Abstract:
Curcumin is a yellow pigment extracted from a spice called turmeric which is commonly used in food. It is also a pH-sensitive compound that has the ability to change color from yellow to orange when exposed with acidic and basic conditions, respectively. As a result, it can be used as an optical sensor to detect volatile amine compounds from meat spoilage. In order to assemble curcumin into a sensor, two methods were introduced: the layer-by-layer assemble and electrospinning. The first technique involves loading curcumin onto two types of polyelectrolyte multilayers i.e. PDADMAC/PSS and CHI/ALG. The latter technique combines PVA with curcumin to produce fibers. Next, potassium hydrogen phosphate buffer and ammonia vapor were used to observe the sensing properties of the curcumin thin films and fibers. UV-vis spectroscopy was used to observe the color of the material and SEM was used to observe the fiber morphology. It was found that the sensing properties of curcumin thin film reacts differently with different polyelectrolyte on the top layer. Curcumin on PDADMAC showed earlier change of color at pH 8 unlike PSS that had later change at pH 10. CH/ALG thin films did not produce orange color at high pH, instead it turns from yellow to colorless at pH 7. Thus, we can tune the pH sensitivity of curcumin thin films. However, the curcumin loaded thin films did not react with ammonia vapor but the fibers changed color at 100 ppm. Conclusively, curcumin fibers are more suitable in ammonia detection; however, both can be used in optical sensor applications.
