A. Rygula and P. Miskowiec
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or in situ analysis with the vibrational spectroscopy is attractive and will be presented in the following chapter.
According to the definition [2, 3], colorants are classified as pigments i.e. small
particles, practically insoluble in those media in which they are applied, and dyes
which are soluble in the solvent. talking about the natural colorants in biological
tissues, these definitions are usually not applied and both terms are used alternatively. It is usually caused by limitation of knowledge about form of dye occurrence.
Colorants are characterized by their ability to absorb or emit light in the visible
range (400–700 nm) (Fig. 10.1) [4]. the colour of matter is visible when the white
light, composed of all wavelengths from the visible spectrum, is partially absorbed
whilst the reflected part of light is observed. generally, organic dyes possess colour
because they have at least one chromophore (a colour-bearing group). the most
common are the molecular structure of dye including a conjugated system responsible for the resonance of electrons [5, 6].
10.1.1 The Classification and Function of Dyes in the Natural
World
Colours in nature are so popular that we usually do not think about them and do
not realize how important they are in our life. the main source of natural pigments
are plants i.e. leaves, fruits and flowers. the animal world is also full of colour as
pigments are present in skin, eyes, and other tissues but also in bacteria and fungi.
the role of pigments in the nature is difficult to overestimate but at the same time,
our knowledge about their distribution, availability and properties is still limited [8].
the coloration patterns of flowers attract insects and contribute to the pollinating
Fig. 10.1 the spectral range of visible light (based on [7]). Below left, the scheme of primary
colours which compose a white light and below right the principle of colour observation for objects
280
or in situ analysis with the vibrational spectroscopy is attractive and will be presented in the following chapter.
According to the definition [2, 3], colorants are classified as pigments i.e. small
particles, practically insoluble in those media in which they are applied, and dyes
which are soluble in the solvent. talking about the natural colorants in biological
tissues, these definitions are usually not applied and both terms are used alternatively. It is usually caused by limitation of knowledge about form of dye occurrence.
Colorants are characterized by their ability to absorb or emit light in the visible
range (400–700 nm) (Fig. 10.1) [4]. the colour of matter is visible when the white
light, composed of all wavelengths from the visible spectrum, is partially absorbed
whilst the reflected part of light is observed. generally, organic dyes possess colour
because they have at least one chromophore (a colour-bearing group). the most
common are the molecular structure of dye including a conjugated system responsible for the resonance of electrons [5, 6].
10.1.1 The Classification and Function of Dyes in the Natural
World
Colours in nature are so popular that we usually do not think about them and do
not realize how important they are in our life. the main source of natural pigments
are plants i.e. leaves, fruits and flowers. the animal world is also full of colour as
pigments are present in skin, eyes, and other tissues but also in bacteria and fungi.
the role of pigments in the nature is difficult to overestimate but at the same time,
our knowledge about their distribution, availability and properties is still limited [8].
the coloration patterns of flowers attract insects and contribute to the pollinating
Fig. 10.1 the spectral range of visible light (based on [7]). Below left, the scheme of primary
colours which compose a white light and below right the principle of colour observation for objects