Europium tetrakis dibenzoylmethide triethylammonium: Synthesis, additives, and applications

Abstract

There are a number of techniques currently being used for damage detection and monitoring of civil, aerospace, and military structures and aircraft. However, the major drawbacks of the current techniques are that they do not provide in situ and distributed sensing. Wiedemann and Schmidt defined triboluminescence (TL) as the emission of light produced by mechanical action. In recent years, triboluminescent materials have been proposed for use as the active element in smart structural sensors. To sense damage, these materials would be embedded into the structure. If damage occurs to this structure, the embedded triboluminescent material would give off visible light. This light could be transferred by lightweight fiber optics or wireless detector to a computer-based detection system to warn occupants in real time that a significant impact event has occurred. In addition, the triboluminescent based sensor could allow for real-time monitoring of both the magnitude and location of damage to the host structure. One of the brightest triboluminescent materials currently known is europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA). This research delved into the feasibility of enhancing the properties of EuD4TEA by (a) modifying the synthesis process and (b) determining the reproducibility of the synthetic procedure by measuring the batch variation error. Further, the study evaluated the possible techniques that can be incorporated in to the synthesis technique to enhance the TL by (a) introducing various inorganic and organic dopants; (b) optimizing dopant concentration; (c) studying solvents effects on TL; and (d) evaluating the effects of ionizing radiation on TL. In addition, the research discusses in depth the experimental development of a simple apparatus for the measurement of TL in the laboratory by using a twofold technique consisting of measuring the triboluminecent intensity and/or spectral characterization. This enabled for the determination of a unique decay time for a particular compound. In addition, impact studies have been conducted to correlate the impact energy (velocity) with triboluminescent emission, thus allowing a system to detect and evaluate the magnitude of the impacts. The spectra of these compounds have been analyzed in detail to investigate the cause of luminescence and designate the transitional energy levels for each of the peaks. Finally in order to study the feasibility for structural and/or sensor application, the effect of introducing EuD4TEA into poly(methyl methacrylate) and its impact on the TL emission spectra are determined.