Synthesis of silica nanoparticles using micromixers and batch reactors

LAURA GUTIERREZ, LEYRE GOMEZ, MANUEL ARRUEBO, JESÚS SANTAMARÍA

Zaragoza

Workshop; 1st Spain\Hong Kong Bilateral Workshop on Micro and Nanosystems & Ibernam Meeting 2010; 2010

Instituto de Nanociancias de Aragón (INA)-Universidad de Zaragoza.

Silica nanoparticles have been synthesized with an interdigital micromixer and with a batch reactor. Micromixers produce narrower particle-size distributions and shorter mixing times than batch reactors. The synthesis reproducibility is also higher when using micromixers. Micromixers offer the possibility of controlling one synthesis parameter independently which is very interesting when synthesizing nanoparticles. The use of microreactors evolves towards the design of completely automated systems in the synthesis of nanoparticles. When using batch reactors in the synthesis of nanoparticles several drawbacks usually come into sight such as: i) an heterogeneous distribution of reactants and temperatures in the reactor, ii) insufficient mixing, iii) variations in the physicochemical characteristics of the resulting products for the different batches, iv) their inherent discontinuity, and v) usually, many post-synthesis purification steps are needed. In order to overcome these disadvantages microfluidic reactors (i.e., micromechanized micromixers, capillaries, junctions, etc.) have been used in the synthesis of nanoparticles to allow controlling the reaction temperature and residence time precisely rendering nanoparticles with narrow particle-size distributions. This defined distribution is desirable because many physical properties (i.e., optical band gaps in semiconductors, plasmon band energy in noble metals, superparamagnetism in metals and metallic oxides, etc.) of nanomaterials depend mainly on their size and shape. In microreactors a continuous-flow synthesis takes place in the interphase of two mixing laminar streams controlled by molecular diffusion on a molecular level, whereas, in batch reactors mixing is accomplished by a fast convective process. The small channel dimensions in the microreactors lead to a large surface area-to-volume ratio (10.000¨C50.000 m2/m3 compared to 100 m2/m3 for batch reactors) and to increased driving forces for heat and mass transports. Thus, this straightforward approach has been used to synthesize nanoparticulated materials such as quantum dots, Au, TiO2, Co, Fe3O4, Ag, BaSO4, SiO2, Cu, NaA zeolites, etc. In the work described here the polydispersity of the obtained products of each synthesis and, at the same time, the polydispersity within multiple syntheses is reported