Remarkable role of positional isomers in the design of sensors for the ratiometric detection of copper and mercury ions in water

Cation sensing properties of the three positional isomers of rhodamine based sensors (1-3) are studied in water. The sensors differ only in the position of pyridine's nitrogen. The chemosensor 1, with pyridine nitrogen at ortho-position, showed a selective colorimetric detection of Cu(II) ions in water, at physiological pH 7.4 and also in medium containing BSA (bovine serum albumin) and blood serum. Notably the compound 2 and 3, with pyridine end located at meta-and para-positions did not show any color change with Cu(II) ions, although both the compounds showed turn-on change both in color and fluorescence with Hg(II) ions specifically. All the probes showed ratiometric changes with the specific metal ions. The changing position of nitrogen also changed the complexation pattern of the sensors with the metal ions. Probe 1 showed 2 : 1 complexation with Cu(II), whereas 2 and 3 showed 1 : 1 complexation with Hg(II) ions. The mechanism investigation showed that the change in color upon addition of metal ions is due to the ring-opening of the spirolactam ring of the probes. Cu(II) interacted with ligand 1 through a three-point interaction mode comprising carbonyl oxygen, amido nitrogen and pyridine nitrogen end. But in case of 2 and 3, Hg2+ only interacted through pyridine nitrogen ends. Quantitative estimation of Cu2+ and Hg2+ in complex biological media such as bovine albumin protein (BSA) and human blood serum were performed using these sensors. Rapid on-site detection as well as discrimination of these toxic ions was demonstrated using easily prepared portable test-strips.

Robust dielectric properties of B-site size-disordered hexagonal Ln(2)CuTiO(6) (Ln = Y, Dy, Ho, Er, and Yb)

Hexagonal Ln(2)CuTiO(6) (Ln = Y, Dy, Ho, Er, and Yb) exhibits a rare combination of interesting dielectric properties, in the form of relatively large dielectric constants (epsilon' > 30), low losses, and extremely small temperature and frequency dependencies, over large ranges of temperature and frequency Choudhury et al., Appl. Phys. Lett. 96, 162903 (2010) and Choudhury et al., Phys. Rev. B 82, 134203 (2010)], making these compounds promising as high-k dielectric materials. The authors present a brief review of the existing literature on this interesting class of oxides, complimenting it with spectroscopic data in conjunction with first-principles calculation results, revealing a novel mechanism underlying these robust dielectric properties. These show that the large size differences in Cu2+ and Ti4+ at the B-site, aided by an inherent random distribution of CuO5 and TiO5 polyhedral units, frustrates the ferroelectric instability, inherent to the noncentrosymmetric P6(3) cm space group of this system, and gives rise to the observed relatively large dielectric constant values. Additionally, the phononic contributions to the dielectric constant are dominated primarily by mid-frequency (>100 cm(-1)) polar modes, involving mainly Ti4+ 3d(0) ions. In contrast, the soft polar phonon modes with frequencies typically less than 100 cm(-1), usually responsible for dielectric properties of materials, are found to be associated with non-d(0) Cu2+ ions and to contribute very little, giving rise to the remarkable temperature stability of dielectric properties of these compounds. (C) 2014 American Vacuum Society.

A Probe for the Selective and Parts-per-Billion-Level Detection of Copper(II) and Mercury(II) using a Micellar Medium and Its Utility in Cell Imaging

A novel colorimetric probe 1 based on the picolyl moiety has been designed and synthesized. Probe 1 is composed of a pyrene and a bispicolyl amine (BPA) unit, in which the BPA moiety acts as a binding unit and the binding phenomenon is sensed from the changes in the signaling subunit. The probe detects Cu2+ specifically in water and both Cu2+ and Hg2+ efficiently in neutral Brij-58 micellar media. The probe shows a color change visible to the naked eye upon addition of metal ions. Notably, in a micellar medium, probe 1 can detect both the Cu2+ and Hg2+ ions even at parts-per-billion levels. Furthermore, the probe shows ratiometric detection of both the metal ions making the sensing quantitative. The two metal ions could be discriminated both visibly under a UV lamp and with the use of fluorescence spectroscopy. The probe could be also used in biological cell lines for the detection of both Hg2+ and Cu2+ ions.

Iminodiacetic acid functionalized polypyrrole modified electrode as Pb(II) sensor: Synthesis and DPASV studies

An electrochemical lead ion sensor has been developed by modification of carbon paste electrode (CPE) using polypyrrole functionalized with iminodiacetic acid (IDA-PPy) containing carboxyl group. The electrochemical response of Pb2+ ion on the IDA-PPy modified CPE has been evaluated and the controling parameters have been optimized using differential pulse anodic stripping voltammetry (DPASV). The IDA-PPy modified CPE shows a linear correlation for Pb2+ concentrations in the range of 1 x 10(-6) to 5 x 10(-9) M and the lower detection limit of Pb2+ has been found to be 9.6 x 10(-9) M concentration. Other tested metal ions, namely Cu2+, Cd2+, Co2+, Hg2+, Ni2+ and Zn2+, do not exhibit any voltammetric stripping response below 1 x 10(-7) M concentration. However, the Pb2+ response is affected in the presence of molar equivalents or higher concentrations of Cu2+, Cd2+ and Co2+ ions in binary systems with Pb2+, consequent to their ability to bind with iminodiacetic acid, while Hg2+, Ni2+ and Zn2+ do not interfere at all. A good correlation has been observed between the lead concentrations as analyzed by DPASV using IDA-PPy modified CPE and atomic absorption spectrophotometry for a lead containing industrial effluent sample. (C) 2014 Elsevier Ltd. All rights reserved.

The effect of Cu addition on the thermoelectric properties of Cu2CdGeSe4

Recently, research in copper based quaternary chalcogenide materials has focused on the study of thermoelectric properties due to the complexity in the crystal structure. In the present work, stoichiometric quaternary chalcogenide compounds Cu2+xCd1-x,GeSe4 (x = 0, 0.025, 0.05, 0.075, 0.1, 0.125) were prepared by solid state synthesis. The powder X-ray diffraction patterns of all the samples showed a tetragonal crystal structure with the space group I-42m of the main phase, whereas the samples with x = 0 and x = 0.025 revealed the presence of an orthorhombic phase in addition to the main phase as confirmed by Rietveld analysis. The elemental composition of all the samples characterized by Electron Probe Micro Analyzer showed a slight deviation from the nominal composition. The transport properties were measured in the temperature range of 300 K-723 K. The electrical conductivity of all the samples increased with increasing Cu content due to the enhancement of the hole concentration caused by the substitution of Cd (divalent) by Cu (monovalent). The positive Seebeck coefficient of all the samples in the entire temperature ranges indicates that holes are the majority carriers. The Seebeck coefficient of all the samples decreased with increasing Cu content and showed a reverse trend to the electrical conductivity. The total thermal conductivity of all the samples decreased with increasing temperature which was dominated by the lattice contribution. The maximum figure of merit ZT = 0.42 at 723 K was obtained for the compound Cu2.1Cd0.9GeSe4. (C) 2014 Elsevier Ltd. All rights reserved.

Thermoelectric properties of a Mn substituted synthetic tetrahedrite

Tetrahedrite compounds Cu12-xMnxSb4S13 (0 <= x <= 1.8) were prepared by solid state synthesis. A detailed crystal structure analysis of Cu10.6Mn1.4Sb4S13 was performed by single crystal X-ray diffraction (XRD) at 100, 200 and 300 K confirming the noncentrosymmetric structure (space group I (4) over bar 3m) of a tetrahedrite. The large atomic displacement parameter of the Cu2 atoms was described by splitting the 12e site into a partially and randomly occupied 24g site (Cu22) in addition to the regular 12e site (Cu21), suggesting a mix of dynamic and static off-plane Cu2 atom disorder. Rietveld powder XRD pattern and electron probe microanalysis revealed that all the Mn substituted samples showed a single tetrahedrite phase. The electrical resistivity increased with increasing Mn due to substitution of Mn2+ at the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. Even though the thermal conductivity decreased as a function of increasing Mn, the thermoelectric figure of merit ZT decreased, because the decrease of the power factor is stronger than the decrease of the thermal conductivity. The maximum ZT = 0.76 at 623 K is obtained for Cu12Sb4S13. The coefficient of thermal expansion 13.5 +/- 0.1 x 10(-6) K-1 is obtained in the temperature range from 460 K to 670 K for Cu10.2Mn1.8Sb4S13. The Debye temperature, Theta(D) = 244 K for Cu10.2Mn1.8Sb4S13, was estimated from an evaluation of the elastic properties. The effective paramagnetic moment 7.45 mu(B)/f.u. for Cu10.2Mn1.8Sb4S13 is fairly consistent with a high spin 3d(5) ground state of Mn.

Thermoelectric properties of Co substituted synthetic tetrahedrite

Transition metal atom (Co) substituted synthetic tetrahedrite compounds Cu12-xCoxSb4S13 (x = 0, 0.5, 1.0, 1.5, 2.0) were prepared by solid state synthesis. X-Ray Diffraction (XRD) patterns revealed tetrahedrite as the main phase, whereas for the compounds with x = 0, 0.5 a trace of impurity phase Cu3SbS4 was observed. The surface morphology showed a large grain size with low porosity, which indicated appropriate compaction for the hot pressed samples. The phase purity, as monitored by Electron Probe Micro Analysis (EPMA) is in good agreement with the XRD data. The elemental composition for all the compounds almost matched with the nominal composition. The X-ray Photoelectron Spectroscopy (XPS) data showed that Cu existed in both +1 and +2 states, while Sb exhibited +3 oxidation states. Elastic modulus and hardness showed a systematic variation with increasing Co content. The electrical resistivity and Seebeck coefficient increased with increase in the doping content due to the decrease in the number of carriers caused by the substitution of Co2+ on the Cu1+ site. The positive Seebeck coefficient for all samples indicates that the dominant carriers are holes. A combined effect of resistivity and Seebeck coefficient leads to the maximum power factor of 1.76 mW m(-1) K-2 at 673 K for Cu11.5Co0.5Sb4S13. This could be due to the optimization in the carrier concentration by the partial substitution of Co2+ on both the Cu1+ as well as Cu2+ site at the same doping levels, which is also supported by the XPS data. The total thermal conductivity systematically decreased with increase of doping content as it is mainly influenced by the decrease of carrier thermal conductivity. The maximum thermoelectric figure of merit zT = 0.98 was obtained at 673 K for Cu11.5Co0.5Sb4S13. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Tungsten-based nanomaterials (WO3 & Bi2WO6): Modifications related to charge carrier transfer mechanisms and photocatalytic applications

Heterogeneous photocatalysis is an ideal green energy technology for the purification of wastewater. Although titania dominates as the reference photocatalyst, its wide band gap is a bottleneck for extended utility. Thus, search for non-TiO2 based nanomaterials has become an active area of research in recent years. In this regard, visible light absorbing polycrystalline WO3 (2.4-2.8 eV) and Bi2WO6 (2.8 eV) with versatile structure-electronic properties has gained considerable interest to promote the photocatalytic reactions. These materials are also explored in selective functional group transformation in organic reactions, because of low reduction and oxidation potential of WO3 CB and Bi2WO6 VB, respectively. In this focused review, various strategies such as foreign ion doping, noble metal deposition and heterostructuring with other semiconductors designed for efficient photocatalysis is discussed. These modifications not only extend the optical response to longer wavelengths, but also prolong the life-time of the charge carriers and strengthen the photocatalyst stability. The changes in the surface-bulk properties and the charge carrier transfer dynamics associated with each modification correlating to the high activity are emphasized. The presence of oxidizing agents, surface modification with Cu2+ ions and synthesis of exposed facets to promote the degradation rate is highlighted. In depth study on these nanomaterials is likely to sustain interest in wastewater remediation and envisaged to signify in various green energy applications. (C) 2015 Elsevier B.V. All rights reserved.

Determina����o do potencial t��xico de cobre e n��quel e seus complexos com EDTA frente �� Daphnia similis

Quando se trata de efluentes muito complexos e de amostras de ��gua ou de sedimento de locais polu��dos, �� invi��vel ou at�� mesmo imposs��vel detectar a presen��a de todas as subst��ncias presentes. Os principais contaminantes associados �� polui����o das ��guas naturais, tem-se os metais pesados, uma classe de compostos de toxicidade elevada e que s��o bioacumulados nos seres vivos. Desses metais, o cobre e o n��quel se destacam, tanto por seu amplo uso em processos industriais, o que acarreta sua presen��a em diversos tipos de despejos, quanto por sua toxicidade elevada. O objetivo deste trabalho foi determinar o potencial t��xico do sulfato de cobre e sulfato de n��quel, de sua mistura e seus complexos com EDTA frente a Daphnia similis para utiliza����o na avalia����o do desempenho do processo de separa����o com membranas no tratamento de efluentes. Em um estudo de toxicidade, as intera����es do metal com o organismo-teste s��o influenciadas pela esp��cie testada, pela combina����o dos metais ou pela composi����o do meio aquoso. O ��on Cu2+ apresentou toxicidade superior ao Ni2+, sendo que na mistura desses dois ��ons, prevaleceu o resultado obtido para o Cu2+, decorrente de sua maior toxicidade. A complexa����o dos metais reduz significativamente o potencial t��xico dos metais

Toxicidade e bioacumula����o de cobre em micro-organismos fotoautotr��ficos

Microalgas e cianobact��rias t��m sido amplamente recomendadas para biomonitora����o de metais pesados e outros poluentes, sendo considerados indicadores sens��veis ��s altera����es ambientais e utilizados como organismos testes na regulamenta����o dos n��veis de metal. Estes micro-organismos fotossintetizantes s��o produtores prim��rios da base da cadeia alimentar aqu��tica e s��o os primeiros a serem afetados pela polui����o por metais pesados. O cobre �� um metal normalmente considerado como nutriente essencial para a vida aqu��tica mas pode ser t��xico para algumas esp��cies. Portanto, neste estudo foram avaliados o efeito t��xico e a bioacumula����o de cobre (II) em quatro esp��cies de micro-organismos fotoautotr��ficos componentes do fitopl��ncton dulc��cola, duas cianobact��rias filamentosas (Anabaena sp. e Oscillatoria sp) e duas microalgas da classe das clorof��ceas (Monorraphidium sp. e Scenedesmus sp.). O meio de cultivo utilizado nos ensaios foi o ASM-1 com e sem a presen��a de cobre (0,6 mg/L a 12 mg Cu2+/L) onde, o efeito t��xico do metal foi monitorado por contagem celular para as microalgas e por peso seco para as cianobact��rias. A bioacumula����o do metal foi avaliada da mesma forma para todos os micro-organismos, atrav��s de coletas de amostras no decorrer do experimento e determina����o da concentra����o de cobre em solu����o por espectrometria de absor����o at��mica com chama. Os resultados obtidos mostram que o efeito t��xico do metal �� diretamente proporcional �� concentra����o inicial para os micro-organismos estudados, mas que o cobre (II) foi mais t��xico para as cianobact��rias que para as microalgas verdes. A bioacumula����o teve uma rela����o direta com o efeito t��xico do metal sobre os micro-organismos. Os resultados obtidos permitem sugerir que cobre (II) tem efeito negativo no fitopl��ncton, inibindo o crescimento e alterando par��metros metab��licos como a fotoss��ntese. A bioacumula����o do metal pode comprometer os n��veis tr��ficos da cadeia alimentar, afetando seu transporte para seres superiores

Recupera����o de cobre de rejeitos de galvanoplastia utilizando resinas de troca i��nica

Neste estudo, a sor����o e recupera����o de ��ons met��licos de res��duos s��lidos industriais provenientes de uma ind��stria de galvanoplastia situada no Rio de Janeiro (Brasil) foram investigadas atrav��s da utiliza����o de duas resinas comerciais de troca i��nica: Lewatit VPOC 1800 (fortemente ��cida, tipo gel) e Lewatit VPOC 1960 (fortemente b��sica, tipo gel), produzidas pela Lanxess-Bayer Chemicals. As caracter��sticas f��sico-quimicas das resinas e do lodo galv��nico foram determinadas. Os estudos de sor����o das resinas foram conduzidos em batelada e em coluna. Baseado nesses estudos, os par��metros de sor����o e das curvas de ruptura foram determinados. Os estudos de equil��brio e cin��tica de sor����o tamb��m foram realizados. O res��duo de galvanoplastia era composto pelos metais: Cu2+, Fe3+, Al3+, Ni2+ e Cr3+. A capacidade de sor����o qe das resinas Lewatit VPOC 1800 variou entre 0,1-1,9 mg g-1 para Cu2+, 0,01-0,6 mg g-1 para Fe3+ e 0,2-0,4 mg g-1 para Al3+. Enquanto que para a resina Lewatit VPOC 1960, os valores de qe variou entre 0,01-0,4 mg g-1 para Cu2+ e 0,01 0,2 mg g-1 para Fe3+ dependendo da concentra����o do metal e do tempo de contato. A capacidade de sor����o para a resina Lewatit VPOC 1960 foi restrita para ��ons Cu2+ e Fe3+ os quais formam complexos ani��nicos com ��ons Cl-. O modelo de Freundlich foi o mais adequado para descrever o equil��brio de troca i��nica de ambas as resinas. J�� em rela����o ao mecanismo de sor����o, o modelo pseudo-segunda ordem tipo 1 foi o mais aplic��vel. O ponto de ruptura das resinas Lewatit VPOC 1800 e Lewatit VPOC 1960 em rela����o aos ��ons Cu2+ocorreu quando passou atrav��s da coluna, 1860 cm3 e 2220 cm3 de solu����o de res��duo s��lido respectivamente (20 g de resina, 100 mg L-1 de ��ons Cu2+, vaz��o de 60 cm3 min-1). Os ��ons met��licos Cu2+, Fe3+, Al3+, foram dessorvidos em alta propor����o da resina Lewatit VPOC 1800 passando pela coluna solu����o aquosa de H2SO4 2,4 mol L-1. J�� os metais Cu2+ e Fe3+ foram elu��dos da resina Lewatit VPOC 1960 com solu����o aquosa de HCl 2,0 mol L-1. A recupera����o seletiva de Cu2+ n��o foi alcan��ada porque Cu2+ e Fe3+ precipitam na mesma faixa de pH

Spectroscopic and thermal properties of short wavelength metal (II) complexes containing alpha-isoxazolylazo-beta-diketones as co-ligands

Two new azo dyes of alpha-isoxazolylazo-beta-dilcetones and their Ni(II) and Cu(II) complexes with blue-violet light wavelength were synthesized using a coupling component, different diazo components and metal (II) ions (Ni2+ and Cu2+). Based on the elemental analysis, MS spectra and FT-IR spectral analyses, azo dyes were unequivocally shown to exist as hydrazoketo and azoenol forms which were respectively obtained from the solution forms and from the solid forms. The action of sodium methoxide (NaOMe) on azo dyes in solutions converts hydrazoketo form into azoenol form, so azo dyes are coordinated with metal (II) ions as co-ligands in the azoenol forms. The solubility of all the compounds in common organic solvents such as 2,2,3,3-tetrafluoro-1-propanol (TFP) or chloroform (CHCl3) and absorption properties of spin-coating thin films were measured. The difference of absorption maxima from the complexes to their ligands was discussed. In addition, the TG analysis of the complexes was also determined, and their thermal stability was evaluated. It is found that these new metal (II) complexes had potential application for high-density digital versatile disc-recordable (HD-DVD-R) system due to their good solubility in organic solvents, reasonable and controllable absorption spectra in blue-violet light region and high thermal stability. (c) 2004 Elsevier B.V. All rights reserved.

CuO,CuCl���P2O5-ZnO-Na2O���������������������

���������������������������������������������������������������������������������������������������,���CuO���CuCl������������Cu2+���������������,���������������������������������,���������Cu2+���������������������������������P2O5-ZnO-Na2O������������������������������������������������������������������������������������������������������,CuO���CuCl������������P2O5-ZnO-Na2O������������������������������������������������������������������������������������������������Cu2+������������������������������������,���Cu2+������������������������6%���,���������1053 nm���������������������59.46 cm-1,���

MOFs basados en CuII-PDC-bpe (PDC= 2,5-piridindicarboxilato, bpe= 1,2-di(4piridil)eteno): Cristaloqu��mica de redes 2D tipo Herringbone

Comunicaci��n a congreso (p��ster): XXIV Simposio del Grupo Especializado de Cristalograf��a y Crecimiento Cristalino, GE3C. 23-26 de junio de 2014, Bilbao

Prepara����o e avalia����o de hidrog��is nanocomp��sitos �� base de alginato na remo����o de Cu (II) e Zn (II) de solu����es aquosas

Esta disserta����o teve como objetivo, a prepara����o de hidrog��is �� base de alginato contendo argila e material magn��tico em sua estrutura. Foram analisadas as modifica����es nas caracter��sticas f��sico-qu��micas dos hidrog��is preparados com diferentes reticulantes (CaCl2 e FeCl3) e diferentes concentra����es de material magn��tico (1 e 3 % m/m) e argila (1, 5 e 10 %). Ap��s isso, os hidrog��is foram avaliados quanto �� capacidade de remo����o de ��ons Cu2+ e Zn2+ de solu����es aquosas. As amostras foram caracterizadas quanto �� composi����o qu��mica por espectroscopia na regi��o do infravermelho (FTIR), quanto �� morfologia por microscopia ��ptica e microscopia eletr��nica de varredura (SEM) e quanto ��s propriedades magn��ticas por magnetometria de amostra vibrante (VSM). Atrav��s da t��cnica de difratometria de raios-X (XRD), foi poss��vel verificar a natureza do material magn��tico e a dispers��o da argila nos hidrog��is. A estabilidade t��rmica das amostras foi analisada por an��lise termogravim��trica (TGA). Os resultados mostraram que tanto a argila como o material magn��tico ficaram bem dispersos nas amostras. De forma geral, foram preparados hidrog��is com morfologia esf��rica, sendo que os hidrog��is de alginato de c��lcio tenderam a apresentar maior resist��ncia t��rmica do que os hidrog��is de alginato de ferro. Todas as amostras magn��ticas apresentaram comportamento superparamagn��tico, por��m as amostras de alginato de ferro mostraram-se quebradi��as ap��s o intumescimento em ��gua. O tempo m��dio de equil��brio de intumescimento foi de 240 minutos. Os resultados de cin��tica de adsor����o mostraram que os hidrog��is de alginato de c��lcio preparados nas condi����es avaliadas nesta Disserta����o foram eficientes na remo����o dos ��ons Cu2+ e Zn2+, sendo que o cobre apresentou maior afinidade pelo hidrogel do que o zinco