Laser Transfer of Upconversion Nanoparticles

A method of the transfer of NaYF₄:Yb³⁺Tm³⁺/NaYF₄ upconversion core/shell nanoparticles with an average size of 30 nm via laser-induced forward transfer is proposed. The method provides a high spatial resolution by creating a “sandwich” structure on the donor substrate: for reliable fixation, nanoparticles are located between gold layers 50 and 20 nm thick. The transfer of upconversion nanoparticles is implemented by focusing nanosecond laser radiation into a 30-μm-diameter spot and at optimal pulse energies of 8.5–25 μJ. It has been shown that, despite large temperature, $$\Delta T > 1000{\kern 1pt} $$ K, and pressure, $$\Delta P > 150{\kern 1pt} $$ MPa, fluctuations upconversion nanoparticles fully retain their photoluminescent characteristics.