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Optical nonlinearities and photophysicochemical behaviour of green and blue forms of lutetium bisphthalocyanines

- Sekhosana, Kutloano Edward, Amuhaya, Edith, Mack, John, Nyokong, Tebello

Authors: Sekhosana, Kutloano Edward , Amuhaya, Edith , Mack, John , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7316 , http://hdl.handle.net/10962/d1020543
Description: A rare earth sandwich-type phthalocyanine: bis-{2,3,9,10,16,17,23,24-octa(4-tert-butylphenoxy) phthalocyaninato} lutetium(III) has been synthesized. The photophysical and nonlinear optical behavior of both the “green” and “blue” forms ([LuIIIPc2] and [LuIIIPc2]−, respectively) of the complex have been investigated. High triplet state and singlet oxygen quantum yield values were obtained for the neutral blue form which contains no unpaired electrons. Relatively high third order susceptibility and hyperpolarizability values of the order of 10−10 and 10−28 esu were obtained for both the green and blue forms, respectively. A very low threshold intensity of 0.00051 J cm−2 was obtained for the blue form. Hence the complex shows promise for non-linear optical applications. , Original publication is available at http://dx.doi.org/10.1039/C4TC00505H
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Optical nonlinearities in non-peripherally substituted pyridyloxy phthalocyanines: a combined effect of symmetry, ring-strain and demetallation

- Sanusi, Kayode, Antunes, Edith M, Nyokong, Tebello

Authors: Sanusi, Kayode , Antunes, Edith M , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7301 , http://hdl.handle.net/10962/d1020375
Description: The optical nonlinearities of six non-peripherally-substituted pyridyloxy phthalocyanines have been studied at 532 nm using a nanosecond Z-scan technique in a dimethyl sulphoxide solution. Ring-strain effects and the absence of a metal center were found to greatly reduce the inherent high nonlinearities expected of some of these phthalocyanine complexes. Of the six molecules investigated, 1(4),8(11),15(18),22(25)-tetrakis-(2-pyridyloxy)phthalocyaninato lead(II) 3, 1(4),8(11),15(18),22(25)-tetrakis-(2-pyridyloxy)phthalocyanine 5, and 1(4),8(11),15(18),22(25)-tetrakis-(4-pyridyloxy)phthalocyanine 6 were found to exhibit negligible nonlinear optical behavior, due to either the absence of asymmetry or central metal and/or the presence of a ring-strain effect. A two-photon absorption process was found to be the major contributor to the observed reverse saturable absorption (RSA) in 1(4),8(11),15(18),22(25)-tetrakis-(4-pyridyloxy)phthalocyaninato lead(II) 4, 1(4)-mono-(2-pyridyloxy)phthalocyaninato lead(II) 7, and 1(4)-mono-(4-pyridyloxy)phthalocyaninato lead(II) 8, with large two-photon absorption cross-section, high hyperpolarizability and high third-order susceptibility values in the range of 4.53 × 10−43–5.33 × 10−42 cm4 s per photon, 1.61 × 10−28–1.89 × 10−27 esu and 9.73 × 10−12–7.05 × 10−11 esu respectively. , Original publication is available at http://dx.doi.org/10.1039/C3DT52462K , Arbortext Advanced Print Publisher 9.1.520/W Unicode , Acrobat Distiller 10.0.0 (Windows); modified using iText� 5.3.3 �2000-2012 1T3XT BVBA (AGPL-version)
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Optical properties and electronic structures of axially-ligated group 9 porphyrins

- Wang, Bei-Bei, Zuo, Huiping, Mack, John, Majumdar, Poulomi, Nyokong, Tebello, Chan, Kin Shing, Shen, Zhen

Authors: Wang, Bei-Bei , Zuo, Huiping , Mack, John , Majumdar, Poulomi , Nyokong, Tebello , Chan, Kin Shing , Shen, Zhen
Language: English
Type: Article
Identifier: vital:7295 , http://hdl.handle.net/10962/d1020358
Description: A series of group 9 metal tetra-(p-tolyl)-porphyrin (M(ttp), M = Co(II), Rh(III), Ir(III)) complexes with axial phenyl substituents have been synthesized and characterized. An aryl bromide cleavage reaction of transition metal complexes was used to prepare the complexes from Co(ttp), Rh(ttp)Cl and Ir(ttp)COCl, respectively. Magnetic circular dichroism (MCD) spectroscopy and TD-DFT calculations have been used to study trends in the optical spectra and electronic structures. The effect of introducing different para-substituents on the phenyl substituents was examined. During fluorescence emission studies, phosphorescence was observed for the Ir(III) complexes in the near infrared (NIR) region. , Original publication is available at http://dx.doi.org/10.1142/S108842461550073X
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Optimisation of cold rolling process parameters to improve surface quality of the AA 3003-H22 treadbright coils

- Makhanya, Lehlohonolo

Authors: Makhanya, Lehlohonolo
Subjects: Aluminum alloys
Language: English
Type: Thesis , Masters , MTech
Identifier: vital:9611 , http://hdl.handle.net/10948/554 , Aluminum alloys
Description: The main objective of this dissertation was to investigate how cold rolling process parameters could be optimised to improve surface quality of the AA 3003 H22 treadbright coils. This treadbright product is one of Hulett Aluminium’s main products and is exported mainly to the North American market. One of its critical requirements is a defect-free bright surface. The literature review was conducted with particular focus on the effects of selected parameters or settings with respect to surface quality and a chapter outlining these aspects has been included. It was clear from the literature review that selected parameters do affect the surface quality and if adjusted accordingly can improve surface quality on treadbright coils. Subsequent chapters after the literature review outline how the tests were conducted, procedures followed and equipments used from the cold rolling machine to laboratories. Surface appearance results after each parameter was adjusted, showed that the surface quality did improve and even got better when other parameters like the colouring roll angle and percentage reduction were adjusted. Correct working limits within which each parameter would yield acceptable surface quality were also established. All experiments conducted had no influence on the microstructure of the metal as it remained the same throughout each experiment. The same has been found with the mechanical properties as percentage reductions experiments led to no change in tensile strength, proof strength and percentage elongation. In conclusion, this research has proved that cold rolling process parameters selected did affect the product surface quality. If controlled they can be used to optimise the surface quality on the treadbright product as required by Hulett Aluminium and its customers.
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Organosilicon compounds as fluorescent chemosensors for fluoride anion recognition

- Gai, Lizhi, Mack, John, Lu, Hua, Nyokong, Tebello, Li, Zhifang, Kobayashi, Nagao, Shen, Zhen

Authors: Gai, Lizhi , Mack, John , Lu, Hua , Nyokong, Tebello , Li, Zhifang , Kobayashi, Nagao , Shen, Zhen
Language: English
Type: Article
Identifier: vital:7241 , http://hdl.handle.net/10962/d1020245
Description: Recent developments in organosilicon-based chemosensors for F− recognition are reviewed. The design strategies for improving the photophysical properties of organosilicon-based chemosensors are elaborated, with an emphasis placed on their utility for biological applications. The photophysical properties and electronic structures are analyzed in depth with reference made to the results of molecular modeling calculation and possible future research directions are assessed. , Original publication is available at http://dx.doi.org/10.1016/j.ccr.2014.10.009
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Perceptions of health care professionals regarding facilitation of resilience in the workplace

- Smith, G

Authors: Smith, G
Subjects: Nurses -- Job stress , Resilience (Personality trait) , Nursing -- Psychological aspects
Language: English
Type: Thesis , Masters , MA
Identifier: vital:10086 , http://hdl.handle.net/10948/d1020948
Description: A person’s career takes up a large portion of his or her life for a minimum of 8 hours per day. A large portion of their time is spent performing their duties which are often accompanied by various demands or pressure that can result in an employee experiencing stress. Over time this build-up of stress due to job demands affects their ability to perform at work. This study aimed to identify, explore and describe the factors that facilitate the resilience of healthcare professionals working at a Campus Health Service at a Higher Education Institution. An exploratory descriptive study consisting of a qualitative nature was employed. Data was obtained from semi-structured interviews. The questions that were posed to participants read as follows: (1) “Tell me about the demands placed on you in your current work situation”, (2) “How do you cope with the demands placed on you?”, (3) “What can be done to assist you to cope better at work?”, and lastly (4) “Any additional questions/comments?”. The fourth question was added by the researcher in order for participants to have the opportunity to add to what they have said previously. Data was gathered until data saturation was reached. Tesch’s model of content analysis as well as Guba’s model of trustworthiness was employed, in order to analyse the data. An independent coder was subsequently employed to ensure the trustworthiness of the data. The findings revealed that all participants found workplace demands to be stressful, in terms of physical, emotional and time-related demands placed on them. Participants identified strategies that could help them cope with their demands such as open air activities, debriefing with colleagues or making use of a wellness line, maintaining a positive attitude, support from management and colleagues, the ability to practice initiative and autonomous decision-making, and lastly, religious practices. In addition, participants made recommendations on how employers can help relieve their stress. The recommendations included developing an in-house wellness programme, providing sufficient staff of the correct categories, providing adequate facilities and equipment to improve efficiency, providing developmental opportunities, scheduling training programmes for less busy times of the year, and lastly, introducing elements of structured flexi-time for employees.
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Philosophies that inform discipline strategies among teachers

- Von Wildemann, Amy-Rose

Authors: Von Wildemann, Amy-Rose
Subjects: School discipline -- South Africa
Language: English
Type: Thesis , Masters , MA
Identifier: vital:9504 , http://hdl.handle.net/10948/1302 , School discipline -- South Africa
Description: Numerous teachers in South Africa are experiencing ill‐discipline within the classroom environment. They are not receiving the necessary support and guidance from the relevant departments, and thus, rely on their own reactive measures to manage the disruptive behaviour present in the classroom. Previous studies have shown that the South African Education Department has not provided all teachers with the necessary training needed to implement the new discipline strategies proposed by the Department of Education. Therefore, teachers rely on what they perceive to be effective in maintaining discipline, which is an indication of their personal teaching philosophy, as they base their own knowledge on what they have experienced and learnt in the past. This study followed a qualitative enquiry, which is descriptive and explorative. The data generation tools that were utilised for the study were, ‘drawing’ and ‘photo album’, both of which represent visual methodology activities. Furthermore, the primary aim of the study is to determine the underlying teaching philosophies that inform selected township teachers’ approaches to discipline in their classrooms. However, the findings indicated that the use of corporal punishment is still visibly prevalent in this township school. Even though it was revealed that the prominent teaching philosophy was not that of fundamental pedagogics, but featured somewhere in between the humanising pedagogy and Noddings’ theory of caring, the effects of teaching during Apartheid under the principles of fundamental pedagogics is still existent in the township.
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Photocatalytic behavior of phthalocyanine-silver nanoparticle conjugates supported on polystyrene fibers

- Khoza, Phindile, Nyokong, Tebello

Authors: Khoza, Phindile , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7317 , http://hdl.handle.net/10962/d1020561
Description: Herein, carbazole derivatized non-peripheral (1,(4)-tetra(carbazol-2-yloxy)phthalocyaninatozinc(II), 3-TCbZnPc) and peripheral (2,(3)-tetra(carbazol-2-yloxy)phthalocyaninato zinc(II), 4-TCbZnPc) are conjugated to silver nanoparticles and their photochemical and photophysical behavior are reported. The presence of silver nanoparticles resulted in reduced fluorescence, and increased triplet and singlet oxygen quantum yields. The conjugates were further electrospun into polystyrene fibers, and employed for the photodegradation of methyl orange. The photodegradation of methyl orange using all functionalized fibers followed first order kinetics, and was faster when the conjugates with silver nanoparticles were used. The non-peripherally substituted 3-TCbZnPc gave better photocatalytic activity compared to its peripherally substituted counterpart (4-TCbZnPc). The hybrid electrospun fibers provide great potential as active photocatalysts for degrading organic pollutants. , Online publication is available at http://dx.doi.org/10.1016/j.molcata.2014.07.031
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Photocatalytic behaviour of zinc tetraamino phthalocyanine-silver nanoparticles immobilized on chitosan beads

- Khoza, Phindile, Nyokong, Tebello

Authors: Khoza, Phindile , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7250 , http://hdl.handle.net/10962/d1020256
Description: Photocatalytic degradation of Rhodamine 6G using unconjugated zinc tetraamino phthalocyanine (ZnTAPc) or when conjugated to Ag nanoparticles (ZnTAPc–AgNPs) is reported. Upon conjugating ZnTAPc to silver nanoparticles, the singlet oxygen production of the phthalocyanine was slightly increased. ZnTAPc and ZnTAPc–AgNPs were immobilized onto chitosan beads for ease of recovery after photocatalysis. Chitosan beads were characterized by FTIR, XRD and TGA. The photodegradation of Rhodamine 6G was used to evaluate the efficiency of the immobilized photocatalysts. In the presence of AgNPs, the photodegradation of Rhodamine 6G was enhanced. The apparent rates (k) were found to be 8.51 × 10−8 and 1.61 × 10−7 mol L−1 min−1 for chitosan supported ZnTAPc or ZnTAPc–AgNPs, respectively. The observation of good photocatalytic activity of the ZnTAPc when immobilized on chitosan proves the uncompromised efficiency of the photocatalysts even when confined in beads, showing great potential for the functionalized beads as heterogeneous catalysts. , Original publication is available at http://dx.doi.org/10.1016/j.molcata.2015.01.017
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Photocopied article from the Jazz Magazine

- Azoulay, Eliane

Authors: Azoulay, Eliane
Subjects: McGregor, Chris--1936-1990 , Jazz , Jazz musicians , Blue Notes (Musical group : South Africa) , Brotherhood of Breath (Musical group) , Dollar Brand , Mabuse, Sipho
Language: French
Type: Article
Identifier: vital:13485 , http://hdl.handle.net/10962/d1005620 , McGregor, Chris--1936-1990 , Jazz , Jazz musicians , Blue Notes (Musical group : South Africa) , Brotherhood of Breath (Musical group) , Dollar Brand , Mabuse, Sipho
Description: Photocopied article in French from Jazz Magazine about the various South African bands who came to and stayed in Europe, because they were forbidden in their country. There is a short interview of Chris McGregor about his return in South Africa in 1987 and announcing his forthcoming recording with the band Brotherhood of Breath.
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Photodynamic antimicrobial chemotherapy activity of gallium tetra-(4-carboxyphenyl) porphyrin when conjugated to differently shaped platinum nanoparticles

- Managa, Muthumuni, Nyokong, Tebello

Authors: Managa, Muthumuni , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7297 , http://hdl.handle.net/10962/d1020360
Description: This work reports on the conjugation of differently shaped Pt nanoparticles (PtNPs) with ClGa(III) 5,10,15,20-tetrakis-(4-carboxyphenyl) porphyrin (ClGaTCPP). The resulting conjugates were used for photodynamic antimicrobial chemotherapy against Staphylococcus aureus. The degree of photo-inactivation is dependent on concentration of the conjugates, light dose (fluence) and illumination time. The log reduction obtained for ClGaTCPP when conjugated to cubic PtNPs was 4.64 log (which indicate 99.99% of the bacteria have been killed), which is much higher than 3.94 log unit for ClGaTCPP-Hexagonal PtNPs and 3.31 log units for ClGaTCPP-Unshaped PtNPs. ClGaTCPP alone gave a log unit reduction of less than 3, showing the importance of conjugation to PtNPs. , Original publication is available at http://dx.doi.org/10.1016/j.molstruc.2015.06.077
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Photodynamic inactivation of Staphylococcus aureus using low symmetrically substituted phthalocyanines supported on a polystyrene polymer fiber

- Masilela, Nkosiphile, Kleyi, Phumelele, Tshentu, Zenixole R, Priniotakis, Georgios, Westbroek, Philippe, Nyokong, Tebello

Authors: Masilela, Nkosiphile , Kleyi, Phumelele , Tshentu, Zenixole R , Priniotakis, Georgios , Westbroek, Philippe , Nyokong, Tebello
Language: English
Type: Article
Identifier: vital:7330 , http://hdl.handle.net/10962/d1020591
Description: This work reports on the antimicrobial photo-activities of a series of low symmetrically substituted phthalocyanine complexes in solution and in a fiber matrix. Phthalocyanine complexes were successfully electrospun into a polystyrene polymer. The fiber diameter ranged from 240 nm to 390 nm in average. The modified polymer fiber showed successful singlet oxygen production with the Ge monocarboxy phthalocyanine modified fiber giving the highest singlet oxygen quantum yield value of 0.46 due to lack of aggregation when in the polymer. All the unsymmetrically substituted complexes showed antimicrobial activity towards S. Aureus under illumination with visible light. The symmetrical ZnPc and ZnTPCPc showed no activity under illumination with light in the fiber matrix due to low singlet oxygen production. , Original publication is available at http://dx.doi.org/10.1016/j.dyepig.2012.10.001
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