Laser Synthesis Of Mesocrystal Cupric Oxide For Gas Sensing

Mesocrystal is known as an unusual material deriving from the self-assembling of nanoparticles and endowed with some obvious characteristics including high specific surface area,pore accessibility;thus,various potential applications such as photocatalysis,lithium-ion batteries,have been extensively reported on mesocrystals in the past few years.On the basis of the moderate electrical conductivity and high density of surface defects,mesocrystal is intrinsically appropriate to gas sensing applications.Nevertheless,few works reported the gas sensors based on mesocrytal materials so far and their gas sensing performance is not as high as expected,which may arise from the existence of a continuous matrix for directing the ordered growth as a template.Pulsed laser ablation in liquid(PLAL)is known as a green,simple and rapid technique for the synthesis of materials,it can create an extremely non-equilibrium environment to produce metastable phases.Herein,we employed PLAL method to synthesize template-free mesocrystals,where colloidal Cu2 O nanoparticles with high stability were first generated by laser ablation,and it proves that their surface charge was partially eliminated through oxidization by testing the zeta potential and observing the self-assembling process,the different atomic distribution of CuO different crystal plane leading to a ordered electrostatic force field which induces the self-assembly of nanoparticles and the formation of highly ordered mesocrystal CuO(M-CuO)with clean surface.We then adopted M-CuO to detect ethanol,a common target gas for CuO sensors,and M-CuO displays the highest sensitivity,the highest selectivity and the shortest recovery time reported so far.Density functional theory(DFT)analysis indicates that mesocrystal is more active than single crystal and polycrystal for adsorbing oxygen molecules,causing thicker depletion layers and extraordinary performance.Our results demonstrate the great potential of mesocrystal materials on the next generation of gas sensors.