The Shapes and Sizes of Self-Assembly

The Moffitt Research Group at UVic

AFM (a) and confocal fluorescence (LSCFM) (b) images of spin-cast 50/50 (w/w) polystyrene-stabilized CdS (PS-CdS)/poly(methyl methacrylate) blend films, prepared using a rotation speed of 3000 rpm. The AFM and LSCFM images have edge lengths of 50 mm. Photoluminescence is from the CdS nanoparticles within the PS-CdS domains. The TEM image (c) of a microtomed section of the same film shows the nano-scale organization of CdS nanoparticles within the PS-CdS domains; the scale bar in the TEM image represents 100 nm (images: C.-W. Wang).

AFM (a,b) and TEM (c,d) of PS-CdS/PS-b-PEO blends self-assembled at the air-water interface with different weight fractions of PS-CdS in the blends, f. Spreading solution concentrations were 2.0 mg/mL and film transfer occurred at 5.0 mN/m in all cases. Arrows highlight nanocables with nanoring connectors. The TEM images show distribution of CdS nanoparticles within the nanocable structures. For low weight fraction of PS-CdS (f = 0.25), nodules are periodically spaced along the length of the aggregate (a). TEM shows that the nanoparticles are localized in the nodules for f = 0.25 (c), but uniformly distributed along the nanocables for f = 0.75 (d) (images: R. B. Cheyne).

TEM images of assemblies of CdS nanoparticle-containing large compound micelles (LCMs). The LCMs assembled within a tear on the formvar film during evaporation. The LCMs are themselves spherical assemblies of multiple PS-CdS particles, and so these structures possess organization on several length scales; the internal structure of the LCMs, showing dark CdS nanoparticles dispersed in the mostly-PS matrix, is visible in the final highest-magnification image (images: H. Gou, S. Sharma).