Alkali metal-incorporated spinel oxide nanofibers enable high performance detection of formaldehyde at ppb level

Sensing material with high sensitivity, excellent selectivity and ultra-low detection limit is crucial for monitoring formaldehyde, which is a kind of hazardous gas to human health at very low concentration. Some one-dimensional semiconductor metal oxides show acceptable responses towards formaldehyde. However, the detection limit and selectivity of these sensors are still not satisfied, especially at ppb level. Herein, alkali metals (K, Na) doped CdGa₂O₄ nanofibers with excellent formaldehyde sensing performance are prepared by an electrospinning method. These nanofibers have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance spectroscopy (EPR), elemental mapping and other techniques. As a result, the sensor based on 7.5 at.% K doped CdGa₂O₄ gives remarkably improved formaldehyde sensing properties compared with that of pristine CdGa₂O₄. The greatly increased sensitivity and selectivity should be attributed to the increased chemisorbed oxygen and the enhanced basicity caused by the additional alkali metal, respectively. All in all, the 7.5 at.% K doped CdGa₂O₄ is a good candidate for the rapid detecting formaldehyde at ppb level.