Papers by Keyword: Localized Surface Plasmon Resonance

Abstract: We report on the thermally-induced precipitation of gold plasmonic nanoparticles in phosphate and silicate glasses, doped with Eu³⁺ and Er³⁺ ions. We studied the structure and optical properties of glasses under the heat treatment below and above glass transition temperature. The heat treatment of the glass at temperatures above transition is shown to facilitate the formation of plasmonic gold nanoparticles and decrease near-infrared luminescence intensity of the ions. The formation of pre-plasmonic gold nanoparticles under the low-temperature heat-treatment leads to the increase of luminescence intensity through the energy transfer process. We showed that nanophase separation in silicate glasses allows precise tuning of localized surface plasmon resonance spectral position of gold nanoparticles and paves the way for the development of new glass-based materials for photonics applications.

Abstract: This study aimed to investigate the effect of pH value raging from pH 4 - 8 on color development of silver colloids. Silver colloids with different colors were synthesized by chemical reduction method using NaBH₄ as a reducing agent and then adjusted pH value by adding dropwise of acetic acid. These silver colloids were characterized by Transmission Electron Microscopy and UV-Vis spectrophotometer. The results showed that the colors of silver colloids ranging from blue to yellow depended on amount of NaBH₄ added. Due to Localized Surface Plasmon Resonance (LSPR) properties, different shapes and sizes of silver nanoparticles resulting in different colors. It was found that the pH value also affected color development of silver colloids. By adjusting the pH value, the colors of silver colloids changed to different colors or shades, which were clarified by the changes in the center as well as intensity of the absorption spectra. Moreover, the silver colloid in an acidic condition led to aggregation of nanoparticles.

Abstract: The aim of this study is to show the possibility to control structural and optical properties of Au nanoparticles (AuNPs) by changing their size and concentration and make comparison between methods of their formation. 1.4 nm thick Au films were formed on borosilicate glass substrates by the vacuum evaporation method. AuNPs were formed on the surface of the substrate by two methods. First is the irradiation by the Nd:YAG laser pulses with intensities from 75 to 180 MW/cm². Second is thermal annealing, at temperature T=400 °C and the time of curing was varied from 24 to 72 hours. The irradiation of Au film by laser leads to formation of AuNPs. The increase of intensity of laser radiation causes the disappearing of small Au nanoparticles and growing of big nanoparticles from 113-180 nm due to the agglomeration of small particles into big ones and, correspondingly, concentration of particles decreases. In contrast, thermal annealing at T=400 °C from 48 to 72 hours leads to the island formation with the non-spherical shape and their dividing into several islands according to the spinodal dewetting model. As a result, the mean diameter of AuNPs is decreased from 161 to 85 nm but concentration increases.

Abstract: In this research, we focused on silver (Ag) nanoparticles that exhibit various colors on the basis of their localized surface plasmon resonance (LSPR). The effects of step-voltage parameters on the coloration of the Ag deposition-based electrochromic device were investigated. Further, we report the use of reduced graphene oxide (RGO)/biaxially oriented polypropylene (BOPP) as the transparent conductive electrode. RGO was synthesized directly from graphite under a microwave heating system. BOPP film was coated with RGO by drop-casting method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), electrical resistance measurements and cyclic voltammetry (CV). The SEM and TEM images exist as typical wrinkled structure, folded region, transparent, indicating these layers are exfoliated to a very large extent. Our results primarily indicate that the novel BOPP/RGO/Ag/RGO/BOPP configuration presents an easy and expeditious way of preparing the voltage-tunable multicolor electrochromic device. The electrochromic device can be switched from the transparent state to the black state and yellow state.

Abstract: Silver (Ag) nanoparticles (NPs) were deposited on the surface of bulk Nitrogen-Boron co-doped 6H silicon carbide (SiC), and the Ag NPs were observed to induce localized surface plasmons (LSP) resonances on the SiC substrate, which was expected to improve the internal quantum efficiency (IQE) of the emissions of the donor-acceptor pairs of the SiC substrate. Room-temperature measurements of photoluminescence (PL), transmittance and time-resolved photoluminescence (TRPL) were applied to characterize the LSP resonances. Through the finite-difference time-domain (FDTD) simulation of the LSP resonance of an Ag nanoparticle on the SiC substrate, it is predicted that when the diameter of the cross section on the xy plane of the Ag nanoparticle is greater than 225 nm, the LSP starts to enhance the PL intensity. With implementation of a 3rd order exponential decay fitting model to the TRPL results, it is found that the average minority carrier lifetime of the SiC substrate decreased.

Abstract: The influence of the optical properties of the core and shell materials on the LSPR strength for nanoshell particles are calculated based on the quasi-static functions. The results show that for particles with the metallic shell and gained core, the desired real and imaginary parts of dielectric function are positive and negative respectively, and both the absolute values increase as the volume fraction of shell material increases while the LSPR strength is strongest. For particles with metallic material core and gained material shell, in order to produce the maximum LSPR strength, gain medium can have two kinds of choices, one is that the real part of the dielectric function is positive and the imaginary part is negative and both the absolute values are relatively large, the other is the real part and imaginary part of gained dielectric function are negative and their absolute values are relatively small, which small change may lead to mobile resonance wavelength greatly.

Abstract: We dominated localized surface plasmon resonance (LSPR) of aluminum (Al) by controlling their size and density. We report the implementation of Al nanoparticles (NPs) fabricated on the surface of the Ta₂O₅ layer on glass for localized surface plasmon resonances (LSPRs) coupling. The size, density controllable small Al NPs were fabricated using oblique angle deposition method. The optical properties of the NPs array were studied by UV spectrophotometer and finite-difference time-domain (FDTD) simulations. We found that the LSP resonance wavelength of different sizes of Al NPs array exists a blue shift in the extinction spectrum as the particle size decreases.

Abstract: Thin gold hollow half-shell nanostructured films are fabricated by deposited gold over regular arrays of polystyrene nanospheres on glass and silicon substrate respectively in an attempt to evaluate their optical properties and SERS activities. Scanning emission microscopy is used to topographically characterize the nanofilms. Optical spectra taken by UV-vis-NIR spectrometer show that the surface plasmon resonance wavelength of films fabricated on glass is shorter than that fabricated on silicon despite the nanoshell thickness is the same on both substrate, and the SERS intensity excited on silicon is stronger than that on glass because the nanofilms are so thin that the silicon can reflect the SERS signal and excited laser.

Abstract: Gold nanorods (AuNRs) are prepared through seeded growth approach. Synthesis parameters of the amount of cetyltrimethylammonium bromide (CTAB), and concentration of ascorbic acid (AA) were studied. It is found that as the concentration of CTAB increases, the yield of NRs increases. As the concentration of AA increased from 0.05M to 0.2M, LSP shifts to longer wavelength but upon further increasing the concentration, LSP shifts back to shorter wavelength. A linear relationship between LSPR wavelength and surrounding medium dielectric constant is obtained, which is in good agreement with the theoretical results.

Abstract: This paper reports an attempt to develop an optical sensor system to detect Bisphenol A (BPA) in water based on plasmonic property of Gold Nanoparticles (GNPs). Spherical GNPs of the average size of ca. 31±7 nm were grown on quartz substrate using seed mediated growth. An optical sensor system was setup, comprises a tungsten lamp light source, a duplex fiber optic probe, a spectrometer and a sensor chamber. Detection of BPA was done by comparing the Localized Surface Plasmon Resonance (LSPR) spectra of the GNPs film immersed in the deionised water and in BPA solutions by varying the concentration of BPA solutions from 58 mg/L to 0.003 ng/L. The LSPR spectra of GNPs sample were very sensitive to the presence of BPA where the shifted of their peaks position and the changed of their intensities are increases with the concentration of the BPA solutions.