Solvent-Dependent Upconversion Luminescent Studies of Single and Colloidal Nanoparticles

The routinely employed ensemble and individual luminescent nanoparticles play pivotal roles in nanoscience applications. In this study, water-dispersed NaYF₄:Yb, Er, and NaYF₄:Yb, Er@SiO₂ nanoparticles were synthesized to investigate solvent-dependent upconversion emissions. These prepared particles were used to examine both ensemble and single-particle behavior in various solvents, including dimethylformamide (DMF), chloroform (CHCl₃), ethanol (C₂H₅OH), acetone (C₃H₆O), deuterium oxide (D₂O), and water (H₂O). It has been observed that the matching of vibration frequency of OH groups in water leads to a substantial quenching in emission in bulk as well as at single particles, whereas D₂O has minimal effect on the upconversion luminescence. In the case of organic medium, the -CH vibrations are responsible for the emission quenching of the upconversion particle. In addition, it is observed that the thin silica shell of thickness ∼3 nm ± 0.5 nm has little influence on the medium-influenced emission quenching. The nature of medium-dependent emission quenching is found to be different for particles in an ensemble as well as at a single-particle level.