Design of highly efficient receptor sites by combination of cyclodextrin units and molecular cavity in TiO2 ultrathin layer

A highly effective approach was developed for sensitive detection of organic substances in water. In order to achieve high sensitivity and selective detection for aromatic compounds, cyclodextrin (CD) hosts and imprinting effects were combined to fabricate binding sites within TiO2 ultrathin layer. The electrode surface was modified with ultrathin TiO2 gel film containing a 2:1 complex of β-CD and bisphenol A (BPA), and then the BPA moiety was removed by washing. The resulting BPA-imprinted TiO2/β-CD film showed specific and sensitive detection of BPA, as confirmed by quartz crystal microbalance (QCM) and cyclic surface-polarization impedance (cSPI) measurements. The high selectivity for BPA relative to structurally related guest molecules was estimated to be 1.6–3.4 at the guest concentration of 2 × 10−7 M, and was considered to arise from the synergic effect of the binding site.