Localized Surface Plasma Resonance Research Articles

Measurement of temperature distribution and evolution during surface plasma resonance heating of gold nanoshells-embedded phantom tissue

This paper presents an experimental study of temperature distribution and evolution in nanoshell colloidal solution and in phantom tissue populated with gold nanoshells under localized surface plasma resonance heating by an NIR laser. Gold nanoshells were synthesized in our laboratory and characterized using the TEM. Their optical properties were measured by a CARY 5000 photospectrometer and the localized surface plasma resonance occurs at 796nm. Two types of temperature measurement systems were used: one for the gold nanoshell colloidal solution and the other for nanoshell-populated phantom tissue. For both cases, heating was initiated by an NIR laser of 808nm. Measured data reveal that the temperature rises rapidly as a result of strong heating of gold nanoshells, which is converted from the absorbed laser energy under localized surface plasma resonance condition. Without nanoshell-mediated resonance absorption and heating, however, the temperature increase is practically negligible. The thermal transport mechanism in nanoshell-embedded tissue appears to be dominant by radiative heat transfer in the laser beam heating region but primarily by thermal conduction away from the laser beam.

金纳米粒子掺杂DNA-CTMA-DPFP薄膜的表面增强拉曼散射特性

The gold nanoparticles were prepared by the reduction of gold chloride with sodium citrate in aqueous solution and the gold-nanoparticles-doped DNA-CTMA complexes were prepared by ion-change method,and the 4-(9,9-diethyl-2-(pyridin-4-yl)-9H-fluoren-7-yl) pyridine(DPFP) was synthesized via a Suzuki coupling reaction.The gold-nanoparticles-doped DNA-CTMA-DPFP film samples were fabricated by spin-coating the mixed butanol solutions of gold-nanoparticles-doped DNA-CTMA complexes and DPFP.The optical spectra properties and surface enhanced Raman scattering(SERS) characteristics of the film samples were characterized by measuring their absorption spectra,fluorescence spectra,and Raman spectra,respectively.The experimental results show that the absorption of film samples in the range of 300-360 nm are derived mainly from the DPFP dye molecule,whereas the absorption ranging from 500 nm to 700 nm come from the local surface plasma resonance(LSPR) of gold nanoparticles,and the fluorescence spectra exhibits well-defined vibronic peaks at 370 nm(S10-S00 transition),386 nm(S10-S01 transition),with a shoulder near 408 nm(S10-S02 transition).The Raman spectra of DPFP dye molecule in the film samples were excited by a laser with the wavelength 785 nm,and the SERS peak intensities of DPFP molecule gradually increase as the increases of gold nanoparticles doped into the DNA-CTMA complexes.Therefore,the gold-naoparticles-doped DNA-CTMA films are suitable as the SERS substrates of many dye molecules.

Tuning surface plasmons in nanorod arrays with ultrasmall spacing

In this work, we first investigate the optical properties of nanorod arrays with normal inter-rod spacing (>100 nm) and realize the tuning of nanorod localized surface plasma resonance (LSPR) by changing array parameters (e.g., periodicity). Then we filter our individual colors in the visible range using nanorod arrays with ultrasmall inter-rod spacing and ultrahigh density fabricated by electron beam lithography (EBL) and ion etching. The functional nanorod arrays developed in this work are compatible with current digital light processing technique, enabling screen with ultrasmall pixels which can find extensive applications in display and imaging.

Gold nanoparticles modified ITO anode for enhanced PLEDs brightness and efficiency

We reported a facile and controllable electrostatic adsorption of gold nanoparticles (Au NPs) on an indium tin oxide (ITO) anode, for applications in polymer light-emitting diodes (PLEDs). Au NPs (size 20 nm) were found to be well dispersed on a pre-treated ITO anode, and the density of Au NPs was well controlled from 0 to 60 μm−2 depending on the adsorption time. By using the Au NPs modified ITO as the anode, the optimized PLEDs showed a 60% enhancement in brightness and 40% enhancement in luminous efficiency. Our results showed that the enhancement of devices performance mainly originated from enhanced photoluminescence, the maximum of luminous efficiency appeared when the distance of Au NPs and light emission profile was about 40–80 nm, which indicated that the origin of enhanced luminescence is due to the “far-field” effect of the Au NPs layer rather than a classical localized surface plasma resonance.

Measurement of Light Attenuation in Phantom Tissue Embedded with Gold Nanoshells

Light attenuation in phantom tissue embedded with gold nanoshells is measured using a photospectrometer with an integrated sphere system. Gold nanoshells are synthesized and a paste is made by mixing them with agar (or phantom tissue); from which slab samples of different nanoshell concentrations and thicknesses are prepared. Light attenuation is measured as a function of light exciting frequencies, nanoshell concentrations and tissue thickness. The nanoshell particle concentrations are determined by matching the Mie solution for a single nanoshell with the measured attenuation coefficient at the local surface plasma resonance frequency. For the range of the concentrations studied, light attenuation is linearly dependent on the nanoshell concentration, and thus the rule of independent scattering/absorption is observed. The frequency of exciting light strongly affects light attenuation in a nanoshell-populated medium, with the largest attenuation occurring at the local surface plasma resonance frequency of the nanoshells, which is consistent with theoretical predictions. For the measured samples of phantom tissue populated with nanoshells, the optical thickness is about ~8 mm.

The Optical Properties of Au/Ag Nanoparticles Coated with Diamond-Like Carbon Films

Abstract. Noble metal nanoparticles have prominent surface effect, quantum size effect and active outer-shell electrons, they cause these particles to present unusual optical phenomenon, display the strong local surface plasma resonance (LSPR) effect. DLC films have good biological compatibility, good wear resistance and corrosion-resisting, it also has high transmissibility in the visible and near-infrared region. A new LSPR interface between diamond-like carbon films and the Au/Ag NPs was formed by Plasma Enhanced Chemical Vapor Deposition (PECVD), The optical and electrical properties of the samples were studied with ultraviolet-visible absorption spectrophotometer and Raman spectrometer. The results indicate that their transmittance decreased with the increase of the film thickness.

In-situ and ex-situ characterization of TiO2 and Au nanoparticle incorporated TiO2 thin films for optical gas sensing at extreme temperatures

Sensor technologies that can operate under extreme conditions including high temperatures, high pressures, highly reducing and oxidizing environments, and corrosive gases are needed for process monitoring and control in advanced fossil energy applications. Sensor technologies based on optical waveguide-based techniques are highly attractive for passive, embedded, and remote sensing. A critical enabling technology for optical waveguide sensors is the development of advanced optical thin film coatings which have a desired set of optical properties that change in a rapid, selective, and sensitive manner to a particular quantity of interest. TiO2 and Au nanoparticle incorporated TiO2 nanocomposite thin films were prepared through sol-gel deposition techniques and their respective optical responses to a 4% H2/N2 mixture were investigated in the visible / near-IR range of 400–1000 nm. A tendency for Au nanoparticles to occupy special sites on the TiO2 microstructure, such as grain boundaries, twin boundaries, and triple points is rationalized in terms of basic surface energy arguments. The Au / TiO2 nanocomposite films showed a useful optical response due to a reversible, rapid, and repeatable shift in the localized surface plasma resonance peak of Au nanoparticles at a temperature of 650 °C and 850 °C. In contrast, high temperature exposure of TiO2 films to reducing gases at 850 °C resulted in the growth of abnormally large grains or “hillocks” that protruded from the sample surface and resulted in light scattering and an irreversible decrease in transmission at short wavelengths. The origin of the observed optical response of Au / TiO2 nanocomposite films is discussed in the context of work by prior investigators in the Au / yttria-stabilized Zirconia (YSZ) system and needs for future research in this area is highlighted.

Propitious Immobilization of Gold Nanoparticles on Poly(dimethylsiloxane) Substrate for Local Surface Plasmon Resonance Based Biosensor

In this work, a simple method for fabricating gold nanoparticle (AuNP) layer on a poly(dimethylsiloxane) (PDMS) substrate based on electrostatic deposition of AuNP colloid onto a chemically-modified PDMS surface using 3-aminopropyltriethoxysilane (γ-APTES) was developed. AuNPs of 100 nm diameter were successfully dispersed and deposited onto the chemically-modified PDMS surface. The morphology and optical property of the AuNP layer were examined by atomic force microscopy (AFM) and UV–visible absorption spectroscopy, respectively. It was found that the prepared AuNP layer on PDMS could work as a localized surface plasma resonance (LSPR) sensor. The sensing characteristics were examined by changing the refractive index of solution surrounding the AuNP and antigen-antibody events on the AuNP surface. Changes in absorbance intensity and peak wavelength shift of the LSPR band were both clearly observed. The developed technique can hopefully expand the applications of PDMS for not only micro channel fabrication, but also sensing construction for easier and simpler preparation of microfluidic biosensors, which were then applied for immunoassays and other biochemical analyses.

Absorbing polarization selective resonant gratings

We introduce resonant absorbers that consist of linear metal wires embedded inside of a titanium dioxide grating. We show that in these structures the guided-mode resonance may lead to the almost total absorption of one polarization component and greatly enhance the absorption in localized surface plasma resonance. In addition, we show that the structures have potential to function as filters or polarizing beamsplitters. Absorption of 99.67 % has been obtained together with the contrast of 6600 at the wavelength of 532 nm. This corresponds the extinction of 8.8597. The results have been verified experimentally by fabricating an absorbing filter with electron beam lithography and atomic layer deposition technique. The absorption is remarkably high considering the thickness of the structures which is only 219-333 nm.

A label-free sensing method for phosphopeptides using two-layer gold nanoparticle-based localized surface plasma resonance spectroscopy

In this study, a new type of localized surface plasmon resonance (LSPR) sensing substrate for phosphopeptides was explored. It has been known that LSPR response for target species is larger in the near-infrared region (NIR) than in the visible region of the electromagnetic spectrum. Several types of noble metal nanoparticles (NPs) with NIR absorption capacities have been previously demonstrated as effective LSPR-sensing nanoprobes. Herein, we demonstrate a straightforward approach with improved sensitivity by simply using layer-by-layer (LBL) spherical Au NPs self-assembled on glass slides as the LSPR-sensing substrates that are responsive in the NIR region of the electromagnetic spectrum. The modified glass slide acquired an LSPR absorption band in the NIR, which resulted from the dipole-dipole interactions between Au NPs. To enable the chip to sense phosphopeptides, the surface of the glass chip was spin-coated with thin titania film (TiO(2)-Glass@Au NPs). Absorption spectrophotometry was employed as a detection tool. Tryptic digest of α-casein was used as a model sample. The feasibility of using the new LSPR approach for detecting a potential risk factor leading to cancers (i.e., phosphorylated fibrinopeptide A) directly from human serum samples was demonstrated. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) was used to confirm the results.

Simulation of biochemical binding kinetics on the microfluidic biochip of fiber-optic localized plasma resonance (FO-LPR)

A reflection-based localized surface plasma resonance fiber-optic probe for chemical and biochemical sensing, called fiber-optic localized plasma resonance (FO-LPR), has been proposed in the literature. Bio-molecular recognition is detected by the unique optical properties of self-assembled gold nanoparticles on the unclad portions of an optical fiber whose surfaces are modified with a receptor. To enhance the performance of the sensing platform, the sensing element is integrated with microfluidic chips to reduce sample and reagent volume, to shorten response time and analysis time, as well as to increase sensitivity. The main purpose of the present study is to simulate the biochemical assays in the FO-LPR microfluidic chip and to investigate the effects parameters, such as inlet concentrations of analyte or the flowrate on the biochemical binding kinetics. The geometry of the grooved channel is also proposed to enhance the biochemical binding on the unclad optical fiber. The results reveal that the chaotic mixing generated by the grooves enhances the biochemical binding when the injected flowrate is high and, because of that, limits the performance of the molecular mixing. The enhancement of biochemical binding performance was significant, especially at the low injected concentration of analyte.

Analysis of sensing performance of Gaussian-shaped metallic nanogratings

A new type of structure which is composed of a Gaussian profile-shaped metallic nanograting, was put forth from the nanofabrication point of view. Dependence of the structural parameters on the sensitivity was analyzed by means of a multiple multipole program (MMP) method. One of the important applications of the nanograting is in biosensing: immunoassay. Our numerical simulation results showed that the sensitivity to refractive index of 490 nm/RIU and the reflection spectra at site of full-width at halfmaximum (FWHM) ~9 nm can be obtained through the optimized structure. The figure of merit (FOM) of the sensor can exceed 55. The resonant wavelength increases linearly with increasing of the refractive index of bio-samples. These reflection properties make the nanograting more suitable to be used in the localized surface plasma resonance (LSPR)-based biosensors for immunoassay.

Detection of Phosphopeptides by Localized Surface Plasma Resonance of Titania-Coated Gold Nanoparticles Immobilized on Glass Substrates

We herein demonstrate a new sensing method for phosphopeptides by localized surface plasmon resonance (LSPR) using titania-coated gold nanoparticles immobilized on the surface of a glass slide as the sensing substrate and using UV-visible spectrophotometry as the detection tool. Titania has been known to be an effective substrate for binding with phosphorylated species. The detection principle is the shift of wavelength of optical absorption due to SPR of the gold nanoparticles induced by binding of phosphorylated species with titania on the surface of the gold nanoparticles. The feasibility of the approach is demonstrated by detection of tryptic digest products of beta-casein and milk. Gold nanoparticles coated with thin films of titania, immobilized on a glass slide, can selectively bind traces of phosphopeptides from complex samples, resulting in a wavelength shift of the absorption band in the SPR spectrum with good reproducibility. The LSPR results are confirmed by matrix-assisted laser desorption/ionization mass spectrometry. The detection limit for the tryptic digest product of beta-casein is 50 nM.