Hydroxide Complexes Research Articles

Investigation of Nitrile Hydration Chemistry by Two Transition Metal Hydroxide Complexes: Mn–OH and Ni–OH Nitrile Insertion Chemistry

Herein we describe the synthesis of a series of nickel complexes, including the formation of [(iPrPNHP)Ni(PMe3)][BPh4] (iPrPNHP = HN(CH2CH2(PiPr2))2). The ability of this phosphine complex to perform the 1,2-addition of H2O to produce the Ni–OH species [(iPrPNHP)NiOH][BPh4] has been investigated. The nucleophilicity of the hydroxide moiety of both [(iPrPNHP)NiOH][BPh4] and the previously reported (iPrPNHP)MnOH(CO)2 was investigated through the hydration of aryl and alkyl nitriles, leading to the formation of a number of metal carboxamide (RC(O)NH–) bonds. This reactivity generated complexes with the general structures of [(iPrPNHP)Ni(NHC(O)R)][BPh4] for nickel and (iPrPNHP)Mn(NHC(O)R)(CO)2 for manganese. Under catalytic conditions, the hydration of nitriles using nickel complexes yielded only a single turnover. However, (iPrPNHP)MnOH(CO)2 produced several turnovers, and the reaction conditions were probed for optimization.

Metalloenzyme Mimicry at the Nodes of Metal-Organic Frameworks

In this issue of Chem, Dincă and co-workers show that the node of the metal-organic framework MFU-4l can be modified by anion exchange to serve as a biomimetic model of carbonic anhydrase given the similarity in their ligand fields. The resulting material, which has reactivity characteristics of the enzyme, gives great promise for CO2-related applications.

Genesis of the South Zhuguang uranium ore field, South China: Fluid inclusion and H–C–O–S–Sr isotopic constraints

The South Zhuguang uranium (U) ore field in South China, which was discovered in the 1950s, contains an estimated >20,000 t of recoverable U. The U ore is hosted by the Zhuguang granite massif, which is located in the South China Block. The main uranium-bearing mineral, pitchblende, is found mainly in veins along high-angle normal faults, associated with hematite, quartz, fluorite, calcite, and locally pyrite. The hydrothermal alteration is generally silicification, illitization, hematization, and chloritization that developed adjacent to the ore-bearing faults and outwards over hundreds of meters into the unaltered granites.The ore-forming fluids in the South Zhuguang U ore field can be classified into two stages. Stage I fluids were acidic and oxidizing, with fluoride and sulfate complexes of UO22+ being the dominant species in the fluid. Stage II fluids were alkaline and oxidizing, with carbonate and hydroxide complexes of UO22+ being the dominant species. δ18O values of syn-ore quartz range from +6.29‰ to +14.30‰, with calculated δ18OW-SMOW values from −1.85‰ to +5.35‰. δDW-SMOW values of the ore-forming fluids were −104.4‰ to −23.1‰. δ18O values of the altered granites increase gradually from ∼+4‰ close to ore, to ∼+12‰ in the nearly unaltered granites. The δ13C and δ18O values for syn-ore calcite range from −10.3‰ to −4.3‰ and −22.41‰ to −16.8‰ relative to Pee Dee Belemnite, respectively, with calculated δ18O and δ13C values for water and CO2 of −2.97‰ to +2.83‰ and −11.2‰ to −5.2‰, respectively. The δ34SV-CDT values of syn-ore pyrite range from −17.1‰ to −3.4‰. Initial 87Sr/86Sr ratios of syn- and post-ore fluorite vary from 0.719250 to 0.721327 and 0.714598 to 0.716299, respectively.The ore-forming fluids in the South Zhuguang U ore field were sourced primarily from Cretaceous–Paleogene redbed basins in the south, and initially derived from meteoric waters. Hydrothermal alteration associated with stage I fluids released considerable amounts of Ca2+ and F− into the ore-forming fluids, increased the fluid pH, decreased the stability of the dominant fluoride complexes, and lowered the saturation solubility of the uranyl ions. Reduction of the ore-forming fluid converted U6+ into U4+, which resulted in the deposition of pitchblende–fluorite–quartz veins of the stage I ore in fractures along with pyrite. During stage II, the U mineralization was controlled mainly by CO2 degassing, which resulted in decomposition of the carbonate complex UO2(CO3)2–, and deposition of U in pitchblende–calcite–quartz veins as the ore-forming fluid was reduced.

Computational Investigation of the Oxygen Evolution Reaction Catalyzed by Nickel (Oxy)hydroxide Complexes

The catalytic behavior of nickel oxy(hydroxide) complexes containing one to four nickel atoms toward the oxygen evolution reaction was investigated with density functional theory (DFT). The accurac...

Kinetic of growth of chemically deposited ZnS films near room temperature conditions

The growth mechanism of ZnS films deposited by chemical bath at temperatures ranging between 25 °C and 55 °C was investigated by a kinetic analysis. For the ZnS thin films deposition, zinc chloride, potassium hydroxide, ammonium nitrate, and thiourea were used as chemical reagents. The effects of the bath temperature, thiourea concentration and deposition time on the ZnS formation were investigated. The species distribution diagrams suggested that the growth mechanism involves bisulfide ions (HS−) for the sulfur species as well as zinc hydroxide complexes ( and ). Higher thickness and growth rates were observed for increased bath temperature. The activation energy of the system was estimated as 127 ± 5 kJ/mole and the order of reaction with a value of 1.03 ± 0.05. These results suggest that the growing mechanism of the ZnS films is a chemical process with formation and absorption of Zn(OH)2 in the substrate followed by an exchange reaction between OH− and HS− ions. Chemical, morphological and optical characterizations of the deposited ZnS thin films are reported. The formation of the ZnS and Zn(OH)2 compounds was identified by x-ray photoelectron spectroscopy technique. An increase in the [Zn]/[S] ratio from 0.367 at 25 °C to 0.906 at 55 °C, was obtained. The estimated bandgap energy of the deposited films ranged from 3.5 to 3.8 eV. Optical transmittance higher than 80% above 500 nm on films makes proper as optical window for thin film solar cells.

Research of the component of the hybrid alumosilicic reagent - aluminum sulfate in the process of water treatment

The work is devoted to theoretical and experimental studies of the process of hydrolysis of an aluminum salt in an aqueous solution. Quantitative dependences of secondary contamination by aluminum ions in the process of hydrolysis of aluminum sulfate on the initial salt concentration and pH of the solution are derived, and the range of pH values at which the largest number of uncharged aluminum hydroxide complexes are formed is determined. Experimental studies have confirmed the theoretical dependence of the pH value of the solution on the amount of aluminum sulfate dissolved in water.

Binding of trivalent ions on fatty acid Langmuir monolayer: Fe3+ versus La3.

Langmuir monolayers consisting of fatty acid molecules were prepared on solutions of FeCl3 and LaCl3 to investigate adsorption of trivalent metal ions on carboxylic headgroups by using sum-frequency vibrational spectroscopy. Fe3+ ions bound to the fatty acid headgroups only in the form of hydroxide complexes (Fe(OH)x +3-x), and sum-frequency intensity of water stretch modes increased markedly upon adsorption of ion hydroxide. On the other hand, La3+ ions bound to the charged anionic headgroup as bare trivalent ions. Upon Fe(OH)x +3-x adsorption, the sum-frequency spectrum of carboxyl headgroups showed significant redshift which is opposite to the case of La3+ as well as those for alkali (Na+, K+) and alkali earth metal (Ca2+, Mg2+) ions, which also supports that Fe3+ binding is by covalent metal-ligand bonding, while La3+ binding is by Coulomb attraction.

Application of Capillary Electrophoresis to the Study of Equilibria on an Example of Gold(III) Complexes

Three systems of gold(III) complexes in an aqueous solution (I = 0.05 M, 25°C) with slow equilibration were studied by capillary electrophoresis. It was shown on an example of mixed chloride–hydroxide complexes Au(OH) i Cl 4- - that, despite close sizes and identical charges of the forms, the mixed forms can be separated if they are kinetically inert. For the equilibria AuCl 4 − + am = AuamCl 2 + + 2Cl– and AuamCl 2 + + am = + Auam23+ + 2Cl–, where am is ethylenediamine (en) and 1,3-diaminopropane (tn), the logarithmic constants were logK2 = 10.4 for en, and logK1 = 16.1 and logK2 = 12.0 for tn, which satisfactorily agrees with the spectrophotometric data. There was a considerable effect of side processes, insignificant under normal conditions.

Study on Mo-doped of Li1.18Ni1/3Co1/3Mn1/3O2 Lithium-rich Ternary Cathode Materials

The layered Li1.18(Ni1/3Co1/3Mn1/3)1-xMoxO2 cathode material was prepared by mixing lithium carbonate with precursor-nickel cobalt manganese hydroxide complex which was prepared by co-precipitation method with Mo-doped. The physical and chemical parameters, crystal structure, morphology and electrochemical properties were investigated by ICP analysis, X-ray diffraction, SEM and electrochemical tests, respectively. XRD results showed that doping Mo had no effect on the structure of pristine materials. However, the second phase of Li2MoO4 was dissected until the Mo loading reached 4 at%. The SEM images exhibited that the primary particles size decreased with the increase of Mo loading. Electrochemical measurements showed that the high rate discharge capability and cycle stability of the material can be improved significantly by a small amount of Mo (2 at%). The sample with 2 at% Mo-doped amount exhibited a high initial discharge capacity of 146.3 mAh g-1 at 0.3C rate under the voltage range of 2.5∼4.2V, as well as better cycle stability after 50 cycles. Therefore, Mo-doped is a useful method to improve large current discharge capability of the lithium insertion nickel cobalt manganese oxides.

Structural determinants of ligand binding in truncated hemoglobins: Resonance Raman spectroscopy of the native states and their carbon monoxide and hydroxide complexes

The ligand binding characteristics of heme-containing proteins are determined by a number of factors, including the nature and conformation of the distal residues and their capability to stabilize the heme-bound ligand via hydrogen-bonding and electrostatic interactions. In this regard, the heme pockets of truncated hemoglobins (TrHbs) constitute an interesting case study as they share many common features, including a number of polar cavity residues. In this review, we will focus on three proteins of group II TrHbs, from Thermobifida fusca (Tf-HbO) and Pseudoalteromonas haloplanktis TAC125 (Ph-HbO). Although the residues in positions G8 (Trp) and B10 (Tyr) are conserved in all three proteins, the CD1 residue is a Tyr in T. fusca and a His in P. haloplanktis. Comparison of the ligand binding characteristics of these proteins, in particular the hydroxo and CO ligands by means of resonance Raman spectroscopy, reveals that this single difference in the key heme cavity residues markedly affects their ligand binding capability and conformation. Furthermore, although the two Ph-HbOs (Ph-HbO-2217 and Ph-HbO-0030) have identical key cavity residues, they display distinct ligand binding properties.

A Reactive Manganese(IV)–Hydroxide Complex: A Missing Intermediate in Hydrogen Atom Transfer by High-Valent Metal-Oxo Porphyrinoid Compounds

High-valent metal-hydroxide species are invoked as critical intermediates in both catalytic, metal-mediated O2 activation (e.g., by Fe porphyrin in Cytochrome P450) and O2 production (e.g., by the Mn cluster in Photosystem II). However, well-characterized mononuclear MIV(OH) complexes remain a rarity. Herein we describe the synthesis of MnIV(OH)(ttppc) (3) (ttppc = tris(2,4,6-triphenylphenyl) corrole), which has been characterized by X-ray diffraction (XRD). The large steric encumbrance of the ttppc ligand allowed for isolation of 3. The complexes MnV(O)(ttppc) (4) and MnIII(H2O)(ttppc) (1·H2O) were also synthesized and structurally characterized, providing a series of Mn complexes related only by the transfer of hydrogen atoms. Both 3 and 4 abstract an H atom from the O-H bond of 2,4-di- tert-butylphenol (2,4-DTBP) to give a radical coupling product in good yield (3 = 90(2)%, 4 = 91(5)%). Complex 3 reacts with 2,4-DTBP with a rate constant of k2 = 2.73(12) × 104 M-1 s-1, which is ∼3 orders of magnitude larger than 4 ( k2 = 17.4(1) M-1 s-1). Reaction of 3 with a series of para-substituted 2,6-di- tert-butylphenol derivatives (4-X-2,6-DTBP; X = OMe, Me, tBu, H) gives rate constants in the range k2 = 510(10)-36(1.4) M-1 s-1 and led to Hammett and Marcus plot correlations. Together with kinetic isotope effect measurements, it is concluded that O-H cleavage occurs by a concerted H atom transfer (HAT) mechanism and that the MnIV(OH) complex is a much more powerful H atom abstractor than the higher-valent MnV(O) complex, or even some FeIV(O) complexes.

Amplicon Sequencing Reveals Microbiological Signatures in Spent Nuclear Fuel Storage Basins.

Water quality is an important determinant for the structural integrity of alloy cladded fuels and assemblies during long-term wet storage. Detailed characterization of a water filled storage basin for spent nuclear reactor fuel was performed following the formation and proliferation of an amorphous white flocculent. White precipitant was sampled throughout the storage basin for chemical and spectroscopic characterization, and environmental DNA was extracted for 454 pyrosequencing of bacterial 16S rRNA gene diversity. Accordingly, spectroscopic analyses indicated the precipitant to be primarily amorphous to crystalline aluminum (oxy) hydroxides with minor associated elemental components including Fe, Si, Ti, and U. High levels of organic carbon were co-localized with the precipitant relative to bulk dissolved organic concentrations. Bacterial densities were highly variable between sampling locations and with depth within the water filled storage basin; cell numbers ranged from 4 × 103to 4 × 104 cells/mL. Bacterial diversity that was physically associated with the aluminum (oxy) hydroxide complexes exceeded an estimated 4,000 OTUs/amplicon library (3% cutoff) and the majority of sequences were aligned to the families Burkholderiaceae (23%), Nitrospiraceae (23%), Hyphomicrobiaceae (17%), and Comamonadaceae (6%). We surmise that episodic changes in the physical and chemical properties of the basin contribute to the polymerization of aluminum (oxy) hydroxides, which in turn can chemisorb nutrients, carbon ligands and bacterial cells from the surrounding bulk aqueous phase. As such, these precipitants should establish favorable microhabitats for bacterial colonization and growth. Comparative analyses of 16S rRNA gene amplicon libraries across a selection of natural and engineered aquatic ecosystems were performed and microbial community and taxonomic signatures unique to the spent nuclear fuel (SNF) storage basin environment were revealed. These insights could spur the development of tractable bio-indicators that are specific of and diagnostic for water quality at discrete locations and finer scales of resolution, marking an important contribution for improved water quality and management of SNF storage facilities.

Syntheses of Molybdenum Oxo Alkylidene Complexes through Addition of Water to an Alkylidyne Complex.

Addition of one equiv of water to Mo(CAr)[OCMe(CF3)2]3(1,2-dimethoxyethane) (2, Ar = o-(OMe)C6H4) in the presence of PPhMe2 leads to formation of Mo(O)(CHAr)[OCMe(CF3)2]2(PPhMe2) (3(PPhMe2)) in 34% yield. Addition of one equiv of water alone to 2 produces the dimeric alkylidyne hydroxide complex, {Mo(CAr)[OCMe(CF3)2]2(μ-OH)}2(dme) (4(dme)) in which each bridging hydroxide proton points toward an oxygen atom in an arylmethoxy group. Addition of PMe3 to 4(dme) gives the alkylidene oxo complex, (3(PMe3)), an analogue of 3(PPhMe2) (95% conversion, 66% isolated). Treatment of 3(PMe3) with two equiv of HCl gave Mo(O)(CHAr)Cl2(PMe3) (5), which upon addition of LiO-2,6-(2,4,6-i-Pr3C6H2)2C6H3 (LiOHIPT) gave Mo(O)(CHAr)(OHIPT)Cl(PMe3) (6). Compound 6 in the presence of B(C6F5)3 will initiate the ring-opening metathesis polymerization of cyclooctene, 5,6-dicarbomethoxynorbornadiene (DCMNBD), and rac-5,6-dicarbomethoxynorbornene (DCMNBE), and the homocoupling of 1-decene to 9-octadecene. The poly(DCMNBD) has a cis,syndiotactic structure, whereas poly(DCMNBE) has a cis,syndiotactic,alt structure. X-ray structures were obtained for 3(PPhMe2), 4(dme), and 6.

High-Nuclearity Lanthanide-Containing Clusters as Potential Molecular Magnetic Coolers.

High-nuclearity cluster-type metal complexes are a unique class of compounds, many of which have aesthetically pleasing molecular structures. Their interesting physical and chemical properties arise primarily from the electronic and/or magnetic interplay between the component metal ions. Among the extensive studies in the past two decades, those on lanthanide-containing clusters, lanthanide-exclusive or heterometallic with transition metal elements, are most notable. The research was driven by both the synthetic challenges for these generally elusive species and their intriguing magnetic properties, which are useful for the development of energy-efficient and environmentally friendly magnetic cooling technologies. Our efforts in this vein have been concentrated on developing rational synthetic methods for high-nuclearity lanthanide-containing clusters. By means of the now widely adopted approach of "ligand-controlled hydrolysis" of lanthanide ions, a great variety of cluster-type lanthanide hydroxide complexes had been prepared in the first half of this developing period (1999-2006). In this Account, our efforts since 2007 are summarized. These include (1) further development of synthetic strategies in order to expand the ligand scope and/or to increase the nuclearity (>25) of the cluster species and (2) magnetic studies pertinent to the pursuit of materials with a large magnetocaloric effect (MCE). Specifically, with the hope of expanding the family of ligands and producing clusters of previously unknown structures, we tested under hydrothermal or solvothermal conditions the use of readily available yet not commonly used ligands for controlling lanthanide hydrolysis; such ligands, carboxylates as mundane examples, tend to form insoluble complexes prior to any possible hydrolysis. We have also validated the use of preformed transition metal complexes as metalloligands for subsequent control of lanthanide hydrolysis toward heterometallic 3d-4f clusters. Furthermore, we demonstrated using ample examples that the presence of small anions as templates is essential to the assembly of high-nuclearity lanthanide-containing clusters and that maintaining a low concentration of the anion template(s) is a key to such success. It has been found that slow production/release of such anion templates by in situ ligand decomposition or absorption of atmospheric CO2 is effective in preventing precipitation of their lanthanide salts, allowing not only controllable lanthanide hydrolysis but also gradual and modular assembly of the giant cluster species. Magnetic studies targeting potential applications of such clusters as molecular magnetic coolers have also been conducted. The results are summarized in the second portion of this Account in an effort to establish a certain magneto-structure relationship. Of particular relevance is the possible correlation between MCE (evaluated using the isothermal magnetic entropy change, -ΔSM) and magnetic density, and the intracluster antiferromagnetic exchange coupling. We have also made some preliminary attempts at preparing processable and practically useful materials in the form of a monodisperse core-shell nanostructure. We succeeded in encapsulating a single nanosized heterometallic molecular cluster in a nanoshell of silica. It was found that such passivation not only helped stabilize the cluster but also reduced the magnetic interactions between individual clusters. These effects are reflected in the slightly enhanced value of -ΔSM for the core-shell composite over the parent unprotected cluster.

Monomeric nickel hydroxide stabilized by a sterically demanding phosphorus-nitrogen PN3P-pincer ligand: synthesis, reactivity and catalysis.

A terminal nickel hydroxide complex (PN3P)Ni(OH) (3) bearing the 2nd generation phosphorus-nitrogen PN3P-pincer ligand has been synthesized and structurally characterized. As a nucleophile, 3 reacts with CO to afford the hydroxycarbonyl complex 4, (PN3P)Ni(COOH). 3 can also activate CO2 and CS2 to produce nickel bicarbonate (PN3P)Ni(OCOOH) (5) and bimetallic dithiocarbonate [(PN3P)NiS]2CO (6) respectively, as well as to promote aryl isocyanate and isothiocyanate insertion into the Ni-OH bond to give the corresponding (PN3P)NiEC(O)NHAr complexes (E = O, 7; E = S, 8). In addition, 3 catalyzes the nitrile hydration to various amides with well-defined intermediates (PN3P)Ni-NHC(O)R (R = Me, 9; R = Ph, 10).

Quantum-chemical analysis of formation reactions of Со<sup>2+</sup> complexes

Based on the analysis of quantum chemical calculations results (GAMESS, density functional theory, B3LYP method) as to coordination compounds of Co2+ions with H2O, NH3, OH–, F–, Cl–, Br–, I–, CN–, Ac–, Ak– generally given by [Co(H2O)6–nLn]2+nx, it has been demonstrated that within the selected series of ligands, there is no correlation between the amount of energy of monosubstituted cobalt aqua complexes formation(∆Е) and pK1,just like between the effective nuclear charge of the central atom (z*Со) and pK1. According to the behavior of ∆Е and z*Со,we identified two groups of ligands. The first group (OH–, F–, Ac–, Ak–, CN–, NH3) demonstrates logical ∆Е decrease caused by the growth of z*Со. On the contrary, the second group (Cl–, Br–, I–) demonstrates ∆Е increase caused by the growth of z*Со. This phenomenon is explained by the change in electronegativity and polarizability of donor atoms in groups and periods of the periodic table. It is established that linear correlations given by lgK = A + B·z*Со can be actualized only for complexes having ligands with similar donor atoms. Referring to the literature on stepwise complex formation of hydroxide, amine and chloride cobalt complexes in combination with z*Со calculations results, we determined A and B constants of lgK, z*Со-correlations for the atoms of oxygen (30.2, –17.7); nitrogen (125.4, –69.9) and chlorine (–6.3, 5.8). The existence of the detected correlation series enables us to lean on lgK,z*М–dependence parameters for the fixed donor atom and to determine Kn values for various complexes with complex-based ligands using calculations and z*М data. This applies to complexes having central atoms of the same nature as well as simple monodentate ligands. The mentioned approach was used to calculate the stability constants for acrylate cobalt complexes (lgK1 = 1.2 и lgК2 = 4.3), which are not covered in literature.

Anhydrous Monoalkylguanidines in Aprotic and Nonpolar Solvents: Models for Deprotonated Arginine Side Chains in Membrane Environments.

In this study, the synthesis of crystalline dodecylguanidine free base and its spectroscopic characterization in nonpolar environments are described. IR as well as 1H and 15N NMR spectra of the free base dissolved in aprotic solvents are substantially different from the previously reported spectra of arginine, or other monoalkylguanidinium compounds, at high hydroxide concentrations. The current results provide improved modeling for the spectroscopic signals that would be expected from a deprotonated arginine in a nonpolar environment. On the basis of our spectra of the authentic dodecylguanidine free base, addition of large amounts of aqueous hydroxide to arginine or other monoalklyguanidinium salts does not deprotonate them. Instead, hydroxide addition leads to the formation of a guanidinium hydroxide complex, with a dissociation constant near ∼500 mM that accounts for the established arginine pK value of ∼13.7. We also report a method for synthesizing a compound containing both phenol and free-base guanidine groups, linked by a dodecyl chain that should be generalizable to other hydrocarbon linkers. Such alkyl-guanidine and phenolyl-alkyl-guanidine compounds can serve as small-molecule models for the conserved arginine–tyrosine groupings that have been observed in crystallographic structures of both microbial rhodopsins and G-protein-coupled receptors.

Element speciation in UK biomass power plant residues based on composition, mineralogy, microstructure and leaching

Biomass ash management is an escalating issue in many countries because of increasing numbers of biomass power plants. Comprehensive characterization of biomass ashes with emphasis on element speciation, and solubility of nutrients (e.g., K and P) and pollutants is essential for potential utilization of these residues for soil nutrition. All the UK biomass ashes investigated, whether from combustion of poultry litter, meat and bone meal, and straw, were alkaline and contained high concentrations of P, K, and Ca. The biomass air pollution control (APC) residues were enriched in K, Cl, S and Zn, and contained less lithophile elements, such as Al, Ca, P, Mg, Si, Ti, and Ba, compared to the bottom ashes. P appeared in: 1) bottom ashes as apatite and other phosphates (potassium hydrogen phosphate and potassium iron phosphate in the bottom ashes from combustion of poultry litter); 2) APC residues from combustion of poultry litter as potassium sodium calcium phosphate. K is present mainly in sylvite, arcanite, and some phosphates. Na, K, Cl, and S were easily leached by water from the biomass APC residues. However, water leaching of P, Ca, and Mg was very low, with leaching of P possibly controlled by hydroxyapatite. Aqueous Zn, Cu and Pb appear to prevail in the form of neutral and anionic hydroxide complexes, which are toxic and easily accessible chemical forms for live organisms. Application of the poultry litter bottom ashes as a PK fertiliser in agriculture is appropriate. However, direct application of APC residues to agricultural fields is not appropriate but recovery of K and P from that material should be considered.

High efficiency dye-sensitized solar cells based on the ZnO nanoparticle aggregation sphere

Sub-micrometer-sized ZnO spheres have been prepared from methanolic zinc acetate dihydrate solution through the aggregation of ZnO nanocrystallites. The ZnO nanocrystallites were aggregated through the hydrolysis reaction of the zinc hydroxide complex due to the decrease of the surface free energy in the precursor solution, finally constructing a hierarchical ZnO nanoparticle aggregation sphere (NAS). Since the ZnO NAS is consisted of the ZnO nanocrystallites and are submicrometer-sized, it is function as efficient light scatters while the nanocrystallites provide the high internal surface area for the dye molecule adsorption in the dye sensitized solar cells (DSSC). The ZnO NAS is quite different from general ZnO colloidal nanocrystal clusters (CNC) in that the structure of ZnO NAS, due to the interconnected nanoparticles, can allow more efficient electron transport and charge collection through a designed path in the solar cell. Owing to the favorable charge collection, long charge diffusion length, and long electron life time, DSSC based on ZnO NAS showed photocurrent density (Jsc) and fill factor (FF) higher than that of ZnO CNC; also, an overall power conversion efficiency of 6.01% was obtained, which represented a remarkable increase compared to that of ZnO CNC (η = 4.59%) which had a similar film thickness.

An internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl to 800 °C and 5 kbar

This study presents an internally consistent thermodynamic dataset for aqueous species in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl, obtained by adding species of calcium, magnesium and carbon to the core system Na-K-Al-Si-O-H-Cl (Miron and others, 2016). Critically evaluated experimental data on mineral solubility (Ca and Mg hydroxides, Ca and Mg silicates, anorthite, Ca and Mg carbonates) in water and aqueous electrolyte solutions over wide ranges in temperature and pressure were added to the database of experimental data. The complete experimental dataset was then used to simultaneously refine the standard state Gibbs energies of all aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers (HKF) equation of state. The thermodynamic properties of the solubility-controlling minerals were accepted from the internally consistent dataset of Holland and Powell (1998; updated Thermocalc dataset ds55). The association equilibria of important hydroxide, chloride, carbonate and silicate complexes were critically reviewed, and their standard state properties and HKF parameters were independently derived from conductance, potentiometric and, in a few cases, solubility measurements. In a global optimization of standard Gibbs energies of aqueous species, performed with the GEMSFITS code (Miron and others, 2015), the association equilibria for aqueous complexes were always maintained. The new thermodynamic dataset reproduces all available fluid-mineral phase equilibria and mineral solubility data in the system Ca-Mg-Na-K-Al-Si-O-H-C-Cl with good accuracy over wide ranges in temperature (25–800 °C), pressure (1 bar – 5 kbar) and composition (salt concentrations up to 5 molal). This makes it possible to perform geochemical and reactive transport modeling of processes in natural and engineered georeservoirs over wide ranges of conditions with an unprecedented level of accuracy and reliability and to address processes of fluid flow and fluid-rock interaction in the Earth9s crust from a new perspective. Using the same strategy as applied in the present study, the internally consistent thermodynamic dataset can be further extended with additional major and trace elements, and the data refinement process can be repeated when new experimental data or next-generation equation of state or activity models for aqueous solutions become available.