EJUST DAR

Our Digital Asset Repository in Egypt-Japan University of Science and Technology

The main goal of E-JUST DAR is creating a digital repository through which creation, use, and preservation of digital resources is available as well as the development of management tools. These tools help E-JUST Library to preserve, manage and share digital assets. The system is based on evolving interoperable digital libraries.

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Fabrication of High Performance Carbon Nanostructured based Electrodes for Supercapacitor Applications
(2021-06) Kadi, Aya Ali Hamed Sami Al; Abdel-Moneim, Ahmed; El-Khouly, Mohamed; Shaalan, Nagih; Nakamura, Koichi
Supercapacitors are the promising next-generation energy storage devices that bridge the gap between traditional capacitors and batteries, but still require their electrode material to be further developed. Here, this thesis aims at the development of novel, simple, scalable, and efficient techniques for fabrication of advanced electrode materials suitable for flexible planar supercapacitors (PSCs). Direct writing technique offers a way to pattern interdigitated electrodes precisely without using masks or cleanroom operations, thus giving the flexibility to produce supercapacitors in various sizes and architectures at low cost. The miniaturization of the electrodes to microscale results in enhanced charge storage capacity and rate capability in addition it promotes on chip integration of SCs. A CO2 Laser machine is used as a direct writing technique. In the first study, a CO2 Laser system is used for concurrent in-situ doping, reduction, and patterning of graphene oxide-based films supported on flexible polyethylene terephthalate (PET) substrate. Three different devices are fabricated using the proposed approach, Laser reduced graphene oxide (LrGO), nitrogen-doped Laser reduced graphene oxide (N-LrGO), and sulfur-nitrogen co-doped Laser reduced graphene oxide (SN-LrGO) PSCs. Structural and elemental characterizations are performed to prove the successful integration of nitrogen and sulfur atoms into the graphene framework with high contents up to 3.71 at% N and 1.82 at% S, and at a low density of structural defects. Electrochemical performance of the devices is tested. An areal capacitance as high as 13.8 mF cm-2 at 10 mV s-1 and a maximum power density of 151.7 mW cm-3 at an energy density of 0.152 mWh cm-3 is achieved by SN-LrGO PSC composed of 10 interdigitated fingers with an excellent retention rate. Furthermore, higher operating voltage window and current ratings were easily achieved via series and parallel combinations of SN-LrGO PSCs directly on the same substrate. This manifests the versatility of the proposed approach for producing flexible and high-performance graphene-based electrochemical storage devices. In the second study, a CO2 Laser system is used to carbonize fine coating of polyaniline supported on polyurethane (PU) nanofibers to produce high quality graphitic carbon. Controlling pore size distribution and structure in conventional carbonization method is challenging. Laser carbonization allow precise control over the distribution of pore size to be in the range of mesoporous(< 50 nm) by tuning Laser parameters . At first, PU is electrospun into fine nanofibers. The electrospinning conditions are tuned to control porosity and the radius of the nanofibers.
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Physics of carbon quantum dots for novel optical sensing applications
(E-JUST, 2021-09) Bakier, Yasmin Mohamed Yousef
Carbon quantum dots (C-dots) are cost-effective, environmental-friendly, and biocompatible nanoparticles with many potential applications in sensing and optoelectronics. A simple controllable synthesis of C-dots with different particle sizes using a hydrothermal process, from folic acid source, is investigated in this thesis. Namely, we have synthesized fluorescent carbon dots from Folic Acid as a single precursor in ultra-pure water. The effect of reaction temperature, between 100°C and 230°C, is studied on the dots' sizes and the fluorescence properties. Results show that the reaction temperature can control both the dots' sizes and the fluorescence. Several techniques have been used to confirm that, including X-ray diffractometer XRD, X-ray Photoelectron Spectroscopy XPS, transmission electron microscope TEM, ultraviolet-visible absorption spectroscopy (UV-Vis), fluorescence spectroscopy (FL), and fluorescence lifetime measuring system. Moreover, the synthesized C-dots were examined as optical-sensor to determine different toxic materials. It was found that the synthesis temperature specifies the appropriate sensor for different hazardous chemicals like pyridine and aniline. Pyridine was realized to quench the fluorescence of the synthesized C-dots that prepared at 300°C effectively. The quenching is explained in terms of the Stern-Volmer relation and confirmed by fluorescence lifetime measurements to have a dynamic character with a predetermined electron transfer. The detection limit for pyridine was found to be 18 nM. To the best of our knowledge, such a small detection limit is more than three orders of magnitude smaller than that obtained so far for pyridine detection using any other facile methods. In addition, whereas aniline can be formed from burning plastics or tobacco and may be use in many industrial sources. Therefore, focus to detect aniline with a sensitive method was one of the aims of this thesis. It was found that C-dots, that was synthesized at low temperature, can be utilized as a turn-off fluorescent chemo-sensor for aniline solution with ultra-law sensitive detection. The fluorescence quenching is described in details by Stern-Volmer relation and was found to have static character as confirmed from nanosecond lifetime fluorescence measurements.