Adsorption and fluorescence detection of nonylphenol in soil samples by cotton fabrics coated with molecularly imprinted polymers/carbon dots

In this study, a novel method for adsorption and detection of nonylphenol (NP) was carried out using a molecularly imprinted polymers/carbon dots (MIP/CDs) coated on cotton fabrics (CF-MIP/CDs) and smartphone-based image analysis. The MIP/CDs using NP template molecule, 3-aminopropyltriethoxysilane (APTES) monomer and tetraethoxysilane (TEOS) cross-linker were simply prepared on the cotton fabrics.  After removal of NP from the CF-MIP/CDs, the adsorption of NP depended on contact time and initial concentration. Compared with the corresponding non-imprinted polymers/carbon dots (CF-NIP/CDs), the CF-MIP/CDs exhibited higher adsorption capacity and selectivity toward NP. The pseudo-first-order and the Freundlich models provided the best description for NP adsorption. Due to high fluorescence emission, the CF-MIP/CDs were used as a sensor for highly selective NP detection. The fluorescence images were taken by smartphone and analyzed by ImageJ program for RGB measurement. The values of DGreen intensity were linearly proportional to NP concentration ranging from 100 to 1000 mg/L with limit of detection and quantification as 35.9 mg/L and 108.9 mg/L, respectively. The CF-MIP/CDs could keep stable in five weeks and use for 4 cycles. The proposed sensor could detect NP in soil samples with well recoveries (92- 116%) and relative standard deviation (< 0.64 %).