Graphitic carbon nitride (g-C₃N₄) nanosheets were exfoliated from bulk g-C₃N₄ and utilized to improve the sensing performance of a pure graphene sensor for the first time. The role of hydrochloric acid treatment on the exfoliation result was carefully examined. The exfoliated products were characterized by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis spectroscopy. The exfoliated g-C₃N₄ nanosheets exhibited a uniform thickness of about 3–5 nm and a lateral size of about 1–2 µm. A g-C₃N₄/graphene nanocomposite was prepared via a self-assembly process and was demonstrated to be a promising sensing material for detecting nitrogen dioxide gas at room temperature. The nanocomposite sensor exhibited better recovery as well as two-times the response compared to pure graphene sensor. The detailed sensing mechanism was then proposed.

We demonstrate a facile synthetic method to prepare lateral size controlled molybdenum diselenide (MoSe₂) nanosheets using liquid phase exfoliated few-layer MoSe₂ nanosheets as a starting material. By precisely controlling the centrifugation condition, preparation of MoSe₂ nanosheets with a narrow size distribution ranging from several hundred nanometers to several micrometers could be realized. The accurate size control of MoSe₂ nanosheets offers us a great opportunity to examine the size dependent sensing properties. The sensing test results demonstrate that the MoSe₂ nanosheets provide competitive advantages compared with conventional graphene based sensors. A tradeoff phenomenon on sensing response and recovery as the lateral size of MoSe₂ nanosheets varies is observed. First principles calculations reveal that the ratio of edge-surface sites is responsible for this phenomenon. The correlation between the lateral size and gas sensing performance of MoSe₂ nanosheets is established.

A large area of randomly distributed nanospike as nanostructured template was induced by femtosecond (fs) laser on a silicon substrate in water. Copper oxide (CuO) and palladium (Pd) heterostructured nanofilm were coated on the nanospikes by magnetron sputtering technology and vacuum thermal evaporation coating technology respectively for the construction of a p-type hydrogen sensor. Compared with the conventional gas sensor based on CuO working at high temperature, nanostructured CuO/Pd heterostructure exhibited promising detection capability to hydrogen at room temperature. The detection sensitivity to 1% H₂ was 10.8%, the response time was 198 s, and the detection limit was as low as 40 ppm, presenting an important application prospect in the clean energy field. The excellent reusability and selectivity of the CuO/Pd heterostructure sensor toward H₂ at room temperature were also demonstrated by a series of cyclic response characteristics. It is believed that our room-temperature hydrogen sensor fabricated with a waste-free green process, directly on silicon substrate, would greatly promote the future fabrication of a circuit-chip integrating hydrogen sensor.

This article proposes a biomimetic multilayer foam-filled structure (BMFS) that mimics the microstructural characteristics of biological structures such as human bone and whale baleen. The lateral compression performance of such structures is investigated using experimental and numerical analyses. The proposed structure consists of three layers of aluminum foam with different densities filled in several concentric circular aluminum tubes. The test includes a solid design (Design-1) and a hollow design (Design-2). A series of quasi-static compression tests and finite element simulations are conducted, and the results show that BMFS exhibits a more advantageous sequential collapse deformation pattern for practical use. An energy absorption analysis of each layer shows that the energy absorption ratio of the foam layer reaches 85%. Comparing Models 1–3 of the two designs shows that the energy efficiency decreases, and the work efficiency increases, as the foam density increases. In addition, the interaction between the tubes and foams enhances the energy absorption properties of the structure. The parameter study shows that the energy absorption characteristics of Design-2 are insensitive to the diameter of the tube. The SEA of Design-1 increases with the thickness of Tube-1.