Photodegradation behavior of ZnO nanorods on various types of organic dyes

In this paper, the effectiveness of ZnO nanorods in degrading various types of organic dyes under UV irradiation was studied. ZnO nanorods were synthesized by solution precipitation method using zinc nitrate tetrahydrate and hexamethylenetetramine as precursors. The nanorods were hexagonal wurtzite ZnO as shown in XRD analysis. The sample displayed strong UV absorption attributed to its wide energy bandgap, i.e. 3.37 eV. The room temperature PL spectrum showed low UV emission with relatively strong visible emission, indicating the presence of large amount of defects in the ZnO nanorods. Three organic dyes, i.e. RhB, MB and MO, were degraded by ZnO nanorods via cycloreversion. The removal efficiencies of ZnO nanorods were 99.3, 96.6 and 74.1% for RhB, MB and MO dyes, respectively after 30 min of UV light (lambda =352 nm) irradiation. The photodegradation of RhB, MB and MO by ZnO nanorods followed the pseudo first-order kinetic reaction. It was proposed that the variation of photodegradation efficiencies by ZnO nanorods was due to the different types of bonding in various organic dyes.