Nanopartides arrays

W. P. McConnell J. P. Novak L. C. Beousseau III R. R. Euierer R. C. Tenent D. L. Eeldheim, Electronic and Optical Properties of Chemically Modified Metal Nanopartides and Molecularly Bridged Nanopartide Arrays, f Phys. Chem. B 2000, 3 04, 8925-8930. 

A further step towards switchable molecular electronic circuits is the light-controlled conductivity of 2-D lattices of gold nanoparticles bridged by photochromic diarylethene molecules [90]. This was demonstrated by van der Molen et al., who first prepared the device as described above [89] and then immersed it in a solution of on state switches so as to obtain an interlinked 2-D nanopartide array (see Figure 5.62a and b). In this case, the nanopartide array serves as a template for the switching molecules which form conductive bridges in-between. 

Fukuoka, A., Araki, H., Sakamoto, Y., Sugjmoto, N., Tsukada, H., Kumai, Y., Akimoto, Y. and Ichikawa, M. (2002) Template synthesis of nanopartide arrays of gold and platinum in mesoporous silica films. Nano Letters, 2, 793. 

The first measurement of comparative electrode kinetics between the nano- and macroscales has been recently reported by Campbell and co-workers. The electrode kinetics and mechanism displayed by the nanopartide arrays were found to be quahtatively and quantitatively different from those of a silver macrodisk. As was argued by Campbell and co-workers, the electrochemical behaviour of nanoparticles can differ from that of macroelectrodes for a variety of reasons. The most significant among them is that the size of the diffusion layer and the diffuse double layer at the nanoscale can be similar and hence diffusion and migration are strongly coupled. By comparison of the extracted electrode... 

Figure 3 Controllable assembly of nanopartides using DNA templates, (a) Topographical atomic force microscopy image of an assembled array of Au nanopartides. (b)TEM image ofthe nanopartide array of 6-nmAu nanopartides, with an average interrow spacing of 60nm. (c) Schematic of the DNA template and nanopartides. Reprinted with permission from Le, J. D. Pinto, Y. Seeman, N. C. etal. Nano Lett. 2004,4,2343-2347. Copyright 2004 American Chemical Society.

Lombardi, 1., Cavallotti, P.L., Carraro, C. and Maboudian, R. (2007) Template assisted deposition of Ag nanopartide arrays for surface-enhanced Raman scattering applications. Sensors and Actuators B-Chemical, 125, 353-6. 

Traditional methods for fabricating nano-scaled arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of self-organizing templates. Due to their intrinsic ability to adopt complex and flexible conformations, proteins have been used to control the size and shape, and also to form ordered two-dimensional arrays of nanopartides. The following examples focus on the use of helical protein templates, such as gelatin and collagen, and protein cages such as ferritin-based molecules. 

Jensen, T.R., Duval, M.L., Kelly, K.L., Lazarides, A.A., Schatz, G.C., and Van Duyne, R.P. (1999) Nanosphere lithography effect of the external dielectric medium on the surface plasmon resonance spectrum of a periodic array of silver nanopartides. Journal of Physical Chemistry E, 103, 9846-9853. 

Other bottom-up manufacturing methods use self-assembly processes to produce larger structures. If the ambient conditions are right, atoms or molecules spontaneously form ordered arrangements of for example, fullerenes or nanotubes and wires and a quickly increasing array of others, often called nanopartide ensembles [11.6]. 

L. Gunnarsson, J. Prikulis, B. Kasemo, and M. Kail, Nanopartide Optics the Importance of Radiative Dipole Coupling in Two-Dimensional Nanoparticle Arrays, J. Phys. Chem. B 107, 7337 (2003)... 

The as-prepared FePt nanopartides exhibited a chemically disordered fee structure, with relatively poor magnetic properties. Thus, fee FePt nanopartides were superparamagnetic at room temperature, and could be handled in the form of a colloidal solution for casting films, and produdng self-assembled arrays, for example (Figure 3.128). Further, the FePt nanopartides could be annealed at 550-600°C... 

One of the first hints that gold nanopartides (AuNPs) could be deposited in an ordered manner was provided by Schiffrin et cd. [35], whenS run gold partides, which had been prepared in a two-phase liquid-liquid system and stabilized by dithiols [36], provided crosslinked assemblies for which the quality of ordering was rather limited compared to recent results. Nonetheless, these preliminary findings confirmed that 2-D self assembled arrays could be produced. 

Taken together, these results showed that SET was not only dependent on the nature of the ligands stabilizing the nanopartides, but also on the composition of the solution surrounding the function array. These points would be usefid when studying chemical signal transduction, where SET currents should be sensitive to single redox or analysis events. 

The planar order of nanostructures deposited by chemical routes has become an important issue, because of the competition with solid-state nanotechnology cap>able of the fabrication of fine two-dimensional structures. The main concern is with the layers of nanopartides produced by chemical self-assembly, because methods of electrostatic self-assembly and LB is not capable of producing two-dimensional ordered arrays of nanopartides. The features of the lateral arrangement of particles, which are buried under layers of either closely packed amphiphilic compounds or polymers, are usually smeared and difficult to observe. In the case of relatively thick (quasi-3D) films, produced by electrodeposition and sol-gel techniques, the morphology study usually reveals polycrystallites. Therefore, the quality of these materials can be assessed by the size of the crystallites and by the presence of preferential orientation, which may cause anisotropy of the electrical and optical prop>erties of materials. 

Block copolymers have been used as a template for creating nanopartide patterns. For example, some applications such as catalysis and magnetic recording necessitate a surface presentation for the nanopartides. For this approach, it is critical that the block copolymers present multiple blocks at or near the free interface. PS-b-PMMA, which has both PS and PMMA domains displayed at the surface at appropriate surface thickness, is frequently utilized for this reason. Figure 3(c) illustrates the selective adsorption of Au onto the PS domains, forming arrays of nanoscale clusters and wires. ... 

Nano-Pardde Conlrollalile Assembly, Rgure 5 TEM image showing S-layer templated periodic array of 5 nm sized gold nanopartides. Scale bar is 100 nm. Reproduced with permission from [15]... 

Single crystal nanowires (SNW) are one-dimensional single crystal nanopartides like fullerenes vs. carbon nanotubes. While retaining the properties of nanopartides, SNW have been made into functional devices such as transistors, nanoelectrode arrays, and probes for biological sensing. Depending on the materials type and diameter, SWN and devices can be made electrically, optically, or magnetically functional. 

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