• Development of Spectrally Tuned, Erbium Doped NaYF4: Yb, Tm, Er Upconverting Nanoparticles and Their Applications

      Romanowski, Marek; Nguyen, Vina; Utzinger, Urs; Kim, Minkyu; Lynch, Ronald (The University of Arizona., 2020)
      Development and characterization of biomaterials capable of upconversion may enable new biomedical applications such as near-infrared (NIR) initiated photochemistry. Most photochemistry requires the 280 nm - 300 nm range of wavelength, regions of UV that often associated with the cause of melanoma, a deadly type of skin cancer, DNA damage, and oxidative stress [1]. Hence the low implementation of photochemical systems in biological environments. The primary characteristic of upconverting systems is the ability of the system to upconvert from energetically low NIR to the energetically high ultra-violet (UV) range. This UV energy can then be sequestered to a substrate to initiate photochemistry. Furthermore, characteristics of these upconverting systems can be modified in a manner that allows for the tuning of their spectral outputs to desired, energetically advantageous, profiles. In this thesis, we seek methods to modify the spectral output in upconversion to demonstrate the possibility of providing spectral output to an external substrate. The principal method to achieve this is to implement an ion Q that would intentionally interfere with the upconversion pathway in these nanoparticles. This quencher ion is tasked with providing a safe down conversion pathway from UV to the low energy region of the spectrum. The spectral output of these nanoparticles is characterized to determine the effects of the manipulation as different combinations of ions are explored. Finally, studies are conducted to demonstrate energy transfer to an external substrate from the nanoparticle to provide an experimental framework for future study of NIR initiated photochemistry.