Ultrasensitive HCHO sensor based on Cr-doped cerium oxide nanoparticles with full recoverability and decisive anti-humidity ability

Abstract

Notably, the Cr-doped sensor sense the 100-ppb formaldehyde which is below the 740-ppb permissible exposure limit (fixed by WHO). A highly crystalline puny-size nanoparticles are obtained by single air-annealing process (400 °C). The size-controlled undoped and Cr-doped cerium nanoparticles produce the oxygen vacancies, helping to expend more active sites to gas molecules. Higher-surface area of doped cerium supports formaldehyde sensing proficiently. The Cr-doped cerium sensor operates at noticeable temperature of 50 and 80 °C for formaldehyde gas where, the sensor responses to ∼2 s and recovered around 3 s (5 ppm), suggesting appreciable signs to formaldehyde detection. The sensor shows the LOD of 0.1 ppm (100 ppb) and unveil the good stability to anti-humidity test. The growing oxygen-vacancies demonstrate the sensor signal increase and also dopant enriches the oxygen-vacancies. The stability of the sensor surface has been identified by ladder-growth of current signal to different concentrations of gas. Current signal to formaldehyde increase implies the enhancement of conductivity. Highly-selective response to formaldehyde attributes to the particle size, oxygen vacancies and bandgap of Cr-doped cerium sensor material. At last, the reproducibility inspection unveils 99.06 % results. Such a high reproducibility confirms the long-term chemical stability and mechanical robustness of sensor, opening a route to developing industrially viable sensor technology.