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We studied exciton diffusion and charge transfer between a metal-organic complex and a MoS monolayer using transient s-SNOM nanoscopy. Measuring vibrational ground state bleach dynamics, we found an exciton diffusion rate of ∼8 × 10 cm s. Nanoscale resolution avoids spatial averaging errors, offering insights for optimizing excitonic processes in light-harvesting devices.
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http://dx.doi.org/10.1039/d5cc02361k | DOI Listing |
Chem Commun (Camb)
August 2025
Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA.
We studied exciton diffusion and charge transfer between a metal-organic complex and a MoS monolayer using transient s-SNOM nanoscopy. Measuring vibrational ground state bleach dynamics, we found an exciton diffusion rate of ∼8 × 10 cm s. Nanoscale resolution avoids spatial averaging errors, offering insights for optimizing excitonic processes in light-harvesting devices.
View Article and Find Full Text PDFNanophotonics
August 2025
Material Property Metrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Republic of Korea.
We directly characterize nanoscale spatiotemporal inhomogeneities of multi-layered molybdenum diselenide (MoSe) in real space and time - the nanometre-femtosecond scale, attributing to local mechanical structures such as strain and surface/subsurface defects, which are critical in semiconductor and optoelectronic applications. This remarkable precision is achieved through the development of a hyper-temporal transient nanoscopy incorporating a sideband-coupled generalized lock-in amplification technique, allowing for characterization of local spatiotemporal defects at each pixel within a subwavelength mapping region. By utilizing this technique, we characterize the nanoscale strain-induced spatiotemporal defects of multi-layered MoSe, including nano-bubbles that exhibit a noticeable reduction in exciton-exciton annihilation rates, which may attribute to the suppressed probability of bimolecular interaction of excitons due to the strain-induced band distortion.
View Article and Find Full Text PDFNat Commun
July 2025
Department of Physics, Chair in Hybrid Nanosystems, Nano-Institute Munich, Ludwig-Maximilians-Universität München, Munich, Germany.
Understanding the biophysical and biochemical properties of molecular nanocarriers under physiological conditions with minimal interference is critical for advancing photopharmacology, drug delivery, nanotheranostics and synthetic biology. However, analytical methods often struggle to combine precise chemical imaging and dynamic measurements without perturbative labeling. This challenge is exemplified by azobenzene-based photoswitchable lipids, which are intriguing reagents for controlling nanocarrier properties on fast timescales, enabling precise light-induced drug release.
View Article and Find Full Text PDFScattering-type scanning near-field optical microscopy (-SNOM) under the excitation of single cycle picosecond (ps) pulse provides access to terahertz (THz) time-resolved nanoscopy. However, the development of THz nanoscopy has been greatly limited due to the inherently low efficiency of the scattered field and the convolution of the intrinsic material response with the extrinsic response of the cantilevered tip. In this work, we quantitatively study the near-field time-delayed pulse transients of resonant cantilevered tips, observing localized tip-enhanced coupling as well as delocalized collective charge oscillations propagating as resonant surface waves along cantilevered tips.
View Article and Find Full Text PDFNano Lett
February 2025
Laser Thermal Laboratory, Department of Mechanical Engineering, University of California, Berkeley, California 94720, United States.
Ultrafast near-field optical nanoscopy has emerged as a powerful platform to characterize low-dimensional materials. While analytical and numerical models have been established to account for photoexcited carrier dynamics, quantitative evaluation of the associated pulsed laser heating remains elusive. Here, we decouple the photocarrier density and temperature increase in near-field nanoscopy by integrating the two-temperature model (TTM) with finite-difference time-domain (FDTD) simulations.
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