White light origin

When hexane, which is a non-solvent for PVK is used, the device emits blue light as a single layer device with C120-PPP. However, if toluene, which is a solvent for both polymers is used, the device emits white light originating from an exciplex emission at the bilayer interface in addition to the exciton emission from C120-PPP.122 The efficiency varies with... 

According to J. Amann,7 brown soln. of iodine contain ultra-microscopic particles, while the violet soln. contain none. The violet-red soln. in benzene, toluene, and xylene are photosensitive in that clouds of ultramicroscopic particles are formed in white light, and the soln. rapidly turn brown. The soln. return to their original state in darkness. In some cases, iodine soln. are true soln. either of free iodine or of an addition compound and in other cases they contain free colloidal iodine or of a polymerized addition compound. In some cases ultra-microscopic suspended particles of iodine are present. 

The first observation of fluorescence in solution occurred in 1565 by the Spanish physician and botanist Nicolas Monardes, who noticed a blue tint in the water contained in a recipient fabricated with a specimen of wood called lignum nephriticum [3, 11]. It was known in 1570 that the blue coloration that is produced by white light from the aqueous extract of the lignum nephriticum or peregrinum disappeared in acid medium. In 1615 a similar behavior was observed from the rind of Aesculos hippocastanum in aqueous medium [4]. When placed in water, the rind of chestnut produces a colorless liquid with bluish reflections today it is known that this originates from aesculin fluorescence [12]. 

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