Glassy Behavior of a Tin Dioxide Nanoparticle Suspension.

Dilute suspensions of charged colloidal particles with a short-range attraction and long-range repulsion can exhibit a variety of arrested states. In many applications using suspensions of charged nanoparticles, the optimization of the process requires the understanding of the mechanism underlying the stability and the rheological properties of the suspensions. In an attempt to clarify the solidification mechanism for dilute suspensions of tin dioxide (SnO2) nanoparticles, we present dynamic viscoelasticity, dynamic and static light scattering, and small-angle X-ray scattering experiments on a SnO2 nanoparticle suspension with a nanoparticle concentration of 25.0 wt % (volume fraction φ = 0.045). The behaviors of the observed dynamic and static structure factors reveal that the aging of SnO2 nanoparticles is Wigner glassy rather than gel-like.

Optically transparent conductive network formation induced by solvent evaporation from tin-oxide-nanoparticle suspensions.

This investigation describes an optically transparent antistatic film composed of antimony-doped tin oxide (ATO) nanoparticles dispersed in a polymer matrix, with remarkably improved electrical and optical properties. The film is fabricated on the basis of a synergistic interaction between self-assembling nanoparticles and self-organizing matrix materials. The antistatic property of the film is obtained at ATO concentrations above a threshold value. A scaling analysis of the data yields an extremely low critical concentration (0.0020 volume fraction), which is considerably lower than the value predicted by percolation theory. Microscopic observations of the film have revealed a characteristic microstructure: "single-stranded" chainlike (linear form or fibrous) aggregates consisting of ATO nanoparticles and large ATO-depleted areas. The experiment results suggest that the high optical transparency and the low critical concentration are derived from the characteristic microstructures of the film.

Self-assembly of tin oxide nanoparticles: localized percolating network formation in polymer matrix.

A novel method to prepare transparent antistatic films by trapping nanoparticles in thin surface layers is proposed, and high performance of the product is demonstrated. Coating solutions consisting of surface-active antimony-doped tin oxide (ATO) nanoparticles, an organic solvent mixture of high affinity with poly(methyl methacrylate) substrate, and an ultraviolet curable resin are used for the film formation. Antistatic property of the layer is obtained at ATO concentrations above the critical concentration for percolation. A scaling analysis of the data shows that the critical concentration (0.004 volume fraction) is extremely low as compared to the value predicted by the percolation theory for randomly packed systems as well as the values in ever developed composite films filled with ATO particles. Microscopic observation of the deposited layers indicates that percolating clusters of ATO particles are localized on the layer surfaces. The excellent electrical and optical properties of the layer are attributed to the characteristic microstructure.