The research on Supramolecular chemistry involves in the interactions of Host-Guest chemistry or Lock-Key concept. The ‘host’ molecule possesses a binding site that is highly specific to a target analyte ‘guest’. Supramolecular chemistry plays an important role in a variety of applications such as molecular sensors. The molecular sensor consists of two parts: a signal unit and a recognition unit. The design concept of these sensors is based on the fundamental requirement for the selective host-guest interactions and is designed based on size fit to ions and/or favorable electrostatic interactions between the host and the guest such as ion-ion interaction, ion-dipole interaction, dipole-dipole interaction, hydrogen bonding, π – π interaction, and cation-π interaction, etc. The stronger interactions between the host and the guest will be, the more effective binding will be.