Two-Photon Sensing and Imaging of Endogenous Biological Cyanide in Plant Tissues Using Graphene Quantum Dot/Gold Nanoparticle Conjugate

One main source of cyanide (CN-) exposure for mammals is through the plant consumption, and thus, sensitive and selective CN- detection in plants tissue is a significant and urgent work. Although various fluorescence probes have been reported for CN- in water and mammalian cells, the detection of endogenous biological CN- in plant tissue remains to be explored due to the high background signal and large thickness of plant tissue that hamper the effective application of traditional one-photo excitation. To address these issues, we developed a new two-photo excitation (TPE) nanosensor using graphene quantum dots (GQDs)/gold nanoparticle (AuNPs) conjugate for sensing and imaging endogenous biological CN-. With the benefit of the high quenching efficiency of AuNPs and excellent two-photon properties of GQDs, our sensing system can achieve a low detection limit of 0.52 mu M and deeper penetration depth (about 400 mu m) without interference from background signals of a complex biological environment, thus realizing sensing and imaging of CN- in different types of plant tissues and even monitoring CN- removal in food processing. To the best of our knowledge, this is the first time for fluorescent sensing and imaging of CN- in plant tissues. Moreover, our design also provides a new model scheme for the development of two-photon fluorescent nanomaterial, which is expected to hold great potential for food processing and safety testing.