Rhodamine Colorant

In Rhodamine 6G, also sold as Rhodamine F5G [989-38-8] (15), the caiboxy estei gioup prevents fiee rotation of the lower phenyl group. Its position is roughly perpendicular to the plane of the other three rings. Retention of color strength is good because there is less electronic interaction between the lower ring and the rest of the molecule. 

A polyester-type fluorescent resin matrix (22) is made by heating trimellitic anhydride, propylene glycol, and phthaUc anhydride with catalytic amounts of sulfuric acid. Addition of Rhodamine BDC gives a bright bluish red fluorescent pigment soluble in DME and methanol. It has a softening point of 118°C. Exceptional heat resistance and color brilliance are claimed for products of this type, which are useful for coloring plastics. 

Note Rhodamine B is a universal reagent that can be used on silica gel, talc, starch [5] and cellulose layers, just as on urea [1] or silver nitrate-impregnated [7] phases. Liquid paraffin-impregnated silica gel and RP layers are less suitable, since the background to the chromatographic zones is also intensely colored. It is often possible to increase the detection sensitivity by placing the plate in an atmosphere of ammonia after it has been sprayed or dipped, alternatively it can be oversprayed with sodium or potassium hydroxide solution. 

The reaction was not particularly sensitive on paraffin-impregnated kieselguhr layers because of background coloration. For quantitation it was better to use the five-fold more sensitive rhodamine 6G reagent (q.v.). 

Exposure of rhodamine 6G-impregnated silica gel layers to iodine vapor for two to five minutes followed by irradiation with UV light leads to the sensitive blue coloration of the chromatogram zones on a greenish fluorescent background [8, 10]. 

Figure 13.2 Fluorescence micrographs of DOPC multi-layer patterns fabricated by dip-pen nanolithography, (a) An array of 25 contiguous line features. Red color is from doped rhodamine-labeled lipid, (b) A higher magnification of the region highlighted by the white square in (a), (c) Two-component patterns containing two different dyes. Green color is from doped NBD-labeled lipid.

The fluorescent properties of NHS-rhodamine are similar to TRITC. The wavelength of maximal absorbance or excitation for the reagent is 544 nm and its emission maximum is 576 nm, exhibiting a visual color of orange-red. Its molar extinction coefficient at 546 nm in a methanol environment is 63,000M 1cm 1. Other components in solution as well as the pH (in aqueous buffers) can change this value. 

Fluorescence detection relies on the visualization of a secondary antibody that has been labeled with a fluorophore such as fluorescein (FITC), Texas Red, Tetramethyl rhodamine (TRITC), or R-phycoerythrin. Although this method of detection has a reduced sensitivity of twofold to fourfold compared to chemiluminescence detection, it presents a tenfold greater linear dynamic range, thus providing better linearity and better quantiflcation within the detection limits. Since secondary antibodies can be labeled with fluor-ophores of distinct colors, multiplexing (simultaneous detection of several antigens) of the same blot is feasible. 

Nonchelating dyes include basic triphenylmethane dyes (e.g., Brilliant Green, Malachite Green, Crystal Violet), xanthene dyes (e.g., Rhodamine B, Rhodamine 6G), azine dyes (e.g., Methylene Blue), and acid dyes (e.g., Eosin, Erythrosin). These are intensely colored and when paired with an oppositely charged analyte ion lead to high sensitivities. 

In general, the chemicals used to create color displays in the daytime are various types of dyes and oils. Though dyes and oils do not fall into the category of pyrolants that generate colored smoke by combustion reactions, they are dispersed in the atmosphere by the combustion or decomposition gases of pyrolants. Typical examples of color dyes are indigo for blue, rhodamine for red, and auramine for yel-... 

On addition of Na -saponite to the rhodamine-ethanol solution and the pyronine-ethanol solution, the color of the solutions gradually faded within a few hours, even at room temperature. All the composites were intensely colored, namely bright red for Rhodamine 590 and cardinal for Pyronine Y. 

Owing to the simphcity and versatility of surface-initiated ATRP, the above-mentioned AuNP work may be extended to other particles for their two- or three-dimensionally ordered assemblies with a wide controllabiUty of lattice parameters. In fact, a dispersion of monodisperse SiPs coated with high-density PMMA brushes showed an iridescent color, in organic solvents (e.g., toluene), suggesting the formation of a colloidal crystal [108]. To clarify this phenomenon, the direct observation of the concentrated dispersion of a rhodamine-labeled SiP coated with a high-density polymer brush was carried out by confocal laser scanning microscopy. As shown in Fig. 23, the experiment revealed that the hybrid particles formed a wide range of three-dimensional array with a periodic structure. This will open up a new route to the fabrication of colloidal crystals. 

Analysis. Colorimetric analysis of Ga permits detection of 20 ppb. Ga or a Ga compound in the flame gives a violet (lilac) color. This is due to its emission of 414.0 nm photons. This photon line allows for the spectrophotometric determination of Ga by AAS, which is sensitive to about 10 ppm. ETAAS increases this sensitivity to 5 ppb, and ICPAES to about 1 ppb, with ICPMS going as low as 0.1 ppb. Rhodamine B is a reagent which facilitates the spottest detection at a level of 10 ppm or above. 

Analysis. Colorimetric analysis using rhodamine B for color development permits the determination of Sb down to 50 ppb. ETAAS and ICPAES are capable of a sensitivity of 5 ppb, and ICPMS extends this to 0.1 ppb. 

In 1890 Otto N. Witt advanced the theory that the dye dissolves in the fabric or the mordant, forming a solid solution. The chief argument in favor of this view was that the color of the dye on the fiber is that of the dissolved dye and not of the solid dye. Magenta, for instance, dyes a red and not a metallic green. Silk dyed with rhodamine fluoresces, while solid rhodamine does not, when obtained on a glass plate by evaporation of an alcoholic solution. 

Experiments with rhodamine B gave results that were similar in type but we are not able at present to accoimt for the colors of the fluorescence in the several cases. Rhodamine B does not fluoresce in the solid state but shows a brownish-yellow fluorescence in aqueous solution. On silk the color is blue-red with a strong red fluoresecnce, on wool a blue-red with a very slight fluorescence and on cotton a blue-pink with no fluorescence. The stannic oxide lake is purple and does not fluoresce. The zinc oxide and the alumina lakes are pink and show a slight yellow fluorescence. The silica lake is pink and shows a distinct yellow fluorescence. 

Silk dyed with rhodamine 6G is yellow-red with a strong yellow fluorescence on wool and cotton the color is yellow-red with little or no fluorescence. 

A S243 Stibine 0.5 HgCl2 coated silica gel Cone. HC1 Color. Rhodamine 0.119-1.008... 

Lacquers or varnishes Many metallic cases and components in contact with explosives are protected by coating of lacquers or varnishes. Some varnishes, even after complete curing, have been found to give high gas rates especially with RDX/TNT. Similarly, the compatibility of lacquers is considerably affected by the use of coloring dyes such as rhodamine red dye. 

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