Novel nanostructured materials are expected to revive materials for chemiresistive sensor applications. MoS2-based gas sensor is widely studied, however, which usually is capable of detecting gas at ppm level. Here, owing to the two-dimensional layered structure that facilitated the surface reaction, sulfur nanosheets (S-NSs) was first designed to composite with MoS2 to improve the sensing performance. Because of the unique electronic and physical properties of S-NSs, the developed chemiresistive sensor based on MoS2@S-NSs nanocomposite demonstrated to realize ultrasensitive detection of NH3 at 0.1 ppt level with a response signal of 68%, and which also showed fast response and recover (9/8.7seconds respectively) at room temperature in air. Except for the good electrical conductivity and the large adsorption site of MoS2, the excellent sensing property of S-NSs itself made the most important contribution to this appealing high sensitivity to NH3. Additionally, this study has also put forth comprehensive gas sensing mechanisms based on experimental results. In essence, this research offers an innovative materials system tailored for the highly efficient detection of NH3.

AbstractCurrently, two-dimensional (2D) layered materials have gained much attention for their outstanding properties. Among these materials, layered sulphur, which is an emerging 2D material, has shown great potential for various applications due to its unique chemical and physical properties. In this study, we present a new electrolytic method for synthesizing layered sulphur using thiourea as the sulphur source and poly-3,4-ethylenedioxy thiophene/polystyrene sulfonate (PEDOT: PSS) as the stabilizer. This method is simple, fast, and has a high yield. Furthermore, a composite material was prepared containing carbon nanotubes (CNTs) and layered sulphur, which was used a cathode material in lithium-sulphur batteries. The prepared cathode exhibited a discharge specific capacity of 450 mAhg−1and a reversible capacity of 46.6% after 40 cycles of reciprocation at 0.1 C cycling current. Electrode design based on layered sulphur composites provides a new idea for the structural design of lithium-sulphur battery cathodes.

Nanomaterials-based gas sensors are conducive to online, real-time monitoring and large-scale production due to their simplicity, low energy consumption and miniaturization. Conventional nanomaterial-based (metal oxide semiconductor or two-dimensional nanomaterials) gas sensors are less sensitive (ppm-ppb level). So, it is significantly meaningful to develop new gas-sensing materials. Herein, Ag@sulfur nanosheets (S-NSs) nanocomposite-based sensor is explored for ultrasensitive detection of NH3 in dry air at room temperature at parts per trillion (ppt) level. Introducing Ag nanoparticles (NPs) on S-NSs, improved electrical conductivity and created more effective adsorption sites, leading to a high response rate of 1.92 for 3 ppt NH3. The developed Ag@ S-NSs sensor showed a linear response to NH3 in the range of 3-70 ppt with correlation coefficient of 0.996. Moreover, the developed Ag@S-NSs sensor showed fast response and recovery time (28/7 s) to NH3. The probable sensing mechanism is supposed that the polarization-induction of NH3 changed of electronic energy level of Ag@S-NSs, and the changed energy is at approximately the same energy level of the Ag@S-NSs itself. Thus, a response signal caused by NH3 with low concentration can also be felt by Ag@S-NSs sensing materials itself.

Using thiourea as a sulfur source, hydrogen peroxide as an oxidant and polyethylene glycol-400 (PEG) as a stabilizer in alkaline medium, a simple hydrothermal method for the synthesis of sulfur quantum dots (S dots) was established. The synthesized S dots have better dispersion in aqueous solution and stronger photoluminescence (PL) intensity. As-synthesized S dots were found to have the ability to generate ·OH and ·O2− radicals in a photocatalysis process, showing good photodegradation performance for rhodamine B (RhB) and good stability. Electrochemiluminescence (ECL) of S dots was observed in alkaline media during oxidation at +1.5 V (vs. Ag/AgCl, sat. with KCl). The method shortens the long synthesis time required during traditional methods. The synthesized S dots were found to be a potential visible-light-active elemental photocatalyst.