Explicating the recognition phenomenon of hazardous nitro-aromatic compound from contaminated environmental and cellular matrices by rationally designed pyridine-functionalized molecular probes.

In the quest of recognizing hazardous nitro-aromatic compounds in water, two pyridine-functionalized Schiff-base chemosensors, DMP ((E)-N-(3,4-dimethoxybenzylidene)(pyridin-2-yl)methanamine)) and MP (4-((E)-((pyridin-2-yl)methylimino)methyl)-2-ethoxyphenol) have been synthesized to detect mutagenic 2,4,6-Trinitrophenol (TNP) in soil, water as well as cellular matrices by producing turn-off emission responses as a combined consequence of PET and RET processes. Several experimental analyses including ESI-MS, FT-IR, photoluminescence, 1H NMR titration, and the theoretical calculations ascertained the formation and sensing efficacies of the chemosensors. The analytical substantiations revealed that structural variation of the chemosensors played a significant role in improving the sensing efficiency, which would certainly be worthwhile in developing small molecular TNP sensors. The present work depicted that the electron density within the MP framework was more than that of DMP due to the intentional incorporation of -OEt and -OH groups. As a result, MP represented a strong interaction mode towards the electron-deficient TNP with a detection limit of 39 µM.

Amine-substituent induced highly selective and rapid "turn-on" detection of carcinogenic 1,4-dioxane from purely aqueous and vapour phase with novel post-synthetically modified d10-MOFs.

Herein, an amine decorated Cd(II) metal-organic framework (MOF) with a uninodal 6-c topology was synthesized as a suitable platform for facile post-synthetic modification (PSM). The as-synthesized parent d10-MOF (1) with free -NH2 centers, when functionalized with two different carbonyl substituents (1-naphthaldehyde and benzophenone) of varying conjugation, produces two novel luminescent MOFs (LMOFs) viz.PSM-1 and PSM-2. The judicious incorporation of carbonyl substituents into the skeleton of 1 was rationalized via ESI-MS, 1H-NMR, FT-IR and PXRD analyses. Interestingly, both PSM-1 and PSM-2 show 'turn-on' luminescent behaviour in the presence of 1,4-dioxane with the limit of detection (LOD) as 1.079 ppm and 2.487 ppm, respectively, with prompt response time (∼55 s & ∼58 s, respectively). The inhibition of PET is comprehended to be the prime reason for luminescence enhancement upon interaction with the targeted analyte which was further validated from DFT calculations. In continuation, the PSM-MOFs were equally responsive towards 1,4-dioxane in several complex environmental matrices and cosmetic products. Additionally, vapor phase detection of 1,4-dioxane using PSM-MOFs has also been demonstrated as an additional advantage ensuring propagation of future research endeavour.

Advancement in functionalized luminescent frameworks and their prospective applications as inkjet-printed sensors and anti-counterfeit materials.

Supramolecular luminescent frameworks with conjugated architectures exhibits interesting photophysical properties with phenomenal chemical and thermal stability. This has instigated global researchers towards its extensive application in toxic analyte detection and the formulation of anti-counterfeit materials. In correlation with this present scenario, luminescent metal-organic frameworks (LMOFs), possessing tailorable structural and functional properties and exceptional physicochemical features, have been categorized as emerging 'smart materials'. Interestingly, LMOFs have assisted in the rapid development of an effectual sensing platform and swift fabrication of anti-counterfeit materials on desirable substrates with the aid of 'Inkjet Printing', which is a viable, low-cost, and high-resolution technology. Inkjet printing is an excellent material deposition technique in the modern era owing to its easy settling over flexible substrates, simplistic emergence of large area image patterns with improved throughput, minimal cost, explicit resolution, and least waste generation. The present review provides state-of-the-art progress on LMOFs based (i) luminescent security ink fabrication with static and dynamic multinodal luminescent materials and (ii) sensory device formulation for the easy and instantaneous recognition of hazardous analytes through the 'Inkjet Printing' technology. This techno-chemical integration will be certainly beneficial to prevent the growth of counterfeit materials and monitor the bioaccumulation of hazardous analytes in our ecological system.

Solvothermal Synthesis of High-Performance d10-MOFs with Hydrogel Membranes @ "Turn-On" Monitoring of Formaldehyde in Solution and Vapor Phase.

Herein, two luminescent porous networks (CMERI-1 & CMERI-2) have been reported for the efficient detection of formaldehyde (FA) from aqueous medium. Judicious solvent screening using a high-throughput solvothermal procedure leads to two completely different metal-organic framework (MOFs) with different architectures. It is perceived that the framework CMERI-1 shows better sensitivity with a very short response time (1 min) in the realm of FA detection due to the facile imine (-N═CH-) formation, which is restricted in the case of CMERI-2. The fluorescence "turn-on" behavior is ascribed due to the inhibition of photoinduced electron transfer (PET) (from amine subunit to secondary building unit) process. The detection limits of CMERI-1 & CMERI-2 toward FA in aqueous medium were found to be 0.62 µM (0.019 ppm) and 1.39 µM (0.041 ppm), respectively, that lie far below the intracellular concentration of formaldehyde (100-400 µM). In addition, MOF-based hydrogel membrane was fabricated, which shows vapor-phase detection of FA, which is hitherto unexplored in this realm. Moreover, the response mechanisms of MOFs are supported by density functional theory (DFT) and Fukui indices analysis. The high stability of the porous frameworks along with its interesting sensing features such as fast recognition phenomenon, appreciable detection limit, etc. instigated us to explore its real-world applicability in various food sample and water analyses. In view of the modular design principle of our polymeric probe, the proposed approach could open a new horizon to construct powerful sensing materials for the ultrafast detection of other industrial pollutants in the domain of supramolecular and analytical chemistry.

Efficient tribological properties of azomethine-functionalized chitosan as a bio-lubricant additive in paraffin oil: experimental and theoretical analysis.

A simple condensation of chitosan (from shrimp shells) and 4-hydroxybenzaldehyde was performed to yield bio-lubricant additive comprised of azomethine functional groups to be used with paraffin lube oil in industries. The synthesized Schiff base derivative of chitosan (SBC) additive was characterized using a CHN analyzer and FT-IR spectroscopy, and the thermal stability was explored using thermogravimetry. The rheological properties of SBC additives in paraffin oil were studied and are discussed herein. The tribological properties of SBC were tested in paraffin as the base oil employing a four-ball tester with different experimental conditions (viz. the concentration of the additive, applied load, speed and time duration), following ASTM D4172A standards. The optimum concentration of the additive in the base oil was found to be 150 ppm, exhibiting minimum coefficient of friction, but with higher concentrations of additive in base oils, the coefficient of friction increased. UV-Vis spectroscopy studies were also performed to confirm the formation of SBC and dispersion stability. The determined tribological parameters, such as the coefficient of friction, mean wear scar diameters and mean wear scar volumes, were found to significantly reduce the coefficient of friction of paraffin oil upon the addition of SBC. The state of steel balls upon exposure to various experimental conditions was analyzed and explained based on outcomes from FESEM, EDX, ferrography and AFM spectroscopy. The insights into interactions of the synthesized SBC with the metal surface were explored using ab initio density functional theory, Fukui indices, molecular dynamics simulation and radial distribution function.