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Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, a patternable oriented MOF film is designed: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylate ligand (Br2 BDC) into a copper-based MOF Cu2 L2 DABCO (DABCO = 1,4-diazabicyclo[2.2.2]octane; L = BDC/Br2 BDC). The lithographed samples act as diffraction gratings upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, the alignment of the dye in the MOF is demonstrated. By controlling the functional response to light, this MOF patterning protocol can be used for the microfabrication of optical components for photonic devices. ispartof: ADVANCED MATERIALS vol:35 issue:25 ispartof: location:Germany status: published

Micropatterning crystalline materials with oriented pores is necessary for the fabrication of devices with anisotropic properties. Crystalline and porous metal-organic frameworks (MOFs) are ideal materials as their chemical and structural mutability enables precise tuning of functional properties for applications ranging from microelectronics to photonics. Herein, we design a patternable oriented MOF film: by using a photomask under X-ray exposure, the MOF film decomposes in the irradiated areas, remaining intact in the unexposed regions. The MOF film acts simultaneously as a resist and as functional porous material. While the heteroepitaxial growth from aligned Cu(OH)2 nanobelts is used to deposit oriented MOF films, the sensitivity to radiation is achieved by integrating a brominated dicarboxylic ligand (Br2BDC) into a copper-based MOF Cu2L2DABCO (L=BDC/Br2BDC). The lithographed samples act as a diffraction grating upon irradiation with a laser, thus confirming the quality of the extended MOF micropattern. Furthermore, the oriented MOF patterns are functionalized with fluorescent dyes. As a result, by rotating the polarization angle of the laser excitation, we demonstrate the alignment of the dye in the MOF. By controlling the functional response to light, this MOF patterning protocol could be used for the microfabrication of optical components for photonic devices.

The deposition of biomolecules on biosensing surface platforms plays a key role in achieving the required sensitivity and selectivity for biomolecular interactions analysis. Controlling the interaction between the surface and biomolecules is increasingly becoming a crucial design tool to modulate the surface properties needed to improve the performance of the assay and the detection outcome. Carboxymethyl-dextran (CMD) coating can be exploited to promote chemical grafting of proteins, providing a hydrophilic, bioinert, nonfouling surface and a high surface density of immobilized proteins. In the present work, we developed and optimized a technique to produce a cost-effective CMD-based patterned surface for the immobilization of biomolecules to be used on standard protocols optimization. They consist of silicon or glass substrates with patterned bioactive areas able to efficiently confine the sampling solution by simply exploiting hydrophilic/hydrophobic patterning of the surface. The fabrication process involves the use of low-cost instruments and techniques, compatible with large scale production. The devices were validated through a chemiluminescence assay we recently developed for the analysis of binding of DNA nanoassemblies modified with an affinity binder to target proteins immobilized on the bioactive areas. Through this assay we were able to characterize the chemical reactivity of two target proteins toward a dextran matrix on patterned surfaces and to compare it with model CMD-based surface plasmon resonance (SPR) surfaces. We found a high reproducibility and selectivity in molecular recognition, consistent with results obtained on SPR sensor surfaces. The suggested approach is straightforward, cheap, and provides the means to assess patterned functionalized surfaces for bioanalytical platforms.

Nanolaminate coatings (NLC) consisting of alternated CrN coupled with either cubic tungsten nitride (β-W2N) or molybdenum nitride (γ-Mo2N) were deposited on cold worked tool steel substrates using reactive DC reactive magnetron sputtering for improved mechanical and corrosion resistance. The CrN/γ-Mo2N and CrN/β-W2N nanolaminate systems were found to perform better than the corresponding single-layer systems, with both mechanical and electrochemical properties improving by decreasing the individual layer thickness from 100 to 5 nm. The CrN/β-W2N NLC combined the high hardness value of W2N with the low corrosion current of CrN. The CrN/γ-Mo2N NLC showed synergistic improvements consisting of both higher hardness and lower corrosion currents with respect to the constituent materials alone. The dependence of mechanical and corrosion properties on the bilayer period is discussed in terms of the grain size, residual stresses and texture of the constituent materials and the nanostructured character of the multilayer architecture.

By means of a combined microscopy-, spectroscopy-, and tomography-based approach, we investigated surface and interface defects in metal-polymer heterostacks. The aim was to characterize both morphological and compositional alterations of the surfaces, originating in the physical vapor deposition (PVD) growth methods adopted in the fabrication process. Synchrotron radiation X-ray computed tomography (CT) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray Spectroscopy (EDS) indicate that both chemical contaminations, introduced in the fabrication process, and growth conditions strongly affect the presence of defects. On the basis of our results, we classified the defects into four main families. Interestingly, the faults are mainly located at the metal-polymer interface. Thanks to this study, we have been able to gain a deeper insight into the defects' origins and nature, allowing the identification of the precise production steps involved in the generation of the selected defects.

Testing devices based on cell tracking are particularly interesting as diagnostic tools in medicine for antibiotics susceptibility testing and in vitro chemotherapeutic screening. In this framework, the application of nanomechanical sensors has attracted much attention, although some crucial aspects such as the effects of the viscous damping, when operating in physiological conditions environment, still need to be properly solved. To address this problem, we have designed and fabricated a nanomechanical force sensor that operates at the interface between liquid and air. Our sensor consists of a silicon chip including a 500 μm wide Si

Here, we report on the conceptual design, the hardware realization, and the first experimental results of a novel and compact x-ray polarimeter capable of a single-pulse linear polarization angle detection in the extreme ultraviolet photon energy range. The polarimeter is tested by performing time resolved pump-probe experiments on a Ni80Fe20 Permalloy film at the M-2,M-3 Ni edge at an externally seeded free-electron laser source. Comparison with similar experiments reported in the literature shows the advantages of our approach also in view of future experiments.

Journal of applied crystallography 54(1), 132 - 141 (2021). doi:10.1107/S1600576720014788, An automatic sample changer system for measurements of large numbers of liquid samples – the µDrop Sample Changer – is presented. It is based on a robotic arm equipped with a pipetting mechanism, which is combined with a novel drop-based sample holder. In this holder a drop of liquid is suspended between two parallel plates by surface tension. The absence of a transfer line benefits the cleaning, improving the background as well as making it faster and more efficient than most comparable capillary-based systems. The µDrop Sample Changer reaches cycle times below 35 s and can process up to 480 samples in a single run. Sample handling is very reliable, with a drop misplacement chance of about 0.2%. Very low sample volumes (, Published by Wiley-Blackwell, [S.l.]

The change in electrical property (capacitance) upon hybridization of the desired ssDNA to a capture probe has been proposed as a promising technology platform in biomedical research and practice. An appropriate mathematical model is needed for understanding and optimizing the process occurring at the electrode/electrolyte interface. It is also informative for examining the forces generated by the AC electric fields on the DNA molecules as well as the suspending buffer solution in the experimental pool. Here, we provide the development, formulation and validation of a semi-analytical model of DNA hybridization with deoxynucleotide molecules chemically tethered to a solid gold electrode. The parameters of the proposed model have been estimated using available experimental data. We demonstrate that the detection limit and specificity of our surface-based genosensor are not only dependent on the probe/target binding affinity, but also on the Self-Assembled Monolayer (SAM) density and on the interfacial electric field. The label-free Electrochemical Impedance Spectroscopy (EIS)-based oligonucleotide biosensor with integrated DC-biased can achieve rapid hybridization, high selectivity and sensitive detection for DNA target samples.SIGNIFICANCEDNA hybridization, wherein strands of DNA form duplex through noncovalent, sequence-specific interactions, is one of the most fundamental processes in biology. Fast and reliable determination of miniature amounts of DNA plays important role in clinical forensic and pharmaceutical applications. Thus, developing a better understanding of the kinetic and dynamic properties of DNA hybridization will help in the elucidation of all mechanisms involved in numerous biochemical processes. Moreover, because DNA hybridization has been widely adapted in biotechnology, its study is invaluable to the development of a range of commercially important processes.To achieve optimal sensitivity with minimum sample size and rapid hybridization, ability to predict the kinetics of hybridization based on the characteristics of the strands is crucial, and hence a computer aided numerical model for the design and optimization of a DNA biosensor has been implemented.

The coupling of plasmonic and mechanical properties at the nanoscale is of great potential for the development of next generation devices capable to detect weak forces, mass changes, minute displacements and temperature-induced effects. Both the transduction of mechanical motion to the scattered light fields in term of polarization or intensity modulation and plasmon-driven mechanical oscillations have already been demonstrated. Quasi static tunable hot spots have recently been designed and applied to surface-enhanced Raman spectroscopy (SERS). Here we fabricated a plasmomechanical device, with a plasmonic hot spot modulated at the oscillator eigenfrequency, and demonstrated that the nonlinear modulation of polarization-dependent SERS signal from a synthetic dye can be analyzed with lock-in techniques, thus, realizing frequency modulated Raman spectroscopy. © 2017 American Chemical Society.

Extracellular vesicles (EVs) are nanometric membranous structures secreted from almost every cell and present in biofluids. Because EV composition reflects the state of its parental tissue, EVs possess an enormous diagnostic/prognostic potential to reveal pathophysiological conditions. However, a prerequisite for such usage of EVs is their detailed characterisation, including visualisation which is mainly achieved by atomic force microscopy (AFM) and electron microscopy (EM). Here we summarise the EV preparation protocols for AFM and EM bringing out the main challenges in the imaging of EVs, both in their natural environment as biofluid constituents and in a saline solution after EV isolation. In addition, we discuss approaches for EV imaging and identify the potential benefits and disadvantages when different AFM and EM methods are applied, including numerous factors that influence the morphological characterisation, standardisation, or formation of artefacts. We also demonstrate the effects of some of these factors by using cerebrospinal fluid as an example of human biofluid with a simpler composition. Here presented comparison of approaches to EV imaging should help to estimate the current state in morphology research of EVs from human biofluids and to identify the most efficient pathways towards the standardisation of sample preparation and microscopy modes.

The quantification of significant amounts of disease biomarkers circulating in the bloodstream represents one of the challenging frontiers in biomedicine. The complexity of blood composition has opened the quest for novel detection technologies, capable of discerning small amount of specific biomarkers from other blood proteins/oligonucleotides and of reliably measuring them. In this context, we have developed a label-free device based on differential double-layer capacitance readout at microfabricated gold electrodes and demonstrated its detection performance in real biosample volumes. By means of electrochemical impedance spectroscopy (EIS) measurements in a three electrodes setup, we first calibrated the system following the in situ hybridization of a self-assembled monolayer of single-stranded, short oligonucleotides on the gold microelectrode through the measurement of differential capacitance changes as a function of time, for different concentrations of complementary DNA in a saline buffer. Based on this calibration we used the device to quantify the presence of microRNAs (miRNAs) in human plasma. We demonstrated that our device is fast, sensitive, reusable, reproducible, and perfectly suited to detect biomarkers in complex matrices, as cell lysate, serum, and blood. We put forward the possibility to apply this platform to the bioaffinity detection of protein biomarkers as well as circulating drugs in blood, for therapeutic drug monitoring applications.

Minimization of contamination associated with the graphene transfer process from the growth substrate to the device surface is a major requirement for large scale CVD graphene device applications. The most widespread transfer methods are based on the use of a thin sacrificial polymeric layer such as poly(methyl methacrylate), but its complete removal after transfer is an unsolved problem; this issue is critical for suspended graphene, since the back surface often results contaminated by the dissolved polymer. Here we present a polymer-free method of commercial CVD-grown graphene transfer from the initial copper substrate to the silicon device, in which a 15 nm-thick titanium layer replaces completely the polymer film as supporting layer during the transfer process. Our approach reduces significantly the level of contaminations for supported and suspended graphene layers. Raman spectroscopy was used to prove the quality of the transferred graphene, not affected by this approach. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy were used to assess the amount of the contaminants left by the transfer process. Overall carbon contamination was reduced by a factor 2, while contaminations originating from the metal etching in hydrofluoric acid, namely titanium and fluorine, were absent within the sensitivity of the used techniques. (C) 2016 Elsevier Ltd. All rights reserved.

Dy- and Tb-doped CeO2-Ni cermets for highly active solid-oxide fuel-cell (SOFC) anodes were fabricated by a one-pot electrodeposition process. Undoped, singly-doped, and co-doped powders were synthesized in an X-ray amorphous state, heat treated in air, and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) at different crystallization stages. In particular, in situ TEM analyses were carried out during heating in an oxygen atmosphere, in order to follow the evolution of structure and morphology and to understand the role of the dopants. The key structural effect of dopants was the inhibition of grain coarsening during heat treatment. Functional tests were carried out with micro-single chamber SOFCs, fed with a CH4/O-2 mixture, the anodes of which were prepared with the CeO2-Ni powders synthesized in this study. A correlation was established between the electrocatalytic performance and the morphology of the anodic material, pinpointing that the finer and more homogeneous nanocrystalline structure of the doped powders results in better-defined and more active catalytic sites, thus improving the performance of the cell.

Micro and nanomechanical resonators represent a promising platform for proteins label-free detection because of their extreme sensitivity, fast response and low cost. Micro-pillars are columnar resonators that can be easily arranged in dense arrays of several thousand sensors in a squared mm. To exploit such a large density, however, a method for tracking independently micropillars resonance frequency is required. Here we present a detection method based on CCD imaging and software image analysis, which can measure the resonance frequency of tens of pillars in parallel. Acquiring simultaneously the frequency shift of up to 40 sensors and applying a proper statistical analysis, we were able to overcome the variability of the single measures improving the device sensitivity at low analyte concentration range. As a proof of concept, this method has been tested for the detection of a tumor marker, the Prostate Specific Membrane Antigen (PSMA). Pillars have been functionalized with an antibody against PSMA. The tumor marker (PSMA) has been detected in a range of concentrations between 300 pM and 100 nM, in buffer and in diluted bovine serum. The sensitivity of our method was limited only by the affinity constant of the antigen–antibody recognition. Moreover, this detection technique demonstrated to be effective in the 1–6 nM range, which is the window of PSMA concentration of clinical interest.

Time-resolved investigations have begun a new era of chemistry and physics, enabling the monitoring in real time of the dynamics of chemical reactions and matter. Induced transient optical absorption is a basic ultrafast electronic effect, originated by a partial depletion of the valence band, that can be triggered by exposing insulators and semiconductors to sub-picosecond extreme-ultraviolet pulses. Besides its scientific and fundamental implications, this process is very important as it is routinely applied in free-electron laser (FEL) facilities to achieve the temporal superposition between FEL and optical laser pulses with tens of femtoseconds accuracy. Here, a set of methodologies developed at the FERMI facility based on ultrafast effects in condensed materials and employed to effectively determine the FEL/laser cross correlation are presented.A description of the novel timing methodologies developed at the FERMI FEL facility is given.

Cell-cell and cell-matrix interactions are essential to the survival and proliferation of most cells, and are responsible for triggering a wide range of biochemical pathways. More recently, the biomechanical role of those interactions was highlighted, showing, for instance, that adhesion forces are essential for cytoskeleton organization. Silicon nanowires (Si NWs) with their small size, high aspect ratio and anisotropic mechanical response represent a useful model to investigate the forces involved in the adhesion processes and their role in cellular development. In this work we explored and quantified, by single cell force spectroscopy (SCFS), the interaction of mouse embryonic fibroblasts with a flexible forest of Si NWs. We observed that the cell adhesion forces are comparable to those found on collagen and bare glass coverslip, analogously the membrane tether extraction forces are similar to that on collagen but stronger than that on bare flat glass. Cell survival did not depend significantly on the substrate, although a reduced proliferation after 36 h was observed. On the contrary both cell morphology and cytoskeleton organization revealed striking differences. The cell morphology on Si-NW was characterized by a large number of filopodia and a significant decrease of the cell mobility. The cytoskeleton organization was characterized by the absence of actin fibers, which were instead dominant on collagen and flat glass support. Such findings suggest that the mechanical properties of disordered Si NWs, and in particular their strong asymmetry, play a major role in the adhesion, morphology and cytoskeleton organization processes. Indeed, while adhesion measurements by SCFS provide out-of-plane forces values consistent with those measured on conventional substrates, weaker in-plane forces hinder proper cytoskeleton organization and migration processes.

Self-assembly methods allow to obtain ordered patterns on surfaces with exquisite precision, but often lack in effectiveness over large areas. Here we report on the realization of hierarchically ordered polymethylmethacrylate (PMMA) nanofibres and nanodots over large areas from solution via a fast, easy and low-cost method named ASB-SANS, based on a ternary solution that is cast on the substrate. Simple changes to the ternary solution composition allow to control the transition from nanofibres to nanodots, via a wide range of intermediate topologies. The ternary solution includes the material to be patterned, a liquid solvent and a solid substance able to sublimate. The analysis of the fibres/dots width and inter-pattern distance variations with respect to the ratio between the solution components suggests that the macromolecular chains mobility in the solidified sublimating substance follows Zimm-like models (mobility of macromolecules in diluted liquid solutions). A qualitative explanation of the self-assembly phenomena originating the observed nanopatterns is given. Finally, ASB-SANS-generated PMMA nanodots arrays have been used as lithographic masks for a silicon substrate and submitted to Inductively Coupled Plasma-Reactive Ion Etching (ICP-RIE). As a result, nanopillars with remarkably high aspect ratios have been achieved over areas as large as several millimeters square, highlighting an interesting potential of ASB-SANS in practical applications like photon trapping in photovoltaic cells, surface-enhanced sensors, plasmonics.

Prussian dyes are characterized by interesting photomagnetic properties due to the photoinduced electron transfer involved in the Fe oxidation and spin state changes. Ferromagnetic Prussian blue (PB) in contact with titanium dioxide (TiO2) can be reduced to paramagnetic Prussian white (PW) upon UV band gap excitation of TiO2. This process is promoted by the presence of a hole scavenger, such as water, fundamental to ensure the overall charge balance and the continuity of the process. In order to clarify the photoinduced reduction mechanism and the role of water, an innovative system of graphene nanobubbles (GNBs) filled with a PB aqueous solution was developed, enabling the application of electron spectroscopies to the liquid phase, up to now limited by the vacuum required to overcome the short electron inelastic mean free path in dense medium. In this work GNBs formed on the photocatalytic substrate are able to act as "nanoreactors", and they can control and take part in the reaction. The evolution of Fe L2,3 edge X-ray absorption spectra measured in total electron yield through the graphene membrane revealed the electron reduction from PB (FeIII-CN-FeII) to PW (FeII-CN-FeII) upon UV irradiation, shedding light on the photoinduced electron transfer mechanism in liquid phase. The results, confirmed also by Raman spectroscopy, unequivocally demonstrate that the reaction occurs preferentially in aqueous solution, where water acts as hole scavenger.

Micro- and nano-mechanical resonators such as cantilevers and pillars are more and more used as molecular sensors, due to their high sensitivity, ease of fabrication and high throughput. In order to modify their wetting properties and to prepare them for the selective adsorption of the molecules of interest, the sensor active surface has to be properly functionalized. This can significantly affect their mechanical performances. In this paper we report on the effect on a micropillar array of different hydrophobic treatments, based on plasma deposition of a fluorocarbon film (FCF) and on the formation of an alkanosilane coating, to obtain a superhydrophobic state. Each treatment was characterized by measuring the change of the quality factor in vacuum, the static contact angle and evaluating the compatibility with gold deposition, to create a bio-functional layer. As case study, DNA self assembled monolayer (SAM) formation and hybridization efficiency were measured. Finally, the superhydrophobicity was tested with diluted human plasma, as preliminary step toward the use of micropillars for biomolecular detection in human samples. (C) 2014 Elsevier B.V. All rights reserved.

Free-electron lasers (FELs) currently represent a step forward on time-resolved investigations on any phase of matter through pump-probe methods involving FELs and laser beams. That class of experiments requires an accurate spatial and temporal superposition of pump and probe beams on the sample, which at present is still a critical procedure. More efficient approaches are demanded to quickly achieve the superposition and synchronization of the beams. Here, we present what we believe is a novel technique based on an integrated device allowing the simultaneous characterization and the fast spatial and temporal overlapping of the beams, reducing the alignment procedure from hours to minutes. (C) 2016 Optical Society of America

The dynamic response of gas sensors based on poly(3-hexylthiophene) (P3HT) nanofibers(NFs) to gaseous acetone was assessed using a setup based on flow-injection analysis, aimed atemulating actual breath exhalation. The setup was validated by using a commercially available sensor.The P3HT NFs sensors tested in dynamic flow conditions showed satisfactory reproducibility down toabout 3.5 ppm acetone concentration, a linear response over a clinically relevant concentration range(3.5-35 ppm), excellent baseline recovery and reversibility upon repeated exposures to the analyte,short pulse rise and fall times (less than 1 s and about 2 s, respectively) and low power consumption(few nW), with no relevant response to water. Comparable responses' decay times under eithernitrogen or dry air suggest that the mechanisms at work is mainly attributable to specific analytesemiconductingpolymer interactions. These results open the way to the use of P3HT NFs-basedsensing elements for the realization of portable, real-time electronic noses for on-the-fly exhaledbreath analysis.

In this paper we report on the fabrication and testing of a novel concept of sealed electrochemical microcell for in situ soft X-ray microspectroscopy in transmission, dedicated for nonvacuum compatible electrolytes. The microcell, fabricated using ultraviolet lithography, at variance with previous versions of electrochemical wet cells, that featured an optical window glued on top of the electrode system and a very limited electrolyte volume, the device presented here is a single solid block based around a microfabricated channel with fixed optical windows and apt for microfluidic work. Moreover, this cell allows to employ an advanced electrodic geometry developed in our group - so far used only in open electrochemical cells for work with vacuum-compatible electrolytes - also with low-vapor pressure liquids, possibly saturated with the required gases. The cell optimal electrode design allows three-electrode electrochemical control typical of traditional electrochemical experiments. The first electrochemical experiments with this new cell explore the electrochemical growth of a Co-polypyrrole, a composite electrocatalyst material with promising performance to replace the expensive Pt catalyst in fuel-cell oxygen electrodes. Morphological and chemical-state distributions of Co codeposited with polypyrrole has been followed as a function of time and position, yielding unprecedented information on the processes relevant to the synthesis of this catalyst.

This paper reports the development and application of a novel thin-layer electrochemical microcell for in situ soft x-ray fluorescence and absorption microspectroscopy. The microcell, fabricated using ultraviolet lithography, is an improved version of concepts previously developed in our group, featuring a wide optical window that allows the extension of the range of accessible in situ microspectroscopy and imaging methods, including those requiring small emission take-off angles. The three-electrode design implemented in the cell enables optimal electrochemical control. The first in situ experiment employing this new cell explores the electrochemical growth of a novel Mn-Co/polypyrrole composite that is a prospective electrocatalyst for Pt replacement in air cathodes. Morphological, compositional, and chemical-state distributions of Mn and Co codeposited with polypyrrole are subsequently performed in situ as a function of time and position, yielding otherwise unachievable information regarding the electrodeposition process.

Catalyst nanoparticles are required in most established synthetic routes for the growth of carbon nano-tubes (CNTs) and semiconductor nanowires (NWs). A simple and widespread method to coat a substrate with metal nanoparticles is based on the dewetting of a thin metal film, often induced by a process of thermal annealing, and resulting in the formation of fine droplets. However, the control of the sole thermodynamic parameters affecting the dewetting results in a rather broad size distribution and random positioning of the catalyst. Efforts aiming at a better control of size and position of the catalytic seeds by top-down and bottom-up patterning techniques are well documented. However, patterning the catalyst may be a useless process step if, once approaching the temperatures at which the growth of nanowires and CNTs is catalyzed, nanoparticles become mobile on the substrates, displacing from their position and altering the initial size distribution due to coalescence. Moving from this observation, we propose a simple and general method to prevent the diffusion of the catalyst during annealing steps or the initial stage of the synthesis of NWs and CNTs. Its principle consists of confining the catalyst nanoparticles on top of vertical columnar structures. This can be achieved by etching the substrate all around the nanoparticles by dry anisotropic etching using the nanoparticles themselves as etch masks. Nanopartides thus sitting on top of nanopillars result effectively confined, even at temperature at which they are found highly mobile on flat substrates of the same material, due to surface tension effects. Experimentally, we demonstrate this principle with iron nanodots obtained on silicon by lift-off starting from a P(MMA-b-S) diblock-copolymer template. The iron nanodots isolated on top of columnar nanostructures, were found to be stable at 600 degrees C, temperature suitable for the growth of CNTs. (C) 2013 Elsevier B.V. All rights reserved.

Surface-enhanced Raman scattering (SERS) has already demonstrated its significant potential in analytical science. Thus, current efforts are focused on the development of affordable and reproducible SERS substrates, which exhibit high enhancement factors and uniform responses. A large number of strategies were adopted to produce effective SERS substrates; however, most of them are tuned for the use of single excitation wavelength and consequently can only be applied for a limited number of analytes. Hence, SERS substrates that demonstrate broadband plasmonic properties represent a more flexible analytical tool for multi-wavelength or tunable light sources, especially for biological applications. In the current study, we demonstrate that direct laser writing (DLW), which activates a photoreactive moiety and immobilizes functionalized gold nanoparticles on chemically modified glass substrates, can be used to produce SERS substrates of various sizes and geometries. We show that by tuning the DLW parameters a broad plasmonic response is obtained, enabling the use of these substrates for multi-wavelength SERS analysis. Two Raman reporters, a small synthetic benzotriazole azo organic dye and a larger biological molecule, hemin, are tested at three fixed excitation wavelengths in the visible range (473 nm, 532 nm and 660 nm). SERS enhancement factors show a weak dependence on the wavelength used and the molecules investigated; moreover, the possibility of creating arbitrary shaped and uniform structures is demonstrated. The reported results show that DLW is an excellent technique to engineer microstructured and broadband SERS substrates.

The role of mechanics in numerous biological processes is nowadays recognized, while in others, such as the fertilization process, it is still neglected. In the case of oocytes the description of their mechanical properties could improve the comprehension of the oocyte-spermatozoon interaction and be helpful for application in in vitro fertilization (IVF) clinics. Herein the mechanical properties of whole human oocytes (HOs) immediately after retrieval are investigated by indentation measurements with atomic force spectroscopy under physiological conditions. Measurements are performed on immature (metaphase I - MI) and mature (metaphase II - MII) HOs. According to their morphological characteristics MII-HOs are classified as "suitable" and "rejected"; these latter would be usually rejected for intracytoplasmic sperm injection (ICSI). For all maturation stages we observe that the elastic response of the zona pellucida (ZP) outer layer was different and distinguishable from the rest of the ZP-HO. The elasticity of this ZP outer layer varies with maturation and quality: stiffness decreases from immature MI to good quality MII, up to poor-quality rejected MII. An indirect analysis with IVF outcome indicates that the ZP outer layer of analysed HOs donated by women who achieved pregnancy is stiffer than that of HOs from women with negative outcome. Our findings suggest that mechanical properties can represent important oocyte quality indicators that may be exploited for the design of innovative ICSI dedicated cell sorters.

Hot spots are defined as nanostructures of noble metal able to locally enhance the electromagnetic field of several orders of magnitude and to confine this effect to a region for several orders of magnitude smaller than the light wavelength. Hot spots are particularly important for the surface enhanced Raman spectroscopy applications, in which the field enhancement is used to amplify the usually weak Raman scattering signal. The hot spots are mostly generated between two or more plasmonic nanostructures separated by nanometric gaps. Several strategies are used to design and realize the hot spots, both in solution, using the noble metal nanoparticles, and on surfaces, using nanolithography and evaporation. In this paper, we demonstrated the fabrication of a nanomechanical plasmonic device for Raman spectroscopy, in which the hot spots are switched on when biased at the resonant frequency and switched off when the actuation signal is removed. Published by AIP Publishing.

The mesenchymal state in cancer is usually associated with poor prognosis due to the metastatic predisposition and the hyper-activated metabolism. Exploiting cell glucose metabolism we propose a new method to detect mesenchymal-like cancer cells. We demonstrate that the uptake of glucose-coated magnetic nanoparticles (MNPs) by mesenchymal-like cells remains constant when the glucose in the medium is increased from low (5.5 mM) to high (25 mM) concentration, while the MNPs uptake by epithelial-like cells is significantly reduced. These findings reveal that the glucose-shell of MNPs plays a major role in recognition of cells with high-metabolic activity. By selectively blocking the glucose transporter 1 channels we showed its involvement in the internalization process of glucose-coated MNPs. Our results suggest that glucose-coated MNPs can be used for metabolic-based assays aimed at detecting cancer cells and that can be used to selectively target cancer cells taking advantage, for instance, of the magnetic-thermotherapy.

Hybrid sol-gel materials are suitable dielectric materials for a range of optical applications, due to the versatility by which their optical and mechanical properties can be adjusted and the easy patterning by various lithographic techniques. We report on the synthesis of engineered epoxy based hybrid organic-inorganic sol-gel materials and on their lithographic processing, specifically applied to the fabrication of microlens arrays. The investigated sol-gel systems exhibit enhanced transparency in the near UV region with respect to most commercial thermoplastic polymers and sol-gel materials, used in embossing and nanoimprinting technology; in addition, they offer a better shape stability and superior mechanical properties, such as higher elastic modulus and hardness, improving the perspectives of the introduction of microstructured and nanostructured surfaces in applications where resistance to environmental mechanical-chemical degradation mechanisms is highly desirable, in particular for outdoor applications.

Organic photovoltaic cells (OPV) are among the most promising systems for energy extraction and conversion from renewable energy sources. However, major problem to be solved before industrial production could become economically viable is represented by their still low conversion efficiency. The organic solar cell architectures are presently the result of a compromise between achieving complete light absorption using active layers that are thicker than the optical absorption length and achieving efficient charge collection at the electrodes which is favoured in thinner layers. We present a concept and its experimental demonstration that would solve efficiently the above trade-off problem by making use of a new type of light trapping elements. The simple fabrication scheme, based on a self-aligned UV exposure process, suggests its potential up-scalability to large systems, at low production cost.

A major limitation in the translation of stem cells technology to clinical applications is the lack of efficient control over their proliferation and differentiation. Recent in vitro research findings suggest that biomaterials with nanoscale surface topography can influence cell behaviour like adhesion, proliferation and differentiation. Therefore, the identification of biomaterials that support appropriate ES cell attachment, proliferation and differentiation into cells of interest is an attractive strategy worth investigation. In this study we present the design and fabrication of thin films of gold with surface topography of varying roughness using a combination of microfabrication techniques. We then explored their biomimetic potential to direct differentiation of ES cell-derived neural precursors. Standard glass coverslips and tissue culture plastic were used as reference materials. Our preliminary results show that ES-derived neural precursors best adhered on gold and underwent the highest differentiation on gold films with root mean square surface roughness (Rq) of 21 nm (72 ± 6%) after five days of culture in the absence of traditional soluble neurotrophic factors. Moreover, when cells were seeded on a combination of micro-scale grooves with nanoscale surface roughness, axonal outgrowth orientation was observed to be influenced by the grating axis. This data identifies gold as a potential biomaterial candidate with suitable cytocompatibility for ES cell research. It further lends support to the hypothesis that biomaterial design may optimize ES cell-derived neural differentiation and organisation. This may find utility as a tool to synergically complement soluble chemical factors currently used in in vitro protocols for the stimulation and modelling of ES differentiation. Ultimately, substrate patterning may hold special utility in the design of neural prostheses because repair of neurological injuries requires directional guidance.

This paper reports an in situ study of the anodic behavior of a model solid oxide electrolysis cell (SOEC) by means of near-ambient pressure X-ray Photoelectron Spectroscopy (XPS) combined with near edge X-ray absorption fine structure (NEXAFS) measurements. The focus is on the anodic surface chemistry of MnOx, a model anodic material already considered in cognate SOFC-related studies, during electrochemical operation in CO2, CO2/H2O and H2O ambients. The XPS and NEXAFS results we obtained, complemented by electrochemical measurements and SEM characterisation, reveal the chemical evolution of Mn under electrochemical control. MnO is the stable chemical form at open-circuit potential (OCP), while Mn3O4 forms under anodic polarisation in all the investigated gas ambients. Carbon deposits are present on the Mn electrode at OCP, but they are readily oxidised under anodic conditions. Prolonged operation of the MnOx anode leads to pitting of the Mn films, damaging of the triple-phase boundary region and also to formation of discontinuities in the Mn patch. This is accompanied by chemical transformations of the electrolyte and formation of ZrC without impact on the surface chemistry of the Mn-based anode.

Poly(3-hexylthiophene) (P3HT) nanofibers fabricated by self-assemby have been used as active sensing layers in chemiresistive gas sensors for acetone, ammonia and water. Their response has been compared to that of analogous devices in which P3HT was present as a plain, non-nanostructured layer. The results of this comparison show that nanofiber-based sensors have faster signal decay times and complete baseline recovery even after being exposed to saturated vapors of the analytes. Moreover, the current response of nanofiber-based devices increases by one order of magnitude or more upon exposure to the analyte, while for plain layers this increase is about 50% at maximum. Finally, on the basis of the collected data, a correlation between the analyte polarizability and the 90% baseline recovery times seems to exist, likely due to the occurrence of just physical adsorption (and not also of vapor penetration) of the analyte onto the polymer surface.

A key challenge for the development of plasmonic nanodevices is their integration into active semiconducting structures. Gold-catalysed semiconductor nanowires are promising candidates for their bottom-up growth process that aligns a single gold nanoparticle at each nanowire apex. Unfortunately these show extremely poor plasmonic properties. In this work, we propose a way to enhance their plasmonic resonance up to those of ideal and isolated gold nanoparticles. A suitable purification protocol compatible with GaAs and ZnSe molecular beam epitaxy of nanowires is used to produce plasmonic active nanowires, which were used to enhance the Raman signal of pentacene and graphene oxide. Enhancement factors up to three orders of magnitude are demonstrated. This journal is

We present a new water-vapour-assisted nanoimprint lithography (NIL) process for the patterning of the conducting poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS). The process was optimized with respect to relative humidity, applied pressure and temperature (RH, p, T). The control of environmental humidity was found to be crucial. High quality nanostructures were reproducibly obtained at high relative humidity values (RH >= 75%), with sub-100 nm resolution features attaining aspect ratios as high as similar to 6 at similar to 95% RH. The developed process of water-vapour-assisted NIL (WVA-NIL) strongly affects the electronic properties of PEDOT: PSS. By current-voltage measurements and ultraviolet photoemission spectroscopy we demonstrate that the process parameters p, T and RH are correlated with changes of PEDOT: PSS conductivity, work function and states of the valence band. In particular, an increase in the films conductivity by factors as high as 105 and a large decrease in the work function, up to 1.5 eV, upon WVA-NIL processing were observed. Employed as an anode buffer layer in P3HT: ICBA bulk heterojunction solar cells, PEDOT: PSS processing was found to affect significantly the device performance.

To fabricate long lifetime polymer solar cells, understanding the fundamental aspects controlling the performances, stability and degradation of the devices is essential. In this study, we compare the chemical and electrical degradation behaviors of polymer solar cells based on active layers of semi-crystalline p-type polymer poly(3hexylthiophene) (P3HT) and different fullerene derivatives as acceptors. Photodegradation study by UV-visible and Fourier transform infrared (FTIR) spectroscopy and photovoltaic performance study by current-voltage measurement were done to understand and compare air stability of P3HT blended with different fullerenes. The used acceptors are indene-C(60) bisadduct (ICBA) and phenyl-C61-butyric acid methyl ester (PCBM). The obtained results show that solar cells fabricated from PCBM as acceptor are more stable than those based on ICBA. Based on the spectroscopic and electrical measurement results, it is safe to conclude that PCBM contributes more to stability of P3HT than ICBA, and that the degradation behavior is compatible with recently proposed mechanisms. Chemical properties of ICBA such as the low electron affinity could be responsible for the relative low stability of the device. (C) 2014 Elsevier B.V. All rights reserved.