Substrate free ultrasonic-assisted hydrothermal growth of ZnO nanoflowers at low temperature.

ZnO nanoflowers (NFs) have been synthesised using a simple cost effective ultrasonic-assisted hydrothermal method at low temperature of 95 °C. Here the NFs consist of petal-like arrangement of several hexagonal-shaped nanorods, the length and diameter of which lie in a range of 100-150 nm and 30-70 nm, respectively. ZnO NFs possess hexagonal wurtzite phase, high crystallinity and strong absorption in the UV region. The optical band gap 3.25 eV of these NFs estimated by two different ways is found to be nearly the same. Room temperature photoluminescence spectrum reveals that the ZnO NFs exhibit dominant UV emission and three major emissions in the visible i.e. violet, blue-green and yellow. NFs are promising nanostructures for application in environment related sensors and antimicrobial activity.