Dyes organic

As already mentioned, the organic dye rhodamine 6G was one of the first luminescent species studied, encapsulated in silica obtained by the SGM [4], It was also mentioned that one important observation at that time was related to the enhanced stability the organic molecule experienced in the xerogel host. Indeed, that first paper opened the road for a multitude of new optical materials involving organic functionalities. Sensors, dye lasers (visible and NIR), photochromic, nonlinear optics, and photovoltaic devices are some of the possible applications for these dyes containing OIH [11,92,93]. 

A number of laser dyes have been incorporated in different sol-gel matrices and solid-state tunable laser action has been demonstrated with these materials 

In our group a versatile OIH host was used since it can be patterned by UV light. Indeed, in Ref [111] planar and UV written channel optical waveguides have been studied in thin films. However, in the case of the DEB lasers described in Ref. [109], a visible laser was used in order to create a dynamic pattern that only exists during the laser pulse, besides exciting the dye. 

One- and two-photon spectroscopy have been explored in Ref. [114] for Rh6G and coumarin 153 (C153) dyes embedded in silica nanoparticles with and without Ti02 scatterers. The presence of scatterers had the effect to quench dyes emission. Moreover, photodegradation of the dyes were observed even for IR excitation. 

Titania and silica-coated titania have been used as scatterers in Ref [120]. Strong dependence of the medium scattering strength on the silica shell thickness was found. Higher efficiency, lower laser threshold, narrower bandwidth. 

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Although better known now for his incorrect theory that cycloalkanes were planar Baeyer was responsible for notable advances in the chemistry of organic dyes such as indigo and was awarded the 1905 Nobel Prize in chemistry for his work in that area... 

The utility of acid-base titrimetry improved when NaOH was first introduced as a strong base titrant in 1846. In addition, progress in synthesizing organic dyes led to the development of many new indicators. Phenolphthalein was first synthesized by Bayer in 1871 and used as a visual indicator for acid-base titrations in 1877. Other indicators, such as methyl orange, soon followed. Despite the increasing availability of indicators, the absence of a theory of acid-base reactivity made selecting a proper indicator difficult. 

Finding the End Point with a Visual Indicator Most indicators for complexation titrations are organic dyes that form stable complexes with metal ions. These dyes are known as metallochromic indicators. To function as an indicator for an EDTA titration, the metal-indicator complex must possess a color different from that of the uncomplexed indicator. Furthermore, the formation constant for the metal-indicator complex must be less favorable than that for the metal-EDTA complex. 

H. Zollinger, Color Chemistry Syntheses, Properties and Applications of Organic Dyes and Pigments, VCH Pubhshers, New York, 1987. 

Fig. 16. Maximum achievable signal-to-noise ratio (SNR) on read-out of different writable optical data storage systems as a function of the writing energy (laser power) (121). SQS = Organic dye system (WORM) PC = phase change system (TeSeSb) MO = magnetooptical system (GbTbFe). See text.

Photochromic Organic Dyes. Intensive investigations into this category of substances have led to numerous patent appHcations. Copper—phthalocyanine pigments, organic dyes based on cyanine (Ricoh, Pioneer), naphthochinone (Nippon Denki), and ben2othiopyrane (Sony) (123) have been described. They did not lead, however, to any commercial use. Surveys on the possibiUties of optical data storage with photochromic dyes can be found (124,125). 

Materials. Beside inorganic materials (eg, barium chloride/fluoride crystals, doped with 0.05% samarium), transparent thermoplasts are preferred for the PHB technique, eg, poly (methyl methacrylate) (PMAIA), polycarbonate, and polybutyral doped with small amounts of suitable organic dyes, organic pigments like phthalocyanines, 9-arninoacridine, 1,4-dihydroxyanthraquinone [81-64-1] (quinizarin) (1), and 2,3-dihydroporphyrin (chlorin) (2). 

Organic Dye Lasers. Organic dye lasers represent the only weU-developed laser type in which the active medium is a Hquid (39,40). The laser materials are dyestuffs, of which a common example is rhodamine 6G [989-38-8]. The dye is dissolved in very low concentration in a solvent such as methyl alcohol [67-56-17, CH OH. Only small amounts of dye are needed to produce a considerable effect on the optical properties of the solution. 

Molybdate orange and red are pigments (qv) that contain lead(II) molybdate [10190-33-3], PbMoO, formulated in mixed phases with PbCrO and PbSO. The mixed phase is more intensely colored than any of the component phases. Concerns about lead content are lessening the use of these materials (see also Paint). Various organic dyes are precipitated with heteropolymolybdates. This process allows the fixation of the dye in various fabrics. The molybdenum anion generally imparts light stabiHty to the colorant as weU (91). 

Sulfonation. Sulfonation of naphthalene with sulfuric acid produces mono-, di-, tri-, and tetranaphthalenesulfonic acids (see Naphthalene derivatives), ah of the naphthalenesulfonic acids form salts with most bases. Naphthalenesulfonic acids are important starting materials in the manufacture of organic dyes (15) (see Azo dyes). They also are intermediates used in reactions, eg, caustic fusion to yield naphthols, nitration to yield nitronaphthalenesulfonic acids, etc. 

As in chemical sensitization, spectral sensitization is usually done after precipitation but before coating, and usually is achieved by adsorbing certain organic dyes to the silver haUde surfaces (47,48,212—229). Once the dye molecule is adsorbed to the crystal surface, the effects of electromagnetic radiation absorbed by the dye can be transferred to the crystal. As a result of this transfer, mobile electrons are produced in the conduction band of the silver haUde grain. Once in the conduction band, the electrons are available to initiate latent-image formation. 

E. A. Clark and P. Anliker, ia O. Hutziager, ed.. Organic Dyes and Pigments, The Handbook ofEnvironmental Chemisty, Vol. 3, Part A, Sptinger-Verlag, Berlin, 1980. 

G. HaUas, in J. Griffiths, ed.. Developments in the Chemistry and Technology of Organic Dyes, BlackweU, Scientific Publishing, Oxford, UK, 1984. 

Acceptor donor CT occurs, eg, in the solution of iodine in ben2ene, where an electron can transfer from the Tt-electron system in ben2ene to the I2 molecule. Organic dyes containing both donor and acceptor groups can also be approached from this viewpoint. 

H. Zollinger, Color Chemisty Syntheses, Properties Applications of Organic Dyes Pigments, 2nd rev. ed., VCH PubHshers, Inc., New York, 1991. 

Color Additives. The FDA has created a unique classification and strict limitations on color additives (see also CoLORANTS FOR FOOD, DRUGS, COSMETICS, AND MEDICAL DEVICES). Certified color additives are synthetic organic dyes that ate described in an approved color additive petition. Each manufactured lot of a certified dye must be analyzed and certified by the EDA prior to usage. Color lakes are pigments (qv) that consist of an insoluble metallic salt of a certified color additive deposited on an inert substrate. Lakes are subject to the color additive regulations of the EDA and must be certified by EDA prior to use. Noncertifted color additives requite an approved color additive petition, but individual batches need not be EDA certified prior to use. 

Orga.nic Colora.nts. The importance of coal-tar colorants cannot be overemphasized. The cosmetic industry, in cooperation with the FDA, has spent a great deal of time and money in efforts to estabUsh the safety of these dyes (see Colorants for food, drugs, cosmetics, and medical devices). Contamination, especially by heavy metals, and other impurities arising from the synthesis of permitted dyes are stricdy controlled. Despite this effort, the number of usable organic dyes and of pigments derived from them has been drastically curtailed by regulatory action. 

The terms FD C, D C, and External D C (Ext. D C), which are part of the name of colorants, reflect the FDA s colorant certification. FD C dyes may be used for foods, dmgs, and cosmetics D C dyes are allowed in dmgs and cosmetics and Ext. D C dyes are permitted only in topical products. Straight colorants include both the organic dyes and corresponding lakes, made by extending the colorant on a substrate such as aluminum hydroxide or barium sulfate. The pure dye content of these lakes varies from 2 to 80% the organic dyes contain over 80% pure dye. Colorants certified for cosmetic use may not contain more than 0.002% of lead, not more than 0.0002% of arsenic, and not more than 0.003% of heavy metals other than lead and arsenic. 

Guanine [7340-5], an organic dye, is also known as Cl 75170 [7340-5], Materials are fusion mixtures. 

In the United States the use of coal-tar dyes ia eye makeup is geaerally prohibited. The use of permanent and temporary hair colorants (Tables 16 and 17) and of organic dyes and their lakes is precluded. As a result, only iasoluble inorganic pigments can be used (Table 9). The sensitivity of the eye... 

A. T. Peters and H. S. Preeman, Color Chemistry The Design and Synthesis of Organic Dyes and Pigments, Elsevier, London, 1991. 

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