Segmented Gas-Liquid Flow for Particle Synthesis

Segmented gas-liquid Taylor fiow was used for particle synthesis within the liquid slugs. Tetraethylorthosilicate in ethanol was hydrolyzed by a solution of ammonia, water, and ethanol (Stober synthesis) [166]. The resulting silicic acid monomer Si (0H)4 is then converted by polycondensation to colloidal monodisperse silica nanoparticles. These particles have industrial application, for example, in pigments, catalysts, sensors, health-care, antireflective coatings, and chromatography. 

More recently, gold nanopartides were synthesized from HAuCU with rapid reduction by NaBH4 [91,167]. It is demonstrated that it is the shp vdodty between the two fluids and internal mixing in the continuous-phase slugs that govern the nature of the particle size distribution. 

The Taylor flow microreactor comprised a micromixer for mixing of the precursors for the particle synthesis followed by a gas inlet for separating this continuous mixed liquid stream into segments separated by gas bubbles [165-167]. 

Silica nanopartides had a diameter of200-500 nm [167], while gold particle sizes was 3.8 0.3, 4.6 2.1, and 4.9 3.0nm at residence times of 10, 20, and 40s, respectively [167]. This is explained by the well-defined residence time with reduced axial dispersion of the liquid segments [165-167]. In addition, by moving the liquid segments through a tube recirculation flow sets in which is very effective in liquid mixing. Moreover, a careful choice of continuous and dispersed phases is necessary to control the nanoparticle size and size distribution. 

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