Application of curcumin nanoparticles in a lab-on-paper device as a simple and green pH probe

This article describes the design and fabrication of a novel lab-on-paper device for pH sensing using curcumin nanoparticles (CURNs). In order to fabricate the lab-on-paper, the wax dipping method was used. The color of loaded paper with CURNs changed from yellow to orange and red to brown in the pH range of 7-13. The image of the lab-on-paper was taken by a digital camera and the picture was processed and analyzed using Adobe Photoshop software. The change in mean color intensity with pH was recorded and employed as an analytical signal for quantitative sensing of pH. The parameters affecting the pH sensor were optimized to enhance the selectivity and sensitivity of the method. Under optimum conditions, the mean color intensity was linearly proportional to the pH in the range of 8-13. The relative standard deviations of 10 replicate measurements of pH 9 and pH 12 were 2.3% and 1.5%, respectively. The developed sensor was successfully applied to the determination of pH in different water samples with satisfactory results.