Research Topics - Heinz Langhals - Popular Information

The research is concentrated to the development and investigation of highly stable fluorescent dyes. These are applied in chemistry, physics (laser dyes, spectral hole burning), analytics (fluorescent labelling), biochemistry and medicine (fluorescent immunoassays). Besides this there are investigations of solvent effects and mechanistic studies. New preparative procedures are developed.

Fluorescent Dyes

Main Topics of the research activities are the chemistry of the perylene dyes (1), the diketopyrrolopyrrole dyes (DPP, 2), rubicene (3) and the dihydroxybipyridyles (4)

 FLUORESCENCE OF S-13  STRUCTURE FORMULA
PERYLENE DYES

The perylene dyes (1) exhibit high fluorescent quantum yields, high photostability and thermal stability (up to 550°C) and chemical inertness. The solubility of the dyes and other properties can be controled with the substituents R and other properties by the modification of the core so that 1 is an ideal building block for functional dyes. A novel ring contraction reaction of 1 to novel dyes has been studied. The unknown heterocycle 1,7-diazaperylene has been synthesized as modified core system of 1. The structures 2 and 4 are bases for the development of fluorescent dyes with large Stokes-Shifts, whereas 3 exhibits high I.S.C. rates.

Optical Information Recording

Dye 2a crystallizes in two allotropic modifications, from which the metastable is orange-brown with nearly no solid-state-fluorescence whereas the stable yellow modification exhibits a very strong yellow solid-state fluorescence. The yellow-brown material is thermally converted at 195°C to the yellow material and reconverted by a crystallization process.

 EOFS DYE  STRUCTURE FORMULA

The reversible switching of a non-fluorescent to a fluorescent modification is used for the developent of erasable optical fluorescent storage (EOFS).

Analysis of Traces

LiposomenFor a universal analysis system antibodies are used as a selectivity determining unit and are attached to a unit which allows a high sensitivity by fluorescence. Therefore antibodies have been linked to liposoms which are doped with up to 500 molecules of fluorescent dyes (1) each. Even single antibodies can be seen under a fluorescent microscope with this technique and they can be optically followed to their binding sites. Applications of this techniques are in medicine and in enviromental analysis.

The analysis of traces of fluorescent dyes have been carried out by low temperature fluorescence measurements. 10-18 Mol of perylene dyes (1) under a dilution of 10-13 mol·L-1 could be determined with an accuracy of 5%.

Determination of Water

For the description of the polarity of binary solvent mixture as a function of their composition a two-parameter-equation has been developed. With this a very simple and precise determination of water in organic solvents is possible by the use of solvatochromic dyes such as 5.

 STRUCTURE FORMULA

Conservation of Artwork

A new method for the conservation of the TERRACOTTA ARMY of the first chinese emperor has been developed.

Terracotta army Profile

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