Study On The Spectral Properties And Applications Of Leuco Dyes

The leuco dyes are widely used as functional materials for their chromogenic nature of pressure or thermal sensitive. It is mainly used in fields of engineering drawings, invoices, fax printing. Fluoran dyes are the most important kind of leuco dyes with the distinguishing feature of sensitive and complete chromatography, which become the mainstream varieties of leuco dyes. In recent years, the application researches of fluoran dyes in biochemical analysis, light-emitting probes, gene sequencing, proteomics and other areas are received extensive attentions.This paper is a combination of three parts, including seven chapters in all.Part I:Chapter1is the first part. In this chapter, the concept, classification, research and development trends of leuco dyes were introduced in brief, and the structure, characters, historical perspective of fluoran dyes were described in detail. The signification, contents and innovation of this thesis were disclosed.Part II:The second part of this thesis includes chapter2, chapter3and chapter4. The synthesis, effects of solvent polarity on the spectrum, application performance and the application of leuco dyes in bioanalysis as a fluorescent probe were studied exhaustively.In chapter2, The chromogenic reaction of leuco dyes:ODB-1、 ODB-2、 B-15、 CK-5、 CK-16and CVL-S were carefully investigated by UV-vis absorption and fluorescence spectra. The structures of leuco dyes in chromogenic reaction were characterized and determined using infrared, nuclear magnetic and melting point instrument.In chapter3, with the character of intramolecular charge-transfer (ICT) arised from its A-π-D structure, the leuco dyes are very sensitive to solvent polarity. The polarity parameters, such as ET(30) and△f which can fairly express the local interaction between solute and solvent were used to discuss the effects of solvent on the spectral properties of leuco dyes for ODB-1、 CK-5and CK-37respectively. The experiment results showed that the excitation and emission wavelengths of compounds shift to long wavelength and Stokes shift increase with the increasing of solution polarity. And the fluorescence of leuco dyes can be quenched by strong polar solvent. The dyes can be used as sensitive fluorescent probes to detect the micro-environment changes in biological system. This research expanded the application of leuco dyes in the field of biological analysis.In chapter4, Uv-vis, fluorescence spectroscopies were used to study the application of leuco dyes ODB-1and CK-37in biological analysis. The interaction mechanisms between dyes and human serum albumin (HSA) were studied using HSA as target molecule. The results demonstrated that leuco dyes have a strong ability to quench the inherent fluorescence of HSA in a static quenching mechanism. In addition, hydrophobic interaction plays an important role in the interaction between HSA and leuco dyes. The combination ratio of dyes and HSA is1:1at different temperatures. The results showes that accumulation structure is formed between the dyes and tryptophan residues in HSA at IIA section.Part III:The third part of the thesis includes chapter5and chapter6. The characters of leuco dyes were studied in writing and printing applications. Leuco dyes which can be decoloured were selected and the decolourable teaching whiteboard inks were prepared. And leuco dyes were used as the coloring agents and water-soluble polymer as the carriers to prepare decolourable water-based ink.In chapter5, two-color (red, blue) whiteboard writing inks were prepared using uniform and orthogonal experiment method by selected leuco dyes and its corresponding embrocation was developed. The coloring agents of writing inks were as following separately:CK-16for red ink; CVL-S or CK-7for blue ink. The work in this chapter exploited the application of leuco dyes in new fields.In chapter6, ODB-2、CK-16、CK-37and CVL-S were used as coloring agents in printing ink. One kind of water-based ink which can be deinked was prepared and the printing effect of the ink and the deinked performance were determined. The results showes that the water-based ink made from leuco dyes have good printing effects and can be deinked quickly under normal temperature and pressure when sodium dodecyl benzene sulfonate (SDBS) existed. The research works in the thesis exploit the application field of leuco dyes.Part IV:(Chapter7) All the experimental results in the thesis were summarized in this part. Further works were proposed as well.