PdO and PtO loaded WS2 boosts NO2 gas sensing characteristics at room temperature

Three-Dimensional Assemblies of Edge-Enriched WSe2 Nanoflowers for Selectively Detecting Ammonia or Nitrogen Dioxide

“…In addition, the 3D arrangement of TMD nanosheets offers plenty of voids for gas diffusion. Indeed, gas adsorption at the edge sites of TMDs is more important compared to their basal plane, which has minimal dangling bonds, and, with the effect of thermodynamic forces, it is very challenging to expose the edges of 2D TMDs to the environment when these lie flat on the application substrate. ,,, …”

“…They are becoming indispensable items in the monitoring of indoor and outdoor toxic gases and thus play an increasing role in environmental monitoring, air quality control, or in safety and security applications. − Among the main toxic and air pollutant gases, we find nitrogen dioxide (NO 2 ) and ammonia (NH 3 ), which are generated from motor vehicle exhaust, refineries, power plants, and so forth. While nitrogen dioxide has a direct contribution in the formation of ground-level ozone in the troposphere, acid rain and is a precursor of inorganic ambient particulate matter, ammonia contributes to acidification, eutrophication and is also a precursor for the formation of ammonium salts, a harmful form of fine particulate matter. − For instance, exposure to nitrogen dioxide and ammonia may cause chronic bronchitis, respiratory irritation, mucous membrane inflammation syndrome, and asthma. , The odor thresholds of NO 2 and NH 3 in the air are around 400 and 40 ppb, respectively, while the threshold limit values (TLV) have been set by the Occupational Safety and Health Administration (OSHA) to 5 and 25 ppm, respectively . Exposure to high concentrations of these gases is a serious health threat.…”

“…Indeed, gas adsorption at the edge sites of TMDs is more important compared to their basal plane, which has minimal dangling bonds, and, with the effect of thermodynamic forces, it is very challenging to expose the edges of 2D TMDs to the environment when these lie flat on the application substrate. 7,17,28,29 In this respect, there are two techniques that are mostly used for the growth of 3D assemblies of edge-enriched WSe 2 nanosheets: hydrothermal and atmospheric pressure chemical vapor deposition methods. 30−32 Hydrothermal synthesis has the advantage of being low cost; however, it is a timeconsuming technique (it involves multistep fabrication), and sometimes, it needs using hazardous precursors, which have hindered its development.…”

The order of loading affects photocatalytic nitrogen fixation activity of the ternary composites of PdO/Au–TiO2

“…4a, the two typical peaks of Au, located at about 83.5 and 87.2 eV, can be ascribed to Au 4f 7/2 and Au 4f 5/2 , respectively, indicating that the Au species in composites were the metallic zero-valence ones. Meanwhile, the peaks at 336.4 and 341.8 eV belong to Pd 3d 5/2 and Pd 3d 3/2 , indicating that the valence state of Pd was +2, 61 as shown in Fig. 4b.…”

Ultrasensitive Room-Temperature NO2 Detection Using SnS2/MWCNT Composites and Accelerated Recovery Kinetics by UV Activation

“…On the other hand, TMDs such as WS 2 , MoS 2 , MoSe 2 , ReS 2 , and SnS 2 demonstrate superior selectivity, higher gas response, and a fast recovery rate at room temperature. This is attributed to their layer-dependent electronic properties, defect-enriched terminated surfaces, and higher electronegativity than graphene. − Among these TMDs, SnS 2 is widely used in Li- or Na-ion batteries, LEDs, and chemiresistive and self-powered gas sensors due to its earth abundance, low toxicity, and stability, which improves gas adsorption and charge transfer. − It can be synthesized in a variety of morphologies for use in chemiresistive gas sensors, including nanosheets, nanoflowers, and nanoflakes. − Despite these advantages, due to their higher resistance, SnS 2 -based sensors exhibit inferior response to lower NO 2 concentrations and require a relatively higher operational temperature (>100 °C). This leads to an increase in power consumption and is inimical to portable or Internet of Things (IoT) applications where low power consumption sensors are required due to limited battery power. − As an alternative to thermal activation, photoactivation can be used to increase the carrier concentration of SnS 2 and improve gas sensitivity.…”