Low cost, flexible and disposable SnSe2 based photoresponsive ammonia sensor for detection of ammonia in urine samples

A low cost, flexible, disposable sensing platform which can detect excess ammonia in biological fluids with an enhanced response is of utmost importance in medical diagnostics for early detection of kidney dysfunction, gastrointestinal bleeding, urinary tract related diseases. This report is the first demonstration of direct growth of 2D Tin Diselenide (SnSe2) on cellulose paper by the hydrothermal method for enhanced photoresponsive ammonia detection in urine samples. X-Ray Diffraction (XRD) and Raman studies confirmed the formation of SnSe2 while field emission scanning electron microscopy (FESEM) studies revealed the uniform distribution of SnSe2 nanoflakes on cellulose paper. The SnSe2 based sensor, when irradiated with Near Infra Red (NIR) light exhibited excellent responsivity, detectivity and external quantum efficiency of 70 mA/W, 11 x 10(7) jones and 4.5% respectively. Furthermore, the photoresponsive sensor responded to a wide range of ammonia concentrations (50 mu M - 500 mu M), with a sensitivity of 0.93 m(-1) in comparison to 0.73 m mu M-1 (without illu- mination) and a limit of detection (LOD) of 11.3 mu M which is far more superior in performance than sensors fabricated using sophisticated techniques. Motivated by this enhanced response of the sensor to ammonia in the aqueous medium, it was further employed in detecting ammonia in human urine samples. The mechanism of detection can be attributed to NIR induced oxygen desorption on the surface of 2D- SnSe2, hence creating more vacant sites for interaction with ammonia molecules. The strategy presented in this work could be a step ahead in developing low cost, point-of-care diagnostics to detect various diseases.