To avoid interference from unexpected background noises and obtain high fidelity voice signal, acoustic sensors with high sensitivity, flat frequency response and high signal-to-noise ratio (SNR) are urgently needed for voice recognition. Graphene-oxide (GO) has received extensive attention due to its advantages of controllable thickness and high fracture strength. However, low mechanical sensitivity (S_M) introduced by undesirable initial stress limits the performance of GO material in the field of voice recognition. To alleviate the aforementioned issue, GO diaphragm with annular corrugations is proposed. By means of the reusable copper mold machined by picosecond laser, the fabrication and transfer of corrugated GO diaphragm are realized, thus achieving a Fabry-Perot (F-P) acoustic sensor. Benefitting from the structural advantage of the corrugated GO diaphragm, our F-P acoustic sensor exhibits high S_M (43.70 nm/Pa@17 kHz), flat frequency response (-3.2 dB to 3.7 dB within 300 Hz~3500 Hz), and high Signal to Noise Ratio (SNR) (76.66 dB@1 kHz). In addition, further acoustic measurements also demonstrate other merits, including an excellent frequency detection resolution (0.01 Hz) and high time stability (output relative variation less than 6.7% for 90 min). Given the merits presented before, the fabricated F-P acoustic sensor with corrugated GO diaphragm can serve as a high-fidelity platform for acoustic detection and voice recognition. In conjunction with the deep residual learning framework, high recognition accuracy of 98.4% is achieved by training and testing the data recorded by the fabricated F-P acoustic sensor.

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.

Sodium ion hybrid capacitors (SIHCs) are regarded as advanced power supply systems. Nevertheless, the kinetics imbalance of cathode and anode suppresses the further performance improvement of SIHCs. The carbonaceous anode materials are promising and many strategies have been utilized to increase the capacity of sloping region or accelerate the reaction rate of plateau region. However, it is still challenging to simultaneously realize high mesopore/micropore volume ratio, large interlayer distance (> 0.37 nm), and abundant and favorable heteroatoms-doping by a simple method. Herein, we report N, P, O ternary-doped mesoporous carbon (PNPOC-T, T = 700, 800 or 900) with large interlayer distance (~0.4 nm) as anode materials. The PNPOC-T were prepared by a simple in-situ polymerization of aniline and phytic acid on the exfoliated graphitic nitrogen carbide (g-C₃N₄) and subsequent carbonization. The obtained PNPOC-800 exhibits an excellent rate performance (101.5 mA·h·g⁻¹ at 20 A·g⁻¹), which can be attributed to the high surface-controlled capacitive behavior ratio and rapid ion diffusion. The optimum SIHCs display a high energy density of 105.48 W·h·kg⁻¹ and a high power density of 13.59 kW·kg⁻¹. Furthermore, the capacitance retention rate of SIHCs can reach 87.43% after 9 000 cycles at 1 A·g⁻¹.