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Recently, palladium diselenide (PdSe2) has emerged as a promising material with potential applications in electronic and optoelectronic devices due to its intriguing electronic and optical properties. The performance of the device is strongly dependent on the charge–carrier dynamics and the related hot phonon behavior. Here, we investigate the photoexcited–carrier dynamics and coherent acoustic phonon (CAP) oscillations in mechanically exfoliated PdSe2 flakes with a thickness ranging from 10.6 nm to 54 nm using time-resolved non-degenerate pump–probe transient reflection (TR) spectroscopy. The results imply that the CAP frequency is thickness-dependent. Polarization-resolved transient reflection (PRTR) measurements reveal the isotropic charge–carrier relaxation dynamics and the CAP frequency in the 10.6 nm region. In addition, the deformation potential (DP) mechanism dominates the generation of the CAP. Moreover, a sound velocity of 6.78 × 103 m s−1 is extracted from the variation of the oscillation period with the flake thickness and the delay time of the acoustic echo. These results provide insight into the ultrafast optical coherent acoustic phonon and optoelectronic properties of PdSe2 and may open new possibilities for PdSe2 applications in THz-frequency mechanical resonators.

Developing highly efficient and economical bifunctional catalysts for overall water splitting is challenging but a great concern for the renewable energy conversion and applied catalysis towards a sustainable development. Herein, by employing first principles calculations, the catalytic performance of various transition metal (TM) atoms supported on single-layer ternary Ga2FeS4 for water splitting has been systematically investigated. Strikingly, it was evidenced that the sandwich Ga2FeS4 can form a tunable interfacial polarization field under external strain, which can effectively regulate its catalytic performance. Specifically, Au-Ga2FeS4 under a 0.5% tensile strain presents good bifunctional catalytic performance, with the low overpotentials of 0.03 and 0.48 eV, respectively, for the HER and OER, outperforming the experimentally identified Pt and IrO2. Considering the massive possibilities of these ternary substrates and the easily accessible characteristic of external strain, the findings highlighted here can provide a useful theoretical guideline for designing efficient bifunctional SACs in overall water splitting.

Two-dimensional (2D) bipolar junction transistors (BJTs) with van der Waals heterostructures play an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT), constructed from black phosphorus and MoS2, with femtosecond laser processing. This SBJT exhibits good bidirectional current amplification owing to its symmetric structure. We placed a top gate on one side of the SBJT to change the difference in the major carrier concentration between the emitter and collector in order to further investigate the effects of electrostatic doping on the device performance. The SBJT can also act as a gate-tunable phototransistor with good photodetectivity and photocurrent gain of β = ∼21. Scanning photocurrent images were used to determine the mechanism governing photocurrent amplification in the phototransistor. These results promote the development of the applications of multifunctional nanoelectronics based on 2D materials.

Recently, palladium diselenide (PdSe

Achieving multifunctional van der Waals nanoelectronic devices on one structure is essential for the integration of 2D materials; however, it involves complex architectural designs and manufacturing processes. Herein, a facile, fast, and versatile laser direct write micro/nanoprocessing to fabricate diode, NPN (PNP) bipolar junction transistor (BJT) simultaneously based on a pre-fabricated black phosphorus/molybdenum disulfide heterostructure is demonstrated. The PN junctions exhibit good diode rectification behavior. Due to different carrier concentrations of BP and MoS2 , the NPN BJT, with a narrower base width, renders better performance than the PNP BJT. Furthermore, the current gain can be modulated efficiently through laser writing tunable base width WB , which is consistent with the theoretical results. The maximum gain for NPN and PNP is found to be ≈41 (@WB ≈600 nm) and ≈12 (@WB ≈600 nm), respectively. In addition, this laser write processing technique also can be utilized to realize multifunctional WSe2 /MoS2 heterostructure device. The current work demonstrates a novel, cost-effective, and universal method to fabricate multifunctional nanoelectronic devices. The proposed approach exhibits promise for large-scale integrated circuits based on 2D heterostructures.

van der Waals p-n heterostructures based on p-type black phosphorus (BP) integrated with other two-dimensional (2D) layered materials have shown potential applications in electronic and optoelectronic devices, including logic rectifiers and polarization-sensitive photodetectors. However, the engineering of carriers transport anisotropy, which is related to the linear dichroism, have not yet been investigated. Here, we demonstrate a novel van der Waals device of orientation-perpendicular BP homojunction based on the anisotropic band structures between the armchair and zigzag directions. The structure exhibits good gate-tunable diode-like rectification characteristics caused by the barrier between the two perpendicular crystal orientations. Moreover, we demonstrate that the unique mechanisms of the polarization-sensitivity properties of this junction are involved with the linear dichroism and the anisotropic carriers transport engineering. These results were verified by the scanning photocurrent images experiments. This work paves the way for 2D anisotropic layered materials for next-generation electronic and optoelectronic devices.

Objective: To study the effect of Claudin6 (CLDN6) gene on cell proliferation and invasionrelated gene expression in meningioma tissue. Methods: Patients with meningioma and patients with brain trauma who received surgical treatment in Yibin First People’s Hospital between May 2014 and March 2017 were selected, the meningioma and normal meninges tissue were collected, the positive protein rate of CLDN6 was determined by immunohistochemical kit, and the protein expression of CLDN6, invasion genes and proliferation genes were determined by the enzyme-linked immunosorbent assay kit. Results: The protein content and positive protein rate of CLDN6 in meningioma tissue were significantly lower than those in normal meninges tissue; PHH3, MCM2, E2F3, MMP2, MMP9, N-cadherin and Vimentin protein contents in meningioma tissue were significantly higher than those in normal meninges tissue while BAG-1 and Caspase-3 protein contents were significantly lower than those in normal meninges tissue; PHH3, MCM2, E2F3, MMP2, MMP9, N-cadherin and Vimentin protein contents in CLDN6-positive meningioma tissue were significantly lower than those in CLDN6- negative meningioma tissue while BAG-1 and Caspase-3 protein contents were significantly higher than those in CLDN6-negative meningioma tissue. Conclusions: The low expression of CLDN6 gene in meningioma tissue is closely related to the abnormal proliferation and invasion of cells.

Anisotropic two-dimensional materials, such as black phosphorus (BP) and rhenium disulfide (ReS2), possess intrinsically in-plane anisotropic properties that can be tuned for advanced applications, like in thin-film polarizers or polarization-sensitive photodetectors. The crystal orientations should be accurately determined before these materials are applied. However, current methods for measuring the crystalline orientation, such as reflection and transmission spectra, and polarized Raman-related techniques, suffer from significant uncertainty and unreliability because of complex interference, the sample thickness and background signals, which can be particularly strong on transparent substrates. Herein, for the first time, we present a new high-accuracy and background-free method, photothermal detection (PTD), for the identification of the crystalline orientation of BP and ReS2 on a transparent substrate. PTD is a refractive index sensing optical technique, in which a modulated pump beam is absorbed by BP or ReS2, leading to a local change in the refractive index of the photothermal medium. The propagation of the probe beam at different wavelengths is modified by the produced periodical change of the refractive index. PTD could be utilized here to identify the crystalline orientation explicitly and accurately. Taking into account the signal generated by the anisotropic optical absorption of the pump beam and the resulting heating of the liquid medium, PTD has no background interference regardless of the excitation wavelength and samples thickness. By analyzing the relationship between the polarization angle of the pump beam and the strength of the photothermal signal, the crystalline orientation can be accurately distinguished. Therefore, PTD overcomes typical challenges associated with transparent substrates, including insulating and rough surfaces, and enables the unambiguous identification of crystalline orientation.

Two-dimensional (2D) bipolar junction transistors (BJTs) with van der Waals heterostructures play an important role in the development of future nanoelectronics. Herein, a convenient method is introduced for fabricating a symmetric bipolar junction transistor (SBJT), constructed from black phosphorus and MoS

Manipulating the polarization of an incident beam using two-dimensional materials has become an important research direction towards the development of nano-optical devices. Black phosphorus (BP) and rhenium diselenide (ReSe2) possess excellent in-plane optical anisotropy with optical birefringence in the visible region, which has led to novel applications in polarizing optics and optoelectronics. Herein, the polarization-dependent absorption of BP and ReSe2 and a modulated pump beam is utilized to obtain the photothermal signal from them. The photothermal anisotropy of BP and ReSe2 has been explored using photothermal detection. Then we have defined the photothermal contrast using the ratio of the maximum to the minimum of the photothermal signal. The photothermal contrast of BP and ReSe2 can be obtained accurately by the relationship between the polarization angle of the pump light and the photothermal signal. We demonstrate that a layered BP with different thicknesses can remarkably change the photothermal contrast. In contrast, the photothermal contrast of ReSe2 does not change with the different thicknesses of the samples. Further, the photothermal anisotropies of BP/ReSe2 heterostructures were also explored. The photothermal contrasts of samples were observed to change with different stacking angles indicating that the photothermal anisotropy of heterostructures is dependent on the stacking angle. Our findings provide new prospects for designing novel optical devices based on two-dimensional anisotropic materials, with potential applications in electronics, photonics, and optoelectronics.