Conjugated supramolecular architectures as state-of-the-art materials in detection and remedial measures of nitro based compounds: A review

Tellurium Containing Long Lived Emissive Fluorophore for Selective and Visual Detection of Picric Acid through Photo-Induced Electron Transfer

A novel tellurium (Te) containing fluorophore, 1 and its nickel (2) and copper (3) containing metal organic complex (MOC) have been synthesized to exploit their structural and optical properties and to deploy these molecules as fluorescent probes for the selective and sensitive detection of picric acid (PA) over other commonly available nitro-explosives. Furthermore, density functional theory (DFT) and single crystal X-ray diffraction (SCXRD) techniques revealed the inclusion of "soft" Tellurium (Te) and "hard" Nitrogen (N), Oxygen (O) atoms in the molecular frameworks. Owing to the presence of electron rich "N" and "O" atoms along with "Te" in the molecular framework, 1 could efficiently and selectively sense PA with more than 80 % fluorescence quenching efficiency in organic medium and having detection limit of 4.60 μM. The selective detection of PA compared to other nitro-explosives follows a multi-mechanism based "turn-off" sensing which includes photo-induced electron transfer (PET), electrostatic (π-π stacking and π-anion/cation) interaction, intermolecular hydrogen bonding and inner filter effect (IFE). The test strip study also establishes the sensitivity of 1 for detection of PA.

Conjugated Polymeric Materials in Biological Imaging and Cancer Therapy

Conjugated polymers (CPs) have attracted much attention in the fields of chemistry, medicine, life science, and material science. Researchers have carried out a series of innovative researches and have made significant research progress regarding the unique photochemical and photophysical properties of CPs, expanding the application range of polymers. CPs are polymers formed by the conjugation of multiple repeating light-emitting units. Through precise control of their structure, functional molecules with different properties can be obtained. Fluorescence probes with different absorption and emission wavelengths can be obtained by changing the main chain structure. By modifying the side chain structure with water-soluble groups or selective recognition molecules, electrostatic interaction or specific binding with specific targets can be achieved; subsequently, the purpose of selective recognition can be achieved. This article reviews the research work of CPs in cell imaging, tumor diagnosis, and treatment in recent years, summarizes the latest progress in the application of CPs in imaging, tumor diagnosis, and treatment, and discusses the future development direction of CPs in cell imaging, tumor diagnosis, and treatment.

Critical Analysis of Association Constants between Calixarenes and Nitroaromatic Compounds Obtained by Fluorescence. Implications for Explosives Sensing

The binding behaviour of two ureido-hexahomotrioxacalix[3]arene derivatives bearing naphthyl (1) and pyrenyl (2) fluorogenic units at the lower rim towards selected nitroaromatic compounds (NACs) was evaluated. Their affinity, or lack of it, was determined by UV-Vis absorption, fluorescence and NMR spectroscopy. Different computational methods were also used to further investigate any possible complexation between the calixarenes and the NACs. All the results show no significant interaction between calixarenes 1 and 2 and the NACs in either dichloromethane or acetonitrile solutions. Moreover, the fluorescence quenching observed is only apparent and merely results from the absorption of the NACs at the excitation wavelength (inner filter effect). This evidence is in stark contrast with reports in the literature for similar calixarenes. A naphthyl urea dihomooxacalix[4]arene (3) is also subject to the inner filter effect and is shown to form a stable complex with trinitrophenol; however, the equilibrium association constant is greatly overestimated if no correction is applied (9400 M^-1 vs 3000 M^-1), again stressing the importance of taking into account the inner filter effect in these systems.

Octylamine as environment friendlier colorimetric detection probe for hazardous 2,4,6-Trinitrophenol from wastewater samples

The precise detection of hazardous 2,4,6-Trinitrophenol (TNP) is essential for the environment and human health. TNP is used as a precursor in whistling fireworks in ammunition, mining, agriculture and is a hazardous environmental pollutant generated from leather, chemical, and dye industries. Exploring rapid and low-cost approaches for the detection and quantification of TNP has attracted many scientists nowadays. The proposed chemosensor utilizes the concept of dispersive liquid-liquid micro-extraction coupled with a UV-visible spectrophotometer for its sensing at the ultra-trace level. Significant changes based on intramolecular interactions followed by a distinct color change to orange-red from yellow in the presence of TNP is an attractive feature for the present study. The successive addition of TNP shows ultra-trace sensitivity (3.9831 μA μM^-1 cm^-1) at detection limit (LOD) of 0.0015 ± 0.03 μM (S/N = 3), a linear range of 0 μM-70 μM, and a response time of <5 min. Different types of real samples such as creatinine testing kit reagent, fireflies crackers, serum, and water samples were used and recovery of TNP was calculated by spiking the known concentration of the standard analyte. The obtained recovery was 93.6-103.6% with RSD range of 1.6-4.53% (n = 3) in different samples. The analytical performance of the colorimetric Chemoprobe in terms of its recovery, linearity range, and limit of detection offers an excellent platform for monitoring hazardous TNP. The results show that the proposed colorimetric chemosensor is easy to use, low-cost, environmentally friendly and offers an easily observable visual color change. Based on these features, the chemosensor can be used for large-scale applications for the detection of TNP in water and other samples.

Multi-stimuli distinct responsive D–A based fluorogen oligomeric tool and efficient detection of TNT vapor

P1 shows distinct emission responses with multi-stimuli, i.e., quenching for TNT sensing, red shifting for acid and base vapors, blue shifting against MFC behavior, and solvent polarity-dependent emission.

Fluorescence-Based Sensing of Pesticides Using Supramolecular Chemistry

The detection of pesticides in real-world environments is a high priority for a broad range of applications, including in areas of public health, environmental remediation, and agricultural sustainability. While many methods for pesticide detection currently exist, the use of supramolecular fluorescence-based methods has significant practical advantages. Herein, we will review the use of fluorescence-based pesticide detection methods, with a particular focus on supramolecular chemistry-based methods. Illustrative examples that show how such methods have achieved success in real-world environments are also included, as are areas highlighted for future research and development.

Fluorescent Calix[4]arene-Carbazole-Containing Polymers as Sensors for Nitroaromatic Explosives

Two highly fluorescent calix[4]arene-containing phenylene-alt-ethynylene-carbazolylene polymers (Calix-PPE-CBZs) were used in the detection of explosives from the nitroaromatic compounds (NACs) family, in solution and in vapour phases. Both fluorophores exhibit high sensitivity and selectivity towards NACs detection. The quenching efficiencies in solution, assessed through static Stern-Volmer constants (KSV), follow the order picric acid (PA) >> 2,4,6-trinitrotoluene (TNT) > 2,4-dinitrotoluene > (2,4-DNT) > nitrobenzene (NB). These correlate very well with the NACs electron affinities, as evaluated from their lowest unoccupied molecular orbitals (LUMOs) energies, indicating a photo-induced electron transfer as the dominant mechanism in fluorescence quenching. Moreover, and most interesting, detection of TNT, 2,4-DNT and NB vapours via thin-films of Calix-PPE-CBZs revealed a remarkably sensitive response to these analytes, comparable to state-of-the-art chemosensors. The study also analyses and compares the current results to previous disclosed data on the detection of NACs by several calix[4]arene-based conjugated polymers and non-polymeric calix[4]arenes-carbazole conjugates, overall highlighting the superior role of calixarene and carbazole structural motifs in NACs’ detection performance. Density functional theory (DFT) calculations performed on polymer models were used to support some of the experimental findings.