Properties of dyes

One characteristic property of dyes is their colour due to absorption from the ground electronic state Sq to the first excited singlet state Sj lying in the visible region. Also typical of a dye is a high absorbing power characterized by a value of the oscillator strength/ (see Equation 2.18) close to 1, and also a value of the fluorescence quantum yield (see Equation 7.135) close to 1. 

Thus the necessary chemical properties of dyes are a chemical stmcture that imparts colors and chemical characteristics that result in the molecule having a lower chemical potential in a fiber than in the dyebath. 

The interaetion of PVP for various moleeular masses (8T0 - 360T0 ) with 3 groups of organie reagents sueh as triphenylmethane, trioxyfluorone and azodyes is established with the methods of UV-, VIS- and IR- speetroseopy. The ehanges of speetroseopie properties of dyes at addition of polymer ar e shown in shift of maximum of absorption bands, displaeement of reagent dissoeiation. The influenee of moleeular masses of polymer on properties of azodye-PVP adduets is studied. 

The potential value of the application of molecular orbital methods in colour chemistry is immense. In essence, the reason for this is that the methods enable, in principle, many of the light absorption properties of dyes, from a knowledge of their chemical structure, to be calculated with the aid of a computer. Thus, the colour properties of any dye whose structure may be drawn on paper may be predicted, with some expectation of accuracy, without the need to resort to devising a method for the... 

The PPP-MO method is suitable for the treatment of large molecules, does not present major computing demands and programs are now routinely used as a tool to calculate the colour properties of dyes. Unlike the HMO method, it handles heteroatomic species well. The method has been remarkably successful in calculating /lmax values for a wide range of dyes from virtually all of the chemical classes. For example, the method provides a reasonably accurate account of substituent effects in the range of aminoazobenzene dyes, including compounds 15a-f and 16a-f which have been discussed in terms of the valence-bond approach in the previous section of this chapter. 

Meier, H. Application of the Semiconductor Properties of Dyes Possibilities and Problems. 61, 85-131 (1976). 

Table 1 Fluorescence properties of dyes 9a-d and lOa-d (5 x 10 6 M) solutions in buffer...

Fluorophores are relative small molecules that, with some exceptions, are not naturally occurring and have to be synthesized chemically. There has been a large development in the synthesis of fluorescent molecules and nowadays there is a vast range of alternatives including dyes with improved photochemical properties, solubility or modified reactivity that allow for conjugation to other molecules of interest and the synthesis and application of fluorescent sensors [10, 13], Although a lot is known about the physics of fluorescence and a lot of information is available about the properties of dyes, their prediction from the chemical structures cannot be accurately done. For this reason, there has been a... 

Virtually all commercial textile dyeing and printing processes take place by the application of a solution or a dispersion of the dyes to the textile material followed by some type of fixation process. The dye solution or dispersion is almost always in an aqueous medium. A major objective of the fixation step is normally to ensure that the coloured textile exhibits satisfactory fastness to subsequent treatment in aqueous wash liquors. In view of the overriding importance of water as a transfer medium in dyeing and printing it seems reasonable to begin with a discussion of the properties of dyes in solution and in dispersion. 

Chapter 8 Functions and properties of dyeing and printing auxiliaries... 

Congo red is the prototype of the substantive cotton dyes of the benzidine group. The tinctorially valuable property of dyeing cotton directly (i.e. without a mordant) is doubtless to he attributed to the intimate adsorption of the colloidal particles of the dye on the fibre. 

The optical properties of a DDSN are mainly determined by the properties of dye molecules. Since silica nanomaterials are effectively transparent they are unlikely to absorb light in the near-infrared, visible or ultraviolet regions, which allows the dye molecules inside the silica matrix to keep their original optical properties [64]. Meanwhile, the presence of the silica matrix provides a new environment for dye molecules and affects dye fluorescence properties. 

The treatment of the fluorescence data can be represented theoretically by the way the probe was constructed. The number of parameters in the equations is dependent on and directly proportional to the number of components affecting the fluorescence signal. The theory described here is intended for a simple probe where the number of parameters involved in the equation have been kept to a minimum (i.e., the interaction of the NIR dye with the metal ions). In addition, it is assumed that no other components in the probe influence the properties of dye or metal. 

El Zayat MY, Saed MO, El Dessouki MS (1998) Photoelectrochemical properties of dye-sensitized Zr-doped SrTiOs electrodes. IntJ Hydrogen Energy 23 259-266... 

Optical Properties of Dyes Incorporated into Clay... 

Application of the Semiconductor Properties of Dyes Possibilities and Problems... 

IV. Connections between the Electrical Properties of Dyes and Industrial... 

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