Project and Construction of a Differential Mobility Analyzer to Produce Monosized Nanoparticles

Abstract

The nanotechnology has become an important area, either because the special features of nanometric particles confer to products, or due to a maximum limit of emission of such particles in air. However, the reduced size of this kind of particle limit them to be separated by conventional techniques, and a good way to ensure an aerosol stream with monodispersed particles is to use the electrical mobility technique. This theory is based on the ability of a charged particle to cross an electrical field, thus depending of the size of particles, the bigger ones will arrive later in the central electrode than the smaller ones, and only a narrow band of sizes will be collected in a slit located in the bottom of the equipment. This work aimed to project and construct a Differential Mobility Analyzer (DMA) in order to produce an aerosol containing NaCl nanoparticles monodispersed, from a aerosol polydispersed produced by an atomizer. The operating principle is to charge NaCl nanoparticles with a neutralizer so that they can be collected according to the voltage applied to the DMA in a specific range of size distribution. The unit comprises a compressor for generating air current, high efficiency filters in order to generate ultrapure air, atomizer, reservoir of NaCl solution to generate aerosol, a diffusion dryer to remove moisture silica current gas, a source of X-rays to charge nanoparticles, a source of high voltage to be applied to the DMA, a DMA to classify the nanoparticles and a particle counter to perform the counting of particles before and after DMA. Preliminary results indicated the dependence of the particle size with the applied electric field. The results were very promising.