Integration of Triboluminescent EuD₄TEA Crystals to Transparent Polymers: Impact Sensor Application

Abstract

Lanthanide-based organometallic materials are well-known candidate triboluminescent (TL) materials that can show bright emission when a mechanical force is applied. These materials are usually in the form of crystalline powders, and it is often useful to integrate these samples into a polymer matrix in order to achieve processability, enabling coating from a solution/molten state or fabrication as a complex-shaped matrix. In this work, micrometer-sized europium tetrakis (dibenzoylmethide) triethylammonium (EuDTEA) crystals were synthesized and integrated with various transparent polymers (PMMA, PS, PVDF, and PU) using two approaches: (i) blending and (ii) surface impregnation. In the former method, the crystalline particles were molecularly dissolved; therefore, a TL response cannot be achieved. More than 10 wt % TL crystals in the composite is needed to obtain TL signals. However, TL signal was achieved at 2.5 wt % when a composite was prepared by the latter approach. TL intensity shows exponential decay with consecutive mechanical action. The TL emission of PU-based surface impregnated composite expires with long-lived emission, and maximum TL response with respect to applied force was measured between 2.45 and 42.0 N.

Effective photosensitized, electrosensitized, and mechanosensitized luminescence of lanthanide complexes

“…Quantitative estimation of the triboluminescence efficiency is important to clarify the mechanism of triboluminescence and to develop strong triboluminescent materials. Generally, the drop-tower method is used to estimate the triboluminescence efficiency [173][174][175] . However, it is difficult to use the drop-tower method as a quantitative estimation (for calculations of the radiative and non-radiative rate constants).…”

Polymeric Planar Microcavities Doped with a Europium Complex

“…As mentioned above, the material shows an intense and sharp near-band-edge exciton emission at 614 nm, where the triboluminescence also occurs [3,10,11]. In spite of its outstanding emissive properties, EuD 4 TEA applications are currently limited to the sensing of mechanical stimulations using the pristine material, or embedding the material into polymer matrices such as poly methyl methacrylate [10]. These applications are allowed by the triboluminescence process, which is the emission of photons resulting from chemical bond breakage within crystalline particles after the application of a mechanical force [12,13].…”

“…In this work, as a proof of principle, we demonstrate polymer planar microcavities doped with EuD 4 TEA embedded into a blend of polystyrene (PS) and PS carboxi-terminated (PSCT). While the pristine PS serves to increase the viscosity of the starting solution to enhance its processability, PSCT serves to stabilize EuD 4 TEA through the -OH group of the carboxylic PS termination [10]. We study the EuD 4 TEA photoluminescence directional and spectral redistribution.…”

“…The synthesis of EuD 4 TEA was carried out by the hot injection method [10]. An aliquot (50 mL) of the solution of 1,3-diphenyl-1,3-dipronedione (Sigma-Aldrich; 98%) in ethanol with a concentration of 58.2 mg/mL was heated until reflux.…”

“…Indeed, its structure consists of four coordinated electron donating groups (1,3-diphenyl-1,3-propanedione), which function as light absorbers; one is triethylamine, which serves to stabilize the complex, and the complexed emissive metal [8,9] (Figure 1). As mentioned above, the material shows an intense and sharp near-band-edge exciton emission at 614 nm, where the triboluminescence also occurs [3,10,11]. In spite of its outstanding emissive properties, EuD 4 TEA applications are currently limited to the sensing of mechanical stimulations using the pristine material, or embedding the material into polymer matrices such as poly methyl methacrylate [10].…”