A dual-functional rhodamine B and azo-salicylaldehyde derivative for the simultaneous detection of copper and hypochlorite: synthesis, biological applications and theoretical insights.

A multifunctional rhodamine derivative containing azo-salicylaldehyde (BBS) was designed and synthesized as a colorimetric and fluorescence turn-on probe for the selective detection of copper cations (Cu) and hypochlorite anions (OCl) in aqueous media. In the presence of Cu, the probe BBS exhibited turn-on absorption and fluorescence change at 554 nm and 585 nm, respectively. The binding mechanism of BBS with Cu induces the opening of a spirolactam ring in the rhodamine moiety by the formation of a metal-ligand complex, achieving 10-fold enhancement in fluorescence and quantum yield, along with a binding constant of 1 × 10 M and a detection limit of 2.

A rapid investigation of near-infrared (NIR) fluorescent switch-on probes for detection and in cellulo tracking of G-quadruplex and double-stranded DNA.

This review provides a comprehensive overview of the recent advancements in Near Infrared (NIR) fluorescence switch-on probes designed for the detection and in cellulo tracking of G-quadruplex and double-stranded DNA (dsDNA). G-quadruplexes, non-canonical DNA structures, play pivotal roles in regulating various biological processes, making them critical targets for therapeutic and diagnostic applications. The unique properties of NIR fluorescence probes, such as deep tissue penetration, minimal photodamage, and low autofluorescence background, offer significant advantages for bioimaging.

A versatile sensor capable of ratiometric fluorescence detection of trace water and turn-on detection of Cu modulating the binding interaction of a Cu(II) complex with BSA and DNA complemented by docking studies.

A fluorescent molecule, pyridine-coupled bis-anthracene (PBA), has been developed for the selective fluorescence turn-on detection of Cu. Interestingly, the ligand PBA also exhibited a red-shifted ratiometric fluorescence response in the presence of water. Thus, a ratiometric water sensor has been utilized as a selective fluorescence turn-on sensor for Cu, achieving a 10-fold enhancement in the fluorescence and quantum yield at 446 nm, with a lower detection limit of 0.

A Prompt Study on Recent Advances in the Development Of Colorimetric and Fluorescent Chemosensors for "Nanomolar Detection" of Biologically Important Analytes.

Fluorescent and colorimetric chemosensors for selective detection of various biologically important analytes have been widely applied in different areas such as biology, physiology, pharmacology, and environmental sciences. The research area based on fluorescent chemosensors has been in existence for about 150 years with the development of large number of fluorescent chemosensors for selective detection of cations as metal ions, anions, reactive species, neutral molecules and different gases etc. Despite the progress made in this field, several problems and challenges still exist.

Comparative analysis of Zn(II)-complexes as model metalloenzymes for mimicking Jack bean urease.

The inhibitory action of Schiff base complexes of 3d metals against the urease enzyme is well explored in the scientific community. However, the ability of such complexes in mimicking active metallobiosites of urease enzymes, possessing ureolytic behavior, still remains unexplored. With this aim firstly, two Zn(II)-complexes (PPR-HMB-Zn and PZ-HMB-Zn) have been developed from two different Schiff base ligands (HL1 = 2-(()-(2-(piperidin-1-yl)ethylimino)methyl)-5-methylphenol and HL2 = 2-(()-(2-(piperizin-1-yl)ethylimino)methyl)-5-methylphenol) and structurally characterized using single crystal XRD.

Viscosity-sensitive and AIE-active bimodal fluorescent probe for the selective detection of OCl and Cu: a dual sensing approach DFT and biological studies using green gram seeds.

A novel dual-mode viscosity-sensitive and AIE-active fluorescent chemosensor based on the naphthalene coupled pyrene (NCP) moiety was designed and synthesized for the selective detection of OCl and Cu. In non-viscous media, NCP exhibited weak fluorescence; however, with an increase in viscosity using various proportions of glycerol, the fluorescence intensity was enhanced to 461 nm with a 6-fold increase in fluorescence quantum yields, which could be utilized for the quantitative determination of viscosity. Interestingly, NCP exhibited novel AIE characteristics in terms of size and growth in HO-CHCN mixtures with high water contents and different volume percentage of water, which was investigated using fluorescence, DLS study and SEM analysis.

A fast survey on recent developments in designing colorimetric and fluorescent sensors for the selective detection of essential amino acids.

Owing to the biological significance of various amino acids, developing accurate and cost-effective sensing techniques for the selective detection of amino acids has recently attracted growing interest. This review discusses the recent advancements of chemosensors in the selective detection of only essential amino acids out of a total of twenty amino acids, which have been applied in chemosensing research, and the mechanism of their action. The focus is directed towards the detection of the most important essential amino acids, like leucine, threonine, lysine, histidine, tryptophan and methionine, since isoleucine and valine are yet to be explored in regard to chemosensing.

Dual-mode chemosensor for the fluorescence detection of zinc and hypochlorite on a fluorescein backbone and its cell-imaging applications.

Fluorescein coupled with 3-(aminomethyl)-4,6-dimethylpyridin-2(1)-one (FAD) was synthesized for the selective recognition of Zn over other interfering metal ions in acetonitrile/aqueous buffer (1 : 1). Interestingly, there was a significant fluorescence enhancement of FAD in association with Zn at 426 nm by strong chelation-induced fluorescence enhancement (CHEF) without interrupting the cyclic spirolactam ring. A binding stoichiometric ratio of 1 : 2 for the ligand FAD with metal Zn was proven by a Jobs plot.

Colorimetric and Fluorimetric DNA Detection with a Hydroxystyryl-Quinolizinium Photoacid and Its Application for Cell Imaging.

The combination of styryl dye properties with the acidity and strong photoacidity of the 2,2'-[(1''-hydroxy-4''-methyl-(E)-2'',6''-phenylene)]-bisquinolizinium enables the detection of DNA by distinct absorption and emission color changes and the fluorimetric detection of DNA in cells with epifluorescence and confocal fluorescence microscopy.

Diphenylaminostyryl-substituted quinolizinium derivatives as fluorescent light-up probes for duplex and quadruplex DNA.

(E)-2-[1'-((Diphenylamino)styryl)quinolizinium (3a) and 2,2'-{(phenylimino)-bis[(E)-1'',1'''-styryl]}-bis[quinolizinium] (3b) were synthesized, and their interactions with duplex DNA and quadruplex DNA were investigated with a particular focus on their ability to operate as DNA-sensitive fluorescent probes. Due to the significantly different size and steric demand of these quinolizinium derivatives they exhibit different binding modes. Thus, 3a intercalates into duplex DNA and binds through π stacking to quadruplex DNA, whereas 3b favours groove binding to both DNA forms.

A concentration dependent auto-relay-recognition by the same analyte: a dual fluorescence switch-on by hydrogen sulfide via Michael addition followed by reduction and staining for bio-activity.

H2S is shown, for the first time, to play an extraordinary dual role due to its nucleophilicity and reducing property with our single chemosensor, PND [4-(piperidin-1-yl) naphthalene-1,2-dione]. The initial nucleophilic attack via Michael addition (a lower concentration of H2S, blue fluorescence) is followed by the reduction of the 1,2-diketo functionality (a higher concentration of H2S, green fluorescence). This chemosensor, which also shows biological response, is remarkably effective in sensing the same analyte (H2S) at its different concentrations in a relay pathway via a fluorescence "off-on-on" mechanism, and this is also supported by DFT calculation and Cyclic voltammograms.

Rapid detection of hydrazine in a naphthol-fused chromenyl loop and its effectiveness in human lung cancer cells: tuning remarkable selectivity via the reaction altered pathway supported by theoretical studies.

Our designed and synthesized chemosensor naphthalene based chromenyl derivative (NAC) [1-(3-hydroxy-3 methyl-3H-benzo[f]chromen-2-yl) ethanone] has been used for fast (<30 s, DL = 0.22 ppb) and selective detection of N2H4 by a new way via the chromenyl ring opening followed by the pyrazole ring formation giving a strong blue fluorescence. The DFT study and the real application in different water samples along with the dipstick method in low cost devices have also been performed here.

Pyrophosphate selective fluorescent chemosensors: cascade recognition of nuclear stain mimicking DAPI.

A new zinc(ii) complex with a condensed hydroxynaphthyl pyridine (SPHN) as the coordinated ligand has been synthesized for the selective recognition of pyrophosphate (PPi) over other anions including phosphate in a mixed aqueous solution. The fluorescence enhancement of SPHN in association with Zn(2+) ions is quenched in the presence of intracellular pyrophosphate. This phenomenon is utilized in the construction of a logic gate.

Nanomolar detection of hypochlorite by a rhodamine-based chiral hydrazide in absolute aqueous media: application in tap water analysis with live-cell imaging.

By employing the oxidation property of hypochlorite (OCl(-)), a novel rhodamine-based hydrazide of the chiral acid ((S)-(-)-2-pyrrolidone-5-carboxylic acid) (RHHP) was designed and synthesized for detection of OCl(-) absolutely in aqueous medium at nanomolar level. The structure of the chiral sensor was also proved by the X-ray crystallography. The bioactivity and the application of the probe for detection of OCl(-) in natural water system have been demonstrated.

A red fluorescence 'off-on' molecular switch for selective detection of Al3+, Fe3+ and Cr3+: experimental and theoretical studies along with living cell imaging.

A spirobenzopyran-quinoline (SBPQ) based sensor was synthesized which selectively detects trivalent ions viz. Al(3+), Fe(3+) and Cr(3+) through a fluorescence turn on signal in the red region (~675 nm) with the detection limit in the order of 10(-8) M. The potentiality of the probe was confirmed by employing it for fluorescence bio-imaging with Al(3+) in three different types of live-cells.

'PET' vs. 'push-pull' induced ICT: a remarkable coumarinyl-appended pyrimidine based naked eye colorimetric and fluorimetric sensor for the detection of Hg2+ ions in aqueous media with test trips.

A novel colorimetric and fluorescent chemosensor based on 7-(diethylamino)-3-(pyrimidin-4-yl)-2H-chromen-2-one (PYC) has been designed and synthesized for the detection of Hg(2+) in the presence of other competing metals in mixed aqueous media. The PYC exhibits naked eye color change from green to red, and the fluorescence color changes from yellowish green to light orange with Hg(2+). It also shows a red shift in wavelength of about 80 nm in absorption spectra.

Visual and near IR (NIR) fluorescence detection of Cr3+ in aqueous media via spirobenzopyran ring opening with application in logic gate and bio-imaging.

A new spirobenzopyran derivative (SPNH) was designed and synthesized which was applied in simultaneous colorimetric and NIR fluorescence detections for Cr(3+). This spirobenzopyran receptor is normally colorless in aqueous organic media but the formation of merocyanine occurs by Cr(3+) showing a yellow color. Here the formation of yellow color in UV-vis spectra and strong NIR fluorescence emission at 675 nm makes SPNH a good sensor for Cr(3+) ion.

Selective detection and bio-imaging of Pd2+ with novel 'C-CN' bond cleavage of cyano-rhodamine, cyanation with diaminomaleonitrile.

A new rhodamine based chemosensor, cyano-rhodamine, has been designed and synthesized with a green approach which shows a specific 'C-CN' bond breaking with the action of the Pd(2+) ion to produce the specific color and fluorescence of rhodamine 6G itself in solution and in HeLa cells.

Ratiometric and absolute water-soluble fluorescent tripodal zinc sensor and its application in killing human lung cancer cells.

A new "naked-eye" and ratiometric fluorescent zinc sensor (TAQ) of carboxamidoquinoline with 2-chloro-N-(quinol-8-yl)-acetamide as a receptor was designed and synthesized. The sensor shows good water solubility and high selectivity for sensing; about a 15-fold increase in fluorescence quantum yield and a 100 nm red-shift of fluorescence emission upon binding Zn²⁺ in aqueous HEPES buffer solution are observed. The human lung cancer cell line (A549) activity is also demonstrated.

Dual channel selective fluorescence detection of Al(III) and PPi in aqueous media with an 'off-on-off' switch which mimics molecular logic gates (INHIBIT and EXOR gates).

In this study, we have synthesized a simple Schiff base type isophthaloyl salicylaldehyde hydrazone (ISH) moiety which selectively detects Al(III) and PPi with a fluorescence enhancement at two different wavelengths in aqueous solution. The sensing phenomenon is also reversible and thus the sensor beautifully mimics logic gates (INHIBIT and EXOR gates).

Resonance-assisted hydrogen bonding induced nucleophilic addition to hamper ESIPT: ratiometric detection of cyanide in aqueous media.

For ratiometric "naked eye" detection of CN(-), an ESIPT exhibiting benzothiazole receptor (BHI) is designed having one aldehyde group ortho and the other aldehyde para to the OH group respectively. Due to RAHBs, the ortho aldehyde group is highly reactive undergoing nucleophilic cyanide addition selectively, which hampered ESIPT. This is also supported by DFT and TD-DFT calculations.

A highly selective and sensitive probe for colorimetric and fluorogenic detection of Cd2+ in aqueous media.

A new rhodamine-quinoline based dyad has been synthesized. It shows a highly selective response to Cd(2+) in the presence of other competing metal ions in aqueous media (pH = 7.1).