Introduction of a planar defect in a molecularly imprinted photonic crystal sensor for the detection of bisphenol A

We use the Langmuir–Blodgett technique to introduce a planar defect layer within an inverse opal hydrogel made of a molecularly imprinted polymer. The resulting defect-embedded imprinted photonic polymer offers improved bisphenol A sensing capacities as compared to the defect-free structure, opening new opportunities for the design of label-free real-time sensing materials. [Display omitted] ► A planar defect was introduced in a molecularly imprinted photonic crystal sensor. ► The inverse opal structure was sensitive to the presence of bisphenol A. ► The defect layer was shown to enhance the sensitivity of the photonic crystal. This paper reports the preparation of a molecularly imprinted inverse opal hydrogel containing a 2D defect layer, by combining the Langmuir–Blodgett technique and the photonic crystal template method. By coupling the exceptional characteristics of molecularly imprinted polymers, sensitive to the presence of a target molecule, and those of photonic crystals in a single device, we could obtain a defect-embedded imprinted photonic polymer consisting in a three-dimensional, highly-ordered and interconnected macroporous array, where nanocavities complementary to analytes in shape and binding sites are distributed. As a proof of concept, we prepared a three-dimensional macroporous array of poly(methacrylic acid) (PMAA) containing molecular imprints of bisphenol A (BPA) and a planar defect layer consisting in macropores of different size. The optical properties of the resulting inverse opal were investigated using reflection spectroscopy. The defect layer was shown to enhance the sensitivity of the photonic crystal material, opening new possibilities towards the development smart optical sensing devices.