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SIMULATION OF PHOTOCHROMIC COMPOUNDS USING DENSITY FUNCTIONAL THEORY METHODS
Title
SIMULATION OF PHOTOCHROMIC COMPOUNDS USING DENSITY FUNCTIONAL THEORY METHODS.
Creator
Patel, Pansy, Masunov, Artem, University of Central Florida
Abstract / Description
This Thesis describes the systematic theoretical study aimed at prediction of the essential properties for the functional organic molecules that belong to diarylethene (DA) family of compounds. Diarylethenes present the distinct ability to change color under the influence of light, known as photochromism. This change is due to ultrafast chemical transition from open to closed ring isomers (photocyclization). It can be used for optical data storage, photoswitching, and other photonic...
Show moreThis Thesis describes the systematic theoretical study aimed at prediction of the essential properties for the functional organic molecules that belong to diarylethene (DA) family of compounds. Diarylethenes present the distinct ability to change color under the influence of light, known as photochromism. This change is due to ultrafast chemical transition from open to closed ring isomers (photocyclization). It can be used for optical data storage, photoswitching, and other photonic applications. In this work we apply Density Functional Theory methods to predict 6 of the related properties: (i) molecular geometry; (ii) resonant wavelength; (iii) thermal stability; (iv) fatigue resistance; (v) quantum yield and (vi) nanoscale organization of the material. In order to study sensitivity at diode laser wavelengths, we optimized geometry and calculated vertical absorption spectra for a benchmark set of 28 diarylethenes. Bond length alternation (BLA) parameters and maximum absorption wavelengths (λmax) are compared to the data presently available from X-ray diffraction and spectroscopy experiments. We conclude that TD-M05/6-31G*/PCM//M05-2X/6-31G*/PCM level of theory gives the best agreement for both the parameters. For our predictions the root mean square deviation (RMSD) are below 0.014 Å for the BLAs and 25 nm for λmax. The polarization functions in the basis set and solvent effects are both important for this agreement. Next we consider thermal stability. Our results suggest that UB3LYP and UM05-2X functionals predict the activation barrier for the cycloreversion reaction within 3-4 kcal/mol from experimental value for a set of 7 photochromic compounds. We also study thermal fatigue, defined as the rate of undesirable photochemical side reactions. In order to predict the kinetics of photochemical fatigue, we investigate the mechanism of by-product formation. It has been established experimentally that the by-product is formed from the closed isomer; however the mechanism was not known. We found that the thermal by-product pathway involves the bicyclohexane (BCH) ring formation as a stable intermediate, while the photochemical by-product formation pathway may involve the methylcyclopentene diradical (MCPD) intermediate. At UM05-2X/6-31G* level, the calculated barrier between the closed form and the BCH intermediate is 51.2 kcal/mol and the barrier between the BCH intermediate and the by-product 16.2 kcal/mol. Next we investigate two theoretical approaches to the prediction of quantum yield (QY) for a set of 14 diarylethene derivatives at the validated M05-2X/6-31G* theory level. These include population of ground-state conformers and location of the pericycylic minimum on the potential energy surface 2-A state. Finally, we investigate the possibility of nanoscale organization of the photochromic material based on DNA template, as an alternative to the amorphous polymer matrix. Here we demonstrate that Molecular Dynamic methods are capable to describe the intercalation of π-conjugated systems between DNA base pairs and accurately reproduced the available photophysical properties of these nanocomposites. In summary, our results are in good agreement with the experimental data for the benchmark set of molecules we conclude that Density Functional Theory methods could be successfully used as an important component of material design strategy in prediction of accurate molecular geometry, absorption spectra, thermal stability of isomers, fatigue resistance, quantum yield of photocyclization and photophysical properties of nanocomposites.
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Date Issued
2010
Identifier
CFE0003136, ucf:48633
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003136
TWO-PHOTON 3D OPTICAL DATA STORAGE VIA FLUORESCENCE MODULATION OF FLUORENE DYES BY PHOTOCHROMIC DIARYLETHENES
Title
TWO-PHOTON 3D OPTICAL DATA STORAGE VIA FLUORESCENCE MODULATION OF FLUORENE DYES BY PHOTOCHROMIC DIARYLETHENES.
Creator
Corredor, Claudia, Belfield, Kevin D., University of Central Florida
Abstract / Description
Three-dimensional (3D) optical data storage based on two-photon processes provides highly confined excitation in a recording medium and a mechanism for writing and reading data with less cross talk between multiple memory layers, due to the quadratic dependence of two photon absorption (2PA) on the incident light intensity. The capacity for highly confined excitation and intrinsic 3D resolution affords immense information storage capacity (up to 1012 bits/cm3). Recently, the use of...
Show moreThree-dimensional (3D) optical data storage based on two-photon processes provides highly confined excitation in a recording medium and a mechanism for writing and reading data with less cross talk between multiple memory layers, due to the quadratic dependence of two photon absorption (2PA) on the incident light intensity. The capacity for highly confined excitation and intrinsic 3D resolution affords immense information storage capacity (up to 1012 bits/cm3). Recently, the use of photochromic materials for 3D memory has received intense interest because of several major advantages over current optical systems, including their erasable/rewritable capability, high resolution, and high sensitivity. This work demonstrates a novel two-photon 3D optical storage system based on the modulation of the fluorescence emission of a highly efficient two-photon absorbing fluorescent dye (fluorene derivative) and a photochromic compound (diarylethene). The feasibility of using efficient intermolecular Förster Resonance Energy Transfer (RET) from the non-covalently linked two-photon absorbing fluorescent fluorene derivative to the photochromic diarylethene as a novel read-out method in a two-photon optical data storage system was explored. For the purpose of the development of this novel two-photon 3D optical storage system, linear and two-photon spectroscopic characterization of commercial diarylethenes in solution and in a polymer film and evidence of their cyclization (O→C) and cycloreversion (C→O) reactions induced by two-photon excitation were undertaken. For the development of a readout method, Resonance Energy Transfer (RET) from twophoton absorbing fluorene derivatives to photochromic compounds was investigated under one and two-photon excitation. The Förster's distances and critical acceptor concentrations were determined for non-bound donor-acceptor pairs in homogeneous molecular ensembles. To the best of my knowledge, modulation of the two-photon fluorescence emission of a dye by a photochromic diarylethene has not been reported as a mechanism to read the recorded information in a 3D optical data storage system. This system was demonstrated to be highly stable and suitable for recording data in thick storage media. The proposed RET-based readout method proved to be non-destructive (exhibiting a loss of the initial fluorescence emission less than 20% of the initial emission after 10,000 readout cycles). Potential application of this system in a rewritable-erasable optical data storage system was proved. As part of the strategy for the development of diarylethenes optimized for 3D optical data storage, derivatives containing π-conjugated fluorene molecules were synthesized and characterized. The final part of this reasearch demonstrated the photostability of fluorine derivatives showing strong molecular polarizability and high fluorescence quantum yields. These compounds are quite promising for application in RET-based two-photon 3D optical data storage. Hence, the photostability of these fluorene derivatives is a key parameter to establish, and facilitates their full utility in critical applications.
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Date Issued
2007
Identifier
CFE0001662, ucf:47210
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0001662
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
TWO-PHOTON CROSS SECTION ENHANCEMENT OF PHOTOCHROMIC COMPOUNDS FOR USE IN 3D OPTICAL DATA STORAGE
Title
TWO-PHOTON CROSS SECTION ENHANCEMENT OF PHOTOCHROMIC COMPOUNDS FOR USE IN 3D OPTICAL DATA STORAGE.
Creator
Luchita, Gheorghe, Belfield, Kevin, University of Central Florida
Abstract / Description
Rewritable photochrome-based 3D optical data storage requires photochromic molecules with high two-photon absorption (2PA) cross sections. Currently, the low value of two-photon absorption cross sections of existing photochromes makes them unsuitable for practical application in 3D data storage. Worldwide attempts to increase the cross section of photochromic molecules by altering the chemical structure have yielded poor results. In this work, two ways to increase the two-photon absorption...
Show moreRewritable photochrome-based 3D optical data storage requires photochromic molecules with high two-photon absorption (2PA) cross sections. Currently, the low value of two-photon absorption cross sections of existing photochromes makes them unsuitable for practical application in 3D data storage. Worldwide attempts to increase the cross section of photochromic molecules by altering the chemical structure have yielded poor results. In this work, two ways to increase the two-photon absorption cross sections of photochromes were investigated. In the first method, partial success demonstrated by extending the conjugation of a photochromic molecule, a high two-photon absorption cross section of the closed form isomer and high photoconversion to the closed form were realized. At the same time, a decrease in photoswitching quantum yield and low photoconversion to open form was observed. A discussion is provided to explain the results, suggesting that the proposed method of extending the conjugation may not solve the problem. For this reason a new method for effective two-photon absorption cross section enhancement of photochromes was proposed. As a proof of principle, a new two-photon absorbing dye with a hydrogen bonding moiety was synthesized and used for the formation of supramolecular structures with a photochromic compound. Theoretical reasoning and experimental demonstration of energy transfer from the dye to the photochrome under one and two-photon excitation confirmed the practical value of the method. The effects of a 2PA dye on the photochromic properties of a diarylethene were investigated using a model compound to simplify data analysis. Formation of supramolecular structures was revealed using 1H NMR spectroscopic methods. The model compound, having the same hydrogen bonding moiety as 2PA dye, has been demonstrated to bind with photochrome molecules at very low concentrations. Photochromic properties of 2,3-bis(2,4,5-trimethyl-3-thienyl)maleimide, including conversions at the photostationary state, extinction coefficients, photoisomerization reaction rates and quantum yields, were shown to be affected by hydrogen bonding with the model compound - 2,6-bis-(acetamido)pyridine. The extent of this change was determined and discussed, demonstrating a balanced supramolecular strategy to modulate photochemical and photophysical properties of this important class of photochromic material.
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Date Issued
2011
Identifier
CFE0003928, ucf:48695
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003928
Data-driven Predictive Analytics For Distributed Smart Grid Control: Optimization of Energy Storage, Voltage and Demand Response
Title
Data-driven Predictive Analytics For Distributed Smart Grid Control: Optimization of Energy Storage, Voltage and Demand Response.
Creator
Valizadehhaghi, Hamed, Qu, Zhihua, Behal, Aman, Atia, George, Turgut, Damla, Pensky, Marianna, University of Central Florida
Abstract / Description
The smart grid is expected to support an interconnected network of self-contained microgrids. Nonetheless, the distributed integration of renewable generation and demand response adds complexity to the control and optimization of smart grid. Forecasts are essential due to the existence of stochastic variations and uncertainty. Forecasting data are spatio-temporal which means that the data correspond to regular intervals, say every hour, and the analysis has to take account of spatial...
Show moreThe smart grid is expected to support an interconnected network of self-contained microgrids. Nonetheless, the distributed integration of renewable generation and demand response adds complexity to the control and optimization of smart grid. Forecasts are essential due to the existence of stochastic variations and uncertainty. Forecasting data are spatio-temporal which means that the data correspond to regular intervals, say every hour, and the analysis has to take account of spatial dependence among the distributed generators or locations. Hence, smart grid operations must take account of, and in fact benefit from the temporal dependence as well as the spatial dependence. This is particularly important considering the buffering effect of energy storage devices such as batteries, heating/cooling systems and electric vehicles. The data infrastructure of smart grid is the key to address these challenges, however, how to utilize stochastic modeling and forecasting tools for optimal and reliable planning, operation and control of smart grid remains an open issue.Utilities are seeking to become more proactive in decision-making, adjusting their strategies based on realistic predictive views into the future, thus allowing them to side-step problems and capitalize on the smart grid technologies, such as energy storage, that are now being deployed atscale. Predictive analytics, capable of managing intermittent loads, renewables, rapidly changing weather patterns and other grid conditions, represent the ultimate goal for smart grid capabilities.Within this framework, this dissertation develops high-performance analytics, such as predictive analytics, and ways of employing analytics to improve distributed and cooperative optimization software which proves to be the most significant value-add in the smart grid age, as new network management technologies prove reliable and fundamental. Proposed optimization and control approaches for active and reactive power control are robust to variations and offer a certain level of optimality by combining real-time control with hours-ahead network operation schemes. The main objective is managing spatial and temporal availability of the energy resources in different look-ahead time horizons. Stochastic distributed optimization is realized by integrating a distributed sub-gradient method with conditional ensemble predictions of the energy storage capacity and distributed generation. Hence, the obtained solutions can reflect on the system requirements for the upcoming times along with the instantaneous cooperation between distributed resources. As an important issue for smart grid, the conditional ensembles are studied for capturing wind, photovoltaic, and vehicle-to-grid availability variations. The following objectives are pursued:- Spatio-temporal adaptive modeling of data including electricity demand, electric vehicles and renewable energy (wind and solar power)- Predictive data analytics and forecasting- Distributed control- Integration of energy storage systemsFull distributional characterization and spatio-temporal modeling of data ensembles are utilized in order to retain the conditional and temporal interdependence between projection data and available capacity. Then, by imposing measures of the most likely ensembles, the distributed control method is carried out for cooperative optimization of the renewable generation and energy storage within the smart grid.
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Date Issued
2016
Identifier
CFE0006408, ucf:51481
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006408
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