Facile green synthesis of 2D hexagonal MoO3 for selective detection of ammonia at room temperature

A facile green synthesis of 2D MoO3 has been demonstrated for detection of ammonia at room temperature. The bulk MoO₃ was exfoliated in water via ultrasonication assisted liquid exfoliation technique. Interestingly, the resulting MoO₃ nanosheets exhibited metastable hexagonal phase unlike the base material (orthorhombic (α) MoO3), as confirmed by different characterization techniques. The phase stability has been confirmed by annealing studies and Thermo-gravimetric analysis (TGA) and the complete transformation back to α-MoO₃ was observed at 300 °C. The phase transformation has been attributed to the intercalation of water molecules in the 2D layers of MoO₃. The dispersion in organic solvents like ethanol further proves this argument as no phase transformation was observed in the later. The exfoliated hexagonal MoO₃ based devices responded fairly well towards ammonia in the concentration range of 0.3 ppm to 5 ppm at room temperature and also superior to the ones prepared in Ethanol medium.