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Plasmon-tunable tip pyramids (PTTPs) are reproducible and efficient nanoantennas for tip-enhanced Raman spectroscopy (TERS). Their fabrication method is based on template stripping of a segmented gold pyramid with a size-adjustable nanopyramid end, which is capable of supporting monopole localized surface plasmon resonance (LSPR) modes leading to high spectral enhancement when its resonance energy is matched with the excitation laser energy. Here, we describe in detail the PTTP fabrication method and report a statistical analysis based on 530 PTTPs' and 185 ordinary gold micropyramids' templates. Our results indicate that the PTTP method generates probes with an apex diameter smaller than 30 nm on 92.4% of the batch, which is a parameter directly related to the achievable TERS spatial resolution. Moreover, the PTTPs' nanopyramid edge size L, a critical parameter for LSPR spectral tuning, shows variability typically smaller than 12.5%. The PTTP's performance was tested in TERS experiments performed on graphene, and the results show a spectral enhancement of up to 72-fold, which is at least one order of magnitude higher than that typically achieved with gold micropyramids. Imaging resolution is in the order of 20 nm. [ABSTRACT FROM AUTHOR]

We discuss test methods and results for determining individual clay platelets shape, size, size distribution, elemental composition, and impurities. Commercial sodium salt varieties of natural, semisynthetic and synthetic clay (Cloisite[R] -[Na.sup.+] Somasif ME-100, and Topy-[Na.sup.+], respectively) were analyzed. In this international collaboration, eight laboratories on three continents carried out the work within the VAMAS TWA-33 activities. There are large differences between the three nanofillers as far as: (1) the platelet orthogonal dimensions, (2) chemical composition, and (3) contaminants (their diversity and quantity) are concerned. Elaborate purification of natural clays leaves behind 2-5 wt% of organic and mineral impurities, whose nature, shape, size, and chemistry depend on the clay origin. These contaminants affect nanocomposite performance, thus controlling their composition and quantity is essential. The article describes the developed methods, summarizes the preliminary results, discusses the encountered difficulties, and proposes methods for solving them. POLYM. ENG. SCI., 51:559-572, 2011. [C]2011 Society of Plastics Engineers, INTRODUCTION As the pace of nanocomposites research and application has intensified, it became apparent that the conventional approach to understand and optimize the polymeric nanocomposites (PNC) performance is unsatisfactory. The [...]

The effect of grain size on iron losses were compared for two electrical steels with 0.5 and 1.5 wt% Si. The results confirm that the optimum grain size for minimizing the energy losses decreases when the electrical resistivity decreases or when the frequency increases. Experimental results are compared to a model which considers the influence of grain size. The recrystallization texture of the alloys varies little with grain size and consists mainly of the fibers {111} and / / RD. Index Terms--Electrical steels, grain size, loss modeling, texture.

This manuscript presents an experimental study on the optical visualization of single- and multi-walled carbon nanotubes. Optical micrographs of single-nanotubes and multi-walled carbon nanotubes sitting on SiO2/Si substrates are presented. Atomic force microscopy and Raman spectroscopy analysis provide morphological and structural characterization of the carbon nanotubes. Measurements taking into account different substrates, and also different values of wavelength of the incoming light, show that the optical contrast between the nanotubes and the SiO2 surface strongly depends on these two factors. A model based on interference effects explains the experimental results and establishes a route for substrate engineering that allows direct and fast observation of carbon nanotubes, as well as the measurement of their refractive indexes. Analysis on the polarization properties of the reflected light confirms the strong anisotropy on the optical absorption of carbon nanotubes. [ABSTRACT FROM AUTHOR]

The role of plasmon resonance on the optical efficiency of nanoantennas for tip-enhanced Raman spectroscopy (TERS) is reviewed. Technical details on surface plasmon polaritons (SPP), localized surface plasmon resonance (LSPR), and the plasmon gap mode are provided. Nanotechnology engineering is necessary to adequate the nanoantenna's size, shape and composition to match resonance conditions with the exciting radiation source. Computational simulation guides the development of new types of plasmonic nanoantennas with different materials and morphologies, specially designed to reach target applications. An overview on a recently developed nanoantenna composed by a truncated micropyramidal body with a nanopyramid end is presented. The characteristic length $L$ of the nanopyramid tip is dimensioned to fine-tune LSPR modes, giving rise to the so-called plasmon-tunable tip pyramid (PTTP). The plasmonic properties of this type of probe were investigated by electron energy loss spectroscopy and computational simulations, reveling that PTTPs act as monopole nanoantennas. TERS results obtained with the PTTPs demonstrate the achievement of unprecedent levels of field enhancement mediated by LSPR with excellent reproducibility rate. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis of well‐controlled palladium nanoparticles (PdNPs) by spontaneous decomposition of tris(dibenzylideneacetone)dipalladium(0) in polyethylene glycol Mw 300 (PEG 300) in the absence of reductant atmosphere or thermal effect is reported. The Pd nanoparticles exhibited a spherical pattern with 2‐ to 4‐nm diameter and low standard deviation according to scanning transmission electron microscopy (STEM) analysis. UV‐vis electronic spectroscopy, dynamic light scattering (DLS) and diffusion ordered spectroscopy (DOSY) mode of 1H nuclear magnetic resonance (NMR) suggested that PEG acts as a template for the formation of PdNPs. These nanoparticles were efficient towards the Suzuki‐Miyaura reaction for the synthesis of 3,6‐diaryl carbazoles. Indeed, the whole catalyst system demonstrated an efficient recyclability (ten consecutive runs) without significant interference of the N−H moiety. Since diaryl carbazoles are the core of a number of compounds contained within components of organic solar cells and photovoltaics, this method should allow additional organic materials substrates under relatively inexpensive catalytic conditions. [ABSTRACT FROM AUTHOR]

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO2-P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at labscale using radiation, which simulated the solar spectrum. TiO2 leaching from the glass and the catalyst regeneration were both demonstrated. Avery low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400°C (TiO2-400°C). The TiO2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO2-400°C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment. [ABSTRACT FROM AUTHOR]

Background: Driven by the potential biological applications of graphene, many groups have studied the response of cells exposed to graphene oxide (GO). In particular, investigations of bacteria indicate that there are 2 crucial parameters, which so far have only been investigated separately: GO size and exposure methodology. Our study took into account both parameters. We carefully characterized the samples to catalog sizes and structural properties, and tested different exposure methodologies: exposure in saline solution and in the presence of growth media. Furthermore, we performed experiments with peripheral blood mononuclear cells exposed to our GO materials. Methods: Atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to characterize the morphology and composition of different samples of GO: GO-H2O, GO-PBS and GO-MG. Our samples had 2D sizes of ~100 nm (GO-H2O and GOPBS) and >2 μm (GO-MG). We tested antibacterial activity and cytotoxicity toward peripheral blood mononuclear cells of 3 different GO samples. Results: A size-dependent growth inhibition of Escherichia coli (DH5 α) in suspension was found, which proved that this effect depends strongly on the protocol followed for exposure. Hemocompatibility was confirmed by exposing peripheral blood mononuclear cells to materials for 24 hours; viability and apoptosis tests were also carried out. Conclusions: Our experiments provide vital information for future applications of GO in suspension. If its antibacterial properties are to be potentiated, care should be taken to select 2D sizes in the micrometer range, and exposure should not be carried out in the presence of grow media. [ABSTRACT FROM AUTHOR]

Wollastonite-poly( n-butyl-2-cyanoacrylate) composite (W-BCA) has been proposed to immobilize anatomically bone fragments in order to achieve an optimal healing process. The present study evaluated the in vitro and in vivo behavior of three types of fillers: powdered natural wollastonite (Wn), synthetic pseudowollastonite powder (Ws), and synthetic pseudowollastonite powder coated with 5% acetyl tributyl citrate (Wst). The Wst-BCA composite underwent a higher degradability in the real-time degradation test and a superior cytotoxic effect; whereas the Wn-BCA composite showed a higher degradability in the accelerated test with no cytotoxicity. The formation of an extracellular collagenous matrix deposit on its surface and the most favorable new bone formation on Wn-BCA indicate its potential for bone adhesive use in unstable orthopedic traumas. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1121-1129, 2014. [ABSTRACT FROM AUTHOR]

In this work, a porous and homogeneous titanium dioxide layer was grown on commercially pure titanium substrate using a micro-arc oxidation (MAO) process and Ca-P-based electrolyte. The structure and morphology of the TiO coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and profilometry. The chemical properties were studied using electron dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy. The wettability of the coating was evaluated using contact angle measurements. During the MAO process, Ca and P ions were incorporated into the oxide layer. The TiO coating was composed of a mixture of crystalline and amorphous structures. The crystalline part of the sample consisted of a major anatase phase and a minor rutile phase. A cross-sectional image of the coating-substrate interface reveals the presence of voids elongated along the interface. An osteoblast culture was performed to verify the cytocompatibility of the anodized surface. The results of the cytotoxicity tests show satisfactory cell viability of the titanium dioxide films produced in this study. [ABSTRACT FROM AUTHOR]

Single-step nano-lithography was performed on graphene sheets using a helium ion microscope. Parallel "defect" lines of ~1 lm length and ≈5 nm width were written to form nanoribbon gratings down to 20 nm pitch. Polarized Raman spectroscopy shows that crystallographic orientation of the nanoribbons was partially maintained at their lateral edges, indicating a high-fidelity lithography process. Furthermore, Raman analysis of large exposure areas with different ion doses reveals that He ions produce point defects with radii ~2× smaller than do Ga ions, demonstrating that scanning- Heþ-beam lithography can texture graphene with less damage. [ABSTRACT FROM AUTHOR]

A combination of first-principles calculations based on density-functional theory, pseudopotentials, and x-ray photoelectron spectroscopy (XPS) measurements is used in order to study Au segregation in Cu3Au(111) surfaces. Our theoretical results suggest Au compositions from 50% to 75% in the topmost layer, depending on the chemical potentials of the atomic species. This strong Au segregation is restricted to the topmost surface plane and it is supported by the XPS measurements in a semiquantitative manner. [ABSTRACT FROM AUTHOR]

The atomic force microscopy (AFM) has been used as a force sensor to measure unbinding forces of single bound complexes in the nanonewton and piconewton range. Force spectroscopy measurements can be applied to study both intermolecular and intramolecular interactions of complex biological and synthetic macromolecules. Although the AFM has been extensively used as a nano force sensor, the commercially available cantilever is limited to silicon and silicon nitride. Those materials reduce the adhesion sensitivity with specific surface and/or molecule. Here, we functionalized the AFM tip with carboxylic groups by applying acrylic acid (AA) vapor at radio frequency plasma treatment at 100 W for 5 min. This method provides a remarkable sensitivity enhancement on the functional group interaction specificity. The functionalized tip was characterized by scanning electron microscopy. The electron beam high resolution images have not shown significant tip sharpness modification. Silicon wafers (1 0 0)-no treated and functionalized by AA plasma treatment-were characterized by Auger electron spectroscopy to elucidate the silicon surface sputtering and demonstrate functionalization. The Fourier transform-infrared spectroscopy spectrum shows a high absorbance of avidin protein over the silicon surface functionalized by AA plasma treatment.We carried out force spectroscopy assay to measure the unbinding force between the well-established pair biotin-avidin. At pulling speed of 2 µm/s, we measured the unbinding force of 106 ± 23 pN, which is in good agreement with the literature, demonstrating the effectiveness of the tip functionalization by AA plasma treatment in biological studies. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]