Дисертації з теми "UV-Visible light"
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1
Chen, Xi. "Noble metal photocatalysts under visible light and UV light irradiation." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/47008/1/Xi_Chen_Thesis.pdf.
Анотація:
One of the greatest challenges for the study of photocatalysts is to devise new catalysts that possess high activity under visible light illumination. This would allow the use of an abundant and green energy source, sunlight, to drive chemical reactions. Gold nanoparticles strongly absorb both visible light and UV light. It is therefore possible to drive chemical reactions utilising a significant fraction of full sunlight spectrum. Here we prepared gold nanoparticles supported on various oxide powders, and reported a new finding that gold nanoparticles on oxide supports exhibit significant activity for the oxidation of formaldehyde and methanol in the air at ambient temperature, when illuminated with visible light. We suggested that visible light can greatly enhance local electromagnetic fields and heat gold nanoparticles due to surface plasmon resonance effect which provides activation energy for the oxidation of organic molecules. Moreover, the nature of the oxide support has an important influence on the activity of the gold nanoparticles. The finding reveals the possibility to drive chemical reactions with sunlight on gold nanoparticles at ambient temperature, highlighting a new direction for research on visible light photocatalysts. Gold nanoparticles supported on oxides also exhibit significant dye oxidation activity under visible light irradiation in aqueous solution at ambient temperature. Turnover frequencies of the supported gold nanoparticles for the dye degradation are much higher than titania based photocatalysts under both visible and UV light. These gold photocatalysts can also catalyse phenol degradation as well as selective oxidation of benzyl alcohol under UV light. The reaction mechanism for these photocatalytic oxidations was studied. Gold nanoparticles exhibit photocatalytic activity due to visible light heating gold electrons in 6sp band, while the UV absorption results in electron holes in gold 5d band to oxidise organic molecules. Silver nanoparticles also exhibit considerable visible light and UV light absorption due to surface plasmon resonance effect and the interband transition of 4d electrons to the 5sp band, respectively. Therefore, silver nanoparticles are potentially photocatalysts that utilise the solar spectrum effectively. Here we reported that silver nanoparticles at room temperature can be used to drive chemical reactions when illuminated with light throughout the solar spectrum. The significant activities for dye degradation by silver nanoparticles on oxide supports are even better than those by semiconductor photocatalysts. Moreover, silver photocatalysts also can degrade phenol and drive the oxidation of benzyl alcohol to benzaldehyde under UV light. We suggested that surface plasmon resonance effect and interband transition of silver nanoparticles can activate organic molecule oxidations under light illumination.
2
Liu, Xiaolu. "UV and Visible Light Active Nanostructure Photocatalysts for Disinfection and Decomposition of Biohazards." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/367249.
Анотація:
Rapid disinfection and effective removal of biohazards from water is important and necessary for safeguarding water, due to availing public health and environmental concerns. To achieve this aim, many techniques such as ultraviolet, chlorination, ultrasonic and ozone have been widely investigated and employed, though there are many drawbacks in these methods which are becoming more problematic in the developing world. In recent decades, two advanced oxidation techniques, photocatalysis (PC) and photoelectrocatalysis (PEC), have drawn extensive attentions, as they have displayed great potentials to be more sustainable, affordable, safer and robust for water purification technologies. There are still many issues however need to be solved, such as the identification of reaction intermediates, development of rate expressions and the photocatalytic efficiencies of the photocatalysts are still far from satisfaction. Therefore, it is necessary to develop high efficiency photocatalysts and study the fundamental mechanisms in the PC and PEC processes.
In this thesis, three types of UV and/or visible light active nanostructured TiO2 films with different structures and crystal phases have been developed, the fundamental aspects such as the electron transport properties in the photocatalyst films have been studied in detail, and the disinfection and decomposition performances of the obtained photocatalysts against Escherichia coli (E. coli) bacteria have been investigated. To achieve these objectives, systematic studies have been performed including the establishment of experimental methodology, characterisations of nanomaterials, performance evaluation and mechanistic aspects.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text
3
Wang, Dongsheng [Verfasser]. "Photoresponsive azobenzene/cyclodextrin supramolecular systems : from UV-light-responsive to visible-light-responsive / Dongsheng Wang." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1130618366/34.
4
Han, Taejun. "Effect of visible and UV radiation on early sporophytes of species of the Laminariales." Thesis, University of Liverpool, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316578.
5
Hudaya, Tedi Chemical Sciences & Engineering Faculty of Engineering UNSW. "Synthesis, characterisation, and activity of novel TiO2-based photocatalysts for organic pollutant photodestruction under UV and visible-light irradiation." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2008. http://handle.unsw.edu.au/1959.4/42612.
Анотація:
Titania-based photocatalysts have been extensively studied for the oxidative photodestruction of organic pollutants in wastewaters, releasing non-toxic substances such as CO2, HCl, and water. However, commercial exploitation of this process is limited by the fact that titania is only active under UV irradiation (wavelength below about 388 nm), which is only less than 5% of solar light energy. Sol-gel synthesised catalyst specimens were characterised to determine the correlation between preparation conditions on morphology (XRD, SEM), optical (bandgap energy level) and physicochemical properties (BET surface area, pore volume, acid site density, acid site strength and type) of the photocatalysts. These spesific properties would then be linked to their photoactivity using aqueous aliphatic and aromatic model pollutants. This study has demonstrated that sol-gel synthesised doped titania photocatalysts, especially Pt/TiO2, may be used to effectively degrade non-volatile acids (DL-malic acid, dichloroacetic acid, and p-hydroxybenzoic acid) under visible light and UV irradiation with significant photoactivity suitable for the solar light application of photocatalytic wastewater treatment. A significant drop in band-gap energy was found for all titania sol-gel catalysts doped with Pt, Co, and Ce with values between 1.41 to 1.78 eV. The BET areas of the photocatalysts were also higher (65-117 m2/g) than that of Degussa P25 (50 m2/g). The visible-light photomineralisation of the three pollutants with Pt-TiO2 specimen were further extended to evaluate the effects of major variables in a bubble-column photoreactor on the photodegradation activities. Those major variables were lamp intensity, oxygen concentration, initial pH, catalyst dosage, and inital pollutant concentration. All the three pollutants seemed to follow the Langmuir-Hinselwood model with dual adsorption sites which implicated a bimolecular surface rate-limiting step probably between the adsorbed organic substrate and a surface hydroxyl (or peroxy) radical. A study of the CeyCoxTi(1-x)O3+d perovskite was conducted to investigate the influence of metal composition and pH on the intrinsic optophysical attributes as well as p-hydroxybenzoic acid degradation under UV irradiation. The perovskite UV photoactivities were lower than that of pure TiO2 likely due to excessive loading (metal content) creating new oxide phases act as electron-hole recombination center, regardless better physicochemical attributes of some of the perovskite samples. The role of aging time and calcination temperature on the sol-gel synthesised TiO2 was also explored. Higher calcination temperature (from 250 to 700 0C) resulted in TiO2 photocatalysts with better crystallinity, which is important for OH group formation as active sites for photodegradation. Despite of some advantages from higher temperature preparation, some detrimental effects such as decreased acidity attributes, surface area, and pore volume were also observed. The significant red-shift of sol-gel synthesized TiO2 into visible light, especially for 250 0C specimen since 600 or 700 0C had extremely low activities, has promising implications that this specimen might be used for solar application to substitute Pt-doped TiO2 in order to produce a more cost effective photocatalyst. Aging period (1 to 14 days) did not have any discernible effect on the band-gap value and acid-site density. Even so, the highest acid site strength was obtained with an aging time of 10 days. From the overall perspective, aging time longer than 3 days did not bring noticeable benefits to both catalyst attributes and photoactivities.
6
Krasnow, Mark Neil. "Analysis of phenolic biosynthesis in Vitis vinifera L. cell suspension cultures to visible light, UV light, and methyl jasmonate treatments /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Matallana, Surget Sabine-Astrid Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Physiological and molecular responses of the marine oligotrophic ultramicrobacterium Sphingopyxis Alaskensis rb2256 to visible light and ultraviolet radiation." Awarded By:University of New South Wales. Biotechnology & Biomolecular Sciences, 2009. http://handle.unsw.edu.au/1959.4/43251.
Анотація:
Ultraviolet radiation reaching the Earths surface (UVR, 280-400 nm) may penetrate deep into the clear oligotrophic waters influencing a large part of the euphotic layer. Marine heterotrophic bacteria at the surface of the oceans are especially sensitive to the damaging solar radiation due to their haploid genome with little or no functional redundancy and lack of protective pigmentation. In a context of climate change and ozone depletion, it is clearly important to understand the physiology and underlying molecular UVR responses of abundant marine bacteria species. We chose the marine ultramicrobacterium Sphingopyxis alaskensis as a reference species to study the impact of solar radiation due to its numerical abundance in oligotrophic waters and its photoresistance, previously reported. For this purpose, we focused on the formation of the two major UVB-induced DNA photoproducts (CPDs and 6-4PPs) as well as the differential protein expression under solar radiation. We first demonstrated that the GC content of prokaryotic genome had a major effect on the formation of UVB-induced photoproducts, quantified by HPLC-MS/MS. Due to its high GC content, S. alaskensis presented a favoured formation of highly mutagenic cytosine-containing photoproducts and therefore would be more susceptible to UVinduced mutagenesis. By comparing S. alaskensis to another marine bacterium Photobacterium angustum, we observed for the latter strain a remarkable resistance to high UVB doses associated with a decrease in the rate of formation of CPDs explained by a non-conventional activity of photolyase. We also demonstrated that DNA damage in S. alaskensis was markedly modulated by growth temperature and time spent in stationary phase. In order to assess the effects that environmental UV-R had on regulatory networks and pathways of S. alaskensis, and determine how the cells physiology was affected, a quantitative proteomics investigation was performed. Changes in proteome were analyzed, with the recent and powerful mass spectrometry based approach using iTRAQ methodology. Approximately, one third of the proteome of S. alaskensis was identified, with 119 statistically and significantly differentially abundant proteins. Cellular processes, pathways and interaction networks were determined and gave us unique insight into the biology of UV response and adaptation of S. alaskensis.
8
Newkirk, Scott Hunter. "Detection levels of drinking water contaminants using field portable ultraviolet and visible light (uv/vis) spectrophotometry /." Download the thesis in PDF, 2005. http://www.lrc.usuhs.mil/dissertations/pdf/NEWKIRK2005.pdf.
9
Nonoyama, Akihisa. "Using Multiwavelength UV-Visible Spectroscopy for the Characterization of Red Blood Cells: An Investigation of Hypochromism." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000508.
10
Pelaez, Miguel. "Development of Novel Visible and Solar Light-Activated Nanostructured Nitrogen-Fluorine Titanium Dioxide Photocatalyst for the Removal of Cyanotoxins in Water." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337958461.
11
Granato, Stefanie [Verfasser]. "The response of silicon PNCCD sensors with aluminum on-chip filter to visible light, UV- and X-ray radiation / Stefanie Granato." Siegen : Universitätsbibliothek der Universität Siegen, 2012. http://d-nb.info/1028112769/34.
12
Hamal, Dambar B. "Design and development of a new generation of UV-visible-light-driven nanosized codoped titanium dioxide photocatalysts and biocides/sporocides, and environmental applications." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2203.
13
Aldoori, Hussam. "Valorisation des déchets plastiques d'équipements électriques et électroniques contenant des retardateurs de flamme bromés." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR053.
Анотація:
L'utilisation des retardateurs de flamme bromées, tels que les polybromodiphényl éthers (PBDE), est aujourd'hui réglementée par la directive européenne RoHS en raison de leur toxicité, leur bioaccumulation et leur persistance dans l'environnement. Cependant, ces molécules toxiques se trouvent encore en grandes quantités dans les plastiques en fin de vie, notamment dans les résidus des équipements électriques et électroniques obsolètes.Par conséquent, ces déchets plastiques chargés en retardateurs de flamme bromés ne peuvent être revalorisés sans un traitement préalable garantissant l'élimination de ces additifs. Ces derniers peuvent, par ailleurs, migrer dans le milieu environnant des sites de stockage de déchets et se dégrader par exposition aux rayonnements solaires pour générer des substances plus nocives comme les dibenzofuranes polybromés (PBDF).Le but de ce travail de thèse, qui s'inscrit dans le cadre du projet Interreg VALBREE, est d'étudier la faisabilité d'un procédé de décontamination des déchets plastiques par irradiation aux rayonnements UV-visibles, une technique qui s'est avérée prometteuse pour l'abattement des molécules bromées incorporées dans la matière plastique, afin de permettre la revalorisation de cette dernière par recyclage mécanique. L'efficacité du traitement radiatif en matière de photodégradation des ignifugeants bromés dans des mélanges polymères/RFB modèles a été confirmée par différentes techniques d'analyse spectroscopiques et chromatographiques. Ainsi l'évaluation de l'état de la matière plastique après l'irradiation a permis d'optimiser les conditions du traitement afin d'éviter la détérioration des propriétés des plastiques décontaminésThe use of brominated flame retardants, such as polybrominated diphenyl ethers (PBDEs), is currently restricted by the European RoHS directive because of their toxicity, bioaccumulation and persistence in the environment. However, these toxic molecules are still found in large quantities in end-of-life plastics, particularly in the residues of obsolete electrical and electronic equipment.Consequently, these plastic wastes loaded with brominated flame retardants cannot be recycled without a prior treatment ensuring the elimination of these additives. Moreover, these additives can migrate in the environment surrounding the waste storage sites and degrade by exposure to solar radiation to generate more harmful substances such as polybrominated dibenzofurans (PBDF).The aim of this thesis, which is part of the Interreg VALBREE project, is to study the feasibility of a decontamination process of plastic waste by irradiation with UV-visible radiation, a technique that has proven promising for the abatement of brominated molecules incorporated in the plastic material, in order to allow the revalorization of the latter by mechanical recycling. The efficiency of the radiative treatment in the photodegradation of brominated flame retardants in model polymer/RFB mixtures has been confirmed by different spectroscopic and chromatographic analysis techniques. Thus, the evaluation of the state of the plastic material after irradiation allowed to optimize the treatment conditions in order to avoid the deterioration of the properties of the decontaminated plastics
14
Yuan, Xiaojiao. "Nanostructures based on conjugated polymer polypyrrole for application in photocatalysis Photocatalytic degradation of organic pollutant with polypyrrole nanostructures under UV and visible light Polypyrrole nanostructures modified with mono- and bimetallic nanoparticles for photocatalytic H2 generation Highly active composite TiO2-polypyrrole nanostructures for water and air depollution under visible light irradiation Highly Promoted Photocatalytic Hydrogen Generation by Multiple Electron Transfer Pathways Visible light-driven simultaneous water oxidationand quinone reduction by a nano-structuredconjugated polymer without co-catalysts." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF011.
Анотація:
Récemment, les nanostructures de polymères conjuguées π (CPN) ont émergé comme une nouvelle classe de catalyseurs pour diverses applications photocatalytiques comme le fractionnement de (ou photosplitting) de l’eau, la réduction du CO2, le traitement de l’eau (dégradation des polluants organiques et réduction de métaux lourds). Parmi la famille des polymères conjugués, le polypyrrole (PPy) a été le plus étudié en raison de sa stabilité environnementale, de sa synthèse facile, de son excellente stabilité. Dans cette thèse, les nanostructures PPy ont été synthétisées par différentes méthodes : polymérisation chimique dans des matrices souples (mésophases hexagonales ou lamellaires) et polymérisation par radiolyse. Ces nanostructures PPy présentent une activité photocatalytique prometteuse pour la dégradation de polluants organiques (phénol et méthylorgange) sous lumière visible et leurs activités sont supérieures à celle du PPy-bulk (PPy massif). De plus, nous avons modifié TiO2 avec du PPy nanostructuré pour la photodégradation de polluants organiques.Le nanocomposite montre une augmentation importante des performances photocatalytiques sous UV et lumière visible par rapport au TiO2 et PPy seuls pour le traitement de l’eau et de l’air. La production d'hydrogène vert par fractionnement photocatalytique de l'eau offre un moyen prometteur pour résoudre les problèmes d'environnement et d'énergie. Dans cette thèse, nous avons montré que les nanostructures depolypyrrole modifiées avec des nanoparticules mono et bimétalliques (Pt, Ni, Pt-Ni) sont très actives pour la génération d'hydrogène et qu'un effet de synergie est obtenu en alliant Pt avec Ni. Enfin, différentes nanostructures ternaires à base du composite PPy-TiO2 modifié de manière contrôlée avec des nanoparticules de platine ont été développées ((Pt-PPy) -TiO2, (Pt-TiO2)-PPy et Pt-(PPy-TiO2)). L'activité photocatalytique de Pt-(PPy-TiO2) pour la génération d'hydrogène sous UV et lumière visible est très élevéeRecently, π-conjugated polymer nanostructures (CPNs) emerge as a new class of catalysts for various photocatalytic applications such as water splitting, CO2 reduction, water treatment (degradation of organic pollutants and heavy metals reduction). Among the family of CPs, polypyrrole PPy has been the most extensively investigated owing to its environmental stability, facile synthesis, excellent stability. In this thesis, PPy nanostructures were synthesized by different methods: chemical polymerization by soft templates (hexagonal or lamellar mesophases) and polymerization by radiolysis. These PPy nanostructures exhibit promising photocatalytic activity for organic pollutants (phenol and methyl organge) degradation under visible light and their activities are higher than that of PPy- bulk.Besides, we modified TiO2 with nanostructured PPy for photodegradation of organic pollutants (methy orange and phenol as model water pollutants and toluene as air pollutant). The nanocomposite shows an important increase of the photocatalytic performance under UV and visible light compared to bare TiO2 and PPy. This work offers a facile and cheap way to fabricate the heterojunction in organic-inorganic hybrid materials interface and the composite nanomaterials represents a promising photocatalyst for water treatment and indoor application. In another hand, green hydrogen production by photocatalytic water splitting offers a promising way to solve environment and energy issues. In this thesis, we have shown that modified conjugated polymer polypyrrole nanostructures with mono- and bimetallic (Pt, Ni, Pt-Ni) nanoparticles are very active for hydrogen generation, and that a synergistic effect is obtained by alloying Pt with Ni. Lastly, different ternary nanostructures based on PPy-TiO2 composites with controlled active sites modification with Pt nanoparticles were developed ((Pt-PPy)-TiO2, (Pt-TiO2)-PPy and Pt-(PPy-TiO2)). The photocatalytic activity of Pt-(PPy-TiO2) for hydrogen generation under UV and visible light is very high and drastically surpasses those of (Pt-PPy)-TiO2 and (Pt-TiO2)-PPy
15
Lederhose, Paul. "From UV to NIR light, photo-triggered 1,3 dipolar cycloadditions as a modern ligation method in solution and on surface." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/105356/1/Paul_Lederhose_Thesis.pdf.
Анотація:
This research synthesised and explored the application of novel chemicals which can be used to create complex polymeric architectures through light irradiation. By tuning the chemical structure, this study utilized ultra-violet, visible and infra-red sources to mediate these reactions. Future applications of this technology include photolithography and design of lab-on-chip sensor materials.
16
Sang-HsuanLu and 呂尚烜. "Synthesis and characterization of V2O5-HfO2 composite for photodegradation under UV and visible light irradiations." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/83659929211931728553.
Анотація:
碩士國立成功大學
材料科學及工程學系
104
A V2O5-HfO2-X composite photocatalyst consisting of one-dimensional high crystallinity V2O5 nanowires with surface HfO2 nanoparticles and zero-dimensional high crystallinity V2O5 nanowires with surface HfO2 nanoparticles are reported. The V2O5 nanowires and HfO2 nanoparticles were synthesized using a microwave hydrothermal method and sol-gel method, respectively. V2O5 has band gap of 2.3 eV, which absorbs visible light. The HfO2 nanoparticles were made to exhibit oxygen defect so that a sub-band structure occurs under the conduction band. We show that such a sub-band energy level help to retard the recombination of electron-hole pairs. The obtained results show that the degradation of methylene blue using V2O5-HfO2-X composite is much better than that using pure V2O5 nanowires under both UV and visible light irradiations. The effects of the composite composition and the oxygen defect in HfO2-x on the catalytic performance has been addressed.
17
"A System for In Situ UV-Visible Illumination of Transmission Electron Microscope Samples." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15192.
Анотація:
abstract: A system for illuminating a sample in situ with visible and UV light inside a transmission electron microscope was devised to study photocatalysts. There are many factors which must be considered when designing and building such a system. These include both mechanical, optical, and electron optical considerations. Some of the restrictions posed by the electron microscope column are significant, and care must be taken not to degrade the microscope's electron optical performance, or to unduly restrict the other current capabilities of the microscope. The nature of these various design considerations is discussed in detail. A description of the system that has been added to the microscope at ASU, an FEI Tecnai F20 environmental transmission electron microscope is also given. The system includes a high brightness broadband light source with optical filters, a fiber to guide the light to the sample, and a system for precisely aligning the fiber tip. The spatial distribution and spectrum of the light reaching the sample has been characterized, and is described in detail.Dissertation/Thesis
M.S. Materials Science and Engineering 2012
18
Lin, Hank Hui-Hsiang, and 林煇翔. "Photocatalytic oxidation of cytostatic drugs via UV and visible light responsive TiO2 in the aqueous environment." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/90938614775181246930.
Анотація:
博士國立臺灣大學
環境工程學研究所
103
Cytostatic drugs are a class of pharmaceuticals that are increasingly used in cancer therapies. However, they have genotoxic, mutagenic, carcinogenic or teratogenic effects in non target organism. They have been detected in the both effluent of the municipal and hospital wastewater treatment plants due to their stability and persistency. 5-fluorouracil and cyclophosphamide are two of the most commonly used cytostatic (antineoplastic) drugs in the world. This study applied photocatalytic oxidation to remove 5-fluorouracil and cyclophosphamide. Degussa P25 showed a higher photocatalytic degradation efficiency for 5-fluorouracil removal than Aldrich TiO2 and ZnO. Under optimal conditions (20 mg L-1 TiO2 at pH 5.8), 200 μg L-1 5-fluorouracil can be removed within 2 h (k = 0.0375 min-1). 5-fluorouracil was found to be decomposed by near-surface ˙OHfree radicals produced from valence holes (h_vb^+). At a relatively high concentration, 5-fluorouracil (27.6 mg L-1) is >99.9% removed within 4 h by 300 mg L-1 Degussa P25, while 24 h is required to reach complete mineralization with 96.7% fluoride recovery. On the other hand. cyclophosphamide (27.6 mg L-1) was also >99.9% eliminated within 4 h, but dechlorination and mineralization reached only 79.9% and 55.1%, respectively, after 16 h of irradiation. Together with the results for MicrotoxR, it is suggested that the oxidation products of cyclophosphamide are even more recalcitrant and toxic. In order to apply photocatalytic oxidation system under visible light, visible light responsive TiO¬¬¬2 has been widely studied for several years. Among visible light responsive TiO2, N-doped TiO2 has been received much more attention because of its higher photoactivity and relatively simple manufacture process. Microwave has been considered as a promising and energy saving process as synthesis in the recent years. The microwave-treated N-doped TiO2 removed 5-fluorouracil with a higher degradation efficiency than N-doped TiO2 synthesized with the traditional thermal treatments. The most efficient N-doped TiO2 (N6) was synthesized using 1 M NH4OH pre-immersion and a 3 h 180°C microwave treatment, followed by 550°C calcination for 6 h. The photocatalytic degradation of 5-fluorouracil achieved 88.8% removal within 20 h of treatment by N6 under visible light, which is higher than that obtained by Degussa P25 TiO2 (61.5%). Higher concentrations of NH4OH and longer calcination times resulted in decreased 5-fluorouracil degradation; the particle size of the synthesized N-doped TiO2 increased after calcination. The surface area decreased while the pore volume and pore size increased after synthesis. Furthermore, the basicity of the sites on the synthesized N-doped TiO2 decreased after calcination. Photocatalytic oxidation was shown to be effective in decomposing 5-fluorouracil and cyclophosphamide, therefore, it has potential to apply to hospital wastewater treatment plants. However, the effects of water matrix, the relationship between toxicity changes and by-products, mineralization must be the important considerations and necessarily investigated before real application.
19
Jia, Weidong. "Study of nifedipine photochemistry induced by visible & UV-A light in aqueous liposome dispersions and in hydrophobic media." 1996. http://hdl.handle.net/1993/19208.
20
Shen, Yun-Hsiang, and 沈運祥. "Photocatalytic Degradation of Phenol Solution in the Presence of Au/TiO2 Catalyst under the Irradiation of UV and Visible Light." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/18023769425197788250.
Анотація:
碩士國立臺灣大學
化學工程學研究所
99
The purpose of this research is to apply Au/TiO2 for the photocatalytic degradation reaction of phenol, a commonly found organic compound in industrial wastewater, and to observe the concentration profiles as well as the selectivity of the intermediates. In addition, we want to investigate whether Localized Surface Plasmon Resonance (LSPR) effect can enhance the reaction rate. This research is divided into three parts. First, we illuminated the phenol solution with 300 nm UV light only. The initial concentration of phenol solution is 250 ppm and 150 ppm, respectively. We found that the reaction rate constant of phenol was nearly independent of the initial concentration. The second part is to explore the temperature effect on the kinetics when using P25 and 2.0 wt% Au/P25 as the catalyst, individually. We observed that when the reaction temperature increased from 32℃ to 38℃, the reaction rate constant of phenol dropped. Even when we elevated the reaction temperature to 55℃, the reaction rate constant of phenol only slightly increased. We suppose that it is because the adsorption step rather than the surface reaction step is the rate-determining step. The third part is to illuminate the phenol solution with 300 nm UV and 575 nm visible light at the same time. The reaction rate constant of phenol became a little larger when applying dual light sources. As for the mono-hydroxylated intermediates, although the increase in the reaction rate constant was not obvious, when compared with the data obtained by illuminating the solution with UV light only, we believe that LSPR must promote the overall reaction rate of the photocatalytic degradation reaction of phenol.
21
Wu, Kun. "Comparison of the mechanisms of anthraquinone and anthracycline aqueous photochemistry induced by UV-A and visible light in solutions and in large unilamellar vesicle dispersions." 1995. http://hdl.handle.net/1993/19042.
22
Sontakke, Sharad M. "Inactivation of Microorganisms by Photocatalysis." Thesis, 2012. http://etd.iisc.ac.in/handle/2005/3141.
Анотація:
Photocatalysis is an advanced oxidation process, which has shown to possess an enhanced capability to remove a wide range of contaminants. It involves the use of a semiconductor photocatalyst and a photon source. Photocatalysis has several advantages such as mild reaction conditions like ambient temperature and pressure, good control over the reaction and faster reaction kinetics. Semiconductor photocatalysts such as TiO2, ZnO, Fe2O3, CdS, ZnS, etc. absorbs light of energy greater than or equal to its band gap and the electron in the valence band gets excited to conduction band leaving behind the hole in valence band. These charge carrier pair results in the formation of various reactive oxygen species such as hydroxyl and superoxide radicals which results in the degradation of chemical contaminants and inactivation of microorganisms.
TiO2 is the most widely used catalyst in photocatalytic studies because of its high photocatalytic activity, non-toxicity and wide availability. Anatase phase TiO2 has been reported to possess higher photocatalytic activity than the rutile phase. Although there are several methods to synthesize TiO2, solution combustion synthesis is a single step process to produce pure anatase phase TiO2. The catalyst produced by this method has been shown to be superior to the commercially available Degussa P-25 catalyst for the degradation of various chemical contaminants. The present investigation focuses on the use of combustion synthesized catalyst for the inactivation of microorganisms. The photocatalytic activity was compared with commercial Degussa P-25 catalyst.
The various aspects of photocatalytic inactivation reactions studied in this dissertation are: i) photocatalytic inactivation of microorganisms in presence of UV light, ii) effect of various parameters on the inactivation, iii) photocatalytic inactivation in presence of visible light, iv) use of immobilized catalyst for the photocatalytic inactivation, v) understanding of mechanism and kinetics of inactivation.
Combustion synthesized TiO2 (CS-TiO2), combustion synthesized 1% Ag substituted TiO2 (Ag/TiO2 (Sub)) and 1% Ag impregnated CS-TiO2 (Ag/TiO2 (Imp)) were used as photocatalysts. The catalysts were characterized by powder XRD, TEM, BET surface area, UV-Vis spectroscopy, TGA and photoluminescence spectroscopy. The photocatalytic inactivation experiments were carried out using E. coli (K-12 MG 1655), a bacterial strain and P. pastoris (X-33), a yeast strain, as model microorganisms.
The results demonstrate higher photocatalytic activity of all the combustion synthesized catalysts than commercial Degussa P-25 catalyst. The optimum catalyst concentration was 0.25 g/L and the maximum inactivation was observed in the presence of Ag/TiO2 (Imp) catalyst. Rapid and complete inactivation of the microorganisms was observed at lower initial cell concentrations. A reduced photocatalytic inactivation was observed in presence of various anions (HCO3¯ , SO4 2¯ , Cl¯ and NO3¯ ) and cations (Na, K, Caand Mg). Even a small addition of H2O2 was observed to improve the photocatalytic inactivation. At higher dosage of H2O2, a 2 min exposure was sufficient to result in a complete inactivation. Changing the initial pH of the solution was observed to have no significant effect on the photocatalytic inactivation.
All the combustion synthesized catalysts showed higher activity as compared to those obtained with commercial Degussa P-25 TiO2 in presence of visible light. The higher photocatalytic activity of combustion synthesized TiO2 can be attributed to the lesser crystallite size, higher surface area, large amount of hydroxyl groups and decreased band-gap energy of the catalyst.
The present study demonstrates the potential use of catalyst immobilized thin films for the photocatalytic inactivation of E. coli in the presence of UV light. The CS-TiO2 catalyst was immobilized on glass substrate by LbL deposition technique. The performance of immobilized CS-TiO2 was compared to commercial Degussa Aeroxide TiO2 P-25 (Aeroxide) catalyst. The effect of various operating parameters like catalyst loading, surface area and number of bilayers on inactivation has been investigated. It was observed that increasing the number of bilayers and the concentration did not influence the inactivation but increased surface area led to an increase in inactivation. It was observed that the catalyst immobilized on glass slides can be used for repeated experimental cycles with the same efficiency. It was observed that the inactivation process can be studied in continuous mode by using catalyst immobilized on glass beads.
The work also focused attention towards understanding the microorganism inactivation mechanism and kinetic aspects. Various microscopy techniques such as optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the inactivation mechanism. From the images obtained, it was suggested that the inactivation is caused due to rupture of cell wall. The mechanism was also examined by carrying out degradation experiments on cell component such as protein and media component such as dextrose. UV alone was
observed to degrade protein and the presence of catalyst showed no additional effect. On the other hand, dextrose does not respond to photocatalytic degradation even at a lower concentration. The photocatalytic degradation of Orange G dye was reduced by addition of dextrose sugar or protein which shows a possibility of competitive degradation.
The kinetics of inactivation was studied by various models available in literature such as the power-law model, Chick-Watson model, modified Hom model, GInaFIT tool and a Langmuir-Hinshelwood type model. It was observed that power-law based kinetic model showed good agreement with the experimental data. A mechanistic Langmuir-Hinshelwood type model was also observed to model the inactivation reactions with certain assumptions.
23
Sontakke, Sharad M. "Inactivation of Microorganisms by Photocatalysis." Thesis, 2012. http://hdl.handle.net/2005/3141.
Анотація:
Photocatalysis is an advanced oxidation process, which has shown to possess an enhanced capability to remove a wide range of contaminants. It involves the use of a semiconductor photocatalyst and a photon source. Photocatalysis has several advantages such as mild reaction conditions like ambient temperature and pressure, good control over the reaction and faster reaction kinetics. Semiconductor photocatalysts such as TiO2, ZnO, Fe2O3, CdS, ZnS, etc. absorbs light of energy greater than or equal to its band gap and the electron in the valence band gets excited to conduction band leaving behind the hole in valence band. These charge carrier pair results in the formation of various reactive oxygen species such as hydroxyl and superoxide radicals which results in the degradation of chemical contaminants and inactivation of microorganisms.
TiO2 is the most widely used catalyst in photocatalytic studies because of its high photocatalytic activity, non-toxicity and wide availability. Anatase phase TiO2 has been reported to possess higher photocatalytic activity than the rutile phase. Although there are several methods to synthesize TiO2, solution combustion synthesis is a single step process to produce pure anatase phase TiO2. The catalyst produced by this method has been shown to be superior to the commercially available Degussa P-25 catalyst for the degradation of various chemical contaminants. The present investigation focuses on the use of combustion synthesized catalyst for the inactivation of microorganisms. The photocatalytic activity was compared with commercial Degussa P-25 catalyst.
The various aspects of photocatalytic inactivation reactions studied in this dissertation are: i) photocatalytic inactivation of microorganisms in presence of UV light, ii) effect of various parameters on the inactivation, iii) photocatalytic inactivation in presence of visible light, iv) use of immobilized catalyst for the photocatalytic inactivation, v) understanding of mechanism and kinetics of inactivation.
Combustion synthesized TiO2 (CS-TiO2), combustion synthesized 1% Ag substituted TiO2 (Ag/TiO2 (Sub)) and 1% Ag impregnated CS-TiO2 (Ag/TiO2 (Imp)) were used as photocatalysts. The catalysts were characterized by powder XRD, TEM, BET surface area, UV-Vis spectroscopy, TGA and photoluminescence spectroscopy. The photocatalytic inactivation experiments were carried out using E. coli (K-12 MG 1655), a bacterial strain and P. pastoris (X-33), a yeast strain, as model microorganisms.
The results demonstrate higher photocatalytic activity of all the combustion synthesized catalysts than commercial Degussa P-25 catalyst. The optimum catalyst concentration was 0.25 g/L and the maximum inactivation was observed in the presence of Ag/TiO2 (Imp) catalyst. Rapid and complete inactivation of the microorganisms was observed at lower initial cell concentrations. A reduced photocatalytic inactivation was observed in presence of various anions (HCO3¯ , SO4 2¯ , Cl¯ and NO3¯ ) and cations (Na, K, Caand Mg). Even a small addition of H2O2 was observed to improve the photocatalytic inactivation. At higher dosage of H2O2, a 2 min exposure was sufficient to result in a complete inactivation. Changing the initial pH of the solution was observed to have no significant effect on the photocatalytic inactivation.
All the combustion synthesized catalysts showed higher activity as compared to those obtained with commercial Degussa P-25 TiO2 in presence of visible light. The higher photocatalytic activity of combustion synthesized TiO2 can be attributed to the lesser crystallite size, higher surface area, large amount of hydroxyl groups and decreased band-gap energy of the catalyst.
The present study demonstrates the potential use of catalyst immobilized thin films for the photocatalytic inactivation of E. coli in the presence of UV light. The CS-TiO2 catalyst was immobilized on glass substrate by LbL deposition technique. The performance of immobilized CS-TiO2 was compared to commercial Degussa Aeroxide TiO2 P-25 (Aeroxide) catalyst. The effect of various operating parameters like catalyst loading, surface area and number of bilayers on inactivation has been investigated. It was observed that increasing the number of bilayers and the concentration did not influence the inactivation but increased surface area led to an increase in inactivation. It was observed that the catalyst immobilized on glass slides can be used for repeated experimental cycles with the same efficiency. It was observed that the inactivation process can be studied in continuous mode by using catalyst immobilized on glass beads.
The work also focused attention towards understanding the microorganism inactivation mechanism and kinetic aspects. Various microscopy techniques such as optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the inactivation mechanism. From the images obtained, it was suggested that the inactivation is caused due to rupture of cell wall. The mechanism was also examined by carrying out degradation experiments on cell component such as protein and media component such as dextrose. UV alone was
observed to degrade protein and the presence of catalyst showed no additional effect. On the other hand, dextrose does not respond to photocatalytic degradation even at a lower concentration. The photocatalytic degradation of Orange G dye was reduced by addition of dextrose sugar or protein which shows a possibility of competitive degradation.
The kinetics of inactivation was studied by various models available in literature such as the power-law model, Chick-Watson model, modified Hom model, GInaFIT tool and a Langmuir-Hinshelwood type model. It was observed that power-law based kinetic model showed good agreement with the experimental data. A mechanistic Langmuir-Hinshelwood type model was also observed to model the inactivation reactions with certain assumptions.
24
Ahlbrink, Ralf. "Laserspektroskopie an Photosystem II Zur Proton-Elektron-Kopplung bei Tyrosin Z und über die Natur der Chlorophyll a Entität P680." Doctoral thesis, 2002. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2002121215.
Анотація:
"Laser flash spectroscopy of photosystem II"
Photosystem II (PS II) of plants and cyanobacteria oxidizes water in a light-powered reaction. Thereby, this protein is the ultimate source of the atmospheric oxygen.
The capacity to oxidize water is owed to two properties of PS II: (i) The midpoint potential of the oxidizing chlorophyll moiety is increased by 0.6 V compared to photosystem I or photochemical reaction centers of anoxygenic bacteria, and (ii) the energy requirements of the four steps needed for the tetravalent oxidation of water are adapted to the energy of red light quanta.
This thesis deals with two particular aspects, namely:
1. The coupling of the electron transfer from tyrosine Z (YZ) to the primary donor (P680+) to proton transfer, and an inquiry on the role of a positive charge on YZox (plus base cluster) in increasing the oxidizing potential at the catalytic site.
2. The localization of the electron hole, P680+, among the excitonically coupled four inner chlorophyll a molecules, and an estimation of the midpoint potential differences between them.
Electron-proton-coupling by YZ
This study was carried out with PS II core complexes from spinach or pea with a deactivated (removed) manganese cluster. The reduction of P680+ was investigated as a function of pH by detecting the laser flash induced absorption changes with nanosecond resolution. Two kinetic components were found with different pH-dependence and activation energies. The alteration of kinetic parameters by H/D isotope substitutions or by addition of divalent cations implied two different types of YZ-oxidation: At acidic pH the electron transfer was coupled with proton transfer, whereas in the alkaline region it was more rapid and no longer controlled by proton transfer. The conversion between both mechanisms occured at pH 7.4. This value corresponds either to the apparent pK of YZ itself (i.e. of the hydroxy group of the phenol ring) or to the pK of an acid-base-cluster, which includes YZ. Independent measurements of pH-transients by following the absorption changes of hydrophilic proton indicators corroborated this notion. The data were interpreted as indicating that the phenolic proton of YZ was released into the medium at acidic, but not at alkaline pH.
The electron transfer and proton release characteristics of intact, oxygen-evolving PS II resembled those in deactivated samples kept at alkaline pH. We concluded that the electron transfer from YZ to P680+ in the native system was not coupled with proton transfer into the bulk. This has shed doubt on a popular hypothesis on the role of YZ as 'hydrogen abstractor' from bound water. On the other hand, the energetic constraints of water oxidation could be eased by the positive upcharging during oxidation of YZox plus its base cluster.
On the localization of the electron hole of P680+
Photooxidation of PS II oxidizes the set of four innermost chlorophyll a molecules giving rise to the only spectroscopically defined species P680+. The deconvolution of difference spectra into bands of pigments is ambiguous. By using photoselective excitation of antennae, i.e. chl a molecules with site specific energies at the long wavelength border of the mean Qy-band, and by polarized detection, it was possible to tag P680+QA-/P680QA and 3P680/P680 difference spectra with a further parameter, the (wavelength-dependent) anisotropy r. Results obtained at liquid nitrogen temperature (77 K) can be clearly interpreted in terms of two chl a monomer bands. The two main components of the P680+QA-/P680QA difference spectrum were marked by two distinct values of the anisotropy and could be interpreted in a straightforward manner: the bleaching of a band at 675 nm belonging to the charged species (chl a+) and an electrochromic blue-shift of a nearby chl a from 684 to 682 nm. The main bleaching band of the 3P680/P680 spectrum (at 77 K) can be apparently attributed to a third (or several) chl a component(s).
The analysis of the P680+QA-/P680QA spectrum at cryogenic temperature is compatible with monomeric chl a bands. On the other hand, one could assume a system of excitonically coupled core pigments, as it was recently introduced in the literature on the basis of energy transfer studies ('multimer model'). However, in view of the clear indications for an electrochromic band shift and the location of the bleaching band, which absorbs in a wavelength region of monomeric chl a, one assumption of the 'multimer model' should be questioned. Presumably, the excitonic couplings are rather weak, in particular between each of the two central chl a-molecules (PA/PB) and its respective accessory chl a (BA/BB), because of (i) the distances and (ii) different site energies of the monomeric chromophores.
At room temperature, the absorption difference and anisotropy spectra of P680+QA-/P680QA were clearly altered. The anisotropy data indicated that the changes could no longer exclusively be ascribed to thermal broadening of individual bands. The localization of the positive charge on one pigment, analogous to the situation at 77 K, was now unlikely. Hence, the midpoint potential differences between the inner four chlorophyll a molecules were small and were estimated as approximately 15 meV.