Application Of DFT Method In Fluorescent Molecularly Imprinted Layer-coated Silica Nanoparticle Sensors

Molecularly imprinted fluorescence sensors on the basis of the recognition of imprinted sites to guest and the resultant changes of fluorescence emission have been studied, but the origin of guest-induced fluorescence enhancement and the function of host molecule are still unclear in theory. In this work, we have first designed three isomers,2-acrylamidoquinoline (2-AAQ),3-acrylamidoquinoline (3-AAQ) and8-acrylamidoquinoline (8-AAQ), with weak fluorescence emission, and used them as both functional monomers and signaling units in molecularly imprinted fluorescence sensors.Subsequently, quantum chemical calculation within the density functional theory (DFT) framework was introduced to accurately evaluate and predict the hydrogen bonding interactions between these monomers and analyte melamine. As a result, the as-synthesized2-AAQ exhibits a highest hydrogen bonding ability and the ideal molar ratio of monomer to template is3:1in molecularly imprinted polymers.The theoretical prediction is in good agreement with the experimental observation. Moreover, the imprinted nanoparticles display significant fluorescence enhancement upon titration with different concentrations of melamine in methanol. It can be ascribe to the hydrogen bonding interactions between MA and2-AAQ, which may restrict the inner molecular rotation of functional monomer and strengthen their structural rigidity. The fluorescence sensors can be applied to detect the melamine. The results reported herein supply an excellent model for the design of molecularly imprinted fluorescence sensors and their prediction of chemical sensitivity to nonfluorescent compounds.