Visible and ultraviolet upconversion emission in LiNbO3 triply doped with Tm3+, Yb3+, and Nd3+

Abstract

Visible and ultraviolet upconversion (UC) emission is observed under 800 nm femtosecond laser excitation in LiNbO3 crystals triply doped with Tm3+, Yb3+, and Nd3+ at room temperature. Energy transfer (ET) from Nd3+ to Yb3+ then to Tm3+ is very important in this UC emission process. The overlapping between the emissions of D12→F34 and G14→H36, which makes up of blue emission band, is confirmed by transient investigation. From the pump energy dependence investigation, it is known that the dominant populating mechanism for the G14 state is the two-photon process, and that for D12 is the three-photon process. In our UC emission model, the G14 state is populated by the ET of F25/2(Yb3+)+H34(Tm3+)→F27/2(Yb3+)+G14(Tm3+), D12 state is populated by the ET of F32+H34→D12+H36 among Tm3+ ions. For LiNbO3 crystals doped with Tm3+ to the concentration of 0.9 mol %, the measured lifetimes of G14 and D12 are ∼80 and 4 μs.

Engineering the Upconversion Nanoparticle Excitation Wavelength: Cascade Sensitization of Tri‐doped Upconversion Colloidal Nanoparticles at 800 nm

“…It has been reported that the excited Nd 3+ on the 4 F 5/2 level can relax to the lower 4 F 3/2 level and then sensitize the ground state Yb 3+ ions nearby via resonance energy transfer . For example, previously, in glass ceramics and bulk crystal materials, spectroscopic physics studies have experimentally validated the feasibility of such a 800 nm pumped upconversion process . However, unlike colloidal dispersible nanoparticles, due to their size dimensions, uncontrolled morphology, low upconversion efficiency, and surface chemistry, these bulk materials are rather problematic for biological usages .…”

“…For example, previously, in glass ceramics and bulk crystal materials, spectroscopic physics studies have experimentally validated the feasibility of such a 800 nm pumped upconversion process . However, unlike colloidal dispersible nanoparticles, due to their size dimensions, uncontrolled morphology, low upconversion efficiency, and surface chemistry, these bulk materials are rather problematic for biological usages . Yet, it has been a great challenge to achieve Nd 3+ sensitized strong upconversion inside small colloidal monodisperse UCNPs.…”

Controlling lanthanide-doped upconversion nanoparticles for brighter luminescence

“…Shifting the excitation wavelength from heating 980 nm of Yb 3+ sensitizers to nonheating 800 nm of Nd 3+ sensitizers is desirable for biological applications. However, detrimental ET processes from activators to Nd 3+ in A,Yb,Nd-tridoped (A = Ho, Tm) systems only allows for the doping of Nd 3+ at very low concentration (typically < 2%) [51][52][53], leading to weak absorption at 800 nm and thus weak UCL compared with that of Yb 3+ -sensitized UCNPs at 980 nm. Remarkably, Nd 3+ -sensitized UCNPs with comparable intensity to Yb 3+ -sensitized ones can be obtained by unidirectional ET of Nd 3+ → Yb 3+ → A 3+ via introducing a rational core@shell structure [50,54]: a high concentration of Nd 3+ (~20%) is selectively doped within the active shell for effective harvesting of light, while keeping a low concentration of dopants within the core to minimize concentration quenching, as shown in figure 5(b).…”

Nd3+ Sensitized Up/Down Converting Dual-Mode Nanomaterials for Efficient In-vitro and In-vivo Bioimaging Excited at 800 nm

“…Interestingly, Yb 3+ ions can play a role of an energy-transfer bridging ions between an energy donor (Nd 3+ ) ion and energy acceptor RE 3+ ions (Er 3+ , Tm 3+ , Ho 3+ , Pr 3+ and Tb 3+ ) under excitation at 800 nm303132. Up to now, the Nd 3+ -Yb 3+ -RE 3+ system has been explored in glass hosts under 800-nm excitation.…”

“…If this Nd 3+ ion sensitized UC system can be realized in the nanomaterials, it could further push forward the bioapplications of UC system with less heat effect and better tissue penetration properties394041. Furthermore, the DC luminescence of Nd 3+ doped bulk materials has also been extensively investigated such as the excellent laser medium due to the large absorption cross section and high optical conversion efficiency (~53%)323334. Therefore, if we can engineer the nanostructure of the nanomaterials with both above mentioned Yb 3+ -Nd 3+ -RE 3+ UC system and Nd 3+ doped DC system at the same time, we could realize the Nd 3+ sensitized UC/DC dual-mode nanoprobe under the single excitation around 800 nm with the low heat effect and highly efficient bioimaging function.…”