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Imine-linked pyridine-coupled (ILPC) receptors have been synthesised and characterised. The absorption and fluorescence properties of these receptors have been explored through a combination of experimental and theoretical studies. The ILPC receptors are processed into organic nanoparticles (ONPs) and then decorated with gold nanoparticles (AuNPs) for the selective recognition of iodide. The selective recognition behaviour is authenticated with the changes in fluorescence spectra, low detection limit (1.4 n M) and no interference in aqueous systems. The present investigation represents the first example of nanomolar detection of iodide in aqueous medium using organic-inorganic hybrid nanoparticles (ONPs-AuNPs). The probe has been utilised successfully for the detection of iodide content in urine samples. [ABSTRACT FROM AUTHOR]

The synthesis of fluorescent organic nanoparticles (FONPs) with an imine-linked 1,8-naphthalimide-based dipodal chemosensor for AgI is described. The FONPs were prepared by using a re-precipitation method, and they were successfully applied for the nanomolar detection of AgI ions in aqueous media. More specifically, the chemosensor was utilized for the selective and ratiometric sensing of AgI in a concentration range 15-65 n M with a 15.5 n M detection limit. The work was extended to monitor the AgI concentration in samples of environmental importance. [ABSTRACT FROM AUTHOR]

Abstract: A tripodal receptor bearing phenol as a hydrogen bond donor site and azo dye as the signaling subunit was synthesized. The receptor had a high binding affinity for CN− as signaled by the change in the color of a solution of sensor 4 upon addition of CN−. Using UV–Vis spectroscopy, the system can be used to quantify 0–19×10−5 molL−1 of CN−, and the sensor was found to successfully function in the presence of other anions. [Copyright &y& Elsevier]

Seven neutral tripodal and dipodal receptors having mesitylene/triethylbenzene as core moiety, urea/thiourea as binding groups and p-nitrobenzene as signalling unit have been reported. The receptors act as selective colorimetric, naked eye sensors for small and spherical F−  ion with some interference from tetrahedral ions. Thiourea derivatives form stable 1:1 H-bonded complexes with F−  anion and to some extent with anions, whereas for urea derivatives, the recognition is simply based on acid–base reaction between ureidic protons and basic F−  ions and is a completely reversible phenomenon. The pre-organisation of thiourea derivatives coupled with their high-intrinsic acidity is supposed to help them in the formation of strong H-bonded complexes with F−  anion. The urea-based receptors do not respond at lower concentrations of the anion, but at higher concentrations, they undergo completely reversible deprotonation concomitant with a colorimetric change, with the production of stable [HF2]−  anion. [ABSTRACT FROM PUBLISHER]

Abstract: We synthesized a novel benzimidazole-based, anthracene-coupled fluorescent receptor capable of recognizing and estimating the concentrations of Fe3+ in semi-aqueous solution by ratiometric estimation. Our sensor can be made highly selective for Fe3+ over other metal ions by changing the solvent composition. [Copyright &y& Elsevier]

Abstract: We synthesized a novel receptor with a unique combination of sp2 nitrogen (–CH) and carbonyl groups from amide linkages. These two moieties are judiciously incorporated into the receptor design such that these sites simultaneous binding a metal ion may generate a stable five-member ring. The receptor has been used to selectively detect Zn2+ through changes in the fluorescence spectra. Upon Zn2+ binding with the receptor, the fluorescence band shifted to enhance fluorescence intensity, allowing ratiometric determination of Zn2+ concentration. [Copyright &y& Elsevier]

Abstract: A novel receptor, designed with a combination of oxygen and nitrogen-binding sites for metal ions and hydrogen bond donor sites for anion binding, was synthesized. The receptor has been explored for the selective detection of I− against a range of physiologically relevant anions and cations through changes in its UV–vis spectra. On the other hand, receptor-binding selectivity for Fe3+ over a wide linear concentration range was observed through changes in the emission spectra. This is the first Letter of a sensor capable of detecting both I− and Fe3+ using two different detection modes. [Copyright &y& Elsevier]

Abstract: We synthesized a novel receptor with benzimidazole moieties in a tripodal framework. The receptor displays rarely observed metal specific fluorescence enhancement at two different wavelengths. The receptor was investigated for the simultaneous analysis of Cu2+ and Fe3+ and successfully quantified the ions without interference over a wide concentration range. [Copyright &y& Elsevier]

Abstract: Polymer 1, a poly(olefin) with pendant Schiff base units is prepared by reacting poly(allylamine) and 2-hydroxynapthaldehyde in methanol. The optical properties of 1 are investigated in THF:H2O (9:1) solvent system buffered at pH 7.0±0.1 using HEPES. When tested against a range of physiological and environmentally relevant cations 1 displays selectivity for Ag+ from changes in the UV–vis spectra with linearity established in the range of 10–60μM. The addition of Ag+ to a solution of 1 also causes a colour change from colourless to dark yellow meaning Ag+ is also detectable by the naked eye. In contrast, selectivity is observed for Mn2+ from changes in the emission spectra again with good linearity observed in the range of 0–50nM. This is the first reported polymeric sensor capable of detecting both Ag+ and Mn2+ using two different detection modes. [Copyright &y& Elsevier]

Abstract: A simple fluorescent sensor 1 has been developed for the determination of Fe(III) in 100% aqueous solution at pH 7.0. The sensor comprises a novel aminobisulfonate receptor joined to a naphthalene fluorophore via a methylene spacer in the fluorophore-spacer-receptor format of photoinduced electron transfer (PET) based sensors. The fluorescence emission of the sensor was quenched upon addition of Fe(III) ions, most likely due to electron/energy transfer between Fe(III) and the excited naphthalene. The sensor displayed good selectivity for Fe(III) over other physiologically relevant metal ions and can estimate Fe(III) concentration between 16 and 63μM. Stern Volmer analysis showed the binding stoichiometry to be 1:1 (host–guest) with a binding constant, calculated using the Benesi–Hilderbrand equation, of (7.6±0.6)×104 M−1. [Copyright &y& Elsevier]

Abstract: A polysiloxane based thiourea coupled sensor has been developed for the determination of anions from changes in the UV–Vis or fluorescence spectra. A comparative account of the photophysical properties of the monomer and polymer units bearing the thiourea moiety revealed better fluoride recognition in the polymeric framework. The fluoride recognition by the polymeric sensor was attributed to co-operative binding involving a DMSO molecule and a fluoride ion between thiourea groups on adjacent residues. The polymeric sensor can measure fluoride at two different concentration ranges by using either absorbance or emission signalling. [Copyright &y& Elsevier]

Abstract: Schiff base sensor 1, containing naphthalene and naphthalimide fluorophores with separate and distinct emission wavelengths, showed good selectivity for Cu(II) over other tested physiological and environmentally important cations through changes in its fluorescence spectra in THF/H2O (9:1) HEPES buffered solution. By taking the ratiometric change of the emissions at 435nm (naphthalene–Schiff base) and 510nm (naphthalimide) good linearity was observed in the 0–10μM range. The enhancement of the 435nm emission upon binding Cu2+ was attributed to a prevention of the rapid Csation that otherwise leads to non-radiative decay, while the quenching of the naphthalimide emission was attributed to electron transfer between the excited naphthalimide fluorophore and the redox active Cu2+. [Copyright &y& Elsevier]

• A cystamine based an organic-inorganic nanohybrid [ L1-ONP-Co(II) ] probe has been synthesized. • The photophysical detection of NADH by L1-ONP-Co(II) with a real time imaging of cancer cells. • The probe has a detection limit as low as 83.89 nM for NADH. • The higher level of NADH in cancer cells 'Turn On' the green colored fluorescence of L1- ONP-Co(II). The pronounced demand of sensing of biological analytes which play a significant role in progress of cancer cells encouraged us to develop a novel chemosensor having high selectivity and sensitivity for NADH. Therefore, imine linked dipodal receptor (L1) was synthesized and its organic nanoparticles (L1-ONP) were prepared using reprecipitation method to enhance their water solubility. These ONPs form a metal complex with Co(II) which was characterized by UV–vis absorption and Fluorescence Spectroscopy. The ONPs show highly sensitive affinity having a low detection limit (LOD) of 16.95 nM for the cobalt ions. The prepared ONPs metal complex exhibits high selectivity and sensitivity to sense the NADH with a very low LOD of 83.89 nM without any interference from other potentially interfering biological molecules. Fluorescence response from NADH was also not affected by pH and UV irradiation. The sensor was also employed for detection of NADH in MCF-7 cells. [ABSTRACT FROM AUTHOR]

The present work depicts the development of a probe based on the organic-inorganic framework that sensitively and selectively recognized furosemide in aqueous medium. An organic receptor 1 is prepared using 1, 8-naphthalic anhydride and diethylenetriamine and the product are further reacted with 1-naphthylisothiocyanate. The receptor is processed into fluorescent organic nanoparticles (FONs); unfortunately, these FONs have not shown any promising sensor activity. The FONs are used as platform for the attachment of gold nanoparticles and the resultant hybrid nanoparticles ( H1 ) are characterized. Hybrid nanoparticles are evaluated for their photophysical studies with fluorescence spectroscopy in aqueous medium and the studies revealed that hybrid nanoparticles selectively recognize furosemide in aqueous medium. The sensor has shown competitive binding for furosemide and no other tested drug has posed any interference in the detection of furosemide. The titrations are performed with furosemide and the lowest detection limit calculated is 551 nM. [ABSTRACT FROM AUTHOR]

A series of mesitylene based ratiometric chromogenic sensors ( 1 – 3 ) have been synthesized and evaluated for selective cyanide detection in aqueous medium. Low hydration energy and high basicity of CN − in water is shown to be responsible for selective behavior of probes in the aqueous medium. Spectroscopic and theoretical studies endorse frozen proton transfer as the sensing mechanism. The compounds also show considerable antimicrobial activity. [ABSTRACT FROM AUTHOR]

Pyrene based Bigineilli compounds 1 – 4 were synthesized through one pot, multicomponent organic synthesis and were assessed for their metal binding ability under both organic medium and through forming their ONPs (aqueous medium). Sensors 3 and 4 selectively bind Zn 2+ in acetonitrile through quenching in fluorescence intensity of excimer peak at 470 nm and amplifying monomer peak (which consist of two shoulder peaks at 380 nm and 395 nm). ONPs of 3 and 4 in aqueous medium displayed AIEE (aggregation induced enhanced emission) phenomenon through enhancement in fluorescence intensity. Furthermore, ONPs of 3 and 4 sense Fe 3+ by quenching fluorescence intensity of both monomer and excimer emission peak. Sensing event of Fe 3+ by organic nanoparticles of 3 and 4 was authenticated with CV profile of 3 and 4 with Fe 3+ . [ABSTRACT FROM AUTHOR]

Abstract: An imine-linked dipodal Zn2+ complex has been synthesized and elevated its binding affinity towards library of metal ions (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ and Bi3+). The recognition properties of receptor 4 were performed in DMSO/H2O (50:50; v/v) and showed quenching upon interaction with Fe3+, Co2+ and Cu2+ ions. A photoinduced electron transfer (PET) is potential mechanism behind quenching. The coordination of such cations with the receptor 4 at amide part of carbonyl oxygen hindered the PET process and accordingly Turn-OFF the fluorescence of the receptor 4. The photophysical properties (fluorescence and absorption spectra) and density functional theory (DFT) clearly explains the binding mode between the receptor 4 and the detected cations. The selectivity and sensitivity of the receptor 4 for Fe3+, Co2+ and Cu2+ ions were acceptable and achieving a detection limit at the nano-molar level. [Copyright &y& Elsevier]

The hexadentate ligands H2L1-L3 with mixed S, N, O donor sites and possessing substituents having either "no" or electron-releasing/withdrawing nature at terminal ends are synthesized. The ligands H2L1-L3 were tested for binding with library of metal ions, wherein maximum efficiency was observed with Ni2+, and it motivated us to prepare the Ni2+ complexes. The ligandH2L1 underwent deprotonation and formed binuclear complex when interacted with Ni2+ as evident from its crystal structure. The H2L2 and H2L3 having electron-withdrawing/electron releasing groups, respectively, were also deprotonated; however, they afforded mononuclear complexes with Ni2+ ion. This signifies the importance of steric parameters instead of electronic factors in these particular cases. Impressed by differential behavior of complexes of H2L1 andH2L2/H2L3 with Ni2+ and their photophysical and electrochemical properties, all the metal complexes were studied for their chemosensing ability. Nowadays with increased use of organophosphate, there is alarming increase of these agents in the environment, and thus we require efficient technique to estimate the level of these agents with high sensitivity and selectivity in aqueous medium. The Ni2+ complexes with hydrophobic nature were suspended into aqueous medium for testing them as sensor for organophosphate. The (L1)2.(Ni2+)2 could sense phosmet with detection limit of 44 nM, whereas L2.Ni2+ and L3.Ni2+ exhibited the detection limits of 62 and 71 nM, respectively, for chlorpyrifos. [ABSTRACT FROM AUTHOR]

A fluorescent based receptor (4Z)-4-(4-diethylamino)-2-hydroxybenzylidene amino)-1,2dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (receptor 3 ) was developed for the highly selective and sensitive detection of Cu 2+ and Zn 2+ in semi-aqueous system. The fluorescence of receptor 3 was enhanced and quenched, respectively, with the addition of Zn 2+ and Cu 2+ ions over other surveyed cations. The receptor formed host-guest complexes in 1:1 stoichiometry with the detection limit of 5 nM and 15 nM for Cu 2+ and Zn 2+ ions, respectively. Further, we have effectively utilized the two metal ions (Cu 2+ and Zn 2+ ) as chemical inputs for the manufacture of INHIBIT type logic gate at molecular level using the fluorescence responses of receptor 3 at 450 nm. [ABSTRACT FROM AUTHOR]

A novel receptor ( E )-1-(phthalazine-4-yl)-2-(1-(pyridine-2-yl)ethylidene) hydrazine ( 3 ) was developed for the detection of trace water content present in methanol. Upon interaction of water molecule with receptor 3 , there appears a significant color change from colorless to yellow green and the absorption band at 355 nm was shifted to 435 nm (i.e. bathochromic or red shift) due to selective encapsulation of water molecule at 1-(pthalazine-4-yl) hydrazine-NH and imine groups leading to tautomeric transformation in the ground state which is caused by an intramolecular proton transfer. Also, there was remarkable enhancement in fluorescence intensity of 3 in methanol upon addition of water. Thus the chemosensor 3 has been developed for chromogenic and fluorogenic investigation of water and the detection limit is 5 ppm in methanol. [ABSTRACT FROM AUTHOR]

The well-known benzene-1,2-diamine structure is considered to be a good model for the development of fluorescence-quenching chemosensors through simple and convenient syntheses. Herein, an original and simple chemosensor molecule, 2-((E)-(-2-aminophenylimino)methyl)-6-isopropyl-3-methylphenol ( 3 ), has been designed by combining a benzene-1,2-diamine and 2-hydroxy-3-isopropyl-6-methyl benzaldehyde, and its structure has been confirmed by the single crystal X-ray method. Further it has shown selectivity and sensitivity for Ni 2+ and Cu 2+ ions in a dual-channel mode (fluorescence emission and UV–Vis). The results indicate that 3 could be applied in multianalyte detection. The mechanism of C N isomerization, coupled with photoinduced energy transfer, is proposed to explain the observed spectral response. The binding constant values for Ni 2+ and Cu 2+ were calculated to be 25 000 and 30 000 M −1 respectively by the Benesi–Hildebrand method. The detection limits of Ni 2+ and Cu 2+ were 100 and 50 nM, which are below the World Health Organisation (WHO) acceptable limits for drinking water. [ABSTRACT FROM AUTHOR]

A glutathione-based tripeptide and imine linked fluorescent sensor has been processed into fluorescent organic nanoparticles (FONs) with average particle size of 69 nm. These FONs has displayed binding affinity for Cr 3+ in aqueous medium. These FONs displays excited-state intramolecular proton transfer (ESIPT) featured two emission bands and performs as highly selective and sensitive sensor for Cr 3+ through ratiometry. To the best of our knowledge, the present system represents the first example of peptide-based fluorescent organic nanoparticles for the ratiometric recognition of Cr 3+ in aqueous medium. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new fluorescent urea and thiol based chemosensor was developed and synthesized. [•] Chemosensor showed excellent selectivity for Fe3+ ions over other interfering ions. [•] Chemosensor can detect Fe3+ up to 0.1μM in semi-aqueous medium (DMSO/H2O, 8:2, v/v). [•] Experimental results have been supported by DFT calculations. [Copyright &y& Elsevier]

Abstract: Imine linked chemosensor has been synthesized and examined for cation recognition properties. The sensor shows strong affinity for Al3+ over other cations such as Na+, K+, Mg2+, Ca2+, Ba2+, Sr2+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Ag+, Hg2+, Pb2+, Zr4+, Th4+ and VO4+. The resultant Al3+ complex has been synthesized and characterized on the basis of elemental analysis, mass spectra, and IR spectra. The recognition behavior of this complex was tested towards various anions and the complex has offered an interesting opportunity for the ratiometric determination of HSO4 − in DMF/H2O (7:3, v/v) solvent system. This is the first Al3+ complex used for the ratiometric determination of HSO4 − in semi-aqueous medium. [Copyright &y& Elsevier]