Development Of Nanoparticle Fractionation System For Water Environment

With the rapid development of nanotechnology, the nanoparticles are widely used in the industrial production and existed in daily supplies, especially in the cosmetic. Therefore the nanoparticles have possiblities to enter the environment with different ways. However, nanoparticle leaves serious and unique challenges on scientificity and methodology to the researchers: a basic one of them is how to detect nanoparticles in the environment, and another one is that different coatings, dimensions, surface charges, functions and forming process of the nanoparticles will observably change the characteristics and toxicity of a known nano material. Furthermore, the manufacturers are keeping manufacturaing new materials. Here, the author set up a novel electrical field-flow fraction system with a new capacitively coupled contactless conductivity detection (C4D) unit to detect the nanoparticles.Firstly, the electrical field-flow fraction device was designed based on the existed theory. In order to assure the applied voltage feasible, efficient and convenient, the section shape of the channel should be rectangle；moreover, to generate parabolic laminar flow when carrier entering the channel, the0.1mm thick channel was designed after calculation. Teflon film as the material of the channel was decided due to its excellent chemical inertness and mechanical properties. In the designing of EFFF device, ITO, a kind of transparent conductive materials, was chosen to be the electrodes for optical observation. Three different leakage tesing were addressed to the cartridge and the system; also the possible dead volume was calculated. Cautions like the assembling of the device, current-carrying solution and the samples, sample volume and flow velocity, the chosen of pipe diameter etc. were also discussed. Secondly, the author developed a C4D device with novel electrodes and circuitfor increasing SNR. The optimum conditions were also discussed, including solution concentration, capillary thickness, capillary material, electrode distance, and the effect on the pick-up signal caused by excitation frequency and amplitude. According to the above conditions, the detection limit of up to0.1μmol/L for KCl solution was acquired, the repeatability of the detection was then measured. Finally, characterization testing was addressed to the EFFF system. The key ofEFFF system is the effective voltage to the particles in the electric field. For the electric potential between the two electrodes, the ions in the carrier solution will move to the electrode opposite to their charge and form double electrode layer, which will affect the efficient electric field inflicted badly. If the voltage is too high, the solution will be electrolyzed. So the resistance of the carrier solution was measured with AC voltage, accordingly efficient electric field strength was calculated. Furthermore, the experiment showed that the flow velocity did not affect the separating strength of the particles; but the conductivity of the carrier solution affected the separating strength, that is, the higher the conductivity is, the stronger it will accelerate the separation. Different elution time and peak intensity of the TiO2nanoparticles were found under different applied voltage. It may show the evidence that the efficient electric field is effective. More performance testing will carry on in the future.