Tetraphenylethene-Based Conjugated Fluoranthene: A Potential Fluorescent Probe for Detection of Nitroaromatic Compounds

This study reports the synthesis and photophysical properties of a star-shaped, novel, fluoranthene-tetraphenylethene (TFPE) conjugated luminogen, which exhibits aggregation-induced blue-shifted emission (AIBSE). The bulky fluoranthene units at the periphery prevent intramolecular rotation (IMR) of phenyl rings and induces a blueshift with enhanced emission. The AIBSE phenomenon was investigated by solvatochromic and temperature-dependent emission studies. Nanoaggregates of TFPE, formed by varying the water/THF ratio, were investigated by SEM and TEM and correlated with optical properties. The TFPE conjugate was found to be a promising fluorescent probe towards the detection of nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) with high sensitivity and a high Stern-Volmer quenching constant. The study reveals that nanoaggregates of TFPE formed at 30 and 70% water in THF showed unprecedented sensitivity with detection limits of 0.8 and 0.5ppb, respectively. The nanoaggregates formed at water fractions of 30 and 70% exhibit high Stern-Volmer constants (K-sv=79998 and 51120m(-1), respectively) towards PA. Fluorescence quenching is ascribed to photoinduced electron transfer between TFPE and NACs with a static quenching mechanism. Test strips coated with TFPE luminogen demonstrate fast and ultra-low-level detection of PA for real-time field analysis

Aggregation behavior in naphthalene-appended diketopyrrolopyrrole derivatives and its gas adsorption impact on surface potential

Diketopyrrolopyrrole derivatives containing phenyl and thiophene units adorned with alkoxynaphthalene (Naph-PDPP and Naph-TDPP) were synthesized by a Suzuki cross-coupling reaction. The effect of the phenyl/thiophene units on the aggregation behavior and detailed photophysical properties were investigated by UV-visible, steady-state, and time-resolved fluorescence spectroscopy. The absorption and fluorescence spectra of Naph-PDPP and Naph-TDPP in the solid-state exhibit red-shifted spectral patterns due to strong intermolecular interactions. The concentration-dependent photophysical properties reveal the formation of J-type aggregates at higher concentrations and in the solid state. The extent of aggregate formation is higher for Naph-TDPP. DFT and TD-DFT studies showed that Naph-TDPP containing a thiophene ring in the backbone adopts a more planar geometry than Naph-PDPP and undergoes strong pi-pi stacking interactions that favor the formation of J-aggregates. Scanning Kelvin probe measurements on the thin films of Naph-PDPP and Naph-TDPP were performed (both in the dark and under visible light) upon exposure to different volatile organic vapors (ethanol and triethylamine). The study reveals that under visible light illumination, the Naph-PDPP thin film has significant gas adsorption towards ethanol vapors and alters its sign of response

Pyrazoloanthrone-functionalized fluorescent copolymer for the detection and rapid analysis of nitroaromatics

The development of sensors for rapid detection of chemical explosives with high sensitivity and selectivity is the focus of many research groups. In this work, we have developed a simple and straightforward synthesis of a block (co)polymer functionalized with pyrazoloanthrone (SP). The block (co)polymer was synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization of 2-hydroxyethyl acrylate using a PEG-functionalized RAFT-agent. Subsequently, the SP was coupled to the poly(2-hydroxyethyl acrylate) block through DCC coupling. The structural and physicochemical properties of the (co)polymer were studied to explore its potential towards the detection of nitroaromatics as a model for explosives. A systematic comparison is made on the chemosensing behavior of the (co)polymer and three small molecule pyrazoloanthrone analogues with different functional groups (SP, SP-OH and SP-COOH). Fluorescence studies demonstrated a significant decrease in the fluorescence intensity of the four fluorophores in the presence of different nitroaromatics and showed unprecedented selectivity for 2,4,6 trinitrophenol (TNP). The Stern-Volmer rate constants (K-sv) of the SP-functionalized copolymer (K-sv = 9.74 x 10(4) M-1) showed an similar to 3.7 times higher quenching rate constant than its monomer analog (SP) for TNP with a limit of detection (LOD) of 19 ppm. A static quenching mechanism with photoinduced electron transfer process, intermolecular hydrogen bonding and electrostatic interactions induce turn off fluorescence behavior. The interference studies with other nitroaromatics in an aqueous medium and real-time analysis in the solid-state methods demonstrate the potential of the block (co)polymer towards practical applications

Development of Gas Sensor Array based on Phthalocyanines Functionalized TiO₂/ZnO Heterojunction Thin Films

Gas sensing properties of diverse phthalocyanines functionalized TiO2/ZnO heterojunction thin films were investigated respect to a number of volatile organic compounds (VOCs) in both dark and light conditions. These studies showed that influence of heterojunction along with functionalization alter the optical properties and gas sensing of sensors. Results show that each sensor exhibits a different pattern of relative sensitivity, and this feature can be used to discriminate among a wide range of VOCs

Fluoranthene-based derivatives for multimodal anti-counterfeiting and detection of nitroaromatics

In this study, we developed two novel sky blue fluorescent fluorophores comprising ethyl alcohol (FOH) and ethanethiol (FSH) units appended to fluoranthene at the periphery. Single Crystal X-Ray Diffraction (SC-XRD) studies reveal that the molecular flexibility of alkyl chains leads to distinct diagonal (FOH) and ladder (FSH) shaped supramolecular arrangements in the crystal lattices. Detailed photophysical and DFT studies showed that FOH and FSH demonstrate high sensitivity and selectivity towards the detection of trinitrophenol (TNP). FSH exhibits high quenching efficiency (similar to 84%), a rate constant of KSV = 1.1 x 104 M-1 with a limit of detection of similar to 97 ppm in THF, and similar to 76 ppm in river water. Mechanistic investigation through NMR and SC-XRD of the FSH adduct with 1,3-dinitrobenzene (DNB) reveal strong pi-pi interactions (3.518 angstrom). Furthermore, photoinduced electron transfer occurs from the fluorophores to the nitro analytes and leads to strong intermolecular interactions using the static quenching mechanism. Both fluorophores were employed in advanced surveillance to identify finger marks on a wide range of substrates (glass, cellophane tape, aluminium foil and floor tiles) with different resolutions to provide an unadorned and lucrative method for viewing the latent fingerprints (LFPs) with exceptionally consistent evidence of up to level 3 and without the requirement for post-treatments, leading to promising applications for onsite forensic analysis. Furthermore, FOH and FSH were evaluated in 72 hpf zebrafish larvae/embryos to demonstrate the non-toxicological behaviour and fluorescence imaging/tracking. Two novel fluoranthene ensembles with ethyl alcohol (FOH) and ethanethiol (FSH) functionality with distinct diagonal and ladder arrangements in the crystal lattices were developed for Latent Fingerprints (LFPs) towards analysis of explosives.Web of Science4236270625