UV Light Generation and Challenging Photoreactions Enabled by Upconversion in Water

Area of Science:

• Photochemistry
• Sustainable Chemistry
• Materials Science

Background:

• Sensitized triplet-triplet annihilation (sTTA) is a key mechanism for visible light energy pooling.
• Previous sTTA applications were confined to organic solvents, with energy limits around 3.6 eV.
• There is a need for efficient upconversion systems in aqueous media for sustainable applications.

Purpose of the Study:

• To demonstrate blue-light driven upconversion in water using novel iridium complexes and naphthalenes.
• To achieve singlet-state energies approaching 4 eV for challenging photoreduction reactions.
• To establish the feasibility of using low-power light sources for water pollutant degradation.

Main Methods:

• Synthesis of tailor-made iridium complexes and naphthalenes.
• Implementation of sensitized triplet-triplet annihilation (sTTA) in aqueous solutions.
• Photoreduction experiments including aryl-bromide bond activation and ammonium compound decomposition.

Main Results:

• Demonstrated blue-light driven upconversion in water with singlet-state energies approaching 4 eV.
• Achieved challenging photoreduction reactions, including aryl-bromide bond activation.
• Successfully decomposed a persistent ammonium compound using a continuous wave laser and an LED light source.

Conclusions:

• The study presents the first proof-of-concept for blue-to-UV upconversion in water.
• Developed a system capable of driving energy-demanding photoreductions with high efficiency.
• Highlights the potential for sustainable light-harvesting applications using low-power light sources.