Planar Optical Waveguide Evanescent Wave ${\rm CO}_{2}$ Sensor Based on a Clad of Alstonia Scholaris Leaf Extract

Abstract

An evanescent wave biosensor is designed and developed using a single mode planar optical waveguide based on a spin coated clad of leaf extract of Alstonia Scholaris. The fabricated sensor showed CO2 concentration dependent response. The specialty of this sensor is that it can be used when stored at room temperature (25degC) up to a maximum of 25-30 days with 90% retention of original sensitivity. These CO2 sensing biochips showed good operational efficiency for 10 cycles. The planar optical waveguide is versatile, easy to fabricate and can be used for ppm level CO2 measurement with good sensitivity. Cross sensitivity with respect to humidity is studied. The sensor exhibited a short response time of 4-5 s and recovery time of 25 s with good repeatability and reproducibility.