Sulfonated reduced graphene oxide-doped polypyrrole film prepared by in situ electropolymerization and coating in fabrication of ammonia gas sensor for exhaled breath analysis of patients with kidney failure.

Detection of the level of ammonia gas in exhaled breath provides non-invasive and fast diagnosis of kidney failure. Here, we fabricated room temperature and sensitive chemiresistive ammonia gas sensor by in situ electropolymerization and deposition of polypyrrole/sulfonated graphene oxide (PPy/SRGO) on/between gold interdigitated electrodes (Au-IDEs). The prepared sensors were characterized by using field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FT-IR). The fabricated ammonia gas sensor was tested at different operating temperatures (26-50°C) and we selected room temperature for simplifying operation (26°C). At this temperature, the sensor showed two linear ranges of 5-40 ppb (R2 = 0.99) and 40-5000 ppb (R2 = 0.98) with the detection limit of 2.7 ppb. The fabricated gas sensor showed good selectivity toward ammonia in comparison with different interfering gases like acetone, dibutylamine, ethanol, methanol, and humid air (RH = 86%). According to the exhaled breath analysis, the fabricated sensor can determine ammonia level in the patient with kidney failure compared with the healthy persons. The results are with a good linear correlation to the clinical blood test. So this study presents the facile, rapid, and sensitive measurement of ammonia gas in human exhaled breath as a non-invasive diagnosis of kidney disease.