Fig.12. Reflection from a hexagonally structured monolayer of gold NPs at water/DCE interface (light propagating from the DCE side at normal incidence), calculated following the Effective Medium Dipole Approximation Theory 36,37 and Drude-Lorentz approximation for dielectric function of gold. The upper panel displays weak reflection from the layer of medium size NPs (of radius 6.25 nm) for indicated values of surface to surface separation, Middle panel shows the effect d. of the size of NPs at dense packing (d =2). The lowest panel shows the effect of surface-to-surface separation for medium size NP, =20 nm. Decrease of surface-to-surface separation moves R maximum of reflection to the red; the effect is stronger for larger NPs. This figure has been reproduced from reference 37 with permission from the American Chemical Society. Fig.13. Calculated reflectivity of an array of core-shell [SiO2@Au] NPs assembled in water at a ITO electrode covered by SAM spacer. Compared are the spectra calculated with the Effective Medium Dipole Approximation theory (solid lines) and finite difference time domain numerical simulations (dotted lines). Optical dielectric constant 1.78; for simplicity the same value is assumed for the spacer. In the results shown, the centres of NPs are aligned in a hexagonal array (at surface coverage = 0.722) in the plane disposed a distance = 18 nm from the surface of the ITO h Γ electrode. The outer radius of NPs, = 16 nm, the optical dielectric constant of silica is taken as Rs 2.25, and the frequency dependent dielectric permittivities of gold and ITO are fitted to the literature experimental data (c.f. 37). Light incidence is from water, normal to the interface. The plot shows the effect of varying shell thickness: = 4 nm (blue), 6 nm (black), and 8 nm (red). This figure has been Rc reproduced from reference 36 with permission from the American Chemical Society. (a) (b)
Fig.12. Reflection from a hexagonally structured monolayer of gold NPs at water/DCE interface (light propagating from the DCE side at normal incidence), calculated following the Effective Medium Dipole Approximation Theory 36,37 and Drude-Lorentz approximation for dielectric function of gold. The upper panel displays weak reflection from the layer of medium size NPs (of radius 6.25 nm) for indicated values of surface to surface separation, d. Middle panel shows the effect of the size of NPs at dense packing (d =2). The lowest panel shows the effect of surface-to-surface separation for medium size NP, R =20 nm. Decrease of surface-to-surface separation moves maximum of reflection to the red; the effect is stronger for larger NPs. This figure has been reproduced from reference 37 with permission from the American Chemical Society. Fig.13. Calculated reflectivity of an array of core-shell [SiO2@Au] NPs assembled in water at a ITO electrode covered by SAM spacer. Compared are the spectra calculated with the Effective Medium Dipole Approximation theory (solid lines) and finite difference time domain numerical simulations (dotted lines). Optical dielectric constant 1.78; for simplicity the same value is assumed for the spacer. In the results shown, the centres of NPs are aligned in a hexagonal array (at surface coverage Γ = 0.722) in the plane disposed a distance h = 18 nm from the surface of the ITO electrode. The outer radius of NPs, Rs = 16 nm, the optical dielectric constant of silica is taken as 2.25, and the frequency dependent dielectric permittivities of gold and ITO are fitted to the literature experimental data (c.f. 37). Light incidence is from water, normal to the interface. The plot shows the effect of varying shell thickness: Rc = 4 nm (blue), 6 nm (black), and 8 nm (red). This figure has been reproduced from reference 36 with permission from the American Chemical Society. (a) (b)
NNP_Rev_Ver27_Final.docx