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Summary: Wireless sensor networks (WSNs) represent the collection of restricted energy sensor nodes that are deployed in an area of target for gathering potential environment data for decision‐making with respect to their objective of application. However, the implementation of energy‐effective data gathering strategies in large‐scale WSNs is the most challenging due to the limited energy resources. Clustering‐based data gathering strategies are identified to be quite effective for energy saving that directly attributes to extended network lifetime. Moreover, optimal path amid the cluster head (CH) and sink node needs to be selected for sustaining energy efficiency and improving network lifespan. In this article, Hybrid Salp Swarm and Improved Whale Optimization Algorithm (HSSIWOA)‐based clustering scheme is proposed for improving the network lifetime and routing optimization with maximized energy efficacy. It integrated the exploration capability of Salp Swarm Optimization Algorithm (SSOA) with exploitation benefits of Improved Whale Optimization Algorithm (IWOA) for balancing the trade‐off between the rate of exploration and exploitation during CH selection process. It utilized the parameters of residual energy, load balance, intra‐cluster distance, inter‐cluster distance, and node centrality into account during the process of fitness evaluation. It performed well by constructing an optimized number of clusters, such that energy stability and network lifetime are maintained in the network. The experimental results of the proposed HSSIWOA scheme confirmed extended network lifetime of 21.64%, minimized energy utilization of 23.42%, and maximized throughput of 18.56%, better than the baseline approaches. [ABSTRACT FROM AUTHOR]

Molybdenum oxides and sulfides stand out as promising materials for chemiresistive gas sensors. In this study, we tailored MoS2/MoO2 heterostructures, adapting pyrolysis-assisted in situ sulfidation of hydrothermally grown MoO3 by tuning the concentration of the sulfur source. The MoS2 flakes adorning a MoO2 cuboid rod heterostructure represent the n-type semiconducting property, confirmed by Hall measurement. Notably, the sensor demonstrated dual selectivity toward NH3 and NOx at room temperature. To our knowledge, the dual selectivity of the MoS2/MoO2 heterostructure has not been reported previously. The heterostructure, characterized by a higher carrier concentration, displayed enhanced sensitivity, yielding responses of 10.3 and 8.4% to 10 ppm of NH3 and NOx, respectively. The lowest detection limits were 0.32 ppm for NH3 and 0.29 ppm for NOx. Furthermore, the heterostructure sensor exhibited commendable cyclic stability and device reproducibility. A long-term stability assessment over 50 days revealed that the response of the sensor remained at 98.6 and 98.4% toward NH3 and NOx, respectively. Our results show that the optimized n–n heterojunction between MoO2 and MoS2 offers superior sensitivity to NH3 and NOx at room temperature. The results could have potential for the development of dual gas sensors suitable for real-time applications. [ABSTRACT FROM AUTHOR]

Molybdenum trioxide (MoO3) is an excellent material for chemiresistive gas sensors. In this report, we investigated the ammonia sensing behavior of hexagonal (h-MoO3) and orthorhombic (α-MoO3) MoO3. X-ray diffraction study verified the existence of two distinct phases of MoO3. Scanning electron microscopic images revealed that the hydrothermally synthesized h-MoO3 showed prismatic sheets while the α-MoO3 prepared by reflux condensation exhibited agglomerated micropellets. The presence of oxygen vacancies in h-MoO3 was confirmed by high-resolution transition electron microscopy and X-ray photoelectron spectroscopy. The as-fabricated h-MoO3 chemiresistive sensor showed an eight-fold higher sensing response than α-MoO3 for ammonia. The calculated limit of detection was 0.47 ppm, and the sensor exhibited good stability for 60 days. The density functional theory simulation suggested that the relatively higher adsorption energy and charge transfer could be the reason for its higher sensitivity when compared to α-MoO3. [ABSTRACT FROM AUTHOR]

In this article, tungsten trioxide (WO3) nanorods were successfully synthesized by a hydrothermal method and used for the detection of NOx. X-ray diffraction analysis revealed the hexagonal phase of WO3. Field emission scanning electron microscopy and transmission electron microscopy showed WO3 nanorods with an average diameter of 200 nm. X-ray photoelectron spectroscopy analysis showed that the oxidation state of tungsten in WO3 was +6. The WO3 sensor exhibited high sensitivity for the detection of NOx (50 ppm) at 250°C. The sensor showed good linearity from 10 to 50 ppm of NOx, with a sensing response of 8–84%. Even under a high humidity (83%) environment, the sensor detected 50 ppm of NOx. The sensor exhibited good selectivity towards NOx compared to other oxidizing and reducing gases. The sensor also showed excellent stability even after 4 weeks. [ABSTRACT FROM AUTHOR]

Herein, a cobalt oxide/tungsten oxide (Co3O4/WO3) p–n heterojunction for NOx detection is developed and optimized. Field‐emission scanning electron microscopy shows that the WO3 nanorods are embellished with Co3O4 nanostructure. X‐ray photoelectron spectroscopy reveals the presence of oxygen vacancy on the Co3O4 coupled with WO3 heterojunction. Compared to bare WO3 and pure Co3O4, the Co3O4/WO3 heterojunction sensor shows significant sensitivity to NOx at 200 °C. The sensor exhibits higher linearity from 0.4 to 10 ppm of NOx, with a sensing response of 4.4–93%. The NOx sensitivity of the Co3O4/WO3 heterojunction sensor is ninefold higher than that of the pure WO3 sensor. Even in a high humidity (84%) environment, the Co3O4/WO3 heterojunction sensor demonstrates high NOx sensitivity. The sensor maintains remarkable stability measured for up to 4 weeks. The possible NOx sensing mechanism of the Co3O4/WO3 heterojunction is additionally discussed. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) was prepared by reduction of melamine by adapting a pyrolysis method. Porous g-C3N4 (P-g-C3N4) was synthesized by altering the surface as well as the morphology of g-C3N4 by treating with oxidizing acids (chemical protonation). The photocatalytic activity of g-C3N4 and P-g-C3N4 are estimated by degrading various organic dyes namely methyl blue (MB), crystal violet (CV), and rhodamine B (Rh-B) irradiated under sunlight. The optical absorption edge of g-C3N4 was found to be blue-shifted from 2.7 eV to 3 eV on protonation. The g-C3N4 shows superior photocatalytic degradation efficiency in comparison with pristine g-C3N4. The P-g-C3N4 shows enhanced photocatalytic degradation efficiency of 98%, 99%, and 90% for MB, CV, and Rh-B, respectively, in 180 mins under sunlight irradiation with a rate of the reaction of about 4.046 min−1, 5.951 min−1, and 2.260 min−1. Reactive oxygen species experiments revealed that the production of. ·OH radicals are responsible for the deterioration of dyes. The boosted degradation efficacy of P-g-C3N4 is attributed to an increase in the surface area thereby exposing a large number of active sites for dye degradation. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4) was prepared by reduction of melamine by adapting a pyrolysis method. Porous g-C3N4 (P-g-C3N4) was synthesized by altering the surface as well as the morphology of g-C3N4 by treating with oxidizing acids (chemical protonation). The photocatalytic activity of g-C3N4 and P-g-C3N4 are estimated by degrading various organic dyes namely methyl blue (MB), crystal violet (CV), and rhodamine B (Rh-B) irradiated under sunlight. The optical absorption edge of g-C3N4 was found to be blue-shifted from 2.7 eV to 3 eV on protonation. The g-C3N4 shows superior photocatalytic degradation efficiency in comparison with pristine g-C3N4. The P-g-C3N4 shows enhanced photocatalytic degradation efficiency of 98%, 99%, and 90% for MB, CV, and Rh-B, respectively, in 180 mins under sunlight irradiation with a rate of the reaction of about 4.046 min−1, 5.951 min−1, and 2.260 min−1. Reactive oxygen species experiments revealed that the production of. ·OH radicals are responsible for the deterioration of dyes. The boosted degradation efficacy of P-g-C3N4 is attributed to an increase in the surface area thereby exposing a large number of active sites for dye degradation. [ABSTRACT FROM AUTHOR]

In this paper, we reported the controlled synthesis of tungsten disulfide/reduced tungsten oxide (WS 2 /W 18 O 49 ) heterojunctions for highly efficient room temperature NO x and ammonia (NH 3 ) sensors. X-ray diffraction analysis revealed the formation of the oxygen-deficient W 18 O 49 phase along with WS 2 . Field-emission scanning electron microscopy and transmission electron microscopy displayed the formation of WS 2 flakes over W 18 O 49 nanorods. X-ray photoelectron spectroscopy showed the presence of tungsten in W 4+ , W 5+ , and W 6+ oxidation states corresponding to WS 2 and W 18 O 49 , respectively. The WS 2 /W 18 O 49 heterojunction sensor exhibited sub-ppm level sensitivity to NO x and NH 3 at room temperature. The heterojunction sensor detected 0.6 ppm NO x and 0.5 ppm NH 3 , with a corresponding response of 7.1 and 3.8%, respectively. The limit of detection of the sensor was calculated to be 0.05 and 0.17 ppm for NH 3 and NO x , respectively. The cyclic stability test showed that the sensor exhibited high stability even after 24 cycles for the detection of NH 3 and 14 cycles for NO x . Compared to pristine WO 3 and WS 2 , the WS 2 /W 18 O 49 heterojunction showed high selectivity toward NO x and NH 3 . The results could be useful for the development of room temperature NO x and NH 3 sensors.