Non-trivial role of surrounding gases in triboluminescence: A comprehensive review

Research on triboluminescence phenomena has been comprehensively reviewed, with a focus on the activation mechanisms resulting from the dissipation of mechanical energy at interfaces. The complexity and interdisciplinary nature of this phenomenon, along with its dependence on gas composition and pressure, have been analyzed. Special attention was given to air, inert gases, polyatomic gases, and hydrocarbon gases. The influence of gas composition on triboluminescence is not straightforward. This is because at least three components are associated with different physical and chemical processes and activation mechanisms. These components include TL1: gas discharge luminescence. This occurs because of the generation of an electric field and dielectric breakdown of gases surrounding the mechanically activated zone of the material; TL2: photoluminescence of mechanically activated material. This results from the excitation of luminescent centers by the absorption of ultraviolet radiation from the gas discharge; TL3: material luminescence not related to photoluminescence. This is the least studied and most complex component. This can be related to the direct coupling of the mechanical force with the energy landscape of defects, impurities, and other centers. These centers can be excited and emit light during deexcitation. Other possibilities include luminescence excited by electric fields, exoelectron emission, etc. Therefore, the gas environment is crucial not only for gas discharge (as various gases can promote or quench it) but also for controlling other excitation and deexcitation processes. These processes occur through interactions of adsorbed films with stressed materials, tribochemical reactions, photochemical reactions, and so on. Furthermore, the potential application of triboluminescence for sensing gas composition is highlighted.