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Since the original work of in the late eighties, several methods for fabricating surface-dissymmetrical particles, called “Janus” particles with reference to the god of the Doors have been reported. [1] Here we report a new method to create Janus nanoparticles in batch. On the basis of the concept that a removable mask can temporary protect a part of an object in a reactive medium, a polymer nodule is grown onto the surface of silica particles to yield silica/polymer dissymmetrical colloids. The synthetic route for making the “Janus” nanoparticles first consists in an emulsion polymerization of styrene in presence of silica particles. In a second step, the specific functionalization of the uncovered silica surface with a trialkoxysilane derivative is carried out. After the separation of the organic and mineral components, the deprotected zone of the silica surface can be specifically functionalized. To demonstrate their regioselective surface modification, gold nanocolloids or a gold cap were used as markers (Figure 1). [2]
Since the original work of in the late eighties, several methods for fabricating surface-dissymmetrical particles, called “Janus” particles with reference to the god of the Doors have been reported. [1] Here we report a new method to create Janus nanoparticles in batch. On the basis of the concept that a removable mask can temporary protect a part of an object in a reactive medium, a polymer nodule is grown onto the surface of silica particles to yield silica/polymer dissymmetrical colloids. The synthetic route for making the “Janus” nanoparticles first consists in an emulsion polymerization of styrene in presence of silica particles. In a second step, the specific functionalization of the uncovered silica surface with a trialkoxysilane derivative is carried out. After the separation of the organic and mineral components, the deprotected zone of the silica surface can be specifically functionalized. To demonstrate their regioselective surface modification, gold nanocolloids or a gold cap were used as markers (Figure 1). [2]
Large amount of Janus silica particles were also prepared through a simple method based on the elaboration of Pickering emulsions of wax-in-water. Controlling the kinetic stabilization of wax droplets allows the fabrication of gram-sized quantities of regular asymmetric inorganic particles. Besides demonstrating the efficiency of using a polymer latex as a protective mask, this work offers a convenient methodology to fabricate large amounts of surface-dissymetrical functional nanoparticles (Figure 2). [3]
These nanostructures may be useful for biomedical applications such as cells or protein binding, biosensors, or may act as particulate surfactants in the stabilization of complex media.
Figure 1. TEM images of the latex and silica particles partially separated and silica nanoparticles decorated by gold nanocolloids.
Figure 2. SEM pictures showing silica particles embeded at the surface of the solid wax droplet. SEM images of janus silica particles t.
Miniaturized autonomous swimmers have become more and more important in many areas of research due to various fields of use, ranging from biomedical to environmental tasks. Precise and predictable control of their trajectories is a key ingredient for increasing their application potential. This can be typically achieved by using Janus particles. An interesting alternative is to use intrinsic features of the swimmers, which allow them to exhibit chemotaxis. Such a built-in “intelligence” enables more complex trajectories, relying on mechanisms that can be considered very basic analogs of decision-making processes.
[1] R. María-Hormigos, A. Escarpa, B. Goudeau, V. Ravaine, A. Perro and A. Kuhn, Oscillatory light-emitting biopolymer based Janus microswimmers, Advanced Materials Interfaces, 7, 1902094 (2020).
[2] A. Perro, F. Meunier, V. Schmitt and S. Ravaine, Colloids and Surface A, 332, 57-62 (2009).
[3] A. Perro, S. Reculusa, S. Ravaine, E. Bourgeat-Lami and E. Duguet, J. Mater. Chem., 15, 3745-3760 (2005).
[4] A. Perro, S. Reculusa, F. Pereira, M.-H. Delville, C. Mingotaud, E. Duguet, E. Bourgeat-Lami and S. Ravaine, Chem. Commun., 5542-5543 (2005).
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