Construction of active-inert core-shell structured nanocrystals for broad range multicolor upconversion luminescence

Area of Science:

• Materials Science
• Nanotechnology
• Photonics

Background:

• Rare earth doped upconversion luminescent nanomaterials display various emission colors.
• Upconversion nanoparticles (UCNPs) are crucial for applications requiring light conversion.

Purpose of the Study:

• To synthesize NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanoparticles.
• To achieve pure red and enhanced blue upconversion emissions.
• To explore multicolor emission generation for advanced applications.

Main Methods:

• Co-precipitation method for nanoparticle synthesis.
• Utilizing 980 nm and 1550 nm laser excitations.
• Characterization of upconversion luminescence properties.

Main Results:

• NaYF4:Er/Ho@NaYF4 nanocrystals produced pure red emission (R/G ratios of 23.3 and 25).
• Emission color shifted from red to yellow with increasing power due to energy level saturation.
• NaYbF4:Tm@NaYF4 nanocrystals showed a 58.3-fold intensity increase after shell coating, with CIE coordinates (0.1646, 0.0602).
• Mixing both types of UCNPs generated broad multicolor emissions (blue to red and yellow).

Conclusions:

• Designed core-shell UCNPs enable tunable and pure color emissions.
• Shell coating significantly enhances luminescence intensity and color purity.
• Mixed UCNPs offer a versatile platform for multicolor displays, anti-counterfeiting, and information coding.