Laser-induced shock wave can spark triboluminescence of amorphous sugars

We investigated the triboluminescence (TL) of sugars using an innovative experimental approach: the laser-induced shock wave (LISW) technique. We found that the LISW could induce very bright TL in crystalline sugars, the intensity of which was shown to be 10(5) times higher than that obtained by conventional manual hand rubbing. We also applied the LISW technique to amorphous sugar samples. Although it was supposed that TL could not be excited in amorphous solids of sugars having isotropic structures, we revealed that LISW could induce bright TL in amorphous sugars similar to that induced in crystalline sugars. On the basis of the experimental results showing the dynamic behavior of the sample fracture combined with those of the TL, we discuss these novel TL mechanisms in sugars. We believe that the shock wave technique opens a new channel for investigating the nature of TL.