Thermodynamic Calculation in Elimination of Water Pollutants at Hydro‐geo‐chemical Barriers

Thermodynamic saturation coefficients (K_s) and transformation indices (I_t) can be used to evaluate the possibility of forming hydro‐geo‐chemical precipitation barriers and assess the solid phase (rock) stability in aquifers. Calculations are made on the basis of data on water pH, E_h, conductivity (x) and some relevant ion concentrations. The dependencies of K₂ and I_t on water pH and E_h values can be expressed graphically to estimate the barriers parameters. Barrier generation leads to a decrease in concentrations of pollutants due mainly to precipitation, co‐precipitation and/or sorption processes. Using the diagram K_s, I_t= f (pH, E_h), supplemented with representative data on concentrations of pollutants before and after the barrier, the elimination and migration of pollutants can be roughly evaluated (predicted) only on the basis of determining pH and E_h values of water and concentrations of ions participating in the barrier formation. The proposed method is applied to assess the migration and elimination of pollutants (U, ²²⁶Ra, β‐emitters, SO₄²) in Bulgarian uranium mine surroundings.     

Two novel organic–inorganic hybrid materials from tetrachloridometallate(II) salts and 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium

Two organic–inorganic hybrid compounds have been prepared by the combination of the 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium cation with perhalometallate anions to give 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium tetrachloridocobaltate(II), (C₁₂H₁₂N₂)[CoCl₄], (I), and 4‐[(E)‐2‐(pyridin‐1‐ium‐2‐yl)ethenyl]pyridinium tetrachloridozincate(II), (C₁₂H₁₂N₂)[ZnCl₄], (II). The compounds have been structurally characterized by single‐crystal X‐ray diffraction analysis, showing the formation of a three‐dimensional network through X—H...Cl_nM⁻ (X = C, N⁺; n = 1, 2; M = Co^II, Zn^II) hydrogen‐bonding interactions and π–π stacking interactions. The title compounds were also characterized by FT–IR spectroscopy and thermogravimetric analysis (TGA).     

The Crystal Structure of InGaO3(ZnO)4: A Single Crystal X‐ray and Electron Diffraction Study

The crystal structure of the mixed oxide InGaO₃(ZnO)₄ has been determined from electron diffraction and single‐crystal X‐ray diffraction data. The compound crystallises in a hexagonal space group (P6₃/mmc; No. 194), deduced from convergent beam electron diffraction (CBED). Single crystals of InGaO₃(ZnO)₄ were grown from a K₂MoO₄ flux in sealed platinum tubes. Single crystal structure refinement from XRD data [a = 3.2850(2) Å; c = 32.906(3) Å; Z = 2; 4232 data, R₁ = 0.0685] reveals a compound with oxygen anions forming a closest‐packed arrangement. Within this packing In³⁺ cations occupy octahedral interstices, forming layers of edge sharing octahedra. In between these layers are regions with composition [Zn₄GaO₅]⁺ forming a wurtzite type of structure. Inversions of the ZnO₄ tetrahedra occurs (i) at the InO₆ octahedral layer and (ii) halfway in the wurtzite type region, where the inversion boundary is built by Ga³⁺ in trigonal bipyramidal coordination with a long Ga–O_apical distance of 2.19(1) Å. The site occupation of Zn²⁺ and Ga³⁺, respectively, was confirmed by bond valence sum calculations. The compounds described here have the same structural charactistics as other known members with general formula ARO₃(ZnO)_m with m = integer.     

Volumetric Properties for the Electrolyte (NaCl,NaBr and NaI) Monosaccharide (D‐Mannose and D‐Ribose)‐Water Systems at 298.15 K

Densities have been measured for the electrolyte (NaCl, NaBr and NaI)‐monosaccharide (D ‐mannose and D‐ribose)‐water solutions at 298.15 K. These data have been used to calculate the apparent molar volumes of the saccharides (V_Φ,S) and electrolytes (V_Φ,E) in the studied solutions. Infinite dilution apparent molar volumes, V_Φ,S⁰ and V_Φ,E⁰, have been evaluated, together with the standard transfer volumes of the saccharides (Δ_tV_S⁰) from water to aqueous electrolyte solutions and those of the electrolytes (Δ_tV_E⁰) from water to aqueous saccharide solutions. It was shown that both the Δ_tV_S⁰ and Δ_tV_E⁰ values are positive and increase with increasing molalities of sodium halides and saccharides, respectively. Overall, the Δ_tV_S⁰ and Δ_tV_E⁰ values have the order of NaCl > NaBr > NaI except for NaI‐ribose and NaI‐ribose. Volumetric interaction parameters for the electrolyte‐monosaccharide pairs in water were obtained and interpreted by the stereochemistry of the monosaccharide molecules and the structural interaction model.     

Toward Ultralow‐Bandgap Liquid Crystalline Semiconductors: Use of Triply Fused Metalloporphyrin Trimer–Pentamer as Extra‐large π‐Extended Mesogenic Motifs

In contrast with their dimeric homologue, triply fused zinc porphyrin trimer–pentamer, as extra‐large π‐extended mesogens, assemble into columnar liquid crystals (LCs) when combined with 3,4,5‐tri(dodecyloxy)phenyl side groups ( 3 P_Zn – 5 P_Zn , Figure 1 ). Their LC mesophases develop over a wide temperature range, namely, 41–280 °C (on heating) for 5 P_Zn , and all adopt an oblique columnar geometry, typically seen in columnar LC materials involving strong mesogenic interactions. These LC materials are characterized by their wide light‐absorption windows from the entire visible region up to a near infrared (NIR) region. Such ultralow‐bandgap LC materials are chemically stable and serve as hole transporters, in which 5 P_Zn gives the largest charge carrier mobility (2.4×10^?2 cm V^?1 s^?1) among the series. Despite a big dimensional difference, they coassemble without phase separation, in which the resultant LC materials display essentially no deterioration of the intrinsic conducting properties.     

Synthesis,Structure, Spectroscopic,and Electrochemical Properties of Highly Fluorescent Phosphorus(V)–meso‐Triarylcorroles

The synthesis, spectroscopic, and electrochemical properties of seven new P^V–meso‐triarylcorroles ( 1 – 7 ) are reported. Compounds 1 – 7 were prepared by heating the corresponding free‐base corroles with POCl₃ at reflux in pyridine. Hexacoordinate P^V complexes of meso‐triarylcorroles were isolated that contained two axial hydroxy groups, unlike the P^V complex of 8,12‐diethyl‐2,3,7,13,17,18‐hexamethylcorrole, which was pentacoordinate, or the P^V complex of meso‐tetraphenylporphyrin, which was hexacoordinate with two axial chloro groups. ¹H and ³¹P NMR spectroscopy in CDCl₃ indicated that the hexacoordinated P^V–meso‐triarylcorroles were prone to axial‐ligand dissociation to form pentacoordinated P^V–meso‐triarylcorroles. However, in the presence of strongly coordinating solvents, such as CH₃OH, THF, and DMSO, the P^V–meso‐triarylcorroles preferred to exist in a hexacoordinated geometry in which the corresponding solvent molecules acted as axial ligands. X‐ray diffraction of two complexes confirmed the hexacoordination environment for P^V–meso‐triarylcorroles. Their absorption spectra in two coordinating solvents revealed that P^V–meso‐triarylcorroles showed a strong band at about 600 nm together with other bands, in contrast to P^V–porphyrins, which showed weak bands in the visible region. These compounds were easier to oxidize and more difficult to reduce compared to P^V–porphyrins. These compounds were brightly fluorescent, unlike the weakly fluorescent P^V–porphyrins, and the quantum yields for selected P^V–corroles were as high as Al^III and Ga^III corroles, which are the best known fluorescent compounds among oligopyrrolic macrocycles.     

Building the “Phosphoindigo” Backbone by Oxidative Coupling of Phosphindolin‐3‐ones with Selenium Dioxide

Oxidative coupling of racemic 1‐ethoxy‐1‐oxophosphindolin‐3‐one ( 1 ) and its 5‐CF₃‐derivative 6 with SeO₂ furnishes 1,1′‐diphosphaindigo derivatives 5 and 7 as bis‐phosphinic esters, i. e. as P^V‐compounds. Like indigo and thioindigo, 5 and 7 exist in the E‐configuration; the crude products of 5 and 7 are mixtures of isomers that are trans‐ and cis‐configurated with respect to the relative orientation of the ester groups oat phosphorus. The structure of the centrosymmetric E‐P(R)P′(S) isomer [(E)‐trans‐isomer] of 5 was determined by X‐ray crystallography. Ester cleavage of 5 , followed by addition of triethylamine to bis‐phosphinic acid 9 (the 1,1,1′,1′‐tetroxide of “phosphoindigo”), furnishes the related bis‐triethylammonium salt 10 as a crystalline hydrate that exhibits an extended hydrogen bonding network.     

Synthesis and properties of mono‐ and di‐fluoro‐substituted 2,3‐didodecylquinoxaline‐based polymers for polymer solar cells

We synthesized two new alternating polymers, namely P(Tt‐FQx) and P(Tt‐DFQx) , incorporating electron rich tri‐thiophene and electron deficient 6‐fluoroquinoxaline or 6,7‐difluoroquinoxaline derivatives. Both polymers P(Tt‐FQx) and P(Tt‐DFQx) exhibited high thermal stabilities and the estimated 5% weight loss temperatures are 425 and 460 °C, respectively. Polymers P(Tt‐FQx) and P(Tt‐DFQx) displayed intense absorption band between 450 and 700 nm with an optical band gap (E_g) of 1.78 and 1.80 eV, respectively. The determined highest occupied/lowest unoccupied molecular orbital's (HOMO/LUMO) of P(Tt‐DFQx) (?5.48 eV/?3.68 eV) are slightly deeper than those of P(Tt‐FQx) ( ?5.32 eV/?3.54 eV). The polymer solar cells fabricated with a device structure of ITO/PEDOT:PSS/ P(Tt‐FQx) or P(Tt‐DFQx) :PC₇₀BM (1:1.5 wt %) + 3 vol % DIO/Al offered a maximum power conversion efficiency (PCE) of 3.65% with an open‐circuit voltage (V_oc) of 0.59 V, a short‐circuit current (J_sc) of 10.65 mA/cm² and fill factor (FF) of 59% for P(Tt‐FQx) ‐based device and a PCE of 4.36% with an V_oc of 0.69 V, a J_sc of 9.92 mA/cm², and FF of 63% for P(Tt‐DFQx) ‐based device. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 545–552     

Carbon‐Nanotube‐Mediated Electrochemical Transition in a Redox‐Active Supramolecular Hydrogel Derived from Viologen and an l‐Alanine‐Based Amphiphile

A two‐component hydrogelator (16‐A)₂‐V²⁺ , comprising an l ‐alanine‐based amphiphile ( 16‐A ) and a redox‐active viologen based partner ( V²⁺ ), is reported. The formation the hydrogel depended, not only on the acid‐to‐amine stoichiometric ratio, but on the choice of the l ‐amino acid group and also on the hydrocarbon chain length of the amphiphilic component. The redox responsive property and the electrochemical behavior of this two‐component system were further examined by step‐wise chemical and electrochemical reduction of the viologen nucleus (V²⁺/V⁺ and V⁺/V⁰). The half‐wave reduction potentials (E_1/2) associated with the viologen ring shifted to more negative values with increasing amine component. This indicates that higher extent of salt formation hinders reduction of the viologen moiety. Interestingly, the incorporation of single‐walled carbon nanotubes in the electrochemically irreversible hydrogel (16‐A)₂‐V²⁺ transformed it into a quasi‐reversible electrochemical system.     

Calculation of Some Thermodynamic Properties and Detonation Parameters of 1‐Ethyl‐3‐Methyl‐H‐Imidazolium Perchlorate, [Emim][ClO4], on the Basis of CBS‐4M and CHEETAH Computations Supplemented by VBT Estimates

This paper estimates some thermochemical (in kcal mol^–1) and detonation parameters for the ionic liquid, [emim][ClO₄] and its associated solid in view of its investigation as an energetic material. The thermochemical values estimated, employing CBS‐4M computational methodology and volume‐based thermodynamics (VBT) include: lattice energy, U_POT([emim][ClO₄]) ≈? 123 ± 16 kcal · mol^–1; enthalpy of formation of the gaseous cation, Δ_fH°([emim]⁺, g) = 144.2 kcal · mol^–1 and anion, Δ_fH°([ClO₄]^–, g) = –66.1 kcal · mol^–1; the enthalpy of formation of the solid salt, Δ_fH°([emim][ClO₄],s) ≈? –55 ± 16 kcal · mol^–1 and for the associated ionic liquid, Δ_fH^o([emim][ClO₄],l) = –52 ± 16 kcal · mol^–1 as well as the corresponding Gibbs energy terms: Δ_fG°([emim][ClO₄],s) ≈? +29 ± 16 kcal · mol^–1 and Δ_fG^o([emim][ClO₄],l) = +24 ± 16 kcal · mol^–1 and the associated standard absolute entropies, of the solid [emim][ClO₄], S°₂₉₈([emim][ClO₄],s) = 83 ± 4 cal · K^–1 · mol^–1. The following combustion and detonation parameters are assigned to [emim][ClO₄] in its (ionic) liquid form: specific impulse (I_sp) = 228 s (monopropellant), detonation velocity (V_oD) = 5466 m · s^–1, detonation pressure (p_C–J) = 99 kbar, explosion temperature (T_ex) = 2842 K.     

Volumetric Properties and Volumetric Interaction Parameters of the CsCl‐saccharides (D‐glucose,D‐fructose)‐water Solutions at 298.15 K

Densities have been measured for the CsCl‐saccharide (D‐glucose, D‐fructose)‐water systems at 298.15 K. These data were used to calculate the apparent molar volume of CsCl (V_φ,E) and the saccharides (V_φ,S), and the infinite dilution apparent molar volume V_φ,E⁰ and V_φ,S⁰ in the studied solutions. In addition, the standard transfer volume Δ_tV_φ,E⁰ of CsCl from water to aqueous saccharides solutions, and Δ_tV_φ,S⁰ of saccharides from water to CsCl solutions have been evaluated and discussed using the structural interaction model. The volumetric interaction parameters for CsCl with saccharide in water were obtained and analyzed by the group additivity principle and the stereochemistry of the saccharide molecules.     

Crystal structure of the thortveitite‐related M phase, (MnxZn1–x)2V2O7 (0.75 < x < 0.913): a combined synchrotron powder and single‐crystal X‐ray study

The determination of the crystal structure of the M phase, (Mn_xZn_1–x)₂V₂O₇ (0.75 < x < 0.913), in the pseudobinary Mn₂V₂O₇–Zn₂V₂O₇ system for x ≃ 0.8 shows that the previously published triclinic unit‐cell parameters for this thortveitite‐related phase do not describe a true lattice for this phase. Instead, single‐crystal X‐ray data and Rietveld refinement of synchrotron X‐ray powder data show that the M phase has a different triclinic structure in the space group P with Z = 2. As prior work has suggested, the crystal structure can be described as a distorted version of the thortveitite crystal structure of β‐Mn₂V₂O₇. A twofold superstructure in diffraction patterns of crystals of the M phase used for single‐crystal X‐ray diffraction work arises from twinning by reticular pseudomerohedry. This superstructure can be described as a commensurate modulation of a pseudo‐monoclinic basis structure closely related to the crystal structure of β‐Mn₂V₂O₇. In comparison with the distortions introduced when β‐Mn₂V₂O₇ transforms at low temperature to α‐Mn₂V₂O₇, the distortions which give rise to the M phase from the β‐Mn₂V₂O₇ prototype are noticeably less pronounced.     

Guest‐Induced Photophysical Property Switching of Artificial Light‐Harvesting Dendrimers

An artificial light‐harvesting multiporphyrin dendrimer ( 8P_ZnP_FB ) composed of a focal freebase porphyrin ( P_FB ) with eight zinc(II) porphyrin ( P_Zn ) wings exhibited unique photophysical property switching in response to specific guest molecule binding. UV/Vis titration studies indicated stable 1:2 host–guest complex formation between 8P_ZnP_FB and meso‐tetrakis(4‐pyridyl)‐porphyrin ( TPyP ) for which the first and second association constants were estimated to be >10⁸ M ^?1 and 3.0×10⁷ M ^?1, respectively. 8P_ZnP_FB originally shows 94 % energy transfer efficiency from P_Zn to the focal P_FB . By the formation of the host–guest complex ( 8P_ZnP_FB? 2 TPyP ) the emission intensity of 8P_ZnP_FB is significantly decreased, and an ultrafast charge separation state is generated. The energy transfer process from P_Zn wings to the P_FB core in 8P_ZnP_FB is almost entirely switched to an electron transfer process by the formation of 8P_ZnP_FB? 2 TPyP .     

Characterizing the Role of Iodine Doping in Improving Photovoltaic Performance of Dye‐Sensitized Hierarchically Structured ZnO Solar Cells

We report two novel types of hierarchically structured iodine‐doped ZnO (I? ZnO)‐based dye‐sensitized solar cells (DSCs) using indoline D205 and the ruthenium complex N719 as sensitizers. It was found that iodine doping boosts the efficiencies of D205 I? ZnO and N719 I? ZnO DSCs with an enhancement of 20.3 and 17.9 %, respectively, compared to the undoped versions. Transient absorption spectra demonstrated that iodine doping impels an increase in the decay time of I? ZnO, favoring enhanced exciton life. Mott–Schottky analysis results indicated a negative shift of the flat‐band potential (V_fb) of ZnO, caused by iodine doping, and this shift correlated with the enhancement of the open circuit voltage (V_oc). To reveal the effect of iodine doping on the effective separation of e^?‐h⁺ pairs which is responsible for cell efficiency, direct visualization of light‐induced changes in the surface potential between I? ZnO particles and dye molecules were traced by Kelvin probe force microscopy. We found that potential changes of iodine‐doped ZnO films by irradiation were above one hundred millivolts and thus significantly greater. In order to correlate enhanced cell performance with iodine doping, electrochemical impedance spectroscopy, incident‐photon‐current efficiency, and cyclic voltammetry investigations on I? ZnO cells were carried out. The results revealed several favorable features of I? ZnO cells, that is, longer electron lifetime, lower charge‐transfer resistance, stronger peak current, and extended visible light harvest, all of which serve to promote cell performance.     

A non‐oxo methanolate‐bridged divanadium(IV) complex with tris(2‐sulfanidylphenyl)phosphane ligands: synthesis,structural characterization and magnetic investigation

Vanadium chemistry is of interest due its biological relevance and medical applications. In particular, the interactions of high‐valent vanadium ions with sulfur‐containing biologically important molecules, such as cysteine and glutathione, might be related to the redox conversion of vanadium in ascidians, the function of amavadin (a vanadium‐containing anion) and the antidiabetic behaviour of vanadium compounds. A mechanistic understanding of these aspects is important. In an effort to investigate high‐valent vanadium–sulfur chemistry, we have synthesized and characterized the non‐oxo divanadium(IV) complex salt tetraphenylphosphonium tri‐μ‐<!?tlsb=‐0.11pt>methanolato‐κ⁶O:O‐bis({tris[2‐sulfanidyl‐3‐(trimethylsilyl)phenyl]phosphane‐κ⁴P,S,S′,S′′}vanadium(IV)) methanol disolvate, (C₂₄H₂₀P)[V^IV₂(μ‐OCH₃)₃(C₂₇H₃₆PS₃)₂]·2CH₃OH. Two V^IV metal centres are bridged by three methanolate ligands, giving a C2‐symmetric V₂(μ‐OMe)₃ core structure. Each V^IV centre adopts a monocapped trigonal antiprismatic geometry, with the P atom situated in the capping position and the three S atoms and three O atoms forming two triangular faces of the trigonal antiprism. The magnetic data indicate a paramagnetic nature of the salt, with an S = 1 spin state.     

Voltammetric Studies of Cadmium‐ and Zinc‐Containing Metallothioneins at Nafion‐Coated Mercury Thin Film Electrodes

Voltammetric studies of rabbit liver metallothioneins (MTs, containing both Zn and Cd ions) and Zn₇‐MT were carried out at Nafion‐coated mercury film electrodes (NCMFEs). The accumulation of MT molecules into the NCMFEs enhances the voltammetric signals and the electrostatic interaction between the Nafion membrane and MT facilitates facile electron transfer reactions. Two well‐defined redox waves, with reduction potential (E_pc) values at ?0.740 and ?1.173 V, respectively, were observed. The peak at E_pc =?0.740 V is attributable to the reduction of the Cd‐MT complex, whereas that at E_pc=?1.173 V was assigned to the reduction of the Zn‐MT complex. Zn₇‐MT exhibits only one redox wave with E_pc=?1.198 V. The NCMFE was found to be more advantageous than thin mercury film electrode (MFE), because the pristine metal ions in MTs (e.g., Cd²⁺ and/or Zn²⁺) are not significantly replaced by Hg²⁺. The NCMFE is also complementary to Nafion‐coated bismuth film electrode in that it has a greater hydrogen overpotential, which allows the reduction of the Zn‐MT complex to be clearly observed. Moreover, intermetallic compound formation between Cd and Zn appears to be less serious at NCMFEs. Consequently, the amounts of Cd and Zn deposited into the electrode upon the reduction reactions can be quantified more accurately.     

Crystallinity and crystalline phase orientation of poly(1,4‐cis‐isoprene) from Hevea brasiliensis and Taraxacum kok‐saghyz

Crystallization is studied for poly(isoprene‐1,4‐cis) from Hevea brasiliensis (natural rubber [NR]) and from taraxacum kok‐saghyz, mainly by collecting wide‐angle X‐ray diffraction patterns after processing and stretching. Although rubber samples before stretching are generally fully amorphous, crystallization can be induced in NR samples by processing at room temperature under moderate pressure. This phenomenon is possibly associated with nucleation by saturated fatty acid components. For rubber samples being fully amorphous in the undeformed state, strain‐induced crystallization occurs only at high strain ratios (α > 4), leading to high degrees of crystalline phase orientation (f_c > 0.9 for α = 5). Rubber samples presenting some crystallinity already in the unstretched state, on the contrary, reach much lower degrees of axial orientation, even for high strain ratios (f_c < 0.7 for α = 5). These differences in crystallinity and in crystalline phase orientations produce large differences in stress–strain behavior of the rubber. By room temperature processing, the considered NR samples can also develop an unreported disordered crystalline modification, with low intensity of 120 and 121 reflections. This disordered crystalline modification, which is also maintained after axial stretching procedures, can rationalized by a structural disorder along the b axis, possibly associated with statistical sequences of A⁺TA^? or A^?T A⁺ conformations for poly(isoprene‐1,4‐cis) chains. Copyright © 2016 John Wiley & Sons, Ltd.     

A bipyridine‐ligated zinc(II) complex with bridging flavonolate ligation: synthesis,characterization, and visible‐light‐induced CO release reactivity

Metal–flavonolate compounds are of significant current interest as synthetic models for quercetinase enzymes and as bioactive compounds of importance to human health. Zinc–3‐hydroxyflavonolate compounds, including those of quercetin, kampferol, and morin, generally exhibit bidentate coordination to a single Zn^II center. The bipyridine‐ligated zinc–flavonolate compound reported herein, namely bis(μ‐4‐oxo‐2‐phenyl‐4H‐chromen‐3‐olato)‐κ³O ³:O ³,O ⁴;κ³O ³,O ⁴:O³‐bis[(2,2′‐bipyridine‐κ²N ,N ′)zinc(II)] bis(perchlorate), {[Zn₂(C₁₅H₉O₃)₂(C₁₀H₈N₂)₂](ClO₄)₂}_n , ( 1 ), provides an unusual example of bridging 3‐hydroxyflavonolate ligation in a dinuclear metal complex. The symmetry‐related Zn^II centers of ( 1 ) exhibit a distorted octahedral geometry, with weak coordination of a perchlorate anion trans to the bridging deprotonated O atom of the flavonolate ligand. Variable‐concentration conductivity measurements provide evidence that, when ( 1 ) is dissolved in CH₃CN, the complex dissociates into monomers. ¹H NMR resonances for ( 1 ) dissolved in d₆‐DMSO were assigned via HMQC to the H atoms of the flavonolate and bipyridine ligands. In CH₃CN, ( 1 ) undergoes quantitative visible‐light‐induced CO release with a quantum yield [0.004 (1)] similar to that exhibited by other mononuclear zinc–3‐hydroxyflavonolate complexes. Mass spectroscopic identification of the [(bpy)₂Zn(O‐benzoylsalicylate)]⁺ ion provides evidence of CO release from the flavonol and of ligand exchange at the Zn^II center.     

Temperature and pressure dependence of the free volume in the perfluorinated polymer glass CYTOP: A positron lifetime and pressure‐volume‐temperature study

The microstructure of the free volume was studied for an amorphous perfluorinated polymer (T_g = 378 K). To this aim we employed pressure–volume–temperature experiments (PVT) and positron annihilation lifetime spectroscopy (PALS). Using the Simha‐Somcynsky equation of state the hole free volume fraction h and the specific free and occupied volumes, V_f = hV and V_occ = (1 ? h)V, were determined. Their expansivities and compressibilities were calculated from fits of the Tait equation to the volume data. It was found that in the glass V_occ has a particular high compressibility, while the compressibility of V_f is rather low, although h (300 K) = 0.108 is large. In the rubbery state the free volume dominates the total compressibility. From the PALS spectra the hole size distribution, its mean, 〈v_h〉, and mean dispersion, σ_h, were calculated. From a comparison of 〈v_h〉 with V_f a constant hole density of N_h′ = 0.25 × 10²¹ g^?1 was estimated. The volume of the smallest representative freely fluctuating subsystem, 〈V_SV〉 ∝ 1/σ_h², is unusually small. This was explained by an inherent topologic disorder of this polymer. 〈v_h〉 and σ_h show an exponential‐like decrease with increasing pressure P at 298 K. The hole density, calculated from N_h′ = V_f/〈v_h〉, seems to show an increase with P which is unexpected. This was explained by the compression of holes in the glass in two, rather than three, dimensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2519–2534, 2007     

Incorporating Zn2SnO4 Quantum Dots and Aggregates for Enhanced Performance in Dye‐Sensitized ZnO Solar Cells

The performance of dye‐sensitized ZnO solar cells was improved by a facile surface‐treatment approach through chemical‐bath deposition. After the surface treatment, the quantum dots of Zn₂SnO₄ were deposited onto ZnO nanoparticles accompanied by the aggregations of Zn₂SnO₄ nanoparticles. The ZnO film displayed a better resistance to acidic dye solution on account of the deposited Zn₂SnO₄ nanoparticles. Meanwhile, the open‐circuit photovoltage was greatly enhanced, which can be ascribed to the increased conduction‐band edge of ZnO and inhibited interfacial charge recombination. Although the deposition of Zn₂SnO₄ decreased the adsorption amounts of N719 dye, the aggregates of Zn₂SnO₄ with a size of 350–450 nm acted as the effective light‐scattering layer, thereby resulting in an improved short‐circuit photocurrent. By co‐sensitizing 10 μm‐thick ZnO film with N719 and D131 dyes, a top efficiency of 4.38 % was achieved under the illumination of one sun (AM 1.5, 100 mW cm^?2).