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Ochratoxin A detection in coffee by competitive inhibition assay using chitosan-based surface plasmon resonance compact system
摘要： This study demonstrates the evaluation of ochratoxin A (OTA) in coffee on compact surface plasmon resonance (SPR) biosensors based on crosslinked chitosan and carboxymethyl chitosan nanomatrix substrates. Ochratoxin A is a toxic secondary metabolite widely produced by Aspergillus and Penicillium fungi and requires regular quantification and detection in food samples. The gold coated SPR chips were synthesized with chitosan and carboxymethyl chitosan through spin coating technique. The SPR nanomatrix chips were used for the immobilization of ochratoxin A-bovine serum albumin (OTA-BSA) conjugate to develop a competitive inhibition immunoassay. The monoclonal ochratoxin A antibodies (mAb-OTA) were used as biological receptors for the detection of OTA in buffer and coffee samples. The limit of detection (LOD) in coffee for chitosan (CS) and carboxymethyl chitosan (CMC) substrates was 5.7 ng/mL and 3.8 ng/mL, respectively. Compact surface plasmon resonance (SPR) system based on chitosan-based (CS-AU) nanomatrix substrates provides a platform for the detection of ochratoxin A with high sensitivity, accuracy, ease-of-use and cost-effectiveness. This compact SPR system can be used at farm and industrial levels for the detection of OTA in food matrices.
关键词： Carboxymethyl chitosan,SPR immunoassay,Coffee,Ochratoxin A,Chitosan
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Generation of light beams by electron beam excited surface plasmons
摘要： Manipulation of Smith-Purcell radiation (SPR) by electron-bunch excitation of localized surface plasmon (LSP) of gold (Au) disc arrays on Au substrate is investigated by FDTD simulation. When the wavelength of LSP mode is within the SPR emission band, SPR is locked and enhanced at the LSP wavelength. The emission angle of LSP-locked SPR still follows the wavelength-angle relation of traditional SPR. Furthermore, both the emission wavelength and angle increase as the radius and height of Au disc increase.
关键词： FDTD simulation,Smith-Purcell radiation (SPR),localized surface plasmon (LSP)
更新于2025-09-23 15:21:21
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[IEEE 2019 IEEE International Conference on Telecommunications and Photonics (ICTP) - Dhaka, Bangladesh (2019.12.28-2019.12.30)] 2019 IEEE International Conference on Telecommunications and Photonics (ICTP) - Sensitivity Enhanced Surface Plasmon Resonance (SPR) Sensors with MoS <sub/>2</sub> /Graphene Hybrid Overlayer
摘要： A performance enhanced surface plasmon resonance sensor has been designed with a molybdenum disulfide (MoS2)/graphene hybrid overlayer. Atomically thin transition metal dichalcogenide (TMDC) nanomaterials like MoS2 have exhibited better optical and electronic properties in the two-dimensional (2D) scale. The MoS2/graphene hybrid overlayer protects the metal layer of the SPR sensor from undesired oxidation and retains higher sensitivity. As they have large surface to volume ratio and adjustable biocompatibility, the sensor performance increases several times than only graphene based configuration. The proposed SPR sensor includes a titanium (Ti) layer which enhances the adherence level between silver and prism glass. Sensitivity factor (SF), sensor merit (SM), full-width at half-maximum (FWHM) and combined sensitivity factor (CSF) have been used to measure the performance of the proposed sensor. The proposed sensor has the SF of 71.260/RIU and CSF of 372.72 RIU-1, which are much higher than the existing sensor configuration without MoS2 overlayer.
关键词： combined sensitivity factor,SPR sensor,MoS2 / graphene hybrid overlayer,sensitivity factor
更新于2025-09-23 15:21:01
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Tuning of surface plasmon resonance of silver nano particles by shock waves for plasmonic device applications
摘要： The present research article demonstrates the findings of the fine tuning of surface plasmon resonance (SPR) and the relationship between structural, optical and morphological properties of shock wave loaded silver nano-particles (Ag NPs). The characteristics of structural, optical and morphological properties of Ag NPs are evaluated by powder XRD (X-ray powder diffraction), UV–Vis (ultra violet- visible) spectroscopy and SEM (scanning electron microscopy) technique, respectively. The test material of Ag NPs is subjected to the shock wave loading with 50,100 and 150 shock pulses, respectively. The PXRD results reveal that the degree of crystalline nature and grain size of the crystal is significantly reduced by the impact of shock waves. The UV–Visible spectrum reveals that the control Ag NPs absorption band at 514 nm has given rise to blue shift (514–403 nm) at 150 shock wave loaded samples. The SEM images reveal that the particle size is considerably reduced by the impact of shock waves with respect to number of shock waves. The tri-angle correlation of structural, optical and morphological properties of shock wave loaded Ag NPs is explored.
关键词： Impact of shock waves,Tuning of SPR,Silver nano particles
更新于2025-09-23 15:21:01
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Optimized sample addressing in prism-coupled surface plasmon resonance experiments
摘要： In this work we study the walk-off of the beam from the interrogation spot during rotation in surface plasmon resonance experiments using prism-based coupling such as the widespread Kretschmann configuration. The impossibility of maintaining a stationary footprint on the sensing surface with a fixed rotation axis can be of high importance. This would be specially so if samples are not homogeneous such as in arrays for multiplexing. By theoretically analyzing the behavior of the walk-off during rotation around an arbitrary fixed axis, we find an optimal and simple configuration to minimize this effect. The proposed setup is experimentally tested to verify the results and to show its ease of implementation. Interestingly, the conclusions reached may also be applied to other techniques employing reflection prisms.
关键词： Rotation axis,Surface plasmon resonance (SPR),Alignment optimization,Prism coupling,Walk-off
更新于2025-09-23 15:21:01
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Development and Validation of a Surface Plasmon Resonance Biosensor for Specific Detection of Porcine Serum Albumin in Food
摘要： Food allergies are a potential food safety and public health concern worldwide. To assure the safety of people who experience allergic reactions, it is necessary to establish effective and reliable methods for rapid detection of food allergens. This paper reports an innovative method for the rapid detection and analysis of porcine serum albumin (PSA), known as a major allergen in pork, based on a surface plasmon resonance (SPR) biosensor. The antibodies known to have a high bioactivity against PSA were verified by competitive indirect-ELISA and then immobilized on the SPR sensor surface, thus allowing them to capture PSA. The developed SPR demonstrated a linear range from 1.0 to 450 ng/mL for the measurement of PSA with a detection limit of 19.81 ng/mL. Within-day RSD (1.97–4.02%) and between-day RSD (1.88–4.15%) were no more than 5%. The SPR was evaluated for analysis of six commercial food samples and showed almost perfect agreement between the results obtained by ELISA test kits without significant differences (P > 0.05). Therefore, this assay permits accurate, specific, and sensitive detection of PSA in pork and pork products.
关键词： food safety,detection,SPR biosensor,food allergies,porcine serum albumin
更新于2025-09-23 15:21:01
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SPR studies on optical fiber coated with different plasmonic metals for fabrication of efficient biosensors
摘要： In the recent years, there have been numerous reports on study of Surface Plasmon Resonance (SPR) in different Plasmonic metals. Optical – fiber based SPR sensors have gained much attention over the years because of their copious advantages over conventional Prism coupled SPR sensors, including miniaturization, ability to perform remote sensing etc. In the present work, Optical – fiber based Surface Plasmon studies are performed on metal – air interface with different Plasmonic metals. Four different metals chosen for the current work are as follows: Gold (Au), Silver (Ag), Aluminum (Al) and Copper (Cu). Thermal Evaporation technique is utilized to deposit the Au, Ag, Al and Cu metal thin films. XRD, AFM and UV–Visible spectroscopy are used for the determination of the structural, morphological and optical characteristics of the deposited metal thin films. SPR transmittance curve is obtained for different metals and their observed SPR wavelength (kspr) matches very well with the reported values. The performance of these metals for their application in SPR based biosensors, was assessed in terms of the Full Width at Half Maxima (FWHM) and minimum transmitted intensity (Tmin) of their SPR transmittance curves and it was found that Ag (50 nm thickness) possesses the least FWHM whereas Au (40 nm thickness) has the lowest Tmin. Suitability of both Ag and Au is discussed for sensing applications and it was concluded that Au (40 nm thickness) is a better candidate for the realization of efficient biosensors.
关键词： SPR,Plasmonic metal,FWHM,Optical fiber,Bio sensor
更新于2025-09-23 15:19:57
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Sensitive Detection of Dengue Virus Type 2 E-Proteins Signals Using Self-Assembled Monolayers/Reduced Graphene Oxide-PAMAM Dendrimer Thin Film-SPR Optical Sensor
摘要： In this work, sensitive detection of dengue virus type 2 E-proteins (DENV-2 E-proteins) was performed in the range of 0.08 pM to 0.5 pM. The successful DENV detection at very low concentration is a matter of concern for targeting the early detection after the onset of dengue symptoms. Here, we developed a SPR sensor based on self-assembled monolayer/reduced graphene oxide-polyamidoamine dendrimer (SAM/NH2rGO/PAMAM) thin film to detect DENV-2 E-proteins. Surface characterizations involving X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirms the incorporation of NH2rGO-PAMAM nanoparticles in the prepared sensor films. The specificity, sensitivity, binding affinity, and selectivity of the SPR sensor were then evaluated. Results indicated that the variation of the sensing layer due to different spin speed, time incubation, and concentration provided a better interaction between the analyte and sensing layer. The linear dependence of the SPR sensor showed good linearity (R2 = 0.92) with the lowest detection of 0.08 pM DENV-2 E-proteins. By using the Langmuir model, the equilibrium association constant was obtained at very high value of 6.6844 TM?1 (R2 = 0.99). High selectivity of the SPR sensor towards DENV-2 E-proteins was achieved in the presence of other competitors.
关键词： optical sensor,E-proteins,SPR sensor,PAMAM dendrimer,reduced graphene oxide,dengue virus,self-assembled monolayer
更新于2025-09-23 15:19:57
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Thermal nanoimprint lithography based plasmonic nanogratings for refractive index sensing of polar solvents
摘要： This work illustrates a facile approach for the design of flexible plasmonic sensors using gold nanograting. The fabrication of surface plasmon resonance (SPR) coupled refractive index (RI) sensor is proposed to sense the various known RIs of polar solvents. Thermal nanoimprint lithography (T-NIL) is used to transfer the nanograting of the processed digital versatile discs (DVDs) through polydimethylsiloxane (PDMS) stamp to thermoplastic polymer coated flexible polyethylene terephthalate (PET) substrate. The gold nanograting sample was obtained after the subsequent deposition of the gold thin film of thickness 60 nm on top of polymer nanograting. The surface plasmon resonance (SPR) modes excited on gold-encrusted polymer nanograting appeared as a dip in the reflectance spectra measured at normal incidence under white light in air and liquid medium. We use refractive index calibration polar solvents [methanol (1.331), water (1.333), acetone (1.359), ethanol (1.361) and isopropanol (1.382)] to determine the refractive index sensitivity of our gold nanograting arrays. This produces a bulk refractive index sensitivity of 535 ± 47 nm/RIU. The real-time kinetic response demonstrates the stability of the sensor with respect to the time and reusability of the sensing chip for multiple measurements. Thus, we envisaged that our proposed sensor can be a potential candidate for the development of highly sensitive plamonic device.
关键词： Nanogratings,surface plasmon resonance (SPR),Thermal nanoimprint lithography (T-NIL),Plasmonic sensor,Polar solvents
更新于2025-09-23 15:19:57
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Narrow resonance and ultrahigh sensitivity plasmonic waveguide refractive index sensor
摘要： A surface plasmon resonance optical refractive index sensor (for aqueous medium) with high angular and spectral sensitivities, S, very small full width at half maxima, w, (narrow resonance) and very high quality factor, χ=S/w, is proposed, which operates in both angular and spectral interrogation modes. The structure consists of a prism and a composite plasmonic waveguide consisting of a high index dielectic layer and a thin metal(Ag) film, separated by a low index layer. Above the metal film, the medium is analyte. It is shown that even with a prism of low index, the proposed sensor offers very small full width at half maxima (FWHM) of reflection spectra which improves the sensor performance. Numerically, an angular sensitivity of 168 degree/RIU and a quality factor, χ= 1680 could be achieved for the proposed configuration. Spectral sensitivity comes out to be 6000 nm/RIU.
关键词： Refractive index sensor,Aqueous medium,Surface Plasmon Resonance (SPR),Bio/Chemical sensor
更新于2025-09-23 15:19:57