Title: Photochemical Upconversion in Water Using Cu(I) MLCT Excited States: Role of Energy Shuttling at the Micellar/Water Interface

Abstract

Photochemical upconversion (UC) through triplet–triplet annihilation (TTA), which employs a visible absorbing triplet photosensitizer and an annihilator, is a process that generates a high energy photon from two lower energy photons. TTA-UC has been largely developed in pure organic solvents and solid-state polymeric constructs while featuring near exclusive use of rare and expensive metals within the photosensitizer. In this current investigation, we demonstrate that TTA-UC from the long lifetime earth-abundant photosensitizer [Cu(dsbtmp)₂](PF)₆ (dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline), abbreviated as Cu-PS, functions in water through encapsulation within a cationic-based assembly. Cetyltrimethylammonium bromide was the surfactant of choice as it electrostatically binds the negatively charged water-soluble 10-phenylanthracene-9-carboxylate (PAC) acceptor/annihilator and ultimately facilitates energy transfer across the interface. Efficient triplet–triplet energy transfer (TTET) from Cu-PS to the PAC acceptor was achieved in this aqueous assembly. Unfortunately, the hindered mobility of the PAC moieties ultimately hampered the annihilation process, and this was reflected in attenuated TTA rates and efficiencies. The combined experimental data illustrated that the water-soluble PAC acceptor was able to vectorially deliver the excited-state energy stored in Cu-PS across the interface into the bulk aqueous solution by engaging in excited-state electron transfer with methyl viologen acceptors. Lastly, these results are important for remotely operatingmore » photoredox reactions in water while rendering a photosensitizer spatially isolated in the hydrophobic core of a micelle.« less

Authors:

Fayad, Remi ^[1]; Bui, Anh Thy ^[2]; Shepard, Samuel G. ^[1]; Castellano, Felix N.  ^[1]

• Search DOE PAGES for author "Castellano, Felix N."
• Search DOE PAGES for ORCID "0000-0001-7546-8618"

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+ Show Author Affiliations

1. North Carolina State Univ., Raleigh, NC (United States)
2. Univ. Rennes (France)

Publication Date:

Thu Dec 10 00:00:00 EST 2020

Research Org.:

North Carolina State University, Raleigh, NC (United States); Princeton Univ., NJ (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1786995

Alternate Identifier(s):

OSTI ID: 1764056

Grant/Contract Number:  

SC0011979; SC0019370

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Energy Materials

Additional Journal Information:

Journal Volume: 3; Journal Issue: 12; Journal ID: ISSN 2574-0962

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; photochemical upconversion; triplet−triplet annihilation; copper(I) MLCT excited states; earth-abundant photosensitizer; energy transfer; photosensitization; luminescence; quantum mechanics; solution chemistry; power