Halogen-Acid-Modified Bi₂S₃ Nanorod Array for the Selective Detection of Food Spoilage Gases

Bismuth sulfide (Bi2S3) has significant potential for gas sensing applications, but its performance is often limited by insufficient active surface sites and suboptimal response efficiency. This study aims to overcome these challenges by developing a halogen-doped Bi2S3 nanostructure sensor array for detecting key gases associated with food spoilage. Halogen doping (Cl, Br, and I) substantially enhances the electronic structure and surface activity of Bi2S3, improving both its selectivity and adsorption properties for target gases. Theoretical calculations reveal that halogen doping not only introduces primary adsorption sites on Bi2S3 nanomaterials but also facilitates electron transfer between gas molecules and the material. The sensor array exhibits excellent sensitivity and accuracy in detecting NH3, H2S, and CO gases, achieving an estimation error of only 0.8% for NH3 concentration when combined with machine learning algorithms. Furthermore, the array successfully distinguishes 18 different gas concentrations and classes, achieving a classification accuracy of 97.8%. The study also investigates the impact of humidity on sensor performance, revealing that Bi2S3–Cl nanorods maintain high NH3 adsorption properties under humid conditions. Practical application in beef freshness detection confirms the sensor array’s potential for real-world use, offering innovative solutions for food quality monitoring.