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[Display omitted] • Ninhydrin and Isatin-based chromogenic chemosensors selective for Cr3+ and Pb2+ ions were established. • NMR, FTIR, UV–vis and ESI-MS spectroscopy methods were used to confirm the probe and interaction of the probe with the analytes. • Probe L1 and L2 effective sense at colorimetric method was observed to be 2.80 × 10-6 M and 1.63 × 10-6 M detection limits. • Test Strip was designed to monitor the absorbance of Cr3+ and Pb2+ ions in real time analysis. • In a molecular logic circuit, the reversible and reproducible colorimetric switching off L1 and L2 was also discovered. A simple and easily synthesizable chromogenic small molecules probe L4 (2-(2-(benzo[ d ]thiazol-2-yl)hydrazono)-1H-indene-1,3(2H)-dione) and L5 (2-(2-(benzo[ d ]thiazol-2-yl)hydrazono)indolin-3-one) have been synthesized and characterized by various spectroscopy techniques such as FT-IR, NMR, and HRMS. The colorimetric naked eye detection of probe L4 showed a color change towards Cr3+ from orange color to pale yellow, whereas in case of L5 Pb2+ yellow to orange color was witnessed. The jobs plot analyses indicate the 1:1 binding stoichiometric for Cr3+ and 1:2 binding stoichiometric for Pb2+ ions with probes L4 and L5 respectively. The binding association constant (k a) values for L4 and L5 were found to be 6.651 × 10-5 M for Cr3+ and 6.493 × 10-5 M for Pb2+ ions. The limit of detection was found to be for Cr3+ (1.69 × 10−7 M) and Pb2+ (1.208 × 10−7 M) are far below than the limit set by the World Health Organization (WHO) for drinking water. Finally, the designed probes were applied for visible colorimetric test kits and real samples for rapid detection of Cr3+ and Pb2+ for all practical purposes, indicating their potential use in environmental samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • An easily designed R1 probe has been developed that demonstrates a rapid response to Cu2+ ions and possesses outstanding absorption and emission properties. • The ability to detect low levels of analytes with the lowest limit of detection (LOD) 3.23 × 10−9 M and quantification (LOQ) 10.79 × 10−9 M. • The R1 probe is capable of monitoring Cu2+ ions under physiological pH (2–10) conditions and exhibits specific selectivity towards cupric ion even in the presence of other competing ions. • The R1 probe was employed for the purpose of identifying the presence of Cu2+ ions in both the water and vegetable samples. In this work, we describe the synthesis of a Schiff base (R1) derived from furfural and 2-hydrazinobenzothiazole which displayed turn-off selective fluorescent chemo-sensing properties for Cu2+ ions in THF: HEPES buffer (9:1, v/v) solution. The molecular structure of the Schiff base (R1) was characterized by various spectroscopic techniques such as FTIR, 1H NMR, 13C NMR, and HRMS. Interestingly, R1 upon interaction with various metal cations displays highly selective colorimetric and fluorescent turn-off response to Cu2+ ions. The UV–Vis absorption study of the R1 with Cu2+ ions exhibits a noticeable color change from yellow to brown color with a redshift (∼60 nm). Upon the addition of Cu2+ ions emission quenching at 529 nm was observed in R1, and the limit of detection (LOD) and limit of quantification (LOQ) were found to be 3.23 × 10−9 M and 10.79 × 10−9 M. The mechanisms of probe R1 for sensing Cu2+ ions have been well demonstrated by Job's plot, Benesi-Hildebrand studies, and Density functional theory calculations (DFT). Owing to practical application, the Cu2+ ions were efficiently determined using a spike and recovery approach from real water and vegetable extract samples. Further, the developed R1 sensors were used for test strips application to detect the Cu2+ ions and achieved naked-eye detection. Therefore, these investigated results demonstrate that sensor R1 has great potential to detect Cu2+ ions in environmental analysis systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrazone based dual mode fluorescence sensor for Zn2+ ("turn-on") and Hg2+ ("turn off"). • Probe C1 selectively sense Zn2+and Hg2+ ions with their lowest detection limits 0.042 μM and 0.081 μM respectively. • The designed probe C1 was studied latent fingerprint analysis in various surfaces. • Live cell imaging studies was performed for probe C1 in presence and absence of Zn2+, Hg2+ ions. A facile Schiff base probe C1 has been developed and evaluated using 1H, 13C NMR, and mass spectroscopy. Fluorescence investigations were conducted to determine probe-sensing behavior. Probe C1 demonstrated sensitive, and selective recognition of Zn2+ and Hg2+ ions by using two distinct processes (i.e., chelation enhanced fluorescence effect and fluorescence quenching) over other cations in ACN-H 2 O (8:2, v/v). The Zn2+ and Hg2+ detection limits of 0.042 and 0.081 μM are achieved with the probe C1. C1 has a binding constant of 3.33 × 103 M−1 for Zn2+ and an emission quenching constant of 1.22 × 104 M−1 for Hg2+. A Jobs plot was used to determine the binding stoichiometry of C1 and Zn2+/Hg2+ ions ratio is 1:1. By using Zn2+/Hg2+ and EDTA additions alternately, the probe's reusability was investigated. Moreover, the probe was found to be highly cytocompatibility using an MTT assay in a mouse fibroblast cell line (NIH3T3). Further, the probe was found to visualize Zn2+ and Hg2+ ions inside the cells, indicating the potential application of the probe as an intracellular probe to detect Zn2+ and Hg2+ ions. The probe shows very good solid-state emission behavior, this motivates us to develop latent fingerprint detection and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]