Coordination-controlled electrodeposition of palladium/copper thin films onto a pyridine-terminated self-assembled monolayer

Support by the Chinese Scholarship Council and the University of St Andrews for a stipend (Z. Y.) are gratefully acknowledged. Electron microscopy was carried out at the Electron Microscopy Facility, School of Chemistry, University of St Andrews and we acknowledge recent funding for the Facility from the EPSRC (EP/T019298/1, EP/L017008/1) and the EPSRC Strategic Resources Grant (EP/R023751/1).A scheme for the electrodeposition of ultrathin bimetallic layers on top of a self-assembled monolayer (SAM) is investigated which combines the deposition of one metal (Pd) coordinated to a functionalized SAM (3-(4-pyridine-4-yl-phenyl)-propane-1-thiol, PyP3) on Au/mica with another metal (Cu) from the bulk electrolyte. The coordination-controlled electrodeposition (CCED) is a four-phase process comprising (i) Pd2+ coordination to the terminal pyridine units of the SAM, (ii) reduction of Pd and nanoparticle formation, (iii) formation of an intermixed shell of Pd and Cu, and (iv) deposition of bulk Cu. Chronoamperometry reveals a fast nucleation phase where Pd nanoparticles form within a few milliseconds and seed the Cu deposition. The Pd-Cu core-shell nature of deposited nanoparticles is confirmed by transmission electron microscopy (TEM). Harnessing the selective coordination of Pd2+ to PyP3, a one-pot procedure is further developed using electrolytes containing both Pd2+ and Cu2+ ions. Thus simplifying complexation and reduction, continuous Pd/Cu films are obtained in a multistep process as verified by scanning tunneling microscopy (STM). With a percolation threshold below 3 nm, CCED, as a SAM-controlled deposition strategy, offers an avenue for generation of ultrathin films.Publisher PDFPeer reviewe

Room temperature exsolution of CdS nanodots on A-site deficient cotton-ball like titanate perovskite nanoparticles for H2 production under visible light

Funding: The authors thank EPSRC for funding for a Critical Mass Project EP/R023522/1 and electron microscopy facilities EP/R023751/1 and EP/L017008/1.Exsolution of nanoparticles followed by chemical treatment (“chemistry at a point”) is a very exciting approach to the smart design of functional materials such as visible light active photocatalysts. Unfortunately, the usually utilized thermal reduction approach is not feasible for low melting point metals and compounds such as Cd and CdO. Here a hydrothermal approach to prepare exsolved CdS nanodots on cotton ball-like perovskite supports is described. The titanate-based photocatalyst is synthesized using a hydrothermal process followed by room-temperature sulfidation. The hydrothermal route directs A-site doping of Cd2+ via hydroxyl group incorporation in the titanate lattice. Formation of CdS via exsolution provides a high H2 production mass activity of 3050 µmol g−1 h−1 under visible light with only 5 mol.% Cd doping of the titanate. Moreover, the strong CdS-support interaction offers good cycling stability under UV–vis and visible light irradiation. This is the first report describing the exsolution of CdS nanodots at room temperature and shows its advantages for photocatalytic activity.Publisher PDFPeer reviewe

Influence of electrode processing and electrolyte composition on multiwall carbon nanotube negative electrodes for sodium ion batteries

Dr. A. Fuente Cuesta would like to thank Agency for Green Technology (AGT), Dr. S. A. M. Dickson would like to thank the Faraday Institution NEXGENNA project (FIRG018), and C. Lonsdale would like to thank the Faraday Institution FUSE Internship Programme for funding. The authors also acknowledge the EPSRC (grant codes EP/L017008/1, EP/T019298/1, and EP/R023751/1).Nanostructured one-dimensional multiwall-carbon nanotubes have a variety of advantageous properties including good electrical conductivity and mechanical strength, and thus have been widely investigated for use in lithium-ion battery electrodes as conductive and microstructural additives, though also possess some electrochemical activity. Their application to sodium-ion batteries has been less extensively researched, and therefore a greater understanding of the electrochemical reaction with sodium, and effects of slurry composition and electrolyte formulation is warranted. Here, we report the fabrication of aqueous and organic multi-wall carbon nanotube negative electrodes processed by ball milling. The binder of choice is noted to greatly affect the electrochemical performance, both in terms of capacity retention and rate capability over a range of current densities from 25 to 500 mA g-1. Switching from a carbonate- to diglyme-based electrolyte considerably improves initial coulombic efficiencies (~10 to 60%), attributed to less extensive formation of solid electrolyte interphase, and enables a reversible mechanism with capacities up to 150 mAh g-1 over 100 cycles depending upon the binder used.Publisher PDFPeer reviewe

The exsolution of Cu particles from doped barium cerate zirconate via barium cuprate intermediate phases

This research was supported by EPSRC research grants EP/R023522/1, EP/T019298/1, EP/R023751/1, EP/L017008/1 the China Scholarship Commission (MW) received financial support from the UK Catalysis Hub funded by EPSRC Grant reference EP/R027129/1.As a low-cost alternative to noble metals, Cu plays an important role in industrial catalysis, such as water-gas shift reaction, methanol or ethanol oxidation, hydrogenation of oils, CO oxidation, among many others. An important step in optimizing Cu catalyst performance is control of nanoparticles size, distribution, and the interface with the support. While proton conducting perovskites can enhance the metal catalytic activity when acting as the support, there has been limited investigation of in situ growth of Cu metal nanoparticles from the proton conductors and its catalytic performance. Here, Cu nanoparticles are tracked exsolved from an A-site-deficient proton-conducting barium cerate-zirconate using scanning electron microscopy, revealing a continuous phase change during exsolution as a function of reduction temperature. Combined with the phase diagram and cell parameter change during reduction, a new exsolution mechanism is proposed for the first time which provides insight into tailoring metal particles interfaces at proton conducting oxide surfaces. Furthermore, the catalytic behavior in the CO oxidation reaction is explored and, it is observed that these new nanostructures can rival state of the art catalysts over long term operation.Publisher PDFPeer reviewe

Enhanced CO2 electrolysis through Mn substitution coupled with Ni exsolution in lanthanum calcium titanate electrodes

Funding: This work was financially supported by the Industrial Decarbonisation Research and Innovation Centre. Further support was kindly provided by EPSRC, under research grant numbers EP/L017008/1, EP/R023751/1 and EP/T019298/1.In this study, perovskite oxides La0.3Ca0.6Ni0.05MnxTi0.95−xO3−γ (x = 0, 0.05, 0.10) are investigated as potential solid oxide electrolysis cell cathode materials. The catalytic activity of these cathodes toward CO2 reduction reaction is significantly enhanced through the exsolution of highly active Ni nanoparticles, driven by applying a current of 1.2 A in 97% CO2 – 3% H2O. The performance of La0.3Ca0.6Ni0.05Ti0.95O3−γ is notably improved by co-doping with Mn. Mn dopants enhance the reducibility of Ni, a crucial factor in promoting the in situ exsolution of metallic nanocatalysts in perovskite (ABO3) structures. This improvement is attributed to Mn dopants enabling more flexible coordination, resulting in higher oxygen vacancy concentration, and facilitating oxygen ion migration. Consequently, a higher density of Ni nanoparticles is formed. These oxygen vacancies also improve the adsorption, desorption, and dissociation of CO2 molecules. The dual doping strategy provides enhanced performance without degradation observed after 133 h of high-temperature operation, suggesting a reliable cathode material for CO2 electrolysis.Peer reviewe

Characterising the HLA-I Immunopeptidome of plasma-derived extracellular vesicles in patients with melanoma

This work was funded by grants from Breast Cancer Now UK (2018JulPR1086), and the Melville Trust for the Care and Cure of Cancer UK (XCT014). We also gratefully acknowledge funding from the EPSRC via EP/L017008/1 for TEM imaging infrastructure, and EP/R023751/1 and EP/T019298/1.Extracellular vesicles (EVs) frequently express human leukocyte antigen class I (HLA-I) molecules. The immunopeptidomes presented on EV HLA-I are being mapped to provide key information on both specific cancer-related peptides, and for larger immunopeptidomic signatures associated with disease. Utilizing HLA-I immunoisolation and mass spectrometry, we characterised the HLA-I immunopeptidome of EVs derived from the melanoma cancer cell line, ESTDAB-026, and the plasma of 12 patients diagnosed with advanced stage melanoma, alongside 11 healthy controls. The EV HLA-I immunopeptidome derived from melanoma cells features T cell epitopes with known immunogenicity and peptides derived from known tumour associated antigens (TAAs). Both T cell epitopes with known immunogenicity and peptides derived from known TAAs were also identifiable in the melanoma patient samples. Patient stratification into two distinct groups with varying immunological profiles was also observed. The data obtained in this study suggests for the first time that the HLA-I immunopeptidome of EVs derived from blood may aid in the detection of important diagnostic or prognostic biomarkers and also provide new immunotherapy targets.Peer reviewe

Manganese catalysed synthesis of polyketones using hydrogen borrowing approach.

We report here a new method to make polyketones from the coupling of diketones and diols using a manganese pincer complex. The methodology allows us to access a new type of polyketone (polyarylalkylketone) containing aryl, alkyl, and ether functionalities bridging the gap between the two classes of commercially available polyketones – aliphatic polyketones and polyaryletherketones. Using this methodology, twelve new polyketones have been synthesized and characterised using various analytical techniques to understand their chemical, physical, morphological, and mechanical properties. Based on previous reports and our studies, we suggest that the polymerization occurs via a hydrogen-borrowing mechanism that involves the dehydrogenation of diols to dialdehyde followed by aldol condensation of dialdehyde with diketones to form chalcone derivatives and their subsequent hydrogenation to form polyarylalkylketones

Direct processing of PbZr0.53Ti0.47O3 films on glass and polymeric substrates

This work was supported by the U.S. National Science Foundation under grant No. CMMI-1537262, Science Foundation Ireland (SFI) under the US-Ireland R&D Partnership Programme Grant Number SFI/14/US/I3113, the China Scholarship Council, and the Department of Education and Learning NI through grant USI-082.This work reports on direct crystallization of PbZr0.53Ti0.47O3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (≤5 nm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For ∼200 nm-thick PZT films on glass substrates, 500 μs-long pulses were required for crystallization, starting with 100 pulses at 350 V, 10 or 25 pulses at 400 V and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4 kW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350–400 V had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For ∼1 μm-thick PZT films on polymeric substrates, 10 to 25 250 μs-long pulses at voltages ranging between 200 to 250 V, corresponding to power densities of ∼2.8 kW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage.PostprintPeer reviewe

Silicon redistribution, acid site loss and the formation of a core-shell texture upon steaming SAPO-34 and their impact on catalytic performance in the methanol-to-olefins (MTO) reaction

IBM has received funding from the Engineering and Physical Sciences Research Council (EPSRC, Centre for Doctoral Training in Critical Resource Catalysis, EP/I017008/1) and Scotland's Chemistry departments (ScotCHEM). IBM also received a scholarship from the SCI and Santander. Johnson Matthey is thanked for in-kind contributions and hosting IBM in their R&D labs. ABN gratefully acknowledges support from the EPSRC (grants EP/L017008/1 and EP/R023751/1). The research data supporting this publication can be accessed at: https://doi.org/10.17630/09ddc03e-f121-4e79-9b55-674f64d9c8c4 [62].SAPO-34 is a commercially-implemented silicoaluminophosphate catalyst for selective high yield production of ethene and propene from methanol, but high temperature regeneration in the presence of steam leads to its deactivation. A comprehensive investigation of the effect of prolonged hydrothermal treatment on the structure and properties of SAPO 34 explains the changes in its catalytic methanol-to-olefins (MTO) performance. Microcrystalline powdered SAPO-34 (ca. 3 µm crystals, Al17.1P15.6Si3.3O72) and two batches of larger single crystals of SAPO-34 of different Si concentration (20-100 µm; Al17.3P14.7Si4.0O72 and Al17.7P12.3Si5.9O72 ) were steamed (pH2O = 0.95 atm) at 873–1023 K for up to 240 h. The acidity (NH3-TPD), crystallinity (PXRD), framework cation environment (solid-state 27Al, 29Si and 31P MAS NMR) and porosity were followed for all materials; larger crystals were amenable to single crystal X-ray diffraction, FIB-SEM and synchrotron IR microspectroscopy, including operando study during methanol and dimethyl ether conversions. Some level of steaming improved the lifetime of all SAPO-34 materials in MTO catalysis without affecting their olefin selectivity, although more severe conditions led to the formation of core-shell structures, microporosity loss and eventually at 1023 K, recrystallization to a dense phase. All these irreversible changes occurred faster in crystals with higher Si contents. The initial increase in catalytic lifetime results from an activated reduction in acid site density (Eact = 146(18) kJ mol⁻1), a result of redistribution of Si within the SAPO framework without porosity loss. Operando IR with online product analysis during methanol conversion suggests similar reaction pathways in calcined and steamed crystals, but with greatly reduced methoxy group densities in the latter. The gradual development of optically dark crystal cores upon progressive steaming was shown by FIB-SEM to be due to the formation of regions with meso- and macropores, and these were shown by IR mapping to possess low hydroxyl densities.PostprintPostprintPeer reviewe

Full control of polarization in ferroelectric thin films using growth temperature to modulate defects

P.P. and C.W. acknowledge partial support by Swiss National Science Foundation Division II grant 200021_178782. L.R.D. acknowledges support from the US National Science Foundation under grant DMR‐1708615. L.W.M. acknowledges support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE‐AC02‐05‐CH11231 (Materials Project program KC23MP) for the growth and study of defect structures in ferroic materials. A.B.N. gratefully acknowledges support from the Engineering and Physics Sciences Research Council (EPSRC) through grants EP/R023751/1 and EP/L017008/1.Deterministic control of the intrinsic polarization state of ferroelectric thin films is essential for device applications. Independently of the well-established role of electrostatic boundary conditions and epitaxial strain, the importance of growth temperature as a tool to stabilize a target polarization state during thin film growth is shown here. Full control of the intrinsic polarization orientation of PbTiO3 thin films is demonstrated-from monodomain up, through polydomain, to monodomain down as imaged by piezoresponse force microscopy-using changes in the film growth temperature. X-ray diffraction and scanning transmission electron microscopy reveal a variation of c-axis related to out-of-plane strain gradients. These measurements, supported by Ginzburg-Landau-Devonshire free energy calculations and Rutherford backscattering spectroscopy, point to a defect mediated polarization gradient initiated by a temperature dependent effective built-in field during growth, allowing polarization control not only under specific growth conditions, but ex-situ, for subsequent processing and device applications.Publisher PDFPeer reviewe