Chiral molecule reflectance spectra

TLCs are optically active mixtures of organic molecules. The correct name for TLCs used for temperature measurements is chiral nematic or cholesteric Uquid crystals. TLCs are characterized by well-analyzed reflections of visible Ught (color play) within a definite bandwidth of temperature. A certain temperature leads to reflections of an explicit spectrum of wavelengths, with a local maximum and a narrow bandwidth. Below the start temperature of the color play, called red-start temperature, the TLCs are transparent, when applied in thin layers the bulk looks milky and white. In this state the molecules, which are elongated like a cigar, have a typical size of about 2-5 nm [1], are well ordered, and are close to each other like in a solid crystal (see Fig. 2a). 

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