Recent advances achieved in triboelectric nanogenerators (TENG) focus on boosting power generation and conversion efficiency. Nevertheless, obstacles concerning economical and biocompatible utilization of TENGs continue to prevail. Being an abundant natural biopolymer from marine crustacean shells, chitosan enables exciting opportunities for low-cost, biodegradable TENG applications in related fields. Here, the development of biodegradable and flexible TENGs based on chitosan is presented for the first time. The physical and chemical properties of the chitosan nanocomposites are systematically studied and engineered for optimized triboelectric power generation, transforming the otherwise wasted natural materials into functional energy devices. The feasibility of laser processing of constituent materials is further explored for the first time for engineering the TENG performance. The laser treatment of biopolymer films offers a potentially promising scheme for surface engineering in polymer-based TENGs. The chitosan-based TENGs present efficient energy conversion performance and tunable biodegradation rate. Such a new class of TENGs derived from natural biomaterials may pave the way toward the economically viable and ecologically friendly production of flexible TENGs for self-powered nanosystems in biomedical and environmental applications.

Molybdenum disulfide (MoS 2 )h as been widely studied as ap otential earth-abundant electrocatalyst for the hydrogen-evolution reaction (HER). Defect engineering and heteroelemental doping are effective methods to enhance the catalytic activity in the HER, so exploring an efficient route to simultaneously achieve in-plane vacancy engineering and elemental doping of MoS 2 is necessary.I nt his study,Z inc, al ow-cost and moderately active metal, has been used to realizethis strategy by generation of sulfur vacancies and zinc doping on MoS 2 in one step.D ensity functional theory calculations reveal that the zinc atoms not only lower the formation energy of Svacancies,but also help to decrease DG H of S-vacancy sites near the Zn atoms.A ta no ptimal zincreduced MoS 2 (Zn@MoS 2 )example,the activated basal planes contribute to the HER activity with an overpotential of À194 mV at 10 mA cm À2 and al ow Tafel slope of 78 mV/dec.

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Two-dimensional (2D) semiconductors have been extensively explored as a new class of materials with great potential. In particular, black phosphorus (BP) has been considered to be a strong candidate for applications such as high-performance infrared photodetectors. However, the scalability of BP thin film is still a challenge, and its poor stability in the air has hampered the progress of the commercialization of BP devices. Herein, we report the use of hydrothermal-synthesized and air-stable 2D tellurene nanoflakes for broadband and ultrasensitive photodetection. The tellurene nanoflakes show high hole mobilities up to 458 cm2/V·s at ambient conditions, and the tellurene photodetector presents peak extrinsic responsivity of 383 A/W, 19.2 mA/W, and 18.9 mA/W at 520 nm, 1.55 μm, and 3.39 μm light wavelength, respectively. Because of the photogating effect, high gains up to 1.9 × 103 and 3.15 × 104 are obtained at 520 nm and 3.39 μm wavelength, respectively. At the communication wavelength of 1.55 μm, the tellurene photodetector exhibits an exceptionally high anisotropic behavior, and a large bandwidth of 37 MHz is obtained. The photodetection performance at different wavelength is further supported by the corresponding quantum molecular dynamics (QMD) simulations. Our approach has demonstrated the air-stable tellurene photodetectors that fully cover the short-wave infrared band with ultrafast photoresponse.

The advent of graphene has evoked the re-examination of band topology of Dirac/Weyl nodal materials which can host low-energy realistic quasiparticles. Under strong magnetic fields, the topological properties of two-dimensional Dirac/Weyl materials can be directly manifested through quantum Hall states. Here we report the first observation of massive Weyl fermions through quantum Hall effect in n-type Weyl semiconductor tellurene (two-dimensional form of tellurium). The n-type doping profile forms a wide quantum well in tellurene, where two correlated layers of electrons create a pair of symmetric-antisymmetric energy states in addition to spin and valley degeneracy, leading to an approximate SU(8) isospin symmetry. The chirality-induced Weyl nodes residing near the edge of the conduction band give rise to radial spin texture, and topologically non-trivial  Berry phase was detected in quantum Hall sequences. Our work presents strong evidence of massive Weyl fermions and expands the spectrum of Weyl matters into semiconductor regime.