Nanoparticle Preparation Via Plasma Reduction Of Noble Metal Elements In Ionic Liquid

Plasma technology has already played an active role in the scientific research and industrial production owing to its low energy cost, high energy density and non-environmental pollution. It is also very promising to utilize the high-energy electrons in the reduction of metal ions. Moreover, plasma reduction is an efficient and green reduction process. Compared to traditional methods, electron itself acts as the direct reductant instead of chemical reducing agents, and the as-prepared supported catalysts show better dispersion and higher activity. Recently, the so-called "liquid-plasma" has been developed as a new direction of plasma technology. In fact, the effective part of this plasma is the liquid-plasma interface, where the active particles in the plasma facilitate chemical reactions or nanoparticles are formed.In this paper, the sub-atmospheric dielectric barrier discharge was used as the plasma source to treat ionic liquids and ionic liquid solution containing noble metal salts. We treated three ionic liquids, [bmim]Cl, [bmim]BF4 and [bmim]PF6 in a certain plasma condition, and studied the characteristics of functional groups by FTIR analyses. We found that the FTIR spectrum was almost in accordance with the corresponding pure sample despite some change in relative intensity of hydroxyl at high wavenumber. It confirmed that both the organic cations and anion groups stayed unchanged and the integral structure kept stable.We report for the first time that SADBD was used to reduce Pd(NO3)2 from its [bmim]BF4 solution to well-dispersed ~5 nm Pd nanoparticles whose surface was dominated by Pd (0). By introducing stabilizers, monodisperse Au nanoparticles with mean size of 1.7 nm, Au nanorods with diameter of 6~7 nm and aspect ratio of 3~7 and Au nanorods with diameter of 20~35 nm and aspect ratio of 4~8 were synthesized respectively in a similar method and modified experimental parameters. In addition, we analyzed the crystal structure of nano Au and the mechanism of crystal nucleation and growth in combination of the high-resolution transmission electron microscopy (HRTEM) image.