A highly selective receptor for serotonin was designed using cages formed by the (R)-lipo-diaza-18-crown-6 self-assembled monolayer (SAM) on gold and experimentally verified by a variety of electrochemical experiments in solutions containing large amounts of dopamine and ascorbic acid, as well as other interferents. The molecular modeling study showed that parameters such as the H-pi interaction provided important driving forces for the cage to form a strong inclusion complex with serotonin. The charge-transfer resistance (R(CT)'s) to/from redox probe ions, Fe(CN)(6)(3-/4-), was greatly enhanced because of their electrostatic attractions to ammonium ions of serotonin molecules captured by cages. The changes in R(CT)-values were shown to be remarkably selective for serotonin in the presence of many interferents.