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LaOCl:Bi3+ phosphor powders were successfully prepared via the solid-state reaction method and compared to LaOBr:Bi3+. Photoluminescence measurements revealed that the phosphors displayed ultraviolet emission around 344 nm for LaOCl:Bi and 358 nm for LaOBr:Bi under excitations of 266 nm and 273 nm, respectively. The optimum Bi doping concentration and annealing temperature were established as 0.7 mol% and 900 °C for both hosts. The scanning electron microscopy data showed that the particles are randomly oriented flat thin plates with diameters close to or larger than 100 nm. The chemical composition of the phosphor was studied by using energy dispersive X-ray spectroscopy, while diffuse reflectance spectroscopy was employed to study the absorption. The ultraviolet emission peaks were assigned to the 3P1 → 1S0 transition of the Bi3+ ions, while additional relatively weak emissions in the visible range were attributed to Bi clustering. LaOCl:Bi was found to undergo a little degradation while exposed to the atmosphere for several months, while LaOBr:Bi was significantly less stable. The LaOBr:Bi phosphor was also found to degrade rapidly under 254 nm ultraviolet excitation, while LaOCl:Bi did not degrade under the same conditions. X-ray photoelectron spectroscopy measurements indicated that similar surface changes occurred for both samples during UV-exposure, suggesting that the cause of degradation is not primarily related to surface changes, but may be due to the greater probability of forming non-radiative defects in the bulk of LaOBr having the smaller bandgap. Luminescence properties of bismuth (Bi) doped lanthanum oxyfluoride (LaOF) were investigated experimentally with samples prepared via the solid-state reaction method using ammonium fluoride, lanthanum oxide and bismuth oxide as precursors. Energy dispersive X-ray spectroscopy data showed that the samples were not completely stoichiometric and that the F/O ratio decreased with increasing synthesis temperature, African Laser Centre (ALC)

The main aim of this project is to study the luminescence properties of Gd2O3:Bi3+ co-doped Ln3+(Yb3+ and Er3+) phosphor powder and thin films to improve the energy conversion efficiency of photovoltaics (PV) by using the solar spectral conversion principle for use in solar cell applications. The luminescence properties of Gd2O3:Bi3+ single doped was investigated. The effect of different annealing temperatures and different concentrations of Bi3+ on the luminescence properties were investigated. The combustion method was used to synthesize all the powders samples. The optimum Bi3+ doping concentration was found to be x = 0.003 and the optimum annealing temperature was found to be 1000 °C (2 h). An increase in the average crystallite size with increasing annealing temperature and a decrease with an increase in Bi3+ doping concentration were obtained. The morphological studies showed small particles (less than 100 nm) that started to agglomerate to form bigger particles with sizes up to close to 400 nm during thermal treatment at higher temperature. Diffuse reflectance measurements of the pure host material showed absorption bands at 250, 275 and 315 nm that were attributed to the 4f-4f transitions of the Gd3+ ions. The bandgap was found to be influenced by the annealing temperature, which was determined to be 5.09 eV for the as prepared Gd2O3 host and then increased with increasing temperature. For all the doped samples the strong band at about 227 nm was observed corresponding to inter-band transitions of the Gd2O3 matrix in addition to three bands located around 260, 335, and 375 nm corresponding to the excitation transitions of Bi3+ ions into the different sites (C2 and S6). The luminescent properties of Gd2-xO3:Bix phosphor powder were investigated and the fluorescence spectra show that the luminescence was stimulated by the emission from two types of centers which exhibited efficient blue-green emission bands. The excitation and emissions that correspond to the, National Research Foundation (NRF), South African Research Chairs Initiative (SARChI), University of the Free State (UFS)

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The molecular design is contrary to that of other semiconductor-insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymerization of polar polythiophenes and urethane segments results in a ductile material that can be used as a free-standing solid. The copolymer displays a storage modulus of 25 MPa at room temperature, elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chemical doping and electrochemical oxidation reveal that the introduction of urethane segments does not unduly reduce the hole charge-carrier mobility and ability to take up charge. Further, stable operation is observed when the copolymer is used as the active layer of organic electrochemical transistors., QC 20210409

The main aim of this project was to investigate the synthesis and characterization of bismuth-doped strontium oxide powder and thin films. Firstly the luminescent properties and stability under electron beam irradiation of the SrO:Bi3+ phosphor powder were investigated and secondly the luminescent properties of SrO:Bi3+ thin films prepared by different techniques were studied. The luminescence from Bi3+ ions can be useful in obtaining blue to red emitting phosphors by using different hosts, when excited by ultraviolet (UV) light due to efficient conversion to longer wavelengths. The energy levels of Bi3+ ions are host dependent. Bi3+ is a low cost activator, which provide strong absorption of UV light and can be efficiently converted to longer wavelengths. These emissions are related to the 3P1 – 1S0 or 1P1 – 1S0 transitions of Bi3+ ions, which are strongly dependent on the host. The alkali-earth oxide phosphors offer a potential low-cost alternative to lanthanide-based blue phosphors. Bi3+ doped strontium oxide (SrO:Bi) phosphor powders were synthesized by the sol-gel combustion method using metal nitrates as precursors and citric acid as fuel. A wide range of temperatures (800 - 1200 °C) and concentrations of Bi3+ (0.05 - 0.7 mol%) were used to determine the optimum sample annealing temperature and Bi3+ concentration. The optimum doping concentration, for a fixed annealing temperature of 1200 °C (2 h), was found to be 0.2 mol% and a further increase in the Bi3+concentration resulted in concentration quenching. Samples of this concentration were annealed at various temperatures and the optimum annealing temperature was found to be 1100 °C (2 h). The X-ray diffraction patterns (XRD) corresponded with the well-known face-centered cubic structure of SrO after high-temperature annealing that ranged between 1100 °C up to 1200 °C. Below 1100 °C strontium hydroxide peaks were also present. Williamson-Hall plots showed that the crystallite size was in the range of ~180 nm., South African Research Chairs Initiative (SARChI), African Laser Center (ALC), University of the Free State

Different concentrations of bismuth doped lanthanum oxide (La2-xO3:Bix) phosphor powder (x = 0.001, 0.002, 0.003, 0.004, 0.006, 0.008 and 0.01) were synthesised by means of the sol-gel combustion method at 250 °C using citric acid as the fuel. The product was annealed at different temperatures and the luminescence properties were investigated. The maximum photoluminescence (PL) emission was obtained for the sample which was doped with x = 0.002 and annealed at 1200 °C in air. The X-ray diffraction (XRD) analysis confirmed that all samples crystallized in the La2O3 hexagonal phase. The scanning electron microscopy (SEM) data showed that the grain size increased with increasing annealing temperature and the shape of the grains changed from rectangular to more round, but faceted, after annealing at 1200 °C in air. Energy dispersive X-ray spectroscopy (EDS) confirmed the chemical composition, while diffuse reflectance spectroscopy was used to study the absorption of the La2-xO3:Bix samples. All the samples were absorbing in the ultraviolet range between 220 to 320 nm. The band gap of the La2O3 pure host sample was obtained from the reflectance data as 5.1 eV. Excitation at a wavelength of 308 nm resulted in a single broad blue luminescence emission band centred at 462 nm. The excitation and emission bands were attributed to transitions between the 1S0 ground state and the 3P1 excited state of Bi3+ ions, with a Stokes shift of 1.35 eV. It was found that the samples no longer exhibited PL after storage of several weeks. Further XRD measurements revealed that the La2O3 had changed to La(OH)3. This is consistent with reports that La2O3 can absorb moisture from the air and transform to La(OH)3, which was observed to occur completely in about a week. Unlike for La2O3:Eu and La2O3:Ho phosphors for which the transformation reduced the luminescence, but did not quench it completely, the luminescence of the degraded La2O3:Bi was negligible so that simply the presence of luminesce, African Laser Centre (ALC)

Eu3+ doped ZnO thin films and ZnO nanorods were successfully prepared by using different techniques. Successful incorporation of Eu3+ ions in the ZnO matrix and preferred orientation along the c-axis for the films and the nanorods were achieved. The structure, morphology, luminescence and stability of the samples under electron beam irradiation were investigated. Firstly: Low Eu3+ concentration (0.4, 0.6, 0.8, and 1 mol%) doped ZnO thin films were successfully prepared using the spin coating technique. The preferred orientation of the films was reduced with increasing Eu3+ content. The average particle sizes and the optical band gap of the films decreased with increasing Eu3+ concentration. The films were excited at 325 nm and 464 nm using a xenon lamp. Upon excitation at 325 nm, the films exhibited band to band emission at ~378 nm and a broad deep level emission due to defects, with a small peak associated with characteristic Eu3+ emission at 614 nm that protruded from the broad band deep level emission. Upon excitation at 464 nm the characteristic Eu3+ emission features were observed and their intensity increased with increasing Eu3+ content until 0.6 mol% of Eu3+ and was then quenched. Multipole-multipole interaction, defects created due to the differences in ionic radii and charge states of Eu3+ and Zn2+ were found to contribute to luminescence quenching. Judd-Ofelt intensity parameters and asymmetry ratio analysis revealed the dependence of the Eu3+ emission intensity on the local environment around the Eu3+ ions in the host. Secondly: ZnO thin films doped with higher Eu3+ concentration up to 4 mol% were also successfully prepared using a sol-gel spin coating technique. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Zn atoms in their doubly ionized state (Zn2+), while Eu atoms were found to be present in their divalent (Eu2+) and trivalent (Eu3+) states. Excitation spectra showed a broad band near 288 nm which was attributed to the charge tran, African Laser Centre (ALC), National Laser Centre (NLC)

Door omvangrijke graafactiviteiten vormt een aantal invasieve uitheemse rivierkreeftensoorten risico’s voor de waterveiligheid, oeverstabiliteit en sedimenthuishouding. Vanwege snelle en wijde verspreiding wordt uitroeiing van de uitheemse rivierkreeftensoorten niet meer haalbaar geacht. Het aanleggen van natuurlijke oevers zou een kansrijk handelingsperspectief kunnen zijn om de draagkracht van het ecosysteem voor uitheemse rivierkreeften duurzaam te verlagen. Dit onderzoek verschaft inzicht in de relatie tussen verschillende typen oevers en het voorkomen van rivierkreeftenholen. De resultaten tonen dat in natuurvriendelijke oevers minder holen van uitheemse rivierkreeften aanwezig zijn dan in onnatuurlijke of semi-natuurlijke oevers.

The aim of this complementary research is to understand experiences of ethnicity, whiteness and sexuality in the lives of people who identify as lesbian and gay in Berlin. The research question of this thesis is: “How is ethnicity, and specifically whiteness, constructed by people who identify as lesbian and gay, and how is this related to experiences of in- and exclusion in Berlin lesbian and gay communities”. Based on three months of extensive anthropological fieldwork in Berlin this thesis focuses on the following topics in order to answer the research question: 1) ‘Differentiating tactics related to in and exclusion; 2) ‘Racialized (and gendered) ethnicities and whiteness’; 3) ‘Racialized sexuality and sexualized racism’. This thesis argues that ethnicity and therefore whiteness as well, is constructed through identifying the Other as ‘ethnic’ and the Self implicitly as white. The categories ‘us’ and ‘them’ gain meaning through intersections of ethnicity, gender and sexuality. The us-them-categorization is inflicted with social hierarchies, associating ‘us’ with social norms: masculinity, whiteness and occasionally heterosexuality. However, the social hierarchies are not only a top down construction, as a subordinate position can be used in order to create a sense of belonging and inclusivity. Constructions of ethnicity and whiteness have a lot of similarities between lesbian and gay communities, as this construction is also part of German national identity building. Furthermore, this research shows that processes of in- and exclusion based on ethnicity, are played out differently between lesbian and gay communities in Berlin. In- and exclusion are not static categorizations, some people are included but differently alongside gendered and racial hierarchies. In short, thesis demonstrates how representations of ethnicity, whiteness and sexuality are strongly related to stereotypes and objectifications based on racialized ethnicities, which form us-them-divides. T

"The aim of this complementary research is to understand experiences of ethnicity, whiteness and sexuality in the lives of people who identify as lesbian and gay in Berlin. The research question of this thesis is: ""How is ethnicity, and specifically whiteness, constructed by people who identify as lesbian and gay, and how is this related to experiences of in- and exclusion in Berlin lesbian and gay communities"". Based on three months of extensive anthropological fieldwork in Berlin this thesis focuses on the following topics in order to answer the research question: 1) 'Differentiating tactics related to in and exclusion; 2) 'Racialized (and gendered) ethnicities and whiteness'; 3) 'Racialized sexuality and sexualized racism'. This thesis argues that ethnicity and therefore whiteness as well, is constructed through identifying the Other as 'ethnic' and the Self implicitly as white. The categories 'us' and 'them' gain meaning through intersections of ethnicity, gender and sexuality. The us-them-categorization is inflicted with social hierarchies, associating 'us' with social norms: masculinity, whiteness and occasionally heterosexuality. However, the social hierarchies are not only a top down construction, as a subordinate position can be used in order to create a sense of belonging and inclusivity. The construction of ethnicity and whiteness has a lot of similarities between lesbian and gay communities, as this construction is also part of German national identity building. Furthermore, this research has shown that processes of in- and exclusion based on ethnicity, are played out differently between lesbian and gay communities in Berlin. In- and exclusion are not static categorizations, this thesis has shown that some people are included, but differently alongside gendered and racial hierarchies. In short, thesis shows how representations of ethnicity, whiteness and sexuality are strongly related to stereotypes and objectifications based on racialized ethnicities

BACKGROUND: The completion of continuing professional development (CPD) is mandatory for medical oncologists and trainees (MO&T). Pharmaceutical companies may fund some CPD activities, but there is increasing debate about the potential for conflicts of interest (COI). AIM: To assess current practices around funding to attend CPD activities. METHODS: An electronic survey was distributed to Australian MO&T. The survey asked questions about current practices, institutional policies and perceptions about attending CPD funded by pharmaceutical companies. The design looked at comparing responses between MO&T as well as their understanding of and training around institutional and ethical process. RESULTS: A total of 157 of 653 (24%) responses was received, the majority from MO (76%). Most CPD activities attended by MO&T were self-funded (53%), followed by funding from institutions (19%), pharmaceutical companies (16%) and salary award (16%). Most institutions allowed MO&T to receive CPD funding from professional organisations (104/157, 66%) or pharmaceutical companies (90/157, 57%). A minority of respondents (13/157, 8%) reported that the process to use pharmaceutical funds had been considered by an ethics committee. Although 103/157 (66%) had received pharmaceutical funding for CPD, most (109/157, 69%) reported never receiving training about potential COI. The lack of education was more noticeable among trainees (odds ratio (OR) 8.61, P = 0.02). MO&T acknowledged the potential bias towards a pharmaceutical product (P = 0.05) but believed there was adequate separation between themselves and pharmaceutical companies (P < 0.01). CONCLUSION: Majority of CPD attended by MO&T is self-funded. There is lack of clarity in institutional policies regarding external funding support for CPD activities. Formal education about potential COI is lacking.

The structure, morphology and optical properties of metal oxides (ZnO, MgO and SrO), their composites (MgO-ZnO, SrO-ZnO) and systems with different x molar concentration values (0.2, 0.4, 0.5, 0.6, 0.7, 0.8) of MgxZn1-xO and SrxZn1-xO, were synthesized via solution combustion method at initial reaction temperature of 600 ˚C for 15 minutes. These properties of the synthesized nanostructures were investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High resolution transmission electron microscope (HR-TEM) and Photoluminescence (PL) spectroscopy. The ZnO, MgO and SrO phosphors were successfully synthesized via solution combustion method and their crystallization was confirmed by XRD analysis. The ZnO powder crystallized in the hexagonal phase. The diffraction patterns of the ZnO samples became sharper and more intense when synthesis temperature was increased from 600 ˚C to 700 ˚C indicating improvement of crystallinity and an increase in crystallite sizes from 23.3 nm to 30.06 nm of the as-prepared undoped ZnO phosphor powder. The MgO powder had cubic crystal structure with Fm-3m space group and crystallized in rocksalt/sodium chloride (NaCl) type cubic structure and the SrO sample indicated the presence of three well-defined crystalline phases which are SrO, Sr(OH)2 and Sr(CO3)2, with Sr(OH)2 appearing as the most prominent phase. With respect to the following systems: MgxZn1-xO and SrxZn1-,xO and their composites, their XRD patterns revealed the presence of two well-defined crystalline phases, namely MgO or SrO and ZnO, the most prominent phase being ZnO. The SEM images of ZnO showed agglomeration of small particles and flower-like morphology. The HR-TEM images showed that the nanoparticles (NPs) were hexagonally shaped and aggregated into clusters. The SEM images of MgO showed spherical cube-like morphology with the appearance of closely-packed or attached particles in all the SEM micrographs. The HR-TEM images show that the NPs were cubic, National Research Foundation (NRF), University of the Free State

Here we report the application of a conjugated copolymer based on thiophene and quinoxaline units, namely poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), to nanoparticle organic photovoltaics (NP-OPVs). TQ1 exhibits more desirable material properties for NP-OPV fabrication and operation, particularly a high glass transition temperature (Tg) and amorphous nature, compared to the commonly applied semicrystalline polymer poly(3-hexylthiophene) (P3HT). This study reports the optimisation of TQ1:PC71BM (phenyl C71 butyric acid methyl ester) NP-OPV device performance by the application of mild thermal annealing treatments in the range of the Tg (sub-Tg and post-Tg), both in the active layer drying stage and post-cathode deposition annealing stage of device fabrication, and an in-depth study of the effect of these treatments on nanoparticle film morphology. In addition, we report a type of morphological evolution in nanoparticle films for OPV active layers that has not previously been observed, that of PC71BM nano-pathway formation between dispersed PC71BM-rich nanoparticle cores, which have the benefit of making the bulk film more conducive to charge percolation and extraction.

Recently, the essence of nanocrystalline phosphor materials to enhance the efficiency of solar cells have been the subject of interest in research. To improve the efficiency of solar cells, special attention has been paid to down-conversion based on nanomaterial phosphor doped with rare earth ions which absorb ultraviolet (UV) from the sun and down-convert them into visible photons that could subsequently be absorbed by solar cells. Titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticulate phosphor were activated with Eu3+ ions. These nanoparticles powders were successfully synthesized by co-precipitation method. The structural properties of TiO2 nanoparticulate phosphor were examined with X-ray diffraction (XRD). The XRD confirmed crystallization of both tetragonal anatase and rutile phases and the average crystallite size of undoped and Eu3+ doped TiO2 were 21 and 8 nm, respectively. Scanning electron microscopy showed that the morphology of TiO2 nanoparticles composed of nanorods with average length and diameter of approximately 410 nm and 73 nm respectively. The optical properties of TiO2 nanoparticulate phosphors were studied using photoluminescence (PL) spectroscopy and ultraviolet-visible (UV-Vis) spectroscopy. At 325 nm excitation wavelength, PL data showed a broad emission from undoped TiO2 centred at 455 nm. This broad emission band was assigned to defects in TiO2. Eu3+ doped TiO2 nanoparticulate phosphors exhibited five emissions which are associated with f→f transitions of Eu3+ ions when excited at 466 nm. The band gaps of the nanophosphors were also determined from the UV-Vis reflectance measurement using Tauc’s plot. The XRD analysis of Eu3+ doped zinc oxide (ZnO) nanoparticulate phosphor was consistent with wurtzite hexagonal structure of ZnO. In addition, the XRD patterns confirmed the presence of secondary phase of Eu2O3. The morphological changes of ZnO nanoparticles due to incorporation of Eu3+ ions were observed from the SEM micrographs. The P, Department of Science and Technology (DST), National Research Foundation (NRF), University of the Free State (UFS)

With the aim of determining the concentration quenching mechanism of Eu2+ doped Ca2BO3Cl, a series of phosphors with a varied Eu2+ concentration (Ca2-xBO3Cl:xEu(2+)) was synthesized by the solid state reaction method. The phase structure was determined by X-ray diffraction. Photoluminescence (PL) measurements showed broad excitation and emission signatures of the allowed f-d transition of Eu2+ ions. The PL emission intensity was found to be increased by increasing the concentration of Eu2+ ions up to x=0.03 and then decreased as a result of the concentration quenching effect. The lifetime of the emission from the Eu2+ ions was measured and the decrease in the lifetime with increasing Eu2+ concentration confirmed that non-radiative energy transfer occurred between Eu2+ ions. From the luminescence data, the value of the critical transfer distance was calculated as 1.5 nm and the corresponding concentration quenching mechanism was verified to be a dipole-dipole interaction. (C) 2015 Elsevier Ltd. All rights reserved., Funding Agencies|South African Research Chairs Initiative of the Department of Science and Technology; National Research Foundation of South Africa; University of the Free State