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 Eu(3+) complexes were synthesized by a step-wise process. The β-diketonate Eu(3+) 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 (5)D(0)→(7)F(J (J = 0–3)) transitions of Eu(3+), respectively. The maximum E(m) peak is at 621 nm, which indicates a strong red E(m) characteristic associated with the electric dipole (5)D(0)→(7)F(2) transition of Eu(3+) 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.