研究目的
To investigate the ultrasound-assisted liquid exfoliation method for mass-producing MoS2 nanomaterials, study the effect of ultrasonic time on their size and yield, fabricate thin film humidity sensors, and examine their sensing performance and mechanism.
研究成果
The ultrasound-assisted exfoliation method successfully produces few-layer MoS2 nanomaterials with controlled size and high yield. Thin film humidity sensors fabricated from these materials exhibit excellent and rapid response, outperforming bulk MoS2 sensors. Longer ultrasonic treatment results in smaller nanosheets with more active edge sites, leading to higher sensing response. This approach enables mass production and practical application of MoS2-based sensors.
研究不足
The study uses a specific solvent mixture and ultrasonic parameters; other conditions might yield different results. The DLS analysis assumes spherical particles, which may not fully capture the disk-like morphology of nanosheets. The sensor fabrication and testing are at room temperature, and performance under other conditions is not explored. The method may not be optimized for all potential applications, and scalability to industrial levels is not addressed.
1：Experimental Design and Method Selection:
Ultrasound-assisted liquid exfoliation method was used to exfoliate MoS2 powder in a solvent mixture of ethanol and deionized water (45:55 ratio) with ultrasonic treatment in iced water for 1-4 hours using a horn probe sonic tip. The ultrasonic power was fixed at 450 W with a pulse of 20s on and 10s off. After treatment, the dispersion was centrifuged at 3000 rpm for 30 minutes to collect the supernatant, repeated once to remove un-exfoliated material. Thin film sensors were fabricated by drop-casting the exfoliated MoS2 solution onto alumina substrates with interdigital Pt electrodes, followed by heating at 80°C for 1 hour and sintering at 300°C in Ar gas for 1 hour. Sensing performance was tested using a home-built setup with humidity gas generated by a bubbling system and mixed with dry air, with total flow set to 1000 sccm, and response measured as resistance change.
2：Sample Selection and Data Sources:
MoS2 powder from Aldrich-Sigma was used as the starting material. The exfoliated nanomaterials were characterized using AFM and DLS for morphology and size analysis.
3：List of Experimental Equipment and Materials:
MoS2 powder (Aldrich-Sigma), ethanol, deionized water, ultrasonic processor (Sonic VCX750 with horn probe tip), centrifuge, AFM (Bruker Nano N8 NEOS), DLS (Malvern Zetasizer Nano ZS with 633 nm HeNe laser), alumina substrates with interdigital Pt electrodes, hot-plate, mass flow controllers, mass flow meters, commercial humidity sensor for validation.
4：Experimental Procedures and Operational Workflow:
Disperse MoS2 powder in solvent, ultrasonicate for specified times, centrifuge to collect supernatant, characterize with AFM and DLS, drop-cast onto substrates, heat and sinter, test sensing response to humidity gas at room temperature with varying relative humidity.
5：Data Analysis Methods:
Sensing response defined as R_H / R_a (resistance in humidity over dry air), response and recovery times measured as time to 90% change. Size analysis from DLS using z-average diameter and equation for disk-like structures.
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