Raman Spectroscopy on Plasmonic Materials: Recent Advances and Applications in Molecular detection

Plasmonic Enhancement of the electric field is the basis of the Surface-enhanced Raman Scattering technique (SERS). This technique is based on the localization of light in the nanoscale occurring in plasmonic materials and provides the best conditions for molecular detection, even single-molecule detection. This can only be achieved by the use of spectroscopy in the nanoscale. The building of functional nanostructured devices to obtain sensitive and selective platforms, with specific applications in molecular detection, biodiagnosis and Cultural Heritage is presented. Plasmonic effects are highly activated in nanostructures substrates containing tips or in interparticle gaps. The nanofabrication of metal nanoparticles with special morphology, such as nanostars is presented here for the specific case of silver. The functionalization with bifunctional molecules gives rise to highly active gaps that can be employed in the molecular detection of pollutants. Another important application of these nanostructured platforms is the functionalization with biological molecules for bioanalytical applications and the detection of colorants with interest for the Cultural Heritage.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Investigation of pigments in artworks by Surface-Enhanced Raman Scattering (SERS)

Opening lecture of the SCORE Master degree course, Ravenna, October the 7th, 2015Peer Reviewe

Recent Advances in Plasmonic-Enhanced Raman Scattering: Applications in Molecular Detection and Cultural Heritage

Università, Ca' Foscari, Venezia, 28 Mar 2019. -- Seminari

Solution SERS of an insoluble synthetic organic pigment-quinacridone quinone-employing calixarenes as dispersive cavitands

3 páginas, 5 figuras.A possibility of getting SERS spectra of insoluble aromatic compounds in colloidal silver solutions is described. The method tested for the organic pigment quinacridone quinone consists of dispersing it in calix[n]arenes. The potentials of such cavitands, both as dispersing and as silver functionalization agents, is reported as a function of the substitution in their lower rim and their cavity size.This work has been financially supported by the Ministerio de Ciencia e Innovacio´n of Spain (Projects FIS2007-63065 and CONSOLIDER CSD2007-0058/TCP) and the Comunidad de Madrid (MICROSERES II Project S2009/TIC1476).Peer reviewe

Hollow Au/Ag nanostars displaying broad plasmonic resonance and high surface-enhanced Raman sensitivity

9 pas.; 7 figs.; 2 tabs.This journal is © The Royal Society of Chemistry. Bimetallic Au/Ag hollow nanostar (HNS) nanoparticles with different morphologies were prepared in this work. These nanoplatforms were obtained by changing the experimental conditions (concentration of silver and chemical reductors, hydroxylamine and citrate) and by using Ag nanostars as template nanoparticles (NPs) through galvanic replacement. The goal of this research was to create bimetallic Au/Ag star-shaped nanoparticles with advanced properties displaying a broader plasmonic resonance, a cleaner exposed surface, and a high concentration of electromagnetic hot spots on the surface provided by the special morphology of nanostars. The size, shape, and composition of Ag as well as their optical properties were studied by extinction spectroscopy, hyperspectral dark field microscopy, transmission and scanning electron microscopy (TEM and SEM), and energy dispersive X-ray spectroscopy (EDX). Finally, the surface-enhanced Raman scattering (SERS) activity of these HNS was investigated by using thioflavin T, a biomarker of the β-amyloid fibril formation, responsible for Alzheimer's disease. Lucigenin, a molecule displaying different SERS activities on Au and Ag, was also used to explore the presence of these metals on the NP surface. Thus, a relationship between the morphology, plasmon resonance and SERS activity of these new NPs was made.This work has been supported by the Spanish Ministerio de Economía y Competitividad (MINECO, grant FIS2014-52212- R). A. G.-L. acknowledges CSIC and FSE 2007–2013 for a JAE-CSIC predoctoral grant.Peer Reviewe

Aplicaciones de la espectroscopía SERS (Surface-Enhanced Raman Scattering) a la detección de pigmentos orgánicos naturales en objetos del Patrimonio Cultural

16 páginas, 17 figuras.La espectroscopía Raman, cuyas prestaciones se han visto considerablemente mejoradas en los últimos 15 años debido a la introducción de técnicas de microscopía (que han sido posibles gracias a importantes avances tecnológicos en filtros ópticos y detectores de alta sensibilidad), se ha convertido en una técnica de identificación molecular de gran utilidad en el campo del Patrimonio Cultural [1]. Al igual que la más conocida espectroscopía Infrarroja, la espectroscopía Raman proporciona información sobre los compuestos moleculares presentes en la muestra bajo estudio, ampliando por ello la información acerca de la presencia de elementos químicos que suministran otras técnicas espectroscópicas tales como XRF, SEM - EDX, PIXE y LIBS utilizadas habitualmente en el análisis de objetos artísticos [2]. Hoy en día podemos encontrar la técnica de microscopía Raman en los departamentos de Conservación y Restauración de los más importantes Museos y Bibliotecas de todo el mundo, utilizándose como técnica no destructiva (incluso in situ) para diagnóstico de diferentes materiales que van desde los pigmentos inorgánicos hasta los biomateriales, en objetos artísticos tan diferentes como manuscritos, pinturas, textiles, cerámicas, vidrios, esculturas, monumentos, e incluso momias o cañones hundidos. La información que se obtiene puede resultar decisiva para la datación y autenticación de las obras artísticas, y ayuda a determinar los cambios físicos y/o químicos que han contribuido a su deterioro a través de la identificación de los productos de degradación de los materiales originales.Agradecemos al MICINN (Proyectos FIS2007-63065 y CONSOLIDER CSD 2007- 0058) y a la Comunidad de Madrid (MICROSERES, S2009TIC-1476) por la financiación parcial de los trabajos aquí expuestos. Agradecemos también el apoyo recibido de la Red Temática de Patrimonio Histórico y Cultural (CSIC). MVC y EdP agradecen al CSIC y al FSE 2007-2013 la concesión de sus respectivos Contratos post- y predoctoral.Peer reviewe

DISEÑO E INTEGRACIÓN DE UNA COMPUTADORA A BORDO PARA VUELOS ESTRATOSFÉRICOS

ResumenEl principal objetivo de realizar vuelos estratosféricos que transportan sistemas electrónicos es la obtención y monitoreo de parámetros que determinen el comportamiento de dichos sistemas bajo condiciones atmosféricas demandantes.El documento en cuestión muestra la implementación de un sistema enfocado a la adquisición y almacenamiento de imágenes y temperatura en condiciones estratosféricas. La integración del prototipo consta de una cámara con comunicación serie asíncrona (UART), sensores de temperatura en circuito integrado y un conjunto de termistores con diferentes rangos para la obtención de temperaturas diversas, una memoria SD y una fuente estable de corriente directa proporcionada por una batería de litio y polímero (LiPo). La plataforma encargada del control y procesamiento de datos se integró a través del microcontrolador ChipKIT UNO32. El diseño del sistema y las pruebas de desempeño pertinentes se realizaron considerando el tiempo máximo del vuelo, de tal forma que la descarga de la batería y la capacidad de almacenamiento de la memora SD fueran suficientes para mantener el ciclo de la obtención de imágenes y temperaturas en forma continua.Por otra parte, además de los beneficios de rendimiento que proporciona la ChipKIT UNO 32, una característica que permite optimizar el tamaño de la carga final, son las dimensiones físicas de la tarjeta en comparación con otros microcontroladores de iguales características.Palabras Claves: ChipKIT UNO32, LiPo, memoria SD, SPI, UART. DESIGN AND INTEGRATION OF A COMPUTER ON BOARD FOR STRATOSPHERIC FLIGHTSAbstractThe main objective of making stratospheric flights that transport electronic systems, is the collection and monitoring of parameters that determine the behavior of such systems under stressful conditions.The document in question shows the implementation of a system focused on the acquisition and storage of images and temperature in stratospheric conditions. The integration of the prototype consists of a camera with serial communication (UART), temperature sensors -integrated circuit sensor and a set of thermistors with different ranges for obtaining the temperature, an SD memory and a stable source of direct current provided by a lithium and polymer battery (LiPo). The platform in charge of control and data processing is performed through the microcontroller ChipKIT UNO32. The design of the system and the relevant performance tests were performed considering the maximum flight time, so that the battery discharge and the storage capacity of the SD memory were sufficient to maintain the cycle of obtaining images and temperatures in continuous form. Besides to the performance benefits provided by ChipKIT UNO 32, a feature that allows you to optimize the size of the final load, are the physical dimensions of the card compared to other microcontrollers with the same characteristics.Keywords: ChipKIT UNO32, LiPo, SD memory, SPI, UART

Adsorption of Polyethyleneimine on Silver Nanoparticles and Its Interaction with a Plasmid DNA: A Surface-Enhanced Raman Scattering Study

Raman spectroscopy is applied in this work to study the adsorption of poly(ethyleneimine) (PEI) on Ag nanoparticles obtained by reduction with citrate, as well as to the study of the interaction between PEI and a plasmid. The surface-enhanced Raman spectroscopy (SERS) affords important information about the interaction and orientation of the polymer on the particles. In particular we have found that this polymer interacts with the surface through their amino groups in an interaction which also involves a change in the protonation state of amino groups as well as an increase of the chain order. This interaction implies a charge-transfer effect as deduced from the strong resonant effect in Raman spectra obtained at different excitation wavelengths. The complex formed by PEI and a plasmid, obtained by encoding the HBV (hepatitis B virus) genome inside the EcoRI restriction site of pGEM vector, was also studied by SERS. The interaction between both polymers leads to a conformational change affecting both macromolecules that can be detected by Raman at different excitation wavelengths. PEI undergoes a change to a more disordered structure as well as an increase of the number of protonated amino groups. The plasmid undergoes a structural change from A-DNA structure to B-DNA, along with a change in the superhelicity resulting in a more lineal structure when the plasmid interacts with PEI.Peer reviewe

Femtosecond laser-controlled self-assembly of amorphous-crystalline nanogratings in silicon

8 págs.; 5 figs.; 1 tab.Self-assembly (SA) of molecular units to form regular, periodic extended structures is a powerful bottom-up technique for nanopatterning, inspired by nature. SA can be triggered in all classes of solid materials, for instance, by femtosecond laser pulses leading to the formation of laser-induced periodic surface structures (LIPSS) with a period slightly shorter than the laser wavelength. This approach, though, typically involves considerable material ablation, which leads to an unwanted increase of the surface roughness. We present a new strategy to fabricate high-precision nanograting structures in silicon, consisting of alternating amorphous and crystalline lines, with almost no material removal. The strategy can be applied to static irradiation experiments and can be extended into one and two dimensions by scanning the laser beam over the sample surface. We demonstrate that lines and areas with parallel nanofringe patterns can be written by an adequate choice of spot size, repetition rate and scan velocity, keeping a constant effective pulse number (N ) per area for a given laser wavelength. A deviation from this pulse number leads either to inhomogeneous or ablative structures. Furthermore, we demonstrate that this approach can be used with different laser systems having widely different wavelengths (1030 nm, 800 nm, 400 nm), pulse durations (370 fs, 100 fs) and repetition rates (500 kHz, 100 Hz, single pulse) and that the grating period can also be tuned by changing the angle of laser beam incidence. The grating structures can be erased by irradiation with a single nanosecond laser pulse, triggering recrystallization of the amorphous stripes. Given the large differences in electrical conductivity between the two phases, our structures could find new applications in nanoelectronics.This work has been supported by the LiNaBioFluid project of the H2020 program of the European Commission (FETOPEN- 665337) as well as by the Spanish TEC2014-52642-C2- 1-R. MG-L and JH-R acknowledge the grants respectively awarded by the Spanish Ministry of Education and the Spanish Ministry of Economy and Competiveness.Peer Reviewe

In situ assessment of carbon nanotube diameter distribution with photoelectron spectroscopy

7 págs.; 6 figs.; 1 tab. ; PACS numberssd: 73.22.2f, 79.60.Jv, 61.46.1wIn situ UV-photoelectron spectroscopy (He I and He II) was performed on multiwalled carbon nanotubes (CNTs) with clearly differentiated diameter distributions. A significant dependence of valence- and conduction-band characteristics on the mean CNT diameter was observed, which was determined by high-resolution TEM and micro-Raman spectroscopy. The decrease of relative intensity of the π states at -3 eV in the He II experiments, indicative of increasing rehybridization between orbitals, was directly correlated with decreasing mean diameters. Furthermore, a progressive broadening of the unoccupied σ* band at 7.6 eV was found in the He I spectra. © 2005 The American Physical Society.J.W.S. is grateful to the Centre Interdisciplinaire de Microscopie Electronique sCIMEd at the Ecole Polytechnique Fédérale de Lausanne sEPFLd for access to TEM and technical support. We also thank the National Centre of Competence in Research for Nanosciences NCCRd and the Swiss National Foundation for financial support.Peer Reviewe