Room-Temperature Upconversion in a Nanosized {Ln₁₅} Molecular Cluster-Aggregate.

Area of Science:

• Materials Science
• Photonics
• Chemistry

Background:

• Molecular upconversion, the process of absorbing low-energy photons to emit higher energy light, is challenging in molecular architectures.
• Existing methods face limitations due to phonon interactions and difficulties in controlling donor-acceptor atom ratios.
• Nanoparticles and solids offer alternatives but lack the precise control of molecular systems.

Purpose of the Study:

• To demonstrate efficient room-temperature molecular upconversion using molecular cluster-aggregates (MCAs).
• To overcome limitations of traditional molecular systems and low-phonon solids for upconversion.
• To develop a method for precise composition control in nanoscale molecular materials for enhanced upconversion.

Main Methods:

• Synthesis of a specific MCA containing 15 lanthanide ions ({Er2Yb13}) with an excess of donor atoms.
• Excitation of the synthesized MCA using ytterbium ion to observe characteristic erbium emissions.
• Preparation and study of four additional MCA compositions to elucidate the upconversion mechanism.

Main Results:

• Achieved characteristic green and red upconverted emissions from erbium at room temperature.
• Synthesized MCAs demonstrated upconversion quantum yields approximately 10^-3%, a significant improvement over previous systems.
• The {Er2Yb13} MCA showed 100,000 times higher efficiency compared to prior lanthanide-based molecular upconverters.

Conclusions:

• Molecular cluster-aggregates (MCAs) are effective for achieving efficient room-temperature molecular upconversion.
• The rational design of MCAs with controlled lanthanide ion composition enables enhanced upconversion properties.
• This approach offers a promising pathway for harnessing upconversion in nanoscale molecular materials.