Laser Zentrum Hannover (LZH) is using the Nanosight nanoparticle characterisation LM-10 system to study metal nanoparticles generated by laser ablation.
The LZH research team, in conjunction with the Medizinische Hochschule in Hannover, has been using nanoparticle tracking analysis to study silver nanoparticles generated in situ using laser-ablation techniques.
Laser-generated nanoparticles show potential for medical applications since they are free of impurities and toxicities.
Furthermore, their electrical properties allow a directionally controlled diffusion under externally applied electric fields enabling deposition on conducting surfaces.
The Nanosight system was selected as it allows particle-to-particle tracking in solution.
By capturing the light scattered by the nanoparticles at a frequency of 30 frames per second, the hydrodynamic diameter of the particles may be calculated.
The chamber of the system has been modified to take a silver target, which is ablated using a Ti:Sapphire laser.
Initial ablation (over a short pulse time - for example, 30 seconds), a range of diameters of particle species are observed in a range of 50-250nm.
However, if the ablation process is increased, for example, to 400 seconds, the distribution shrinks to a single peak of approximately 50nm.
This stabilisation process is due to interaction of the freshly generated colloidal particles with the incident laser light.
This is essentially a de-agglomeration effect, which is in accordance with observations of UV-VIS spectra.
The chamber of the system has been further modified to house a pair of electrodes.
This enables the mobility of the nanoparticles to be monitored as a function of their charge.
This has been applied to develop an electrodeposition technique that is now being used for the deposition of gold on neuro implant electrodes.
This work was reported at the LPM2008 9th International Symposium on Laser Precision Microfabrication.
It clearly shows the relationship of the number of pulses to the hydrodynamic diameter of the nanoparticles being produced - a result that could not have been readily observed using conventional particle-characterisation techniques such as electron microscopy or dynamic light scattering.
