Optical brightener

A white surface treated with an optical brightener can emit more visible light than that which shines on it, making it appear brighter.

The global OBA production for paper, textiles, and detergents is dominated by just a few di- and tetra-sulfonated triazole-stilbenes and a di-sulfonated stilbene-biphenyl derivatives.

The stilbene derivatives are subject to fading upon prolonged exposure to UV, due to the formation of optically inactive cis-stilbenes.

Brighteners can be "boosted" by the addition of certain polyols, such as high molecular weight polyethylene glycol or polyvinyl alcohol.

Excess brightener will often cause a greening effect as emissions start to show above the blue region in the visible spectrum.

[5] Paper used for banknotes does not contain optical brighteners, so a common method for detecting counterfeit notes is to check for fluorescence.

Laundry detergent fluorescing under ultraviolet light
4,4′-diamino-2,2′-stilbenedisulfonic acid is a popular optical brightener.
4,4'-bis(benzoxazolyl)-cis-stilbene and 2,5-bis(benzoxazol-2-yl)thiophene (shown here) are also intensely fluorescent and used as optical brighteners, e.g., in laundry detergents. [ 3 ]