Effect of metal oxidation state on FRET: a Cu(I) silent but selectively Cu(II) responsive fluorescent reporter and its bioimaging applications

Copper(II) and copper(I) complexes of a newly designed and crystallographically characterized Schiff base (HL) derived from rhodamine hydrazide and cinnamaldehyde were isolated in pure form formulated as Cu(L)(NO3)] (L-Cu) (1) and Cu(HL)(CH3CN)(H2O)]ClO4 (HL-Cu) (2), and characterized by physicochemical and spectroscopic tools. Interestingly, complex 1 but not 2 offers red fluorescence in solution state, and eventually HL behaves as a Cu(II) ions selective FRET based fluorosensor in HEPES buffer (1 mM, acetonitrile-water: 1/5, v/v) at 25 degrees C at biological pH with almost no interference of other competitive ions. The dependency of the FRET process on the +2 oxidation state of copper has been nicely supported by exhaustive experimental studies comprising electronic, fluorimetric, NMR titration, and theoretical calculations. The sensing ability of HL has been evaluated by the LOD value towards Cu(II) ions (83.7 nM) and short responsive time (5-10 s). Even the discrimination of copper(I) and copper(II) has also been done using only UV-Vis spectroscopic study. The efficacy of this bio-friendly probe has been determined by employing HL to detect the intercellular distribution of Cu(II) ions in HeLa cells by developing image under fluorescence microscope.

Synergistic Effect of Mo plus Cu Codoping on the Photocatalytic Behavior of Metastable TiO2 Solid Solutions

Codoping with Cu and Mo is shown to have a synergistic effect on the photocatalytic activity of TiO2. The enhancement in activity is observed only if the synthesis route results in TiO2 in which (Cu, Mo) codopants are forced into the TiO2 lattice. Using X-ray photoelectron spectroscopy, Cu and Mo are shown to be present in the +2 and +6 oxidation states, respectively. A systematic study of the ternary system shows that TiO2 containing 6 mol % CuO and 1.5 mol % MoO3 is the most active ternary composition. Ab initio calculations show that codoping of TiO2 using (Mo, Cu) introduces levels above the valence band, and below the conduction band, resulting in a significant reduction in the band gap (similar to 0.8 eV). However, codoping also introduces deep defect states, which can have a deleterious impact on photoactivity. This helps rationalize the narrow compositional window over which the enhancement in photocatalytic activity is observed.

Ionic Bonding between Artificial Atoms

Conventional solids are prepared from building blocks that are conceptually no larger than a hundred atoms. While van der Waals and dipole-dipole interactions also influence the formation of these materials, stronger interactions, referred to as chemical bonds, play a more decisive role in determining the structures of most solids. Chemical bonds that hold such materials together are said to be ionic, covalent, metallic, dative, or otherwise a combination of these. Solids that utilize semiconductor nanocrystal quantum dots as building units have been demonstrated to exist; however, the interparticle forces in such materials are decidedly not chemical. Here we demonstrate the formation of charge transfer states in a binary quantum dot mixture. Charge is observed to reside in quantum confined states of one of the participating quantum dots. These interactions lead to materials that may be regarded as the nanoscale analog of an ionic solid. The process by which these materials form has interesting parallels to chemical reactions in conventional chemistry.

Synthesis, crystal structure and spectroscopic and electrochemical properties of bridged trisbenzoato copper-zinc heterobinuclear complex of 2,2 `-bipyridine

The synthesis of the heterobinuclear copper-zinc complex CuZn(bz)(3)(bpy)(2)]ClO4 (bz = benzoate) from benzoic acid and bipyridine is described. Single crystal X-ray diffraction studies of the heterobinuclear complex reveals the geometry of the benzoato bridged Cu(II)-Zn(II) centre. The copper or zinc atom is pentacoordinate, with two oxygen atoms from bridging benzoato groups and two nitrogen atoms from one bipyridine forming an approximate plane and a bridging oxygen atom from a monodentate benzoate group. The Cu-Zn distance is 3.345 angstrom. The complex is normal paramagnetic having mu(eff) value equal to 1.75 BM, ruling out the possibility of Cu-Cu interaction in the structural unit. The ESR spectrum of the complex in CH3CN at RT exhibit an isotropic four line spectrum centred at g = 2.142 and hyperfine coupling constants A(av) = 63 x 10(-4) cm(-1), characteristic of a mononuclear square-pyramidal copper(II) complexes. At LNT, the complex shows an isotropic spectrum with g(parallel to) = 2.254 and g(perpendicular to) =2.071 and A(parallel to) = 160 x 10(-4) cm(-1). The Hamiltonian parameters are characteristic of distorted square pyramidal geometry. Cyclic voltammetric studies of the complex have indicated quasi-reversible behaviour in acetonitrile solution. (C) 2014 Elsevier B.V. All rights reserved.

High-Temperature Deformation Processing Map Approach for Obtaining the Desired Microstructure in a Multi-component (Ni-Ti-Cu-Fe) Alloy

An equiatomic NiTiCuFe multi-component alloy with simple body-centered cubic (bcc) and face-centered cubic solid-solution phases in the microstructure was processed by vacuum induction melting furnace under dynamic Ar atmosphere. High-temperature uniaxial compression experiments were conducted on it in the temperature range of 1073 K to 1303 K (800 degrees C to 1030 degrees C) and strain rate range of 10(-3) to 10(-1) s(-1). The data generated were analyzed with the aid of the dynamic materials model through which power dissipation efficiency and instability maps were generated so as to identify the governing deformation mechanisms that are operative in different temperature-strain rate regimes with the aid of complementary microstructural analysis of the deformed specimens. Results indicate that the stable domain for the high temperature deformation of the multi-component alloy occurs in the temperature range of 1173 K to 1303 K (900 degrees C to 1030 degrees C) and (epsilon) over dot range of 10(-3) to 10(-1.2) s(-1), and the deformation is unstable at T = 1073 K to 1153 K (800 degrees C to 880 degrees C) and (epsilon) over dot = 10(-3) to 10(-1.4) s(-1) as well as T = 1223 K to 1293 K (950 degrees C to 1020 degrees C) and (epsilon) over dot = 10(-1.4) to 10(-1) s(-1), with adiabatic shear banding, localized plastic flow, or cracking being the unstable mechanisms. A constitutive equation that describes the flow stress of NiTiCuFe multi-component alloy as a function of strain rate and deformation temperature was also determined. (C) The Minerals, Metals & Materials Society and ASM International 2015

Synthesis, X-ray structure and in vitro cytotoxicity studies of Cu(I/II) complexes of thiosemicarbazone: special emphasis on their interactions with DNA

4-(p-X-phenyl)thiosemicarbazone of napthaldehyde {where X = Cl (HL1) and X = Br (HL2)}, thiosemicarbazone of quinoline-2-carbaldehyde (HL3) and 4-(p-fluorophenyl) thiosemicarbazone of salicylaldehyde (H2L4) and their copper(I) {Cu(HL1)(PPh3)(2)Br]center dot CH3CN (1) and Cu(HL2)(PPh3)(2)Cl]center dot DMSO (2)} and copper(II) {((Cu2L2Cl)-Cl-3)(2)(mu-Cl)(2)]center dot 2H(2)O (3) and Cu(L-4)(Py)] (4)} complexes are reported herein. The synthesized ligands and their copper complexes were successfully characterized by elemental analysis, cyclic voltammetry, NMR, ESI-MS, IR and UV-Vis spectroscopy. Molecular structures of all the Cu(I) and Cu(II) complexes have been determined by X-ray crystallography. All the complexes (1-4) were tested for their ability to exhibit DNA-binding and - cleavage activity. The complexes effectively interact with CT-DNA possibly by groove binding mode, with binding constants ranging from 10(4) to 10(5) M-1. Among the complexes, 3 shows the highest chemical (60%) as well as photo-induced (80%) DNA cleavage activity against pUC19 DNA. Finally, the in vitro antiproliferative activity of all the complexes was assayed against the HeLa cell line. Some of the complexes have proved to be as active as the clinical referred drugs, and the greater potency of 3 may be correlated with its aqueous solubility and the presence of the quinonoidal group in the thiosemicarbazone ligand coordinated to the metal.

Influence of deposition time on the properties of electrodeposited Cu(In,Al)Se-2 thin films

Cu(In,Al)Se-2 films are grown using single step electrodeposition technique. The film properties are studied by varying the deposition time from 500 to 2000 s. Peaks corresponding to elemental Se and Cu2Se phase started appearing from 1200 s of deposition. The composition is changed significantly after 1500 S. Se concentration increased from 57 to 68% with the increase in the deposition time. The Cu2Se phase is dominant in the films deposited for a duration of 2000 s and the grain size increased from 1.12 to 2.15 mu m in this film. Raman analysis confirmed the presence of Se and Cu2Se phase in C1200. In C1500 and C2000 the spectra showed prominent mode corresponding to Cu2Se. The thickness of the film increased from 0.85 to 2.3 mu m with the increase in the deposition time. All the films showed p-type conductivity and resistivity reduced with increased thickness. (C) 2015 Elsevier Ltd. All rights reserved.

Structural diversities in Cu(I) and Ag(I) sulfonate coordination polymers and their anion exchange properties

Two new Cu(I) compounds, namely Cu-2(bds)(bpy)(2)]center dot 2H(2)O (1) and Cu-4(bds)(2)(azpy)(4)]center dot 6H(2)O (3) (where bds = benzene-1,3-disulfonate, bpy = 4,4'-bipyridine and azpy = 4,4'-azopyridine), and four Ag(I) compounds, namely Ag-2(bds)(bpy)(2)]center dot 2H(2)O (2), Ag-2(bds)(azpy)(2)]center dot 4H(2)O (4), Ag(bds)(1/2)(bpe)]center dot 3H(2)O (5), and Ag-4(bds)(2)(tmdp)(4)]center dot 9H(2)O (6) (where bpe = 1,2-di(4-pyridyl) ethylene and tmdp = 4,4'trimethylenedipyridine), have been synthesized, and their structures were determined and characterized by elemental analysis, IR, UV-vis and thermal studies. The structure of the compounds changed from 1D (1 and 2) to 2D (3-5) and interpenetrated 3D (6). In the case of 5, a solid-state 2 + 2] photochemical cycloaddition reaction has been performed. Compound 2 exhibits a reversible anion exchange for perchlorate and permanganate, whereas the other compounds (1, 3-6) exhibit an irreversible anion exchange behaviour for perchlorate. Catalytic studies on 2 indicate Lewis acidity.

Effect of Ni content on the diffusion-controlled growth of the product phases in the Cu(Ni)-Sn system

A strong influence of Ni content on the diffusion-controlled growth of the (Cu,Ni)(3)Sn and (Cu,Ni)(6)Sn-5 phases by coupling different Cu(Ni) alloys with Sn in the solid state is reported. The continuous increase in the thickness ratio of (Cu,Ni)(6)Sn-5 to (Cu,Ni)(3)Sn with the Ni content is explained by combined kinetic and thermodynamic arguments as follows: (i) The integrated interdiffusion coefficient does not change for the (Cu,Ni)(3)Sn phase up to 2.5 at.% Ni and decreases drastically for 5 at.% Ni. On the other hand, there is a continuous increase in the integrated interdiffusion coefficient for (Cu,Ni)(6)Sn-5 as a function of increasing Ni content. (ii) With the increase in Ni content, driving forces for the diffusion of components increase for both components in both phases but at different rates. However, the magnitude of these changes alone is not large enough to explain the high difference in the observed growth rate of the product phases because of Ni addition. (iv) Kirkendall marker experiments indicate that the Cu6Sn5 phase grows by diffusion of both Cu and Sn in the binary case. However, when Ni is added, the growth is by diffusion of Sn only. (v) Also, the observed grain refinement in the Cu6Sn5 phase with the addition of Ni suggests that the grain boundary diffusion of Sn may have an important role in the observed changes in the growth rate.

Effect of Ga content in Cu(Ga) on the growth of V3Ga following bronze technique

Diffusion controlled growth rate of V3Ga in the Cu(Ga)/V system changes dramatically because of a small change in Ga content in Cu(Ga). One atomic percent increase from 15 to 16 leads to more than double the product phase layer thickness and a decrease in activation energy from 255 to 142 kJ/mol. Kirkendall marker experiment indicates that V3Ga grows because of diffusion of Ga. Role of different factors influencing the diffusion rate of Ga and high growth rate of V3Ga are discussed. (C) 2015 Elsevier Ltd. All rights reserved.

Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 degrees C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating. (C) 2016 Elsevier B.V. All rights reserved.

Graphene as a diffusion barrier for isomorphous systems: Cu-Ni system

Electrochemical exfoliation technique using the pyrophosphate anion derived from tetra sodium pyrophosphate was employed to produce graphene. As-synthesized graphene was then drop dried over a cold rolled Cu sheet. Ni coating was then electrodeposited over bare Cu and graphene-Cu substrates. Both substrates were then isothermally annealed at 800 degrees C for 3 h. WDS analysis showed substantial atomic diffusion in annealed Ni-Cu sample. Cu-graphene-Ni sample, on the other hand, showed negligible diffusion illustrating the diffusion barrier property of the graphene coating. (C) 2016 Elsevier B.V. All rights reserved.

Stabilization of Cu-7 clusters in azide networks: syntheses, structures and magnetic behaviour

Two new azide bridged copper(II) coordination polymer compounds, Cu-7(N-3)(14)(C3H10N2)(C4H13N3)]n (I) and Cu-7(N-3)(14)(C3H10N2)(C5H15N3)(2)](n) (II) where C3H10N2 = 1,2-diaminopropane (1,2-DAP); C4H13N3 = di-ethylenetriamine (DETA); C5H15N3 = N-2-aminoethyl-1,3-propanediamine (AEDAP)] were prepared by employing a room temperature diffusion technique involving three layers. Single crystal studies reveal that both compounds I and II, have similar connectivity forming Cu7 clusters through end-on (EO) bonding of the azide. The Cu-7 clusters are connected through end-to-end (EE) connectivity of the azides forming three-dimensional structures. Magnetic studies confirmed the ferromagnetic interactions within the Cu-7 units and revealed the occurrence of concomitant ferro- and antiferro-magnetic interactions between these clusters. As a result I behaves as a weak-ferromagnet with T-C = 10 K.

Comments on ``Influence of chemical reaction and viscous dissipation on MHD mixed convection flow'' by K. Das JMST 28 (5) (2014) 1881 similar to 1885] and ``Cu-water nanofluid flow and heat transfer over a shrinking sheet'' by K. Das JMST 28 (12) 5089 similar to 5094]

In this letter, we submit our comment on the following recently published papers by Kalidas Das: (1) ``Influence of chemical reaction and viscous dissipation on MHD mixed convection flow,'' Journal of Mechanical Science and Technology 28 (5) (2014) 1881-1885; and (2) ``Cu-water nanofluid flow and heat transfer over a shrinking sheet,'' Journal of Mechanical Science and Technology 28 (12) (2014) 5089-5094. The authors attempt to present the similarity solutions in both papers. We comment that the similarity transformations considered in Refs. 1, 2] are incorrect. Thus, the results presented by Kalidas Das lead to invalid conclusions.

Tailored specular reflectance properties of bulk Cu based novel intermetallic alloys

Significant research has been pursued to develop solar selective metallic coatings using a variety of coating deposition techniques, with limited attempts to assess the properties of bulk metallic materials for solar energy applications. In developing bulk solar reflectors with good reflectance in the entire solar range, we report a new class of reflector materials based on Cu-Sn intermetallics with tailored substitution of aluminium or zinc. Our experimental results suggest that the arc melted-suction cast Cu (78.8 at%)-Al (21.2 at%) alloy with nanoscale surface roughness can exhibit a combination of 89% bulk specular reflectance and 83% bulk solar reflectance, together with a hardness of 2 GPa. We show that the present alloy design approach paves the way for further opportunities of tuning the spectral properties of this new class of solar reflector material. (C) 2016 Elsevier B.V. All rights reserved.