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Numerical study of nanoscale biosensor based on surface plasmon polariton propagation in Mach-Zehnder interferometer structure
摘要： In this paper, we numerically investigate a nanoscale plasmonic biosensor based on Mach-Zehnder interferometry. The operation of Mach-Zehnder interferometer (MZI) biosensor is examined based on two methods. In the first method, in which the transmission of surface plasmon polariton (SPP) modes is investigated under different refractive indices of sample medium as well as different dimensions, the best transmission rate achieved about 56.6% which is resulted by refractive index variation about 0.045 for the length 12 μm and width 80 nm of the gold layer. Also, the sensitivity, figure of merit (FOM) and quality factor (Q-factor) of MZI are examined for different geometries by utilizing the alternative method. It is realized that for the constant length, increasing the thickness of gold layer has significantly led to increased Q-factor and FOM. On the other hand, considering fixed thickness of the Au layer and three different lengths, the major outcome is that as the length of biosensor increases, the sensitivity, Q-factor as well as FOM follow an upward trend. Finally, inserting two distinct additional gold layers on top of the main gold layer, resulted in an extreme increase for the sensitivity and FOM of the plasmonic MZI biosensors with respect to the MZI biosensor without additional layer.
关键词： Plasmonic biosensor,Surface plasmon polariton (SPP),Mach-Zehnder interferometer (MZI),Finite difference time domain (FDTD)
更新于2025-09-23 15:23:52
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Establishment of a universal and sensitive plasmonic biosensor platform based on the hybridization chain reaction (HCR) amplification induced by a triple-helix molecular switch
摘要： Herein, we established a universal and sensitive plasmonic sensing strategy for biomolecule assays by coupling the hybridization chain reaction (HCR) strategy and a triple-helix molecular switch. Upon the recognition of the target, a single-stranded DNA as a universal trigger (UT) was released from the triple-helix molecular switch (THMS). Thus, the HCR process can be triggered between two hairpins M1 and M2, resulting in the aggregation of gold nanoparticles (AuNPs) via the hybridization between the tail sequence on M1 (or M2) and a DNA–AuNP probe with a dramatic change in the absorbance at 521 nm. More specifically, the strategy, which was conducted by the introduction of target-specific recognition of THMS and universalized by virtue of altering the aptamer or DNA sequence without changing the triple-helix structure, enables simple design for multiple target detection. By taking advantage of THMS, this strategy could enable stable and sensitive detection of a variety of targets including nucleic acids, small molecules and proteins, which may possess great potential for practical applications.
关键词： gold nanoparticles,biomolecule detection,plasmonic biosensor,triple-helix molecular switch,hybridization chain reaction
更新于2025-09-19 17:13:59
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Analysis and simulation of a plasmonic biosensor for hemoglobin concentration detection using noble metal nano-particles resonances
摘要： In this paper, three different shapes (sphere, cubic, and cylinder) silver plasmonic nano-particles for the detection of hemoglobin concentration in blood is analyzed. This work is done to determine the hemoglobin concentration in blood using a sensing feature by changing hemoglobin concentration from 0 to 140g/l. The impact of hemoglobin concentration on refractive index changes in the surrounding medium of nano-particles is considered. Simulated results show that, scattering cross-section has a sharp peak for cubic nano-particles with the full width at half maximum (FWHM) of 50nm. FWHM is 64nm and 94nm for sphere and cylinder nanoparticles, respectively. Exactly, after applying the hemoglobin refractive index in each concentration to the surrounding medium, an increase in resonance wavelength in extinction cross-section is obtained. The wavelength shifts of 3.3nm, 3.7nm, and 5.5nm are obtained for hemoglobin concentration of 140g/l using sphere, cubic, and cylinder shapes nano-particles, respectively. Further, changing the simulated structure parameters can manage the plasmonic resonance wavelength and it is applicable to detect other biological samples.
关键词： hemoglobin detection,Plasmonic biosensor,Surface plasmon resonance,extinction cross-section,noble metal
更新于2025-09-16 10:30:52
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Plasmonic Contrast Imaging Biosensor for the Detection of H3N2 Influenza Protein-Antibody and DNA-DNA Molecular Binding
摘要： We report a plasmonic contrast imaging biosensor. It measures the intensity difference between the p- and s-polarization images at plasmonic excitation. At plasmonic resonance, only the p- polarization light is excited, while s-polarization light remains the same. Image intensity subtraction between both polarizations can eliminate common system noise and enhance sensor resolution. In refractive index measurements, the sensor resolution was found to be 4.36 × 10-7 RIU. The plasmonic contrast imaging sensor has further been demonstrated for H3N2 influenza antibody detection and DNA-DNA molecular binding detections. The detection limit was found to be 8.6nM (320 ng mL-1) for H3N2 influenza antibodies. This value is 56% and 216% better than the detection limit reported for influenza antibody detection with commercial Biacore systems. A computer control device prototype has further been developed based on the optical design, which is ready for various bio-molecular binding detections.
关键词： Label free,DNA,SPR imaging,Plasmonic biosensor,Resonator,Influenza
更新于2025-09-16 10:30:52
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Fiber optic sensor based on ZnO nanowires decorated by Au nanoparticles for improved plasmonic biosensor
摘要： Fiber-optic-based localized surface plasmon resonance (FO-LSPR) sensors with three-dimensional (3D) nanostructures have been developed. these sensors were fabricated using zinc oxide (Zno) nanowires and gold nanoparticles (Aunps) for highly sensitive plasmonic biosensing. the main achievements in the development of the biosensors include: (1) an extended sensing area, (2) light trapping effect by nanowires, and (3) a simple optical system based on an optical fiber. The 3D nanostructure was fabricated by growing the ZnO nanowires on the cross-section of optical fibers using hydrothermal synthesis and via immobilization of Aunps on the nanowires. the proposed sensor outputted a linear response according to refractive index changes. The 3D FO-LSPR sensor exhibited an enhanced localized surface plasmon resonance response of 171% for bulk refractive index changes when compared to the two-dimensional (2D) FO-LSPR sensors where the AuNPs are fixed on optical fiber as a monolayer. In addition, the prostate-specific antigen known as a useful biomarker to diagnose prostate cancer was measured with various concentrations in 2D and 3D FO-LSPR sensors, and the limits of detection (LODs) were 2.06 and 0.51 pg/ml, respectively. When compared to the 2D nanostructure, the LOD of the sensor with 3D nanostructure was increased by 404%.
关键词： fiber optic sensor,plasmonic biosensor,Au nanoparticles,localized surface plasmon resonance,ZnO nanowires,FO-LSPR sensors
更新于2025-09-12 10:27:22
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Size effect of metal nanodome arrays on performance of plasmonic biosensor
摘要： Size effect of metal nanodome arrays on performance characteristics of a plasmonic biosensor is investigated using reflection spectroscopy. Ag and Au nanodome arrays are created by a bottom-up nanofabrication process by which the dome diameter and metal thickness can be controlled. Reflectivity measurements of metal nanodome arrays showed that the wavelengths and width of resonance dip were changed by the dome diameter and metal thickness, respectively. Bulk refractive index (RI) sensing and detection of DNA hybridization were performed to characterize the sensing performance of metal nanodome arrays. Bulk RI sensitivity were significantly improved as the dome diameter enlarged from 100 to 500 nm. In contrast, metal nanodome arrays with smaller diameter exhibited higher sensor signals against the immobilization of DNA modified gold nanoparticles used for signal amplification indicating strong plasmonic coupling effects. With respect to the dome diameter, the effect of metal thickness was moderate for the presented sensing scheme.
关键词： plasmonic biosensor,metal nanodome arrays,bulk refractive index sensitivity,DNA hybridization,reflection spectroscopy
更新于2025-09-11 14:15:04
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Two-dimensional plasmonic biosensing platform: Cellular activity detection under laser stimulation
摘要： Combining biosensors with nanoscience provides great advantages such as being label-free and real time, highly sensitive, and small in size, as well as providing a low limit of detection and integration to other systems. That is why plasmonics finds various applications in drug detection, food safety, agriculture, photothermal therapy, etc. In this paper, we have fabricated a two-dimensional plasmonic grating biosensor using a soft lithography technique, which has eliminated some disadvantages of conventional plasmonic structures like expensive fabrication cost, inflexibility, and lack of mass production. On the other hand, we benefited from infrared neural stimulation for regulating membrane depolarization, which was based on photothermal mechanism and provided a contact-free and high spatial/temporal resolution. Eventually, the membrane depolarization of two different cell types of Hep G2 and mesenchymal stem cells cultured on two-dimensional plasmonic structure has been investigated under infrared neural stimulation. After preparing the soft plasmonic crystal, its reflection spectra and respective ellipsometry parameters were analyzed before and after cell culture with/without stimulation (near-infrared immune region ～1450 nm). By comparing the obtained ellipsometry results for HEP G2 and mesenchymal stem cells, it is observed that the behavior of two cell types with respect to IR stimulation was the same as well as providing us the possibility of distinguishing the level of membrane depolarization under various stimulating frequencies. The strength of this integrated system for membrane depolarization detection has been shown experimentally, which can open new avenues toward neuroplasmonic application in the future.
关键词： infrared neural stimulation,membrane depolarization,ellipsometry,soft lithography,plasmonic biosensor
更新于2025-09-11 14:15:04
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Quasi-D-Shaped Fiber Optic Plasmonic Biosensor for High-Index Analyte Detection
摘要： In this paper, we propose a highly sensitive quasi-D-shaped fiber optic biosensor for detection of high refractive index (RI) liquid analytes via surface plasmon resonance. The main mechanism of sensing is interplay between photonic crystal fiber fundamental mode and plasmonic mode which leads to formation of different resonance peaks depending on the analyte RI. We numerically analyze the structure sensitivity to design parameters and demonstrate the sensing performance of the proposed biosensor using both spectral sensitivity and amplitude sensitivity methods. The proposed biosensor has a RI detection range of 0.15 refractive index unit (RIU) from 1.45 to 1.6. The sensor exhibits linear sensing performance with a RI spectral sensitivity of 9300 nm/RIU for analyte RI ranging from 1.45 to 1.525, 1176 nm/RIU for analyte RI ranging from 1.525 to 1.6 and in particular, 11800 nm/RIU for analyte RI between 1.475 and 1.5. Furthermore, an average RI sensitivity of 4800 nm/RIU for analyte RI ranging from 1.45 to 1.6 is demonstrated. We also study the amplitude sensitivities of the proposed sensor which show promising maximum values of 183.6 RIU-1 for 785 nm excitation and 820 RIU-1 for 1050 nm excitation. Due to the simple structure of the proposed biosensor, large detection range, high sensitivity and promising linear sensing performance, the proposed biosensor can be a promising candidate for detecting various high RI chemical and biochemical samples.
关键词： plasmonic biosensor,photonic crystal fiber,high index analyte detection,Fiber optic sensor,refractive index sensing
更新于2025-09-11 14:15:04
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3D-FDTD modelling of optical biosensing based on gold-coated nanoporous anodic alumina
摘要： The suitability of using gold-coated nanoporous anodic alumina structures as a platform for reflectometry-based plasmonic biosensors is investigated by numerical simulation. Reflectance spectra of such structures has been obtained using 3D-FDTD while the sensing capabilities have been evaluated as the change in spectra upon the adsorption of a layer of a biological-related molecule (biolayer) on the gold coating and inner pore surface. Results show that the gold-coated nanoporous structure enables the coupling of normally incident light to a localized surface plasmon resonance, and that such resonance shifts upon the adsorption of the biolayer. A sensitivity can be defined as the resonance wavelength shift with the biolayer refractive index. It is demonstrated that smaller gold coating thicknesses result in an increase in sensitivity, but at the cost of a decrease in the resonance sharpness, what suggests the existence of an optimal gold coating thickness.
关键词： Gold-coated nanoporous anodic alumina,Biolayer,FDTD simulation,Reflectometry-based plasmonic biosensor
更新于2025-09-10 09:29:36