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Hierarchical honeycomb structures utilized a dissipative process
Synthetic Metals 147 (2004) 237–240
Hierarchical honeycomb structures utilized a dissipative process Sachiko I. Matsushitaa , Nobuhito Kuronoa , Tetsuro Sawadaishia , Masatsugu Shimomuraa,b,∗ a
b
Dissipative-Hierarchy Structures Laboratory, Spatio-Temporal Function Materials Research Group, RIKEN Frontier Research System, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan Nanotechnology Research Center, Research Institute for Electronic Science, Hokkaido University, N21W10, Sapporo 001-0021, Japan Received 28 April 2004; accepted 26 May 2004
Abstract Water droplets, which were surrounded by polymers, were used as capsules to form dissipative-hierarchy structures. Such droplets were spontaneously formed on an organic solvent surface in high-humidity air. Water suspension of polystyrene particles was dropped onto the organic solvent in high-humidity air. Consequently, polystyrene particles were transferred into the water droplets, due to lateral capillary force, and formed a honeycomb structure. The size of high-hierarchy (=polymer capsules) was 1–3 m, and the size of small-hierarchy (=polystyrene particles) was 0.05–1 m. The results suggest the possibility that any material that can be suspended in water would form into a periodic structure by the dissipative process. © 2004 Elsevier B.V. All rights reserved. Keywords: Self-assembly; Self-organization; Emulsion; Breath figure; Latex
1. Introduction Various production methods, such as conventional lithography [1], soft lithography [2], and self-assembly [3–6], are used to obtain nanoscale to microscale structures. These structures are considered extremely important from the viewpoint of devices, such as photonic crystals [7–10], electron emitters [11–13] high-density optical storage media [14], and catalytic systems [15]. Since, Prigogine won the Novel Prize in 1977, the dissipative process has become well known because it is a great scientific and technological interest as a simple, self-assembly process with an inexpensive system to prepare a wide range of structures, from nanometer to micrometer size. In particular, one of the important points of the dissipative process is the capability to make hierarchy structures that give rise to diversity and complexity [16,17]. Among the many dissipative structures, we focus on honeycomb-like structures [18–20]. Honeycomb-like structures (also named “breath figures” [21,22]) can be formed ∗
Corresponding author. E-mail address: sachiko [email protected] (M. Shimomura).
0379-6779/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2004.05.035
by a vaporization of polymer suspensions through exposure in humid air, and the final structure has hexagonal holepacked air spheres (0.2–10 m diameter) like the honeycomb of bees. Possible applications of such honeycomb structures include membranes for separation, microreactors, biointerfaces [23,24], catalysts, microstructured electrode surfaces, and photonic applications [25,26]. In this paper, we report a new application of the honeycomb porous structure: a selfassembly system for preparing hierarchical structures. Honeycomb structures are basically made from water droplets covered with surface-active agents [4]. On the basis of this knowledge, we attempted to insert some materials into such water droplets to form honeycomb structures of those materials.
2. Experimental 2.1. Synthesis of surfactants Typically, in our experiments, the honeycomb-like film was synthesized from two monomers. One monomer,
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S.I. Matsushita et al. / Synthetic Metals 147 (2004) 237–240
N-(carboxyl pentyl)acrylamide, was obtained by the addition of diethyl ether solution of acryloyl chloride into an aqueous solution of 6-aminohexanoic acid and NaOH. Another monomer, N-dodecyl acrylamide was obtained through a conventional method. Polymerization of two these monomers was carried out using these acryl amide derivatives in the ratio of 1:10 (N-(carboxyl pentyl)acrylamide:N-dodecyl acrylamide) in the presence of azobisisobutyronitrile. The mean molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the resulting material, copolymer 1, estimated by gel permation chromatography, were 1.9 × 104 and 1.58, respectively. 2.2. Preparation of honey-beads Casting from homogeneous solutions of water-immiscible organic solvents, e.g., chloroform, or benzene in highhumidly atmosphere can easily yield the self-organized honeycomb morphology of polymers [4]. The condensation of water droplets leads to the formation of a hexagonal array in situ template of water droplets around which the polymer assembles. Forty microliters of benzene solution of copolymer 1 (concentration: 0.5 and 1 mg/ml) was spread over a non-fluorescent glass substrate (Matsunami). As the material to form honeycomb structures, polystyrene particles were selected. Polystyrene particle is attracted because the diameter is monodispersed and the behavior in colloidal system is well studied. Ten microliters of water suspension of green-fluorescent polystyrene particles (λex /λem , 458/540 nm) of essentially the same dimensions (0.140, 0.254, 0.499, 0.603, 1.0, 1.9 m diameter; Polymer microspheres green fluorescing, 1% Solids, Duke Scientific Co.) was dropped onto the benzene solution of copolymer 1. The solution was evaporated to form a film by blowing humidified air (Fig. 1a) at the temperature of 20.0–20.6 ◦ C and humidity of 10.0–34.8%. The samples, thus prepared were characterized by optical microscopy (BX-60; Olympus) and scanning electron microscopy (SEM; S-3500N, Hitachi).
3. Results and discussions Fig. 1b is a digital camera image of the top of a sample after drying. The remaining particle suspension was removed using a pipette, thus our black experimental bench could be seen at the center of the film. A normal honeycomb-like structure was observed in the gray area. Most of the fluorescent particle suspension remained at the dropped position, i.e., the center of the copolymer 1 film. Nevertheless, we could confirm, with the naked eye, that some of the fluorescent particle suspension was moved by water droplets, which were produced from the water vapor, and formed a green ring (Fig. 1b). For our convenience, the combination of the honeycomb-like structure and fine particle beads was named a “honey-bead”. In situ, optical microscopic observation of the formation of honey-beads was carried out. The focal point of the objec-
Fig. 1. Schematic model of preparation of a dissipative-hierarchical structure, “honey-bead” (a), and top view of honey-bead composed of flouorescent 250-nm-diameter polystyrene particles (b). Benzene solution with 1 mg/ml polymer was used.
tive lens was set at the edge of the water suspension droplet of 500-nm-diameter green-fluorescent polystyrene particles. We used 1.0 mg/ml copolymer 1. Brownian motion of the particles inside the polymer capsules was observed. Some capsules contained no particle. Polymer capsules both with and without particles were self-assembled. This is due to the lateral capillary force between the capsules [27]. Particle flow to the edge of the meniscus was strong. This is because of the thin meniscus of the water suspension on the benzene solution. Consequently, the capillary force to the edge of the meniscus became strong enough to cause the injection of the particles into the water droplets at the air–water interface. An optical microscopic image of 1.0 mg/ml benzene solution of copolymer 1 and 250 nm particles is shown in Fig. 2a. The diameter of the polymer capsule is approximately 2.9 m. Honey-beads were formed in some places, and the numbers of particles in emulsion are different. Figs. 2b and c are SEM images of the same sample as in Fig. 2a. When the number of particles was small, particles covered the walls of emulsions (Fig. 2b). On the other hand, when the number of particles was large, particles showed high-density, highly oriented packing (Fig. 2c). Fig. 2a is the optical microscopic image of the same area as in Fig. 2c. The orange iridescent color observed in each unit of the honeycomb is due to the diffraction by the packing periodicity of 250-nm-diameter particles. Multilayers of honey-beads were also confirmed. An SEM image of a double layer of honey-beads is shown in Fig. 3a.
S.I. Matsushita et al. / Synthetic Metals 147 (2004) 237–240
239
Fig. 3. Optical microscopic image (a) and scanning electron microscopic image (b) of multilayers of honey-beads. The diameter of the particles is 250 nm and benzene solution with 1 mg/ml polymer was used.
Fig. 2. Optical microscopic image (a) and scanning electron microscpic images (b and c) of a single layer of honey-beads, composed of fluorescent 250-nm-diameter polystyrene particles. Benzene solution with 1 mg/ml polymer was used.
The diameter of the particles used was 250 nm and the concentration of the polymer in benzene solution was 1.0 mg/ml. Through the empty emulsion on the top layer, we can observe the packing of particles in the bottom layer. The particles showed three-dimensional closest packing in the emulsions (Fig. 3a). There are some places in which polymer capsules are not ordered (Fig. 3b). We can also see the disorder in a normal honeycomb-like structure. The size of the polymer capsules is not uniform in the disordered areas, and the diameter of polymer capsules is approximately 2.1–7.5 m. The emulsions show iridescent color in visible light. This is also considered
to be a result of the diffraction due to the closest packing of particles in the capsules, as discussed in Fig. 2. The influence of the concentration of the polymer solution and the influence of the diameter of the particles on honeybead formation were examined. Researchers have reported that the size of the polymer capsules in honeycomb-like structures is defined by the concentration of the polymer solution and the amount of cast solution [24]. The same relationships were observed in the honey-bead system. Under our experimental conditions, the diameters of the water droplets using 1.0 mg/ml copolymer 1 and 0.5 mg/ml copolymer 1 were approximately 3 and 2 m, respectively. The maximum diameters of particles that can form the honey-bead structure using 1.0 mg/ml copolymer 1 and 0.5 mg/ml copolymer 1 are 1 and 0.6 m, respectively. The amount of polymer surrounding a water droplet using 0.5 mg/ml polymer solution is less than that using 1 mg/ml polymer solution. Consequently, it can be considered that the wall of the polymer capsule is weak and unable to endure the Brownian motion of l-m-diameter particles. In the case of small polystyrene particles of less than 0.14 m diameter, there were some places where polystyrene had dissolved in the benzene solution. Still, small particles (such as 0.05-m-diameter polystyrene particles) could be formed the honey-bead structure independent of the concentration of polymer.
4. Conclusions We reported a new application of honeycomb-like structures: a self-assembly system for preparing hierarchical struc-
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tures. The resulting combination of honeycomb-like structure and fine particles, named “honey-bead”, indicated the possibility that any material that can be suspended in water could be formed into a periodic structure by the dissipative process. Even 50-nm-diameter polystyrene particles, which are dissolved in benzene solution, could form the honey-bead structure. Consequently, it is considered that other organic materials, such as viruses (10–200 nm diameter) and liposomes (20–50 nm), and inorganic materials, such as fine metal particles (10 nm) and fine semiconductor particles (20 nm), can form the dissipative structures. Acknowledgments The present work has been partially supported by the Ministry of Education, Culture, Sports, Science and Technology, and the Yazaki Memorial Foundation for Science and Technology. References [1] T. Ito, S. Okazaki, Nature 406 (2000) 1027. [2] C. Haginoya, M. Ishibashi, K. Koike, Appl. Phys. Lett. 71 (1997) 2934. [3] D.K. Yi, E.-M. Seo, D.-Y. Kim, Appl. Phys. Lett. 80 (2002) 225. [4] O. Karthaus, N. Maruyama, X. Cieren, M. Shimomura, H. Hasegawa, T. Hahimoto, Langmuir 16 (2000) 6071. [5] Y.-H. Ye, S. Badilescu, V.-V. Truong, P. Rochon, A. Natansohn, Appl. Phys. Lett. 79 (2001) 872. [6] I. Yamashita, Thin Solid Films 393 (2001) 12. [7] K. Ohtaka, Phys. Rev. B 19 (1979) 5057. [8] J.D. Joannopoulos, R.D. Meade, J.N. Winn, Photonic Crystals, Princeton University Press, New Jersey, 1995.
[9] T. Fujimura, T. Itoh, A. Imada, R. Shimada, T. Koda, N. Chiba, H. Muramatsu, H. Miyazaki, K. Ohtaka, J. Lumin. 87–89 (2000) 954. [10] S.I. Matsushita, Y. Yagi, T. Miwa, D.A. Tryk, T. Koda, A. Fujishima, Langmuir 16 (2000) 636. [11] A.A. Talin, K.A. Dean, J.E. Jaskie, Solid-State Electron. 45 (2001) 963. [12] D.S. Mao, X. Wang, W. Li, X.H. Liu, Q. Li, J.F. Xu, K. Okano, J. Vac. Sci. Technol. B 18 (2000) 242. [13] S. Okuyama, S.I. Matsushita, A. Fujishima, Langmuir 18 (2002) 8282. [14] R. Micheletto, H. Fukuda, M. Ohtsu, Langmuir 11 (1995) 3333. [15] S.I. Matsushita, T. Miwa, D.A. Tryk, A. Fujishima, Langmuir 14 (1998) 6441. [16] I. Prigogine, The End of Certainty, The Free Press, New York, 1997. [17] S. Camazine, J.-L. Deneubourg, N.R. Franks, J. Sneyd, G. Theraulaz, E. Bonabeau, Self-Organization in Biological Systems, Princeton University Press, New Jersey, 2001. [18] G. Widawski, M. Rawiso, B. Franc¸ois, Nature 369 (1994) 387. [19] N. Maruyama, T. Koito, J. Nishida, T. Sawadaishi, X. Cieren, K. Ijiro, O. Karthaus, M. Shimomura, Thin Solid Films 327–329 (1998) 854. [20] S.X. Wang, M.T. Wang, Y. Lei, L.D. Zhang, Mater. Res. Bull. 35 (2000) 1625. [21] A. Steyer, P. Guenoun, D. Beysens, C.M. Knobler, Phys. Rev. B 42 (1990) 1086. [22] M. Srinivasarao, D. Collings, A. Philips, S. patel, Science 292 (2001) 79. [23] T. Nishikawa, J. Nishida, R. Ookura, S. Nishimura, S. Wada, T. Karino, M. Shimomura, Mater. Sci. Eng. C 10 (1999) 141. [24] T. Nishikawa, R. Ookura, J. Nishida, K. Arai, J. Hayashi, N. Kurono, T. Sawadaishi, M. Hara, M. Shimomura, Langmuir 18 (2002) 5734. [25] B. de Boer, U. Stalmach, P.F. van Hutten, C. Melzer, V.V. Krasnikov, G. Hadziioannou, Polymer 42 (2001) 9097. [26] B. de Boer, U. Stalmach, C. Melzer, G. Hadziioannou, Synth. Met. 121 (2001) 1541. [27] P.A. Kralchevsky, K. Nagayama, Langmuir 10 (1994) 23.
Hierarchical honeycomb structures utilized a dissipative process Sachiko I. Matsushitaa , Nobuhito Kuronoa , Tetsuro Sawadaishia , Masatsugu Shimomuraa,b,∗ a
b
Dissipative-Hierarchy Structures Laboratory, Spatio-Temporal Function Materials Research Group, RIKEN Frontier Research System, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan Nanotechnology Research Center, Research Institute for Electronic Science, Hokkaido University, N21W10, Sapporo 001-0021, Japan Received 28 April 2004; accepted 26 May 2004
Abstract Water droplets, which were surrounded by polymers, were used as capsules to form dissipative-hierarchy structures. Such droplets were spontaneously formed on an organic solvent surface in high-humidity air. Water suspension of polystyrene particles was dropped onto the organic solvent in high-humidity air. Consequently, polystyrene particles were transferred into the water droplets, due to lateral capillary force, and formed a honeycomb structure. The size of high-hierarchy (=polymer capsules) was 1–3 m, and the size of small-hierarchy (=polystyrene particles) was 0.05–1 m. The results suggest the possibility that any material that can be suspended in water would form into a periodic structure by the dissipative process. © 2004 Elsevier B.V. All rights reserved. Keywords: Self-assembly; Self-organization; Emulsion; Breath figure; Latex
1. Introduction Various production methods, such as conventional lithography [1], soft lithography [2], and self-assembly [3–6], are used to obtain nanoscale to microscale structures. These structures are considered extremely important from the viewpoint of devices, such as photonic crystals [7–10], electron emitters [11–13] high-density optical storage media [14], and catalytic systems [15]. Since, Prigogine won the Novel Prize in 1977, the dissipative process has become well known because it is a great scientific and technological interest as a simple, self-assembly process with an inexpensive system to prepare a wide range of structures, from nanometer to micrometer size. In particular, one of the important points of the dissipative process is the capability to make hierarchy structures that give rise to diversity and complexity [16,17]. Among the many dissipative structures, we focus on honeycomb-like structures [18–20]. Honeycomb-like structures (also named “breath figures” [21,22]) can be formed ∗
Corresponding author. E-mail address: sachiko [email protected] (M. Shimomura).
0379-6779/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2004.05.035
by a vaporization of polymer suspensions through exposure in humid air, and the final structure has hexagonal holepacked air spheres (0.2–10 m diameter) like the honeycomb of bees. Possible applications of such honeycomb structures include membranes for separation, microreactors, biointerfaces [23,24], catalysts, microstructured electrode surfaces, and photonic applications [25,26]. In this paper, we report a new application of the honeycomb porous structure: a selfassembly system for preparing hierarchical structures. Honeycomb structures are basically made from water droplets covered with surface-active agents [4]. On the basis of this knowledge, we attempted to insert some materials into such water droplets to form honeycomb structures of those materials.
2. Experimental 2.1. Synthesis of surfactants Typically, in our experiments, the honeycomb-like film was synthesized from two monomers. One monomer,
238
S.I. Matsushita et al. / Synthetic Metals 147 (2004) 237–240
N-(carboxyl pentyl)acrylamide, was obtained by the addition of diethyl ether solution of acryloyl chloride into an aqueous solution of 6-aminohexanoic acid and NaOH. Another monomer, N-dodecyl acrylamide was obtained through a conventional method. Polymerization of two these monomers was carried out using these acryl amide derivatives in the ratio of 1:10 (N-(carboxyl pentyl)acrylamide:N-dodecyl acrylamide) in the presence of azobisisobutyronitrile. The mean molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the resulting material, copolymer 1, estimated by gel permation chromatography, were 1.9 × 104 and 1.58, respectively. 2.2. Preparation of honey-beads Casting from homogeneous solutions of water-immiscible organic solvents, e.g., chloroform, or benzene in highhumidly atmosphere can easily yield the self-organized honeycomb morphology of polymers [4]. The condensation of water droplets leads to the formation of a hexagonal array in situ template of water droplets around which the polymer assembles. Forty microliters of benzene solution of copolymer 1 (concentration: 0.5 and 1 mg/ml) was spread over a non-fluorescent glass substrate (Matsunami). As the material to form honeycomb structures, polystyrene particles were selected. Polystyrene particle is attracted because the diameter is monodispersed and the behavior in colloidal system is well studied. Ten microliters of water suspension of green-fluorescent polystyrene particles (λex /λem , 458/540 nm) of essentially the same dimensions (0.140, 0.254, 0.499, 0.603, 1.0, 1.9 m diameter; Polymer microspheres green fluorescing, 1% Solids, Duke Scientific Co.) was dropped onto the benzene solution of copolymer 1. The solution was evaporated to form a film by blowing humidified air (Fig. 1a) at the temperature of 20.0–20.6 ◦ C and humidity of 10.0–34.8%. The samples, thus prepared were characterized by optical microscopy (BX-60; Olympus) and scanning electron microscopy (SEM; S-3500N, Hitachi).
3. Results and discussions Fig. 1b is a digital camera image of the top of a sample after drying. The remaining particle suspension was removed using a pipette, thus our black experimental bench could be seen at the center of the film. A normal honeycomb-like structure was observed in the gray area. Most of the fluorescent particle suspension remained at the dropped position, i.e., the center of the copolymer 1 film. Nevertheless, we could confirm, with the naked eye, that some of the fluorescent particle suspension was moved by water droplets, which were produced from the water vapor, and formed a green ring (Fig. 1b). For our convenience, the combination of the honeycomb-like structure and fine particle beads was named a “honey-bead”. In situ, optical microscopic observation of the formation of honey-beads was carried out. The focal point of the objec-
Fig. 1. Schematic model of preparation of a dissipative-hierarchical structure, “honey-bead” (a), and top view of honey-bead composed of flouorescent 250-nm-diameter polystyrene particles (b). Benzene solution with 1 mg/ml polymer was used.
tive lens was set at the edge of the water suspension droplet of 500-nm-diameter green-fluorescent polystyrene particles. We used 1.0 mg/ml copolymer 1. Brownian motion of the particles inside the polymer capsules was observed. Some capsules contained no particle. Polymer capsules both with and without particles were self-assembled. This is due to the lateral capillary force between the capsules [27]. Particle flow to the edge of the meniscus was strong. This is because of the thin meniscus of the water suspension on the benzene solution. Consequently, the capillary force to the edge of the meniscus became strong enough to cause the injection of the particles into the water droplets at the air–water interface. An optical microscopic image of 1.0 mg/ml benzene solution of copolymer 1 and 250 nm particles is shown in Fig. 2a. The diameter of the polymer capsule is approximately 2.9 m. Honey-beads were formed in some places, and the numbers of particles in emulsion are different. Figs. 2b and c are SEM images of the same sample as in Fig. 2a. When the number of particles was small, particles covered the walls of emulsions (Fig. 2b). On the other hand, when the number of particles was large, particles showed high-density, highly oriented packing (Fig. 2c). Fig. 2a is the optical microscopic image of the same area as in Fig. 2c. The orange iridescent color observed in each unit of the honeycomb is due to the diffraction by the packing periodicity of 250-nm-diameter particles. Multilayers of honey-beads were also confirmed. An SEM image of a double layer of honey-beads is shown in Fig. 3a.
S.I. Matsushita et al. / Synthetic Metals 147 (2004) 237–240
239
Fig. 3. Optical microscopic image (a) and scanning electron microscopic image (b) of multilayers of honey-beads. The diameter of the particles is 250 nm and benzene solution with 1 mg/ml polymer was used.
Fig. 2. Optical microscopic image (a) and scanning electron microscpic images (b and c) of a single layer of honey-beads, composed of fluorescent 250-nm-diameter polystyrene particles. Benzene solution with 1 mg/ml polymer was used.
The diameter of the particles used was 250 nm and the concentration of the polymer in benzene solution was 1.0 mg/ml. Through the empty emulsion on the top layer, we can observe the packing of particles in the bottom layer. The particles showed three-dimensional closest packing in the emulsions (Fig. 3a). There are some places in which polymer capsules are not ordered (Fig. 3b). We can also see the disorder in a normal honeycomb-like structure. The size of the polymer capsules is not uniform in the disordered areas, and the diameter of polymer capsules is approximately 2.1–7.5 m. The emulsions show iridescent color in visible light. This is also considered
to be a result of the diffraction due to the closest packing of particles in the capsules, as discussed in Fig. 2. The influence of the concentration of the polymer solution and the influence of the diameter of the particles on honeybead formation were examined. Researchers have reported that the size of the polymer capsules in honeycomb-like structures is defined by the concentration of the polymer solution and the amount of cast solution [24]. The same relationships were observed in the honey-bead system. Under our experimental conditions, the diameters of the water droplets using 1.0 mg/ml copolymer 1 and 0.5 mg/ml copolymer 1 were approximately 3 and 2 m, respectively. The maximum diameters of particles that can form the honey-bead structure using 1.0 mg/ml copolymer 1 and 0.5 mg/ml copolymer 1 are 1 and 0.6 m, respectively. The amount of polymer surrounding a water droplet using 0.5 mg/ml polymer solution is less than that using 1 mg/ml polymer solution. Consequently, it can be considered that the wall of the polymer capsule is weak and unable to endure the Brownian motion of l-m-diameter particles. In the case of small polystyrene particles of less than 0.14 m diameter, there were some places where polystyrene had dissolved in the benzene solution. Still, small particles (such as 0.05-m-diameter polystyrene particles) could be formed the honey-bead structure independent of the concentration of polymer.
4. Conclusions We reported a new application of honeycomb-like structures: a self-assembly system for preparing hierarchical struc-
240
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tures. The resulting combination of honeycomb-like structure and fine particles, named “honey-bead”, indicated the possibility that any material that can be suspended in water could be formed into a periodic structure by the dissipative process. Even 50-nm-diameter polystyrene particles, which are dissolved in benzene solution, could form the honey-bead structure. Consequently, it is considered that other organic materials, such as viruses (10–200 nm diameter) and liposomes (20–50 nm), and inorganic materials, such as fine metal particles (10 nm) and fine semiconductor particles (20 nm), can form the dissipative structures. Acknowledgments The present work has been partially supported by the Ministry of Education, Culture, Sports, Science and Technology, and the Yazaki Memorial Foundation for Science and Technology. References [1] T. Ito, S. Okazaki, Nature 406 (2000) 1027. [2] C. Haginoya, M. Ishibashi, K. Koike, Appl. Phys. Lett. 71 (1997) 2934. [3] D.K. Yi, E.-M. Seo, D.-Y. Kim, Appl. Phys. Lett. 80 (2002) 225. [4] O. Karthaus, N. Maruyama, X. Cieren, M. Shimomura, H. Hasegawa, T. Hahimoto, Langmuir 16 (2000) 6071. [5] Y.-H. Ye, S. Badilescu, V.-V. Truong, P. Rochon, A. Natansohn, Appl. Phys. Lett. 79 (2001) 872. [6] I. Yamashita, Thin Solid Films 393 (2001) 12. [7] K. Ohtaka, Phys. Rev. B 19 (1979) 5057. [8] J.D. Joannopoulos, R.D. Meade, J.N. Winn, Photonic Crystals, Princeton University Press, New Jersey, 1995.
[9] T. Fujimura, T. Itoh, A. Imada, R. Shimada, T. Koda, N. Chiba, H. Muramatsu, H. Miyazaki, K. Ohtaka, J. Lumin. 87–89 (2000) 954. [10] S.I. Matsushita, Y. Yagi, T. Miwa, D.A. Tryk, T. Koda, A. Fujishima, Langmuir 16 (2000) 636. [11] A.A. Talin, K.A. Dean, J.E. Jaskie, Solid-State Electron. 45 (2001) 963. [12] D.S. Mao, X. Wang, W. Li, X.H. Liu, Q. Li, J.F. Xu, K. Okano, J. Vac. Sci. Technol. B 18 (2000) 242. [13] S. Okuyama, S.I. Matsushita, A. Fujishima, Langmuir 18 (2002) 8282. [14] R. Micheletto, H. Fukuda, M. Ohtsu, Langmuir 11 (1995) 3333. [15] S.I. Matsushita, T. Miwa, D.A. Tryk, A. Fujishima, Langmuir 14 (1998) 6441. [16] I. Prigogine, The End of Certainty, The Free Press, New York, 1997. [17] S. Camazine, J.-L. Deneubourg, N.R. Franks, J. Sneyd, G. Theraulaz, E. Bonabeau, Self-Organization in Biological Systems, Princeton University Press, New Jersey, 2001. [18] G. Widawski, M. Rawiso, B. Franc¸ois, Nature 369 (1994) 387. [19] N. Maruyama, T. Koito, J. Nishida, T. Sawadaishi, X. Cieren, K. Ijiro, O. Karthaus, M. Shimomura, Thin Solid Films 327–329 (1998) 854. [20] S.X. Wang, M.T. Wang, Y. Lei, L.D. Zhang, Mater. Res. Bull. 35 (2000) 1625. [21] A. Steyer, P. Guenoun, D. Beysens, C.M. Knobler, Phys. Rev. B 42 (1990) 1086. [22] M. Srinivasarao, D. Collings, A. Philips, S. patel, Science 292 (2001) 79. [23] T. Nishikawa, J. Nishida, R. Ookura, S. Nishimura, S. Wada, T. Karino, M. Shimomura, Mater. Sci. Eng. C 10 (1999) 141. [24] T. Nishikawa, R. Ookura, J. Nishida, K. Arai, J. Hayashi, N. Kurono, T. Sawadaishi, M. Hara, M. Shimomura, Langmuir 18 (2002) 5734. [25] B. de Boer, U. Stalmach, P.F. van Hutten, C. Melzer, V.V. Krasnikov, G. Hadziioannou, Polymer 42 (2001) 9097. [26] B. de Boer, U. Stalmach, C. Melzer, G. Hadziioannou, Synth. Met. 121 (2001) 1541. [27] P.A. Kralchevsky, K. Nagayama, Langmuir 10 (1994) 23.