Dual Improvement in Sensitivity and Humidity Tolerance of a NO2 Sensor Based on 3-Aminopropyltriethoxysilane Self-Assembled Monolayer-Functionalized SnSe2 for Explosive Photolysis Gas Detection.

Explosives can be analyzed for their content by detecting the photolytic gaseous byproducts. However, to prevent electrostatic sparking, explosives are frequently preserved in conditions with low temperatures and high humidity, impeding the performance of gas detection. Thus, it has become a research priority to develop gas sensors that operate at ambient temperature and high humidity levels in the realm of explosive breakdown gas-phase detection. In this work, 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer-functionalized tin diselenide (APTES-SnSe2) nanosheets were synthesized via a facile solution stirring strategy, resulting in a room-temperature NO2 sensor with improved sensitivity and humidity tolerance. The APTES-SnSe2 sensor with moderate functionalization time outperforms the pure SnSe2 sensor in terms of the response value (317.51 vs 110.98%) and response deviation (3.11 vs 24.13%) under humidity interference to 500 ppb NO2. According to density functional theory simulations, the stronger adsorption of terminal amino groups of the APTES molecules to NO2 molecules and stable adsorption energy in the presence of H2O are the causes of the improved sensing capabilities. Practically, the APTES-SnSe2 sensor achieves accurate detection of photolysis gases from trace nitro explosives octogen, pentaerythritol tetranitrate, and trinitrotoluene at room temperature and various humidity levels. This study provides a potential strategy for the construction of gas sensors with high responsiveness and antihumidity capabilities to identify explosive content in harsh environments.

2D SnSe2 nanoflakes decorated with 1D ZnO nanowires for ppb-level NO2 detection at room temperature.

The detection of air pollutant nitrogen dioxide (NO2) is of great importance arising from its great harm to the ecological environment and human health. However, the detection range of most NO2 sensors is ppm-level, and it is still challenging to achieve lower concentration (ppb-level) NO2 detection. Herein, 2D tin diselenide nanoflakes decorated with 1D zinc oxide nanowires (SnSe2/ZnO) heterojunctions were first reported by facile hydrothermal and ultra-sonication methods. The response of the fabricated SnSe2/ZnO sensor enhances 3.41 times on average compared with that of pure SnSe2 sensor to 50-150 ppb NO2 with a high detection sensitivity (22.57 ppm-1) at room temperature. In addition, the SnSe2/ZnO sensor has complete recovery, negligible cross-sensitivity, and small relative standard deviation (6.98%) during the 1 month sensing test, which can meet the requirements for NO2 detection in environmental monitoring. The enhanced NO2 sensing performance can be attributed to the n-n heterojunction constructed between SnSe2 and ZnO. The as-prepared sensor based on SnSe2/ZnO hybrid significantly promotes the development of the low detection limit of the NO2 sensor at room temperature.

Hollow Cu2O nanospheres loaded with MoS2/reduced graphene oxide nanosheets for ppb-level NO2 detection at room temperature.

Low energy consumption, high sensing response and high selectivity are the important indexes of metal oxide semiconductor (MOS) gas sensors applied in many application fields. However, the high working temperature and poor selectivity of MOS sensors severely restrict their scope of application in the Internet of Things (IoT). Herein, ternary MoS2-rGO-Cu2O (MG-Cu) composites with boosting ppb-level NO2 sensing characteristics are synthesized by combining hydrothermal method and soft-template method. The optimal proportion of MoS2, rGO and Cu2O is systematically explored. The SEM and TEM analyses confirm the hollow Cu2O is anchored on the surface of MG. The gas sensing tests illustrate that optimum composite sensor exhibits highest response to 500 ppb NO2 at room temperature, which is 11 and 5 times higher compared to pure MoS2 and binary MG15, respectively. Besides, it displays excellent selectivity and superior stability. The synergy of shell-structure with abundant mesoporous, heterojunction construction and enhanced conductivity lead to the enhanced sensing performance of ternary sensor.

Development of a rGO-BiVO4 Heterojunction Humidity Sensor with Boosted Performance.

Humidity sensors with good repeatability, low hysteresis, and low-power consumption are increasingly important for environmental monitoring and industrial control applications. Herein, an impedance-type humidity sensor under low working voltage (5 mV) utilizing a rGO-BiVO4 nanocomposite is demonstrated. The rGO-BiVO4 humidity sensor exhibits superior sensing performances, including good repeatability, negligible hysteresis (0.47%), fast response and recovery time, low power consumption, good stability, and anti-interference ability. The ultraviolet-visible absorption spectrum reveals that the narrow band gap of the rGO-BiVO4 nanocomposite is conductive to the electron transfer. The complex impedance spectra and the energy band structure analysis further suggest that the boosted humidity performance results from the formation of a heterojunction and the decrease of the heterojunction barrier height. The facile fabrication route, enhanced sensing performance, and excellent device reliability make the rGO-BiVO4 sensor highly attractive for high-end humidity sensing applications.

Enhanced ammonia sensing performance based on MXene-Ti3C2Tx multilayer nanoflakes functionalized by tungsten trioxide nanoparticles.

Low-power consumption and high sensitivity are highly desirable for a vast range of NH3 sensing applications. As a new type of two-dimension (2D) material, Ti3C2Tx is extensively studied for room temperature NH3 sensors recently. However, the Ti3C2Tx MXene based gas sensors suffer mainly from low sensitivity. Herein, we report a sensitive Ti3C2Tx/WO3 composite resistive sensor for NH3 detection. The Ti3C2Tx/WO3 composite consisting of WO3 nanoparticles anchored on Ti3C2Tx nanoflakes were synthesized successfully with a facile ultra-sonication technique. The composite sensor with optimized components exhibits a high sensitivity of 22.3% for 1 ppm NH3 at room temperature, which is 15.4 times higher than the pure Ti3C2Tx sensor. Furthermore, the composite sensor has excellent reproducibility, good long-term stability, and high selectivity to NH3. The relative humidity influence on NH3 gas sensing properties of the sensors was systematically studied. This research provides an efficient route for the preparation of novel MXene-based sensitive materials for high-performance NH3 sensors.