Differential fluorescence from molecularly imprinted polymers containing europium ions as a transducer element

Molecularly imprinted polymers (MIPs) have the potential to provide a unique combination of high chemical selectivity and environmental stability and are, therefore, being widely studied in chemical sensor applications. Optical interrogation of the MIP-chemical interaction is very convenient for the detection of fluorescent compounds, but is problematic for the detection of non-fluorescent species. Doping MIPs with Eu3+ is one approach that can facilitate the optical detection of non-fluorescent species. Eu3+ has absorption in the near UV and the doped MIP can, therefore, be excited with a commercially available laser diode at 375nm. In the present paper MIPs doped with Eu3+ and imprinted to methyl salicylate (MES), a chemical warfare agent simulant, were prepared in the form of a thin film on a quartz substrate. Non-imprinted (Blank) polymer films were also prepared using the same imprinting procedure, but without introducing the MES template. Both polymers were tested to MES and the structurally similar compound methyl 3,5-dimethylbenzoate (DMB) in hexane. For MES, the fluorescence intensity of the MIP was significantly stronger than for the Blank, while for the methyl 3,5-dimethylbenzoate, the Blank polymer exhibited the stronger fluorescence signal. A portable chemical sensor employing differential fluorescence from MIP/Blank polymer pairs is under development and allows target discrimination without the need for spectroscopic analysis of the emission spectra.