Nanoparticle geometry

Nanoparticle Geometry at Oxide-supported Metal Catalysts... 

The main results of experimental studies of size effects in nanoferroics are presented in second chapter. In particular, we collect the extensive experimental data about size effects in nanoparticles and thin films of ferroelectrics, ferroelastics and magnetically ordered ferroics. The data have been collected for different nanoparticles geometries like spherical and cylindrical as well as for nanowires, nanotubes and nanopills. As for nanosizes the local properties play a decisive role, we pay attention to the results of electron spin resonant measurements, which are sensitive to the local properties. To obtain the reliable information about the physical properties of the entire nanostructure, the above local methods should be augmented by other experimental techniques like dielectric, magnetic and optical methods. We hope that our collection of available experimental data will give the idea about both local and average static and dynamic properties of nanostructures. 

It has been often stressed that low eoordinated atoms (defeets, steps, and kink sites) play an important role in surfaee ehemistry. The existenee of dangling bonds makes steps and kinks espeeially reaetive, favoring the adsorption of intermediate species on these sites. Moreover, smdies of single-crystal surfaces with a eomplex geometry have been demonstrated very valuable to link the gap between fundamental studies of the basal planes [Pt( 111), Pt( 100), and Pt(l 10)] and applied studies of nanoparticle eatalysts and polycrystalline materials. In this context, it is relevant to mention results obtained with adatom-modified Pt stepped surfaces, prior to discussing the effect of adatom modification on electrocatalysis. 

Anandan et al. [37] reported the sonochemical synthesis of gold-silver bimetallic nanoparticles with core-shell geometry by the sonochemical co-reduction of Au and... 

Fig. 18.8 SERS detection in LC ARROW, (a) Top view of experimental beam geometry excitat ing rhodamine 6G molecules bound to silver nanoparticles (leyLC) excitation beam, 1R Raman signals) (b) R6G concentration dependent SERS power for three representative Raman peaks PI P3, inset spectra at various excitation powers...

A major obstacle in making precise structures with metal colloids has been the control of aggregation and particle size distribution. The use of micelles has allotted some success in this regard with the formation of different metal colloid geometries [30]. It is known that the nanoparticles must be stabilized by organic molecules attached to their surface [31] and in general must be embedded in a solid matrix [32], This is done to prevent agglomeration and precipitation as... 

Fig. 5 A proposed mechanism for enhanced emission (or AIEE) in solid-state organic dye nanoparticles. The dye considered here is trans-biphenylethylene (CN-MBE) compound. The geometry is optimized by the density functional theory (DFT) calculation at the B3LYP/6-31G level. Molecular distortion such as twisting and/or subsequent planarization causes prevention of radiationless processes along with specific aggregation such as the /-aggregate in the nanoparticles...

Fig. 15.16 HRTEM images of Pd nanoparticles deposited (a) on the CNF surface and (b) on the N-doped CNF surface (right) showing spherical and flattened geometries, respectively. Courtesy...

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