Performance of magnetic nanocomposites for the removal of some selected contaminants from aqueous solution
- Authors: Ojemaye, Mike Onyewelehi
- Date: 2017
- Subjects: Nanocomposites (Materials)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8746 , vital:33508
- Description: In this thesis, the performances of magnetic nanoparticles based materials were assessed for the removal or reduction of heavy metals in aqueous solutions. The successful synthesis of a novel adsorbent, azomethine functionalized magnetic nanoparticles (MNP-Maph) by covalent bonding between the amine group (-NH2) of amine functionalized magnetic nanoparticles (MNP-NH2) and carboxylic group (-COOH) of 4-{[(E)-phenylmethylidene]amino}benzoic acid (Maph-COOH) was achieved. This adsorbent was examined for the removal of di and trivalent ions (Cu2+, Zn2+, As3+, Pb2+ and Hg2+) from aqueous solutions. Also, magnetic photocatalyst with silica interlayer (NiFe2O4-SiO2-TiO2) was synthesized and employed for the reduction of Cr(VI) in aqueous solution. The photocatalytic reduction efficiency of this material was compared with that of magnetic titanium dioxide (NiFe2O4-TiO2) photocatalyst and titanium dioxide (TiO2) to ascertain the material with the best photocatalytic efficiency and ease of separation. All synthesized materials were characterized by using XRD, FT-IR, TEM, SEM, TGA and VSM before application. For the adsorption processes, the effects of pH, contact time, adsorbent dose and temperature were examined to ascertain the experimental condition necessary for the optimal removal of metal ions from solution. The data obtained from all experiments were fitted into four kinetic models; pseudo-first order, pseudo-second order, elovich and intra particle diffusion models to determine the mechanism involved in the adsorption of these di and trivalent ions while two isotherm models were employed in the adorption processes; these include: Langmuir and Freudlich models. Also, for the photocatalytic experiment, the effects of pH, contact time and photocatalyst dose were investigated to determine the experimental conditions necessary for the optimal reduction of Cr(VI) in aqueous solution. MNP-Maph showed excellent removal capacities of 34.08, 35.83, 50.08, 58.24 and 59.24 mg g-1 for Cu2+, Zn2+, As3+, Pb2+ and Hg2+ respectively compared to data previously reported in literature. This is as a result of the high affinity of azomethine group towards metal ions which tremendously enhanced removal of metal ions by adsorption. The incorporation of azomethine to magnetic nanoparticles improved the affinity towards metal ions removal forming strong electrostatic interaction between the adsorbent active sites and adsorbates. Also, the utilization of NiFe2O4-SiO2-TiO4, NiFe2O4-TiO2 and TiO2 for the reduction of Cr(VI) in aqueous solution showed a good photocatalytic performance with NiFe2O4-SiO2-TiO2 showing to be better in terms of both photocatalytic reduction and magnetic separation. TiO2 was observed to have 96.7percent reduction efficiency within 240 min while NiFe2O4-SiO2-TiO2 has 96.5percent reduction efficiency within 300 min and NiFe2O4-TiO2 gave 60percent reduction efficiency within 300 min of UV irradiation. This magnetic photocatalyst composite (NiFe2O4-SiO2-TiO2) gives the advantage of avoiding the problem of separation often encountered with most photocatalyst materials including TiO2 by allowing separation with the aid of a magnetic field. The adsorption processes were all described by pseudo-second order and Langmuir isotherm models while the photocatalytic process was described by Langmuir-Hinshelwood (L-H) kinetic model. Furthermore, thermodynamic experiment studied for the adsorption processes showed that all metal ion adsorption except Hg2+ by MNP-Maph were endothermic in nature, rapid and spontaneous indicating the feasibility of the sorbent material for the removal of metal ions from aqueous solutions. Also, regenerability study conducted to determine the reusability of sorbent material after seven cycles showed the potential to reuse sorbent material seven times or more. The reusability of the sorbent material was observed to show a percentage of an average of 78percent using 50:50 mixture of 0.1 mol dm-3 HNO3 and HCl for all adsorption processes. For the photocatalytic experiment, regenerability using 0.1 mol dm-3 for 1 h was observed to be very impressive after 3 runs for all synthesized photocatalytic materials. This thereby implies that the removal of metal ions by these materials will not in any way introduce secondary pollutants into the environment. Rather, it will avert the production of secondary pollutants. Also, the use of simple conventional chemicals for the regeneration of synthesized materials showed that regeneration in this study is cost effective as regeneration has been known to cost about three quarter of the total operation and maintenance of an adsorption or photocatalytic process. Application of MNP-Maph to real wastewater sampled from five different wastewater treatment plants in Eastern Cape Province for the removal of Cu2+, Zn2+ and As3+ showed that removal efficiencies of approximately 80 percent were achieved for all three metal ions upon adsorption by MNP-Maph. These therefore show that the introduction of metal loving ligand such as Maph-COOH improved the efficiency of MNP towards the removal of heavy metal ions from aqueous solution. Also, silica positively influenced the performance of magnetic titanium dioxide towards Cr(VI) reduction and separation from aqueous solution. This study therefore showed that these materials should be considered for future applications in the area of water/wastewater decontamination.
- Full Text:
- Date Issued: 2017
- Authors: Ojemaye, Mike Onyewelehi
- Date: 2017
- Subjects: Nanocomposites (Materials)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8746 , vital:33508
- Description: In this thesis, the performances of magnetic nanoparticles based materials were assessed for the removal or reduction of heavy metals in aqueous solutions. The successful synthesis of a novel adsorbent, azomethine functionalized magnetic nanoparticles (MNP-Maph) by covalent bonding between the amine group (-NH2) of amine functionalized magnetic nanoparticles (MNP-NH2) and carboxylic group (-COOH) of 4-{[(E)-phenylmethylidene]amino}benzoic acid (Maph-COOH) was achieved. This adsorbent was examined for the removal of di and trivalent ions (Cu2+, Zn2+, As3+, Pb2+ and Hg2+) from aqueous solutions. Also, magnetic photocatalyst with silica interlayer (NiFe2O4-SiO2-TiO2) was synthesized and employed for the reduction of Cr(VI) in aqueous solution. The photocatalytic reduction efficiency of this material was compared with that of magnetic titanium dioxide (NiFe2O4-TiO2) photocatalyst and titanium dioxide (TiO2) to ascertain the material with the best photocatalytic efficiency and ease of separation. All synthesized materials were characterized by using XRD, FT-IR, TEM, SEM, TGA and VSM before application. For the adsorption processes, the effects of pH, contact time, adsorbent dose and temperature were examined to ascertain the experimental condition necessary for the optimal removal of metal ions from solution. The data obtained from all experiments were fitted into four kinetic models; pseudo-first order, pseudo-second order, elovich and intra particle diffusion models to determine the mechanism involved in the adsorption of these di and trivalent ions while two isotherm models were employed in the adorption processes; these include: Langmuir and Freudlich models. Also, for the photocatalytic experiment, the effects of pH, contact time and photocatalyst dose were investigated to determine the experimental conditions necessary for the optimal reduction of Cr(VI) in aqueous solution. MNP-Maph showed excellent removal capacities of 34.08, 35.83, 50.08, 58.24 and 59.24 mg g-1 for Cu2+, Zn2+, As3+, Pb2+ and Hg2+ respectively compared to data previously reported in literature. This is as a result of the high affinity of azomethine group towards metal ions which tremendously enhanced removal of metal ions by adsorption. The incorporation of azomethine to magnetic nanoparticles improved the affinity towards metal ions removal forming strong electrostatic interaction between the adsorbent active sites and adsorbates. Also, the utilization of NiFe2O4-SiO2-TiO4, NiFe2O4-TiO2 and TiO2 for the reduction of Cr(VI) in aqueous solution showed a good photocatalytic performance with NiFe2O4-SiO2-TiO2 showing to be better in terms of both photocatalytic reduction and magnetic separation. TiO2 was observed to have 96.7percent reduction efficiency within 240 min while NiFe2O4-SiO2-TiO2 has 96.5percent reduction efficiency within 300 min and NiFe2O4-TiO2 gave 60percent reduction efficiency within 300 min of UV irradiation. This magnetic photocatalyst composite (NiFe2O4-SiO2-TiO2) gives the advantage of avoiding the problem of separation often encountered with most photocatalyst materials including TiO2 by allowing separation with the aid of a magnetic field. The adsorption processes were all described by pseudo-second order and Langmuir isotherm models while the photocatalytic process was described by Langmuir-Hinshelwood (L-H) kinetic model. Furthermore, thermodynamic experiment studied for the adsorption processes showed that all metal ion adsorption except Hg2+ by MNP-Maph were endothermic in nature, rapid and spontaneous indicating the feasibility of the sorbent material for the removal of metal ions from aqueous solutions. Also, regenerability study conducted to determine the reusability of sorbent material after seven cycles showed the potential to reuse sorbent material seven times or more. The reusability of the sorbent material was observed to show a percentage of an average of 78percent using 50:50 mixture of 0.1 mol dm-3 HNO3 and HCl for all adsorption processes. For the photocatalytic experiment, regenerability using 0.1 mol dm-3 for 1 h was observed to be very impressive after 3 runs for all synthesized photocatalytic materials. This thereby implies that the removal of metal ions by these materials will not in any way introduce secondary pollutants into the environment. Rather, it will avert the production of secondary pollutants. Also, the use of simple conventional chemicals for the regeneration of synthesized materials showed that regeneration in this study is cost effective as regeneration has been known to cost about three quarter of the total operation and maintenance of an adsorption or photocatalytic process. Application of MNP-Maph to real wastewater sampled from five different wastewater treatment plants in Eastern Cape Province for the removal of Cu2+, Zn2+ and As3+ showed that removal efficiencies of approximately 80 percent were achieved for all three metal ions upon adsorption by MNP-Maph. These therefore show that the introduction of metal loving ligand such as Maph-COOH improved the efficiency of MNP towards the removal of heavy metal ions from aqueous solution. Also, silica positively influenced the performance of magnetic titanium dioxide towards Cr(VI) reduction and separation from aqueous solution. This study therefore showed that these materials should be considered for future applications in the area of water/wastewater decontamination.
- Full Text:
- Date Issued: 2017
Performance of project management units (PMUS): the case of Sarah Baartman District Municipality
- Authors: Monare, Thabang
- Date: 2017
- Subjects: Project management -- South Africa -- Eastern Cape -- Evaluation , Construction industry -- South Africa -- Eastern Cape -- Management Construction industry -- South Africa -- Eastern Cape -- Quality control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19081 , vital:28771
- Description: The Municipal Infrastructure Grant programme (MIG) is South Africa’s largest local government infrastructure development funding. Designed to improve service delivery through financing the cost of eradicating basic services backlogs created by Apartheid’s legacy of ‘separate development’, MIG is also intended to be part of government’s overall strategy to eliminate the ‘triple challenge’ of poverty, unemployment and growing inequality. Through government’s active policy which sought to transform and enhance the municipal infrastructure service delivery capacity, effective project management was identified as an integral function of municipalities with a developmental role in terms of the Constitutional mandate. This led to the establishment of Project Management Units (PMUs) tasked with administering the MIG funds and managing the infrastructure projects effectively. Whilst MIG’s overall key principles were clearly defined in the MIG policy framework, the attainment of project success has proved elusive for most municipalities and this manifestation has only been partially examined. The purpose of this study is to explore factors affecting project success with the establishment of PMUs in Sarah Baartman District Municipality (SBDM) in the Eastern Cape Province in South Africa, with the aim of contributing to the refinement of best-practice for project implementation. A multiple case study approach was preferred, preceded by an extensive review of relevant literature on the basic tenets of project success. This exercise culminated in the refinement of research questions which were then posed in interviews to a purposive sample of PMU managers within SBDM. The findings from the study revealed the centrality of the dominant features required to influence the probability of positive outcomes such as institutional capacity, organisational culture and infrastructure governance. The research concludes by proposing ways of improving on these three components in the delivery of municipal infrastructure.
- Full Text:
- Date Issued: 2017
- Authors: Monare, Thabang
- Date: 2017
- Subjects: Project management -- South Africa -- Eastern Cape -- Evaluation , Construction industry -- South Africa -- Eastern Cape -- Management Construction industry -- South Africa -- Eastern Cape -- Quality control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19081 , vital:28771
- Description: The Municipal Infrastructure Grant programme (MIG) is South Africa’s largest local government infrastructure development funding. Designed to improve service delivery through financing the cost of eradicating basic services backlogs created by Apartheid’s legacy of ‘separate development’, MIG is also intended to be part of government’s overall strategy to eliminate the ‘triple challenge’ of poverty, unemployment and growing inequality. Through government’s active policy which sought to transform and enhance the municipal infrastructure service delivery capacity, effective project management was identified as an integral function of municipalities with a developmental role in terms of the Constitutional mandate. This led to the establishment of Project Management Units (PMUs) tasked with administering the MIG funds and managing the infrastructure projects effectively. Whilst MIG’s overall key principles were clearly defined in the MIG policy framework, the attainment of project success has proved elusive for most municipalities and this manifestation has only been partially examined. The purpose of this study is to explore factors affecting project success with the establishment of PMUs in Sarah Baartman District Municipality (SBDM) in the Eastern Cape Province in South Africa, with the aim of contributing to the refinement of best-practice for project implementation. A multiple case study approach was preferred, preceded by an extensive review of relevant literature on the basic tenets of project success. This exercise culminated in the refinement of research questions which were then posed in interviews to a purposive sample of PMU managers within SBDM. The findings from the study revealed the centrality of the dominant features required to influence the probability of positive outcomes such as institutional capacity, organisational culture and infrastructure governance. The research concludes by proposing ways of improving on these three components in the delivery of municipal infrastructure.
- Full Text:
- Date Issued: 2017
Performance of Xhosa-speaking adults on the Rey-Osterrieth Complex Figure test : an extension of a prior South African normative database
- Mabusela, Ntombizanele Tebello Iris
- Authors: Mabusela, Ntombizanele Tebello Iris
- Date: 2017
- Subjects: Neuropsychological tests Neuropsychological tests--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Masters , Counselling Psychology
- Identifier: http://hdl.handle.net/10353/16313 , vital:40709
- Description: The aim of the study was to develop preliminary normative indications for the Rey-Osterrieth Complex figure test (ROCF). The ROCF was administered in English on the performance of Xhosa-speaking, unskilled workers (N=40), from the Eastern Cape Province. As a mode of collecting data, the research study made use of convenience sampling which ultimately led to snowball sampling. The ROCF was administered and scored according to Rey Osterrieth’s initial standardised administration instructions (Meyers & Meyers, 1995a). For all trials of the ROCF (Copy, Immediate and Delayed Recall), a score of 0-2 points were allocated to each of the 18 structural elements of the figure. The total scores were calculated out of 36, as originally defined by Osterrieth. There was no statistically significant difference in performance for the quality of education for any of the ROCF test trials (p≥0.05 in all instances). Similarly, no significant difference is indicated for the Copy and Immediate Recall (IR) trial for sex indications, whilst the Delayed Recall (DR) trial shows statistically significant differences. Age effects appeared to have an influence on test performance on all ROCF test trials, as a significant difference was identified for all instances. Descriptively and statistically, the present local sample’s mean performance was compared to a demographically equivalent local study (de Kock’s study, which the present study is doing an extension on) and non-local normative studies. The results indicate the need for culturally-relevant South African psychological assessment measures. It also emphasises the importance of making a psychological measure more applicable and relevant to a specific context. Consideration of socio-cultural factors for norm purposes is strongly recommended by this study.
- Full Text:
- Date Issued: 2017
- Authors: Mabusela, Ntombizanele Tebello Iris
- Date: 2017
- Subjects: Neuropsychological tests Neuropsychological tests--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Masters , Counselling Psychology
- Identifier: http://hdl.handle.net/10353/16313 , vital:40709
- Description: The aim of the study was to develop preliminary normative indications for the Rey-Osterrieth Complex figure test (ROCF). The ROCF was administered in English on the performance of Xhosa-speaking, unskilled workers (N=40), from the Eastern Cape Province. As a mode of collecting data, the research study made use of convenience sampling which ultimately led to snowball sampling. The ROCF was administered and scored according to Rey Osterrieth’s initial standardised administration instructions (Meyers & Meyers, 1995a). For all trials of the ROCF (Copy, Immediate and Delayed Recall), a score of 0-2 points were allocated to each of the 18 structural elements of the figure. The total scores were calculated out of 36, as originally defined by Osterrieth. There was no statistically significant difference in performance for the quality of education for any of the ROCF test trials (p≥0.05 in all instances). Similarly, no significant difference is indicated for the Copy and Immediate Recall (IR) trial for sex indications, whilst the Delayed Recall (DR) trial shows statistically significant differences. Age effects appeared to have an influence on test performance on all ROCF test trials, as a significant difference was identified for all instances. Descriptively and statistically, the present local sample’s mean performance was compared to a demographically equivalent local study (de Kock’s study, which the present study is doing an extension on) and non-local normative studies. The results indicate the need for culturally-relevant South African psychological assessment measures. It also emphasises the importance of making a psychological measure more applicable and relevant to a specific context. Consideration of socio-cultural factors for norm purposes is strongly recommended by this study.
- Full Text:
- Date Issued: 2017
Performing mindful creativity
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225574 , vital:49236 , xlink:href="https://doi.org/10.5920/pam.2017.05"
- Description: This essay is grounded in the practical experience of three South African theatre practitioners who have all had some experience of mindfulness. It's based on interviews conducted with a performer (Andrew Buckland), a director (Janni Young), and a designer (Illka Louw). The aim of my conversations with these three was to explore ways in which mindfulness continues to enhance artistic practises, seeing our dialogues as a springboard to exploring intersections between creative practise and theories about mindfulness. To assist me in this process, I also interviewed Rob Nairn - co-founder of both the Mindfulness Association (UK) and Mindfulness Africa (RSA) - about key issues highlighting convergences between creativity and mindfulness. Some of the issues which are addressed include: the artist's relationship with fear, differing definitions of the value of conceptualisation, as well as whether or not the monkey mind (that is, the wandering mind) might hamper or help creativity.
- Full Text:
- Date Issued: 2017
- Authors: Krueger, Anton
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225574 , vital:49236 , xlink:href="https://doi.org/10.5920/pam.2017.05"
- Description: This essay is grounded in the practical experience of three South African theatre practitioners who have all had some experience of mindfulness. It's based on interviews conducted with a performer (Andrew Buckland), a director (Janni Young), and a designer (Illka Louw). The aim of my conversations with these three was to explore ways in which mindfulness continues to enhance artistic practises, seeing our dialogues as a springboard to exploring intersections between creative practise and theories about mindfulness. To assist me in this process, I also interviewed Rob Nairn - co-founder of both the Mindfulness Association (UK) and Mindfulness Africa (RSA) - about key issues highlighting convergences between creativity and mindfulness. Some of the issues which are addressed include: the artist's relationship with fear, differing definitions of the value of conceptualisation, as well as whether or not the monkey mind (that is, the wandering mind) might hamper or help creativity.
- Full Text:
- Date Issued: 2017
Personality and self-esteem as predictors of employability among final year students at a previously disadvantaged South African University
- Authors: Muzerengwa, Cedric
- Date: 2017
- Subjects: Unemployment -- Psychological aspects Personality and occupation Self-esteem in young adults
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10353/4594 , vital:28464
- Description: Orientation: The high unemployment level in South Africa has caused even graduates to be unemployed and yet they hold university degrees. This has increased pressure on the job seeking students to develop factors that influence employability, hence the study seeks to identify whether personality and self-esteem act as predictors of employability among final year university students. Research purpose: The objectives of this investigation were to examine whether personality, as is typically found in personality type research tool such as the, (Myers Briggs personality indicator) and self-esteem positively predict employability among final year university students. Secondly, to determine the personality types that significantly predict employability among final year university students. The last objective was to determine whether self-esteem significantly predicts employability among final year university students. Motivation for the study: This investigation is particularly important because it looks at the non-academic attributes that make job-seeking students able to attain a job and also sustain that job. The 21st century workplace is ever changing, and students are required to build proactive personalities that help them increase their employability level and stand a higher chance of getting employed. Research design, approach and method: A quantitative survey research design was used and a questionnaire was self-administered to a stratified simple random sample consisting of 238 Management and Commerce final year students at the university of Fort Hare. The study used quantitative approach and a positivism paradigm. To measure personality, TIPI scale was used and had 10 items. Employability was measured using the student self-perceived employability scale and self-esteem was measured using the Rosenberg self-esteem scale. Main findings: The results of this study showed a similarity with others obtained in prior studies. The results drawn from the statistical analysis of this study showed that there is a significant relationship between personality types such as perceiving, extraversion and feeling with employability among final year management and commerce students at the university of Fort Hare. However, the results showed that there is no positive relationship that exists between self-esteem and employability among final year job-seeking students. Practical implications: The research findings provided evidence that personality had a positive relationship with employability in an academic context. This makes it clear that student career exploration process can only be successful when special attention is given to developing individual’s human capital skills and proactive personalities. Institutions of higher learning should take advantage of some career experts in their countries and in their universities to provide students with employability lessons and guidelines. Contribution: The most important contribution of this study is that it helps to extend knowledge and understanding on the issues concerning the relationship between personality, self-esteem and employability in an academic setting. The research magnified the frame of information in the area personality in relation to employability in academic contexts. It makes available more literature that looks into these two variables (personality and self-esteem) in an African context.
- Full Text:
- Date Issued: 2017
- Authors: Muzerengwa, Cedric
- Date: 2017
- Subjects: Unemployment -- Psychological aspects Personality and occupation Self-esteem in young adults
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10353/4594 , vital:28464
- Description: Orientation: The high unemployment level in South Africa has caused even graduates to be unemployed and yet they hold university degrees. This has increased pressure on the job seeking students to develop factors that influence employability, hence the study seeks to identify whether personality and self-esteem act as predictors of employability among final year university students. Research purpose: The objectives of this investigation were to examine whether personality, as is typically found in personality type research tool such as the, (Myers Briggs personality indicator) and self-esteem positively predict employability among final year university students. Secondly, to determine the personality types that significantly predict employability among final year university students. The last objective was to determine whether self-esteem significantly predicts employability among final year university students. Motivation for the study: This investigation is particularly important because it looks at the non-academic attributes that make job-seeking students able to attain a job and also sustain that job. The 21st century workplace is ever changing, and students are required to build proactive personalities that help them increase their employability level and stand a higher chance of getting employed. Research design, approach and method: A quantitative survey research design was used and a questionnaire was self-administered to a stratified simple random sample consisting of 238 Management and Commerce final year students at the university of Fort Hare. The study used quantitative approach and a positivism paradigm. To measure personality, TIPI scale was used and had 10 items. Employability was measured using the student self-perceived employability scale and self-esteem was measured using the Rosenberg self-esteem scale. Main findings: The results of this study showed a similarity with others obtained in prior studies. The results drawn from the statistical analysis of this study showed that there is a significant relationship between personality types such as perceiving, extraversion and feeling with employability among final year management and commerce students at the university of Fort Hare. However, the results showed that there is no positive relationship that exists between self-esteem and employability among final year job-seeking students. Practical implications: The research findings provided evidence that personality had a positive relationship with employability in an academic context. This makes it clear that student career exploration process can only be successful when special attention is given to developing individual’s human capital skills and proactive personalities. Institutions of higher learning should take advantage of some career experts in their countries and in their universities to provide students with employability lessons and guidelines. Contribution: The most important contribution of this study is that it helps to extend knowledge and understanding on the issues concerning the relationship between personality, self-esteem and employability in an academic setting. The research magnified the frame of information in the area personality in relation to employability in academic contexts. It makes available more literature that looks into these two variables (personality and self-esteem) in an African context.
- Full Text:
- Date Issued: 2017
Perspectives of social media's influence on university students' social lives : a case study of the University of Fort Hare, Alice campus
- Mazaiwana, Tanyaradza Sandra
- Authors: Mazaiwana, Tanyaradza Sandra
- Date: 2017
- Subjects: University of Fort Hare Social media Universities and colleges
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/13128 , vital:39467
- Description: The main purpose of this study was to explore the perspectives of social media‘s influence on students‘ social life and the study made use of the University of Fort Hare Alice Campus as a case study. The internet and new media technology has brought about communication systems such as social media which has taken over the communication media world and is seen as an important socializing agent that students make use of. The study was therefore based on the premise that social media is enhancing the social interaction of people. It has become clear that most studies look at how social media enrich the life of students but little information is there on the kind of influence that it has on their social life. The study employed a quantitative approach to find out the effects of social media on social lives. The population was drawn from the four faculties at the University of Fort Hare, Alice campus and the sample size was 190. The data was collected using a standardized questionnaire and proportioned stratified random sampling was used to ensure a representative sample. The data was analysed using the Statistical Package for Social Sciences (SPSS) and descriptive statistics was used to analyse the demographical and general factors on the perceptions of students‘ social life. The perceptions of the respondents about social media and their social life was that it plays a great role in improving their social life as they are able to maintain relationships, they are always up to date with what is going on in their environment and it makes communication a lot more easier. In addition the results and discussion of this study confirmed that there is another dark side of social media which is hardly acknowledged by most scholars. Social media has a negative side towards students‘ social life which include isolation, depression, and distraction from reality, cyberbullying and low self- esteem. The study confirmed that students spent most of their time on social media and that their social life is affected as they have little or no time to socialise.
- Full Text:
- Date Issued: 2017
- Authors: Mazaiwana, Tanyaradza Sandra
- Date: 2017
- Subjects: University of Fort Hare Social media Universities and colleges
- Language: English
- Type: Thesis , Masters , MSoc
- Identifier: http://hdl.handle.net/10353/13128 , vital:39467
- Description: The main purpose of this study was to explore the perspectives of social media‘s influence on students‘ social life and the study made use of the University of Fort Hare Alice Campus as a case study. The internet and new media technology has brought about communication systems such as social media which has taken over the communication media world and is seen as an important socializing agent that students make use of. The study was therefore based on the premise that social media is enhancing the social interaction of people. It has become clear that most studies look at how social media enrich the life of students but little information is there on the kind of influence that it has on their social life. The study employed a quantitative approach to find out the effects of social media on social lives. The population was drawn from the four faculties at the University of Fort Hare, Alice campus and the sample size was 190. The data was collected using a standardized questionnaire and proportioned stratified random sampling was used to ensure a representative sample. The data was analysed using the Statistical Package for Social Sciences (SPSS) and descriptive statistics was used to analyse the demographical and general factors on the perceptions of students‘ social life. The perceptions of the respondents about social media and their social life was that it plays a great role in improving their social life as they are able to maintain relationships, they are always up to date with what is going on in their environment and it makes communication a lot more easier. In addition the results and discussion of this study confirmed that there is another dark side of social media which is hardly acknowledged by most scholars. Social media has a negative side towards students‘ social life which include isolation, depression, and distraction from reality, cyberbullying and low self- esteem. The study confirmed that students spent most of their time on social media and that their social life is affected as they have little or no time to socialise.
- Full Text:
- Date Issued: 2017
Perturbation–Response Scanning reveals key residues for Allosteric Control in Hsp70:
- Penkler, David L, Sensoy, Özge, Atilgan, Canan, Tastan Bishop, Özlem
- Authors: Penkler, David L , Sensoy, Özge , Atilgan, Canan , Tastan Bishop, Özlem
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148195 , vital:38718 , DOI: 10.1021/acs.jcim.6b00775
- Description: Hsp70 molecular chaperones play an important role in maintaining cellular homeostasis, and are implicated in a wide array of cellular processes, including protein recovery from aggregates, cross-membrane protein translocation, and protein biogenesis. Hsp70 consists of two domains, a nucleotide binding domain (NBD) and a substrate binding domain (SBD), each of which communicates via an allosteric mechanism such that the protein interconverts between two functional states, an ATP-bound open conformation and an ADP-bound closed conformation. The exact mechanism for interstate conversion is not as yet fully understood. However, the ligand-bound states of the NBD and SBD as well as interactions with cochaperones such as DnaJ and nucleotide exchange factor are thought to play crucial regulatory roles. In this study, we apply the perturbation–response scanning (PRS) method in combination with molecular dynamics simulations as a computational tool for the identification of allosteric hot residues in the large multidomain Hsp70 protein.
- Full Text:
- Date Issued: 2017
- Authors: Penkler, David L , Sensoy, Özge , Atilgan, Canan , Tastan Bishop, Özlem
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148195 , vital:38718 , DOI: 10.1021/acs.jcim.6b00775
- Description: Hsp70 molecular chaperones play an important role in maintaining cellular homeostasis, and are implicated in a wide array of cellular processes, including protein recovery from aggregates, cross-membrane protein translocation, and protein biogenesis. Hsp70 consists of two domains, a nucleotide binding domain (NBD) and a substrate binding domain (SBD), each of which communicates via an allosteric mechanism such that the protein interconverts between two functional states, an ATP-bound open conformation and an ADP-bound closed conformation. The exact mechanism for interstate conversion is not as yet fully understood. However, the ligand-bound states of the NBD and SBD as well as interactions with cochaperones such as DnaJ and nucleotide exchange factor are thought to play crucial regulatory roles. In this study, we apply the perturbation–response scanning (PRS) method in combination with molecular dynamics simulations as a computational tool for the identification of allosteric hot residues in the large multidomain Hsp70 protein.
- Full Text:
- Date Issued: 2017
Pessimistic assessment of white shark population status in South Africa: comment on Andreotti et al.(2016)
- Irion, Dylan T, Noble, Leslie R, Kock, Alison A, Gennari, Enrico, Dicken, Matthew L, Hewitt, Adrian M, Towner, Alison V, Booth, Anthony J, Smale, Malcolm J, Cliff, Geremy
- Authors: Irion, Dylan T , Noble, Leslie R , Kock, Alison A , Gennari, Enrico , Dicken, Matthew L , Hewitt, Adrian M , Towner, Alison V , Booth, Anthony J , Smale, Malcolm J , Cliff, Geremy
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:35799 , https://doi.10.3354/meps12283
- Description: Andreotti et al. (2016; Mar Ecol Prog Ser 552:241−253) estimate an abundance (N) of 438 white sharks Carcharodon carcharias and a contemporary effective population size (CNe) of 333 individuals along the South African coast. N was estimated by using a mark-recapture analysis of photographic identification records from a single aggregation site (Gansbaai). CNe was calculated based on the levels of pairwise linkage disequilibrium of genetic material collected from 4 aggregation sites across approximately 965 km of South African coastline. However, due to the complex stock structure of white sharks and the model assumptions made by Andreotti et al. (2016), the conclusions drawn cannot be supported by their methods and data.
- Full Text:
- Date Issued: 2017
- Authors: Irion, Dylan T , Noble, Leslie R , Kock, Alison A , Gennari, Enrico , Dicken, Matthew L , Hewitt, Adrian M , Towner, Alison V , Booth, Anthony J , Smale, Malcolm J , Cliff, Geremy
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/${Handle} , vital:35799 , https://doi.10.3354/meps12283
- Description: Andreotti et al. (2016; Mar Ecol Prog Ser 552:241−253) estimate an abundance (N) of 438 white sharks Carcharodon carcharias and a contemporary effective population size (CNe) of 333 individuals along the South African coast. N was estimated by using a mark-recapture analysis of photographic identification records from a single aggregation site (Gansbaai). CNe was calculated based on the levels of pairwise linkage disequilibrium of genetic material collected from 4 aggregation sites across approximately 965 km of South African coastline. However, due to the complex stock structure of white sharks and the model assumptions made by Andreotti et al. (2016), the conclusions drawn cannot be supported by their methods and data.
- Full Text:
- Date Issued: 2017
Pharmacological evaluation of phragmanthera capitata (sprengel) balle, loranthaceae :a parasiticmistletoe growing on rubber trees
- Ohikhena, Franklin Uangbaoje
- Authors: Ohikhena, Franklin Uangbaoje
- Date: 2017
- Subjects: Hevea Hevea -- Diseases and pests Rubber
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8899 , vital:33937
- Description: Rubber tree (Hevea brasiliensis Muell.) is the world’s major source of natural rubber and a major non-oil, agricultural export commodity in the producing countries in Africa. However, it is highly susceptible to specific mistletoes of the Loranthaceae family. Phragmanthera capitate (Sprengel) Balle is the major mistletoe parasitizing the rubber tree plantations in Africa and hence, alongside with other mistletoes, has attracted indiscriminate destruction from plantation owners. Indiscriminate destruction of plants could be as a result of ignorance of the importance or benefit(s) of the plants and this could lead to their extinction if not checked. Hence, there is the need for scientific documentation of plants and their uses because, from the pharmacological perception, the destruction of a plant could result in the permanent loss of a potential drug. Therefore, this study was aimed at documenting and evaluating the pharmacological potentials of P. capitata collected from rubber tree. Fresh leaves were gently rinsed with water and dried. Dried leaves were pulverised and kept at 4oC when not in use. Pulverised leaves were extracted with acetone, methanol, ethanol and water and concentrated to give the respective solvent crude extracts used in most of the assays. From the extraction, Methanol had the highest yield of 21.5percent, water had 10.8percent and acetone was 6.87percent while ethanol had the lowest yield of 4.3percent. Standard spectrophotometry assays on the extracts were used to quantify some major phytochemicals of pharmacological interest and also to determine the antioxidant potentials of the sample. The result revealed high amounts of phenols (175.53 ± 0.32 mg GAE/g to 218.62 ± 3.38 mg GAE/g), flavonoids (197.06 ± 3.80 mg QE/mg to 679.82 ± 6.26 mg QE/g) and proanthocyanidins (128.83 ± 1.69 mg CE/g to 645.68 ± 6.35 mg CE/g) with the acetone extract having the highest amount of the phytochemicals while the aqueous extract had the least. The results of the antioxidant assays revealed that the sample had high radical scavenging potentials with comparable inhibitory concentrations to standard antioxidant drugs. The proximate and mineral analysis on the pulverised sample showed that it is rich in carbohydrate with a composition of 57.73 ± 0.33 g/100 g. Protein, fat and fibre compositions were 12.50 ± 0.50 g/100 g, 3.34 ± 0.18 g/100 g and 11.66 ± 0.54 g/100g. The total energy composition was 310.97 ± 2.30 Kcal/100 g. The mineral composition revealed high potassium level of 1047.83 ± 34 mg/100g. Calcium (6.22.58 ± 0.01 mg/100g), magnesium (361.15 ± 0.01 mg/100 g) and phosphorous (115.40 ± 0.01 mg/100 g) were also present in appreciable amounts. The toxicity of the four extracts was assayed using brine shrimp. The LC50 in all the solvent extracts was greater than 1 mg/mL which according to Meyer’s index and other indexes signify “no toxicity” for crude plant extracts. Antimicrobial activity of the extracts was done using the minimal inhibitory concentration (MIC) assay against 10 bacteria (Enterococcus faecalis, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Streptococcus pyogenes, Vibrio cholera, Klebsiella pneumonia, Pseudomonas aeruginosa, Salmonella typhi and Escherichia coli) and 4 fungi (Trichophyton mucoides, Trichophyton tonsurans, Candida albicans and Aspergillus niger) of human pathogenic strains. The MIC of the antibacterial assay ranged from 1.25 mg/mL to 5 mg/mL for the organic extracts while no activity was observed in the aqueous extract at the highest concentration tested. However, the aqueous extract had a great inhibitory activity on all four of the tested fungi with a MIC of ≤ 0.3125 mg/mL to 1.25 mg/mL while only two fungi (Trichophyton Tonsurans and Aspergillus niger) were susceptible to the organic extracts. The MIC of the TB causative pathogen, Mycobacterium tuberculosis (H37Rv) strain ranged from 25 μg/mL (acetone and aqueous extracts) to 50 μg/mL in the ethanol extract while it was > 50 μg/mL (highest concentration tested) in the methanol extract. This study revealed that the sample has the potential in phytotherapy against oxidative stresses (inflammations) caused by free radicals. It could also be a useful herb in combating diseases caused by pathogenic organisms. The high anti-Mycobacterium tuberculosis activity observed in this study suggests it could be a plant with high promise in the fight against tuberculosis. The toxicity evaluation signifies it is safe for further plant-based pharmaceutical explorations. This study also validated some reported ethnopharmacological uses of this plant and call for its protection from indiscriminate destruction in rubber plantations and other crop gardens/plantations in the world.
- Full Text:
- Date Issued: 2017
- Authors: Ohikhena, Franklin Uangbaoje
- Date: 2017
- Subjects: Hevea Hevea -- Diseases and pests Rubber
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8899 , vital:33937
- Description: Rubber tree (Hevea brasiliensis Muell.) is the world’s major source of natural rubber and a major non-oil, agricultural export commodity in the producing countries in Africa. However, it is highly susceptible to specific mistletoes of the Loranthaceae family. Phragmanthera capitate (Sprengel) Balle is the major mistletoe parasitizing the rubber tree plantations in Africa and hence, alongside with other mistletoes, has attracted indiscriminate destruction from plantation owners. Indiscriminate destruction of plants could be as a result of ignorance of the importance or benefit(s) of the plants and this could lead to their extinction if not checked. Hence, there is the need for scientific documentation of plants and their uses because, from the pharmacological perception, the destruction of a plant could result in the permanent loss of a potential drug. Therefore, this study was aimed at documenting and evaluating the pharmacological potentials of P. capitata collected from rubber tree. Fresh leaves were gently rinsed with water and dried. Dried leaves were pulverised and kept at 4oC when not in use. Pulverised leaves were extracted with acetone, methanol, ethanol and water and concentrated to give the respective solvent crude extracts used in most of the assays. From the extraction, Methanol had the highest yield of 21.5percent, water had 10.8percent and acetone was 6.87percent while ethanol had the lowest yield of 4.3percent. Standard spectrophotometry assays on the extracts were used to quantify some major phytochemicals of pharmacological interest and also to determine the antioxidant potentials of the sample. The result revealed high amounts of phenols (175.53 ± 0.32 mg GAE/g to 218.62 ± 3.38 mg GAE/g), flavonoids (197.06 ± 3.80 mg QE/mg to 679.82 ± 6.26 mg QE/g) and proanthocyanidins (128.83 ± 1.69 mg CE/g to 645.68 ± 6.35 mg CE/g) with the acetone extract having the highest amount of the phytochemicals while the aqueous extract had the least. The results of the antioxidant assays revealed that the sample had high radical scavenging potentials with comparable inhibitory concentrations to standard antioxidant drugs. The proximate and mineral analysis on the pulverised sample showed that it is rich in carbohydrate with a composition of 57.73 ± 0.33 g/100 g. Protein, fat and fibre compositions were 12.50 ± 0.50 g/100 g, 3.34 ± 0.18 g/100 g and 11.66 ± 0.54 g/100g. The total energy composition was 310.97 ± 2.30 Kcal/100 g. The mineral composition revealed high potassium level of 1047.83 ± 34 mg/100g. Calcium (6.22.58 ± 0.01 mg/100g), magnesium (361.15 ± 0.01 mg/100 g) and phosphorous (115.40 ± 0.01 mg/100 g) were also present in appreciable amounts. The toxicity of the four extracts was assayed using brine shrimp. The LC50 in all the solvent extracts was greater than 1 mg/mL which according to Meyer’s index and other indexes signify “no toxicity” for crude plant extracts. Antimicrobial activity of the extracts was done using the minimal inhibitory concentration (MIC) assay against 10 bacteria (Enterococcus faecalis, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Streptococcus pyogenes, Vibrio cholera, Klebsiella pneumonia, Pseudomonas aeruginosa, Salmonella typhi and Escherichia coli) and 4 fungi (Trichophyton mucoides, Trichophyton tonsurans, Candida albicans and Aspergillus niger) of human pathogenic strains. The MIC of the antibacterial assay ranged from 1.25 mg/mL to 5 mg/mL for the organic extracts while no activity was observed in the aqueous extract at the highest concentration tested. However, the aqueous extract had a great inhibitory activity on all four of the tested fungi with a MIC of ≤ 0.3125 mg/mL to 1.25 mg/mL while only two fungi (Trichophyton Tonsurans and Aspergillus niger) were susceptible to the organic extracts. The MIC of the TB causative pathogen, Mycobacterium tuberculosis (H37Rv) strain ranged from 25 μg/mL (acetone and aqueous extracts) to 50 μg/mL in the ethanol extract while it was > 50 μg/mL (highest concentration tested) in the methanol extract. This study revealed that the sample has the potential in phytotherapy against oxidative stresses (inflammations) caused by free radicals. It could also be a useful herb in combating diseases caused by pathogenic organisms. The high anti-Mycobacterium tuberculosis activity observed in this study suggests it could be a plant with high promise in the fight against tuberculosis. The toxicity evaluation signifies it is safe for further plant-based pharmaceutical explorations. This study also validated some reported ethnopharmacological uses of this plant and call for its protection from indiscriminate destruction in rubber plantations and other crop gardens/plantations in the world.
- Full Text:
- Date Issued: 2017
Pharmacological investigations of Kedrostis africana (L.) Cogn. and Vernonia mespilifolia Less. used in folk medicine in the Eastern Cape, South Africa
- Authors: Unuofin, Jeremiah Oshiomame
- Date: 2017
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9231 , vital:34307
- Description: The prevalence of obesity and its co-morbidity is increasing in South Africa. High calorie diet, sedentary lifestyle and the cultural belief that being fat or obese signifies beauty, wellness and wealth are major causative factors. This study was undertaken to scientifically validate two major medicinal plants used traditionally in the Raymond Mhlaba Municipality for the mespilifolia Less. were used singly and in combination. According to ethnobotanical studies,these two plants are regarded as wild plants and are only used for medicinal purposes. There has been a dearth of scientific reports on the two plants and to the best of our knowledge, this study is the first to investigate the nutritional, antioxidant, antimicrobial, safety and anti-obesity potentials of the two plants and their combination. This study revealed that both plants are rich in nutrients. K. africana had greater ash (16.28 percent), crude fat (1.12 percent), Ca (2505 mg/100g), Mg (485 mg/100g) and Fe (89.95 mg/100g) while V. mespilifolia showed higher crude fibre (29.24 percent), crude protein (10.75 percent), P (400 mg/100g), Na (570 mg/100g), Cu (1.55 mg/100g) and Mn (4.70 mg/100g). K. africana and V. mespilifolia both contributed 223.37 Kcal/kg and 237.37 Kcal/kg of energy respectively. The polyphenolic evaluation of the acetone, aqueous and ethanol extracts of the plants revealed that the acetone extract of the combination of both plants had higher total phenol (144.59 mgGAE/g) and flavonoid (803.93 mgQE/g) contents, the ethanol extract of the combined plant also had the highest tannin contents (1.25 mgTAE/g), while the acetone extracts of K. Africana had the highest proanthocyanidin content (585 mgCE/g). The antioxidant assays revealed that the ethanol extract for V. mespilifolia had higher scavenging potentials of ABTS, DPPH and vinitric oxide radicals while the aqueous extract of the combination of both had higher scavenging potential for hydrogen peroxide radicals. Evaluation of antimicrobial potential of the extracts using the minimial inhibitory concentration (MIC) assay against 6 bacteria (Actinomyces odontolyticus, Lactobacillus sakei, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa and Bacteriodes thetaiotomicron) and 4 fungi (Candida albicans, Microsporium gypsum, Penicillium chrysogenum and Trichophyton tonsurans) revealed that the plants possess antimicrobial activity. The MIC of the extracts against the tested bacterial strains ranged from 2.5 mg/mL to 5 mg/mL acetone and ethanol extracts of V. mespilifolia and the combined plants as well as the ethanol extracts of K. africana. However, no activity was observed for the acetone extract of K. africana and aqueous extracts of V. mespilifolia and the combination of both plants. Only three fungal strains (Candida albicans, Microsporium gypsum and Penicillium chrysogenum) were susceptible to the organic extracts with an MIC 0.3125 mg/mL to 5 mg/mL while the aqueous extracts showed no activity against all the fungal strains. None of the plant extracts showed any activity against Trichophyton tonsurans. The brine shrimp toxicity test revealed that all the three extracts of V. mespilifolia, aqueous and ethanol extracts of K. africana and aqueous and acetone extracts of the combination of both plants were toxic in relative to Meyer’s index and other indices of toxicity. The cytotoxic effect of the aqueous and ethanol extracts of V. mespilifolia, K. africana and their combination were also evaluated using HeLa cells. From this study, all the extracts tested had IC50 values were greater than 20 μg/mL which connotes that they are not toxic. According to the American National Cancer Institute, crude plant extracts are considered cytotoxic in an in vitro assay when concentrations 20 μg/mL and below produce 50% inhibition of tumor cells, after an exposure time of 48 hours. In vivo acute evaluation of single oral administration of 2000 and 5000/kg body weight did not produce mortality or significant behavioral changes during 14 days observation. In addition, the sub-acute administration of the aqueous extract at 200, 400 and 600 mg/kg/bwt/ day over a period of 28 days revealed no mortality or morbidity. The weekly body and organ weight of the rats were not significantly different from those of the controls and extract treated rats. The aqueous extracts at all doses did not show any significant (p > 0.05) effect on biomarkers of liver and renal damage. Haematological evaluation revealed that oral administration of aqueous extracts of K. africana, V. mespilifolia and the combination of both plants did not induce anaemia or leucocytosis in the animals. Furthermore, histopathological evaluation of the internal organs revealed no detectable inflammation at the the doses administered over a period of 28 days. These results demonstrated that the aqueous extracts of K. africana, V. mespilifolia and the combination of both plants was potentially safe for consumption orally even in chronic administration. Enzyme based in-vitro antiobesity evaluation of the aqueous and ethanolic extracts of K. africana, V. mespilifolia and their combination revealed that the ethanol extracts of both plants and their combination exhibited moderate inhibitory activities against α-amylase, α- glucosidase and pancreatic lipase. However, the standards used for the various inhibition assays exhibited much higher inhibitory actions when compared to any of the extracts. This suggests that the mechanism by which these two plants and their combination exert anti-obesity effects are probably not by inhibition of key enzymes of carbohydrate and fat metabolism.
- Full Text:
- Date Issued: 2017
- Authors: Unuofin, Jeremiah Oshiomame
- Date: 2017
- Subjects: Medicinal plants -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9231 , vital:34307
- Description: The prevalence of obesity and its co-morbidity is increasing in South Africa. High calorie diet, sedentary lifestyle and the cultural belief that being fat or obese signifies beauty, wellness and wealth are major causative factors. This study was undertaken to scientifically validate two major medicinal plants used traditionally in the Raymond Mhlaba Municipality for the mespilifolia Less. were used singly and in combination. According to ethnobotanical studies,these two plants are regarded as wild plants and are only used for medicinal purposes. There has been a dearth of scientific reports on the two plants and to the best of our knowledge, this study is the first to investigate the nutritional, antioxidant, antimicrobial, safety and anti-obesity potentials of the two plants and their combination. This study revealed that both plants are rich in nutrients. K. africana had greater ash (16.28 percent), crude fat (1.12 percent), Ca (2505 mg/100g), Mg (485 mg/100g) and Fe (89.95 mg/100g) while V. mespilifolia showed higher crude fibre (29.24 percent), crude protein (10.75 percent), P (400 mg/100g), Na (570 mg/100g), Cu (1.55 mg/100g) and Mn (4.70 mg/100g). K. africana and V. mespilifolia both contributed 223.37 Kcal/kg and 237.37 Kcal/kg of energy respectively. The polyphenolic evaluation of the acetone, aqueous and ethanol extracts of the plants revealed that the acetone extract of the combination of both plants had higher total phenol (144.59 mgGAE/g) and flavonoid (803.93 mgQE/g) contents, the ethanol extract of the combined plant also had the highest tannin contents (1.25 mgTAE/g), while the acetone extracts of K. Africana had the highest proanthocyanidin content (585 mgCE/g). The antioxidant assays revealed that the ethanol extract for V. mespilifolia had higher scavenging potentials of ABTS, DPPH and vinitric oxide radicals while the aqueous extract of the combination of both had higher scavenging potential for hydrogen peroxide radicals. Evaluation of antimicrobial potential of the extracts using the minimial inhibitory concentration (MIC) assay against 6 bacteria (Actinomyces odontolyticus, Lactobacillus sakei, Staphylococcus aureus, Enterobacter cloacae, Pseudomonas aeruginosa and Bacteriodes thetaiotomicron) and 4 fungi (Candida albicans, Microsporium gypsum, Penicillium chrysogenum and Trichophyton tonsurans) revealed that the plants possess antimicrobial activity. The MIC of the extracts against the tested bacterial strains ranged from 2.5 mg/mL to 5 mg/mL acetone and ethanol extracts of V. mespilifolia and the combined plants as well as the ethanol extracts of K. africana. However, no activity was observed for the acetone extract of K. africana and aqueous extracts of V. mespilifolia and the combination of both plants. Only three fungal strains (Candida albicans, Microsporium gypsum and Penicillium chrysogenum) were susceptible to the organic extracts with an MIC 0.3125 mg/mL to 5 mg/mL while the aqueous extracts showed no activity against all the fungal strains. None of the plant extracts showed any activity against Trichophyton tonsurans. The brine shrimp toxicity test revealed that all the three extracts of V. mespilifolia, aqueous and ethanol extracts of K. africana and aqueous and acetone extracts of the combination of both plants were toxic in relative to Meyer’s index and other indices of toxicity. The cytotoxic effect of the aqueous and ethanol extracts of V. mespilifolia, K. africana and their combination were also evaluated using HeLa cells. From this study, all the extracts tested had IC50 values were greater than 20 μg/mL which connotes that they are not toxic. According to the American National Cancer Institute, crude plant extracts are considered cytotoxic in an in vitro assay when concentrations 20 μg/mL and below produce 50% inhibition of tumor cells, after an exposure time of 48 hours. In vivo acute evaluation of single oral administration of 2000 and 5000/kg body weight did not produce mortality or significant behavioral changes during 14 days observation. In addition, the sub-acute administration of the aqueous extract at 200, 400 and 600 mg/kg/bwt/ day over a period of 28 days revealed no mortality or morbidity. The weekly body and organ weight of the rats were not significantly different from those of the controls and extract treated rats. The aqueous extracts at all doses did not show any significant (p > 0.05) effect on biomarkers of liver and renal damage. Haematological evaluation revealed that oral administration of aqueous extracts of K. africana, V. mespilifolia and the combination of both plants did not induce anaemia or leucocytosis in the animals. Furthermore, histopathological evaluation of the internal organs revealed no detectable inflammation at the the doses administered over a period of 28 days. These results demonstrated that the aqueous extracts of K. africana, V. mespilifolia and the combination of both plants was potentially safe for consumption orally even in chronic administration. Enzyme based in-vitro antiobesity evaluation of the aqueous and ethanolic extracts of K. africana, V. mespilifolia and their combination revealed that the ethanol extracts of both plants and their combination exhibited moderate inhibitory activities against α-amylase, α- glucosidase and pancreatic lipase. However, the standards used for the various inhibition assays exhibited much higher inhibitory actions when compared to any of the extracts. This suggests that the mechanism by which these two plants and their combination exert anti-obesity effects are probably not by inhibition of key enzymes of carbohydrate and fat metabolism.
- Full Text:
- Date Issued: 2017
Phenomenology: preconceptions and experiences of non-chemists at Rhodes University using milk paint
- Authors: Kelly, Kelvin Leigh
- Date: 2017
- Subjects: Phenomenology , Art and science , Casein , Paint , Chemistry -- Study and teaching , Science -- Study and teaching -- Philosophy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37942 , vital:24711
- Description: There exists an ever-increasing crisis in science education where students experience disinterest because of an inability to grasp true understanding of scientific subjects, and therefore there should be a call to increase the research of phenomenology in combination with science education. A rebalance and paradigm shift in the focus of the modes of teaching could result in a great improvement in the learning, comprehension, and intellectual self-confidence of students interested in the sciences. To study this, three research questions were established: How is chemistry perceived by non-chemists; what is the experience of the participants’ during the chemistry practical in a laboratory and; do the participants’ perspectives about chemistry change during the experience. The performed study consisted of a chemistry practical, two art works and, in some cases, an interview. Nine participants were asked to create the art under specific instructions of points of focus, namely their preconceptions prior to the practical (Artwork 1) and their lived experience during the practical (Artwork 2). Participants’ artworks were examined using methods of visual semiotics and classical art analysis techniques, looking at line, shape, and colour choice. The iterative analysis of the interviews from participants 1, 2, 7, and 9 coded with ATLAS.ti 7 software, led to the emergence of themes that constitute the core of the participants’ experience. This phenomenological study presents a path to engage the non-chemist with processes taking place in the laboratory by using ‘Kitchen Chemistry’ and illustrates how a phenomenological engagement with chemistry can make the subject more applicable to the general population of non-chemists.
- Full Text:
- Date Issued: 2017
- Authors: Kelly, Kelvin Leigh
- Date: 2017
- Subjects: Phenomenology , Art and science , Casein , Paint , Chemistry -- Study and teaching , Science -- Study and teaching -- Philosophy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/37942 , vital:24711
- Description: There exists an ever-increasing crisis in science education where students experience disinterest because of an inability to grasp true understanding of scientific subjects, and therefore there should be a call to increase the research of phenomenology in combination with science education. A rebalance and paradigm shift in the focus of the modes of teaching could result in a great improvement in the learning, comprehension, and intellectual self-confidence of students interested in the sciences. To study this, three research questions were established: How is chemistry perceived by non-chemists; what is the experience of the participants’ during the chemistry practical in a laboratory and; do the participants’ perspectives about chemistry change during the experience. The performed study consisted of a chemistry practical, two art works and, in some cases, an interview. Nine participants were asked to create the art under specific instructions of points of focus, namely their preconceptions prior to the practical (Artwork 1) and their lived experience during the practical (Artwork 2). Participants’ artworks were examined using methods of visual semiotics and classical art analysis techniques, looking at line, shape, and colour choice. The iterative analysis of the interviews from participants 1, 2, 7, and 9 coded with ATLAS.ti 7 software, led to the emergence of themes that constitute the core of the participants’ experience. This phenomenological study presents a path to engage the non-chemist with processes taking place in the laboratory by using ‘Kitchen Chemistry’ and illustrates how a phenomenological engagement with chemistry can make the subject more applicable to the general population of non-chemists.
- Full Text:
- Date Issued: 2017
Photolytic changes in the morphology of porphyrin-phthalocyanine nanostructures (P-PcNs) in the presence of platinum and gold salts
- George, Reama C, D'Souza, Sarah, Durmus, Mahmut, Nyokong, Tebello
- Authors: George, Reama C , D'Souza, Sarah , Durmus, Mahmut , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190416 , vital:44992 , xlink:href="https://doi.org/10.1080/24701556.2017.1284085"
- Description: Porphyrin-phthalocyanine nanostructures (P-PcNs) have been fabricated by electrostatic self-assembly of two oppositely charged molecules. The negatively charged molecule, meso-tetra-(4-phenylsulphonate)porphyrin (HT) and the positively charged species; {1,(4)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] chloro gallium(III)} sulphate, {2,(3)-tetrakis-[(N-methyl{(2-mercaptopyridine) phthalocyaninato} hydroxy manganese(III)} sulphate, {1,(4)-tetrakis-[(N-methyl-(3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, {2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese(III)} sulphate, {2,(3)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] choro gallium(III)} sulphate, {2,3-octakis-[(N-methy-3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, and {2,(3)-tetrakis-[(N-methyl (3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate. Transmission electron microscopic (TEM) images showed that the formed nanostructures ranged from nanosheets to nanorods and nanotubes. The UV-Vis spectra confirmed that the molecules formed J-aggregates. The P-PcNs were exposed to incandescence light in the presence of platinum and gold salts. It was observed that the presence of platinum salts resulted in the destruction of the P-PcNs with possible formation of a Pt-Pc complex. While with the gold salt, the structures of P-PcNs were not only retained but were also enhanced to longer nanorods and nanofibers with the formation of gold nanoparticles.
- Full Text:
- Date Issued: 2017
- Authors: George, Reama C , D'Souza, Sarah , Durmus, Mahmut , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190416 , vital:44992 , xlink:href="https://doi.org/10.1080/24701556.2017.1284085"
- Description: Porphyrin-phthalocyanine nanostructures (P-PcNs) have been fabricated by electrostatic self-assembly of two oppositely charged molecules. The negatively charged molecule, meso-tetra-(4-phenylsulphonate)porphyrin (HT) and the positively charged species; {1,(4)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] chloro gallium(III)} sulphate, {2,(3)-tetrakis-[(N-methyl{(2-mercaptopyridine) phthalocyaninato} hydroxy manganese(III)} sulphate, {1,(4)-tetrakis-[(N-methyl-(3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, {2,3-octakis-{[(N-methyl-2-mercaptopyridine) phthalocyaninato] acetato manganese(III)} sulphate, {2,(3)-tetrakis-[(N-methyl(3-pyridyloxy) phthlocyaninato] choro gallium(III)} sulphate, {2,3-octakis-[(N-methy-3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate, and {2,(3)-tetrakis-[(N-methyl (3-pyridyloxy) phthalocyaninato] chloro indium(III)} sulphate. Transmission electron microscopic (TEM) images showed that the formed nanostructures ranged from nanosheets to nanorods and nanotubes. The UV-Vis spectra confirmed that the molecules formed J-aggregates. The P-PcNs were exposed to incandescence light in the presence of platinum and gold salts. It was observed that the presence of platinum salts resulted in the destruction of the P-PcNs with possible formation of a Pt-Pc complex. While with the gold salt, the structures of P-PcNs were not only retained but were also enhanced to longer nanorods and nanofibers with the formation of gold nanoparticles.
- Full Text:
- Date Issued: 2017
Photophysical and nonlinear optical study of benzothiazole substituted phthalocyanines in solution and thin films
- Nwaji, Njemuwa, Bankole, Owolabi M, Britton, Jonathan, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Bankole, Owolabi M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233088 , vital:50055 , xlink:href="https://doi.org/10.1142/S1088424617500079"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of zinc and gallium phthalocyanine complexes: tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato]zinc(II) (3), tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6), were investigated both in solution and when embedded in polystyrene thin films using 532 nm laser excitation at 10 ns pulses. It was also observed that complexes that have higher triplet state absorption also possessed enhanced nonlinear and optical limiting behavior. Superior optical performance was observed when the complexes were embedded in thin films compared to when they are in solution. Complex 6 in thin films gave the highest imaginary third-order susceptibility (Imm[X(3)(3)]) and hyperpolarizability (γ)γ) at 4.61 × 10-7-7 esu and 3.44 × 10-26-26 esu, respectively, with a low Ilimlim value of 0.06 J.cm-2.
- Full Text:
- Date Issued: 2017
- Authors: Nwaji, Njemuwa , Bankole, Owolabi M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233088 , vital:50055 , xlink:href="https://doi.org/10.1142/S1088424617500079"
- Description: In this study, the photophysical, nonlinear absorption and nonlinear optical limiting properties of zinc and gallium phthalocyanine complexes: tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato]zinc(II) (3), tetrakis[(benzo[d]thiazol-2-yl phenoxy)phthalocyaninato] gallium(III) chloride (4), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] zinc(II) (5), tetrakis[(benzo[d]thiazol-2-ylthio)phthalocyaninato] gallium(III) chloride (6), were investigated both in solution and when embedded in polystyrene thin films using 532 nm laser excitation at 10 ns pulses. It was also observed that complexes that have higher triplet state absorption also possessed enhanced nonlinear and optical limiting behavior. Superior optical performance was observed when the complexes were embedded in thin films compared to when they are in solution. Complex 6 in thin films gave the highest imaginary third-order susceptibility (Imm[X(3)(3)]) and hyperpolarizability (γ)γ) at 4.61 × 10-7-7 esu and 3.44 × 10-26-26 esu, respectively, with a low Ilimlim value of 0.06 J.cm-2.
- Full Text:
- Date Issued: 2017
Photophysical and optical limiting properties of a novel distyryl-BODIPY with fused crown ether moieties
- May, Aviwe K, Stone, Justin, Ngoy, Bokolombe P, Mack, John, Nyokong, Tebello, Kimura, Mutsumi, Kobayashi, Nagao
- Authors: May, Aviwe K , Stone, Justin , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello , Kimura, Mutsumi , Kobayashi, Nagao
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239621 , vital:50749 , xlink:href="https://doi.org/10.1142/S1088424617500869"
- Description: The synthesis and characterization of a crown-ether-substituted 3,5-distyrylBODIPY dye with a 4-dimethylaminophenyl group at the meso-position is reported. The optical limiting properties were investigated at 532 nm, and the dye was found to have enhanced reverse saturable absorption responses during z-scan measurements. Theoretical calculations suggest that this may be due to the large dipole moment that is introduced by the benzo-fused crown ether and 4-dimethylaminophenyl substituents.
- Full Text:
- Date Issued: 2017
- Authors: May, Aviwe K , Stone, Justin , Ngoy, Bokolombe P , Mack, John , Nyokong, Tebello , Kimura, Mutsumi , Kobayashi, Nagao
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/239621 , vital:50749 , xlink:href="https://doi.org/10.1142/S1088424617500869"
- Description: The synthesis and characterization of a crown-ether-substituted 3,5-distyrylBODIPY dye with a 4-dimethylaminophenyl group at the meso-position is reported. The optical limiting properties were investigated at 532 nm, and the dye was found to have enhanced reverse saturable absorption responses during z-scan measurements. Theoretical calculations suggest that this may be due to the large dipole moment that is introduced by the benzo-fused crown ether and 4-dimethylaminophenyl substituents.
- Full Text:
- Date Issued: 2017
Photophysical behavior and photodynamic therapy activity of conjugates of zinc monocarboxyphenoxy phthalocyanine with human serum albumin and chitosan
- Oluwole, David O, Prinsloo, Earl, Nyokong, Tebello
- Authors: Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188497 , vital:44759 , xlink:href="https://doi.org/10.1016/j.saa.2016.09.032"
- Description: Zincmonocarboxyphenoxy phthalocyanine (ZnMCPPc) was linked to human serum albumin (HSA) and chitosan via amide bond formation. The photophysical behavior and photodynamic therapy (PDT) activity (against human breast adenocarcinoma cell line (MCF-7 cells) of ZnMCPPc alone and its conjugates were investigated. The conjugates showed improved fluorescence, triplet and singlet oxygen quantum yields when compared to ZnMCPPc alone. The in vitro dark cytotoxicity and PDT studies were carried out at a dose of 3.6 μg/mL to 57.1 μg/mL. The in vitro dark cytotoxicity studies of ZnMCPPc showed cell viability more than 50% at 28.6 μg/mL and 57.1 μg/mL, while the conjugates showed > 50% in all their tested concentrations (3.6 to 57.1) μg/mL. Thus, conjugation of ZnMCPPc to HSA and chitosan improves its dark cytotoxicity, an important criteria for molecules meant for photodynamic therapy. Complex 1 showed the most efficacious PDT activity with cell viability more than 50% at concentration range of (14.3 to 57.1) μg/mL in comparison to the conjugates which only showed more than 50% cell viability at 28.6 μg/mL and 57.1 μg/mL for 1-HSA and 57.1 μg/mL for 1-Chitosan.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Prinsloo, Earl , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188497 , vital:44759 , xlink:href="https://doi.org/10.1016/j.saa.2016.09.032"
- Description: Zincmonocarboxyphenoxy phthalocyanine (ZnMCPPc) was linked to human serum albumin (HSA) and chitosan via amide bond formation. The photophysical behavior and photodynamic therapy (PDT) activity (against human breast adenocarcinoma cell line (MCF-7 cells) of ZnMCPPc alone and its conjugates were investigated. The conjugates showed improved fluorescence, triplet and singlet oxygen quantum yields when compared to ZnMCPPc alone. The in vitro dark cytotoxicity and PDT studies were carried out at a dose of 3.6 μg/mL to 57.1 μg/mL. The in vitro dark cytotoxicity studies of ZnMCPPc showed cell viability more than 50% at 28.6 μg/mL and 57.1 μg/mL, while the conjugates showed > 50% in all their tested concentrations (3.6 to 57.1) μg/mL. Thus, conjugation of ZnMCPPc to HSA and chitosan improves its dark cytotoxicity, an important criteria for molecules meant for photodynamic therapy. Complex 1 showed the most efficacious PDT activity with cell viability more than 50% at concentration range of (14.3 to 57.1) μg/mL in comparison to the conjugates which only showed more than 50% cell viability at 28.6 μg/mL and 57.1 μg/mL for 1-HSA and 57.1 μg/mL for 1-Chitosan.
- Full Text:
- Date Issued: 2017
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
Photophysical properties of GaCl 5, 10, 15, 20-tetra (1-pyrenyl) porphyrinato incorporated into Pluronic F127 micelle
- Managa, Muthumuni, Britton, Jonathan, Amuhaya, Edith K, Nyokong, Tebello
- Authors: Managa, Muthumuni , Britton, Jonathan , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233101 , vital:50056 , xlink:href="https://doi.org/10.1016/j.jlumin.2016.12.043"
- Description: GaCl 5,10,15,20-Tetra(1-pyrenyl)porphyrin (GaClTPyP) was successfully synthesised and encapsulated into Pluronic F127. The unmetallated 5,10,15,20-tetra(1-pyrenyl)porphyrin (H2TPyP) precursor was also encapsulated into Pluronic F127. The fluorescence quantum yield for GaClTPyP at 0.045 was lower than that of H2TPyP at 0.13 due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state, lowering the fluorescence. Fluorescence quantum yield values increased when GaClTPyP or H2TPyP were encapsulated in Pluronic F127. GaClTPyP/Pluronic F127 showed higher values of the binding constant (Kb) as well as Stern-Volmer constant (Ksv) when compared to H2ClTPyP/Pluronic F127. It was determined from fluorescence quenching studies for GaClTPyP was located more in the inner core (hydrophobic) of Pluronic F127 and H2TPyP more on the outer region. Single oxygen quantum yields (Ф△) were determined to be 0.32 and 0.53 for GaClTPyP and GaClTPyP/Pluronic F127 respectively, an increase for the latter compared to the former.
- Full Text:
- Date Issued: 2017
- Authors: Managa, Muthumuni , Britton, Jonathan , Amuhaya, Edith K , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233101 , vital:50056 , xlink:href="https://doi.org/10.1016/j.jlumin.2016.12.043"
- Description: GaCl 5,10,15,20-Tetra(1-pyrenyl)porphyrin (GaClTPyP) was successfully synthesised and encapsulated into Pluronic F127. The unmetallated 5,10,15,20-tetra(1-pyrenyl)porphyrin (H2TPyP) precursor was also encapsulated into Pluronic F127. The fluorescence quantum yield for GaClTPyP at 0.045 was lower than that of H2TPyP at 0.13 due to the heavy atom effect of Ga in the former which encourages intersystem crossing to the triplet state, lowering the fluorescence. Fluorescence quantum yield values increased when GaClTPyP or H2TPyP were encapsulated in Pluronic F127. GaClTPyP/Pluronic F127 showed higher values of the binding constant (Kb) as well as Stern-Volmer constant (Ksv) when compared to H2ClTPyP/Pluronic F127. It was determined from fluorescence quenching studies for GaClTPyP was located more in the inner core (hydrophobic) of Pluronic F127 and H2TPyP more on the outer region. Single oxygen quantum yields (Ф△) were determined to be 0.32 and 0.53 for GaClTPyP and GaClTPyP/Pluronic F127 respectively, an increase for the latter compared to the former.
- Full Text:
- Date Issued: 2017
Photophysical studies of 2, 6-dibrominated BODIPY dyes substituted with 4-benzyloxystyryl substituents
- Ngoy, Bokolombe Pitchou, Molupe, Nthabeleng, Harris, Jessica, Fomo, Gertrude, Mack, John, Nyokong, Tebello
- Authors: Ngoy, Bokolombe Pitchou , Molupe, Nthabeleng , Harris, Jessica , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233068 , vital:50053 , xlink:href="https://doi.org/10.1142/S1088424617500420"
- Description: A series of novel 2,6-dibrominated BODIPY dyes with styryl groups at the 3,5-positions has been prepared, and their photophysical properties have been analyzed to assess their potential utility for use as photosensitizers in photodynamic therapy and in bioimaging.
- Full Text:
- Date Issued: 2017
- Authors: Ngoy, Bokolombe Pitchou , Molupe, Nthabeleng , Harris, Jessica , Fomo, Gertrude , Mack, John , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233068 , vital:50053 , xlink:href="https://doi.org/10.1142/S1088424617500420"
- Description: A series of novel 2,6-dibrominated BODIPY dyes with styryl groups at the 3,5-positions has been prepared, and their photophysical properties have been analyzed to assess their potential utility for use as photosensitizers in photodynamic therapy and in bioimaging.
- Full Text:
- Date Issued: 2017
Photophysical studies of conjugates of upconversion nanoparticles with aluminium phthalocyanines
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
- Authors: Watkins, Zane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4964 , vital:20747
- Description: NaYF4 :Yb/Er/Gd upconversion nanoparticles (UCNP) were synthesised and their photoemission stabilised by embedding these nanoparticles in electrospun fibres. The photophysical behaviour of chloro aluminium tetrasulfo-phthalocyanine chloride (ClAlTSPc) was studied in the presence of UCNPs on mixing the two species in solution. The fluorescence lifetimes for UCNPs were shortened at 658 nm in the presence of ClAlTSPc when the former was embedded in fibre and suspended in a dimethyl sulfoxide solution of the latter. A clear singlet oxygen generation by ClAlTSPc through Forster resonance energy transfer (FRET) was demonstrated using a singlet oxygen quencher, 1,3-diphenylisobenzofuran. UCNP capped with amino groups were then covalently attached to chloro aluminium tetrasulphonated phthalocyanine (ClAlTSPc) and chloro aluminium tetracarboxy phthalocyanine (ClAlTCPc). The conjugates were characterized using different techniques such as infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). There was a decrease in fluorescence emission spectra of the UCNPs at 658 nm in the presence of the phthalocyanines. This decrease indicates an energy transfer between the donor UCNP and conjugated accepting phthalocyanine (Pc), due to FRET. Low FRET efficiencies of 18 and 21 % for ClAlTSPc and ClAlTCPc, respectively, were obtained.
- Full Text:
- Date Issued: 2017
Photophysical studies of meso-tetrakis (4-nitrophenyl) and meso-tetrakis (4-sulfophenyl) gallium porphyrins loaded into Pluronic F127 polymeric micelles
- Managa, Muthumuni, Ngoy, Bokolombe P, Mafukidze, Donovan M, Britton, Jonathan, Nyokong, Tebello
- Authors: Managa, Muthumuni , Ngoy, Bokolombe P , Mafukidze, Donovan M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233132 , vital:50060 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.08.033"
- Description: 5,10,15,20-Tetra(4-nitrophenyl) porphyrinato gallium chloride (ClGaTNPP) and 5,10,15,20-tetra(4-sulfophenyl) porphyrinato gallium chloride (ClGaTSPP) and their metal free derivatives were successfully synthesised and were added to Pluronic F127 polymeric micelles to form ClGaTNPP-F127 (or H2TNPP-F127) and ClGaTSPP-F127 (or H2TSPP-F127), respectively. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. The fluorescence lifetimes were short-lived upon incorporation into the polymer, compared to the porphyrin alone; suggesting the quenching of the lifetimes of the porphyrin by the polymers. Singlet oxygen quantum yields were determined to be 0.55 and 0.59 for ClGaTSPP and ClGaTSPP-F127, respectively. Thus there is an increase in singlet oxygen quantum yields in the presence of Pluronic F127 compared to the porphyrin alone. ClGaTSPP-F127 (or H2TSPP-F127) showed higher values of the binding constant (Kb) as well as high values of the Stern-Volmer constant (Ksv) compared to ClGaTNPP-F127 (or H2TNPP-F127).
- Full Text:
- Date Issued: 2017
- Authors: Managa, Muthumuni , Ngoy, Bokolombe P , Mafukidze, Donovan M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233132 , vital:50060 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.08.033"
- Description: 5,10,15,20-Tetra(4-nitrophenyl) porphyrinato gallium chloride (ClGaTNPP) and 5,10,15,20-tetra(4-sulfophenyl) porphyrinato gallium chloride (ClGaTSPP) and their metal free derivatives were successfully synthesised and were added to Pluronic F127 polymeric micelles to form ClGaTNPP-F127 (or H2TNPP-F127) and ClGaTSPP-F127 (or H2TSPP-F127), respectively. The fluorescence and singlet oxygen generating behaviour of the porphyrins were investigated following incorporation. The fluorescence lifetimes were short-lived upon incorporation into the polymer, compared to the porphyrin alone; suggesting the quenching of the lifetimes of the porphyrin by the polymers. Singlet oxygen quantum yields were determined to be 0.55 and 0.59 for ClGaTSPP and ClGaTSPP-F127, respectively. Thus there is an increase in singlet oxygen quantum yields in the presence of Pluronic F127 compared to the porphyrin alone. ClGaTSPP-F127 (or H2TSPP-F127) showed higher values of the binding constant (Kb) as well as high values of the Stern-Volmer constant (Ksv) compared to ClGaTNPP-F127 (or H2TNPP-F127).
- Full Text:
- Date Issued: 2017