Colloidal monolayers

Grabar K C ef a/1997 Nanoscale characterization of gold colloid monolayers—a comparison of four techniques Anal. Chem. 69 471... 

F. Burmeister, C. Schlafle, B. Keilhofer, C. Bechinger, J. Boneberg, P. Leiderer. From mesoscopic to nanoscopic surface structures lithography with colloid monolayers. Adv Mater 70 495—497, 1998. 

Fig. 31. Fractal structures obtained experimentally at different stages of aggregation of a colloidal monolayer of 1 /im sulfonated polystyrene particles on the surface of an aqueous calcium chloride solution, initially uniformly distributed (Robinson and Earnshaw, 1992).

Long period gratings modified by the deposition of a self-assembled colloid monolayer of gold have been shown to enhance SRI sensitivity, which was attributed to the localized surface plasmon resonance (LSPR) of gold nanoparticles61. The system was used after functionalization of the gold nanoparticles with dini-trophenyl (DNP) antigen, for the detection of anti-(DNP) with a limit of detection as low as 9.5 x 10 10 M. 

Bright RM, Walter DG, Musick MD, Jackson MA, Allison KJ, Natan MJ (1996) Chemical and electrochemical Ag deposition onto preformed Au colloid monolayers Approaches to uniformly-sized surface features with Ag-like optical properties. Langmuir 12 810-817... 

Kinetics and Thermodynamics of Au Colloid Monolayer Self-Assembly 111... 

Freeman RG, Grabar KC, Allison KJ, Bright RM, Davis JA, Guthrie AP, Hommer MB, Jackson MA, Smith PC, Walter DG, Natan MJ. Self-assembled metal colloid monolayers an approach to SERS substrates. Science 1995, 267, 1629-1632. 

Boneberg, J., et al. (1997), The formation of nano-dot and nano-ring structures in colloidal monolayer lithography, Langmuir, 13,7080-7084. 

Freeman, G.R., et al. (1995) Self-assembled metal colloid monolayers An approach to SERS sub ates. Science 267 1629-1632. 

Grabar KC, Freeman RG, Hommer MB, Natan MJ (1995) Preparation and characterization of au colloid monolayers. Anal Chem 67(4) 735-743... 

Grabar KC, Brown KR, Keating CD, Stranick SJ, Tang S-L, Natan MJ (1997) Nanoscale characterization of gold colloid monolayers a comparison of four techniques. Anal Chem 69(3) 471 77... 

Figure 4. Electron micrograph of a 2D gold colloid monolayer prepared on carbon-coated copper grids (coating thickness 100 A) by electrophoresis of a 0.5 mM citrate stabilized Au sol at an applied positive voltage of 50 mV. Reprinted with permission from ref 27. Copyright 1993 American Chemical Society.

Zhang, K.-Q. Liu, X.Y. In situ observation of colloidal monolayer nucleation driven by an alternating electric field. Nature 2004, 429, 740-743. 

Okamoto T, Yamaguchi I, Kobayashi T (2000) Local plasmon sensor with gold colloid monolayers deposited upon glass substrates. Opt Lett 25 372-374... 

A. Armstrong, Defect Mediated Melting in Colloidal Monolayers, Ph.D. thesis. University of Colorado. Boulder, 1988. 

Grabar, K.C. Deutsch J.E. Natan M.J. Polymer-suported Gold Colloid Monolayers - A new approach to biocompatible metal-surfaces. Abstracts of papers of the American Chemical Society Apr. 2 1995,209 27-Poly, Part 2... 

M. A. Hayat. Colloidal Gold Methods and Applications. Academic, San Diego, CA, 1989 C. D. Keating, M. D. Musick, M. H. Keefe, and M. J. Natan. Kinetics and thermodynamics of Au colloid monolayer self-assembly - undergraduate experiments in surface and nanomaterials chemistry. J. Chem. Education, 76 949-955, 1999... 

Others authors propose alternative ways to conduct or discuss an experiment that is already commonly used in the teaching of chemical kinetics. For example the presentation of a videotaped clock (iodine-azide) reaction which is suitable for videotaping and which has an easily determined mechanism (Haight Jones, 1987) the determination of a reaction mechanism of the blue bottle reaction (Engerer Cook, 1999). Others may be used to discuss thermodynamics and kinetics simultaneously, e.g., from the study of the surface of nanomaterials (such as a gold colloid monolayer) (Keating, Musick, Keefe Natan, 1999), and from the study of a chemical equihbrium in solution (Leenson, 1986). 

M. Giersig and P. Mulvaney, Preparation of ordered colloid monolayers by electrophoretic deposition, Langmuir, 9 (1993) 3408-3413. 

Figure 5.21. A typical SEM image of the colloidal monolayer obtained by the vertical deposition method. The Dh and polydispersity index of the spheres are 195 nm and 0.04, respectively. Source From Li et al., 2005a.

Li YB, Deng YH, He YN, Tong XL, Wang XG. 2005a. Amphiphilic azo pol5mer spheres, colloidal monolayers, and photoinduced chromophore orientation. Langmuir 21 6567 6571. 

Giersig M, Mulvaney P. 1993. Preparation of ordered colloid monolayers by electrophore tic deposition. Langumuir 9 3408 3413. 

Wettability and Superhydrophobicity of 2-D Ordered Nano-structured Arrays Based on Colloidal Monolayers... 

Based on colloidal monolayers of polystyrene spheres, we have prepared various two-dimensional nano-structured arrays by solution routes and electrodeposition. Many ordered structured arrays generated using these methods are of surface roughness on the nano- and micro-scales, and could be superhydrophobic or superhydrophilic. The nano-devices based on such nano-structured arrays would be waterproof and selfcleaning, in addition to their special device functions. In this article, taking silica, ZnO and gold as examples of the insulators, semiconductors and metals, respectively, we report some of our recent results to demonstrate controlled wettability and superhydrophobicity of two-dimensional ordered nano-stmctured arrays with centimeter square-size based on colloidal monolayers. 

D nano-stmctured arrays, wettability, superhydrophobicity, colloidal monolayer crystal... 

Figure 1. Photograph (left) and field emission scanning electron microscopic (FESEM) image (right) of PS colloidal monolayer on the glass substrate.

Further, if the colloidal monolayer is heated above its glass-transition temperature, the colloidal monolayer will be deformed. Based on the 2-D heat-deformed colloidal monolayers, we presented a simple approach to prepare large-sized hexagonal nano-pillar arrays by solution-dipping method [30]. In this method, first, the... 

Figure 8a shows the ordered array of silica triangular prism shaped pillars by the deformed colloidal monolayer which was sintered at 120°C for 10 min. Before modification with fluoroalkylsilane, such film also exhibits superhydrophilic-ity (CA < 5°). After modification, however, its water CA increased to 165°. The... 

Figure 13. FESEM images of (a) ordered alumina through-pore array induced by solution-dipping on PS (1000 nm in diameter) colloidal monolayer using 0.2 M A1(N03>3 and (b)Au particle array by deposition (for 20 min at 1 mA/cm ) on the template shown in (a). Inset of (b) water droplet on the surface after modification with 1-hexadecanethiol. (c) Magnified image of a local area in (b). Scale bars are 1000 nm for (a) and (b) and 200 nm for (c). (d) Photograph of a water droplet on the Au particle array on ITO.

In summary, our results have demonstrated that a colloidal monolayer can be used as a flexible template to create ordered nano-structured arrays. Combining it with other techniques, a series of ordered nano-structured arrays with centimeter size could be easily fabricated on many different substrates. These nano-structured arrays are of surface roughness on the nano- and micro-scales, or similar to the microstructure of lotus leaves. Our results have demonstrated that such micro/nano-structured arrays, not only of insulators and semiconductors but also of metals, display morphology-dependent wettability. Significant enhancement of both hydrophobicity and hydrophilicity can be achieved by fabricating special surface micro/nano-structure on any material. This means that we can also realize tunable and controllable wettability of surface of any material by designing the proper surface structure. From this study, it can thus be expected that the nano-devices based on our nano-structured arrays would be waterproof and self-cleaning, in addition to their special device functions. 

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