Two-photon Chromophores as Switches and Sensitizers
Author | : Elizabeth Boreham |
Publisher | : |
Total Pages | : |
Release | : 2016 |
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ISBN | : |
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Author | : Elizabeth Boreham |
Publisher | : |
Total Pages | : |
Release | : 2016 |
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Total Pages | : 37 |
Release | : 1998 |
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Two-photon absorption spectra have been measured for bis-donor diphenylpolyene derivatives with varying conjugation lengths and end groups. Large two-photon absorptivities are observed via nanosecond nonlinear transmission measurements in comparison to picosecond nonlinear transmission and two-photon excited fluorescence methods, which suggests a large contribution of excited-state absorption to the nanosecond nonlinear transmission results. Chromophores with conformationally locked bridges have been synthesized and the optical nonlinearity and thermal stability has been examined. It was found that relative to the normal polyene bridges, chromophores with confirmationally locked bridges exhibit improved thermal stability without a significant change in optical nonlinearity. A series of chromophores containing diarylamino donors have been synthesized and exhibit large optical nonlinearities, good thermal-thermal stabilities and enhance photochemical stabilities relative to compounds with dialkylamino donors. Functionalized versions of these chromophores have been synthesized for covalent incorporation into high performance polymers, for electro-optic applications.
Author | : Cristina Cepraga |
Publisher | : |
Total Pages | : 282 |
Release | : 2020 |
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Photodynamic therapy (PDT) is an alternative treatment of cancer requiring the use of chromophore molecules (photosensitizers), which can induce cell death after light excitation. Gold nanoparticles (AuNP), exhibiting localized Surface Plasmon Resonance, can enhance the photophysical response of chromophores located in their vicinity, and thus improve their therapeutic action. Moreover, the use of highly localized two-photon chromophores (photosensitizers and fluorophores), capable to undergo a localized excitation by light in the Near InfraRed region, should increase the penetration depth into tissues, thus improve the treatment efficiency (by PDT) and the imaging (by fluorescence microscopy) of cancer tissues.In this work, we describe the elaboration of water-soluble hybrid nano-objects for PDT and fluorescence bioimaging applications, composed of two-photon chromophore-polymer conjugates grafted onto gold nanoparticles. In order to obtain these nano-objects we follow a multistep strategy: i) the synthesis of a well-defined water-soluble chromophore-polymer conjugates; ii) the end-group oriented grafting of chromophore-polymer conjugates onto 20 nm AuNP. The coupling of hydrophobic two-photon chromophores on linear water-soluble copolymer chains (poly(N-acryloylmorpholine-co-N-acryloxysuccinimide)), obtained by controlled/living RAFT polymerization, resulted in well-defined water-soluble chromophore-polymer conjugates, with different polymer lengths (2 000 g.mol-1
Author | : Semere G. Bairu |
Publisher | : |
Total Pages | : 216 |
Release | : 2013 |
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Materials with large two photon absorption cross sections found applications in several areas such as sensor protection, 3D micro/nano fabrication, photodynamic therapy, optical data storage, multi-photon sensing, multi-photon microscopy and imaging. Several successful research strategies were developed in literature to achieve 2PA materials with enhanced cross sections. However, the obtained cross sections are far from adequate and there is a need to develop new strategies. In a parallel development, numerous research efforts were focused on studying the dynamics of interfacial charge transfer across chromophore semiconductor interfaces, especially in the context of dye sensitized solar cells. While investigating the fundamentals of ICT, it was found that these interfaces provide greater dipolar coupling and can create surface electric fields. Thus, the hypothesis of the present thesis is to use the local electric fields and interfacial interactions to enhance the 2PA cross sections of attached chromophores. This strategy of chromophores stationed at interfaces can lead to synergistic 2PA enhancement. To prove the hypothesis and design better 2PA materials, the following research work was undertaken. Firstly, ICT dynamics on three anthracene derivatives sensitized TiO2 nanoparticles was studied to understand the influence of anchoring groups and corroborate the presence of local electric fields. Secondly, investigations were continued to probe the dynamics of electron injection and transient Stark effects in a donor acceptor chromophore sensitized TiO2 nanoparticles. Thirdly, new chromophores are synthesized that can possess strong interfacial electronic coupling with the semiconductor and create local electric fields. The 2PA cross section measurements of these chromophore sensitized semiconductor nanoparticles have shown unprecedented 2PA enhancements as high as 20-fold when the chromophores are attached to the semiconductor nanoparticles. The mechanism behind the enhancement was probed with ultrafast luminescence and absorption and the results confirmed the presence of a charge transfer state. Finally, the interfacial electric field generated at the interface of charged micelle and water was used to enhance the 2PA cross sections of chromophore that was solubilized in that region. The results presented in the thesis have confirmed that local electric fields exist at the interfaces and they can be successfully utilized to design efficient 2PA materials.
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Total Pages | : 15 |
Release | : 2006 |
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There has been much interest in the development of two-photon absorbing materials and many efforts to understand the nonlinear absorption properties of these dyes, but this area is still not well understood. A computational model has been developed in our lab to understand the nanosecond nonlinear absorption properties that incorporate all of the measured one-photon photophysical parameters of a class of materials called AFX. We have investigated the nonlinear and the photophysical properties of the AFX chromophores including the two-photon absorption cross-section, the excited state cross-section, the intersystem crossing quantum yield, and the singlet and triplet excited state lifetimes using a variety of experimental techniques that include UV-visible, fluorescence and phosphorescence spectroscopy, time correlated single photon counting, ultrafast transient absorption, and nanosecond laser flash photolysis. The model accurately predicts the nanosecond nonlinear transmittance data using experimentally measured parameters.
Author | : Nisan Naftali Siegel |
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Total Pages | : |
Release | : 2010 |
Genre | : Lasers |
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Author | : Stephanie J. Pond |
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Total Pages | : 0 |
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Genre | : Chemistry |
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Total Pages | : 17 |
Release | : 2006 |
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Large two-photon and excited state absorption have been reported in donor-acceptor-substituted pi-conjugated molecules. We have performed detailed nonlinear absorption and photophysical measurements on a system of AFX chromophores and calculate the nonlinear transmission based on an effective three-level model. A numerical model that includes far wing linear absorption has been developed and compared with an analytical three-photon absorption model. The models are in accordance and yield excellent agreement with experimental nonlinear transmission date of 0.02-M AFX solutions up to laser intensities ~1GW/cm2. Concentration effects at this intensity become increasingly evident. We have extended our modeling efforts to include some new effects that may be anticipated in this regime, such as stimulated scattering are included. We report on our experimental observations of various materials and discuss results with respect to our extended theoretical models.
Author | : Axel Griesbeck |
Publisher | : CRC Press |
Total Pages | : 1607 |
Release | : 2019-04-05 |
Genre | : Medical |
ISBN | : 1466561254 |
The only combined organic photochemistry and photobiology handbookAs spectroscopic, synthetic and biological tools become more and more sophisticated, photochemistry and photobiology are merging-making interdisciplinary research essential. Following in the footsteps of its bestselling predecessors, the CRC Handbook of Organic Photochemistry and Pho
Author | : |
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Release | : 2009 |
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The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D(prime) or A(prime) units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted multidimensional ICT while providing for spatial control of emission localization. Such route could be extended to more intricate (dendritic) and multipolar systems (3D).