ABSTRACT
Effective strategies for the detection and identification of explosives are highly desirable. Herein, we illustrate the efficient optoelectronic detection of nitroaromatic and peroxide-based explosives using amine- and phosphine-substituted diketopyrrolopyrroles. Selective quenching and an unprecedented enhancement of thin-film emission in the presence of nitroaromatic vapors are demonstrated via the judicious choice of amine substituents. The modulation of fluorescence emission in each case is shown to be dominated by electronic and thermodynamic effects, the vapor pressure of explosives, and the thin-film morphology. For peroxide detection, we describe an approach exploiting redox-mediated functional group transformation. The rapid oxidation of triphenylphosphine to phosphine oxide with hydrogen peroxide affords a significant increase in fluorescence emission, facilitating the sensitive turn-on detection of an important class of explosives at ppb concentrations.
ABSTRACT
Development of novel bioimaging materials that exhibit organelle specific accumulation continues to be at the forefront of research interests and efforts. Among the various subcellular organelles, mitochondria, which are found in the cytoplasm of eukaryotic cells, are of particular interest in relation to their vital function. To date, most molecular probes that target mitochondria utilise delocalised lipophilic cations such as triphenylphosphonium and pyridinium. However, the use of such charged motifs is known to be detrimental to the working function of the mitochondrial transmembrane potential and there remains a strong case for development of neutral mitochondrial fluorescent probes. Herein, we demonstrate for the first time the exploitation of diketopyrrolopyrrole-based chemistries for the realisation of a neutral fluorescent probe that exhibits organelle specific accumulation within the mitochondria at the nanomolar level. The synthesised probe, which bears a neutral triphenylphosphine oxide moiety, exhibits a large Stokes shift and high fluorescence quantum yield in water, both highly sought-after properties in the development of bioimaging agents. In vitro studies reveal no interference with cell metabolism when tested for the human MCF7 breast cancer cell and nanomolar subcellular organelle colocalisation with commercially available mitochondrial staining agent Mitotracker Red. In light of its novelty, neutral structure and the preferential accumulation at nanomolar concentrations we anticipate this work to be of significant interest for the increasingly larger community devoted to the realisation of neutral mitochondrial selective systems and more widely to those engaged in the rational development of superior organic architectures in the biological field.
