Liquid PEG Polymers Containing Antioxidants: A Versatile Platform for Studying Oxygen-Sensitive Photochemical
Cédric Mongin1, Jessica H Golden2, Felix N Castellano1
1Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States.
ACS Applied Materials & Interfaces
|August 2, 2016
Summary
Green liquid polyethylene glycol (PEG) polymers with oleic acid (OA) offer a novel, oxygen-depleted medium for studying sensitive photochemical processes like triplet-sensitized upconversion. This stable, accessible system enhances photochemical reactions and opens doors for new applications.
Area of Science:
- Photochemistry
- Materials Science
- Green Chemistry
Background:
- Oxygen-sensitive photochemical processes are often hindered by dissolved oxygen, limiting experimental conditions and applications.
- Traditional methods for oxygen removal can be cumbersome or lead to solvent degradation.
- There is a need for stable, accessible, and environmentally friendly media for studying oxygen-intolerant photochemistry.
Purpose of the Study:
- To investigate the use of "green" liquid polyethylene glycol (PEG) polymers with oleic acid (OA) as an oxygen-depleted medium for photochemical studies.
- To evaluate the efficiency of triplet-sensitized photochemical upconversion in PEG media.
- To explore the potential of these PEG-based systems for long-term, stable photochemical applications.
Main Methods:
- Three PEG polymers (PEG-200, PEG-400, PEG-600) were used as reaction media, with oleic acid as an oxygen scavenger.
- Triplet-sensitized upconversion using platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as sensitizer and 9,10-bisphenylethynylanthracene (BPEA) as acceptor/annihilator was investigated.
- Oxygen consumption, excited-state lifetimes, upconversion quantum efficiency, and long-term stability were measured under ambient conditions.
Main Results:
- PEG polymers provided an oxygen-depleted environment superior to common organic solvents, with high chromophore solubility and diffusion.
- Efficient and quantitative oxygen consumption was achieved in PEG, leading to increased sensitizer excited-state lifetimes.
- Bright and stable upconverted singlet fluorescence from BPEA was observed, with no intensity decrease over 20 hours in PEG 200, achieving a 31% quantum efficiency.
Conclusions:
- Liquid PEG polymers with OA are effective, stable, and green media for studying oxygen-sensitive photochemistry, particularly triplet-sensitized upconversion.
- The developed PEG systems offer significant advantages over traditional organic solvents, enabling high quantum efficiencies and long-term stability.
- The potential for solid-state integration suggests broad applicability in real-world photochemical devices and studies.
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