Nb₂C-MXene/UIO-66-COOH Hybrid-Modified MZI Sensor for Improved Riboflavin Detection

A fiber-optic Mach-Zehnder interferometer (MZI) biosensor modified by a Nb₂C-MXene/UIO-66-COOH composite and adenosine has been developed for the detection of trace concentrations of riboflavin. The sensing interface of the sensor is constructed by self-assembling UIO-66-COOH and adenosine using Nb₂C-MXene nanosheets as the supporting substrate. The isoxazine ring of the riboflavin molecule can be specifically captured by the adenine ring of the adenosine molecule and then produces an adenosine/riboflavin complex that causes a small change in the refractive index (RI) of the fiber surface, which in turn causes a change in the transmission spectrum of the sensor as an indicator signal for riboflavin detection. The experimental results showed that the sensitivity of the sensor is 16.46 nm/μM and the limit of detection (LOD) is as low as 0.0271 μM within the riboflavin concentration range of 0-0.664 μM. For the in situ measurement experiment, the sensitivity of the sensor to riboflavin is 55.51 nm/OD, with an LOD of OD = 0.0081. It dramatically reduces the detection time for microbial corrosion to just 184 s with good stability. In the shelf life test experiment, the sensor performed well and could be stored in a low-temperature, hermetically sealed environment for 7 days.