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Photonic crystal heterostructures have been obtained by mixing a styreneÀhydroxyethylmethacrylate (ST-HEMA) colloidal dispersion with Au colloidal solution (1:5 volume ratio). To modify the heterogeneous photonic crystal with Rh, the first step has been the chemical attachment of HO-R-SH to the surface of Au particles. The next reaction was the esterification of hydroxyl modified photonic crystal with Rh. In UVÀvis spectra the peak at 600 nm is possible due to the Bragg diffraction of dye molecule aggregates. In the case of ST-HEMA-Au-SH-Rh, the same signal has been shifted to 625 nm, induced by the existence of preformed particles. A decrease in the reflection response of Rh is noticed, and this corresponds to the absorption domain of dye, namely, the Q-band. The large decrease in area for particles ST-HEMA-Au-SH-Rh could be attributed to the overlapping of the Rh reflection band with the photonic crystal stop band. In the case of fluorescence, to the same excitation wavelength, for the ST-HEMA-Au-SH-Rh film, the emissions have been amplified compared with the signal of Rh film. A preliminary test has been performed for putting into evidence the chemosensor properties of ST-HEMA-Au-SH-Rh film modified with triethylenetetramine.

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