Variation in Singlet Oxygen Generation in Dye-Conjugated Satellite Silver Nanoparticles on Silica Nanoparticles

Understanding singlet oxygen (¹O₂) generation in plasmon-coupled photosensitiser systems is important for the design of photodynamic nanomaterials. In this study, silica nanoparticles decorated with satellite silver nanoparticle-photosensitiser conjugates (SiO₂-Ag-dye) were prepared using three representative photosensitisers: Rose Bengal (RB), protoporphyrin IX (PpIX), and coumarin-3-carboxylic acid (C3CA). ¹O₂ generation measurements showed lower singlet oxygen quantum yields (Φ_Δ) for all nanoparticle-bound dyes than for the corresponding free dyes. Among the investigated systems, SiO₂-Ag-PpIX retained approximately 80% of the ¹O₂ generation activity observed for the corresponding free dye (Φ_Δ = 0.45 ± 0.04), whereas SiO₂-Ag-RB (Φ_Δ = 0.31 ± 0.15) and SiO₂-Ag-C3CA (Φ_Δ = 0.12 ± 0.02) retained only approximately 40% of the corresponding free-dye activity. These results suggest that the photophysical behaviour and ¹O₂ generation efficiency of Ag-based dye-nanoparticle systems depend strongly on the immobilised photosensitiser. The findings provide insight into the interactions between plasmonic nanostructures and photosensitisers and may assist the future design of photodynamic nanomaterials. The present study should be regarded as a proof-of-concept demonstration of dye-dependent plasmonic modulation of ¹O₂ generation. Evaluation of practical photodynamic performance, photostability, and reusability will be the subject of future studies.