Surface-Enhanced Raman Scattering Holography

Nanometric probes based on surface-enhanced Raman scattering (SERS) are promising candidates for all-optical environmental, biological and technological sensing applications with intrinsic quantitative molecular specificity. However, the effectiveness of SERS probes depends on a delicate trade-off between particle size, stability and brightness that has so far hindered their wide application in SERS imaging methodologies. In this Article, we introduce holographic Raman microscopy, which allows single-shot three-dimensional single-particle localization. We validate our approach by simultaneously performing Fourier transform Raman spectroscopy of individual SERS nanoparticles and Raman holography, using shearing interferometry to extract both the phase and the amplitude of wide-field Raman images and ultimately localize and track single SERS nanoparticles inside living cells in three dimensions. Our results represent a step towards multiplexed single-shot three-dimensional concentration mapping in many different scenarios, including live cell and tissue interrogation and complex anti-counterfeiting applications.Peer ReviewedPostprint (author's final draft

Spontaneous and stimulated electron–photon interactions in nanoscale plasmonic near fields

The interplay between free electrons, light, and matter offers unique prospects for space, time, and energy resolved optical material characterization, structured light generation, and quantum information processing. Here, we study the nanoscale features of spontaneous and stimulated electron–photon interactions mediated by localized surface plasmon resonances at the tips of a gold nanostar using electron energy-loss spectroscopy (EELS), cathodoluminescence spectroscopy (CL), and photon-induced near-field electron microscopy (PINEM). Supported by numerical electromagnetic boundary-element method (BEM) calculations, we show that the different coupling mechanisms probed by EELS, CL, and PINEM feature the same spatial dependence on the electric field distribution of the tip modes. However, the electron–photon interaction strength is found to vary with the incident electron velocity, as determined by the spatial Fourier transform of the electric near-field component parallel to the electron trajectory. For the tightly confined plasmonic tip resonances, our calculations suggest an optimum coupling velocity at electron energies as low as a few keV. Our results are discussed in the context of more complex geometries supporting multiple modes with spatial and spectral overlap. We provide fundamental insights into spontaneous and stimulated electron-light-matter interactions with key implications for research on (quantum) coherent optical phenomena at the nanoscale

Ultrasensitive multiplex optical quantification of bacteria in large samples of biofluids

Efficient treatments in bacterial infections require the fast and accurate recognition of pathogens, with concentrations as low as one per milliliter in the case of septicemia. Detecting and quantifying bacteria in such low concentrations is challenging and typically demands cultures of large samples of blood (~1 milliliter) extending over 24-72 hours. This delay seriously compromises the health of patients. Here we demonstrate a fast microorganism optical detection system for the exhaustive identification and quantification of pathogens in volumes of biofluids with clinical relevance (~1 milliliter) in minutes. We drive each type of bacteria to accumulate antibody functionalized SERS-labelled silver nanoparticles. Particle aggregation on the bacteria membranes renders dense arrays of inter-particle gaps in which the Raman signal is exponentially amplified by several orders of magnitude relative to the dispersed particles. This enables a multiplex identification of the microorganisms through the molecule-specific spectral fingerprints

Extraordinarily transparent compact metallic metamaterials

The design of achromatic optical components requires materials with high transparency and low dispersion. We show that although metals are highly opaque, densely packed arrays of metallic nanoparticles can be more transparent to infrared radiation than dielectrics such as germanium, even when the arrays are over 75% metal by volume. Such arrays form effective dielectrics that are virtually dispersion-free over ultra-broadband ranges of wavelengths from microns up to millimeters or more. Furthermore, the local refractive indices may be tuned by altering the size, shape, and spacing of the nanoparticles, allowing the design of gradient-index lenses that guide and focus light on the microscale. The electric field is also strongly concentrated in the gaps between the metallic nanoparticles, and the simultaneous focusing and squeezing of the electric field produces strong 'doubly-enhanced' hotspots which could boost measurements made using infrared spectroscopy and other non-linear processes over a broad range of frequencies

Morpho-chemical characterization of new confectionery sunflower (Helianthus annuus L.) genotypes from Argentina

Argentina is the world’s leading exporter of confectionery sunflower. This work characterized the morphometric and nutritional composition of sunflower seeds from new confectionery genotypes. Average morphometric variables per seed were: weight 0.11 and 0.06 g with and without achene, respectively; length 15.2 mm; and width 8.50 mm, with most calibers greater than 9.51 mm. Proximate analysis indicated that seeds without shell were an important source of lipids (49 %), as well as proteins (28 %), carbohydrates (11 %), and minerals (4.8 % ashes). Fatty acid composition showed that polyunsaturated fatty acids were the major components (56 %), followed by monounsaturated ones (34 %), and saturated ones (11 %). The mid-oleic genotype developed by INTA showed significantly greater oleic acid (47 %) and lower linoleic acid (42 %) than the commercial hybrid. Proteic composition showed 33 % of essential amino acids (EAA) while fiber and sugars represented 3.9 % and 7.3 % respectively; macroelements such as K, Mg and Ca, and microelements such as Mn, Fe, Cu, Zn, Se, Co, Mo and Na. New confectionery sunflower hybrids developed by INTA stand out for their high quality in edible oil, proteins and essential components, all very valuable for the food industry.Argentina es el principal exportador mundial de girasol confitero. Este trabajo caracterizó la composición morfométrica y nutricional de nuevos genotipos de girasol confitero. Las variables morfométricas promedio por semilla fueron: peso 0,11 g y 0,06 g, con y sin aquenio respectivamente; longitud 15,2 mm; ancho 8,50 mm; la mayoría de calibres superiores a 9,51 mm. El análisis composicional indicó que las semillas sin cáscara aportan 49 % de lípidos, 28 % de proteínas, 11 % de carbohidratos y 4,8 % de minerales. La composición de ácidos grasos mostró que los poliinsaturados fueron los componentes principales (56 %), seguidos de los monoinsaturados (34 %) y los saturados (11 %). El genotipo medio oleico presentó porcentaje de ácido oleico significativamente mayor (47 %) y porcentaje de ácido linoleico menor (42 %) que el híbrido comercial. La composición de proteínas fue de 33 % de aminoácidos esenciales (AAE); fibra y azúcares de 3,9 % y 7,3 %, respectivamente; macroelementos K, Mg y Ca, y microelementos Mn, Fe, Cu, Zn, Se, Co, Mo y Na. Los nuevos híbridos de girasol confitero desarrollados por INTA se destacan por la alta calidad del aceite, proteínas y componentes esenciales, todos estos de importancia para la industria alimenticia.Fil: Sandrinelli Tesán, Rebeca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Alvarez, D.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Silva, M. P.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Aguilar, R.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Pazos, A.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; ArgentinaFil: Balzarini, Monica Graciela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatología y Modelización Agrícola - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Fitopatología y Modelización Agrícola; ArgentinaFil: Martínez, María José. Instituto Nacional de Tecnología Agropecuaria; Argentin

Performance of the LHCb Silicon Tracker with first data

The LHCb Silicon Tracker consists of two sub-detectors the Tracker Turicensis and Inner Tracker that are constructed from silicon microstrip technology. Performance studies of both sub-detectors using data taken during the LHC synchronization tests are described

Commissioning of the LHCb Silicon Tracker using data from the LHC injection tests

LHCb is a single-arm forward spectrometer dedicated to the study of the CP-violation and rare decays in the b-quark sector. An efficient and high precision tracking system is a key requirement of the experiment. The LHCb Silicon Tracker Project consists of two sub-detectors that make use of silicon micro-strip technology: the Tracker Turicensis located upstream of the spectrometer magnet and the Inner Tracker which covers the innermost part of the tracking stations after the magnet. In total an area of 12 m^2 is covered by silicon. In September 2008 and June 2009, injection tests from the SPS to the LHC were performed. Bunches of order 5x10^9 protons were dumped onto a beam stopper (TED) located upstream of LHCb. This produced a spray of ~10 GeV muons in the LHCb detector. Though the occupancy in this environment is relatively large, these TED runs have allowed a first space and time alignment of the tracking system. Results of these studies together and the overall detector performance obtained in the TED running will be discussed

The LHCb Silicon Tracker

The Silicon Tracker is a large-surface silicon micro-strip detector that covers the full acceptance of the experiment in a single tracking station upstream of the spectrometer magnet and the inner-most part of the three tracking stations downstream of the magnet. Special emphasis has been put on module quality assurance at all stages of the production. Various tests are performed after each production step and each module goes through several burn-in cycles. The design of the LHCb silicon detectors is described and the main lessons learnt from the R&D phase are summarized. Focus will be on the experience from module production and the quality assurance program