INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Substrate/Nanoparticle plasmon coupling: Electrodynamic calculations for TERS geometrical optimization
Autor/es:
E. A. CORONADO; L. A. PÉREZ
Lugar:
Fortaleza
Reunión:
Congreso; XXV International Conference on Raman Spectroscopy; 2016
Institución organizadora:
ICORS
Resumen:
One of the areas within nanoscience in which significant progress has been made in recent years is plasmonics. In plasmonics the interaction of electromagnetic radiation (usually visible light) with noble metals, sometimes combined with other material nanostructures give rise to optical phenomena that somehow allow us to "manipulate" the light.[1] One of the main characteristic is the confinement of the electric field and its enhancement near the nanostucture surface (near field enhancement). This amplification induces an enhancement of the spectroscopic signals of fluorescent or Raman probes molecules. A recent application of this concept that combines the control of nanopositioning such as in atomic force microscopy (AFM) with the enhancement of the near field has resulted in a new spectroscopy called TERS (Tip Enhanced Raman Spectroscopy), where the tip is a modified AFM probe with a metal allowing both a simultaneous control of the distance between the tip and the substrate with nanometer precision, as well as the confinement of the near field upon illumination of the metal tip, a feature that could be used to obtain spectroscopic information with resolution below the diffraction limit. While the TERS technique is a promising approach, it has experimental and instrumental difficulties.[2] One of the parameters to take into consideration is the angle of incidence of radiation with respect to the surface. For example, it is known that there is a dependence of the near field enhancement produced between two nanoparticles depending on the polarization of the incident light.This communication presents a systematic set of electrodynamic calculations on model systems formed by a 60 nm nanoparticle located at small distances (1 to 10 nm) on a flat substrate, varying the angle of incidence of the incident beam with respect to the flat surface, illuminating the TERS tip (nanoparticle) with a 633 nm wavelength light. The optimum angle that produce the maximum enhancement of the near field changes by using different materials for the substrate. For a gold nanoparticle on a gold substrate the maximum field enhancement occurs upon irradiating at an angle of 59° with respect to the normal to the substrate (Figure 1), while when the substrate is silver this maximum is obtained for an angle of incidence of 48°. The average area of maximum enhancement was also found to be dependent on the nature of the substrate. Thus , for an insulating substrate (silica) and semiconductor (ZnO, Si) the area of maximum enhancement was found to be significantly lower than for metallic substrates, illuminating at the optimum incident angle. The present results obtained from the electrodynamic calculations could be useful and important for the experimental design of optimal TERS configurations and for a rational choice of the substrate.ACKNOWLEDGMENTSWe thank CONICET, FONCyT and SECyT-UNC for fnancial support. L.A.P. also thankCONICET for the fellowships granted.REFERENCES[1] Kelly KL, Coronado EA, Zhao LL, Schatz GC, J Phys. Chem. B 2003; 107: 668-677.[2] Pérez LA, Dalfovo MC, Troiani H, Soldati AL, Lacconi GI, Ibañez FJ, J Phys.Chem. C 2016; 120: 8315-8322.