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

All in good time: The effects of the solvothermal reaction time on the crystalline phase of polyethylenimine-coated NaYF₄ : Yb³⁺/Er³⁺ upconversion nanoparticles (UCNPs) were studied. Reaction time prolongation was effective in increasing the ratio of green (²H_11/2 and ⁴S_3/2→⁴I_15/2) to red (⁴F_9/2→⁴I_15/2) emission (G/R ratio) without morphological changes as well as the α- to β- phase conversion. This resulted in a high quantum yield of upconversion and an appropriate G/R ratio for the photosensitization of singlet oxygen generation. Consequently, the efficiency of the amyloid fibril decomposition cascade was enhanced.

Abstract

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 α- to hexagonal β-forms with a higher upconversion quantum yield. In addition, the prolonged reaction time effectively increased the ratio of green (²H_11/2 and ⁴S_3/2→⁴I_15/2) to red (⁴F_9/2→⁴I_15/2) emissions, increasing the ¹O₂ 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.

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