Fibered Optical Sensor Based on the Integration of Quantum Dots on a Polymer Tip

In this article, we report on a novel approach developed for the fabrication of luminescent optical fibered tips containing quantum dots (QDs). It is based on a sequential process involving photopolymerization of pentaerythritol triacrylate through an optical fiber to create a first polymer tip and then a second tip based on diazonium salt chemistry for surface functionalization and QD immobilization via electrostatic interactions. The resulting luminescent tip has a radius of curvature of 60.7 nm and exhibits the same luminescence spectrum as colloidal QDs. To evaluate the potential of this QD-tip structure in sensing applications, it was immersed in an ethanol solution of ZnO nanoparticles of various concentrations (7-35 mg/mL), which resulted in QD luminescence quenching. A 17.9-fold quenching of the luminescence intensity was achieved at a maximum concentration of 35 mg/mL. The change in the photoluminescence lifetime was proposed as a sensing criterion since it is more sensitive to the environment than the luminescence intensity. The calibration curve was obtained, showing the potential of such type of tips as sensors for a new nondestructive method for the determination of nanoparticle concentration in solution.