ABSTRACT
In this chapter, we will address our recent work on the optimization of surface-enhanced Raman scattering (SERS) substrates for biosensor applications. This kind of sensor is of great interest concerning the metrology of the environment. It is a very promising technique that can allow in situ or on-site measurements to ensure
water surveillance and monitoring. The optimization of SERS performances is considered in two aspects, increasing of SERS sensitivity by using the molecule adhesion layer between gold nanostructures and glass and nonpolarization-dependent SERS detection with apolar plasmonic nanostructures. All the works are based on the optimization of localized surface Plasmon resonance (LSPR) of metallic nanostructures; thus the methods could also be generalized to other surface-enhanced spectroscopies (SESs). 1.1 IntroductionThe latest European regulations (directives 2000/60/EC, 2006/118/EC, and 2006/11/EC) on water quality aim to achieve good ecological and chemical status for water bodies by 2015. To ensure water surveillance (fresh, surface, ground, coastal, and transitional waters), a measurement network has been set up to conduct sustainable monitoring of aquatic environments, in particular to assess the impacts of human activities generating industrial and agricultural pollutant emissions. The most common approach to contaminant measurements consists of sporadic sampling by laboratory analysis. This approach remains unsatisfactory for several reasons. First, it is costly as it requires time and human resources. Second, sample contamination, a frequent occurrence due to adsorption onto sampling tubes, distorts the quantities present in samples. Furthermore, changes in temperature, pressure, and CO2 and O2 content cause alterations in the pH, redox potential, and species status. In addition to these factors, microbial activity during sampling and the transport of samples can also affect the speciation of original samples. In hardly accessible areas, the large sample volume required can sometimes be prohibitive. To overcome this obstacle of environmental metrology, original field measurement chains are very useful for the detection of contaminants in aquatic environments. In this aim, optical spectroscopies are well-adapted techniques for on-site or in situ measurements [1]. The innovative aspect of this kind of method lies in the coupling of a (bio)chemical sensor, able to collect the contaminants from water, to SERS selected for its qualitative and quantitative analytical performance.
