Papers by Keyword: Surface Plasmon Resonance

Abstract: The current research work analysis the surface plasmons produced in the bimetallic thin films. The study aimed to understand the nature of surface plasmons produced from single metal thin film of copper and then to investigate the effect of addition of another metal thin layer above it. The research work was carried out via simulation analysis using Kretschmann-Raether configuration. Angular interrogation method and wavelength interrogation method was used to optimize the surface plasmon response from copper thin film in the nanometer range. On the optimized film of copper, another thin layer of gold and silver was added and nature of surface plasmons produced was analyzed. The results show better SPR response from Cu-Au and Cu-Ag bimetallic thin films than using single metal films. The reflected light intensity in the SPR response shows a drastic reduction from 15% to 5% for bimetallic Cu-Au thin film and to 2% for Cu-Ag thin film. The FWHM measurements also displays the reduction from 0.7724^o for Cu monometallic film to 0.4319^o for Cu-Au bimetallic films and 0.2460^o for Cu-Ag bimetallic thin film. The results obtained from this analysis certainly benefits the optical sensor applications in medical and biological fields.

Abstract: The application of an external electric field to the surface plasmon resonance (SPR) system of green-synthesized magnetite (Fe₃O₄) nanoparticles (MNPs) is very promising for increasing the SPR detection signal. Electro-optic surface plasmon resonance (EOSPR) behavior of MNPs has been successfully carried out. The EOSPR system was investigated using the Kretschmann configuration with the prism/Au thin film/MNPs/air layer arrangement and applying an electric voltage of 0 V, 2 V, 4 V, and 6 V. In this study, we synthesized MNPs using the green synthesis approach from moringa oleifera extract. The benefits of green synthesis include being safe, affordable, clean, and ecologically friendly processes. X-ray diffraction results obtained crystal size of the MNPs is about 9.2 nm with inverse spinel face-centered cubic crystal structure. Fourier transforms infrared characterization showed the presence of Fe-O bonds at wave numbers 569 cm^-1 and 629 cm^-1, indicating that MNPs were successfully formed. The saturation magnetization of the samples is 55.3 emu/g. The SPR angle of the SPR system Prism/Au thin film/air without the addition of MNPs is 44.66°. After being deposited by MNPs and induced by a voltage of 0 V, 2 V, 4 V, and 6 V, the SPR angles changed to 44.87°, 44.90°, 44.95° and 45.12°. The addition of MNPs and an external electric field causes the SPR angle to increase. The results of this study can provide new insights into the development of optical devices that can be manipulated electrically and have the potential for future biosensor applications.

Abstract: The effect of electrical and thermal treatment on silver nanowire (AgNW) network morphology and its impact on ultraviolet-visible (UV/Vis) and luminescence spectra is reported. The results exhibit that the conductivity enhancing welding of the single AgNWs at connection points changes the network morphology towards an increased proportion of spherical like structures. This inhomogeneity which is particularly noticeable for joule heated films not only gives rise to an inhomogeneous line broadening in absorption and luminescence spectra but also causes a red shift of the surface plasmon resonances in comparison to a non post-treated AgNW network. With increasing inhomogeneity either due to welding or beginning degradation the d-sp interband excitation pathway is especially efficient for the decay of surface plasmons and shows the strong coupling of the corresponding exciting and emitting photons to the surface plasmon excitation.

Abstract: Silver nanoparticles were synthesized using locally purchased honey and silver nitrate solution. This method provides a simplistic and straightforward approach to the formation of silver nanoparticles. The silver nanoparticles with varying amounts of silver nitrate solution were characterized using ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. In addition, dynamic light scattering characterization was used to determine the average size and size distribution of silver nanoparticles. Experimental results revealed that varying the amount of silver nitrate solution can control the size and absorption spectra of silver nanoparticles. A large amount of silver nitrate solution will exhibit a peak in the higher wavelength. The shifting of the absorption peaks at 401, 406, 407, 408, and 409 nm are believed to be related to the wavelength of the surface plasmon resonance. Moreover, a larger amount of silver nitrate solution also results in an increasing size with 27.2, 57.9, and 63.4 nm as revealed in the size distribution via dynamic light scattering. This green synthesis method of silver nanoparticles will provide a cost-effective production as an alternative to commercial antibacterial agents.

Abstract: Ag nanoparticles (NPs) have been successfully synthesized by the green synthesis method using Moringa oleifera (MO) extract with various incubation times (24 and 48 hours) as an active material for surface plasmon resonance (SPR) biosensor. Transmission electron microscopy analysis indicated the formation of spherical particles with an average crystal size of 29 nm. Selected area electron diffraction confirmed that Ag NPs is face-centered cubic (FCC) crystal structure. Fourier-transform infrared measurements show the band at 3330 cm^-1, 2067 cm^-1, 1634 cm^-1 for an incubation time of 24 hours and 3328 cm^-1, 2063 cm^-1, 1633 cm^-1 for an incubation time of 48 hours. The results prove the proteins and phenolics compound present in the MO extract responsible as reducing agents. The maximum absorption of the green-synthesized Ag NPs in the UV-Vis spectra shows the SPR band at 326 nm and 328 nm for an incubation time of 24 and 48 hours, respectively, and absorption intensity decrease with the increase of incubation time. The result shows the SPR angle shifted to the larger angle of incident light by using green-synthesized Ag NPs. However, the increased incubation time affects the angle shift to the lower angle of the SPR shift. The addition of the green-synthesized Ag NPs leads to enhance the sensitivity of the SPR biosensor.

Abstract: In this work, silver (Ag) nanoparticles were synthesized using plasma-assisted hot-filament evaporation, both with and without plasma deposition environments. This technique was used for the deposition of the nanoparticles in high-density, with controlling the size and interparticle separation. The size and interparticle separation acted as the primary factors of the variation of the localized surface plasmon resonance characteristics of the nanoparticles. The Ag nanoparticles reflected an additional layer in a typical organic light-emitting diode (OLED). The OLED with the Ag nanoparticles layer resulted in a low operating voltage, with a high luminance that reached 62.9 % under the hydrogen plasma environment, as compared to the reference device (OLED without the Ag nanoparticles layer). The effects of the Ag nanoparticles synthesis layer, both with and without plasma deposition on the OLED luminance, were also discussed.

Abstract: The development of highly selective and sensitive surface plasmon resonance (SPR) immunoassay for the rapid detection of illegal compound using secondary antibody interaction labelled nanoparticle was conducted. For the construction of SPR sensor surface, the illegal compound (clenbuterol) was immobilized as antigen onto gold succinimide-terminated monolayer to perform amide-coupling reaction. In order to avoid non-specific reaction, the blocking agent (ethanol amine) was injected to the SPR system. Furthermore, indirect competitive inhibition method was employed in the detection of clenbuterol. In this work, the antibody solution (PBS solution containing clenbuterol antibody) premixed with a sample solution (PBS solution containing antigen) before the injection into the sensing system. As the premixed solution flowed over the sensor surface, the SPR senses the dielectric constant change at the interface due to the binding of the unreacted primary antibody to antigen-immobilized on the sensor surface. After this primary antibody detection, secondary antibody was injected to the SPR sensor surface. Here, we compared the signal difference of secondary antibody injection labelled Au nanoparticles (d = 40 nm). For the regeneration of the sensor surface, 0.1 M NaOH was used, so primary and secondary antibodies could be detached from the sensor surface. According to the indirect competitive inhibition method, it was found that the sensitivity for clenbuterol detection was enhanced from 2.5 ppt to 0.07 ppt.

Abstract: The development of nanotechnology applications is rapidly growing in many sectors. One of them is silver nanoparticles (AgNPs) which are metal nanoparticles that play an important role, especially in nanomedicine. The most effective method of purifying to obtain stable AgNPs is very important to study. Experiments on the separation of AgNPs have been carried out using the size exclusion chromatography and centrifugation methods to see the effectiveness of refining the two methods. This experiment begins with the synthesis of AgNPs using the chemical reduction method. Then, the synthesized AgNPs were purified by Size Exclusion Chromatography (SEC) and centrifugation method then analyzed using UV-Vis spectrophotometer to determine the maximum peaks before and after purification. The experimental results were obtained that centrifugation methods and SEC having the same effectiveness in refining AgNPs. The centrifugation method at various speed (0, 3000, 6000, 9000, 12000 and 15000 rpm) gave wavelength results 403, 404, 404, 405, 404, and 404 nm. The SEC method using Sephadex-25 column showed the 4^th to 8^th fractions gave the maximum wavelength 404, 404, 404, 405, and 404 nm, respectively. The maximum wavelength of both methods showed the surface plasmon resonance characteristic of AgNPs. However, centrifugation at 3000 rpm has better homogeneity than SEC method.

Abstract: Surface plasmon resonance (SPR) based biosensor is a gold standard optical sensor for biological protein interaction in life science. In this paper, we firstly discuss how the SPR based sensor can give unique advantages over other sensing techniques for food safety and food quality control in food industry. We discuss the differences in sample preparation process for the SPR system and other screening methods and point out that the SPR can reduce the food screen quality control cost and time. A brief review of food analysis that has been tested under SPR system. Key requirements for building up a surface plasmon resonance based sensor for food industry especially in Thailand are highlighted. An SPR based sensor has been recently developed and constructed based on the requirements. We also discuss practical issues and how to possibly get around them.

Abstract: We have observed surface plasmon resonances (SPR) in Au thin films between 18 nm to 27 nm thick deposited onto glass substrates. The observed resonance angles are between 15.5 to 18.75 degrees, which are lower than predicted theoretical values for thicker films. The shift of resonances with the change of refractive index of surrounding confirms its application for nanobio-sensing. A thorough topological surface analysis and transmitted spectra were performed. Au thin films were annealed in Argon and the analysis repeated and compared with those from pre-annealing. The annealing process will cause a sharper appearance of surface plasmon resonances which will make these thin film devices a more suitable candidate for nanobio-sensing applications.