Effect of Ag2WO4 on the electrical and optical properties of AgI-AgPO3 glasses and fibers for electrophysiology applications

Abstract Glasses and fibers belonging to the AgI−AgPO3−Ag2WO4 system are investigated for their combined optical transmission in the visible region and AC electrical conductivity. These glasses combine characteristics that are essentials for a direct application in the fields of optogenetic and electrophysiology. The addition of silver tungstate (Ag2WO4) into the pseudo binary silver iodide phosphate glasses (AgI−AgPO3) allows to increase the durability of the materials against hydrolysis while maintaining an optical transparency in the visible range (450 to 900 nm). AC electrical conductivity ranging from 10−3 up to 10−2 S·cm−1 at 1 MHz frequency was measured on the bulk glasses at room temperature. Moreover, the progressive addition of silver tungstate from 0 to 20 mol% results in a linear increase of the glass transition temperature from 106 to 219 °C. Electric conductor and light guiding glass fibers of 175 μm core diameter were then successfully fabricated by glass preform drawing. Their electrical conductivity at room temperature was measured to be around 0.26 S·cm−1 at an AC frequency of 1 MHz. These fibers also show optical losses around 5 dB·m−1 between 400 and 500 nm, making them suitable for the transmission in the blue spectral region used in optogenetic/electrophysiology. This new AgI−AgPO3−Ag2WO4 vitreous system offers glass compositions that are more appropriate in terms of optical transmission to produce multifunctional fibers for electrophysiology experiments than AgI−AgPO3−WO3 glasses previously reported.