Special Issue "Advanced Materials for Gas Sensors".

Today's view on gas sensors end-users is more directed toward miniaturization, low power consumption, and intelligent device integration aiming to reply to several hot issues such as high sensitivity, optimum selectivity, fast response/recovery transients, and good long time stability [...

CuWO with CuO and Cu(OH) Native Surface Layers for HS Detection under in-Field Conditions.

The paper presents the possibility of detecting low HS concentrations using CuWO. The applicative challenge was to obtain sensitivity, selectivity, short response time, and full recovery at a low operating temperature under in-field atmosphere, which means variable relative humidity (%RH). Three different chemical synthesis routes were used for obtaining the samples labeled as: CuW1, CuW2, and CuW3.

Methane Combustion Using Pd Deposited on CeO-MnO/La-AlO Pellistors.

Pd deposited on CeO-MnO/La-AlO has been prepared as a sensitive material for methane (CH) detection. The effect of different amounts (1.25%, 2.

Nanostructured Cobalt Doped Barium Strontium Titanate Thin Films with Potential in CO Detection.

In this work, (BaSr) (TiCo) O perovskite nanostructured material, denoted subsequently as Co-doped BaSrTiO, was synthesized in a one-step process in hydrothermal conditions. The obtained powder was heat-treated at 800 °C and 1000 °C, respectively, in order to study nanostructured powder behavior during thermal treatment. The Co-doped BaSrTiO powder was pressed into pellets of 5.

CeO:MnO Catalytic Micro-Converters Tuned for CH Detection Based on Catalytic Combustion under Real Operating Conditions.

Mesoporous CeO:MnO materials (3:7 and 7:3 molar ratio) were prepared by co-precipitation and deposited as porous thick films over alumina (AlO) planar substrate provided with Pt meander. The aim was oriented towards detecting low levels methane (CH) at moderate operating temperatures. Herein we demonstrated that the sensitivity of catalytic micro-converters (CMCs) towards a given peak of CH concentration corresponds to specific gas-surface interaction phenomena.

Humidity-Tolerant Ultrathin NiO Gas-Sensing Films.

When the gas sensor active layer film thickness is decreased, increased sensitivity to changes in the adsorbate concentration is expected when measuring the resistance of the layer, in particular when this thickness is on the order of the Debye length of the material (one-tens of nanometers); however, this is demonstrated only for a limited number of materials. Herein, ultrathin NiO films of different thicknesses (8-21 nm) have been deposited via chemical vapor deposition to fabricate gas sensor devices. Sensor performance for a range of NO concentrations (800 part-per-billion to 7 part-per-million) was evaluated and an optimum operating temperature of 125 °C determined.

Conductance Model for Single-Crystalline/Compact Metal Oxide Gas-Sensing Layers in the Nondegenerate Limit: Example of Epitaxial SnO(101).

Semiconducting metal oxide (SMOX)-based gas sensors are indispensable for safety and health applications, for example, explosive, toxic gas alarms, controls for intake into car cabins, and monitor for industrial processes. In the past, the sensor community has been studying polycrystalline materials as sensors where the porous and random microstructure of the SMOX does not allow a separation of the phenomena involved in the sensing process. This led to conduction models that can model and predict the behavior of the overall response, but they were not capable of giving fundamental information regarding the basic mechanisms taking place.

Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH Catalytic Combustion.

This study presents the synthesis and characterization of lanthanum-modified alumina supported cerium-manganese mixed oxides, which were prepared by three different methods (coprecipitation, impregnation and citrate-based sol-gel method) followed by calcination at 500 °C. The physicochemical properties of the synthesized materials were investigated by various characterization techniques, namely: nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and H-temperature programmed reduction (TPR). This experimental study demonstrated that the role of the catalytic surface is much more important than the bulk one.

The Effect of Film Thickness on the Gas Sensing Properties of Ultra-Thin TiO₂ Films Deposited by Atomic Layer Deposition.

Analyte sensitivity for gas sensors based on semiconducting metal oxides should be highly dependent on the film thickness, particularly when that thickness is on the order of the Debye length. This thickness dependence has previously been demonstrated for SnO₂ and inferred for TiO₂. In this paper, TiO₂ thin films have been prepared by Atomic Layer Deposition (ALD) using titanium isopropoxide and water as precursors.

Sensors based on mesoporous SnO-CuWO with high selective sensitivity to HS at low operating temperature.

Development of new sensitive materials by different synthesis routes in order to emphasize the sensing properties for hazardous HS detection is one of a nowadays challenge in the field of gas sensors. In this study we obtained mesoporous SnO-CuWO with selective sensitivity to HS by an inexpensive synthesis route with low environmental pollution level, using tripropylamine (TPA) as template and polyvinylpyrrolidone (PVP) as dispersant/stabilizer. In order to bring insights about the intrinsic properties, the powders were characterized by means of a variety of complementary techniques such as: X-Ray Diffraction, XRD; Transmission Electron Microscopy, TEM; High Resolution TEM, HRTEM; Raman Spectroscopy, RS; Porosity Analysis by N adsorption/desorption, BET; Scanning Electron Microscopy, SEM and X-ray Photoelectron Spectroscopy, XPS.