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SYNTHESIS OF NOVEL FLUORENE-BASED TWO-PHOTON ABSORBING MOLECULES AND THEIR APPLICATIONS IN OPTICAL DATA STORAGE, MICROFABRICATION, AND STIMULATED EMISSION DEPLETION
Title
SYNTHESIS OF NOVEL FLUORENE-BASED TWO-PHOTON ABSORBING MOLECULES AND THEIR APPLICATIONS IN OPTICAL DATA STORAGE, MICROFABRICATION, AND STIMULATED EMISSION DEPLETION.
Creator
Yanez, Ciceron, Belfield, Kevin, University of Central Florida
Abstract / Description
Two-photon absorption (2PA) has been used for a number of scientific and technological applications, exploiting the fact that the 2PA probability is directly proportional to the square of the incident light intensity (while one-photon absorption bears a linear relation to the incident light intensity). This intrinsic property of 2PA leads to 3D spatial localization, important in fields such as optical data storage, fluorescence microscopy, and 3D microfabrication. The spatial confinement that...
Show moreTwo-photon absorption (2PA) has been used for a number of scientific and technological applications, exploiting the fact that the 2PA probability is directly proportional to the square of the incident light intensity (while one-photon absorption bears a linear relation to the incident light intensity). This intrinsic property of 2PA leads to 3D spatial localization, important in fields such as optical data storage, fluorescence microscopy, and 3D microfabrication. The spatial confinement that 2PA enables has been used to induce photochemical and photophysical events in increasingly smaller volumes and allowed nonlinear, 2PA-based, technologies to reach sub-diffraction limit resolutions. The primary focus of this dissertation is the development of novel, efficient 2PA, fluorene-based molecules to be used either as photoacid generators (PAGs) or fluorophores. A second aim is to develop more effective methods of synthesizing these compounds. As a third and final objective, the new molecules were used to develop a write-once-read many (WORM) optical data storage system, and stimulated emission depletion probes for bioimaging. In Chapter I, the microwave-assisted synthesis of triarylsulfonium salt photoacid generators (PAGs) from their diphenyliodonium counterparts is reported. The microwave-assisted synthesis of these novel sulfonium salts afforded reaction times 90 to 420 times faster than conventional thermal conditions, with photoacid quantum yields of new sulfonium PAGs ranging from 0.01 to 0.4. These PAGs were used to develop a fluorescence readout-based, nonlinear three-dimensional (3D) optical data storage system (Chapter II). In this system, writing was achieved by acid generation upon two-photon absorption (2PA) of a PAG (at 710 or 730 nm). Readout was then performed by interrogating two-photon absorbing dyes, after protonation, at 860 nm. Two-photon recording and readout of voxels was demonstrated in five and eight consecutive, crosstalk-free layers within a polymer matrix, generating a data storage capacity of up to 1.8 x 1013 bits/cm3. The possibility of using these PAGs in microfabrication is described in Chapter III, where two-photon induced cationic ring-opening polymerization (CROP) crosslinking of an SU8 resin is employed to produce free-standing microstructures. Chapter IV describes the investigation of one- and two-photon stimulated emission transitions by the fluorescence quenching of a sulfonyl-containing fluorene compound in solution at room temperate using a picosecond pump-probe technique. The nature of stimulated transitions under various fluorescence excitation and quenching conditions were analyzed theoretically, and good agreement with experimental data was demonstrated. Two-photon stimulated transitions S1 to S0 were shown at 1064 nm. The two-photon stimulated emission cross section of the sulfonyl fluorophore was estimated as aproximately 240 - 280 GM, making this compound a good candidate for use in two-photon stimulated emission depletion (STED) microscopy.
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Date Issued
2009
Identifier
CFE0002913, ucf:48003
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0002913
Investigating New Guaiazulenes and Diketopyrropyrroles for Photonic Applications
Title
Investigating New Guaiazulenes and Diketopyrropyrroles for Photonic Applications.
Creator
Ghazvini Zadeh, Ebrahim, Belfield, Kevin, Campiglia, Andres, Yuan, Yu, Zou, Shengli, Cheng, Zixi, University of Central Florida
Abstract / Description
?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced...
Show more?-Conjugated systems have been the focus of study in recent years in order to understand their charge transport and optical properties for use in organic electronic devices, fluorescence bioimaging, sensors, and 3D optical data storage (ODS), among others. As a result, several molecular building blocks have been designed, allowing new frontiers to be realized. While various successful building blocks have been fine-tuned at both the electronic and molecular structure level to provide advanced photophysical and optoelectronic characteristics, the azulene framework has been under-appreciated despite its unique electronic and optical properties. Among several attributes, azulenes are vibrant blue naturally occurring hydrocarbons that exhibit large dipolar character, coupled with stimuli-responsive behavior in acidic environments. Additionally, the non-toxic nature and the accompanying eco-friendly feature of some azulenes, namely guaiazulene, may set the stage to further explore a more (")green(") route towards photonic and conductive materials.The first part of this dissertation focuses on exploiting guaiazulene as a natural building block for the synthesis of chromophores with varying stimuli-responsiveness. Results described in Chapter 1 show that extending the conjugation of guaiazulene through its seven-membered ring methyl group with aromatic substituents dramatically impacts the optical properties of the guaiazulenium carbocation. Study of these ?(-)stabilized tropilium ions enabled establishing photophysical structure-property trends for guaiazulene-terminated ?-conjugated analogs under acidic conditions, including absorption, emission, quantum yield, and optical band gap patterns. These results were exploited in the design of a photosensitive polymeric system with potential application in the field of three dimensional (3D) optical data storage (ODS).Chapter 2 describes the use of guaiazulene reactive sites (C-3 and C-4 methyl group) to generate a series of cyclopenta[ef]heptalenes that exhibit strong stimuli-responsive behavior. The approach presents a versatile route that allows for various substrates to be incorporated into the resulting cyclopenta[ef]heptalenes, especially after optimization that led to devising a one-pot reaction toward such tricyclic systems. Examining the UV-vis absorption profiles in neutral and acidic media showed that the extension of conjugation at C(4) of the cyclopenta[ef]heptalene skeleton results in longer absorption maxima and smaller optical energy gaps. Additionally, it was concluded that these systems act as sensitizers of a UV-activated ((<) 300 nm) photoacid generator (PAG), via intermolecular photoinduced electron transfer (PeT), upon which the PAG undergoes photodecomposition resulting in the generation of acid.In a related study, the guaiazulene methyl group at C-4 was employed to study the linear and nonlinear optical properties of 4-styrylguaiazulenes, having the same ?(-)donor with varying ?-spacer. It was realized that the conjugation length correlates with the extent of bathochromic shift of the protonated species. On the other hand, a trend of decreasing quantum yield was established for this set of 4-styrylguaiazulenes, which can be explained by the increasingly higher degree of flexibility.The second part of this dissertation presents a comprehensive investigation of the linear photophysical, photochemical, and nonlinear optical properties of diketopyrrolopyrrole (DPP)-based derivatives, including two-photon absorption (2PA), femtosecond transient absorption, stimulated emission spectroscopy, and superfluorescence phenomena. The synthetic feasibility, ease of modification, outstanding robustness, and attractive spectroscopic properties of DPPs have motivated their study for fluorescence microscopy applications, concluding that the prepared DPP's are potentially suitable chromophores for high resolution stimulated emission depletion (STED) microscopy.
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Date Issued
2015
Identifier
CFE0006034, ucf:50986
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006034