The leaf extract of Azadirachta indica (Neem) plant was utilized as reducing agent for the green synthesis of Mn3O4 nanoparticles (NPs). The crystalline analysis demonstrated the typical tetragonal hausmannite crystal structure of Mn3O4, which confirmed the formation of Mn3O4 NPs without the existence of other oxides. Green synthesized Mn3O4 NPs were applied for the catalytic thermal decomposition of ammonium perchlorate (AP) and as working electrode for fabricating the chemical sensor. The excellent catalytic effect for the thermal decomposition of AP was observed by decreasing the decomposition temperature by 175 degrees C with single decomposing step. The fabricated chemical sensor based on green synthesized Mn3O4 NPs displayed high, reliable and reproducible sensitivity of similar to 569.2 mu A mM(-1) cm(-2) with reasonable limit of detection (LOD) of similar to 22.1 mu M and the response time of similar to 10 s toward the detection of 2-butanone chemical. A relatively good linearity in the ranging from similar to 20 to 160 mu M was detected for Mn3O4 NPs electrode based 2-butanone chemical sensor. (C) 2016 Elsevier Inc. All rights reserved.