In the case of TPP, the molecules are preferentially oriented with the porphyrin ring parallel to the gold surface [37]. Sandwich film Comparison of the surfaces of Au/TPP and Au/TPP/Au before annealing indicates that the surface of Au/TPP/Au is more flat than that of Au/TPP. A possible explanation consists in the flattening of roughening of the Au/TPP surface during deposition of additional layer of Au. Probably, Au atoms migrate on the surface after contact with the substrate and tend to stand in the region of ‘valley’, which leads to surface smoothening. Enhancement of the Soret band

occurs in the case of the sandwich Au/TPP/Au system. This phenomenon is of similar nature to the case of Au/TPP films, and it is related to photon-plasmon conversion. However, in this case, a suppression of one of the two luminescence maxima in luminescence spectra is evident. According to the semi-classical Franck-Condon principle, www.selleckchem.com/products/sn-38.html two luminescence peaks appear due to transition of excited

energy from the TPP’s lowest vibration excited state to two vibration states of TPP Selleckchem Y 27632 in the ground state. When TPP is sandwiched between Au layers, one of these radiative transitions is suppressed and the second luminescence peak increases approximately twice. It indicates that the excited TPP molecule can return to only one vibration ground state. We propose that one of the TPP’s vibration states is partially forbidden due to space confinement of the TPP layer by Au layers. Comparison of the luminescence spectra of Au/TPP and Au/TPP/Au indicates weaker luminescence in the case of Au/TPP/Au. A possible explanation consists in particular screening of active porphyrin layer by

additional gold layer. The screening can affect both the intensity of incident beam from the light source and the intensity of luminescence light passing the detector. As to luminescence quenching occurring after annealing, we propose elimination of porphyrin from Au structures Aspartate during annealing. In this case, the top and bottom Au layers coalesce each other and exclude porphyrin molecules. As a result, nonradiative relaxation of the porphyrin excited state becomes dominant, due to mutual aggregation of porphyrin molecules and their interaction with gold clusters. Optical properties of porphyrins depend strongly on the deposited molecule’s orientation relative to the substrate. Photophysical properties of deposited porphyrins depend on surface plasmon resonance occurring in gold structures [38]. In the case of covalently bound porphyrins, luminescence quenching generally occurs and depends on the spacer between porphyrin and gold [39]. Additionally, quenching of luminescence depends on the particle size and shape in the case of porphyrin attachment to gold nanoparticles [40]. The position of the porphyrin selleck fluorescence peak can be affected by combination with noble metals [41, 42].