Photoinduced Charge Transfer and Trapping on Single Gold Metal Nanoparticles on TiO.

We present a study of the effect of gold nanoparticles (Au NPs) on TiO on charge generation and trapping during illumination with photons of energy larger than the substrate band gap. We used a novel characterization technique, photoassisted Kelvin probe force microscopy, to study the process at the single Au NP level. We found that the photoinduced electron transfer from TiO to the Au NP increases logarithmically with light intensity due to the combined contribution of electron-hole pair generation in the space charge region in the TiO-air interface and in the metal-semiconductor junction.

The use of artificial neural networks in electrostatic force microscopy.

The use of electrostatic force microscopy (EFM) to characterize and manipulate surfaces at the nanoscale usually faces the problem of dealing with systems where several parameters are not known. Artificial neural networks (ANNs) have demonstrated to be a very useful tool to tackle this type of problems. Here, we show that the use of ANNs allows us to quantitatively estimate magnitudes such as the dielectric constant of thin films.

Field-induced formation of nanometer-sized water bridges.

A method to form and manipulate the properties of nanometer-size liquid bridges by an external electric field is discussed. The properties of bridges are shown to be the result of an interplay among the field-induced polarization of the water layer adsorbed on the surface, the surface energy, and the water condensation from the humid air. For a given tip-sample separation, a simple model predicts the existence of a threshold voltage V(th) to form the bridge in full agreement with experiments.