Lanthanide-doped KMgF₃ upconversion nanoparticles for photon avalanche luminescence

Lanthanide (Ln³⁺)-doped photon avalanche (PA) upconversion nanoparticles (UCNPs) will be utilized in super-resolution bioimaging, miniaturized lasers, single-molecule monitoring and quantum optics.

Nevertheless, it stays difficult to comprehend photon avalanche in colloidal Ln³⁺-doped UCNPs at room temperature because of the deleterious quenching impact related to floor and lattice OH^– defects.

A analysis group led by Prof. Chen Xueyuan from the Fujian Institute of Analysis on the Construction of Matter of the Chinese language Academy of Sciences has developed a novel strategy primarily based on the pyrolysis of KHF₂ for managed synthesis of Ln³⁺-doped KMgF₃ UCNPs, which may successfully defend Ln³⁺ from luminescence quenching by floor and inner OH^– defects, and thereby increase upconversion luminescence.

The research was printed in Nano Letters on Sept. 8.

The researchers demonstrated that the KHF₂ precursor might successfully forestall the technology of OH^– defects through the progress of UCNPs, which resulted in extremely environment friendly upconversion luminescence in Yb³⁺/Er³⁺ and Yb³⁺/Ho³⁺ co-doped KMgF₃ UCNPs, with upconversion quantum yields of ～3.8% and ～1.1%, respectively, underneath 980 nm excitation at a energy density of 20 W cm^-2.

Particularly, because of the suppressed OH^– defects and enhanced cross-relaxation fee between Tm³⁺ ions within the aliovalent Tm³⁺-doped system, the researchers realized environment friendly photon avalanche luminescence from Tm³⁺ at 802 nm in KMgF₃: Tm³⁺ UCNPs upon 1,064 nm excitation at room temperature, with a large nonlinearity of ～27.0, a photon avalanche rise time of 281 ms, and a threshold of 16.6 kW cm^-2.

Moreover, the researchers revealed the distinctive benefits of KHF₂ for the managed synthesis of KMgF₃: Ln³⁺ UCNPs, which endowed the UCNPs with tunable measurement, improved crystallinity, a lowered variety of floor and lattice defects (usually OH^–), and concomitantly improved upconversion luminescence and near-infrared-II downshifting luminescence efficiencies.

This research gives an strategy for the event of extremely environment friendly photon avalanche UCNPs with large nonlinearities by way of aliovalent Ln³⁺ doping and crystal lattice engineering.