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Low power, high sensitivity, and selectivity chemiresistive gas sensors are in urgent demand for hydrogen sulfide (H2S) detection to protect human health and the world's ecosystem. In this study, multiwalled carbon nanotubes (MWCNTs) and copper oxide (CuO) submicrometer size particles' compositions were utilized to fabricate low-temperature H2S gas sensors, which were prepared using a screen-printing technique on inter-digited patterned SiO2/Si substrates. The heterostructure of MWCNT@CuO was confirmed through high-resolution transmission electron microscopy analysis and x-ray diffraction patterns. The x-ray photoelectron spectroscopy analysis reveals the chemical states, binding energies, and oxygen vacancy (Ov). Brunauer–Emmett–Teller analysis of nitrogen physisorption analysis was conducted on the samples to analyze sensor surface areas and pore size distribution. The as-fabricated MWCNT@CuO sensor shows a relative response (ΔR/R%) of 73% toward 10 ppm H2S at 50 °C temperature in a selective manner, which is 1.6 times higher than that of devices based on bare CuO. The MWCNT@CuO interface modifies the morphology and also constructs a p–p heterojunction. This leads to the reforming of the band structure and results in a low resistance of the matrix, as well as a high chemisorbed oxygen content. The use of metal oxide semiconductors with MWCNTs offers a promising approach for the development of high-performance gas sensors that are energy-efficient. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) has a crucial role in advancing various fields such as Industry 4.0, Big Data, and Machine-to-Machine technologies. All systems continuously gather information on various parameters such as temperature, speed, pressure, health data, environmental conditions, and consumption. Considering this, we've developed a novel fabrication method for H 2 S gas sensor prototypes. These sensors are based on noble metal-functionalized on metal oxide semiconductor (MOS) chemiresistors. The fabrication process involved growing CuCrO 2 sensing thin film on SiO 2 /Si substrates using the RF sputtering method. Subsequently, Pd nanoparticles, known for their excellent gas-sensing catalyst properties, were functionalized onto the CuCrO 2 films using DC sputtering with varying sputtering times of 3, 6, 9, and 12 s. Nanorice morphology boosts gas absorption, capturing more target molecules. A 9 s Pd sputtering time greatly improved H 2 S sensing over other gases. CuCrO 2 film with Pd showed the highest 72.3% response to 50 ppm H 2 S, detecting down to 0.5 ppm. These results were achieved at the optimal working temperature of 150 °C. After optimizing parameters, we transferred the technology to develop a sensor module for the prototype with IoT integration. The prototype sensor connects to NODEMCU-ESP8266 Wi-Fi, which links to a smartphone through a mobile hotspot. [Display omitted] • Fabrication of Pd anchored CuCrO 2 nano rice morphology for highly toxic H 2 S gas sensors. • Pd NPs increase surface-to-volume ratio and improved the sensing performance due to spillover effect. • The measured sensing response was 72.3% at 150 °C for 50 ppm of H 2 S around with a lower detection limit of.5 ppm. • In Pd/CuCrO 2 better selectivity as compared to pristine CuCrO 2 and drastic improvement in sensitivity is observed. • Optimized sensor is interface with IoT platform for the real-life application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comprehensive review of 2D transition metal dichalcogenides (TMDs) based gas sensors. • Approaches to develop room temperature gas sensors. • Strategies to fabricate low power and highly selective 2D materials-based gas sensor. • Discussion of different strategies such as doped, decorated and composite 2D MoS2 and MoSe2-based gas sensors. • Detailed explanation of gas sensing mechanisms of gas sensors. The goal of current research in gas sensor technology is the development of a highly effective, small gas sensor that is able to operate at room temperature. There has been a surge in interest in 2D nanomaterials for the fabrication of high-performance gas sensor devices after graphene because of the exceptional physical, chemical, optical, and electrical properties of two-dimensional semiconductor nanomaterials. Among various 2D nanomaterials, we are focusing on transition metal dichalcogenides (TMDs) used for the fabrication of room temperature (RT) gas sensors because of their high surface area, large surface activity, extremely high carrier mobility, narrow bandgap, and high conductivity. Molybdenum disulfide (MoS 2) and molybdenum diselenide (MoSe 2), a well-researched TMDs, have drawn considerable attention across diverse domains for gas sensing materials at RT due to their intriguing two-dimensional layered structures and electrochemical features. The fabrication of chemiresistor sensors using MoS 2 and MoSe 2 has shown immense promise in meeting present-day demands, highlighting the remarkable technological advancements over the last several decades. It is anticipated that the strategic modification of the surface of MoS 2 and MoSe 2 nanomaterials using the decoration of nanoparticles will play a key role in the development of nanomaterials with unique chemical and physical properties as well as catalytic power, allowing them to boost the overall performance of gas sensors at RT. Herein, this review article provides an in-depth overview of the latest advancements made in MoS 2 and MoSe 2 nanomaterial-based chemiresistive gas sensors for the sensing of toxic gases at RT. Initially, we outline the method for synthesis and growth of MoS 2 and MoSe 2 nanomaterials, and the basic principles of sensing mechanisms are elucidated, relying on the charge transfer dynamics between gas species and MoS 2 and MoSe 2 nanomaterials. Furthermore, this article examines the current developments in the performance of gas sensors based on MoS 2 and MoSe 2 nanomaterials through the combination of nanocomposites, van der Waals heterostructures, doping, and decoration of nanoparticles, as well as their capabilities in sensing gases. Finally, this review offers insights into numerous emerging challenges and potential avenues for future research on gas sensor technologies utilising diverse 2D MoS 2 and MoSe 2 nanomaterials. [ABSTRACT FROM AUTHOR]