Olivier Peron

Detection of polycyclic aromatic hydrocarbon (PAH) compounds in artificial sea-water using surface-enhanced Raman scattering (SERS)

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.

First Steps of in situ Surface-Enhanced Raman Scattering during Shipboard Experiments

It is shown that the surface-enhanced Raman scattering (SERS) technique can be applied to detect organic molecules during in situ experiments. To this purpose, we used trans-1,2-bis(4-pyridyl)ethylene (BPE) as a target molecule. Adsorbed on the SERS chemosensor surface and excited under laser, the vibration modes of the molecules can be identified. SERS chemosensors are based on quartz substrates functionalized by silanization and partially coated with gold nanoparticles. SERS measurements during shipboard experiments were made with a home-made in situ Raman spectrometer connected to a marinized micro-fluidic system. The device was designed to host chemosensors in order to ensure measurements with a flow cell. A theoretical limit of detection was estimated in the range of picomolar (pM) concentrations based on Freundlich isotherm calculations.

Towards in situ detection of PAH trace in seawater using SERS-active sensors

This paper reports the development of a sensor based on surface-enhanced Raman scattering (SERS) for analyses in seawater. Polycyclic aromatic hydrocarbons (PAHs) are targeted by these sensors and their detection in situ summons up chemical synthesis and optical development. Firstly, a relevant synthesis of SERS active substrates based on gold nanostructures is presented. Different kinds of substrates have been synthesized under variable experimental conditions to modify some parameters such as i) gold shape, size and distribution and such as ii) chemical functionalization: (i) gold nanoparticles were prepared either by chemical reduction of HAuCl4 or by physical deposition. (ii) Substrates were functionalized by hydrophobic films to allow nonpolar molecules pre-concentration. Low concentration from ppb to ppm of PAHs were detected with a Raman microscope designed for lab experiments. Sensors 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 with limits of detection of 10ppb for both with a short integration time (10s) and a low incident laser power (~0.1mW). Active substrate surface morphology was characterized with scanning electron microscopy (SEM) measurements. Secondly, an home-made in situ Raman spectrometer was developed and has been connected to a micro-fluidic system. This system was designed to host SERS-active sensors in order to ensure measurements with a flow cell. This original configuration of in situ Raman spectroscopy was then achieved. Such a device is now ready to use to confirm the PAH detection at ppb levels during the offshore experiments thanks to SERS sensors.

Surface enhanced Raman scattering optimization of gold nanocylinder arrays: Influence of the localized surface plasmon resonance and excitation wavelength

We 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.

Surface Enhanced Raman Scattering Of Gold Nanostructures: Role Of Dipolar And Multipolar Localized Surface Plasmons

We have studied the Surface‐Enhanced Raman Scattering (SERS) of shape controlled metallic nanoparticles: nanocylinders and nanowires, designed through electron beam lithography and lift off techniques. We have notably studied the influence of Localized Surface Plasmon Resonance (LSPR) on the efficiency of SERS. We will demonstrate that the nanowires have specific enhancement behavior and can actually act as nano‐antenna.

SERS Optimization Of Gold Nanocylinders Arrays: Influence Of The Surrounding Medium And Application For Polycyclic Aromatic Hydrocarbons Detection

This study describes the effect of the surrounding medium on the SERS efficiency using nanolithographied substrates on which Polycyclic Aromatic Hydrocarbons are investigated. We will show that the optimum nanocylinder size is shifted to lower diameter by increasing the dielectric constant of the liquid medium. This rule is discussed in terms of Localized Surface Plasmon Resonance since its position influences directly SERS intensity. This study is done for two excitation wavelengths: 632.8 nm and 785 nm. The aim of this work is collect information in order to product future active SERS sensors suitable for in situ environmental analysis.

New SERS Substrates For Polycyclic Aromatic Hydrocarbon (PAH) Detection: Towards Quantitative SERS Sensors For Environmental Analysis

In the investigation of chemical pollutions, 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.

Rare earth doped fluoride glass ceramics: Fabrication of waveguides by PVD and application

Er³⁺-doped fluoride glass ceramics planar waveguides containing LaF<inf>3</inf> or binary LaF<inf>3</inf>-ZrF<inf>4</inf> nanocrystals have been fabricated by Physical Vapor Deposition (PVD). A quantitative analysis of the photoluminescence of the 1.54 µm emission band of Er³⁺ ions has demonstrated that erbium ions are partitioned in both crystals and vitreous phase. The solubility of Er³⁺ in the segregated LaF<inf>3</inf> nanocrystals can reach 30 mol%. The emission bandwidth has been found to be greater than that of the precursor glass (71 nm at the half-height width). In order to increase the luminescence of Er³⁺, codoping with Yb³⁺ and Ce³⁺ has also been studied. The high Er³⁺ concentration and spectral width could make this nanostructured fluoride material suitable for planar amplifier in the C telecommunication band.

Application of PVD technique to the fabrication of erbium doped ZrF 4 -based glass ceramic for optical amplification

This paper presents the first optical and spectroscopic characterization of zirconium based fluoride planar waveguides ZE (ZrF4-ErF3) and ZLE (ZrF4-LaF3-ErF3) that have been fabricated by Physical Vapor Deposition (PVD) in dual evaporation configuration [1]. Transparent thin films have been obtained by adjusting vaporization temperature, composition of the ZrF4-based glass and the LaF3-ErF3 batch. In order to improve resistance to moisture, a low refractive index (~1.32) KAlF4 cladding has also been deposited. Infrared spectrum of the waveguides has confirmed the protecting role of the cladding layer for the active layer regarding hydrolysis. Luminescence measurements on waveguide samples have shown promising properties compared with the bulk samples, indicating that this system may be suitable for ceramization like in bulk configuration [2-3].