Gas sensing property of lithium tetraborate clad modified fiber optic sensor

The micro structured plate-like lithium tetraborate, Li2B4O7 (1 μm in diameter) has been prepared by sol–gel method and characterized structurally by X-ray diffraction and morphologically by scanning electron microscopy. UV–Vis spectrum shows about 60% transparency in the visible region and the optical energy band gap is found to be 3.5 eV which is also confirmed by strong near band edge emission from luminescence spectrum. The spectral characteristics of the cladding modified fiber optic sensor coated with microcrystalline Li2B4O7 are studied for various concentrations of ethanol, methanol and ammonia (50–500 ppm). At 298 K, the sensitivity for ethanol is −10 counts/ppm which is relatively higher than ammonia (−4 counts/ppm) and methanol (−3 counts/ppm). The time response of the sensor is presented for pure Li2B4O7 with ethanol gas.