ABSTRACT
One of the important characteristics of organic molecules is the flexibility of structural frameworks in contrast to metals and semiconductors. In this chapter we discuss the use of flexible organic molecules as molecular probes for na noenvironments based on detecting fluorescence in the visible spectral region, expecting such molecules to probe nanostructures of condensed matter including polymers and proteins. We consider conjugated molecules whose size is larger than that of benzene but smaller than polymers, and thus refer to them as chro mophores. The flexibility, which is closely related to the electronic configura tions, will be enhanced especially when such molecules are in the electronic ex ited states. The intrinsic flexibility of molecular structures and electronic config urations, plus the use of standard visible fluorometry, make it possible and easy to use such molecules as sensitive probes of the immediate local environments around themselves. Especially when such molecules are in the single molecule regime the ability will be exhibited considerably. We will first focus on triph enyl methane (TPM) dyes as a representative for flexible conjugated molecules [1]. We will then discuss two kinds of chromophores other than TPM dyes.
