Title: Supramolecular Packing Controls H ₂ Photocatalysis in Chromophore Amphiphile Hydrogels

Abstract

Light harvesting supramolecular assemblies are potentially useful structures as components of solar-to-fuel conversion materials. The development of these functional constructs requires an understanding of optimal packing modes for chromophores. Here, we investigated assembly in water and the photocatalytic function of perylene monoimide chromophore amphiphiles with different alkyl linker lengths separating their hydrophobic core and the hydrophilic carboxylate headgroup. We found that these chromophore amphiphiles (CAs) self-assemble into charged nanostructures of increasing aspect ratio as the linker length is increased. The addition of salt to screen the charged nanostructures induced the formation of hydrogels and led to internal crystallization within some of the nanostructures. For linker lengths up to seven methylenes, the CAs were found to pack into 2D crystalline unit cells within ribbon-shaped nanostructures, whereas the nine methylene CAs assembled into long nanofibers without crystalline molecular packing. At the same time, the different molecular packing arrangements after charge screening led to different absorbance spectra, despite the identical electronic properties of all PMI amphiphiles. While the crystalline CAs formed electronically coupled H-aggregates, only CAs with intermediate linker lengths showed evidence of high intermolecular orbital overlap. Photocatalytic hydrogen production using a nickel-based catalyst was observed in all hydrogels, with the highest turnoversmore » observed for CA gels having intermediate linker lengths. Lastly, we conclude that the improved photocatalytic performance of the hydrogels formed by supramolecular assemblies of the intermediate linker CA molecules likely arises from improved exciton splitting efficiencies due to their higher orbital overlap.« less

Authors:

Weingarten, Adam S. ^[1]; Kazantsev, Roman V. ^[1]; Palmer, Liam C. ^[2]; Fairfield, Daniel J. ^[3]; Koltonow, Andrew R. ^[3]; Stupp, Samuel I. ^[4]

---

+ Show Author Affiliations

1. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, United States
2. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States, Simpson Querrey Institute for BioNanotechnology, Northwestern University, Chicago, Illinois 60611, United States
3. Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
4. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States, Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208, United States, Simpson Querrey Institute for BioNanotechnology, Northwestern University, Chicago, Illinois 60611, United States, Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States, Department of Medicine, Northwestern University, Chicago, Illinois 60611, United States

Publication Date:

Sat Nov 21 00:00:00 EST 2015

Research Org.:

Northwestern Univ., Evanston, IL (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Inst. of Healh; National Science Foundation (NSF)

OSTI Identifier:

1226681

Alternate Identifier(s):

OSTI ID: 1235481; OSTI ID: 1378689; OSTI ID: 1820610

Grant/Contract Number:  

AC02-06CH11357; SC0001059; 5P41RR007707; 8P41GM103543; DMR-1121262; EEC-0647560; CHE-9871268

Resource Type:

Published Article

Journal Name:

Journal of the American Chemical Society

Additional Journal Information:

Journal Name: Journal of the American Chemical Society Journal Volume: 137 Journal Issue: 48; Journal ID: ISSN 0002-7863

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; 99 GENERAL AND MISCELLANEOUS; Molecular packing; Nanostructures; Supramolecular structures and assemblies; Solution chemistry; Absorption; Molecular packing, Nanostructures, Supramolecular structures and assemblies, Solution chemistry, Absorption