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Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy. Such catalyst systems have yet to be practically utilized. Here, we demonstrate a compact electrically heated photo- and thermal annular reactor module to reduce CO2 to CO, via the reverse water gas shift reaction. A first-principles-based design approach was taken in developing a SiO2 on an Al photo- and thermal catalyst system for the model photo- and thermal indium oxide hydroxide (In2O3-x(OH)y) catalysts. A 5-fold light enhancement in the CO production rate and over 70 h of stable CO production were achieved. This represents the highest light enhancement effect reported for this model photocatalyst to date. The reactor presented herein allows continuous operation and a significant reduction of 31% in heater power consumption when provided with an additional 2 suns of irradiation, demonstrating the strong photo- and thermal-harvesting performances of the catalyst system developed in this work.

The rapid increase in global energy demand and the need to replace carbon dioxide (CO2)-emitting fossil fuels with renewable sources have driven interest in chemical storage of intermittent solar and wind energy1,2. Particularly attractive is the electrochemical reduction of CO2 to chemical feedstocks, which uses both CO2 and renewable energy3–8. Copper has been the predominant electrocatalyst for this reaction when aiming for more valuable multi-carbon products9–16, and process improvements have been particularly notable when targeting ethylene. However, the energy efficiency and productivity (current density) achieved so far still fall below the values required to produce ethylene at cost-competitive prices. Here we describe Cu-Al electrocatalysts, identified using density functional theory calculations in combination with active machine learning, that efficiently reduce CO2 to ethylene with the highest Faradaic efficiency reported so far. This Faradaic efficiency of over 80 per cent (compared to about 66 per cent for pure Cu) is achieved at a current density of 400 milliamperes per square centimetre (at 1.5 volts versus a reversible hydrogen electrode) and a cathodic-side (half-cell) ethylene power conversion efficiency of 55 ± 2 per cent at 150 milliamperes per square centimetre. We perform computational studies that suggest that the Cu-Al alloys provide multiple sites and surface orientations with near-optimal CO binding for both efficient and selective CO2 reduction17. Furthermore, in situ X-ray absorption measurements reveal that Cu and Al enable a favourable Cu coordination environment that enhances C–C dimerization. These findings illustrate the value of computation and machine learning in guiding the experimental exploration of multi-metallic systems that go beyond the limitations of conventional single-metal electrocatalysts. Machine learning predicts Cu-Al electrocatalysts provide better efficiency and productivity than copper when using intermittent renewable electricity to convert carbon dioxide to useful chemicals and fuels.

Previous extensive studies were performed at Surface Science Western on the treatment of III-V semiconductors to produce surfaces suitable for subsequent epitaxial growth. X-ray photoelectron spectroscopy (XPS) was used to study oxide formation and capping techniques, and to monitor changes that would occur upon thermal desorption. The effects of a remote plasma on these surfaces were studied as well as to apply thin dielectric films of Si3N4 in order to study interfacial properties. Angle-resolved XPS (ARXPS) was performed in many cases to ascertain oxide layer thickness, uniformity, and structure. For the types of surfaces studied—mirror finished semiconductors, ARXPS is straightforward, and the angular dependence is obtained by physically altering the surface orientation with respect to the analyser. While the sample can be repositioned with care to analyse the same spot, changing the angle will effectively change the sampling area, further, surface topography can preclude the use of ARXPS. Use of parallel PARXPS, now available on recent instrumentation, can alleviate these problems. In this case, photoelectrons are collected simultaneously from a large angle. A multichannel detector allows this to be split into smaller angles thereby giving the PARXPS spectra without physically tilting the sample. Further, because the sample is not tilted, topographical effects are minimised allowing meaningful data to be extracted from not so perfect samples. To illustrate this, a detailed PARXPS study on a gallium Indium eutectic (EGaIn) will be presented. Various methods of extracting the depth information from these spectra will be discussed. Finally, the application of using PARXPS to study buried interfaces will be briefly discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Additives are key to achieving optimal morphologies and efficient performance in bulk heterojunction organic photovoltaics. In this work we analyze the impact of three insulating polymers [ethylene acrylic elastomers, polystyrene and poly(methyl methacrylate)] in prototypical small molecule and polymer photovoltaic devices. We find that small molecule–semiconductors and polymer–semiconductors vary remarkably in their tolerance of the type of insulator as well as the degree of insulator incorporation. Insulating polymers capable of self-assembly or infiltration into the organic–semiconductor matrix have a positive or negligible impact on the performance of both small molecule and polymer devices. The spontaneous migration of ethylene acrylic elastomers to the device surface make them adverse additives, however our preliminary data indicates their potential application as a spontaneously forming cathode interlayer in small molecule devices where they match or exceed the performance of evaporated LiF interlayers.

Metal-dielectric multilayers are versatile optical devices that can be designed to combine the visible transmittance of dielectrics with the electronic properties of metals for plasmonic and meta-material applications. However, their performances are limited by an interfacial optical absorption often attributed entirely to the metal surface roughness. Here, we show that during deposition of AlN/Ag/AlN and SiNx/Ag/SiNx multilayers, significant diffusion of Ag into the top dielectric layer form Ag nanoparticles which excite localized surface plasmon resonances that are primarily responsible for the interfacial optical absorption. Based on experimental depth profiles, we model the multilayer’s silver concentration profile as two complementary error functions: one for the diffused Ag nanoparticles and one for the interface roughness. We apply the Maxwell-Garnett and Bruggeman effective medium theories to determine that diffusion characteristics dominate the experimental absorption spectra. The newfound metal nanoparticle diffusion phenomenon effectively creates a hybrid structure characteristic of both metal-dielectric multilayer and metal-dielectric composite.

We report the synthesis and characterization of cadmium selenide nanocrystals with electroactive ligands directly attached to the surface. The conventional surfactant-assisted synthesis yields nanocrystals with surfaces functionalized with insulating organic ligands. These insulating ligands act as a barrier for charge transport between nanocrystals. Electroactive (reducing/oxidizing) ligands like ferrocene and cobaltocene have potential for applications as photoexcited hole conductors and photoredox systems. Although ferrocene ligands anchored to the nanocrystal surface through insulating long-chain hydrocarbon spacers have previously been reported, this approach is limited because the charge transfer between nanocrystal and ferrocene is highly sensitive to their separation. We report here ferrocene directly bound to the inorganic core of the nanocrystal, and as a result the distance between the nanocrystals and the electroactive moiety is minimized.

Layered-structure materials are currently relevant given their quasi-2D nature. Knowledge of their physical properties is currently of major interest. Niobium ditelluride possesses a monoclinic layered-structure with a distortion in the tellurium planes. This structural complexity has hindered the determination of its fundamental physical properties. In this work, NbTe2 crystals were used to elucidate its structural, compositional, electronic and vibrational properties. These findings have been compared with calculations based on density functional theory. The chemical composition and elemental distribution at the nanoscale were obtained through atom probe tomography. Ultraviolet photoelectron spectroscopy allowed the first determination of the work function of NbTe2. Its high value, 5.32 eV, and chemical stability allow foreseeing applications such as contact in optoelectronics. Raman spectra were obtained using different excitation laser lines: 488, 633, and 785 nm. The vibrational frequencies were in agreement with those determined through density functional theory. It was possible to detect a theoretically-predicted, low-frequency, low-intensity Raman active mode not previously observed. The dispersion curves and electronic band structure were calculated, along with their corresponding density of states. The electrical properties, as well as a pseudo-gap in the density of states around the Fermi energy are characteristics proper of a semi metal.

Poly(dimethylsiloxane) (PDMS) is a commonly used elastomer for fabricating microfluidic devices, but it has previously been shown to absorb hydrophobic molecules. Although this has been demonstrated for molecules such as estrogen and Nile Red, the absorption of small hydrophobic molecules in PDMS specifically used to treat cancer and its subsequent impact on cytotoxicity measurements and assays have not been investigated. This is critical for the development of microfluidic chemosensitivity and resistance assay (CSRA) platforms that have shown potential to help guide clinical therapy selection and which rely on the accuracy of the readout involving interactions between patient-derived cells and cancer drugs. It is thus important to address the issue of drug absorption into device material. We investigated drug absorption into microfluidic devices by treating multiple myeloma (MM) tumor cells with two MM drugs (bortezomib (BTZ) and carfilzomib (CFZ)) in devices fabricated using three different materials (polystyrene (PS), cyclo-olefin polymer (COP), and PDMS). Half-maximal inhibitory concentrations (IC

Non-specific adsorption of biomolecules (or “biofouling”) is a major problem in microfluidics and many other applications. The problem is particularly pernicious in digital microfluidics (DMF, a technique in which droplets are manipulated electrodynamically on an array of electrodes coated with a hydrophobic insulator), as local increases in surface energy that arise from fouling can cause droplet movement to fail. We report a new solution to this problem: a device coating bearing a combination of fluorinated poly(ethylene glycol) functionalities (FPEG) and perfluorinated methacrylate (FA) moieties. A range of different FPEG-FA copolymers were synthesized containing varying amounts of FPEG relative to the fluorinated backbone. Coatings with low%FPEG were found to result in significant reductions in protein adsorption and improvements in device lifetime (up to 5.5-fold) relative to the state of the art. An analysis of surface topology and chemistry suggests that FPEG-FA surfaces undergo a dynamic reconstruction upon activation by applying DMF driving potentials, with FPEG groups forming vertical protrusions out of the plane of the device surface. An analysis of changes in surface wettability and adhesion as a function of activation supports this hypothesis. This innovation represents an advance for digital microfluidics, and may also find use in other applications that are currently limited by biofouling.

Tunneling junctions having the structure Ag-TS-S(CH2)(n-1)CH3//Ga2O3/EGaIn allow physical-organic studies of charge transport across self-assembled monolayers (SAMs). In ambient conditions, the surface of the liquid metal electrode (EGaIn, 75.5 wt % Ga, 24.5 wt % In, mp 15.7 degrees C) oxidizes and adsorbs-like other high-energy surfaces-adventitious contaminants. The interface between the EGaIn and the SAM thus includes a film of metal oxide, and probably also organic material adsorbed on this film; this interface will influence the properties and operation of the junctions. A combination of structural, chemical, and electrical characterizations leads to four conclusions about Ag-TS-S(CH2)(n-1)CH3//Ga2O3/EGaIn junctions. (i) The oxide is similar to 0.7 nm thick on average, is composed mostly of Ga2O3, and appears to be self-limiting in its growth. (ii) The structure and composition (but not necessarily the contact area) of the junctions are conserved from junction to junction. (iii) The transport of charge through the junctions is dominated by the alkanethiolate SAM and not by the oxide or by the contaminants. (iv) The interface between the oxide and the eutectic alloy is rough at the micrometer scale.

Cataloged from PDF version of article. There has always been a fascination with "impossible" compounds, ones that do not break any rules of chemical bonding or valence but whose structures are unstable and do not exist. This instability can usually be rationalized in terms of chemical or physical restrictions associated with valence electron shells, multiple bonding, oxidation states, catenation, and the inert pair effect. In the pursuit of these "impossible" materials, appropriate conditions have sometimes been found to overcome these instabilities and synthesize missing compounds, yet for others these tricks have yet to be uncovered and the materials remain elusive. In the scientifically and technologically important field of periodic mesoporous silicas (PMS), one such "impossible" material is periodic mesoporous hydridosilica (meso-HSiO1.5). It is the archetype of a completely interrupted silica open framework material: its pore walls are comprised of a three-connected three-dimensional network that should be so thermodynamically unstable that any mesopores present would immediately collapse upon removal of the mesopore template. In this study we show that meso-HSiO1.5 can be synthesized by template-directed self-assembly of HSi(OEt)3 under aqueous acid-catalyzed conditions and after template extraction remains stable to 300 °C. Above this temperature, bond redistribution reactions initiate a metamorphic transformation which eventually yields periodic mesoporous nanocrystalline silicon-silica, meso-ncSi/SiO2, a nanocomposite material in which brightly photoluminescent silicon nanocrystallites are embedded within a silica matrix throughout the mesostructure. The integration of the properties of silicon nanocrystallinity with silica mesoporosity provides a wealth of new opportunities for emerging nanotechnologies. © 2011 American Chemical Society.

A group of ancient coins is among the Diniacopoulos collection of Central and Eastern Mediterranean antiquities housed at Queen's University. At first glance, nine coins in the collection appear to be billon tetradrachms minted in Alexandria, Egypt, dating to the period of the Emperor Claudius (41–54 AD). On the obverse, there is a portrait of the Emperor Claudius, on the reverse his wife Messalina is holding their two children. A closer examination reveals, however, that each of these coins weighs substantially less than the majority of specimens belonging to the same issues. All of the coins appear to have silver-rich plated surfaces with copper-rich cores. Questions are raised, therefore, about their authenticity and methods of manufacture. The surfaces display a variety of corrosion products, some of which may also indicate past restoration treatments. A single coin was selected for time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and energy dispersive...

To optimize the performance of the inkjet printing process it is of significant importance to have greater understanding of the spatial arrangement of not only ink colourant, but also other ink components such as surfactant, solvent and/or cosolvent. In this work, the capabilities of Time-of-Flight (ToF) SIMS are applied to study the spreading (xy distribution) of a custom inkjet ink formulation, containing cationic crystal violet dye, ethoxylated surfactant and ink vehicle/solvent marked by lithium salt on uncoated and coated papers. High spatially resolved images obtained by ToF-SIMS clearly illustrate differentiation of individual ink components, with irregular spreading on uncoated paper leading to poor edge definition, and as a result, poor print quality. ToF-SIMS images and distribution profiles of ink components on ‘best’ and ‘worst’ commercial paper samples show that the cationic dye is preferentially adsorbed by both substrates, colocalizing with the surfactant. However, the solvent, marked by lithium salt, spreads 20% more than cationic dye on coated paper, and 25% more than the dye on uncoated paper. The variability in preferential absorption of ink components due to morphology, chemistry and topography of paper, may be taken as an indication of print quality. Copyright © 2010 John Wiley & Sons, Ltd.

In this work, we present the rational synthesis of a novel, highly selective etchant, N-(4-methoxybenzyl)-(pyren-1-yl)amine, enabling the facile and direct fabrication of free-standing 3D structures within an arsenic−sulfide all-inorganic photoresist, patterned via 3D direct laser writing. The chemical and physical underpinnings of this novel wet etchant are described in detail. Our novel molecule enables the fabrication of intricate, shrinkage-free 3D structures with minimum feature sizes of 180 nm in only one etching step. Because of the high transparency of arsenic−sulfide glass in the telecommunication window, structures fabricated along these lines could be well-suited as final structural elements for 3D optical structures and devices in the sub-micrometer scale. The results presented here enable their facile realization, thus making this material a desirable alternative to traditional photopolymers.

The dehydrocoupling of the fluorinated secondary phosphine-borane adduct RjPH.BH 3 (R = p-CF 3 C 6 ,H 4 ) at 60 °C is catalyzed by the rhodium complex x [[Rh(H-Cl)(l,5-cod)) 2 ] to give the four-membered chain R 2 PH-BH 2 -R 2 P-BH 3 . A mixture of the cyclic trimer [R 2 P-BH 2 ] 3 , and tetramer [R 2 P-BH 2 ] 4 was obtained from the same reaction at a more elevated temperature of 100 °C. The analogous rhodium-catalyzed dehydrocoupling of the primary -phosphine-borane adduct RPH 2 .BH 3 at 60°C gave the high molecular weight polyphosphinoborane polymer [RPH-BH 2 ]n (M w , = 56170. PDI = 1.67). The molecular weight was investigated by gel permeation chromatography and the compound characterized by multinuclear NMR spectroscopy. Interestingly, the electron-withdrawing fluorinated aryl substituents have an important influence on the reactivity as the dehydrocoupling process occurred efficiently at the mildest temperatures observed for phosphine-borane adducts to date. Thin films of polymeric [RPH-BH 2 ]n (R = p-CF 3 C 6 ,H 4 ) have also been shown to function as effective negative-tone resists towards electron beam (e-beam) lithography (EBL). The resultant patterned bars were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS).

Metastatic brain cancers, in particular cancers with multiple lesions, are one of the most difficult malignancies to treat owing to their location and aggressiveness. Chemotherapy for brain metastases offers some hope. However, its efficacy is severely limited as most chemotherapeutic agents are incapable of crossing the blood-brain barrier (BBB) efficiently. Thus, a multifunctional nanotheranostic system based on poly(methacrylic acid)-polysorbate 80-grafted-starch was designed herein for the delivery of BBB-impermeable imaging and therapeutic agents to brain metastases of breast cancer. In vivo magnetic resonance imaging and confocal fluorescence microscopy were used to confirm extravasation of gadolinium and dye-loaded nanoparticles from intact brain microvessels in healthy mice. The targetability of doxorubicin (Dox)-loaded nanoparticles to intracranially established brain metastases of breast cancer was evaluated using whole body and ex vivo fluorescence imaging of the brain. Coexistence of nanoparticles and Dox in brain metastatic lesions was further confirmed by histological and microscopic examination of dissected brain tissue. Immuno-histochemical staining for caspase-3 and terminal-deoxynucleotidyl transferase dUTP nick end labeling for DNA fragmentation in tumor-bearing brain sections revealed that Dox-loaded nanoparticles selectively induced cancer cell apoptosis 24 h post-injection, while sparing normal brain cells from harm. Such effects were not observed in the mice treated with free Dox. Treatment with Dox-loaded nanoparticles significantly inhibited brain tumor growth compared to free Dox at the same dose as assessed by in vivo bioluminescence imaging of the brain metastases. These findings suggest that the multifunctional nanoparticles are promising for the treatment of brain metastases.

Meso-HSiO1.5 is synthesized by template-directed self-assembly of HSi(OEt)3 under aqueous acid-catalyzed conditions from mixtures of Pluronic-123 surfactant, NaCl, aqueous HCl, BuOH, and HSi(OEt)3 (room temperature, 12 h).

Cataloged from PDF version of article. Periodic mesoporous hydridosilica, PMHS, is shown for the first time to function as both a host and a mild reducing agent toward noble metal ions. In this archetypical study, PMHS microspheres react with aqueous Ag(I) solutions to form Ag(0) nanopartides housed in different pore locations of the mesostructure. The dominant reductive nucleation and growth process involves groups located within the pore walls and yields molecular scale Ag(0) nanoclusters trapped and stabilized in the pore walls of the PMHS microspheres that emit orange-red photoluminescence. Lesser processes initiated with pore surface SiH groups produce some larger spherical and worm-shaped Ag(0) nanoparticles within the pore voids and on the outer surfaces of the PMHS microspheres. The intrinsic reducing power demonstrated in this work for the pore walls of PMHS speaks well for a new genre of chemistry that benefits from the mesoscopic confinement of Si-H groups.

In order to determine the presence of collagen molecules at the surface of a collagen-modified poloxamine hydrogel (a semi-interpenetrating network), the surface composition was studied using Time-of-Flight Secondary Ion Mass Spectra (ToF-SIMS). Collagen was added to the poloxamine hydrogel (poloxamine is a commercially available four-arm poly(ethylene oxide)/poly(propylene oxide) block copolymer, PEO/PPO) to promote the attachment of endothelial or liver cells. X-ray photoelectron spectroscopy (XPS) of dry samples showed a sharp increase in the N content from 0.6% in a pure poloxamine hydrogel to 8.8% in the collagen-containing material. Afterwards, the surface was studied by a 'deep freezing' ToF-SIMS approach under progressive heating from -120 to -60 degrees C. The positive spectrum of collagen/poloxamine at -65 degrees C displayed distinct signals corresponding to different amino acid fragments such as CH4N+ (30 m/z, Gly), C3HN2+ (43 m/z, Arg), C2H6N+ (44 m/z, Ala) and C4H5N2+(81m/z, His) and others corresponding to the PEO and PPO blocks of poloxamine. In addition, the negative spectrum showed peaks at 26 m/z (CN-), 32 m/z (S-) and 42 m/z (CNO-) characteristic of fragments of the collagen molecule. Imaging experiments indicated the homogeneous distribution of the collagen on the surface. These results supported the use of ToF-SIMS for the surface characterization of hydrated hydrogels and confirmed the collagen presence as the means whereby cells attach to the modified poloxamine matrix.

As part of an investigation of new cathode materials for intermediate temperature solid oxide fuel cells, we have investigated particular perovskite oxides with ordered A cations which, in turn, localize the oxygen vacancies into layers. The oxygen exchange kinetics of polycrystalline samples of the oxygen-deficient double perovskite PrBaCo2O5+x (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). The ECR and IEDP measurements reveal that PBCO has high electronic conductivity and rapid oxygen ion diffusion and surface exchange kinetics. Both techniques demonstrate that the oxygen kinetics in this structure type are significantly faster than in corresponding disordered perovskites.

The oxygen exchange kinetics of thin films of the oxygen-deficient double perovskite PrBaCo2O5+δ (PBCO) have been determined by electrical conductivity relaxation (ECR) and by oxygen-isotope exchange and depth profiling (IEDP). Microstructural studies indicate that the PBCO films, prepared by pulsed laser deposition, have excellent single-crystal quality and epitaxial nature. The ECR and IEDP measurements reveal that the PBCO films have high electronic conductivity and rapid surface exchange kinetics, although the ECR data indicate the presence of two distinct kinetic pathways. The rapid surface kinetics compared with those of other perovskites suggest the application of PBCO as a cathode material in intermediate-temperature solid oxide fuel cells.

Ordered 2D arrays of ferromagnetic Fe/Co alloy nanoparticle rings with diameters of 2–12 µm were fabricated via plasma etching and subsequent pyrolytic treatment of template directed self-assembled rings of a highly metallized polyferrocenylsilane metallopolymer precursor.