Simultaneous Observation of Visible Upconversion and Near-Infrared Downconversion in SrF₂:Nd³⁺/Yb³⁺/Er³⁺ Nanocrystals and Their Application for Detecting Metal Ions under Dual-Wavelength Excitation

Abstract

In this work, a sequence of Nd 3+ , Yb 3+ , and Er 3+ tridoped SrF 2 nanocrystals (NCs) is synthesized by a hydrothermal method. Both the efficient near-infrared downconversion luminescence (DCL) and visible upconversion luminescence (UCL) of the Er 3+ and Nd 3+ ions are simultaneously observed and systematically demonstrated under dual-wavelength excitation (808 and 980 nm continuous-wave lasers). Subsequently, the SrF 2 :Nd 3+ /Yb 3+ /Er 3+ (15/4/0.2 mol %) NCs with the strongest luminescence were utilized for detecting the metal ion concentrations under 808 nm excitation. The results reveal that both the UCL and DCL gradually decrease as the metal ion concentrations increase, and high sensitivity is obtained for Cu 2+ ions with a detection limit of 0.22 nM (∼650 nm) and 0.63 nM (∼976 nm). In addition, these SrF 2 :Nd 3+ /Yb 3+ /Er 3+ NCs are further demonstrated to achieve a solid-state display under 980 nm excitation, exhibiting obvious “red” and “green” patterns by varying the doping rare earth ion concentrations.

Toward Ultra-High Sensitivity Optical Thermometers and Bright Yellow LEDs Based on Phonon-Assisted Energy Transfer in Rare Earth-Doped La2ZnTiO6 Double Perovskite

“…The only difference is that Er 3+ and Nd 3+ will undergo cross-relaxation after codoping: (Nd 3+ : 4 I 9/2 ) + (Er 3+ : 4 F 9/2 ) → (Er 3+ : 4 I 15/2 ) + (Nd 3+ : 4 F 9/2 ). This process promotes the particle number distribution of (Nd 3+ : 4 F 9/2 ), which then radiates to 4 F 7/2 and achieves emission at 759 nm ( 4 F 7/2 → 4 I 9/2 ) …”

“…This process promotes the particle number distribution of (Nd 3+ : 4 F 9/2 ), which then radiates to 4 F 7/2 and achieves emission at 759 nm ( 4 F 7/2 → 4 I 9/2 ). 38 2.5. The Temperature Sensing Properties in LZTO: Yb 3+ , Ln 3+ Phosphors.…”

Achieving ultrasensitive temperature sensing through non-thermally coupled energy levels to overcome energy gap constraints

“…[1][2][3] Actually, there exists a series of temperature-dependent optical parameters that can be employed for the purpose of temperature detection, among which the fluorescence intensity ratio (FIR) between two thermally coupled energy levels (TCLs) of lanthanide ions shows tremendous potential to accurately extract the temperature information due to its independence of background noise, excitation source and other factors. 4,5 For instance, our group has reported the temperature sensing performance of BaY 2 O 4 :Yb 3+ /Er 3+ based on the thermally coupled Stark sublevels of the Er 3+ : 4 F 9/2 state, revealing high thermometric sensitivity with the penetration depth in the biological tissues of approximately 6 mm. [6][7][8] Generally speaking, the thermometric sensitivity of TCLbased optical thermometers is proportional to the corresponding energy gaps (ΔE), which are confined within the range of 200 cm −1 -2000 cm −1 to avoid the occurrence of the decoupling effect.…”