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

The core-shell structure of poly(St- -MAA) nanoparticles containing β-diketonate Eu complexes were synthesized by a step-wise process. The β-diketonate Eu complexes of Eu (TFTB) (MAA)P(Oct) [europium (III); 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione = TFTB; trioctylphosphine = (P(Oct) ); methacrylic acid = MAA] were incorporated to poly(St- -MAA). The poly(St- -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- -MAA) further chelated with europium complex and polymerize between acrylic groups of poly(St- -MAA) and Eu(TFTB) (MAA)P(Oct) . The spectra of europium complexes consist of multiple bands of at 585, 597, 612 and 650 nm, which are assigned to D → F transitions of Eu , respectively. The maximum peak is at 621 nm, which indicates a strong red characteristic associated with the electric dipole D → F transition of Eu complexes. The cell-specific fluorescence of Eu(TFTB) (MAA)P(Oct) @poly(St- -MAA) indicated endocytosis of Eu(TFTB) (MAA)P(Oct) @poly(St- -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) (MAA)P(Oct) @poly(St- -MAA) synthesized in this work can be excited in the full UV range with a maximum at 619 nm. Moreover, these particles can substitute red luminescent organic dyes for intracellular trafficking and cellular imaging agents.