Selective Recognition of Cobalt (II) Ion by a New Cryptand Compound with N2O2S2 Donor Atom Possessing 2-Hydroxy-1-Naphthylidene Schiff Base Moiety

A new cryptand compound carrying 2-hydroxy-1-naphthylidene Schiff base moiety (3) was designed and synthesized by reaction of the corresponding macrobicyclic amine compound (1) and 2-hydroxy-1-naphthaldehyde (2). The influence of metal cations such as Mg²⁺, Ca²⁺, Sr²⁺, Fe²⁺,Co²⁺, Mn²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Al³⁺ and Pb²⁺ on the spectroscopic properties of the new fluoroionophore was investigated in acetonitrile-dichloromethane solution (9.5/0.5) by means of absorption and emission spectrometry. The blue shifts on the fluorescence spectrum were observed for all metal cations at 504nm. At the same time the fluorescence spectrum of the ligand showed quenching in the intensity of the signal at 504 nm for all metal cations except for Zn²⁺. Interaction of Co²⁺ with the ligand caused quenching of naphtyl fluorescence higher than 84%. The method showed good selectivity and sensitivity for Co²⁺ with respect to other metal cations with linear range and detection limit of 1.5 × 10⁻⁷ to 3.3 × 10⁻⁶M and 4.8 × 10⁻⁸M respectively.     

The Smart 2-(2-Fluorobenzoyl)-N-(2-Methoxyphenyl)Hydrazinecarbothioamide Functionalized as Ni(II) Sensor in Micromolar Concentration Level and its Application in Live Cell Imaging

In recent years, fluorescent probes for the detection of environmentally and biologically important metal cations have received extensive attention for designing and development of fluorescent chemosensors. Herein, we report the photophysical results of 2-(2-fluorobenzoyl)-N-(2-methoxyphenyl) hydrazinecarbothioamide (4) functionalized as Ni (II) sensor in micromolar concentration level. Through fluorescence titration at 488 nm, we were confirmed that ligand 4 showed the remarkable emission by complexation between 4 and Ni (II) while it appeared no emission in case of the competitive ions (Cr³⁺, Fe²⁺, Co²⁺, Ba²⁺, Cu²⁺, Ca²⁺, Na⁺, K⁺, Cu⁺, Cs⁺). Furthermore, ligand 4 exhibited no toxicity with precise cell permeability toward normal living cells using L929 cell lines in bio imaging experiment investigated through confocal fluorescence microscope. The non-toxic behavior of ligand 4 (assessed by MTT assay) and its ability to track the Ni²⁺ in living cells suggest its possibility to use in biological system as nickel sensor.

Effect of Pendant Group Length Upon Metal Ion Complexation in Acetonitrile by Di-Ionized Calix[4]Arenes Bearing Two Dansyl Fluorophores

A series of three di-ionizable calix[4]arenes with two pendant dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims was synthesized. Structures of the three ligands were identical except for the length of the spacers which connected the two dansyl groups to the calix[4]arene scaffold. Following conversion of the ligands into their di-ionized di(tetramethylammonium) salts, absorption and emission spectrophotometry were utilized to probe the influence of metal cation (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ag⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and Fe³⁺) complexation in acetonitrile. Upon complexation with these metal cations, emission spectra underwent marked red shifts and quenching of the dansyl group fluorescence for the di-ionized ligand with the shortest spacer. A similar effect was noted for the di-ionized ligand with an intermediate spacer for all of the metal ions, except Ba²⁺. For the di-ionized ligand with the longest spacer, the metal cations showed different effects on the emission spectrum. Li⁺, Mg²⁺, Ca²⁺ and Ba²⁺ caused enhancement of emission intensity with a red shift. Other metal cations produce quenching with red shifts in the emission spectra. Transition metal cations interacted strongly with all three di-ionized ligands. In particular, Fe³⁺ and Hg²⁺ caused greater than 99% quenching of the dansyl fluorescence in the di-ionized ligands.     

Highly selective fluorescent chemosensor for detecting Hg(II) in water based on pyrene functionalized core–shell structured mesoporous silica

Novel pyrene functionalized mesoporous core–shell structured silica (denoted as SiO₂@mSiO₂/Py-Si) was designed and synthesized as a highly selective fluorescent chemosensor for detecting Hg²⁺ in water. The core–shell structured silica was prepared by a simple sol–gel process through coating SiO₂ nanospheres with a layer of ordered mesoporous silica. The surface of outer mesoporous silica shell was then further functionalized by the fluorescent chromophore alkoxysilane modified pyrene (Py-Si). XRD data confirmed that the hexagonal ordered mesoporous structure was preserved after functionalization. The chemosensing material successfully exhibited a remarkable “turn on” response toward Hg²⁺ over miscellaneous metal ions. A good linear response towards Hg²⁺ in the concentration range of 10^?8–10^?4 M was constructed with R²=0.9913. Most importantly, a satisfactory detection limit of 3.4×10^?9 g mL^?1 (down to ppb level) was obtained, which is 100 times lower than our previous report of covalently grafted Py-OH to the bulk mesoporous silica SBA-15. These results indicated that SiO₂@mSiO₂/Py-Si can be used as a highly selective and sensitive fluorescence sensor for Hg²⁺.     

A fluorescent probe for zinc detection based on organically functionalized SBA-15

In this study, highly ordered mesoporous silica material (SBA-15) functionalized with N-(quinoline-8-yl)-2-(3-triethoxysilyl-propylamino)-acetamide (QTPA) as zinc probe has been reported. The anchoring to the surface of the SBA-15 was carried out by the reaction between the precursor and the hydroxyl groups available on the inner surface of the support. The primary ordered mesoporous structure of SBA-15 was well preserved after the grafting procedure. Fluorescence characterization showed that the obtained organic-inorganic hybrid composite displayed highly selective and sensitive to Zn²⁺ ion over other cations such as Cd²⁺, Pb²⁺, Ni²⁺ and Co²⁺. And the hybrid material has ideal chemical and spectroscopic properties for further biological and environmental applications.     

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⁺.     

Spectroscopic study on the 4′-(4-pyridyl)-2,2′:6′,2′′-terpyridine and its metal complexes

Multitopic ligand, 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine (pyterpy), has attracted growing attention because of its unique structural features, optical and electrochemical properties. Here, we report spectroscopic studies of pyterpy and its metal complexes in methanol solution. For the pure pyterpy, the ligand emission intensity increased with its concentration in the dilute solution, but decreased when its concentration was over 1.3×10⁻⁵ mol/l due to the concentration quenching. No significant influence on the ligand luminescence was observed for the Zn²⁺-pyterpy complex but strong luminescence quenching was observed for the electroactive Fe²⁺- and Co²⁺-pyterpy complexes. The lanthanide (Sm³⁺, Eu³⁺ and Tb³⁺) complexes of the pyterpy showed both ligand and lanthanide ion emissions, especially for the Tb³⁺-pyterpy complex, suggesting that the excited energy of pyterpy ligand could be efficiently transferred to the central Tb³⁺ ions. The luminescence was pH sensitive with the strongest emission in the neutral solution. The results indicated that the multitopic ligand of pyterpy could not only act as linkers for the metal-directed building blocks, but also act as optical materials with its own emission at about 364 nm and as light antenna for the lanthanide ions.     

Experimental and Theoretical Studies of the Pyrazoline Derivative 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4,5-dihydro-1H-Pyrazole and its Application for Selective Detection of Cd2+ ion as Fluorescent Sensor

A simple fluorescent chemosensor 5-(4-methylphenyl)-3-(5-methylfuran-2-yl)-1-phenyl-4, 5-dihydro-1H-pyrazole (PY) has been synthesized for the detection of Cd²⁺ ion.The fluorescent probe PY shows high selectivity for Cd²⁺in the presence of othermetal ions (Co²⁺, Cu²⁺, Hg²⁺, Mn²⁺, Zn²⁺, Fe³⁺, Pb²⁺, Ni²⁺, and Al³⁺). The fluorescence intensity of the PY has been strongly quenched with increasing concentration of Cd²⁺ (0–0.9 μM)via photoinduced electron transfer mechanism. The binding constant of Cd²⁺ to PY for the 1:1 complex isfound to be 5.3?×?10⁵ M^?1with a detection limit of 0.09 μM. The chemosensor was successfully applied for determination of Cd²⁺ in different water samples (tap, river, and bottled water) showing good recovery values in the range of 94.8–101.7% with RSD less than 3%. Density functional theory (DFT) calculations were also performed to investigate electronic and spectral characteristics which are quite agreeable with the experimental value. The results show that the synthesized fluorescent chemosensor shows good selectivity towards Cd²⁺ and can be readily applied for the detection of Cd²⁺ in real samples including water samples.

Graphical Abstract

     

Selective extraction of palladium(II) using hydrazone ligand: A novel fluorescent sensor

The acyclic tridentate blue luminescent ligand (λ_ex=300 nm, λ_em=415 nm) quinoline-2-carboxaldehyde 2-pyridylhydrazone, HL, 1, was recognized as a new fluorescent chemosensor for Pd²⁺. In alkaline methanol complete fluorescent quenching was observed in the presence of 2 equivalents of Pd²⁺ that was further reflected in the solid phase fluorescence microscopic study.Ligand formed 1:1 complexes with Ni²⁺, Cu²⁺, Zn²⁺, Pd²⁺ and 1:2 complexes with Co²⁺, Fe²⁺ as obtained from Job's plot of continuous variation. The binding constants of different metal complexes (Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pd²⁺) were estimated by fluorescence titrations. The ligand can selectively extract significant amount of Pd²⁺ from the aqueous mixture of metal ions, and the extraction efficiency was increased from 80% to 95% with increase in the molar ratio of HL, 1, to Pd²⁺ from 1 to 3. No significant interference was observed up to 2-fold excess addition of Cu²⁺ and Zn²⁺ and 100-fold excess addition of Co²⁺, Fe²⁺ and Ni²⁺over the Pd²⁺ ion concentration (1.0×10⁻³ M).     

2-(3’,4’-二羧基苯氧基)苯甲酸配体桥联的锌(Ⅱ)配合物的合成、结构及荧光性质

以2-(3’,4’-二羧基苯氧基)苯甲酸(H3DPBA)和1,3-二(4-吡啶基)-丙烷(bpp)为配体,与Zn(Ac)2通过水热反应,获得了一维链状配合物Zn(DPBA)(bpp)。该配合物的一个不对称单元包括一个Zn(Ⅱ)离子,一个DPBA配体和一个bpp配体。Zn(Ⅱ)离子与四个氧原子及一个氮原子配位,其配位数为5。固态配合物在375nm处出现强的发射峰,来自于配体的π~*—π跃迁。与配体的荧光发射光谱比较,配合物的荧光发射峰发生了蓝移,而且配合物的荧光发射强度有大幅度增强。讨论了配合物在常见溶剂中和金属阳离子中的荧光性质。实验结果表明不同有机小分子或不同金属阳离子对配合物的荧光强度有不同程度的影响,有机小分子硝基苯和Fe~(3+)使配合物荧光猝灭,该Zn(Ⅱ)-配合物可用于硝基苯的检测以及水和乙醇体系中Fe~(3+)的检测。     

A Novel Highly Sensitive and Selective Fluorescent Sensor for Imaging Copper (II) in Living Cells

In this work, we designed and synthesized a novel quinolin-based derivative which exhibited signaling behaviors for Cu²⁺. Upon the addition of Cu²⁺ to the solution of the molecule, it displayed an obvious fluorescence quenching in a linear fashion due to the formation of a 1:1 metal–ligand complex. This fluorescent sensor exhibited a rare sensitivity toward Cu(II) (the level of magnitude could be 6?×?10^?8), a rapid response (<10 s) and also high selectivity toward Cu²⁺ over other metal ions such as Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Fe³⁺, Mn²⁺, Hg²⁺, Pb²⁺, Cd²⁺, Cr³⁺, Co²⁺, Zn²⁺ and Al³⁺. Simultaneously, the cell imaging experiments and filter paper test demonstrated its extensive applicability.     

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.     

Coumarin Based Fluorescent Probe for Colorimetric Detection of Fe<Superscript>3+</Superscript> and Fluorescence Turn On-Off Response of Zn<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A new coumarin based Schiff-base chemosensor-(E)-7-(((8-hydroxyquinolin-2-yl)methylene) amino)-4-methyl-2H-chromen-2-one (H ₁₁ L) was synthesized and evaluated as a colorimetric sensor for Fe³⁺ and fluorescence “turn on-off” response of Zn²⁺ and Cu²⁺ using absorption and fluorescence spectroscopy. Upon treatment with Fe³⁺ and Zn²⁺, the absorption intensity as well as the fluorescence emission intensity increases drastically compared to other common alkali, alkaline earth and transition metal ions, with a distinct color change which provide naked eye detection. Formation of 1:1 metal to ligand complex has been evaluated using Benesi-Hildebrand relation, Job’s plot analyses, ¹H NMR titration as well as ESI-Mass spectral analysis. The complex solution of H ₁₁ L with Zn²⁺ ion exhibited reversibility with EDTA and regenerate free ligand for further Zn²⁺ sensing. H ₁₁ L exhibits two INHIBIT logic gates with two different chemical inputs (i) Zn²⁺ (IN1) and Cu²⁺ (IN2) and (ii) Zn²⁺ (IN1) and EDTA (IN2) and the emission as output. Again, an IMPLICATION logic gate is obtained with Cu²⁺ and EDTA as chemical inputs and emission as output mode. Both free ligand as well as metal-complexes was optimized using density functional theory to interpret spectral properties. The corresponding energy difference between HOMO-LUMO energy gap for H ₁₁ L, H₁₁L-Zn²⁺ and H₁₁L-Cu²⁺ are 2.193, 1.834 and 0.172 eV, respectively.     

Rhod-5N as a Fluorescent Molecular Sensor of Cadmium(II) Ion

The photophysical and complexing properties of Rhod-5N (commercially available) in MOPS buffer are reported. This fluorescent molecular sensor consists of a BAPTA chelating moiety bound to a rhodamine fluorophore. Its fluorescence quantum yield is low and a drastic enhancement of fluorescence intensity upon cation binding was observed. Special attention was paid to the complexation with Cd²⁺, a well known toxic metal ion. Possible interference with other metal ions (Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, Pb²⁺) was examined. Rhod-5N was found to be highly selective of Cd²⁺ over those interfering cations except Pb²⁺. The limit of detection is 3.1 μg l⁻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.     

Preparation,characterization, and ion exchange behavior of nanocomposite polyaniline zirconium(IV) selenotungstophosphate for the separation of toxic metal ions

A conducting polymer-based advanced nanocomposite ion exchanger was synthesized by incorporating polyaniline (PANI) into the inorganic counterpart zirconium(IV) selenotungstophosphate (ZSWP). The nanocomposite exhibited an excellent ion exchange capacity of 1.20 meq g^?1 in addition to high thermal stability. The polymeric–inorganic nanocomposite ion exchanger was characterized by Fourier transform infrared (FTIR), XRD, SEM, and TEM studies. The DC conductivity of PANI/ZSWP was also investigated. The nanocomposite ion exchanger was found to be highly selective for Cu²⁺ ions with a distribution coefficient value of 650 mL/g. The analytical applications of the material were explored by achieving selective separations of Cu²⁺ and Ca²⁺ ions from a synthetic mixture of Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Fe³⁺, Mg²⁺, and Al³⁺ and Ca²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Al³⁺, Mg²⁺, and Ba²⁺.     

Synthesis and characterization of two new fluorescent macrocycles: A novel fluorescent chemosensor for zinc ion

Two new macrocyclic systems (L¹, L²) containing two emissive naphthalene were synthesized and characterized. The macrocycles were studied by ¹H NMR, ¹³C NMR, COSY, HMQC, DEPT, microanalysis and mass spectroscopy. The influence of metal cations Na⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺ on the spectroscopic properties of the macrocyclic systems in acetonitrile/DMF 9:1 (v/v) mixtures were investigated by means of absorption and emission spectrophotometry. The macrocycle L¹ was found to be as an effective fluorescence sensor for Zn²⁺ ions. Zn²⁺ and Cd²⁺ ions show the most effects on the fluorescence intensity of L².     

Synthesis of Ag metallic nanoparticles by 120 keV Ag− ion implantation in TiO2 matrix

TiO₂ thin film synthesized by the RF sputtering method has been implanted by 120 keV Ag^? ion with different doses (3?×?10¹⁴, 1?×?10¹⁵, 3?×?10¹⁵, 1?×?10¹⁶ and 3?×?10¹⁶ ions/cm²). Further, these were characterized by Rutherford back Scattering, XRD, X-ray photoelectron spectroscopy (XPS), UV–visible and fluorescence spectroscopy. Here we reported that after implantation, localized surface Plasmon resonance has been observed for the fluence 3?×?10¹⁶ ions/cm², which was due to the formation of silver nanoparticles. Ag is in metallic form in the matrix of TiO₂, which is very interestingly as oxidation of Ag was reported after implantation. Also, we have observed the interaction between nanoparticles of Ag and TiO₂, which results in an increasing intensity in lower charge states (Ti³⁺) of Ti. This interaction is supported by XPS and fluorescence spectroscopy, which can help improve photo catalysis and antibacterial properties.     

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.     

Preparation, characterization, and luminescence properties of novel hybrid material containing europium(III) complex covalently bonded to MCM-41

In this paper, a novel luminescent organic-inorganic hybrid material containing covalently bonded ternary europium complex in mesoporous silica MCM-41 has been successfully prepared by co-condensation of tetrethoxysilane (TEOS) and the modified ligand 2-phenyl-1H-imidazo[4,5-f][1,10]phen-3-(triethoxysilyl)propylcarbamate (PIP-Si) in the presence of cetyltrimethylammonium bromide (CTAB) surfactant as template. PIP-Si containing 1,10-phenanthroline covalently grafted to 3-(triethoxysilyl)propyl isocyanate is used not only as a precursor but also as the second ligand for Eu(TTA)₃·2H₂O (TTA: 2-thenoyltrifluoroacetate) complex to prepare a novel functionalized mesoporous material. The resulted mesoporous composite materials, which demonstrate strong characteristic emission lines of Eu³⁺⁵D₀-⁷F_J (J=0, 1, 2, 3, 4), were characterized by Fourier transform infrared (FT-IR), small-angle X-ray diffraction, excited-state decay analysis. Emission intensity of the Eu(III) complex covalently linked to MCM-41 (Eu-MCM-41) increases with the increasing irradiation time, demonstrating better photostability compared with both pure Eu(III) complex and physically incorporated sample.