Nanoparticle surface

Adsorption of surfactant molecules and/or of suitable coating agents at the nanoparticle surface... 

The time evolution of the mean size of CdS and ZnS nanoparticles in water/AOT/ -heptane microemulsions has been investigated by UV-vis spectrophotometry. It was shown that the initial rapid formation of fractal-hke nanoparticles is followed by a slow-growing process accompanied by superficial structural changes. The marked protective action of the surfactant monolayer adsorbed on the nanoparticle surface has been also emphasized [230,231],... 

The last problem of this series concerns femtosecond laser ablation from gold nanoparticles [87]. In this process, solid material transforms into a volatile phase initiated by rapid deposition of energy. This ablation is nonthermal in nature. Material ejection is induced by the enhancement of the electric field close to the curved nanoparticle surface. This ablation is achievable for laser excitation powers far below the onset of general catastrophic material deterioration, such as plasma formation or laser-induced explosive boiling. Anisotropy in the ablation pattern was observed. It coincides with a reduction of the surface barrier from water vaporization and particle melting. This effect limits any high-power manipulation of nanostructured surfaces such as surface-enhanced Raman measurements or plasmonics with femtosecond pulses. 

Keywords Organometallic Nanoparticles Surface chemistry Self-organization Catalysis... 

Since 1976 until present time Toshima-t5q)e nanocolloids always had a major impact on catalysis and electrocatalysis at nanoparticle surfaces [47,210-213,398-407]. The main advantages of these products lie in the efficient control of the inner structure and morphology especially of bimetallic and even multimetallic catalyst systems. 

T. Teranishi, N. Toshima, in A. Woekowski, E. R. Savinova, C. G. Vayenas (eds.). Catalysis and Electrocatalysis at Nanoparticle Surfaces, Marcel Dekker, New York, 2003. 

This approach of using 2D and 3D monodisperse nanoparticles in catalytic reaction studies ushers in a new era that will permit the identification of the molecular and structural features of selectivity [4,9]. Metal particle size, nanoparticle surface-structure, oxide-metal interface sites, selective site blocking, and hydrogen pressure have been implicated as important factors influencing reaction selectivity. We believe additional molecular ingredients of selectivity will be uncovered by coupling the synthesis of monodisperse nanoparticles with simultaneous studies of catalytic reaction selectivity as a function of the structural properties of these model nanoparticle catalyst systems. 

All Pt(0) nanoparticles were washed with water and ethanol to completely remove physisorbed polymers from the nanoparticle surface. The final particles were stable and stored in water at the same concentration (3 x 10 M based on the original Pt salt concentration). The long-term stability is attributed to PVP monolayer(s) coating the... 

Figure 6. Thermogravimetric analysis (TGA) of free 55 K PVP and 7.1 nm Pt-PVP nanoparticles in oxygen. Oxidative decomposition of free PVP begins at 573K, while significant weight loss due to the catalyzed oxidation of PVP on PVP-protected Pt nanoparticles occurs at 473 K. It appears that PVP layer is not a complete monolayer or the entanglement of PVP chains causes a porous polymer layer enabling oxygen diffusion to the nanoparticle surface [17]. (Reprinted from Ref [17], 2006, with permission from Springer.)...

In 1994, thiols were firstly used as stabilizers of gold nanoparticles [6a]. Thiols form monolayer on gold surface [18] and highly stable nanoparticles could be obtained. Purification of nanoparticles can be carried out, which makes chemical method of metal nanoparticles a real process for nanomaterial preparation. Various thiol derivatives have been used to functionalize metal nanoparticles [6b, 19]. Cationic and anionic thiol compounds were used to obtain hydrosols of metal nanoparticles. Quaternary ammonium-thiol compounds make the nanoparticle surface highly positively charged [20]. In such cases, cationic nanoparticles were densely adsorbed onto oppositely charged surfaces. DNA or other biomolecule-attached gold nanoparticles have been proposed for biosensors [21]. 

Koper MTM, van Santen RA, Neurock M. 2003. Theory and modeling of catalytic and electro-catalytic reactions. In Savinova ER, Vayenas CG, Wieckowski A, eds. Catalysis and Electrocatalysis at Nanoparticle Surfaces. New York Marcel Dekker. pp. 1-34. 

Pant and Levinger have measured the solvation dynamics of water at the surface of semiconductor nanoparticles [48,49]. In this work, nanoparticulate Zr02 was used as a model for the Ti02 used in dye-sensitized solar photochemical cells. Here, the solvation dynamics for H2O and D2O at the nanoparticle surface are as fast or faster than bulk water motion. This is interpreted as evidence for reduced hydrogen bonding at the particle interface. 

For an initial concentration of 2.5 pg/ml of GFP solution, the maximum amount of GFP adsorbed on Aerosil was 120.8 jLtg/g, whilst using calcined SBA-15 was 166.5 pg/g, corresponding to 72.5% and 99.9% of the initial concentration, respectively. This result is an indication that the inner surface of the mesoporous material plays a key role in the immobilisation of guest molecules. The relatively small difference in adsorption between the two materials suggests also that the GFP molecules might form multiple layers on the Aerosil nanoparticle surface. 

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