A new highly selective fluorescent K+ sensor

We describe the synthesis, properties, and application of a new fluorescent potassium chemosensor, KS2, for K(+) sensing and imaging in live cells. By virtue of a strong electron-withdrawing group, 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF), with a triazacryptand ligand, the new sensor can respond to K(+) up to 1.6 M. This is the first highly selective intracellular sensor suitable for sensing K(+) over a broad and high concentration range. Confocal fluorescence microscopy has established the utility of KS2 for live-cell K(+) detection. The application of KS2 combined with other sensors will be of great benefit for investigating cellular metabolism, detecting and diagnosing diseases including cancer, and monitoring responses to therapy.     

Anthracene cycloadducts as highly selective chiral auxiliaries

A new chiral auxiliary was designed and easily prepared from a Diels-Alder cycloadduct of an enantiomerically pure anthracene with maleimide. Excellent diastereoselectivities in Diels-Alder reactions, conjugate additions, and aldol reactions employing these auxiliaries are now reported.     

A highly selective fluorescent chemosensor for Pb2+

A new fluorescent sensor based on rhodamine B for Pb2+ was synthesized. The new fluorescent sensor showed an extreme selectivity for Pb2+ over other metal ions examined in acetonitrile. Upon the addition of Pb2+, an overall emission change of 100-fold was observed, and the selectivity was calculated to be 200 times that of Zn2+. The signal transduction occurs via of reversible CHEF (chelation-enhanced fluorescence) with this inherent quenching metal ion.     

Pd-Ga intermetallic compounds as highly selective semihydrogenation catalysts

The intermetallic compounds Pd(3)Ga(7), PdGa, and Pd(2)Ga are found to be highly selective semihydrogenation catalysts for acetylene outperforming established systems. The stability of the crystal and electronic structure under reaction conditions allows the direct relation of structural and catalytic properties and a knowledge-based development of new intermetallic catalyst systems. In the crystal structure of PdGa palladium is exclusively surrounded by gallium atoms. The alteration of the Pd coordination in PdGa leads to a strong modification of the electronic structure around the Fermi level in comparison to elemental Pd. Electronic modification and isolation of active sites causes the excellent catalytic semihydrogenation properties.     

A Novel Vanadosilicate with Hexadeca‐Coordinated Cs+ Ions as a Highly Effective Cs+ Remover

The effective removal of ¹³⁷Cs⁺ ions from contaminated groundwater and seawater and from radioactive nuclear waste solutions is crucial for public health and for the continuous operation of nuclear power plants. Various ¹³⁷Cs⁺ removers have been developed, but more effective ¹³⁷Cs⁺ removers are still needed. A novel microporous vanadosilicate with mixed‐valence vanadium (V⁴⁺ and V⁵⁺) ions is now reported, which shows an excellent ability for Cs⁺ capture and immobilization from groundwater, seawater, and nuclear waste solutions. This material is superior to other known materials in terms of selectivity, capacity, and kinetics, and at very low Cs⁺ concentrations, it was found to be the most effective material for the removal of radioactive Cs⁺ ions under the test conditions. This novel vanadosilicate also contains hexadeca‐coordinated Cs⁺ ions, which corresponds to the highest coordination number ever described.     

Aminopyridyl derivative of thiacalix[4]arene-carboxylic acid as ionizable highly selective Ag+ ionophore

A novel mono-ionizable receptor 2 possessing three aminopyridyl and one carboxylic group in 1,3-alternate conformation based on thiacalix[4]arene, confirmed by single crystal X-ray analysis, was prepared. For competitive solvent extraction of alkali metal (Na⁺, K⁺ and Cs⁺) and some transition metal (Cu²⁺, Zn²⁺, TI⁺, Ag⁺) cations from aqueous solutions into chloroform, it was found that the introduction of proton-ionizable group (carboxylic acid moiety) into the aminopyridyl-thiacalix[4]arene derivative could further improve its Ag⁺ extractability with high selectivity.     

A highly selective charge transfer fluoroionophore for Cu2+

A dual fluorescent charge transfer fluoroionophore (1) with its ionophore incorporated in the electron acceptor was developed and was found to show a highly selective fluorescent response to Cu2+ with a dramatic enhancement in its CT emission.     

Solvent extraction studies using tetracycline as complexing agent

The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products¹³⁷Cs,¹⁴⁰Ba,¹⁴⁰La,¹⁴¹Ce,¹⁰³Ru,⁹⁵Zr and⁹⁵Nb from each other and from uranium is presented. The same study has been made for¹³¹I,^99mTc,⁹⁹Mo,¹³²Te,²³⁹Np and uranium and the steps necessary for the separation of these elements are proposed.From a thesis submitted by I. I. L. CUNHA to the Instituto de Pesquisas Energéticas e Nucleares-University of São Paulo in partial fulfillment of the requirements for a Doctor of Science's Degree. Work supported by Comissão Nacional de Energia Nuclear.     

Application of an Hg2+ selective imprinted polymer as a new modifying agent for the preparation of a novel highly selective and sensitive electrochemical sensor for the determination of ultratrace mercury ions

A simple and very selective electrode, based on a mercury ion imprinted polymer (IIP), and its application for the determination of Hg(2+) ions in the real samples is introduced. Mercury ion selective cavities were created in the vinyl pyridine based cross-linked polymer. In order to fabricate the sensor carbon particles and polymer powder were mixed with melted n-eicosane. An explicit difference was observed between the responses of the electrodes modified with IIP and non imprinted polymer (NIP), indicating proper performance of the recognition sites of the IIP. Various factors, known to affect the response behavior of selective electrode, were investigated and optimized. The interference of different ionic species with the response of the electrode was also studied. The results revealed that, compared to previously developed mercury selective sensors, the proposed sensor was more selective, regarding the common potential interferer. This sensor showed a linear response range of 2.5 × 10(-9)-5.0 × 10(-7) M and lower detection limit of 5.2 × 10(-10) M (S/N). The sensor was successfully applied to the determination of mercury in real samples.     

A new thioether functionalized organic-inorganic mesoporous composite as a highly selective and capacious Hg2+ adsorbent

A new thioether functionalized organic-inorganic ordered mesoporous composite as a highly selective and capacious Hg2+ adsorbent was synthesized by one-step co-condensation of (1,4)-bis(triethoxysilyl)propane tetrasufide (BTESPTS, (CH3CH2O)3Si(CH2)3S-S-S-S(CH2)3Si(OCH2CH3)3) and tetraethoxysilane (TEOS), with tri-block copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) EO20PO70EO20 as template.     

A highly selective and colorimetric naked-eye chemosensor for Cu2+

A sample and practical colorimetric naked-eye chemosensor 3-nitro-4-ethylenediamido-nitrobenzene (2) for metal cations was designed and synthesized. It displays high selectivity and sensitivity for Cu2+ by the UV absorption which appeared a new peak at 525 nm and color change from yellow to red by naked-eye in CH3OH/H2O pH 7.6.     

A highly selective and sensitive fluorescent chemosensor for Zn^2＋

A new selective Zn^2＋ fluorescent chemosensor, o-vanillin-4-ethoxybenzoylhydrazone （1）, was designed and prepared. Free 1 mainly displayed very weak fluorescence at 480 nm upon excitation at 403 nm. It displayed high selectivity for Zn^2＋ and had a 518- fold fluorescent enhancement upon binding of Zn^2＋, while the other cation ions had only little influence on the fluorescence of 1. Mechanism of enhancement of l＇s fluorescence by Zn^2＋ was briefly discussed.     

Cyclohexane as a Li+ selective ionophore

The M+[cyclohexane][Ar] (M = Li, Na, and K) cluster ions were investigated using infrared photodissociation spectroscopy in the C-H stretching region. The alkali metal cation binds to the cyclohexane ring above the ring on the S6 axis via eta3 coordination. The C-H stretching modes are perturbed due to binding of the metal cation and display a significant spread in frequency. The shifts are greatest for the Li+ and decrease for Na+ and K+ with increasing ionic radius. It has been observed that cyclohexane displays greater selectivity for Li+ over Na+ than the cyclic ether, 12-crown-4. The charge transfer interaction between Li+ and cyclohexane is believed to be responsible for the selectivity of Li+ over other alkali metal ions.     

Solvent extraction studies using tetracycline as a complexing agent

Stability constants for thorium complexes with tetracycline were determined by the methods of average number of ligands, the limiting value, the two parameters and by weighted least squares. The solvent extraction technique was used to obtain the required data for the determination of the constants. Work partly supported by the Brazilian Atomic Energy Commission.     

Solvent extraction studies using tetracycline as a complexing agent

Stability constants for uranium-tetracycline complexes were determined by the method of average number of ligands, the method of limiting values, the method of two parameters and the method of weighted least squares. Solvent extraction technique was used to obtain experimental data.     

Magic sized ZnS quantum dots as a highly sensitive and selective fluorescence sensor probe for Ag+ ions

A green and simple chemical synthesis of magic sized water soluble blue-emitting ZnS quantum dots (QDs) has been accomplished by reacting anhydrous Zn acetate, sodium sulfide and thiolactic acid (TLA) at room temperature in aqueous solution. Refluxing of this mixture in open air yielded ZnS clusters of about 3.5 nm in diameter showing very strong and narrow photoluminescence properties with long stability. Refluxing did not cause any noticeable size increment of the clusters. As a result, the QDs obtained after different refluxing conditions showed similar absorption and photoluminescence (PL) features. Use of TLA as a capping agent effectively yielded such stable and magic sized QDs. The as-synthesized and 0.5 h refluxed ZnS QDs were used as a fluorescence sensor for Ag(+) ions. It has been observed that after addition of Ag(+) ions of concentration 0.5-1 μM the strong fluorescence of ZnS QDs was almost quenched. The quenched fluorescence can be recovered by adding ethylenediamine to form a complex with Ag(+) ions. The other metal ions (K(+), Ca(2+), Au(3+), Cu(2+), Fe(3+), Mn(2+), Mg(2+), Co(2+)) showed little or no effect on the fluorescence of ZnS QDs when tested individually or as a mixture. In the presence of all these ions, Ag(+) responded well and therefore ZnS QDs reported in this work can be used as a Ag(+) ion fluorescence sensor.     

A novel di-triazole based peptide as a highly sensitive and selective fluorescent chemosensor for Zn2+ ions

A di-triazole based peptide has been synthesised by copper catalyzed Huisgen cycloaddition. Fluorescence intensity is enhanced selectively in the presence of Zn(2+), which is ascribed to reversal of photoelectron transfer. Compound 7 was found to self-assemble in the presence of Zn(ClO(4))(2) in an exclusive 2:1 ratio, which is supported by (1)H NMR titration and mass spectral data. The fluorescence intensity of 7 shows a subsequent ON-OFF phenomenon upon repetitive and alternate addition of Zn(ClO(4))(2) and HClO(4).