Photochemical Interaction of Polystyrene Nanospheres with 193 nm Pulsed Laser Light

Abstract

The photochemical interaction of 193 nm light with polystyrene nanospheres is used to produce particles with a controlled size and morphology. Laser fluences from 0 to 0.14 J/cm 2 at 10 and 50 Hz photofragment nearly monodisperse 110 nm spherical polystyrene particles. The size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and the morphology of the irradiated particles is examined with a transmission electron microscope (TEM). The results show that the irradiated particles have a smaller mean diameter (∼25 nm) and a number concentration more than an order of magnitude higher than nonirradiated particles. The particles are formed by nucleation of gas-phase species produced by photolytic decomposition of nanospheres. A nondimensional parameter, the photon-to-atom ratio (PAR), is used to interpret the laser-particle interaction energetics.

Laser ablation of nanoscale particles with 193 nm light

“…2(b)). Spheres with a mean diameter of~23 nm are also observed with polystyrene after irradiation at 0.12 J/cm 2 [8]. The electron microscope images of all particles examined are qualitatively consistent with the SMPS results.…”

“…When polystyrene size distributions at different laser conditions were non-dimensionalized using number and volume concentrations, a universal size distribution was observed, suggesting that the irradiated particles are formed by the same mechanism [8]. The nanospheres observed with the irradiated polystyrene and gold indicate that these particles are formed by nucleation of the photolyzed species rather than fracture of the original particles.…”

“…The experimental apparatus for the laser ablation of nanoparticles was described previously [6][7][8][9]. Soot particles are generated from a CH 4 −air nonpremixed flame, while polystyrene, gold, and NaCl particles are produced from a nebulizer (BGI, CN-24).…”

“…Here, we review our recent studies [6][7][8][9] on 193 nm laser ablation of nanoscale polystyrene, soot, NaCl, and gold particles in a constrained gas stream. These particles are chosen because they represent different classes of materials, and their size distributions and morphology are different.…”

Geometrical Factors in Conductance Through Molecular Films

“…Thus the present mechanism may be one of the sources of the temperature dependence of the conductance. NOTE ADDED IN PROOF: Some recent experimental results 23,24 have been interpreted as a possible realization of the mechanism described in this paper. It also may be relevant to the conformational switching in single molecules reported by Donhauser et al 22…”