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 Em spectra of europium complexes consist of multiple bands of Em at 585, 597, 612 and 650 nm, which are assigned to 5 D0 →7 FJ (J = 0-3) transitions of Eu3+ , respectively. The maximum Em peak is at 621 nm, which indicates a strong red Em characteristic associated with the electric dipole 5 D0 →7 F2 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 Em at 619 nm. Moreover, these particles can substitute red luminescent organic dyes for intracellular trafficking and cellular imaging agents.