Tb3+/Eu3+ Complex-Doped Rigid Nanoparticles in Transparent Nanofibrous Membranes Exhibit High Quantum Yield Fluorescence

Red-Emitting Latex Nanoparticles by Stepwise Entrapment of β-Diketonate Europium Complexes

The core-shell structure of poly(St-co-MAA) nanoparticles containing β-diketonate Eu³⁺ complexes were synthesized by a step-wise process. The β-diketonate Eu³⁺ complexes of Eu (TFTB)₂(MAA)P(Oct)₃ [europium (III); 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione = TFTB; trioctylphosphine = (P(Oct)₃); methacrylic acid = MAA] were incorporated to poly(St-co-MAA). The poly(St-co-MAA) has highly monodispersed with a size of 300 nm, and surface charges of the poly(St-co-MAA) are near to neutral. The narrow particle size distribution was due to the constant ionic strength of the polymerization medium. The activated carboxylic acid of poly(St-co-MAA) further chelated with europium complex and polymerize between acrylic groups of poly(St-co-MAA) and Eu(TFTB)₂(MAA)P(Oct)₃. The E_m spectra of europium complexes consist of multiple bands of E_m at 585, 597, 612 and 650 nm, which are assigned to ⁵D₀→⁷F_{J (J = 0-3)} transitions of Eu³⁺, respectively. The maximum E_m peak is at 621 nm, which indicates a strong red E_m characteristic associated with the electric dipole ⁵D₀→⁷F₂ transition of Eu³⁺ complexes. The cell-specific fluorescence of Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA) indicated endocytosis of Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA). There are fewer early apoptotic, late apoptotic and necrotic cells in each sample compared with live cells, regardless of the culture period. Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA) synthesized in this work can be excited in the full UV range with a maximum E_m at 619 nm. Moreover, these particles can substitute red luminescent organic dyes for intracellular trafficking and cellular imaging agents.

Stable Fluorescence of Eu3+ Complex Nanostructures Beneath a Protein Skin for Potential Biometric Recognition

We designed and realized highly fluorescent nanostructures composed of Eu3+ complexes under a protein coating. The nanostructured material, confirmed by photo-induced force microscopy (PiFM), includes a bottom fluorescent layer and an upper protein layer. The bottom fluorescent layer includes Eu3+ that is coordinated by 1,10-phenanthroline (Phen) and oleic acid (O). The complete complexes (OEu3+Phen) formed higher-order structures with diameter 40-150 nm. Distinctive nanoscale striations reminiscent of fingerprints were observed with a high-resolution transmission electron microscope (HRTEM). Stable fluorescence was increased by the addition of Eu3+ coordinated by Phen and 2-thenoyltrifluoroacetone (TTA), and confirmed by fluorescence spectroscopy. A satisfactory result was the observation of red Eu3+ complex emission through a protein coating layer with a fluorescence microscope. Lanthanide nanostructures of these types might ultimately prove useful for biometric applications in the context of human and non-human tissues. The significant innovations of this work include: (1) the structural set-up of the fluorescence image embedded under protein "skin"; and (2) dual confirmations of nanotopography and unique nanofingerprints under PiFM and under TEM, respectively.

NIR-Fluorescent Hybrid Materials of Tm3+ Complexes Carried by Nano-SiO2 via Improved Sol-Gel Method

Tm³⁺ has obvious emission characteristics in the near-infrared band. Thulium ions combined with different organic ligands lead to different fluorescent properties. In the near-infrared region, Tm³⁺ is a down-conversion fluorescent material that is unstable under high temperature and acidic conditions. Moreover, in those complex environments, the fluorescence from Tm³⁺ complex is usually degraded. In this work, two kinds of near-infrared fluorescent complexes, Tm(TTA)₃phen and Tm(DBM)₃phen, were prepared, and the intensity of their fluorescence is compared. The fluorescence intensity at 802 nm is greatly improved compared with Tm(TTA)₃phen, and the intensity of the emission at 1235 nm and 1400-1500 nm is also enhanced. Moreover, the emission lifetime of SiO₂-Tm(TTA)₃phen is 50.38 μs. Tm(TTA)₃phen complex and SiO₂-Tm(TTA)₃phen hybrid materials have better fluorescence than Tm(DBM)₃phen and SiO₂-Tm(DBM)₃phen. Therefore, HTTA is a better choice of organic ligands for Tm³⁺. The NIR-fluorescent hybrid materials prepared have stronger fluorescence after combining with nano-SiO₂compared with pure Tm³⁺ complexes, and have stronger structural stability compared with pure nano-SiO₂.

Energy Transfer Study on Tb3+/Eu3+ Co-Activated Sol-Gel Glass-Ceramic Materials Containing MF3 (M = Y, La) Nanocrystals for NUV Optoelectronic Devices

In the present work, the Tb³⁺/Eu³⁺ co-activated sol-gel glass-ceramic materials (GCs) containing MF₃ (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 °C. The studies of Tb³⁺ → Eu³⁺ energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4fⁿ–4fⁿ optical transitions of Tb³⁺ (⁵D₄ → ⁷F_J, J = 6–3) as well as Eu³⁺ ions (⁵D₀ → ⁷F_J, J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the ⁵D₄ (Tb³⁺) and the ⁵D₀ (Eu³⁺) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET efficiency was also observed (from η_ET ≈ 16% for xerogels up to η_ET = 37.3% for SiO₂-YF₃ GCs and η_ET = 60.8% for SiO₂-LaF₃ GCs). The changes in photoluminescence behavior of rare-earth (RE³⁺) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO₂-MF₃:Tb³⁺, Eu³⁺ GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation.