Ruqiang Bao

Excimer laser ablation of a Pt target in water: the observation of hollow particles

Micro/nanoparticles were fabricated by pulsed-excimer-laser ablation of a Pt target in water. Three kinds of hollow Pt particles (coalesced by micrograins, assembled by nanocrystals or with smooth shells) were observed together with solid particles using different laser fluences (2.3-6.8 J cm(-2)) and after 6000 laser shots. We propose that the hollow particles were formed on laser-produced bubbles which provided thermodynamically preferred nucleation sites and diffusion sinks for the laser-fabricated Pt clusters or particles. Although the hollow particles are a small proportion, the results have extended the scope of particles that pulsed-laser ablation in liquid can fabricate, and have enriched the mechanistic scenario of laser ablation and nanostructure formation in liquid.

Hollow nanoparticle generation on laser-induced cavitation bubbles via bubble interface pinning

We report the self-assembly of ZnOx (0≤x≤1) (and permalloy) nanoclusters into hollow nanoparticles using pulsed laser ablation of bulk Zn (or permalloy) in ethanol–water binary mixture. The self-assembly is due to the trapping of laser-produced nanoclusters by the interfaces of cavitation bubbles and the bonding of the nanoclusters by capillary attraction. It was found that the bubbles generated in the mixture have significantly longer lifetimes compared to water alone, which provide an increasing chance to absorb diffusive nanoclusters. The mixture could be adjusted by adding viscous surfactant that makes the pulsed laser ablation in liquid a promising method for the discovery and fabrication of other hollow geometries.

Generation of Ag2O Micro-/Nanostructures by Pulsed Excimer Laser Ablation of Ag in Aqueous Solutions of Polysorbate 80

A new route to synthesis of Ag(2)O micro-/nanostructures, including a mixture of cubes, pyramids, triangular plates, pentagonal rods, and bars, has been developed by pulsed excimer laser ablation of bulk silver in water using polysorbate 80 as surfactant. The polysorbate 80 played an important role in the formation of the Ag(2)O structures, and similar structures could be obtained in polysorbates 20 and 40 aqueous solutions. We have proposed a mechanism to explain the formation of Ag(2)O structures. This laser ablation method provides a unique approach to discover and fabricate new Ag(2)O morphologies.

Fabrication and formation mechanism of hollow MgO particles by pulsed excimer laser ablation of Mg in liquid.

We report on the formation of hollow MgO particles by excimer laser ablation of bulk Mg in water and aqueous solutions of sodium dodecyl sulfate (SDS) and sodium citrate (SC). Lamellar nanostructures of Mg(OH)(2) also formed in water, but the formation could be avoided by the addition of SDS or SC. Laser ablation produced not only Mg species that were oxidized into MgO and Mg(OH)(2) in water, but also cavitation bubbles. The bubble interfaces trapped the MgO nanoparticles to decrease the surface free energy of the system, finally resulting in hollow particles.

Charge carrier lifetime in boron carbide thin films

Charge carrier lifetime is a critical parameter to improve the conversion efficiency of radioisotope power sources and the sensitivity of neutron detectors based on boron carbide thin films. The effective charge carrier lifetime in B4C boron carbide films has been investigated by using transient photoconductivity decay. The carrier lifetime depends on the characterization conditions as well as the structure of the films. The measured lifetime could be up to ∼1 ms in B4C film, which is much longer than that in conventional semiconductors. The photoresistance change in B4C films and the photovoltaic response of B4C/n-Si(100) heterojunctions have also been studied.

Fabrication of Dispersed Permalloy Nanoparticles by Pulsed Laser Ablation in Aqua

Permalloy (Ni 81 Fe 19 ) nanoparticles with diameters of hundreds of nanometers have been successfully fabricated by pulsed laser ablation (PLA) in air, distilled water, pure ethanol and sodium dodecyl sulfate (SDS) aqueous solutions. The permalloy nanoparticles made in SDS solutions are typically spherical in shape. Lower laser energy with lower frequency leads to the formation of smaller permalloy nanoparticles. Higher concentration of SDS results in smaller nanoparticles. Lastly, we found some unusual permalloy nanoparticles with interesting morphologies made by PLA in air, distilled water and ethanol.