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Alginate hydrogel beads were loaded with bimetallic NiPt nanoparticles by in situ reduction of the respective polymer matrix containing precursor metallic ions using a NaBH

The development of water electrolysis devices is crucial for the sustainable production of green hydrogen fuel. However, the slow kinetics and high overpotential are key shortfalls for hydrogen production during the half-cell hydrogen evolution reaction (HER) and significantly reduce the overall efficiency. Here we fabricated two micro-and mesoprorous cobalt MOFs [Co(BDC)(DMSO)(DMF)]n and [Co(NH2-BDC)(DMSO)(DMF)]n (labeled Co-1 and Co-2, respectively) by using a benezenedicarboxylic acid (H2BDC) linker and its amine-derivative (H2N-BDC). The chemical functionalization of organic linkers in MOFs enhances catalytic activity by providing Lewis acidity or basicity, potentially enhancing electrocatalytic activity. Co-1 MOF ([Co(BDC)(DMSO)]n) had a rod-like morphology, while Co-2 MOF ([Co(NH2-BDC)(DMSO)]n) was in the form of two-dimensional sheets. After characterizing the materials using PXRD, SEM-EDX, XPS, TGA, FTIR, and gas sorption, we explored the electrocatalytic activity of the MOFs for hydrogen evolution reaction (HER). The presence of surface amino functions slightly improved HER activity of Cobalt MOFs in terms of overpotential (? from 0.217 V to 0.215 V @ 25mAcm2-) and Tafel slope (from 95mVdec-1 to 91mVdec-1). However, Co-2 showed better stability and high Faradic efficiency (97 %), which we attribute to morphological features, mesoporosity, and the presence of basic surface functionalities.

Converting solar energy directly into electricity as a clean and renewable energy resource is immensely important to solving the energy crisis and environmental pollution problems induced by the consumption of fossil fuels. Dye-sensitized solar cells (DSSCs) provide a technically and economically credible alternative that could challenge the dominance of conventional p-n junction photovoltaic devices in the solar energy market. DSSCs use dye molecules adsorbed at the surface of nanocrystalline oxide semiconductors such as TiO2 to collect sunlight. These thin films require a large surface area, to adsorb many dye molecules, and mesoporous channels so the electrolyte can permeate the film and regenerate the dye molecules. This favourable morphology is traditionally achieved by the random assembly of a network of nanoparticles by the sintering process. Two-photon polymerization is a 3D printing technique used to fabricate structures with feature resolutions down to 100 nm. We use this technique to fabricate TiO¬2 thin films of optimised 3D micro-design for use in DSSCs. Our films have a considerable advantage over the conventional (random assembly) films as it allows the implementation of light scattering designs which are shown to significantly enhance photocurrent in the cell by up to ~25%.

We present a series of three studies investigating the potential application of high vacuum electrospray deposition to construct molecular electronic devices. Through the use of time of flight secondary ion mass spectrometry we explore the use of this novel deposition technique to fabricating multilayer structures using materials that are compatible with the same solvents and films containing a mixture of molecules from orthogonal solvents. Using X-ray photoelectron spectroscopy we study the deposition of a polymer blend using electrospray and find evidence of preferential deposition of one of the components.

Monolayers of C60 and the functionalised fullerene phenyl-C61-butyric acid methyl ester (PCBM) have been prepared on Au(1 1 1) by in situ electrospray deposition. The observation of super-spectator/super-Auger decay in resonant photoemission spectroscopy (RPES) of C60 confirms monolayers prepared using electrospray undergo ultra-fast charge transfer as per previous studies of C60 monolayers on Au(1 1 1) prepared by sublimation. For PCBM, X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) show the lowest unoccupied molecular orbital (LUMO) of the molecule overlaps the Fermi-level of the metal surface. Despite this, no evidence of ultra-fast charge transfer is observed in the RPES of PCBM.

We demonstrate in this work the deposition of a large biological molecule (fibronectin) on polymeric substrates in a high vacuum environment using an electrospray deposition system. Fibronectin was deposited and its distribution and structure investigated and retention of function (ability to promote cell adhesion) on return to liquid environment is shown. AFM was used to monitor changes in the morphology of the surface before and after fibronectin deposition, whilst the biological activity of the deposited protein is assessed through a quantitative analysis of the biomolecular adhesion and migration of fibroblast cells to the modified surfaces. For the first time we have demonstrated that using high vacuum electrospray deposition it is possible to deposit large protein molecules on polymeric surfaces whilst maintaining the protein activity. The deposition of biological molecules such as proteins with the retention of their activity onto clean well-controlled surfaces under vacuum condition, offers the possibility for future studies utilizing high resolution vacuum based techniques at the atomic and molecular scale providing a greater understanding of protein–surface interface behaviour of relevance to a wide range of applications such as in sensors, diagnostics and tissue engineering.

The adsorption of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) on Au(1 1 1) has been studied using synchrotron-based X-ray photoelectron spectroscopy and in situ scanning tunnelling microscopy. Direct topographic and surface coverage information provided by the scanning probe measurements have enabled us to correlate peaks in the relatively complex carbon core-level photoemission to interactions of the surface with different parts of the PTCDI molecule. A strong interaction between the imide ends of the molecule with the underlying gold substrate is evidenced by a large chemical shift in the imide carbon peaks, which is observed only for the first adsorbed layer.

Here we present the characteristic signatures in X-ray absorption and photoemission spectroscopy for molecular damage in adsorbed monolayers of bi-isonicotinic acid on a rutile TiO2(1 1 0) surface. Bi-isonicotinic acid is the anchor ligand through which many important inorganic complexes are bound to the surface of TiO2 in dye-sensitized solar cells. The nature of the damage caused by excessive heating of the adsorbed monolayer is consistent with splitting the molecule into two adsorbed isonicotinic acid molecular fragments. The effect on the lowest unoccupied molecular orbitals (involved in electron transfer in the molecule) can be understood in terms of the adsorption geometry of the reaction products and their nearest neighbor interactions.

We have used the established technique of electrospray in developing a portable vacuum electrospray system which can deposit, in vacuo, dissolved molecules onto a sample which may then be analysed by UHV techniques. As an initial test of the system we have analysed silicon samples with an electrosprayed layer of poly(ethylene) oxide (PEO) using atomic force microscopy (AFM). The polymer forms different structures depending on the voltage applied to the emitter, and solution composition. The system is part of our ongoing effort to deposit other materials such as nanoparticles, and large dye molecules for developing molecular dye sensitised solar cells.

In this study, metal-free phthalocyanine has been deposited on a conducting glass surface by two methods: by spreading the molecular powder directly on the substrate in air and by vapor sublimation under ultra-high vacuum conditions (evaporation). The films have been characterized by means of core level X-ray Photoemission Spectroscopy, X-ray Absorption Spectroscopy (XAS) and Ultra Violet and Visible absorption spectroscopy (UV-Vis). Our results show that the two deposition methods produce molecular overlayers in different polymorphic phases; the UV-Vis measurements indicate that the film obtained by powder deposition is of x-phase type whereas sublimation leads to an α-polymorph structure. The XAS results show that in the powder deposited film the molecules are mainly oriented parallel to the surface. This is opposite to the case of the vapor deposited film, where the molecules mainly are oriented orthogonal to the surface.

The adsorption of monolayers of the pyridine-carboxylic acid monomers (isonicotinic acid, nicotinic acid, and picolinic acid) on rutile TiO2(1 1 0) has been studied by means of X-ray photoemission spectroscopy. An investigation of the O 1s spectra shows that the molecular carboxylic groups are deprotonated and, hence, that the molecules bind to the surface in a bidentate mode. Moreover, the binding energy of those core levels that are related to the pyridine ring atoms shift as a function of molecule relative to the substrate O 1s and Ti 3p levels, while the position of the core levels related to emission from the carboxylic group are constant relative to the substrate levels. The molecule-dependent shifts are attributed to local intermolecular interactions that determine the proximity of adjacent molecular rings and thus the core-hole screening response of the neighbouring molecules. We propose a simple molecular arrangement for each case which satisfies the known constraints. (C) 2003 Elsevier B.V. All rights reserved. (Less)

We show that Cr subcoatings in beamline optical elements can introduce an additional structure in C K-edge X-ray absorption measurements, which somewhat resembles the well-known losses produced by carbon contamination. The photon throughput variations induced by Cr and C require different treatments when correcting absorption spectra. The potential difficulties in unravelling the two effects could be avoided with efficient filtration of higher-order light.

The interaction of alkali metals (lithium, sodium, potassium) with an Ni(110)-O surface has been studied using X-ray photoelectron spectroscopy (XPS). The reaction at 300 K gives rise to a peroxide species together with a degree of reduction of the oxide to metallic nickel. With sodium an Ni(2p) feature attributed variously to Ni 3+ or a final-state effect for Ni 2+ is suppressed, consistent with its origins in an intersite screening process in NiO. At higher temperatures, lithium and potassium participate in a solid-state reaction with the oxide in which a trivalent nickel oxidation state (as LiNiO 2 and KNiO 2 ) is formed. Analogous reactions with sodium form the divalent nickelate Na 2 NiO 2 . Coadsorption of the alkali metal and oxygen on clean Ni(110) provides for optimum nickelate formation, whereas the presence of water inhibits the formation of Ni 3+ significantly. Similar experiments on NiO(100) suggest that the widespread practice of using thin oxide films to mimic bulk oxides may not always be justified.

The interaction of potassium with an oxidised Ni(110) single-crystal surface has been investigated using X-ray photoelectron spectroscopy (XPS). Incorporation of the alkali metal at room temperature results in suppression of the Ni(2p) satellite structure of NiO and is explained on the basis of a recent theoretical model. Unambiguous evidence is provided for the formation of Ni3+ after annealing this surface, and at 600 K it is the majority species in the surface region.