Nanoparticle ordering

Figure 2.5. Transmission electron micrographs of prismatic BaCr04 nanoparticles ordered into chains (a) and rectangular superlattice of BaCr04 nanoparticles (b). Reproduced with permission from [60].

Nanoparticle monolayers and multilayers can also be prepared directly by electrochemistry without performation of the nanoparticles. For example, Ag nanoparticles monolayer can be formed by Ag grafted on 4-aminophenyl monolayer on highly oriented pyrolytic graphite followed by pulse electroreduction, and then the uniformly dispersed Ag nanoparticles as ordered monolayers are prepared. By a similar design Pd and Pt ordered monolayers can also be fabricated. For Pt (or Pd) nanoparticle ordered multilayers, they can be assembled with PtCl (or PdCl4 ) and CoTMPyP alternatively followed by electroreduction. The Pt or Pd nanoparticle ordered multilayers formed on the electrode surface demonstrate high catalytic activity to O2 and H2O2 reduction. 

Another approach to prepare nanoparticle ordered multilayers by preceding the formation of the nanoparticle monolayer can be achieved by a bottom-up... 

Keywords Confined water Interfacial hydrogen bonds Nanoparticle ordering Nanoscale electrowetting... 

The synthesis route for nanoparticle ordered structures with homogeneous composition and preparation conditions influences the sintering temperature, grain sizes, and grain boundary. 

The chapter addresses the ordering of Si nanoparticles in thin liquid films. While hydrophilic Si nanoparticles order in the film core perpendicular to the outer film surfaces, partially hydrophobized Si particles can also adsorb at the (fiuid) surface of foam films or emulsion films. Lateral ordering becomes important for the stability of the respective macroscopic systems (foams and emulsions). 

Figure 3 Self-assembled ultrathin nanoparticle film. Above TEM Image of a gold nanoparticle monolayer freely suspended over a hole with a 250 nm radius In the SI substrate. The nanoparticle ordering Inside and outside the hole Is clearly visible. Below schematic diagram of the array configuration Inside a hole. Reprinted with permission from Mueggenburg, K. E. Lin, X.-M. Goldsmith, R. H. Jaeger, H. Nat. Mater. 2007, 6, 656. ...

The optical properties of metal nanoparticles have traditionally relied on Mie tlieory, a purely classical electromagnetic scattering tlieory for particles witli known dielectrics [172]. For particles whose size is comparable to or larger tlian tire wavelengtli of the incident radiation, tliis calculation is ratlier cumbersome. However, if tire scatterers are smaller tlian -10% of tire wavelengtli, as in nearly all nanocrystals, tire lowest-order tenn of Mie tlieory is sufficient to describe tire absorjDtion and scattering of radiation. In tliis limit, tire absorjDtion is detennined solely by tire frequency-dependent dielectric function of tire metal particles and the dielectric of tire background matrix in which tliey are... 

Ebbesen[4] was the first to estimate a conductivity of the order of lO fim for the black core bulk material existing in two thirds of tubes and one third of nanoparticles. From this observation, it may naturally be inferred that the carbon arc deposit must contain material that is electrically conducting. An analysis of the temperature dependence of the zero-field resistivity of similar bulk materials[14,15] indicated that the absolute values of the conductivity were very sample dependent. 

Fig. 2. Raman spectra (T = 300 K) from various sp carbons using Ar-ion laser excitation (a) highly ordered pyrolytic graphite (HOPG), (b) boron-doped pyrolytic graphite (BHOPG), (c) carbon nanoparticles (dia. 20 nm) derived from the pyrolysis of benzene and graphitized at 2820°C, (d) as-synthesized carbon nanoparticles ( 850°C), (e) glassy carbon (after ref. [24]).

Considering all the spectra from nested tubule samples first, it is clear from Table 1 that the data from four different research groups are in reasonable agreement. The spectral features identified with tubules appear very similar to that of graphite with sample-dependent variation in the intensity in the D (disorder-induced) band near 1350 cm" and also in the second-order features associated with the D-band (i.e., 2 X D <= 2722 cm ) and -f- D 2950 cm . Sample-dependent D-band scattering may stem from the relative admixture of nanoparticles and nanotubes, or defects in the nanotube wall. 

An important question frequently raised in electrochemical promotion studies is the following How thick can a porous metal-electrode deposited on a solid electrolyte be in order to maintain the electrochemical promotion (NEMCA) effect The same type of analysis is applicable regarding the size of nanoparticle catalysts supported on commercial supports such as Zr02, Ti02, YSZ, Ce02 and doped Zr02 or Ti02. What is the maximum allowable size of supported metal catalyst nanoparticles in order for the above NEMCA-type metal-support interaction mechanism to be fully operative ... 

In order to explain how the trajectory of the nanoparticle and the damage region of the surface are formed, the... 

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. 

Douglas and coworkers were the first one that described a bottom-up approach based on S-layers as templates for the formation of perfectly ordered arrays of nanoparticles [128]. The S-layer lattice was used primarily to generate a nanometric lithographic mask for the subsequent deposition of metals. In this approach a thin Ta-W film was deposited... 

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