The adsorption of beta(2)-adrenergic agonist (βAA) drugs clenbuterol, salbutamol, and terbutaline on metal surfaces has been investigated in this work by means of surface-enhanced Raman scattering (SERS). To assist in this investigation, a previous vibrational (IR and normal Raman) characterization of these drugs was performed, supported by ab initio density functional theory calculations. The application of SERS was aimed to apply this highly sensitive technique, based on localized surface plasmon resonance, in the detection of βAA at trace concentrations and as a possible alternative method which can be postulated in routine antidoping analysis. The adsorption of these drugs was studied in depth at different experimental conditions: on Au and Ag, at different pHs, and with varying adsorbate concentration. Moreover, plasmon resonance spectroscopy was employed to investigate the adsorption of these drugs on the metal nanoparticles as well as their aggregation. It was found that the adsorption of these molecules is more effective on gold nanoparticles and at acidic pH, based on the direct interaction of the aromatic or aliphatic moieties through ionic or coordination bonds with the metal. These drugs followed a Langmuir adsorption model from which the adsorption constant and the limit of detection can be determined.

A comparative study of different plasmonic nanoparticles with different morphologies (nanospheres and triangular nanoprisms) and metals (Ag and Au) was done in this work and applied to the ultrasensitive detection of aminoglutethimide (AGI) drug by surface enhanced Raman spectroscopy (SERS) and plasmon resonance. AGI is an aromatase inhibitor used as an antitumoral drug with remarkable pharmacological interest and also in illegal sport doping. The application of very sensitive spectroscopic techniques based on the localization of an electromagnetic field on plasmonic nanoparticles confirms the previous study of the adsorption of drugs onto a metal surface due to the near field character of these techniques. The adsorption of AGI on the above substrates was investigated at different pH values and surface coverages, and the results were analyzed on the basis of AGI/metal affinity, considering the interaction mechanism, the existence of two binding sites in AGI, and the influence of the interface on the adsorption in terms of surface charge due to the presence of other ions linked to the surface. Finally, a comparative quantitative detection of AGI was performed on both spherical and triangular nanoprism nanoparticles, and a limit of detection lower than those reported so far was deduced on the latter nanoparticles.

The adsorption and self-assembly of alpha,omega-aliphatic diamines on silver nanoparticles is studied in this work by surface-enhanced Raman scattering (SERS) spectroscopy and plasmon resonance. These bifunctional diamines can act as linkers of metal nanoparticles (NPs) inducing the formation of hot spots (HS), i.e. interparticle junctions or gaps between metal NPs, which are points where a huge intensification of the electromagnetic field occurs. In addition, the dicationic nature of these diamines leads to the formation of cavities just at the induced hot spots which can be applied to molecular recognition of analytes. The influence of the surface coverage and the aliphatic chain length in diamines on their self-assembly was tested by the vibrational spectra and correlated to the different plasmon resonances of the dimers detected in the extinction spectra. These factors can be used for tuning the plasmon resonance of dimers formed by two metal nanoparticles where interparticle hot spots are formed. Finally, the analytical potential of these functionalized Ag nanoparticles is demonstrated for the trace detection of the pesticide aldrin.

Fabrication of freestanding, three-dimensional microstructures having gold nanoparticles as building blocks has been achieved using two-photon lithography. The reported constructions hold structural coherence without the need of a polymeric network to embed the nanoparticles. The Au nanoparticles are produced by radical-mediated photoreduction and immediately self-arrange in micrometre-sized cylinders, which are used as the building units of the 3D structure writing. The manufactured structures present plasmonic activity, as well as excellent properties as substrates for Surface-Enhanced Raman Spectroscopy, in key issues such as reproducibility in intensity or enhancement factor. Such is calculated to be above 8 Â 10 6 for the non-resonant probe molecule trans-1,2-bis-4-pyridylethylene. The option of repeated use of the substrates is confirmed, and they are successfully applied for detection of the fungicide thiabendazole.

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