Efficient Sensing of Explosives by Using Fluorescent Nonporous Films of Oligophenyleneethynylene Derivatives Thanks to Optimal Structure Orientation and Exciton Migration

Abstract

The fluorescence of thin films of a diimine-substituted phenyleneethynylene compound can be efficiently quenched by nitroaromatic vapors, which is not the case for the unsubstituted parent compound. Thin-film porosity is usually considered to be an essential factor for efficient quenching, but in the present case the origin of the quenching is completely different, as both films are nonporous and hermetic to 2,4-dinitrotoluene (DNT) molecules. The molecular organization in the two crystallized thin films offers a low level of π stacking for both compounds, but the orientation of the phenylenethynylene fluorophore differs markedly with respect to the surface of the films. For the substituted compound, the fluorophore is almost parallel to the surface, thus making it readily available to molecules of a nitroaromatic quencher. This rationale is also observed in the case of a related compound bearing methoxy side chains instead of the long octyloxy moieties. Fluorescence-lifetime experiments show that the efficient quenching process in the nonporous crystallized films of the substituted compound is due to a fast (<70 ps) diffusion of excitons from the bulk of the film toward the surface where they are quenched, thus providing evidence of antenna effects.

Photoactive thin films of terphenylene-based amorphous polymers. Synthesis, electrooptical properties, and role of photoquenching and inner filter effects in the chemosensing of nitroaromatics

“…The DFT results of the calculations performed on trimers follows closely the tendency observed in the experimental determinations (Fig. 2), though discrepancies are observed, as usual, between the absolute values of both sets [46].…”

Theoretical Investigations on the Detecting Mechanism of a Typical 2,4,6-Trinitrophenol Fluorescence Sensor and Its Design Strategy

“…Herein, achieving precise detection of TNP is of fundamental importance to homeland security and environment protection. In recent years, sensing of TNP based on small organic molecules has gained increasing attention. ,,, Compared to supermolecules such as metal–organic frameworks (MOFs) and polymers, small organic molecules have several advantages such as straightforward synthesis, easy purification, high quantum yield, as well as better reproducibility. − Besides, it is easy to modify the functional groups of the sensor to coordinate its sensitivity. In recent years, dozens of fluorescence sensors based on small organic molecules have been developed to detect TNP. ,,, Most of these works place emphasis on introducing the synthesis procedure and reporting the detecting limit.…”

Assessing the potential of quartz crystal microbalance to estimate water vapor transfer in micrometric size cellulose particles

“…This technique is well known to follow the thickness of a deposited layer during its growth in a vacuum deposition technique, knowing the mass density of the deposited material. During the last years, the QCM has been extensively used as a sensor devoted to the study of the detection of numerous biomolecules (Villares, Moreau, Dammak, Capron, & Cathala, 2015), to analyze selective membranes and sensors to a specific gas (Caron et al, 2014;Jia, Yu, Zhang, Dong, & Li, 2016;Michalzik, Wilke, & Büttgenbach, 2005;Passamano & Pighini, 2006) and to evaluate interfacial polymer behavior (Ahola, Myllytie, Österberg, Teerinen, & Laine, 2008;Marx, 2003;Tammelin et al, 2015). QCM with dissipation monitoring (QCM-D) could be useful to investigate viscoelastic properties of the adsorbed layer and take into consideration energy dissipation effects (Hakalahti, Faustini, Boissière, Kontturi, & Tammelin, 2017;Kontturi, Kontturi, & Laine, 2013;Niinivaara, Faustini, Tammelin, & Kontturi, 2015.…”