:
• Part (I): It illustrates the principles and main components of potentiometric sensors and an overview of conventional ion-selective electrodes (ISEs) with their limitations. The transformation from conventional ISEs contain liquid contacts (typically referred to as inner filling solutions) to solid-contact ISE. The difficulties facing solid-contact ISE and the types of materials used to act as ion-to-electron transducers with their mechanism of response. Finally, Challenges facing potentiometric solid-contact ion-selective electrodes (SC-ISEs).
• Part (II): Magnetic Nanoparticles (MNPs) have attracted a great interest due to their superior magnetic properties, high adsorption capacity, surface area-to-volume ratio, simple chemical composition, and wide applications in a number of fields including wastewater treatments that greatly affects the community health and economic well-being. In this part, I will give an overview of magnetic nanoparticles, especially metal ferrites (MFe2O4), their types, methods of preparation, and modification for the removal of hazardous environmental pollutants.
Chapter (II): Novel Magnetic Nickel Ferrite Nanoparticles Modified with Poly(aniline-co-o-toluidine) for the Removal of Hazardous 2,4-Dichlorophenol Pollutant from Aqueous Solutions:
In this chapter, A novel nickel ferrite (NiFe2O4) nano composite modified with poly(aniline-co-o-toluidine) (PAOT) is prepared, characterized and used for the removal of some organic chlorinated environmental pollutants. The morphological properties of the composite are characterized by Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and Brunauer–Emmett -Teller (BET) methods. The prepared composite is tested for the removal of the hazardous dichlorophenol pollutant from aqueous solutions. Under optimized conditions and with effective controlling parameters including, contact time, pH of the test solution, adsorbent dose, and temperature, over 83% of the pollutant is adsorbed and removed. The adsorption capacity is 162 mg/g. Adsorption kinetics, adsorption isotherm and some physicochemical parameters of the reaction are evaluated. Redlich-Peterson isothermal model is the appropriate model for describing the adsorption process. These results indicate that NiFe2O4/PAOT nanocomposites are promising adsorbent for the removal of persistent organic pollutants (e.g., DCP) from aqueous solutions. The results also reveal that modification of NiFe2O4 particles with poly(aniline-co-o-toluidine) (PAOT) significantly enhances the adsorption capacity of the adsorbent. This is probably due to the electrostatic attraction and non-covalent interactions (e.g. π–π) between the aromatic rings in both dichlorophenol and poly(aniline-co-o-toluidine) copolymer. Advantages offered by using NiFe2O4/PAOT nanocomposites are the high stability, reasonable efficiency, reusability for at least five adsorption-desorption cycles and the ability to remove the adsorbent from aqueous solutions for reuse using an external magnetic field.
Chapter (III): A Novel Screen-Printed Potentiometric Sensor with Carbon Nanotubes/Polyaniline Transducer and Molecularly Imprinted Polymer For The Determination of Nalbuphine In Pharmaceuticals and Biological Fluids:
In this chapter, A novel screen-printed planar sensor is described. It consists of a 0.1 x 29 mm flexible PET (substrate) imprinted with a 4 mm diameter circular carbon layer and coated with a transducer and recognition layers. Carboxylated multi-walled carbon nano-tubes /polyaniline nano composite (f-MWCNTs/PANI) is used as an ion-to- electron transducer and is covered by a recognition sensing layer consisting of a plasticized membrane prepared by dissolving molecularly imprinted drug polymer (MIP) beads dispersed in plasticized poly(vinyl chloride). Both layers are prepared, characterized and used as a sensor for determining a synthetic narcotic, nalbuphine. The sensor displays a Nernstian response with a slope of 60.3±1.2 mV/decade (R2 = 0.999) over the concentration range 2.4x10-7 – 5.0x10-2 mol/L and a detection limit of 1.1x10-7 mol/L (0.04 µg/mL). A sensor similarly prepared without the suggested transducer layer shows a much inferior response. The interfacial capacitance of the proposed SPEs is measured using chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the interfacial capacitance reached 52.5 µF is obtained. The use of
f-MWCNTs/PANI nanocomposite layer completely eliminates the formation of a water-layer between the sensing membrane and the conducting substrate. This prevents membrane delamination and increases potential stability. High selectivity, sensitivity potential stability and fast response are offered by the proposed sensor. The sensor is satisfactorily used for the determination of nalbuphine in some pharmaceuticals and in spiked human urine samples. The efficiency of the proposed screen printed electrode in complex urine matrices suggests its applicable in hospitals for rapid diagnosis of overdose patients and for quality control/quality assurance in pharmaceutical industry.
Chapter (IV): All-Solid-State Paper-Based Potentiometric Sensors Modified With Reduced Graphene Oxide (rGO) For Monitoring Losartan Potassium In Pharmaceutical Products And Biological Samples:
In this chapter, Cost-effective, highly selective and sensitive paper-based potentiometric sensors for sensing losartan potassium have been fabricated and characterized. where The Graphene oxide (GO) was prepared chemically using the modified Hammer’s method followed by reduction using ascorbic acid to obtain the reduced graphene oxide (rGO) to act as an ion-to-electron transducer layer. Copper (II)-Neocuproine complex was prepared followed by the formation of ion-pair complex with losartan (LOS) in its anion form. The ion-pair complex was characterized and incorporated into the ion-selective polyvinyl chloride (PVC) membrane as sensing material (sensor I). A molecular imprinted polymer (MIP) for LOS was also prepared, characterized and incorporated into the ion-selective PVC membrane as a receptor element (sensor II) for the potentiometric determination of LOS. These ion-selective electrodes (ISEs) were used after integrated with a solid-state polyvinyl butyral (PVB) reference electrode supported on a paper substrate coated with conductive carbon paint to obtain all-solid-state paper-based sensors. These two sensors after modification with rGO showed a noticeable improvement in their potentiometric response with a Nernstian slope of -60.09 mV/decade (R2 = 0.9996) in a linear range 9.16x10-8 - 6.9x10-4 mol/L with a detection limit of 4.41x10-8 mol/L and a Nernstian slope of -59.69 mV/decade (R2 = 0.9994) in a linear range 4.88x10-7 - 6.9x10-4 mol/L with a detection limit of 2.39x10-7 mol/L for sensor (I) and (II), respectively. Both of them showed high selectivity toward various species especially those used by the COVID-19 patients such as paracetamol, ascorbic acid and dextromethorphan HBr (DXM HBr). Besides, chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) were performed, which resulted in an increase in the capacitance of the interfacial double-layer capacitance after modification with rGO. In addition, The thin water layer formed between the conductive paper substrate and the ion selective membrane was eliminated for both sensors. Subsequently, These modified sensors were applied to monitor LOS-K in some pharmaceutical products and spiked human urine samples which showed high selectivity as the average recovery was 99.4% and 96.3% in pharmaceutical products, 99.6% and 98.7% in the spiked urine samples for sensor (I) and (II), respectively. This demonstrates the applicability of these sensors in the pharmaceutical industries and for the rapid and immediate diagnosis of hospital overdose patients as well as their incorporation into wearable devices.
Chapter (V): Fabrication and characterization of Bismuth Oxide Film Deposited on a Fluorine Doped Tin Oxide Glass Substrate (FTO) Using Spray Pyrolysis Technique and its application as a Miniaturized Potentiometric Sensor for pH Monitoring:
Conventional glass electrodes are commonly used for pH monitoring due to their high sensitivity, long-term stability, high selectivity and wide operating range, but they have other drawbacks such as mechanical fragility, difficulty in miniaturization, high cost and conditional storage which hinder their application in miniaturized systems and some unusual applications. Hence, metal oxides have gained increasing attention due to their high sensitive due to their high nanoscale size and surface area. Hence, Metal oxides have gained increasing interest in incorporating them into potentiometric sensing electrodes such as pH sensors due to their high sensitivity to change in pH as well as their nanoscale size and high surface area. In this work, a thin film of bismuth oxide Bi2O3 deposited on a fluorine doped tin oxide glass substrate (FTO) using the spray pyrolysis technique at three different temperatures (450, 500 and 550 °C) for a total deposition time of 10 min. the deposited Bi2O3 was characterized using some techniques, including X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDS) which indicated the presence of the tetragonal phase of Bi2O3 with a porous and high roughness film surface with nano cracks for the most sensitive Bi2O3 deposited film (550 °C). The fabricated Bi2O3/FTO were applied as a miniaturized potentiometric sensor for monitoring pH in wide range (2-12). The Bi2O3/FTO electrodes fabricated at 500 and 550 °C showed an ideal Nernstian slope of -59.4 ± 0.517 and -62.05 ± 0.342 mV/decade, respectively with a response time using Bi2O3/FTO (550 °C). while Bi2O3/FTO (450 °C) showed a non-Nernstian slope of -41.5 ± 0.979 mV/decade. This attributed to the effect of temperature in forming a porous and high roughness thin film of Bi2O3 with nano cracks on the FTO substrate, which improved the sensitivity in pH monitoring. The selectivity of the proposed electrodes were studied using the Two solutions method (TSM) toward some common interfering ions, which showed the superiority of the Bi2O3/FTO (550 °C) electrode. These Bi2O3/FTO electrodes were applied in real water samples and compared with the conventional pH glass electrode, which showed a high efficiency in monitoring pH making it applicable in water quality and environmental monitoring.