A sol-gel derived molecular imprinted luminescent PET sensing material for 2,4-dichlorophenoxyacetic acid

A novel sol-gel derived molecular imprinted luminescent sensing material has been fabricated by a conventional sol-gel process. 2,4-Dichlorophenoxyacetic acid (2,4-D) was used as template for the imprinting process and a tailor-made organosilane, 3-[N,N-bis(9-anthrylmethyl)amino]propyltriethoxysilane (1), was used as the functional monomer. Luminescent properties of I were perturbed by acid-base ion-pair formation with 2,4-D leading to suppression of photoinduced electron transfer (PET) quenching of its anthryl fluoyophores. Such PET fluorescent response was preserved after the preorganized monomer-template aggregates were cross-linked by a sol-gel process. The resultant sol-gel derived luminescent material was found to selectively respond to 2,4-D in aqueous media at pH 7. Average binding affinity of recognition sites in the material for 2,4-D was estimated to be (2.23±0.5) × 10⁶ M^-1. Selectivity of the MIP was also evaluated. The present study demonstrated the feasibility of using a PET mechanism as a means of signal transduction for molecular imprinted polymer (MIP) based luminescent sensing of non-fluorescent analytes.