Search

Interest in the importance of gas sensing devices has increased significantly due to their critical function in monitoring the environment and controlling pollution, resulting in an increased market demand. The present review explores perovskite La-Fe-O based gas sensors with a special focus on LaFeO 3 and evaluates their sensitivity to a diverse range of practical target gases that need to be monitored. An analysis has been conducted to assess different routes not only of synthesizing LaFeO 3 material but also of characterization with the targeted use for their gas sensing abilities. Additionally, a comprehensive analysis has been performed to explore the effect of introducing other elements through doping. In view of the LaFeO 3 sensing performance, more common gases like acetone, ethanol, methanol, formaldehyde, NO x , and CO 2 have been targeted. In addition, a discussion on uncommon gases such as CO, SO 2 , TEA, C 2 H 5 , C 6 H 6 , and others is also made to give a complete picture of LaFeO 3 -based gas sensors. The summary and conclusion section of the study addresses the primary obstacles in the synthesis process, the variables that restrict the sensing capabilities of LaFeO 3 , and its commercial fulfillment., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

We report citrate gel-assisted autocombusted spinel-type Co 2+ -substituted NiCuZn ferrites and their electromagnetic properties. Several complementary techniques were used to investigate the influence of Co on structural and electromagnetic properties of Ni 0.25- x Co x Cu 0.20 Zn 0.55 Fe 2 O 4 with x = 0.00-0.25 (step of 0.05). XRD analysis confirmed the highly crystalline single-phase cubic spinel structure with a prominent peak of the (311) plane. FE-SEM analysis showed the loss of porous gel structure (colloidal backbone) due to addition of cobalt into the present ferrite system. The EDAX analysis confirmed the presence of Ni, Cu, Zn, Co, and O in accordance with the relative stoichiometry of Co-substituted NiCuZn ferrite. The electrical resistivity of ferrites is observed to decrease when Co 2+ ions are substituted, regardless of AC and DC. The dielectric properties (ε' and ε″) of ferrites exhibited a consistent decrease as the frequency increased, and this trend persisted even at higher frequencies. VSM analysis showed the normal magnetic hysteresis of the developed ferrite system. At x = 0.05, the saturation magnetization of the ferrite was obtained to be the highest among the other substitution levels of Co. The Curie temperature fell down when there was a higher concentration of cobalt in the ferrite system ( x = 0.20). After reaching a specific temperature, the μ i values decreased abruptly, with an increase in the temperature. The steady state may be deduced from the fact that the constant real component of the initial permeability, μ', remained unchanged. However, with decreasing frequency, the values of μ″ decreased dramatically. The present NiCuZn ferrite series displays the enhanced dielectric properties suggesting the capability of potential candidates for microwave absorption applications with enhanced electromagnetic properties., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Surface area and surface active sites are two important key parameters in enhancing the gas sensing as well as photocatalytic properties of the parent material. With this motivation, herein, we report a facile synthesis of Reduced Graphene Oxide/Tungsten Oxide RGO/WO 3 hierarchical nanostructures via simple hydrothermal route, and their validation in accomplishment of improved H 2 S sensing and highly efficient solar driven photo-degradation of RhB Dye. The self-made RGO using modified Hummer's method, is utilized to develop the RGO/WO 3 nanocomposites with 0.15, 0.3 and 0.5 wt% of RGO in WO 3 matrix. As-developed nanocomposites were analyzed using various physicochemical techniques such as XRD, FE-SEM, TEM/HRTEM, and EDAX. The creation of hierarchic marigold frameworks culminated in a well affiliated mesoporous system, offering efficient gas delivery networks, leading to a significant increase in sensing response to H 2 S. The optimized sensor (RGO/WO 3 with 0.3 wt% loading) exhibited selective response towards H 2 S, which is ~ 13 times higher (R a /R g  = 22.9) than pristine WO 3 (R a /R g  = 1.78) sensor. Looking at bi-directional application, graphene platform boosted the photocatalytic activity (94% degradation of Rhodamine B dye in 210 min) under natural sunlight. The RGO's role in increasing the active surface and surface area is clarified by the H 2 S gas response analysis and solar-driven photo-degradation of RhB dye solution. The outcome of this study provides the new insights to RGO/WO 3 based nanocomposites' research spreadsheet, in view of multidisciplinary applications.

We report on the electromagnetic properties of Co 2+ substituted spinel MgCuZn ferrites developed via a facile molten salt synthesis (MSS) route. The choice of synthesis route in combination with cobalt substitution led to strong electromagnetic properties such as high saturation magnetization (i.e., 63 emu/g), high coercivity (17.86 gauss), and high initial permeability (2730), which are beneficial for the multilayer chip inductor (MLCI) application. In a typical process, the planned ferrites were synthesized at 800 °C using sodium chloride as a growth inhibitor, with dense morphology and irregularity in the monolithicity of the grains. The compositional analysis of as-prepared ferrite confirms the presence of desired elements with their proportion. The crystallite size (using X-ray diffraction (XRD) analysis) for different samples varies in the range of 49-51 nm. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis showcases the compact morphology of the developed samples, which is typical in the ferrite system. The dielectric properties (dielectric-loss and dielectric-constant) in the frequency range of 100Hz-1MHz suggest normal dielectric distribution according to interfacial polarization from Maxwell-Wagner. From the developed ferrites, upon comparison with a low dielectric loss with high permeability value, Mg-Cu-Zn ferrite with Co = 0.05 substitution proved to be a stronger material for MLCIs with high-performance applications.

A robust synthesis approach to develop CuO/ZnO nanocomposites using microwave-epoxide-assisted hydrothermal synthesis and their proficiency toward H 2 S gas-sensing application are reported. The low-cost metal salts (Cu and Zn) as precursors in aqueous media and epoxide (propylene oxide) as a proton scavenger/gelation agent are used for the formation of mixed metal hydroxides. The obtained sol was treated using the microwave hydrothermal process to yield the high-surface area (34.71 m 2 /g) CuO/ZnO nanocomposite. The developed nanocomposites (1.25-10 mol % Cu doping) showcase hexagonal ZnO and monoclinic CuO structures, with an average crystallite size in the range of 18-29 nm wrt Cu doping in the ZnO matrix. The optimized nanocomposite (2.5 mol % Cu doping) showed a lowest crystallite size of 21.64 nm, which reduced further to 18.06 nm upon graphene oxide addition. Morphological analyses (scanning electron microscopy and transmission electron microscopy) exhibited rounded grains along with copious channels typical for sol-gel-based materials . Elemental mapping displayed the good dispersion of Cu in the ZnO matrix. When these materials are employed as a gas sensor, they demonstrated high sensitivity and selectivity toward H 2 S gas in comparison with the reducing gases and volatile organic compounds under investigation. The systematic doping of Cu in the ZnO matrix exhibited an improved response from 76.66 to 94.28%, with reduction in operating temperature from 300 to 250 °C. The 2.5 mol % doped Cu in ZnO was found to impart a response of 23 s for 25 ppm of H 2 S. Gas-sensing properties are described using an interplay of epoxide-assisted sol-gel chemistry and structural and morphological properties of the developed material., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

We report a facile, green synthesis of graphene/Ag/ZnO nanocomposites and their use as acetone sensors via a medicinal plant extraction assisted precipitation process. The choice of plant extract in combination with metal nitrates led to self-sustaining colloid chemistry. Along with the green synthesis strategy, structural, morphological and gas sensing properties are described., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report a facile synthesis of Cerium doped MgFe 2 O 4 nanocomposite ferrite and its usability as gas-sensor via simple and robust synthesis approach of glycine-combustion-process. The route utilizes metal nitrates (Ce, Mg, Fe -nitrates) and glycine, in aqueous solution. The involved sol-gel concept was explained on the basis of zwitterion characteristic of glycine. The analysis of the developed ferrite was done in two different ways - i) effect of Ce-doping concentration, and ii) effect of sintering temperature. With the ferrite system MgFe 2-x Ce x O 4 , the doping concentration of Ce was varied from 0.04 to 0.12 with the step x = 0.04, and sintering was done at two different temperatures i.e. 973K and 1173K. As-produced composite system was examined for their gas response towards reducing gases such as LPG, ethanol, acetone and ammonia. The material displayed excellent gas sensing properties towards acetone for wide operating temperature range of 575-675 K. The XRD analysis revealed nanocrystallinity with crystallite size in the range of 28-34 nm. Microstructural analysis confirmed the porous morphology due to auto-ignition during the combustion reaction. The present investigations confirm the produced MgFe 2-x Ce x O 4 is a promising candidate for fabricating high performance acetone sensor.

We report a facile synthesis of Ru-loaded WO3 marigold structures through a hydrothermal route and their bidirectional applications as enhanced H2S gas sensors and efficient sunlight-driven photocatalysts. The developed hierarchical marigold structures provide effective gas diffusion channels via a well-aligned mesoporous framework, resulting in remarkable enhancement in the sensing response to H2S. The temperature and gas concentration dependence on the sensing properties reveals that Ru loading not only improves the sensing response, but also lowers the operating temperature of the sensor from 275 to 200 °C. The 0.5 wt% Ru-loaded WO3 shows selective response towards H2S, which is 45 times higher (142) than that of pristine WO3 (3.16) sensor, whereas the 0.25 wt% Ru-loaded WO3 exhibits the highest photocatalytic activity, as shown by the degradation of rhodamine B (RhB) under natural sunlight. The gas sensing and photocatalytic properties are explained through the role of Ru and the structural and morphological properties of the developed material.