Cucurbit[8]uril-stabilized charge transfer complexes with diquat driven by pH: a SERS study

Abstract

In this work, we have studied the pH-dependence of the formation of DQCB[8] complexes by surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectra suggest that at acidic pH CB[8] can form a binary complex with the dication DQ⁺² while at higher pH ternary complexes with the radical cation dimer (DQ⁺˙)₂ and the radical cation–dication dimer (DQ⁺˙DQ⁺²) are formed. The pH-enhanced diquat (DQ) dimerization inside the cucurbit[8]uril cavity has not been reported until now. In addition, this study provides very valuable information regarding the use of CB[8] functionalized silver nanoparticles as SERS substrate for sensing applications.