Surfactant-Mediated Morphological Alteration of WO3 Nanostructures for Efficient NO2 Sensing

Abstract

The addition of surfactant during hydrothermal growth greatly affect the surface morphology of nanostructures [1]. Here, to see the impact of surfactant in the hydrothermal growth of WO3 nanostructures, we have used Cetyl trimethyl ammonium bromide (CTAB) and Sodium chloride (NaCl) as surfactants during WO3 nanostructure formation. Flower-like WO3 nanostructure were successfully grown by CTAB surfactant while nanorod-like structures were obtained in the presence of NaCl at an optimized pH level. Na2WO4·2H2O salt was used with CTAB and NaCl surfactant separately in acidic (HCl (3M)) medium for the hydrothermal growth. The shape of nanostructures plays a crucial role for gas sensing [2]. WO3 nanorods grown by NaCl surfactant exhibited excellent sensitivity for NO2 at ppm level as compared to WO3 nanoflowers grown CTAB surfactant. In addition to the surface area, current conduction also depends on the surface morphology which is helpful to improve the response-recovery characteristics of the sensing device. Interestingly, we observe that hydrothermally grown WO3 with NaCl surfactant is an ideal candidate for NO2 sensing. Fig. 1 FESEM image of WO3 nanostructure with (a) CTAB surfactant, (b) NaCl surfactant and (c) exhibit the sensitivity of WO3 with NaCl and CTAB surfactant at 150 °C on 100 ppm NO2 . Figure 1