Active-ion-gated room temperature acetone gas sensing of ZnO nanowires array

In Situ Local Band Engineering of Monolayer Graphene Using Triboelectric Plasma

Graphene, a promising material with excellent properties, suffers from a major limitation in electronics due to its zero bandgap. The gas molecules adsorption has proven to be an effective approach for band regulation, which usually requires a harsh environment. Here, O2 - ions produced with triboelectric plasma are used for in situ regulation of graphene, and the switching ratio can reach 1010. The O2 - ions physical adsorption will reduce the Fermi-level (EF) of graphene. As the EF of graphene is lower than the lowest unoccupied molecular orbital (LUMO) level of O2-, the adsorption of O2 - changes from uniform physical adsorption to local chemical adsorption, thereby realizing the semiconductor properties of graphene. The local graphene bandgap is calculated to be 83.4 meV by the variable-temperature experiment. Furthermore, annealing treatment can restore to 1/10 of the initial conductance. The C─O bond formed by O2 - adsorption has low bond energy and is easy to desorb, while the C═O bond formed by adsorption on defects and edges has higher bond energy and is difficult to desorb. The study proposes a simple in situ method to investigate the microscopic process of O2 - adsorption on the graphene surface, demonstrating a new perspective for local energy band engineering of graphene.

CuO/TiO2/MXene-Based Sensor and SMS-TENG Array Integrated Inspection Robots for Self-Powered Ethanol Detection and Alarm at Room Temperature

In this study, a high-precision CuO/TiO2/MXene ethanol sensor operating at room temperature was prepared. The sensor exhibits excellent response value (95% @1 ppm ethanol), extremely low detection limit (0.3 ppm), fast response/recovery time (16/13 s), and remarkable long-term stability for trace detection of ethanol gas at room temperature, attributed to the p-n heterojunction formed by CuO and TiO2, as well as the rich functional groups and large specific surface area of MXene. Furthermore, a high-performance triboelectric nanogenerator (SMS-TENG) was developed through the introduction of the silicone/Mxene@silicone dual dielectric layer as the triboelectric layer, which improves the charge storage capacity of the dielectric layer and greatly enhances the output performance of the TENG. At the optimal doping ratio, the open-circuit voltage of the SMS-TENG can reach 1160 V, which is sufficient to light 720 LEDs. By combining the sensor and SMS-TENG, the resistive response of ethanol sensing is converted to a voltage response, which amplifies the response value up to 15.8 times. Finally, the designed SMS-TENGs are expected to be arrayed on an inspection robot as energy supply and combined with the CuO/TiO2/Mxene ethanol sensor to build a self-powered ethanol detection alarm system, endowing the inspection robot with the capability of self-powered ethanol detection at ppb level. This work provides an effective pathway for the intelligence of ethanol detection.

In situ assembly of one-dimensional Pt@ZnO nanofibers driven by a ZIF-8 framework for achieving a high-performance acetone sensor

To obtain a high-performance gas sensor, it is essential to ingeniously design sensing materials containing the features of high catalytic performance, abundant oxygen vacancies, and splendid grain dispersibility through a simple method. Inspired by the fact that ZIF-8 contains semiconductor metal atoms, well-arranged ZnO nanoparticle (NP)-in situ assembled one-dimensional nanofibers (NFs) are obtained by one-step electrospinning. By incorporating Pt NPs into the cavity of ZIF-8 NPs, well-dispersed Pt@ZnO NPs driven by Pt@ZIF-8 composites are obtained after annealing. The well-arranged Pt@ZnO NP-assembled NFs not only exhibit abundant oxygen vacancies but also avoid the self-aggregation of ZnO and Pt NPs. Meanwhile, the small Pt NPs could improve the catalytic effect in return. Therefore, the gas sensor fabricated based on the above materials exhibits an acetone sensitivity of 6.1 at 370 °C, compared with pristine ZnO NFs (1.6, 5 ppm). Moreover, the well-arranged Pt@ZnO NP-assembled NFs show exceptional sensitivity to acetone with a 70.2 ppb-level detection limit in theory. The synergistic advantages of the designed sensing material open up new possibilities for non-invasive disease diagnosis.

Designing advanced S-scheme CdS QDs/La-Bi2WO6 photocatalysts for efficient degradation of RhB

Finding effective strategies to design efficient photocatalysts and decompose refractory organic compounds in wastewater is a challenging problem. Herein, by coupling element doping and constructing heterostructures, S-scheme CdS QDs/La-Bi2WO6 (CS/LBWO) photocatalysts are designed and synthesized by a simple hydrothermal method. As a result, the RhB degradation efficiency of the optimized 5% CS/LBWO reached 99% within 70 min of illumination with excellent stability and recyclability. CS/LBWO shows improvement in the adsorption range of visible light and promotes electron-hole pair generation/migration/separation, attributing the superior degradation performance. The degradation RhB mechanism is proposed by a free radical capture experiment, electron paramagnetic resonance, and high-performance liquid chromatography-mass spectrometry results, indicating that h+ and •O2 - play a significant role during four degradation processes: de-ethylation, chromophore cleavage, ring opening, and mineralization. Based on in situ irradiated X-ray photoelectron spectroscopy, Mulliken electronegativity theory, and the work function results, the S-scheme heterojunction of CS/LBWO promotes the transfer of photogenerated electron-hole pairs and promotes the generation of reactive radicals. This work not only reports that 5% CS/LBWO is a promising photocatalyst for degradation experiments but also provides an approach to design advanced photocatalysts by coupling element doping and constructing heterostructures.