Fe3O4 nanoparticles modified WS2 microflakes for ammonia detection at room temperature

The WS2 microflakes heterostructured with n-type Fe3O4 have been explored herein for chemiresistive-type NH3 sensors at room temperature. The microjunctions formed between the two heteromaterials WS2 and Fe3O4 effectively modulate the response of the sensor to ammonia. The Fe3O4/WS2 heterostructured sensor found a three times higher response relative to the single WS2 based one. The optimized concentration of Fe3O4 in the heterostructure sample is 0.2 at%. The sensor also indicates an excellent selectivity to several volatile organic compounds (VOCs) such as formaldehyde, toluene, methanol, ethanol, and acetone. The sensing mechanism of the sensor to NH3 at room temperature were examined using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It reveals that the redox reactions of NH3 on Fe3O4/WS2 were more prominent compared to the WS2 alone. The enhanced sensitivity of the Fe3O4/WS2 based sensor could thus be attributed to the joint effects of both electronic and chemical sensitizations induced by the Fe3O4/WS2 heterostructures.