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Bis(bithienyl)-1,2-dicyanoethene (4TCE) is a photoswitch that operates via reversible E / Z photoisomerization following absorption of visible light. cis -to- trans photoisomerization of 4TCE requires excitation below 470 nm, is relatively inefficient (quantum yield < 5%) and occurs via the lowest-lying triplet. We present excitation-wavelength dependent (565–420 nm) transient absorption (TA) studies to probe the photophysics of cis -to- trans isomerization to identify sources of switching inefficiency. TA data reveals contributions from more than one switch conformer and relaxation cascades between multiple states. Fast (∼4 ps) and slow (∼40 ps) components of spectral dynamics observed at low excitation energies (>470 nm) are readily attributed to deactivation of two conformers; this assignment is supported by computed thermal populations and absorption strengths of two molecular geometries (P A and P B ) characterized by roughly parallel dipoles for the thiophenes on opposite sides of the ethene bond. Only the P B conformer is found to contribute to triplet population and the switching of cis -4TCE: high-energy excitation (<470 nm) of P B involves direct excitation to S 2 , relaxation from which prepares an ISC-active S 1 geometry (ISC QY 0.4–0.67, k ISC ∼ 1.6–2.6 × 10 −9 s −1 ) that is the gateway to triplet population and isomerization. We ascribe low cis -to- trans isomerization yield to excitation of the nonreactive P A conformer (75–85% loss) as well as loses along the P B S 2 → S 1 → T 1 cascade (10–20% loss). In contrast, electrocyclization is inhibited by the electronic character of the excited states, as well as a non-existent thermal population of a reactive “antiparallel” ring conformation.
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Direct conversion of thermal energy to stored electrochemical energy via a self-charging pyroelectrochemical cell
The concept of a pyroelectrochemical cell (PEC) as a self-charging power source for Internet of Things (IoT) sensors is explored through experimentation and simulation.
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- Award ID(s):
- 1936636
- PAR ID:
- 10562201
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Energy & Environmental Science
- Volume:
- 17
- Issue:
- 6
- ISSN:
- 1754-5692
- Page Range / eLocation ID:
- 2117 to 2128
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3EE03497F
