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peer-reviewed The nickel substituted (Ni4[(P8W48O184)(WO2)]28–, crown type polyoxometalate was electrochemically polymerised with conducting polymer pyrrole for the electrocatalytic reduction of bromate in water. The immobilized films of different thickness were characterised by electrochemical and surface based techniques. The resulting films were found to be extremely stable towards redox switching between the various redox states associated with the incorporated POM. This system was found to effectively electrocatalyse the reduction of bromate in water without the interference of other common anions. The detection limit was found to be 0.2 µm, with a linear region from 0.1 mm up to 2 mm bromate. The resulting POM doped polypyrrole films were found to be highly conductive by AC impedance. Surface characterization of the polymer films was carried out by using X‐ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy.

Dawson-type 18-molybdodisulphate anion [S2Mo18O62](4-) has been immobilized within polypyrrole film by means of electrochemical polymerization. The polymer modified electrodes have been characteriz ...

This study is focused on the development of a novel method for designing high-end interference fit fasteners. In this work, a new surface laser treatment process was utilized to enable enhanced usability and bond strength control of press-fit connections. Cylindrical 10 mm diameter pins of 316L were textured over a 10 mm length using a pulsed CO2 laser beam focused one millimeter below the surface, with the thermal energy adjusted to bring the surface to just above the melting point of the metal. The pin surface morphology and dimensions were precisely controlled by controlling the laser processing parameters specifically the laser beam power, the pulse repetition frequency, and the overlap between scan tracks. The pin was inserted into a hub hole diameter of 10.05 ± 0.003 mm and pull out joint bond strengths were examined. The results of this study showed that surface thus altered provided improved control of the bond strength which is a particular novelty of this new interference fit joining method. Surface roughness, Ra, from 40 to 160 μm, melt pool depths from 0.4 to 1.7 mm, increases in the pin outer diameter from 0.5 to 1.1 mm, and pull out forces of up to 7.51 kN were achieved. The bond joint was found to re-grip before final failure providing a more secure joint and increased safety. This joining method allows for the possibility of joining different materials. The pulse repetition frequency was measured to be the most significant processing parameter for control of the resulting mechanical properties and the bond strength with a clear inverse relationship.

peer-reviewed Flexible and conductive nanocomposites with enhanced mechanical and dielectric properties have been fabricated from reduced graphene oxide (RGO) reinforced polychloroprene rubber (CR). Composites were prepared on a two-roll mixing mill and the morphological analysis using SEM and TEM showed good dispersibility and exfoliation of RGO layers in the matrix. It imparted a critical role in the enhancement of mechanical and electrical properties of the composites. Composites with 0.9 phr of RGO showed an enhancement in tensile strength, tensile modulus and electrical conductivity as 92%, 75%, and 103 % respectively more than the pristine polychloroprene. RGO formed a good conducting percolating network in the polychloroprene matrix and it led to the formation of a dielectric composite material with enhanced electrical properties.

Improving the properties of polyvinyl chloride matrix by the incorporation of carbonaceous filler by melt mixing is an unusual thought in the polymer research. Here we incorporated reduced graphene oxide (RGO) as a filler into plasticized polyvinyl chloride (PPVC) matrix by melt mixing, an eco-friendly method. The effect of addition of filler in the morphology of the PPVC nanocomposites was analyzed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Raman spectroscopy. The mechanical response of the nanocomposites to an applied stress was studied. A 50% improvement in mechanical properties was obtained at a low filler loading. A decrease in elongation was observed at higher RGO loading. The dynamic mechanical analysis (DMA) of the nanocomposites indicated an increase in glass transition temperature of the PVC up on the addition of RGO. This has confirmed the confinement of PVC chains at the graphene surface. As a result, the storage modulus of the nanocomposites showed an increase up on the addition of the nanofiller. Theoretical values of the storage modulus were calculated using various theoretical equations. The effectiveness of filler on the storage modulus is estimated and is found to be consistent with the results obtained experimentally. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

The transition metal-substituted Krebs-type polyoxometalates (POMs) [Sb2W20M2O70(H2O)6]n−, M = Fe(III), Co(II), or Cu(II), were surface immobilized within the conducting polymer 3,4-ethylenedioxythiophene (PEDOT) on glassy carbon electrode surfaces. The immobilized films of different thicknesses were characterized by electrochemical and surface-based techniques. The inherent redox activity for the Krebs-type POMs, [Sb2W20M2O70(H2O)6]n−, M = Fe(III), Co(II), or Cu(II), that were observed in the solution phase were maintained in the polymeric PEDOT matrix. The resulting films were found to be extremely stable toward redox switching between the various POM-based redox states. The films exhibited pH-dependent redox activity and thin layer behavior up to 100 mV s–1. The films were found to be highly conductive through the employment of electrochemical impedance spectroscopy. Surface characterization of the films was carried out by X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron...

Parylene is commonly used as thin film polymer for MEMS devices and smart materials. This paper investigates the impact on bulk properties due to annealing various types of Parylene films. A thin film of Parylene N, C and a hybrid material consisting of Parylene N and C were deposited using a standard Gorham process. The thin film samples were annealed at varying temperatures from room temperature up to 300 °C. The films were analyzed to determine the mechanical and crystallinity effects due to different annealing temperatures. The results demonstrate that the percentage of crystallinity and the full-width-half-maximum value on the 2θ X-ray diffraction scan increases as the annealing temperature increases until the melting temperature of the Parylene films was achieved. Highly crystalline films of 85% and 92% crystallinity were achieved for Parylene C and N respectively. Investigation of the hybrid film showed that the individual Parylene films behave independently to each other, and the crystallinity of one film had no significant impact to the other film. Mechanical testing showed that the elastic modulus and yield strength increase as a function of annealing, whereas the elongation-to-break parameter decreases. The change in elastic modulus was more significant for Parylene C than Parylene N and this is attributed to the larger change in crystallinity that was observed. Parylene C had a 112% increase in crystallinity compared to a 61% increase for Parylene N, because the original Parylene N material was more crystalline than Parylene C so the change of crystallinity was greater for Parylene C.

Submitted by António Freitas (amsf@uma.pt) on 2021-04-15T20:40:03Z No. of bitstreams: 1 Polylactic acid nano chitosan composite fibers and their morphological, physical characterization for the removal of cadmium.pdf: 5096005 bytes, checksum: 7c5c2155f86a01e74f93df42c793eefe (MD5) Made available in DSpace on 2021-04-15T20:40:03Z (GMT). No. of bitstreams: 1 Polylactic acid nano chitosan composite fibers and their morphological, physical characterization for the removal of cadmium.pdf: 5096005 bytes, checksum: 7c5c2155f86a01e74f93df42c793eefe (MD5) Previous issue date: 2020 info:eu-repo/semantics/publishedVersion

Multilayer assemblies composed of the crown type polyoxometalate, Ni4[(P8W48O148)(WO2)]28−, and silver nanoparticles, have been immobilised onto glassy carbon electrode surfaces through the layer-by-layer (LBL) technique. The resulting thin films have been characterised by electrochemical and surface based techniques with the multilayers showing electrocatalytic ability towards the reduction of chlorate in solution. The layers exhibited redox activity for both the POM and silver nanoparticle moieties with the layers showing good stability towards redox cycling and thin layer behaviour. The layers were found to be highly conductive due to the presence of the nanoparticles as shown by AC impedance and resulting charge transfer resistance values (Rct) obtained for the layers. A clear and significant catalytic ability of Ni4[(P8W48O148)(WO2)]28/AgNP's assembly towards the chlorate reduction was observed with a measured sensitivity of 32.3mAcm−2/(μM).

peer-reviewed This topical review will provide a survey of the current state of the art in 'hyphenated' techniques for characterisation of bulk materials, surface, and interfaces, whereby two or more analytical methods investigating different properties are applied simultaneously to the same sample to better characterise the sample than can be achieved by conducting separate analyses in series using different instruments. It is intended for final year undergraduates and recent graduates, who may have some background knowledge of standard analytical techniques, but are not familiar with 'hyphenated' techniques or hybrid instrumentation. The review will begin by defining 'complementary', 'hybrid' and 'hyphenated' techniques, as there is not a broad consensus among analytical scientists as to what each term means. The motivating factors driving increased development of hyphenated analytical methods will also be discussed. This introduction will conclude with a brief discussion of gas chromatography-mass spectroscopy and energy dispersive x-ray analysis in electron microscopy as two examples, in the context that combining complementary techniques for chemical analysis were among the earliest examples of hyphenated characterisation methods. The emphasis of the main review will be on techniques which are sufficiently well-established that the instrumentation is commercially available, to examine physical properties including physical, mechanical, electrical and thermal, in addition to variations in composition, rather than methods solely to identify and quantify chemical species. Therefore, the proposed topical review will address three broad categories of techniques that the reader may expect to encounter in a well-equipped materials characterisation laboratory: microscopy based techniques, scanning probe-based techniques, and thermal analysis based techniques. Examples drawn from recent literature, and a concluding case study, will be used to explain the practical issues that arise in combining different techniques. We will consider how the complementary and varied information obtained by combining these techniques may be interpreted together to better understand the sample in greater detail than that was possible before, and also how combining different techniques can simplify sample preparation and ensure reliable comparisons are made between multiple analyses on the same samples—a topic of particular importance as nanoscale technologies become more prevalent in applied and industrial research and development (R&D). The review will conclude with a brief outline of the emerging state of the art in the research laboratory, and a suggested approach to using hyphenated techniques, whether in the teaching, quality control or R&D laboratory

peer-reviewed We report the effect of surface modification of multi-walled carbon nanotubes (MWCNTs) by an ionic liquid, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl). An apparent physical (cation-π/π-π) interaction between the ionic liquid and MWCNTs was revealed by Raman and UV-visible spectroscopies. The composite loaded with 10 phr MWCNTs exhibits impressive enhancements in tensile strength (381% increase), hardness (34% increase), and abrasion resistance. High electrical conductivity was also achieved at MWCNT loading levels beyond 3 phr loading, with a low percolation threshold (0.023 vol%) for the composites. The microstructural development of conductive networks and uniform dispersion of MWCNTs in the presence of ionic liquid were analysed by TEM and AFM. The experimentally observed mechanical and electrical properties have been compared with theoretical predictions, and confirm that the dramatic improvement in mechanics and electrical conductivity is the outcome of the extremely fine dispersion, the strong secondary network of MWCNTs and improved interaction at the interface via thermodynamically-induced adsorption and physical interlocking of polymer chains in the nanoscopic MWCNT structure. This study demonstrates a simplified and ecofriendly approach to develop multifunctional advanced materials based on ionic liquid modified MWCNT elastomer composites with a much better balance among mechanical properties, conductivity and filler content.

Over the past two decades atomic force microscopy (AFM) has become one of the most frequently used tools for studying polymer crystallization. The combination of high resolution, minimal sample preparation and the ability to image non-destructively has allowed visualisation of crystallization, melting and re-ordering processes at a lamellar and sub-lamellar scale, revealing complexities that could only previously be guessed at. Here the insights that AFM has provided into some of the main over-arching questions relating to polymer crystallization are reviewed. The emphasis is on the use of AFM to image growth in real time, and on contributions that have been made to our understanding of polymer crystallization in general, rather than to specific systems.

Coccoid cells of the bacterial species Staphylococcus aureus have been mechanically trapped in lithographically patterned substrates and imaged under growth media using atomic force microscopy (AFM) in order to follow cellular processes. The cells are not perturbed as there is no chemical linkage to the surface. Confinement effects are minimized compared to trapping the cells in porous membranes or soft gels. S. aureus cells have been imaged undergoing cell division whilst trapped in the patterned substrates. Entrapment in lithographically patterned substrates provides a novel way for anchoring bacterial cells so that the AFM tip will not push the cells off during imaging, whilst allowing the bacteria to continue with cellular processes.

Nanodroplets of isotactic polypropylene (iPP) were observed using temperature-controlled AFM in order to study the polymer's crystallization behavior. The nucleation, growth, and transformation of iPP crystals on heating have been directly imaged. The strong confinement of the polymer into nanoscale droplets has allowed the controlled observation of polymer nucleation as well as access to crystal growth at exceptionally high supercooling in iPP. Different modes of crystal growth were observed depending on the film thickness, including the formation of multiple independent homogeneous nuclei within single droplets. The temperature at which the onset of nucleation was observed in individual droplets was found to be dependent on the thickness as well as the volume of the droplets. For droplets with smaller thicknesses (

The effect of microfillers on the thermal stability of natural rubber (NR), carboxylated styrene butadiene rubber (XSBR) latices, and their 70/30 NR/XSBR blend were studied using thermogravimetric method. Microcomposites of XSBR and their blend were found to be thermally more stable than unfilled samples. The activation energy needed for the degradation of polymer chain was calculated from Coats-Redfern plot. Activation energy needed for the thermal degradation of filled samples was higher than unfilled system. It indicated the improved thermal stability of the filled samples. The ageing resistance of the micro-filled samples was evaluated from the mechanical properties of aged samples. The thermal ageing was carried out by keeping the samples in hot air oven for 7 days at 70°C. The mechanical properties such as tensile strength, modulus at 300% elongation, and strain at break were computed. As compared to unfilled samples, micron-sized fillers reinforced systems exhibited higher ageing resistance. Finally, an investigation was made on the influence of ion-beam irradiation on microcomposites of NR, XSBR latices, and their 70/30 blend systems using 28Si8+ performed at 100 MeV. The surface changes of the samples after irradiation were analyzed using X-ray photoelectron spectroscopy. The results of XPS measurements revealed that the host elements were redistributed without any change in binding energies of C1s, O1s, and Si2p. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Thin films of polystyrene (PS)/poly (methyl methacrylate) (PMMA) blends with different end groups were investigated using TOF-SIMS and AFM. PS with -OH and -NH2 end groups were blended in toluene solvent with pure PMMA homopolymer, and PMMA having anhydride end group. The ToF-SIMS spectra of PS-OH/PMMA resembled that of pure PS-PMMA blends showing an increase of PMMA intensity after annealing. On the contrary, the PS-NH2 blended with PMMA showed an increase in PS intensity on the surface after annealing. The ToF-SIMS spectra were similar to that of a pure PS-PMMA di-block copolymer. These results indicate copolymer formation at the surface. The PS-NH2 with PMMA-anhydride blend spectra showed very slight changes in spectra before and after annealing and the AFM images revealed spinodal bicontinuous structures on the surface before and after annealing. The copolymer formation is found to occur in the as-cast film itself and not after thermal treatment. (c) 2006 Elsevier B.V. All rights reserved.

The surface behaviour of a two-phase polymer mixture depends on the chemical structure of the polymer components, the interaction between the two polymers and the processing conditions. The microscopic morphology and the surface composition need to be known in order to fully utilize the thin film properties. The technique of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used to obtain the molecular surface composition of thin films of blends and block copolymers. The depth profiling tool of Nano-SIMS, a dynamic SIMS technique, helps to provide the chemical mapping of the surface in 2D and 3D. The surface morphology is investigated using AFM. Thin films of PS and PMMA diblock copolymers with molecular weight of 12K-12K and 10K-10K and blends of PS/PMMA (10K/10K) for thicknesses ranging from 5 nm to 50 nm are examined. For the blends, the ToF-SIMS spectra for all the thicknesses show the same behaviour of a high increase of PMMA on the surface after annealing. Nano-SIMS images reveal the formation of nanostructures on the annealed surfaces and AFM studies show these nanostructures to be droplets having distinct phase shift from the surrounding matrix. The droplet dimensions increase with the increase of the thickness of the film but the absolute intensity from the ToF-SIMS spectra for all the annealed films remains almost the same. For the copolymers, the ToF-SIMS spectra show that there is a decrease of PMMA on the surface for the annealed films when compared to the as-cast ones. AFM morphology reveals that, for different thicknesses, annealing induces different topographical features like droplets, holes, spinodal patterns, etc. but with no distinct phase shift between the patterns and the surrounding matrix. The two different copolymers of comparable molecular weight are found to exhibit very different topography even when the thickness of the films remained the same. The surface composition from the ToF-SIMS data, however, was not found to vary even when the topography was completely different.

Immiscible polymer systems are known to form various kinds of phase-separated structures capable of producing self-assembled patterns at the surface. In this study, different surface characterization methods were utilized to study the surface morphology and composition produced after annealing thin polymer films. Two different SIMS techniques - static time-of-flight secondary ion mass spectrometry (ToF-SIMS) and dynamic nano-SIMS - were used, complemented by x-ray photoelectron spectrometry (XPS) and atomic force microscopy (AFM). Thin films (spin-coated onto silicon wafers) of polystyrene (PS)-poly(methyl methacrylate) (PMMA) symmetric blends and diblock copolymers of similar molecular weight were investigated. Surface enrichment by PS was found on all as-cast samples. The samples were annealed at 160D C for different time periods, after which the blend and the copolymer films exhibited opposite behaviour as seen by ToF-SIMS and XPS. The annealed blend surface presented an increase in the PMMA concentration whereas that of copolymers showed a decrease in PMMA concentration compared with the as-cast sample. For blends, the nano-SIMS as well as AFM images revealed the formation of phase-separated domains at the surface. The composition information obtained from ToF-SIMS and XPS, as well as the surface mapping by nano-SIMS and AFM, allowed us to conclude that PS formed phase separated droplet-like domains on a thin PMMA matrix on annealing. The three-dimensional nano-SIMS images showed that the PS droplets were supported inside a rim of PMMA and that these droplets continued from the surface like columnar rods into the film until the substrate interface. In the case of annealed copolymer samples, the AFM images revealed topographical features resembling droplet-like domains on the surface but there was no phase difference between the domains and the matrix. In the case of copolymers, owing to the covalent bonding between the blocks, complete phase separation was not possible. The three-dimensional nano-SIMS images showed domain structures in the form of striations inside the film, which were not continuous until the substrate interface. Information from the different techniques was required to gain an accurate view of the surface composition and topographical changes that have occurred under the annealing conditions. Copyright C 2005 John Wiley & Sons, Ltd.

Surface characterization of thin films of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and diblock copolymers was done using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) in order to compare their annealing behaviour. The spin-cast films, of 12 nm thickness, were annealed at 160 degreesC for different time periods ranging from 2 hours to 1 week. ToF-SIMS spectra of annealed blends showed a decrease in the concentration of PS and an increase in the concentration of PMMA on the surface as compared to the as-cast sample. The spectra of copolymers showed an increase in concentration of PS on the surface on annealing, with PMMA concentration decreasing. AFM images with the help of SIMS information allowed us to conclude that in the case of blends, PS formed droplet-like domains on a PMMA matrix and, in copolymers, PS with its lower surface free energy segregated to the surface without complete phase separation, which is not possible for copolymers. Copyright (C) 2004 John Wiley Sons, Ltd.

Thin films of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blends and block copolymers were characterized by two different SIMS instruments. ToF-SIMS was used to obtain the molecular composition of the upper most surface while nano-SIMS allowed us to visualize the surface morphology with submicrometer lateral resolution. The blends and copolymers showed different effects on annealing. ToF-SIMS spectra of annealed blends showed a decrease in the concentration of PS and an increase in the concentration of PMMA as compared to the pristine sample. By contrast, the spectra of annealed copolymers showed a decrease in the concentration of PMMA and an increase in the concentration of PS. The result obtained from the nano-SIMS imaging of the blends and copolymers revealed the formation of submicron domains at the surface on annealin. In case of blends, the images showed a strong oxygen signal on the surface suggesting a higher PMMA concentration, while for copolymers, the oxygen signal was quite low. ToF-SIMS spectra combined with nano-SIMS images help to interpret the surface topographical changes that the PS/PMMA blend and copolymer thin films undergo on annealing. (C) 2004 Elsevier B.V. All rights reserved.

Changes in the surface composition of chemically treated cellulose fibres obtained from the sheath of banana plants were investigated using electrokinetic (ζ-potential) measurements. Scanning electron microscopy (SEM) was used to observe changes in the surface morphology of the fibres. Spectroscopic methods were also used to analyse the changes on the cellulose fibre surface. Chemical treatments such as alkali treatment, acetylation, treatment with a triazine coupling agent, various silanes, etc. reduced the hydrophilicity of the fibres. The surface morphology of the fibres showed considerable changes. Chemical treatments reduced the acidity of the already polar cellulose fibre. The high iso-electric point (IEP) of the silane A1100-treated fibres shows that basic groups dominate at these surfaces. The observations are consistent with the values obtained using solvatochromic measurements.

Bacteria of the Bacillus cereus family form highly resistant spores, which in the case of the pathogen B. anthracis act as the agents of infection. The outermost layer, the exosporium, enveloping spores of the B. cereus family as well as a number of Clostridia , plays roles in spore adhesion, dissemination, targeting, and germination control. We have analyzed two naturally crystalline layers associated with the exosporium, one representing the “basal” layer to which the outermost spore layer (“hairy nap”) is attached, and the other likely representing a subsurface (“parasporal”) layer. We have used electron cryomicroscopy at a resolution of 0.8–0.6 nm and circular dichroism spectroscopic measurements to reveal a highly α-helical structure for both layers. The helices are assembled into 2D arrays of “cups” or “crowns.” High-resolution atomic force microscopy of the outermost layer showed that the open ends of these cups face the external environment and the highly immunogenic collagen-like fibrils of the hairy nap (BclA) are attached to this surface. Based on our findings, we present a molecular model for the spore surface and propose how this surface can act as a semipermeable barrier and a matrix for binding of molecules involved in defense, germination control, and other interactions of the spore with the environment.

The bacterial cell wall is essential for viability and shape determination. Cell wall structural dynamics allowing growth and division, while maintaining integrity is a basic problem governing the life of bacteria. The polymer peptidoglycan is the main structural component for most bacteria and is made up of glycan strands that are cross-linked by peptide side chains. Despite study and speculation over many years, peptidoglycan architecture has remained largely elusive. Here, we show that the model rod-shaped bacterium Bacillus subtilis has glycan strands up to 5 μm, longer than the cell itself and 50 times longer than previously proposed. Atomic force microscopy revealed the glycan strands to be part of a peptidoglycan architecture allowing cell growth and division. The inner surface of the cell wall has a regular macrostructure with ≈50 nm-wide peptidoglycan cables [average 53 ± 12 nm ( n = 91)] running basically across the short axis of the cell. Cross striations with an average periodicity of 25 ± 9 nm ( n = 96) along each cable are also present. The fundamental cabling architecture is also maintained during septal development as part of cell division. We propose a coiled-coil model for peptidoglycan architecture encompassing our data and recent evidence concerning the biosynthetic machinery for this essential polymer.

A large scan area high-speed scan stage for atomic force microscopy using the resonant oscillation of a quartz bar has been constructed. The sample scanner can be used for high-speed imaging in both air and liquid environments. The well-defined time-position response of the scan stage due to the use of resonance allows highly linearized images to be obtained with a scan size up to 37.5 mum in 0.7 s. The scanner is demonstrated for imaging highly topographic silicon test samples and a semicrystalline polymer undergoing crystallization in air, while images of a polymer and a living bacteria, S. aureus, are obtained in liquid.