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1
Zheng, Meng. "Graphene based donor acceptor systems." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422210.
Повний текст джерелаАнотація:
An efficient method to exfoliate graphite to prepare exfoliated few-layer graphene (EXG) was carried out in this thesis. Through proper centrifugation at different rounds per minute (rpm), three kinds of exfoliated graphene flakes (EXG 800, EXG 1500 and EXG 3000) with different qualities were obtained. The qualities of these EXG flakes were characterized by TEM, TGA and Raman spectroscopy. Raman spectra also states that the EXG 3000 flakes were of good quality and can be highly functionalized. Further research was focussed on the functionalization of EXG 3000 with charge donating π-centre based on diketopyrollopyrrole (DPP). The resulting hybrids graphene material has good solubility in organic solvent and wide light absorption (500 nm - 800 nm) features. Electron or energy transfer from DPP chromophores to EXG flakes was confirmed by the efficient fluorescence quenching of DPP chromophores. The new hybrid materials are under investigation as a third component in P3HT: PCBM bulk-heterojunction blends for organic photovoltaic applications.In questa tesi è stato condotto un metodo efficiente per esfoliare la grafite per preparare il grafene a pochi strati esfoliato (EXG). Attraverso un'adeguata centrifugazione a diversi giri al minuto (rpm), sono stati ottenuti tre tipi di scaglie di grafene esfoliate (EXG 800, EXG 1500 ed EXG 3000) con qualità diverse. Le qualità di questi fiocchi EXG erano caratterizzate dalla spettroscopia TEM, TGA e Raman. Gli spettri Raman affermano inoltre che i fiocchi EXG 3000 erano di buona qualità e possono essere altamente funzionalizzati. Ulteriori ricerche si sono concentrate sulla funzionalizzazione di EXG 3000 con donazione di carica π-center basata sul diketopirollopirrolo (DPP). Il risultante materiale ibrido di grafene presenta una buona solubilità in solventi organici e ampie caratteristiche di assorbimento della luce (500 nm - 800 nm). Il trasferimento di elettroni o di energia dai cromofori DPP ai fiocchi EXG è stato confermato dall'efficace spegnimento della fluorescenza dei cromofori DPP. I nuovi materiali ibridi sono in fase di studio come terzo componente di P3HT: miscele di eterogiunzione di massa PCBM per applicazioni fotovoltaiche organiche.
2
Guégano, Xavier. "Synthetic exploration of tetrathiafulvalene based donor-acceptor systems /." [S.l.] : [s.n.], 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000288151.
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3
Thomas, Michael Brandon. "Donor-Acceptor Systems: Photochemistry and Energy Harvesting Applications." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703335/.
Повний текст джерелаАнотація:
Donor-acceptor systems have unique properties that make them ideal candidates for solar energy harvesting through mimicry of natural photosynthesis. This dissertation is focused on unraveling those unique properties in various types of donor-acceptor systems. The systems investigated are categorized as closely linked, push-pull, supramolecular, and multi-unit. As part of the study, photosynthetic analogues based on BF2-chelated dipyrromethene (BODIPY), porphyrin, phthalocyanine, truxene, ferrocene, quinone, phenothiazine (PTZ), perylenediimide (PDI), fullerene (C60), dicyanoquinodimethane (DCNQ), tetracyanobutadiene (TCBD), and triphenylamine (TPA) are investigated. The effects of proximity between donor-acceptor entities, their geometrical orientation relative to each other, push-pull character of substituents, and competitive energy and electron transfer are examined. In all systems, primary events of photosynthesis are observed, that is absorption and energy transfer and/or electron transfer is witnessed. Ultrafast transient absorption spectroscopy is utilized to characterize the photo-induced events, while other methods such as steady-state luminescence, cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and computational calculations are used to aid in the characterization of the donor-acceptor systems, in particular their applicability as solar energy harvesters.
4
Martin, P. J. P. "Electrical, magnetic and optical characterisation of donor-acceptor systems." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/10404.
Повний текст джерелаАнотація:
Three novel donor-acceptor systems have been characterised through their spectroscopic properties, magnetic susceptibility, conductivity and second harmonic generation. The magnetic properties of (H2DPE)xx+(DPE)^ x(TCNQ)gX and (H2DPA)xx+(DPA) 1 x(TCNQ)gX' where DPE = 1,2-di(4-pyridyl)ethylene, DPA = 1,2-di(4-pyridyl)ethane, TCNQ = tetracyanoquinodimethane and H2 signifies proton diquaternisation, have been found to depend upon the stoichiometry: For x > \ the magnetic susceptibility decreases with increasing x whereas for x ~ \ it is anomolously large, being ferromagnetically enhanced above the Curie Law value. A possible model involving spin dilution is proposed and its predictions are compared with the experimental results. Langmuir-Blodgett (LB) films of the long-chained analogues of the materials, (C^g)2DPE (TCNQ) 2 and (Cig^DPE^TCNQ)^" where (C16) 2 = bis(hexadecyl) were deposited and characterised. The conductivities of the LB films of the mixed valence system were found to be ~ 1000 times greater than those of the system lacking TCNQ^ molecules. Multiple layer LB films of trans-4-[4- (dimethylamino)styryl]-1- octadecylpyridinium iodide and trans-4-[4-(dimethylamino)styryl]-1- octadecylquinolinium iodide interleaved with 4,4'-dioctadecyl-3,5,3',5' -tetramethyldipyrrylmethene hydrobromide were deposited. The materials form an interlocking bilayer structure which renders their LB films exceptionally well-organised. The films’ second harmonic generation was investigated and one film was found to give the largest second harmonic signal yet seen from an LB structure.
5
Yu, Craig. "Design and Synthesis of Donor-Acceptor π-Conjugated Systems". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37930.
Повний текст джерелаАнотація:
Organic π-conjugated molecules have garnered significant attention in the past twenty years for their potential applications in low-cost, lightweight, and flexible electronic devices. In particular, donor-acceptor (D-A) systems that involve the combination of electron-rich and electron-poor moieties in a molecule have been extensively studied due to tunability in intramolecular orbital interactions and materials properties. The theme of the current thesis is on the investigations of three different forms of D-A systems. Chapter 2 focuses on the design and synthesis of halogen-bonded organic frameworks using π-conjugated precursors as halogen bond donors and acceptors. The resulting co-crystals were subjected to single-crystal, thermal stability, and solid-state photophysical studies. In chapter 3, a series of D-A π-conjugated small molecules containing triphenylamine as the donor and an SF5 group as the acceptor was designed. The investigations include their synthesis, intramolecular orbital interactions, and photophysical properties. Chapter 4 introduces a pyrazine-containing D-A polymer using two metal-free polymerization methods, and the photophysical properties of the polymer can be significantly tuned using postpolymerization techniques.
6
Das, Sushanta Kumar. "Carbon Nanostructure Based Donor-acceptor Systems for Solar Energy Harvesting." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407823/.
Повний текст джерелаАнотація:
Carbon nanostructure based functional hybrid molecules hold promise in solarenergy harvesting. Research presented in this dissertation systematically investigates building of various donor-acceptor nanohybrid systems utilizing enriched single walled carbon nanotube and graphene with redox and photoactive molecules such as fullerene, porphyrin, and phthalocyanine. Design, synthesis, and characterization of the donor-acceptor hybrid systems have been carefully performed via supramolecular binding strategies. Various spectroscopic studies have provided ample information in terms of establishment of the formation of donor-acceptor hybrids and their extent of interaction in solution and eventual rate of photoinduced electron and/or energy transfer. Electrochemical studies enabled construction of energy level diagram revealing energetic details of the possible different photochemical events supported by computational studies carried out to establish the HOMO-LUMO levels in the donor acceptor systems. Transient absorption studies confirmed formation of charge separated species in the donor-acceptor systems which have been supported by electron mediation experiments. Based on the photoelectrochemical studies, IPCE of 8% was reported for enriched SWCNT(7,6)-ZnP donor-acceptor systems. In summary, the present investigation on the various nanocarbon sensitized donor-acceptor hybrids substantiates tremendous prospect, that could very well become the next generation of materials in building efficient solar energy harvesting devices andphotocatalyst.
7
Xu, Yunhua. "Synthesis and Photoinduced Electron Transfer of Donor-Sensitizer-Acceptor Systems." Doctoral thesis, Stockholm : Department of Organic Chemistry, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-411.
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8
Kercher, Michael. "Ruthenium tris(bipyridine) derivatives photoactive units in supramolecular donor acceptor systems /." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966018834.
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9
Kimura, Akihiro. "General theory of excitation energy transfer in donor-mediator-acceptor systems." American Institite of Physics, 2009. http://hdl.handle.net/2237/12630.
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10
Stelzig, Timea [Verfasser]. "Donor–acceptor systems in the quest for organic semiconductors / Timea Stelzig." Mainz : Universitätsbibliothek Mainz, 2012. http://d-nb.info/1022300717/34.
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11
Christensen, Christian Ausig. "Redox active cyclophanes and donor-acceptor systems from new TTFAQ building blocks." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/3880/.
Повний текст джерелаАнотація:
The saddle-shaped electron donor 9,10-his(l,3-dithiol-2-ylidene)-9,10-dihydroanthracene (TTFAQ) 49, which oxidises in a single, quasi-reversible, two-electron wave, accompanied by a dramatic conformational change, has been incorporated into donor-acceptor system 130. However, no significant charge-transfer interaction was observed. Pyrrolo-annelated TTFAQ derivatives 173 and 174 were synthesised, and donor-acceptor dyads, which showed intramolecular charge-transfer interactions, derived. TTFAQ cyclophanes 206 and 207 were synthesised in good yields, paving the way for the incorporation of more elaborate functionalities into TTFAQ cyclophanes, as exemplified by the synthesis of a TTFAQ- phenanthroline cyclophane with potential use as an electroactive sensor. A new methodology for the synthesis of TTFAQ derivatives has been developed, allowing the synthesis of cyanoethyl protected TTFAQ thiolate derivatives. These derivatives afforded several TTFAQ cyclophanes, of which the most interesting were the double-bridged cyclophanes 291 and 292. Due to the rigidity imposed by the two bridges, little conformational change is possible upon oxidation, which for the first time allowed us to study the elusive TTFAQ cation radical using cyclic voltammetry and spectroelectrochemistry, since 291 and 292 are oxidised in two, reversible, one-electron waves. The X-ray crystal structures of numerous new TTFAQ derivatives are also presented.
12
Castagnola, Norma B. "Spectroscopic studies and photochemical charge separation in Zeolite encapsulated donor-acceptor systems /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488190595942664.
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13
Ochsmann, Julian Robert [Verfasser]. "Excited-state dynamics in donor-acceptor systems for energy conversion / Julian Robert Ochsmann." Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1079623396/34.
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14
Döring, Robin Carl [Verfasser]. "Charge-transfer dynamics in molecular donor-acceptor systems and heterostructures / Robin Carl Döring." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/116655855X/34.
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15
KC, Chandra Bikram. "Design, Synthesis and Study of Supramolecular Donor – Acceptor Systems Mimicking Natural Photosynthesis Processes." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822757/.
Повний текст джерелаАнотація:
This dissertation investigates the chemical ingenuity into the development of various photoactive supramolecular donor – acceptor systems to produce clean and carbon free energy for the next generation. The process is inspired by the principles learned from nature’s approach where the solar energy is converted into the chemical energy through the natural photosynthesis process. Owing to the importance and complexity of natural photosynthesis process, we have designed ideal donor-acceptor systems to investigate their light energy harvesting properties. This process involves two major steps: the first step is the absorption of light energy by antenna or donor systems to promote them to an excited electronic state. The second step involves, the transfer of excitation energy to the reaction center, which triggers an electron transfer process within the system. Based on this principle, the research is focused into the development of artificial photosynthesis systems to investigate dynamics of photo induced energy and electron transfer events. The derivatives of Porphyrins, Phthalocyanines, BODIPY, and SubPhthalocyanines etc have been widely used as the primary building blocks for designing photoactive and electroactive ensembles in this area because of their excellent and unique photophysical and photochemical properties. Meanwhile, the fullerene, mainly its readily available version C60 is typicaly used as an electron acceptor component because of its unique redox potential, symmetrical shape and low reorganization energy appropriate for improved charge separation behavior. The primary research motivation of the study is to achieve fast charge separation and slow charge recombination of the system by stabilizing the radical ion pairs which are formed from photo excitation, for maximum utility of solar energy. Besides Fullerene C60, this dissertation has also investigated the potential application of carbon nanomaterials (Carbon nanotubes and graphene) as primary building blocks for the study of the artificial photosynthesis process.
16
Shao, Shuai. "Synthesis and Studies of Wide-Band Capturing BODIPY-Fullerene Based Donor-Acceptor Systems." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703394/.
Повний текст джерелаАнотація:
Artificial photosynthesis is the process, which mimics the natural photosynthesis process in order to convert solar energy to chemical energy. This process can be separated into four parts, which are antenna system, reaction center, water oxidation center, and proton reduction center. If we only focus on the ‘antenna system and reaction center' modules, expanding the absorption band in antenna system and generating long-lived charge separated state in reaction center are two fantastic strategies to design the molecules in order to improve the efficiency of the artificial photosynthesis process.
In the first work of this dissertation, mono-18-crown-6 and mono-ammonium binding strategy was used to connect BODIPY- C60 supramolecular based donor–acceptor conjugates. The meso- position of BODIPY was modified by benzo-18-crown-6, and the 3, 5 methyl positions were replaced by two styryl groups, which covered additional donor (triphenylamine or 10-methylphenothiazine). The acceptor is a fulleropyrrolidine derivative, which included an ethyl ammonium cation. The absorbance wavelengths of the donor covered 300-850 nm, which is the visible/near IR region (wide band capturing). The ultrafast charge separation and relatively slow charge recombination was found from femtosecond transient absorption study.
Next, a ‘two point' bis-18-crown-6 and bis-ammonium binding strategy was utilized to link BODIPY- C60 supramolecular based donor–acceptor conjugates. In this case, the meso- position of the BODIPY was modified by a secondary donor (triphenylamine, phenothiazine, or ferrocene). And the 3, 5 methyl positions were replaced by two styryl groups, which included benzo-18-crown-6. The acceptor (fulleropyrrolidine) was functionalized by bis-alky ammonium cations. The absorbance/ fluorescence emission titration and computational studies supported that the ‘two-point' strategy has stronger binding than ‘one-point' strategy. The relatively slow charge separation was found in these donor-acceptor conjugates.
To extend the second work, a pristine BODIPY was linked to the meso- position of the BODIPY-bis-benzo-18-crown-6. When the acceptor (C60-bis- ammonium) was added to the system, a sequential energy transfer (EnT) followed by electron transfer (ET) process was performed. The energy transfer was found from absorbance/ fluorescence emission studies, and the photoinduced electron transfer was observed from femtosecond and nanosecond transient absorption study. This is a great mode to mimic the ‘antenna-reaction center' events of natural photosynthesis.
In the last work of this dissertation, triplet sensitizers (I2BODIPY and I2azaBODIPY) covalently linked with a C60 to form the donor-acceptor system. In this work, triplet charge separated state (long-lived charge separated state) was expected. According to the femtosecond transient absorption studies, we observed the singlet charge separation was faster than the intersystem crossing process, that was the reason that only singlet charge separated state was found for I2BODIPY-C60, and no electron transfer was found for I2 azaBODIPY-C60.
17
Döring, Robin [Verfasser]. "Charge-transfer dynamics in molecular donor-acceptor systems and heterostructures / Robin Carl Döring." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/116655855X/34.
Повний текст джерела
18
Collini, Melissa A. "Synthesis and Studies of AzaBODIPY Derived Donor-Acceptor Systems for Light Induced Charge Separation." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404570/.
Повний текст джерелаАнотація:
The efficiency and mechanism of electron- and energy transfer events occurring in both in natural and synthetic donor-acceptor systems depend on their distance, relative orientation, and the nature of the surrounding media. Fundamental knowledge gained from model studies is key in building efficient energy harvesting and optoelectronic devices. Faster charge separation and slower charge recombination in donor-acceptor systems is often sought out. In our continued effort to build donor-acceptor systems using near-IR sensitizers, in the present study, we report ground and excited state charge transfer in newly synthesized, directly linked, tetrads featuring bisdonor (donor = phenothiazine and ferrocene), BF2-chelated azadipyrromethane (azaBODIPY) and C60 entities. The tetrads synthesized using multi-step synthetic procedure revealed strong charge transfer interactions in the ground state involving the donor and azaBODIPY entities. The near-IR emitting azaBODIPY acted as a photosensitizing electron acceptor along with fullerene while the phenothiazine and ferrocene entities acted as electron donors. The triads (bisdonor-azaBODIPY) and tetrads revealed ultrafast photoinduced charge separation leading to D•+-azaBODIPY•–-C60 and D•+-azaBODIPY-C60•– (D = phenothiazine or ferrocene) charge separated states from the femtosecond transient absorption spectral studies in both polar and nonpolar solvent media. The charge separated states populated the triplet excited state of azaBODIPY prior returning to the ground state.
19
Duva, Giuliano [Verfasser]. "Structural and Spectroscopic Studies of Molecular Semiconductor Donor : Acceptor Systems for Organic Optoelectronics / Giuliano Duva." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/122488227X/34.
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20
Webre, Whitney Ann. "Spectral, Electrochemical, Electron Transfer, and Photoelectrochemical Studies of Tetrapyrrole Derived Supramolecular Systems." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609091/.
Повний текст джерелаАнотація:
Energy- and electron-transfer processes in molecular and supramolecular donor-acceptor systems are of current interest in order to develop light-energy harvesting systems through designing covalently linked donor-acceptor systems or utilizing self-assembled donor-acceptor systems. The research presented in this dissertation deals with the electrochemical, anion binding, and photochemical studies of various oxoporphyrinogen (OxPs), porphyrin, corrole, and phenothiazine systems. The first chapter provides a brief introduction to the material discussed in the subsequent chapters. The second chapter discusses the bromination of meso-tetraarylporphyrings and how that affects their electrochemical, catalytic, and other properties. Bromination of these porphyrins and oxoporphyrinogens allow the HOMO-LUMO gap to increase revealing blue-shifted absorption. Brominated OxPs and bis-crown ether OxP self-assembled with anions depending on strength of the anion and size of the binding site. The addition of crown ethers allows a cation binding site which makes a self-assembled donor-acceptor supramolecular system.Chapters 5 and 6 discuss a series of donor-acceptor conjugates based on zinc porphyrin as the electron donor and copper(III) corrole as the electron acceptor. These studies illustrate the importance of copper(III) corrole as a potent electron acceptor for the construction of energy harvesting model compounds, and constitute the first definitive proof of charge separation in ZnP-CuIIIC systems.Chapter 7 summarizes several interesting observations made in the present study on DSSCs built on two types of phenothiazine dyes having one or two cyanocinnamic acid groups.
21
Wallin, Staffan. "The Fate of Electronically Excited States : Ultrafast Electron and Energy Transfer in Solvated Donor-Acceptor Systems." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis (AUU) : Universitetsbiblioteket [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6135.
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22
Gobeze, Habtom Berhane. "Ultrafast Photoinduced Energy and Electron Transfer Studies in Closely Bound Molecular and Nanocarbon Donor-Acceptor Systems." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248516/.
Повний текст джерелаАнотація:
As part of the study, photosynthetic system constructs based on BF2-chelated dipyrromethene (BODIPY), BF2-chelated azadipyrromethene (AzaBODIPY), porphyrin, phthalocyanine, oxasmaragdyrin, polythiophene, fullerene (C60), single-walled carbon nanotube and graphene are investigated. Antenna systems of BODIPY dyads and oligomers having BODIPY as an excitation energy donor connected to different acceptors including BODIPY, azaBODIPY, oxasmaragdyrin and aluminum porphyrin are studied. Different synthetic methodologies are used to afford donor-acceptor systems either directly linked with no spacer or with short spacers of varying length and orientation. The effect of donor orientation, donor optical gap as well as nature of donor-acceptor coupling on the donor-acceptor spectral overlap and hence the rate of excitation energy transfer is investigated. In all these systems, an ultrafast energy transfer followed by electron transfer is observed. In particular, in a directly connected BODIPY-azaBODIPY dyad an unusually ultrafast energy transfer (~ 150−200 f) via Förster mechanism is observed. The observation of energy transfer via Förster instead of Dexter mechanism in such closely coupled donor-acceptor systems shows the balance between spatial and electronic coupling achieved in the donor-acceptor system.
Moreover, in donor-acceptor systems involving semiconducting 1D and 2D materials, covalently functionalized single-walled carbon nanotubes via charge stabilizing (TPA)3ZnP and noncovalently hybridized exfoliated graphene via polythiophene chromophores are studied for their charge transportation functions. In both cases, not only an ultrafast charge transfer in the range of (~ 2−5 p) is observed but also the charge-separated states were long lived implying the potential of these functionalized materials as efficient charge transporting substrates with organic chromophores for photovoltaic and optoelectronic applications where ultrafast intercomponent charge transfer is vital. In addition, as a final part of this dissertation, the mechanisms of electron injection and back electron transfer in heterogeneous systems involving supramolecularly anchored high potential chromophores on TiO2 film are studied by femtosecond transient absorption spectroscopy. In this study, not only are important insights gained on the utilization of supramolecular anchoring of chromophores such as porphyrins, phthalocyanines, and their perflorinated high potential analogues, chromophores currently showing promise as highly efficient sensitizers in dye sensitized solar cells, on TiO2 film but also on the effect of anchor length and sensitizer orientation on the rates of electron injection and back electron transfer at the sensitizer-TiO2 interface.
23
Obondi, Christopher O. "High-Energy, Long-Lived Charge Separated States via Molecular Engineering of Triplet State Donor-Acceptor Systems." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc1248463/.
Повний текст джерелаАнотація:
Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an ‘antenna' system causing an electron transfer into the ‘reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy.
In this dissertation, we report on the design and synthesis of donor–acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the greatest amount of energy but must be fast to out compete intersystem crossing. To address this limitation, we have designed novel donor –acceptor conjugates that use high-energy triplet sensitizers in which electron transfer is initiated from the long lived triplet state of the donor. The triplet photosensitizers used were palladium(II) porphyrin and platinum(II) porphyrin. Heavy metal effect in these porphyrins promoted intersystem crossing and the energies of their excited state was quite high. For the case of palladium (II) porphyrin the energy stored was found to 1.89 eV and that of platinum(II) porphyrin 1.84 eV.
In addition to using triplet photosensitizers as donors, we have used donors that are difficult to oxidize and hence producing long lived charge separated states with adequate amount of stored energy. The system that was used for this study is zinc porphyrin with meso-aryl pentafluorophenyl substituents and fullerene, C60 as the acceptor. The presence of fluorine substituents on zinc porphyrin makes it harder to undergo oxidation. When this high potential donor-acceptor system undergoes a photoinduced charge-separation, the estimated energy stored was found to be 1.70 eV, one of the highest reported in literature so far. To further extend the lifetime of the charge separated states generated in this high-potential zinc porphyrin-fullerene dyad a pyridine functionalized tetrathiafulvalene was axially coordinated to the Zn metal producing a supramolecular triad capable of producing long-lived charge separated state.
In a subsequent study, a multi-modular donor-acceptor system composed of a porphyrin, fullerene (C60) and a BF2-chelated dipyrromethene (BODIPY) with a supramolecular arrangement in the form of porphyrin-BODIPY-C60, one of the few reported in literature. By selectively exciting BODIPY and ZnP moieties, efficient singlet-singlet energy transfer from 1BODIPY * to ZnP in toluene was observed in the case of the dyad ZnP-BODIPY. However, when ZnP is excited, electron transfer occurred with the formation ZnP.+-BODIPY-C60.- charge separated state persisting for microseconds.
24
Obondi, Christopher O. "High-Energy, Long-Lived Charge-Separated States via Molecular Engineering of Triplet State Donor-Acceptor Systems." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248463/.
Повний текст джерелаАнотація:
Molecular engineering of donor-acceptor dyads and multimodular systems to control the yield and lifetime of charge separation is one of the key goals of artificial photosynthesis for harvesting sustainably solar energy. The design of the donor-acceptor systems mimic a part of green plants and bacterial photosynthetic processes. The photochemical events in natural photosynthesis involve the capturing and funneling of solar energy by a group of well-organized chromophores referred to as an ‘antenna' system causing an electron transfer into the ‘reaction center,' where an electron transfer processes occur resulting a long-lived charge separated state. Over the last two to three decades, many efforts have been directed by the scientific community designing of multi-modular systems that are capable of capturing most of the useful sunlight and generating charge separated states of prolonged lifetimes with adequate amounts of energy.
In this dissertation, we report on the design and synthesis of donor–acceptor conjugates with the goal of modulating the yield and lifetime of their charge separated states and hence, improving the conversion of light energy into chemical potential. In simple donor-acceptor systems, generally, the energy and electron transfer events originate from the singlet excited state of the donor or acceptor and can store the greatest amount of energy but must be fast to out compete intersystem crossing. To address this limitation, we have designed novel donor –acceptor conjugates that use high-energy triplet sensitizers in which electron transfer is initiated from the long lived triplet state of the donor. The triplet photosensitizers used were palladium(II) porphyrin and platinum(II) porphyrin. Heavy metal effect in these porphyrins promoted intersystem crossing and the energies of their excited state was quite high. For the case of palladium (II) porphyrin the energy stored was found to 1.89 eV and that of platinum(II) porphyrin 1.84 eV.
In addition to using triplet photosensitizers as donors, we have used donors that are difficult to oxidize and hence producing long lived charge separated states with adequate amount of stored energy. The system that was used for this study is zinc porphyrin with meso-aryl pentafluorophenyl substituents and fullerene, C60 as the acceptor. The presence of fluorine substituents on zinc porphyrin makes it harder to undergo oxidation. When this high potential donor-acceptor system undergoes a photoinduced charge-separation, the estimated energy stored was found to be 1.70 eV, one of the highest reported in literature so far. To further extend the lifetime of the charge separated states generated in this high-potential zinc porphyrin-fullerene dyad a pyridine functionalized tetrathiafulvalene was axially coordinated to the Zn metal producing a supramolecular triad capable of producing long-lived charge separated state.
In a subsequent study, a multi-modular donor-acceptor system composed of a porphyrin, fullerene (C60) and a BF2-chelated dipyrromethene (BODIPY) with a supramolecular arrangement in the form of porphyrin-BODIPY-C60, one of the few reported in literature. By selectively exciting BODIPY and ZnP moieties, efficient singlet-singlet energy transfer from 1BODIPY * to ZnP in toluene was observed in the case of the dyad ZnP-BODIPY. However, when ZnP is excited, electron transfer occurred with the formation ZnP.+-BODIPY-C60.- charge separated state persisting for microseconds.
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Karolewski, Andreas [Verfasser], and Stephan [Akademischer Betreuer] Kümmel. "Describing Charge Transfer in Extended Donor-Acceptor Systems with Density Functional Theory / Andreas Karolewski. Betreuer: Stephan Kümmel." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059352494/34.
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Sage, Ashley Bryan. "Donor/acceptor systems for modelling mechanisms and kinetics of hydrogen transfer reactions in relation to coal liquefaction." Thesis, Staffordshire University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309786.
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Rattananakin, Pornpun. "Ab initio study of the rotation around the carbon-carbon double bond in push-pull systems." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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Feilitzsch, Till von. "On the mechanism of photoinduced electron transfer in bridged donor-acceptor systems ferrocenophane-nileblue and rhodamine6G endcapping the DNA duplex /." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972589198.
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Lefarth, Jens [Verfasser]. "Intermolecular [2+2]-Photocycloaddition Reactions of complex Acceptor-Donor Systems and Developement of an Enantioselective Photocatalyzed Hydroformylation Reaction / Jens Lefarth." München : Verlag Dr. Hut, 2021. http://nbn-resolving.de/urn:nbn:de:101:1-2021100123325739335454.
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GALLONI, PIERLUCA. "Construction of electron-active complex systems as model for artificial photosynthesis." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2004. http://hdl.handle.net/2108/202905.
Повний текст джерелаАнотація:
La fotosintesi artificiale è un obiettivo ambizioso per la scienza moderna, che richiede una comprensione completa dei sistemi naturali. La comprensione di tutte le diverse reazioni del sistema è uno degli aspetti fondamentali nella ricerca chimica, fisica e biologica. Lo studio delle reazioni di trasferimento elettronico tra un accettore e un donatore è un punto cruciale, sia per lo sviluppo di sistemi artificiali sintetici, sia per possibili applicazioni nella costruzione di dispositivi elettronici e materiali fotosensibili. Lo scopo di questa tesi è stato quello di investigare reazioni di trasferimento elettronico e di energia, per avere informazioni riguardo le leggi che regolano questi sistemi complessi, usando diversi sistemi donatore-accettore, tra i quali particolare attenzione è stata rivolta al C60 come accettore e al ferrocene come donatore. Il lavoro sintetico è stato una parte importante della tesi, richiedendo tempo per ottimizzare le condizioni di reazione, le procedure di purificazione e per la completa caratterizzazione dei prodotti. Numerosi nuovi composti sono stati sintetizzati e sono state migliorate le rese per alcuni prodotti noti da letteratura. Un aspetto importante del lavoro ha riguardato lo studio dell’interazione tra donatore e l’accettore in alcune delle diadi ottenute, sia allo stato fondamentale, sia nello stato eccitato. Tra i vari risultati, i più interssanti possono essere riassunti nei seguenti punti. a) Un andamento peculiare emerge dagli esperimenti fotofisici e computazionali e dalle misure elettrochimiche e degli spettri di assorbimento nelle diadi fluorene-fullerene: cambia l’interazione, cambiando la posizione del fluorene che lega il fullerene. b) Risultati molto interessanti sono stati ottenuti quando ferrocene e fullerene sono uniti tramite legame spiro, dando una diade dalla geometria rigida. Difatti, confrontando le proprietà nello stato eccitato di questa diade con quelle della N-metil-2-ferrocenil-[3,4]-fulleropirrolidina, con maggiore libertà conformazionale, è stata osservata una reazione di trasferimento elettronico più veloce, indice di una maggiore interazione tra i due componenti. c) In diadi supramolecolari composte da ZnSalen e N-metil-2-piridil-[3,4]-fulleropirrolidina è stato osservato un efficiente trasferimento di energia. Questo sistema può essere usato come modello nei sistemi impiegati nella cattura della luce. d) Un efficiente trasferimento di elettroni avviene tra la tetraferrocenilporfirina di zinco e la N-metil-2piridil-[3,4]-fulleropirrolidina in una diade supramolecolare, come è stato osservato tramite la spettroscopia transiente, dove un tempo di vita di 800 ps della specie eccitata a separazione di carica è stato ottenuto in un solvente apolare come il toluene. In conclusione, sono stati ottenuti nuovi sistemi per lo studio delle reazioni di trasferimento di energia e di elettroni, che sono stati studiati usando diversi approcci sperimentali. I risultati possono essere di aiuto sia per una miglior comprensione dei fenomeni naturali, sia per lo sviluppo e la costruzione di dispositivi fotosensibili.Artificial photosynthesis is an ambitions target of modern science that obviously requires a complete understanding of natural photosynthesis. The understanding of all steps involved is one of the most important topic in chemical, biological, and physical research. The study of electron transfer reaction between donor and acceptor molecules is a crucial key point, both for development of artificial photosynthesis and for application in electronic devices and photosensible materials. The aim of this thesis was to investigate electron and energy transfer reactions, as source of information about the mechanisms that rule this complex reaction, using different donor-acceptor systems, among which attention have been focused at C60 as acceptor and ferrocene as donor. Synthetic work constituted a major task in this thesis, requiring several attempts in order to optimize reaction conditions, purification procedures and full characterization of products. A number of new compounds was obtained together with improved yields of known products. Another important aspect of the work involved investigation of donor-acceptor interaction in some of the dyads, both in ground and in excited states. Among all the results, the most significant ones may be summarized in the following points. a) A peculiar behaviour emerged from photophysical and computational experiments, electronic spectra and electrochemical measurements of fluorene-fullerene dyads. Different interaction was the result of changing the position through which the two moieties are connected. b) Very interesting results emerged when a frozen structure was obtained from connecting ferrocene and fullerene moieties in a rigid assembly. In fact, in comparison with a dyad with flexible connection, a faster electron transfer rate - and therefore an enhanced interaction - was observed in the excited state. c) Efficient energy transfer was observed with supramolecular (ZnSalen)-(N-methyl-2-pyridyl-[3,4]fulleropyrrolidine) dyads. This system can be used as a good model for light harvesting model. d) Very efficient electron transfer reaction occurred between zinctetraferrocenylporphyrin and pyridylfulleropyrrolidine in supramolecular (ZnFc4Porph)-(N-methyl-2-pyridyl-[3,4]-fulleropyrrolidine) dyad, as observed by transient spectroscopy, even in non polar solvent such as toluene. In conclusion, new good systems for energy an electron transfer were obtained and investigated by different approaches. They can be used to reach a deeper knowledge of complex phenomena that rule natural photosynthesis as well as to build photosensible devices.
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Alves, Jessica. "Advanced photochemical reaction systems for molecular design." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/227734/1/Jessica_Alves_Thesis.pdf.
Повний текст джерелаАнотація:
Direct laser writing is a technique for printing complex 3D structures with high resolution by irradiating a photoresist in a two-photon process. Improved resolution and dynamic material properties of the printed structures is critical. Herein, advanced photochemical systems were investigated, potentially enabling dual-wavelength direct laser writing. Such systems consisting of organic photoswitches enable the formation of a single product only when irradiated with two wavelengths. A well-known class of photoswitches was investigated for this purpose and its chemistry was carefully explored. Further, photocatalysis combined with a photoswitch was identified as a possible strategy for the two-colour activated photoresist development.
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Browning, Charles. "Diimine(dithiolate)platinum(ii) Chromophores: Synthesis, Spectroscopy, and Material Applications." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699877/.
Повний текст джерелаАнотація:
A series of 28 square-planar dithiol(diimine)platinum(II) chromophoric complexes have been synthesized, characterized, and evaluated for potential efficacy in sensitization of solid state photovoltaic devices to the near-infrared regions of the electromagnetic spectrum. The effect of molecular stacking in the solid state and self-association in solution are shown to influence spectral, electronic, and magnetic properties of the chromophores. Such properties are investigated in the pure form and as partners in donor-acceptor charge transfer adducts. Finally, selected chromophores have been incorporated into single layer schottky diodes as neat films and as dopants in multi-layer organic photovoltaic devices. Evaluation of the devices internal quantum efficiency and voltage-current was measured as proof of concept.
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Kaiser, Conrad [Verfasser], Christoph [Gutachter] Lambert, and Ingo [Gutachter] Fischer. "Donor-Bridge-Acceptor Systems with Varying Bridge Units for the Investigation of Intramolecular and Intermolecular Electron Transfer Processes / Conrad Kaiser. Gutachter: Christoph Lambert ; Ingo Fischer." Würzburg : Universität Würzburg, 2014. http://d-nb.info/1102825794/34.
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Maibach, Julia [Verfasser], Wolfram [Akademischer Betreuer] Jaegermann, and Heinz von [Akademischer Betreuer] Seggern. "Preparation and Characterization of Solution Processed Organic Semiconductor Interfaces: Electronic Properties of Thiophene-Fullerene based Donor-Acceptor Systems / Julia Maibach. Betreuer: Wolfram Jaegermann ; Heinz von Seggern." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2014. http://d-nb.info/1110901321/34.
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Gupta, Gaurav Kumar [Verfasser], Thomas [Akademischer Betreuer] Thurn-Albrecht, Christine M. [Akademischer Betreuer] Papadakis, and Wolfgang [Akademischer Betreuer] Paul. "Structural investigations on semiconducting donor-acceptor block copolymers and related model systems for organic photovoltaics / Gaurav Kumar Gupta. Betreuer: Thomas Thurn-Albrecht ; Christine M. Papadakis ; Wolfgang Paul." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2014. http://d-nb.info/1052221262/34.
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Nicoletta, Francesca. "Design and synthesis of new processable materials for application in organic devices." Doctoral thesis, Università di Catania, 2017. http://hdl.handle.net/10761/3977.
Повний текст джерелаАнотація:
New materials were designed and synthetized for photovoltaic applications featuring ability to be processed from green solvents including alcohol or water.
In the synthesis of semiconductor materials, the well-known diketopyrrolopyrrole (DPP) unit was used as main building block for its features as excellent electron-acceptor unit in compounds with low bandgap.
Six small molecules, based on DPP unit endcapped with triazolo group were synthetized and functionalized with solubilizing peripheral chains that allowed the dispersion in nonorganic and toxic solvents. All molecules were characterized through NMR and IR spectroscopy; in addition, physicochemical properties of the derivatives including solubility in variety of solvents, solution and film absorption and emission, and cyclic voltammetry (CV) were studied. Bulk heterojunction solar devices, using the synthetized materials as donors and PC60BM as acceptors were fabricated and tested.
Furthermore, some polymers were designed to comprise DPP unit with polar triethylen glycol (Teg) side chains and different comonomers including vinyl, ethylhexyloxy benzodithiophene or functionalized thiophene ring. The majority of materials were synthesized using the Stille condensation reaction, but also an environmentally friendly process, the Direct Heteroarylation Polymerization (DAHP) reaction was profitably used.
All materials were extensively characterized exhibiting low values of bandgaps and tested as donors in blends with PC70BM for photovoltaic response in both conventional and inverted device architectures, demonstrating, for the best polymer, a power conversion efficiency (PCE) around 1.5%. Interestingly, in field effect transistors, the same material, shows hole mobility approaching 0.015 cm2/Vs.
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Linton, Katharine Elizabeth. "New bipolar organic materials for optoelectronic applications." Thesis, Durham University, 2012. http://etheses.dur.ac.uk/4437/.
Повний текст джерелаАнотація:
The literature surrounding organic small-molecule donor-acceptor systems is summarised for a range of optoelectronic applications (OLEDs, OPVs, OFETs etc.). There is a focus on the key building blocks: 1,3,4-oxadiazole (OXD), diphenylamine (DPA), carbazole (Cbz) and fluorene (F). The incorporation of such moieties into various donor-acceptor systems is discussed with further reference to selected alternative organic donor and acceptor systems. The syntheses of novel bipolar molecules based on a donor-spacer-acceptor (DPA/Cbz-F-OXD) structure and the incorporation of these molecules into single-layer OLEDs is presented. It is demonstrated how the emission colour can be tuned from green to deep blue by systematic manipulation of the structure. A significant result is that high efficiency accompanied with pure, deep blue emission in single-layer OLEDs can be achieved with this structural motif. The incorporation of these materials as part of a simple two-component blend to produce white OLEDs is presented and the modification of the materials to improve electron-transport properties is discussed. The synthesis of DPA-bridge-OXD wire systems is presented with the use of oligo-p-phenyleneethynylene units as a bridge of varying length to investigate the effect on charge transfer between the donor and acceptor. Photophysical studies demonstrate the change in absorption, emission and fluorescence lifetimes as the length scale of the molecules is altered. The synthesis of a series of planarised and twisted DPA-bridge-OXD systems based upon phenylene linkers is discussed. Finally, a series of DPA-F-OXD-anchor molecules is presented for incorporation into DSSC devices. The synthesis of these materials is described and the suitability of various anchoring groups for DSSCs is analysed through photophysical and device studies.
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Marushchak, Denys. "Fluorescence studies of complex systems : organisation of biomolecules." Doctoral thesis, Umeå : Department of Chemistry, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-979.
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Busseau, Antoine. "Synthèse et caractérisations de nouveaux penta(organo)[60]fullerènes pour la formation d’assemblages supramoléculaires." Thesis, Angers, 2017. http://www.theses.fr/2017ANGE0033/document.
Повний текст джерелаАнотація:
La structure unique et les propriétés des fullerènes ont suscité l’intérêt des chercheurs, en particulier dans les domaines de l’électronique et de l’optoélectronique. Dans ce contexte, plusieurs mono- et de poly-adduits du fullerène ont été décrits pour leurs développements comme nouveaux matériaux originaux et comme polymères supramoléculaires. Nous présentons ici les synthèses et les études de nouveaux polymères supramoléculaires donneur-accepteur à base de penta(organo)[60]fullerènes. La parfaite régiosélectivité de la réaction de pentafonctionnalisation sur le [60]fullerène permet de former une cavité conique formée de cinq fragments éthynylaryles. A cette structure, différentes unités électro et/ou photoactives (tétrathiafulvalène et porphyrine de zinc) ont été liés par des liaisons covalentes via cinq réactions de cycloaddition 1,3- dipolaire. Le composé hôte-invité avec ses propriétés donneur-accepteur permet la formation d’assemblages par des interactions supramoléculaires. Nous avons réalisé les synthèses des penta(organo)[60]fullerènes comme nouveaux matériaux donneur-accepteur et nous avons étudié les propriétés des assemblages supramoléculaires en solution et à l’état solideThe unique structure and properties of fullerenes have attracted wide interest especially in electronic and optoelectronic fields. In this context, a variety of mono-and poly-fullerene adducts have been described for theirs interest in the development of new complex materials and supramolecular polymers. Here, we present the synthesis and studies of new donor-acceptor supramolecular polymers based on penta(organo)[60]fullerenes. The perfect regioselectivity of the [60]fullerene pentafunctionalization reaction has provided us a singular conical structure formed by five ethynylaryl fragments. To this structure different electro and/or photoactive fragments (tetrathiafulvalene or zinc-porphyrin) were covalently linked using five simultaneous 1,3-dipolar cycloaddition reactions. The formed host-cavity together with the donor-acceptor properties of these system allow their assembly by supramolecular interactions. We have realized the synthesis of these penta(organo)[60]fullerenes as new donor-acceptor materials and the studies of their remarkable supramolecular arrangement in solution and solid state
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Vilmercati, Paolo. "Ultra-fast charge transfer dynamic in thin and ultra-thin films of organics studied with synchrotron radiation." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2564.
Повний текст джерелаАнотація:
2006/2007The increasing energy crisis has induced science and technology world to drive a lot of efforts in the study of new materials suitable to develop renewable and with a low environmental impact energy sources as an alternative to petroleum. In this context photo-voltaic cells are a good solution, nevertheless the high costs and the low light-to-current efficiency still inhibits a large production and a common usage. The employment of organic based materials, i.e. the materials inspired by biological processes, finds a place in this research field. The wide availability of these materials in nature, the ease in material processing and the intriguing chemical and physical properties places the organics as good candidates in the production of photovoltaic devices. Moreover, their electronic properties allow a usage as charge injector to enhance the light-to-current efficiency in inorganic-based photovoltaic devices (Gratzel-cells). The aim of this thesis is to study the growth, the electronic properties, and the chargetransfer dynamic in thin and ultra-thin film(single molecular layer) composed by zinc-tetraphenylporphyrin and C70 and thicker melanin films. We choose these molecules both because of their high visible light sensitivity and because porphyrins are electron donor and fullerenes are electron acceptors. In fact, it is well know in biology that the chlorophyll (Mg-poprhyrin) when illuminated with visible light, act as an electron injector in the biochemical environment supplying the amount of energy needed to activate the production of glucose starting from water and carbon dioxide (chlorophyll synthesis). The fullerene C70 consist in an arrangement of 70 carbon atoms in a closed cage structure and is a good electron acceptor. Then, the our purpose is to use the different electronic properties of these molecules to generate donor/acceptor junctions at the molecular scale. Melanin is a natural pigment present in living beings responsible, in human body, of the colour of skin and of its variation due to the exposition to the sun light; it is a semiconductor with electron donor properties. The combined usage of the properties of these molecules opens the way to the production of complexes to realize high-efficiency and low cost photovoltaic devices. In this context, and at the present state of the art in the production of organic-based photovoltaic devices, investigations about the basic mechanism of molecular interaction and electronic properties are needed to clarify the problems that are still open. In fact the light-tocurrent conversion is just one of the possible processes successive to the absorption of a visible photon in a material. In fact the large number of dissipative processes dissipates the charges excited by the light and inhibits the light-to-current conversion efficiency. In this context, two aspect are fundamental: the presence of empty states in the conduction band that are not allowed for dipole transitions from the valence band but energetically favourable with respect to the first allowed ones, in order to brake the excitonic bond and a good charge mobility in order to transport the excited charges up to the collecting electrodes of the device. because the mobility is higher in ordered systems instead of non ordered ones, the molecular interaction and the growth condition have a fundamental role because they determine the molecular packing in the film. In this sense we used soft X-rays and UV-rays photoemission to study the interaction between ZnTPP and C70 and between these molecules and the Si(111)7x7 surface, one of the most common substrate used to produce electronic devices. We studied the order in the various films in the sense of “orientational order” using Near Edge Absorption Fine structure Spectroscopy at SuperESCA and ALOISA beamlines at ELETTRA synchrotron radiation facility in Trieste. Because the NEXAFS spectra, obtained with linearly polarized radiation, are sensitive to the direction of the chemical bonds, the dependence of the absorption structures intensity on the angle between the electrical field of the incoming radiation and the direction of the empty states yields informations about the geometrical (orientational) arrangements of the molecules in the film. The films were produced by sublimation in ultra-high-vacuum in order to obtain a film as pure as possible. We produced a melanin film via “drop casting”, by in air deposition of a suspension of synthetic melanin powder in mineral free water on a polycristal copper surface and drying the water. We obtained the first photoemission data available in literature about this system. A particular attention was dedicated to the ultra-fast delocalization processes of the excited charges. We used Resonant Photoemission technique (SuperESCA beamline at ELETTRA) to study the excitation de-excitation processes: a core electron is pumped to an empty state in the conduction band, the following decay of the core hole (scale of fs) reveals time scale of the excited charge delocalization with a chemical sensitivity typical of core spectroscopies
La crescente crisi energetica ha indotto la scienza e la tecnologia ad indirizzarsi verso lo studio di nuovi materiali da utilizzarsi per sviluppare fonti di energia alternative al petrolio che siano rinnovabili e a basso impatto ambientale. In questo ambito le celle foto-voltaiche sono una buona risposta, tuttavia i costi elevati e la bassa efficienza nella conversione luce-corrente fanno sì che esse non siano ancora di uso comune. Lo studio dei materiali organici, ovvero di quelli ispirati da processi biologici, trova spazio in questo ambito di ricerca. La larga diffusione in natura dei costituenti, la facilità nel processare il materiale, e le interessanti proprietà chimico-fisiche fanno dei materiali organici una delle possibili scelte nella realizzazione di dispositivi fotovoltaici. Inoltre, la versatilità di questi materiali li rende utilizzabili anche come iniettori di cariche per aumentare l’efficienza di conversione luce-corrente se accoppiati con semiconduttori inorganici (Gratzel-cells). Oggetto di questa tesi è lo studio della crescita e delle proprietà elettroniche di trasferimento di carica di film sottili e monostrati molecolari composti di zinco-tetrafenil-porfirina e C70, e film di melanina. La scelta di queste molecole origina sia dalle loro proprietà di sensibilità alla luce visibile che dalle loro proprietà elettroniche di essere donori ed accettori di elettroni. Infatti, è ben noto in natura che la clorofilla (magnesio-porfirina) svolge la funzione di iniettore di carica nell’ambiente biochimico per fornire l’energia necessaria all’attivazione della produzione di glucosio a partire da acqua e anidride carbonica, quando esposta a luce solare. Il fullerene C70 è una molecola costituita da settanta atomi di carbonio disposti in una struttura chiusa a gabbia ed ha la proprietà di essere un accettare di elettroni. Uno degli obiettivi è, quindi sfruttare le diverse proprietà elettroniche di queste molecole per realizzare delle giunzioni donore/accettore su scala molecolare. La melanina è il pigmento naturale presente negli esseri viventi responsabile, nel corpo umano, del colore della pelle e del suo cambiamento in seguito all’esposizione alla luce ed è anch’essa un semiconduttore con proprietà di donore di elettroni. L’uso combinato di queste caratteristiche apre la strada alla realizzazione di materiali complessi che possano essere utilizzati nella realizzazione di dispositivi fotovoltaici. In questo contesto, e all’attuale stato dell’arte della realizzazione di dispositivi fotovoltaici basati su molecole organiche è necessario lo studio di base delle proprietà elettroniche dei film composti di queste molecole per affrontare problematiche aperte. Infatti il processo di conversione della luce in corrente è solo uno di quelli possibili in seguito all’assorbimento di un fotone visibile da parte di un materiale. Infatti un gran numero di processi dissipativi rende le cariche eccitate in gran parte inutilizzabili ai fini della conversione della luce in corrente. Due aspetti sono fondamentali affinché il materiale possa essere efficiente nella conversione luce-corrente: la presenza di stati di conduzione vuoti non accessibili tramite eccitazione con radiazione elettromagnetica ma energeticamente favorevoli rispetto a quelli accessibili, e una buona mobilità delle cariche eccitate in modo da essere trasportate senza dissipazione verso gli elettrodi di raccolta. Dal momento che la mobilità delle cariche è maggiore in sistemi ordinati, diventano cruciali sia le tecniche di crescita che le interazioni molecolari che determinano l’impacchettamento delle molecole a formare il film. In questo senso ci siamo avvalsi della spettroscopia di fotoemissione nel regime dei raggi X soffici e di raggi UV per studiare sia l’interazione tra le due specie molecolari e substrato (superficie (111) del silicio) che tra porfirina e porfirina e porfirina e fullerene, crescendo films a spessori via via crescenti. Per quanto riguarda la crescita, e quindi l’ordine con cui sono stati cresciuti i films abbiamo utilizzato la spettroscopia di assorbimento vicino soglia (NEXAFS, esperimenti eseguiti sulla beamline ALOISA ad ELETTRA). Poiché gli spettri di assorbimento sono sensibili alla direzione di legami chimici qualora eccitati con radiazione polarizzata linearmente, la dipendenza dell’intensità dei singoli picchi di assorbimento dall’angolo tra il vettore campo elettrico della radiazione e la direzione del legame fornisce informazioni circa la geometria del sistema. I films sono stati ottenuti per sublimazione di polveri in ultra alto vuoto al fine di ottenere un sistema chimicamente puro. Per quanto riguarda la melanina, abbiamo realizzato un film utilizzando la tecnica del “drop casting” depositando una sospensione di acqua e melanina su una superficie di rame policristallino e lasciando evaporare l’acqua. Sono stati raccolti, quindi, i primi dati di fotoemissione presenti in letteratura riguardo questo sistema. Particolare attenzione è stata rivolta ai processi ultraveloci di delocalizzazione delle cariche in stati eccitati. A tale scopo abbiamo utilizzato la tecnica di fotoemissione risonante (ResPES, esperimenti eseguiti sulla beamline SuperESCA ad ELETTRA), in cui un elettrone di core viene eccitato da radiazione di sincrotrone a riempire uno stato di conduzione, il successivo decadimento della buca di core (scala temporale dei fs) permette di individuare l’avvenuta delocalizzazione dell’elettrone eccitato ed ottenere una stima dell’efficienza di trasferimento di carica con specificità chimica
XX Ciclo
1973
41
Pokethitiyook, Prayad. "Nitrate utilization as the final electron acceptor in a biological phosphorus removal system." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040836/.
Повний текст джерела
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Song, Baiyun. "Studies on High Potential Porphyrin-fullerene Supramolecular Dyads." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc407825/.
Повний текст джерелаАнотація:
Photoinduced electron transfer in self-assembled via axial coordination porphyrin-fullerene dyads is investigated. Fullerene functionalized with imidazole and fullerenes functionalized with pyridine are chosen as electron acceptors, while zinc pophyrin derivatives are utilized as electron donors. The electron withdrawing ability of halogen atoms make the porphyrin ring electrophilic, which explained the binding of (F20TPP)Zn with fullerene derivatives having the highest binding constant around 105M-1. Another important observation is that the fullerene imidazole binding to zinc pophyrin had higher stability than fullerene pyridine-porphyrin dyad. Computational DFT B3LYP-21G(*) calculations are used to study the geometric and electronic structures. The HOMO and LUMO was found to be located on the porphyrin and fullerene entities, respectively. Photoinduced electron transfer is investigated by the steady-state absorption and emission, differential pulse voltammetry, and nanosecond and femtosecond transient absorption studies. The measurements provided the same conclusion that the increasing number of the halogen atoms on the porphyrin ring leads to the higher binding of porphyrin-fullerene supramolecular dyads and efficient charge separation and charge recombination processes.
43
Vartanian, Maida. "Cu(I) catalyzed alkyne-azide cycloaddition as a synthetic tool for the preparation of complex C60 derivatives." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF016.
Повний текст джерелаАнотація:
La présente thèse décrit la synthèse de briques de base de fullerènes pour la préparation de dispositifs moléculaires photoactifs combinant C60 et porphyrines. La cycloaddition alcyne-azoture catalysée au cuivre (I) a été utilisée comme outil de synthèse pour la préparation des dérivés C60 complexes.L’utilité synthétique de synthons C60 a été montrée avec la préparation d’édifices moléculaires complexes présentant des propriétés spécifiques pour diverses applications. Ainsi, un système photoactif flexible combinant C60 et porphyrine a été synthétisé. Cependant la flexibilité de l’espaceur liant les sous-unités de ce composé conduit à des variations de structurales importantes et complique ainsi l’analyse des études photophysiques.Dans ce contexte, nous nous sommes proposé dans une première partie de la présente thèse de parfaitement contrôler l’orientation et la distance des différentes sous-unités au sein de systèmes C60-donneurs. Afin de répondre à ce besoin, nous avons construit une brique de base de C60 rigide ayant un groupe azoture aromatique. Ainsi, la réaction « click » avec un phénylacétylène conjugué au groupement donneur conduit à un espaceur rigide entre les deux sous-unités.La deuxième partie de ce travail a été consacrée à la synthèse d’hexa-adduits du C60 portant différents groupements fonctionnels. Une méthode de synthèse permettant de préparer des hexa-adduits du C60 fonctionnalisés a été mise au point au laboratoire.Cette stratégie a été modifiée et des composés de C60 comportant dix fonctions azotures et une fonction alcyne protégée ont été synthétisés; dans ce cas il est possible d’introduire dans un premier temps par une réaction click dix groupes fonctionnels. Et dans un second temps; après déprotection de la fonction alcyne, une seconde réaction de click permet alors de greffer un fonctionnel différentThe present PhD thesis manuscript is focused on the use of fullerene building blocks for the preparation of photoactive molecular devices combining C60 and porphyrins. Cu(I) Catalyzed alkyne-azide cycloaddition was used as a synthetic tool for the preparation of complex C60 derivatives. Specifically, in the first part (Chapter II-B), a flexible fullerene-porphyrin triad has been developed and the photophysical studies were performed. The flexible linker between the fullerene core and the azide groups prevented any conformational control on the relative orientation and distance between the two photoactive subunits connected together. This prompted the development of an analogous building block in which the azide unit is directly connected to the bridging phenyl ring (Chapter II-C). In this way, the click reaction with porphyrin-alkyne derivatives give access to hybrid systems with a controlled relative orientation of the two moieties. This is of fundamental importance for a better understanding of the structural parameters affecting the electron and/or energy transfer kinetic in such dyads.In the second part (Chapter III), a fullerene hexaadduct scaffold is used to build up sophisticated multiporphyrin systems for various applications. The preparation of these multi-chromophoric ensembles relies on the click-click approach developed in our group
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Manda, Venkata Ramana. "Enhancing the Photovoltaic Performance of P3HT/PDIB Silsesquioxane Donor-Acceptor System Using Spray Deposition Fabrication Technique." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1336.
Повний текст джерелаАнотація:
In the past few years, the solution-processed organic based solar cells gained more importance by meeting the demands for cost effective photovoltaic devices. To date, the focus of the organic photovoltaic devices has been on the optimization of the processing the materials to improve photo conversion efficiency and also by modifying the active components of the organic materials. Recently, it has been recognized that the deposition techniques also plays a major role in enhancing the power conversion efficiencies. Currently, though the most common deposition technique for organic solar cells is spin coating, which does not allow scaling up of the large device area. As an alternative method, a simple airbrush spray deposition technique has been developed to fabricate the test devices. The film thickness of the layers was characterized under scanning electron microscope. Devices with different thickness (1000 nm, 500 nm, 240 nm) of poly(3,4-ethylenedioxythipohene) polystyrene sulfonate (PEDOT.PSS) and active layers are prepared and their photovoltaic performances have been evaluated and compared by plotting the IV curves with respect to each thickness. Maintaining the distance between the substrate and the airbrush nozzle the thickness of the layers was controlled. From the results, we found that the test devices with 500 nm thickness of PEDOT.PSS and active layers shows the best device performance with highest current density of 3.97 mA/cm2, open circuit voltage of 1.3 V and power conversion efficiency of 2.34%. As a control experiment, devices were also developed using the standard poly(3- hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) system, but the power conversion efficiencies of these devices were not promising with respect to the literature results. Future studies of this project will focus on improving the power conversion efficiency of poly(3-hexylthiophene-2,5-diyl)/perylenediimide bridged system (P3HT/PDIB) by developing a new device architecture called “tandem solar cells” which consists of multiple layers of different donor and acceptor blends with inorganic transition metal oxides such as zinc oxide and molybdenum oxides.
45
Pelchen-Matthews, A. "Distribution of functional acceptors for dendrotoxin and B-bungarotoxin in the central nervous system." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47216.
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46
Gunes, Arzu. "Synthesis Of A Novel Series Of Furan And Fluorene Containing Monomers And Their Polymers." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613768/index.pdf.
Повний текст джерелаАнотація:
In this study, a novel series of conjugated monomers containing furan and fluorene units2,7-di(furan-2-yl)-9H-fluoren-9-one (FOF), 2-(2-(furan-2-yl)-9H-fluoren-7-yl)furan (FFF), and 2-(2-(furan-2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan (FHF) were synthesized and their electrochemical polymerization were achieved via potential cycling. Optical and electrochemical properties of the polymers, poly(2,7-di(furan-2-yl)-9H-fluoren-9-one) (PFOF), poly(2-(2-(furan-2-yl)-9H-fluoren-7-yl)furan (PFFF) and poly(2-(2-(furan-2-yl)-9,9-dihexyl-9H-fluoren-7-yl)furan) (PFHF) were investigated and it was found that polymer films exhibit reversible redox behavior (Epox = 1.083 V for PFOF, Epox= 0.915 V for PFFF and Epox= 0.985 V for PFHF) accompanied with a reversible electrochromic behavior, orange to green for PFOF, yellow to dark blue for PFFF and orange to green for PFHF during oxidation. Their band gap values (Eg) were found to be 2.32, 2.49 and 2.61 eV for PFOF, PFFF and PFHF, respectively.
47
Dirksen, Elena [Verfasser], Thomas J. J. [Gutachter] Müller, and Klaus [Gutachter] Schaper. "Synthese neuartiger Acceptor-substituierter Phenothiazine als Systeme für photoinduzierten intramolekularen Elektronentransfer / Elena Dirksen ; Gutachter: Thomas J. J. Müller, Klaus Schaper." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2019. http://d-nb.info/1189901714/34.
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Kneeshaw, Tara Ann. "Evaluation of kinetic controls on sulfate reduction in a contaminated wetland-aquifer system." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2972.
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Hanson, Christina J. "Building model systems to understand Proton-Coupled Electron Transfer in heme : spectroscopic investigation of charge transfer to axially bound diimide acceptors." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79268.
Повний текст джерелаАнотація:
Thesis (S.M. in Inorganic Chemistry)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013."February 2013." Vita. Cataloged from PDF version of thesis.
Includes bibliographical references.
Proton-Coupled Electron Transfer (PCET) is an important mechanistic motif in chemistry, which allows for efficient charge transport in many biological systems. We seek to understand how the proton and electron motions are coupled in a bidirectional system allowing for individual turning of the kinetics and thermodynamics. The target of interest is a biomimedic heme system allowing for a detailed mechanistic study of the formation of the oxidation states of heme, of particular interest the highly reactive Fe(IV)=O species. The bidirectional model is prepared using a hangman porphyrin with an axially coordinated to the metal center, and the electron transfer event is triggered by excitation of the porphyrin. The synthesis of this motif is discussed as well as initial studies into the binding of a coordinated electron acceptor to the metal center. In the future, the excited state of the acceptor will be used to trigger the electron transfer portion of the PCET event. To understand the signatures of different electron acceptors and binding to the metal center, a redox inactive zinc porphyrin is used as a model to allow for longer excited state lifetimes and well known transient signatures. Three diimide acceptors have been coordinated through a pyridine ring to the metal center of the porphyrin, and electron transfer was triggered both by excitation of the porphyrin and the acceptor. Lifetimes of the charge separated state were determined using picoseconds and nanosecond transient absorption. The acceptors are then coordinated to a symmetrical iron porphyrin in an attempt to understand the behavior of charge separation in the more complicated open d shell system. Spectroscopic data of both systems is shown.
by Christina J. Hanson.
S.M.in Inorganic Chemistry
50
Quinton, Cassandre. "Dérivés de s-tétrazine et de triphénylamine : du design aux applications." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00957915.
Повний текст джерелаАнотація:
Les travaux présentés dans ce mémoire de thèse portent sur la synthèse et l'étude des propriétés spectroscopiques et électrochimiques de systèmes donneur-accepteur conçus pour des applications variées telles que l'électrofluorochromisme, l'absorption à deux photons et le photovoltaïque. La s-tétrazine a été choisie comme accepteur pour sa forte affinité électronique, ses propriétés émissives remarquables et sa capacité à s'organiser via des interactions intermoléculaires de type --stacking. La triphénylamine a été sélectionnée comme donneur pour son faible potentiel d'ionisation, ses propriétés spectroscopiques (fortes absorption et émission) et la modulation facile de ses propriétés par changement de substituants. Sept dérivés de triphénylamine ont été synthétisés ainsi que dix-huit nouveaux composés multichromophoriques à base de tétrazine et de triphénylamine présentant cinq liens différents et des substituants variés. Ils ont été caractérisés par électrochimie et spectroscopie (stationnaire et résolue en temps). L'étude de la modulation de leurs propriétés photophysiques par le changement de l'état rédox a ensuite été réalisée. Dix composés présentant un lien permettant la conjugaison entre la triphénylamine et la tétrazine ont été synthétisés et caractérisés par électrochimie et spectroscopie. Compte-tenu de leurs propriétés, six d'entre eux ont été testés en absorption à deux photons et deux ont étés retenus pour être utilisés comme donneurs dans une cellule photovoltaïque organique. Par ailleurs, deux réactions ont été étudiées en détail pour expliquer la formation des produits obtenus, inattendus à un premier abord.