A Comparison of ACQ, AIE and AEE-Based Polymers Loaded on Polyurethane Foams as Sensors for Explosives Detection

Abstract

An aggregation-caused quenching (ACQ)-active polymer (PF), an aggregation-induced emission (AIE)-active polymer (PFTPE) and an aggregation-enhanced emission (AEE)-active polymer (PTTPE) were synthesized by tetraphenylethane (TPE), fluorene and thiophene moieties. Polyurethane (PU) foams modified by PF, PFTPE and PTTPE, namely PU-PF, PU-PFTPE and PU-PTTPE, using ultrasonication-assisted method have been prepared. A comparative study of PU-PF, PU-PFTPE and PU-PTTPE for detection explosives had been performed, and significant fluorescence quenching was observed with the introduction of PA solutions. The as-prepared PU-PF, PU-PFTPE and PU-PTTPE sensors exhibited a superior sensitivity for PA solutions with different concentrations. Remarkably, PU-PF gave a quenching efficiency of 96.2%, higher than 93.5% for PU-PFTPE and 86.7% for PU-PTTPE at a PA concentration of 180 µg·mL−1 in methanol, which was attributed to the effective energy transfer from the fluorophore (PF) to the nitro explosive (PA). This suggested that some ACQ polymers, applied to detect explosives, could afford better performances than AIE or AEE polymers through modification of structures and selection of adequate carriers. At the same time, these chemical sensors can be recycled many times.

Clusterization-triggered emission: Uncommon luminescence from common materials

“…It is known that nitro-explosive molecules are typically electron-deficient substrates that can easily bind to electron-rich sites via donor−acceptor interactions, quenching luminescence from electron-rich substrates by electron or charge transfer [200][201][202] . Clusteroluminogens are good candidates to detect nitro-explosive molecules because of the abundance of n-or πelectrons in their structures.…”

Aggregation-Induced Emission Properties in Fully π-Conjugated Polymers, Dendrimers, and Oligomers

“…For this reason, it is more frequent to find, in the literature, polymers that contain more than one luminogen in their structure. As we have commented in the previous section, polyfluorene suffers ACQ, and several authors have described polymeric structures in which fluorene is combined with TPE to invert this phenomenon ( 65 ) ( Figure 28 ) [ 111 , 114 , 115 , 116 ]. In all cases the polymers were prepared by Suzuki coupling using dibrominated TPE and the boronic acid derivative of fluorene, obtaining molecular weights between 10,900 and 16,400 Da and PDI between 1.76 and 3.80.…”

“…As we have seen, the incorporation of the TPE structure or similar in a polymer seems to induce the RIM effect to it and in all cases, polymers with AIE or AIEE properties are obtained. However, this does not happen with all luminogens; for instance, polymers based exclusively on TPA or fluorene lead to ACQ processes [ 110 , 111 ]. Sometimes, the simple addition of a disruptive element that breaks this sequence is enough to convert TPA polymers into luminescent ones when they are aggregated.…”

“…When water fractions are added, the fluorescence increases until reaching Φ = 27% for a f w = 99%. These polymers have been used for the detection of explosives [ 111 , 114 ], lead ion sensors [ 116 ], and as efficient electroluminescent materials [ 114 , 115 ], With similar applications and prepared in the same way, TPE and carbazole polymers have also been described ( 66 ) [ 114 , 115 ]. Spectroscopic data are also comparable with a low THF emission centered at 508 nm and an AIE effect when aggregation is induced that can reach 28% for a f w = 90%.…”

Novel AIEgen-Functionalized Diselenide-Crosslinked Polymer Gels as Fluorescent Probes and Drug Release Carriers

“…Fluorescent probes are highly efficient and sensitive bio-optical detectors that have demonstrated a significant value in bioimaging and biosensing applications [15][16][17]. Recently, fluorescent probes based on the aggregation-induced emission (AIE) effect have attracted great attention [18][19][20][21], especially tetraphenylethylene (TPE) has been extensively studied for its high quantum yield and facile synthesis. In 2016, Ishiwari et al introduced TPE molecules into polyacrylic acid hydrogels, showing enhanced fluorescence emission after adding Ca 2+ due to significant chain folding thereof [22].…”