Dissertation > Excellent graduate degree dissertation topics show

Molecular Thermometers and Molecular Logic Gates Based on Reversible Water Additions and Conjugate Conversions of Hemicyanes

Author: LiuChang
Tutor: ZengXianShun
School: Tianjin University of Technology
Course: Condensed Matter Physics
Keywords: styrylindolium dye water addition aggregate thermo-response logic gates
CLC: TQ610.1
Type: Master's thesis
Year: 2013
Downloads: 2
Quote: 0
Read: Download Dissertation

Abstract

The thermo-responsive fluorescence probes based on the signaling mechanisms of photoinduced electron transfer, intramolecular charge transfer, fluorescence resonance energy transfer and fluorescence lifetime have got great progress in recent years. These probes with highly sensitivity have a great advantage over other thermometers which can be used in small space temperature measurement. But to the best of our knowledge, this is a novel prototype of thermo-responsive material based on the special reversible water addition to the charged C=N double bond.And hemicyanine-based dyes with excellent spectroscopic properties have been widely used. However, aggregate species can still be observed in some cases which are important factors that influence the photophysical properties. So a series of fluorescence thermo-responsive probes have been synthesized based on hemicyanine-dyes which included electron withdrawing groups, electron-donating groups and proton transter groups of water addition, aggregate and conjudged system changes.The fluorescence thermo-responsive of strylindolium dyes (0107,0531Al,0531A2) with electron-donating groups were synthesized. These probes were characterized by1H NMR,13C NMR, ESI-HRMS and elemental analysis. The photophysical properties of the styrylindolium dyes are strongly influenced by external environments. Firstly, the dyes present mainly in the monomeric form in freshly prepared solutions. A small portion of D-aggregate, H-aggregate and J-aggregate can be observed in some cases. In equilibrium solutions, however, significant changes are observed in most solvents with different polarities. The J-aggregate is an unstable state which is irreversibly converted to other species. The monomer converts reversibly among D-aggregate, H-aggregate and water adducts at the equilibrium state. Meanwhile, the formation of water adducts by the reaction of water residue in solvent with the charged electron-deficient C=N double bond of the dyes is an important factor that influences the optical properties of the dyes because the addition reaction breaks the dye’s π-conjugate. At the same time, the water adducts are sensitive to external environments and its content can be modulated by temperature and pH conditions. However, the dyes existed mainly in the form of D-aggregate in strong acidic media which can be convered to the monomer upon increasing the temperature.Two novel fluorescent derivatives0626A1and0626A2based on NO2-withdrawing group were synthesized. In different solvents, the aggregates of the dyes could be observed. The spectroscopic studies revealed the dyes present mainly in the monomeric form and H-aggragtate in freshly prepared solutions, and the process of convertion is quick. Meanwhile, the dyes in ethyl acetate can convert to water adducts quickly and its content can be modulated by temperature and pH conditions, increasing temperature is favor of D-aggregate conversion to Monomer and Monomer transformation into water adduts. Because the dyes included NO2-withdrawing group which can form a coplanar structure with benzene ring are sensitive to the temperature, so this kind of dyes can further contain the methoxyl thermo-responsive probes can not be detected in the temperature range. Based on a single conversion performance of the dyes in alkaline and strong acidic environment can be used as temperature-response material.Fluorescence thermo-response probes of0730,0131and0130based on proton tansfer causing conjugated system changes were achieved. The fluorescence probes have different absorption positions in different solvents; in H2O and DMF, the degree of conjugated system for three dyes is the minimum and maximum respectively; in other solvents, the dyes exist in the form of mixture of the conjugated system structure. Compared with the polarity of the solvent affect, pH influence significantly. Under acidic conditions, moleclules probes exist with a positive charge; in natural and weak base, the lactam carbonyl group of the uracil convers to a hydroxyl and another carbonyl presents in the form of negative charged; however, the formation of a spiro ring induced the conjugated system is greatly reduced in the strong base solutions. We constructed the half-substractor and half-adder molecular logic gates by the influence of pH on the structure of uracil-containing with inputing different signals.

Related Dissertations

CLC: > Industrial Technology > Chemical Industry > Dyes and intermediates industry > General issues > Basic theory
© 2012 www.DissertationTopic.Net Mobile