Halloysite Nanotube-Modified Plasmonic Interface for Highly Sensitive Refractive Index Sensing

We propose and demonstrate a novel strategy to modify the plasmonic interface by using a thin layer of halloysite nanotubes (HNTs). The modified surface plasmon resonance (SPR) sensor achieves a greatly improved sensitivity because the large surface area and high refractive index of the HNTs layer significantly increase the probing electric field intensity and hence the measurement sensitivity. More significantly, the thickness of the HNTs layer can be tailored by spraying different concentrations of HNTs ethanol suspension. The proposed sensors show significant superiority in terms of the highest sensitivity (10431 nm/RIU) and the enhancement fold (5.6-folds) over those reported previously. Additionally, the proposed approach is a chemical-free and environment-friendly modification method for the sensor interface, without additional chemical or biological amplification steps (no toxic solvents are used). These unique features make the proposed HNTs-SPR biosensor a simple, biocompatible, and low-cost platform for the trace-level detection of biochemical species in a rapid, sensitive, and nondestructive manner.