Study of a formaldehyde sensor based on cellulose nanocrystals

Since formaldehyde poses a major threat to human health, it is critical to perform convenient, rapid, and specific formaldehyde detection. Owing to their interesting optical features, iridescent films consisting of chiral nematic liquid crystal phases of cellulose nanocrystals (CNC) have attracted the attention of researchers. As a result, the widebandgap n-type semiconductor SnO2 and CNC, which have stable and outstanding gas-sensitive features as well as high optoelectronic performance, were combined to create biomass-derived chiral nematic composite films. Therefore, a biomass-derived chiral nematic composite film was prepared by combining the wide-band-gap n - type semiconductor SnO2 with stable, excellent gas-sensing characteristics and optoelectronic properties with CNC. Formaldehyde can be integrated into the nematic layer of CNC films and the formaldehyde gas is detected on the CNC. The formed composite film shows yellow, green, and purple structural colors for different formaldehyde concentrations, realizing the recognition by the naked eye of formaldehyde. This produces a red shift in the reflected wavelength and an effective chromaticity jump. This hybrid thin film is expected to advance a new gas-sensing system for rapid and efficient in situ qualitative investigations.