Interaction between 1-[p-(dimethylamino) benzoyl]-4′-phenyl-semicarbazide and Cu

A new compound, 1-[p-(dimethylamino)benzoyl]-4′-phenyl-semicarbazide (1) was synthesized and showed highly selective response to Cu²⁺ over other metal ions such as Pb²⁺, Mg²⁺, Fe²⁺, Co²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Ni²⁺, Ca²⁺, Ag⁺, Na⁺, K⁺, and Li⁺. The control compound, 1-[p-(dimethylamino)benzoyl]-4-phenyl-thiosemicarbazide (2), showed different fluorescence spectral response to Cu²⁺. A 1:1 complex between Cu²⁺ and 1 was formed while 1:1 and 1:2 complexes between Cu²⁺ and 2 were formed. The binding model between the receptor (1 or 2) and Cu²⁺ was supported by IR spectra, mass spectra, and computation model. 1 possessed higher selectivity towards Cu²⁺ compared with 2 owing to the difference of complexation ability between urea and thiourea groups.     

A new PET fluorescent sensor for Zn

A new Zn²⁺ fluorescent sensor NIDPA, with 1,8-naphthalimide as reporting group and di-2-picolylamine (DPA) as recognizing group, has been synthesized via simple steps. Based on photo-induced electron transfer (PET) mechanism, NIDPA has a five-fold fluorescent enhancement and 10 nm absorption blue-shift under simulated physiological conditions corresponding to the binding of Zn²⁺. Apparent dissociation constant for Zn²⁺ (K_d) is 0.83 nM, and Ca²⁺, Mg²⁺, Fe²⁺, Ni²⁺ and Cr³⁺have little influence on fluorescent enhancement. These results suggest that NIDPA can be used to quantitatively and selectively measure the concentration of Zn²⁺ around sub-nanomolar range.     

An asymmetric imidazole derivative as potential fluorescent chemosensor for Fe in aqueous solution

A novel conjugated molecule, L, based on 2,4,5-triphenylimidazole and 6-phenyl-2,2′-bipyridine (HC^∧N^∧N) was synthesized in two steps. The molecule can recognize Fe³⁺ in aqueous solution (THF/H₂O, 1/1, v/v) by the appearance of new emission bands at 416 and 442 nm, which can be attributed to the emission of the newly formed L-Fe³⁺ complex. The binding constant of the complex was calculated to be (6.6±0.39)×10³ M⁻¹, and its formation was also confirmed by the appearance of isosbestic points at 312 and 381 nm in the UV-visible spectral titration experiment. While other transition and rare-earth metal ions, such as Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, Eu³⁺ and Nd³⁺, can only cause some decrease of L's fluorescence, alkali and alkaline earth metal ions, such as Li⁺, Na⁺, K⁺, Mg²⁺ and Ca²⁺, almost have no effect on L's fluorescence. The fluorescence of L can be recovered by the addition of EDTA to the L-Fe³⁺ system just due to EDTA's stronger chelating ability than that of L.     

A New Highly Sensitive and Selective Fluorescent Cadmium Sensor

Condensation product (L) of salicylaldehyde and semicarbazide behaves as a fluorescent sensor for Cd²⁺ ion, in 1:1 DMSO:H₂O, over Mn²⁺, Fe²⁺, Ni²⁺, Co²⁺, Cu²⁺, Pb²⁺ and Hg²⁺ ions. The emission peak of L at λ_max = 520 nm, on excitation with 420 nm wavelength photons, showed an enhancement in intensity of ca 60-fold when interacted with Cd²⁺ ion. The intensity was however found to remain unaltered when interacted with metal ions—Mn²⁺, Fe²⁺, Ni²⁺, Co²⁺, Cu²⁺, Pb²⁺ and Hg²⁺. The intensity increases by approximately 20 fold on interaction with Zn²⁺ ion. The increase in the fluorescent peak can be explained on the basis of photo induced electron transfer (PET) mechanism. A 1:1 complexation between Cd²⁺ and L with log β = 4.25 has been proved.     

A New Piperidine Derivatized-Schiff Base Based “Turn-on” Cu<Superscript>2+</Superscript>Chemo-Sensor

In this study, we report the synthesis of new Schiff base E-1-(((1-benzylpiperidin-4-yl)imino)methyl)naphthalenee-2-ol (L) and evaluation of its fluorescence response toward Cu²⁺ ion. Preliminary, solvent effect, metal selectivity and metal ligand ratio were analyzed through UV-Visible study. Fluorescence response toward Cu²⁺ was carried to assess the fluorescent property of synthesized Schiff base. The probe exhibited a higher fluorescence enhancement in the presence of Cu²⁺ over other metal ions (Ni²⁺, Zn²⁺, Hg²⁺, Co²⁺, Cd²⁺, Al³⁺, Fe²⁺, and Pb²⁺). The binding stoichiometry between L and Cu²⁺ has been investigated using Job’s plot and Benesi-Hildebrand equation and it was found that ligand L can form 1:1 L-Cu²⁺ complex with binding constant (K _a) of 4?×?10⁴ LM^?1.     

A Pyrene-based Highly Selective Turn-on Fluorescent Chemosensor for Iron(III) Ions and its Application in Living Cell Imaging

A new pyrene-based chemosensor (1) exhibits excellent selectivity for Fe³⁺ ions over a wide range of tested metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Hg²⁺, K⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺. The binding of Fe³⁺ to chemosensor 1 produces an emission band at 507 nm due to the formation of a Py-Py* excimer that is induced by Fe³⁺-binding. The binding ratio of 1-Fe³⁺ was determined to be 1:1 from a Job plot. The association constant of 1-Fe³⁺ complexes was found to be 1.27?×?10⁴ M^?1 from a Benesi-Hildebrand plot. In addition, fluorescence microscopy experiments show that 1 can be used as a fluorescent probe for detecting Fe³⁺ in living cells.     

Fluorescent and Chromogenic Receptor Bearing Amine and Hydroxyl Functionality for Iron (III) Detection in Aqueous Solution

The noncyclic 2,2′-[ethane-1,2-diylbis (iminomethanediyl)]diphenol (4) fluorescent receptor bearing two amine and hydroxyl groups have been designed and investigated for their binding properties towards various cations. The fluorescent spectral measurements revealed that receptor 4 is a selective fluorescent sensor for Fe³⁺ ions but not for metal ions such as Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Bi³⁺. The binding ability was confirmed with spectroscopic methods and density functional theory calculation (DFT). This straightforward and cost effective receptor provides rapid detection of Fe³⁺ ions at concentrations as low as 2.5 μM and expected to be useful to design efficient chemically and biological sensor.     

An NBD-based Sensitive and Selective Fluorescent Sensor for Copper(II) Ion

A new 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived fluorescent probe (1) exhibiting high selectivity for Cu²⁺ detection, produced significant fluorescence quenching in the presence of Cu²⁺ ion, while the metal ions Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ produced only minor changes in fluorescence. The apparent association constant (K _a) for Cu²⁺ binding in chemosensor 1 was found to be 1.22 × 10³ M⁻¹. The maximum fluorescence quenching activity caused by Cu²⁺ binding to 1 was observed over the pH range 6–10.     

Urea Based Dipodal Fluorescence Receptor for Sensing of Fe3+ Ion in Semi-Aqueous Medium

Urea based fluorescent chemosensor 1 was synthesized. Receptor 1 shows unique selectivity for the Fe³⁺ion and no such significant response was noticed with other metal ions (Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Bi³⁺) in DMSO/H₂O (50:50,v/v) semi-aqueous solution. The binding features have been established by absorption and fluorescence spectroscopic methods. The binding constant (K) values obtained from Benesi-Hildebrand, Scatchard and Connor plot for receptor 1 is (8.3?±?0.3) × 10³ M^?1 and has good detection limit 0.7?μM. The stoichiometry of 1.Fe³⁺ complex was confirmed by mass spectroscopy and Job’s plot.

A New On-fluorescent Probe for Manganese (II) Ion

A new fluorescent probe for Mn²⁺ ion, (6E)-N-((E)-1,2-diphenyl-2-(pyridin-2-ylimino)ethylidene)pyridin-2-amine (L), has been synthesized from benzil and 2-amino pyridine and characterized. In 1:1 (v/v) CH₃CN:H₂O (pH 4.0, universal buffer) L exhibits fluorescent intensity with emission peak at λ_max 360 nm on excitation with photons of 310 nm. Fluorescent intensity of L increases distinguishingly on interaction with Mn²⁺ ion compared to metal ions—Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Ag⁺ individually or all together. The enhancement in fluorescent intensity is due to snapping of photoinduced electron transfer (PET) prevailed in free L. Fluorescence and UV/visible spectral data analysis shows that binding stoichiometry between Mn²⁺ and L is 1:1 with log β?≈?3.0. Both L and its Mn²⁺ complex were optimised using density functional theory (DFT) and vibrational frequency calculations confirm that both are at local minima on the potential energy surfaces.     

A Pyrene-based Highly Selective Turn-on Fluorescent Sensor for Copper(II) Ion and its Application in Live Cell Imaging

A new pyrene derivative (chemosensor 1) containing a picolinohydrazide moiety exhibits high selectivity for Cu²⁺ ion detection in mixed aqueous media (CH₃OH:H₂O = 7:3). Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Hg²⁺, K⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence for the system. The apparent association constant (K _a) of Cu²⁺ binding in chemosensor 1 was found to be 2.75*10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5–8. Moreover, by means of fluorescence microscopy experiments, it is demonstrated that 1 can be used as a fluorescent probe for detecting Cu²⁺ in living cells.     

Thermodynamics of substituted coumarin VII: Potentiometric and spectrophotometric studies of 1-acetyl-2-(coumarin-iminecarboxamide-3-yl) hydrazine transition metal complexes

The dissociation constant of l-acetyl-2-(coumariniminecarboxamide-3-yl) hydrazine (ACCH) has been determined potentiometrically in 0.1 M KC1 and 40% (v/v) ethanol-water mixture. The stepwise stability constants of the formed complexes of Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and UO₂ ²⁺ with ACCH have been determined. The stability constants were found to UO₂ ²⁺ > Cu²⁺> Zn²⁺ > Ni²⁺ < CO²⁺ < Mn²⁺. The effect of temperature on the dissociation of ACCH and the stability of its formed complexes were studied. The corresponding thermodynamic functions were also determined and discussed. The spectral data of ACCH were investigated in pure organic solvents as well as in Britton Robinson buffer solutions of varying pH values. The dissociation constant pK^H ₁ of ACCH and the overall stability constants logβ of their complexes were determined in 20% (v/v) ethanol-water mixture at 298K.     

Microstructures, surface bonding states and room temperature ferromagnetisms of Zn0.95Co0.05O thin films doped with copper

Zn_0.95−xCo_0.05Cu_xO (ZCCO, where x = 0, 0.005, 0.01 and 0.015) thin films were deposited on Si (1 0 0) substrates by pulsed laser deposition technique. Crystal structures, surface morphologies, chemical compositions, bonding states and chemical valences of the corresponding elements for ZCCO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). XRD and FESEM results indicate that crystallite sizes of the highly (0 0 2)-oriented ZCCO films slightly decrease with increasing Cu content. When the Cu content increases from 0 to 0.015, Zn 2p_3/2, Co 2p, Cu 2p_3/2 and O 1s peaks of the ZCCO film shift towards higher or lower binding energy regions, and the reasons for these chemical shifts are investigated by fitting the corresponding XPS narrow-scan spectra. Both in-plane and out-of-plane magnetization-magnetic field hysteresis loops of the ZCCO films reveal that all the films have room temperature ferromagnetisms (RTFMs). The conceivable origin of the RTFM is ascribed to the combined effects of the local structural disorder resulted from (Co²⁺, Cu²⁺, Cu¹⁺)-cations which substitute Zn²⁺ ions in the ZnO matrices, ferromagnetic coupling between coupled dopant atoms caused by Co²⁺ (3d⁷4s⁰) and Cu²⁺ (3d⁹4s⁰) spin states, and exchange interactions between the unpaired electron spins originating from lattice defects induced by Cu doping in the Zn_0.95Co_0.05O matrices.     

8-Hydroxyquinoline Functionalized Graphene Oxide: an Efficient Fluorescent Nanosensor for Zn<Superscript>2+</Superscript> in Aqueous Media

A nanosensor, based on 8-hydroxyquinoline functionalized graphene oxide, was developed for the fluorescence detection of Zn²⁺. It showed high selectivity and sensitivity for Zn²⁺ion in aqueous solution over other metal ions such as Li⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Cd²⁺, Co²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Fe²⁺, Fe³⁺and Cr³⁺. Due to the linearity of the emission intensity toward Zn²⁺ concentration, fluorescent technique could be used for the detection of Zn²⁺ ion even at very low concentrations.     

A New Sensitive and Selective Off-On Fluorescent Zn<Superscript>2+</Superscript> Chemosensor Based on 3,3′,5,5′-Tetraphenylsubstituted Dipyrromethene

3,3′,5,5′-Tetraphenyl-2,2′-dipyrromethene was described as a highly sensitive and selective Off-on fluorescent colorimetric chemosensor for Zn²⁺ based on the chelation-enhanced fluorescence (CHEF) effect. The reaction of dipyrromethene ligand with Zn²⁺ induces the formation of the [ZnL₂] complex, which exhibits the increasing fluorescence in 120 fold compared with ligand in the propanol-1/cyclohexane (1:30) binary mixture. The Zn²⁺ detection limit was 1.4 × 10^?7 М. The UV-Vis and fluorescence spectroscopic studies demonstrated that the dipyrromethene sensor was highly selective toward Zn²⁺ cations over other metal ions (Na⁺, Mg²⁺, Co²⁺, Ni²⁺, Fe³⁺, Cu²⁺, Mn²⁺, Cd²⁺ and Pb²⁺), excluding Hg²⁺.     

Bis-Benzimidazolyl Diamide Based Fluorescent Probe for Copper(II): Synthesis, Structural and Fluorescence Studies

A new fluorescent probe based on a bis-benzimidazole diamide N ²,N ^2′-bis[(1-ethyl-benzimidazol-2-yl)methyl]biphenyl-2,2′-dicarboxamide ligand L ₁ with a biphenyl spacer group and a Copper(II) trinuclear metallacycle has been synthesized and characterized by X-ray single crystallography, elemental and spectral (FT-IR, ¹H & ¹³C NMR, UV-Visible) analysis. The fluorescence spectra of L ₁ in MeOH show an emission band centered at 300 nm. This band arises due to benzimidazolyl moiety in the ligating system. The diamide L ₁ in the presence of Cu²⁺ show the simultaneous ‘quenching’ of (300 nm) and ‘enhancement’ of (375 nm) emission band. Similar fluorescence behavior was found in water–methanol mixture (9:1). The new emission band at 375 nm is attributed to intra ligand π–π* transition of the biphenyl moiety. L ₁ exhibited high selectivity and sensitivity towards Cu²⁺ in both the medium over other common metal ions like Ni²⁺, Co²⁺, Mn²⁺, Mg²⁺, Zn²⁺, Pb²⁺ and Hg²⁺. The binding constant with Cu²⁺ was calculated by the Benesi-Hildebrand equation. Selective “off-on-off” behavior of L ₁ in methanol has also been studied. The fluorescent intensity of 375 nm bands in L ₁ enhances (turns-on) upon addition of Cu²⁺ and quenches (turn-off) upon addition of Na₂-EDTA.     

Sensing of Zn2+ion by N-Furfurylsalicylaldimine Based on CHEF Process†

The recognition ability of N-Furfurylsalicylaldimine (HL) toward various cations (Pb²⁺, Hg²⁺, Ba²⁺, Cd²⁺, Ag⁺, Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, K⁺, Sr²⁺, and Na⁺) has been studied by UV–Vis and fluorescence spectroscopy. The compound showed highly selective fluorescence signaling behaviour for Zn²⁺ ions in methanol-water medium based on CHEF process and is capable of distinguishing Zn²⁺ from Cd²⁺ ion. From single crystal X-ray analysis it is revealed that a Zn²⁺ ion binds two ligand molecules through imine nitrogen and phenolate oxygen atom.

Prepare high efficiency Mn-doped Zn2SiO4 green phosphors in air using nano-particles

In this study, nano-scale precursors of ZnO, SiO₂, and MnO₂ powders were used to prepare mixtures with the compositions of 2ZnO+SiO₂+X mol% MnO₂ (X=MnO₂/2ZnO, abbreviated as Zn₂SiO₄-X-MnO₂), where 2≤X≤5. The mixed Zn₂SiO₄-X-MnO₂ mixtures were calcined from 900 to 1300 °C in air in order to synthesize Zn₂SiO₄:Mn²⁺ green phosphors. The X-ray diffraction patterns of Zn₂SiO₄-X-MnO₂ particles indicated that ZnO was present in the 900 °C-calcined Zn₂SiO₄-X-MnO₂ phosphors, but not in particles calcined at temperatures of 1000 °C and higher. However, the unapparent secondary phase of ZnMnO₃ was found in the 1200 and 1300 °C-calcined Zn₂SiO₄-5-MnO₂ compositions. The luminescent characteristics of Zn₂SiO₄-X-Mn²⁺ phosphors were compared with that of a commercial product (Nichia Corp., Japan). The photoluminescence (PL) intensity of 1200 °C-calcined Zn₂SiO₄-4-MnO₂ phosphors was higher and the decay times of all synthesized Zn₂SiO₄-X-MnO₂ phosphors were longer than those of the commercial product.     

N-benzoate-N′ salicylaldehyde ethynelediamine: A new fluorescent sensor for Zn2+ ion by “off-on” mode

Imbalance of zinc ion (Zn²⁺) in human body causes diseases like Alzheimer’s and Parkinson’s and therefore Zn²⁺ estimation in biological fluids has diagnostic values. Fluorescence “off-on” sensors have advantages of high sensitivity and in situ application over other sensors. A new fluorescent “off-on” Zn²⁺ sensor, N-benzoate-N′ salicylaldehyde ethynelediamine (L), has been synthesisied. In 1:1(v/v) CH₃OH:PBS (PBS?=?phosphate buffer solution), L shows ca. 20 times enhancement in fluorescence intensity on interaction with Zn²⁺, due to snapping of photoinduced electron transfer (PET) process, which is selective over metal ions - Na⁺, K⁺, Ca²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺. These metal ions either individually or all together does not interfere the sensing ability of L towards Zn²⁺. A 1:1 interaction between L and Zn²⁺ ion with binding constant 10^4.25 has been established from spectroscopic data.     

Azathia crown ethers carrying pyrene pendant as receptor molecules for metal sensor systems

A series of crown ethers carrying a pyrene group with nitrogen–sulfur donor atoms, that differ in having three, four and five sulfur atoms in the macrocycle was designed and synthesized by the reaction of the corresponding macrocyclic compound and 1-bromomethylpyrene. The influence of metal cations such as Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺ and Al³⁺ on the spectroscopic properties of the ligands was investigated in acetonitrile–dichloromethane (1:1) by means of absorption and emission spectrometry. Absorption spectra show isosbestic points in the spectrophotometric titration of Fe²⁺, Zn²⁺, Cu²⁺, Pb²⁺ and Hg²⁺. The results of spectrophotometric titration experiments disclosed the complexation compositions and complex stability constants of the novel ligands with Fe²⁺, Zn²⁺, Cu²⁺, Pb²⁺ and Hg²⁺ cations. The monoazatetrathia crown ether showed good sensitivity for Cu²⁺ with linearity in the range 5.0×10^?7–2.5×10^?6 M and detection limit of 1.6×10^?8 M.