Enhancing generating and collecting efficiency of single particle upconverting luminescence at low-level power excitation

Upconverting luminescent nanoparticles are photostable, non-blinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probe at single-molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) is achieved with highly doped rare-earth ions co-doped (20% Yb 3+ ) using high excitation power (>2.5 MW/cm 2 ). However, such particles are inadequate for in-vitro live-cell imaging and single-particle tracking since high excitation power can cause photodamage. Here, we compared UCNPs luminescence intensities with different dopants concentrations and presented a more efficient (∼7x) UCNPs at low excitation power by increasing the concentrations of Yb 3+ and Tm 3+ dopants (NaYF 4 : 60% Yb 3+ , 8% Tm 3+ ) and adding a core-shell structure.