Graphene quantum dots and their metallophthalocyanines nanoconjugates as novel photoluminescent nanosensors
- 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.
- Full Text:
- Date Issued: 2018
- 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.
- Full Text:
- Date Issued: 2018
Sociocultural and sociomaterial mediation of children’s connectedness-with-nature: a case study of Hobbiton
- Authors: Ward-Smith, Chesney Fenella
- Date: 2018
- Subjects: Environmental psychology South Africa Eastern Cape , Experiential learning South Africa Eastern Cape , Environmental education Activity programs South Africa Eastern Cape , Nature study Activity programs South Africa Eastern Cape , Outdoor education South Africa Eastern Cape , Ethnoecology
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61918 , vital:28083
- Description: An increasingly large body of literature sees disconnection from nature as central to the convergent social-ecological crisis, rooted in anthropocentric ontologies. This study explored the potential for embodied, sociomaterial nature-based activities to engender shifts in children’s perceptions of, and sense of connectedness with, nature. Equally it explored how children’s socio-cultural-historical value positionings (SCHVP) mediated their perceptions of, and connectedness with, nature. The nature-based activities, spread over five-day camps, were located at Hobbiton-on-Hogsback, a centre that has existed for decades to provide experiential learning and graded exposure to natural spaces, aiming to increase environmental knowledge and nature-connection. The experiences of two groups of children from wide-ranging socioeconomic and socio-cultural backgrounds in the Eastern Cape Province of South Africa were explored using interpretive case study methodology. Through semi-structured interviews and focus groups with selected children (aged 10-14) and the Hobbiton staff members who worked with them, as well as participant observation, data were collected and analysed thematically. This study was guided by a layered theoretical framework that included Deep Ecology as an under-labourer, and Cultural Historical Activity Theory (CHAT) as a substantive, analytical framework. Interactions between participants’ SCHVP and the sociomateriality of the nature- based activities were analysed in relation to the children’s nature-perceptions and sense of Connectedness-With-Nature. The findings highlight both the importance of the children’s SCHVP and the sociomateriality of the nature-based activities in mediating their prior perceptions of, and connectedness with nature. The nature-based activities acted as a primary stimulus for developing environmental empathy, awareness and pro-environmental intentions. In essence, Hobbiton acted as a primary ‘seed planter’ towards greater feelings of Connectedness-With-Nature. However, recommendations are put forward for more decolonised, ethics-oriented and sociomaterial design of Hobbiton’s nature-based activities, with an emphasis on integrating children’s SCHVP into the pedagogical-design process in relation to the sociomaterial elements of the nature-based activities. Emically integrating the children’s multiplicities of knowing, doing, valuing and being into the pedagogical-design process could contribute to the decolonisation of nature-based experiences in such contexts cultural, socio and political diversity.
- Full Text:
- Date Issued: 2018
- Authors: Ward-Smith, Chesney Fenella
- Date: 2018
- Subjects: Environmental psychology South Africa Eastern Cape , Experiential learning South Africa Eastern Cape , Environmental education Activity programs South Africa Eastern Cape , Nature study Activity programs South Africa Eastern Cape , Outdoor education South Africa Eastern Cape , Ethnoecology
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61918 , vital:28083
- Description: An increasingly large body of literature sees disconnection from nature as central to the convergent social-ecological crisis, rooted in anthropocentric ontologies. This study explored the potential for embodied, sociomaterial nature-based activities to engender shifts in children’s perceptions of, and sense of connectedness with, nature. Equally it explored how children’s socio-cultural-historical value positionings (SCHVP) mediated their perceptions of, and connectedness with, nature. The nature-based activities, spread over five-day camps, were located at Hobbiton-on-Hogsback, a centre that has existed for decades to provide experiential learning and graded exposure to natural spaces, aiming to increase environmental knowledge and nature-connection. The experiences of two groups of children from wide-ranging socioeconomic and socio-cultural backgrounds in the Eastern Cape Province of South Africa were explored using interpretive case study methodology. Through semi-structured interviews and focus groups with selected children (aged 10-14) and the Hobbiton staff members who worked with them, as well as participant observation, data were collected and analysed thematically. This study was guided by a layered theoretical framework that included Deep Ecology as an under-labourer, and Cultural Historical Activity Theory (CHAT) as a substantive, analytical framework. Interactions between participants’ SCHVP and the sociomateriality of the nature- based activities were analysed in relation to the children’s nature-perceptions and sense of Connectedness-With-Nature. The findings highlight both the importance of the children’s SCHVP and the sociomateriality of the nature-based activities in mediating their prior perceptions of, and connectedness with nature. The nature-based activities acted as a primary stimulus for developing environmental empathy, awareness and pro-environmental intentions. In essence, Hobbiton acted as a primary ‘seed planter’ towards greater feelings of Connectedness-With-Nature. However, recommendations are put forward for more decolonised, ethics-oriented and sociomaterial design of Hobbiton’s nature-based activities, with an emphasis on integrating children’s SCHVP into the pedagogical-design process in relation to the sociomaterial elements of the nature-based activities. Emically integrating the children’s multiplicities of knowing, doing, valuing and being into the pedagogical-design process could contribute to the decolonisation of nature-based experiences in such contexts cultural, socio and political diversity.
- Full Text:
- Date Issued: 2018
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