Molecularly imprinted polymer on cotton materials as substrates for smartphone-based image and distance-based analysis of Cu(II) in water samples.

Cotton fabric was used as a substrate for smartphone-based image analysis of Cu(II) in drinking water. To enhance its selective and specific binding sites on the cotton surface, a molecularly imprinted polymer (MIP) was introduced using color complexes of 4-(2-pyridylazo)resorcinol-Cu(II) (PAR-Cu(II)) as the template molecule, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, tetraethoxysilane (TEOS) as the crosslinker and NH as the catalyst. After achieving optimum conditions, the obtained CF-MIP/PAR-Cu(II) presented a red color, which was changed to yellow upon the removal of Cu(II) with 1.5 M HCl. After using CF-MIP/PAR to detect Cu(II), the red, green and blue intensities of the images captured using a smartphone were analyzed using the ImageJ program. For the calibration curve plotted between Δgreen intensity and Cu concentration, the linear range was 0.10-1.0 mg L with the best correlation coefficient () of 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 0.038 and 0.11 mg L, respectively. To obtain a distance-based device, MIP-modified cotton thread (CT-MIP/PAR) with a four-channel design was used as an alternative device. The distance of red color development was measured after using CT-MIP/PAR to detect Cu(II). The linear range was 0.50-3.0 mg L with an of 0.997. The LOD and LOQ were 0.18 and 0.56 mg L, respectively. The proposed methods provide simple, portable and inexpensive devices with high accuracy and precision for the detection of Cu(II) in drinking water.