Resonant position tracking method for smartphone-based surface plasmon sensor.

We propose a position-sensitive measurement method for tracking resonant signals of surface plasmon resonance (SPR) in periodic metallic nanostructures. Compared with conventional measurement methods, such as wavelength interrogation, intensity interrogation and spectral integration, this approach provides superior noise reduction and simple calculation process. Experimental results show that the limit of detection reaches to 5.88 × 10-6 RIU by using a portable spectrometer with a spectral resolution of 0.4 nm. The relationship between shot noise and signal noise was theoretically compared. The superior noise reduction of the resonant position tracking method is useful for the smartphone-based SPR measurement. The protein-antibody interactions using the smartphone and gold nanoslit arrays as the SPR sensor are demonstrated. It verifies that a smartphone can be used for sensitive measurement of binding-kinetics of the proteins.