Ruthenium (II) complexes of mixed bipyridyl and dithiolate/thiourea ligands :|bsynthesis, characterization, photophysical and electrochemical studies
- Authors: Nkombi, Pelokazi
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10134 , vital:35358
- Description: Energy is one of the most important factor to influence human lives. The increased in energy demand as well as the detrimental effects posed by emission of greenhouse gases due to continue use of fossil fuels for electricity generation has led to a renewed focus on energy production using renewable energy sources which are relatively cheap, clean and environmentally sustainable. Among the various renewable energy sources used so far, the Dye Synthesized Solar Cells (DSSCs), a form of photovoltaic device is reported for their better efficiencies despite their low cost of production and ability to work relatively under low light conditions. A recent report on the solar-to-electricity conversion efficiency of a typical DSSC sensitizer made from zinc based porphyrin dye coupled with sintered titanium(IV) oxide as semiconductor was 13 percent. In this study, 2,2-bipyridyl-4,4-dicarboxylic acid (bpydc) was used as mixed ligand and four dithiolate ligands; L1 = dipotassium ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate, L2 = dipotassium bis(ethoxycarbonyl)ethane-2,2-dithiolate, L3 = dipotassium cyanodithio imidocarbonate and L4 = dipotassium 2,2-dicyanoethylene-2,2-dithiolate were synthesized while four alkyl thiourea ligands, L5 = 1,3-dimethyl thiourea, L6 = 1,3-diethyl thiourea, L7 = 1,3-diisopropyl thiourea and L8 = 1-methyl thiourea were purchased and used as supplied without further purification. These ligands were used to prepare eight ruthenium(II) complexes of mixed bipyridyl/dithiolate/thiourea. The compounds were characterised by elemental analysis and spectroscopic techniques, namely: Fourier transform infrared (FTIR), Nuclear Magnetic Resonance (NMR), ultraviolet-visible and photoluminescence (PL). Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used for the electrochemical studies. Photoluminescence and UV-Vis spectroscopies were used for geometric and photophysical studies of the complexes respectively. FTIR spectra confirmed presence of functional groups in ligands and coordination of these ligands to ruthenium(II) ions to form complexes. The UV-Vis confirmed that the Ru(II) dithiolene complexes exhibited square planar geometries while the Ru(II) thiourea complexes gave octahedral geometries, this was deduced from the transitions assigned to the complexes. All the ruthenium(II) complexes synthesized showed photoluminescence properties that are suitable for light harvesting and application for dye-sensitized solar cells. Cyclic and square wave voltammetry show Ru(II) thiourea complexes have better redox properties when compared to Ru(II) dithiolate complexes which is ascribed to ligand strength field possibly due to contribution from the two bonded NCS groups.
- Full Text:
- Date Issued: 2018
- Authors: Nkombi, Pelokazi
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds Ligands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10134 , vital:35358
- Description: Energy is one of the most important factor to influence human lives. The increased in energy demand as well as the detrimental effects posed by emission of greenhouse gases due to continue use of fossil fuels for electricity generation has led to a renewed focus on energy production using renewable energy sources which are relatively cheap, clean and environmentally sustainable. Among the various renewable energy sources used so far, the Dye Synthesized Solar Cells (DSSCs), a form of photovoltaic device is reported for their better efficiencies despite their low cost of production and ability to work relatively under low light conditions. A recent report on the solar-to-electricity conversion efficiency of a typical DSSC sensitizer made from zinc based porphyrin dye coupled with sintered titanium(IV) oxide as semiconductor was 13 percent. In this study, 2,2-bipyridyl-4,4-dicarboxylic acid (bpydc) was used as mixed ligand and four dithiolate ligands; L1 = dipotassium ethoxycarbonyl-1-cyanoethylene-2,2-dithiolate, L2 = dipotassium bis(ethoxycarbonyl)ethane-2,2-dithiolate, L3 = dipotassium cyanodithio imidocarbonate and L4 = dipotassium 2,2-dicyanoethylene-2,2-dithiolate were synthesized while four alkyl thiourea ligands, L5 = 1,3-dimethyl thiourea, L6 = 1,3-diethyl thiourea, L7 = 1,3-diisopropyl thiourea and L8 = 1-methyl thiourea were purchased and used as supplied without further purification. These ligands were used to prepare eight ruthenium(II) complexes of mixed bipyridyl/dithiolate/thiourea. The compounds were characterised by elemental analysis and spectroscopic techniques, namely: Fourier transform infrared (FTIR), Nuclear Magnetic Resonance (NMR), ultraviolet-visible and photoluminescence (PL). Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used for the electrochemical studies. Photoluminescence and UV-Vis spectroscopies were used for geometric and photophysical studies of the complexes respectively. FTIR spectra confirmed presence of functional groups in ligands and coordination of these ligands to ruthenium(II) ions to form complexes. The UV-Vis confirmed that the Ru(II) dithiolene complexes exhibited square planar geometries while the Ru(II) thiourea complexes gave octahedral geometries, this was deduced from the transitions assigned to the complexes. All the ruthenium(II) complexes synthesized showed photoluminescence properties that are suitable for light harvesting and application for dye-sensitized solar cells. Cyclic and square wave voltammetry show Ru(II) thiourea complexes have better redox properties when compared to Ru(II) dithiolate complexes which is ascribed to ligand strength field possibly due to contribution from the two bonded NCS groups.
- Full Text:
- Date Issued: 2018
Synthesis, characterization and evaluation of photophysical and electrochemical properties of ruthenium(II) complexes for dye-sensitized solar cells
- Authors: Adjogri, Shadrack John
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/17828 , vital:41363
- Description: Eight series of thirty (30) novel heteroleptic ruthenium(II) complexes were designed, synthesized and spectroscopically characterized, with the following general molecular formulae as [Ru(bdmpmar)(H2dcbpy)(NCS)]+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2+,[Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ where bdmpmar is a tridentate ligand of N,N-bis(3, 5-dimethylpyrazol-1-yl-methyl) aromatic organic compound (such aromatic organic compounds(Ar) are anthranilic acid, 4-methoxy-2-nitroaniline, aniline, toluidine, cyclohexylamine and anisidine), vpdiinp represents a monodentate ligand of 11-(4-vinylphenyl)diindeno[1,2-b:2’,1’-e]pyridine, vpbpp represents a monodentate ligand of 4-(4-vinylphenyl)-2.6-bis(phenyl)pyridine and vptpy represents a tridentate ligand of 4’-(4-vinyl)-2,2’:6’,2’’-terpyridine. Meanwhile, N^ represents any of the monodentate ligands of either vpdiinp or vpbpp and (N^^^) represents any of the monodentate ligands either of vpdiinp or vpbpp or NCS as disclosed in series VIII. The complexes were characterized by conductivity measurement, solubility, melting point, UV-Vis, PL, FTIR (ATR), NMR, Cyclic and square wave voltammetry. Nine chelating ligands, comprising of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand, were used for the synthesis of ruthenium(II) complexes ATR-FTIR spectra of all the ruthenium(II) complexes measured as solid samples, exhibited fine resolution IR bands in region between 3473-3438 cm-1 of carboxylic group in H2dcbpy. The bands in the range 3040-2950 cm-1 were ascribed to C-H bond stretching for the CH3 groups. The coordination of NCS group in the sphere of ruthenium(II) complexes related to series I, IV, VI VII and one compound of series VIII was investigated by ATR-FTIR spectroscopy. Bands in the range of 2116-2106 cm-1 and 777-770 cm-1 are ascribed to the respective N=C and the C=S bond stretching vibration which confirms the N-coordination of the SCN group. For all the complexes, the stretching vibration of Ru-N bonding was between 466 and 411 cm-1 due to coordination of the nitrogen atoms of the ligands to ruthenium central metal atom. The introduction of the two vinyl monodentate ligands (vpdiinp and vpbpp) in the coordination sphere of [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2+, [Ru(bdmpmar) (vpbpp)(H2dcbpy)]2+, [Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, all related to series II, III, IV, V, VI, VII and two compounds of series VIII ruthenium(II) complexes, has been studied using the 1H and 13C NMR spectroscopy techniques. The 1H NMR spectra of series II-VII and the two compounds of series VIII of the ruthenium(II) complexes show multiplets in the aromatic region above 6 ppm due to the presence of either vpdiinp or vpbpp ligand, situated in different magnetic environment. However, no splitting pattern was observed in series I and part of VIII complexes possibly due to the absence vinyl monodentate subunits (vpdiinp and vpbpp) in series I and one of compound in series VIII ruthenium(II) complexes show no signals of complex splitting patterns. Carbon-13 NMR spectra data of series I to VIII ruthenium(II) complexes show most resonance signals range in the aromatic region of (δ 116.54-199.63ppm) corresponding to the molecular formulation of ruthenium(II) complexes incorporating 4,4-dicarboxy-2,2’-bipyridine, bdmpmar, vptpy, vpdiinp or vpbpp and NCS ligands respectively, depending on the intrinsic ligand variations. Carbon-13 NMR spectra data of series I, IV, VI VII and one compound in VIII show resonance peaks within the range 130-135 ppm are ascribed to NCS ligand confirming the presence of N-coordinated thiocyanate. Cyclic voltammograms of series I-IV and VI-VIII complexes display ruthenium-based oxidative peaks and the pyridines ligand-based reductive peaks. The redox behavior of complexes 4-12, 14-16, 18-20, 24-26 and 30 is dominated by the Ru(II)/R(III) redox couple in region (E1/2 between 0.53 and 1.18) and the pyridines ligand-based redox couples in the region between (E1/2 between −0.25 and −1.45). The photophysical property studies of the Ru(II) complexes are determined through the acquisitions of the absorption spectra, which tends to have profound effect on the short circuit current of DSSC. The absorption maxima were tuned by the introduction and variation of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand. From the studies, the results show that series IV, V, VI, VII and VIII complexes of molecular formula [Ru(H2dcbpy)2(N^)(NCS)]2+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2]2+, [Ru(H2dcbpy)(N^)(NCS)3]2+ and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, have higher and multiple local absorption maxima near-IR region than the complexes of series I, II and III of molecular [Ru(bdmpmar)(H2dcbpy)(NCS)]2,+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2,+respectively.
- Full Text:
- Date Issued: 2018
- Authors: Adjogri, Shadrack John
- Date: 2018
- Subjects: Ruthenium Ruthenium compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/17828 , vital:41363
- Description: Eight series of thirty (30) novel heteroleptic ruthenium(II) complexes were designed, synthesized and spectroscopically characterized, with the following general molecular formulae as [Ru(bdmpmar)(H2dcbpy)(NCS)]+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2+,[Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ where bdmpmar is a tridentate ligand of N,N-bis(3, 5-dimethylpyrazol-1-yl-methyl) aromatic organic compound (such aromatic organic compounds(Ar) are anthranilic acid, 4-methoxy-2-nitroaniline, aniline, toluidine, cyclohexylamine and anisidine), vpdiinp represents a monodentate ligand of 11-(4-vinylphenyl)diindeno[1,2-b:2’,1’-e]pyridine, vpbpp represents a monodentate ligand of 4-(4-vinylphenyl)-2.6-bis(phenyl)pyridine and vptpy represents a tridentate ligand of 4’-(4-vinyl)-2,2’:6’,2’’-terpyridine. Meanwhile, N^ represents any of the monodentate ligands of either vpdiinp or vpbpp and (N^^^) represents any of the monodentate ligands either of vpdiinp or vpbpp or NCS as disclosed in series VIII. The complexes were characterized by conductivity measurement, solubility, melting point, UV-Vis, PL, FTIR (ATR), NMR, Cyclic and square wave voltammetry. Nine chelating ligands, comprising of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand, were used for the synthesis of ruthenium(II) complexes ATR-FTIR spectra of all the ruthenium(II) complexes measured as solid samples, exhibited fine resolution IR bands in region between 3473-3438 cm-1 of carboxylic group in H2dcbpy. The bands in the range 3040-2950 cm-1 were ascribed to C-H bond stretching for the CH3 groups. The coordination of NCS group in the sphere of ruthenium(II) complexes related to series I, IV, VI VII and one compound of series VIII was investigated by ATR-FTIR spectroscopy. Bands in the range of 2116-2106 cm-1 and 777-770 cm-1 are ascribed to the respective N=C and the C=S bond stretching vibration which confirms the N-coordination of the SCN group. For all the complexes, the stretching vibration of Ru-N bonding was between 466 and 411 cm-1 due to coordination of the nitrogen atoms of the ligands to ruthenium central metal atom. The introduction of the two vinyl monodentate ligands (vpdiinp and vpbpp) in the coordination sphere of [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2+, [Ru(bdmpmar) (vpbpp)(H2dcbpy)]2+, [Ru(H2dcbpy)2(N^)(NCS)]+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2], [Ru(H2dcbpy)(N^)(NCS)3]– and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, all related to series II, III, IV, V, VI, VII and two compounds of series VIII ruthenium(II) complexes, has been studied using the 1H and 13C NMR spectroscopy techniques. The 1H NMR spectra of series II-VII and the two compounds of series VIII of the ruthenium(II) complexes show multiplets in the aromatic region above 6 ppm due to the presence of either vpdiinp or vpbpp ligand, situated in different magnetic environment. However, no splitting pattern was observed in series I and part of VIII complexes possibly due to the absence vinyl monodentate subunits (vpdiinp and vpbpp) in series I and one of compound in series VIII ruthenium(II) complexes show no signals of complex splitting patterns. Carbon-13 NMR spectra data of series I to VIII ruthenium(II) complexes show most resonance signals range in the aromatic region of (δ 116.54-199.63ppm) corresponding to the molecular formulation of ruthenium(II) complexes incorporating 4,4-dicarboxy-2,2’-bipyridine, bdmpmar, vptpy, vpdiinp or vpbpp and NCS ligands respectively, depending on the intrinsic ligand variations. Carbon-13 NMR spectra data of series I, IV, VI VII and one compound in VIII show resonance peaks within the range 130-135 ppm are ascribed to NCS ligand confirming the presence of N-coordinated thiocyanate. Cyclic voltammograms of series I-IV and VI-VIII complexes display ruthenium-based oxidative peaks and the pyridines ligand-based reductive peaks. The redox behavior of complexes 4-12, 14-16, 18-20, 24-26 and 30 is dominated by the Ru(II)/R(III) redox couple in region (E1/2 between 0.53 and 1.18) and the pyridines ligand-based redox couples in the region between (E1/2 between −0.25 and −1.45). The photophysical property studies of the Ru(II) complexes are determined through the acquisitions of the absorption spectra, which tends to have profound effect on the short circuit current of DSSC. The absorption maxima were tuned by the introduction and variation of six (6) tripodal chelating ligands, two (2) vinyl monodentate ligands and one (1) vinyl tridentate ligand. From the studies, the results show that series IV, V, VI, VII and VIII complexes of molecular formula [Ru(H2dcbpy)2(N^)(NCS)]2+, [Ru(H2dcbpy)2(N^)2]2+, [Ru(H2dcbpy)(N^)2(NCS)2]2+, [Ru(H2dcbpy)(N^)(NCS)3]2+ and [Ru(vptpy)(H2dcbpy)(N^^^)]2+ respectively, have higher and multiple local absorption maxima near-IR region than the complexes of series I, II and III of molecular [Ru(bdmpmar)(H2dcbpy)(NCS)]2,+, [Ru(bdmpmar)(vpdiinp)(H2dcbpy)]2,+, [Ru(bdmpmar)(vpbpp)(H2dcbpy)]2,+respectively.
- Full Text:
- Date Issued: 2018
Synthesis, characterization and photophysical studies of RU(II)bipyridyl-dithiocarbamate complexes as sensitizers for dye sensitized solar cells
- Authors: Fudo, Zintle
- Date: 2018
- Subjects: Dye-sensitized solar cells Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6168 , vital:29498
- Description: The depletion of fossil fuels and the increasing energy demand for energy has led to the search for better and improved technologies with special focus renewable energy, especially solar cells. The first generation solar cells based on silicon are expensive, hence dye sensitized solar cells come in as a better alternative as these solar cells are environmental friendly, they have moderately good conversion efficiency and they are relatively cheap to produce. Dithiocarbamate ligands have been widely used in many research fields, as these are versatile ligands. Coordination of dithiocarbamates with metals such as ruthenium has produced high conversion efficiency and have the ability to extend the MLCT absorptions, and this can further extend their wavelength. In this study five dithiocarbamate sodium salt ligands were prepared and were coded as FL1= Aniline, FL2= p- toluidine, FL3= p- anisidine, FL4=dibenzyl, FL5=diphenyl. These ligands were used to synthesize Ru(II) metal complexes which were formulated as [Ru(FLx)(dcbpy)(NCS)] and [Ru(FLx)2(dcbpy)] where FLx is the dithiocarbamate ligand and dcbpy is 2,2-bipyridine-4,4’-dicarboxylic acid and the complexes were coded as FCx. The synthesized compounds were characterized using techniques such as the melting point, molar conductivity, FT-IR and NMR spectroscopy. For spectroelectrochemical studies of the metal complexes, techniques such as UV-Vis and photoluminescence spectroscopy were carried out. Furthermore, redox properties of the complexes were analyzed using cyclic and square wave voltammetry. The FT-IR displayed all the expected peaks of interest both in the dithiocarbamate ligands and in the metal complexes. The electronic spectra confirmed the successful coordination of ligand to the metal centre, the electronic spectra of the complexes also confirmed the six coordinate octahedral geometry of the complexes. The complexes exhibited some photoluminescence properties that are suitable for dye sensitization. The cyclic voltammogram of the complexes displayed more reduction potentials that could be attributed to the π-conjugation in the ligands incorporated during synthesis. The square wave voltammogram of the complexes is in agreement with the results obtained in cyclic voltammetry.
- Full Text:
- Date Issued: 2018
- Authors: Fudo, Zintle
- Date: 2018
- Subjects: Dye-sensitized solar cells Renewable energy sources
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6168 , vital:29498
- Description: The depletion of fossil fuels and the increasing energy demand for energy has led to the search for better and improved technologies with special focus renewable energy, especially solar cells. The first generation solar cells based on silicon are expensive, hence dye sensitized solar cells come in as a better alternative as these solar cells are environmental friendly, they have moderately good conversion efficiency and they are relatively cheap to produce. Dithiocarbamate ligands have been widely used in many research fields, as these are versatile ligands. Coordination of dithiocarbamates with metals such as ruthenium has produced high conversion efficiency and have the ability to extend the MLCT absorptions, and this can further extend their wavelength. In this study five dithiocarbamate sodium salt ligands were prepared and were coded as FL1= Aniline, FL2= p- toluidine, FL3= p- anisidine, FL4=dibenzyl, FL5=diphenyl. These ligands were used to synthesize Ru(II) metal complexes which were formulated as [Ru(FLx)(dcbpy)(NCS)] and [Ru(FLx)2(dcbpy)] where FLx is the dithiocarbamate ligand and dcbpy is 2,2-bipyridine-4,4’-dicarboxylic acid and the complexes were coded as FCx. The synthesized compounds were characterized using techniques such as the melting point, molar conductivity, FT-IR and NMR spectroscopy. For spectroelectrochemical studies of the metal complexes, techniques such as UV-Vis and photoluminescence spectroscopy were carried out. Furthermore, redox properties of the complexes were analyzed using cyclic and square wave voltammetry. The FT-IR displayed all the expected peaks of interest both in the dithiocarbamate ligands and in the metal complexes. The electronic spectra confirmed the successful coordination of ligand to the metal centre, the electronic spectra of the complexes also confirmed the six coordinate octahedral geometry of the complexes. The complexes exhibited some photoluminescence properties that are suitable for dye sensitization. The cyclic voltammogram of the complexes displayed more reduction potentials that could be attributed to the π-conjugation in the ligands incorporated during synthesis. The square wave voltammogram of the complexes is in agreement with the results obtained in cyclic voltammetry.
- Full Text:
- Date Issued: 2018
Remediation of metal ions in aqueous solution using activated carbon from Zea may stem
- Authors: Matandabuzo, Mzukisi
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11360 , http://hdl.handle.net/10353/d1021328
- Description: Zea mays stem and its activated carbon were prepared through chemical activation method using four different activating reagents (NaOH, H₃PO₄, H₂SO₄, KOH) and were used as adsorbents for the removal of Pb(II), Cu(II), Hg(II) and Cr(III) from aqueous solution. The results shows that activated carbon has high surface area and pore volume compared to the powdered raw Zea mays stem. Prepared activated carbon was characterized using physico-chemical properties such as carbon yield, iodine number, moisture content, percentage adsorption, and analytical instruments such as Fourier transform Infrared spectroscopy (FTIR), atomic absorption spectrometer (AAS), scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDS), powder X-ray Diffraction (pXRD). The adsorption of Pb(II), Cu(II), and Cr(III) ions were pH, contact time, and concentration dependent. Based on the results obtained from the batch experiments, activated carbon prepared from Zea mays stem is not good enough for the removal of Hg(II) from aqueous solution. Adsorption ability was calculated and found to be 66.67% for activated carbon obtained from H₂SO₄, 21.21% for activated carbon obtained from KOH, and 20% for activated carbons obtained from NaOH and H₃PO₄. The pH 5-6 was chosen for all experiments, contact time was 2 hours, and adsorbent dosage was 2 g, initial concentration range from 200, 400, 600, 800, and 1000 ppm at room temperature. The metal ion removal trend was found in the order Pb(II)>Cu(II)>Cr(III)>>Hg(II). The Langmuir model fitted well in most of the cases with > 0.99. Consequently, the adsorption of Pb(II) and Cu(II) followed Langmuir isotherm model while that of Cr(III) best fitted the Freundlich isotherm model. The results indicated that the adsorption process followed two possible mechanisms. (I) Metal ion – adsorbent complex model and (II) Metal ion – ion-exchange adsorbent complex model.
- Full Text:
- Date Issued: 2016
- Authors: Matandabuzo, Mzukisi
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11360 , http://hdl.handle.net/10353/d1021328
- Description: Zea mays stem and its activated carbon were prepared through chemical activation method using four different activating reagents (NaOH, H₃PO₄, H₂SO₄, KOH) and were used as adsorbents for the removal of Pb(II), Cu(II), Hg(II) and Cr(III) from aqueous solution. The results shows that activated carbon has high surface area and pore volume compared to the powdered raw Zea mays stem. Prepared activated carbon was characterized using physico-chemical properties such as carbon yield, iodine number, moisture content, percentage adsorption, and analytical instruments such as Fourier transform Infrared spectroscopy (FTIR), atomic absorption spectrometer (AAS), scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDS), powder X-ray Diffraction (pXRD). The adsorption of Pb(II), Cu(II), and Cr(III) ions were pH, contact time, and concentration dependent. Based on the results obtained from the batch experiments, activated carbon prepared from Zea mays stem is not good enough for the removal of Hg(II) from aqueous solution. Adsorption ability was calculated and found to be 66.67% for activated carbon obtained from H₂SO₄, 21.21% for activated carbon obtained from KOH, and 20% for activated carbons obtained from NaOH and H₃PO₄. The pH 5-6 was chosen for all experiments, contact time was 2 hours, and adsorbent dosage was 2 g, initial concentration range from 200, 400, 600, 800, and 1000 ppm at room temperature. The metal ion removal trend was found in the order Pb(II)>Cu(II)>Cr(III)>>Hg(II). The Langmuir model fitted well in most of the cases with > 0.99. Consequently, the adsorption of Pb(II) and Cu(II) followed Langmuir isotherm model while that of Cr(III) best fitted the Freundlich isotherm model. The results indicated that the adsorption process followed two possible mechanisms. (I) Metal ion – adsorbent complex model and (II) Metal ion – ion-exchange adsorbent complex model.
- Full Text:
- Date Issued: 2016
Synthesis and characterization of group 12 dithiolate complexes as single source precursors for the preparation of hexadecylamine capped metal sulfide nanoparticles and polymer
- Authors: Osuntokun, Jejenija
- Date: 2016
- Subjects: Nanotechnology Nanoparticles Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/14060 , vital:39801
- Description: A series of heteroleptic mixed ligand complexes of some alkyl substituted thiourea, tetramethyl thiuram disulfide and 1-cyano-1-carboethoxy-2,2 ditholate of Zn(II) Cd(II) and Hg(II) have been synthesized by stoichiometry reactions of the ligands with respective metal salts. They have been characterized with analytical and spectroscopic techniques. Seven out of the 19 complexes synthesized are pyridine 2, 2 bipyridine and 1, 10 phenanthroline adducts of dissopropyl parent adducts of Zn(II) and Cd(II) complexes. All the complexes are proposed as four coordinate except the pyridine adducts, 2, 2’ bipyridine and 1, 10 phenanhroline adducts that are proposed as five and six coordinate respectively. All the complexes are solid, air stable and moisture stable for a many months. They are not soluble in common organic solvents but partially soluble in coordinating solvents like DMF and DMSO and due to their insolubility problems all attempts to grow single crystal of the complexes proved abortive. The complexes gave respective metal sulfide on thermal decomposition in TGA and this makes them to be potentially useful single source precursor for the synthesis of metal sulfide. All the complexes were invariably thermolysed in HDA to synthesis a series of HDA-capped ZnS, CdS and HgS nanoparticles. The optical properties of the nanoparticles reveal that they are all blue-shifted from the absorbance edge and this confirms quantum confinement of the nanoparticles. The transmittance electron microscope showed that the nanoparticles are in nanodimension. ZnS nanoparticles from the pyridine adducts gave HDA-capped ZnS nanoparticles with a mixture of hexagonal and cubic phases while the HDA capped CdS from the 2, 2 bipyridine and 1,10 phenanthroline gave anisotropic nanoparticles. The sizes of the CdS from the 1,10 phenanthroline adducts were also found to be biggest while CdS nanoparticles from 2,2 bipyridine adduct were also revealed to be bigger than the particle sizes obtained from the parent complex, (1-cyano-1 carboethoxyethylene-2,2-dithiolato- κ,S’S)-bis(N, N’-diisopropylthiourea -κS)cadmium(II). ZnS and CdS polymer encapsulated nanocomposites were also synthesized using a solution casting method. The polymers employed were; Polymethyl metharcrylate (PMMA), Poly(vinly alcohol) (PVA), and poly vinyl pyrrolidone (PVP). The structural and thermal properties of the pure polymers and the respective nanocomposites were investigated. It was observed that the ZnS/PVA and CdS/PVA were the most thermally stable composites when the thermal stability of the pure polymers were compared relative to the nanocomposites using data obtained from thermal decomposition results of the TGA.
- Full Text:
- Date Issued: 2016
- Authors: Osuntokun, Jejenija
- Date: 2016
- Subjects: Nanotechnology Nanoparticles Semiconductors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/14060 , vital:39801
- Description: A series of heteroleptic mixed ligand complexes of some alkyl substituted thiourea, tetramethyl thiuram disulfide and 1-cyano-1-carboethoxy-2,2 ditholate of Zn(II) Cd(II) and Hg(II) have been synthesized by stoichiometry reactions of the ligands with respective metal salts. They have been characterized with analytical and spectroscopic techniques. Seven out of the 19 complexes synthesized are pyridine 2, 2 bipyridine and 1, 10 phenanthroline adducts of dissopropyl parent adducts of Zn(II) and Cd(II) complexes. All the complexes are proposed as four coordinate except the pyridine adducts, 2, 2’ bipyridine and 1, 10 phenanhroline adducts that are proposed as five and six coordinate respectively. All the complexes are solid, air stable and moisture stable for a many months. They are not soluble in common organic solvents but partially soluble in coordinating solvents like DMF and DMSO and due to their insolubility problems all attempts to grow single crystal of the complexes proved abortive. The complexes gave respective metal sulfide on thermal decomposition in TGA and this makes them to be potentially useful single source precursor for the synthesis of metal sulfide. All the complexes were invariably thermolysed in HDA to synthesis a series of HDA-capped ZnS, CdS and HgS nanoparticles. The optical properties of the nanoparticles reveal that they are all blue-shifted from the absorbance edge and this confirms quantum confinement of the nanoparticles. The transmittance electron microscope showed that the nanoparticles are in nanodimension. ZnS nanoparticles from the pyridine adducts gave HDA-capped ZnS nanoparticles with a mixture of hexagonal and cubic phases while the HDA capped CdS from the 2, 2 bipyridine and 1,10 phenanthroline gave anisotropic nanoparticles. The sizes of the CdS from the 1,10 phenanthroline adducts were also found to be biggest while CdS nanoparticles from 2,2 bipyridine adduct were also revealed to be bigger than the particle sizes obtained from the parent complex, (1-cyano-1 carboethoxyethylene-2,2-dithiolato- κ,S’S)-bis(N, N’-diisopropylthiourea -κS)cadmium(II). ZnS and CdS polymer encapsulated nanocomposites were also synthesized using a solution casting method. The polymers employed were; Polymethyl metharcrylate (PMMA), Poly(vinly alcohol) (PVA), and poly vinyl pyrrolidone (PVP). The structural and thermal properties of the pure polymers and the respective nanocomposites were investigated. It was observed that the ZnS/PVA and CdS/PVA were the most thermally stable composites when the thermal stability of the pure polymers were compared relative to the nanocomposites using data obtained from thermal decomposition results of the TGA.
- Full Text:
- Date Issued: 2016
Synthesis and structural studies of NiS and PdS nanoparticles/nanocomposites from dithiocarbamates single source precursors
- Authors: Nqombolo, Azile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11359 , http://hdl.handle.net/10353/d1021326
- Description: The main aim of this research is to synthesize Ni(II) and Pd(II) dithiocarbamate complexes and use them as single source precursors for the synthesis of NiS and PdS nanoparticles and metal sulphides potato starch nanocomposites. Four dithiocarbamate ligands were synthesized and characterized using elemental analysis and spectroscopic techniques. The ligands were used to prepared homoleptic Ni(II) and Pd(II) complexes of the dithiocarbamate ligands. The metal complexes were characterized with elemental analysis, UV-Vis, FTIR and 1H-NMR spectroscopic techniques. Conductivity measurements indicate that all the complexes are non-electrolytes in solution and results from the electronic spectra studies confirmed the proposed 4-coordinate square planar geometry around the metal ions. The nickel complexes showed d-d transitions around 477 nm while in the palladium complexes, no d-d transitions were observed but the compounds showed strong metal to ligand charge transfer transitions. From the FTIR spectra studies, it can be confirmed that the complexes were successfully synthesised because all peaks of interest were observed at expected regions from the literature. The νC-N was observed around 1469-1495 cm-1, νC=S around 1101-1188 cm-1 and νC-S around 738-1060 cm-1 for both Ni(II) and Pd(II) complexes. νNi-S was observed around 375-543 cm-1 and νPd-S around 529-545 cm-1. The FTIR also confirmed that the dithiocarbamate ligands act as bidentate chelating ligands through the sulfur atoms. The complexes were used as single source precursors and thermolysed in hexadecylamine (HDA) at 220 °C to prepare four HDA-capped nickel sulfide nanoparticles and four palladium sulfide nanoparticles. The as-prepared nanoparticles were studied with optical absorption spectra, photoluminescence, powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The optical studies results showed that NiS have large band gaps that are greater than that of the bulk, therefore they are found to be blue shifted relative to the bulk, which shows that they have small particle size and thus confirming their quantum confinement effect. PL spectra reveal that the emission peaks are red shifted compared to the absorption band edges of the nanoparticles. The XRD patterns confirmed the formation of cubic and rhombohedral phase for NiS nanoparticles and cubic phase for PdS nanoparticles. SEM images of both NiS and PdS show uniform surface morphology at low and high magnification with different shapes. EDS analyses confirmed the presence of Ni, S, and Pd in each of the spectrum indicating that the nanoparticles were successfully synthesized. TEM images showed that the synthesised nanoparticles have uniform and narrow size distribution with no agglomeration. The sizes of the NiS nanoparticles were found to be in the range of 12-38 nm for NiS1, 8-11 nm for NiS2, 9-16 nm for NiS3 and 4-9 nm for NiS4. The TEM images for the as-prepared PdS nanoparticles showed that the average crystallite sizes are 6.94-9.62 nm for PdS1, 8-11 nm for PdS2, 9-16 nm for PdS3 and 4-9 nm for PdS4 respectively. The nanoparticles were used to prepare potato starch nanocomposites and SEM images indicate that the surface morphology of starch polymer nanocomposites compose of potato starch and few particles in between the pores of the matrix, this is due to the small ratio of nanoparticles used.
- Full Text:
- Date Issued: 2016
- Authors: Nqombolo, Azile
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11359 , http://hdl.handle.net/10353/d1021326
- Description: The main aim of this research is to synthesize Ni(II) and Pd(II) dithiocarbamate complexes and use them as single source precursors for the synthesis of NiS and PdS nanoparticles and metal sulphides potato starch nanocomposites. Four dithiocarbamate ligands were synthesized and characterized using elemental analysis and spectroscopic techniques. The ligands were used to prepared homoleptic Ni(II) and Pd(II) complexes of the dithiocarbamate ligands. The metal complexes were characterized with elemental analysis, UV-Vis, FTIR and 1H-NMR spectroscopic techniques. Conductivity measurements indicate that all the complexes are non-electrolytes in solution and results from the electronic spectra studies confirmed the proposed 4-coordinate square planar geometry around the metal ions. The nickel complexes showed d-d transitions around 477 nm while in the palladium complexes, no d-d transitions were observed but the compounds showed strong metal to ligand charge transfer transitions. From the FTIR spectra studies, it can be confirmed that the complexes were successfully synthesised because all peaks of interest were observed at expected regions from the literature. The νC-N was observed around 1469-1495 cm-1, νC=S around 1101-1188 cm-1 and νC-S around 738-1060 cm-1 for both Ni(II) and Pd(II) complexes. νNi-S was observed around 375-543 cm-1 and νPd-S around 529-545 cm-1. The FTIR also confirmed that the dithiocarbamate ligands act as bidentate chelating ligands through the sulfur atoms. The complexes were used as single source precursors and thermolysed in hexadecylamine (HDA) at 220 °C to prepare four HDA-capped nickel sulfide nanoparticles and four palladium sulfide nanoparticles. The as-prepared nanoparticles were studied with optical absorption spectra, photoluminescence, powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The optical studies results showed that NiS have large band gaps that are greater than that of the bulk, therefore they are found to be blue shifted relative to the bulk, which shows that they have small particle size and thus confirming their quantum confinement effect. PL spectra reveal that the emission peaks are red shifted compared to the absorption band edges of the nanoparticles. The XRD patterns confirmed the formation of cubic and rhombohedral phase for NiS nanoparticles and cubic phase for PdS nanoparticles. SEM images of both NiS and PdS show uniform surface morphology at low and high magnification with different shapes. EDS analyses confirmed the presence of Ni, S, and Pd in each of the spectrum indicating that the nanoparticles were successfully synthesized. TEM images showed that the synthesised nanoparticles have uniform and narrow size distribution with no agglomeration. The sizes of the NiS nanoparticles were found to be in the range of 12-38 nm for NiS1, 8-11 nm for NiS2, 9-16 nm for NiS3 and 4-9 nm for NiS4. The TEM images for the as-prepared PdS nanoparticles showed that the average crystallite sizes are 6.94-9.62 nm for PdS1, 8-11 nm for PdS2, 9-16 nm for PdS3 and 4-9 nm for PdS4 respectively. The nanoparticles were used to prepare potato starch nanocomposites and SEM images indicate that the surface morphology of starch polymer nanocomposites compose of potato starch and few particles in between the pores of the matrix, this is due to the small ratio of nanoparticles used.
- Full Text:
- Date Issued: 2016
Ni(II) and Pb(II) dithiocarbamate complexes as precursors for the synthesis of HDA-capped NiS and PbS nanoparticles
- Authors: Chintso, Thobani
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11349 , http://hdl.handle.net/10353/d1020201
- Description: Ni(II) and Pb(II) dithiocarbamate complexes were synthesized and characterized by elemental analysis, UV-Vis, FTIR and TGA and some of the Ni(II) complexes and one Pb(II) were further analyzed by 1H-NMR and 13C-NMR spectroscopy. Generally all the dithiocarbamate ligands are soluble in water while the complexes were soluble mostly in solvents such as chloroform, toluene, DMSO and DCM. Based on the elemental analysis, the dithiocarbamate complexes are formulated as four coordinate (tetrahedral or square planar) compounds. However, the FTIR showed that each of the dithiocarbamate ligands acted as bidentate ligand through two sulfur atoms. The TGA of the most complexes showed one major decomposition step to give respective metal sulfide above 200 oC. In this research project, dithiocarbamate complexes were used as single source precursor for the synthesis of metal sulfide nanoparticles. We studied the optical and structural properties of metal sulfide nanoparticles using UV-Vis, photoluminescence (PL), powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorption spectra of the metal sulfide nanoparticles are blue shifted in respect to bulk material and they also showed broad emission. The XRD of the NiS nanoparticles were indexed to the cubic and rhombohedral phase, with crystallite sizes of 15 - 18 nm. The XRD of PbS nanoparticles were indexed to the face centered cubic and cubic rock salts, with the crystallite sizes 12 - 18 nm. The TEM images of the metal sulfide nanoparticles showed particles with spherical and rectangular shapes with crystallite sizes 4 - 35 nm.
- Full Text:
- Date Issued: 2015
- Authors: Chintso, Thobani
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11349 , http://hdl.handle.net/10353/d1020201
- Description: Ni(II) and Pb(II) dithiocarbamate complexes were synthesized and characterized by elemental analysis, UV-Vis, FTIR and TGA and some of the Ni(II) complexes and one Pb(II) were further analyzed by 1H-NMR and 13C-NMR spectroscopy. Generally all the dithiocarbamate ligands are soluble in water while the complexes were soluble mostly in solvents such as chloroform, toluene, DMSO and DCM. Based on the elemental analysis, the dithiocarbamate complexes are formulated as four coordinate (tetrahedral or square planar) compounds. However, the FTIR showed that each of the dithiocarbamate ligands acted as bidentate ligand through two sulfur atoms. The TGA of the most complexes showed one major decomposition step to give respective metal sulfide above 200 oC. In this research project, dithiocarbamate complexes were used as single source precursor for the synthesis of metal sulfide nanoparticles. We studied the optical and structural properties of metal sulfide nanoparticles using UV-Vis, photoluminescence (PL), powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The absorption spectra of the metal sulfide nanoparticles are blue shifted in respect to bulk material and they also showed broad emission. The XRD of the NiS nanoparticles were indexed to the cubic and rhombohedral phase, with crystallite sizes of 15 - 18 nm. The XRD of PbS nanoparticles were indexed to the face centered cubic and cubic rock salts, with the crystallite sizes 12 - 18 nm. The TEM images of the metal sulfide nanoparticles showed particles with spherical and rectangular shapes with crystallite sizes 4 - 35 nm.
- Full Text:
- Date Issued: 2015
Synthesis and characterization of Ru(II) phenyl-3-indenylidene olefin metathesis type complexes
- Authors: Yalezo, Ntsikelelo
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11351 , http://hdl.handle.net/10353/d1021128
- Description: In this study, a series of Ru(II) phenyl-3-indenylidene complexes with general formula of [RuCl2(NHC)(Ind)(L)] (where L= triphenylphosphine, pyridine and NHC = five different types of N-heterocyclic carbene ligands), have been synthesized and characterized using FT-IR, UV-Vis, elementally analysis and melting/decomposition point. The N,N’-diarylimidazolinium chlorides have been used as N-heterocyclic carbene precursors and were synthesized from their corresponding N,N’-diarylformamidines and further characterized using 1H-NMR, 13C-NMR, FTIR and melting point determination. The infrared spectra of the N,N’-diarylimidazolinium chlorides show a quaternary nature (R2N=C+) with broad vibration band in region 3300-3400 cm-1. The disappearance of this vibration band in the infrared spectra of the ruthenium(II) complexes was used to confirm the coordination of the ligand to the ruthenium ions. The percentage analysis of carbon, hydrogen and nitrogen obtained corresponded with the calculated percentages of these atoms in the complexes with the slight difference of less than 1%. The electronic spectra of the complexes show three distinct absorption bands. The two bands are due to intraligand charge transfers transition assigned to π→π*, n→π* and third band is due to d-d transition, signifying the presence of the metal ion. The synthesized Ru(II) complexes did not show any of melting, however a change in colour was observed signifying the decomposition of the complexes.
- Full Text:
- Date Issued: 2015
- Authors: Yalezo, Ntsikelelo
- Date: 2015
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11351 , http://hdl.handle.net/10353/d1021128
- Description: In this study, a series of Ru(II) phenyl-3-indenylidene complexes with general formula of [RuCl2(NHC)(Ind)(L)] (where L= triphenylphosphine, pyridine and NHC = five different types of N-heterocyclic carbene ligands), have been synthesized and characterized using FT-IR, UV-Vis, elementally analysis and melting/decomposition point. The N,N’-diarylimidazolinium chlorides have been used as N-heterocyclic carbene precursors and were synthesized from their corresponding N,N’-diarylformamidines and further characterized using 1H-NMR, 13C-NMR, FTIR and melting point determination. The infrared spectra of the N,N’-diarylimidazolinium chlorides show a quaternary nature (R2N=C+) with broad vibration band in region 3300-3400 cm-1. The disappearance of this vibration band in the infrared spectra of the ruthenium(II) complexes was used to confirm the coordination of the ligand to the ruthenium ions. The percentage analysis of carbon, hydrogen and nitrogen obtained corresponded with the calculated percentages of these atoms in the complexes with the slight difference of less than 1%. The electronic spectra of the complexes show three distinct absorption bands. The two bands are due to intraligand charge transfers transition assigned to π→π*, n→π* and third band is due to d-d transition, signifying the presence of the metal ion. The synthesized Ru(II) complexes did not show any of melting, however a change in colour was observed signifying the decomposition of the complexes.
- Full Text:
- Date Issued: 2015
Copper dithiocarbamate complexes and copper sulfide nanoparticles : Synthesis, characterization and antifungal studies
- Botha, Nandipha Loveness https://orcid.org/0000-0001-8353-3512
- Authors: Botha, Nandipha Loveness https://orcid.org/0000-0001-8353-3512
- Date: 2015-01
- Subjects: Copper sulfide , Complex compounds , Nanoparticles
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24283 , vital:62598
- Description: Six dithiocarbamate ligands were synthesized from anisidine, aniline, ethyl aniline, butyl amine, morpholine and piperidine and used to synthesize homoleptic copper(II) dithiocarbamate complexes. The ligands and their corresponding complexes were characterized by conductivity measurement, FTIR and UV-Vis spectroscopy. The ligands were further characterized using NMR spectroscopy. The electronic spectra of the complexes showed that the coordination geometries around the Cu2+ ion is four coordinate square planar. FTIR spectroscopic studies indicated that the dithiocarbamate ligands are bidentately coordinated to the copper ion through the sulfur atoms with the C-S stretching frequencies changing from two peaks in the ligands to single sharp peaks in the corresponding metal complexes. The complexes were used as single source precursors to synthesize copper sulfide nanoparticles. All the six complexes were thermolysed at 180 oC to prepare copper sulfide nanoparticles and three of them were further thermolysed at 120 oC to study the effects of temperature on size and shape of the nanoparticles. All the nanoparticles were characterized with UV-Vis, PL, XRD, TEM, SEM and EDX. The optical properties of the as-prepared CuS nanoparticles showed that they are quantum confined with absorption band edges that are blue shifted compared to bulk CuS and all the as-prepared CuS nanoparticles showed narrow emission curves. The XRD diffraction patterns were indexed to the hexagonal covellite CuS crystalline phase with estimated particle sizes of 15.8-23.24 nm. These sizes are significantly different from the values, 3.02-98.94 nm obtained from TEM studies. The TEM images also showed nanoparticles with varied shapes with some agglomerations. SEM micrographs showed that the morphologies of the nanoparticles are mostly smooth surfaces and EDX spectra analyses confirmed the formation of the nanoparticles. Thermolysis of three of the complexes at 120 oC confirmed that temperature do affect the optical and structural properties of the CuS nanoparticles. Only three complexes soluble in DMSO were screened for their antimicrobial activity. Three complexes C1, C4 and C5 were screened against four fungi organisms, namely: Candida rugosa, Candida neoformans, Candida albicans and Trychophyton mucoides. All the compounds were promising as shown by the minimum inhibitory concentrations determined. C5 was the most active compound against all the organisms. They were also screened against four bacteria organisms and they were all active but not as they were against fungi organisms. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-01
- Authors: Botha, Nandipha Loveness https://orcid.org/0000-0001-8353-3512
- Date: 2015-01
- Subjects: Copper sulfide , Complex compounds , Nanoparticles
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24283 , vital:62598
- Description: Six dithiocarbamate ligands were synthesized from anisidine, aniline, ethyl aniline, butyl amine, morpholine and piperidine and used to synthesize homoleptic copper(II) dithiocarbamate complexes. The ligands and their corresponding complexes were characterized by conductivity measurement, FTIR and UV-Vis spectroscopy. The ligands were further characterized using NMR spectroscopy. The electronic spectra of the complexes showed that the coordination geometries around the Cu2+ ion is four coordinate square planar. FTIR spectroscopic studies indicated that the dithiocarbamate ligands are bidentately coordinated to the copper ion through the sulfur atoms with the C-S stretching frequencies changing from two peaks in the ligands to single sharp peaks in the corresponding metal complexes. The complexes were used as single source precursors to synthesize copper sulfide nanoparticles. All the six complexes were thermolysed at 180 oC to prepare copper sulfide nanoparticles and three of them were further thermolysed at 120 oC to study the effects of temperature on size and shape of the nanoparticles. All the nanoparticles were characterized with UV-Vis, PL, XRD, TEM, SEM and EDX. The optical properties of the as-prepared CuS nanoparticles showed that they are quantum confined with absorption band edges that are blue shifted compared to bulk CuS and all the as-prepared CuS nanoparticles showed narrow emission curves. The XRD diffraction patterns were indexed to the hexagonal covellite CuS crystalline phase with estimated particle sizes of 15.8-23.24 nm. These sizes are significantly different from the values, 3.02-98.94 nm obtained from TEM studies. The TEM images also showed nanoparticles with varied shapes with some agglomerations. SEM micrographs showed that the morphologies of the nanoparticles are mostly smooth surfaces and EDX spectra analyses confirmed the formation of the nanoparticles. Thermolysis of three of the complexes at 120 oC confirmed that temperature do affect the optical and structural properties of the CuS nanoparticles. Only three complexes soluble in DMSO were screened for their antimicrobial activity. Three complexes C1, C4 and C5 were screened against four fungi organisms, namely: Candida rugosa, Candida neoformans, Candida albicans and Trychophyton mucoides. All the compounds were promising as shown by the minimum inhibitory concentrations determined. C5 was the most active compound against all the organisms. They were also screened against four bacteria organisms and they were all active but not as they were against fungi organisms. , Thesis (MSc) -- Faculty of Science and Agriculture, 2015
- Full Text:
- Date Issued: 2015-01
Computational studies, synthesis and characterization of ruthenium (ii) anticancer complexes
- Authors: Adeniyi, Adebayo Azeez
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11338 , http://hdl.handle.net/10353/d1015577
- Description: This thesis is centred on the application of Ru-based complexes as a promising alternative to cis-platin in cancer chemotherapy. Cis-platin is known to be the most prescribed chemotherapy which has more than 70% application in cancer cases especially the testicular cancer. An insight is provided in Chapter One and Two into the literatures reports on the application of Ru(II)-based complexes in cancer chemotherapy. In order to address some of the pressing challenges in rational design of Ru-based anticancer complexes, section 3.3 and 3.4 deal with efforts to elucidate the complication of their chemistry and instability while in section 3.5 efforts are made to find solution to the lack of proper knowledge of their targets using different theoretical approaches as presented in Chapter Three. In addition to the theoretical study, this thesis also comprises of the synthesis of the bis-pyrazole derivatives type of ligands and the derivatives of their Ru(II)-based complexes as provided in Chapter Four and Five respectively. Also the computational methods were used to elucidate the structural and spectroscopic properties of the synthesised ligands and their Ru(II)-based complexes. The geometrical and electronic properties are studied in relation to the stability and the reported anticancer activities of Ru(II)-based complexes in section 3.3. In subsection 3.3.1, several quantum properties including the natural energy decomposition analysis (NEDA) and quantum theory of atoms in a molecule (QTAIM) are computed on three models of RAPTA-C complexes using DFT with hybrid functional and basis set with ECP and without ECP. The higher stability of Carbo-RAPTA-C and Oxalo-RAPTA-C over RAPTA-C comes from the lower exchange repulsion and higher polarization contributions to their stability which gives insight into experimental observation. A similar study was carried out in subsection 3.3.2 on half-sandwich Ru(II)-based anticancer complexes with 6-toluene and 6-trifluorotoluene.
- Full Text:
- Date Issued: 2014
- Authors: Adeniyi, Adebayo Azeez
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11338 , http://hdl.handle.net/10353/d1015577
- Description: This thesis is centred on the application of Ru-based complexes as a promising alternative to cis-platin in cancer chemotherapy. Cis-platin is known to be the most prescribed chemotherapy which has more than 70% application in cancer cases especially the testicular cancer. An insight is provided in Chapter One and Two into the literatures reports on the application of Ru(II)-based complexes in cancer chemotherapy. In order to address some of the pressing challenges in rational design of Ru-based anticancer complexes, section 3.3 and 3.4 deal with efforts to elucidate the complication of their chemistry and instability while in section 3.5 efforts are made to find solution to the lack of proper knowledge of their targets using different theoretical approaches as presented in Chapter Three. In addition to the theoretical study, this thesis also comprises of the synthesis of the bis-pyrazole derivatives type of ligands and the derivatives of their Ru(II)-based complexes as provided in Chapter Four and Five respectively. Also the computational methods were used to elucidate the structural and spectroscopic properties of the synthesised ligands and their Ru(II)-based complexes. The geometrical and electronic properties are studied in relation to the stability and the reported anticancer activities of Ru(II)-based complexes in section 3.3. In subsection 3.3.1, several quantum properties including the natural energy decomposition analysis (NEDA) and quantum theory of atoms in a molecule (QTAIM) are computed on three models of RAPTA-C complexes using DFT with hybrid functional and basis set with ECP and without ECP. The higher stability of Carbo-RAPTA-C and Oxalo-RAPTA-C over RAPTA-C comes from the lower exchange repulsion and higher polarization contributions to their stability which gives insight into experimental observation. A similar study was carried out in subsection 3.3.2 on half-sandwich Ru(II)-based anticancer complexes with 6-toluene and 6-trifluorotoluene.
- Full Text:
- Date Issued: 2014
Structural, optical and electrical characterization of nano-sized c-tio2 quamtum dots synthesized by spray pyrolysis
- Authors: Taziwa, Raymond Tichaona
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11342 , http://hdl.handle.net/10353/d1016089
- Description: In the 21st century, scientific communities face challenges and opportunities concerning future development, where innovations must be a key driver over the past, evolution of African societies were based on incomplete models, only taking into account economical growth and not paying attention to environmental deterioration as a consequence of anthropogenic activity and environmental pollution. We have to learn from our past mistakes in order not to repeat them. Education and research of today as the embryonic stages of the development models of tomorrow should be directed toward a sustainable mentality. In this sense, solar energy technologies have emerged as key instruments for minimizing environmental impact as well as reducing economic cost in the field of renewable energies. Titanium dioxide is a fascinating low cost material exhibiting unique properties of stability and photo catalytic activities, leading to clean technologies in water purification and energy conversion of sunlight. However, conventional techniques (high temperature, high vacuum, high pressures) of processing titanium dioxide are a technological limitation due to excessive energy consumption. This poses a handicap for practical applications in areas such as preparation of hybrid organic/Titanium dioxide materials or devices on thermo flexible substrates such as plastic material. It is for this reason that the investigation presented in this Ph.D thesis deals with the development of spray pyrolysis techniques for preparation of carbon doped titanium dioxide nano powders for solar cell applications. This thesis is therefore structured as follows: Chapter 1 gives a general overview of the work done in this thesis. This work relies greatly on the excellent structural optical and electrical properties of TiO2 thin films, as well as its chemical resistance and insulating properties. A summary of the physical, optical, electrical and chemical properties reported in the literature, with an emphasis on those relevant to solar cell fabrication, is presented in Chapter 2. Chapter 3 gives a concise literature review on models governing droplet formation in ultrasonic spray pyrolysis (USP) techniques, the limitations of these models have been exposed and a new relation model for estimating the final particle size given a set of initial reaction conditions has been proposed. The presently derived model is quite advantageous in that it does not require the investigator to look up values of surface tension and density for every precursor solution. Chapter 4 presents in detail the designed and constructed spray pyrolysis system capable of realizing desired nano structures for photovoltaic applications. The first system employed an ultrasonic atomization spray nozzle in order to create an aerosol of the TiO2 precursor. The reasons for choosing ultrasonic spray deposition (USP) and the TiO2 precursors, titanium iso propoxide and titanium tetra butoxide are discussed. Chapter 5 outlines experimental methodologies used in synthesis and characterization of the materials used in this study. Chapter 5 further provides experimental methodologies used in fabrication of a new type of photo electrochemical solar cells (PECs). Chapter 6 reveals the opto-electrical results of PECs solar cells fabricated. There are numerous properties that are affected by the size but emphasis will be placed on nano-size and confinement effects. Chapter 7 presents a confirmation of the phonon confinement effects in C-TiO2 QDs for the first time. In addition Chapter 7 also presents a new phonon confinement model. Chapter 8 reveals the optical, structural and electronic properties of C-TiO2 QDs synthesized by USP and PSP techniques. In addition the electrical properties of C-TiO2 QDs PEC solar cells devices are reported in Chapter 8. Concluding remarks, with potential future research projects are presented in Chapter 9. Through these 9 chapters, all research questions have been answered satisfactorily and all objectives met. Most of the work contained in this thesis has been subjected to external reviews through publication of these peer reviewed articles.
- Full Text:
- Date Issued: 2014
- Authors: Taziwa, Raymond Tichaona
- Date: 2014
- Language: English
- Type: Thesis , Doctoral , PhD (Chemistry)
- Identifier: vital:11342 , http://hdl.handle.net/10353/d1016089
- Description: In the 21st century, scientific communities face challenges and opportunities concerning future development, where innovations must be a key driver over the past, evolution of African societies were based on incomplete models, only taking into account economical growth and not paying attention to environmental deterioration as a consequence of anthropogenic activity and environmental pollution. We have to learn from our past mistakes in order not to repeat them. Education and research of today as the embryonic stages of the development models of tomorrow should be directed toward a sustainable mentality. In this sense, solar energy technologies have emerged as key instruments for minimizing environmental impact as well as reducing economic cost in the field of renewable energies. Titanium dioxide is a fascinating low cost material exhibiting unique properties of stability and photo catalytic activities, leading to clean technologies in water purification and energy conversion of sunlight. However, conventional techniques (high temperature, high vacuum, high pressures) of processing titanium dioxide are a technological limitation due to excessive energy consumption. This poses a handicap for practical applications in areas such as preparation of hybrid organic/Titanium dioxide materials or devices on thermo flexible substrates such as plastic material. It is for this reason that the investigation presented in this Ph.D thesis deals with the development of spray pyrolysis techniques for preparation of carbon doped titanium dioxide nano powders for solar cell applications. This thesis is therefore structured as follows: Chapter 1 gives a general overview of the work done in this thesis. This work relies greatly on the excellent structural optical and electrical properties of TiO2 thin films, as well as its chemical resistance and insulating properties. A summary of the physical, optical, electrical and chemical properties reported in the literature, with an emphasis on those relevant to solar cell fabrication, is presented in Chapter 2. Chapter 3 gives a concise literature review on models governing droplet formation in ultrasonic spray pyrolysis (USP) techniques, the limitations of these models have been exposed and a new relation model for estimating the final particle size given a set of initial reaction conditions has been proposed. The presently derived model is quite advantageous in that it does not require the investigator to look up values of surface tension and density for every precursor solution. Chapter 4 presents in detail the designed and constructed spray pyrolysis system capable of realizing desired nano structures for photovoltaic applications. The first system employed an ultrasonic atomization spray nozzle in order to create an aerosol of the TiO2 precursor. The reasons for choosing ultrasonic spray deposition (USP) and the TiO2 precursors, titanium iso propoxide and titanium tetra butoxide are discussed. Chapter 5 outlines experimental methodologies used in synthesis and characterization of the materials used in this study. Chapter 5 further provides experimental methodologies used in fabrication of a new type of photo electrochemical solar cells (PECs). Chapter 6 reveals the opto-electrical results of PECs solar cells fabricated. There are numerous properties that are affected by the size but emphasis will be placed on nano-size and confinement effects. Chapter 7 presents a confirmation of the phonon confinement effects in C-TiO2 QDs for the first time. In addition Chapter 7 also presents a new phonon confinement model. Chapter 8 reveals the optical, structural and electronic properties of C-TiO2 QDs synthesized by USP and PSP techniques. In addition the electrical properties of C-TiO2 QDs PEC solar cells devices are reported in Chapter 8. Concluding remarks, with potential future research projects are presented in Chapter 9. Through these 9 chapters, all research questions have been answered satisfactorily and all objectives met. Most of the work contained in this thesis has been subjected to external reviews through publication of these peer reviewed articles.
- Full Text:
- Date Issued: 2014
Synthesis and characterization of metal sulfide nanoparticles/polymer nanocomposites
- Authors: Mbese, Johannes Zanoxolo
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11344 , http://hdl.handle.net/10353/d1016190
- Description: The focus of this project was to synthesize and characterize metal sulfide nanoparticles /polymer nanocomposites. The work involved the synthesis of dithiocarbamato ligands and complexes derived from aniline. Zn(II), Cd(II) and Hg(II) dithiocarbamato complexes were used as single-molecule precursors for the synthesis of the ZnS, CdS and HgS nanoparticles and their optical and structural properties studied. The other focus of this work was to synthesize a combined functionality metal sulfide nanoparticles/polymer nanocomposites by dispersing as-synthesized ZnS, CdS and HgS nanoparticles in polymethyl methacrylate (PMMA) matrix. The characterization of the ligands, complexes, nanoparticles and nanocomposites were investigated using relevant instrumental tools like UV-Vis, photoluminescence (PL), Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersion X-ray (EDX), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
- Full Text:
- Date Issued: 2013
- Authors: Mbese, Johannes Zanoxolo
- Date: 2013
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11344 , http://hdl.handle.net/10353/d1016190
- Description: The focus of this project was to synthesize and characterize metal sulfide nanoparticles /polymer nanocomposites. The work involved the synthesis of dithiocarbamato ligands and complexes derived from aniline. Zn(II), Cd(II) and Hg(II) dithiocarbamato complexes were used as single-molecule precursors for the synthesis of the ZnS, CdS and HgS nanoparticles and their optical and structural properties studied. The other focus of this work was to synthesize a combined functionality metal sulfide nanoparticles/polymer nanocomposites by dispersing as-synthesized ZnS, CdS and HgS nanoparticles in polymethyl methacrylate (PMMA) matrix. The characterization of the ligands, complexes, nanoparticles and nanocomposites were investigated using relevant instrumental tools like UV-Vis, photoluminescence (PL), Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersion X-ray (EDX), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
- Full Text:
- Date Issued: 2013
The characterization and electrochemistry of dye-sensitized solar cells
- Authors: Caga, Noloyiso
- Date: 2013
- Subjects: Dye-sensitized solar cells , Acetonitrile , Electrochemistry , Spectrum analysis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11341 , http://hdl.handle.net/10353/d1016069 , Dye-sensitized solar cells , Acetonitrile , Electrochemistry , Spectrum analysis
- Description: In this study a presentation of the technology behind dye-sensitized solar cells, their design as well as the role of the different parts of the cell. The characterization of the cell is divided into four sections namely: the characterization of the paste required to make the TiO2 film and its optical properties using SEM-EDX and XRD analytical techniques; Analysis of the various absorptions of three Ru-based dyes using UV-Vis spectroscopy, Photoluminescence and Fourier Transform Infra-Red spectroscopy; the characterization and the analyses of the entire cell using Electrochemical Impedance Spectroscopy. The nine cells were prepared by examining RuL2(CN)2 , RuL2(NCS)2 or N3 dye and RuL2(NCS)2 TBA+ or N719 dye. [L = 2,2'-bipyridyl-4,4'-dicarboxylic acid ;TBA = tetra-butyl ammonium] were combined with three electrolytes namely: Z–150 , AN–50 and PN–50. The Iodolyte PN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called propionitrile (PN). The Iodolyte AN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called acetonitrile (AN). The Iodolyte Z–150 is an iodide based low viscosity electrolyte with 150 mM of tri-iodide dissolved in a solvent called 3-methoxypropionitrile (MPN) and with additives such an ionic liquid, malkylbenziimidazole and guanidine thiocyanate. A solar simulator was utilized with which the standard solar irradiation can be created in laboratory conditions. The fill factors as well as overall performance efficiencies of the these cells are quite low < 1.0%,.
- Full Text:
- Date Issued: 2013
- Authors: Caga, Noloyiso
- Date: 2013
- Subjects: Dye-sensitized solar cells , Acetonitrile , Electrochemistry , Spectrum analysis
- Language: English
- Type: Thesis , Masters , MSc (Chemistry)
- Identifier: vital:11341 , http://hdl.handle.net/10353/d1016069 , Dye-sensitized solar cells , Acetonitrile , Electrochemistry , Spectrum analysis
- Description: In this study a presentation of the technology behind dye-sensitized solar cells, their design as well as the role of the different parts of the cell. The characterization of the cell is divided into four sections namely: the characterization of the paste required to make the TiO2 film and its optical properties using SEM-EDX and XRD analytical techniques; Analysis of the various absorptions of three Ru-based dyes using UV-Vis spectroscopy, Photoluminescence and Fourier Transform Infra-Red spectroscopy; the characterization and the analyses of the entire cell using Electrochemical Impedance Spectroscopy. The nine cells were prepared by examining RuL2(CN)2 , RuL2(NCS)2 or N3 dye and RuL2(NCS)2 TBA+ or N719 dye. [L = 2,2'-bipyridyl-4,4'-dicarboxylic acid ;TBA = tetra-butyl ammonium] were combined with three electrolytes namely: Z–150 , AN–50 and PN–50. The Iodolyte PN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called propionitrile (PN). The Iodolyte AN–50 is an iodide based low viscosity electrolyte with 50 mM of tri-iodide dissolved in a solvent called acetonitrile (AN). The Iodolyte Z–150 is an iodide based low viscosity electrolyte with 150 mM of tri-iodide dissolved in a solvent called 3-methoxypropionitrile (MPN) and with additives such an ionic liquid, malkylbenziimidazole and guanidine thiocyanate. A solar simulator was utilized with which the standard solar irradiation can be created in laboratory conditions. The fill factors as well as overall performance efficiencies of the these cells are quite low < 1.0%,.
- Full Text:
- Date Issued: 2013
Group 12 metal chalcogenides as single source molecular precursors for the preparation of metal sulfide nanoparticles
- Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Authors: Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Date: 2013-01
- Subjects: Ligands , Chalcogenides , Chemistry, Inorganic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27428 , vital:67295
- Description: Twelve Zn(II), Cd(II) and Hg(II) complexes of mixed ligands: alkyl thiourea, 1-ethoxylcarbonyl-1-cyanoethylene-2,2-dithiolate and tetramethylthiuram disulfide were synthesized by the reaction between the ligands and the respective metal salts. The compounds were characterized by elemental analysis, infrared (IR), 1H- and 13C-NMR spectroscopy. Four coordinate geometries were proposed for the compounds based on elemental and spectroscopic analyses. The metal complexes were at best sparingly soluble in polar coordinating solvents such as DMSO and DMF and insoluble in most organic solvents. This makes it practically impossible to grow single crystals suitable for X-ray crystallographic analysis and also resulted in extremely poor 13C-NMR spectra for some of the complexes. Thermogravimetric analysis on some of the complexes showed that they decomposed to their respective metal sulfides and thus suitable as single molecular precursors for the preparation of metal sulfide nanoparticles. Nine of the complexes with good yield were thermolysed and used as single source precursors to synthesized hexadexylamine capped metal sulfide nanoparticles. The optical and structural properties of the nanoparticles were studied using UV-Visible, photoluminescence (PL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX). The absorption and emission spectra of the nanoparticles show quantum confinement. The SEM showed the morphology of the particles as nearly spherical, the EDX spectra revealed peaks corresponding to respective metal and sulfur with traces of contaminants being phosphorus from tri-n-octylphosphine (TOP). , Thesis (MSc) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-01
- Authors: Osuntokun, Jejenija https://orcid.org/0000-0003-0886-2732
- Date: 2013-01
- Subjects: Ligands , Chalcogenides , Chemistry, Inorganic
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/27428 , vital:67295
- Description: Twelve Zn(II), Cd(II) and Hg(II) complexes of mixed ligands: alkyl thiourea, 1-ethoxylcarbonyl-1-cyanoethylene-2,2-dithiolate and tetramethylthiuram disulfide were synthesized by the reaction between the ligands and the respective metal salts. The compounds were characterized by elemental analysis, infrared (IR), 1H- and 13C-NMR spectroscopy. Four coordinate geometries were proposed for the compounds based on elemental and spectroscopic analyses. The metal complexes were at best sparingly soluble in polar coordinating solvents such as DMSO and DMF and insoluble in most organic solvents. This makes it practically impossible to grow single crystals suitable for X-ray crystallographic analysis and also resulted in extremely poor 13C-NMR spectra for some of the complexes. Thermogravimetric analysis on some of the complexes showed that they decomposed to their respective metal sulfides and thus suitable as single molecular precursors for the preparation of metal sulfide nanoparticles. Nine of the complexes with good yield were thermolysed and used as single source precursors to synthesized hexadexylamine capped metal sulfide nanoparticles. The optical and structural properties of the nanoparticles were studied using UV-Visible, photoluminescence (PL), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive spectroscopy (EDX). The absorption and emission spectra of the nanoparticles show quantum confinement. The SEM showed the morphology of the particles as nearly spherical, the EDX spectra revealed peaks corresponding to respective metal and sulfur with traces of contaminants being phosphorus from tri-n-octylphosphine (TOP). , Thesis (MSc) -- Faculty of Science and Agriculture, 2013
- Full Text:
- Date Issued: 2013-01
Synthesis, characterization and antibacterial studies of metal complexes of substituted thiourea
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
- Authors: Zulu, Happy Nonkululeko
- Date: 2012-03
- Subjects: Complex compounds , Halides , Ligands
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/24327 , vital:62636
- Description: Eighteen complexes Co(II), Cu(II), Zn(II), and Fe(III) with phenylthiourea, diethylthiourea, disopropylthiourea and dimethylthiourea were synthesized and characterized by elemental analysis, UV-Vis, FTIR, conductivity measurements. The complexes were formulated as either four coordinate for the metal(II) or six coordinate for Fe(III). The proposed formulations are consistent with the spectroscopic data for the complexes. The single crystal X-ray structure of the Zn(II) complex of phenylthiourea, Co(II) complex of diethylthiourea and Zn(II) complex of diisopropylthiourea are also reported. The X-ray crystal structures for these complexes revealed distorted tetrahedral geometry around the metal ions showed that the metal ions are coordinated to two molecules of the substituted thiourea through the sulphur atom and two either acetates or chlorides ions complete the four-coordinate geometry. The in vitro antibacterial activity of the complexes was studied against six bacterial strains using disc diffusion and broth micro-dilution methods. The complexes showed selective antibacterial activity. , Thesis (MSc) -- Faculty of Science and Agriculture, 2012
- Full Text:
- Date Issued: 2012-03
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24365 , vital:62645
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to- electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
Functionalized Ru(II) polypyridines and phthalocyanines: Potential dyes for dye-sensitized solar cells(DSSCs)
- Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
- Authors: Adeloye, Adewale Olufunsho https://orcid.org/0000-0003-1736-5738
- Date: 2011-01
- Subjects: Phthalocyanines , Dye-sensitized solar cells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/24343 , vital:62638
- Description: This study describes the design, synthesis, characterization and preliminary investigation of the solar-to-electrical energy conversion efficiency of ruthenium(II) functionalized polypyridine and phthalocyanine complexes with extended π-conjugation. Polypyridinyl functionalized with anthracene, 2,3-dimethylacrylic acid and 1-methoxy-1-buten-3-yne were synthesized and characterized by infrared, UV-Vis, photoluminescence, 1H and 13C NMR and elemental analysis. The functionalized polypyridine molecules were used to synthesize various ruthenium(II) homoleptic/heteroleptic and/or heteronuclear complexes and their photophysical and electrochemical properties evaluated. The preliminary results of the solar-to-electrical conversion efficiencies of some synthesized Ru(II) polypyridyl complexes were presented in chapter 5. It was found out as expected that the ruthenium(II) polypyridine complexes containing either heteronuclear polypyridine ligands or their thiocyanate analogues of the types [Ru(L1)2L2(PF6)2], [RuL1(L2)2(PF6)2] and [RuL1L2(NCS)2], showed better photophysical properties (red-shifted metal-to-ligand charge-transfer (MLCT) transitions concomitant with enhanced molar extinction coefficients), luminescence and interesting electrochemical redox properties than those containing homonuclear ligand types [Ru(L1)3(PF6)2]. The ruthenium(II) anthracenyl functionalized phthalocyanine complexes which were obtained by electrophilic aromatic substitution reactions in the peripheral positions gave good solubility properties in various organic solvents and also showed interesting near infrared absorption and electroredox characteristics. Cyclic and square wave voltammetries of these complexes revealed major redox processes and the numbers of electron(s) transfer were determined by chronocoulometry. It was established that a mono- and/or multi-electronic transfer reactions can occur in the various ruthenium(II) complexes. The photophysical properties of some complexes showed them to be better and promising candidates in the design of chemosensors, organic light emitting diodes (OLEDs) and as photosensitizers, while their redox-active natures make them potential mediators in electron-transfer for various photochemical processes. However, due to low surface concentration and/or adsorption of some tested complexes on TiO2 semiconductor nanocrystalline particle, low currents were generated and the highest solar-to-electrical conversion efficiency recorded in this study was 0.10 percent. , Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Full Text:
- Date Issued: 2011-01
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