Limits...
Self-assembly of octapod-shaped colloidal nanocrystals into a hexagonal ballerina network embedded in a thin polymer film.

Arciniegas MP, Kim MR, De Graaf J, Brescia R, Marras S, Miszta K, Dijkstra M, van Roij R, Manna L - Nano Lett. (2014)

Bottom Line: In the resulting structure, each octapod is oriented like a "ballerina", that is, only one pod sticks out of the polymer film and is perpendicular to the polymer-air interface, while the opposite pod (with respect to the octapod's center) is fully immersed in the film and points toward the substrate, like a ballerina performing a grand battement.As the solvent evaporates, the octapods form a ballerina-rich octapod-polymer composite in which the octapods are in close contact with the substrate.Finally, we found that the resulting octapod-polymer composite is less hydrophilic than the polymer-only film.

View Article: PubMed Central - PubMed

Affiliation: Istituto Italiano di Tecnologia (IIT) , via Morego 30, IT-16163 Genova, Italy.

ABSTRACT
Nanoparticles with unconventional shapes may exhibit different types of assembly architectures that depend critically on the environmental conditions under which they are formed. Here, we demonstrate how the presence of polymer (polymethyl methacrylate, PMMA) molecules in a solution, in which CdSe(core)/CdS(pods) octapods are initially dispersed, affects the octapod-polymer organization upon solvent evaporation. We show that a fast drop-drying process can induce a remarkable two-dimensional (2D) self-assembly of octapods at the polymer/air interface. In the resulting structure, each octapod is oriented like a "ballerina", that is, only one pod sticks out of the polymer film and is perpendicular to the polymer-air interface, while the opposite pod (with respect to the octapod's center) is fully immersed in the film and points toward the substrate, like a ballerina performing a grand battement. In some areas, a hexagonal-like pattern is formed by the ballerinas in which the six nonvertical pods, which are all embedded in the film, maintain a pod-pod parallel configuration with respect to neighboring particles. We hypothesize that the mechanism responsible for such a self-assembly is based on a fast adsorption of the octapods from bulk solution to the droplet/air interface during the early stages of solvent evaporation. At this interface, the octapods maintain enough rotational freedom to organize mutually in a pod-pod parallel configuration between neighboring octapods. As the solvent evaporates, the octapods form a ballerina-rich octapod-polymer composite in which the octapods are in close contact with the substrate. Finally, we found that the resulting octapod-polymer composite is less hydrophilic than the polymer-only film.

No MeSH data available.


Related in: MedlinePlus

(a) SEI-SEM image afterremoving the polymer (via an oxygen plasmatreatment) evidencing that the ballerinas are standing on the substrate.The inset shows a close-up view of an ordered domain. The scale baris 60 nm. (b) HAADF-STEM images at different tilt angles confirmingthe pod–pod parallel arrangement between octapods forming thehexagonal array of ballerinas. (c) Cartoon explaining the formationof the ballerinas at the droplet/air interface. (I). The particlesare constrained to move toward the interface and remain trapped thereduring drying; weak vdW and interfacial interactions are responsiblefor the pod–pod configuration (II–III).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3924848&req=5

fig4: (a) SEI-SEM image afterremoving the polymer (via an oxygen plasmatreatment) evidencing that the ballerinas are standing on the substrate.The inset shows a close-up view of an ordered domain. The scale baris 60 nm. (b) HAADF-STEM images at different tilt angles confirmingthe pod–pod parallel arrangement between octapods forming thehexagonal array of ballerinas. (c) Cartoon explaining the formationof the ballerinas at the droplet/air interface. (I). The particlesare constrained to move toward the interface and remain trapped thereduring drying; weak vdW and interfacial interactions are responsiblefor the pod–pod configuration (II–III).

Mentions: Detailed SEM observation of samples from whichthe polymer wasremoved by an oxygen plasma treatment confirmed that the ballerina-hexagonalarrangement of the octapods consisted of one single layer on the substrate(see Figure 4a). This arrangement was furtherconfirmed by HAADF- STEM images taken at different tilt angles (seeFigure 4b, Supporting Information Figure S4 and movie SI1.avi and SI2.avi). The pod–pod parallelconfiguration of neighboring octapods is indeed consistent with thehexagonal-like arrangements of the bright posts viewed in SEM (Figure 2) and in HAADF-STEM plan-view images (Figure 3b).


Self-assembly of octapod-shaped colloidal nanocrystals into a hexagonal ballerina network embedded in a thin polymer film.

Arciniegas MP, Kim MR, De Graaf J, Brescia R, Marras S, Miszta K, Dijkstra M, van Roij R, Manna L - Nano Lett. (2014)

(a) SEI-SEM image afterremoving the polymer (via an oxygen plasmatreatment) evidencing that the ballerinas are standing on the substrate.The inset shows a close-up view of an ordered domain. The scale baris 60 nm. (b) HAADF-STEM images at different tilt angles confirmingthe pod–pod parallel arrangement between octapods forming thehexagonal array of ballerinas. (c) Cartoon explaining the formationof the ballerinas at the droplet/air interface. (I). The particlesare constrained to move toward the interface and remain trapped thereduring drying; weak vdW and interfacial interactions are responsiblefor the pod–pod configuration (II–III).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3924848&req=5

fig4: (a) SEI-SEM image afterremoving the polymer (via an oxygen plasmatreatment) evidencing that the ballerinas are standing on the substrate.The inset shows a close-up view of an ordered domain. The scale baris 60 nm. (b) HAADF-STEM images at different tilt angles confirmingthe pod–pod parallel arrangement between octapods forming thehexagonal array of ballerinas. (c) Cartoon explaining the formationof the ballerinas at the droplet/air interface. (I). The particlesare constrained to move toward the interface and remain trapped thereduring drying; weak vdW and interfacial interactions are responsiblefor the pod–pod configuration (II–III).
Mentions: Detailed SEM observation of samples from whichthe polymer wasremoved by an oxygen plasma treatment confirmed that the ballerina-hexagonalarrangement of the octapods consisted of one single layer on the substrate(see Figure 4a). This arrangement was furtherconfirmed by HAADF- STEM images taken at different tilt angles (seeFigure 4b, Supporting Information Figure S4 and movie SI1.avi and SI2.avi). The pod–pod parallelconfiguration of neighboring octapods is indeed consistent with thehexagonal-like arrangements of the bright posts viewed in SEM (Figure 2) and in HAADF-STEM plan-view images (Figure 3b).

Bottom Line: In the resulting structure, each octapod is oriented like a "ballerina", that is, only one pod sticks out of the polymer film and is perpendicular to the polymer-air interface, while the opposite pod (with respect to the octapod's center) is fully immersed in the film and points toward the substrate, like a ballerina performing a grand battement.As the solvent evaporates, the octapods form a ballerina-rich octapod-polymer composite in which the octapods are in close contact with the substrate.Finally, we found that the resulting octapod-polymer composite is less hydrophilic than the polymer-only film.

View Article: PubMed Central - PubMed

Affiliation: Istituto Italiano di Tecnologia (IIT) , via Morego 30, IT-16163 Genova, Italy.

ABSTRACT
Nanoparticles with unconventional shapes may exhibit different types of assembly architectures that depend critically on the environmental conditions under which they are formed. Here, we demonstrate how the presence of polymer (polymethyl methacrylate, PMMA) molecules in a solution, in which CdSe(core)/CdS(pods) octapods are initially dispersed, affects the octapod-polymer organization upon solvent evaporation. We show that a fast drop-drying process can induce a remarkable two-dimensional (2D) self-assembly of octapods at the polymer/air interface. In the resulting structure, each octapod is oriented like a "ballerina", that is, only one pod sticks out of the polymer film and is perpendicular to the polymer-air interface, while the opposite pod (with respect to the octapod's center) is fully immersed in the film and points toward the substrate, like a ballerina performing a grand battement. In some areas, a hexagonal-like pattern is formed by the ballerinas in which the six nonvertical pods, which are all embedded in the film, maintain a pod-pod parallel configuration with respect to neighboring particles. We hypothesize that the mechanism responsible for such a self-assembly is based on a fast adsorption of the octapods from bulk solution to the droplet/air interface during the early stages of solvent evaporation. At this interface, the octapods maintain enough rotational freedom to organize mutually in a pod-pod parallel configuration between neighboring octapods. As the solvent evaporates, the octapods form a ballerina-rich octapod-polymer composite in which the octapods are in close contact with the substrate. Finally, we found that the resulting octapod-polymer composite is less hydrophilic than the polymer-only film.

No MeSH data available.


Related in: MedlinePlus