Fluorometric sensing of Hg2+ ions in aqueous medium by nano-aggregates of a tripodal receptor

Quantitative Hg2+ detection via forming three coordination complexes using a lysosome targeting quinoline - Fisher aldehyde fluorophore

This work describes (Z)-N-((Z)-2-(1,3,3-trimethylindolin-2ylidene)ethylidene)quinoline-8-amine (LYSO-QF), a high-performing and biocompatible dye comprised of quinoline and Fisher aldehyde moieties linked via an imine vinyl backbone with lysosome targeting ability that can be used to quantitatively detect the mercury ion (Hg²⁺) in biosystems and the natural environment. This is achieved by forming three different tetrameric, trimeric and dimeric complexes between Hg²⁺ and LYSO-QF with the limit of detection (LOD) of 11 nm. The complexes formed were analyzed with the aid of time-dependent density functional theory (TD-DFT) calculations. The concentration dependence of the Hg²⁺ complex fluorescence emission changes from grey-green to jade green and then to red as the different types of complex are formed. The favorable sensor properties of the LYSO-QF probe are demonstrated by monitoring different Hg²⁺ concentrations in buffer solutions, HeLa cells, zebrafish model samples and several different types of water sample. Experiments with Whatman paper strips demonstrate that the cost-effective LYSO-QF also has considerable potential for use in on-site Hg²⁺ detection with the naked eye.

A fluorescent zirconium organic framework displaying rapid and nanomolar level detection of Hg(II) and nitroantibiotics

The solvothermal reaction of ZrCl4 with benzo[1,2-b:4,5-b’]dithiophene-2,6-dicarboxylic acid linker molecule in presence of trifluoro acetic acid modulator afforded the UiO-66 type of metal organic framework (MOF) (IITG-5, IITG = Indian...

Naphthalimide-gold-based nanocomposite for the ratiometric detection of okadaic acid in shellfish

Okadaic acid (OA) is one of the known marine biotoxins produced by various dinoflagellates and exists in seafood such as shellfish. The consumption of contaminated shellfish with OA leads to diarrheic shellfish poisoning (DSP), which results in the inhibition of protein phosphatase enzymes in humans. This poisoning can cause immunotoxicity and tumor promotion due to the accumulation of okadaic acid in more than the allowed limit in bivalve molluscs. The reported methods for the detection of okadaic acid include mouse bioassays, immunoassays, chromatography coupled with spectroscopic techniques, electrochemical sensors and immunosensors. We have developed a naphthalimide-gold-based nanocomposite for the detection of okadaic acid. Individually, the organic nanoparticles (ONPs) of synthesized naphthalimide-based receptors and gold-coated ONPs are less sensitive for detection. However, fabrication of the composite of Au@ONPs and ONPs enhance the sensing properties and selectivity. The composite shows a ratiometric response in the UV-Vis absorption spectrum and quenching in the fluorescence profile with a detection limit of 20 nM for OA in aqueous medium. In cyclic voltammetry, a shift was observed in the cathodic peak (-0.532 V to -0.618 V) as well as in the anodic peak (-0.815 V to -0.847 V) with the addition of okadaic acid. To study the quick binding of the composite with OA, a time response experiment was performed. Also, the developed sensor retains its sensing ability in the pH range of 5-9 and in high salt conditions. Our developed composite can be used for the detection of OA in real applications.

Design and synthesis of a novel coumarin-based framework as a potential chemomarker of a neurotoxic insecticide, azamethiphos

A coumarin based receptor has been synthesised and its organic nanoparticles were prepared. Further, these nanoparticles were explored as a chemosensor for copper(ii) ions and azamethiphos.

IL@CQD catalyzed active ester rearrangement for the detection and removal of cyanide ions

Recognition of cyanide ion with IL@CQDs catalyzed rearranged product.

Aggregation-Induced Emission-Active Hydrazide-Based Probe: Selective Sensing of Al3+, HF2 -, and Nitro Explosives

(E)-N'-((2-Hydroxynaphthalen-1-yl)methylene)picolinohydrazide (H-PNAP) shows aggregation-induced emission (AIE) strictly in a 90% water/MeOH (v/v) mixture at 540 nm, and the solid-state emission is blue-shifted to 509 nm upon excitation at 400 nm. The AIE activity of H-PNAP is selectively quenched by 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenol (DNP) out of different nitroaromatic compounds with a limit of detection (LOD) of 7.79 × 10^-7 and 9.08 × 10^-7 M, respectively. The probe is nonemissive in aqueous medium (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, HEPES buffer, pH 7.2); however, it shows a strong emission to Al³⁺ (λ_em, 490 nm) in the presence of 17 other biological metal ions, and the LOD is 2.09 nM which is far below the WHO recommended value (7.41 mM). The emission of the [Al(PNAP)(NO₃)₂] complex is quenched by HF₂ ^- (F^- and PO₄ ^3- are weak quencher), and the LOD is as low as 15 nM. The probable mechanism of the sensing feature of the probe has been authenticated by ¹H nuclear magnetic resonance titration, mass spectrometry, Fourier transform infrared spectroscopy, Benesi-Hildebrand plot, and Job's plot in each case. The probe has some practical applications such as recovery of Al³⁺ from the drinking water sample, construction of the INHIBIT logic gate, and detection kits for Al³⁺ and TNP/DNP by simple paper test strips. The probe, H-PNAP, has successfully been applied to the detection of intracellular Al³⁺ and HF₂ ^- ions in the human breast cancer cell, MDA-MB-468.

Fluorescent organic nanoparticles (FONs) as convenient probes for metal ion detection in aqueous medium

Fluorescent organic nanoparticle (FON)-based chemosensors are emerging as a valuable tool for the fast and accurate detection of metal ions in aqueous media. In this review, we highlight the recent developments in this field.

Graphene-Rhodamine Nanoprobe for Colorimetric and Fluorimetric Hg(2+) Ion Assay

This article reveals the first ever prospective application of Graphene-Rhodamine array (GRH) as a colorimetric and fluorimetric sensor for Hg(2+) ions. The duality of Graphene to undergo π-π and dispersive interactions with Rhodamine as well as to act as a selective adsorbent for Hg(2+) is conceptualized in this study. These interactions lead to decrease in absorbance of the dye in the presence of graphene, which is restored when kept in contact with Hg(2+) ions. The feasibility of the mechanism has been proved using EDTA as the coordinating ligand. It is noteworthy that all the optical variations occurred in the visible scale of the electromagnetic spectrum. The GRH array exhibited higher sensitivity toward the target ion with a limit of detection of 2 ppb. A perfect linear variation of absorbance at 554 nm with Hg(2+) concentration was observed in 0-1000 nM range, enabling the use of the system as a quantitative sensor for the test ion. The commendable selectivity of the array toward Hg(2+) ion has been investigated by observing the optical response in the presence of other environmentally relevant metal ions. A reversible turn off and turn on INHIBIT logic gate has been proposed which extends the scope of the designed array for the development of automated chemical systems. The fluorescence resonance energy transfer (FRET) ability of graphene paves the backbone for the fluorimetric detection. Fluorimetric strategy yielded a much lower limit of detection of 380 ppt using this probe, which makes a significant advance in trace detection of Hg(2+) ions.

Fluorescent Chemosensors for Selective and Sensitive Detection of Phosmet/Chlorpyrifos with Octahedral Ni(2+) Complexes

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 Ni(2+), and it motivated us to prepare the Ni(2+) complexes. The ligand H2L1 underwent deprotonation and formed binuclear complex when interacted with Ni(2+) 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 Ni(2+) ion. This signifies the importance of steric parameters instead of electronic factors in these particular cases. Impressed by differential behavior of complexes of H2L1 and H2L2/H2L3 with Ni(2+) 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 Ni(2+) complexes with hydrophobic nature were suspended into aqueous medium for testing them as sensor for organophosphate. The (L1)2.(Ni(2+))2 could sense phosmet with detection limit of 44 nM, whereas L2.Ni(2+) and L3.Ni(2+) exhibited the detection limits of 62 and 71 nM, respectively, for chlorpyrifos.

Identifying the preferred interaction mode of naringin with gold nanoparticles through experimental, DFT and TDDFT techniques: insights into their sensing and biological applications

In this work, the binding behaviour of naringin – a flavonoid with AuNPs is explained by combining experimental and theoretical approaches.

Structural, optical and photoconductivity characteristics of pristine FeO·Fe2O3 and NTPI–FeO·Fe2O3 nanocomposite: aggregation induced emission enhancement of fluorescent organic nanoprobe of thiophene appended phenanthrimidazole derivative

In this manuscript we report the successful synthesis of pristine FeO·Fe₂O₃, 1-(naphthalen-1-yl)-2-(thiophen-2-yl)-1H-phenanthro[9,10-d]imidazole (NTPI), fluorescent organic nanoparticles (FONs) of NTPI and NTPI–FeO·Fe₂O₃ nanocomposite.

Optical probes for the detection of protons, and alkali and alkaline earth metal cations

Luminescent sensors and switches continue to play a key role in shaping our understanding of key biochemical processes, assist in the diagnosis of disease and contribute to the design of new drugs and therapies. Similarly, their contribution to the environment cannot be understated as they offer a portable means to undertake field testing for hazardous chemicals and pollutants such as heavy metals. From a physiological perspective, the Group I and II metal ions are among the most important in the periodic table with blood plasma levels of H(+), Na(+) and Ca(2+) being indicators of several possible disease states. In this review, we examine the progress that has been made in the development of luminescent probes for Group I and Group II ions as well as protons. The potential applications of these probes and the mechanism involved in controlling their luminescent response upon analyte binding will also be discussed.

A turn-on fluorogenic Zn(ii) chemoprobe based on a terpyridine derivative with aggregation-induced emission (AIE) effects through nanofiber aggregation into spherical aggregates

The self-assembly of the terpyridine-based ligand exhibited strong emission in the presence of Zn²⁺ due to the formation of coordination bonds between the terpyridine moieties and the Zn²⁺ by the aggregation-induced emission effect.

High selective fluorescence imaging of cesium distribution in Arabidopsis using a bis(trihydroxyphenyl)-appended fluorescent probe with a turn-on system

The bis(trihydroxyphenyl)-appended ligand 1 was found to display dramatically enhanced fluorescence upon the addition of Cs⁺, but not with any other metal ions.

Fluorescent organic nanoparticles of dihydropyrimidone derivatives for selective recognition of iodide using a displacement assay: application of the sensors in water and biological fluids

Fluorescent organic nanoparticles (FON's) derived from dihydropyrimidone derivatives (1–4) were developed and evaluated for their sensor properties.

Triazole-appended BODIPY–piperazine conjugates and their efficacy toward mercury sensing

A selective chromo- and fluorogenic sensor for Hg²⁺ based on triazole-appended BODIPY–piperazine conjugates has been presented.