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

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 degrees C. Electric conductor and light guiding glass fibers of 175 mu m 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.