Ultraviolet upconversion enhancement in triply doped NaYF4:Tm3+, Yb3+ particles: The role of Nd3+ or Gd3+ Co-doping

Abstract

Upconversion (UC) particles are currently under intensive investigation, normally for their visible instead of ultraviolet (UV) light luminescence under near-infrared (NIR)irradiation. As a commonly studied host, NaYF 4 in particular is known to have low phonon energy and high UC efficiency. Here, we present our work on enhancing UC luminescence in the UV region by adding a third dopant into a binary-doped NaYF 4 :Yb 3+ ,Tm 3+ host. More specifically, neodymium (Nd 3+ ) or gadolinium (Gd 3+ ) ions was co-doped into parent NaYF 4 :20mol%Yb 3+ ,0.5mol%Tm 3+ UC particles to enhance their UV UC luminescence. Experimental results demonstrated that these particles exhibited the highest degree of UV UC enhancements when co-doped with 0.05mol% Nd 3+ or 2.0mol% Gd 3+ , expanding the potential of this type of materials into many possible applications by directly converting NIR irradiation into UV light.Fundamentally, the UV UC emission dependence of these triply doped NaYF 4 :Yb 3+ ,Tm 3+ particles with different Nd 3+ and Gd 3+ doping concentrations was investigated in terms of ground state absorption, excited state absorption and energy transfer UC mechanisms.

Upconversion Luminescence of Silica–Calcia Nanoparticles Co-doped with Tm3+ and Yb3+ Ions

“…Rare-earth-activated systems have been demonstrated to be the pillar of photonic technologies enabling a broad spectrum of crucial applications in strategic social and economic priorities [1][2][3][4][5]. Systems based on rare-earth-doped upconverters are largely employed in bioimaging, drug delivery, laser, lighting, photon management, environmental sensing, and nanothermometry [6][7][8][9][10][11][12][13][14][15]. Upconversion (UC) mechanism is a process of energy transfer from a sensitizer in a proper host matrix, which is excited under lowenergy radiation (usually near infrared, NIR), to an emitter that emits higher energy photons than the excitation ones.…”

Ultraviolet Upconversion Luminescence in a Highly Transparent Triply-Doped Gd3+–Tm3+–Yb3+ Fluoride–Phosphate Glasses

“…Recently, special attention has been paid to various materials, particularly low-phonon energy fluoride nanocrystals as NaYF 4 and NaGdF 4 , jointly doped with Tm 3+ and Yb 3+ and triply-doped with Gd 3+ , Tm 3+ , and Yb 3+ . − Thulium ions have received increased interest because they have suitable metastable levels for UV UC emissions. Owing to their unique and simple energy level diagram with only a single transition ( 2 F 7/2 → 2 F 5/2 ), ytterbium ions are frequently introduced as sensitizer centers at ∼1 μm pumping wavelength, producing large enhancements of UC luminescence of Tm 3+ ions activators.…”

“…Thus, efficient UV UC emissions induced by near-IR light have been reported for some Tm 3+ –Yb 3+ codoped materials. − Owing to the large energy gap (32 000 cm –1 ) separating the Gd 3+ ground state 8 S 7/2 and the first excited state 6 P 7/2 , Gd 3+ levels cannot be populated directly by IR pumping. On the other hand, introduction of Gd 3+ to Tm 3+ –Yb 3+ codoped materials can provide additional UV UC emissions, important for building UV compact devices. ,,− Four UC emission peaks of Gd 3+ were observed in the range 190–210 nm, one at 253 nm, − three in the range 270–281 nm, − and one at 311 nm − involving up to seven photons processes. In glasses, some works report UV UC in Tm 3+ –Yb 3+ codoped fluoride glasses, , with the shortest emission observed at 290 nm upon near-IR excitation.…”

Eu3+ Sensitization via Nonradiative Interparticle Energy Transfer Using Inorganic Nanoparticles

“…Although this approach works for high migration ion concentrations, metal-to-metal charge transfer quenching is easily thermally activated and still dominates at elevated temperatures . In addition, energy migration effectively prevents charge transfer quenching only when no back-transfer to the sensitizer ion can occur, which is shown to be problematic for blue-excitable sensitizers such as cerium-doped garnets in combination with, for example, Tb 3+ or Pr 3+ . , Efficient nonradiative energy transfer and suppression of metal-to-metal charge transfer have also been demonstrated by physically separating sensitizer and emitter lanthanide ions in core/shell nanocrystal (NC) geometries − and have even been suggested for micrometer-sized particles . Core/shell geometries, however, greatly limit the choice of host lattice combinations because the crystal lattice parameters of the materials must be matched.…”