The diffusion and coalescence of metal nanoparticles play important roles in many phenomena. Here, we offer a new integrated overview of the main factors that control the nanoparticle coalescence process. Three factors are considered in our description of the coalescence process: nanoparticle diffusion across the surface, their physical and thermodynamic properties, and the mechanism of coalescence. We demonstrate that the liquid-like properties of the surface layers of the nanoparticles play an essential role in this process. We present experimental evidence for our opinion, based on the high-resolution electron microscopic analysis of several different types of nanoparticles.

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The interaction between multiwalled carbon nanotubes (MWCNTs) and aqueous poly(diallyl dimethylammonium) chloride (PDDA) was studied by X-ray photoelectron (XPS) and photoacoustic Fourier transform infrared (PA-FTIR) spectroscopies. We have found that the mild sonication of MWCNTs in aqueous PDDA results in a significant improvement of CNT dispersibility and greatly enhances their adhesion to Au and Si substrates. The MWCNT-PDDA interaction is due to the presence of an unsaturated contaminant in the PDDA chain, as confirmed by both XPS and PA-FTIR, which enters into a pi-pi interaction with the CNTs. Electrostatic group repulsions of the coated CNTs then provide the dispersibility and adhesion.

3D Pt nanoflowers, which are composed of numerous single‐crystal nanowires, are successfully synthesized by a facile chemical procedure, at room temperature, without surfactant or template. The Pt nanoflowers adhere to carbon paper, exhibiting an enlarged electroactive surface area comparable to that of a commercial Pt/C electrode.

The X-ray photoelectron spectroscopic characterizations of Pt nanoparticles evaporated onto untreated and Ar+-treated highly oriented pyrolytic graphite surfaces, with, respectively, low and high surface defect densities have been studied using multicomponent analysis with symmetric line shapes:  each Pt4f spectral component (f7/2 and f5/2) was deconvoluted into three symmetric peaks. On analyzing the relationships among the Pt4f, C1s, and O1s spectra, we attribute these peaks to the existence of surface oxidation on the platinum nanoparticles and to the different electronic configurations of surface and bulk Pt atoms. We use the varying intensities of these component peaks, as a function of deposited Pt, to explain the changing shape of the Pt4f asymmetric envelope with nanoparticle size.