Journal
NANO LETTERS
Volume 21, Issue 8, Pages 3540-3547Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.1c00413
Keywords
Heat transport; time-resolved microscopy; subdiffusion; self-assembled nanocrystals; tortuosity; thermoreflectance
Categories
Funding
- Photonics at Thermodynamic Limits Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0019140]
- SIMES Institute for Energy Sciences from the Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division [DE-AC02-76SF00515]
- Office of Basic Energy Sciences, the U.S. Department of Energy [DE-SC0019375]
- NIH [S10OD023532]
- Camille and Henry Dreyfus Foundation
- Arnold and Mabel Beckman Foundation
- Alfred P. Sloan Research Fellowships
- David and Lucile Packard Foundation Fellowships for Science and Engineering
- Camille and Henry Dreyfus Teacher-Scholar Awards
- U.S. Department of Energy (DOE) [DE-SC0019375] Funding Source: U.S. Department of Energy (DOE)
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The study reveals that heat transport at the nanoscale appears subdiffusive due to the tortuosity of heat flow caused by a distribution of nonconductive voids. This finding suggests that heat can navigate circuitous pathways in disordered films of gold nanocrystals.
Investigating the impact of nanoscale heterogeneity on heat transport requires a spatiotemporal probe of temperature on the length and time scales intrinsic to heat navigating nanoscale defects. Here, we use stroboscopic optical scattering microscopy to visualize nanoscale heat transport in disordered films of gold nanocrystals. We find that heat transport appears subdiffusive at the nanoscale. Finite element simulations show that tortuosity of the heat flow underlies the subdiffusive transport, owing to a distribution of nonconductive voids. Thus, while heat travels diffusively through contiguous regions of the film, the tortuosity causes heat to navigate circuitous pathways that make the observed mean-squared expansion of an initially localized temperature distribution appear subdiffusive on length scales comparable to the voids. Our approach should be broadly applicable to uncover the impact of both designed and unintended heterogeneities in a wide range of materials and devices that can affect more commonly used spatially averaged thermal transport measurements.
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