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With this research we set out to develop a number of coumarin-based ‘AND’ logic fluorescence probes that were capable of detecting a chosen analyte in the presence of HCys. Probe JEG-CAB was constructed by attaching the ONOO� reactive unit, benzyl boronate ester, to a HCys/Cys reactive fluorescent probe, CAH. Similarly, the core unit CAH was functionalised with the nitroreductase (NTR) reactive p-nitrobenzyl unit to produce probe JEG-CAN. Both, JEG-CAB and JEG-CAN exhibited a significant fluorescence increase when exposed to either HCys and ONOO� (JEG-CAB) or HCys and NTR (JEG-CAN) thus demonstrating their effectiveness to function as AND logic gates for HCys and a chosen analyte.

Owing to their easy accessibility and high degree of structural and functional diversity, many multicomponent reactions (MCRs) have been a rich source of conjugate π-systems, functionalised chromophores (or fluorophore) and redox active molecules. Despite their high explorative potential and practical benefits, only a few MCR products have been so far investigated for their metal sensing abilities. In the present report, two furopyrimidinones (FPys) based molecular systems have been synthesized by [4 + 1] cycloaddition based MCR sequence. Designed chemosensors displayed optic (absorption spectra) as well as electroanalytical (ion selective electrode) response toward Cu2 + ion in solution and membrane phase respectively (dual channel sensing). Different aspects of both the sensing phenomena such as selectivity, association constants, detection limit, membrane composition etc. were studied in detail using UV–Vis spectroscopy, NMR titration and cell assembly. Both the compounds showed excellent performance characteristics such as high selectivity, acceptable affinity and low detection limits (10− 7 M) in both sensing assays with potential utility in the area of sample monitoring.

With this research we set out to develop a coumarin-based novel fluorescent probe NTR-AHC for the detection of biological thiols and nitroreductase (NTR). Probe NTR-AHC was constructed by attaching the NTR trigger moiety (p-nitrobenzyl) and biothiol acceptor (maleic acid monoamide), to the core fluorophore AHC. In the presence of both glutathione (GSH) and NTR, probe NTR-AHC produced a >8-fold increase in fluorescence intensity at 463 nm.

New antipyrine Schiff bases 2,3-dimethyl-4-(3-oxo-1,3-diphenylpropylideneamino)-1-phenyl-1,2-dihydropyrazol-5-one ( AP1 ) and 2,3-dimethyl-4-(2-oxo-1,2-diphenylethylideneamino)-1-phenyl-1,2-dihydropyrazol-5-one ( AP2 ) have been synthesized by simple condensation method and investigated their metal recognition abilities. Different aspects of metal sensing phenomena were extensively studied and results indicated that Schiff base AP1 and AP2 exhibited selective colorimetric and fluorescent sensing behavior towards Al 3+ and Cr 3+ in methanol with high binding nature, which could be directly detected by the naked-eye. Stoichiometry of metal-ligand complexes were determined by job's plots titrations and further verified with HRMS data. Both sensors exhibited excellent fluorescent sensing behavior in acidic and neutral pH with low detection limits 0.49, 0.96 μM for AP1 + Al 3+ , AP1 + Cr 3+ and 0.73, 1.21 μM for AP2 + Al 3+ and AP2 + Cr 3+ , respectively.

A new rhodamine-derived Schiff base RH was synthesized and its sensing behavior toward various metal ions was investigated by UV–vis and fluorescence spectroscopic techniques. The sensor exhibited highly selective and sensitive colorimetric response to Cu2+ and Al3+, and “off–on” fluorescence response toward Fe3+ in semi-aqueous media. The spectral changes obtained are large enough in the visible region of the spectrum and thus enable naked-eye detection. Experimentally proved that the formation of RH–Al3+ complex is fully reversible and can sense to AcO−/F− via break the complex. The results revealed that the sensor offers the sequential detection of Al3+ and AcO−/F−.

The present report highlights the role of comprehensive structure property relationships (SPRs) in the discovery of a new and more effective molecular system for sensing purposes. From an extensive survey of different classes of amino substituted annulated furanones, it was realized that with some exceptions, these functionalized furanones could sense Cu2+ ions in the semi-aqueous phase irrespective of the nature of substituents; furthermore the same scaffolds could also detect Al3+, if the aldehydic position is specifically filled by a 3-indoyl group. As a result, amino substituted annulated furanones with 3-indoyl groups could detect both metal ions, response time of which mainly depends on the overall molecular framework. After replacing different furanone frameworks, a dual metal ion sensor (for Cu2+ and Al3+) with short response time and high selectivity and association constant was identified. The proposed bifunctional sensor displayed a distinct but observable response (turn off colorimetric for Cu2+ and turn on fluorescence for Al3+) to both metal ions with potential applications in the area of real sample analysis and membrane sensing.

Furans are an important class of compounds and exhibit a diverse range of activities and properties. As such, improved synthetic access to furans is an important research goal. In the present report, a solvent- and catalyst-free reaction between 5,5-dimethyl-1,3-cyclohexanedione (dimedone), an aryl aldehyde and an isocyanide under microwave irradiation is presented. This method is significantly improved from previously described protocols in terms of applicability of wide ranging aryl aldehydes, better yields, shorter reaction times, facile work up and essentially no need of column chromatography. The photophysical properties of this series of compounds were studied for their possible applicability in the field of metal ion sensors. In solution, two compounds, 2-(cyclohexylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 i) and 2-(tert-butylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 j), underwent an observable color change from yellow to colorless in the presence of aluminum(III) ions. Further studies to investigate the UV absorption and luminescence behavior of these compounds revealed their utility as "naked-eye sensors" for aluminum detection.

Phthalocyanine tetrasulfonic acid (PCTS) performed as a optical probe for selective detection of Cu2+ in DMSO solution over other metal ions used. The complexation behavior of chemodosimeter toward various metal ions has been studied via UV–vis absorption and fluorescence emission spectra. Induced changes were found to be observable from naked eye. The association constant (Ka) and low limit of detection were found to be 8.80 × 105 M−1 and 5.53 × 10−7 M, respectively. The optode showed excellent selectivity behavior in the environmental pH range.

In this research, multiwalled carbon nanotubes (MWCNTs) was oxidized and chemically modified through reaction with 3-(trimethoxysilyl)propan-1-amine (TMSPA) and their subsequent reaction with 2-hydroxy-3-methoxy benzaldehyde. Subsequently, this material was metalized by reaction with copper acetate that lead to formation and impergeation of 2-methoxy-6-((3-(trimethoxysilyl)propylimino)methyl)phenol MMSPIMPMWCNT-Cu. This novel material was identified with different techniques such as SEM and FT-IR analysis. In this work, the reported material are exhibited high accurate and repeatable monitoring of iodide due to its high surface area with various reactive centre. It exhibited selectivity for iodide over the wide linear dynamic range between 1.8×10−6 and 1.15×10−1 M, with a Nernstian slope of −59.12±0.7 mV per decade of activity and detection limit of 1.8×10−6 M. Copper sulfide nanoparticles were prepared and their effect on the electrode response was investigated. The results were improved in the presence of nanoparticles with fast and stable response, good reproducibility, long-term stability, high selectivity over the presence of common organic and inorganic anions, high detection limit and dynamic range. The proposed sensor has been applied as potentiometric determination of some iodine species over a pH range of 2.5–10.

A new azo compound, 1-(2-pyridylazo)-2-naphthol, has been prepared and characterized. The synthesized compound shows a very high affinity for aluminium. The complexation reaction of aluminium has been explored by Colorimetry, FT-IR, 1 H NMR, HRMS and fluorescence spectroscopy. The detection limit has been found to be 1.81 × 10 −8 M estimated by the titration method. The turn-on fluorescence behaviour of aluminium interaction with ligand has been found to be so fast (

Antipyrine schiff bases 4-(4-hydroxy-3-methoxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one (L1) was successfully synthesized and characterized. The complexation behavior of chemosensor with different metal ions including Zn2+ ions in methanolic solution was studied on UV–vis absorption spectra and Photofluorescent spectra. Results showed that the chemosensor (L1) exhibited 55 fold enhancements in fluorescence at 533 nm after adding Zn2+ ions. Such fluorescent responses could be detected by naked eye under UV-lamp. The limit of detection was calculated to be 10−7 M by titration method. The chemosensor (L1) showed excellent selectivity fluorescent behavior in acidic pH range. The complex solution (L1-Zn2+) exhibited reversibility with EDTA.

Thiazole Schiff bases 2-(4-phenyl-1,3-thiazol-2-yliminomethyl)phenol (L 1 ) and 1-(4-phenyl-1,3-thiazol-2-yliminomethyl)naphthalen-2-ol (L 2 ) have synthesized and characterized. The interaction of Schiff bases with different metal ions has been studied over UV–vis absorption spectra and photofluorescent spectra. The results are indicated that Schiff base L 1 and L 2 exhibited turn-on fluorescent behavior with Al 3+ ions in methanol, which could be directly detected by the naked-eye under the UV-lamp. The limits of detection were calculated for L 1 and L 2 since 1.0 × 10 −6 and 7.5 × 10 −7 by the titration method. Both sensors exhibited excellent fluorescent behavior in 5.0–13.5 pH range. The fluorescent behavior of legends-aluminum complex solution goes to turn-off in the presence of Ni 2+ and EDTA.

A new gadolinium(III) selective electrode has been developed from poly vinyl chloride (PVC) matrix membrane which is based on synthesized neutral carrier [L1] 2-(2-aminothiazol-4-yl)phenol and [L2] 2-(4-phenyl-1,3-thiazol-2-yliminomethyl)phenol as ionophores. The membrane having a composition of ionophore (L2):PVC:plasticizer (acetophenone):additive (sodium tetraphenylborate) in the ratio of 5:33:60:2 exhibited calibration performance over a wide range of concentration of gadolinium (9.38 × 10−7 to 1.0 × 10−2 M) and exhibited a Nernst slope of 19.5 ± 0.5 mV per decade of Gd(III) activity. It exhibited a quick response time of 8 s and its potential response was independent of pH across the pH range of 3.5–8.5. The membrane can be used with a good reproducibility over a period of 3 months. Membrane sensor was used as a indicator electrode for determination of end point in potentiometric titration of Gd (III) ion with EDTA. The proposed membrane electrodes were successfully applied for the determination of the concentration of gadolinium (III) ion in a mineral sample.

Furans are an important class of compounds and exhibit a diverse range of activities and properties. As such, improved synthetic access to furans is an important research goal. In the present report, a solvent- and catalyst-free reaction between 5,5-dimethyl-1,3-cyclohexanedione (dimedone), an aryl aldehyde and an isocyanide under microwave irradiation is presented. This method is significantly improved from previously described protocols in terms of applicability of wide ranging aryl aldehydes, better yields, shorter reaction times, facile work up and essentially no need of column chromatography. The photophysical properties of this series of compounds were studied for their possible applicability in the field of metal ion sensors. In solution, two compounds, 2-(cyclohexylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 i) and 2-(tert-butylamino)-3-(1H-indol-3-yl)-6,6-dimethyl-6,7-dihydrobenzofuran-4(5H)-one (1 j), underwent an observable color change from yellow to colorless in the presence of aluminum(III) ions. Further studies to investigate the UV absorption and luminescence behavior of these compounds revealed their utility as "naked-eye sensors" for aluminum detection.

A new rhodamine functionalized fluorogenic Schiff base CS was synthesized and its colorimetric and fluorescence responses toward various metal ions were explored. The sensor exhibited highly selective and sensitive colorimetric and "off-on" fluorescence response towards Al(3+) in the presence of other competing metal ions. These spectral changes are large enough in the visible region of the spectrum and thus enable naked-eye detection. Studies proved that the formation of CS-Al(3+) complex is fully reversible and can sense to AcO(-)/F(-) via dissociation. The results revealed that the sensor provides fluorescence "off-on-off" strategy for the sequential detection of Al(3+) and AcO(-)/F(-).