**6. Conclusions and outlook**

the nanoparticles are not toxic to the cells. Gambhir and co-workers have injected Au@SiO<sup>2</sup> nanoparticles into a live mouse and have studied the mouse's liver through the skin using SERS mapped images [221]. In addition, Firkala el al. have reported, for the first time, the application of surface enhanced Raman imaging on pharmaceutical tablets containing an API

It is of special interest to mention in the context of this chapter that SERS imaging has been a useful technique to identify the SERS active sites in polymer based nanocomposite substrates [60, 63, 67, 68, 73, 93, 160]. SERS imaging has been applied to Ag/agarose beads films, giving an idea of the distribution of the *hot spots* in the polymer matrix [63]. Highly sensitive biological imaging of HEK293 cells expressing PLCγ1 cancer markers were obtained, using Au/Ag coreshell NPs, conjugated with monoclonal antibodies [93]. A porphyrin−phospholipid conjugate with quenched fluorescence have been reported as a Raman reporter molecule for SERS based

**Figure 7.** (1) AFM topography image of Ag/P*t*BA composites prepared by (mini)emulsion polymerization (A) before and (B) after the addition of 10 μL of an ethanolic solution of thiosalicylic acid 10−3 M; C) optical photograph of the sample with the scanned area marked in red; D) Raman images obtained using the integrated intensity of the Raman band at 1035 cm−1 in the SERS spectra of thiosalicylic acid 10−3 M using the Ag/P*t*BA composite as substrates; E) SERS spectrum of thiosalicylic acid (10−3 M) using Ag/P*t*BA composites as substrate (laser source: 532 nm); (2) Optical photograph (left) and combined Raman image (right), using two different Raman spectra of methylene blue (100 μM) adsorbed on Ag/ linen composite Inset: Raman spectra of monomer form and a mixture of monomer and dimer of MB used to create the

combined Raman image [68].

in very low concentrations, using Ag colloids as SERS probes [209].

108 Raman Spectroscopy

The development of polymer based composites as active SERS substrates has contributed considerably to the rise of this methodology as an important and significantly tool in several analytical contexts. This improvement could only be achieved due to the development of more versatile and powerful instruments, including portable Raman equipment, and a deeper knowledge about the underlying mechanisms in the Raman effect that occur in molecules adsorbed at metal surfaces. It should be also emphasized the unprecedented progress observed in the past decades on the synthesis of nanostructures having controlled morphology. Interestingly, it has become clear that improvements in SERS have also impact on the knowledge that we have about the materials required as substrates for applying such spectroscopic technique. In this chapter, the most recent developments in metal loaded polymer nanocomposites for SERS studies were reviewed, showing their applicability into diverse areas due to their multifunctional properties. The vestigial SERS detection of specific molecules using Raman reporters, SERS tags and specific external stimuli are examples of further developments in SERS technologies dependent on materials development. This research has also shown that Raman imaging combined with other techniques such as SERS are valuable assets that complement or eventually provide unique characterization data, with particular relevance in the use of polymer based composites as SERS platforms.
