Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

The fulgide and fulgimide family constitutes an important class of organic photochromic compounds. The ability of fulgides and fulgimides to interconvert between two key forms by irradiation of different wavelength of light has made them promising material in optical memory devices, optical switches and sensors, and specialty dyes and inks. Thermal stability and hydrolytic stability of fulgides and fulgimides are essential for their practical applications. A deuterated trifluoromethyl indolylfulgide was synthesized based on the synthetic pathway of the proteo trifluoromethyl indolylfulgide using commercially available deuterated starting materials. Deuteration of the isopropylidene group improved the thermal stability of the indolylfulgide by a factor of 7. Fulgimides are the most important fulgide derivatives. Fulgimides improve the hydrolytic stability of fulgides by replacing the succinic anhydride ring with a succinimide ring. A novel trifluoromethyl N-ethoxycarbonylmethyl indolylfulgimide was synthesized from trifluoromethyl indolylfulgide. The trifluoromethyl indolylfulgide was synthesized on a large scale in five steps with an overall yield of 18%. The indolylfulgide was then converted to indolylfulgimide by aminolysis follow by dehydration. The N-ethoxycarbonylmethyl indolylfulgimide showed enhanced hydrolytic stability and photochemical stability in 70/30 ethanol/water. Three novel aqueous soluble fulgimides, trifluoromethyl carboxylic acid indolylfulgimide, dicarboxylic acid indolylfulgimide, and H-carboxylic acid indolylfulgimide, were synthesized. In sodium phosphate buffer (pH 7.4) at 37 ºC, an unusual hydrolysis of the trifluoromethyl group of the closed form of the carboxylic acid indolylfulgimide resulted in the dicarboxylic acid indolylfulgimide which has an additional carboxylic acid group. The closed form of dicarboxylic acid indolylfulgimide was further decarboxylated to generate H-carboxylic acid indolylfulgimide which was not photochromic. The trifluoromethyl dicarboxylic acid indolylfulgimide is the most robust fulgimide yet reported in aqueous solution. A novel aqueous soluble methyl carboxylic acid indolylfulgimide was synthesized from methyl indolylfulgide. The methyl indolylfulgide was synthesized in five steps with an overall yield of 21%. The methyl carboxylic acid indolylfulgimide was synthesized by aminolysis follow by dehydration. The methyl carboxylic acid indolylfulgimide is expected to have improved thermal and photochemical stability in aqueous solutions relative to the trifluoromethyl analog.

No description available.

I believe that my research work will provide an in-depth understanding of the basic chemical and physical properties of plasmonic gold nanorods. These works can inspire future applications of plasmonic nanostructures on biotechnology, optoelectronics and solar energy conversion. - / I will first introduce my studies on high-index-faceted gold nanocrystals. Elongated tetrahexahedral (THH) gold nanocrystals have been prepared in high yields using a seed-mediated growth method. Structural characterizations reveal that they are single crystals enclosed by 24 high-index facets. Electrochemical measurements have proven that these THH Au nanocrystals are more chemically active than octahedral Au nanocrystals that are enclosed by low-index {1111} facets. Next, I will demonstrate the formation of large-area, 3D ordered assemblies of Au nanostructures that have different sizes and shapes, including nanorods, polyhedra, nanocubes, and bipyramids, by droplet evaporation. The nature of the resultant assemblies is strongly dependent on the shape of Au nanostructures for single-component systems; while the assembly of binary nanorod mixtures is dependent on the relative diameters of two nanorod samples for the nanorods used in our experiments. / Most applications of plasmonic nanostructures are based on their interactions with other chemical/physical species. In my research work, gold nanorods interacting with photochromic molecules and fluorophores are extensively studied. For the case of photochromic molecules, I have demonstrated a plasmonic switch on the basis of the resonance coupling between single Au nanorods and photochromic molecules. An individual plasmonic switch is composed of a single nanorod and the surrounding photochromic molecules. Its modulation depth reaches 7.2 dB. The estimated power and energy required for operating such a single-nanorod plasmonic switch are ∼13 pW and ∼39 pJ. For the case of fluorophores, I will give a systematic description of my research on plasmon-fluorophore interactions. Excitation polarization-dependent plasmon-enhanced fluorescence, polarized emission, and modulation of fluorophore emission spectra by localized plasmon resonances will be experimentally demonstrated. The interactions between the plasmonic nanorods and the fluorophore molecules can be temporally separated into plasmon-enhanced excitation and coupled emission processes under unsaturated excitation conditions. Finite-difference time-domain (FDTD) method will be employed to explain the origin of the excitation and emission polarization dependence. A term "plasmophore", which is corned by Lakowicz et al., is quoted to describe the artificially prepared quantum emitters that are composed of plasmonic structure and fluorophore. / Noble metal nanocrystals have drawn great attention in a wide range of research fields due to their extraordinary localized surface plasmon resonances, which are essentially collective charge density oscillations confined in metallic nanostructures. Their applications range from bioimaging, sensing and therapy in life sciences to plasmonic circuits and optical data storage in micro-optoelectronics. More attractively, they can be used to enhance light harvesting in solar energy conversion systems. In this thesis, I will systematically describe the preparation and assembly of gold nanorods and their interactions with fluorophores and photochromic molecules, both experimentally and theoretically. / Ming, Tian = 金納米棒的生長、組裝以及他們與螢光團或光至變色分子的相互作用 / 明天. / Adviser: Jianfang Wang. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Ming, Tian = Jin na mi bang de sheng chang, zu zhuang yi ji ta men yu ying guang tuan huo guang zhi bian se fen zi de xiang hu zuo yong / Ming Tian.

The goal of this thesis is to design both liquid crystal hosts and photochromic dopants terminated with short siloxane oligomers in order to produce homogeneous liquid crystal mixtures containing a photochromic component for liquid crystal photoswitches. Some of the liquid crystals terminated with short siloxane oligomers were also found to form 'de Vries'-type SmA phases, which minimize the formation of chevrons and zigzag defects that severely degrade the quality of electro-optic devices. In the first part of the thesis, siloxane-terminated phenylpyrimidine liquid crystals were synthesized and characterized. They form SmC phases and, in some cases, SmA phases. Addition of a terminal halogen substituent on the alkoxy side-chain broadens the SmA temperature range. It was shown that combining a structural element that promotes the formation of a SmC phase with one that promotes the formation of a SmA phase in a mesogen with a 2-phenylpyrimidine core results in a maximum layer contraction of 1.6% for 2-(4-(11-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)undecyloxy)phenyl)-5-(1-chlorooctyloxy)pyrimidine (33a), which may be considered a ‘de Vries’ material. As an extension of the result obtained in the first project, siloxane-terminated biphenyl benzoate and phenyl benzoate liquid crystals were synthesized and their phase behavior studied. They form SmC phases and, in some cases, SmA and SmI phases. Addition of a terminal chloro substituent on alkoxy side-chain results in a broader SmA temperature range and, in some cases, also affects the nature of the mesophase formed. The compound 4-[6-(1,1,1,3,3,5,5-heptamethyltrisiloxanyl)hexanoyloxy]phenyl 4-(8-chlorooctyloxy)benzoate (40b) is characterized by a maximum layer shrinkage of only 1.7%, which may be considered to possess some ‘de Vries’ character. Finally, siloxane-terminated fulgide derivatives were designed as photochromic dopants for liquid crystal photoswitches. Compound 41 was designed and synthesized and proved to be an oil at room temperature. Solid fulgide precusors 42, 43a and 44b were then assessed as photochromic dopants in terms of fast switching and high quantum yield requirements of a photoswitch, and their photophysical properties were studied in solution. The isomer composition at the photostationary state suggests that the competition from E-Z isomerization is likely too high for compounds 42, 43a and 44b to be suitable as photochromic dopants for photoswitches. / Thesis (Ph.D, Chemistry) -- Queen's University, 2009-05-28 12:46:13.992

The objective of this thesis is to prepare new photochromic N,C-chelate four-coordinate organoboron compounds and investigate their photophysical and photochemical properties. Phenylpyridine-based organoboron compound (PhPyBMes2) was prepared and studied with NMR, X-ray, and UV-Vis. Experimental and theoretical results established that PhPyBMes2 is photochromic and the photoisomerization process involves a reversible intramolecular C-C bond formation/breaking. The structure of the dark colored isomer of PhPyBMes2 was established by 2D NMR experiments and computational studies. The discovery of the photochromic behavior of PhPyBMes2 led to the investigation of other phenylpyridine-based organoboron compounds. A series of substituted PhPyBMes2 compounds were synthesized with substituents on the phenyl ring or the pyridine ring of the N,C-chelate. Two other compounds were synthesized by substituting the mesityl rings in PhPyBMes2 with phenyl or pentaflurophenyl rings. The photophysical and photochemical properties of these compounds were studied by NMR, UV-Vis, and DFT/TD-DFT. The studies established that the steric hindrance imposed by the mesityl groups and the nature of substituents on the N,C-chelate have substantial effects on the photoisomerization process. New organoboron compounds based on N,C-chelates other than phenylpyridine were prepared and their photochemical and photophysical properties studied using NMR, UV-Vis, and DFT/TD-DFT. The phenyl group in the N,C-chelate was replaced by TMS-furan, TMS-thiophene, benzofuran, benzothiophene, and N-phenyl pyridylindole groups. The conducted studies show that these new compounds have photochromic properties similar to those of phenylpyridine-based compounds. Crystals of the dark isomer of the N-phenyl pyridylindole organoboron compound were successfully grown and the structure of the dark isomer was determined by X-ray diffraction. New organoboron compounds based on phenyl-benzoxazole and phenyl-benzothiazole have been also prepared and studied. The photoisomerization of these compounds is similar to the other N,C-chelate organoboron compounds but their thermal behavior is different. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-08-22 11:50:50.811

Thesis (Ph.D.)--Ohio University, November, 2007. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: photochromic; spirooxazine; Ormosil Includes bibliographical references (p.52-54).

Photochromism has been investigated extensively during recent years. The large interest for information storage in memory applications is associated with the bi-stable character of the photochromism phenomena. In molecular photochromics, two isomers with different absorption spectrum can be obtained according to the specific wavelength of the light exposure. This reversible transformation process can be considered as optical writing/erasing step of a memory. Here we first report the absorption spectra of solid-state films based on the blends consisting of PC molecules, the spirooxazine 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3’-[3H]phenanthr[9,10-b](1,4)oxazine] (PIII, Sigma-Aldrich, 32,256-3) and a polymer matrix host, poly(2-methoxy-5(2’-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). The bi-stability in conjugated polymer matrix is studied by following the time evolution of the optical properties of the blends. Thereafter, the electrical performance of PC-polymer diodes is characterized and reported. While the PIII molecules in the blend bulks are switched to their low energy gap state, forming external energy levels above the valence band of MEH-PPV, the injected charges (hole-dominated) will be trapped by the low energy gap isomer of PIII and that leads to current modulation. PIII molecules can be switched between two energy gap states upon the photo-stimulation, and the I-V characteristics of the device can also be controlled reversibly via the photoisomerization. The retention time of the diode’s electrical switching fits quite well with the absorption characteristics of the blend films; this correspondence builds a good link between the film property and the device behavior. Furthermore, we observed a two-trap system in the blend diodes from the I-V curves, and a model is proposed which can explain the schematic concept of the trap-limited current modulation. To combine the knowledge and information from the investigations above, we tested a novel device design based on a bi-layer of the PC and polymer materials, and the promising result for future work is presented in the end.

No description available.