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Objectives:\ud Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions.\ud \ud Methods:\ud Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated.\ud \ud \ud Results:\ud The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats.\ud \ud Significance:\ud Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.

Phosphate-based glasses are a very promising class of multifunctional biomaterials. Being bioresorbable, they are capable of inducing simultaneous regeneration of tissue and delivery of drugs/therapeutic molecules and ions. Therefore, they can be used both as temporary implants and as controlled local delivery systems. Biomaterial-related infections, often causing revision surgery, could be prevented by incorporating into the biomaterial device antimicrobial agents that will be slowly released as the implant degrades. To date, the conventional technique used to prepare phosphate-based glasses is the melt-quenching process, which requires the melting of oxide powders at high temperatures (1000–1200 °C) followed by rapid cooling. However, this method often leads to non-homogeneous, bulk glasses that cannot be used for hosting temperature-sensitive molecules and can lead to reduction of antibacterial ions. Composition is also difficult to control because of the loss of volatile phosphate species during heating. This chapter describes two in-solution techniques for the synthesis of phosphate-based glasses alternative to the melt-quenching one: sol–gel and coacervation. A review of the literature published so far on the topics and a summary of key results is presented.

Materials that display strong capabilities for lithium insertion without significant change in unit cell size on cycling are of considerable importance for electrochemical applications. Here, we present V2O3(SO4)2 as a host for lithium-ion batteries. Electrochemically, 2.0 Li+ ions can be inserted, giving Li2V2O3(SO4)2 with an oxidation state of V4+, as determined by X-ray absorption spectroscopy. The capacity of V2O3(SO4)2 can be increased from 157 mA h g−1 to 313 mA h g−1 with the insertion of two additional Li+ ions which would drastically improve the energy density of this material, but this would be over a wider potential range. Chemical lithiation using n-butyllithium was performed and characterisation using a range of techniques showed that a composition of Li4V2O3(SO4)2 can be obtained with an oxidation state of V3+. Structural studies of the lithiated materials by X-ray diffraction showed that up to 4.0 Li+ ions can be inserted into V2O3(SO4)2 whilst maintaining its framework structure.

Increased demand for lithium products for use in lithium-ion batteries has led to a search for new lithium resources in recent years to meet projected future consumption. One potential lithium resource is low lithium bearing brines that are discharged from hydraulically fractured oil and gas wells as flowback and produced water (FPW). In this way, hydraulic fracturing presents an opportunity to turn what is normally considered wastewater into a lithium resource. In this research, two manganese-based lithium-selective adsorbents were prepared using a co-precipitation method and were employed for lithium recovery from FPW. At optimized conditions, lithium uptake reached 18 mg g−1, with a > 80% lithium recovery within 30 min. The recovered lithium was isolated and concentrated to 15 mM in an acidic final product. The degree of sorbent loss during acid desorption of lithium was significantly higher for sorbents used in the FPW as compared to recovery from a synthetic lithium-bearing brine (4.5% versus 0.8%). Thus, we propose that organic molecules present in the FPW reduce manganese in the sorbent structure during lithium sorption, leading to increased sorbent loss through reductive dissolution. Systematic characterization including wet chemical manganese valence measurements, along with EXAFS, XPS, and TEM-EELS show that exposure to FPW causes tetravalent manganese in the bulk sorbent structure to be reduced during lithium sorption, which subsequently dissolves during acid desorption. Partial removal of these organic molecules by nanofiltration leads to decreased sorbent dissolution in acid. In this way, we show that dissolved organic molecules represent a critical control on the reductive dissolution of manganese-based lithium ion exchange sorbents. This research provides promising results on the use of manganese-based lithium sorbents in FPW.

Phosphate-based glasses (PBGs) are traditionally prepared using the high temperature melt quenching route (MQ) or via the more recent sol-gel method (SG) that requires the use of organic solvents. The coacervation method represents an excellent inexpensive and green alternative to MQ and SG, being performed in aqueous solution and at room temperature. Coacervation is particularly applicable for the production of PBGs designed for biomedical applications, because it allows for the inclusion of temperature sensitive molecules and it does not require the use of toxic solvents. Whereas the atomic structure of the melt quenched and sol-gel PBGs is known, the atomic structure of those prepared via coacervation has yet to be investigated.\ud In this study, a comprehensive advanced structural characterization has been performed on phosphate-based glasses in the system P2O5–CaO–Na2O–Ag2O (Ag2O mol% = 0, 1, 3, 5, 9 and 14) prepared via the coacervation method. Glasses within this system should find application as bioresorbable biomaterials thanks to their ability to release bioactive ions in a controlled manner. In particular, they possess antibacterial properties, inferred by the release of Ag+ over time. \ud High energy X-ray diffraction (HEXRD), 31P and 23Na solid state magic angle spinning nuclear magnetic resonance (MAS NMR) and X-ray Absorption (XAS) at the Ag K-edge were used to probe the atomic structure of the glasses after drying in vacuum and after calcination at 300 °C. \ud The length of the polyphosphate chains in the solid state appears to be independent of silver concentration, however, significant degradation of these chains is seen after calcination at 300 °C. Atomic-scale structure results indicate that the structure of these glasses is akin to that of other silver doped phosphate glasses prepared using the MQ and SG method. This suggests that phosphate-based glasses prepared using milder and greener conditions may have similar chemical and physical properties such as solubility, biocompatibility, and antibacterial properties.

EJK would like to thank the Alistore ERI for the award of a studentship. This work was supported by the Faraday Institution (grant number FIRG018). Additional capacity delivered by oxygen redox activity may in principle represent a means of enhancing the electrochemical performance of layered sodium transition metal oxides. However, irreversible structural changes occurring during cycling typically cause significant capacity fade with limited reversibility of oxygen redox processes. Here, P3-structure Na0.67Co0.2Mn0.8O2 was synthesised under two different reaction conditions. Both materials exhibit very stable cycling performance in the voltage range 1.8-3.8 V where the redox couples of transition metals entirely dominate the electrochemical reaction. For the compound prepared under more oxidising conditions, anion redox activity is triggered in the wider voltage window 1.8-4.4 V in a reversible manner with exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition metal layers is shown to play a critical role not only in generating unpaired O 2p states but also in stabilising the crystal structure in the high voltage region. Postprint Postprint

EJK would like to thank the Alistore ERI for the award of a studentship. This work was supported by the Faraday Institution (grant number FIRG018). Lithium-rich layered oxides and sodium layered oxides represent attractive positive electrode materials exhibiting excess capacity delivered by additional oxygen redox activity. However, structural degradation in the bulk and detrimental reactions with the electrolyte on the surface often occur, leading to limited reversibility of oxygen redox processes. Here we present the properties of P3-type Na0.67Mg0.2Mn0.8O2 synthesized under both air and oxygen. Both materials exhibit stable cycling performance in the voltage range 1.8-3.8 V where the Mn3+/Mn4+ redox couple entirely dominates the electrochemical reaction. Oxygen redox activity is triggered for both compounds in the wider voltage window 1.8-4.3 V with typical large voltage hysteresis from non-bonding O 2p states generated by substituted Mg. Interestingly, for the compound prepared under oxygen, an additional reversible oxygen redox activity is shown with exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition metal layers is shown to play a critical role not only in forming unpaired O 2p states independent of substituted elements but also in stabilising the P3 structure during charge with reduced structural transformation to the O’3 phase at the end of discharge. This study reveals the important role of vacancies in P3-type sodium layered oxides to increase energy density using both cationic and anionic redox processes. Postprint Postprint

The effects of mechanochemical synthesis and postsynthetic grinding on the spin crossover material [Fe(atrz)3](BF4)2 was examined in detail using a combination of X-ray diffraction, magnetometry, EXAFS and TEM. Mechanochemical synthesis yielded a different polymorph (&beta, phase) to the solution synthesised sample (&alpha, phase), with a lower temperature spin crossover. Milling duration did not significantly affect this temperature but did result in the production of smaller nanoparticles with a narrower size distribution. It is also possible to convert from &alpha, to the &beta, phase via postsynthetic grinding.

The defect density of a material is central to its properties. Here, we show, employing EXAFS measurements and MD simulation, how the Ba-Li antisite defect density of perovskite-structured BaLiF3 nanoparticles can be tuned. In particular, we show that ball milling reduces the defect content. Conversely, thermal annealing increases the defect density. The work represents a first step toward tailoring the properties of a material via defect tuning postsynthesis.

Ionic conductivity is ubiquitous to many industrially important applications such as fuel cells, batteries, sensors, and catalysis. Tunable conductivity in these systems is therefore key to their commercial viability. Here, we show that geometric frustration can be exploited as a vehicle for conductivity tuning. In particular, we imposed geometric frustration upon a prototypical system, CaF2, by ball milling it with BaF2, to create nanostructured Ba1–xCaxF2 solid solutions and increased its ionic conductivity by over 5 orders of magnitude. By mirroring each experiment with MD simulation, including “simulating synthesis”, we reveal that geometric frustration confers, on a system at ambient temperature, structural and dynamical attributes that are typically associated with heating a material above its superionic transition temperature. These include structural disorder, excess volume, pseudovacancy arrays, and collective transport mechanisms; we show that the excess volume correlates with ionic conductivity for the Ba1–xCaxF2 system. We also present evidence that geometric frustration-induced conductivity is a general phenomenon, which may help explain the high ionic conductivity in doped fluorite-structured oxides such as ceria and zirconia, with application for solid oxide fuel cells. A review on geometric frustration [ Nature 2015, 521, 303] remarks that classical crystallography is inadequate to describe systems with correlated disorder, but that correlated disorder has clear crystallographic signatures. Here, we identify two possible crystallographic signatures of geometric frustration: excess volume and correlated “snake-like” ionic transport; the latter infers correlated disorder. In particular, as one ion in the chain moves, all the other (correlated) ions in the chain move simultaneously. Critically, our simulations reveal snake-like chains, over 40 Å in length, which indicates long-range correlation in our disordered systems. Similarly, collective transport in glassy materials is well documented [for example, J. Chem. Phys. 2013, 138, 12A538]. Possible crystallographic nomenclatures, to be used to describe long-range order in disordered systems, may include, for example, the shape, length, and branching of the “snake” arrays. Such characterizations may ultimately provide insight and differences between long-range order in disordered, amorphous, or liquid states and processes such as ionic conductivity, melting, and crystallization.

EJK would like to thank the Alistore ERI for the award of a studentship and Ok Sung Jeon at Yonsei University for ICP-OES measurement. The authors are grateful for the provision of beam time and assistance from instrument scientists at beamlines B18 at the Diamond Light source (as part of the Energy Materials Block Allocation Group SP14239), BL27SU at Spring 8 and GEM diffractometer at ISIS at the Rutherford Appleton Laboratory. Increasing dependence on rechargeable batteries for energy storage calls for the improvement of energy density of batteries. Toward this goal, introduction of positive electrode materials with high voltage and/or high capacity is in high demand. The use of oxygen chemistry in lithium and sodium layered oxides has been of interest to achieve high capacity. Nevertheless, a complete understanding of oxygen-based redox processes remains elusive especially in sodium ion batteries. Herein, a novel P3-type Na0.67Ni0.2Mn0.8O2, synthesized at low temperature, exhibits oxygen redox activity in high potentials. Characterization using a range of spectroscopic techniques reveals the anionic redox activity is stabilized by the reduction of Ni, because of the strong Ni 3d–O 2p hybridization states created during charge. This observation suggests that different route of oxygen redox processes occur in P3 structure materials, which can lead to the exploration of oxygen redox chemistry for further development in rechargeable batteries. Postprint

Phosphate-based glasses are materials of great interest for the regeneration and repair of damaged hard or soft tissues. They have the desirable property of slowly dissolving in the physiological environment, eventually being totally replaced by regenerated tissue. Being bioresorbable, they can simultaneously induce tissue regeneration and deliver therapeutic agents (e.g. antibacterial ions) in a controlled way. In this work, we have synthesised a series of glasses in the P2O5–CaO–Na2O system doped with Ag2O using the coacervation method. The addition of silver is known to provide the glass with antibacterial properties due to the release of Ag+ ions into the body fluid. The coacervation method is a facile, water-based technique which offers significant advantages over the conventional melt-quench route for preparing phosphate-based glasses which requires melting of metal oxide powders at high temperatures (1000–1200 °C). The properties of the initial colloidal polyphosphate systems (coacervates) as a function of the Ag2O content were characterised using rheology and liquid state 31P NMR. The effect of Ag+ addition on the final dried glasses was investigated using thermal analysis, Raman spectroscopy and X-ray diffraction. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus), a bacterial strain commonly found in post-surgery infections. A dose-dependent antimicrobial effect was seen with an increasing silver content.

Many phosphate-based glasses (PBGs) for biomaterial applications have been developed from the Na2O-CaO-P2O5 system. The common base compositions for PBGs are (55-x)Na2O-xCaO-45P2O5 and 20Na2O.30CaO.50P2O5, where the later corresponds to a metaphosphate, and there is a wealth of experimental data for 50Na2O.50P2O5, 50CaO.50P2O5 and 20Na2O.30CaO.50P2O5 metaphosphate glasses. A classical molecular dynamics (MD) method has been used to model Na2O-CaO-P2O5 glass structures, and the results have been closely compared with experimental data for the same glasses. The MD models show the phosphate network to be dominated by Q2 units, as expected, and to have short range order parameters that are in good agreement with neutron and X-ray di?raction results. Typical coordination numbers of Na and Ca are 5 and 6, respectively. The modifer cation distributions have been examined in detail through the correlation functions TMM(r), with M=Na and/or Ca. The TMM(r) functions show the expected dependence of peak position on modifer cation size, and peak height on modifer cation concentration. The numbers of M-M nearest neighbours are in agreement with a statistical model, in which modifer cations are bonded to nonbridging oxygens, Onb, and M(Onb)N polyhedra are predominantly connected to each other by corner-sharing.

During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.

Defects of various types in crystalline and nanocrystalline materials govern a range of electrical, optical and mechanical properties. In particular, they are at the heart of translational ion dynamics in solid electrolytes. One of the most prominent examples revealing a drastic increase in ionic conductivity σDC by several orders of magnitude when going from an ordered crystalline matrix to a structurally disordered one is lithium tantalate. Here, structurally disordered, nanocrystalline LiTaO3 served as a model substance to shed light on the question to what extent the degree of disorder decreases upon annealing an originally defect-rich oxide. Disorder can be introduced by high-energy ball milling of LiTaO3 crystallites with diameters in the μm range. Broadband conductivity spectroscopy, EXAFS and positron annihilation lifetime spectroscopy were used to correlate ion transport properties with interatomic distances, bond distortions and positron lifetimes. It turned out that milling times of only 30 min are sufficient to generate a highly defective oxide. Upon annealing at temperatures of T = 200 °C the defects can almost be preserved. Annealing at 750 °C for 1 h is needed to induce healing of the defects. Although we observe a recovery of the original interatomic distances and an increase in activation energy Ea for ionic transport from 0.75 eV to 0.81 eV, the initial transport properties of the unmilled sample (0.97 eV) cannot be fully restored. Most interestingly, the change in Ea is accompanied by a change of the entropy-controlled Arrhenius pre-factor governing the temperature dependence of σDCT. Moreover, positron lifetimes remain high in the annealed samples. Hence, our results point to samples with fewer distortions but still rich in vacancy-type defects. Altogether, the combination of ball milling and annealing helps adjust ionic conductivities in LiTaO3 to vary over 4 to 5 orders of magnitude.

Correction for ‘Lithiation of V2O3(SO4)2 – a flexible insertion host’ by Stephanie F. Linnell et al., J. Mater. Chem. A, 2020, DOI: 10.1039/d0ta06608g.

DSC thanks Johnson Matthey for the award of a CASE studentship. The I11 beamtime was obtained through the Diamond Light Source Block Allocation Group award “Oxford Solid State Chemistry BAG to probe composition-structure-property relationships in solids” (EE13284). The rhodium (III) hydrogarnets Ca3Rh2(OH)12 and Sr3Rh2(OH)12 crystallise as polycrystalline powders under hydrothermal conditions at 200 °C from RhCl3·3H2O and either Ca(OH)2 or Sr(OH)2 in either 12 M NaOH or KOH. Rietveld refinements against synchrotron powder X-ray diffraction (XRD) data allow the first crystal structures of the two materials to be determined. If BaO2 is used as a reagent and the concentration of hydroxide increased to hydroflux conditions (excess NaOH) then single crystals of a new complex rhodium hydroxide, BaNaRh(OH)6, are formed in a phase-pure sample, with sodium included from the flux. Structure solution from single-crystal XRD data reveals isolated octahedral Rh centres that share hydroxides with 10-coordinate Ba and two independent 8-coordinate Na sites. 23Na magic-angle spinning NMR confirms the presence of the two crystallographically distinct Na sites and also verifies the diamagnetic nature of the sample, expected for Rh(III). The thermal behaviour of the hydroxides on heating in air was investigated using X-ray thermodiffractometry, showing different decomposition pathways for each material. Ca3Rh2(OH)12 yields CaRh2O4 and CaO above 650 °C, from which phase-pure CaRh2O4 is isolated by washing with dilute nitric acid, a material previously only reported by high-pressure or high-temperature synthesis. Sr3Rh2(OH)12 decomposes to give a less crystalline material with a powder XRD pattern that is matched to the 2H-layered hexagonal perovskite Sr6Rh5O15, which contains mixed-valent Rh3+/4+, confirmed by Rh K-edge XANES spectroscopy. On heating BaNaRh(OH)6 a complex set of decomposition events takes place via transient phases. Postprint

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2\(p\) orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li\(^+\)–O(2\(p\))–Li\(^+\) interactions). Na\(_{2/3}\)[Mg\(_{0.28}\)Mn\(_{0.72}\)]O\(_2\) exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg\(^{2+}\) resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na\(_{2/3}\)[Mg\(_{0.28}\)Mn\(_{0.72}\)]O\(_2\) does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg\(^{2+}\) remains in Na\(_{2/3}\)[Mg\(_{0.28}\)Mn\(_{0.72}\)]O\(_2\), which stabilizes oxygen.

Bioactive sol-gel calcia-silica glasses can regenerate damaged or diseased bones due to their ability to stimulate bone growth. This capability is related to the formation of a hydroxyapatite layer on the glass surface, which bonds with bone, and the release of soluble silica and calcium ions in the body fluid which accelerates bone growth. The addition of s ilver ions imbues the glass with antibacterial properties due to the release of antibacterial Ag + ion. The antibacterial activity is therefore closely dependent on the dissolution properties of the glasses which in turn are related to their atomic-level structure. Structural characterization of the glasses at the atomic level is therefore essential in order to investigate and control the antibacterial properties of the glass. We have used neutron diffraction to investigate the structure of silver-containing calcia-silica sol-gel bioactive glasses with different Ag 2 O loading (0, 2, 4, 6 mol%). The presence of the silver had little effect on the host glass structure, although some silver metal nanoparticles were present. Results agreed with previous computer simulations.

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li

NXFitis a program for obtaining optimized structural parameters from amorphous materials by simultaneously fitting X-ray and neutron pair-distribution functions. Partial correlation functions are generated inQspace, summed and Fourier transformed for comparison with the experimental data inrspace.NXFituses the Nelder–Mead method to vary a set of `best guess' parameters to achieve a fit to experimentally derived data. The output parameters fromNXFitare coordination number, atomic separation and disorder parameter for each atomic correlation used in the fitting process. The use ofNXFithas been demonstrated by fitting both X-ray and neutron diffraction data from two quite different amorphous materials: a melt-quenched (Na2O)0.5(P2O5)0.5glass and a (TiO2)0.18(SiO2)0.82sol–gel.

Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/4+) in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li(+)/Li. The capacity at 4.5 V is dominated by oxidation of the O(2-) anions accounting for ∼0.43 e(-)/formula unit, with an additional 0.06 e(-)/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ∼0.08 e(-)/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal-oxygen interaction on anion redox in lithium rich cathode materials.

The synthesis of high surface area xerogels has been achieved using the sol-gel route. Heptane washing was used during the stages of drying to minimise capillary pressures and hence preserve pore structure and maximise the surface area. SAXS data have identified that heptane washing during drying, in general, results in a preservation of the pore structure and surface areas of up to 450 m(2) g(-1). O-17 NMR showed that Ti is fully mixed into the silica network in all of the samples. XANES data confirm that reversible 4-fold Ti sites are more prevalent in samples with high surface areas, as expected. The calcined xerogels were tested for their catalytic activity using the epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) as a test reaction, with excellent selectivities and reasonable percentage conversions. FT-IR spectroscopy has revealed that the catalytic activity is correlated with the intensity of the Si-O-Ti signal, after accounting for variations in Si-OH and Si-O-Si. The most effective catalyst was produced with heptane washing, a calcination temperature of 500 degreesC, and a heating rate of 5 degreesC min(-1).

Sol-gel-synthesized bioactive glasses may be formed via a hydrolysis condensation reaction, silica being introduced in the form of tetraethyl orthosilicate (TEOS), and calcium is typically added in the form of calcium nitrate. The synthesis reaction proceeds in an aqueous environment; the resultant gel is dried, before stabilization by heat treatment. These materials, being amorphous, are complex at the level of their atomic-scale structure, but their bulk properties may only be properly understood on the basis of that structural insight. Thus, a full understanding of their structure-property relationship may only be achieved through the application of a coherent suite of leading-edge experimental probes, coupled with the cogent use of advanced computer simulation methods. Using as an exemplar a calcia-silica sol-gel glass of the kind developed by Larry Hench, in the memory of whom this paper is dedicated, we illustrate the successful use of high-energy X-ray and neutron scattering (diffraction) methods, magic-angle spinning solid-state NMR, and molecular dynamics simulation as components to a powerful methodology for the study of amorphous materials.

The emerging field of lead-based hybrid organic–inorganic perovskite (HOIP) photovoltaic devices has attracted a great deal of attention due to their very high conversion efficiencies and straightforward fabrication methods. Unfortunately, a major obstacle to commercialization remains the high toxicity of lead. Whilst to date the focus has been on understanding and improving device performance, there has been no reported effort to develop methods to recover and recycle the lead from these materials. In this work we demonstrate a simple, low-cost and environmentally friendly method of recycling lead from HOIP photovoltaics by dissolution and selective electrodeposition using a deep eutectic solvent. We demonstrate that up to 99.8% of the lead is removed from the solvent. The results presented here provide a viable solution to lead-based HOIP photovoltaic recycling, and also open the possibility for providing an alternative method to conventional smelting in the recovery and recycling of different lead-based energy materials.

Thin films of NiSb(0001) have been grown using molecular beam epitaxy on GaAs(111)B substrates and characterized with a variety of structural and surface-specific techniques supported by density functional theory calculations. Several differences were observed between NiSb and the more widely studied MnSb. A new (4×4) surface reconstruction was seen on NiSb(0001), along with other reconstructions common to MnSb or MnAs. Strain relaxation differs between NiSb and MnSb, with strained layers 10 nm thick persisting in NiSb and some crystallites of ( 1 1 ¯ 01 ) orientation appearing in thick (0001) films. Ga segregation through NiSb(0001) films does not occur, unlike in MnSb, and the native oxide of NiSb is more benign than the Mn-rich oxides of MnSb.

Development of controlled, targeted drug delivery systems represents one of the frontier areas of biomaterials science, where a multidisciplinary approach is of direct benefit to human healthcare. We demonstrate herein the potential of sol–gel derived phosphate-based glass for use in drug delivery applications. Our low-temperature sol–gel synthesis of phosphate-based glasses has made it possible to incorporate relatively unstable functional molecules for controlled release. We demonstrate the potential of this approach by incorporating the chemotherapy agent cisplatin in a CaO–Na2O–P2O5 glass. X-ray absorption spectroscopy is used to show that the chlorine ligands of cisplatin undergo exchange with oxygen during the synthesis, consistent with binding to the phosphate groups of the sol–gel. UV–visible spectroscopy reveals the subsequent release of cisplatin into an aqueous medium.

An array of different structural probes has been used to define the effect of adding Zn and Ti to a sodium-calcium phosphate glass. X-ray absorption spectroscopy at the Zn K-edge suggests that the Zn atoms occupy mixed (4- and 6-fold) sites within the glass matrix. X-ray diffraction reveals a feature at 2.03 angstrom that develops with the addition of Zn and Ti and is consistent with Zn-O and Ti-O near-neighbour distances. Neutron diffraction is used to resolve two distinct P-O distances and highlights the decrease in P center dot center dot center dot P coordination number from 2.0 to 1.7 as the Ti metal concentration rises, which is attributed to the O/P fraction moving away from the metaphosphate value of 3.0 to 3.1 with the addition of Ti. Other correlations, such as those associated with CaO(x) and NaO(x) polyhedra, remain largely unaffected. These results suggest that the network forming P center dot center dot center dot P correlation is most disrupted, with the disorder parameter rising from 0.07 to 0.10 angstrom with the additional modifiers. Zn appears to be introduced into the network as a direct replacement for Ca and causes no structural variation over the composition range studied.

The structure of aged melt-quenched sodium borophosphate glasses of composition (P2O5)(40)(B2O3)(x)(Na2O)(60-x) (with x in the range 10-40) has been studied by high-energy X-ray diffraction (HEXRD), P-31 and B-11 magic angle spinning (MAS) NMR. Similar to the fresh samples, both P-O-P and P-O-B linkages are found to be present in these glasses. All three techniques show that the cross-linking between borate and phosphate units increases with boron oxide content. Distinctively upon aging, the glass is found to hydrolyze causing the network to degrade. At the same time, crystalline phases are now also observed. XRD and DTA show that the samples have a higher tendency towards crystallization with increasing boron oxide content upon exposed to moisture. P-31 and B-11 MAS NMR results are in agreement with these findings. TGA data show that samples with higher boron oxide content take up more moisture upon aging, suggesting that crystallization may be associated with glass hydrolysis. HEXRD results also suggest that sodium ions are preferentially associated with borate units with increasing boron oxide content. (C) 2008 Elsevier B.V. All rights reserved.

This paper reports the results of an investigation into the mechanisms that have led to the build up of sulfuric acid in the timbers of the Mary Rose , with a particular focus on recently recovered timbers. Measurements have been made by sulfur and iron K-edge X-ray absorption near edge spectroscopy (XANES), X-ray microscopy and by X-ray diffraction (XRD). Results from S K-edge XANES studies reveal that the concentration of highly oxidised S decreases with depth into the timber, from ∼15 at.% of S at the surface to negligible levels after approximately 50 mm. Fe K-edge XANES reveals little variation with depth in which Fe 3+ ions are dominant. This sheds some light on the sulfur oxidation path, and indicates Fe 3+ ions are produced by the oxidation mechanisms that are currently underway. XRD studies have identified several mineral components that may form part of the oxidation chain. These are magnetite (Fe 3 O 4 ), jarosite (KFe 3 (SO 4 ) 2 (OH) 6 ) and calcite (CaCO 3 ).

Ti K-edge XANES (X-ray absorption near edge structure) spectroscopy has been used to study the local coordination of titanium in biocompatible and bioresorbable TiO2-CaO-Na2O-P2O5 glasses. Both conventional melt-quenched glasses of composition (TiO2) (x)(CaO)(0.30)(Na2O)((0.20-x))(P2O5)(0.50), where x = 0.01, 0.03 and 0.05, and sol-gel derived (TiO2)(0.25)(CaO)(0.25)(P2O5)(0.50) glass have been studied. The results show that in all the materials studied, titanium is surrounded by an octahedron of oxygen atoms. Further analysis reveals that the TiO6 site in the amorphous samples is not heavily distorted relative to that in rutile, anatase or CaSiTiO5. The spectra from the (TiO2)(0.25)(CaO)(0.25)(P2O5)(0.50) sol-gel samples reveal greater distortion in the TiO6 site in the dried gel compared to the heat-treated sol-gel glass. The XANES spectra from melt-quenched glass samples soaked in distilled water for various times do not shown any evidence of degradation of the titanium site over periods of up to 14 days.

Glasses from the CaO-TiO2-P2O5 system have potential use in biomedical applications. Here a method for the sol-gel synthesis of the ternary glass (CaO)(0.25)(TiO2)(0.25)(P2O5)(0.5) has been developed. The structures of the dried gel and heat-treated glass were studied using high-energy X-ray diffraction. The structure of the binary (TiO2)(0.5)(P2O5)(0.5) sol-gel was studied for comparison. The results reveal that the heat-treated (CaO)(0.25)(TiO2)(0.25)(P2O5)(0.5) glass has a structure based on chains and rings of PO4 tetrahedra, held together by a combination of electrostatic interaction with Ca2+ ions and by corner-sharing oxygen atoms with TiO6 octahedra. In contrast, the (TiO2)(0.5)(P2O5)(0.5) glass has a structure based on isolated P2O7 units linked together by corner-sharing with TiO6 groups. The results suggest that both the dried gels possess open porous structures. For the (CaO)(0.25)(TiO2)(0.25)(P2O5)(0.5) sample there is a significant increase in Ca-O coordination number with heat treatment.

High energy X-ray diffraction (HEXRD) has been used to study the atomic structure of (Ta2O5) (x) (SiO2)(1-x) (x = 0.05, 0.11 and 0.25) xerogels; the direct interpretation of the resultant data has been augmented using reverse Monte Carlo (RMC) modelling. For the first time in this type of material, two Ta-O correlations have been identified (at similar to 1.8 angstrom and 2.0 angstrom). The RMC modelling approach explicitly used MAS-NMR data to define its constraints; when combined with HEXRD data, it helps to confirm the more directly determined total coordination of five for the two Ta-O correlation distances and suggests Ta center dot center dot center dot Si and Ta center dot center dot center dot Ta coordination distances of similar to 3.3 angstrom and similar to 3.8 angstrom, respectively. The O center dot center dot center dot O and Si center dot center dot center dot Si distances and coordination numbers associated with the host silica network suggest that the Ta (V) is acting as a network modifier. The way in which the Ta-O correlations are affected by composition and calcination temperature suggest some phase separation in the (Ta2O5)(0.25)(SiO2)(0.75) sample. However, in general, the results indicate good mixing of the component oxides.

A novel synthetic strategy has been developed for the fabrication of mesostructured titanosilicate with very high titanium content. By the combination of ultrasound radiation and a separate hydrolysis procedure, highly ordered MCM-41 titanosilicates can be synthesized within 3 h from gels with Ti/Si ratios up to 1. The physicochemical properties of the materials were characterized by means of XRD, TEM, FT-IR, UV-Vis DRS, 2 9 Si MAS NMR, and liquid nitrogen adsorption-desorption measurements. The results suggested that during crystallization, sonication re-dispersed and accelerated the condensation of inorganic species, and resulted in more condensed pore walls compared to those synthesized with the conventional methods. The presence of silica and ultrasound radiation remarkably suppressed the aggregation of titanium species, thus, at the medium titanium level, a relatively homogeneous dispersion of titanium within the MCM-41 framework was attained.

Neutron diffraction with isotopic titanium substitution allows the nature of the cation sites to be determined beyond nearest-neighbor distances for the first time in a sol–gel derived titania–silica glass. Reverse Monte Carlo (RMC) modelling of the results shows unequivocally that titanium substitutes for silicon within the homogeneous glass network, existing mostly as TiO 4 , with a minority TiO 6 component. The fundamental scientific interest, and wide-ranging technologically significant properties of titania additions to silica, demand an understanding of the precise nature of the titanium site.

A new synthetic method has been developed and demonstrated for the utilization of commercially cheap MnO2 for the production of nanoparticles of LiMn2O4 spinel as a cathode material for Li-ion batteries. The process involves the insertion of lithium into electrolytic manganese dioxide (EMD) in an aqueous medium with glucose as a mild reductant in open air. The material resulting from calcination is pure, spinel-structured Li0.96Mn2O4 particles of sub-micrometric and nanometric size that exhibit promising electrochemical behavior in nonaqueous Li-salt solutions. Further development of this process may be interesting for the commercial production of LiMn2O4 for Li-ion batteries.

A combination of extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES), Fourier transform infrared (FTIR), and 17O nuclear magnetic resonance (NMR) spectroscopies, small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD) has been used to study the atomic structure of (TiO2)x(ZrO2)y(SiO2)1-x-y xerogels (0.05 ≤ x, y ≤ 0.15). The samples were prepared by reacting Ti butoxide and Zr n-propoxide with acetylacetone, to reduce reactivity of the metal alkoxides, and then reacting with partially hydrolyzed tetraethyl orthosilicate. EXAFS and XANES results imply that simultaneous insertion of Zr and Ti oxides into a silica host network causes the metals to adopt environments similar to those observed for the corresponding binary Zr oxide− and Ti oxide−silica systems. XANES, SAXS, and XRD indicate that the samples with up to 20 mol % total metal loading remain homogeneous with heat treatment up to 500 °C. 17O NMR indicates that both Ti- and Zr-rich samples with 20 mol...

6Li magic angle spinning (MAS) nuclear magnetic resonance spectroscopy has been used to study the structure of a series of LiMn2O4 spinel samples prepared using different annealing methods. The results show that the annealing conditions affect the number of defect sites within the structure; higher annealing temperatures leading to a spinel sample with fewer defects. Analysis of the peak intensities in the NMR spectra revealed that the structural evolution of the spinel samples with temperature is dependent upon particle size. A series of chemically delithiated samples have also been studied using a combination of 6Li MAS NMR, X-ray diffraction and infrared spectroscopy in order to follow the structural changes that occur upon delithiation. The NMR spectra of the delithiated samples, LixMn2O4, exhibit a gradual shift in the position of main spinel resonances (i.e. Li in 8a tetrahedral sites) with decreasing lithium content for 0.3 < x < 1.0. For x < 0.3, the delithiated samples exhibit a new 6Li resonance at ∼950 ppm. This resonance is assigned to lithium present in 8a sites in a Mn4+-rich phase at the centre of the spinel particles. This assignment is supported by FT-IR data and crystallite size measurements (XRD), which suggest that HMn2O4 forms on the surface of the particles in the heavily delithiated samples.

The incorporation of transition-metal oxides into silica can give materials with useful optical, electronic or catalytic properties. For example, ZrO2-SiO2 and HfO2-SiO2 materials are of interest due to their high dielectric constants. Here we present a comparison of extended X-ray absorption fine structure and small-angle X-ray scattering results for acid-catalysed binary (MO2) x (SiO2)1 − x (M = Ti, Zr or Hf) xerogels, with x up to 0.4 and heat treatments up to 750°C. Detailed observations for TiO2-SiO2 and ZrO2-SiO2 xerogels provide a basis for interpretation of new results for HfO2-SiO2 xerogels. At low concentrations metal atoms are homogeneously incorporated into the silica network. Ti adopts coordinations of 4 or 6, and Zr and Hf both adopt higher coordination of 6 or 7 (the larger coordinations being due to ambient moisture). At higher concentrations, phase separation of metal oxide occurs. Such regions become clearly separated from the silica network for TiO2, but remain very finely mixed with silica network for ZrO2 and HfO2.

There has been much work on the binary TiO2-SiO2 and ZrO2-SiO2 materials prepared by sol-gel because of the beneficial properties resulting from incorporation of Ti and Zr. In contrast the ternary TiO2-ZrO2-SiO2 xerogels have been relatively little studied. We report the results of a study of those xerogels having Zr:Ti:Si ratios of 5:15:80, 10:10:80 and 15:5:80 heated to 750°C and to 1000°C. The study includes X-ray diffraction, small angle X-ray scattering, X-ray absorption spectroscopy at Ti and Zr K-edges, and 17O MAS-NMR. The study has benefited from close comparison with similar previous studies of the binary systems. The metal atoms in the ternary systems are shown to be predominantly homogeneously mixed in the silica network, as observed for the respective binary systems. The clear exception is for the sample with a minority of Zr, which after heat treatment at 750°C shows the presence of phase separation attributed to the formation of an amorphous precursor of ZrTiO4; at 1000°C this phase crystallises. In samples with higher Zr content the crystallisation of a ZrO2 tetragonal phase was observed. The data obtained illustrate well the strength of a research methodology in which a common batch of samples is studied using a coherent suite of modern structural probes.

We report here a novel method of catalytic transformation of amorphous carbon to CNT. The method involves Fe(CO)5 thermolysis in the presence of carbon black at high pressure. A mechanism is proposed; it is verified by solid-state NMR measurements.

Previous work has shown that nanocrystalline samples of lithium tantalate and titanate prepared by high-energy milling show unusually high lithium ion conductivity. Here, we report an X-ray absorption spectroscopy (XAS) study at the Ti K-edge and the Ta L3 edge of samples that have been milled for various lengths of time. For both systems the results show that milling creates amorphous material whose quantity increases with the milling time. The more extensive data for the tantalate shows that milling for only 30 minutes generates ~25% amorphous content in the sample. The content rises to ~60% after 16 hours. It is suggested that it is the motion of the lithium ions through the amorphous content that provides the mechanism for the high ionic conductivity.

The calcination of a (TiO2)(0.18)(SiO2)(0.82) aerogel has been followed using in situ high-temperature Ti K-edge 'quick EXAFS' and XANES measurements. The results clearly show that the coordination of Ti in this material changes from a mixture of four- and sixfold to predominantly fourfold as the temperature is increased from ambient to 300 degreesC. The decrease in static disorder, as the environment of Ti converts to predominantly a single site, is such that the overall Debye-Waller factor for the Ti-O shell decreases markedly even as the temperature increases to 700 degreesC. Combined 'quick EXAFS' and XANES measurements are shown to be valuable tools for in situ studies of structural changes associated with thermal treatment of amorphous materials.

In situ high temperature x-ray diffraction measurements have been performed on a (TiO2)(0.18) (SiO2)(0.82) xerogel using a 185 mm radius curved image-plate. The results clearly show that the coordination of Ti in this material changes from predominantly sixfold to predominantly fourfold as the temperature is increased from 25 degrees C to 310 degrees C An increase in the average O-O distance associated with this change is also identified. The use of the curved image-plate is shown to be a valuable technique for in situ studies of structural changes associated with thermal treatment of materials.

X-ray absorption spectroscopy at the Zr K-edge is an important technique for probing the environment of Zr. Here it is applied to zirconia-silica xerogels with composition 0.07 less than or equal to x less than or equal to 0.40, where x is the molar ratio Zr : (Zr + Si). Reference samples of crystalline ZrO2, ZrSiO4, BaZrO3 and liquid Zr n-propoxide were also examined. New XANES (X-ray adsorption near edge structure) results are presented for zirconia-silica xerogels, and compared with previous EXAFS (extended X-ray absorption fine structure) results. For high Zr contents (x = 0.4) there is a separate, amorphous ZrO2 phase, which before heat treatment is similar to Zr hydroxide, and after heat treatment at 750 degrees C is similar to an amorphous precursor of tetragonal ZrO2. For low Zr contents (x = 0.1) there is atomic mixing of Zr in the SiO2 network, and the environment of Zr is more similar to that in Zr n-propoxide compared to other reference samples. New in situ XANES and EXAFS results are presented for x = 0.1 xerogels heated at 250 degrees C. These clearly show that the Zr environment depends on ambient moisture in addition to heat treatment.

A variable-temperature (79, 145, and 293 K) extended x-ray absorption fine structure study, using rare-earth LIII absorption edges, is reported for phosphate glasses doped with rare-earth elements (R, where R = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) with compositions close to metaphosphate, R(PO3)3. The results yield nearest-neighbor R–O distances that demonstrate the lanthanide contraction in a glassy matrix and an R–O coordination intermediate between 6 and 7 for rare-earth ions with smaller atomic number (Z) and 6 for rare-earth ions with largerZ. Thermal parameters show no significant changes in R–O distances or coordination numbers between 293 and 79 K. There is evidence of an R–P correlation between 3.3 and 3.6 Å and the beginning of a second R–O correlation at approximately 4 Å. No R–R correlations up to a distance of approximately 4 Å were observed.

Accurate measurements of the height and position of the preedge peak in Ti K-edge XANES (X-ray absorption near-edge structure) can distinguish 4-, 5-, and 6-fold coordination of Ti by O (Ti-[4], Ti-[5], and Ti-[6], respectively), and mixtures thereof. This approach has been applied to titania-silica xerogels, (TiO2)(x)(SiO2)(1-x), prepared from Si and Ti alkoxides using a prehydrolysis step and acid catalyst, with 0.18 < x < 0.75. As expected, samples with x = 0.75 contain phase-segregated, amorphous, pre-anatase Ti-[6], which is converted to anatase after heating at 500 degrees C. Samples with x = 0.18 contain a majority of isolated, distorted Ti-[6] before heating, which is converted to Ti-[4] substituted for Si after heating at 750 degrees C. This is the first time that the changes in the coordination of isolated Ti have been unambiguously described. Xerogels with 0.25 < x < 0.35 and heat treatment at 750 degrees C showed concentration limits of Ti-[4] substitution for Si of 10-15mol %. Slightly higher values were obtained for xerogels prepared using acetylacetone, but the main difference was that the latter had a significantly larger content of distorted Ti-[6] before heat treatment. There is no evidence of significant amounts of Ti-[5].

A combination of 29 Si and 17 O MAS NMR, EXAFS and FTIR spectroscopy have been used to study the atomic structure of (TiO 2 ) x (SiO 2 ) 1–x (x=0.18, 0.30 and 0.41) xerogels prepared using an acetylacetone stabilised Ti(OPr i ) 4 precursor. In the as-prepared materials, Ti is present in a distorted octahedral coordination with a significant proportion still complexed by acetylacetone. For the first time in such an amorphous solid, a 17 O NMR resonance has been observed at 110 ppm which is attributed to (O 5 )Ti-O-Si groups. Heat treatment of these xerogels tends to convert TiO 6 into TiO 4 where the Ti is substituted into the silica network. Our results are in accord with previous work which suggests that the upper limit for solubility of TiO 2 in SiO 2 is ca. 15 mol%. Clear evidence of some phase separation in the (TiO 2 ) 0.41 (SiO 2 ) 0.59 sample after heat treatment to 750 °C is presented, although the 17 O MAS NMR results show that the use of acetylacetone significantly increases the amount of Ti-O-Si bonding at this composition compared to samples prepared without it.

In spite of extensive studies, using a variety of physical and chemical techniques, no consensus has yet been reached even as to the basic structural unit present in a-MoS3, a material with interesting catalytic and electrochemical properties. Here we present neutron diffraction data for a-MoS3 which are compared in both reciprocal- and real-space with the predictions of different structural models. We conclude that a-MoS3 is built from MoS6 groups (〈rMoS〉=2.44 ± 0.01 A), linked together by shared sulfurs to form Mo2S9 units, with the two molybdenum atoms forming Mo–Mo bonds at 2.75 ± 0.02 A. The presence of triangular Mo3 units in a-MoS3 is ruled out by the poor fit to the data of models based on these clusters. The results are consistent with chain models built from Mo2S9 units, with two of the bridging sulfur atoms bonded as a disulfide group. These units link together to form extended chains by sharing of the terminal monosulfides, creating a second (non-bonded) Mo–Mo distance at around 3.3 A.