State Structural Transformation Research Articles

Structural and phase transformations control in Ti and Al cathode materials, WC-Co substrate, and Ti1-xAlxN coating to improve their physico-mechanical and wear properties

The paper analyzed temperature ranges of aggregate/polymorphic state changes, phase and structural transformations in Al, Ti, WC-Co, and Ti1-xAlxN, leading to the gradient of thermo-physical and physico-mechanical properties of cathodes, substrate, and coating. The critical temperatures for Al and Ti are the points of the exo- or endothermic effect occurrence at 933 K (TmAl) and 1155.5 K (Tα-Ti→β-Ti), respectively. The hardness of the WC-Co / Ti1-xAlxN composition varies with the heating temperature of the WC-Co before coating deposition. The optimal heating interval for WC-Co is 873…963 K. The structuring process of the Ti1-xAlxN coating was investigated in the temperature range 673…1073 K before the spinodal decomposition of c-TiAlN into metallic c-TiN and dielectric-semiconductor c-AlN. Physico-mechanical properties of the Ti1-xAlxN coatings were determined using a FISCHERSCOPEH100C measurement system per the standard DINENISO14577-1. Wear tests were carried out according to the “finger-disk” scheme in a coolant-cutting fluid on a laboratory friction machine. The optimal temperature conditions for the deposition of a nanostructured Ti1-xAlxN coating with a minimum phase and elemental composition gradient and microdroplets number, a complex of high physico-mechanical properties, wear, and cracking resistance have been established. The Ti1-xAlxN coatings efficiency has been increased by controlling the thermo-physical and physico-mechanical properties of Ti and Al cathodes, the substrate (hard alloy WC-Co), and the Ti1-xAlxN coating in-process of their heating and cathodic arc evaporation. Multifunctional dependency graphs of the physico-mechanical properties and the friction coefficient of the Ti1-xAlxN coatings on the Al = x content have been developed. The relationship between the resistance of the coating to plastic deformation and the coefficient of friction has been established.

Paradigm of state regulation and structural transformation of the national economy from the standpoint of homeostasis

Paradigm of state regulation and structural transformation of the national economy from the standpoint of homeostasis

State intervention, South-South cooperation and structural transformation: the (ignored) case of Brazil-Venezuela cooperation for equity of access to university education, 2003-2016

State intervention, South-South cooperation and structural transformation: the (ignored) case of Brazil-Venezuela cooperation for equity of access to university education, 2003-2016

Excited State Electronic Interconversion and Structural Transformation of Engineered Red-Emitting Green Fluorescent Protein Mutant.

Red fluorescent proteins with a large Stokes shift offer a limited autofluorescence background and are used in deep tissue imaging. Here, by introducing the free amino group in Aequorea victoria, the electrostatic charges of the p-hydroxybenzylidene imidazolinone chromophore of green fluorescent protein (GFP) have been altered resulting in an unusual, 85 nm red-shifted fluorescence. The structural and biophysical analysis suggested that the red shift is due to positional shift occupancy of Glu222 and Arg96, resulting in extended conjugation and a relaxed chromophore. Femtosecond transient absorption spectra exhibited that the excited state relaxation dynamics of red-shifted GFP (rGFP) (τ4 = 234 ps) are faster compared to the A. victoria green fluorescent protein (τ4 = 3.0 ns). The nanosecond time-resolved emission spectra of rGFP reveal the continuous spectral shift during emission by a solvent reorientation in the chromophore. Finally, the molecular dynamics simulations revealed the rearrangement of the hydrogen bond interactions in the chromophore vicinity, reshaping the symmetric distribution of van der Waals space to fine tune the GFP structure resulting from highly red-shifted rGFP.

A reversible photochemical solid-state transformation in an interpenetrated 3D metal-organic framework with mechanical softness.

We synthesized a two-fold interpenetrated 3D MOF with two crystallographically distinct C[double bond, length as m-dash]C bonds, which undergoes [2+2] photo-cycloaddition and thermal reversible reaction, in a single-crystal-to-single-crystal (SCSC) manner. The softer nature and comparable mechanical properties of the crystals of the parent and cyclized MOFs revealed by nanoindentation allowed rationalizing their structural softness and SCSC transformation behaviour.

Recent Advances in Single-Crystal-to-Single-Crystal Transformation at the Discrete Molecular Level

The present review focuses on the solid state structural transformations in discrete molecules. Since the molecules in the crystal lattice are closely packed, any transformation in the solid state is difficult due to restricted movement of the molecules. These transformations can be triggered by external stimuli, such as light, heat, uptake or exchange of solvent, mechanochemical force, etc. which may be observed by a change in their physical properties like color, magnetism, porosity, and optical. Single-crystal-to-single-crystal (SCSC) transformations in metal–organic frameworks and coordination polymers are well documented; however, reports on SCSC transformations at the discrete molecular level still remain scarce. In this review, we have compiled some interesting examples from the literature on SCSC transformation at the discrete molecular level using various external stimuli.

A molecular beacon-based DNA switch for reversible pH sensing in vesicles and live cells.

In this Communication, a molecular beacon-based DNA switch (LMB) is developed as an efficient and reversible pH sensing probe. Remarkably, LMB exhibited reversible structural transition between the closed (molecular beacon) and open (A-motif) states very efficiently in synthetic vesicles and live cells without the need for any transfection agents.

Highly efficient syntheses of nano mixed-anions lead(II) thiocyanate/nitrate and lead(II) thiocyanate coordination polymers by sonochemical process

Nanostructures of the three-dimensional coordination polymers with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), [Pb(4-bpdh)(NO3)(μ-NCS)]n (1) and [Pb(4-bpdh)(μ-NCS)2]n (2), have been synthesized by a sonochemical process at different concentrations and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The solid state structural transformations of nano-compounds 1, 2 by anion-replacement processes under mechanochemical reaction, have been verified by IR and PXRD measurements. The SEM images showed that morphology change occurs on nanostructures during solid state anion-replacements.

Irreversible Crystal to Crystal Transformation of Nano Lead(II) Coordination Polymer by Solid State Anion-Replacement

Irreversible crystal-to-crystal transformation of 3D lead (II) coordination polymer with the ligand 1H-1,2,4-triazole-3-carboxylic acid (HL), [Pb (L)(μ1,1-NCS)(H2O)]n (1) to 3D supramalecular compound [Pb (L)(μ2-I)]n (2) by solid state anion-replacement have been studied. Structural determination of compound 2 reveals the Pb (II) ion is five coordinated with hemidirected geometry, bonded to one nitrogen atom, two oxygen atoms from the Lˉ ligand and two iodide ions. The irreversible solid state structural transformation of compound 1 to compound 2, by anion-replacement processes under mechanochemical reaction have been verified by PXRD measurements. Nanoparticles of compound 1 was synthesized by sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that no morphology change occur during this solid state anion-replacement.

Mechanochemical dehydrochlorination and chelation reaction in the solid state: from a molecular salt to a coordination complex

We report the solid state structural transformation of a hydrogen bonded complex salt into a metal complex via dehydrochlorination using mechanochemistry. A crystalline salt containing a large and flexible bidentate dication hydrogen bonded to a tetrachlorometalate (II) anion has been ground in the presence of KOH. Substitution of charge-assisted hydrogen bonding interactions by coordination bonds via chelation has been demonstrated by single-crystal and powder X-ray diffraction analysis. By-product water molecules are included in the structure, playing an important role establishing electrostatic interactions. The irreversibility property of the transformation of the coordination complex into a hydrogen bonded complex salt was determined experimentally. Density functional calculations were used to attempt a rationalisation of the structural results into the mechanochemical reactions.

Solid state structural transformation of bromide coordination polymer to chloride by anion replacement; new precursors for preparation of PbBr2 and PbCl2 nanoparticles

Reversible anion-exchange of 2D lead(ii) coordination polymers from [Pb(4-bpdb)Br2]n (1) to [Pb(4-bpdb)Cl2]n (2) by solid state anion-replacement has been studied.

Mechanochemical solid state anion-exchange of lead(ii) coordination polymers via an intermediate coordination polymer; new precursors for the preparation of PbBr2/Pb3O2Br2, PbBr(OH) and PbO nanoparticles

The reversible crystal-to-crystal transformations of a 1D lead(II) coordination polymer with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), from [Pb(4-bpdh)Br2]n () to intermediate [Pb(4-bpdh)(Br)(NO3)]n () and [Pb(4-bpdh)(NO3)2(H2O)]n () by a solid state anion-replacement processes under mechanochemical reactions, have been studied. The reversible solid state structural transformation of compound to compound and then by anion replacement have been verified by PXRD and IR measurements. PbBr2, PbBr(OH), Pb3O2Br2 and PbO nanoparticles were obtained by the thermal decomposition of compounds , and in oleic acid at 180 °C in an air atmosphere, respectively. These nanoparticles were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM).

Solid state and sonochemical syntheses of nano lead(II) chloride and bromide coordination polymers from its nitrate analog via mechanochemical crystal to crystal transformations

Reversible crystal-to-crystal transformations of 3D lead(II) coordination polymers with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), from nitrate analoge [Pb(4-bpdh)(NO3)2(H2O)]n (1) to [Pb(4-bpdh)(NO3)(Br)]n (2), [Pb(4-bpdh)(Br)2]n (3), [Pb(4-bpdh)(NO3)(Cl)]n (4) and [Pb(4-bpdh)(Cl)2]n (5) by solid state anion-replacement processes under mechanochemical reactions, have been studied. The reversible solid state structural transformations of compounds 1–5, by anion-replacement processes under mechanochemical reaction, have been verified by PXRD measurements. Nanoparticles of compounds were synthesized by sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that morphology change occurs during solid state anion-replacements of nanocrystals.

Solid state syntheses of nano lead(II) iodide triazole carboxylate coordination polymer from its bromide/thiocyanate/chloride analogs via mechanochemical crystal to crystal transformations

Irreversible crystal-to-crystal transformations of 3D lead(II) coordination polymers with the ligand 1H-1,2,4-triazole-3-carboxylic acid (HL), [Pb(L)(μ2-Br)(H2O)]n (1), [Pb(L)(μ1,1-NCS)(H2O)]n (2) and [Pb(L)(μ2-Cl)(H2O)]n (3) to 3D supramolecular compound [Pb(L)(μ2-I)]n (4) by solid state anion-replacement processes under mechanochemical reactions, have been studied. The thermal stabilities of compounds 1–4 were studied by thermogravimetric and differential thermal analyses. The irreversible solid state structural transformations of compounds 1–4, by anion-replacement processes under mechanochemical reaction, have been verified by PXRD measurements. Nanoparticles of compounds 1 and 2 were synthesized by sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy, elemental analyses, thermogravimetric and differential thermal analyses. The SEM images showed that no morphology change occurs during solid state anion-replacements of nanocrystals.

Solid State Structural Transformation of Tetraborate into Monoborate in the Interlayer Galleries of Reconstructed ZnAl Layered Double Hydroxide

Remediation of borate in wastewaters using adsorbents is important from an environmental perspective. Understanding the nature of borate species and their relative abundance is essential in its remediation which varies with the local environment offered by the adsorbent. ZnAl oxide (ZnAl2-Cl CLDH) obtained by calcination of ZnAl layered double hydroxide (LDH) with Zn/Al atomic ratio of 2.0 and chloride as interlayer anion (ZnAl2-Cl LDH) was studied for borate uptake. Uptake of borate reconstructed the oxide phase to tetraborate containing LDH phase. On slow drying of this sample, a solid state structural transformation of tetraborate to monoborate occurred in the intergalleries of LDH. This transformation in solid state was probed by powder X-ray diffraction (PXRD), Fourier-transformed infrared (FT-IR) spectroscopy, 11B and 1H magic-angle spinning (MAS), nuclear magnetic resonance (NMR), and thermogravimetric analysis. Hydrolytic dissociation of intercalated tetraborate (B4O72–) into monoborate species co...

Solid state structural transformation of 1D to intermediate 2D and then to 3D porous coordination polymer by anion replacement; new precursors for preparation of PbCl2, Pb3O2Cl2 and PbO nanoparticles

A reversible anion exchange of 1D lead(II) coordination polymers with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), from [Pb(4-bpdh)Cl2]n (1) to intermediate 2D [Pb(4-bpdh)(Cl)(NO3)]n (2) and then 3D porous coordination polymer [Pb(4-bpdh)(NO3)2(H2O)]n (3) by solid state anion replacement processes under mechanochemical reactions, have been studied. The reversible solid state structural transformations of compound 1 to compound 2 and then 3 by anion replacement have been verified by PXRD and IR spectroscopy. PbCl2, Pb3O2Cl2 and PbO nanoparticles were obtained by thermal decomposition of compounds 1, 2 and 3 in oleic acid as surfactant at 180 °C under an air atmosphere, respectively. These nanoparticles were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM).

Sports Cars, Sleaze and Gamma Rays: Rhineland-Palatinate Elects its First Red-Green Government

The 2011 election in Rhineland-Palatinate was a political earthquake: Following a string of political scandals, the SPD lost almost ten percentage points of their support, while the CDU could hardly improve on their disastrous 2006 result. The FDP is no longer represented in the state parliament. The Greens more than tripled their last result, allowing them to enter a coalition with the SPD for the first time. Analyses at the municipal level show that the party improved most in their urban strongholds while still showing a (relatively) weak performance in rural areas. This will make it difficult to sustain the momentum of their victory. Moreover, the SPD is battered and bruised and needs to select a new leader, but veteran minister president Kurt Beck shows no inclination to step down. This does not bode well for a coalition that needs to organise the state's fiscal consolidation and structural transformation.

Reversible luminescence switching between single and dual emissions of bipyridinium-type organic crystals

An excitation-wavelength-dependent luminescence behavior of a bipyridinium derivative, together with its luminescence switching between single- and dual-emissions upon reversible solid state structural transformation, has been presented.

Solid-state structural transformations in metal organic-inorganic hybrids constructed from terbium(iii) complexes and iodocuprate clusters

Using precursors of the type [Tb(DMSO)8]I3 (a) and [Tb(DMF)8]I3 (b), syntheses of two new heterometal organic–inorganic hybrid complexes based on discrete iodocuprate clusters [Tb(DMSO)8][Cu2I5] (1) and [Tb(DMF)8][CuI3][I] (2), respectively, are reported. Though stable in air for few days, the colorless complex 1 slowly turns into a purple-colored mixture over the course of several days. Two complexes, namely [Tb(DMSO)8][CuI3][I] (3) and [Tb(DMSO)8](I)2(I3) (4), were isolated from this mixture and characterized structurally, the I3− anion in latter being responsible for the purple color of this mixture. In comparison, complex 2 is quite deliquescent in air but undergoes solid state structural transformation in a confined environment of paratone to afford a 2D honeycomb-like microporous structure containing mixed-valent copper atoms [Tb(DMF)6(H2O)3][CuII2CuI7I14]2∞ (5), the bifurcate H-bonding between water ligands on terbium and iodides of the Cu–I cluster playing a pivotal role in the evolution of its structure. Single crystal X-ray structures are reported for all the complexes. Thermal and luminescent properties of 1 and 2, complexes, which were obtained exclusively and in pure form, are described. Compared to the precursor terbium iodide complexes (a) and (b), the high energy transitions in the excitation spectra of the complexes 1 and 2 are quenched by auto-ionization of the carriers in the material.

Reversible solid state structural transformation of a polyhapto lead(ii) polymeric chain to a tetrahapto lead(ii) two-dimensional network by thermal dehydration with no change in nanoplate morphology

A reversible solid state structural transformation of a new 1D lead(II) coordination polymer [Pb(MPOAc)2(H2O)]n (1), (MPOAc−: mono phenyl acetate) involving in situ ligand synthesis with O7Pb⋯C6 coordination sphere to a 2D supramolecular network [Pb(MPOAc)2]n (2) with O6Pb⋯C4 coordination environment has been observed upon heating and dehydration. This change in coordination-mode was confirmed by single-crystal X-ray diffraction analyses of compounds 1 and 2. Thermogravimetric (TG) and differential thermal analyses (DTA) were employed to study the thermal stabilities of compounds 1 and 2. Powder X-ray diffraction experiments showed that the structural transformation occurs in the batch powder samples and lead to monophasic products. Nanoplates of compound 1 were synthesized by a microwave-assisted process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that no morphology change occurs during this solid state structural transformation.