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Wasielewski, Michael R. (ORCID:0000000329205440)

Publications and source records attributed to Wasielewski, Michael R. (ORCID:0000000329205440).

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A 2D chiral microcavity based on apparent circular dichroism

Abstract Engineering asymmetric transmission between left-handed and right-handed circularly polarized light in planar Fabry–Pérot (FP) microcavities would enable a variety of chiral light-matter phenomena, with applications in spintronics, polaritonics, and chiral lasing. Such symmetry breaking, however, generally requires Faraday rotators or nanofabricated polarization-preserving mirrors. We present a simple solution requiring no nanofabrication to induce asymmetric transmission in FP microcavities, preserving low mode volumes by embedding organic thin films exhibiting apparent circular dichroism (ACD); an optical phenomenon based on 2D chirality. Importantly, ACD interactions are opposite for counter-propagating light. Consequently, we demonstrated asymmetric transmission of cavity modes over an order of magnitude larger than that of the isolated thin film. Through circular dichroism spectroscopy, Mueller matrix ellipsometry, and simulation using theoretical scattering matrix methods, we characterize the spatial, spectral, and angular chiroptical responses of this 2D chiral microcavity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Long-lived electronic spin qubits in single-walled carbon nanotubes

Abstract Electron spins in solid-state systems offer the promise of spin-based information processing devices. Single-walled carbon nanotubes (SWCNTs), an all-carbon one-dimensional material whose spin-free environment and weak spin-orbit coupling promise long spin coherence times, offer a diverse degree of freedom for extended range of functionality not available to bulk systems. A key requirement limiting spin qubit implementation in SWCNTs is disciplined confinement of isolated spins. Here, we report the creation of highly confined electron spins in SWCNTs via a bottom-up approach. The record long coherence time of 8.2 µs and spin-lattice relaxation time of 13 ms of these electronic spin qubits allow demonstration of quantum control operation manifested as Rabi oscillation. Investigation of the decoherence mechanism reveals an intrinsic coherence time of tens of milliseconds. These findings evident that combining molecular approaches with inorganic crystalline systems provides a powerful route for reproducible and scalable quantum materials suitable for qubit applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Mechanically interlocked pyrene-based photocatalysts

Triplet excited-state organic chromophores present countless opportunities for applications in photocatalysis. Here we describe an approach to the engineering of the triplet excited states of aromatic chromophores, which involves incorporating pyrene into pyridinium-containing mechanically interlocked molecules (MIMs). The π-extended nature of the pyrenes enforces [π···π] stacking, affording an efficient synthesis of tetrachromophoric octacationic homo[2]catenanes. These MIMs generate triplet populations and efficient intersystem crossing on account of the formation of a mixed charge-transfer/exciplex electronic state and a nanoconfinement effect, which leads to a high level of protection of the triplet state and extends the triplet lifetimes and yields. These compounds display excellent catalytic activity in photo-oxidation, as demonstrated by the aerobic oxidation of a sulfur-mustard simulant. Furthermore this research highlights the benefits of using the mechanical bond to fine-tune the triplet photophysics of existing aromatic chromophores, providing an avenue for the development of unexplored MIM-based photosensitizers and photocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Two-photon excited deep-red and near-infrared emissive organic co-crystals

Abstract Two-photon excited near-infrared fluorescence materials have garnered considerable attention because of their superior optical penetration, higher spatial resolution, and lower optical scattering compared with other optical materials. Herein, a convenient and efficient supramolecular approach is used to synthesize a two-photon excited near-infrared emissive co-crystalline material. A naphthalenediimide-based triangular macrocycle and coronene form selectively two co-crystals. The triangle-shaped co-crystal emits deep-red fluorescence, while the quadrangle-shaped co-crystal displays deep-red and near-infrared emission centered on 668 nm, which represents a 162 nm red-shift compared with its precursors. Benefiting from intermolecular charge transfer interactions, the two co-crystals possess higher calculated two-photon absorption cross-sections than those of their individual constituents. Their two-photon absorption bands reach into the NIR-II region of the electromagnetic spectrum. The quadrangle-shaped co-crystal constitutes a unique material that exhibits two-photon absorption and near-infrared emission simultaneously. This co-crystallization strategy holds considerable promise for the future design and synthesis of more advanced optical materials.

36 MATERIALS SCIENCE↗