Exfoliated near infrared fluorescent silicate nanosheets for (bio)photonics

Abstract

Imaging of complex (biological) samples in the near-infrared (NIR) is beneficial due toreduced light scattering, absorption, phototoxicity, and autofluorescence. However, there arefew NIRfluorescent materials known and suitable for biomedical applications. Here weexfoliate the layered pigment $CaCuSi_4O_{10}$ (Egyptian Blue, EB) via ball milling and facile tipsonication into NIRfluorescent nanosheets (EB-NS). The size of EB-NS can be tailored todiameters <20 nm and heights down to 1 nm. EB-NSfluoresce at 910 nm and thefluorescenceintensity correlates with the number of $Cu^{2+}$ ions. Furthermore, EB-NS display no bleachingand high brightness compared with other NIRfluorophores. The versatility of EB-NS isdemonstrated by in-vivo single-particle tracking and microrheology measurements inDro-sophila melanogasterembryos. EB-NS can be uptaken by plants and remotely detected in alow-cost stand-off detection setup. In summary, EB-NS have the potential for a wide range ofbioimaging applications.