A Simple Phase-Sensitive Surface Plasmon Resonance Sensor Based on Simultaneous Polarization Measurement Strategy.

Meng-Chi Li,Li-Chen Su,Chien-Cheng Kuo,Yu-Xen Lin,Kai-Ren Chen

doi:10.3390/s21227615

Abstract

The SPR phenomenon results in an abrupt change in the optical phase such that one can measure the phase shift of the reflected light as a sensing parameter. Moreover, many studies have demonstrated that the phase changes more acutely than the intensity, leading to a higher sensitivity to the refractive index change. However, currently, the optical phase cannot be measured directly because of its high frequency; therefore, investigators usually have to use complicated techniques for the extraction of phase information. In this study, we propose a simple and effective strategy for measuring the SPR phase shift based on phase-shift interferometry. In this system, the polarization-dependent interference signals are recorded simultaneously by a pixelated polarization camera in a single snapshot. Subsequently, the phase information can be effortlessly acquired by a phase extraction algorithm. Experimentally, the proposed phase-sensitive SPR sensor was successfully applied for the detection of small molecules of glyphosate, which is the most frequently used herbicide worldwide. Additionally, the sensor exhibited a detection limit of 15 ng/mL (0.015 ppm). Regarding its simplicity and effectiveness, we believe that our phase-sensitive SPR system presents a prospective method for acquiring phase signals.

Highlights

Surface plasmon resonance (SPR) has become known for the rapid, sensitive, and labelfree sensing of physical andchemical processes at interfaces [1,2]
Sensors 2021, 21, 7615 simpler than the traditional phase-sensitive SPR sensors; the internal referencing is helpful in degrading the effect of microfluctuations of temperature, which plays a key role in the SPR detection performance
The SPR-induced phase difference between the p-polarized and s-polarized components was extracted from the polarization-dependent signals which were recorded by the pixelated polarization camera (PPC)

Summary

Introduction

Surface plasmon resonance (SPR) has become known for the rapid, sensitive, and labelfree sensing of physical and (bio)chemical processes at interfaces [1,2]. The resonance conditions (wavelength and angle) of SPR are affected by the changes in the refractive index surrounding the metal surface. Such changes can be measured by the shift in the resonance angle [5,6], the resonance wavelength [7,8,9], or the intensity of the reflected light [10,11,12], which are the three commonly used types of SPR interrogation technologies. SPR sensors are frequently implemented to detect the refractive index changes caused by binding events between analytes and receptors on the metallic sensor surface, which relates to the mass deposited on the SPR sensing surface. The direct detection of small molecules is a challenge for the detection sensitivity of SPR sensors [13]

Methods

Results

Conclusion