Highly Sensitive Optical Fiber Dissolved Oxygen Sensor Based on Organic Modified Silicate Porous Matrix by Sol-Gel Method

The sensing sensitivity and response are highly dependent on the pore size and hydrophobicity of the matrix for optical fiber dissolved oxygen (DO) sensors. This work describes the development of a DO sensor with high sensitivity and fast response. The sensor is based on an organically modified silicate (ORMOSIL) xerogel film that has been through a sol-gel procedure to sequester tris(4,7-diphenyl-1,10-phenanthrolin) ruthenium dichloride complex (Ru(dpp) $_{{3}}^{{2}+}{}$ ). The xerogels were prepared with tetraethoxysilane (TEOS), n-octyltrimethoxysilane(OTMS)/TEOS, and n-propyltrimethoxysilane(PTMS)/OTMS/TEOS. Asymmetry (ASY) was used to evaluate the response time of sensors, indicating a relationship with the pore size and diffusion coefficient of the film. Through transmission electron microscope (TEM) and Barrett-Joyner-Halenda (BJH) characterization, we conclude that organic modified groups with high spatial site resistance and hydrophobicity can increase the pore size, hydrophobicity, and diffusion coefficient, thereby improving the response and sensitivity of the sensor. According to the experimental results, the sensor based on PTMS/OTMS/TEOS xerogel has a response time of 3 s and a sensitivity of 73.4 in the 0–18.54-mg/L range of DO content. This article provides new insights for the future design of high-performance DO sensors.