[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: For the last few years there is a more and more pressing need to develop system for detecting HAB at their early stage. Researchers have then been working on new in situ sensor. In this paper a submarine transducer based on surface plasmon resonance is reported. It demonstrated a refractive index resolution of 3.10<sup>-6</sup>, which is promising for later phytoplankton detection.
[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: Among marine algae species, Alexandrium minutum produces a phycotoxin called paralytic shellfish poisoning (PSP) that is introduced in the food chain through the ingestion of phytoplankton by shellfishs, and later by human consumers. Thus, in situ monitoring of A. minutum proliferation in coastal seawater is of great economical importance for marine resources exploitation. Here, we propose a rapid test for the detection of A. minutum by surface plasmon resonance spectroscopy. First, whole genomic DNA is extracted from the algae. Second, a 677 bp long portion of the 28S ribosomal DNA is amplified by PCR. Third, the PCR product is detected by surface plasmon resonance spectroscopy onto a DNA functionalized gold substrate.
Sensors Applications Symposium, 2009. SAS 2009. IEEE; 03/2009