Communication: An alpha-helix peptide (17 amino acids) bearing gamma-cyclodextrin (gamma-CD) and two naphthyl units (gamma-N(2)17) was designed and prepared as a new type of chemo-sensor The alpha-helix peptide with gamma-CD sandwiched between two naphthyl moieties exhibits excimer emission by inserting the two naphthalene moieties into the gamma-CD cavity from the opposite sides in the side chain of the peptide. The two reference peptides, which have one naphthalene moiety and one gamma-CD unit, exhibit only monomer fluorescence and have larger binding constants for the examined guests than gamma-N(2)17.