Enhanced Singlet Oxygen Generation via Near-Infrared Photo-Activated Upconversion: Application to Amyloid Fibril Degradation

In this study, we attempted to improve the quantum yield of upconversion nanoparticles to achieve high efficiency of amyloid fibril decomposition cascade induced by near-infrared-active upconversion nanoparticles complexed with photosensitizers. The effects of the solvothermal reaction time on the crystalline phase of polyethylenimine-coated NaYF4 : Yb3+/Er3+ were studied, while maintaining constant reaction temperature and concentration of the dopants Yb3+ and Er3+. We found that an increased reaction time resulted in the conversion of the crystalline phase from the cubic alpha- to hexagonal beta-forms with a higher upconversion quantum yield. In addition, the prolonged reaction time effectively increased the ratio of green (H-2(11/2) and S-4(3/2)-> I-4(15/2)) to red (F-4(9/2)-> I-4(15/2)) emissions, increasing the O-1(2) generation via photosensitization to approximately 10 times that of conventional ones. Consequently, the efficiency of the amyloid fibril decomposition cascade induced by upconversion nanoparticles complexed with photosensitizers was improved.