Electronic sensitization enhanced p-type ammonia gas sensing of zinc doped MoS2/RGO composites

Room Temperature and Humidity Resistant NH3 Detection Based on a Composite of Hydrophobic CNTs with Sulfur Nanosheets

A composite of sulfur nanosheets (S-NSs) with hydrophobic carbon nanotubes (H-CNTs) was designed, and a chemiresistive gas sensor based on this composite material was constructed for breath analysis of NH3 detection at room temperature. Taking advantage of the capillary condensation of CNTs, the hydrophobic effect of hexadecyltrimethoxysilane (HDTMS), and the high sensitivity of S-NSs to NH3 detection, the constructed sensor showed an improved humidity-resistant capacity and is capable of detecting breath-relevant NH3 concentrations down to ppb level under high humidity. The fabricated gas sensor exhibited fast response/recovery (18/26 s) and good stability. Online monitoring for exhaled breath analysis shows good recovery with a stable baseline, providing a potential practical application. The research also facilitates the development of commercial low-cost breath analysis sensors.

Harnessing mixed-phase MoS2 for efficient room-temperature ammonia sensing

Molybdenum disulfide (MoS2), a notable two-dimensional (2D) material, has attracted considerable interest for its potential applications in gas sensing, despite its typically insulating characteristics, which have limited its practical use. In this study, we present the use of mixed phase MoS2 (1T@2H-MoS2) to overcome sensing limitations of MoS2 material by enhancing its conductivity and demonstrating its high-performance characteristics for sensing ammonia (NH3) at room temperature (20 °C). The 1T@2H-MoS2 was synthesized via a hydrothermal process, and the coexistence of two different phases (the 1T and 2H phases) was confirmed by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. The flower-like morphology was confirmed by field emission scanning electron microscopy (FESEM) and TEM. Our results indicate that the presence of both 1T and 2H phases within the material introduces sulfur vacancies, which we propose are critical to significantly enhancing its sensitivity to NH3 gas. The ammonia-sensing performance of the 1T@2H-MoS2 material was evaluated, and it demonstrated rapid and selective detection of NH3 gas across a wide concentration range (2 ppm to 100 ppm), with a very swift response time (7 s), fast recovery and high selectivity at room temperature without requiring heating. This improvement is attributed to the increased conductivity and effective active sites provided by the sulfur defects. This study underscores the potential of mixed-phase MoS2 in developing rapidly responsive and highly selective NH3 sensors, paving the way for the safety monitoring of hazardous gases in various industrial settings.

Solution-Processable and Printable Two-Dimensional Transition Metal Dichalcogenide Inks

Two-dimensional (2D) transition metal dichalcogenides (TMDs) with layered crystal structures have been attracting enormous research interest for their atomic thickness, mechanical flexibility, and excellent electronic/optoelectronic properties for applications in diverse technological areas. Solution-processable 2D TMD inks are promising for large-scale production of functional thin films at an affordable cost, using high-throughput solution-based processing techniques such as printing and roll-to-roll fabrications. This paper provides a comprehensive review of the chemical synthesis of solution-processable and printable 2D TMD ink materials and the subsequent assembly into thin films for diverse applications. We start with the chemical principles and protocols of various synthesis methods for 2D TMD nanosheet crystals in the solution phase. The solution-based techniques for depositing ink materials into solid-state thin films are discussed. Then, we review the applications of these solution-processable thin films in diverse technological areas including electronics, optoelectronics, and others. To conclude, a summary of the key scientific/technical challenges and future research opportunities of solution-processable TMD inks is provided.