Synthesis Of Carbon And Metal Oxide Nanomaterials By Laser Ablation

High energy laser could result in the vaporation of materials and the formation of plasma plume with high temperature and high pressure. When the temperature and pressure of the plasma plume start to drop down, the condensation of the plasma would result in the formation of nanomaterials. Although most of the widely used nanosecond pulsed lasers could output laser beam with high power density to facilitate the synthesis of nanomaterials, the short pulse width (nanosecond) also means the madly short effective acting time that is not conducive to productivity. The long-pulse-width laser (millisecond) has a pulse width million times longer than the nanosecond laser, which is much of meaningful for the growth and yield of nanomaterials.This paper focuses on the preparation of new carbon materials (nanodiamodns, carbon nanotubes, carbon onions, graphene, and fluorescent carbon nanoparticles) by the change of pulse width and starting materials (graphite and carbon black), introduction of catalyst using millisecond laser. Not only the physical and chemical conditions generated by laser with different pulse width and the growth process of nanodiamonds were comparative analyzed, but the equilibrium sizes and growth sizes of nanodiamonds were calculated by combing the thermodynamics and dynamics. Theortical calculations were in good agreement with experimental results and gave reasonable explanation on the formation of nanodiamonds with different sizes. According to the thermodynamics and high resolution transmission electron microscope results, we proposed the formation of multiply twining strtuture (MTS) of nanodiamonds and the corresponding growth theory. Carbon onions with hydrophilic characteristics were synthesized through irradiating carbon black suspension using millisecond pulsed laser at room temperature. Laser energy absorption resulted in the structure transformation of carbon black and the formation of hydrophilic groups on the surface of carbon onion. Carbon onions with hollow cores and the incomplete graphitic shells were produced from the starting materials under high and low laser power density, respectively. All the experimental results showed that the hydrophilic properties of carbon nanoonions orginated from surface hydrophilic ligands. Graphene with single or multiply layer structure were prepared using graphte/nanosized nickel powder as starting material by laser ablation. Carbon nanotubes were synthesized using carbon black/microsized nickel powder by laser ablation. Biocompatible fluorescent carbon nanoparticles (CNPs) were prepared by laser ablating carbon black or graphite suspended in the organic solvents, the tunable of peak in the PL spectrum was realized by adjusting the solvents. Carbon material molecular dynamics simulation results showed that the laser lead to the formation of carbon atoms immediately after laser ablation, the sp1,sp2,sp3 hybridized carbon atoms could exist during the cooling process, the nanodiamonds, carbon nanotubes, graphene could be formed under different environmental conditions.The NiO nanocubes were prepared by laser ablating a nickel target immered in water, the extreme nonequilibrium condition was responsible for the formation of NiO nanocubes generated by laser ablation. Mixed-phase (rutile and anatase) titania nanospheres (MTNs) were prepared by long-pulse-width laser ablation of a bulk titanium target in water. We proposed a mechanism of the formation of MTNs, where thermal dynamics and the long lifetime of plasma plume were responsible for the co-existence of rutile and anatase phases. The photocatalytic properties of MTNs exhibit significant improvement compared with the commercial titania powder. The ablation of metal target immersed in different liquid is promising for the synthsis of nanomaterials with controllable morphology, composition and structure.