The present invention relates to compounds of formula and processes for preparing such compounds, their use in the treatment of obesity, psychiatric and neurological disorders, to methods for their therapeutic use and to pharmaceutical compositions containing them. Other imaging systems and a method are also disclosed. The synthesized ZnO2 nanoparticles are suspended in dimethyl formamide in the presence of Nafion, and then ultrasonicated to create a homogenous suspension, which is used to prepare a thin film of ZnO2 nanoparticles on a metal electrode. In the present invention, it can warn immediately and notice the failures when the output voltage of the LED backlight driving circuit is too high or the failure happens.