Localized surface plasmon resonance biosensor: an improved technique for SERS response intensification

Surface plasmonic biosensors: principles, designs and applications

Recently, surface plasmon resonance (SPR) biosensors have been widely used in environmental monitoring, food contamination detection and diagnosing medical conditions due to their superior sensitivity, label-free detection and rapid analysis speed. This paper briefly elaborates on the development history of SPR technology and introduces SPR signal sensing principles. A summary of recent applications of SPR sensors in different fields is highlighted, including their figures of merit and limitations. Finally, the personal perspectives and future development trends about sensor preparation and design are discussed in detail, which may be critical for improving the performance of SPR sensors.

Design and analysis of a highly sensitive SPR based PCF biosensor with double step dual peak shift sensitivity

This paper introduces a comprehensive study of a quad-cluster multi-functional Photonic Crystal Fiber (PCF) sensor where gold and Aluminum doped with zinc oxide (AZO) were used as plasmonic materials. A maximum Amplitude Sensitivity (AS) of 5336 RIU-1 and Wavelength Sensitivity (WS) of 40,500 nm/RIU in y pol was obtained incorporating Gold as plasmonic material. When AZO was included as the plasmonic material, AS of 3763 RIU-1 & WS of 9100 nm/RIU for y polarization were determined. The RI detecting range was increased from 1.32 to 1.43 to 1.19-1.42 after using AZO instead of Au that opens up a new horizon for detection. A novel detection technique, 'Double Step Dual Peak Shift Sensitivity (DS-DPSS)' was proposed in sensing temperature where highest sensitivity of 1.05 nm/°C having resolution of 0.095 °C for x pol. was achieved. Due to its diverse functionality, the suggested sensor represents a significant advancement in the detection of numerous analytes in biochemical applications.

Au-TiO2-Coated Spectroscopy-Based Human Teeth Disorder Detection Sensor: Design and Quantitative Analysis

Human tooth functionality is the most important for the human body to become fit and healthy. Due to the disease attacks in human teeth, parts may lead to different fatal diseases. A spectroscopy-based photonic crystal fiber (PCF) sensor was simulated and numerically analyzed for the detection of dental disorders in the human body. In this sensor structure, SF11 is used as the base material, gold (Au) is used as the plasmonic material, and TiO₂ is used within the gold and sensing analyte layer, and the sensing medium for the analysis of the teeth parts is the aqueous solution. The maximum optical parameter values for the human tooth parts enamel, dentine, and cementum in terms of wavelength sensitivity and confinement loss were obtained as 28,948.69 nm/RIU and 0.00015 dB/m for enamel, 33,684.99 nm/RIU and 0.00028 dB/m, and 38,396.56 nm/RIU and 0.00087 dB/m, respectively. The sensor is more precisely defined by these high responses. The PCF-based sensor for tooth disorder detection is a relatively recent development. Due to its design flexibility, robustness, and wide bandwidth, its application area has been spreading out. The offered sensor can be used in the biological sensing area to identify problems with human teeth.

Refractive index based optically transparent biosensor device design for early detection of coronavirus

For the quick detection of the new Coronavirus (COVID-19), a highly sensitive D-shaped gold-coated surface Plasmon resonance (SPR) biosensor is presented. The COVID-19 virus may be quickly and accurately identified using the SPR-based biosensor, which is essential for halting the spread of this excruciating epidemic. The suggested biosensor is used for detection of the IBV i.e. infectious bronchitis viruses contaminated cell that belongs to the family of COVID-19 having a refractive index of - 0.96, - 0.97, - 0.98, - 0.99, - 1 that is observed with the change in EID concentration. Some important optical parameter variations are examined in the investigation process. Multiphysics version 5.3 with the Finite element method is used for the proposed biosensor. The proposed sensor depicts maximum wavelength sensitivity of 40,141.76 nm/RIU. Some other parameters such as confinement loss, crosstalk, and insertion loss are also analyzed for the proposed sensor. The reported minimum insertion loss for the refractive index (RI) - 1 is 2.9 dB. Simple design, good sensitivity, and lower value of losses make the proposed sensor proficient for the detection of infectious bronchitis viruses belonging to COVID-19.

Graphical abstract

Plasmonic Sensors beyond the Phase Matching Condition: A Simplified Approach

The conventional approach to optimising plasmonic sensors is typically based entirely on ensuring phase matching between the excitation wave and the surface plasmon supported by the metallic structure. However, this leads to suboptimal performance, even in the simplest sensor configuration based on the Otto geometry. We present a simplified coupled mode theory approach for evaluating and optimizing the sensing properties of plasmonic waveguide refractive index sensors. It only requires the calculation of propagation constants, without the need for calculating mode overlap integrals. We apply our method by evaluating the wavelength-, device length- and refractive index-dependent transmission spectra for an example silicon-on-insulator-based sensor of finite length. This reveals all salient spectral features which are consistent with full-field finite element calculations. This work provides a rapid and convenient framework for designing dielectric-plasmonic sensor prototypes-its applicability to the case of fibre plasmonic sensors is also discussed.

Recent Advances in Surface Plasmon Resonance Sensors for Sensitive Optical Detection of Pathogens

The advancement of science and technology has led to the recent development of highly sensitive pathogen biosensing techniques. The effective treatment of pathogen infections requires sensing technologies to not only be sensitive but also render results in real-time. This review thus summarises the recent advances in optical surface plasmon resonance (SPR) sensor technology, which possesses the aforementioned advantages. Specifically, this technology allows for the detection of specific pathogens by applying nano-sized materials. This review focuses on various nanomaterials that are used to ensure the performance and high selectivity of SPR sensors. This review will undoubtedly accelerate the development of optical biosensing technology, thus allowing for real-time diagnosis and the timely delivery of appropriate treatments as well as preventing the spread of highly contagious pathogens.

Graphene-Coated Highly Sensitive Photonic Crystal Fiber Surface Plasmon Resonance Sensor for Aqueous Solution: Design and Numerical Analysis

This paper presents the design and analysis of a surface plasmon resonance (SPR) sensor in a photonic crystal fiber (PCF) platform, where graphene is used externally to attain improved sensing performance for an aqueous solution. The performance of the proposed sensor was analyzed using the finite element method-based simulation tool COMSOL Multiphysics. According to the simulation results, the proposed sensor exhibits identical linear characteristics as well as a very high figure of merit (FOM) of 2310.11 RIU−1 in the very low detection limit of 10−3. The analysis also reveals the maximum amplitude sensitivity of 14,847.03 RIU−1 and 7351.82 RIU−1 for the x and y polarized modes, respectively, which are high compared to several previously reported configurations. In addition, the average wavelength sensitivity is 2000 nm/RIU which is comparatively high for the analyte refractive index (RI) ranging from 1.331 to 1.339. Hence, it is highly expected that the proposed PCF-based SPR sensor can be a suitable candidate in different sensing applications, especially for aqueous solutions.

Dual-polarized highly sensitive surface-plasmon-resonance-based chemical and biomolecular sensor

As the research work in surface plasmon resonance (SPR)-based photonic crystal fiber (PCF) is getting tighter, a perfectly circular-shaped PCF with elliptical air holes is proposed where the performance parameters are improved significantly. The performances among our designed elliptical, circular, and rectangular air holes are compared, and the best result is achieved with the elliptical air holes. The technique used for the investigation is the finite element method, and for the simulation of data COMSOL Multiphysics 5.3a software is used. The method covers a wider range of the optical spectrum from 0.59 to 1.05 µm. The highest confinement loss achieved through our design is 340 dB/cm. The wavelength sensitivity and amplitude sensitivity are 13,000 nm/RIU and ${1189.46}\;{{\rm RIU}^{ - 1}}$1189.46RIU^-1, respectively. The sensor resolution is ${7.69} \times {{10}^{ - 6}}$7.69×10^-6 for our proposed design. The proposed sensor also achieved a maximum birefringence of ${2.8} \times {{10}^{ - 3}}$2.8×10^-3, which is, to our knowledge, the highest birefringence reported so far for a PCF-SPR sensor. This enables the fiber to be operated in a dual-polarized mode. The RI for the analyte ranges from 1.33 to 1.40. Based on all the characteristics, the proposed PCF structure can be used effectively for chemical and biomolecular sensing.

Analysis of a highly sensitive side polished hollow fiber plasmonic sensor and its application as a magnetometer

A highly sensitive hollow fiber (HF) sensor based on surface plasmon resonance is proposed and analyzed numerically. The sensor design involves a side polished HF with a nanoscale gold film deposited over the polished surface and an analyte filled core. The hollow portion of the fiber serves simultaneously as an analyte channel and core, when filled with high refractive index liquid. By analyzing the modal characteristics of the sensor using the finite element method, it is found that the wavelength sensitivity of the HF sensor varies from 25,642 nm/RIU (refractive index unit) to 60,000 nm/RIU in the range 1.45 to 1.47 RIU along with highest amplitude sensitivity of ${4231.7}\,\,{{\rm RIU}^{-1}}$4231.7RIU^-1. The minimum measurable alteration by the sensor lies in the order of ${{10}^{-6}}\,\,{\rm RIU}$10^-6RIU. The sensor also exhibits a high value of figure of merit (FOM) up to ${976}\,\,{{\rm RIU}^{-1}}$976RIU^-1 representing a very good overall performance. Moreover, due to the feasibility of design, the specific application of the sensor to magnetic field sensing is also demonstrated and achieved maximum sensitivity of 1361 pm/Oe.