Showing items 581 - 600 of 791

Your selections:

Stronger induction of callose deposition in barley by Russian wheat aphid than bird cherry-oat aphid is not associated with differences in callose synthase or ≤-1,3-glucanase expression

  • Authors: Saheed, Sefiu A , Cierlik, Izabela , Larsson, Kristina A E , Delp, Gabriele , Bradley, Graeme , Jonsson, Lisbeth M V , Botha, Christiaan E J
  • Date: 2009
  • Language: English
  • Type: Article
  • Identifier: vital:6542 , http://hdl.handle.net/10962/d1005984
  • Description: The effects of infestation by the bird cherry-oat aphid (BCA), (Rhopalosiphum padi L) and the Russian wheat aphid (RWA) (Diuraphis noxia Mordvilko) on callose deposition and gene expression related to callose accumulation were investigated in barley (Hordeum vulgare L. cv. Clipper). The BCA, which gives no visible symptoms, induced very limited callose deposition, even after 14 days of infestation. In contrast, RWA, which causes chlorosis, white and yellow streaking and leaf rolling, induced callose accumulation already after 24h in longitudinal leaf veins. The deposition was pronounced after 72 h, progressing during 7 and 14 days of infestation. In RWA-infested source leaves, callose was also induced in longitudinal veins basipetal to the aphid-infested tissue, whereas in sink leaves, more callose deposition was found above the feeding sites. Nine putative callose synthase genes were identified in a data base search, of which eight were expressed in the leaves, but with similar level of expression in control and aphid-infested tissue. Four out of 12 examined β-1,3-glucanases were expressed in the leaves, and three of them were up-regulated in aphid-infested tissue. They were all more strongly induced by RWA than BCA. The results suggest that callose accumulation may be partly responsible for the symptoms resulting from RWA feeding and that a callose-inducing signal may be transported in the phloem. Furthermore it is concluded that the absence of callose deposition in BCA-infested leaves is not due to a stronger induction of callose-degrading β-1,3-glucanases in this tissue, as compared to RWA-infested leaves.
  • Full Text:
  • Date Issued: 2009

Student's van Hiele levels of geometric thought and conception in plane geometry: a collective case study of Nigeria and South Africa

  • Authors: Atebe, Humphrey Uyouyo
  • Date: 2009
  • Subjects: Geometry -- Study and teaching (Secondary) -- Nigeria -- Case studies Geometry -- Study and teaching (Secondary) -- South Africa -- Case studies Mathematics -- Study and teaching (Secondary) -- Nigeria -- Case studies Mathematics -- Study and teaching (Secondary) -- South Africa -- Case studies
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:1777 , http://hdl.handle.net/10962/d1003662
  • Description: This study is inspired by and utilises the van Hiele theory of geometric thought levels, currently acclaimed as one of the best frameworks for studying teaching and learning processes in geometry. The study aims both to explore and explicate the van Hiele levels of geometric thinking of a selected group of grade 10, 11 and 12 learners in Nigerian and South African schools. The study further aims to provide a rich and indepth description of the geometry instructional practices that possibly contributed to the levels of geometric conceptualisation exhibited by this cohort of high school learners. This collective case study, presented in two volumes, is oriented within an interpretive research paradigm and characterised by both qualitative and quantitative methods. The sample for the study comprised a total of 144 mathematics learners and 6 mathematics teachers from Nigeria and South Africa. They were selected using both purposive and stratified sampling techniques. In using the van Hiele model to interrogate both learners’ levels of geometric conceptualisation and teaching methods in geometry classrooms, the study employs a qualitative and qunatitative approach to the data-collection process, involving the use of questionnaires (in the form of various pen-and-paper tests, hands-on activity-based tests), interviews and classroom videos. Although the data analysis was done largely through descriptive statistics, the whole process inevitably incorporated elements of inferential statistics (e.g. ANOVA and Tukey HSD post-hoc test) in the quest for indepth analysis and deeper interpretation of the data. Learners were assigned to various van Hiele levels, mainly according to Usiskin’s (1982) forced van Hiele level determination scheme. The whole process of analysing the classroom videos involved a consultative panel of 4 observers and 3 critical readers, using the checklist of van Hiele phase descriptors to guide the analysis process. Concerning learners’ levels of geometric conceptualisation, the results from this study reveal that the most of the learners were not yet ready for the formal deductive study of school geometry, as only 2% and 3% of them were respectively at van Hiele levels 3 and 4, while 47%, 22% and 24% were at levels 0, 1 and 2, respectively. More learners from the Nigerian subsample (53%) were at van Hiele level 0 than learners from the South African subsample (41%) at this level. No learner from the Nigerian subsample was at van Hiele level 4, while 6% of the South African learners were at level 4. In general, learners from the Nigerian subsample had a poorer knowledge of school geometry than their peers from the South African subsample, as learners from the latter subsample obtained significantly higher mean scores in the van Hiele Geometry Test (VHGT) and each of the other tests used in this study. Results relating to gender differences in performance generally favour the male learners in this study. For each of the participating schools, learners’ van Hiele levels (as determined by their scores on the VHGT) strongly correlate with their performance in geometry content tests and mathematics generally. For each of the Nigerian and South African subsamples, for n ≤ 2, learners at van Hiele level n obtained higher means on nearly all the tests administered in this study than their peers at level n–1. This finding provides support for the hierarchical property of the van Hiele levels.
  • Full Text:
  • Date Issued: 2009

Student-athletes' attitude formation towards sport or other psychology services

  • Authors: Wilmot, Gregory Thomas Charlton
  • Date: 2009
  • Subjects: Sports -- Psychological aspects Attitude (Psychology) Stereotypes (Social psychology) Clinical psychology Athletes -- Counseling of Athletes -- Attitudes
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3086 , http://hdl.handle.net/10962/d1002595
  • Description: This qualitative study aims to explore attitude formation within a small sample of Tertiary level student-athletes in relation to their antecedent experiences, individual knowledge about psychology and the social factors impacting on their attitude formation. The study is intended to allow for the development of themes related to the participants’ personal responses to the questions posed to them. The participants’ answers from the interviews will allow for an in-depth analysis and interpretation of the constituents influencing attitude formation towards sport psychology consultation. Primarily, the study aims to explore how attitudes towards clinical and sport psychology practitioners are constructed in this sample. Clinical psychology is used as a contrasting reference point to explore attitude formation in sport psychology. The participants’ beliefs, knowledge sources and attitude toward clinical psychology are examined to understand the fundamental constituents of their attitudes and to understand how this might be related to attitude formation towards sport psychology. It is intended that exploration of the participants’ knowledge sources (e.g. parents, peers, media and coaches) and additional influences on attitudes towards clinical psychology are used to provide insight into how they might shape attitude formation toward sport psychology. This is viewed as particularly important as sport psychology is an increasingly important tool in assisting the enhancement of sporting performance output. This qualitative study uses four elite student-athletes from the same sporting discipline and contextual background to allow for close linkages between the participants’ responses about attitude formation to be made. The study further aims to explore and understand how similarities and differences occur between the participants’ responses which will be completed through analysing and drawing parallels within themes relating to the literature or emerging separately. The Literature Review is intended to help guide the research through providing a reference source for contextualizing individual, public and socially generated beliefs and knowledge (literacy) about mental health / psychology, the constituents of attitude formation and the student-athlete’s context. These factors were identified in the literature as crucial components in attitude formation and also assisted in the development of initial themes, thus guiding the research. Unfortunately, there was limited literature pertaining to attitude formation in relation to sport psychology services and thus provide justification for using clinical psychology to explore attitude formation in sport psychology. This initial exploration of attitude formation in clinical psychology was used as a ‘template’ for contrasting attitude formation in the sample student-athletes as an indication of attitude formation in sport psychology. The Literature Review is viewed as an integral and active component of the study that is used as a body of reference guiding the exploration and interpretation of the emergent themes. This is done through the iterative reference to past research relating to attitude formation, health beliefs, and the numerous sources of information influencing attitude formation within clinical psychology and the student-athlete context. Most importantly, the Literature Review provides a significant base of information that guides the Research Question and the particular factors that have been noted as the most significant to the research. The Literature Review is intended to guide the Research Question and highlight the significant components that need to be taken into consideration in exploring attitude formation. This study, having taken the numerous individual, social, contextual and other factors into consideration, seeks to understand how such factors combine to shape attitudes and influence attitude formation. The collection of literature on social, knowledge and antecedent factors are significant in their role of shaping attitude formation and thus have been included within the Research Question. Furthermore, the Research Question and Literature Review had an impact on the Methodology and why Thematic Analysis was selected. Given the similarities in the participants’ sporting and contextual backgrounds (e.g., being in the same crew, university and social context), it was felt that the primary determinants of attitude formation, within antecedent experiences, knowledge and social influences, would emerge in related themes and thus provide greater insight into attitude formation within the student-athlete context. A limiting factor however, does lie in the small number of participants from a limited diversity of backgrounds, experiences or factors that could assist in allowing broader generalisations of the findings. However, this study aims to understand how the particular factors influence or shape attitudes towards sport and other psychology services and aims to understand the more specific or ‘fundamental’ components of attitude formation that are experienced within the student-athlete’s context and environment.
  • Full Text:
  • Date Issued: 2009

Students as Agents of Social Change-Student Initiatives at Rhodes University, South Africa

  • Authors: Togo, Muchaiteyi
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/386561 , vital:68151 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122830"
  • Description: Rhodes University has a diversity of sustainable development initiatives meant for students and in a range of cases activities are initiated by students themselves with the support of the university. Results of a sustainability assessment revealed the involvement of students in environmental societies, environmental awareness campaigns, campus sustainability initiatives and community sustainability projects. Though most of the projects are still in their infancy and some challenges are yet to be overcome, the sustainability initiatives are gaining momentum and have contributed to improving the overall picture of sustainability at the university. Based on the results of the Rhodes University case study, the underpinning viewpoint in this paper is that university students are not merely recipients of Education for Sustainable Development but have the capacity to become agents for social change.
  • Full Text:
  • Date Issued: 2009

Studies towards the synthesis of novel tridentate ligands for use in ruthenium metathesis catalysts

  • Authors: Millward, Tanya
  • Date: 2009
  • Subjects: Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4360 , http://hdl.handle.net/10962/d1005025 , Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
  • Description: This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.
  • Full Text:
  • Date Issued: 2009

Study of the photophysical behavior of tetrasulfonated metallophthalocyanines in the presence of CdTe quantum dots

  • Authors: Idowu, Mopelola , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/264138 , vital:53701 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
  • Description: Förster resonance energy transfer (FRET) studies were carried out with CdTe quantum dots (QDs) synthesized in aqueous phase and various tetrasulfonated metallophthalocyanines (MPcS4, M = aluminum ((OH)AlPcS4), zinc (ZnPcS4), silicon ((OH)2SiPcS4) and germanium ((OH)2GePcS4) in a H2O:MeOH (1:1) solvent mixture. The QDs studied were capped with thioglycolic acid (TGA) or mercaptopropionic acid (MPA) with sizes ranging from 2.3 to 3.7 nm. Non-radiative energy transfer from QDs emission to MPcS4 complexes was observed. Study of the photophysics of the MPcs in the presence of the QDs revealed high triplet state quantum yields (ΦT, ranging from 0.41 to 0.85 in the presence of QDs), with corresponding long triplet state lifetimes (τT, which ranged from 140 to 610 μs in the presence of QDs) to allow for photosensitized reactions to occur. The efficiency of energy transfer and the donor–acceptor distance between the MPcs and the QDs were also evaluated.
  • Full Text:
  • Date Issued: 2009

Study South Africa

  • Authors: International Education Association of South Africa (IEASA) , Jooste, Nico
  • Date: 2009
  • Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/64983 , vital:28642 , ISBN 9780620448161
  • Description: [Extract from message from Minister of Higher Education and Training, Hon. Dr BE Nzimande]: It gives me pleasure to provide support to the International Education Association of South Africa’s (IEASA) 9th edition of the Study South Africa publication. The focus of this edition, which is Higher Education and Development in South Africa, is most appropriate today as South Africa continuously strives to ensure that higher education remains relevant and responsive to the developmental needs of the country. To this end, we always have to bear in mind that South Africa is a developing country, and as such still confronts challenges such as poverty and under-development. These challenges are characteristic of most developing countries, particularly in sub-Saharan Africa. Thus, our higher education sector, through its core functions of teaching, research, and community engagement, should seek to address these issues especially as they affect the poor and other vulnerable members of our society. Since we became a democratic state in 1994, South Africa has gone a long way to transform and restructure our higher education system to ensure amongst others equity with regard to the demographics of our staff and student population. The gender and racial profile of our students has improved significantly over the years to the extent that we now have black and female students constituting the majority at our institutions, especially at undergraduate level. It is also pleasing to note that our institutions enjoy good international standing. South African researchers and institutions continue to engage in research collaborations with their peers and counterparts around the world, and thus, are integral parts of research programmes and networks. With respect to student mobility, our higher education institutions continue to attract large numbers of international students, particularly from other parts of Africa. In 2007 the number of international students enrolled at our institutions was counted at 59 209, a significant increase from 44 439 in 2000. About 85% of these students originate from the African continent, more specifically the Southern African Development Community (SADC) region. Several factors account for the increase in the number of international students coming to South Africa. These include the country’s natural and ecological resources, rich and diverse cultural heritage, and the stable socio-political conditions. The consistent growth in the number of international students seeking to study in South Africa is a positive affirmation on the quality of the country’s institutions and the international reputation of their academics and qualifications. As a country, we see this growth as a positive development as it provides us with the opportunity not only to impart or relate our experiences, but also, to learn from others, and by so doing further enhance the international standing of our higher education system. , 9th Edition
  • Full Text:
  • Date Issued: 2009

Substantive equality and proof of employment discrimination

  • Authors: Loyson, Madeleine
  • Date: 2009
  • Subjects: Discrimination in employment -- South Africa , Labor laws and legislation -- South Africa , Affirmative action programs -- Law and legislation -- South Africa
  • Language: English
  • Type: Thesis , Masters , LLM
  • Identifier: vital:10208 , http://hdl.handle.net/10948/1059 , Discrimination in employment -- South Africa , Labor laws and legislation -- South Africa , Affirmative action programs -- Law and legislation -- South Africa
  • Description: This dissertation is a journey through the legislative changes and case law in order to analyse and evaluate the changing nature of South African jurisprudence in respect of the notions of equality, discrimination and affirmative action and the manner in which these issues are proved and dealt with in our courts. It focuses firstly on the emergence of the post-Wiehahn labour laws and the developing jurisprudence concerning discrimination in South Africa towards the end of a long period of isolation from the international world. It witnesses the growing cognizance which was taken of international guidelines and their slow and gradual incorporation into our jurisprudence before the institution of the new democratic government, in the days when the country was still firmly in the grip of a regime which prided itself on its discriminatory laws. It also deals in some depth with the new laws enacted after the first democratic government was installed, especially in so far as the Constitution was concerned. The first clutch of cases dealing with discrimination which were delivered by the Constitutional Court and their effects on decisions of the labour courts thereafter, are dealt with in great detail, indicating how important those judgments were and still are ten years later. A special chapter is devoted to the Harksen case, still a leading authority on how to deal with allegations of unfair discrimination. Having traversed several of the judgments of the labour courts after Harksen, several observations are made in the conclusion of the study which, it is hoped, summarize the major areas of concern in respect of the task of testing claims of unfair discrimination arising in our Courts.
  • Full Text:
  • Date Issued: 2009

Suitability of total coliform beta-D-galactosidase activity and CFU counts in monitoring faecal contamination of environmental water samples

  • Authors: Wutor, V C , Togo, C A , Pletschke, Brett I
  • Date: 2009
  • Language: English
  • Type: Article
  • Identifier: vital:6477 , http://hdl.handle.net/10962/d1006165 , http://www.scielo.org.za/scielo.php?pid=S1816-79502009000100010&script=sci_arttext
  • Description: Total coliforms are a group of bacteria found in high numbers in mammalian intestines; hence their presence in water indicates the possible contamination with faecal material. Total and faecal coliform counts were monitored over a period of 18 months using mFC, m-Endo and CM1046 media together with enzymatic assays on 215 environmental water samples obtained from the Eastern Cape Province of South Africa. A positive correlation, with an R2 value of 0.9393 was observed between faecal and total coliform colony units employing mFc and m-Endo media, and 0.8818 using CM1046 media. Also, a positive correlation was observed between Escherichia coli colony-forming units and β-D-galactosidase (B-GAL) activity (R2=0.8542). Overall, this study indicated that faecal contamination of environmental water samples could be monitored by measuring total coliform β-galactosidase activity and total coliform colony-forming units.
  • Full Text: false
  • Date Issued: 2009

Synthesis and characterization of electrocatalytic conjugates of tetraamino cobalt (II) phthalocyanine and single wall carbon nanotubes

  • Authors: Mugadza, Tawanda , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/263341 , vital:53619 , xlink:href="https://doi.org/10.1016/j.electacta.2009.05.074"
  • Description: In this paper we report on the synthesis and characterization of electrocatalytic conjugates of tetraamino cobalt (II) phthalocyanine and single walled carbon nanotubes (CoTAPc–SWCNT-linked) for use as electrode surface modifiers. FTIR, UV–vis and Raman spectroscopies were used to ascertain the chemical linkage between CoTAPc and SWCNT while cyclic voltammetry and rotating disk electrode voltammetry were used to assess the electrocatalytic efficiency of the linked product towards the oxidation of 2-mercaptoethanol. The CoTAPc–SWCNT-linked-GCE demonstrated very good catalytic efficiency relative to CoTAPc–SWCNT-mixed-GCE, CoTAPc-GCE and f-SWCNTs-GCE (functionalised SWCNT). CoTAPc–SWCNT-linked-GCE gave a sensitivity of 0.2 μA/μM and a limit of detection (LOD) of 1.2 × 10−7 M for 2-mercaptoethanol (2-ME) at pH 4.
  • Full Text:
  • Date Issued: 2009

Synthesis and characterization of novel platinum complexes : their anticancer behaviour

  • Authors: Myburgh, Jolanda
  • Date: 2009
  • Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
  • Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
  • Full Text:
  • Date Issued: 2009

Synthesis and electrochemistry of octapentylthio phthalocyanine complexes of manganese, titanium and vanadium

  • Authors: Mbambisa, Gcineka
  • Date: 2009
  • Subjects: Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4368 , http://hdl.handle.net/10962/d1005033 , Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
  • Description: Synthesis of new thio derivatised Pcs with manganese, titanium and vanadium as a central metal is reported. The complexes synthesised were characterised using spectroscopic and electrochemical means. The complexes displayed interesting spectroscopic properties with absorption of the Q band being observed in the near infrared region. These complexes have unusual colours for MPc complexes, with purple or red colour being observed in solution. Interesting electrochemical properties were observed, with rare observation of the MnIV/MnIII redox couple. There was observation of oxidation peaks for the pentylthio derivatised Pc with titanium as the central metal; this is unusual since for reported thio derivatives based on TiPc, no oxidation was observed. The vanadium based Pc showed an interesting spectrum for the first ring based reduction. The absorption spectrum obtained for the 1st reduction of the vanadium complex using spectroelectrochemistry would normally indicate a metal based process but comparing with literature it was concluded that it is a ring based reduction process. Generally all the MPc complexes formed a well ordered stable monolayer on the gold electrode. Electrocatalytic studies using L-cysteine revealed that the SAM based on manganese (III) octapentylthio phthalocyanine (AcOMnOPTPc) was the most effective since it catalyses L-cysteine at much lower oxidation potentials and it is also much more stable.
  • Full Text:
  • Date Issued: 2009

Synthesis and Pd(II) binding studies of octasubstituted alkyl thio derivatised phthalocyanines

  • Authors: Ogunbayo, T B , Nyokong, Tebello
  • Date: 2009
  • Language: English
  • Type: Article
  • Identifier: vital:6587 , http://hdl.handle.net/10962/d1004170
  • Description: Synthesis and characterization of non-peripherally (4,5) and peripherally (6,7) substituted metal free and Pd octapentylthiophthalocyanine and coordination of palladium ions to these Pcs are reported. The unmetalated complexes (4 and 6) show Pd coordination at the central metal and at the ring. The number of Pd ions bound to complex 4 were found to be five and to complex 6 were three. The equilibrium constant for the binding of Pd to complexes 4 was lower (K = 1.2 × 109 dm3 mol−1) than for complex 6 (K = 5.7 × 1010 dm3 mol−1).
  • Full Text:
  • Date Issued: 2009

Synthesis and photophysical behavior of axially substituted phthalocyanine, tetrabenzotriazaporphyrin, and triazatetrabenzcorrole phosphorous complexes

  • Authors: Antunes, Edith M , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/264518 , vital:53741 , xlink:href="https://doi.org/10.1142/S1088424609000048"
  • Description: The synthesis of phosphorous phthalocyanines, triazatetrabenzcorroles, and tetrabenzotriazaporphyrins with a variety of axial ligands is reported. The new complexes are: phosphorous dihydroxy tetrabenzotriazaporphyrin (5, PV(OH)2TBTAP), diphenyl phosphorous phthalocyanine (6, [PV(Ph)2Pc](OH)), diphenyl phosphorous triazatetrabenzcorrole (7, PV(Ph)2TBC), and dioctyl phosphorous triazatetrabenzcorrole (8, PV(C8H17)2TBC). The complexes are not aggregated in dimethylsulfoxide (DMSO) and pyridine. Upon axial coordination of a phenyl or octyl group, the complexes are soluble (and not aggregated) in dichloromethane (DCM) and tetrahydrofuran (THF). The triplet lifetimes range from 395 to 546 μs (for complexes 5 to 8), with the P(Ph)2TBC (7) complex showing the longest triplet lifetime (546 μs), while the smallest triplet quantum yield (ΦT = 0.27) was obtained for the [P(Ph)2Pc](OH) (6) complex. [P(OH)2Pc](OH) (3) showed the shortest triplet lifetime (113 μs) and the largest triplet quantum yield (ΦT = 0.52).
  • Full Text:
  • Date Issued: 2009

Synthesis and photophysical properties of antimony and lead phthalocyanines

  • Authors: Modibane, Kwena Desmond , Guest
  • Date: 2009 , 2009-02-27
  • Subjects: Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4370 , http://hdl.handle.net/10962/d1005035 , Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
  • Description: This work hereby presents the synthesis, spectroscopic and photophysical properties of newly synthesized lead (PbPc) and antimony (SbPc) phthalocyanines. The complexes are either unsubstituted or substituted at the peripheral and non-peripheral positions with phenoxy, 4-t-butylphenoxy and 4-benzyloxyphenoxy groups. The photophysical properties of these complexes were studied in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform as solvents. The fluorescence spectra for PbPc complexes were different to that of the excitation spectra due to demetallation upon excitation. On the other hand, the excitation spectra of oxidized antimony (Sb(V)Pc) derivatives were found to be similar to absorption spectra. High triplet quantum yields for PbPc and SbPc complexes ranging from 0.70 to 0.86, low triplet lifetimes (20–60 μs in DMSO, while they were <10 μs in the rest of the solvents) and low fluorescence quantum yields were observed and is attributed to the presence of heavy atoms (Pb and Sb ions). The nonlinear optical properties of PbPc complexes were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.8 W/cm2. The photodegradation studies of the PbPc and SbPc complexes synthesized showed that then are stable.
  • Full Text:
  • Date Issued: 2009

Synthesis of molecularly imprinted polymer for selective solid-phase extraction of Salbutamol from urine samples

  • Authors: Mohammadi, Ali , Alizadeh, Taher , Dinarvand, Rassoul , Ganjali, Mohammed M , Walker, Roderick B
  • Date: 2009
  • Language: English
  • Type: Article
  • Identifier: vital:6410 , http://hdl.handle.net/10962/d1006496
  • Description: A highly selective methacrylic based molecularly imprinted polymer (MIP) was synthesized and applied for the separation and the pre-concentration of salbutamol in urine samples. Spectrophotometric determination of salbutamol was achieved using 2,6-dichloroquinone chlorimide as colorimetric reagent. The detection limit of the method was ca. 13 ng/mL in urine after pre-concentration of the samples by MIP-SPE andanalysis with an optimized and sensitive spectrophotometric method. The linear dynamic range for salbutamol determination in urine was 0.04-0.75 μg mL-1. The recovery for the affinity based solid-phase extraction (SPE) with the MIP was more than 96 %.
  • Full Text:
  • Date Issued: 2009

Synthesis, photophysical and nonlinear optical properties of microwave synthesized 4-tetra and octa-substituted lead phthalocyanines

  • Authors: Modibane, Desmond K , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/263452 , vital:53629 , xlink:href="https://doi.org/10.1016/j.poly.2009.03.013"
  • Description: This work presents the photophysical and nonlinear optical behaviour of newly synthesized complexes: 2,(3)-tetrakis(4-benzyloxyphenoxyphthalocyaninato) lead (5a) and 2,3-octakis(4-benzyloxyphenoxyphthalocyaninato) lead (6a). The nonlinear optical behaviour of complexes 5a and 6a are compared with those of 2,(3)-tetraphenoxyphthalocyaninato lead (5b), 2,(3)-tetrakis(4-t-butylphenoxyphthalocyaninato) lead (5c), 2,3-octaphenoxyphthalocyaninato lead (6b) and 2,3-octakis(4-t-butylphenoxyphthalocyaninato) lead (6c). The synthesis of 5a and 6a was performed using microwave irradiation. Photophysical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.80 to 0.86 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom. Nonlinear optical properties were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.6 W/cm2.
  • Full Text:
  • Date Issued: 2009

Synthesis, photophysical and photochemical properties of novel soluble tetra [4-(thiophen-3yl)-phenoxy] phthalocyaninato zinc (II) and Ti (IV) O complexes

  • Authors: Erdoğmuş, Ali , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/263318 , vital:53617 , xlink:href="https://doi.org/10.1016/j.ica.2009.07.015"
  • Description: The synthesis, photophysical and photochemical properties of zinc and oxo-titanium phthalocyanine derivatives 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)zinc(II), (2); and 4-(tetra[4-(thiophen-3yl)-phenoxy]phthalocyaninato)oxo-titanium(IV), (3), are described for the first time. These peripherally substituted complexes (2 and 3) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic spectroscopy. The compounds (2 and 3) have good solubility in organic solvents such as CHCl3, DCM, DMSO, DMF, THF and toluene and are not aggregated within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO, DMF and THF. Compound 2 has higher fluorescence quantum yields, triplet quantum yields and triplet life times than 3, however, the former has lower singlet oxygen quantum yields and photodegradation quantum yields than the latter.
  • Full Text:
  • Date Issued: 2009

Synthesis, photophysical and photochemical properties of octa-substituted antimony phthalocyanines

  • Authors: Modibane, Desmond Kwena , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/264226 , vital:53711 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.052"
  • Description: This work reports on the synthesis and photophysicochemical parameters of unsubstituted [SbIIIPc]+I3- and octa-phenoxy ([SbIIIOPPc]+I3-) and -4-t-butylphenoxy ([SbIIIOTBPPc]+I3-) substituted antimony phthalocyanines. Photophysical and photochemical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide and toluene. The excitation spectra of oxidized antimony (Sb(V)Pc) derivates were similar to absorption spectra. Low fluorescence quantum yields, high triplet quantum yields and low triplet lifetimes were observed as the result of heavy atom (antimony ion).
  • Full Text:
  • Date Issued: 2009

Synthesis, photophysical and photochemical studies of water soluble cationic zinc phthalocyanine derivatives

  • Authors: Idowu, Mopelola , Nyokong, Tebello
  • Date: 2009
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/264245 , vital:53712 , xlink:href="https://doi.org/10.1016/j.poly.2008.11.021"
  • Description: Peripherally and non-peripherally 2-diethylaminoethanethiol tetra-substituted zinc phthalocyanine (5a and 6a) and their quaternized derivatives (5b and 6b) have been synthesized and characterized. The quaternized derivatives (5b and 6b) show excellent solubility in aqueous medium. The photophysical and photochemical properties of the 2-diethylaminoethanethiol appended zinc phthalocyanine in dimethylsulfoxide (DMSO) for the non-ionic (5a and 6a) and in both DMSO and aqueous medium (phosphate buffered saline solution PBS, pH 7.4) (in the presence and absence of cremophore EL (CEL)) for the quaternized (5b and 6b) derivatives were studied and compared with that of the peripherally octa-substituted derivatives (7a and 7b). The complexes have intense absorption in the visible/near-IR region though the quaternized forms (5b, 6b and 7b) were slightly blue shifted and highly aggregate in aqueous solution. The triplet state quantum yields (ΦT) and the triplet lifetimes (τT) were found to be higher in DMSO (ΦT values ranged from 0.57 to 0.75 while τT values ranged from 190 to 220 μs in DMSO for all complexes) compared to aqueous medium (ΦT values ranged from 0.15 to 0.17 while τT values ranged from 20 to 70 μs in pH 7.4 buffer). Addition of cremophore EL in aqueous solution resulted in induced disaggregation leading to increased ΦT and τT.
  • Full Text:
  • Date Issued: 2009
  • Disclaimer
  • Privacy
  • Copyright
  • Contact