Refractive index-sensitive optofluidic nanosensor using plastic optical fiber decorated with mono/bimetallic plasmonic nanoparticles

Fiber optic sensing has been applied currently as a more viable alternative for microorganism detection due to the accurate response, fast analysis time, and low measure cost. Usually, microorganism fiber optic sensing is measured in non-portable equipments due to the microorganism circulation process. Nonetheless, we have developed a microfluidic system to make the process portable. The optofluidic nanosensor mechanism based on the physical principle of sensitivity to the refractive index variation of the external medium. This phenomenon is enhanced owing to the localized surface plasmon resonance, which is recurrent due to nanoparticle fixation on the U-shaped plastic optical fiber (POF) surface. In this case, gold (Au) and silver (Ag) nanoparticles, including AgAu nanodendrites morphology, were synthesized and deposited on the sensing surface of the optical fiber . It was verified that Au nanoparticles exhibited increased light absorption with a significant increase in absorbance peaks when exposed to variations in external medium refractive index . Furthermore, the observed shift in peak wavelength, indicating localized surface plasmon resonance, under a medium refraction index (RI) variation of 0.05. The optofluidic coupling aims to promote an increase in the immunocapture process and to attribute portability to the device, which requires low sample volumes and has a low manufacturing cost. In the food industry, this optofluidic nanosensor is intended for biological application in the fast detection of pathogens, safety production, or contamination detection.