Orthogonal shortwave infrared emission based on rare earth nanoparticles for interference-free logical codes and bio-imaging.

Shortwave infrared (SWIR) photoluminescence has received intense interest in many fields in recent years thanks to the advantages of its wide wavelength range and high tissue imaging ability and it is invisible to the naked eye. However, achieving orthogonal SWIR emission still remains a challenge. In the present study, synthesized NaErF@NaLuF (Er@Lu) and NaYF:Nd@NaLuF (Y:Nd@Lu) nanoparticles emitted atom-like SWIR emission, and the separation distance between the SWIR emission was beyond 50 nm, which permitted orthogonal SWIR signal acquirement with optical filters. Furthermore, an invisible logical code was designed by manipulating the orthogonal SWIR emission of the lanthanide fluoride nanoparticles, and was further operated by basic logical operations and applied in information encryption and anti-counterfeit fields. In addition, the emission between these two hydrophilic nanoparticles could also be separated without signal interference and the orthogonal SWIR imaging mode was achieved, which was demonstrated in a bio-imaging experiment . This demonstration extended the orthogonal SWIR emission capacity by controlling the orthogonal emission, opening new opportunities in the fields of data security, disease diagnosis and non-interference label .