Triboluminescence

Triboluminescence is the phenomenon that is observed when coloured light is emitted on grinding, crushing or fracturing certain crystalline compounds, e.g. the bluish white light emitted from sugar. This phenomenon has been known for over 300 years but has remained a curiosity without an obvious application, until very recently when Sage postnlated that this effect could be used to detect flaws in composite materials.  

This was based on the reported high tribolnminescence efficiency exhibited by certain crystalline componnds, especially complexes with lanthanides (Table 3.15), some of which have already been described nnder electrolnminescence (section 3.8.5.1). The light emission from a few of these materials is snfficient for the phenomenon to be observed in a well-lit room. 

The mechanism of the origin of the tribolnminescence effect is not fnlly nnder-stood bnt there appears to be three types. 

Sage and his co-workers have nsed this tribolnminescent phenomenon in devising 

Campbell, Chemiluminescence. Principles and Applications in Biology and Medicine, VCH, Weinheim, 1988. 

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Crystals of uranium nitrate are triboluminescent. Uranium salts have also been used for producing yellow "vaseline" glass and glazes. Uranium and its compounds are highly toxic, both from a chemical and radiological standpoint. 

The acid occurs both as colorless triclinic prisms (a-form) and as monoclinic prisms ( 3-form) (8). The P-form is triboluminescent and is stable up to 137°C the a-form is stable above this temperature. Both forms dissolve in water, alcohol, diethyl ether, glacial acetic acid, anhydrous glycerol, acetone, and various aqueous mixtures of the last two solvents. Succinic acid sublimes with partial dehydration to the anhydride when heated near its melting point. 

Tribolumineszenz, /, triboluminescence. Tribune,/. platform, rostrum gallery. Tricarbonsaure, /, tricarboxylic acid. Trichinoyl, n, triquinoyL Trichloressigsaure, /. trichloroacetic acidj trichroitisch, a. trichroic,... 

Uranyl Nitrate (Uranium Nitrate, UNH, Yellow Salt). U02(N03)2.6H20, mw 502.18, N 5.58% yellow rhomb crysts, greenish luster by reflected light mp 60.2°, bp 118°, d 2.807g/cc, RI 1.4967. Sol in 1.5p w, freely in ale and eth. Prepd by the action of nitric acid on U octoxide. When shaken, rubbed, or crushed, the crysts show remarkable triboluminescence with occasional detonations. It is highly toxic, and a severe fire and expln risk when shocked or heated,... 

Emission of li t accompanying the crystallization of certain crystals from solution and probably arising from cleavages occurring during the growth of individual crystals. Thus, it is a form of triboluminescence. Luminescence which appears when crystals dissolve is termed lyoluminescence. 

A. Triboluminescence Emission from shaking, rubbing, or crushing crystals... 

Associated with structural rearrangements in solids ° Triboluminescence (piezoluminescence)... 

Mechanoluminescence or triboluminescence arises from the mechanical action on solids lyoluminescence is where the emission of light occurs when a material goes into solution. Thermoluminescence is observed during the heating of a solid that has previously absorbed energy from radiation, as ions trapped in the solid recombine. (See also Glossary for an explanation of the terms.)... 

Triboluminescence Mechanical shaking, rubbing or crushing Crack detection in composite materials... 

Mechanoluminescence arises from mechanical action on solids (also called piezoluminescence or triboluminescence). 

Piezoluminescence is luminescence brought about by pressure (see also triboluminescence). 

The same laboratory describes a group of complexes with a unique property among metal complexes, referred to as luminescence tribochromism [39], which is a substantial change in the emission of the solid upon application of pressure. This phenomenon contrasts with the more common triboluminescence, which refers to the transient emission seen upon sample grinding or crushing. In this case, the effect was observed in a set of complexes of formula [Au2( J.-TU)((j,-dppm)]Y and [Au2( i-MeTU)( i-dppm)]Y (TU = 2-thiouracyl MeTU = 6-methyl-2-thiouracyl Y = CF3COOT NCV, CKV, Au(CN)2 ). 

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