Self-assembled multidye-sensitized erbium single molecules for boosting energy transfer light upconversion in...

Area of Science:

• Photochemistry and Photophysics
• Supramolecular Chemistry
• Materials Science

Background:

• Efficient light upconversion requires high absorption coefficients and quantum yields for maximum brightness.
• Molecular upconversion is limited by non-radiative relaxation due to the thermal vibrational bath, restricting quantum yields.
• Achieving detectable linear light upconversion in single molecules necessitates the arrangement of multiple dye molecules around lanthanide ions.

Purpose of the Study:

• To develop a molecular system for efficient near-infrared (NIR) to visible (VIS) light upconversion.
• To overcome the limitations of low quantum yields in molecular upconversion through strategic molecular design and self-assembly.
• To demonstrate a record brightness for molecular-based upconversion processes.

Main Methods:

• Synthesized a trinuclear triple-stranded helicate complex, [ZnErZn(L5)3]10+, featuring a central Er(III) ion coordinated by three cationic IR-780 cyanine dyes.
• Utilized self-assembly processes to achieve precise arrangement of dye molecules around the lanthanide ion.
• Investigated the upconversion process via energy transfer upconversion (ETU) mechanism upon excitation with NIR light (801 nm) in acetonitrile at room temperature.

Main Results:

• Demonstrated NIR to VIS light upconversion in the synthesized molecular complex.
• Achieved a quantum yield (ΦUC) of 3.6 × 10^-8 for the upconversion process.
• Reported a record brightness (B^UC) of 2.8 × 10^-2 M^-1 cm^-1 for a molecular-based upconversion system.

Conclusions:

• The self-assembly strategy enables efficient light upconversion by maximizing the proximity and interaction between sensitizer dyes and the lanthanide emitter.
• The developed molecular system exhibits unprecedented brightness for molecular upconversion, paving the way for applications in sensing, imaging, and energy conversion.
• This work highlights the potential of supramolecular chemistry in designing advanced photofunctional materials.