Surfactant assisted low temperature synthesis of nanocrystalline ZnO and its gas sensing properties

Vertically aligned ZnO nanorods, faceted microrods, nanoneedles and nanotowers were grown on glass substrates by a cost effective and low temperature aqueous chemical method. Various polymers viz. polyethylenimine (PEI), polyacrylic acid (PAA) and diaminopropane (DAP) were used as structure directing agents. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED) pattern. The aligned ZnO nanorod formation takes place with the predominant orientation along (0 0 2) plane. These nanocrystalline ZnO samples were used to explore gas response properties for acetone, ammonia, LPG and ethanol. It is observed that the sensors based on DAP-directed nanoneedles showed higher response (90%) for acetone gas at 275 °C. The high acetone gas sensitivity and low operating temperature of ZnO nanoneedles can be attributed to the surface morphology.