Chemically Converted Graphene Induced Molecular Flattening of 5,10,15,20-Tetrakis(1-methyl-4-pyridinio)porphyrin and Its Application for Optical Detection of Cadmium(II) Ions

Complexation of cationic 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (TMPyP) and negatively charged chemically converted graphene (CCG) sheets was performed by simply mixing the diluted aqueous solutions of both components. During this process, a large bathochromic shift of porphyrin Soret band from 421 to 458 nm was observed, which is attributed to the flattening of TMPyP molecules induced by CCG through electrostatic and pi-pi stacking cooperative interactions. Furthermore, the coordination reaction between TMPyP and Cd2+ ions was greatly accelerated from 20 h to 8 min under ambient conditions by introducing CCG sheets. On the basis of this phenomenon, we used the complex of TMPYP and CCG as an optical probe for rapid and selective detection of Cd2+ ions in aqueous media.