List of Titles

Classification and clustering based methods for outlier detection of solar resource data

Authors: Abrahams, Waldo
Date: 2022-04
Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
Language: English
Type: Master's theses , text
Identifier: http://hdl.handle.net/10948/55423 , vital:51996
Description: Almost 90% of the primary global energy demand is serviced from the burning of fossil fuels (Abas, Kalair & Khan, 2015). Owing to the detrimental environmental impact of this, a global energy transition to the use of renewable energy, including solar energy, is needed (Gielen et al., 2019). An important aspect that inhibits the growth of solar energy is accurate solar resource data. Such data is needed because knowledge of the future reliability and quality of energy production is required to analyse a system’s performance and determine financial implications (Sengupta et al., 2017). Existing methods used to detect outliers in solar resource data do not efficiently identify outliers and an accurate and robust approach is required (Eastwood, 2019). Using simulated and real-world data, this study investigates the use of several classification methods, along with a two-stage clustering-classification approach to accurately identify outliers in solar resource data. The Treebag method proves to be an adequate outlier detection method for solar resource data. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2022
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Date Issued: 2022-04

The potential for concept cartoons to assist natural sciences teachers with developing scientific jargon for primary school learners

- Abrahams, Warda

Authors: Abrahams, Warda
Date: 2019
Subjects: Science--Study and teaching
Language: English
Type: Thesis , Masters , MEd
Identifier: http://hdl.handle.net/10948/40219 , vital:35984
Description: The study was undertaken to investigate whether a teaching tool Concept Cartoons may assist Intermediate Phase (IP) Natural Sciences teachers with the development and understanding of scientific jargon, when implemented in Natural Sciences investigations. As a novice Natural Sciences teacher it was important to find a teaching tool which would assist second language learners with scientific concepts, particularly focusing on science investigations. The focal aim was to search for a fun, captivating, educational resource that would cater for these learners’ barriers to science learning. This research falls within a constructivist worldview, and the research method employed was a case study. Data were collected through qualitative approach, via semi-structured interviews. A total of nine participating Intermediate Phase Natural Sciences teachers from the Port Elizabeth Northern Areas schools contributed towards the findings of this study. This study was an investigation undertaken to see whether a different teaching approach may encourage change. The findings of this study suggested that Concept Cartoons used in Natural Sciences investigations created an educational effect towards the learners understanding of science concepts. Intermediate Phase learners were introduced to Concept Cartoons to assist with their understanding of science terminology during practical investigations. The results of this investigation suggested that Concept Cartoons assisted English second-language learners with scientific jargon and served as an educative curriculum material for Intermediate Phase teachers. Furthermore Grade 4 findings suggested English home-language speakers struggled with scientific language, compared to their second-language peers who achieved greater results due to the amount of effort and determination they dedicated to translating these concepts. Further studies suggested this maybe because science terminology does not form part of their everyday vocabulary, therefore experiencing difficulty with scien1. Concept Cartoons: teachers and scientific investigations 2. Concept Cartoons: design, characters and speech bubbles 3. Concept Cartoons: enabling scientific talk 4. Concept Cartoons: scientific jargon 5. Concept Cartoons: scientific jargon and ESL learners 6. Concept Cartoons: teacher learning. This study, which aimed at introducing Concept Cartoons as an educative curriculum tool in Natural Sciences investigations, is expected to fill an important gap in literature surrounding teaching science jargon to English second-language learners.
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Date Issued: 2019

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An entrepreneurial framework for new venture property development projects

- Abrey, Mark Henry Shaw

Authors: Abrey, Mark Henry Shaw
Date: 2015
Subjects: Real estate development -- South Africa , Entrepreneurship -- South Africa , Land subdivision -- South Africa
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:9709 , http://hdl.handle.net/10948/d1020162
Description: The business of real estate is one of the largest suppliers of employment, and contributes significantly to the gross domestic product of numerous countries worldwide. It is, therefore, imperative that new real estate development entrepreneurs entering the market identify key competitiveness indicators in order to survive and ensure their success within an ever-changing market. However, property development is a complex process and considered to be 'too risky' Consequently, property development entrepreneurs lack the skills and expertise to effectively manage their business enterprises and the associated risks from project inception to completion, and commissioning. The study was conducted by means of a review of the related literature and by conducting an empirical study. The empirical study was conducted using a quantitative statistical approach by distributing research questionnaires to members falling within the sample population. The primary objective of the study was to develop an entrepreneurial framework for perceived success of new venture property development projects. A descriptive survey was conducted among professionals registered with the South African Property Owners Association (SAPOA) and property development practitioners within South Africa. The salient findings suggest that the following variables positively influence the perceived success of new venture property development projects: Entrepreneurial vision; Strategic management; Stakeholders‘ interests; Professional feasibility and viability reporting; Procurement; Communication; Consumer confidence; Risk management; Governance structures; Specialist advice; The entrepreneurial framework, and The project management body of knowledge (PMBOK). Furthermore, the following variables were identified in the empirical framework affecting the perceived success of new venture property development projects: Entrepreneurial Vision; Strategic Management; Stakeholders‘ Interest; Professional Feasibility and Viability Reporting; Procurement; Communication; Consumer Confidence; Risk Management; Governance Structures; Specialist Advice, and The Project Management Body of Knowledge (PMBOK). This study contributed to the South African property development body of knowledge by addressing the challenges faced by inexperienced entrepreneurs entering the property development market. Furthermore, this study aimed to improve the framework utilised by emerging property developers.
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Date Issued: 2015

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Decentralization and quality assurance in the Ugandan primary education sector

- Abu-Baker, Mutaaya Sirajee

Authors: Abu-Baker, Mutaaya Sirajee
Date: 2018
Subjects: Schools -- Decentralization -- Uganda , Education, Primary -- Uganda , Educational change -- Uganda
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/57390 , vital:26897
Description: The study presented in this thesis is a case study analysis of decentralization and quality assurance in a decentralized set up of the Ugandan Primary Schooling. The research looked at how the monitoring and evaluation informed the policy formulation process to regulate quality assurance in a decentralized governance of primary education. The Study was positioned in the critical realist paradigm, interpretive in orientation and used both coding and thematic techniques to understand the teachers’, SMC members’, and officers’ (at district and ministry levels) experiences and perceptions of quality assurance in a decentralized set up. Data was gathered using interviews, document analysis and observation methods. The findings indicated that the study was affected by eleven themes: Management System and Leadership, Human Resource Management, Finance Administration and Management, Parenting and Nutrition, Politics, Motivation, Social Structures and Patterns, Legislative Process and Policies, Infrastructure Development and Management, Community Involvement in Education and Curriculum and Professionalism. The monitoring and evaluation system had a framework in which it operates, though there was no quality assurance policy to guide the provision of quality education. The study finally indicated that there are more threats in a decentralized set up that put Quality in danger. Secondly, there was absence of supervision/inspection in schools as there was no evidence to prove this due to absence of reports. However, document analysis indicated visits of officers to schools. Records management was a problem to schools. Decentralization was adopted at different levels by different countries to address specific problems identified in view of service delivery. Finally, though monitoring and evaluation results informed the policy and decision makers, there was no quality assurance policy to guide the provision of quality education in institutions.
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Date Issued: 2018

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Relative contribution of wild foods to individual and household food security in the context of increasing vulnerability due to HIV/AIDS and climate variability

- Abu-Basutu, Keitometsi Ngulube

Authors: Abu-Basutu, Keitometsi Ngulube
Date: 2014
Subjects: Wild foods -- South Africa -- Eastern Cape , Food security -- South Africa , Food supply -- South Africa , AIDS (Disease) -- Social aspects -- South Africa , HIV infections -- Social aspects -- South Africa , Chronically ill -- South Africa -- Economic conditions , Chronically ill -- South Africa -- Social conditions , Food -- Social aspects -- South Africa , Food -- Economic aspects -- South Africa
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:4774 , http://hdl.handle.net/10962/d1010864 , Wild foods -- South Africa -- Eastern Cape , Food security -- South Africa , Food supply -- South Africa , AIDS (Disease) -- Social aspects -- South Africa , HIV infections -- Social aspects -- South Africa , Chronically ill -- South Africa -- Economic conditions , Chronically ill -- South Africa -- Social conditions , Food -- Social aspects -- South Africa , Food -- Economic aspects -- South Africa
Description: Wild foods are an integral component of the household food basket, yet their quantified contribution to food security relative to other sources in the context of HIV/AIDS, climate change and variability remains underexplored. This study was carried out in Willowvale and Lesseyton which are rural communities in the Eastern Cape province of South Africa. Willowvale is a relatively remote, medium-rainfall coastal community, while Lesseyton is a peri-urban low rainfall inland community. Qualitative and quantitative methods were used to collect data from 78 HIV/AIDS afflicted households with 329 individuals and 87 non-afflicted households with 365 individuals in the two study sites. Households were visited quarterly over 12 months to assess food acquisition methods, dietary intake and quality, and levels of food security, and to determine strategies employed by households to cope with droughts. The wild foods investigated were wild meat, wild birds, wild fish, wild mushrooms, wild leafy vegetables and wild fruits. Diets were moderately well-balanced and limited in variety, with cereal items contributing 52 % to total calorie intake. Mid-upper arm circumference measurements showed that all respondents were adequately nourished. The bulk of the food consumed by households was purchased, with supplementation from own production, wild vegetables and wild fruits. In Willowvale, wild vegetables comprised 46 % of overall vegetable consumption for afflicted households and 32 % for non-afflicted households, while own fruit production comprised 100 % of fruit consumption. In Lesseyton, wild vegetables comprised only 6 % and 4 % of vegetable consumption for afflicted and non-afflicted households, while wild fruit comprised 63 % and 41 % for afflicted and non-afflicted households. More than 80 % of respondents from both afflicted and non-afflicted households had sufficient daily kilocalories, although the majority of afflicted households felt they were food insecure and sometimes collected wild foods as one of their multiple coping strategies. Hunting and gathering of wild foods was associated with site, household affliction status, gender, age and season. More than 80 % of respondents ate wild vegetables and said they were more drought tolerant than conventional vegetables, making them the most consumed wild food and approximately 16 % of respondents ate wild birds, making them the least consumed wild food. Approximately 14 % of respondents from afflicted households in Willowvale sold wild fish, whilst 34 % of respondents from afflicted households and 7 % from non-afflicted households sold wild fruits in Lesseyton. Strategies adopted by households to cope with droughts were different between the two study sites, and households in Willowvale used a wider range of strategies. Given the devastating effects of HIV/AIDS coupled with the drawbacks of climate change and variability on food security, wild foods represent a free and easy way for vulnerable households to obtain food.
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Date Issued: 2014

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Exploring the diverse racialised responses to the ‘Ashwin Willemse incident’ through theories of race and coloniality of being

- Accom, Abner

Authors: Accom, Abner
Date: 2022-10-14
Subjects: Willemse, Ashwin, 1981- , Ethnic attitudes South Africa , Race awareness South Africa , Postcolonialism South Africa , South Africa Race relations , Decolonization South Africa , Racism in sports South Africa
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/405908 , vital:70218
Description: On 19 May 2018 Ashwin Willemse, a coloured Springbok rugby player walked off the SuperSport set, a DSTV sports program, during a live broadcast. He accused his white co-hosts Nick Mallet and Naas Botha (two white apartheid-era Springboks) of patronising him (SABC News, 2018; Eyewitness News, 2018). Responses to the Willemse incident reflected racial divisions in the country. It appeared that many white South Africans criticised Willemse’s behaviour, while many black South Africans stated that they could identify with his response to the subtle racisms experienced in everyday life, and which he claimed to have experienced on the SuperSport program (SABC News, 2018; Eyewitness News, 2018). The racialised media outcry led Professor Jonathan Jansen, to ask: “why do two groups of people, staring at the same event ‘see’ two different realities” (Maleka, 2018: 4)? This thesis probes possible answers to Jonathan Jansen’s question regarding the Ashwin Willemse walkout. The thesis explores and analyses the diverse racialised responses to the ‘Willemse walkout’ through race theories and ‘coloniality of being’. Qualitative research methods were used in the form of a reception analysis involving two racially homogenous (black and white) focus group interviews, two in-depth individual interviews with black research participants, three in-depth individual interviews with white research participants, and a sample of tweets from black and white commentators who had opinions about the ‘Willemse walkout’. The thesis concludes that most black research participants supported Willemse’s actions and most of the white people in the group disagreed with Willemse’s behaviour. Their various opinions were largely due to their different lived experiences which were a consequence of South Africa’s colonial history, apartheid, and racial discrimination. , Thesis (MA) -- Faculty of Humanities, School of Journalism and Media Studies, 2022
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Date Issued: 2022-10-14

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An investigation of the learning processes that take place during practical work activities when using electrical circuit boards in grade: a case study

- Accom, Gerald Charles

Authors: Accom, Gerald Charles
Date: 2012
Subjects: Competency-based education -- South Africa -- Eastern Cape -- Case studies Educational tests and measurements -- South Africa -- Eastern Cape -- Case studies Education -- Evaluation -- South Africa -- Eastern Cape -- Case studies
Language: English
Type: Thesis , Masters , MEd
Identifier: vital:1961 , http://hdl.handle.net/10962/d1009687
Description: Since the introduction of Outcomes Based Education (OBE) as a preferred method of teaching and learning with Curriculum 2005 in 1997, its existence has come under continuous threat for the past thirteen years. Its teething experiences included a revision in 2004 which saw the introduction of the Revised National Curriculum Statements (RNCS) and most recently, we are now standing on the threshold of the implementation of the Curriculum Assessment Policy Statements (CAPS) in 2012. Throughout the turbulent educational milieu, social constructivism has always been upheld as the preferred teaching and learning methodology and millions of rands have been invested in this regard. This study is thus premised on the concern that now after all the years of actively promoting social constructivist methodologies, the implementation of the CAPS could seriously negate reasonable strides made in this regard. Triggered by these curricular issues, a qualitative case study was conducted at a school in Grahamstown in the Eastern Cape, South Africa, investigating the learning processes occurring in group work sessions during lessons involving practical work in electricity using circuit boards in grade 8. Underpinned by an interpretivist paradigm, the study took place in two phases. The data was mainly generated through audio and video recording of two focus groups. An open coding system was employed to derive analytical categories and frequency tables were used to establish trends. In order to validate the data, two observer teachers were involved throughout the research process and this was followed up with semistructured interviews after the second phase. The two case studies, involving learners fitting a similar profile in respect of mother-tongue and age group, were engaged in a similar activity for almost a year apart. This study anticipated the revelation of the extent to which group practical activities in electricity promoted learning, how knowledge is constructed in group-settings and whether practical activities involving electrical circuit boards in grade 8 enhance learning? The main findings of my study revealed that these practical activities can promote learning and therefore should remain a preferred method of teaching.
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Date Issued: 2012

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Photos convey magic of '60s jazz scene

- Accone, Darryl

Authors: Accone, Darryl
Date: 1989
Subjects: McGregor, Chris -- 1936-1990 , Jazz , Jazz musicians , Breakey, Basil , Mpale, Dennis , Blue Notes (Musical group : South Africa) , Brotherhood of Breath (Musical group) , Ibrahim, Abdullah -- 1934- , Dollar Brand -- 1934-
Language: English
Type: Article
Identifier: vital:13467 , http://hdl.handle.net/10962/d1001383 , McGregor, Chris -- 1936-1990 , Jazz , Jazz musicians , Breakey, Basil , Mpale, Dennis , Blue Notes (Musical group : South Africa) , Brotherhood of Breath (Musical group) , Ibrahim, Abdullah -- 1934- , Dollar Brand -- 1934-
Description: Photocopied article form the newspaper Star Tonight about Basil Breakey and how he met other contemporary jazz musicians such as Chris McGregor and Abdullah Ibrahim.
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Date Issued: 1989

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Rural Tourism and Inclusive Development in Port St. Johns - South Africa

- Acha-Anyi, Paul Nkemngu, Ndolose, Ludwe, Solomon, Khunou Pula

Authors: Acha-Anyi, Paul Nkemngu , Ndolose, Ludwe , Solomon, Khunou Pula
Date: 2021
Subjects: Rural tourism Community Inclusive development; Sustainable development Article
Language: English
Type: text , article
Identifier: http://hdl.handle.net/11260/7023 , vital:52758 , xlink:href=":https://doi.org/10.46222/ajhtl.19770720.197"
Description: The purpose of this study was to explore ways of achieving an inclusive approach to tourism development in rural communities. Although tourism has generally been recommended as a means of orchestrating development in rural communities, achieving this laudable goal has often been illusive due to the fragmented approach adopted by tourism stakeholders. An exploratory quantitative research approach was adopted by using a structured survey instrument to generate 307 valid responses from community members in Port St. John in the Eastern Cape Province (ECP) of South Africa. Results obtained reveal similarities and some differences based on demographic characteristics with regards to the benefits of rural tourism to the community. Importantly, the study illuminates the fragmented way in which residents perceive tourism benefits, both from a gender perspective and personal benefit versus community dichotomy. The paper discusses policy as well as practical local economic development implications. Keywords: Rural tourism; community; Port St. Johns; inclusive development; sustainable development
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Date Issued: 2021

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An Analysis of Employee Motivation in a Multinational Context in Sub Saharan Africa

- Acha-Anyi, Paul Nkemngu, Masaraure, Robson

Authors: Acha-Anyi, Paul Nkemngu , Masaraure, Robson
Date: 2021
Subjects: Employee motivation Sub-Saharan Africa Article
Language: English
Type: text , article
Identifier: http://hdl.handle.net/11260/7021 , vital:52757 , xlink:href=":https://doi.org/10.46222/ajhtl.19770720-119"
Description: This study assesses motivational preferences of employees in a multinational context in Sub Saharan Africa. Using the Grundfos group operating sites in Ghana, Kenya and South Africa as a case study, the study explores quantitative data on possible differences in employee motivational factors based on selected variables such as location, length of service and managerial status. Questionnaires were employed in collecting data from 131 participants from the three locations of Grundfos Sub Saharan Africa (SSA). Results of the study reveal that the factor “equal treatment of employees” is considered most important among the respondents. It is also noted that there were no significant statistical differences among the participants based on the examined variables. Policy and practical implications of the findings of this study are discussed, particularly around the development and implementation of Human resources policies that address employee perceptions of equity. This study makes a contribution to existing literature on employee motivation in multinational settings. Keywords: Employee motivation, motivational factors, multinational context, Sub-Saharan Africa
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Date Issued: 2021

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Graphene quantum dots functionalized with 4-amino-2, 2, 6, 6-tetramethylpiperidine-N-oxide as fluorescence “turn-on” nanosensors

- Achadu, Ojodomo J, Britton, Jonathan, Nyokong, Tebello

Authors: Achadu, Ojodomo J , Britton, Jonathan , Nyokong, Tebello
Date: 2016
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/239854 , vital:50773 , xlink:href="https://doi.org/10.1007/s10895-016-1916-y"
Description: In this study, we report on the fabrication of simple and rapid graphene quantum dots (GQDs)-based fluorescence “turn-ON” nanoprobes for sensitive and selective detection of ascorbic acid (AA). Pristine GQDs and S and N co-doped-GQDs (SN-GQDs) were functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4-amino-TEMPO, a nitroxide free radical). The nitroxide free radicals efficiently quenched the fluorescence of the GQDs and upon interaction of the nanoconjugates with ascorbic acid, the quenched fluorescence was restored. The linear ranges recorded were 0.5–5.7 μM and 0.1–5.5 μM for GQDs-4-amino-TEMPO and SN-GQDs-4amino-TEMPO nanoprobes, respectively. Limits of detection were found to be 60 nM and 84 nM for SN-GQDS-4-amino-TEMPO and GQDs-4-amino-TEMPO for AA detection, respectively. This novel fluorescence “turn-ON” technique showed to be highly rapid and selective towards AA detection.
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Date Issued: 2016

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Fluorescence behaviour of supramolecular hybrids containing graphene quantum dots and pyrene-derivatized phthalocyanines and porphyrins

- Achadu, Ojodomo John, Managa, Muthumuni, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Managa, Muthumuni , Nyokong, Tebello
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188953 , vital:44801 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.10.029"
Description: Novel pyrene-derivatized zinc and cobalt phthalocyanines (Pcs) and porphyrins (Ps) were immobilized on graphene quantum dots (GQDs) to form GQDs-Pcs and GQDs-Ps supramolecular hybrids via the π–π stacking interaction method. Spectroscopic evidence shows that the resultant hybrids were stable owing to the strong π–π stacking interaction between the GQDs and the respective Pcs and Ps, thus leading to the fabrication of interesting and functional supramolecular hybrids by taking advantage of the delocalized π electron systems of GQDs and the macrocycles. The conjugates showed increased fluorescence quantum yields for the Pcs/Ps, but decreased values for the GQDs in the conjugates. These novel hybrid materials could potentially be deployed for studies in both fundamental and applied perspectives due to the synergistic contributions resulting from the combination of their excellent electronic and optical properties.
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Date Issued: 2017

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Interaction of graphene quantum dots with 4-acetamido-2, 2, 6, 6-tetramethylpiperidine-oxyl free radicals

- Achadu, Ojodomo John, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Nyokong, Tebello
Date: 2016
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/189031 , vital:44810 , xlink:href="https://doi.org/10.1007/s10895-015-1712-0"
Description: We report on the interaction of graphene quantum dots (GQDs) with 4-acetamido-2,2,6,6-tetramethylpiperidineoxyl (4-acetamido-TEMPO) free radicals. The GQDs were N and S, N doped. The fluorescence quantum yields were higher for the doped GQDs compared to the undoped. The interaction is assessed by spectrofluorimetric, steady state/time resolved fluorescence and electron paramagnetic resonance (EPR) techniques. Fluorescence quenching was observed upon the addition of 4-acetamido-TEMPO to the GQDs. Photoinduced electron transfer (PET) mechanism was suggested as the plausible mechanism involved in the fluorescence quenching in which 4-acetamido-TEMPO acted as the electron acceptor.
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Date Issued: 2016

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Graphene quantum dots and their metallophthalocyanines nanoconjugates as novel photoluminescent nanosensors

- Achadu, Ojodomo John

Authors: Achadu, Ojodomo John
Date: 2018
Subjects: Quantum dots , Graphene , Phthalocyanines , Nanoconjugates , Novel photoluminescent nanosensors , Metallophthalocyanines
Language: English
Type: text , Thesis , Doctoral , PhD
Identifier: http://hdl.handle.net/10962/60719 , vital:27821
Description: The fabrication and application of graphene quantum dots (GQDs)-based photoluminescent probes for the detection of analytes is presented. GQDs were functionalized with complexes such as metallophthalocyanines (MPcs), metal nanoparticles (Au@Ag NPs), 2,2,6,6-tetramethyl(piperidin-1-yl)oxyl (TEMPO), maleimide and thymine for the sensing of target analytes such as ascorbic acid (AA), biothiols (cysteine, homocysteine and glutathione) and mercury ion (Hg²+). The design strategy and approach was based on the quenching of the fluorescence of the GQDs upon functionalization with the above-mentioned complexes, which could be restored in the presence of the target analytes (due to their specific interaction affinity with the complexes). For the detection of AA, GQDs were covalently and/or non-covalently conjugated to TEMPO-bearing complexes to form GQDs-4A-TEMPO and GQDs-TEMPO-MPc systems with nanomolar limits of detection. For the detection of biothiols, Au@Ag NPs and maleimide-bearing complexes (MPc), which have specific affinity to interact with biothiols, were deployed. Hg²+ detection involved the use of GQDs and/or MPcs with thiol and thymine groups, respectively. In addition, a smart sensing platform was designed for the dual detection of biothiols and Hg²+ using supramolecular hybrid of polyethyleneimine functionalized-GQDs and MPc-Au@Ag conjugate. The probe could detect, in a sequential manner, Hg²+ and biothiols with high sensitivity. Results obtained from the LODs of the probes showed that GQDs sensing performances could be enhanced in the presence of MPcs. The probes designed in this work were successfully deployed in the assays of the target analytes in real samples and the recoveries obtained confirmed the analytical applicability of the probes.
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Date Issued: 2018

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The interaction between graphene quantum dots grafted with polyethyleneimine and Au@ Ag nanoparticles

- Achadu, Ojodomo John, Uddin, Imran, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Uddin, Imran , Nyokong, Tebello
Date: 2016
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188679 , vital:44775 , xlink:href="https://doi.org/10.1016/j.jphotochem.2016.03.016"
Description: Graphene quantum dots grafted with polyethyleneimine (GQDs-PEI) and Au@Ag core-shell nanoparticles blend was demonstrated to be a novel biosensing nanoprobe for the rapid and highly sensitive detection of biothiols such as cysteine (Cys), homocysteine (Hcys) and glutathione (GSH). The fluorescence emission of GQDs-PEI was quenched efficiently upon interaction with Au@Ag core-shell nanoparticles. The quenched fluorescence emission of the GQDs-PEI was restored in the presence of the biothiols. The fluorimetric sensing is based on the strong affinity between the mercapto (SH) groups of the biothiols and the Au@Ag core-shell nanoparticles by which the interaction between GQDs-PEI and Au@Ag core-shell nanoparticles was disrupted with a consequent modulation (‘turn-on’) of the quenched GQDs-PEI emission. Thus, a new, simple, rapid and highly sensitive fluorescence nanoprobe for detecting biothiols has been developed in this work.
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Date Issued: 2016

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Fluorescence behavior of nanoconjugates of graphene quantum dots and zinc phthalocyanines

- Achadu, Ojodomo John, Uddin, Imran, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Uddin, Imran , Nyokong, Tebello
Date: 2016
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188777 , vital:44784 , xlink:href="https://doi.org/10.1016/j.jphotochem.2015.11.006"
Description: Graphene quantum dots (GQDs) and zinc phthalocyanines interactions in different modes (covalent and non-covalent) are reported in this study. GQDs were covalently attached to the following complexes: zinc tetraamino phthalocyanine (ZnTAPc) via amide coupling, zinc tetracarboxyphenoxy Pc (ZnTCPPc) (π–π interaction) and cationic zinc tetrapyridiloxy Pc (ZnTmPyPc) (ionic interaction). GQDs fluorescence was quenched in the presence of the ZnPc derivatives. The nanoensembles of GQDs–ZnPcs showed stimulated emissions of the ZnPcs. The suggested quenching mechanism is through Förster resonance energy transfer (FRET). These novel nanoensembles hold promise for various optical and luminescence based applications.
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Date Issued: 2016

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Application of graphene quantum dots functionalized with thymine and thymine-appended zinc phthalocyanine as novel photoluminescent nanoprobes

- Achadu, Ojodomo John, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Nyokong, Tebello
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188508 , vital:44760 , xlink:href="https://doi.org/10.1039/C6NJ03285K"
Description: Graphene quantum dots (GQDs) and zinc phthalocyanine (ZnPc) were separately modified with thymine to obtain thymine-functionalized GQDs (T-GQDs) and ZnPc (T-ZnPc). T-GQDs and nanoconjugates of T-ZnPc with pristine GQDs (represented as pristine GQDs–T-ZnPc) or T-GQDs (represented as T-GQDs–T-ZnPc) were employed as fluorescent probes for the detection of mercury(II) ions (Hg2+). The as-synthesized T-GQDs alone demonstrated a highly sensitive and selective fluorescence “turn-OFF” process for Hg2+ detection due to the specific interaction between the thymine functionality on the T-GQDs with Hg2+. On the other hand, the fluorescence of pristine GQDs and T-GQDs was quenched (“turn-OFF”) upon coordination with T-ZnPc. However, the fluorescence emission was selectively restored (“turn-ON” process) in the presence of Hg2+ resulting in the sensitive detection of Hg2+ in the nanomolar concentration range (limit of detection = 0.05 nM, for the pristine GQDs–T-ZnPc probe). The probe containing pristine GQDs and the T-ZnPc complex demonstrated a higher specific and sensitive recognition of Hg2+ as compared to the T-GQDs alone or T-GQDs–T-ZnPc probes which are ascribed to the fluorescence “turn-ON” process of the former. Screening of different metal ions and counter ions proved that the probes are specifically suited for Hg2+ detection.
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Date Issued: 2017

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Graphene quantum dots decorated with maleimide and zinc tetramaleimido-phthalocyanine: Application in the design of “OFF-ON” fluorescence sensors for biothiols

- Achadu, Ojodomo John, Nyokong, Tebello

Authors: Achadu, Ojodomo John , Nyokong, Tebello
Date: 2017
Subjects: To be catalogued
Language: English
Type: text , article
Identifier: http://hdl.handle.net/10962/188282 , vital:44741 , xlink:href="https://doi.org/10.1016/j.talanta.2017.01.031"
Description: The fabrication of maleimide-derivatized graphene quantum dots (M-GQDs) and zinc phthalocyanine (2) as novel sensor probes for the selective detection of biothiols (cysteine, homocysteine or glutathione) through the rapid and specific Michael addition reaction between biothiols and the maleimide-derivatized probes is presented in this study. GQDs directly functionalized with maleimide units (M-GQDs) were synthesized and deployed for biothiols recognition following the principle of Michael addition. M-GQDs probe was found to be highly sensitive and selective towards biothiols detection in the nanomolar range in aqueous solution and at physiological pH (7.0). On the other hand, non-covalent interaction between pristine GQDs and novel zinc tetramaleimido-derivatized phthalocyanine resulted in the quenching of the pristine GQDs fluorescence emission which was switched back to the “ON” mode by Michael addition mechanism in the presence of biothiols. Tested relevant biomolecules did not interfere in the quantitative recognition of the biothiols. The probes showed to be highly sensitive, specific and selective for biothiols sensing in simulated real samples.
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Date Issued: 2017

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