Carbon quantum dots modification on hydrangea-like In2O3 for ppb-level formaldehyde detection: Experimental performance and theoretical insight

With the growing demands on environmental protection and human health, numerous efforts have been devoted to the high-efficiency detection of formaldehyde gas. Herein, a simple and green manner was adopted to generate a 3D/0D heterogeneous structure. It was found that the morphology evolution of the In2O3-based sample could be fine-tuned through changing the addition concentration. Impressively, the unique hydrangea-like structure was assembled by connecting In2O3 nanosheets. Furthermore, the carbon quantum dots were incorporated to upgrade the performance. The hydrangea-like IO-2@CQDs, hence, exhibits remarkable sensitivity, excellent response repeatability, superior selectivity as well as reliable long-term stability at 160 °C. An outstanding limit of detection can be as low as 86.23 ppb. In addition, the corresponding CQDs sensitization mechanism was comprehensively elaborated with experimental performance, DFT calculations (16 models, 41 images), and surface depletion theory. The active surface sites, n-p hetero-interface, and unique hydrangea-like morphology account for the boosted HCHO-sensitive performance. This work not only highlights the promising combination of metal oxides and CQDs but also provides valuable inspiration and theoretical perspectives for 3D/0D heterojunction construction.