Localized Surface Plasmon Resonance for Optical Fiber-Sensing Applications

It is well known that optical fiber sensors have attracted the attention of scientific community due to its intrinsic advantages, such as lightweight, small size, portability, remote sensing, immunity to electromagnetic interferences and the possibility of multiplexing several signals. This field has shown a dramatic growth thanks to the creation of sensitive thin films onto diverse optical fiber configurations. In this sense, a wide range of optical fiber devices have been successfully fabricated for monitoring biological, chemical, medical or physical parameters. In addition, the use of nanoparticles into the sensitive thin films has resulted in an enhancement in the response time, robustness or sensitivity in the optical devices, which is associated to the inherent properties of nanoparticles (high surface area ratio or porosity). Among all of them, the metallic nanoparticles are of great interest for sensing applications due to the presence of strong absorption bands in the visible and near-infrared regions, due to their localized surface plasmon resonances (LSPR). These optical resonances are due to the coupling of certain modes of the incident light to the collective oscillation of the conduction electrons of the metallic nanoparticles. The LSPR extinction bands are very useful for sensing applications as far as they can be affected by refractive index variations of the surrounding medium of the nanoparticles, and therefore, it is possible to create optical sensors with outstanding properties such as high sensitivity and optical self-reference. In this chapter, the attractive optical properties of metal nanostructures and their implementation into different optical fiber configuration for sensing or biosensing applications will be studied

Corrosion of cast aluminum alloys: a review

Research on corrosion resistance of cast aluminum alloys is reviewed in this article. The effect of the main microstructural features of cast aluminum alloys such as secondary dendrite arm spacing (SDAS), eutectic silicon morphology, grain size, macrosegregation, microsegregation, and intermetallic compounds is discussed. Moreover, the corrosion resistance of cast aluminum alloys obtained by modern manufacturing processes such as semi-solid and additive manufacturing are analyzed. Finally, the protective effects provided by different coatings on the aluminum cast alloys?such as anodized, plasma electrolytic oxidation (PEO), and laser?is reviewed. Some conclusions and future guidelines for future works are proposed

Effect of Ti on microstructure, mechanical properties and corrosion behavior of a nickel-aluminum bronze alloy

Nickel-aluminum bronze (NAB) alloys are suitable, in cast condition, to be used in marine propellers due to its excellent behavior avoiding erosion and cavitation as well as corrosion. A complex microstructure, intrinsic to this copper base system, is the result of a well-controlled chemical composition. There are few works related to the effect of adding small quantities of specific chemical elements on NAB alloys properties. The aim of this paper is to study the effect of Ti on the microstructure, mechanical properties, and corrosion behavior of a particular NAB alloy, CuAl10Fe5Ni5 (C95500), and the comparison to the Ti-free NAB alloy. Although the as- cast microstructure is very similar for both materials, the addition of only 120 ppm Ti leads to a significant grain refinement that plays a key role on the mechanical properties. It has been observed an increase in both microhardness and nanohardness as well as in the resultant Young moduli values, meanwhile no significant impact on the corrosion susceptibility has been observed.The authors are grateful to the company Wärtsilä Iberica S.A. Cantabria. Spain, for the supply of NAB samples

Advanced Surface Treatments for Improving the Biocompatibility of Prosthesis and Medical Implants

During the last two decades, numerous surface treatments have been developed to improve the biocompatibility of different types of prosthesis and other medical implants. Some of these devices are subject to demanding loading and friction conditions (e.g., hip, knee, and spine prosthesis). However, for other implants, there are more specific requirements as it happens for coronary stents or pacemaker electrodes. The materials used for the manufacture of the aforementioned devices are subjected to very high restrictions in terms of biocompatibility, in particular on chemical composition, corrosion resistance, or ion release. As a consequence, most of prosthesis and other implants are made of a limited number of materials such as titanium alloys, stainless steels, cobalt-chromium alloys, UHMWPE, or PEEK. Unfortunately, from a strict point of view, none of these materials meet all the requirements that would be desirable in terms of durability and prevention of infections and inflammatory processes. Coatings and other surface treatments have been developed to solve these problems and to improve biocompatibility. In this chapter, we present an updated review of the most used surface engineering technologies for biomaterials, like novel PVD coatings, ion implantation, and other plasma spray treatments, as well as a critical review of the characterization techniques. This study is completed with an insight into the future of the field

Evaluation of the photocatalytic activity and anticorrosion performance of electrospun fibers doped with metallic oxides

This paper reports the development and characterization of a multifunctional coating that combines anticorrosion and photocatalytic properties, deposited by means of the electrospinning technique. In the first step, a functional electrospun fiber mat composed of poly(acrylic acid) (PAA) and β-cyclodextrin (β-CD) was obtained, showing high water insolubility and great adhesion increased by means of a thermal crosslinking process (denoted as PAA + β-CD). In the second step, the fibers were doped with particles of titanium dioxide (denoted as PAA + β-CD/TiO2) and titanium dioxide plus iron oxide (denoted as PAA + β-CD/TiO2/Fe2O3). The morphology and fiber diameter of the electrospun mats were evaluated by using confocal microscopy, whereas the presence of the metal oxides in the electrospun fibers was corroborated by scanning electron microscopy (SEM) and X-ray fluorescence (XRF), respectively. In addition, electrochemical tests in saline solution revealed that the sample composed of PAA + β-CD/TiO2/Fe2O3 showed the highest corrosion protection efficiency of all the samples, which was directly associated to lower corrosion current density and higher corrosion potential. Furthermore, the paper reports a novel approach to in situ determination of methylene blue (MB) degradation onto the coating. The results revealed complete degradation of MB, which is perfectly appreciated by total discoloration of the film in the irradiated zone (from bluish to a white spot). The main conclusions of this research are the efficiency of the electrospun system PAA + β-CD/TiO2/Fe2O3 for developing photocatalytic activity and corrosion protection and the utility of the dry MB discoloration tests to evaluate photocatalytic activity.This research was funded by the Government of Navarra-Department of Economic Development (Project ARGITU) and by the Public University of Navarre (Project PJUPNA1929)

Electrospinning Technique as a Powerful Tool for the Design of Superhydrophobic Surfaces

The development of surface engineering techniques to tune-up the composition, structure, and function of materials surfaces is a permanent challenge for the scientific community. In this chapter, the electrospinning process is proposed as a versatile technique for the development of highly hydrophobic or even superhydrophobic surfaces. Electrospinning makes possible the fabrication of nanostructured ultra-thin fibers, denoted as electrospun nanofibers (ENFs), from a wide range of polymeric materials that can be deposited on any type of surface with arbitrary geometry. In addition, by tuning the deposition parameters (mostly applied voltage, flow rate, and distance between collector/needle) in combination with the chemical structure of the polymeric precursor (functional groups with hydrophobic behavior) and its resultant viscosity, it is possible to obtain nanofibers with highly porous surface. As a result, functionalized surfaces with water-repellent behavior can be implemented in a wide variety of industrial applications such as in corrosion resistance, high efficient water-oil separation, surgical meshes in biomedical applications, or even in energy systems for long-term efficiency of dye-sensitized solar cells, among others

Self-referenced optical fiber sensor for hydrogen peroxide detection based on LSPR of metallic nanoparticles in layer-by-layer films

Intensity-based optical fiber sensors are one of the most studied sensor approaches thanks to their simplicity and low cost. Nevertheless, their main issue is their lack of robustness since any light source fluctuation, or unexpected optical setup variation is directly transferred to the output signal, which, significantly reduces their reliability. In this work, a simple and robust hydrogen peroxide (H2O2) optical fiber sensor is proposed based on the Localized Surface Plasmon Resonance (LSPR) sensitivity of silver and gold metallic nanoparticles. The precise and robust detection of H2O2 concentrations in the ppm range is very interesting for the scientific community, as it is a pathological precursor in a wide variety of damage mechanisms where its presence can be used to diagnose important diseases such as Parkinson's disease, diabetes, asthma, or even Alzheimer's disease). In this work, the sensing principle is based the oxidation of the silver nanoparticles due the action of the hydrogen peroxide, and consequently the reduction of the efficiency of the plasmonic coupling. At the same time, gold nanoparticles show a high chemical stability, and therefore provide a stable LSPR absorption band. This provides a stable real-time reference that can be extracted from the spectral response of the optical fiber sensor, giving a reliable reading of the hydrogen peroxide concentration.This work has been supported by the Spanish Economy and Competitiveness TEC2016-78047-R grant and the PhD research grants of the Public University of Navarre

A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films

UPNa. Departamento de Ingeniería Eléctrica y Electrónica. Laboratorio de Dispositivos Ópticos NanoestructuradosIn this work, a comparative study about the incorporation of silver nanoparticles (AgNPs) into thin films is presented using two alternative methods, the in situ synthesis process and the layer-by-layer embedding deposition technique. The influence of several parameters such as color of the films, thickness evolution, thermal post-treatment, or distribution of the AgNPs along the coatings has been studied. Thermal post-treatment was used to induce the formation of hydrogel-like AgNPs-loaded thin films. Cross-sectional transmission electron microscopy micrographs, atomic force microscopy images, and UV-vis spectra reveal significant differences in the size and distribution of the AgNPs into the films as well as the maximal absorbance and wavelength position of the localized surface plasmon resonance absorption bands before and after thermal post-treatment. This work contributes forThis work was supported by the Spanish Ministry of Economy and Competitiveness through TEC2010-17805 Research Project, Innocampus Program and Public University of Navarra (UPNA) research grants