Ni(II), Cu(II), and Zn(II) Cryptate-Enhanced Fluorescence of a Trianthrylcryptand: A Potential Molecular Photonic OR Operator

Mango Leaves (Mangifera indica)-Derived Highly Florescent Green Graphene Quantum Dot Nanoprobes for Enhanced On-Off Dual Detection of Cholesterol and Fe2+ Ions Based on Molecular Logic Operation

In the present study, we have engineered a molecular logic gate system employing both Fe2+ ions and cholesterol as bioanalytes for innovative detection strategies. We utilized a green-synthesis method employing the mango leaves extract to create fluorescent graphene quantum dots termed "mGQDs". Through techniques like HR-TEM, i.e., high-resolution transmission electron microscopy, Raman spectroscopy, and XPS, i.e., X-ray photoelectron spectroscopy, the successful formation of mGQDs was confirmed. The photoluminescence (PL) characteristics of mGQDs were investigated for potential applications in metal ion detection, specifically Fe2+ traces in water, by using fluorescence techniques. Under 425 nm excitation, mGQDs exhibited emission bands at 495 and 677 nm in their PL spectrum. Fe2+-induced notable quenching of mGQDs' PL intensity decreased by 97% with 2.5 μM Fe2+ ions; however, adding 20 mM cholesterol resulted in a 92% recovery. Detection limits were established through a linear Stern-Volmer (S-V) plot at room temperature, yielding values of 4.07 μM for Fe2+ ions and 1.8 mM for cholesterol. Moreover, mGQDs demonstrated biocompatibility, aqueous solubility, and nontoxicity, facilitating the creation of a rapid nonenzymatic cholesterol detection method. Selectivity and detection studies underscored mGQDs' reliability in cholesterol level monitoring. Additionally, a molecular logic gate system employing Fe2+ metal ions and cholesterol as a bioanalyte was established for detection purposes. Overall, this research introduces an ecofriendly approach to craft mGQDs and highlights their effectiveness in detecting metal ions and cholesterol, suggesting their potential as versatile nanomaterials for diverse analytical and biomedical applications.

Pyrene-Hydrazone-π···Hole Coupled Turn-on Fluorescent and Naked- Eye Colorimetric Sensor for Cyanide: Role of Homogeneous π-Hole Dispersion in Anion Selectivity

A pyrene based probe associated with π···hole - hydrazone as one of the recognizing elements is synthesized and its turn in to a selective colorimetric and turn-on fluorescent sensor, (L³) for cyanide anion. This chemo sensor show high selectivity towards cyanide anion through photo electron transfer (PET) mechanism. The binding strength and sensitivity of the chemo sensor L³ towards cyanide are found to be 2.0 X 10⁴, and 4.44 x 10^-4 respectively. We have compared this high selectivity of the receptor towards cyanide, with our previously reported receptors L¹ and L². The detailed UV-Vis, Emission, ¹H-NMR, IR spectroscopic and Molecular Electrostatic Potential (MEP) studies reveals that the homogeneous π···hole dispersion in the aromatic ring governing the selectivity of the receptor towards cyanide anion. Such a positive π···hole homogeneous dispersion is missing in the case of sensor L², instead we have polarized π···hole dispersion towards 2^nd and 4^th position of di-nitrophenyl chromophoric unit in L².

Naphthalenediimides with High Fluorescence Quantum Yield: Bright-Red, Stable, and Responsive Fluorescent Dyes

The naphthalenediimide (NDI) scaffold in contrast to its higher congeners possess low-fluorescence. In spite of elegant synthetic developments, a highly emissive NDI is quite rare to find, as well as, a green-light-emitting NDI is yet to be explored. Herein, we report a novel class of symmetric and asymmetric NH₂ -substituted core-NDIs (1-5) with tunable fluorescence in the visible region and extending to the NIR frontier. Importantly, the bis-NH₂ -substituted NDI 2 revealed quantum yield, Φ f of ≈81 and ≈68 % in toluene and DMSO, respectively, suggesting versatility of the fluorophore in a wide range of solvent polarity. The dye 1 is shown to be the first NDI-based green-light emitter. The donor piperidine group in 5 diminish the Φ f by 40-fold providing a lever to modulate the excited-state intramolecular proton transfer (ESIPT) process. Our synthetic protocol applies a Pd catalyst and a benign hydride source simplifying the non-trivial -NH₂ group integration at the NDI-core. TD-DFT calculations predicted strong intramolecular hydrogen bonds in the excited state in the bulk nonpolar medium and responsiveness to solvent polarity. The maximization of the NDI emission outlined here would further boost the burgeoning repertoire of applications of the NDI scaffold.

Discovery of a novel camphor-based fluorescent probe for Co2+ in fresh vegetables with high selectivity and sensitivity

Cobalt is an essential micronutrient for human beings. The excessive intake of cobalt may lead to heart-related diseases. In this work, a novel fluorescent probe 1,1'-(((6,11,11-trimethyl-6,7,8,9-tetrahydro-6,9-methanopyridazino[4,5-b]quinoxaline-1,4-diyl)bis(azanylylidene))bis(methanylylidene))bis(naphthalen-2-ol) (PDS) was synthesized from camphor. The probe PDS could be utilized to selectively recognize Co²⁺ over other metal ions. There is a good linear relationship between fluorescence intensity of PDS and Co²⁺ concentration within 0-20 μM, and its detection limt was found to be 0.925 μM, which is far lower than the national standard for cobalt in drinking water in China. The possible coordination mechanism of PDS with Co²⁺ was determined by nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS) and density functional theory (DFT). The probe PDS was also successfully applied in detection of Co²⁺ in tap water and fresh vegetables.

Insight into the formation of H-bonds propagating the monomeric zinc complexes of a tridentate reduced Schiff base to form an infinite chain

The formation of an infinite 1D assembly is governed by the H-bonding interactions in the solid state structure of the two zinc complexes. It has been analyzed energetically using DFT calculations and several computational tools.

Fluorophoric [2]rotaxanes: post-synthetic functionalization, conformational fluxionality and metal ion chelation

Fluorophoric [2]rotaxanes form an exciplex upon interpenetration and the exciplex signals are used to monitor the chelation properties of the interlocked systems.

A Cu(II) Indicator Platform Based on Cu(II) Induced Swelling that Changes the Extent of Fluorescein Self-Quenching

In this study, we established a new fluorescent indicator platform. The responsive element consists of poly(N-isopropylacrylamide) nanospheres that include small percentages of fluorescein and a ligand, anilinodiacetate (phenylIDA). Nanosphere diameters were determined to be in the range from 50 to 90 nm by scanning electron microscopy. They were entrapped in a polyacrylamide gel to prevent nanosphere aggregation. At pH 6, the ligand is negatively charged in the absence of metal ions. Charge-charge repulsion causes the nanosphere to swell. Dynamic light scattering measurements show that these nanospheres do not shrink and aggregate at high temperature. Cu(II) binding neutralizes the charge causing the particles to shrink. This brings fluoresceins closer together, increasing the degree of self-quenching. The intensity decreases by 30% as Cu(II) concentration increases. To rule out the possibility that the observed decrease in intensity was due to Cu(II) quenching of fluorescence, we also added Zn(II) and observed a decrease in intensity. This approach can be adapted to sense different metal ions and different concentrations of Cu(II) by changing the ligand.

A turn-on fluorescent probe with a dansyl fluorophore for hydrogen sulfide sensing

Hydrogen sulfide (H₂S) is a biologically relevant molecule that has been newly identified as a gasotransmitter and is also a toxic gaseous pollutant. In this study, we report on a metal complex fluorescent probe to achieve the sensitive detection of H₂S in a fluorescent “turn-on” mode. The probe bears a dansyl fluorophore with multidentate ligands for coordination with copper ions. The fluorescent “turn-on” mode is facilitated by the strong bonding between H₂S and the Cu(ii) ions to form insoluble copper sulfide, which leads to the release of a strongly fluorescent product. The H₂S limit of detection (LOD) for the proposed probe is estimated to be 11 nM in the aqueous solution, and the utilization of the probe is demonstrated for detecting H₂S in actual lake and mineral water samples with good reproducibility. Furthermore, we designed detector vials and presented their successful application for the visual detection of gaseous H₂S.

H₂S turn on the fluorescence of DNS–Cu complex probe.

Novel chemical sensor for detection Ca(II) ions based on ferutinin

A new optical chemical sensor based on medicinal compound, jaeschkeanadiol p-hydroxyben-zoate (Ferutinin), has been designed and utilized for Ca(II) ions detections. This natural optical sensor exhibits immense selectivity including fluorescence and absorption ratiometric for Ca(II) ions within precious physiological pH range. Further, the chelation process of the Ca(II) ions with the medicinal optical sensor ferutinin yields a 1:1 (metal: ligand) complex which is accompanied by fluorescence enhancement of the main emission band centered at 355 nm of the medicinal probe. The fluorescence "turn-on" effect is a clear evidence for the chelation process between ferutinin medicinal probe and Ca(II) ions and this could be simply detected. The new sensor was proposed depending on significant fluorescence mechanism, (MLCT, metal-ligand charge transfer). However, the interaction of the medicinal optical sensor with Ca(II) in presence of other cations was examined without any significant interference. Also, the new developed optical sensor consecutively exhibits low limit of detection (LOD) 1.5 nM for Ca(II) which is detected in very significant physiological pH range (pH = 7.4). Also, the probe provides high binding affinity towards Ca(II) with large binding constant K_b 5.97 × 10⁴ M^-1. As a result, this optical sensor may apply for detection Ca(II) in cell or biological samples.

Achieving selectivity for copper over zinc with luminescent terbium probes bearing phenanthridine antennas

A family of terbium probes was synthesized and evaluated for the luminescence detection of copper and zinc in water at neutral pH. Each probe incorporates a terbium ion chelated by a macrocyclic polyaminocarboxylate and conjugated to either one, two, or three phenanthridine antennas via a diamine linker. All three probes, Tb-1Phen, Tb-2Phen, and Tb-3Phen, exhibit similar responses toward copper and zinc. In each case, the terbium-centered time-gated phosphorescence decreases upon binding either Cu^I or Cu^II but not upon addition of Zn^II. The phosphorescence of Tb-2Phen is also not significantly affected by other metal ions including Mg^II, Ca^II, Mn^II, Fe^II, Ni^II, Cd^II, and Hg^II. Tb-1Phen, on the other hand, responds weakly to Mn^II, Fe^II and Ni^II. The lack of affinity of each probe for Zn^II was further confirmed by competition experiments with Cu^I and Cu^II. Notably, whereas the terbium-centered emission of each probe is quenched upon copper coordination, the phenanthridine-centered luminescence emission is not. As such, each probe functions as a ratiometric probe for the selective detection of copper over zinc. Theoretical calculations further demonstrate that the turn off response of the probe is due to an increase in the distance separating the lanthanide ion from its phenanthridine antennas upon coordination of copper, which in turn decreases the efficiency of terbium sensitization by the phenanthridines.

Highly efficient and selective visible-light driven CO2-to-CO conversion by a Co-based cryptate in H2O/CH3CN solution

A Co-based cryptate exhibits highly efficient and selective photocatalytic CO₂-to-CO conversion under either pure CO₂ or 10% CO₂ in a water-containing system.

Group 12 metal complexes of (2-piperazine-1-yl-ethyl)-pyridin-2-yl-methylene-amine: rare participation of terminal piperazine N in coordination leads to structural diversity

Changing from 3d¹⁰–4d¹⁰–5d¹⁰ in presence of a Schiff-base ligand we obtained complexes having different nuclearities with participation of piperazine nitrogen. DFT analysis confirms coordination environment around metal centre.

Thioacetamide-derived nitrogen and sulfur co-doped carbon nanoparticles used for label-free detection of copper(ii) ions and bioimaging applications

Thioacetamide-derived nitrogen and sulfur co-doped carbon nanoparticles as photoluminescent probes for the efficient detection of Cu²⁺ ions.

Metal ion binding by laterally non-symmetric macrobicyclic oxa–aza cryptands

Laterally non-symmetric oxa–aza cryptands are versatile supramolecular synthons.

A rhodamine embedded bio-compatible smart molecule mimicking a combinatorial logic circuit and ‘key-pad lock’ memory device for defending against information risk

A rhodamine-based chemosensor LC with a colorimetric response towards Al³⁺ and Cu²⁺ and only a fluorescence response to Al³⁺ enables us to fabricate a ‘key-pad-logic’ function.

A ratiometric and selective fluorescent chemosensor for Ca(ii) ions based on a novel water-soluble ionic Schiff-base

A new, simple and water-soluble chemosensor, based on the ionic Schiff-base (ISB), 1-(4-hydroxy-3-((2-mercaptophenylimino)methyl)-5-methoxybenzyl)-4-methoxypyridiniumchloride (3), was synthesized and applied to fluorescently sense Ca(ii) ions.

A colorimetric and fluorometric investigation of Cu(ii) ion in aqueous medium with a fluorescein-based chemosensor

A colorimetric and fluorometric chemosensor, 1,4-bis(1-fluorescein)-2,3-diaza-1,3-butadiene (L, 3) as Schiff base is developed for naked-eye detection of Cu²⁺ ion in aqueous medium due to the formation of a 1 : 1 copper–ligand complex.

A dithienosilole-based fluorescent chemosensor for multiple logic operations at the molecular level

A chemosensor consisting of two terpyridines covalently linked to a dithienosilole unit (1) has been synthesized, and its optical and metal sensing properties have been investigated. Due to the metal-organic coordination function, 1 can bind with many transition metal ions and display different fluorescence responses that cause it to function as a "turn-off" fluorescent chemosensor. A significant bathochromic shift in the fluorescence spectra is observed in the presence of Zn(2+). Meanwhile, the emission of 1 is weakened upon exposure to Ag(+) and Fe(2+) and completely quenched by Ni(2+), Co(2+), and Cu(2+). Based on the observed results, several logic gates, such as XNOR, INHIBIT, and IMPLICATION, have been achieved by controlling the chemical inputs.

Preparation of polyaniline grafted graphene oxide–WO3 nanocomposite and its application as a chromium(iii) chemi-sensor

Polyaniline-grafted-GO@WO₃ was prepared and deposited on a Ag electrode with conducting binders to give a sensor with a fast selective response for Cr³⁺ in the liquid phase. The sensitivity and detection limit are ∼4.4251 mA mM⁻¹ cm⁻² and 0.031 ± 0.010 nM.

A series of Zn(ii) terpyridine complexes with enhanced two-photon-excited fluorescence for in vitro and in vivo bioimaging

TPA cross sections are enhanced for the complexes containing D–A type ligandL1.1exhibits specificity in two-photon fluorescence imaging.

Direct evidence of a blocking heavy atom effect on the water-assisted fluorescence enhancement detection of Hg2+ based on a ratiometric chemosensor

The heavy atom effect of Hg²⁺ could be inhibited by water and other solvent molecules based on results using the chemosensor L.