Molecularly imprinted nanocomposites of CsPbBr3 nanocrystals: an approach towards fast and selective gas sensing of explosive taggants

Abstract

Chemical sensors based on metal halide perovskites have recently attracted tremendous interest because of their excellent photophysical properties. In this work, we report the synthesis of a solid-state luminescent gas sensor based on a nanocomposite of CsPbBr₃ nanocrystals (NCs) embedded in a molecularly imprinted polymer (MIP) using 3-nitrotoluene (3-NT) and nitromethane (NM) as template molecules. The MIP sensor fabrication is straightforward and low-cost: the molecular imprinting process occurs inside the nanocomposite of CsPbBr₃ NCs in polycaprolactone (PCL) during the baking step after spin-coating. The sensing capability of the MIP sensors was evaluated and compared to that of the non-imprinted polymer (NIP) by monitoring the photoluminescence (PL) upon exposure to vapours of different explosive taggants, nitro-containing molecules and some organic solvents. The nanocomposite sensors show a fast response time to analytes below 5 s. The molecular imprinting enhances the PL response of MIP sensors and a robust specificity to 3-NT, and an excellent selectivity towards nitro-containing molecules, particularly when NM is used as the template molecule. Chromatography confirms that molecular imprinting of CsPbBr₃–PCL with NM provides two times more selective binding sites than 3-NT and four times more sites than non-imprinted polymer sensors. Surface topography also suggests that the molecular imprinting in NM MIP is higher than that in 3-NT MIP. These facts confirm that molecular imprinting successfully generates specific recognition sites, allowing fast detection of 3-NT below 3 s with a limit of detection as low as 0.218 μg mL⁻¹.