Synthesis of Au decorated V2O5 microflowers with enhanced sensing properties towards amines

The enhanced sensing properties of MOS-based resistive gas sensors by Au functionalization: a review

Gas sensors are essential for detecting toxic gases that can harm social life or industrial production. Traditional metal oxide semiconductor (MOS)-based sensors suffer from shortcomings such as high operating temperature and slow response time, which limits their detection capabilities. Thus, there is a need to improve their performance. One useful technique is noble metal functionalization, which can effectively enhance the response/recovery time, sensitivity and selectivity, sensing response, and optimum operating temperature of MOS gas sensors. Among the noble metals, Au NPs are considered a promising material for forming composite sensing materials to achieve better sensing performance. This paper aims to review and discuss the recent research on Au-decorated MOS-based sensors, including Au/n-type MOS-based sensors, Au/p-type MOS-based sensors, Au/MOS/carbon composite materials, and Au/MOS/perovskite composite materials. The sensing mechanism of Au-functionalized MOS-based materials will also be examined.

Advances in Noble Metal-Decorated Metal Oxide Nanomaterials for Chemiresistive Gas Sensors: Overview

Highly sensitive gas sensors with remarkably low detection limits are attractive for diverse practical application fields including real-time environmental monitoring, exhaled breath diagnosis, and food freshness analysis. Among various chemiresistive sensing materials, noble metal-decorated semiconducting metal oxides (SMOs) have currently aroused extensive attention by virtue of the unique electronic and catalytic properties of noble metals. This review highlights the research progress on the designs and applications of different noble metal-decorated SMOs with diverse nanostructures (e.g., nanoparticles, nanowires, nanorods, nanosheets, nanoflowers, and microspheres) for high-performance gas sensors with higher response, faster response/recovery speed, lower operating temperature, and ultra-low detection limits. The key topics include Pt, Pd, Au, other noble metals (e.g., Ag, Ru, and Rh.), and bimetals-decorated SMOs containing ZnO, SnO2, WO3, other SMOs (e.g., In2O3, Fe2O3, and CuO), and heterostructured SMOs. In addition to conventional devices, the innovative applications like photo-assisted room temperature gas sensors and mechanically flexible smart wearable devices are also discussed. Moreover, the relevant mechanisms for the sensing performance improvement caused by noble metal decoration, including the electronic sensitization effect and the chemical sensitization effect, have also been summarized in detail. Finally, major challenges and future perspectives towards noble metal-decorated SMOs-based chemiresistive gas sensors are proposed.

Mixed-metal nanoparticles: phase transitions and diffusion in Au-VO clusters

Nanoparticles with diameters in the range of a few nanometers, consisting of gold and vanadium oxide, are synthesized by sequential doping of cold helium droplets in a molecular beam apparatus and deposited on solid carbon substrates. After surface deposition, the samples are removed and various measurement techniques are applied to characterize the created particles: scanning transmission electron microscopy (STEM) at atomic resolution, temperature dependent STEM and TEM up to 650 °C, energy-dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). In previous experiments we have shown that pure V₂O₅ nanoparticles can be generated by sublimation from the bulk and deposited without affecting their original stoichiometry. Interestingly, our follow-up attempts to create Au@V₂O₅ core@shell particles do not yield the expected encapsulated structure. Instead, Janus particles of Au and V₂O₅ with diameters between 10 and 20 nm are identified after deposition. At the interface of the Au and the V₂O₅ parts we observe an epitaxial-like growth of the vanadium oxide next to the Au structure. To test the temperature stability of these Janus-type particles, the samples are heated in situ during the STEM measurements from room temperature up to 650 °C, where a reduction from V₂O₅ to V₂O₃ is followed by a restructuring of the gold atoms to form a Wulff-shaped cluster layer. The temperature dependent dynamic interplay between gold and vanadium oxide in structures of only a few nanometer size is the central topic of this contribution to the Faraday Discussion.

Room Temperature Ammonia Gas Sensor Based on p-Type-like V2O5 Nanosheets towards Food Spoilage Monitoring

Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V₂O₅ nanosheets operating at room temperature. The small thickness and porosity of the V₂O₅ nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH₃) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V₂O₅ is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device's performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chain.

Vanadium oxide nanorods as an electrode material for solid state supercapacitor

The electrochemical properties of metal oxides are very attractive and fascinating in general, making them a potential candidate for supercapacitor application. Vanadium oxide is of particular interest because it possesses a variety of valence states and is also cost effective with low toxicity and a wide voltage window. In the present study, vanadium oxide nanorods were synthesized using a modified sol-gel technique at low temperature. Surface morphology and crystallinity studies were carried out by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy analysis. To the best of our knowledge, the as-prepared nanorods were tested with magnesium ion based polymer gel electrolyte for the first time. The prepared supercapacitor cell exhibits high capacitance values of the order of ~ 141.8 F g^-1 with power density of ~ 2.3 kW kg^-1 and energy density of ~ 19.1 Wh kg^-1. The cells show excellent rate capability and good cycling stability.

A Review of Nanostructured Resistive-Based Vanadium Oxide Gas Sensors

Vanadium pentoxide (V2O5) is a transition metal oxide with features such as high availability, good catalytic activity, unique electrical properties and high conductivity which are appropriate for gas sensing applications. In this review, we discuss different gas sensing aspects of V2O5 in pristine, doped, decorated and composite forms. Depending on its synthesis procedure, morphology, sensing temperature and surface conditions, the V2O5-based gas sensors show different responses to target gases. Herein, we have discussed the behavior of V2O5-based gas sensors to different gases and associated sensing mechanisms. This review paper can be a useful reference for the researchers who works in the field of gas sensors.

Nickel/iron-based bimetallic MOF-derived nickel ferrite materials for triethylamine sensing

The sensors based on the different sized MOF derived NiFe₂O₄ polyhedrons exhibit fast TEA response speed and distinguishing sensitivity.