High Intensity Triboluminescence in Europium Tetrakis (Dibenzoylmethide)-triethylammonium

Abstract

THE emission of light which accompanies mechanical deformation or fracture of certain crystalline compounds is designated as triboluminescence. Stranski et al.^1,2 investigated some 1,700 organic and inorganic substances and found 356 of them to exhibit triboluminescence. Special impact mechanisms and complete darkness are required to observe the triboluminescent emission from all previously reported triboluminescent materials. In addition, a number of these compounds showed detectable triboluminescence only in a small range of environmental gas pressure and low temperature. Triboluminescence emission from europium tetrakis (dibenzoylmethide)-triethylammonium (EuD₄TEA) is clearly visible in broad daylight at room temperature when crystals are broken with a glass rod or spatula in a test-tube. Apparently this property is common to most europium tetrakis (dibenzoylmethide) complexes which contain a variety of organic cations derived from aliphatic amines. The relative intensity of triboluminescent emission, however, varies significantly with the nature of the substituted ammonium ion, the method of preparation, average size of crystals, and recrystallization solvent.