Volume 7, No. 1, March 2007, Pages 1-16 PDF(493 KB)
Using a Fast-Scanning Electrical Nanoparticle Sizer to Characterize Nanoparticles from Laser Ablation
Chaolong Qi1, Da-Ren Chen1 , Meng-Dawn Cheng2
1 Environmental Engineering Science Program Washington University in St. Louis, Campus Box 1180, One Brookings Drive, St. Louis, MO 63130
2 Environmental Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
A Fast-Scanning Electrical Nanoparticle Sizer (FSENS) consisting of a Po210 bipolar charger, a Nano-DMA, and an aerosol electrometer was used to characterize nanoparticles generated by laser ablating the surfaces of cement, chromium-embedded cement, stainless steel, and alumina samples. Different from previous studies, bimodal size distributions, with the nucleation mode having a geometric mean diameter ranging from 5.7-6.6 nm and a geometric standard deviation varying from 1.225-1.379, were observed for all the experimental runs. The curve fitting shows that the bimodal size distribution produced in the laser ablation can be best fitted by a lognormal distribution for the nucleation mode and a Rosin-Rammler distribution for the coagulation mode. At steady state the geometric mean diameter of the coagulation mode was affected by the laser wavelength and target material, but was less influenced by laser energy for a given wavelength. The total particle number concentrations of the two modes appear to be parabolic with respect to the laser fluence. At a given fluence, the stainless-steel sample produced the highest particle number concentration with 532- and 1064-nm lasers; the alumina sample produced the lowest particle number concentration with 266- and 1064-nm lasers. The chromium-embedded cement sample produced fewer particles with 532- and 1064 nm lasers than the pure cement sample. This study also demonstrated that FSENS can provide snapshots of the nanoparticle dynamics during laser ablation in cases of low laser fluence.
Nanoparticle; Laser ablation; Nanoparticle dynamics.