Metal oxide nanoparticles have been widely utilized for the fabrication of functional gas sensors to determine various flammable, explosive, toxic, and harmful gases due to their advantages of low cost, fast response, and high sensitivity. However, metal oxide-based gas sensors reveal the shortcomings of high operating temperature, high power requirement, and low selectivity, which limited their rapid development in the fabrication of high-performance gas sensors. The combination of metal oxides with two-dimensional (2D) nanomaterials to construct a heterostructure can hybridize the advantages of each other and overcome their respective shortcomings, thereby improving the sensing performance of the fabricated gas sensors. In this review, we present recent advances in the fabrication of metal oxide-, 2D nanomaterials-, as well as 2D material/metal oxide composite-based gas sensors with highly sensitive and selective functions. To achieve this aim, we firstly introduce the working principles of various gas sensors, and then discuss the factors that could affect the sensitivity of gas sensors. After that, a lot of cases on the fabrication of gas sensors by using metal oxides, 2D materials, and 2D material/metal oxide composites are demonstrated. Finally, we summarize the current development and discuss potential research directions in this promising topic. We believe in this work is helpful for the readers in multidiscipline research fields like materials science, nanotechnology, chemical engineering, environmental science, and other related aspects.

Two-dimensional materials (2DMs) exhibited great potential for applications in materials science, energy storage, environmental science, biomedicine, sensors/biosensors, and others due to their unique physical, chemical, and biological properties. In this review, we present recent advances in the fabrication of 2DM-based electrochemical sensors and biosensors for applications in food safety and biomolecular detection that are related to human health. For this aim, firstly, we introduced the bottom-up and top-down synthesis methods of various 2DMs, such as graphene, transition metal oxides, transition metal dichalcogenides, MXenes, and several other graphene-like materials, and then we demonstrated the structure and surface chemistry of these 2DMs, which play a crucial role in the functionalization of 2DMs and subsequent composition with other nanoscale building blocks such as nanoparticles, biomolecules, and polymers. Then, the 2DM-based electrochemical sensors/biosensors for the detection of nitrite, heavy metal ions, antibiotics, and pesticides in foods and drinks are introduced. Meanwhile, the 2DM-based sensors for the determination and monitoring of key small molecules that are related to diseases and human health are presented and commented on. We believe that this review will be helpful for promoting 2DMs to construct novel electronic sensors and nanodevices for food safety and health monitoring.

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Mechanical energy can be directly transformed into chemical energy by piezoelectric materials, namely, piezocatalysis, which is a potential tactic for renewable clean energy collection and environmental purification. The piezocatalytic efficiency strongly relies on the piezoelectric property and free charge concentration of piezocatalysts. Here, four samarium-doped (1 – x)­Pb­(Mg1/3Nb2/3)­O3-xPbTiO3 nanostructures were designed to investigate the correlation between the piezoelectric property and piezocatalytic performance. The diverse dye degradation efficiencies confirmed the high piezoelectric coefficient toward high catalytic activity. The degradation efficiency for acid orange 7 (AO7) was 100% within 20 min, while those for methyl orange (MO), methylene blue, and rhodamine B dyes were 97, 78, and 72%, respectively, within 40 min under ultrasonic vibration only. Furthermore, high catalytic efficiency of 96% was still maintained for AO7 degradation after 10 consecutive degradation cycles for samarium-doped 0.70Pb­(Mg1/3Nb2/3)­O3-0.30PbTiO3 due to its high piezoelectric coefficient. The investigation of the catalytic mechanism demonstrated that hole and superoxide radicals were the primary active species toward AO7 degradation, whereas hydroxyl and hole radicals were for MO degradation. This work not only demonstrates the highly efficient catalytic activity of samarium-doped (1 – x)­Pb­(Mg1/3Nb2/3)­O3-xPbTiO3 nanostructures but also gives a deep comprehension of the correlation between the piezoelectric property and catalytic performance of piezocatalysts.

Fiber identification is the primary task of waste textile recycling, which plays an important guiding role in the recovery and reuse of waste textiles. In this study, 186 pure spinning textiles with different fiber species were chosen as the raw materials, the near-infrared spectra were collected and the differences among various fibers species were also studied. The fast and accurate classification/identification model of textile fiber was established using the near-infrared spectral modeling technique. The soft independent modeling of class analogy method was used to construct the model. The results show that the model recognition rate can be up to 97% after selecting the wavenumber range of 6800–5300 cm–1 with the first derivative treatment on the spectra. It was found by external validation that the prediction accuracy of the model was 100% for polyester, polyamide, acrylic, silk and wool. The prediction accuracy of cotton fiber and polyester fabric was higher than 90%. The above result demonstrated that the textile fiber identification model established in this study can be used for fast and accurate identification and sorting of waste textiles.