Bismuth-doping Induced Enhanced Humidity Sensing Properties of Spinel NiFe2O4 Nanoparticles

Bi-doped NiFe2O4 nanoparticles were tested for humidity detection at various RH levels at room temperature. The findings indicated that sensors with higher Bi concentrations, particularly the ones with 20 % Bi doping, showed significantly enhanced sensing response—up to 97 %, a sixfold increase compared to undoped sensors. This significant improvement suggests that Bi contributes to synergistic effects that boost sensor performance. Density Functional Theory (DFT) calculations support this by showing that Bi introduces acceptor electronic states, heightening electrical responsiveness to moisture. These Bi-doped sensors exhibit quick response times, high accuracy, negligible hysteresis, and impressive stability, making them promising candidates for reliable humidity detection. [Display omitted] •The solution combustion method creates NiFe2-xBixO4 NPs with shape change due to Bi doping.•Bi-doping increases NiFe2O4 NPs' surface area, enhancing sensor capability.•TEM analysis confirms pure cubic ferrite structure.•BET analyses show porosity increase with Bi.•Humidity sensing response improves with Bi; 20 % Bi-doped NPs perform best.