Applicability Comparison of 800 nm and 980 nm Excitable Upconversion Nanoparticles to Single Biological Molecule Study

For many years upconversion nanoparticles based on rare earth doping of inorganic crystal matrices have been proposed as a useful instrument for single molecule biological experimentation. Recently the nanoscale temperature sensing capabilities of Erbium sensitized upconversion nanoparticles has come into strong focus indicating yet another advantage over conventional fluorescent dyes for single molecule study. However, the fluences necessary for two photon upconversion must be compatible with the biological molecules of study in aqueous environments. This has led to many investigations of the ability of Neodymium doping to improve the efficiency of upconversion nanoparticles at 800 nm excitation thus improving their compatibility to biological experimentation. In this work, a comparison of the photophysics and nanothermal sensing ability of 800 nm and 980 nm excitation in Erbium activated upconversion nanoparticles is presented. Further, Ytterbium only sensitization is contrasted with dual sensitization with Ytterbium and a Neodymium doped shell. In addition, the compatibility of DNA molecules in tightrope scenarios with fluences necessary for efficient upconversion is examined.