Enhanced fluorescence and structural characteristics of carboxymethyl cellulose/Eu(III) nano-complex: Influence of reaction time

• The fluorescent CMC/Eu nanocomplexes were developed.
• Reaction time has influence on the particle size and fluorescence intensity.
• CMC can play as a sensitizer to transfer energy to the Eu(III).
• The optimal reaction time of the CMC/Eu was 35 min.

CMC/Eu(III) nano-complexes were synthesized by reacting Eu3+ with carboxymethyl cellulose (CMC). The SEM and EDS showed that particle size was less than 100 nm and evenly distributed. FTIR and XPS indicated that the oxygen atoms in COO -, OH, and COC were involved in the complexation with Eu3+, yet, the O atoms were involved in different positions on anhydroglucose rings depending on reaction time. It was found that there were good energy matches between energy levels on ground state of CMC and 5D0 Eu(III). Moreover, the intensities of 5D0 → 7F2 of the nano-complexes were stronger than that of 5D0 → 7F1, which indicated that the Eu(III) was not in the center of symmetry. The optimized reaction time was 35 min, at this reaction time the smallest particle size and uniform distribution was obtained, the coordination structure was advantageous for the energy absorption transfer and emission.