ABSTRACT
In this work, we report the fast and ultrasensitive detection of a nerve agent simulant in the gas phase, diethyl chlorophosphate (DCP), by using carbazole-based nanofibers from 1. When exposed to trace DCP, the formed pyridine-phosphorylated product in 1 nanofibers can cause amplified ratiometric fluorescence responses, i.e., amplified fluorescence quenching via quenching excitons within the diffusion length of 1 nanofibers and simultaneously amplified turn-on fluorescence responses via harvesting excitons within the diffusion length to give the intramolecular charge transfer (ICT) emission at a longer wavelength. On the basis of these amplified ratiometric fluorescence responses, detection of DCP with fast response (ca. 3 s), ultrasensitivity (4 ppb), and improved selectivity is achieved.
ABSTRACT
In this work, we develop fluorescent hierarchical nanofiber bundles 1, which involve the internanofiber hydrogen-bonding interactions, for rapid and sensitive detection of diethyl chlorophosphate (DCP) vapor. First, the internanofiber hydrogen-bonding strength can be weakened by photoexcitation, which thereby increases the internanofiber spacing and decreases the fluorescence intensity. Then, when exposed to trace DCP vapor, the strong interactions between DCP and hydroxyl groups on the nanofibers can effectively retighten the nanofibers and enhance the fluorescence as the detection signal. In contrast, the interferences, such as common organic solvents, cannot retighten nanofiber bundles 1 because of the lack of strong interactions with the nanofibers. On the basis of this novel detection mechanism, fluorescence detection of DCP with rapid signal response (ca. 3 s) and high sensitivity (15 ppb) is achieved.
ABSTRACT
In this work, we report a two-member fluorescence array sensor for the effective discrimination of five classes of explosives. This smallest array sensor is composed of tricarbazole-based nanofibers (sensor member 1) and nanoribbons (sensor member 2) deposited as two film bands in a quartz tube. On the basis of a simple comparison of the resulting fluorescence quenching ratios between two sensor members and the response reversibility upon exposure to vaporized explosives, five classes of explosives can be sensitively detected and easily discriminated. This array sensor that has only two sensor members and no complex data analysis represents a new design way for discrimination of a broad class of explosives.
ABSTRACT
Kinetic control over the assembly pathways towards novel metastable functional materials or far-from-equilibrium systems has been much less studied compared to the thermodynamic equilibrium self-assembly. Herein, we report the distinct morphological transformation between nanocoils and nanoribbons in the self-assembly of unsymmetric perylene diimide (PDI) molecules. We demonstrate that the morphological transformation of the kinetically trapped assemblies into the thermodynamically stable forms proceeds via two distinct mechanisms, i.e., a direct structural rearrangement (molecule 1 or 2) and a fragmentation-recombination mechanism (molecule 4), respectively. The subtle interplay of the steric hindrance of the bulky substituents and the flexibility of the linker structure between the bulky moiety and the perylene core was demonstrated to enable the effective modulation of the energetic landscape of the assemblies and thus modulation of the assembly pathways. Herein, our work presents a new approach to control the self-assembly pathways and thereby can be used to achieve novel far-from-equilibrium systems.
ABSTRACT
Highly fluorescent bilayer nanotubes with a right- or left-handed helical sense were assembled from a chiral asymmetric perylene diimide for the first time, which constitute a new family member of self-assembled organic nanotubes.
