Systematic cation engineering in spinel ferrites (MFe2O4, M = Fe, Co, Ni, Zn) for sub-ppm acetone sensing in non-invasive breath-based diabetes diagnosis

The non-invasive detection of acetone in exhaled breath via gas sensors offers a simple and efficient strategy for the auxiliary diagnosis of diabetes. Spinel ferrites have emerged as promising candidates for sub-ppm acetone detection due to their outstanding physicochemical and electronic properties. Despite the development of diverse spinel ferrites, the intrinsic correlation between cation type (i.e., M 2 + in the MFe 2 O 4 structure) and these materials’ gas-sensing properties has not been systematically elucidated. In this study, spinel ferrites with different metal ions (MFe 2 O 4 , M = Fe, Co, Ni and Zn) were synthesized via a facile one-step solvothermal method. The effects of cation type on the crystal structure, microstructural features, and acetone-sensing performance of these ferrites were systematically studied. It demonstrates that the cation type exerts a significant influence on the grain size, morphological and microstructural characteristics, and gas-sensing kinetics of these ferrites, thereby regulating their overall acetone-sensing performance. Notably, the NiFe 2 O 4 sensor exhibits superior acetone-sensing properties toward 1.0 ppm acetone at its optimal operating temperature, including a high response value, a low detection limit, excellent humidity tolerance, outstanding selectivity, and long-term stability. Furthermore, the NiFe 2 O 4 sensor can effectively distinguish acetone concentration differences in exhaled breath between healthy individuals and diabetic patients (using simulated samples). These results clarify the intrinsic correlation between cation type and acetone-sensing performance of spinel ferrites, providing practical guidance for the rational design of high-performance acetone-sensing materials and promoting their application in breath-based auxiliary diagnosis of diabetes.