Understanding the substrate and temperature effect on thermal transport properties of transition metal dichalcogenides (TMDs) monolayers are crucial for their future applications. Herein, a dual-wavelength flash Raman (DF-Raman) method is used to measure the thermal conductivity of monolayer WS₂ at a temperature range of 200–400 K. High measurement accuracy can be guaranteed in this method since the influence of both the laser absorption coefficient and temperature-Raman coefficient can be eliminated through normalization. The room-temperature thermal conductivity of suspended and supported WS₂ are 28.5 ± 2.1 (30.3 ± 2.0) and 15.4 ± 1.9 (16.9 ± 2.1) W/(m·K), respectively, with a ~ 50% reduction due to substrate effect. Molecular dynamics (MD) simulations reveal that the suppression of acoustic phonons is mainly responsible for the striking reduction. The behaviors of optical phonons are also unambiguously investigated using Raman spectroscopy, and the in-plane optical mode, E ${}_{2\mathrm{g}}^1$(Γ), is surprisingly found to be slightly enhanced while out-of-plane mode, A_1g(Γ), is suppressed due to substrate interaction, mutually verified with MD results. Our study provides a solid understanding of the phonon transport behavior of WS₂ with substrate interaction, which provides guidance for TMDs-based nanodevices.

Flexible wearable electronics, when combined with outstanding thermoelectric properties, are promising candidates for future energy harvesting systems. Graphene and its macroscopic assemblies (e.g., graphene-based fibers and films) have thus been the subject of numerous studies because of their extraordinary electrical and mechanical properties. However, these assemblies have not been considered suitable for thermoelectric applications owing to their high intrinsic thermal conductivity. In this study, bromine doping is demonstrated to be an effective method for significantly enhancing the thermoelectric properties of graphene fibers. Doping enhances phonon scattering due to the increased defects and thus decreases the thermal conductivity, while the electrical conductivity and Seebeck coefficient are increased by the Fermi level downshift. As a result, the maximum figure of merit is 2.76 × 10^-3, which is approximately four orders of magnitude larger than that of the undoped fibers throughout the temperature range. Moreover, the room temperature power factor is shown to increase up to 624 μW·m^-1·K^-2, which is higher than that of any other material solely composed of carbon nanotubes and graphene. The enhanced thermoelectric properties indicate the promising potential for graphene fibers in wearable energy harvesting systems.

Graphene, a two-dimensional material with extraordinary electrical, thermal, and elastic performance, is a potential candidate for future technologies. However, the superior properties of graphene have not yet been realized for graphenederived macroscopic structures such as graphene fibers. In this study, we systematically investigated the temperature (T)-dependent transport and thermoelectric properties of graphene fiber, including the thermal conductivity (λ), electrical conductivity (σ), and Seebeck coefficient (S). λ increases from 45.8 to 149.7 W·m^–1·K^–1 and then decreases as T increases from 80 to 290 K, indicating the boundary-scattering and three-phonon Umklapp scattering processes. σ increases with T from 7.1 × 10⁴ to 1.18 × 10⁵ S·m^–1, which can be best explained by the hopping mechanism. S ranges from–3.9 to 0.8 μV·K^–1 and undergoes a sign transition at approximately 100 K.