Materials Chemistry

Both the pancake coiling and conductor on round core (CORC) cabling processes consist of winding second-generation high-temperature superconducting tape (REBCO) in a core. The contact behavior between the tape and the core during the winding process directly affects the critical current, cable flexibility, mechanical support and electrical contact resistance. Therefore, the winding process needs to be optimized to produce pancake coils and CORC cables with the desired electrical and mechanical properties. This paper comprehensively considers the role of the relaxation and Poisson effects. The theoretical model and the finite element model (FEM) for calculating the contact stress during the winding process are established, and a formula for the estimation of the contact force is proposed. The suitable winding pre-tension force, winding curvature radius of SCS2030 (2 mm width and 30 µm substrate thickness) and SCS4050 (4 mm width and 50 µm substrate thickness) of REBCO tapes are obtained and discussed by accounting for the relaxation effect and the critical current degradation limit. With consideration of the Poisson effect, the nonlinear contact behavior is investigated. In addition, the relaxation effect, Poisson effect and plasticity of the REBCO tape are taken into account in the FEM model. The results show that the axial strain in the REBCO layer during the winding process is related to the contact behavior. The greater the winding pre-tension force, the smaller the helical curvature radius, and the greater the contact force. The distribution of contact stress for several winding factors (winding pre-tension force, winding angle and the core radius) is divided into three contact types: the single-line contact, the double-line contact and the surface contact. The FEM model results are consistent with the theoretical evaluation and are more suitable for practical winding cases. This research is the basis for designing and optimizing pancake coils and CORC cables.

Sporoderms, the outer layers of plant spores and pollen grains, are some of the most robust biomaterials in nature. In order to evaluate the potential of sporoderms in biomedical applications, we studied the biodegradation in simulated gastrointestinal fluid of sporoderm microcapsules (SDMCs) derived from four different plant species: lycopodium (Lycopodium clavatum L.), camellia (Camellia sinensis L.), cattail (Typha angustifolia L.), and dandelion (Taraxacum officinale L.). Dynamic image particle analysis (DIPA) and field-emission scanning electron microscopy (FE-SEM) were used to investigate the morphological characteristics of the capsules, and Fourier-transform infrared (FTIR) spectroscopy was used to evaluate their chemical properties. We found that SDMCs undergo bulk degradation in a species-dependent manner, with camellia SDMCs undergoing the most extensive degradation, and dandelion and lycopodium SDMCs being the most robust.

Spin-cast Intermolecular interactions in conjugated polymer films lead to formation of excited states delocalized over a few oriented and tightly-packed conjugated segments. The optoelectronic properties of conjugated polymers are strongly depended on the presence of such oriented domains at nanoscale. We observe oriented domains as large as several micrometres in size spontaneously formed in spin-cast PBDT-TPD films. Two-dimensional polarization imaging of fresh and photodegraded films showed a much higher visibility of the oriented domains in the degraded samples. We propose that the film is a mixture of two phases with different degrees of chain alignment. The photoluminescence of the more anisotropic phase is more stable against photodegradation in comparison with the less anisotropic phase. Photodegradation predominately quenches photoluminescence of the less anisotropic phase making the oriented domains more visible in the polarization contrasts. Spectral and energy transfer properties of the more oriented phase allowed us to assign it to weakly coupled H-aggregates with the suppressed 0-0 vibronic transition. Stable photoluminescence of H-aggregates in comparison with that of non-aggregated (less oriented) chains may help to understand degradation mechanisms of polymer devices and shows the role of energy transfer in this process. Selective degradation-induced quenching can reveal hidden inhomogeneity of conjugated polymer films.

Self-assembled multilayers are of interest for a variety of applications because of the potential for controlling individual layer composition and properties within layered assemblies on surfaces. Such potential applications include use as active components in nonlinear optical devices, 1,2 stable charge-separated assemblies, 3 and materials with selective chemical responses for sensor applications. 4,5 Among the different chemical strategies which have been developed to date for multilayer self-assembly, 1,4,6-9 multilayers prepared by alternate deposition of metal ions and bis(phosphonate) moieties onto an appropriately functionalized sub-strate are currently under intense investigation for all of these applications. 3, The metal-bis(phosphonate) (MBP) system provides well-ordered multilayer films made of alternating organic and inorganic layers that are robust and relatively easy to prepare. To increase the number of potential applications and to expand the types of chemistry available for building multilayer structures, we have been developing alternative "inorganic/organic" systems suitable for self-assembly of multilayer films. In particular, we have developed systems based on transition-metal coordination chemistry 12 which provide new opportunities for preparing self-assembled multilayers and for building superstructures. Several other examples of multilayer deposition utilizing metal-ligand coordination chemistry have been reported recently including pyrazines with Ru, 13 dithiols with Cu, 14 diamines with Ru, and diamines with Ni-Pt(CN) 4 . We report here a new selfassembly system based on a the cobalt-diisocyanide system. This system utilizes the strong coordination of the isocyanide ligand to a metal center as demonstrated by Feinstein-Jaffe et al., 17 who made two-and threedimensional polymers consisting of rhodium(I) and several diisocyanides.

In this paper, we tried to find answers to safety problems due to use of transition metal oxide as positive electrodes in the lithium ion batteries. The exothermic reaction at high temperature induced by the contact between positive electrode in the charged state, such as LiNi 0.8 Co 0.2 O 2 and the liquid electrolyte solution based of LiPF6 (EC, DMC) is reduced by formation of ceramic oxide. Al 2 O 3 -and ZnO-coated are synthesized on the surface of LiNi 0.8 Co 0.2 O 2 particles by chemical vapor deposition. The influences of deposit on the properties of starting material, in particular the thermal stability, are characterized by using, X-ray diffraction, electrochemical measurements and differential scanning calorimeter (DSC). Al 2 O 3 -coated sample show fading specific capacity during the first cycle. However, after several cycles a retention capacity is observed. ZnO-coated LiNi 0.8 Co 0.2 O 2 is inactive electrochemically as shown by X-rays diffraction pattern by the existence of two phases. With regard to DSC analysis in Al 2 O 3 -coated, one observe about 35% of reduction of heat flow during the exothermic reaction. The CVD method must be improved to obtain interesting results with regard to the electrochemical performances of treated material.

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Alkaline paper has advantages in their high shelf life (permanence) compared to paper made in acidic conditions. The conversion from acidic papermaking process to alkaline process is a major change experienced by the paper industry. In alkaline papermaking, one of the internal sizing agent used is Alkylketene Dimer (AKD). This additive is used to improve the resistance of paper to liquid penetration. Changes to the use of sizing agents are also followed by other changes; one of them is the change in the retention aids used. The use of Cationic Polyacrylamide (C-PAM) as retention aid on alkaline papermaking which is sized by AKD has been investigated. In this study, 100% Leaf Bleached Kraft Pulp (LBKP) as a fiber source was refined in a laboratory beater up to 400 mLCSF of freeness and then mixed with paper additives i.e. 0.1% AKD as sizing agent, 15% calcium carbonate as filler and 1% cationic starch as dry strength agent. The addition of C-PAM was varied in the range of 0% -0.4% based on dry weight of fiber. After being mixed thoroughly, the handsheets of 60 g/m2 grammage were made and then tested for tensile strength and water absorption (Cobb-60). The addition of 0.1% C-PAM resulted paper with good tensile strength and improved the resistance to liquid penetration.

Used beverage carton (UBC), is one type of used paper/cardboard that has potential as a recycled fiber source. UBC is composed of 3 components, namely paper, polyethylene and aluminum foil with a composition of 74-80%, 20-21%, and 5% respectively. UBC recycling initially aimed to recover fiber component which is the largest component that can be reused as paper/paperboard raw material. However, the UBC recycling also obtained by-products in the form of polyethylene (PE) and aluminum that can be used as composite raw materials. In general, a composite is expected to have high strength but light weight. The PE-aluminum composite has high strength but is rather heavy. So that, the experiments of making PEaluminum composites with the addition of fiber have been done. The usage of PE-g-MA (polyethylenegrafted-maleic anhydride) as a compatibiliser was also studied. Composites from a mixture of PEaluminum and fiber (ratio 4:1) have been made with the variations of 0-5% PE-g-MA. The temperature of hot press were also varied 140 o C and 165 o C. As a control, composite of 100% PE-aluminum without PE-g-MA was also made. The resulting composites were tested for density (SNI ISO 534:2011), moisture content (SNI ISO 287:2009), water absorption (SNI 01-4449-2006 Item 8.2.5), and dimensional stability. The presence of fiber in the PE-aluminum composite was able to reduce the density, moisture content and water absorption properties of the resulting composite, but the dimensional changes after being immersed in water for 24 hours increased. The addition of PE-g-MA as an additive to a mixture of PE-aluminum and fiber composites, at a hot press temperature of 165 o C, further reduced the water content and water absorption of the composites with a density close to the density of PE. The role of PE-g-MA as an interface component between the fiber phase and the PE-aluminum phase were shown in the 50x magnification of the composite cross-section using SEM (Scanning Electron Microscope) although its distribution in the composite is still uneven.

Refining of pulp is an important stage on papermaking process in developing the fiber properties in order to meet the paper quality requirements. Separate refining is general practice implemented by industry which uses more than one kind of pulp. However, combined or mixed refining of two kinds of pulp has an advantageous especially in the view of energy. Mixed refining of BCTMP (Bleached Chemi-Thermo-Mechanical Pulp) and LBKP (Leaf Bleached Kraft Pulp) mixture has been investigated. The experiments were carried out at a mixture composition of 10% BCTMP and 90% LBKP compared to the same mixture composition of pulps which were refined separately, as well as 100% BCTMP and 100% LBKP. The result showed that the average fiber length of pulps mixture from mixed refining was the lowest, but its' maximum fiber length was still quite good, closed to LBKP fibers. Compared to separate refining, mixed refining of pulps produced good sheet strength, while the other sheet properties were not significantly influenced.

In this study, we report the newly engineered functional polymeric vesicles as the robust nanostructured materials for the recognition and quantification of transition metal cations i.e. Hg(II) and Cr(III) as the naked eye recognition architectures in aqueous solution. The as prepared visual detector was synthesized by the combination of a hyperbranched poly(3-ethyl-3-oxetanemethanol)-star-poly(ethylene oxide) (HBPO-star-PEO, HSP) functionalized with rhodamine-2-amino-5-bromopyrimidine based chemosensor (RBP). The nanostructured vesicular sensor was regarded as HSP-RBP sensor. The naked eye detection owes from the spriolactam ring opening of the rhodamine based sensor (RBP) which was grafted onto the multiarm hyperbranched amphiphilic polymer. This newly synthesized sensor can facilely self-assemble into vesicles with enriched RBP groups on the outer surface of amphiphilic polymer. As a result of the introduction of these analytes (Hg 2+ /Cr 3+ ) the structural changes of RBP takes place and a transition in color change from colorless solution to pink colored solution takes place. This transition of color can clearly be seen with bare eye. Therefore, the term visual detection can be coined for the vesicular sensor. Furthermore, the limit of detection for Hg 2+ and Cr 3+ was calculated as low as 1.2 and 2.9 μM respectively. The striking feature of the newly prepared sensor, is its extraordinary ability for the recognition and quantification of Hg 2+ /Cr 3+ with outstanding selectivity in raw water samples.

In this study, we report the newly engineered functional polymeric vesicles as the robust nanostructured materials for the recognition and quantification of transition metal cations i.e. Hg(II) and Cr(III) as the naked eye recognition architectures in aqueous solution. The as prepared visual detector was synthesized by the combination of a hyperbranched poly(3-ethyl-3-oxetanemethanol)-star-poly(ethylene oxide) (HBPO-star-PEO, HSP) functionalized with rhodamine-2-amino-5-bromopyrimidine based chemosensor (RBP). The nanostructured vesicular sensor was regarded as HSP-RBP sensor. The naked eye detection owes from the spriolactam ring opening of the rhodamine based sensor (RBP) which was grafted onto the multiarm hyperbranched amphiphilic polymer. This newly synthesized sensor can facilely self-assemble into vesicles with enriched RBP groups on the outer surface of amphiphilic polymer. As a result of the introduction of these analytes (Hg 2+ /Cr 3+ ) the structural changes of RBP takes place and a transition in color change from colorless solution to pink colored solution takes place. This transition of color can clearly be seen with bare eye. Therefore, the term visual detection can be coined for the vesicular sensor. Furthermore, the limit of detection for Hg 2+ and Cr 3+ was calculated as low as 1.2 and 2.9 μM respectively. The striking feature of the newly prepared sensor, is its extraordinary ability for the recognition and quantification of Hg 2+ /Cr 3+ with outstanding selectivity in raw water samples.

Table is essential for life and if it contains metal impurities, it can affect the people that consume it. The Komenda Edina Eguafo Abrem municipality makes salt by evaporating brine from the Benya Lagoon. Benya lagoon is a lagoon known to be polluted due to various anthropogenic activities within its environs. The concentration of eight metals, Arsenic (As), Cadmium (Cd), Manganese (Mn) Lead (Pb), Aluminium (Al), Copper (Cu), Magnesium (Mg), and Vanadium (V) have been determined in salt mined using water from the Benya lagoon. Salt samples were selected from five fixed-sampling stations and the concentrations of the metals determined using Neutron Activation Analysis. The ranges of the measured concentrations in the salts are as follows: 161.04-632.63 mg/kg for Al, 0.001-0.004 mg/kg for As, 1.50-2.70 mg/kg for Mg, 49.14-3883.00 mg/kg for Mg, 17.24-110.96 mg/kg for Mn, and 2.85-7.10 mg/kg for V. An assessment according to the metal concentration marked Mg as the most abundant, whiles Cd and Pb the least being 0.001 mg/kg at all the five stations. Principal Component Analysis also established Mg to be the most abundant metal, and used to identify two major clusters; Group 1 (stations 4 and 5) and Group 2 (stations 1, 2 and 3). Group 2 recorded higher intensities of Mg. Using Pearson's correlation coefficient, significant correlations were drawn between Al and Mg (r = -0.862), Mg and Mn (r = 0.863) and Mn and V (r = 0.735), indicating the same or similar source inputs for each pair. Comparison with Codex Standard for Food Grade Salt showed that concentration values recorded for Al, Mg and Mn were above recommended limits. The contamination factor (CF) and degree of contamination (CD) confirmed this level of contamination for Al, Mg and Mn for all the five Stations, with Station 2 recording the highest Degree of Contamination. the least and corroborated salt from station 2 as most contaminated considering the combined toxicity at each station. Using an average daily salt intake of 6,000 mg, the mean daily intake of the elements when one consumes salt mined from the Benya lagoon was found to be above each element's Upper Tolerable Limit of its Recommended Dietary Allowable for the various Life Stage Groups. The associated Hazard Index suggests the probability of adverse effects when consumed. High standard deviation values for Al and Mn indicated the non-uniform spatial distribution of the individual metal contaminates at the various stations.

Instrumentation: UV-vis spectra were recorded on a Hewlett Packard 8453 spectrophotometer equipped with either constant temperature circulating water bath or a liquid nitrogen cryostat (Unisoku) with a temperature controller. Electrospray ionization mass spectra (ESI-MS) were recorded on a Waters (Micromass MS Technologies) Q-TOF Premier mass spectrometer by infusing samples directly into the source at 15 μL/min using a syringe pump. The spray voltage was set at 2 kV and the capillary temperature at 80 °C. Reactivity Studies: All reactions were run in a 10 mm path length UV cuvette by monitoring UV-vis spectral changes of reaction solutions. The rate constants were determined by fitting the changes in absorbance of the intermediates under study. Reactions were run at least in triplicate, and the data reported represent the average of these reactions. All calculations use procedures we previously employed for calculations on [Fe(IV)=O(N4Py)] 2+ and [Fe(IV)=O(Bn-tpen)] 2+ and their reactivity patterns. 7 Geometries were fully optimized using density functional theory methods as implemented in Gaussian-09, 8 and utilize the unrestricted hybrid density functional B3LYP. 9 We used a Los Alamos type double- quality basis set on Fe that contains a core potential, 10 an aug-cc-pV5Z-PP basis set on bromine, 11 and 6-31G on the rest of the atoms: basis set B1. 12 Subsequent single point calculations used the LACV3P+ basis set with core potential on Fe, an aug-cc-pV5Z-PP basis set on Br, and 6-311+G* on the rest of the atoms: basis set B2. Our calculated models were [Fe III OOH(N4Py)---Br -] + and [Fe III OOH(Bntpen)---Br -] + , and due to the charge distributions in these models we decided to do full geometry optimizations and frequencies using the continuum polarized conductor model (CPCM) 13 as implemented in Gaussian-09 using either acetonitrile or methanol as the solvent. All geometries were fully optimized without geometric constraints. The local minima are characterized with real frequencies only, whereas the transition states had one imaginary frequency for the correct mode. Transition states were located by first running detailed geometry scans between reactants and products with the reaction coordinate fixed at specific intervals, while optimization the rest of the geometry. The maximum of these scans was then used as a starting point for a full transition state geometry optimization.

Ag-Cu nanoalloys were synthesized by chemical co-reduction of their metal salts in aqueous solution with hydrazine hydrate, in the presence of complexing agent and stabilizer, preventing the oxidation of copper, as revealed by XPS. Their antibacterial behavior was tested against Escherichia coli strains, attesting far better ability of the Ag-Cu compared to Ag-only nanoparticles. Single metal nanoparticles have recently been in focus for their particle characteristics, size dependent properties, easy synthesis and chemical modifications. They also exhibit increased photochemical activity, modified chemical, biomedical and biological properties due to their high surface to volume ratios and unique properties that are different from their bulk. Preparation and characterization of the monometallic nanoparticles using different synthesis methods have been investigated for many years, whereas metal nanoalloy syntheses have not been as widespread due to handling problems and difficulties in preparation. Copper-only and silver-only nanoparticles (NPs) can be synthesized by the chemical reduction of copper and silver ions, which are produced by dissolving the salts of copper and silver in aqueous media, with the help of a reducing agent according to different procedures. Silver and copper alloy nanoparticles can also be prepared by co-reduction of their salts in aqueous solutions. The aqueous chemical reduction method is preferred over other nanoparticle preparation techniques because of its ease of application, variation in particle characteristics and different experimental parameters such as concentration, temperature and pH. 7 For the synthesis of the silver and copper nanoalloys (NAs) the main problems encountered are their high air sensitivity, low stability, and reactivity of the copper nanoparticles that cause the formation of copper oxide in the end product. To suppress the oxidation problem of copper in the nanoalloy synthesis, purging of the reaction media with inert gases, use of non-aqueous media, very strong reducing agents, complexing agents, surfactants and different kinds of stabilizers are the commonly employed procedures to prevent oxide formation both during preparation and storage.

Near-infrared-to-visible up-conversion of light by rare earth ion-doped nanophosphors (NaYF 4 : Yb 3þ ,Er 3þ ) opens new possibilities for improved biolabeling. A major obstacle to applications of upconverting nano phosphors (UCNPs) has been obtaining samples stable in serum media for biological applications. Previous researchers have made UCNPs stable in DI water, but not serum media. In this study, hexagonal phase nanophosphors were prepared using one-step cothermolysis utilizing oleic acid (OA) and trioctyl phosphine (TOP) ligands. Two routes to polymer surface modification of the UCNPs were studied: direct ligand exchange using poly(acrylic acid) (PAA) and amphiphilc copolymer encapsulation via flash nano-precipitation (FNP). FNP-coated UCNPs were produced using three block-copolymers: poly(ethylene glycol)-block-poly(caprolactone) (PEGb-PCL), poly(ethylene glycol)-block-poly(lactic-coglycolic acid) (PEG-b-PLGA), and poly((ethylene glycol)-block-lactic acid) (PEG-b-PLA). Both surface modification routes produced colloidally stable UCNP dispersions in DI water. However, for the first time, we report the successful preparation of colloidal UCNPs stable in buffers and serum media (Leibovitz L-15 media with added fetal bovine serum) using FNP and PEG surface coatings. The stabilizing block-copolymer layer added ca. 15 nm to the diameter of the phosphor crystals. UCNPs assembly of amorphous PLA or PLGA is strikingly different than for crystallizable PCL. These polymer-modified UCNPs provide promising new materials for applications in bioimaging and photodynamic therapy.

The effort to drive solution-based perovskite solar cells towards higher efficiency has been considerable, reaching over 24%. Such progress has been made possible by the low-energy barrier to crystallization. The low-energy barrier in the reverse direction, however, also renders them susceptible to dissociation from heat, moisture, and photoexcitation. Consequently, studies that provide information on the stability of perovskites are of considerable importance. It has been reported that perovskite crystals formed using different stoichiometries of the organic precursors and metal halide are equivalent. Our findings, however, suggest that the difference in reaction pathways affects the quality of the final crystal and that changes in morphology and the production of any defects can lead to differences in behavior under illumination. Here, we present photoluminescence spectra subsequent to nanosecond photoexcitation of perovskites synthesized under various conditions. Our results indicate that the presence of excess precursors (i.e., CH3NH3X, X= I and surfactant) gives rise to an ~20-nanosecond relaxation time with which the photoluminescence spectrum achieves its equilibrium value. This relaxation is absent in bulk, polycrystalline material. This is, to our knowledge, the first report of the ~20-ns relaxation time, which we attribute to cation migration. These structural changes are not detectable subsequent to photoexcitation by x-ray diffraction, nor are they detectable by in situ x-ray diffraction during photoexcitation.

Novel modification of ethylene-vinyl alcohol copolymers were carried out. The modifications of series of the copolymers were carried out by reacting them with chloroacetyle chloride followed by amination with ethylene diamine which used for many applications, such as water sterilization, drugs, soil sterilization, biomedical-device sterilization, and prevention of the microbial contamination of shipboard, water compensated, and hydration fuel tanks. The structure of the resulting materials was characterized with Fourier transform infrared-spectroscopy, TGA analysis and elemental analysis. The antimicrobial activity of the polymers against variety of test microorganisms was examined by the cut plug and viable cell counting methods. It was found that the immobilized polymers exhibited antimicrobial activity against the Gram negative bacteria (Escherichia coli ATCC 8739), Gram-positive bacteria (Staphylococcus aureus ATCC 6633), fungi (Candida albicans and Aspergillus niger. The growth inhibition of the test microorganisms (ratio of surviving cell number, M/C) varied according to the composition of the active group in the polymer and the test organism. It increased by increasing the concentration of the modified copolymers.

A variety of metal tungstates have been synthesised in a microwave assisted oven at 100 and 150˚C and corresponding autogenous water vapour pressure within a time frame of 30 minutes to 2 hours. The crystals formed are of submicrometer size and show equidimensional and needle-like crystals. Increasing the synthesis time and temperature results in the disappearance of the needles and the growth of the equidimensional crystals. The Raman spectra are consistent with those reported for the natural equivalents of these tungstates. The lead tungstate ν 1 (A g ) mode is observed at 904 cm -1 , while the ν 2 (A g ) vibration is observed as a strong band at at 326 cm -1 accompanied by a weak ν 2 (B g ) . at 356 cm -1 . The ν 3 (B g ) vibration is located around 741 cm -1 , whereas the ν 3 (E g ) is found at 751 cm -1 . Finally, the ν 4 (B g ) vibration is completely overlapping with the ν 2 (A g ) vibration. The band around 271 cm -1 may be the equivalent of the infrared active ν 4 (A u ) activated due to strain in the crystal. The two bands at 190 and 177 cm -1 are ascribed to the ν(Pb-O) and as a translational mode of the WO 4 group in stolzite.

A variety of metal tungstates have been synthesised in a microwave assisted oven at 100 and 150˚C and corresponding autogenous water vapour pressure within a time frame of 30 minutes to 2 hours. The crystals formed are of submicrometer size and show equidimensional and needle-like crystals. Increasing the synthesis time and temperature results in the disappearance of the needles and the growth of the equidimensional crystals. The Raman spectra are consistent with those reported for the natural equivalents of these tungstates. The lead tungstate ν 1 (A g ) mode is observed at 904 cm -1 , while the ν 2 (A g ) vibration is observed as a strong band at at 326 cm -1 accompanied by a weak ν 2 (B g ) . at 356 cm -1 . The ν 3 (B g ) vibration is located around 741 cm -1 , whereas the ν 3 (E g ) is found at 751 cm -1 . Finally, the ν 4 (B g ) vibration is completely overlapping with the ν 2 (A g ) vibration. The band around 271 cm -1 may be the equivalent of the infrared active ν 4 (A u ) activated due to strain in the crystal. The two bands at 190 and 177 cm -1 are ascribed to the ν(Pb-O) and as a translational mode of the WO 4 group in stolzite.

Synthesis conditions strongly influence the yield of the tridecameric polymer All3 ([AlO4Al12(OH)24(H20)12] 7+). All amount of 68% tridecamer was achieved by injection of alkali through a capillary tube into a 5 × 10 -2 M A1 solution at a rate of 0.015 ml/s up to an OH/AI ratio of 2.2. Dropwise addition of alkali yielded significantly less tridecameric polymer. During progressive hydrolysis the monomeric Al NMR resonance moved from 0.1 to 0.9 ppm and the linewidth increased from 37 to 112 Hz. Simultaneously the resonance at 63.3 ppm due to tridecameric fourfold coordinated Al changed by 0.02 ppm. During aging the tridecamer rearranged to polymers undetectable by NMR, due to loss of the tetrahedral symmetry of the central AI, which was deduced from the decrease in intensity and the broadening of the 63.3 ppm resonance. The formation of tetrahedral AI(OH)4, due to the inhomogeneous conditions at the point of base introduction, is essential for the synthesis of Al13. Aging over a period of 1 year caused a strong decrease in All3 concentration, which showed that A113 is a metastable polymer.

Stepwise heating to 85°C in the N M R apparatus does not notably change the monomer and tridecamer (All3) concentrations in a 0.2M AI(NO3) 3 solution neutralized with 0.2M N a O H up to an O H / A I molar ratio of 2.4. Upon heating the fourfold coordinated 27A1 N M R signal of All3 at 63.3 ppm and the very broad sixfold coordinated 27Al N M R signal of All3 at 12 ppm exhibit an increasing intensity and decreasing linewidth, due to diminishing 'missing intensity' and 'quadrupole relaxation', respectively. An analogous effect for a NazCO 3 neutralized 0.2M A1CI 3 solution confirmed that the 12 ppm signal must be assigned to the sixfold coordinated Al of the All3 complex. The surface ratio of fourfold coordinated Al to sixfold coordinated Al of the All3 complex experimentally established is smaller than the theoretical 1:12 ratio. During heating, a more intensive exchange interaction between monomer and other Al-species is proposed without any effect on the actual concentrations. High symmetry in the All3 complex is determined at elevated preparation temperatures from the decreasing linewidth of the 63.3 ppm resonance. Above 85°C the tridecamer transforms to other species, which cannot be observed with NMR.

Rechargeable Mg batteries are promising candidates for high energy density storage in theory, when a Mg metal anode is combined with an oxide cathode material. Despite the widely observed sluggish Mg 2+ diffusion in most oxide lattices, recent first-principles calculations predicted low diffusion barriers in the calcium ferrite (CF)-type post-spinel structures. In the present work, we experimentally examine the prospect of CF-type NaV 1.25 Ti 0.75 O 4 as a Mg cathode. The Na + ions, which lie in the ion migration pathway, need to be removed or exchanged with Mg 2+ to allow Mg 2+ de/ intercalation. Partial desodiation was achieved through chemical and electrochemical methods, as proven by X-ray diffraction and X-ray absorption spectroscopy, but deep desodiation was accompanied by partial amorphization of the material. Mg 2+ ion exchange at moderate temperature (80 °C) resulted in the formation of Na 0.19 Mg 0.41 V 1.25 Ti 0.75 O 4 ; however, phase transformation was observed when higher temperatures were applied to attempt complete ion exchange. Such phenomena point to the instability of the CF lattice when the tunnel is empty or occupied by a small ion (Mg 2+ ). Thus, while the low migration barrier predicted by computation is partly based on the relative metastability of the theoretical CF-Mg x V 1.25 Ti 0.75 O 4 lattice, the difficulty in stabilizing it also renders the material synthetically nonaccessible, hindering this post-spinel's application as an electrode material.

The electrochromic behaviour, spectroscopic properties and gas chemisorption of ultra thin films of lutetium octa-4-phenyldiphthalocyanine ( L u P c ~~~) , and the lutetium octa-3-bromoocta-5-tert-butylphthalocyanine (LuPcztBr) are reported. Electrochromism was observed for Langmuir-Blodgett (LB) and films cast onto indium tin oxide (ITO) coated glass electrodes in aqueous KC104 solution. Mixed LB films supported on IT0 glass electrodes were more stable to repetitive cycling than cast films. Films of LuPcZPh and LuPcPBr were sensitive to electronacceptor gases as observed by the changes in the electronic absorption spectra and the surfaceenhanced resonance Raman scattering (SERRS) spectra. The presence of electron-withdrawing bromine atoms in the phthalocyanine ring increased the rate of desorption for chemisorbed electron-acceptor molecules.

A molecular precursor approach to titania (anatase) nanopowders modified with different amounts of rare-earth elements (REEs: Eu, Sm, and Y) was developed using the interaction of REE nitrates with titanium alkoxides by a two-step solvothermal-combustion method. The nature of an emerging intermetallic intermediate was revealed unexpectedly for the applied conditions via a single-crystal study of the isolated bimetallic isopropoxide nitrate complex [Ti 2 Y( i PrO) 9 (NO 3 ) 2 ], a nonoxo-substituted compound. Powders of the final reaction products were characterized by powder X-ray diffraction, scanning electron microscopy-energy-dispersive spectroscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy, and photoluminescence (PL). The addition of REEs stabilized the anatase phase up to ca. 700 °C before phase transformation into rutile became evident. The photocatalytic activity of titania modified with Eu 3+ and Sm 3+ was compared with that of Degussa P25 titania as the control. PL studies indicated the incorporation of Eu and Sm cations into titania (anatase) at lower annealing temperatures (500 °C), but an exclusion to the surface occurred when the annealing temperature was increased to 700 °C. The efficiency of the modified titania was inferior to the control titania while illuminated within narrow wavelength intervals (445-465 and 510-530 nm), but when subjected to a wide range of visible radiation, the Eu 3+ -and Sm 3+ -modified titania outperformed the control, which was attributed both to doping of the band structure of TiO 2 with additional energy levels and to the surface chemistry of the REE-modified titania.

Crystallization of a perovskite mixed conductor is coupled to oxidation, which drives defect chemistry, ion coordination, polyhedra alignment, hierarchical microstructure, and property evolution – including a boost to electrical conductivity.

State-of-the-art high temperature oxide melt solution calorimetry and density functional theory were employed to produce the first systematic study of thermodynamic stability in a series of binary and ternary Chevrel phases. Rapid microwave-assisted solid-state heating methods facilitated the nucleation of pure-phase polycrystalline M y Mo 6 S 8 (M = Fe, Ni, Cu; y = 0, 1, 2) Chevrel phases, and a stability trend was observed wherein intercalation of M y species engenders stability that depends on both the electropositivity and ionic radii of the intercalant species. Ab initio calculations indicate that this stability trend results from competing ionic and covalent contributions, where transition metal intercalation stabilizes the Chevrel structure through increased ionicity but destabilizes the structure through reduced covalency of the Mo 6 S 8 clusters. Our calculations predicted that over intercalation of high-valent M y species leads to slight destabilization of the Mo 6 octahedral cores, which we confirm using calorimetry and X-ray absorption spectroscopy. Our combined computational and calorimetric analysis reveals the interplay of the foundational principles of ionic and covalent bonding characteristics that govern the thermodynamic stability of Chevrel and other inorganic phases.

This paper reports our initial efforts to promote electronic communications across polycyclic aromatic molecules through intervening metal halide moieties. Such efforts stand as part of the larger scheme to overcome the limitation of the van der Waals barrier in molecular semiconductors. In particular, the polycyclic aromatic ligands of 2,3,6,7,10,11-hexakis(alkylthio)triphenylene (alkyl: methyl, ethyl, and isopropyl; corresponding abbreviations for the molecules, HMTT, HETT, and HiPTT) were synthesized in an improved method, and interacted with bismuth(III) bromide and chloride to produce in high yields of a series of semiconductive hybrid networks featuring flexible network dimensionalities and electronic properties, as well as promising solution processing properties. Enlarging the side group from methyl to ethyl and to isopropyl groups effectively reduces the dimensionality of the bismuth halide components (and consequently the dimensionality of the overall coordination framework). Solid-state optical absorption measurements indicate effective electronic interactions between the organic π-system and the bismuth trihalide component, and the electronic band gap decreases monotonically with increasing dimensionality of the coordination network. As compared to molecular semiconductors, these integrated hybrid networks feature stronger electronic communication across the organic molecules, and point to potentially higher charge carrier mobilities.

The complex metal oxides Ni 2 InSbO 6 (NISO) and Ni 2 ScSbO 6 (NSSO) have been prepared in form of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties of the compounds were investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric and magnetic measurements. The compounds adopt a trigonal structure, space group R3, of the corundum related Ni 3 TeO 6 (NTO) type. Only one of the octahedral Ni positions (Ni(2)) of the NTO structure was found to be occupied by In (Sc). NTO has non-centrosymmetric structure and is ferroelectric below 1000 K, dielectric and second harmonic measurements suggest that also NISO and NSSO are correspondingly ferroelectric. Magnetization measurements signified antiferromagnetic ordering below T N =60 K (NSSO) and 76 K (NISO). The magnetic structure is formed by two antiferromagnetically coupled incommensurate helices with the spiral axis along the b-axis and propagation vector k = [0, k y ,0] with k y = 0.036(1) (NSSO) and k y = 0.029(1) (NISO). The observed structural and magnetic properties of NISO and NSSO are discussed and compared with those of NTO.

Strongly luminescent CuInS 2 /ZnS core/shell nanocrystals were synthesized from copper iodide, indium acetate, zinc stearate, and dodecanethiol as starting compounds in octadecene solvent. The as-prepared core/shell nanocrystals exhibit a low size distribution (<10%), and present photoluminescence in the range of 550-815 nm with a maximum fluorescence quantum yield (QY) of 60%. Time-resolved fluorescence spectroscopy revealed that the lifetimes of the different spectral components are on the order of hundreds of nanoseconds, indicating that donor-acceptor pair recombinations are at the origin of the observed emission bands. The CuInS 2 /ZnS nanocrystals were subsequently transferred to the aqueous phase via surface ligand exchange with dihydrolipoic acid and used as fluorescent labels for in vivo imaging. After tail vein injection into nude mice, the biodistribution of the quantum dots was monitored during 24 h using fluorescence reflectance imaging.

Two-dimensional hexagonal arrays of interconnected Co 3 O 4 nano-rods or disconnected monodimensional Co 3 O 4 nano-rods were nano-cast fabricated using SBA-15 as hard template with or without intra-wall microporosity, respectively. A clean, efficient and facile high temperature steam posttreatment is proposed to control the microporosity and the interconnectivity of the nanocasted oxide phase. Characterization by small-angle X-ray diffraction (XRD), nitrogen adsorption, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) suggests that the selective removal of micropores is resulted from hydrothermal restructuring within the pore wall of calcined SBA-15 followed by a sequential process, including hydrolysis and re-condensation of internal surface siloxane bonds and dissolution-migration-deposition of amorphous debris external onto the SBA-15 under the atmosphere of pure water vapor.

Since 2000, the intensive effort in materials research to develop a diluted magnetic semiconductor exhibiting high-temperature (HT) ferromagnetism above room temperature was not successful. Here, the possible first bulk diluted HT-ferromagnetic non-metallic materials, based on the perovskite-type oxynitrides LaTa1-xCox(O,N)3-δ (x = 0.01, 0.03, 0.05) are realized. The Curie temperature of the synthesized powders exceeds 600 K and the sample magnetizations are large enough to be directly attracted by permanent magnets. Cobalt clusters as a possible source for the observed HT-ferromagnetism can be excluded, since all applied characterization methods verify phase purity. Applied conventional and element-specific magnetometry imply ferromagnetic intermediate spin (IS) Co 3+ which is included in a ferromagnetic host matrix. This indicates a complex magnetic interplay between the existing crystal structure, the observed anionic vacancies, and the introduced cobalt ions. These results lay the foundation for the experimental investigation and design of further diluted HT-ferromagnetic semiconductors.

Structural Defects Induced in ETS-10 by Postsynthesis Treatment with H 2 O 2 Solution. -Treatment of ETS-10 titanosilicate M2TiSi5O13•nH2O (M: Na, K) with H2O2 leads to a partial removal of Ti atoms, resulting in the interruption of TiO2 chains and the consequent formation of larger micropores (supermicropores) without substantial degradation of crystallinity. The presence of supermicropores in the structure is revealed by TEM. The interruption of Ti-O-Ti chains and the formation of new accessible Ti centers is indicated by Raman, DRIFT, an DR UV/VIS spectroscopy. Supermicropores in ETS-10 crystallites make these materials interesting for fields in which transport limitations of molecules play an important role, e.g., for catalysis and gas separation.

Liquid crystals have become pivotally important to a variety of image displaying technologies. They have drawn much attention due to their ability to confer luminescent properties to a wide spectrum of image-based devices. The purpose of this research is to describe a new methodology for an efficient synthesis of luminescent ionic liquid crystals including a discussion of their applications in the biological/medicinal sciences.

Al 2 O 3 films were deposited by atomic layer deposition (ALD) at temperatures as low as 33 °C in a viscous-flow reactor using alternating exposures of Al(CH 3 ) 3 (trimethylaluminum [TMA]) and H 2 O. Low-temperature Al 2 O 3 ALD films have the potential to coat thermally fragile substrates such as organic, polymeric, or biological materials. The properties of lowtemperature Al 2 O 3 ALD films were investigated versus growth temperature by depositing films on Si(100) substrates and quartz crystal microbalance (QCM) sensors. Al 2 O 3 film thicknesses, growth rates, densities, and optical properties were determined using surface profilometry, atomic force microscopy (AFM), QCM, and spectroscopic ellipsometry. Al 2 O 3 film densities were lower at lower deposition temperatures. Al 2 O 3 ALD film densities were 3.0 g/cm 3 at 177 °C and 2.5 g/cm 3 at 33 °C. AFM images showed that Al 2 O 3 ALD films grown at low temperatures were very smooth with a root-mean-squared (RMS) roughness of only 4 ( 1 Å. Current-voltage and capacitance-voltage measurements showed good electrical properties of the low-temperature Al 2 O 3 ALD films. Elemental analysis of the films using forward recoil spectrometry revealed hydrogen concentrations that increased with decreasing growth temperature. No other elements were observed by Rutherford backscattering spectrometry except the parent aluminum and oxygen concentrations. Low-temperature Al 2 O 3 ALD at 58 °C was demonstrated for the first time on a poly(ethylene terephthalate) (PET) polymeric substrate. Al 2 O 3 ALD coatings on PET bottles resulted in reduced CO 2 gas permeabilities.

Intercalation and ion-exchange reactions have been used for the synthesis of novel inorganic-organic hybrid materials comprised of tetrathiafulvalene (TTF) conducting chains interleaved with insulating zirconium phosphate layers. Two different synthetic strategies are described. In the first approach, we have attempted the oxidative insertion of neutral TTF into a Zr(PO 4 )(HPO 4 ) 2 ‚2H 2 O host preexchanged with Cu 2+ . In the second method, surfactant or long-chain alcohols have been used to expand the layers of the host structure, allowing the intercalation of partially charged TTF molecules. This latter approach produced materials with metal-like conductivity that exceeds by a factor of 10 7 that of the precursors. These compounds have been characterized by vibrational, UV-vis, and EPR spectroscopies, and transport properties (conductivity and thermoelectrical power) have been measured as a function of the temperature from -150 to 50 °C. The properties observed show marked similarity with those displayed by mixed valence TTF halides and pseudohalides. The reactions occur topotactically, and the increase in interlayer distance is compatible with an orientation of TTF perpendicular, or nearly, to the host layers. † Dedicated to Professor Dr. Walter Siebert on the occasion of his 60th birthday.

The synthesis, characterization, and optical properties of high quality straight and branched CdTe nanowires (NWs) are described. A solution-based (solution-liquid-solid) approach is used to synthesize the NWs by employing a low melting bimetallic nanoparticle catalyst to induce one-dimensional (1D) growth. This leverages advances in the development of high quality colloidal quantum dots (QDs) with emerging techniques for manufacturing 1D nanomaterials. Resulting straight and branched CdTe NWs have diameters below twice the corresponding bulk exciton Bohr radius and, as a consequence, exhibit confinement effects in their linear absorption. Size distributions range from 15% to 20%, with NW lengths commonly exceeding 10 µm. Intrawire diameter variations are on the order of 5%. High-resolution transmission electron microscopy (TEM) images reveal that the wires are crystalline and grow exclusively along the <111> and <0001> directions of the corresponding zincblende and wurtzite phases. Branched NW morphologies include tripod, v-shape, y-shape, "merge-y", and "higher-order" structures. Preliminary optical studies of both straight and branched NWs are reported, including estimates of the absorption cross section and electrochemical band offsets. Such NWs open up avenues for further investigating the effects of size and shape on the optical/electrical properties of 1D nanomaterials and also have potential uses as active elements in photovoltaics and/or polarization sensitive photodetectors.