utilizing upconverting nanoparticles as optical pH sensors

The ability to measure pH on a cellular scale has a wide range of potential use in biology and medicine. In this paper, we describe our work on creating a nanoscale pH sensor via the conjugation of upconverting nanoparticles (UCNPs) with a fluorescent dye. We will the explain the origin of the optical pH sensitivity, the conjugation procedure, as well as the various measurement techniques used to confirm the sensitivity. These nanoparticles allow simple optical sensing of pH without complicated intensity calibration process and could thus be widely applicable to many complex biological systems.