Quench particle geometry

Many of the adsorbents used have rough surfaces they may consist of clusters of very small particles, for example. It appears that the concept of self-similarity or fractal geometry (see Section VII-4C) may be applicable [210,211]. In the case of quenching of emission by a coadsorbed species, Q, some fraction of Q may be hidden from the emitter if Q is a small molecule that can fit into surface regions not accessible to the emitter [211]. 

With some assumptions (basically that process yield is close to unity, that is that all the available polymer is used to form the nanoparticles, with concentration at the exit close to equilibrium and polymer solubility in the quenched suspension considered negligible), from the measured particle size it is possible to estimate the number of particles formed, and thus to evidence the dependence of nucleation rate on initial polymer concentration and also the effect of the mixer geometry (details of the calculation procedure can be found in [107]). Figure 9.16 confirms that with the same feeding conditions a larger number of particles is formed in the CIJ with respect to the Tee mixer as there are imcertainties in the effective density of the nanoparticles, the particles concentration, referred to as the inlet solvent volume times the polymer particle density, is plotted. 

Figure 9.16 Influence of the mixer geometry on nucleation rate the estimated number of nanospheres produced (calculated from exit particle size assuming imit yield and saturated solution at the exit). CIJ and Tee mixer (d = 1 mm) are compared, PEGylated copolymer in acetone quench volumetric ratio = 0.2.

Figure 9.17 Comparison of nano spheres size produced in CIJ and Vortex mixer with different number of inlets d. = 1 mm). Particle size is plotted versus the inlet jet velocity MIV has the feeding geometry shown in Figure 9.3a, with alternate solvent-containing-polymer and antisolvent streams, and obviously allow a throughput two times larger than the other devices at same feeding velocity. PEGylated copolymer in acetone, 6 mg/mL quench volumetric ratio = 1.

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