High-performance biosensors based on angular plasmonic of a multilayer design: new materials for enhancing sensitivity of one-dimensional designs.

In this study, a theoretical examination is conducted to investigate the biosensing capabilities of different surface plasmon resonance (SPR) based hybrid multilayer structures, which are composed of two-dimensional (2D) materials. The transfer matrix formulation is implemented to calibrate the results of this study. A He-Ne laser of wavelength = 632.8 nm is used to simulate the results. Many permutations and combinations of layers of silver (Ag), aluminum oxynitride (AlON), and 2D materials were utilized to obtain the optimized structure. Ten dielectrics and twelve 2D materials were tested for a highly sensitive multilayer hybrid sensing design, which is composed of the prism (Ohara S-FPL53)/Ag/AlON/WS2/AlON/sensing medium. The optimized biosensing design is capable of sensing and detecting analytes whose refractive variation is limited between 1.33 and 1.34. The maximum sensitivity, which is achieved by using the proposed design is 488.2° per RIU. Additionally, the quality factor, figure of merit, detection limit, and qualification limit values of the optimized design were also calculated to obtain a true picture of the sensing capabilities. The designing approach based on the multilayer hybrid SPR biosensors has the potential to develop various plasmonic biosensors that are related to food, chemical, and biomedical engineering fields.

A theoretical approach for a new design of an ultrasensitive angular plasmonic chemical sensor using black phosphorus and aluminum oxide architecture.

In this study, the biosensing capabilities of conventional and hybrid multilayer structures were theoretically examined based on surface plasmon resonance (SPR). The transfer matrix method is adopted to obtain the reflectance spectra of the hybrid multilayer structure in the visible region. In this regard, the considered SPR sensor is configured as, [prism (CaF2)/Al2O3/Ag/Al2O3/2D material/Al2O3/Sensing medium]. Interestingly, many optimization steps were conducted to obtain the highest sensitivity of the new SPR biosensor from the hybrid structure. Firstly, the thickness of an Al2O3 layer with a 2D material (Blue P/WS2) is optimized to obtain an upgraded sensitivity of 360° RIU-1. Secondly, the method to find the most appropriate 2D material for the proposed design is investigated to obtain an ultra-high sensitivity. Meanwhile, the inclusion of black phosphorus (BP) increases the sensor's sensitivity to 466° RIU-1. Thus, black phosphorus (BP) was obtained as the most suitable 2D material for the proposed design. In this regard, the proposed hybrid SPR biosensing design may pave the way for further opportunities for the development of various SPR sensors to be utilized in chemical and biomedical engineering fields.

Analysis and detection of women's reproductive hormones using a bistable and reconfigurable 1D annular photonic crystal composed of the Ge2Sb2Te5 phase-change material.

In this study, the reconfigurable biosensing capabilities of the one-dimensional annular photonic structure, (AB)5CDC(AB)5, was examined theoretically. The proposed structure was made of concentric cylindrical layers of periodically modulated refractive indices, which were restricted in one direction only. Germanium antimony telluride (GST), which belongs to the class of phase-change materials (PCMs), was used in the fabrication of the proposed biosensing design. The entire study was carried out in the near-infrared region of the electromagnetic spectrum. The suggested biosensing structure was constructed by depositing alternate periodic cylindrical layers of SiO2 and Si with a central air core. An air cavity coated on both sides by a phase-change chalcogenide material (Ge2Sb2Te5) was introduced at the centre of the 1D annular photonic crystal to realize the (AB)5CDC(AB)5 structure. The simulation results of the proposed work were obtained using the MATLAB computational tool taking into consideration the modified transfer matrix method. The primary focus of this study was to measure the change in the position and intensity of the defect mode with respect to the change in the concentration levels of analytes containing progesterone and estradiol reproductive hormones separately in the amorphous and crystalline phases of the Ge2Sb2Te5 material. Interestingly, a strong tunability in the position of the central wavelength of the defect mode inside the photonic band gap (PBG) was noticed during the phase transition of the GST material from amorphous to crystalline and back. In both the phases of the GST material, our design could identify minute refractive index variations in blood samples containing reproductive hormones at different concentrations for monitoring various gynaecological disorders in women. Besides sensitivity, other important parameters such as the limit of detection, signal-to-noise ratio, and quality factor were estimated to evaluate the biosensing capabilities of the proposed design.

Biophotonic sensor design using a 1D defective annular photonic crystal for the detection of creatinine concentration in blood serum.

A new biophotonic sensor composed of a porous silicon (PSi)-based one-dimensional (1D) defective annular photonic crystal (APC) was designed and theoretically investigated using a modified transfer matrix method (TMM) in terms of cylindrical coordinates. The proposed biosensor was found to be capable of sensing very minute variations in the refractive index of blood serum samples of different creatinine concentrations. It can be considered as a useful tool for diagnosing mild to chronic kidney diseases by measuring the creatinine concentration in the blood serum samples of patients. The biosensor design [(AB) N/2D(AB) N/2/Si] is composed of two 1D APCs (AB) N/2 associated with a defect layer D of a blood serum sample of thickness d d whose creatinine concentration is to be determined. Both 1D APCs are made up of two alternate PSi layers A and B with porosity ratios of 34% and 87%, respectively. Moreover, our proposed biophotonic sensor demonstrated a high value of sensitivity (S) between 637.73 and 640.29 nm per RIU, a quality factor (Q) between 1.51 × 105 and 0.74 × 105, and a figure of merit (FOM) between 2.6 × 104 and 1.96 × 104 RIU, corresponding to a blood serum sample whose creatinine concentration varied between 80.90 to 85.28 µmol L-1. The limit of detection (LOD) was of the order of 10-6 RIU. This low value LOD confirmed that our biosensor is capable of noticing any minute change in the wavelength up to an order of 10-6. Compared with previous works, the proposed biosensor design can be easily realized and offers high performance at normal incidence, which allows overcoming the complications involved while achieving a high value of sensitivity in planar PC-based biosensor designs at oblique incidence. Beside this, there is also a possibility to explore this work further for the development of various APC-based biosensing designs with the aim to study various human body fluids.