Interrupting the flux of delocalized electrons on a dibenzo-18-crown-6-embedded graphite sheet and its relative counteraction in the presence of potassium ions.

Delocalized electrons are free to move throughout a graphite sheet. Based on the interruption of this flux, a new strategy has been developed to establish a highly sensitive impedimetric sensing device for K(+) ions. Here, we report on the successful application of a simple graphite paste incorporated into dibenzo-18-crown-6 (DB18C6), which effectively impedes the electron flux on the graphite sheet. Most importantly, this interruption can be selectively obviated in the presence of potassium ion. Our quantum mechanics-density functional theory (QM-DFT) calculations revealed that, among the possible surface-configurations of the ligand on the graphite surface, the "distorted concave" form is a more energy-favorable configuration and existed in a higher probability. This form is capable of impeding the passage of delocalized electrons over the graphite sheets. From modeling of the detecting processes, the surface configuration of DB18C6 in treating with K(+) was intensely changed to "convex", which facilitates the passage of electrons along the graphite sheet. Optimizations of the structures of DB18C6 and its 1 : 1 and 2 : 1 complexes with potassium ion were also performed using QM-DFT calculations. On the other hand, the modeling of the graphene sheet was performed using the molecular mechanics MMFF94 method, which was used to model the detecting process. The proposed sensor was found to quantify the potassium ion by faradaic impedance spectroscopy in the range of 50 to 1500 pM with a detection limit of 35 pM.