Arrays of Metallic Nanoparticles

From a practical sensing point of view, regardless of the specific detection technique, the Ag nanostructures that best fit the diagnostic purpose should meet the following requirements  

In the case of SERS, for example, practical appHcation of the remarkable analytical sensitivity of SERS has not been widely accepted as a viable diagnostic technique due to problems in preparing robust substrates of the correct surface morphology to provide maximum SERS enhancements [94). Some of the most important requirements for an ideal SERS substrate in practical diagnostic applications are that the substrate (i) produces a high enhancement (ii) generates a 

Fabrication steps 3 steps 3 steps 3 steps 2 steps 1-2 steps 

Cost Expensive Inexpensive Inexpensive Inexpensive Moderate 

NA = no data available in the literature NSL = nanosphere lithography OAD = oblique angle deposition. 

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Fu X, Wang Y, Huang L, Sha Y, Gui L, Lai L, Tang Y. Assemblies of metal nanoparticles and self-assembled peptide fibrils—formation of double helical and single-chain arrays of metal nanoparticles. Adv Mater 2003 15 902-906. 

The fabrication of regular arrays of metallic nanoparticles by molecular templating is of great interest in order to prepare nanometre structures for future use in nanoelectronics, optical and chemical devices.43 A sensitive, rapid and powerful direct analytical method is required for the quantitative analysis of high purity platinum or palladium nanoclusters produced by biomolecular... 

Gopinath A, Boriskina SV, Reinhard BM, Dal Negro L (2009) Deterministic aperiodic arrays of metal nanoparticles for surface-enhanced Raman scattering (SERS). Opt Express 17(5) 3741-3753... 

Dirix, Y., Bastiaansen, C., Caseri, W., and Smith, R, Oriented pearl-necklace arrays of metallic nanoparticles in polymers a new route toward polarization-dependent color filters, Adv. Mater, 11, 223-227 (1999a). 

Chan YH, Chen J, Wark SE et al (2009) Using patterned arrays of metal nanoparticles to probe plasmon enhanced luminescence of CdSe quantum dots. ACS Nano 3 1735-1744... 

Y. Dirix, C. Bastiaansen, W. Caseri and P. Smith, Oriented pearl-necklace arrays of metallic nanoparticles... 

Figure 6.1 This is a simulated NanoCell with five I/O leads on each side. Within the cell is a planar array of metallic nanoparticles and molecules (dark and light lines). The molecules can be in a high conducting state (dark lines) or a low conducting state (whilte lines).

Bifunctional spacer molecules of different sizes have been used to construct nanoparticle networks formed via self-assembly of arrays of metal colloid particles prepared via reductive stabilization [88,309,310]. A combination of physical methods such as TEM, XAS, ASAXS, metastable impact electron spectroscopy (MIES), and ultraviolet photoelectron spectroscopy (UPS) has revealed that the particles are interlinked through rigid spacer molecules with proton-active functional groups to bind at the active aluminium-carbon sites in the metal-organic protecting shells [88]. 

Common methods for the fabrication of metallic nanoparticle arrays are electron beam lithography, photolithography, laser ablation, colloidal synthesis, electrodeposition and, in recent time, nanosphere lithography for which a monodisperse nanosphere template acts as deposition mask. A review on advances in preparation of nanomaterials with localized plasmon resonance is given in [15]. 

Metal nanoparticles housed in zeolites and aluminosilicates can be regarded as arrays of microelectrodes placed in a solid electrolyte having shape and size selectivity. Remarkably, the chemical and electrochemical reactivity of metal nanoparticles differ from those displayed by bulk metals and are modulated by the high ionic strength environment and shape and size restrictions imposed by the host framework. In the other extreme end of the existing possibilities, polymeric structures can be part of the porous materials from electropolymerization procedures as is the case of polyanilines incorporated to microporous materials. The electrochemistry of these types of materials, which will be termed, sensu lato, hybrid materials, will be discussed in Chapter 8. 

As illustrated in Scheme 3.14, Ag nanoparticles were prepared within the tubes via a reaction with Ag[PF6]. We found that partial preoxidation of the PFS domains with an organic oxidant such as tris(4-bromophenyl)aminium hexachloroantimonate is a key step for the efficient formation of one-dimensional arrays of silver nanoparticles confined within the nanotubes (Figure 3.10).50 Further attempts to synthesize metal nanowires through this encapsulation method are currently in progress. 

The ordered P AA back-side and structured Al surface were used to produce self-organized metal nanoparticles. We used Au or amorphous carbon as add-layer for deposition of Ti or Fe nanostmctures. Both these metals have a weak wetting of the add-layer. The deposition was performed by a laser induced plasma deposition technique. In this process the energy of ions was about 20 eV. The highly ordered curved substrate surface defined position of the deposited clusters providing formation of highly ordered arrays of metal nanoclusters. A perspective application of such structures for terabit memory was demonstrated. For example, Ti nanoclusters covered by native oxide demonstrated irreversible transformation of I-V characteristics from barrier-like to the ohmic behavior after the action of current supplied by a tip of conductive AFM. 

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