Using rice straw as a carbon source, photoluminescent carbon nanodots (CNDs) were quickly prepared by pyrolysis under insufficient air flow and ultrasonic methods without the addition of other chemical reagents. This method is simple and environmentally friendly. The prepared CNDs have quasispherical nanoparticles with the average diameter of 5.8 nm observed from TEM image, and have good fluorescence performance with the quantum yield of 5.1%. The CNDs possess a clear correlation between photoluminescence wavelength and intensity and excitation wavelength, as well as good water solubility and salt resistance. In addition, the luminescent CNDs can not only be effectively taken up by HeLa cells and HUVECs but also exhibit low cytotoxicity and good biocompatibility from CCK8 test and laser confocal imaging observations, respectively, making them promising complement to future cellular imaging assay applications. Moreover, the prepared CNDs can be used as ion sensors to selectively and sensitively detect Fe3+ ions in the concentration range of 0–1000 μM with a detection limit of 300 nM. Our proposed strategy for preparing carbon nanodots explores a new way to obtain fluorescent carbon materials and avoid environmental pollution caused by burning straw.
