Three-Dimensional Interstitial Nanovoid of Nanoparticulate Pt Film Electroplated from Reverse Micelle Solution
Original entry by A.J. Kumar, APPHY 225 Fall 2009
Sejin Park, Sun Young Lee, Hankil Boo, Hyun-Mi Kim, Ki-Bum Kim, Hee Chan Kim, Youn Joo Song, and Taek Dong Chung. Chem. Mater. 2007, 19, 3373-3375 Home
In this article, the authors explore the use of reverse micelles in the formation of nanoporous metal thin films. Creating nanoporous materials is of great interest for a number of reasons. Depending on mass transport properties, these materials could be useful filters for chemical processes or water filtration. The high surface area provided by the porous materials also make them strong catalysts. This makes them exciting materials for tackling environmental and energy issues. The pores could also be used in storage and delivery, which makes these materials of interest to bioengineering as potentially useful in drug delivery.
The authors assert that previous work has relied on either types of surfactant-based templates or potential-controlled micelle assembly. Both of these result in hexagonally ordered, one dimensional pores. This limitation would reduce the usefulness of the material because mass transport would be compromised by blocking the pores. One can imagine an interconnected network of pores being more robust because of one pore was blocked, the channel behind it could be filled by the interconnecting tubes. The authors propose to solve this problem by considering the reverse micelle phase (<math>L_2</math>).
Electroplating allows the controllable growth of thin metal films on a substrate. Whether using micelles or reverse micelles to pattern pores, the procedure is roughly the same. In this case, a gold substrate was used. The electroplating solution contains ions and also a concentration of surfactant high enough to have micelles. In this study, Triton X-100 was used. As the metal film is deposited, the micelles (or in this case reverse micelles) will form small voids in the structure, leading to an overall network of pores for long enough micelles. In their experiment, the authors succeed in making a thin film of platinum with this process. The film is composed of porous nanoparticles that have grown together and exhibit three dimensional pores.
Perhaps I need to read some more papers in the field, but it would have been nice to have a more detailed discussion on why previous methods only allowed 1D pores while the use of reverse micelles allows 3D pores to form. Apart from this criticism, I found the paper quite interesting and pertinent to materials development.
Soft Matter Connection
This is an interesting connection about how soft matter can be relevant to fields like condensed matter and materials science, which typically focus on "hard" matter. Here, micelles are exploited to create novel structures with highly desirable properties. Given that our knowledge of things like polymers and micelles is still under great development, one can imagine that as new things are discovered about these in the soft matter field, even more uses could be found in other fields to apply this knowledge.
Here are some older papers about the formation of nano-porous materials using micelles and surfactants.
 "Engineering the Structures of Nanoporous Clays with Micelles of Alkyl Polyether Surfactants" H. Y. Zhu and G. Q. Lu. Langmuir 2001, 17, 588-594
 "The Formation of Ordered Nanoporous Structure with Controlled Micelle Size" Jeongho Chang, Yongsoon Shin, Li-Qiong Wang, and Gregory J. Exarhos. Mat. Res. Soc. Symp. Proc. Vol. 733E. 2002 Materials Research Society