Insight into Intermolecular Charge Transfer Determined by Two Packing Mode Cocrystals

Guo

et al. 2022

Nanomaterials

One-dimensional (1D) nanostructures possess huge potential in electronics and optoelectronics, but the axial alignment of such 1D structures is still a challenging task. Herein, we report a simple method that enables two-dimensional (2D) C60 microsheets to evolve into highly ordered nanorod arrays using rubrene as a structure-directing agent. The structural transformation is accomplished by adding droplets of rubrene-m-xylene solution onto C60 microsheets and allowing the m-xylene solvent to evaporate naturally. In sharp contrast, when rubrene is absent from m-xylene, randomly oriented C60 nanorods are produced. Spectroscopic and microscopic characterizations collectively indicate a rather plausible transformation mechanism that the close lattice match allows the epitaxial growth of rubrene on C60 microsheets, followed by the reassembly of dissolved C60 along the aligned rubrene due to the intermolecular charge-transfer (CT) interactions, leading to the formation of ordered nanorod arrays. Due to the aligned structures and the CT interactions between rubrene and C60, the photocurrent density of the nanorod arrays is improved by 31.2% in the UV region relative to the randomly oriented counterpart. This work presents a facile and effective strategy for the construction of ordered fullerene nanorod arrays, providing new ideas for the alignment of fullerene and other relevant organic microstructures.

Section: Resultssupporting

confidence: 84%

Rubrene-Directed Structural Transformation of Fullerene (C60) Microsheets to Nanorod Arrays with Enhanced Photoelectrochemical Properties

Guo

et al. 2022

Nanomaterials

“…A similar transient absorption of the excited CT state was also detected at 615 and 677 nm for the 1,3,5-trimethoxybenzene− (TMOB−) PMDA cocrystal in our previous study on its excited state evolution. 39 In addition, there is a wide negative absorption band with a central wavelength at 506 nm at 96.8 fs, which is caused by the ground state bleaching. The transient absorption peaks at 613 and 666 nm, as well as the negative absorption band at 506 nm, both red-shifted and disappeared in the time range from 96.8 to 805 fs.…”

Section: T H Imentioning

confidence: 99%

Unprecedented Improvement of Near-Infrared Photothermal Conversion Efficiency to 87.2% by Ultrafast Non-radiative Decay of Excited States of Self-Assembly Cocrystal

Sun

Huang

et al. 2021

J. Phys. Chem. Lett.

Self Cite

Near-infrared (NIR) photothermal conversion is of great interest in many fields. Here, a self-assembly organic cocrystal (N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) and pyromellitic dianhydride (PMDA)) with strong absorption in NIR range is constructed, with widespread absorption (200–1500 nm) and very high NIR photothermal conversion efficiency (87.2%). Essentially, in this cocrystal, a small HOMO–LUMO gap of donor–acceptor pair boosts the absorption ability of this cocrystal in the NIR range. The mixed stacking structure significantly enhances the intermolecular interactions as well as the electron–hole delocalization, suppressing the emission processes, leading to nonradiative decay processes from excited states. Strong intermolecular interactions enable the cocrystal to have dense electronic energy levels, leading to a high proportion (94.4%) vibrational cooling and internal conversion processes with ultrafast excited-state relaxation (0.12 ps), which contributes to high NIR photothermal conversion efficiency. Furthermore, the cocrystal has exhibited capable ability for being an excellent candidate for a NIR photothermal therapy agent.

“…Remarkably, the optical physical behavior of these cocrystals is not closely related to the conjugation degree of three tetracyanides. Therefore, the evolution processes of the excited states of these three cocrystals are tracked by fs-TA − to investigate the essential difference in these cocrystals. With 800 nm excitation, PEC and PQC show obvious transient absorption peaks centered at 470 and 573 nm at 0.35 and 0.9 ps (Figures S24 and S25), respectively, which can be attributed to the excited charge-transfer state of these two cocrystals.…”

Section: Results and Discussionmentioning

confidence: 99%

Tailormade Nonradiative Rotation Tuning of the Near-Infrared Photothermal Conversion in Donor–Acceptor Cocrystals

Zhang

et al. 2021

J. Phys. Chem. C

Self Cite

Organic donor–acceptor cocrystals can improve the light-harvesting ability in visible or near-infrared regions, having a good photothermal conversion efficiency in some cases. While the photothermal conversion mechanism of organic cocrystals is still ambiguous. Here, the fluorescent molecule pyrene with a wide energy gap is selected as a donor, and the conjugated tetracyanide molecules are chosen as the acceptors. Pyrene and tetracyanide molecules are readily self-assembled into cocrystals (pyrene-tetracyanobenzene (PBC), pyrene-tetracyanoethylene (PEC), and pyrene-tetracyanoquinodimethane (PQC)) through intermolecular charge transfer. By changing the framework of acceptors, the optical properties of these cocrystals are tuned from photoluminescence (PBC) to photothermal conversion (PEC and PQC). PEC and PQC have an excellent photothermal conversion efficiency under near-infrared laser (808 nm) irradiation, its values can reach 80.9 and 83.3%, respectively. Based on the intermolecular interactions of cocrystals, femtosecond transient absorption, and excited-state theoretical calculation studies, the excellent photothermal conversion is attributed to the free rotation of the −C(CN)2 group, which opens a tailormade channel for the effective nonradiative decay of the excited charge-transfer state. This study paves a way to design organic donor–acceptor cocrystal materials with high photothermal conversion efficiency.