Improved ammonia sensing performance achieved through defect modulation by Li doping in cauliflower-like ZnO for exhaled breath analysis towards renal diseases detection: An experimental venture supported by DFT calculation

Abstract

Excess ammonia (NH3) in human exhaled breath serves as a biomarker for renal disease and helicobacter pylori-related gastropathy. A highly sensitive and selective ammonia sensor enables early non-invasive diagnosis of such diseases. Herein, lithium-doped ZnO nanoparticles with varying doping content (1, 5, 10-wt%) were synthesized by reflux method which can detect trace ammonia very efficiently. Specially, the sensor with 5-wt % lithium-doped ZnO (LZ-5) demonstrates remarkable selective sensitivity (43 %) to 1 ppm ammonia, paired with ultrafast response(0.72s)/recovery(1s), stability, and resilience against moisture. Comprehensive structural, morphological, and chemical characterization indicates that significant enhancement in gas sensing of LZ-5 due to increased surface area, elevated oxygen defects and higher donor defects. Density functional theory reveals that Li-doping notably decrease the adsorption energy, thereby improving the ammonia sensing performance. The efficacy of the LZ-5 sensor was evaluated using both real and simulated breath demonstrating its potential for monitoring renal diseases.