Fluorescence properties of alloyed ZnSeS quantum dots overcoated with ZnTe and ZnTe/ZnS shells
- Adegoke, Oluwasesan, Mashazi, Philani N, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Mashazi, Philani N , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240754 , vital:50868 , xlink:href="https://doi.org/10.1016/j.optmat.2016.02.024"
- Description: Fluorescent alloyed ternary ZnSeS quantum dots (QDs) have been synthesized via the pyrolysis of organometallic precursors. The effects of passivation of ZnTe and ZnTe/ZnS shells on the optical properties of the ternary alloyed ZnSeS core have been studied. A ligand exchange reaction using L-cysteine as a capping ligand was used to obtain water-soluble nanocrystals. The nanocrystals were each characterized by UV/vis absorption and fluorescence spectroscopy, transmission electron microscopy, X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) quantum yield (QY) of alloyed ZnSeS QDs was 14% and this value increased to 27% when ZnTe was overcoated around the surface but further coating with a ZnS shell decreased the PL QY slightly to 24%. This implies that ZnTe shell suppressed non-radiative recombination exciton states in the alloyed core while further layering with a ZnS shell offered no further improvement in suppressing the defect states. XPS analysis confirmed the presence of the first shell layering but showed a weakened intensity signal of S (2p) and Se (3d) for the ZnSeS/ZnTe/ZnS QDs. Our work demonstrates for the first time that shell passivation of alloyed Zn-based QDs can offer improved optical properties. We hope the optical information presented in this work will be useful in the selection of alloyed Zn-based QDs appropriate for the intended application.
- Full Text:
- Date Issued: 2016
- Authors: Adegoke, Oluwasesan , Mashazi, Philani N , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/240754 , vital:50868 , xlink:href="https://doi.org/10.1016/j.optmat.2016.02.024"
- Description: Fluorescent alloyed ternary ZnSeS quantum dots (QDs) have been synthesized via the pyrolysis of organometallic precursors. The effects of passivation of ZnTe and ZnTe/ZnS shells on the optical properties of the ternary alloyed ZnSeS core have been studied. A ligand exchange reaction using L-cysteine as a capping ligand was used to obtain water-soluble nanocrystals. The nanocrystals were each characterized by UV/vis absorption and fluorescence spectroscopy, transmission electron microscopy, X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The photoluminescence (PL) quantum yield (QY) of alloyed ZnSeS QDs was 14% and this value increased to 27% when ZnTe was overcoated around the surface but further coating with a ZnS shell decreased the PL QY slightly to 24%. This implies that ZnTe shell suppressed non-radiative recombination exciton states in the alloyed core while further layering with a ZnS shell offered no further improvement in suppressing the defect states. XPS analysis confirmed the presence of the first shell layering but showed a weakened intensity signal of S (2p) and Se (3d) for the ZnSeS/ZnTe/ZnS QDs. Our work demonstrates for the first time that shell passivation of alloyed Zn-based QDs can offer improved optical properties. We hope the optical information presented in this work will be useful in the selection of alloyed Zn-based QDs appropriate for the intended application.
- Full Text:
- Date Issued: 2016
Nanoconjugates of CdTe@ ZnS quantum dots with cobalt tetraamino-phthalocyanine
- Adegoke, Oluwasesan, Antunes, Edith M, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242049 , vital:50996 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.02.010"
- Description: The covalent linking of thiol-capped CdTe@ZnS QDs with cobalt tetraamino-phthalocyanine (CoTAPc) has been successfully carried out. Several techniques such as time-resolved fluorescence measurements, thermal gravimetric analysis,transmissionelectronmicroscopy andspectrophotometric techniques were employed to characterize the nanoconjugates. Covalent binding of the QDs with CoTAPc resulted in the fluorescence quenching of the former. In the presence of varying concentrations of superoxide anion (O2 •−), the fluorescence of the QDs in the conjugate was gradually enhanced and the detection limits obtained were 2.1 and 2.4 nM for the smaller and larger QDs, respectively. Based on the excellent selectivity displayed by the nanoconjugates towards O2 •− over other biologically active species, a potential nanosensor was developed.
- Full Text:
- Date Issued: 2013
- Authors: Adegoke, Oluwasesan , Antunes, Edith M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/242049 , vital:50996 , xlink:href="https://doi.org/10.1016/j.jphotochem.2013.02.010"
- Description: The covalent linking of thiol-capped CdTe@ZnS QDs with cobalt tetraamino-phthalocyanine (CoTAPc) has been successfully carried out. Several techniques such as time-resolved fluorescence measurements, thermal gravimetric analysis,transmissionelectronmicroscopy andspectrophotometric techniques were employed to characterize the nanoconjugates. Covalent binding of the QDs with CoTAPc resulted in the fluorescence quenching of the former. In the presence of varying concentrations of superoxide anion (O2 •−), the fluorescence of the QDs in the conjugate was gradually enhanced and the detection limits obtained were 2.1 and 2.4 nM for the smaller and larger QDs, respectively. Based on the excellent selectivity displayed by the nanoconjugates towards O2 •− over other biologically active species, a potential nanosensor was developed.
- Full Text:
- Date Issued: 2013
Fluorescence “switch on” of conjugates of CdTe@ ZnS quantum dots with Al, Ni and Zn tetraamino-phthalocyanines by hydrogen peroxide
- Adegoke, Oluwasesan, Khene, Samson M, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Khene, Samson M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241750 , vital:50966 , xlink:href="https://doi.org/10.1007/s10895-013-1222-x"
- Description: In this study, we have developed a novel nanoprobe for H2O2 based on the conjugation of CdTe@ZnS quantum dots (QDs) to different metal tetraamino-phthalocyanine (MTAPc): (M = (OAc)Al, {OAc = acetate}, Ni and Zn). Chemical coordination of the QDs to the MTAPc resulted in the fluorescence “switch off” of the linked QDs which was associated with Förster resonance energy transfer (FRET). In the presence of varying concentration of H2O2, the fluorescence of the linked QDs was progressively “switched on” and the FRET mechanism between the QDs and the MTAPc was disrupted. The sensitivity/limit of detection of the nanoprobe followed the order: QDs-ZnTAPc (2.2 μM) > QDs-NiTAPc (4.4 μM) > QDs-AlTAPc (9.8 μM) while the selectivity followed the order: QDs-NiTAPc > QDs-AlTAPc > QDs-ZnTAPc. The varying degree of sensitivity/selectivity and mechanism of detection is discussed in detail.
- Full Text:
- Date Issued: 2013
- Authors: Adegoke, Oluwasesan , Khene, Samson M , Nyokong, Tebello
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/241750 , vital:50966 , xlink:href="https://doi.org/10.1007/s10895-013-1222-x"
- Description: In this study, we have developed a novel nanoprobe for H2O2 based on the conjugation of CdTe@ZnS quantum dots (QDs) to different metal tetraamino-phthalocyanine (MTAPc): (M = (OAc)Al, {OAc = acetate}, Ni and Zn). Chemical coordination of the QDs to the MTAPc resulted in the fluorescence “switch off” of the linked QDs which was associated with Förster resonance energy transfer (FRET). In the presence of varying concentration of H2O2, the fluorescence of the linked QDs was progressively “switched on” and the FRET mechanism between the QDs and the MTAPc was disrupted. The sensitivity/limit of detection of the nanoprobe followed the order: QDs-ZnTAPc (2.2 μM) > QDs-NiTAPc (4.4 μM) > QDs-AlTAPc (9.8 μM) while the selectivity followed the order: QDs-NiTAPc > QDs-AlTAPc > QDs-ZnTAPc. The varying degree of sensitivity/selectivity and mechanism of detection is discussed in detail.
- Full Text:
- Date Issued: 2013
Optical properties of water-soluble l-cysteine-capped alloyed CdSeS quantum dot passivated with ZnSeTe and ZnSeTe/ZnS shells
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7260 , http://hdl.handle.net/10962/d1020269
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing l-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed l-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties. , Original publication is available at http://dx.doi.org/10.1016/j.optmat.2015.05.024
- Full Text: false
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7260 , http://hdl.handle.net/10962/d1020269
- Description: Alloyed quantum dots (QDs) passivated with shell materials have valuable optical characteristics suitable for a wide array of applications. In this work, alloyed ternary CdSeS QDs passivated with ZnSeTe and ZnSeTe/ZnS shells have been synthesized via a hot-injection method and a ligand exchange reaction employing l-cysteine as a thiol ligand has been used to obtain these water-soluble nanocrystals for the first time. The photoluminescence (PL) quantum yield (QY) of alloyed l-cysteine-capped CdSeS was 71.2% but decreased significantly to 5.2% upon passivation with a ZnSeTe shell. The red shift in PL emission of the CdSeS/ZnSeTe QDs was attributed to be strain-induced whilst a lattice-induced process likely created defect states in the core/shell interface hence contributing to the decline in the PL QY. Nonetheless, the fluorescence stability of CdSeS/ZnSeTe QDs in aqueous solution was unperturbed. Further passivation with a ZnS shell (CdSeS/ZnSeTe/ZnS) improved the PL QY to a value of 58.7% and thus indicates that the defect state in the QDs core/shell/shell structure was reduced. PL lifetime exciton measurements indicated that the rates of decay of the QDs influenced their photophysical properties. , Original publication is available at http://dx.doi.org/10.1016/j.optmat.2015.05.024
- Full Text: false
- Date Issued: 2015
CdTe quantum dots functionalized with 4-amino-2, 2, 6, 6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion
- Adegoke, Oluwasesan, Hosten, Eric, McCleland, Cedric, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
Deposition of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shells around CdSeTe alloyed core quantum dots: effects on optical properties
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7289 , http://hdl.handle.net/10962/d1020342
- Description: In this work, we synthesized water-soluble L-cysteine-capped alloyed CdSeTe core quantum dots (QDs) and investigated the structural and optical properties of deposition of each of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed that the overcoating of a CdS shell around the alloyed CdSeTe core [quantum yield (QY) = 8.4%] resulted in effective confinement of the radiative exciton with an improved QY value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS surface decreased the QY value to 24.7%, but an increase in the QY value of up to 49.5% was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe surface. QDs with shell layers showed improved stability relative to the core. Data obtained from time-resolved fluorescence measurements provided useful insight into variations in the photophysical properties of the QDs upon the formation of each shell layer. Our study suggests that the formation of CdSeTe/CdS core/shell QDs meets the requirements of quality QDs in terms of high photoluminescence QY and stability, hence further deposition of additional shells are not necessary in improving the optical properties of the core/shell QDs. Copyright © 2015 John Wiley & Sons, Ltd. , Original publication is available at http://dx.doi.org/10.1002/bio.3013
- Full Text: false
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Language: English
- Type: Article
- Identifier: vital:7289 , http://hdl.handle.net/10962/d1020342
- Description: In this work, we synthesized water-soluble L-cysteine-capped alloyed CdSeTe core quantum dots (QDs) and investigated the structural and optical properties of deposition of each of CdS, CdS/ZnSe and CdS/ZnSe/ZnS shell layers. Photophysical results showed that the overcoating of a CdS shell around the alloyed CdSeTe core [quantum yield (QY) = 8.4%] resulted in effective confinement of the radiative exciton with an improved QY value of 93.5%. Subsequent deposition of a ZnSe shell around the CdSeTe/CdS surface decreased the QY value to 24.7%, but an increase in the QY value of up to 49.5% was observed when a ZnS shell was overcoated around the CdSeTe/CdS/ZnSe surface. QDs with shell layers showed improved stability relative to the core. Data obtained from time-resolved fluorescence measurements provided useful insight into variations in the photophysical properties of the QDs upon the formation of each shell layer. Our study suggests that the formation of CdSeTe/CdS core/shell QDs meets the requirements of quality QDs in terms of high photoluminescence QY and stability, hence further deposition of additional shells are not necessary in improving the optical properties of the core/shell QDs. Copyright © 2015 John Wiley & Sons, Ltd. , Original publication is available at http://dx.doi.org/10.1002/bio.3013
- Full Text: false
- Date Issued: 2015
Conjugation of mono-substituted phthalocyanine derivatives to CdSe@ ZnS quantum dots and their applications as fluorescent-based sensors
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189842 , vital:44936 , xlink:href="https://doi.org/10.1016/j.synthmet.2013.11.016"
- Description: Unsymmetrically substituted derivatives of aluminium amino phthalocyanines were synthesized for the first time, fully characterized and conjugated to CdSe@ZnS quantum dots (QDs). The conjugates were employed as fluorescence-based sensors for anion sensing. Among the anions that enhanced the fluorescence of the probe, fluoride ion was chosen as the test ion to test the efficacy of the probe. Förster resonance energy transfer from the QDs to the phthalocyanine was observed as an indication for the fluorescence quenching of the QDs upon binding to the phthalocyanine. The fluorescence of the linked QDs was progressively enhanced, and linearly proportional to increasing concentrations of fluoride ion. The type of substituent attached to the phthalocyanine ring influenced the efficiency of fluorescence enhancement. The proposed nanoprobe has been employed to detect fluoride ion in cell culture medium and tap water.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189842 , vital:44936 , xlink:href="https://doi.org/10.1016/j.synthmet.2013.11.016"
- Description: Unsymmetrically substituted derivatives of aluminium amino phthalocyanines were synthesized for the first time, fully characterized and conjugated to CdSe@ZnS quantum dots (QDs). The conjugates were employed as fluorescence-based sensors for anion sensing. Among the anions that enhanced the fluorescence of the probe, fluoride ion was chosen as the test ion to test the efficacy of the probe. Förster resonance energy transfer from the QDs to the phthalocyanine was observed as an indication for the fluorescence quenching of the QDs upon binding to the phthalocyanine. The fluorescence of the linked QDs was progressively enhanced, and linearly proportional to increasing concentrations of fluoride ion. The type of substituent attached to the phthalocyanine ring influenced the efficiency of fluorescence enhancement. The proposed nanoprobe has been employed to detect fluoride ion in cell culture medium and tap water.
- Full Text:
- Date Issued: 2014
Unsymmetrically Substituted Nickel Triazatetra-Benzcorrole and Phthalocynanine Complexes: Conjugation to Quantum Dots and Applications as Fluorescent “Turn ON” Sensors
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7311 , http://hdl.handle.net/10962/d1020403
- Description: We report on the design and application of fluorescent nanoprobes based on the covalent linking of L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg2+ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg2+ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg2+ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs. , Original publication is available at http://dx.doi.org/10.1007/s10895-013-1317-4
- Full Text: false
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7311 , http://hdl.handle.net/10962/d1020403
- Description: We report on the design and application of fluorescent nanoprobes based on the covalent linking of L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg2+ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg2+ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg2+ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs. , Original publication is available at http://dx.doi.org/10.1007/s10895-013-1317-4
- Full Text: false
Effects of analytes on the fluorescence properties of CdTe@ ZnS quantum dots decorated with cobalt tetraamino-phthalocyanine
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189829 , vital:44935 , xlink:href="https://doi.org/10.1016/j.jlumin.2013.09.079"
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189829 , vital:44935 , xlink:href="https://doi.org/10.1016/j.jlumin.2013.09.079"
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe.
- Full Text:
- Date Issued: 2014
Unsymmetrically substituted nickel triazatetra-benzcorrole and phthalocynanine complexes
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189818 , vital:44934 , xlink:href="https://doi.org/10.1007/s10895-013-1317-4"
- Description: We report on the design and application of fluorescent nanoprobes based on the covalent linking of L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg2+ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg2+ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg2+ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Date: 2014
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/189818 , vital:44934 , xlink:href="https://doi.org/10.1007/s10895-013-1317-4"
- Description: We report on the design and application of fluorescent nanoprobes based on the covalent linking of L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg2+ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg2+ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg2+ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs.
- Full Text:
- Date Issued: 2014
The design of quantum dots and their conjugates as luminescent probes for analyte sensing
- Authors: Adegoke, Oluwasesan
- Date: 2014
- Subjects: Quantum dots Anolytes Luminescent probes Luminescence spectroscopy Phthalocyanines Nanoparticles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4457 , http://hdl.handle.net/10962/d1010866
- Description: The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
- Full Text:
- Date Issued: 2014
- Authors: Adegoke, Oluwasesan
- Date: 2014
- Subjects: Quantum dots Anolytes Luminescent probes Luminescence spectroscopy Phthalocyanines Nanoparticles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4457 , http://hdl.handle.net/10962/d1010866
- Description: The design and applications of quantum dots (QDs) as fluorescent probes for analyte sensing is presented. Cadmium based thiol-capped QDs were employed as probe for the detection of analytes. Comparative studies between core CdTe and core-shell CdTe@ZnS QDs showed that the overall sensitivity and selectivity of the sensor was dependent on the nature of the capping agent and the QDs employed, hence making CdTe@ZnS QDs a more superior sensor than the core. To explore the luminescent sensing of QDs based on the fluorescence “turn ON” mode, L-glutathione-capped CdTe QDs was conjugated to 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT) to form a QDs-4AT conjugate system. The QDs-4AT nanoprobe was highly selective and sensitive to the detection of bromide ion with a very low limit of detection. Subsequently, metallo-phthalocyanines (MPcs) were employed as host molecules on the surface of QDs based on the covalent linking of the QDs to the MPc. Elucidation of the reaction mechanism showed that the fluorescence “turn ON” effect of the QDs-MPc probe in the presence of the analyte was due to axial ligation of the analytes to the Pc ring. Studies showed that the type of substituent attached to the MPc ring influenced the overall sensitivity of the probe. Additionally, a comparative investigation using newly synthesized phthalocyanine and triaza-benzcorrole complexes was conducted when these complexes were conjugated to CdSe@ZnS QDs for analyte sensing. Results showed that the triaza-benzcorrole complex can be employed as a host-molecule sensor but displayed a lower sensitivity for analyte sensing in comparison to the phthalocyanine complex.
- Full Text:
- Date Issued: 2014
Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B C
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B C
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193575 , vital:45349 , xlink:href="https://doi.org/10.1016/j.jallcom.2015.05.083"
- Description: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.
- Full Text:
- Date Issued: 2015
Effects of analytes on the fluorescence properties of CdTe@ZnS quantum dots decorated with cobalt tetraamino-phthalocyanine
- Adegoke, Oluwasesan, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7315 , http://hdl.handle.net/10962/d1020541
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe. , Original publication is available at http://dx.doi.org/10.1016/j.jlumin.2013.09.079
- Full Text: false
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello
- Language: English
- Type: Article
- Identifier: vital:7315 , http://hdl.handle.net/10962/d1020541
- Description: In this work, we have carried out an investigation on the effects of different biologically active analytes on the fluorescence response of glutathione-capped CdTe@ZnS quantum dots (QDs)-colbalt tetraamino-phthalocyanine nanoconjugate system. Firstly, fluorescence quenching occurred. Experimental results showed that some analytes either “turned on”, others further quenched or showed no effect on the fluorescence emission of the nanoprobe. , Original publication is available at http://dx.doi.org/10.1016/j.jlumin.2013.09.079
- Full Text: false
Photophysical properties of a series of alloyed and non-alloyed water-soluble l-cysteine-capped core quantum dots
- Adegoke, Oluwasesan, Nyokong, Tebello, Forbes, Patricia B
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
- Authors: Adegoke, Oluwasesan , Nyokong, Tebello , Forbes, Patricia B
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188486 , vital:44758 , xlink:href="https://doi.org/10.1016/j.jallcom.2016.10.276"
- Description: Photophysical properties of quantum dots (QDs) such as their photoluminescence (PL) quantum yield (QY), exciton lifetime and PL stability are important parameters used to unravel their chemical and physical characteristics. In this work, we have comparatively investigated the photophysical properties of a series of L-cysteine-capped non-alloyed (CdTe and CdSe) and alloyed (CdZnTe, CdSeS, CdSeTe and CdSeTeS) core QDs. Each of the QDs varied in their size and PL emission wavelength. We observe no physical relationship between the PL QY of the QDs and their PL stability. Based on the PL stability assessment, CdTe QDs with a high PL QY value of 88% exhibited poor PL stability while moderate PL stability was observed for CdZnTe (QY = 78%); CdSe (QY = 3%); and CdSeTe QDs (QY = ∼3%). Alloyed CdSeS (QY = ∼69%) and CdSeTeS (QY = 23%) QDs exhibited good PL stability and can serve as potential fluorophores for a wide range of chemical and biological applications. Generally, it is proposed that the structural nature of the QDs played a significant role in their overall photophysical properties. The information provided in this work will assist in the selection of core QDs suitable for different applications.
- Full Text:
- Date Issued: 2017
Interaction of CdTe quantum dots with 2, 2-diphenyl-1-picrylhydrazyl free radical
- Adegoke, Oluwasesan, Chidawanyika, Wadzanai J U, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245751 , vital:51402 , xlink:href="https://doi.org/10.1007/s10895-011-1012-2"
- Description: The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH● is proposed.
- Full Text:
- Date Issued: 2012
- Authors: Adegoke, Oluwasesan , Chidawanyika, Wadzanai J U , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/245751 , vital:51402 , xlink:href="https://doi.org/10.1007/s10895-011-1012-2"
- Description: The interaction of 2,2-diphenyl-1-picrylhydrazyl (DPPH●) free radical with thiol-capped CdTe quantum dots (QDs) has been studied by UV–vis spectroscopy, steady state and time resolved fluorescence measurements. Addition of DPPH● radical to CdTe QDs resulted in fluorescence quenching. The interaction occurs through static quenching as this was confirmed by fluorescence lifetime measurements. Time course absorption studies indicates that DPPH● may be reduced by interaction with QDs to the substituted hydrazine form (2,2-diphenyl-1-picrylhydrazine) DPPH-H. The mechanism of fluorescence quenching of CdTe QDs by DPPH● is proposed.
- Full Text:
- Date Issued: 2012
Assessing teaching strategies of grade four English second language teachers in Amathole District, Eastern Cape Province, South Africa
- Authors: Adegoriolu, Emmanuel Tobi
- Date: 2018
- Subjects: Education--South Africa English language--Study and teaching--Foreign speakers Second language acquisition
- Language: English
- Type: Thesis , Masters , Applied Linguistics
- Identifier: http://hdl.handle.net/10353/15474 , vital:40411
- Description: The intention of this study was to assess the teaching strategies of Grade 4 English second language teachers in the Amathole district of the Eastern Cape. The objectives of the study were firstly, to identify the teaching strategies currently employed by Grade 4 teachers in the teaching of English as a second language in selected schools in Amathole district of the Eastern Cape in South Africa. Secondly, the study sought to establish how the existing teaching strategies impacted on the performance of the learners of English as a second language in the selected schools in Amathloe district of the Eastern Cape, and to establish the teachers‟ perceptions on the most effective teaching strategies in the selected schools. The study used translanguaging and communicative language teaching as the theoretical lens and guide in data collection and analysis. The study employed the use of mixed methods of both quantitative and qualitative research design. Data was collected through the use of eight comprehensive classroom observations and eight teacher questionnaires in four different primary schools. The conclusion of the study as established in the outcome of data showed that there was no recommended teaching strategy by the Department of Education for English second language teachers teaching Grade 4. The study observed that the language teachers made use of various teaching strategies in the instruction of Grade 4 learners. In addition, it was concluded that the placement of the English language subject on the timetable affected the performance of young learners during the summer period. Moreover, the absence of teacher-learner cordial relationship compromised learning outcomes and performance of Grade 4 learners in the skills of English second language. The study recommends that teachers of English as a second language be trained on communicative language teaching in order to achieve positive outcomes in the classroom.
- Full Text:
- Date Issued: 2018
- Authors: Adegoriolu, Emmanuel Tobi
- Date: 2018
- Subjects: Education--South Africa English language--Study and teaching--Foreign speakers Second language acquisition
- Language: English
- Type: Thesis , Masters , Applied Linguistics
- Identifier: http://hdl.handle.net/10353/15474 , vital:40411
- Description: The intention of this study was to assess the teaching strategies of Grade 4 English second language teachers in the Amathole district of the Eastern Cape. The objectives of the study were firstly, to identify the teaching strategies currently employed by Grade 4 teachers in the teaching of English as a second language in selected schools in Amathole district of the Eastern Cape in South Africa. Secondly, the study sought to establish how the existing teaching strategies impacted on the performance of the learners of English as a second language in the selected schools in Amathloe district of the Eastern Cape, and to establish the teachers‟ perceptions on the most effective teaching strategies in the selected schools. The study used translanguaging and communicative language teaching as the theoretical lens and guide in data collection and analysis. The study employed the use of mixed methods of both quantitative and qualitative research design. Data was collected through the use of eight comprehensive classroom observations and eight teacher questionnaires in four different primary schools. The conclusion of the study as established in the outcome of data showed that there was no recommended teaching strategy by the Department of Education for English second language teachers teaching Grade 4. The study observed that the language teachers made use of various teaching strategies in the instruction of Grade 4 learners. In addition, it was concluded that the placement of the English language subject on the timetable affected the performance of young learners during the summer period. Moreover, the absence of teacher-learner cordial relationship compromised learning outcomes and performance of Grade 4 learners in the skills of English second language. The study recommends that teachers of English as a second language be trained on communicative language teaching in order to achieve positive outcomes in the classroom.
- Full Text:
- Date Issued: 2018
Parents’ involvement in education of their children: case study of two selected secondary schools in the Amathole West District
- Authors: Adelabu, O J
- Date: 2020-10
- Subjects: Education -- Parent participation , Parent-teacher relationships
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19969 , vital:44857
- Description: Parents’ involvement is a very important element that has an influence on children’s education. However, research has shown that parents’ involvement is the biggest challenge facing South African schools. The study sought to investigate parents’ involvement in the education of their children at secondary school in Amathole West District, Eastern Cape Province of South Africa. The study was underpinned by Epstein’s theory of parental involvement and the Ecological framework. A qualitative approach was adopted in this study which was located within an interpretivist paradigm and used a case study approach with a sample of 26 participants which includes (2 school principals, 6 educators, 6 parents and 12 learners) were selected conveniently, data was collected using focus group discussions, interviews and document analysis. The study revealed that although schools have employed various strategies to improve parental involvement in their children’s education, there are still challenges which inhibit the effectiveness of these strategies. The study also revealed that most parents are unable to get involved as expected by the school due to some challenges such as poverty, unemployment, educational background, distance and illiteracy. Consequently, the study recommended that parents must be more actively involved in the school and collaborate with their children’s teacher in order to bring out the best in their children. Furthermore, to ensure effective parents’ involvement, schools may have activities that can develop, improve and encourage parents’ involvement in such areas as parenting, communication, learning at home, volunteering, decision making and community collaboration. , Thesis (MEd) -- Faculty of Education, 2020
- Full Text:
- Date Issued: 2020-10
- Authors: Adelabu, O J
- Date: 2020-10
- Subjects: Education -- Parent participation , Parent-teacher relationships
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/19969 , vital:44857
- Description: Parents’ involvement is a very important element that has an influence on children’s education. However, research has shown that parents’ involvement is the biggest challenge facing South African schools. The study sought to investigate parents’ involvement in the education of their children at secondary school in Amathole West District, Eastern Cape Province of South Africa. The study was underpinned by Epstein’s theory of parental involvement and the Ecological framework. A qualitative approach was adopted in this study which was located within an interpretivist paradigm and used a case study approach with a sample of 26 participants which includes (2 school principals, 6 educators, 6 parents and 12 learners) were selected conveniently, data was collected using focus group discussions, interviews and document analysis. The study revealed that although schools have employed various strategies to improve parental involvement in their children’s education, there are still challenges which inhibit the effectiveness of these strategies. The study also revealed that most parents are unable to get involved as expected by the school due to some challenges such as poverty, unemployment, educational background, distance and illiteracy. Consequently, the study recommended that parents must be more actively involved in the school and collaborate with their children’s teacher in order to bring out the best in their children. Furthermore, to ensure effective parents’ involvement, schools may have activities that can develop, improve and encourage parents’ involvement in such areas as parenting, communication, learning at home, volunteering, decision making and community collaboration. , Thesis (MEd) -- Faculty of Education, 2020
- Full Text:
- Date Issued: 2020-10
Incidence and molecular characterization of Hepatitis E virus from swine herds in the Eastern Cape province, South Africa
- Authors: Adelabu, Olusesan Adeyemi
- Date: 2016
- Subjects: Hepatitis -- South Africa -- Eastern Cape Virology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13966 , vital:39734
- Description: Hepatitis E virus-mediated infection is a serious public health concern in economically developing nations of the world. Globally, four major genotypes of HEV have been documented and the swine HEV identified to date in different countries belongs to either genotype 3 or 4. It has been reported to cross species barrier and cause infections in humans. Hence, Hepatitis E has been suggested to be zoonotic owing to the increase of evidence through various studies. Thus far, genotypes 1 and 2 are exclusively found in human population. However, little data are available regarding the occurrence of HEV in South Africa, especially in the Eastern Cape Province. Hence, this study was designed to assess the prevalence of Hepatitis E Virus among swine herd in selected communal and commercial farms in the Eastern Cape Province of South Africa. A total of 160 faecal samples were collected from swine herds in Amathole and Chris Hani District Municipalities of Eastern Cape Province and screened for the presence of HEV. Faecal samples were collected, using sterile swabs, from swine between the age of 2 to 6 months old, placed on ice and transported to the laboratory for further analysis. Viral RNA extraction was carried out followed by nested reverse-transcriptase polymerase chain reaction was used for amplification, after which the amplified products were examined by electrophoresis and viewed under ultraviolet illumination. The positive PCR products were sent for sequencing. Of the 160 faecal samples screened, only seven were positive (4.4percent) for HEV. The nucleotide sequence analyses revealed isolates UFT 01-03 sharing 82percent to 99percent identities with other strains with accession numbers KX896664, KX896665 and KX896666 and UMCF 01-04 with KX896667, KX896668, KX896669 and KX896670 from different regions of the world Phylogenetic analysis also showed that all seven isolates from this study clustered with both human and swine HEV from different geographical regions of the world especially with Japan Human and swine strains, Netherland swine HEV strains (AY032758, AF332620) and human HEV strain from France (JQ763611). We conclude that HEV is present among swine in the Eastern Cape Province, albeit in low incidence, and this does have public health implications. There is need for maintenance of high hygienic standards in order to prevent human infections through swine faecal materials and appropriate cooking of pork is highly advised.
- Full Text:
- Date Issued: 2016
- Authors: Adelabu, Olusesan Adeyemi
- Date: 2016
- Subjects: Hepatitis -- South Africa -- Eastern Cape Virology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13966 , vital:39734
- Description: Hepatitis E virus-mediated infection is a serious public health concern in economically developing nations of the world. Globally, four major genotypes of HEV have been documented and the swine HEV identified to date in different countries belongs to either genotype 3 or 4. It has been reported to cross species barrier and cause infections in humans. Hence, Hepatitis E has been suggested to be zoonotic owing to the increase of evidence through various studies. Thus far, genotypes 1 and 2 are exclusively found in human population. However, little data are available regarding the occurrence of HEV in South Africa, especially in the Eastern Cape Province. Hence, this study was designed to assess the prevalence of Hepatitis E Virus among swine herd in selected communal and commercial farms in the Eastern Cape Province of South Africa. A total of 160 faecal samples were collected from swine herds in Amathole and Chris Hani District Municipalities of Eastern Cape Province and screened for the presence of HEV. Faecal samples were collected, using sterile swabs, from swine between the age of 2 to 6 months old, placed on ice and transported to the laboratory for further analysis. Viral RNA extraction was carried out followed by nested reverse-transcriptase polymerase chain reaction was used for amplification, after which the amplified products were examined by electrophoresis and viewed under ultraviolet illumination. The positive PCR products were sent for sequencing. Of the 160 faecal samples screened, only seven were positive (4.4percent) for HEV. The nucleotide sequence analyses revealed isolates UFT 01-03 sharing 82percent to 99percent identities with other strains with accession numbers KX896664, KX896665 and KX896666 and UMCF 01-04 with KX896667, KX896668, KX896669 and KX896670 from different regions of the world Phylogenetic analysis also showed that all seven isolates from this study clustered with both human and swine HEV from different geographical regions of the world especially with Japan Human and swine strains, Netherland swine HEV strains (AY032758, AF332620) and human HEV strain from France (JQ763611). We conclude that HEV is present among swine in the Eastern Cape Province, albeit in low incidence, and this does have public health implications. There is need for maintenance of high hygienic standards in order to prevent human infections through swine faecal materials and appropriate cooking of pork is highly advised.
- Full Text:
- Date Issued: 2016
A qualitative assessment of the achievement of gender equality under education for all (EFA) goals : study of Lagos State, Nigeria
- Authors: Adeleke, Adawi Adeola
- Date: 2018
- Subjects: Sex discrimination in education -- Nigeria Sexism in education -- Nigeria Educational equalization -- Nigeria
- Language: English
- Type: Thesis , Doctoral , Education
- Identifier: http://hdl.handle.net/10353/9500 , vital:34357
- Description: The importance of education cannot be overemphasized. Education has been identified as the most critical instrument for empowering individuals with the necessary knowledge and skills, which can give them access to productive employment. Also, the future of a country is based on the quality of education acquired by its citizens which helps in transforming it from pre-literate to contemporary nationhood. Many international treaties and initiatives in the world have made special provisions for education as a duty of every government which must be given to every citizen as of right, irrespective of gender or social class. Amongst these international initiatives is the Education for All (EFA) Goals, a time-bound global movement towards the provision of education for every one led by the United Nations Educational, Scientific and Cultural Organization (UNESCO). There are six goals in all. This study investigated one of the EFA goals, the goal 5. The aim of the study was a qualitative assessment of the achievement of gender equality goal under the Education for All (EFA) goals, a study of Lagos State, Nigeria. The theoretical framework of the study is informed by the Social Justice Theory and the Social Justice Praxis Theory. Scholarly works and literatures on girl-child education, gender and education, and gender balancing in education were reviewed. The study followed qualitative research approach which utilizes an interpretive research paradigm that provides a collective voice from the participants. The research area was purposively selected as Lagos State being a former capital of Nigeria and still the commercial nerve centre of the nation. Although it is the smallest state in Nigeria in term of size, it remains the most populous in the country with a projected population of 20,546,999 (13.5percent Nigeria’s total population). A sample of 16 participants were purposively selected because they were the officers directly in charge of the implementation government policies on education in the State. The data was collected through in-depth recorded interview sessions and secondary data were sourced through official documents downloaded online and from Lagos State Ministry of Education. Based on the thematic analysis of the data collected, the study found out that the State government had established policies and measures to provide qualitative education for all the citizens on a non-discriminatory basis. Thus, the goal of gender parity in terms of enrollment of boys and girls has been relatively achieved in the state. However, there were still some challenges of equality in the learning process and outcome. The study therefore recommends that schools should be made attractive and conducive as possible to assist the educational attainment of any student. This could be achieved by promoting positive values and attitudes towards education, all the stakeholders in the education sector must be involved in the business of running the school. There should also be a form of resourcing and expansion of the school facilities through the Public - Private Partnership in education.
- Full Text:
- Date Issued: 2018
- Authors: Adeleke, Adawi Adeola
- Date: 2018
- Subjects: Sex discrimination in education -- Nigeria Sexism in education -- Nigeria Educational equalization -- Nigeria
- Language: English
- Type: Thesis , Doctoral , Education
- Identifier: http://hdl.handle.net/10353/9500 , vital:34357
- Description: The importance of education cannot be overemphasized. Education has been identified as the most critical instrument for empowering individuals with the necessary knowledge and skills, which can give them access to productive employment. Also, the future of a country is based on the quality of education acquired by its citizens which helps in transforming it from pre-literate to contemporary nationhood. Many international treaties and initiatives in the world have made special provisions for education as a duty of every government which must be given to every citizen as of right, irrespective of gender or social class. Amongst these international initiatives is the Education for All (EFA) Goals, a time-bound global movement towards the provision of education for every one led by the United Nations Educational, Scientific and Cultural Organization (UNESCO). There are six goals in all. This study investigated one of the EFA goals, the goal 5. The aim of the study was a qualitative assessment of the achievement of gender equality goal under the Education for All (EFA) goals, a study of Lagos State, Nigeria. The theoretical framework of the study is informed by the Social Justice Theory and the Social Justice Praxis Theory. Scholarly works and literatures on girl-child education, gender and education, and gender balancing in education were reviewed. The study followed qualitative research approach which utilizes an interpretive research paradigm that provides a collective voice from the participants. The research area was purposively selected as Lagos State being a former capital of Nigeria and still the commercial nerve centre of the nation. Although it is the smallest state in Nigeria in term of size, it remains the most populous in the country with a projected population of 20,546,999 (13.5percent Nigeria’s total population). A sample of 16 participants were purposively selected because they were the officers directly in charge of the implementation government policies on education in the State. The data was collected through in-depth recorded interview sessions and secondary data were sourced through official documents downloaded online and from Lagos State Ministry of Education. Based on the thematic analysis of the data collected, the study found out that the State government had established policies and measures to provide qualitative education for all the citizens on a non-discriminatory basis. Thus, the goal of gender parity in terms of enrollment of boys and girls has been relatively achieved in the state. However, there were still some challenges of equality in the learning process and outcome. The study therefore recommends that schools should be made attractive and conducive as possible to assist the educational attainment of any student. This could be achieved by promoting positive values and attitudes towards education, all the stakeholders in the education sector must be involved in the business of running the school. There should also be a form of resourcing and expansion of the school facilities through the Public - Private Partnership in education.
- Full Text:
- Date Issued: 2018
Ultraprecision Diamond Turning of Monocrystalline Germanium
- Authors: Adeleke, Adeniyi Kehinde
- Date: 2021-04
- Subjects: Precision , Diamond Turning
- Language: English
- Type: Master's theses , Thesis
- Identifier: http://hdl.handle.net/10948/44453 , vital:37835
- Description: Infrared lens production demands a surface with a high degree of accuracy and integrity. Surface roughness is a critical index of the measure of any product’s surface integrity. As a result of this, ultra-high machining technology has enjoyed extensive application, due to the continuous request for components within the range of 1 – 10nm roughness value. This technology has brought about the increased productivity and manufacture of quality products with a top-notch surface finish. Brittle materials such as germanium are hard to machine through the conventional processes such as lapping and polishing. Hence, the ultra-precision machining technology based on single point diamond turning (SPDT), is now been applied to machine germanium in the ductile mode, where material chip removal occurs by plastic deformation instead of a brittle fracture. During machining, selecting the optimal cutting conditions which includes cutting parameters and tool geometry, will not only improve productivity but ensure the minimisation of operating cost. In this research work, SPDT operation was used to conduct two experiments on a (monocrystalline germanium) workpiece. The first experiment was carried out using a diamond tool with a 1.5 mm nose radius, while the second experiment employed the use of a tool having a nose radius of 1.0 mm. A combination of machining parameters for each of the experimental runs were derived from a Box-Behnken method of design and the surface roughness was measured at each interval for both experiments with the aid of a Taylor Hopson PGI Dimension XL profilometer. Acoustic emission (AE) was also used as a quality sensing and tool-monitoring technique, to acquire signals and give indications of the expected surface roughness. Predictive models based on response surface methodology (RSM) and artificial neural networks (ANN), were developed for determining surface roughness. Optimisation was performed using RSM to determine the optimal set of machining factors, which results in optimal condition of the output response. Further investigations on the acquired signals were carried out using signal-processing techniques. Time-domain and time-frequency domain features acquired from the AE signals, together with the process parameters, were employed as input variables in the neural network design, having shown a good association with the surface roughness. ix Conclusively, it can be observed that the predictive model results and the experimental roughness measurements are in good agreement with each other. For accuracy and cost of computation, the RSM and ANN developed models for single-crystal germanium are compared using mean absolute error (MAE). , Thesis (M.Eng) -- Faculty of Engineering, the built environment & Information Technology, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Adeleke, Adeniyi Kehinde
- Date: 2021-04
- Subjects: Precision , Diamond Turning
- Language: English
- Type: Master's theses , Thesis
- Identifier: http://hdl.handle.net/10948/44453 , vital:37835
- Description: Infrared lens production demands a surface with a high degree of accuracy and integrity. Surface roughness is a critical index of the measure of any product’s surface integrity. As a result of this, ultra-high machining technology has enjoyed extensive application, due to the continuous request for components within the range of 1 – 10nm roughness value. This technology has brought about the increased productivity and manufacture of quality products with a top-notch surface finish. Brittle materials such as germanium are hard to machine through the conventional processes such as lapping and polishing. Hence, the ultra-precision machining technology based on single point diamond turning (SPDT), is now been applied to machine germanium in the ductile mode, where material chip removal occurs by plastic deformation instead of a brittle fracture. During machining, selecting the optimal cutting conditions which includes cutting parameters and tool geometry, will not only improve productivity but ensure the minimisation of operating cost. In this research work, SPDT operation was used to conduct two experiments on a (monocrystalline germanium) workpiece. The first experiment was carried out using a diamond tool with a 1.5 mm nose radius, while the second experiment employed the use of a tool having a nose radius of 1.0 mm. A combination of machining parameters for each of the experimental runs were derived from a Box-Behnken method of design and the surface roughness was measured at each interval for both experiments with the aid of a Taylor Hopson PGI Dimension XL profilometer. Acoustic emission (AE) was also used as a quality sensing and tool-monitoring technique, to acquire signals and give indications of the expected surface roughness. Predictive models based on response surface methodology (RSM) and artificial neural networks (ANN), were developed for determining surface roughness. Optimisation was performed using RSM to determine the optimal set of machining factors, which results in optimal condition of the output response. Further investigations on the acquired signals were carried out using signal-processing techniques. Time-domain and time-frequency domain features acquired from the AE signals, together with the process parameters, were employed as input variables in the neural network design, having shown a good association with the surface roughness. ix Conclusively, it can be observed that the predictive model results and the experimental roughness measurements are in good agreement with each other. For accuracy and cost of computation, the RSM and ANN developed models for single-crystal germanium are compared using mean absolute error (MAE). , Thesis (M.Eng) -- Faculty of Engineering, the built environment & Information Technology, 2021
- Full Text:
- Date Issued: 2021-04