Optical Properties of Composite Membranes Containing Arrays of Nanoscopic GoldCylinders

摘要

Nano-chemistry, physics and materials are important and evolving fields in modernscience. One of the most interesting aspects of nanomaterials concerns the optical properties of nanoscopic metal particles. While bulk metals are optically opaque, effective medium theory (EMT) predicts that collections of small metal particles can be transparent, provided that the wavelength of light employed is much greater than a characteristic dimension of the particle. Hence, EMT can be used as a guide to prepare metal-containing composites that are both electronically conductive and optically transparent. We have recently shown that composites of this type can be prepared by electrochemical deposition of metals within the pores of a microporous template membrane. In this report we show for the first time that composite membranes prepared via this template route can be optically transparent throughout the near infrared (NIR) and into the visible region of the electromagnetic spectrum Furthermore, we show that by changing the shapes of the particles prepared, the color of the composite membrane can be reproducibly and predictably varied. Finally we show that these results are in general agreement with the predictions of the appropriate formulation of EMT. Transparent metals, nano materials, effective medium theory.