Analytical Sciences

Film-Thickness-Controllable System for Preparing Silver Nanofilms through Absorbance Monitoring of the Thickness during a Silver-Mirror Reaction

Kenji MORITA,* Kazuhiro MORIOKA,* Hizuru NAKAJIMA,** Katsumi UCHIYAMA,** Akio YANAGIDA,* and Atsushi SHOJI*

*School of Pharmacy, Tokyo University Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
**Department of Applied Chemistry, Graduate School of Urban Environmental Science, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan

An innovative technique is proposed for forming silver thin films of nanometer-order thickness via a silver-mirror reaction. This approach is made possible by the real-time monitoring of the thickness of a silver thin film formed on the edge surface of a fiber core during the silver-mirror reaction using a homemade absorbance measurement system. The monitored absorbance value increases as silver plating progresses, and the relationship between the absorbance values and the thickness of the silver thin film is linear in the thickness range from approximately 30 to 60 nm. This technique was applied to the preparation of a fiber-optic surface plasmon resonance (FO-SPR) sensor. The sensor was successfully used to measure sucrose solutions with concentrations of less than 16% (w/v). The sensitivity of the sensor probe was estimated to be 2205 nm/RIU in the refractive index range of 1.333 – 1.357. The relative standard deviation of the wavelength shift obtained from measurements using different sensor probes was estimated to be less than 3.3%.

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