Electrical Conductivity at Surfaces of Silica Nanoparticles with Adsorbed Water at Various Relative Humidities

• Published in: E-journal of surface science and nanotechnology Vol. 16; p. 376
• Main Authors: Umezawa, Ryosuke, Katsura, Makoto, Nakashima, Satoru
• Format: Journal Article
• Language: Japanese
• Published: Tokyo Japan Science and Technology Agency 01.01.2018
• Subjects: Electrical conduction; Electrical resistivity; Microbalances; Nanoparticles; Quartz crystals; Relative humidity; Scanning microscopy; Silica glass; Silicon dioxide; Thickness; Thin films; Water film
• ISSN: 1348-0391
• DOI: 10.1380/ejssnt.2018.376

Electrical conductivity of silica nanoparticles deposited on electrodes from colloidal suspension were measured under controlled relative humidity (RH). The electrical conductivity values at 1 kHz increased with increasing RH. Amounts of water adsorbed on silica nanoparticles were measured by quartz crystal microbalance (QCM) and they also increased with increasing RH. An empirical power law relation was observed between the reported surface conductivity and RH data for a silica glass. By applying this relation to the silica nanoparticles, the water film thicknesses are estimated to be from 0.08 nm to 0.23 nm. The corresponding specific surface area (SSA) becomes smaller (102 m2g−1) than the reported value (215 m2g−1), indicating aggregation of the nanoparticles. In fact, aggregated rod-like structures were observed under electron and laser scanning microscopy. The electrical conduction of deposited silica nanoparticles under various RH can be understood by surface conduction in thin water films adsorbed on the nanoparticles. [DOI: 10.1380/ejssnt.2018.376]