Materials Chemistry

Qilei Song1,4, Shuai Cao2, Shan Jiang3, Andrew I. Cooper3, Anthony K. Cheetham2, and Easan Sivaniah1,5 Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK Department of Chemistry, University of Liverpool, Liverpool UK Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto 606-8501, Japan Email: q.song@imperial.ac.uk

A simple and versatile biomimetic strategy for the fabrication of silica films on a variety of substrates including gold, polystyrene and silicon wafers was developed using nanogram amounts per cm 2 of silicatein. The strategy exploits the adhesive property of 3,4-dihydroxyphenylalanine (DOPA) and a decapeptide (Ala-Lys-Pro-Ser-Tyr-DHP-Hyp-Thr-DOPA-Lys), important components of mussel adhesive proteins, to modify the surface of substrates. DOPA molecules polymerize to poly(DOPA) and the decapeptide forms thin films on gold substrates at pH 8.5, rendering the substrate compatible for silicatein immobilization. Nearly 50 ng cm À2 of silicatein is immobilized on poly(DOPA) and decapeptide coated surfaces where these polymer films act as ''cushion'' to protect the active structure and maintain the activity of the largely chemically adsorbed silicatein at ca. 95% of that experienced in solution. Uniform silica films of thickness 130-140 nm and roughness 12-14.5 nm were fabricated on coated gold surfaces. Evidence to show that this method is also applicable for the fabrication of uniform silica films on polystyrene and silicon substrates over multiple length scales in an economical way is also presented.

New methods for peptide modification are in high demand in drug discovery, chemical biology and materials chemistry; methods that modify natural peptides are particularly attractive. A Pd-catalyzed, C-H functionalization protocol for the olefination of phenylalanine residues in peptides is reported, which is compatible with common amino acid protecting groups, and the scope of the styrene reaction partner is broad. Bidentate coordination of the peptide to the catalyst appears crucial for the success of the reaction.

Using self-assembly, nanoscale materials can be fabricated from the bottom up. Opals and inverse opals are examples of self-assembled nanomaterials made from crystallizing colloidal particles. As self-assembly requires a high level of control, it is challenging to use building blocks with anisotropic geometry to form complex opals, which limits the realizable structures. Typically, spherical colloids are employed as building blocks, leading to symmetric, isotropic superstructures. However, a significantly richer palette of directionally dependent properties are expected if less symmetric, anisotropic structures can be created, especially originating from the assembly of regular, spherical particles. Here we show a simple method to introduce anisotropy into inverse opals by subjecting them to a post-assembly thermal treatment that results in directional shrinkage of the silica matrix caused by condensation of partially hydrated sol-gel silica structures. In this way, we can tailor the shape of the pores, and the anisotropy of the final inverse opal preserves the order and uniformity of the self-assembled structure, while completely avoiding the need to synthesize complex oval-shaped particles and crystallize them into such target geometries. Detailed X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy studies clearly identify increasing degrees of sol-gel condensation in confinement as a mechanism for the structure change. A computer simulation of structure changes resulting from the condensation-induced shrinkage further confirmed this mechanism. As an example of property changes induced by the introduction of anisotropy, we characterized the optical spectra of the anisotropic inverse opals and found that the optical properties can be controlled in a precise way using calcination temperature. Inverse opals with high long-range order can be made using a co-assembly process. 11 A thin film is grown by evaporative deposition of polymeric colloids in the presence of a silica sol-gel precursor that condenses in the colloidal crystal interstitial spaces. The co-assembly method allows the growth of extremely highly ordered crystals with single domains stretching over macroscopic dimensions. 11 Upon calcination, the polymeric colloids are completely combusted and the silica precursor fuses into a dense silicon dioxide scaffold, creating a hexagonally closepacked array of interconnected voids. Highly interconnected porosity and long-range order are two key attributes of inverse opal structures that make them valuable for a variety of applications. Due to their periodic nature, inverse opals are a versatile material platform for controlling electromagnetic 12-14 and acoustic 15 wave propagation. In particular, if their periodicity is tailored to the length scale of the wavelength of visible light, inverse opals interact strongly with visible light, allowing applications in solar cells, as light emitting diodes, 18 and as structural color-based coatings. In addition, inverse opals' interconnected porosity and high surface area are essential for their use in many other contexts, 21 including batteries and catalysts, as well as sensors of liquid media, 26 scaffolds for tissue engineering, 27 substrates for omniphobic surfaces, and for studying diffusion processes in confinement. All of these remarkable properties of inverse opals depend strongly on precise control over the structural uniformity. Spherical colloids are simple to synthesize and crystallize, so they are typically used as templates. However, anisotropic structures would offer a range of unique, direction-dependent properties due to the changes in the angular periodicities and directional porosity, and are therefore highly desirable, but a simple method to obtain anisotropic inverse opals is necessary in order to investigate these directional properties.

The intrinsic defects of (Na 0.5 K 0.5 )NbO 3 (NKN) ceramics fabricated by high-energy ball-milling have been studied. In order to obtain the different amounts of Na/K evaporation, NKN ceramics were sintered in air (NKN exposed samples) and in calcined NKN powder (NKN buried samples), respectively. Compared with the dielectric and piezoelectric properties of the buried samples, the exposed samples exhibited a donor doped behavior at room temperature. A dielectric relaxation, induced by intrinsic oxygen vacancies, was detected in paraelectric phase region. The activity energies of intrinsic oxygen vacancies are 1.04 eV and 1.47 eV for the exposed samples and buried samples, respectively. The difference of activity energies resulted from singly ionized oxygen vacancies translating into doubly ionized oxygen vacancies with the increase of Na/K evaporation.

In this paper we report on crystal structure and oxygen storage properties of A-site cation ordered BaLnMn 2 O 5+d (Ln: Pr, Nd, Sm, Gd, Dy, Er and Y) perovskite-type oxides. The materials show practically complete and reversible change between fully reduced BaLnMn 2 O 5 and oxidized BaLnMn 2 O 6 , which occurs at moderate temperatures (300-500 C) during changes of the oxygen partial pressure (air, 5 vol.% H 2 in Ar). Based on the thermogravimetric measurements, reversible oxygen storage capacity, characteristic temperature of oxidation and reduction, as well as kinetics of these processes are given. Structural characterization was performed at room temperature for the reduced and oxidized materials by Rietveld analysis of the XRD data. These results are accompanied by in situ high temperature XRD measurements of the oxidation process, performed for BaNdMn 2 O 5 in air.

A facile, mechanical milling method resulting in a significant improvement of the oxygen release kinetics from cation-ordered BaLnMn 2 O 5+δ -type (Ln: selected lanthanides) materials is shown for Pr-and Sm-containing compounds. Synthesized by a soft chemistry method, BaPrMn 2 O 5 and BaSmMn 2 O 5 oxides were milled in an appropriately selected conditions, which allowed to obtain samples with largely decreased crystallite size, increased specific surface area, and likely, having a partial Ba-Ln disorder. Such materials were characterized in terms of their oxygen storage-related properties and were found to exhibit enhanced oxygen release kinetics, with a reduction rate parameter being increased several times. The milling process did not influence the mechanism of the oxygen release significantly. A decrease of a characteristic temperature of reduction was also noticed, however, while the oxygen storage capacity of BaSmMn 2 O 5+δ was found to increase after milling, it decreased for BaPrMn 2 O 5+δ . It seems that the enhanced reduction rates can be related to a diminished tendency of a formation of the oxygen vacancy-ordered BaLnMn 2 O 5.5 . The reported studies are supplemented by scanning electron microscopy and X-ray photoelectron spectroscopy measurements.

Nanosheets of Cu2-xS having discrete thicknesses of 5, 6, and 8 crystallographic monolayers are prepared by adaptation of literature methods. These are converted to CuInS2 nanosheets having the same, discrete, monolayer thicknesses by cation-exchange reactions. The 6-and 8-monolayer CuInS2 nanosheets exhibit broad, nearly featureless extinction (absorption) spectra that are generally characteristic of CuInS2 nanocrystals. However, the thinnest, 5monolayer CuInS2 nanosheets exhibit structured extinction spectra having a well-resolved doublet feature with peaks at 2.74 and 2.54 eV. An exciton-splitting (valence-band-splitting) model assigns the transitions to excitons derived from inequivalent A, B, and C holes from the bulk band structure of CuInS2. This splitting is analogous to the heavy-hole, light-hole splitting observed in the absorption spectra of III-V quantum wells, and pseudo-2D II-VI nanocrystals. The model semi-quantitatively accounts for the magnitude of the observed splitting, which is largely due to quantum confinement and the differing A, B, and C hole effective masses. The lack of resolved splitting in CuInS2 nanocrystals having larger dimensions is also accounted for.

n-Tetradecylphosphonic acid (TDPA) is an acid and also a source for a strong-binding ligand, n-tetradecylphosphonate (TDPT), for the preparation of the cadmium precursor Cd(DOPT)x(TDPT)1-0.5x (where DOPT = di-n-octylphosphinate). The reaction chemistry of the cadmium precursor and tri-n-octylphosphine telluride (TOPTe) is manipulated to favor the formation of a CdTe solute if the catalytic role of TDPA as an acid is predominant, otherwise the stabilization of the cadmium precursor by TDPT incorporation results in a significant excess of Te in the reaction mixture. These exert opposite consequences on the crystal-phase purity of colloidal CdTe quantum wires (QWs) grown from initial bismuth (Bi) nanoparticles. Primary dissolution of the available CdTe or Te into Bi nanoparticles affords liquid (y  z) or solid (y « z) BixCdyTez catalysts, respectively. The solid catalysts enable the solution-solid-solid growth of nearly phase-pure wurtzite QWs, whereas the liquid catalysts fulfill the solution-liquid-solid growth of polytypic QWs, having wurtzite and zinc blende alternations. This work reveals the dual role of TDPA and rationalizes its use in the crystal-phase controlled synthesis of catalytically grown colloidal QWs.

Herein, we report the detailed pathway for the formation of CdSe quantum belts (QBs). We show that CdX 2 (X = OAc, I) compounds in long-chain primary-amine solvents form lamellar structures that serve as templates for the formation of (CdSe) 13 nanoclusters. The resulting amine-template nanocluster composites spontaneously organize into double-lamellar assemblies. Recrystallization of the nanoclusters within the templates affords CdSe quantum belts (QBs) having widths and thicknesses determined by the periodicities of the double-lamellar nanostructures. This template synthesis affords excellent control over QB thickness and accounts for the excellent optical properties of the QBs. The preparation of CdSe nanoribbons, nanoplatelets, and nanosheets was reported independently by Hyeon and coworkers 1,2 and by Ithurria and Dubertret 3,4 under synthetic conditions similar to those employed here. We subsequently demonstrated that CdSe quantum belts, which were morphologically comparable to the nanoribbons of Hyeon and co-workers, 1 exhibit photoluminescence quantum yields of 30 ( 10%. 5 Such high photoluminescence efficiencies are unprecedented for pseudo-one-dimensional colloidal semiconductor nanostructures and indicate that excitons are effectively transported over micrometerscale diffusion distances parallel to the QB long axes. A remarkable aspect of the nanoribbon, nanoplatelet, nanosheet, and QB syntheses is the flat, layer-like, morphologies of the nanocrystals. Normally, nanocrystals grown in solution have dot 6 or rod-like morphologies, 7À10 or wire morphologies if appropriate catalyst nanoparticles are present, 11À13 or a selfassembly mechanism is active. 14À17 Additionally, the reaction temperatures employed (∼70À120 °C) are quite low for nanocrystal syntheses. Consequently, the mechanisms or pathway by which these nanostructures form must be unusual. Hyeon and co-workers, who demonstrated that dissolution of CdCl 2 in primary-amine solvents resulted in the formation of lamellar CdCl 2 (amine) 2 complexes. 2 They showed that such lamellar precursors served as templates for the formation of planar CdSe nanosheets. In a subsequent paper, Hyeon and coworkers determined that (CdSe) 33,34 and (CdSe) 13 nanoclusters were intermediates in the process. Here, we elucidate a similar pathway for the formation of CdSe QBs with experimental detail that accounts for the morphology produced. We demonstrate that the templates adopt doublelamellar structures that are responsible for the QB morphologies. We confirm that the intermediate nanoclusters are indeed entrained within the template structures. We show that the conversion of (CdSe) 13 nanoclusters to CdSe QBs is reversible. We also show that the double-lamellar assemblies of (CdSe) 13 nanoclusters and CdSe QBs dissociate or unbundle in different dimensions, the (CdSe) 13 nanoclusters into lateral sheets and the QBs into vertical stacks. Finally, we report the synthesis of QBs of two specific thicknesses and demonstrate that the thinner QBs are intermediates in the formation of the thicker QBs. ' EXPERIMENTAL SECTION Materials. n-Octylamine (n-OA) from Aldrich (+99%) and Alfa Aesar (99%), selenourea (99.9%, metal basis) from Alpha Aesar, Cd(OAc) 2 3 2H 2 O (Aldrich), trioctylphosphine (TOP) from Sigma-Aldrich (97%), and oleylamine (or cis-9-octadecenylamine) from TCI (>40.0% by GC) and Sigma-Aldrich (technical grade, 70%) were used as received and stored under N 2 . Toluene from Sigma-Aldrich

The aggregative growth and oriented attachment of nanocrystals and nanoparticles are reviewed, and they are contrasted to classical LaMer nucleation and growth, and to Ostwald ripening. Kinetic and mechanistic models are presented, and experiments directly observing aggregative growth and oriented attachment are summarized. Aggregative growth is described as a nonclassical nucleation and growth process. The concept of a nucleation function is introduced, and approximated with a Gaussian form. The height (Γ max ) and width (Δt n ) of the nucleation function are systematically varied by conditions that influence the colloidal stability of the small, primary nanocrystals participating in aggregative growth. The nucleation parameters Γ max and Δt n correlate with the final nanocrystal mean size and size distribution, affording a potential means of achieving nucleation control in nanocrystal synthesis.

Defect engineering is a strategy that has been widely used to design active semiconductor photocatalysts. However, understanding the role of defects, such as oxygen vacancies, in controlling photocatalytic activity remains a challenge. Here we report the use of chemically-triggered fluorogenic probes to study the spatial distribution of active regions in individual tungsten oxide nanowires using super-resolution fluorescence microscopy. The nanowires show significant heterogeneity along their lengths for the photocatalytic generation of hydroxyl radicals. Through quantitative, coordinate-based colocalization of multiple probe molecules activated by the same nanowires, we demonstrate that the nanoscale regions most active fo the photocatalytic generation of hydroxyl radicals also possess a greater concentration of oxygen vacancies. Chemical modifications to remove or block access to surface oxygen vacancies, supported by calculations of binding energies of adsorbates to different surface sites on tungsten oxide, show how these defects control catalytic activity at both the ensemble and single-particle level. These findings reveal that clusters of oxygen vacancies activate surface-adsorbed water molecules towards photooxidation to produce hydroxyl radicals, a critical intermediate in several photocatalytic reactions.

Tri-n-octylphosphine oxide (TOPO) is the most commonly used solvent for the synthesis of colloidal nanocrystals. Here we show that the use of different batches of commercially obtained TOPO solvent introduces significant variability into the outcomes of CdSe quantum-wire syntheses. This irreproducibility is attributed to varying amounts of phosphorus-containing impurities in the different TOPO batches. We employ 31 P NMR to identify 10 of the common TOPO impurities. Their beneficial, harmful, or negligible effects on quantum-wire growth are determined. The impurity din-octylphosphinic acid (DOPA) is found to be the important beneficial TOPO impurity for the reproducible growth of high-quality CdSe quantum wires. DOPA is shown to beneficially modify precursor reactivity through ligand substitution. The other significant TOPO impurities are ranked according to their abilities to similarly influence precursor reactivity. The results are likely of general relevance to most nanocrystal syntheses conducted in TOPO.

Combinatorially selected peptides and peptide-organic conjugates were used as linkers with controlled structural and organizational conformations to attach quantum dots (QDs) at addressable distances from a metal surface. This study demonstrates an approach towards nanophotonics by integrating inorganic, organic, and biological constructs to form hybrid nanoassemblies through template-directed self-assembly. Peptide-organic-linked QD arrays showed stronger fluorescence than peptide-linked QD arrays. We attribute this difference primarily to the increased number density of QDs on peptide-organic-linked QD arrays.

In 2017, we discovered quaternary i-MAX phases -atomically layered solids, where M is an early transition metal, A is an A group element, and X is C -with a (M 1 2/3 M 2 1/3 )2AC chemistry, where the M 1 and M 2 atoms are in-plane ordered. Herein we report on the discovery of a class of magnetic i-MAX phases in which bi-layers of a quasi-2D magnetic frustrated triangular lattice overlays a Mo honeycomb arrangement and an Al Kagomé lattice. The chemistry of this family is (Mo2/3RE1/3)2AlC, and the rare earth elements, RE, are Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. The magnetic properties were characterized and found to display a plethora of ground states, resulting from an interplay of competing magnetic interactions in the presence of magnetocrystalline anisotropy.

We deposited Os atoms on S-and Se-doped boronic graphenic surfaces by electron bombardment of micelles containing 16e complexes [Os(p-cymene)(1,2-dicarba-closo-dodecarborane-1,2diselenate/dithiolate)] encapsulated in a triblock copolymer. The surfaces were characterized by energy-dispersive X-ray (EDX) analysis and electron energy loss spectroscopy of energy filtered TEM (EFTEM). Os atoms moved ca. 26× faster on the B/Se surface compared to the B/S surface (233 ± 34 pm•s -1 versus 8.9 ± 1.9 pm• s -1 ). Os atoms formed dimers with an average Os-Os distance of 0.284 ± 0.077 nm on the B/Se surface and 0.243 ± 0.059 nm on B/S, close to that in metallic Os. The Os 2 molecules moved 0.83× and 0.65× more slowly than single Os atoms on B/S and B/Se surfaces, respectively, and again markedly faster (ca. 20×) on the B/Se surface (151 ± 45 pm•s -1 versus 7.4 ± 2.8 pm•s -1 ). Os atom motion did not follow Brownian motion and appears to involve anchoring sites, probably S and Se atoms. The ability to control the atomic motion of metal atoms and molecules on surfaces has potential for exploitation in nanodevices of the future.

We deposited Os atoms on S-and Se-doped boronic graphenic surfaces by electron bombardment of micelles containing 16e complexes [Os(p-cymene)(1,2-dicarba-closo-dodecarborane-1,2diselenate/dithiolate)] encapsulated in a triblock copolymer. The surfaces were characterized by energy-dispersive X-ray (EDX) analysis and electron energy loss spectroscopy of energy filtered TEM (EFTEM). Os atoms moved ca. 26× faster on the B/Se surface compared to the B/S surface (233 ± 34 pm•s -1 versus 8.9 ± 1.9 pm• s -1 ). Os atoms formed dimers with an average Os-Os distance of 0.284 ± 0.077 nm on the B/Se surface and 0.243 ± 0.059 nm on B/S, close to that in metallic Os. The Os 2 molecules moved 0.83× and 0.65× more slowly than single Os atoms on B/S and B/Se surfaces, respectively, and again markedly faster (ca. 20×) on the B/Se surface (151 ± 45 pm•s -1 versus 7.4 ± 2.8 pm•s -1 ). Os atom motion did not follow Brownian motion and appears to involve anchoring sites, probably S and Se atoms. The ability to control the atomic motion of metal atoms and molecules on surfaces has potential for exploitation in nanodevices of the future.

A series of solid sorbent materials, including alumina (Al 2 O 3 ), magnesia (MgO), titania (TiO 2 ), silica (SiO 2 ), and carbon, of widely varying physical properties, have been studied as sorbents for two toxic substances: sulfur dioxide gas (SO 2 ) and chemical warfare surrogate 2-chloroethyl ethyl sulfide (2-CEES, ClCH 2 CH 2 SCH 2 CH 3 ). Sorbent surface areas, average pore sizes, pore volumes, surface hydroxyl groups, and nitrogen adsorption-desorption isotherms were measured. Surface areas varied from 18 m 2 /g to over 1000 m 2 /g, pore volumes from 0.04 to 1.2 cm 3 /g, and pore diameters from 1.7 to 4.9 nm. Breakthrough studies of SO 2 and 2-CEES sorption yielded information about the effectiveness of each sorbent. Carbon samples worked well for 2-CEES but not SO 2 , while silica samples were poor for both. The best MgO and TiO 2 samples were good for both SO 2 and 2-CEES, and overall, the highest surface area (459 m 2 /g) TiO 2 sample was the superior sorbent. The important features for an effective sorbent under the conditions employed are high surface area and high pore volume, possessing isolated surface -OH groups, mesoporous nature, and a polar surface (Lewis base and Lewis acid sites).

Physico-chemical properties of soils of a particular area is crucial for determination of its potential and constraints based on which appropriate management interventions could be applied for enhanced and sustained agricultural production and productivity. Therefore, the objectives of this study were to determine physico-chemical properties of the soils of Ambukuna microcachment and to identify its potentials and constraints for crop production.  Five sites representing a soil each were opened and profile in each site was described for its morphological, physical and chemical characteristics according to standard procedures. A total of 20 disturbed soil samples and 16 core ring samples were collected from five representative sites. The samples were analyzed in the laboratory for texture, BD, FC, PWP, Soil pH, EC, OC, TN, av.P, av.K, exchangeable bases and CEC. The results of the study showed that the proportions of soil separates varied among sites. The BD varied from 1.13 in the s...

Introducing point defects in two dimensional, 2D, materials can alter or enhance their properties. Here, we demonstrate how etching a laminated (Nb2/3Sc1/3)2AlC MAX phase (solid solution) of both the Sc and Al atoms, results in a 2D Nb1.33C material (MXene) with a large number of vacancies and vacancy clusters. This method is applicable to any quaternary, or higher, MAX phase wherein one of the transition metals is more reactive than the other and could be of vital importance in applications such as catalysis and energy storage. We also report, for the first time, on the existence of (Nb2/3Sc1/3)3AlC2 and (Nb2/3Sc1/3)4AlC3 phases.

High-entropy (HE) ceramics, by analogy with HE metallic alloys, are an emerging family of multielemental solid solutions. These materials offer a large compositional space, with a corresponding large range of properties. Here, we report the experimental realization of a 3D HE MAX phase, Ti 1.0 V 0.7 Cr 0.05 Nb 1.0 Ta 1.0 AlC 3 , and a corresponding 2D HE MXene in the form of freestanding flakes of average composition Ti 1.1 V 0.7 Cr x Nb 1.0 Ta 0.6 C 3 T z (T z = -F, -O, -OH), as produced by selective removal of Al from the HE MAX phase in aqueous hydrofluoric acid (HF). Initial tests on HE MXene "paper" electrodes show their high potential as electrode materials in supercapacitors through volumetric and gravimetric capacitances of 1688 F/cm 3 and 490 F/g, respectively, originating from a combination of diffusion-and surface-controlled charge storage processes. The introduction of the HE concept into the field of 2D materials suggests a wealth of future 2D materials and applications.

Ti 3 C 2 T x MXene intercalated with Li + ions was produced and ion-exchanged with a series of trimethylalkylammonium (AA) cations of increasing alkyl chain length. A discontinuous expansion in the MXene layer spacing was observed, attributed to complete packing of the interlayer space at a critical chain length. The latter was used to estimate the number of cations per Ti 3 C 2 formula unit, which was found to be in good agreement with similar quantification obtained from X-ray photoelectron spectroscopy, energy-dispersive spectroscopy, and elemental analysis. The system was also modeled using density functional theory and molecular dynamics, arriving at cation concentrations in the same range. The intercalated AA cations led to tunable increases in resistivity of the normally highly electrically conductive MXene, and were investigated as interlayer pillars in electrochemical capacitors.

This article presents the synthesis and the blend of bismuth complexes in polystyrene based plastic scintillators. A specific design has enabled the fabrication of a scintillator loaded with up to 17 wt% of bismuth. Tri-carboxylate and triaryl bismuth compounds were used to explore and understand the influence of bismuth loading on the two main criteria of plastic scintillation: light yield and detection efficiency of γ-rays. For gamma radiation with an energy <200 keV, bismuth loaded scintillators demonstrate the ability to produce a photoelectric peak (total absorption peak) in pulse height spectra. The increase of interactions due to bismuth doping was quantified and fitted with standard models. Finally the performance of our bismuth loaded scintillators was evaluated to be better than that of a commercial lead loaded counterpart. A1. The general procedure was applied with 1.95 mL of monomers (78 wt%), 0.3 g of PPO (13 wt%), 0.2 mg of POPOP (0.1 wt%), and 0.2 g of [2] (8 wt%). A2. The general procedure was applied with 19.5 mL of monomers (78 wt%), 3 g of PPO (13 wt%), 2 mg of POPOP (0.1 wt%), and 2 g of [2] (8 wt%). A3. The general procedure was applied with 3.50 mL of monomers (58 wt%), 95 mg of PPO (1.7 wt%), 0.6 mg of bis-MSB (0.03 wt%), and 2.24 g of [5] (40 wt%). A4. The general procedure was applied with 8.70 mL of monomers (58 wt%), 95 mg of PPO (1.7 wt%), 0.6 mg of bis-MSB (0.1 wt%), and 2.37 g of [6] (40 wt%). B1. The general procedure was applied with 10.6 mL of monomers (94 wt%), 0.67 g of [7] (1 mmol, 6.2 wt%), 0.2 g of butyl-PDB (1.8 wt%), and 10 mg of POPOP (0.1 wt%). B2. The general procedure was applied with 10.6 mL of monomers (90 wt%), 0.44 g of [1] (1 mmol, 4.0 wt%), 0.46 g of biphenyl (3 mmol, 4.1 wt%), 0.2 g of butyl-PDB (1.8 wt%), and 10 mg of POPOP (0.1 wt%). The general procedure was applied with 10.6 mL of monomers (94 wt%), 0.46 g of biphenyl (3 mmol, 4.2 wt%), 0.2 g of Bu-PDB (1.8 wt%), and 10 mg of POPOP (0.1 wt%). C1. The general procedure was applied with 21.4 mL of monomers (76.8 wt%), 6.0 g of PPO (23.1 wt%), 20 mg of POPOP (0.1 wt%). C2. The general procedure was applied with 21.4 mL of monomers (74.1 wt%), 6.0 g of PPO (22.2 wt%), 20 mg of POPOP (0.1 wt%), and 1 g of [1] (3.7 wt%). C3. The general procedure was applied with 21.4 mL of monomers (71.5 wt%), 6.0 g of PPO (21.4 wt%), 20 mg of POPOP (0.1 wt%), and 2 g of [1] (7.1 wt%). C4. The general procedure was applied with 21.4 mL of monomers (66.7 wt%), 6.0 g of PPO (20.0 wt%), 20 mg of POPOP (0.1 wt%), and 4 g of [1] (13.3 wt%). C5. The general procedure was applied with 21.4 mL of monomers (62.5 wt%), 6.0 g of PPO (18.8 wt%), 20 mg of POPOP (0.1 wt%), and 6 g of [1] (18.7 wt%). C6. The general procedure was applied with 21.4 mL of monomers (58.8 wt%), 6.0 g of PPO (17.6 wt%), 20 mg of POPOP (0.1 wt%), and 8 g of [1] (23.5 wt%). X-ray radiography was performed with a Yxlon™ Comet MXR-451 apparatus with the tension set at 50 kV, recorded on a Kodak M-type argentic film.

Recently, copper selenides have shown to be promising thermoelectric materials due to their possible superionic character resulting from mobile copper cations. Inspired by this recent development in the class of quaternary copper selenides we have focused on the structure-to-property relationships in the solid solution series Cu 2 ZnGeSe 4Àx S x . The material exhibits an insulator-to-metal transition at higher temperatures, with a transition temperature dependent on the sulfur content. However, the lattice parameters show linear thermal expansion at elevated temperatures only and therefore no indication of a structural phase transformation. 63 Cu nuclear magnetic resonance shows clear indications of Cu located on at least two distinct sites, which eventually merge into one (apparent) site above the phase transformation. In this manuscript the temperature dependent lattice parameters and electronic properties of the solid solution Cu 2 ZnGeSe 4Àx S x are reported in combination with 63 Cu NMR, and an attempt will be made to relate the nature of the electronic phase transformation to a superionic phase transformation and a changing covalent character of the lattice upon anion substitution in this class of materials.

Nanostructured tin dioxide was synthesized by making use of the catalytic activity of silicatein-α. TEM, HRTEM, and XRD revealed the formation of cassiterite SnO 2 . Surface bound silicatein retains its biocatalytic activity. This was demonstrated by immobilizing silicatein on glass surfaces using a histidine-tag chelating anchor. The subsequent deposition of SnO 2 on glass was monitored by quartz crystal microbalance (QCM) measurements and scanning electron microscopy (SEM). This new aspect of silicatein activity toward the formation of metal oxides other than SiO 2 , TiO 2 , and BaTiO 3 opens up new vistas in composite material synthesis.

The effect of prolonged storage at relatively high temperature on the crystallization kinetics of polyamide 12 (PA12) has been studied by using Flash DSC. • The results were implemented in a multi-phase crystallization model that allows us to calculate growth and nucleation rates for different PA12 crystal phases. • It is shown that thermal annealing results in a significant increase in molecular weight due to post condensation and this reduces the crystallization rate. • There is no noticeable effect on the crystallization kinetics at low (below 90°C) and high (above 150°C) temperature range. • The results can provide a better insight of the effect of reusing PA12 powder the SLS process.

We present a complete model that can predict the local complex structure formation of iPP in conditions comparable to real life processing. • The model can predict the local crystalline composition, distinguishing between the multiple phases and multiple morphologies and couples structure formation with rheology. • It includes a full coupling between non-isothermal flow, non-linear viscoelastic flow behavior and (flow enhanced) crystallization. • The finite element implementation is applicable to general processing applications. • Model validation is done by comparison with the unique in situ X-ray and rheology data set.

Many recent investigations have confirmed the presence of surface barriers in a variety of zeolites. These surface barriers can have a significant effect on the overall rates of mass transfer and have the potential to significantly reduce the effectiveness of zeolites in industrial applications. In this study, the strength of the surface barrier was manipulated in a well-defined way and correlated with the rate of isobutane uptake. Silicalite-1 crystals were synthesized and were surface treated with trimethyl-, triethyland tripropylchlorosilanes. It was hypothesized that with the increasing size of the alkyl group the pore windows would be increasingly blocked, thereby effectively decreasing the pore size and increasing the surface barriers. The rates of adsorption and desorption of isobutane in untreated and treated samples were monitored by infrared microscopy. For differential pressure steps, adsorption and desorption responses were mirror images of one another. For large pressure steps, the rate of adsorption was much higher than that of desorption, indicating a significant variation of intracrystalline diffusivity with loading. The adsorption/desorption curves were analyzed considering (1) the presence of only intracrystalline diffusion and (2) surface barrier followed by intracrystalline diffusion. The measured rates of adsorption/desorption were significantly lower for the surface treated samples when compared with those for the untreated samples. Moreover, the strength of the surface resistance increased with the size of the alkyl group in chlorosilanes used for surface treatment.

The coated PET fabric with atomic ratios of Ti/(Ti+Zn) of 100%, 75%, 50%, 25%, and 0% was successfully prepared via sol–gel process from directly mixing TiO2/ZnO sol. The scanning electron microscopy (SEM) observation, energy dispersive spectroscopy (EDS) and the X-ray diffraction method (XRD) measurements revealed that the microstructural morphology and the crystallization behavior of the composite film were essentially related to the atomic ratio of Ti/(Ti+Zn). The UV irradiated degradation of Methylen blue (MB) solution using the coated fabrics as catalyst showed a tendency of the photocatalytic activity of the film against the value of Ti/(Ti+Zn). Photocatalytic activity was observed for the film with Ti/(Ti+Zn) 25% , which has been attributed to the high degredation of MB.

A new synthetic route for the deposition of CoAl 2 O 4 thin films at low temperature via MOCVD using the single-source precursor {Co have been investigated by means of NMR spectroscopy, mass spectrometry, and thermal analysis. Deposits have been characterized by XRD, AFM, UV-vis, and SIMS measurements.

x N y films were produced from single-source precursors in a chemical vapor deposition process. The boranes were introduced as precursors at low pressure conditions and at a temperature of 700 C, whereas the borazine was handled at 400 C and with a plasma enhancement at an electrical power input of 40 W. Additionally, as inert or reactive gases, H 2 , He, N 2 , and NH 3 , respectively, were used. The films deposited on Si(100) substrates were chemically characterized by X-ray photoelectron spectroscopy and by synchrotron radiation-based total-reflection X-ray fluorescence combined with near-edge X-ray absorption fine structure and quantified elementally by energy-dispersive X-ray spectroscopy. The results are critically compared. With the application of boranes without NH 3 , compounds with a dominating carbidic character were identified, whereas with the addition of NH 3 to the boranes, a nitridic character was prevalent. In case of using borazine for the synthesis, the nitridic character was found at the application of all auxiliary gases. For both groups stoichiometric formulas derived from energy-dispersive X-ray spectroscopy are proposed: B 3.5-4 C 4 N 2-2.5 for the carbidic region and B 3.5 C 1.5 N 5 for the nitridic region.

Largest diff. peak and hole 1.026 and -0.808 e.Å -3 N(1)-H(6) 0.9100 N(1)-H(7) 0.9100 C(1)-C(3) 1.493(13) C(1)-C(2) 1.517(14) C(1)-H(8) 1.0000 C(2)-H(9) 0.9800 C(2)-H(10) 0.9800 C(2)-H(11) 0.9800 C(3)-H(12) 0.9800 C(3)-H(13) 0.9800 C(3)-H(14) 0.9800 N(2)-C(4) 1.453(10) N(2)-H(15) 0.9100 N(2)-H(16) 0.9100 N(2)-H(17) 0.9100 C(4)-C(5)#1 1.483(10) C(4)-C(5) 1.483(10) C(4)-H(18) 1.0000 C(5)-H(19) 0.9800 C(5)-H(20) 0.9800 C(5)-H(21) 0.9800

We used partially fluorinated alkyl and aromatic phosphonates as model systems with similar molecular dipole moments to form self-assembled monolayers (SAMs) on the Zn-terminated ZnO(0001) surface. The introduced surface dipole moment allows tailoring the ZnO work function to tune the energy levels at the inorganic-organic interface to organic semiconductors, which should improve the efficiency of charge injection/extraction or exciton dissociation in hybrid electronic devices. By employing a wide range of surface characterization techniques supported by theoretical calculations, we present a detailed picture of the phosphonates' binding to ZnO, the molecular orientation in the SAM, their packing density, as well as the concomitant work function changes. We show that for the aromatic SAM the interaction between neighboring molecules is strong enough to drive the formation of a more densely packed monolayer with a higher fraction of bidentate binding to ZnO, whereas for the alkyl SAM a lower packing density was found with a higher fraction of tridentate binding.

Quite a few low molecular mass organic gelators 1 (LMOGs) and their applications 2 have been reported so far. These physical gels obtained from LMOGs depend on relatively weak interactions, for example, hydrogen bonding, to form a 3-D network that immobilize the solvent molecules, leading to gel formation. During the course of our investigations in the area of crystal engineering of an organic acid-base adduct, 3 we recently found that a simple organic salt 4 can harden few organic solvents. We, therefore, launched an extensive search for new LMOGs based on organic salts. We decided to work on secondary ammonium (dicyclohexylammonium) salt of chloro-substituted monocarboxylic acid (2-, 3-, and 4-chloro cinnamic acid) because of the following reasons: (i) The hydrogen bonding network in such salt is expected to be one-dimensional (through COO -‚‚‚H-R 2 N + -H‚‚‚ -OOC hydrogen bonding), which

The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr 0.28 Zr 0.10 O 0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO 2 formation starting at ∼750-800 °C, followed by decomposition of the a-Cr 2 O 3 structure in conjunction with bcc-Cr formation, starting at ∼950 °C. The resulting coating after annealing to 1140 °C is a mixture of t-ZrO 2 , m-ZrO 2 , and bcc-Cr. The air-annealed sample shows t-ZrO 2 formation starting at ∼750 °C. The resulting coating after annealing to 975 °C is a mixture of t-ZrO 2 and a-Cr 2 O 3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO 2 fraction compared with a-Cr 2 O 3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 °C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.

Many of the moving components in accelerator and target environments require lubrication. Lubricants in such environments are exposed to high fluxes of secondary radiation, which originates from beam interactions with the target and from beam losses. The secondary radiation is a mix of components, which can include significant fractions of neutrons. Lubricants are radiation-sensitive polymeric materials. The radiation-induced modifications of their structure reduce their service lifetime and impose additional facility maintenance, which is complicated by the environmental radioactivity. The study of the lubricants radiation resistance is therefore necessary for the construction of new generation accelerators and target systems. Nevertheless, data collected in mixed radiation fields are scarce. Nine commercial greases were irradiated at a TRIGA Mark II Research Reactor to serve for the construction of new accelerator projects like the European Spallation Source (ESS) at Lund (Sweden) and Selective Production of Exotic Species (SPES) at Legnaro, (Italy). Mixed neutron and gamma doses ranging from 0.1 MGy to 9.0 MGy were delivered to the greases. For an experimental quantification of their degradation, consistency was measured. Two of the greases remained stable, while the others became fluid. Post-irradiation examinations evidence the cleavage of the polymeric structure as the dominant radiation effect. Dose and fluence limits for the use of each product are presented. Apart from the scientific significance, the results represent an original and useful reference in selecting radiation resistant greases for accelerator and target applications.

A general synthetic strategy for controlling the shape of gold domains grown onto CdS semiconductor nanocrystals is presented. The colloidal growth of Au nanoparticles is based on the temperature-controlled reduction of Au-oleate complexes on the surface of CdS and allows for precise tuning of nanoparticle diameters from 2.5 to 16 nm simply by adjusting the temperature of the growth solution, whereas the shape of Au/CdS nanocomposites can be controllably switched between matchsticks and barbells via the reaction rate. Depending on the exact morphology of Au and CdS domains, fabricated nanocomposites can undergo evaporation-induced self-assembly on a substrate either through end-to-end coupling of Au domains, resulting in the formation of onedimensional chains or via side-by-side packing of CdS nanorods, leading to the onset of twodimensional superlattices.

The loading of a Zn-terephthalate based MOF in the inner cavity as well as on the outer walls of a hollow carbon nanofiber (CNF) creates MOF@CNF hybrids. This hybrid ''MOF@CNF'' displayed improved thermal stability as well as gas adsorption compared to the individual counterparts.

Targeting the spleen with nanoparticles could increase the efficacy of vaccines and cancer immunotherapy, and have the potential to treat intracellular infections including leishmaniasis, trypanosome, splenic TB, AIDS, malaria, and hematological disorders. Although, nanoparticle capture in both the liver and spleen has been well documented, there are only a few examples of specific capture in the spleen alone. It is proposed that the larger the nanoparticle size (> 400 nm) the greater the specificity and capture within the spleen. Here, we synthesized five nanostructures with different shapes (ranging from spheres, worms, rods, nanorattles and toroids) and poly(N-isopropylacrylamide), PNIPAM, surface coating using the temperature-directed morphology transformation (TDMT) method. Globular PNIPAM (i.e. water insoluble) surface coatings have been shown to significantly increase cell uptake and enhanced enzyme activity. We incorporated a globular component of PNIPAM on the nanostructure surface, and examined the in vivo biodistribution of these nanostructures and accumulation in various tissues and organs in a mouse model. The in vivo biodistribution as a function of time was influenced by the shape and PNIPAM surface composition, in which organ capture and retention was the highest in the spleen. The rods (~150 nm in length and 15 nm in width) showed the highest capture and retention of greater than 35% to the initial injection amount compared to all other nanostructures. It was found that the rods specifically targeted the cells in the red pulp region of the spleen due to the shape and PNIPAM coating of the rod. This remarkable accumulation and selectively into the spleen represents new nanoparticle design parameters to develop new splenotropic effects for vaccines and other therapeutics.