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Optimizing the Distance between Upconversion Thin Films and Silver Nanoprisms for the Design of a High-Performance
Jotaro Honda1, Kosuke Sugawa1, Seiya Fukumura1
1Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Chiyoda, Tokyo 101-8308, Japan.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 3, 2023
Summary
Researchers explored how distance affects triplet-triplet annihilation upconversion (TTA-UC) with silver nanoprisms. Optimal enhancement occurred at 12.6 nm, longer than typical metal-enhanced fluorescence, due to competing beneficial and detrimental effects.
Area of Science:
- Plasmonics
- Photochemistry
- Materials Science
Background:
- Metal-enhanced fluorescence (MEF) distance dependence is well-studied.
- Distance dependence of triplet-triplet annihilation upconversion (TTA-UC) is unexplored.
- TTA-UC systems combine sensitizers and emitters for light upconversion.
Purpose of the Study:
- Investigate the influence of spatial distance between silver nanoprisms (AgPRs) and TTA-UC films on upconverted (UC) emission.
- Determine the optimal distance for maximizing UC emission enhancement.
- Understand the competing mechanisms governing plasmonic enhancement in TTA-UC.
Main Methods:
- Fabrication of TTA-UC thin films with palladium octaethylporphyrin (PdOEP) sensitizer and 9,10-diphenylanthracene (DPA) emitter.
- Controlled spatial separation of AgPRs and TTA-UC films.
- Spectroscopic analysis of UC emission and related photophysical parameters.
Main Results:
- Optimal UC emission enhancement observed at a distance of 12.6 nm, significantly longer than typical MEF systems.
- AgPRs enhance PdOEP photoexcitation rate but detrimentally affect triplet-triplet energy transfer (TTET), triplet excited DPA lifetime, and DPA fluorescence efficiency.
- UC emission quenching is primarily due to decreased triplet excited DPA lifetime and secondarily due to reduced DPA fluorescence efficiency, especially at short distances.
Conclusions:
- The distance dependence of plasmonic enhancement in TTA-UC systems arises from a balance between enhanced photoexcitation and plasmon-induced nonradiative decay.
- Detrimental effects on triplet and singlet excited states are significant, particularly at short AgPR-TTA-UC distances.
- Findings provide guidelines for designing efficient plasmonic TTA-UC systems by optimizing the AgPR-TTA-UC spatial relationship.
