Particle arrays

The production of fatty acid-capped silver nanoparticles by a heating method has been reported [115]. Heating of the silver salts of fatty acids (tetradecanoic, stearic, and oleic) under a nitrogen atmosphere at 250°C resulted in the formation of 5-20-nm-diameter silver particles. Monolayers of the capped particles were spread from toluene and transferred onto TEM grids. An ordered two-dimensional array of particles was observed. The oleic acid-capped particle arrays had some void regions not present for the other two fatty acids. 

However, the application potential can be fnlly exploited only if suitable methods to control the structure and to prepare ordered particle arrays over macroscopic dimensions are available. Various methods have been tried to organize mesoscale particles in two or three dimensions. Among them are methods already being used for the organization of molecules at interfaces, while other methods were developed especially for the organization of particles ... 

Oxide surfaces, and in particular oxide films, are versatile substrates for the preparation of model catalysts. Quite a few of these systems show nanoscale reconstructions, which can be employed as templates for the growth of ordered model catalysts of reduced complexity. In order to efficiently control the growth of nanostructured metal particle arrays, two conditions have to be met. First, the template must provide sites of high interaction energy that trap the deposited metals. Second, the kinetics of the growth process must be carefully controlled by choosing... 

Liao P.F., Stem M.B., Surface-enhanced Raman-scattering on gold and aluminum particle arrays, Opt. Lett. 1982 7 483-185. 

Stevens P.W., Wang C.H.J., Kelso D.M., Immobilized particle arrays coalescence of planar- and suspension-array technologies, Anal Chem 2003 75 1141-1146. 

Figure 6.10 A procedural schematic representation for deposition of two kinds of particle arrays on the patterned template. Reprinted with permission from Zheng et al. (2002). Copyright 2002 Wiley InterScience.

Zheng HP, Lee 1, Rubner MF, Hammond PT. Two component particle arrays on patterned polyelectrolyte multilayer templates. Adv Mater 2002 14 569-572. 

Hulteen JC, Van Duyne RP. Nanosphere lithography a materials general fabrication process for periodic particle array surfaces. Journal of Vacuum Science and Technology A 1995, 13, 1553-1558. 

Wirth, S. von Molnar, S. Magnetic interactions in nanometer-scale particle arrays grown onto permalloy films. J. Appl. Phys. 87, 7010-7012 (2000). 

Equation (4.16) can be reduced to Eq. (4.15) as dj becomes infinitely large. For a packed bed of monodispersed spheres arranged in a cubic particle array, the mean thickness of the shell of gas surrounding the particle can be approximated by... 

In general, there are two approaches to assemble nanostructured materials, namely, physical assembly and chemical assembly. Physical assembly techniques are based on the assembly of nonfunctionalized nanoparticles on surfaces by physical forces, which include convective or capillary assembly,3,4 spin coating,5 and sedimentation.6 The physical assembly of nanoparticles generally results in relatively simple, closely packed two- or three-dimensional particle arrays. In addition, the physically assembled nanoparticle structures lack long term stability because they were deposited at relatively low surface pressures.7... 

Figure 13.10 Reaction scheme for the stepwise preparation of multicomponent particle arrays by photolithography.72 Chemically patterned amino-functionalized surfaces were formed by selectively exposing the NVOC substrate by UV exposure. Multicomponent amino-functionalized nanocrystals were subsequently adsorbed via ligand exchange.

MODIFIED STONER-WOHLFARTH THEORY FOR HARD-MAGNETIC PARTICLE ARRAYS... 

Fig. 4 Representative topography images of the particle arrays a SEM for 0.1 pm particle layer b SFM for 0.5 pm particle layer c optical microscopy (MicroGlider) for 1.2 pm particles d optical microscopy (MicroGlider) for 2.5 pm particle layer, e optical microscopy (MicroGlider) for 2.5 pm particle layer (larger scale)...

When applied to fluidization, the empirical correlation between the drag coefficient CD and the Reynolds number Re needs to be extended to account for the automatic adjustment in particle array that results in a regular increase in the fraction void e in the interstitial spaces with increased fluid flow— that is,... 

One would therefore expect that vibrational spectra of CO adsorbed on the platinum particle array should resemble spectra of CO on stepped high Miller index platinum single crystals. However, in preparation for UHV experiments, the... 

What is surprising is that platinum nanoparticle arrays with similar mean partiele diameters still exhibited very different SFG intenities (752). For example, for 40-nm platinum particle arrays, the enhancement for ssp polarization was the relatively small value of approximately 4200 (whereas for 45-nm platinum articles it was approximately 11 800). Indeed, the calculations suggested the same enhaneement for these particle sizes. For 6-nm platinum partieles evaporated onto Si02, the calculations suggest a plasmon enhaneement of 28 and a substrate enhancement of 76, yielding a total enhaneement of approximately 2100 for ssp. However, an... 

Further enhancement of the SERS can be achieved through precise control over the parameters at the metal particle size scale [10] Most SERS-active substrates were made from pure metallic nanostructures such as metal nanoparticles [33-35], metal particle arrays [5], roughened metal surfaces [36], or a combination with metal nanostructures and other nanomaterials [17, 18, 29, 37-39]. Recently, many strategies have shown the adsorbation of molecules on the surface of Ag and Au substrates for SERS applications [40]. SERS-active Ag nanostructures substrates are required to satisfy certain conditions with good reproducibility and stability [39]. For this reason, it is indispensable to develop and optimize the methods to prepare the SERS-active Ag substrates [41]. 

Searching for appropriate preparation techniques of nanoparticles leading to SERS-active particle arrays with preferably tailored structure... 

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