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Synthesis of Nanostructured Metal Oxides and Sulfides for High Performance Energy Devices.

Thesis Info

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Author

Bibi, Nasreen

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

science

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10296/1/Nasreen%20Bibi_Chem_2019_QAU_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727488769

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In the last few decades, energy crises enforced scientists and researchers to search for the new nanostructured materials that may have a potential for energy harvesting and storage devices. Energy storage have earned a key position in energy devices due to its viability as compared to energy harvesting devices. Metal oxide and sulfides nanostructured materials have an enormous potential for energy devices owing to their high electrochemical performance and excellent stability. In the current study, hydrothermal method has been employed for the synthesis of Ce2Zr2O7, CeO2, Y2Zr2O7, PbS, CeS2, MnS and nanocomposite of Ce2Zr2O7/PbS, CeO2/CeS2 and Y2Zr2O7/MnS materials. The synthesized nanostructured materials have been characterized to find their applications in supercapacitor devices. Structural and morphological studies have confirmed the purity and the clear morphology of the materials. Electrochemical study using three-electrode system demonstrates that metal sulfide has higher specific capacitance than metal oxide but metal oxide reveals superiority in the cyclic stability. Therefore, due to synergistic effect, the nanocomposite of metal oxide and sulfide gain the conductivity of the sulfide and the stability of the oxide. As a result, the nanocomposites depict the better electrochemical performance in a sense of capacitance retention and cyclic stability with good rate capability. Specific capacitance (Csp), energy density (E) and power density (P) of the nanostructured electrode using Ni foam as a substrate have been measured with threeelectrode system by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques. The Csp and E of Ce2Zr2O7/PbS, CeO2/CeS2, Y2Zr2O7/MnS are 219, 420, 221 F/g and 6.7, 21.2, 10 Wh/kg at a constant applied current density of 1 A/g, respectively. The Csp of Ce2Zr2O7/PbS, CeO2/CeS2, Y2Zr2O7/MnS nanocomposites electrode after 1000 successive CV cycles are 116, 700, 261 F/g, correspondingly. The iii electrode consisting of SrZrO3 nanorods exhibits remarkably high Csp of 1225 F/g and 65 Wh/kg energy density. The excellent results of SrZrO3 nanorods are owing to its high specific surface area, small pore size and unique morphology. Cyclic stability analysis reveals an excellent stability of the studied electrodes due to their unique morphologies and conductive nature of the substrate (Ni foam). Csp remains constant in Ce2Zr2O7/PbS, while in case of CeO2/CeS2 and Y2Zr2O7/MnS, the Csp increases continuously up to 1000 successive CV cycles. The SrZrO3 nanorods shows high cyclic stability up to 1000 cycles. Above studies, suggest a significant promise of aforementioned materials for their use in future generation supercapacitors electrodes.
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شاہدہ جبین

شاہدہ جبین

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Prevalence and Characterization of Fungal Pathogens Associated With Loquat Eriobotrya Japonica in Punjab Pakistan

In Pakistan, loquat (Eriobotrya japonica) is becoming a major fruit crop for local and export markets but its yield is continuously declining. The aims of the current study were to determine the geographical distribution, incidence and morpho-molecular identification of major fungal pathogens associated with loquat in Punjab, Pakistan. For this purpose, a total number of 34 loquat orchards were surveyed during summer and winter 2014 and summer and winter 2015 in loquat growing areas of Punjab. A total number of 2720 samples (fruit, leaves and twigs) were collected from Taxila, Wah Cantt, Khanpur, Tret, Chatar, Murree, Kalar Kahar and Choa Saiden Shah. Alternaria leaf spots and fruit rot, twig dieback, anthracnose, Curvularia leaf spot and fruit rot and Fusarium fruit rot were recorded in all locations. Fungal diseases were found in all orchards and average incidence was recorded as 25.55 percent and 27.6 percent of tree in two consecutive years. The environmental conditions for the development of fungal diseases were more favorable in summer as compared to winter and due to this, the disease incidences recorded higher in summer. During the second year, increases in fungal diseases incidence were recorded in Taxila (6 percent), Wah Cantt (5.5 percent), Khanpur (1.7 percent), Tret (1.65 percent), Choa Saiden Shah (1 percent), Chatar (0.85 percent) and Murree (0.65 percent), due to dispersal of infected loquat debris in loquat orchards. A reduction in disease incidence was observed in Kalar Kahar (1 percent) due to the proper sanitation measures. Alternaria alternata, A. mali, Curvularia lunata, C. geniculata, Colletotrichum gloeosporioides, C. capsici, Fusarium solani and F. equiseti were isolated from the infected loquat fruit and leaves while only Lasiodiplodia theobromae was observed to cause twig dieback of xvii loquat. A total number of 843 isolates were confirmed through morphological characterizations. Alternaria sp. was exhibiting the maximum (168) isolates followed by L. theobromae (146), Colletotrichum capsici (140), Fusarium sp. (136), C. gloeosporioides (131) and Curvularia sp. (122) and Alternaria leaf spot and fruit rot was prominent in Tret (26.54 percent), Khanpur (26.19 percent), Taxila (25.76 percent) and Wah Cantt (19.23 percent) while maximum incidence of Curvularia leaf spot and fruit rot, Fusarium fruit rot, twig dieback and anthracnose (C. capsici) was recorded in Chatar (20.59 percent), Murree (20.58 percent), Choa Saiden Shah (20 percent) and Kalar Kahar (17.86 percent) respectively. The pathogenic abilities of each isolate were checked on healthy loquat plants, detached leaves and fruit. The internal transcribed spacer regions (ITS1, 5.8S and ITS2) of 44 highly virulent fungal isolates was amplified through PCR assay and sequencing analysis of ITS regions exhibited 99 to 100 percent genetic homology with previously reported isolates. Five multi-genes sequence analysis viz ITS, translocation elongation factor 1-α (EF), beta-tubulin (BT), actin (ACT) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) confirmed these pathogens at species level. The morphological characterization and multigene sequence analysis confirmed Lasiodiplodia theobromae, Curvularia lunata, C. geniculata, Colletotrichum gloeosporioides, C. capsici, Alternaria mali, A. Alternata, Fusarium solani and F. equiseti. The geographical distributions, incidences and morpho-molecular identification of major fungal pathogens is providing the guidelines for new researcher working on disastrous pathogens of loquat in Punjab Pakistan and this information will act as a remedy for development strategies of proper management of these destructive fungal pathogens.