A novel TiO-modified THPP-BCP composite optical waveguide sensor for the determination of ethylenediamine at ppb level.

Composite thin films OWG sensors show higher sensitivity than single film-based OWG sensors, making them particularly useful in the detection of trace gases. In this work, we developed a new tetra hydroxyphenyl porphyrin (THPP)-bromocresol purple (BCP)/TiO gel composite film-based OWG (THPP-BCP/TiO-OWG) sensor for identifying ethylenediamine (EDA) gas. The fabricated sensor was characterized using ultraviolet and infrared spectroscopy and atomic force microscopy. The test result shows that the response of the THPP-BCP/TiO-OWG composite film sensor to analytes was 3-4 times higher than that of the single film THPP-OWG sensor. The THPP-BCP/TiO-OWG sensor exhibited excellent selectivity and remarkable response to EDA gas at a concentration of < 1 ppb at room temperature, with fast response (1 s) and recovery (3 s) times. The high refractive index TiO film contributes to OWG's sensitivity, while the THPP and BCP's sensitivity to bases further increased the sensor's response to EDA gas. The combination of THPP-BCP thin film and TiO gel film provides a powerful platform for OWG sensors that are highly sensitive, specific, and stable in the detection of trace gases.