A fast response colorimetric sensor based on food color for ammonia detection

Ammonia as a pollutant is present in natural waters and also spill out as industrial waste. Its long-term exposure to humans can cause health problems and presence in water can affect ecosystem. Halochromic sensors for monitoring and visual detection of basic environments in both aqueous and open environment are highly valuable. The existing sensors are based on synthetic dyes which are itself toxic in nature. Herein, a non-toxic probe which is a food color (Sunset Yellow, SY) was used to fabricate the sensor. First the halochromic potential of SY was evaluated. In solution form, SY showed color transformation from orange to blood red at pH 10 or higher. Then, electrospun nanofibres composed of polymer blend (PAN 80%, PEG 20%) and loaded with SY was fabricated for the visual detection of ammonia. Fabricated sensor membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD) and Scanning electron microscope (SEM). The nanofibers membranes showed a good response against acids and bases. Moreover, 5% loaded SY showed linear colorimetric response against ammonia in liquid and gas phase. Fabricated sensor is suitable to monitor real time ammonia visualization in liquid as well as gaseous state. Therefore, membranes can be used as indicators in hazardous places and as smart fabric.