Vinod Kumar Jain

Selective Fe ³⁺ sensing by an oxacalix[4]arene-based fluorescent receptor via ICT suppression and LMCT.

The use of rhodium nanoparticles (RhNPs) in biomedical, environmental and industrial applications is highly significant due to their unique catalytic, physical and chemical properties. Further, NPs encapsulated within macrocyclic structures with inherent hollow cavities are able to boost their catalytic activity. Here we are reporting for the first time, a versatile, non-toxic, third-generation supramolecule, calixarene, stabilised RhNPs. The novel sulphonic-acid functionalized oxacalix[4]arene derivative satbilized RhNPs (DSOC@RhNPs) were synthesised by a simple one-pot NaBH₄ reduction method at room temperature. The resulting DSOC@RhNPs were successfully characterized using UV-Vis, FT-IR, PXRD, HRTEM and EDX. The self-assembled, well-dispersed and spherical (average size of 6–8 nm) DSOC@RhNPs exhibited heterogeneous catalytic activity in the reduction of three, cationic, anionic and neutral carcinogenic azo dyes (methylene blue, methyl orange and neutral red). DSOC@RhNPs has the potential to reduce hazardous pollutants Like 4-nitrophenol (4-NP), retaining its catalytic efficiency across four consecutive cycles. The catalytic reduction of 4-NP and the formation of 4-AP were confirmed by UV-Vis and ESI-MS data. Further, newly systhesized DSOC@RhNPs exhibited excellent sensitivity in detecting Al³⁺ ions (LOD 9 µM). Therefore, the newly developed DSOC@RhNPs represent a versatile nanomaterial with potential for synergistic catalytic and sensing applications across diverse fields. Graphical Abstract

This research presents the application of Dinaphthoylated Oxacalix[4]arene (DNOC) as a novel fluorescent receptor for the purpose of selectively detecting nitroaromatic compounds (NACs). The characterization of DNOC was conducted through the utilization of spectroscopic methods, including ¹H-NMR, ¹³C-NMR, and ESI-MS. The receptor demonstrated significant selectivity in acetonitrile towards several nitroaromatic analytes, such as MNA, 2,4-DNT, 2,3-DNT, 1,3-DNB, 2,6-DNT, and 4-NT. This selectivity was validated by the measurement of emission spectra. The present study focuses on the examination of binding constants, employing Stern-Volmer analysis, as well as the determination of the lowest detection limit (3σ/Slope) and fluorescence quenching. These investigations aim to provide insights into the inclusion behavior of DNOC with each of the six analytes under fluorescence spectra investigation. Furthermore, the selectivity trend of the ligand DNOC for NAC detection is elucidated using Density Functional Theory (DFT) calculations conducted using the Gaussian 09 software. The examination of energy gaps existing between molecular orbitals, namely the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), provides a valuable understanding of electron-transfer processes and electronic interactions. Smaller energy gaps are indicative of heightened selectivity resulting from favorable electron-transfer processes, whereas bigger gaps suggest less selectivity attributable to weaker electronic contacts. This work integrates experimental and computational methodologies to provide a full understanding of the selective binding behavior of DNOC. As a result, DNOC emerges as a viable chemical sensor for detecting nitroaromatic explosives. Graphical Abstract

This research introduces Dinaphthoylated Oxacalix[4]arene (DNOC) as a novel fluorescent receptor for selective detection of nitroaromatic compounds (NACs). DNOC was characterized using ¹H-NMR, ¹³C-NMR, and ESI-MS spectroscopic techniques. The receptor exhibited remarkable selectivity in acetonitrile towards various nitroaromatic analytes, including MNA; 2,4-DNT; 2,3-DNT; 1,3-DNB; 2,6-DNT and 4-NT as confirmed through emission spectra analysis. Investigation of binding constants, Stern-volmer analysis, lowest of detection limit (3σ/Slope) and fluorescence quenching sheds light on DNOC's inclusion behaviour. Additionally, Density Functional Theory (DFT) calculations using Gaussian 09 program elucidate the selectivity trend of the ligand DNOC for NAC detection. Analysing energy gaps between molecular orbitals (HOMO and LUMO) offers insights into electron-transfer mechanisms and electronic interactions. Smaller energy gaps indicate higher selectivity through favourable electron-transfer processes, while larger gaps imply reduced selectivity due to weaker electronic interactions. This interdisciplinary study combines experimental and computational approaches to comprehensively understand DNOC's selective binding behaviour, rendering it a promising chemical sensor for nitroaromatic explosives.

We present the synthesis of a new oxacalix[4]arene system, DMANSOC, wherein two 5-(dimethylamino)-1-naphthalene sulfonamide subunits are attached to the lo

We present the synthesis of a new oxacalix[4]arene system, DMANSOC, wherein two 5-(dimethylamino)-1-naphthalene sulfonamide subunits are attached to the lower rims of the basic oxacalix[4]arene platform. Extensive spectrophotometric studies were conducted to investigate the selectivity and sensitivity of DMANSOC towards nitroaromatic explosives. Detailed analysis of spectrophotometric data, utilizing techniques such as Stern-Volmer, Benesi-Hildebrand, Job's plot, and interference study, unequivocally demonstrated the effectiveness of DMANSOC as a highly efficient fluorescent sensor for 2,4,6-trinitrophenol explosive (TNP) detection in an aqueous medium. The sensor exhibited a linear concentration range of 7.5 µM to 50 µM, with a low detection limit of 4.64 µM and a high binding affinity of 2.45 × 10⁴ M towards TNP. Furthermore, the efficiency of the sensor in environmental samples contaminated with TNP was evaluated, yielding excellent recovery rates. Complementary DFT calculations and molecular dynamics simulations were performed to elucidate the mechanism behind the selective fluorescence quenching of DMANSOC in the presence of TNP.

Globally 3 billion people are consuming water with moderately high concentrations of fluoride and arsenic. The development of a simple point of care (PoC) device or home device for the detection of fluoride/arsenic ensures safety before consuming water. Till date, lateral flow assay (LFA) based PoC devices can detect nucleic acids, viruses and diseases. An aluminium complex of rhodamine B functionalized oxacalix[4]arene (L) was designed to execute the LFA-based PoC device. Initially, Al³⁺ and Fe³⁺ ions were involved in complexation with the rhodamine B functionalized oxacalix[4]arene (L), resulting C₁ (L-Al³⁺) and C₂ (L-Fe³⁺) complexes respectively. The receptor L, as well as the probes (C₁, C₂), were characterized thoroughly using mass spectroscopy, FTIR, NMR, and EA. C₁ and C₂ were further utilized as recyclable probes for the detection of aqueous fluoride (21 ppb) and arsenate (1.92 ppb) respectively. The computational calculation indicates that upon complexation, the spirolactam ring opening at the rhodamine B site leads to optoelectronic changes. The consistency of LFA-based portable sensing device has been tested with water samples, synthetic fluoride standards and dental care products like toothpaste and mouthwash with concentrations ≥ 3 ppm. Moreover, fixed cell imaging experiments were performed to ascertain the in-vitro sensing phenomena.