Microcapillary-Based Integrated LSPR Device for Refractive Index Detection and Biosensing

A microcapillary-based localized surface plasmon resonance (LSPR) sensor with a large dynamic refractive index (RI) detection range was reported in the present article. Au nanoparticles (NPs) were immobilized onto the inner wall of microcapillary to achieve LSPR sensing. By establishing an energy loss model for evanescent field, we investigate the optical characteristics of Au NPs in microcapillary-based evanescent field and the sensing properties of LSPR sensors systematically. Unlike traditional LSPR sensors, simulated and experimental results demonstrate that these sensors possesses a large dynamic detection range and high tunable-sensitivity due to the extinction efficiency of Au NPs in evanescent field. In addition, the hollow structure of microcapillary can be used as a sensing element as well as a fluid channel. It can reduce the length of sensing region and realize the extraction and detection of trace sample simultaneously, which is very helpful for achieving miniaturization and integration of sensing system. The proposed sensor can achieve a large dynamic RI detection range between 1.328 and 1.470 and offer favorable biosensing property with 3 nm detection limit for human IgG. Being cost-effective, miniaturized and integrated, it is potentially used for environmental monitoring and minimally invasive medical diagnostics.