ABSTRACT
A photonic antenna is an organized multicomponent arrangement in which several chromophores absorb the incident light and channel the excitation energy to a common acceptor component. Imaginative attempts to build an artificial antenna different from ours have been presented in the literature. Multinuclear luminescent metal complexes, multichromophore cyclodextrins, Langmuir-Blodgett films, dyes in polymer matrices, and dendrimers have been investigated. Sensitization processes in silver halide photographic materials and also the spectral sensitization of polycrystalline titanium dioxide films bear, in some cases, aspects of artificial antenna systems (for references see Ref. 1). The materials which have been reported by us so far are of a bidirectional type. They are based on zeolite L as a host and able to collect and transport excitation energy [1-5]. The transport is enabled by specifically organized dye molecules which mimic the natural function of chlorophyll. The zeolite L crystals consist of a continuous one-dimensional tube system. We have filled each tube with chains of joined but electronically noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to a desired
Figure 1 Representation of a cylindrical nanocrystal consisting of organized dye molecules acting as donors (light gray rectangles) and acceptors (dark gray rectangles). (a) The donors are in the middle part of the crystal and the acceptors at the front and the back of each channel. (b) The donors are at the front and the back of each channel and the acceptors are in the middle part. The enlargements show details of a channel with a dye and its electronic transition moment (arrow), which is parallel with respect to the channel axis for long molecules and bent for shorter ones. The diameter of the channel windows is 0.71 nm and the largest free diameter is 1.26 nm. The center-to-center distance between two channels is 1.84 nm.
