Highly sensitivity streptomycin sulfate sensor based on microfiber coupler with vernier effect

Streptomycin sulfate (STS) is one of the major sources of contamination in water. Excessive intake of STS can be a serious health hazard to humans, causing vestibular and auditory nerve damage, nephrotoxicity, myasthenia gravis or Parkinson’s disease. To address this, we propose an STS concentration sensor leveraging multiwalled carbon nanotubes (MWCNTs) and the vernier effect of a microfiber coupler (MFC). The vernier effect of MFC is caused by the interference of two supermodes in two orthogonal polarizations in a refringent optical fiber, and the high sensitivity can be achieved directly by monitoring the vernier envelope. MWCNTs can adsorb more biomolecules to enhance the light absorption of analytes to further improve the detection sensitivity. The influence of MFC structure parameters on sensor performance is analyzed by simulation and verified by experiment. Theoretical analyses and experimental results indicate that for specific diameter MFC, the sensor will have better performance. The sensor exhibits a remarkably high sensitivity of 1577.5 nm/(mg/ml) in the detection range of 0.02-0.1 mg/ml, namely sensitivity amplification factor nearly one order of magnitude, and the sensor achieves an ultralow limit of detection of 12.68 ng/ml. The vernier effect of MFC and the modification of MWCNTs effectively enhance the sensitivity of the STS sensor. The device does not require complex pretreatment or antibody preparation, making it highly promising for applications in food safety, environmental pollution, and health monitoring.