Spelling suggestions: "subject:"light harvesting"" "subject:"light karvesting""
21 |
Electrical performance study of organic photovoltaics for indoor applications : with potential in Internet of Things devices / Studie av elektriska egenskaper hos organiska solceller för inomhusbruk : med potential för enheter inom Internet of ThingsAndersson, August January 2020 (has links)
The evolution of the internet of things (IoT) opens the market opportunity for organic photovoltaic cells, especially for indoor applications where the lifetime of the organic cells is longer than outdoor. For example, IoT requires off-grid energy sources for many devices with low power consumption. In this work, new materials were tested as candidate components in the active layer of printed organic photovoltaics by fabrication of devices. The initial electrical performance of these devices and their stability over time were investigated by measurements of the current-voltage characteristics. Three selected active layers were further investigated with atomic force microscopy (AFM) measurements. The current-voltage measurements showed that the addition of a solvent additive to the active layer ink affects the initial electrical performance as well as the stability of the devices. The AFM measurements showed that the surface topography of the active layer was affected by the sort of solvent additive that was used. Three new electron acceptor material and two solvent additives showed promising electrical performance and stability.
|
22 |
Synthesis of Optical Materials Based on Element-Blocks and Their Properties / 元素ブロックを基盤とした光学材料の合成とその特性Yeo, Hyeonuk 23 March 2017 (has links)
京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13098号 / 論工博第4159号 / 新制||工||1677(附属図書館) / (主査)教授 中條 善樹, 教授 秋吉 一成, 教授 古賀 毅 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM
|
23 |
Self-assembled Two-component Organic Tubes: Structures And ApplicationsLiang, Wenlang 01 January 2013 (has links)
Bile acids are physiologically important metabolites, which are synthesized in liver as the end products of cholesterol metabolism and then secreted into the intestines. They play a critical role in the digestion and absorption of fats and fat-soluble vitamins through emulsifications. The amphipathic and chiral nature of bile acids makes their unique building blocks for assembling supramolecular structures including vesicles, fibers, ribbons and hollow tubes. Lithocholic acid (LCA) is a secondary bile acid. Our studies show LCA can selfassemble into helical tubes in aqueous solution by the linear aggregation and fusion of vesicles. The objective of this dissertation is to tune the structure of helical tubes and functionalize them by the co-assembly of ionic LCA and cationic cetyltrimethylammonium bromide (CTAB) and ionic LCA and cationic cyanine dye (CD), respectively. The first part of this dissertation focuses on the ionic-assembly of LCA and CTAB to synthesize the helical tubes with varied diameters and pitches. Our studies show that LCA and CTAB can self-assemble into helical tubes in NH4OH aqueous solution. The diameter of the helical tubes can be changed by adjusting the molar ratio of LCA and CTAB. The pitch of the helical tubes can be tuned by varying NH4OH concentrations. Differential scanning calorimetry studies indicate that there is a homogeneous composition distribution in the LCA/CTAB helical tubes. X-ray diffraction analysis studies show that the helical tubes have multibilayer walls with an average d-spacing of 4.11nm. We demonstrate that the helical tubes with varied diameters and pitches can be transformed into helical silica through the sol-gel transcription of tetraethoxysilane (TEOS). The second part of this dissertation is to use the ionic self-assembly of LCA and CD to design light-harvesting tubes iv by mimicking green sulfur bacteria that are known to be a highly efficient photosynthesizer. Xray diffraction and optical spectra show that LCA and CD can co-assemble into J- or Haggregate tubes, depending the condition under which the self-assembly occurs. We demonstrate the feasibility of using the J-aggregate nanotubes in the sensitive and selective detection of mercury (II) ions by the photoinduced electron transfer under sunlight. The presence of mercury (II) ions in aqueous solution could be detected for concentrations as low as 10 pM.
|
24 |
Utilizing NAD+/NADH Analogs for the Solar Fuel Forming ReductionsIlic, Stefan 08 August 2017 (has links)
No description available.
|
25 |
Development of ab initio models for lipid embedded photo-active complexesHino, Alexander T. 16 July 2024 (has links)
Numerous pigment protein complexes exist in natural systems to harvest light energy such as photosystem II and Nanosalina xenorhodopsin. However, the mechanisms of these lipid embedded photo-active complexes have yet to be fully understood. Photosystem II is of interest due to being a compact complex which can perform the three initial key steps of photosynthesis: absorb light, transfer the excitation from the antennae to reaction center, and perform efficient charge separation. Despite considerable theoretical and experimental effort the exact mechanism of this process remains uncertain. Nanosalina xenorhodopsin is a more recently discovered inwards proton pump with minimal studies into the inwards proton pumping mechanism. Nanosalina xenorhodopsin is of interest as it contrasts with other known and well studied rhodopsins which serve as outwards proton pumps, moving H+ ions out of a cell.
In this work, we use the Hamiltonian ensemble method to construct the first fully ab initio computational models of these systems which will be used to determine the mechanisms of these systems. To construct these models we first investigated the effect of the modeled surrounding membrane and simulated temperature. The effect of the extended modeled environment on calculated results is often overlooked but important for the construction of an accurate ab initio model.
Our models showed that both membrane composition and temperature result in significant changes in the behavior of the extended membrane system, relative excitation energies of chromophores, and energy dynamics of a pigment protein complex. The absolute excitation energies of chromophores, absorption spectra, and linear dichroism spectra were comparatively insensitive to changes in the modeled environment. With the effect of the environment established, we present a preliminary method to extend our photosystem II model to include charge transfer states, and a preliminary model of Nanosalina xenorhodopsin which can determine the photocycle states through validation of calculated spectra against experimental results.
|
26 |
Single Molecule Spectroscopy Studies of Membrane Protein Dynamics and Energetics by Combined Experimental and Computational AnalysesRajapaksha, Suneth P. 23 July 2012 (has links)
No description available.
|
27 |
Femtosecond pump probe spectroscopy of light harvesting complexes and PhthalocyaninesOmbinda-Lemboumba, Saturnin 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The generation of ultrafast light pulses and the development of time resolved
spectroscopic techniques, such as the femtosecond pump probe spectroscopy
technique, have facilitated the study of ultrafast energy transfer in the photosynthetic
systems of green plants and photodynamic therapy drugs. It has
allowed the investigation of biological and chemical processes that take place on
the ultrafast timescale and has allowed us to obtain spectral and kinetic information
on energy transfer. In addition, it has allowed time resolved experiments
in which the transient absorption of species under investigation was observed
and has elucidated molecular dynamics. In the present work this was done with
a temporal resolution of approximately 200 fs and covering a pump-to-probe
delay range of 300 fs to 2 ns.
The main aims of this study were to characterise the femtosecond pump probe
spectroscopy system, to investigate the energy transfer in the natural light
harvesting complex II (LHC II) in view of future expansion to the study of
synthesized arti cial functional light harvesting complexes and nally to study
ultrafast processes in zinc phthalocyanine (ZnPc) systems.
In photosynthetic organisms, LHC II is the most abundant light harvesting
complex and it plays an important role in light harvesting and photoprotection.
The light energy is absorbed by light harvesting complexes and transferred to
a reaction centre (RC) in an ultrafast timescale.
Phthalocyanines are a new class of photosensitiser used for photodynamic
therapy. These drugs are used to treat small and super cial tumours. The
energy transfer from the singlet excited state to the triplet excited state occurs
on an ultrafast timescale. However, recent work done on zinc phthalocyanine has
proved that the determination of the ultrafast component remains a challenge.
Several ultrafast studies carried out on ZnPc in solvents have been not only
unsuccessful to give a clear picture of the ultrafast dynamics but have also
produced divergent results.
In this study, a characterisation of the femtosecond pump probe spectroscopy
setup was done. The samples under investigation were probed by a white light
continuum. The generation of the white light continuum introduced chirp,
which in uenced the temporal evolution of the transient absorption results.
The technique used to correct the chirp introduced by white light generation
is discussed in detail. Our femtosecond pump probe spectroscopy setup was
benchmarked by using a well known dye, namely malachite green. In addition,
the investigation of the transient absorption change of LHC II, an active component
in photosynthesis, as extracted from spinach leaves and the ultrafast
dynamics of a promising photosensitiser ZnPc in dimethyl sulfoxide (DMSO) as well as in dimethyl formamide (DMF) was done. The spectral and dynamic results
obtained using these three samples are described and exponential ts to the
absorbance decay curves used to estimate the timescales of the energy transfer
processes are presented. In this experiment, the dynamics and measured time
constants related to the energy transfer between the different types of chlorophyll
in LHC II was monitored, whereas with ZnPc, the dynamics and the
measured time constants associated with solvation dynamics and vibrational
relaxation was examined. / AFRIKAANSE OPSOMMING: Die vorming van ultravinnige lig pulse en die ontwikkeling van tyd opgelosde
spektroskopiese tegnieke, soos die femtosekonde pomp proef spektroskopie tegniek,
het die studie van ultravinnige energie oordrag in fotosintetiese stelsels van
groen plante en chemiese prosesse gefasiliteer, wat kan plaasvind op die ultravinnige
tyd skaal en laat dit toe om spektrale en kinetiese informasie oor die energie
oordrag te kan bepaal. Dit het ook dit moontlik gemaak om tyd opgelosde
eksperimente te kan doen waarin ons veranderlike absorbsie van die monster kon
ondersoek en die molekulere dinamika kon ontrafel. In hierdie werk is dit gedoen
met n tyd resolusie van omtrent 200 fs termyl 'n pomp-tot-proef tydvertraging
van 300 fs tot 2 ns gebruik is.
Die hoof doelwitte van hierdie werk was om 'n femtosekonde pomp proef
spektroskopie stelsel te karakteriseer, die energie oordrag in die natuurlike ligoes
kompleks II te ondersoek met die toekomstige uitbreiding van die studie na
sintetiese lig-oes komplekse as oogmerk en laastens om ultravinnige prosesse in
Sink Ftalosianiene stelsels te ondersoek.
In fotosintetiese organismes, is lig oes kompleks II die mees volop lig oes
kompleks en speel 'n belangrike rol in lig oes en foto skerming. Die lig energie
word geabsorbeer deur lig oes komplekse en dan oorgedra na reaksie middelpunte
in 'n ultravinnige tydskaal.
Ftalosianiene is 'n nuwe klas fotosensiteerder wat gebruik word in fotodinamiese
terapie. Hierdie dwelms word gebruik om klein en oppervlakkige
gewasse te behandel. Die energie oordrag van die opgewekte singlet tot die
triplet toestand vind plaas op die ultravinnige tydskaal. Onlangse navorsingswerke
het getoon dat die bepaling van die ultravinnige komponent 'n uitdaging
bly. Verskeie vorige ondersoeke is gedoen op Sink Ftalosianiene in verskeie
oplosmiddels, en nie net het hierdie studies nie 'n helder prentjie verskaf van die
ultravinnige dinamika nie, maar het ook divergerende resultate opgelewer.
In hierdie werk word 'n karakterisering van die femtosekonde pomp proef
spektroskopie stelsel gedoen. Die monsters is ondersoek met 'n wit lig kontinuum
proef. Die vorming van die wit lig kontinuum het tjirp veroorsaak, wat
die tyd evolusie van die veranderlike absorbsie resultate beinvloed het. Die tegniek
wat gebruik was om die tjirp te korregeer word bespreek. Ons femtosekonde
pomp proef spektroskopie stelsel is gestandardiseer deur die welbekende kleurstof
malachiet groen. Ons het ook die veranderlike absorbsie van lig oes kompleks II
ondersoek, 'n aktiewe komponent in fotosintese, soos dit onttrek is uit spinasie
blare, asook die ultravinnige dinamika van die belowende photosensitizer Sink
Ftalosianiene in DMSO asook DMF. Die spektrale en dinamiese resultate verkry
vanaf hierdie drie monsters word beskryf en eksponensiele passings aan die absorbsie verval kurwes is gebruik om die tydskale van die energie oordrag prosesse
te skat. In hierdie eksperiment is dinamika en gemete tydkonstantes waargeneem
wat toegeskryf kan word aan die energie oordrag tussen verskillende
soorte chloro l in lig oes kompleks II. In die Sink Ftalosianien eksperimente is
dinamika en gemete tydkonstantes waargeneem wat toegeskryf kan word aan
solverings dinamika asook vibrasionele ontspanning.
|
28 |
DNA origami structures for artificial light-harvesting and optical voltage sensingHemmig, Elisa Alina January 2018 (has links)
In the past decade, DNA origami self-assembly has been widely applied for creating customised nanostructures with base-pair precision. In this technique, the unique chemical addressability of DNA can be harnessed to create programmable architectures, using components ranging from dye or protein molecules to metallic nanoparticles. In this thesis, we apply DNA nanotechnology for developing novel light-harvesting and optical voltage sensing nano-devices. We use the programmable positioning of dye molecules on a DNA origami plate as a mimic of a light-harvesting antenna complex required for photosynthesis. Such a structure allows us to systematically analyse optimal design concepts using different dye arrangements. Complementary to this, we use the resistive-pulse sensing technique in a range of electrolytes to characterise the mechanical responses of DNA origami structures to the electric field applied. Based on this knowledge, we assemble voltage responsive DNA origami structures labelled with a FRET pair. These undergo controlled structural changes upon application of an electric field that can be detected through a change in FRET efficiency. Such a DNA-based device could ultimately be used as a sensitive voltage sensor for live-cell imaging of transmembrane potentials.
|
29 |
Applied Studies of Metal-Based Light Scattering Layer and External Lightguide on Dye-Sensitized Solar CellsTsai, Ming-Lang 08 July 2012 (has links)
Dye-sensitized solar cells (DSSCs), based on use of a black counter electrode (BCE) and thin TiO2 electrode (photoelectrode), have been developed to reduce related manufacturing costs. Despite their effectiveness in lowering manufacturing cost, the above DSSCs have a low photovoltaic performance, owing to their insufficient light harvesting efficiency.
This work presents a novel metal-based light scattering layer (MLSL), which can be formed either on a black counter electrode or on a thin TiO2 electrode, to reflect the light passing through the latter. The proposed MLSL increases the light harvesting efficiency from the interior of the cell, thus enhancing the photovoltaic performance of DSSC. Experimental results indicate that the proposed MLSL also reduces the internal resistance, as well as increases the electron collection efficiency of DSSC, subsequently increasing the power conversion efficiency by 116%.
This work also designs a low-cost external lightguide (EL), which is disposed on the exterior of photoelectrode of DSSC, to direct light towards the dye-covered nanoporous TiO2 film (D-NTF) of the photoelectrode. Incorporating EL can increase the light harvesting efficiency from the exterior of the cell, thus enhancing the photovoltaic performance of DSSC. Furthermore, in addition to increasing the light harvesting efficiency by 30.69%, the proposed EL increases the photocurrent density by 38.12% and power conversion efficiency by 25.09%.
|
30 |
Teplotní závislost triplet-tripletního přenosu energie ve fotosyntetických světlosběrných komplexech / Temperature dependence of the triplet-triplet energy transfer in photosynthetic light-harvesting complexesVinklárek, Ivo January 2017 (has links)
Toxic singlet oxygen can be populated by the quenching of triplet states of chlorophyll (Chl). In photosynthetic light-harvesting complexes (LHCs), the gen- eration of singlet oxygen is prevented by a photoprotective mechanism based on an energy transfer from Chl triplets to carotenoids, which occurs via a Dexter mechanism (DET). The temperature dependence of the DET was studied in three selected LHCs by means of transient absorption spectroscopy. The emphasis was on a chlorophyll a-chlorophyll c2-peridinin-protein complex (acpPC) of Dinoflagel- late Amphidinium carterae. The results obtained from acpPC were compared with those for LHC-II from pea and chlorosomes of Chloroflexus aurantiacus. All three antennas exhibit high efficiency and fast rate of chlorophyll triplet quenching by carotenoids at room temperature, which prevents the accumulation of Chl triplets. The fast rate of quenching persists at low temperatures (≥77 K) in the case of LHC-II. However, the efficiency of the Chl triplets quenching is lower as proved by a detection of long-lived Chl triplets with a millisecond lifetime. These triplets were assigned to peripheral Chls that are not neighbouring with carotenoids active at 77 K. A similar population of long-lived Chl triplets was detected in the acpPC complex. In acpPC, the rate of the...
|
Page generated in 0.1178 seconds