Fluorescence Sensors for Bismuth (III) Ion from Pyreno[4,5-d]imidazole Derivatives

Imidazole Compounds: Synthesis, Characterization and Application in Optical Analysis

Imidazole is a five-membered heterocyclic ring containing three carbon atoms, two nitrogen atoms, and two double bonds. Among two nitrogen atoms, one of which carries with a hydrogen atom is a pyrrole-type nitrogen atom, another is a pyridine type nitrogen atom. Hence, the imidazole ring belongs to the π electron-rich aromatic ring and can accept strong suction to the electronic group. Moreover, the nitrogen atom of the imidazole ring is coordinated with metal ions to form metal-organic frameworks. In recent years, because of imidazole compounds' unique optical properties, their applications have attracted more and more attention in optical analysis. Thus, this review has summarized the synthesis, characterization, and application with emphasis on the research progress of imidazole compounds in optical analysis, including fluorescence probe, colorimetric probe, electrochemiluminescence sensor, fiber optical sensor, surface plasmon resonance, etc. This paper will suggest the direction for the development of imidazole-containing sensors with high sensitivity and selectivity.

Silkworm-derived carbon nano rods (swCNR) for detection of bismuth ions (Bi3+) in aquatic medium and their antiradical properties

The extensive utilization of bismuth and its derivatives in many industries, such as chemical, semiconductor, pharmaceutical, and cosmetics, leads to their accumulation in wastewater, posing a risk to both human health and the environment. Carbon nanorods (CNR) are fluorescent nanoparticles with an ability to detect various analytes as sensing probes. This study focuses on the production, structure, and chemical composition characterization of silkworm-derived CNR (swCNR) and their ability to detect bismuth ions (Bi3+) and inhibit radicals. The optimum wavelength for exciting the fluorescence of swCNR was 370 nm, and the resulting emission peak was observed at 436 nm. The prepared swCNR showed static fluorescence quenching mechanism-based sensing of Bi3+ ions with a limit of detection of 175 nM and two linear ranges from 0.5 to 5 μM (R2 = 0.9997) and 10-50 μM (R2 = 0.9995). The swCNR demonstrated high selectivity in detecting Bi3+ ions in the spiked river water samples, thus establishing the swCNR's role as a nano fluorescence probe designed for the selective detection of Bi3+ ions among other metal ions. Favorable results for the antiradical ability of swCNR were obtained against hydroxyl, 2,2 diphenyl-1 picrylhydrazyl, and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radicals with scavenging percentages of 15, 32, and 90, respectively. The possible applications of swCNR in the environmental and antioxidant sectors are proposed in this study.

A Porphyrin-based NIR Fluorescent Probe for Bi3+ and Potential Applications

Herein, we have prepared a 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (P) which acts as a probe for selective and sensitive detection of Bi3+ ions. Probe P was obtained by reacting pyrrole with 4-hydroxyl benzaldehyde and characterized by NMR, IR, and ESI-MS. All photo-physical studies of P were tested in DMSO:H2O (8:2, v/v) media by spectrophotometry and spectrofluorometry respectively. The selectivity of P was tested with different metal ions in solution as well as in the solid phase, only Bi3+ showed red fluorescence quenching while with other metal ions, no such effect was observed. The Job's plot unveiled the 1:1 stoichiometric binding ratio of the probe with Bi3+ and anticipated association constant of 3.4 ×105 M-1, whereas the Stern-Volmer quenching constant was noticed to be 5.6 ×105 M-1. Probe P could detect Bi3+ down to 27 nM by spectrofluorometric. The binding mechanism of P with Bi3+ was well supported with NMR, mass, and DFT studies. Further, the P was applied for the quantitative determination of Bi3+ in various water samples and the biocompatibility of P was examined using neuro 2A (N2a) cells. Overall, probe P proves promising for the detection of Bi3+ in the semi-aqueous phase and it is the first report as a colorimetric and fluorogenic probe.

Ratiometric Fluorescent Sensor for Copper(II) and Phosphate Ions from Aminopyrene Derivatives

Three derivatives of 1-aminopyrene are functionalized with 2-picolyl and 2-picolinyl groups and are tested as fluorescent sensors for metal ions. The target compounds are successfully synthesized in yields of 50-90% and characterized by ¹ H-NMR, ¹³ C-NMR, and HRMS. The compound with an amino picolyl group (P1) exhibits an excellent selectivity toward Cu(II) ion as the fluorescent signal shifts from 433 to 630 nm. From a fluorescence titration experiment, the limit of detection for Cu(II) ion is estimated as 0.19 µm. The fluorescence spectral shift by Cu(II) ion is reliant on the use of acetonitrile as a co-solvent, and the results from cyclic voltammetry and UV-Vis spectroscopy suggest that the sensing mechanism involves a coordination complex between the P1, acetonitrile and Cu(II) ion. Furthermore, this P1-Cu complex can also be used as a selective fluorescent sensor for PO₄ ^3- ion with a detection limit of 0.44 µm.