In an effort to optimize both the optical properties and chemical stability of plasmonic platforms for surface-enhanced fluorescence spectroscopy, a series of multi-layered heterometallic structures were prepared. Gold-silver multilayered array of prisms were designed, where the gold layers acts as protective layers for the silver and extends the spectral range of the resulting localized surface plasmon resonances. Herein, we report an experimental study of the enhanced near-field fluorescence from quantum dots deposited at the surface of these platforms. This was performed using near field scanning optical microscopy yielding simultaneous measurements of topographical features and near-field fluorescence of the prismatic arrays. Hence, the individual localized fluorescent hot-spots could be imaged and spatially correlated with the geometry of the nanostructures for distinct polarization configuration of the excitation light with respect to the orientation of the structures. Furthermore, the fluorescence enhancement was evaluated spatially and temporally for the series of the nanoprism platforms. In particular, the quenching of the near-field fluorescence due to the metal structures was carefully evaluated for the metal fluorophore hybrid systems.

Molecular plasmonics relies on the development of conductive nanostructures to yield large local electromagnetic enhancement enabling the detection of molecules located in their vicinity. Although various spectroscopic techniques benefit from such enhancement, performing different spectroscopic measurements on the same platform, remains a challenge. As such, the rational design of structures capable of enhancement effects over a large spectral range, particularly from the visible to the mid-infrared, is of great interest. Herein, we have developed a series of metallic patterns, consisting of superimposed arrays of gold nanoprisms, that have the potential for surface-enhanced Raman spectroscopy (SERS), surface-enhanced fluorescence (SEF), and surface-enhanced infrared absorption (SEIRA). We first demonstrate that a modified version of the nanosphere lithography method can be used to fabricate such platforms. Patterns with selected sizes can further be produced by electron-beam lithography with virtually no defects, thus yielding tunable and precise optical resonances from the visible to the mid-infrared range. The hexagonal lattices were composed of smaller prisms (0.25 mu m prism base length) incorporated for SERS and SEF applications and larger triangles (1-2 mu m base size) for SEIRA purposes. The superimposed patterns display regions that are compatible with SEF, SERS, and SEIRA, thus opening promising applications for multispectral detection of molecules.

The behavior of the electromagnetic field interaction with gold nanotriangles organized in bow-tie arrays is investigated. A side-by-side comparison between the measured absorbance of the array and the modelled integrated electric field resonances confined around the gold structures is presented and discussed to explain the spectral shift between both parameters. Finite difference time domain calculations and Raman measurements of gold triangles of different sizes and periodicity are systematically performed. Numerical calculations show that the spectral maximum of the electric field varies in distinct areas over the metallic structures.

The photochemical and thermal reactivity of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single-crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection-absorption infrared spectroscopy by observation of C=O and N3 bands at 1700 cm(-1), and 2100 and 1300 cm(-1) respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm(-1) with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles.

Surface modification technology has made significant advances in recent years towards the miniaturization and organization of traditional cell culture systems. However, the capability of directing transfected cells and neuronal connections to probe small structures such as spines is still under development. In the current work, interactions of different micropatterned substrates with HEK 293, CF10 cell lines, and primary neuronal cultures are evaluated. Using conventional and confocal fluorescence microscopies, several morphological and behavioral aspects of all three cell types were investigated. The immortalized cell lines were able to attach to the substrate and interact with neighboring cells. Similarly, cortical neurons formed connections guided by the micropatterns. Transfection of HEK 293 or CF10 cell lines with specific members of the G protein-coupled receptor family did not alter the behavior of these cells in the micropatterns. On the other hand, neuronal projections were efficiently isolated by the patterns, simplifying the localization of spines with nano-scale resolution probed by atomic force microscopy. This work presents a valuable approach to isolate cells or to constrain important cell structures to grow along a desired pattern, thus facilitating advanced biological studies.

An analytic approximation is presented that allows a straightforward calculation of impurity concentration depth profiles from a measured Rutherford backscattering spectrum. The depth scale calculations consider energy-dependent stopping power data. Calculation of the concentration assumes Rutherford cross sections including electron screening effects. The solution for the depth scale has been verified to be within 2% of the exact numerical solution in the energy range down to 20% of the incident energy. The experimental depth profiles obtained for Au in Al and Ir in Si using MeV 12C projectile ions show good agreement with the present approximation.

The paper reviews recent advances in the understanding of hydrogen adsorption on the Si (100)−(2 × 1) surface. Absolute measurement of deuterium coverage over a wide range of exposure allow us to identify different reaction process. Channeling analysis sees changes of surface structure down several layers below the surface on various hydride terminated Si(100) surfaces.

Irradiation of saturated monolayers of 3- and 4-substituted pyridyl diazoacetates on single-crystal Pt surfaces leads to either the corresponding reactive carbene or stable ketene intermediate with the chemoselectivity determined by the position of the photoreactive substituent on the pyridyl ring, which ultimately directs the available interactions with neighboring substrates.

Silicon carbide (SiC) thin films are attractive for a wide range of applications ranging from microelectronic and opto-electronic devices to protective and tribological coatings. In this paper, we will demonstrate that silicon carbide films can be successfully deposited by pulsed laser deposition (PLD) technique over large areas, with good uniformity in thickness, composition, and film-specific properties. Amorphous SiC films were grown on silicon wafers of 75-mm diameter over a temperature range of 25 – 650°C using a KrF excimer laser at a wavelength 248 nm and a repetition rate of 100 Hz. The large-area uniform coverage was obtained by rastering the laser beam over the radius of a rotating SiC target of 90-mm diameter, while the substrate was rotated simultaneously. The uniformity of film composition over the 75-mm wafers was characterized by Auger electron spectroscopy (AES), while the crystallinity of films was investigated by X-ray diffraction (XRD). The morphology of the films was evaluated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thickness of the coatings, and the index of refraction, n, along the wafer radii were measured optically using a spectrophotometer.

Fluorescence in situ hybridization (FISH) is widely used for diagnosis of genetic abnormalities. We have developed multimodal, nanoscale imaging methods using a combination of fluorescence and atomic force microscopy to determine the precise binding location of FISH probes. The use of high resolution imaging methods is important to validate and improve the binding efficiency for small single copy FISH probes that are being developed for cytogenetic analysis at higher genomic resolution than is possible with current commercial FISH probes. Chromosome topography is imaged by AFM and superimposed on FISH probe location determined by confocal or epifluorescence microscopy. Image processing procedures are used to quantify probe context, relative to neighboring 30 nm chromatin fiber bundles imaged by AFM, and to quantify probe binding to homologs within the same cell. We have correlated optical and topographic images of multicopy centromeric probe for chromosome 17 and have examined the spatial relationship between centromeric DNA and the formation of kinetochore structures and sister chromatid segregation. Interestingly, segregation of sister chromatids is not coordinated with the formation of these structures within individual homologous chromosomes, occurring after the formation of these structures. We hypothesize that asynchronous segregation of previously replicated sister chromosomes may account for differences in the hybridization patterns for probes in different cells from the same individual.

A two-dimensional array of gold nanotriangles inscribed onto glass coverslips were optimized for the surface-enhanced Raman detection of streptavidin/biotin monolayer assemblies. The nanostructures were fabricated by electron beam lithography, and its optical parameters were optimized to be probed under a Raman microscope with a linearly polarized He-Ne laser with an excitation wavelength of λ = 632.8 nm. The platforms were first tested against a monolayer of biotinylated alkanethiols (BAT) functionalized over the gold nanostructure, showing that good-quality spectra could be acquired with a short acquisition time. The supramolecular interaction of streptavidin (strep) with BAT showed subsequent modification of the Raman spectrum that implies a change in the secondary structure of the host biomolecule (streptavidin). Compared to gold surfaces without nanoscale structures, the local enhancement that results from our nanostructured surfaces allows one to detect the vibrational signal of monolayers within a time on the order of seconds and under modest laser intensity, further demonstrating the utility of using plasmonic metallic nanostructures for molecular recognition.

Thin TiO2 films were deposited uniformly using a thermal evaporation method in a high vacuum system. The films were primarily composed of Ti(IV) (98.3–98.4%) and O2− (71.8–71.9%) with only a small concentration of defects. Hydrogen absorption by the deposited oxide films, measured using a Devanathan cell, occurred at E<−0.37V. In the range −0.3 to −0.8V, the capacitance of the oxide increased with a decrease in potential, while the resistance of the oxide decreased significantly. At E<−0.8V, the kinetics of hydrogen absorption by the oxide were controlled by a diffusion process, and the reduction of water and evolution of hydrogen remained strongly inhibited on the oxide surface. Hydrogen transport in Pd was studied using the time-lag method under galvanostatic hydrogen-charging conditions. Reversible and irreversible trap sites have a noticeable retardation effect on hydrogen transport in the metal. Hydrogen permeation in the TiO2 films is a function of the hydrogen-charging current. When the hydrogen-charging current was >40nAcm−2, more than 70% of the hydrogen produced on the oxide surface permeated through the oxide. Increasing the hydrogen-charging current resulted in an exponential decrease in the time lag in the oxide. The potential at which the oxide became transparent to hydrogen was decreased with an increase in the charging current. E=−0.37VSCE may represent an absorption threshold for hydrogen absorption. The apparent diffusion coefficient of hydrogen in the oxide is in the range of 10−18–10−17cm2s−1. The coefficient increased with an increase in hydrogen-charging current. A theoretical model for permeation in the oxide is under development.

The electric field interaction of hexagonal arrays of gold nanotriangles positioned on glass slides was studied using finite-difference time domain (FDTD) simulations. The length of the triangles (L = 100-300 nm), the irradiation wavelength (lambda = 400-1100 nm), and the direction of the linearly polarized input field (either Px or Py) were the three variables considered in the calculation of the electric field spectra and the localized surface plasmons. The results show that the plasmonic properties of this array of nanostructures are susceptible to modification by changing any of these variables, and provide important information into the design of experiments where high electric field enhancement is required.

An interfacial force microscope (IFM) was employed to measure the inter-particle forces between two individual glass beads with diameters varying from 8 to 20 mu m With the feedback function of IFM turned off attractive forces were obtained The forces varied in the range of 0 1-0 34 mu N and their validity was confirmed by a theoretical analysis of the van der Waals force between the same glass beads With the feedback function switched on no attractive forces between particles were detected by the IFM when the probe approached the sample substrate This may be attributed to the dramatic change of the attractive forces within a very short separation distance and/or the relatively poor signal-to-noise ratio of the IFM (C) 2010 Chinese Society of Particuology and Institute of Process Engineering Chinese Academy of Sciences Published by Elsevier B V All rights reserved

. Recent studies on a variety of metal phosphates (MP) have revealed that MPs tend to be soft at ambient pressure if the coordination on the metal cation is low and the degree of hydration or hydrogenation is high, while they are stiff otherwise. In addition, the softer MPs were found to stiffen dramatically more quickly with increasing pressure than the stiffer MPs. Here we review these findings and support their relevance with new results on the mechanical properties of tribofilms aged in air of relative humidity, which were produced from commercial, zinc phosphate-containing lubricant packages via heating and rubbing. We find that the films can soften quite substantially after having been exposed to humidity, as to be expected from the studies of bulk MPs. Moreover, when the hydrated films are exposed to high loads, the force-distance withdrawal curve becomes identical to that of unaged, non-hydrated films. A straightforward explanation of this observation is that large pressure reverses the hydration of the tribofilms.

A modified Devanathan dual cell was used in environmentally assisted cracking (EAC) tests to independently control the concentration of dissolved hydrogen and anodic current density. The experimental evidence indicates that the corrosion may reduce the micro-hardness of steel, suggesting a dissolution-induced degradation of the mechanical properties in the surface layer. An EAC model is described in which surface micro-plastic deformation can be enhanced by the dissolved hydrogen and anodic dissolution, and plays a crucial role in cracking processes. The model can provide a reasonable prediction for the dependence of the cracking resistance of pipeline steel on the applied potential.

We report the fabrication and the optical study of Fisher's patterns inscribed on glass slides. Such structures, fabricated by electron beam lithography, consist of gold nanotriangles, organized in a hexagonal arrangement. By changing the fabrication conditions, it is possible to control precisely the size of the structures and the gap distance between facing triangles but most importantly, to finely tune their localized surface plasmon resonance. In addition to the experimental studies, the plasmonic properties of the Fischer's patterns were characterized as a function of the polarization of the incoming light. Finite difference time domain (FDTD) method was used to support the experimental results and to investigate the electromagnetic field enhancement on a Fischer's pattern lattice unit for different wavelengths and polarization of the irradiation source.

A gold marker technique that allows to measure wear with nanometer resolution laterally and normal to a materials surface has been developed. By way of analysis of gold concentration profiles before and after rubbing, the method can distinguish newly added from original material and afford information on phase-specific wear and sub-surface processes that occur in aluminium-silicon alloys.

The minimization of sources of uncertainty in nanoindentation experiments is crucial for accurate determination of nanomechanical properties. A common source of uncertainty in these measurements is the estimation of tip shape and size. Besides the experimental determination of the indenter's real geometry, determination of the instrument's compliance is also necessary. We use an atomic-force-microscope-based procedure for the determination of nanoindentation tip parameters needed to account for errors induced by tip shape nonideality and to permit the evaluation of the relative contributions of the instrumental errors associated with the experimentally determined values of hardness and modulus. We compare the definitions of the currently used tip shape area function based on physically relevant parameters with the scan and propose a hyperbolic definition that meets all physically relevant criteria while being simple enough to yield good results with numerical nonlinear fitting routines.

The surface of a poly(dimethylsiloxane) (PDMS) film was imparted with patterned functionalities at the micron-scale level. Arrays of circles with diameters of 180 and 230μm were functionalized using plasma oxidation coupled with aluminum deposition, followed by silanization with solutions of 3-aminopropyltrimethoxy silane (3-APTMS) and 3-mercaptopropyltrimethoxy silane (3-MPTMS), to obtain patterned amine and thiol functionalities, respectively. The modification of the samples was confirmed using X-ray photoelectron spectroscopy (XPS), gold nanoparticle adhesion coupled with optical microscopy, as well as by derivatization with fluorescent dyes. To further exploit the novel surface chemistry of the modified PDMS, samples with surface amine functionalities were used to develop a protein assay as well as an array capable of cellular capture and patterning. The modified substrate was shown to successfully selectively immobilize fluorescently labeled immunoglobulin G (IgG) by tethering Protein A to the surface, and, for the cellular arrays, C2C12 rat endothelial cells were captured. Finally, this novel method of patterning chemical functionalities onto PDMS has been incorporated into microfluidic channels. Finally, we demonstrate the in situ chemical modification of the protected PDMS oxidized surface within a microfluidic device. This emphasizes the potential of our method for applications involving micron-scale assays since the aluminum protective layer permits to functionalize the oxidized PDMS surface several weeks after plasma treatment simply after etching away the metallic thin film.