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The elastic, electronic, and dielectric properties of layered transition metal dichalcogenides MX2 (M = Zr and Hf; X = S, Se) have been investigated using density functional theory (DFT) with van der Waals correction. The elastic modulus indicate that the structures belong to brittle materials. The band gaps of these materials through Heyd-Scuseria-Ernzerhof hybrid functional are in reasonable agreement with the experimental data. Partial density of state analysis suggests that the metallic atoms play a dominant role in the conduction band and the chalcogenide atoms have the main effect on the valence band. The presence of peaks in the dielectric constant spectra mainly result from the transition between first, second, third valence bands and the first conduction bands and the direction is from Γ to M, M to K, and K to Γ of the high symmetry k-points for bulk and monolayer structures, respectively. What is more, parallel band effect has been observed in monolayer structures, which suggests strong light-matter interactions in these materials. This work promotes the property understanding of these materials and holds potential for the development of optoelectronic devices based on these layered materials. [ABSTRACT FROM AUTHOR]

Band alignment based on mixed van der Waals heterostructures is vital to design new types of photoanodes based on transition metal dichalcogenides. Herein, different mixed ratios of WS2/MoS2 photoanodes are made using a liquid‐phase exfoliation method. The WS2/MoS2 photoanode is characterized by high‐resolution X‐ray photoelectron spectroscopy, which suggests type‐II heterostructure with a conduction band offset of 0.54 eV and a valence band offset of 0.55 eV. Herein, it is observed that the maximum photocurrent density at the ratio WS2/MoS2 (1:1) is eight times and four times larger than pure WS2 and MoS2, respectively. The amperometric I–t, Mott–Schottky, and Nyquist measurements are used to analyze the photoelectric enhancement, which suggests efficient charge separation in the photoelectrodes and low electrode–electrolyte interface resistance. Raman spectroscopy and X‐ray diffraction spectroscopy with the mode shift confirm the charge transfer and lattice change in the mixed heterostructure. The charge density difference of WS2/MoS2 also confirms charge redistribution after heterostructure formation to accelerate charge transfer at the heterostructure interface efficiently. Herein, a cheap and easy way to design WS2/MoS2 heterojunction‐based photoanodes for photoelectrochemical devices is explained. [ABSTRACT FROM AUTHOR]

A scalable liquid exfoliation of layered Bi 2 S 3 employing a mixed-solvent strategy was used for the fabrication of Bi 2 S 3 nanosheets. We found that 10% deionized water in 90% isopropyl alcohol is the best mixed solvent for the efficient and effective exfoliation of layered Bi 2 S 3 . These results are consistent with the absorbance spectra and enthalpy of mixing theory. The obtained Bi 2 S 3 nanosheets had few-quintuple layers and were investigated by transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. These Bi 2 S 3 nanosheets can be used to fabricate large-scale thin films by filtration method; the films demonstrated sensitive photoelectric response with the rise and decay response of photocurrent on the sub-second scale under visible light excitation. The electronic structures of bulk and one-quintuple layer Bi 2 S 3 are calculated by first-principle calculation for better understanding of the photoelectric response. A green mixed-solvent processing of Bi 2 S 3 opens up the potential application of Bi 2 S 3 optoelectric films to photoelectric detection and solar energy conversion devices.