Nanoparticle reprecipitation method

Keywords Aggregation-induced enhanced emission (AIEE) Fluorescent organic nanoparticles Ion-association method Organic dye nanoparticles Reprecipitation method Restriction of intramolecular rotation Size-dependent optical properties... 

Organic dye nanoparticles of DHIA and DHBIA (the chemical structures are shown in Fig. 1) have been synthesized in THF/water mixed solvent by a reprecipitation method [32]. These dye molecules possess a 2-(2-hydroxyphenyl) benzothiazole (HBT) unit, which is known to be more stable as an enol imine form in the ground state and as a keto amine form in the excited state [32, 33] (Fig. 6). The nanoparticles exhibited the AIEE phenomenon mainly due to a restricted intramolecular motion, that is, impediment to free rotation of two end-substituted HBT units around single bonds. It is interesting to note that the... 

Figure 4. Schematic representation of PI nanoparticles via the reprecipitation method.

Zhao G, Ishizaka T, Kasai H, Oikawa H, Nakanishi H (2007) Fabrication of Unique Porous Polyimide Nanoparticles Using Reprecipitation Method. Chem. Mater. 19 1901-1905. 

PDLLA (NatureWorks, PLA 2002D, D-content 4.25%, p= 2A g/cm ) nanoparticles can be prepared either by the miniemulsion method or the reprecipitation method. In the present case, for the miniemulsion method PDLLA was dissolved in chloroform (CHCI3), at a 0.2 wt% concentration. The polymer solution was added to a 1 wt% aqueous surfactant solution of sodium dodecyl sulfate (SDS). Pre-emulsification was obtained by stirring at room temperature for... 

PDLLA nanoparticles were also prepared by the reprecipitation method. Specifically, 15 mg of PDLLA were dissolved in 5 mL of tetrahydrofuran (THE). The solution was left under stirring at room temperature for 30 min. Afterwards, in order to remove any macroscopic residues, the solution was filtered. Finally, the polymer solution was rapidly injected into a beaker filled with distilled water. This emulsion was left under stirring at room temperature for 90 min and then for 120 min at 66 °C to allow complete removal of the solvent. Figure 6.6 shows AFM topography images of the prepared PDLLA nanoparticles. 

Figure 6.6a, b show AFM topography images of the PDLLA nanoparticles prepared by the miniemulsion and reprecipitation method, respectively. In both cases, the nanoparticles consist of polymer nanospheres, without signs of... 

Fig. 6.6 AFM topography images and size distribution of PDLLA nanoparticles prepared by the miniemulsion method (a, c) and reprecipitation method (b, d). Size distribution was quantified on the AFM images by measuring the nanoparticles diameters. Continuous black line represents a Gaussian fit to the distribution...

Organic nanoparticles of AIEE molecules can be highly emissive and thus be a useful fluorescence probe. In what follows, some examples prepared by the reprecipitation and ion-association methods are presented. 

Peng, H.S., Wu, C.F., Jiang, Y.F. et al. 2007a. Highly luminescent Eu3+ chelate nanoparticles prepared by a reprecipitation-encapsulation method. Langmuir 23(4) 1591-1595. 

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