Imprinted polyethylene terephthalate: novel plutonium-selective substrates for ultra-trace detection

Extractive substrates capable of extraction and preconcentration coupled with scintillation-based monitoring show great potential for the detection of alpha-emitting radionuclides such as Pu in the environment. However, the estimation of low activity of Pu in the presence of other alpha emitters such as U and Am poses a significant challenge in terms of achieving the required detection limits. In this work, we developed a highly selective phosphate-based extractive substrate for the detection of very low activities of Pu, approaching nearly the best possible detection limits through radiometry. The polyethylene terephthalate (PET) substrate was surface grafted with a phosphate-based monomer, bis[2-(methacryloyloxy)ethyl] phosphate (BMEP). The extraction of Pu(IV) by the substrate was further enhanced through ozone exposure and homologue (Ce(IV)) imprinting, which was corroborated using DFT calculations. The substrates were found to be selective for Pu(IV) in the presence of Am and U in 2 mol L^-1 HNO₃ and could successfully estimate Pu activities as low as ∼0.8 mBq mL^-1 corresponding to ∼0.3 ppt ²³⁹Pu. Poly(BMEP)-PET-based extractive substrates coupled with a polystyrene scintillation film serve as an easily replenishable detector, which is ideal for the low level detection of plutonium. The present system is easily adaptable for environmental applications, with the possibility of remote monitoring and automation for in-field real time applications.