Plasmon Resonance Waveguide Sensor Research Articles

Coupling plasmon-waveguide resonance and multiple plasma modes in hyperbolic metamaterials for high-performance sensing

A sensor based on plasmon-waveguide resonance (PWR) exhibits an impressive narrow linewidth and has attracted extensive attention in plasmon label-free sensing. However, the low surface electric field intensity limits the detection ability of biomolecules, where the refractive index changes are restricted at the sensor surface. In this study, we study the coupling of PWR and multiple plasma modes in a hyperbolic metamaterial (HMM), combining narrow linewidth and electric field enhancement advantages. The PWR-HMM sensor includes a gold film, lossless dielectric layer, and metal/dielectric multilayer HMM array composed of 2-layer Au/Al2O3 stacks. The evanescent field of PWR is used to excite multiple plasma modes in the HMM. The figure of merit of the proposed structure reaches 5417/RIU owing to the existence of lossless dielectric layer, which is 11.7 times than the conventional gold film structure. The maximum bulk sensitivity of the PWR-HMM sensor was 43 000 nm/RIU. In comparison with PWR, the surface electric field intensity and the surface sensitivity of PWR-HMM increase by four and two times, respectively. Furthermore, comparing the sensing performance of the PWR-HMM sensor and PWR-nanoparticle (NP) sensor (coupling PWR and localized surface plasmon resonance), it was found that PWR-HMM has 20% higher surface sensitivity than the PWR-NP. A sensing mechanism coupling PWR and multiple plasma modes in the HMMs opens a gate to significantly improve the PWR sensors performance, which is expected to be used to resolve urgent issues in biological, medical and clinical applications.

The Optimization of Metal Nitride Coupled Plasmon Waveguide Resonance Sensors Using a Genetic Algorithm for Sensing the Thickness and Refractive Index of Diamond-like Carbon Thin Films

We theoretically designed the Kretschmann configuration coupled plasmon-waveguide resonance (CPWR) sensors, composed of thin films of metal nitrides. The thicknesses of the layers of the CPWR sensors were optimized using a genetic algorithm. The optimized CPWR sensors were applied to simultaneously measure the thickness and refractive index (RI) of diamond-like carbon (DLC) films. The field profiles and the sensitivity of the CPWR sensors in response to thin DLC films were studied using the finite-different time-domain technique and the transfer matrix method. The genetic algorithm method predicted that the two-mode CPWR sensors could simultaneously analyze the thickness and RI of the DLC films as thin as 1.0 nm at a wavelength of 1550 nm. The simulations showed that the angular sensitivity toward the refractive index changes of the DLC films of the optimized CPWR sensors was comparable to that of traditional CPWR sensors.

Kinetic analysis of nanoparticle-protein interactions using a plasmon waveguide resonance.

A plasmon waveguide resonance (PWR) sensor is proposed for studying the interaction between gold nanoparticles and proteins. The ability of the PWR sensor to operate in both TM and TE Polarizations, i.e. its polarization diversity, facilitates the simultaneous spectroscopy of the nanoparticles surface reactions using both polarizations. The response of each polarization to streptavidin-biotin binding at the surface of gold nanoparticles is investigated in real time. Finally, using the principles of multimode spectroscopy, the nanoparticle's surface reactions are decoupled from the bulk solution refractive index variations. Schematic diagram of the NP-modified PWR sensor.

Plasmon waveguide resonance sensor using an Au-MgF2 structure.

We report an Au − MgF(2) plasmon waveguide resonance (PWR) sensor in this work. The characteristics of this sensing structure are compared with a surface plasmon resonance (SPR) structure theoretically and experimentally. The transverse-magnetic-polarized PWR sensor has a refractive index resolution of 9.3 × 10(-7) RIU, which is 6 times smaller than that of SPR at the incident light wavelength of 633 nm, and the transverse-electric-polarized PWR sensor has a refractive index resolution of 3.0 × 10(-6) RIU. This high-resolution sensor is easy to build and is less sensitive to film coating deviations.

Self-referenced spectroscopy using plasmon waveguide resonance biosensor.

A plasmon waveguide resonance (PWR) sensor is designed, fabricated, and tested for self-referenced biosensing. The PWR sensor is able to support two different polarizations, TM and TE. The TM polarization has a large sensitivity to variations in the background refractive index while the TE polarization is more sensitive to the surface properties. The ability of the PWR sensor to simultaneously operate in both TM and TE modes is used to decouple the background index variations (bulk effects) from the changes in adlayer thickness (surface effects) via multimode spectroscopy. To benchmark the performance of the PWR, a conventional surface plasmon resonance (SPR) sensor is fabricated and tested under the same conditions.

An improved refractive index sensor based on genetic optimization of plasmon waveguide resonance

Plasmon waveguide resonance (PWR) sensors are particularly useful for biosensing due to their unique ability to perform sensing with two different polarizations. In this paper we report a comprehensive performance comparison between the surface plasmon resonance (SPR) sensor and the PWR sensor in terms of the sensitivity and the refractive index resolution. Both sensors were optimized using a genetic algorithm to acquire their best performance for bulk sensing applications. The experimental results show that the PWR sensor has a refractive index resolution of 5 × 10(-7) RIU which is 6 times smaller than that of the optimized SPR sensor. The TE polarization in the PWR sensor has a resolution of 1.4 × 10(-6) RIU which is smaller than the SPR sensor. The polarization diversity in the PWR sensor is another advantage which can be used to improve the measurement reliability.

Sensitivity comparison of surface plasmon resonance and plasmon-waveguide resonance biosensors

Plasmon-waveguide resonance (PWR) sensors are particularly useful for the investigation of biomolecular interactions with or within lipid bilayer membranes. Many studies demonstrated their ability to provide unique qualitative information, but the evaluation of their sensitivity as compared to other surface plasmon resonance (SPR) sensors has not been broadly investigated. We report here a comprehensive sensitivity comparison of SPR and PWR biosensors for the p-polarized light component. The sensitivity of five different biosensor designs to changes in refractive index, thickness and mass are determined and discussed. Although numerical simulations show an increase of the electric field intensity by 30–35% and the penetration depth by four times in PWR, the waveguide-based method is 0.5–8-fold less sensitive than conventional SPR in all considered analytical parameters. The experimental results also suggest that the increase in the penetration depth in PWR is made at the expense of the surface sensitivity. The physical and structural reasons for PWR sensor limitations are discussed and a general viewpoint for designing more efficient SPR sensors based on dielectric slab waveguides is provided.

Effects of sphingomyelin, cholesterol and zinc ions on the binding, insertion and aggregation of the amyloid Aβ1−40 peptide in solid‐supported lipid bilayers

We utilized plasmon-waveguide resonance (PWR) spectroscopy to follow the effects of sphingomyelin, cholesterol and zinc ions on the binding and aggregation of the amyloid beta peptide(1-40) in lipid bilayers. With a dioleoylphosphatidylcholine (DOPC) bilayer, peptide binding was observed, but no aggregation occurred over a period of 15 h. In contrast, similar binding was found with a brain sphingomyelin (SM) bilayer, but in this case an exponential aggregation process was observed during the same time interval. When the SM bilayer included 35% cholesterol, an increase of approximately 2.5-fold occurred in the amount of peptide bound, with a similar increase in the extent of aggregation, the latter resulting in decreases in the bilayer packing density and displacement of lipid. Peptide association with a bilayer formed from equimolar amounts of DOPC, SM and cholesterol was followed using a high-resolution PWR sensor that allowed microdomains to be observed. Biphasic binding to both domains occurred, but predominantly to the SM-rich domain, initially to the surface and at higher peptide concentrations within the interior of the bilayer. Again, aggregation was observed and occurred within both microdomains, resulting in lipid displacement. We attribute the aggregation in the DOPC-enriched domain to be a consequence of lipid mixing within these microdomains, resulting in the presence of small amounts of SM and cholesterol in the DOPC microdomain. When 1 mM zinc was present, an increase of approximately threefold in the amount of peptide association was observed, as well as large changes in mass and bilayer structure as a consequence of peptide aggregation, occurring without loss of bilayer integrity. A structural interpretation of peptide interaction with the bilayer is presented based on the results of simulation analysis of the PWR spectra.