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Two-dimensional optical spectroscopy experiments have examined photoprotective mechanisms in the Fenna–Matthews–Olson (FMO) photosynthetic complex, showing that exciton transfer pathways change significantly depending on the environmental redox conditions. Higgins et al. [Proc. Natl. Acad. Sci. U. S. A. 118(11), e2018240118 (2021)] have theoretically linked these observations to changes in a quantum vibronic coupling, whereby onsite energies are altered under oxidizing conditions such that exciton energy gaps are detuned from a specific vibrational motion of the bacteriochlorophyll a. These arguments rely on an analysis of exciton transfer rates within Redfield theory, which is known to provide an inaccurate description of the influence of the vibrational environment on the exciton dynamics in the FMO complex. Here, we use a memory kernel formulation of the hierarchical equations of motion to obtain non-perturbative estimations of exciton transfer rates, which yield a modified physical picture. Our findings indicate that onsite energy shifts alone do not reproduce the reported rate changes in the oxidative environment. We systematically examine a model that includes combined changes in both site energies and the frequency of a local vibration in the oxidized complex while maintaining consistency with absorption spectra and achieving qualitative, but not quantitative, agreement with the measured changes in transfer rates. Our analysis points to potential limitations of the FMO electronic Hamiltonian, which was originally derived by fitting spectra to perturbative theories. Overall, our work suggests that further experimental and theoretical analyses may be needed to understand the variations of exciton dynamics under different redox conditions. 

Phase stability between pulse pairs defining Fourier-transform time delays can limit resolution and complicates development and adoption of multidimensional coherent spectroscopies. We demonstrate a data processing procedure to correct the long-term phase drift of the nonlinear signal during two-dimensional (2D) experiments based on the relative phase between scattered excitation pulses and a global phasing procedure to generate fully absorptive 2D electronic spectra of wafer-scale monolayer MoS₂. Our correction results in a ∼30-fold increase in effective long-term signal phase stability, from ∼λ/2 to ∼λ/70 with negligible extra experimental time and no additional optical components. This scatter-based drift correction should be applicable to other interferometric techniques as well, significantly lowering the practical experimental requirements for this class of measurements. 

Abstract Although sonodynamic therapy (SDT) has shown promise for cancer treatment, the lack of efficient sonosensitizers (SSs) has limited the clinical application of SDT. Here, a new strategy is reported for designing efficient nano‐sonosensitizers based on 2D nanoscale metal–organic layers (MOLs). Composed of Hf‐oxo secondary building units (SBUs) and iridium‐based linkers, the MOL is anchored with 5,10,15,20‐tetra(p‐benzoato)porphyrin (TBP) sensitizers on the SBUs to afford TBP@MOL. TBP@MOL shows 14.1‐ and 7.4‐fold higher singlet oxygen (¹O₂) generation than free TBP ligands and Hf‐TBP, a 3D nanoscale metal–organic framework, respectively. The¹O₂generation of TBP@MOL is enhanced by isolating TBP SSs on the SBUs of the MOL, which prevents aggregation‐induced quenching of the excited sensitizers, and by triplet–triplet Dexter energy transfer between excited iridium‐based linkers and TBP SSs, which more efficiently harnesses broad‐spectrum sonoluminescence. Anchoring TBP on the MOL surface also enhances the energy transfer between the excited sensitizer and ground‐state triplet oxygen to increase¹O₂generation efficacy. In mouse models of colorectal and breast cancer, TBP@MOL demonstrates significantly higher SDT efficacy than Hf‐TBP and TBP. This work uncovers a new strategy to design effective nano‐sonosensitizers by facilitating energy transfer to efficiently capture broad‐spectrum sonoluminescence and enhance¹O₂generation.