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This study presents series of direct band gap Pb-free double perovskite Cs2AgInxBi1−xCl6, Cs2NaxAg1−xInCl6:Bi and Cs2KxAg1−xInCl6:Bi nanocrystal systems [Cs2B′(I)B′′(III)Cl6] synthesised using a colloidal hot-injection route. The structural properties investigated using powder XRD, TEM, solid state NMR and materials modelling approaches demonstrate that the incorporation of K+ cations into the double perovskite nanocrystal structure occurs simultaneously on both the Cs (A) site and Ag (B′(I)) positions within a series of closely related cubic and monoclinic structures. As a result of defect passivation, significant improvements in the photoluminescence quantum yield (PLQY) of ∼4.7× and ∼1.8× are exhibited in comparison to the Cs2AgInxBi1−xCl6, and Cs2NaxAg1−xInCl6:Bi nanocrystal systems, respectively. Materials modelling using the Ab Initio Random Structure Search (AIRSS) method, and the GIPAW DFT calculation of the NMR parameters from the derived structural realisations, shows that K+ incorporation induces significant short-range structural disorder and multi-phase formation. This is highlighted by the large 133Cs and 39K chemical shift dispersion characterising the MAS NMR data. Density of States (DoS) calculations describing these AIRSS generated structures suggest that increasing ionic character and reduced structural rigidity are strongly correlated with A site substitution of the K+ cation into these cubic and monoclinic phases. The 39K MAS NMR data reveals that the increasing PLQY performance maps directly with the K+ incorporation into the cubic CsKyAg1−yInCl6 phase supporting B site occupancy which is observed to be maximized at a 60 ml% K+ incorporation level. However, additional evidence indicates that low level K+ substitution primarily targets A site occupancy in a surface passivation role. The improvement to the optical properties induced by K+ and Na+ incorporation is rationalised in terms of increased covalent character and structural rigidity associated with decreased Cs+, Na+ and K+ cation mobility, as evidenced by the large (∼2 orders of magnitude) variation in the 133Cs T1 data across each compositional range.

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.

This study reports the synthesis and characterization of a porous geopolymer systems based a naturally occurring Moroccan pyrophyllite clay. The contribution of pyrophyllite in geopolymerization reaction was very low, the geopolymer matrix formed was assured by alkaline activation of the metakaolin present in the sample. The pyrophyllite role is forming of disordered and heterogeneous geopolymer promote the pore creation. The structure and morphology of the raw natural clay, calcined meta-pyrophyllite phase and prepared geopolymer samples are characterized by several methods namely, X-ray Diffraction (XRD), 29Si and 27Al magic-angle -spinning nuclear magnetic resonance (MAS NMR) analysis, Fourier Transform Infra-Red (FTIR) spectroscopy, Differential Thermal Analysis (DTA) and Thermal Gravimetric Analysis (TGA), N2 adsorption/desorption isotherm analysis by the Brunauer-Emmett-Teller (BET) method and Scanning Electron Microscopy (SEM). The specific surface area (SBET) and pore volume (Vp) measured from products utilizing the calcined meta-pyrophyllite precursor (SBET = 86 m2/g and Vp = 0.08 cm3/g) have both increased markedly compared to those values determined using a raw pyrophyllite clay phase (SBET = 30 m2/g and Vp = 0.05 cm3/g). The methylene blue (MB) molecular adsorption experiment realized in water medium exhibited Pseudo Second Order (PSO) rate kinetics and adopted a Langmuir adsorption model. The thermodynamics data shows that the chemisorption is spontaneous, irreversible, and endothermic, with the quantity of MB molecules retained by the porous geopolymer specimen reaching 64.10 mg/g.

Rare-earth (RE) containing alkali aluminoborosilicate glasses find increasingly broad technological applications, with their further development only impeded by yet-poor understanding of coordination environment and structural role of RE ions in glasses. In this work we combine free induction decay (FID)-detected electron paramagnetic resonance (EPR), electron spin echo envelope modulation (ESEEM), and MAS NMR spectroscopies, to examine the coordination environment and the clustering tendencies of RE3+ in a series of peralkaline aluminoborosilicate glasses co-doped with Nd2O3 (0.001-0.1 mol%) and 5 mol% La2O3. Quantitative EPR spectral analysis reveals three different Nd3+ forms coexisting in the glasses: isolated Nd3+ centers, dipole-coupled Nd clusters (Nd-O-X-O-Nd, where X = Si/B/Al), and spin-exchange-coupled Nd clusters, (Nd-O-Nd) and (Nd-O-La-O-Nd). Extensive RE clustering is observed at high RE2O3 concentrations, with more than 90% REs converting to dipole- and exchange-coupled Nd clusters already at [RE2O3] = 0.01 mol%. ESEEM analysis of the EPR-detectable Nd centers indicates a Na/Si-rich environment (four Na+ per Nd3+) for the isolated Nd3+ centers and the Na/Si/B-rich environment (2-3 Na+ and 1-2 boron per each Nd3+) for the dipole-coupled Nd clusters, while the EPR-undetectable exchanged-coupled RE clusters are predicted to exist in a Na/B-rich environment. The RE clustering induces nano-scale glass phase separation, while the Na/B-rich environment of the RE clusters implies a depletion of the same elements from the remaining host glass. Based on our results, we develop a mechanistic model that explains the high tendency of RE3+ to form clusters in alkali aluminoborosilicate glasses.

Inorganic nanomaterials hold immense potential in theranostics, but their translation is limited by the toxicity resulting from non-degradability. Bulk phosphate-based glasses offer great biodegradability, biocompatibility, and ease in incorporating imaging dyes and drugs. However, the facile and mild solution-based synthesis of micro-/nanoparticles of this material is yet to be explored. Inspired by the biosilicification process in the diatom, we created polyethylenimine (PEI)/phosphate aggregates via the hydrogen bonding between amine (PEI) and hydroxyl (phosphate) groups, which was proved by dynamic light scattering and 1H solution nuclear magnetic resonance. The sol–gel reaction between the calcium precursor and PEI/phosphate aggregates yielded degradable PEI/calcium phosphate (PEI/CP) micro-/nano-composites with versatile sizes (396 ± 128 nm to 63 ± 8 μm) and morphologies (hexagonal micro-disc, micro-flower, micro-leaf, nano-butterfly, and nano-ribbon). The PEI/CP composition and chemical structure were examined. PEI/CP has negligible cell cytotoxicity and degrades within 24 h. In vitro studies showed the promise for PEI/CP in transient ultrasound and photoluminescence imaging.\ud \ud

Methylammonium (MA+) lead halide perovskites (MAPbX3) have been widely investigated for photovoltaic applications, with the addition of Cs improving structural and thermal stability. This study reports the complete A site miscibility of Cs+ and MA+ cations in the lead chloride and lead bromide perovskites with nominal stoichiometric formulae (CsxMA1−x)Pb(Cl/Br)3 (x = 0, 0.13, 0.25, 0.37, 0.50, 0.63, 0.75, 0.87, 1). These suites of materials were synthesized mechanochemically as a simple, cost-effective synthesis technique to produce highly ordered, single phase particles. In contrast to previous studies using conventional synthetic routes that have reported significant solubility gaps, this solvent-free approach induces complete miscibility within the dual cation Cs+/MA+ system, with the resultant structures exhibiting high short-range and long-range atomic ordering across the entire compositional range that are devoid of solvent inclusions and disorder. The subtle structural evolution from cubic to orthorhombic symmetry reflecting PbX6 octahedral tilting was studied using complementary high resolution TEM, powder XRD, multinuclear 133Cs/207Pb/1H MAS NMR, DSC, XPS and UV/vis approaches. The phase purity and exceptional structural order were reflected in the very high resolution HRTEM images presented from particles with crystallite sizes in the ∼80–170 nm range, and the stability and long lifetimes of the Br series (10–20 min) and the Cl series (∼30 s–1 min) under the 200 kV/146 μA e− beam. Rietveld refinements associated with the room temperature PXRD study demonstrated that each system converged towards single phase compositions that were very close to the intended target stoichiometries, thus indicating the complete miscibility within these dual cation Cs+/MA+ solid solution systems. The multinuclear MAS NMR data showed a distinct sensitivity to the changing solid solution compositions across the MAPbX3–CsPbX3 partition. In particular, the 133Cs shifts demonstrated a sensitivity to the cubic–orthorhombic phase transition while the 133Cs T1s exhibited a pronounced sensitivity to the variable Cs+ cation mobility across the compositional range. Variable temperature PXRD studies facilitated the production of phase diagrams mapping the Cs+/MA+ compositional space for the (CsxMA1−x)PbCl3 and (CsxMA1−x)PbBr3 solid solution series, while Tauc plots of the UV/vis data exhibited reducing bandgaps with increasing MA+ incorporation through ranges of cubic phases where octahedral tilting was absent.\ud \ud

Methylammonium (MA

Alkali-activated materials (AAMs) have been known as an alternative cementitious binder in construction for more than 120 years. Several buildings utilizing AAMs were realized in Europe in the 1950s-1980s. During the last 30 years, the interest towards AAMs has been reinvigorated due to the potentially lower CO

Phosphate-based glasses are well-studied biodegradable materials in the bulk. However, less is known about the synthesis and properties of phosphate glass when prepared as microparticles or nanopar...

Two-dimensional (2D) phenylethyl ammonium (PEA+)-methyl ammonium (MA+) lead iodide ((PEA)2(MA)[Pb2I7]) hybrid perovskite exists as temperature-dependent dimorphs exhibiting an ill-defined phase transition occurring over the 150–200 K range. Raman scattering, photoluminescence, optical absorbance and solid state MAS NMR spectroscopic methods are employed to investigate the structural complexity, disorder and structure/function of this system. The Raman and 1H MAS NMR data indicate that the lower bounds of the phase transition at ∼150 K are characterised by attenuated rotational modes and slower motional dynamics throughout the disordered MA+ organic sublattice, inducing a strengthening of the MA+⋯I hydrogen bonds and a 5 meV increase in the excitonic and photoluminescence energies. It is evident that different recombination mechanisms are dominant for the room temperature and low temperature phases reflecting the importance of MA+ dynamics in the optical properties of the material. Single crystal X-ray studies are unable to position the organic cations within the Pb2I7 framework; however, 1H/13C MAS NMR measurements describe elements of local structural disorder based on conformational isomerism within the PEA+ sublattice. Concomitant I− and Pb2+ migration and [Pb2I7]3− framework defects create stacking disorder, dislocations and dispersed octahedral tilting leading to additional disorder and distributed MA+ and PEA+ cation dynamics.\ud \ud

Struvite-K (MgKPO4·6H2O) is a magnesium potassium phosphate mineral with naturally cementitious properties, which is finding increasing usage as an inorganic cement for niche applications including...

Inorganic cesium lead halide perovskite nanocrystals are promising materials for optoelectronic applications as they exhibit high thermal stability alongside precise color tunability and high color purity; however, their optical properties are degraded by surface defects. This work demonstrates a room temperature synthesis of CsPbBr3 nanocrystals facilitating in situ surface passivation via the incorporation of Zn2+ cations. The facile incorporation ZnBr2 into the precursor solution facilitates Zn2+ and Br− substitution into the nanocrystal surface/subsurface layers to induce passivation of existing Pb2+ and Br– vacancies and increase the photoluminescence quantum yield from ∼48 to 86%. The XPS and solid-state 1H MAS NMR techniques show that the key modification is a reduction of the octylamine:oleic acid ratio leading to a near-neutral surface charge; this is accompanied by the appearance of larger nanosheets and nanowires observed by quantitative powder XRD and HR-TEM. The suitability of these perovskite nanocrystals for electrically driven applications was confirmed by the fabrication of light-emitting diodes, which demonstrate that the in situ Zn2+ passivation strategy enhanced the external quantum efficiency by ∼60%. National Research Foundation (NRF) PV acknowledges a Presidential Postdoctoral Fellowship from Nanyang Technological University (NTU), Singapore via grant 04INS000581C150OOE01. We acknowledge financial support from the Singapore National Research Foundation, Prime Minister’s Office, through the Competitive Research Program (CRP Award No. NRF-CRP14-2014-03). The authors would like to acknowledge the Facility for Analysis, Characterization, Testing and Simulation (FACTS) at NTU, Singapore, for use of their electron microscopy and X-ray diffraction facilities. We would also like to acknowledge the NTU Center of High Field NMR Spectroscopy and Imaging for the use of their NMR facilities. The authors would also like to thank Prof. Nripan Mathews and Dr. Nur Fadilah Jamaludin for the valuable discussion, Mr. Sai S. H. Dintakurti for discussions with aspects of the crystallographic analysis and Mr. Gautam V. Nutan for assistance with the XPS measurements. JVH acknowledges financial support for the solid state NMR instrumentation at Warwick used in this research which was funded by EPSRC (grants EP/M028186/1 and EP/K024418/1), the University of Warwick, and the Birmingham Science City AM1 and AM2 projects which were supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF). AAMB acknowledges the Tizard studentship from the Faculty of Engineering and Physical Sciences at University of Southampton.

Inorganic/organic sol–gel hybrids consist of co-networks of inorganic and organic components that can lead to unique properties, compared to conventional composites, especially when there is covalent bonding between the networks. The aim here was to develop new electrospun silica/gelatin sol–gel hybrids, with covalent coupling and unique 3D cotton–wool-like morphology for application as regenerative medicine scaffolds. Covalent coupling is critical for obtaining sustained dissolution of the fibres and we identified the sol–gel synthesis conditions needed for coupling within the electrospun fibres. Under carefully controlled conditions, such as constant humidity, we investigated the effect of the electrospinning process variables of sol viscosity (and aging time) and amount of coupling agent on the 3D morphology of the fibres, their structure (bonding) and dissolution, identifying a detailed optimised protocol for fibre scaffold production.

The facile and efficient reaction of graphene oxide (GO) and 2-Ureido-4[1H]-pyrimidinone (UPy), an isocyanate terminated 4-site hydrogen-bonding moiety, produces a functionalised GO (f-GO) that readily self-assembles into a freestanding nacre-like film using a vacuum filtration process. The reaction of UPy with GO occurs predominately via the epoxide and hydroxyl groups on the GO which was confirmed from a combination of Fourier-transform infrared (FTIR), Raman and X-ray photoelectron spectroscopy (XPS) and 13C Solid State Nuclear Magnetic Resonance (SSNMR) measurements. The nacre-like films obtained were typically 50µm to 100µm thick, from cross-section scanning-electron microscopy (SEM) imaging. The GO d-spacing (X-ray diffraction, XRD) increased with increasing UPy content from 0.934nm to 1.45nm, resulting in porous films with reduced tortuosity to oxygen, carbon dioxide and water. However, at higher UPy content reduced tortuosity is, balanced with the ability of UPy dimers to readily dissociate and exchange with water. The tensile strength and tensile toughness of the GO nacre-like film increased by up to 470% and 1100% and the maximum strain by a factor of ~2, for the film with the highest UPy content. These improvements are achieved through a mechanism of extension and unfolding of the linear chain of six carbon atoms in UPy, enhancing strain under tensile loading permitting the platelets to slide more before failure. This work highlights the impact of enhanced interlayer interactions via hydrogen bonding in producing polymer-free nacre-like films.

Vinyl trimethoxysilane (VTMOS) functionalized reduced graphene oxide (rGO) was melt blended with low-density polyethylene (LDPE) and cross-linked through the vinyl group using a free radical initiator, dicumyl peroxide (DCP), in an extruder. The cross-linking reaction of the pendant vinyl group on the silane with LDPE via peroxide initiation was confirmed by solid-state magic angle spinning (MAS) 13C and 29Si nuclear magnetic resonance (NMR) measurements. The Raman spectrum of the cross-linked VTMOS-rGO and LDPE confirmed the formation of a 3D network. Scanning electron (SEM) and transmission electron (TEM) microscopy with elemental mapping showed the VTMOS forms nanospheres located interstitially between rGO layers dispersed within the LDPE matrix. From oscillatory rheology measurements, the transition to more “solid-like” behavior due to cross-linking was detected from a significant decrease in the crossover frequency (G′ vs G″) from 31.6 to as low as 0.603 rad/s and an increase in relaxation times (λ) from 0.032 to 1.66 s for a rGO loading of 1 wt %. The formation of a 3D interconnected cross-linked VTMOS-rGO-LDPE network resulted in an increase in the tensile strength (↑31%) and tensile stress at break (↑55%) of LDPE. The onset of thermal degradation of LDPE was delayed by up to 31 °C due to the formation of cross-links and inclusion of silane functionalized rGO which requires a higher activation energy to initiate degradation.

A combined multinuclear solid state NMR and gauge included projected augmented wave, density functional theory (GIPAW DFT) computational approach is evaluated to determine the four heteronuclear 1J(13C,17O) couplings in solid 17O enriched naphthalaldehydic acid. Direct multi-field 17O magic angle spinning (MAS), triple quantum MAS (3QMAS) and double rotation (DOR) experiments are initially utilised to evaluate the accuracy of the DFT approximations used in the calculation of the isotropic chemical shifts (δiso), quadrupole coupling constants (CQ) and asymmetry (ηQ) parameters. These combined approaches give δiso values of 313, 200 and 66 ppm for the carbonyl (C[double bond, length as m-dash]O), ether (-O-) and hydroxyl (-OH) environments, respectively, with the corresponding measured quadrupole products (PQ) being 8.2, 9.0 and 10.6 MHz. The geometry optimised DFT structure derived using the CASTEP code gives firm agreement with the shifts observed for the ether (δiso = 223, PQ = 9.4 MHz) and hydroxyl (δiso = 62, PQ = 10.5 MHz) environments but the unoptimised experimental XRD structure has better agreement for the carbonyl group (δiso = 320, PQ = 8.3 MHz). The determined δiso and ηQ values are shown to be consistent with bond lengths closer to 1.222 Å (experimental length) rather than the geometry optimised length of 1.238 Å. The geometry optimised DFT 1J(13C,17O) coupling to the hydroxyl is calculated as 20 Hz and the couplings to the ether were calculated to be 37 (O-C[double bond, length as m-dash]O) and 32 (O-C-OH) Hz. The scalar coupling parameters for the unoptimised experimental carbonyl group predict a 1J(13C,17O) value of 28 Hz, whilst optimisation gives a value of 27 Hz. These calculated 1J(13C,17O) couplings, together with estimations of the probability of each O environment being isotopically labelled (determined by electrospray ionisation mass spectrometry) and the measured refocussable transverse dephasing (T2') behaviour, are combined to simulate the experimental decay behaviour. Good agreement between the measured and calculated decay behaviour is observed.

The fluorination mechanism of low-level fluorinated materials obtained by calcination of Bayer gibbsite at different temperatures was studied by 27Al and 19F solid-state NMR spectroscopy and X-ray diffraction. Gibbsite was calcined at 400, 600, 800, and 1000 °C followed by treatment with anhydrous HF/N2 gas at 100 °C. Three types of Al–F species on the surface of fluorinated gibbsite calcined at 400, 600, and 800 °C are proposed on the basis of the 19F magic angle spinning (MAS) NMR spectra, which show peaks at about −132, −137, and −163 ppm, while the spectrum of fluorinated gibbsite calcined at 1000 °C showed five additional peaks, at about −139, −164, −176, −183, and −191 ppm. The fluorination process in aluminas is based on elementary exchange reactions in which F− replaces surface –OH groups according to their basicity. The 27Al MAS NMR and 19F-27Al cross-polarization–MAS experiments confirmed the presence of octahedral Al species.

A combination of charge density studies and solid state nuclear magnetic resonance (NMR) 1 J NC coupling measurements supported by periodic density functional theory (DFT) calculations is used to characterise the transition from an n–π* interaction to bond formation between a nucleophilic nitrogen atom and an electrophilic sp 2 carbon atom in a series of crystalline peri‐substituted naphthalenes. As the N⋅⋅⋅C distance reduces there is a sharp decrease in the Laplacian derived from increasing charge density between the two groups at ca. N⋅⋅⋅C = 1.8 Å, with the periodic DFT calculations predicting, and heteronuclear spin‐echo NMR measurements confirming, the 1 J NC couplings of ≈3–6 Hz for long C−N bonds (1.60–1.65 Å), and 1 J NC couplings of 2.1 Å., A combination of charge density measurements, solid‐state NMR 1 J NC couplings, and DFT calculations is presented to characterise the transition from an n–π* interaction to bond formation for a series of model crystalline peri‐substituted naphthalenes.

(Calcium,alkali)-aluminosilicate gel frameworks are the basis of modern cements and alkali-activated materials for sustainable infrastructure and radioactive waste immobilization and also find application in glass alteration, mineral weathering, and zeolite synthesis. Here, we resolve the nanostructure of these gels that dictates mass transport, solubility, and mechanical properties. The key structural motifs comprising hydrous (calcium,alkali)-aluminosilicate gels are identified via 17O, 23Na, and 27Al triple-quantum magic angle spinning and 29Si magic angle spinning nuclear magnetic resonance spectroscopy of a novel class of stoichiometrically controlled 17O-enriched multiphase gels. Increased Ca content promotes low-Al, high-Ca chain-structured “C-S-H-type” products exhibiting significant nanostructural ordering, low levels of chain cross-linking, predominant Ca coordination of nonbridging oxygen atoms, and an increase in proton association with CaO layers to form Ca–OH sites. Al substitution is identified in multiple sites in the silicate chains, including cross-linking, bridging, and pairing tetrahedra. Increased Al content increases the proportion of cross-linking sites and gel disorder. The large increase in SiIV–O–AlIV sites increases the relative amounts of Na+ and AlV species charge-balancing AlO4– tetrahedra and results in the formation of an additional disordered low-calcium, framework-structured alkali aluminosilicate (“N-A-S-H-type”) gel, with high Al and Na contents. Changes in bulk composition significantly alter the nanostructures of the C-S-H-type and N-A-S-H-type gels. Mean SiIV–O–AlIV bond angles for each type of AlIV site environment are highly consistent, with compositional changes dictating the relative proportions of individual AlIV species but not altering the local structure of each AlIV site. These findings reveal the molecular interactions governing the (calcium,alkali)-aluminosilicate gel nanostructure, which are crucial in controlling material properties and durability.

Calcium phosphate glasses are a promising new generation of biomaterials that can simultaneously induce tissue regeneration and controlled release of therapeutic molecules. In this work, novel calcium phosphate glasses containing 0, 2, 4, and 6 mol % Cu2+ were synthesized via room temperature precipitation reaction in aqueous solution. The effect of Cu2+ addition on the glass properties and structure was investigated using thermal analysis, 31P solid-state MAS NMR, Raman spectroscopy, and X-ray diffraction. All glasses crystallize at temperature >500 °C and are mainly formed by Q1 groups. The release of P, Ca, and Cu in solution over time was monitored via inductively coupled plasma-optical emission spectroscopy. It was found that with increasing Cu content, the amount of P and Ca released decreases whereas the amount of Cu released increases. The effect of Cu2+ release on the antibacterial activity against S. aureus, a bacterial strain commonly found in postsurgery infections, has been investigated. The addition of copper has been shown to infer the glasses antibacterial properties. As expected, the antibacterial activity of the glasses increases with increasing Cu2+ content. Cytocompatibility was assessed by seeding human osteoblast-like osteosarcoma cells Saos-2 (HTB85) on the glass particles. A significant increase in cell number was observed in all the glasses investigated. The copper-doped calcium phosphate glasses have proven to be multifunctional, as they combine bone regenerative properties with antibacterial activity. Therefore, they have great potential as antibacterial bioresorbable materials for hard tissue regeneration.

International audience; A glass‐ceramic waste form is being developed for immobilization of waste streams of alkali (A), alkaline‐earth (AE), rare earth (RE), and transition metals generated by transuranic extraction for reprocessing of used nuclear fuel. Benefits over an alkali borosilicate waste form are realized by the partitioning of the fission product fraction insoluble in glass into a suite of chemically durable crystalline phases through controlled cooling, including (AE,A,RE)MoO4 (powellite) and (RE,A,AE)10Si6O26 (oxyapatite). In this study, a simplified 8‐oxide system (SiO2‐Nd2O3‐CaO‐Na2O‐B2O3‐Al2O3‐MoO3‐ZrO2) was melted, then soaked at various temperatures from 1450 to 1150°C, and subsequently quenched, in order to obtain snapshots into the phase distribution at these temperatures. For these samples, small angle X‐ray and neutron scattering, quantitative X‐ray diffraction, electron microscopy, 23Na nuclear magnetic resonance, Nd3+ visible absorption, and temperature‐dependent viscosity were characterized. In this composition, soak temperatures of urn:x-wiley:00027820:media:jace16406:jace16406-math-00011250°C were necessary to nucleate calcium molybdate (~10‐20 nm in diameter). Further cooling produced oxyapatite and total crystallization increased with lower soak temperatures. Both Na and Nd entered the crystalline phases with lower‐temperature soak conditions. Slow cooling or long isothermal treatments at ~975°C produced significantly higher crystal fractions.

Nuclear wastes generated from reprocessing of used nuclear fuel tend to contain a large fraction of rare earth (RE, e.g., Nd3+), transition (TM, e.g., Mo6+, Zr4+), alkali (A, e.g., Cs+), and alkaline earth cations (AE, e.g., Ba2+, Sr2+). Various strategies have been considered for immobilizing such waste streams, varying from nominally crystal-free glass to glass-ceramic to multi-phase ceramic waste forms. For glass and glass-ceramic waste forms, the added glass-forming system is generally alkali-alkaline earth-aluminoborosilicate (i.e., Na-Ca-Al-B-Si oxide). In a US-UK collaborative project, summarized here, we investigated the glass structure and crystallization dependence on compositional changes in simulated nuclear waste glasses and glass-ceramics. Compositions ranged in complexity from five – to – eight oxides. Specifically, the roles of Mo and rare earths are investigated, since a proposed glass-ceramic waste form contains crystalline phases such as powellite [(AE,A,RE)MoO4] and oxyapatite [(RE,AE,A)10Si6O26], and the precipitation of molybdenum phases is known to be affected by the rare earth concentration in the glass. Additionally, the effects of other chemical additions have been systematically investigated, including Zr, Ru, P, and Ti. A series of studies were also undertaken to ascertain the effect of the RE size on glass structure and on partitioning to crystal phases, investigating similarities and differences in glasses containing single RE oxides of Sc, Y, La, Ce, Nd, Sm, Er, Yb, or Lu. Finally, the effect of charge compensation was investigated by considering not only the commonly assessed peralkaline glass but also metaluminous and peraluminous compositions. Glass structure and crystallization studies were conducted by spectroscopic methods (i.e., Raman, X-ray absorption, nuclear magnetic resonance (NMR), optical absorption, photoluminescence, photoluminescence excitation, X-ray photoelectron spectroscopy), microscopy (i.e., scanning electron microscopy, transmission electron microscopy, electron probe microanalysis), scattering (i.e., X-ray and neutron diffraction, small angle measurements), and physical characterization (i.e., differential thermal analysis, liquidus, viscosity, density). This paper will give an overview of the research program and some example unpublished results on glass-ceramic crystallization kinetics, microstructure, and Raman spectra, as well as some examples of the effects of rare earths on the absorption, luminescence, and NMR spectra of starting glasses. The formal collaboration described here has resulted in the generation of a large number of results, some of which are still in the process of being published as separate studies.

Bioactive glass nanoparticles (BGNPs) can be internalized by cells, allowing the intracellular release of dissolution products with therapeutic benefit. Different therapeutic ions can be incorporated into the glass network that can promote angiogenesis via simulation of hypoxia conditions and consequent activation of pro-angiogenic genes. Here, novel monodispersed spherical dense BGNPs were obtained by a modified Stober method with the SiO2–CaO–CoO composition, with diameters of 92 ± 1 nm, with cobalt as the pro-angiogenic ion. The presence of Co2+ species and the role of Co and Ca as network modifiers in the silica glass were confirmed by X-ray photoelectron spectroscopy and 29Si solid-state magic-angle spinning nuclear magnetic resonance, respectively. Controlled Co2+ ion release was observed in culture media, and no cytotoxicity was observed by (4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cell viability assay on human osteosarcoma cells in direct contact with the nanoparticles. This study demonstrated that Co2+ ions can be incorporated into dense and spherical BGNPs, and these materials exhibit great potential as intracellular ion delivery systems with therapeutic properties.

There has been a huge amount of interest in perovskites recently and new structures of hybrid perovskites are frequently reported. The classification of perovskites has been unambiguous in the discussion of 3D and layered 2D perovskites due to the dimensional constraints. However, in 1D perovskites, the additional degrees of freedom have resulted in a large number of possible structural configurations. The new proposed notation aims to classify these structures based on the connectivity of the octahedra of the perovskite, which has a periodic repeating pattern. However, the notation should be restricted to simple 1D perovskites and haloplumbate structures as the notation would become too cumbersome when applied to an exotic framework which has 3D characteristics, such as perovskite polytypes. National Research Foundation (NRF) Published version The following funding is acknowledged: National Research Foundation Singapore (grant No. NRF-CRP14-2014-03).

Ceramics based around silicon aluminum oxynitrides are of both fundamental structural chemistry and technological interest. Certain oxynitride crystal structures allow very significant compositional variation through extensive Si/N exchange for Al/O, which implies a degree of atomic ordering. In this study, solid-state 29Si MAS NMR and variable field 1D and 2D 27Al MAS NMR measurements are combined with density functional theory calculations of both the structural and NMR interaction parameters for various points across the Y4Si2O7N2-Y4Al2O9 compositional range. This series provides numerous possibilities for significant variation of atomic ordering in the local ditetrahedral (Si,Al)2O7-xNx units. The two slightly structurally inequivalent aluminum sites in Y4Al2O9 are unambiguously assigned to the observed resonances. Computational findings on Y4Si2O7N2 demonstrate that the single observed 29Si NMR resonance covers a range of local inequivalent silicon environments. For the first time, the MAS NMR and neutron diffraction data from the Y4SiAlO8N structure have been directly reconciled, thus establishing aspects of atomic order and disorder that characterize this system. This comparison suggests that, although the diffraction data indicates long-range structural order supporting a highly crystalline character, the short-range information afforded by the solid-state NMR measurements indicates significant atomic disorder throughout the (Si,Al)2O7-xNx units.

Graphene oxide (GO) was reduced (rGO) and then functionalised with an amino terminated thiol molecule (cysteamine) via a thiol-ene click chemistry reaction to produce reduced graphene oxide-cysteamine (rGO-cyst). The presence of the C–S bond in the X-ray photoelectron spectrum (XPS) confirmed the reaction between the thiol in cysteamine and both the double bonds present on the rGO surface and the pyrazolic structures formed due to reduction. The rGO-cysyteamine was reacted with polypropylene-graft-maleic anhydride (PP-g-MA) to produce PP-g-MA-rGO-cysteamine, where the free amino group present on the rGO-cysteamine reacts with the maleic anhydride group of PP-g-MA. This was confirmed from solid state 13C Magic-Angle-Spinning, Nuclear Magnetic Resonance (MAS NMR), Fourier transform infrared (FTIR) and XPS studies which demonstrated that a mixture of open and closed ring structures based on amides, imides and imines were formed. Growth of the PP chain on the rGO surface was observed from electron microscopy imaging. Cysteamine acts like a ‘cross-linker’ between the rGO and PP-g-MA, increasing interfacial interaction between the two phases resulting in increased thermal stability and altering the crystallization behaviour of the maleated PP. The approach described could be used to compatabilise graphene oxide and a range of polymers to produce functional composite materials.

Triple-negative breast cancers are extremely aggressive with limited treatment options because of the reduced response of the cancerous cells to hormonal therapy. Here, monodispersed zinc-containing mesoporous silica nanoparticles (MSNPs-Zn) were produced as a tuneable biodegradable platform for delivery of therapeutic zinc ions into cells. We demonstrate that the nanoparticles were internalized by cells, and a therapeutic dose window was identified in which the MSNPs-Zn were toxic to breast cancer cells but not to healthy epithelial (MCF-10a) cells or to murine macrophages. A significant reduction in the viability of triple negative MDA-MB-231 and MCF-7 (ER+) breast cancer cells was seen following 24 h exposure to MSNPs-Zn. The more aggressive MDA-MB-231 cells, with higher metastatic potential, were more sensitive to MSNPs-Zn than the MCF-7 cells. MSNPs-Zn underwent biodegradation inside the cells, becoming hollow structures, as imaged by high-resolution transmission electron microscopy. The mesoporous silica nanoparticles provide a biodegradable vehicle for therapeutic ion release inside cells.

A combined multinuclear solid state NMR and gauge included projected augmented wave, density functional theory (GIPAW DFT) computational approach is evaluated to determine the four heteronuclear 1J(13C,17O) couplings in solid 17O enriched naphthalaldehydic acid. Direct multi-field 17O magic angle spinning (MAS), triple quantum MAS (3QMAS) and double rotation (DOR) experiments are initially utilised to evaluate the accuracy of the DFT approximations used in the calculation of the isotropic chemical shifts (δiso), quadrupole coupling constants (CQ) and asymmetry (ηQ) parameters. These combined approaches give δiso values of 313, 200 and 66 ppm for the carbonyl (C[double bond, length as m-dash]O), ether (-O-) and hydroxyl (-OH) environments, respectively, with the corresponding measured quadrupole products (PQ) being 8.2, 9.0 and 10.6 MHz. The geometry optimised DFT structure derived using the CASTEP code gives firm agreement with the shifts observed for the ether (δiso = 223, PQ = 9.4 MHz) and hydroxyl (δiso = 62, PQ = 10.5 MHz) environments but the unoptimised experimental XRD structure has better agreement for the carbonyl group (δiso = 320, PQ = 8.3 MHz). The determined δiso and ηQ values are shown to be consistent with bond lengths closer to 1.222 Å (experimental length) rather than the geometry optimised length of 1.238 Å. The geometry optimised DFT 1J(13C,17O) coupling to the hydroxyl is calculated as 20 Hz and the couplings to the ether were calculated to be 37 (O-C[double bond, length as m-dash]O) and 32 (O-C-OH) Hz. The scalar coupling parameters for the unoptimised experimental carbonyl group predict a 1J(13C,17O) value of 28 Hz, whilst optimisation gives a value of 27 Hz. These calculated 1J(13C,17O) couplings, together with estimations of the probability of each O environment being isotopically labelled (determined by electrospray ionisation mass spectrometry) and the measured refocussable transverse dephasing (T2') behaviour, are combined to simulate the experimental decay behaviour. Good agreement between the measured and calculated decay behaviour is observed.

Aqueous asymmetric supercapacitors (ASC) is considered to fulfill the safety and high energy-power requirements simultaneously towards building next-generation storage devices. One of the most attractive electrolytes is multiple ion-based water-in-salt (WIS) solutions, which are steadily conquering the field of rechargeable batteries/capacitors. Stabilizing the pH value is one of the efficient ways to improve the energy density of the charge storage system by widening the operating potential. In this line, we report that acetate ions could help to neutralize the pH of sodium(I)bis(fluorosulfonyl)imide-based WIS electrolyte by diluting the free water molecules without any precipitation or recrystallization, and allow to widen the operating potential window from ~2.7 to 3.1 V. The Physico-chemical properties of mixed anions-based electrolytes are explored from confocal-Raman and Nuclear magnetic resonance studies. In addition, we performed ab-initio density functional theory calculations to study the co-ordination environment. Apparently, the acetate (OAcˉ) ions show a stronger interaction with Na+ ion compared to weakly coordinating imide (FSIˉ) analogues. The Na0.44MnO2 and prosopis juliflora derived activated carbon (PJAC) based ASC, and PJAC based symmetric supercapacitor (SSC) using mixed WIS electrolyte is cycled up to 5000 times. Further, the influence of environmental conditions (60 and −20 °C) is also studied in detail for the WIS based electrolyte for both ASC and SSC. National Research Foundation (NRF) This research is supported by grants from the National Research Foundation, Prime Minister's Office, Singapore under its Campus of Research Excellence and Technological Enterprise (CREATE) programme under the Singapore-HUJ Alliance for Research and Enterprise Ltd (SHARE), NEW-CREATE which is joint research programme between the Hebrew University of Jerusalem (HUJ, Israel) and Nanyang Technological University (NTU, Singapore). ROR acknowledges the Department of Science & Technology (DST), Science & Engineering Research Board (SERB) for the Early Career Research Award (ECR/2016/000041). VA acknowledges financial support from the SERB, a statutory body of the DST, Govt. of India, through the Ramanujan Fellowship (SB/S2/RJN-088/2016).

Driven by the clinical need for a strong tissue adhesive with elastomeric material properties, a departure from legacy crosslinking chemistries was sought as a multipurpose platform for tissue mending. A fresh approach to bonding wet substrates has yielded a synthetic biomaterial that overcomes the drawbacks of free-radical and nature-inspired bioadhesives. A food-grade liquid polycaprolactone grafted with carbene precursors yields CaproGlu. The first-of-its-kind low-viscosity prepolymer is VOC-free and requires no photoinitiators. Grafted diazirine end-groups form carbene diradicals upon low energy UVA (365 nm) activation that immediately crosslink tissue surfaces; no pre-heating or animal-derived components are required. The hydrophobic polymeric environment enables metastable functional groups not possible in formulations requiring solvents or water. Activated diazirine within CaproGlu is uniquely capable of crosslinking all amino acids, even on wet tissue substrates. CaproGlu undergoes rapid liquid-to-biorubber transition within seconds of UVA exposure–features not found in any other bioadhesive. The exceptional shelf stability of CaproGlu allows gamma sterilization with no change in material properties. CaproGlu wet adhesiveness is challenged against current unmet clinical needs: anastomosis of spliced blood vessels, anesthetic muscle patches, and human platelet-mediating coatings. The versatility of CaproGlu enables both organic and inorganic composites for future bioadhesive platforms. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) Published version NTU-Surgery ACP, Strategic Joint Research Fund (SJRF): Fast, 2 min surgical procedure for splicing of blood vessels; Singapore General Hospital Research Grant (SRGOF16Jan29): Dynamic release of local anaesthetics through novel tissue adhesives; Ministry of Education Tier 1 Grant: Coil Expanding Layers (COELS) For Intravascular Repairs; Ministry of Education Tier 2 Grant: Tailored soft-tissue bioadhesives for site-specific therapy (MOE2012-T2-2-046) & CaproGlu, Double sided wet-tissue adhesives (MOE2018-T2-2-114); NTU-Northwestern Institute for Nanomedicine Grant: 3D-Printing of Electro-Curing Nanocomposite Living Electrodes for Cardiac Tissue Regeneration; NTUitive POC (Gap) Fund Aesthetic Applications of CaproGlu Bioadhesives NGF/2018/05/; A*Star IAF PP Grant (H19/01/a0/0II9): CathoGlu Bioadhesivespreventing catheter extravasation and skin infections. JVH acknowledges support for the solid state NMR instrumentation at Warwick used in this research which was funded by EPSRC (grants EP/M028186/1 and EP/K024418/1) the University of Warwick, and the Birmingham Science City AM1 and AM2 projects which were supported by Advantage West Midlands (AWM) and the European Regional Development Fund (ERDF).

Graphical abstract, Highlights • Multiple MQMAS experiments acquired simultaneously. • Time savings by interleaved experiments. • Solid State NMR using multiple receivers for materials., A procedure to acquire two Multiple-Quantum Magic Angle Spinning (MQMAS) NMR experiments with the same instrument time is presented. A triply tuned probe is utilized with multiple receivers to collect data with staggered acquisitions and thus more efficiently use the instrument time. The data for one nucleus is collected during the recovery delay of the other nucleus, and vice versa. The instrument time is reduced to 60–80% of the time needed for the single acquisition collection Specifically our approach is presented for recording triple-quantum (3Q) 17O and either 3Q or quintuple-quantum (5Q) 27Al MAS NMR spectra of a 1.18Na2O•5SiO2•Al2O3 glass gel.

Voltage-activated adhesion is a relatively new discovery that relies on direct currents for initiation of cross-linking. Previous investigations have found that direct currents are linearly correlated to the migration rates of electrocuring, but this is limited by high voltages exceeding 100 V with instances of incomplete curing of voltage-activated adhesives on semiconducting substrates. Practical applications of electrocuring would benefit from lower voltages to mitigate high-voltage risks, especially with regard to potential medical applications. Alternative electrocuring strategies based on alternating current (AC), electrolyte ionic radius, and temperature are evaluated herein. Square-waveform AC electric field is hypothesized to initiate a two-sided curing progression of voltage-activated adhesive (PAMAM-g-diazirine, aka Voltaglue), where initiation occurs at the cathode terminal. Structure–activity relationships of Voltaglue as a function of AC frequency at currents of 1–3 mA are evaluated against direct currents, migration rate, storage modulus, and lap-shear adhesion on ex vivo tissue mimics. Numerous improvements in electrocuring are observed with AC stimulation vs direct current, including a 35% decrease in maximum voltage, 180% improvement in kinetic rates, and 100% increase in lap-shear adhesion at 2 mA. Li+ ion electrolytes and curing at 4 °C shifts curing kinetics by +104% and −22% respectively, with respect to the control ion (Na+ ion at 24 °C), suggesting that electrolyte migration is the rate-limiting step. Li+ ion electrolytes and curing at 50 °C improve storage modulus by 110% and 470%, respectively. Further evaluations of electrocured matrices with 19F NMR, solid-state NMR, and infrared spectroscopy provide insights into the probable cross-linking mechanisms. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

Organic metal halide perovskite nanocrystals are promising candidates for light-emitting diodes due to their narrow emission bandwidth, high photoluminescence quantum yield (PLQY), and color tunability. Nevertheless, these systems suffer from thermal instability, phase impurities, and a sensitivity to processing techniques. This study reports the first synthesis of novel Cs-containing triple cation perovskite nanocrystals with nominal stoichiometry Csx(MA0.17FA0.83)1−xPbBr3 (x = 0–0.15). The effect of Cs+ cation incorporation is thoroughly investigated using diffraction, microscopy and solid state MAS NMR techniques. The solid state 133Cs MAS NMR results reveals the distribution of the Cs+ cations is highly concentration and particle size dependent, with maximized surface/subsurface Cs+ concentrations being achieved with the smaller 5 mol% Cs system. These characteristics directly correlate improved surface passivation and environmental stability of the triple cation system. These triple cation nanocrystals exhibit a maximum photoluminescence quantum yield of ∼93% which upon translation to nanocrystalline LED devices delivers a maximum EQE of 7.4% (30 cd A−1) corresponding to a power efficiency of 34.87 lm W−1. This performance represents a marked improvement compared to CsPbBr3 nanocrystals (PL quantum yield ∼50%; maximum EQE of 2.5% (7.2 cd A−1)) fabricated under similar conditions.

The strong directing effects and difficulties in the removal of organic based surfactants makes the templated synthesis of nanoparticles in solid porous structures of defined molecular sizes such as SBA-15, without the use of surfactants, considerably attractive. However, the effects of their internal surface structures, adsorption affinities, and lattice mismatch on the particle morphology grown therein have not been fully appreciated. Here, we report the internal surface of the silica preferentially hosts isolated tetrahedrally coordinated oxidic Zn species on the molecular walls of the SBA-15 channels from wet impregnated Zn2+ and Pt2+ species. This leads to a less thermodynamically stable but kinetically controlled configuration of atomic zinc deposition on core platinum nanoparticles with unique confined lattice changes and surface properties to both host and guest structures at the interface upon reduction of the composite. This method for the formation templated nanoparticles may generate interest in forming new tunable materials as dehydrogenation catalysts.

Multinuclear (1H, 13C, 25Mg) solid‐state NMR data is reported for a series of magnesium acetate phases Mg(CH3COO)2 ⋅ nH2O (n=0 (two polymorphs), 1, 4). The central focus here is 25Mg as this set of compounds provides an expanded range of local magnesium coordinations compared to what has previously been reported in the literature using NMR. These four compounds provide 10 distinct magnesium sites with varying NMR interaction parameters. One of the anhydrous crystal structures (α) has an MgO7 site which is reported, to the best of our knowledge, for the first time. For those phases with a single crystal structure, a combination of magic angle spinning (MAS) NMR at high magnetic field (20 T) and first principles density functional theory (DFT) calculations demonstrates the value of including 25Mg in NMR crystallography approaches. For the second anhydrate phase (β), where no single crystal structure exists, the multinuclear NMR data clearly show the multiplicity of sites for the different elements, with 25Mg satellite transition (ST) MAS NMR revealing four inequivalent magnesium environments, which is new information constraining future refinement of the structure. This study highlights the sensitivity of 25Mg NMR to the local environment, an observation important for several sub‐disciplines of chemistry where the structural chemistry of magnesium is likely to be crucial.

A new structural model of hydrous alkali aluminosilicate gel (N-A-S-H) frameworks is proposed, in which charge-balancing extra-framework Al species are observed in N-A-S-H gels for the first time. This model describes the key nanostructural features of these gels, which are identified through the application of 17O, 23Na, and 27Al triple quantum magic angle spinning solid-state nuclear magnetic resonance spectroscopy to synthetic 17O-enriched gels of differing Si/Al ratios. The alkali aluminosilicate gel predominantly comprises Q4(4Al), Q4(3Al), Q4(2Al), and Q4(1Al) Si units charge-balanced by Na+ ions that are coordinated by either 3 or 4 framework oxygen atoms. A significant proportion of Al3+ in tetrahedral coordination exist in sites of lower symmetry, where some of the charge-balancing capacity is provided by extra-framework Al species which have not previously been observed in these materials. The mean SiIV–O–AlIV bond angles for each type of AlIV environments are highly consistent, with compositional changes dictating the relative proportions of individual AlIV species but not altering the local structure of each individual AlIV site. This model provides a more advanced description of the chemistry and structure of alkali aluminosilicate gels and is crucial in understanding and controlling the molecular interactions governing gel formation, mechanical properties, and durability.

Industrial grade perlite and expanded perlite systems were investigated by multifield and multinuclear Solid State Nuclear Magnetic Resonance (SSNMR), Fourier Transform Infra-Red (FTIR) spectroscopies and Scanning Electron Microscopy (SEM). The SSNMR studies focussed on the 1 H, 29 Si and 27 Al nuclei using single pulse excitation (SPE) and 1 H, 29 Si cross-polarization Magic-Angle-Spinning (CP-MAS) conditions, with 27 Al Triple Quantum Magic-Angle-Spinning (3QMAS) measurements also being implemented. The resonances at ~ 52 ppm detected in the 27 Al MAS NMR spectra of the industrial grade and expanded systems are tentatively assigned to tetrahedrally coordinated aluminium, while the resonance at ~ 5 ppm, which was only observed in the industrial grade perlite spectrum, is attributed to octahedrally coordinated aluminium. In neither case could the pentahedrally coordinated positions be identified using 27 Al MAS and 3QMAS techniques. 27 Al data suggests that tetrahedrally coordinated aluminium atoms do not have a significant role in the grain expansion process. The broad resonance envelopes found in the 29 Si MAS NMR and FTIR data of both perlites were analyzed by the second-order derivative. The analyses confirmed complex Q n configurations for the perlitic structure suggesting the prevalence of Q 3 and Q 4 species. 1 H- 29 Si CP-MAS spectra support the presence of Q 2 units suggested by FTIR and SPE data. SEM micrographs revealed the honeycomb morphology of expanded domains in perlite after heat treatment.

The ability to clearly relate local structure to function is desirable for many catalytically relevant Pd-containing systems. This report represents the first direct 105Pd solid state NMR measurements of diamagnetic inorganic (K2Pd(IV)Cl6, (NH4)2Pd(IV)Cl6 and K2Pd(IV)Br6) complexes, and micron- and nano-sized Pd metal particles at room temperature, thereby introducing effective 105Pd chemical shift and Knight shift ranges in the solid state. The very large 105Pd quadrupole moment (Q) makes the quadrupole parameters (CQ, ηQ) extremely sensitive to small structural distortions. Despite the well-defined high symmetry octahedral positions describing the immediate Pd coordination environment, 105Pd NMR measurements can detect longer range disorder and anisotropic motion in the interstitial positions. The approach adopted here combines high resolution X-ray pair distribution function (PDF) analyses with 105Pd, 39K and 35Cl MAS NMR, and shows solid state NMR to be a very sensitive probe of short range structural perturbations. Solid state 105Pd NMR observations of ∼44–149 μm Pd sponge, ∼20–150 nm Pd black nanoparticles, highly monodisperse 16 ± 3 nm PVP-stabilised Pd nanoparticles, and highly polydisperse ∼2–1100 nm biomineralized Pd nanoparticles (bio-Pd) on pyrolysed amorphous carbon detect physical differences between these systems based on relative bulk:surface ratios and monodispersity/size homogeneity. This introduces the possibility of utilizing solid state NMR to help elucidate the structure–function properties of commercial Pd-based catalyst systems.\ud \ud

Novel blue-emitting phosphors based on Eu2+ ions dispersed within chemosynthetic aluminosilicate and gallium silicate inorganic polymer (geopolymer) hosts were prepared by heat treatment of Eu3+-exchanged inorganic polymers in reducing conditions and investigated using photoluminescence spectroscopy, 29Si, 27Al and 71Ga MAS NMR spectroscopy, XRD, and XPS. Eu2+ photoluminescence could be distinguished from the photoluminescence of the inorganic polymer host after heating at ≥ 400 °C in the case of the aluminosilicate inorganic polymer and ≥ 600 °C in the case of the gallium silicate inorganic polymer and became more intense as the reduction temperature was increased up to 1000 °C. The gallium silicate-based phosphors heated at ≥ 900 °C contained small amounts of crystalline KGaSi2O6 or β-Ga2O3, but the X-ray amorphous structure of the inorganic polymer was retained. After heating at 1000 °C, the Eu2+ photoluminescence intensity was substantially more intense for the aluminosilicate phosphor, but the shape of the excitation and emission spectra of the aluminosilicate and gallium silicate phosphors were similar, with a broad emission band centred at 440–475 nm when excited at 240–400 nm. This band shifted to longer wavelengths as the ion exchange solution concentration was increased from 0.001M to 0.03 M.

The facile silane functionalization of graphene oxide (GO) was achieved yielding vinyltrimethoxysilane-reduced graphene oxide (VTMOS-rGO) nanospheres located in the inter-layer spacing between rGO sheets via an acid–base reaction using aqueous media. The successful grafting of the silane agent with pendant vinyl groups to rGO was confirmed by a combination of Fourier-transform infrared (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The structure and speciation of the silane-graphene network (nanosphere) and, the presence of free vinyl groups was verified from solid-state magic angle spinning (MAS) and solution 13C and 29Si nuclear magnetic resonance (NMR) measurements. Evidence from Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HRTEM) and TEM-High-Angle Annular Dark-Field (TEM-HAADF) imaging showed that these silane networks aided the exfoliation of the rGO layers preventing agglomeration, the interlayer spacing increased by 10 Å. The thermal stability (TGA/DTA) of VTMOS-rGO was significantly improved relative to GO, displaying just one degradation process for the silane network some 300 °C higher than either VTMOS or GO alone. The reduction of GO to VTMOS-rGO induced sp2 hybridization and enhanced the electrical conductivity of GO by 105 S m−1.\ud \ud

With increasing ZnO content, short term aqueous durability enhancement of all elements in borosilicate glasses containing 1.0 and 3.85 wt% ZnO was evident in 7-day PCT-B tests. In 14-day MCC-1 type leach tests conducted at 90 °C, surface alteration was very clear in the undoped glass via the formation of strongly altered amorphous material which tended to spall off the surface. No sign of crystallinity was detected by grazing incidence X-ray diffraction or electron microscopy of the surface layers and the surface material was very rich in silica. For the ZnO-bearing glasses, significant growth of particles following PCT leaching for 7 days was observed, due to a build-up of surface ZnO-containing Si-rich material and possible agglomeration. This alteration layer was also observed in MCC-1 type experiments in which cross-section SEM-EDS data were obtained. Raman, infrared and 11 B and 29 Si MAS NMR spectroscopy showed only slight changes in boron speciation on the addition of up to 9.1 wt% ZnO. Bulk positron annihilation lifetime spectra (PALS) of glasses containing 0–3.85 wt% ZnO could be analysed with three distinct lifetimes and also showed only slight differences. These results indicate that the basic glass structure was essentially not influenced by the ZnO content and that the passivation of the alteration layer is promoted by ZnO content.

Bioactive glasses can heal bone defects and bond with bone through formation of hydroxyl carbonate apatite (HCA) surface layer. Sol-gel derived bioactive glasses are thought to have potential for improving bone regeneration rates over melt-derived compositions. The 58S sol-gel composition (60 mol% SiO2, 36 mol% CaO, and 4 mol% P2O5) has appeared in commercial products. Here, hydroxyapatite (HA) was found to form within the 58S glass during sol-gel synthesis after thermal stabilization. The preformed HA may lead to rapid release of calcium orthophosphate, or nanocrystals of HA, on exposure to body fluid, rather than the release of separate the calcium and phosphate species. Increasing the P2O5 to CaO ratio in the glass composition reduced preformed HA formation, as observed by XRD and solid-state NMR. Instead, above 12 mol% phosphate, a phosphate glass network (polyphosphate) formed, creating co-networks of phosphate and silica. Nanopore diameter of the glass and rate of HCA layer formation in simulated body fluid (SBF) decreased when the phosphate content increased.

Novel photoluminescent materials were prepared by ion exchange of a potassium gallium silicate inorganic polymer host with Sm 3 + and Eu 3 + . The host materials and phosphors were characterised by XRD, 71 Ga and 29 Si MAS NMR, PIXE, XPS, and photoluminescence spectroscopy. The phosphors exhibited the characteristic 4f-4f emission peaks of Sm 3 + and Eu 3 + ions, and also broad blue and green emission bands associated with the inorganic polymer host. The rare earth photoluminescence intensity of the Sm 3 + - and Eu 3 + - exchanged potassium gallium silicate inorganic polymers could be considerably enhanced by heat treatment in air at 1000 °C. The heated materials consisted of a mixture of crystalline β-Ga 2 O 3 and remaining amorphous gallium silicate inorganic polymer phase with an increased silica content.