1 - ArticleWe here emphasize that the surface enhanced Raman scattering (SERS) intensity has to be optimized by choosing the appropriate gold nanoparticles size for two excitation wavelengths; 632.8 and 785 nm. We discuss the role of the position and of the order of the localized surface plasmon resonance (LSPR) in such optimization for both wavelengths. At 632.8 nm, the best SERS intensity is reached for a LSPR located between the excitation and Raman wavelengths whereas at 785 nm, the LSPR should be placed outside this range. The third order of LSPR is shown to have no influence on the SERS intensity. (C) 2010 American Institute of Physics

This paper reports an accurate synthesis of surface-enhanced Raman scattering (SERS) active substrates, based on gold colloidal monolayer, suitable for in situ environmental analysis. Quartz substrates were functionalized by silanization with (3-mercaptopropyl)trimethoxysilane (MPMS) or (3-aminopropyl)trimethoxysilane (APTMS) and they subsequently reacted with colloidal suspension of gold metal nanoparticles: respectively, the functional groups SH and NH(2) bound gold nanoparticles. Gold nanoparticles were prepared by the chemical reduction of HAuCl(4) using sodium tricitrate and immobilized onto silanized quartz substrates. Active substrate surface morphology was characterized with scanning electron microscopy (SEM) measurements and gold nanoparticles presented a diameter in the range 40-100 nm. Colloidal hydrophobic films, allowing nonpolar molecule pre-concentration, were obtained. The surfaces exhibit strong enhancement of Raman scattering from molecules adsorbed on the films. Spectra were recorded for two PAHs, naphthalene and pyrene, in artificial sea-water (ASW) with limits of detection (LODs) of 10 ppb for both on MPMS silanized substrates.

<p><strong>Abstract.</strong> The rapid response of benthic foraminifera to environmental factors (e.g., organic matter quality and quantity, salinity, pH) and their high fossilisation potential make them promising bio-indicators for the intensity and recurrence of brine formation in Arctic seas. Such approach, however, requires a thorough knowledge of their modern ecology in such extreme settings. To this aim, seven stations along a N–S transect across the Storfjorden (Svalbard archipelago) have been sampled using an interface multicorer. This fjord is an area of intense sea ice formation characterised by the production of Brine-enriched Shelf Waters (BSW) as a result of a recurrent latent-heat polynya. Living (Rose Bengal stained) foraminiferal assemblages were analysed together with geochemical and sedimentological parameters in the top five centimetres of the sediment. Three major biozones were distinguished: (i) the <q>inner fjord</q> dominated by typical glacier proximal calcareous species which opportunistically respond to fresh organic matter inputs; (ii) the <q>deep basins and sill</q> characterised by glacier distal agglutinated faunas. These latter are either dominant because of the mostly refractory nature of organic matter and/or the brine persistence that hampers the growth of calcareous species and/or causes their dissolution. (iii) The <q>outer fjord</q> characterised by typical North Atlantic species due to the intrusion of the North Atlantic water in the Storfjordrenna. The stressful conditions present in the <q>deep basins and sill</q> (i.e. acidic waters and low food quality) result in a high agglutinated/calcareous ratio (A / C). This supports the potential use of the A / C ratio as a proxy for brine persistence and overflow in Storfjorden.</p>

In the investigation of chemical pollutants, such as PAHs (Polycyclic Aromatic Hydrocarbons) at low concentration in aqueous medium, Surface-Enhanced Raman Scattering (SERS) stands for an alternative to the inherent low cross-section of normal Raman scattering. Indeed, SERS is a very sensitive spectroscopic technique due to the excitation of the surface plasmon modes of the nanostructured metallic film. The surface of quartz substrates was coated with a hydrophobic film obtained by silanization and subsequently reacted with polystyrene (PS) beads coated with gold nanoparticles. The hydrophobic surface of the SERS substrates pre-concentrates non-polar molecules such as naphthalene. Under laser excitation, the SERS-active substrates allow the detection and the identification of the target molecules localized close to the gold nanoparticles. The morphology of the SERS substrates based on polystyrene beads surrounded by gold nanoparticles was characterized by scanning electron microscopy (SEM). Furthermore, the Raman fingerprint of the polystyrene stands for an internal spectral reference. To this extent, an innovative method to detect and to quantify organic molecules, as naphthalene in the range of 1 to 20 ppm, in aqueous media was carried out. Such SERS-active substrates tend towards an application as quantitative SERS sensors for the environmental analysis of naphthalene.