Probing chiral biomolecules based on a surface plasmon resonance sensor

A Kretschmann configuration surface plasmon resonance (SPR) sensor is proposed to detect the chirality parameter and refractive index of chiral biomolecules based on the propagation matrix method in this paper. Biomolecules exhibit optical activity (chirality, enantiomerism) that a molecule is not identical to its mirror image. The chirality parameter can strongly influence their functionalities. Therefore, the sensing, detection, and characterization of the chirality parameter are important for the concentration of a chiral sample, enantiomeric purity test, biological processes, and so on. Four wave vectors in a chiral medium and 4 × 4 transfer matrices are derived by using magnetoelectric coupling constitutive relations for a chiral medium. The transfer matrix connects four eigenstates and traces four transverse field components through adjacent layer to explain cross-polarization coupling because of the chirality parameter. The validation of the propagation matrix method is confirmed by means of numerical results. A sandwich-like sensor composed of graphene is employed. The effects of the temperature and chemical potential, which can be tuned either by the carrier density (chemical doping) or by a gate voltage, of the graphene on the sensing characteristics of the SPR sensor are discussed. The reflectivity and resonance angle of the SPR biosensor influenced by media parameters of the senor and chiral molecules are demonstrated. This work may provide some guidelines for a better design of surface plasmon resonance sensors against the chirality parameter and refractive index variations and may speed up prism SPR sensors’ applications in detecting the chirality parameter of chiral molecules in the solid state, as well as in the solution state.
Audience take away:

• The propagation matrix method is given to probe chiral biomolecules via a Kretschmann configuration SPR sensor.
• Structure of a Kretschmann configuration surface plasmon resonance sensor is presented.
• Effects of Graphene on sensing characteristics of the SPR sensor are discussed.