Green and Red Three‐Photon Upconversion from Polymeric Lanthanide(III) Complexes

Sensitization of Near‐Infrared‐Emitting Lanthanide Cations in Solution by Tropolonate Ligands

“…NIR luminescent lanthanide complexes are very promising reporters for detection in biological media for several reasons: 1) most lanthanide complexes do not photobleach,5 2) they display sharp emission bands that can be easily discriminated from background fluorescence,6 and 3) they exhibit long luminescent lifetimes, which allow the removal of background fluorescence (autofluorescence) and increased assay sensitivity through time‐resolved measurements 7. 8 Recent advances in technology allow such complexes to be excited in the NIR domain by using multiphoton excitation techniques 9. 10 So far, Nd and Yb complexes have been reported as NIR‐luminescent reporters for these applications.…”

Simultaneous Observation of Green Multiphoton Upconversion and Red and Blue NLO Processes from Polymeric Terbium(III) Complexes

“…[3] Multiphoton excitation allows molecules that typically absorb in the UV region to be excited with red or NIR light. The photoluminescence processes from organolanthanide complexes are usually induced by an organic chromophoric ligand that absorbs incident light and transfers its resultant excitation energy to the lanthanide ion.[4] Until now, only a few multiphoton processes in organolanthanide complexes have been observed owing to the limitations of experimental measurements.[5] Although there have been reports on lanthanide complexes that display second harmonic generation, these have been limited and focused only on glassy doped lanthanide materials.[6] In recent years, our group [7] and others [8] have investigated several high-order multiphoton processes from organic ligands and metal complexes. Herein we report, to the best of our knowledge, the first observation of rare multiphoton upconversion emission from a lanthanide complex as well as SHG and THG transmission phenomena, which occur simultaneously from the same excitation source in the IR region at l % 1.26 and 1.34 mm.…”

“…The chromophores and complexes are known to absorb two or more photons (l ex = 650 and 800 nm) and be excited to higher energy states with further energy transfer to the terbium center to produce green f-f emission (Figure 3 a). [7] Ligand L shows upconversion emission in the blue region (S 1 !S 0 ) upon three-photon absorption at l % 800 nm and four-photon absorption at l % 1.26 mm (see Supporting Information). Complex 1 exhibits a strong multiphoton absorption when excited by ultrashort laser pulses at l % 1.26 mm to produce the green structured upconversion emission bands of 1 that arise from the f-f transitions of the 5 D 4 !…”

“…However, the blue and green upconversion luminescence from both the ligand and the lanthanide complex can be seen under excitation at l = 1.26 and % 1.34 mm when generated by a Ti:sapphire laser. The chromophore absorbs at l % 330 nm (30 303 cm À1 ), [7] which indicates that the absorption of at least four photons is required for upconversion upon excitation at l % 1.26 mm (7937 cm À1 ) and % 1.34 mm (7462 cm À1 ), whereas for the ligand the accumulation of more than three photons is needed upon excitation at l % 1.34 mm to reach its lowest emitting state for upconversion emission. The Soga equation [9] is used in auxiliary to verify these SHG, THG, and upconversion processes (Figure 4 a-d).…”

Recent Progress in Photonic Upconversion Materials for Organic Lanthanide Complexes

“…The structure of the polymeric chain [Ln L15L16L17 (NO 3 ) 3 ] is shown in Figure 2 . At 845 nm excitation, Tb and Eu polymer chains exhibited green and red light, respectively, based on the ESA mechanism [ 34 ].…”