We have manipulated raw and functionalized gold nanoparticles (with a mean diameter of 25 nm) on silicon substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles stick to silicon until a critical amplitude is reached by the oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry and adhesion to the substrate. Higher and lower mobility were observed when the gold particles were coated with methyl- and hydroxyl-terminated thiol groups, respectively, which suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. Under ultrahigh vacuum conditions, where the water layer is absent, the particles did not move, even when operating the atomic force microscope in contact mode. We have also investigated the influence of the temperature (up to 150 degrees C) and of the geometrical arrangement of the particles on the manipulation process. Whereas thermal activation has an important effect in enhancing the mobility of the particles, we did not find differences when manipulating ordered versus random distributions of particles.

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We investigated the formation of complex aggregation patterns during the drying of nanocolloidal dispersion drops on various surfaces. Our results show that large-scale and well-organized multibranched surface aggregates can form during this drying process. Both the emergence and topological features of these complex patterns were found to be controlled by two parameters:  (1) the actual volume fraction of the drop in the late step of the drying and (2) the hydrodynamic shear involved in the rupture−dewetting and receding motion of the residual suspension drop. A simple phenomenological model was proposed, which accounts for the experimental results and their analogy with shear instabilities and structure formation in purposely designed Hele-Shaw cells.

A self-assembled monolayer of decyltrichlorosilane (CLSi(CH2)9CH3) supported on elastomeric polydimethylsiloxane (PDMS) was used as a model system to study the adsorption of a nonionic surfactant EH(CH2) 1 2(OCH2CH2)70H] at the solid-liquid interface. The deformation produced on contacting a semispherical lens of the elastomer with a flat sheet under water varied systematically in response to the amount of surfactant added to the aqueous phase. The JKR theory of contact deformation in conjunction with the Gibbs' theory of interfacial thermodynamics yielded the required interfacial tension and surface excess quantities at solid-liquid interface.

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We report for the first time the formation of spherical and branched structures when polymerizing maleic anhydride under very low power with pulsed plasma polymerization. A factorial experimental design evidenced duty cycle, frequency and their interactions as decisive factors for the formation and growth of these structures. A mechanism involving the decoupling of deposition (nucleation) and diffusion rates of active species was proposed to relate structure formation to processing parameters. While differences in surface chemistry were not detectable by surface spectroscopy (PM‐IRRAS, XPS), AFM force measurements on a carefully designed sample evidenced differences in adhesion and thus surface chemistry between the different film morphologies.

SummaryOne key component in the assembly of nanoparticles is their precise positioning to enable the creation of new complex nano-objects. Controlling the nanoscale interactions is crucial for the prediction and understanding of the behaviour of nanoparticles (NPs) during their assembly. In the present work, we have manipulated bare and functionalized gold nanoparticles on flat and patterned silicon and silicon coated substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles adhere to silicon until a critical drive amplitude is reached by oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry, size and adhesion to the substrate. Higher and respectively, lower mobility was observed when the gold particles were coated with methyl (–CH3) and hydroxyl (–OH) terminated thiol groups. This major result suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. The influence of critical parameters on the manipulation was investigated and discussed viz. the shape, size and grafting of the NPs, as well as the surface chemistry and the patterning of the substrate, and finally the operating conditions (temperature, humidity and scan velocity). Whereas the operating conditions and substrate structure are shown to have a strong effect on the mobility of the particles, we did not find any differences when manipulating ordered vs random distributed particles.