Ultrasensitive Optofluidic Interferometer for Online Monitoring of Photocatalytic Reactions

Ultrasensitive sensing devices contribute to the accurate detection and quantitation of chemical and biochemical reaction processes such as photocatalysis. This study proposes a simplified type of on-chip optofluidic sensor constructed by combining a fiber optic interferometer with a microfluidic chip to obtain an integrated and ultrasensitive device for the quantitative measurement of fluids. In the sensing region, the microchip splits the optical beam in half, forcing the transmission of one part through the polydimethylsiloxane material and that of the other part through the fluids in the microfluidic channel. This leads to the formation of a Mach-Zehnder interferometer that shows a strong response to the refractive index (RI) variation of fluids (22,331 nm/RIU). As an example, the photocatalytic degradation of rhodamine 6G was considered. Results indicate that the proposed optofluidic sensor has a low limit of detection (0.3125 μM) as well as a capacity of dynamic monitoring of photochemical reaction. With a simplified and compact structure, this mass-producible optofluidic sensor can potentially be applied in the fields of energy and environment.