there is also a partial understanding of the whole
process underlying the growth of nanostructures. As far as the wet
chemistry synthesis of ZnO crystals is concerned,the role of the
most used reducing agent,hexamethylenetetramine(HMTA),is
currently under debate.Heo et al. [15] described that one-di-
mensional single crystal ZnO nanorods were successfully synthesized on ZnO seed layer substrates by wet chemical method.The effect of HMTA concentration on the functional properties of ZnO
nanostructures was studied.However,the precise effect mechanism of HMTA concentration on the synthesis of ZnO nanostructures has not been revealed. Govenderetal. [16] proposed that
HMTA slowly releases the OH ions by its thermal decomposition
to formaldehyde and ammonia. Ashfold et al. [17]