Hybridization of localized surface plasmon resonance-based Au-Ag nanoparticles

The hybrid Au - Ag triangular nanoparticles were proposed for the purpose of biosensing. To construct the nanoparticles, an Au thin film was deposited on top of the Ag nanoparticles supported with glass substrate. The hybrid nanoparticles can prevent oxidation of the pure Ag nanoparticles due to the Au protective layer caped on the Ag nanoparticles. The hybrid nanoparticles were designed using finite-difference and time-domain algorithm. Extinction spectra of the hybrid nanoparticles excited by visible light beam with plane wave were calculated, and the corresponding electric fields at peak position of the extinction spectra were expressed also. It is clear that the hybrid nanoparticles can excite the localized surface plasmon resonance wave which can be used to detect biomolecules. As an application example, we presented relevant detection results by means of using protein A to covalently link surface of the hybrid nanoparticles. Refractive index sensitivity of the hybrid nanoparticles was derived through both computational numerical calculation and experimental detection. Both the calculated and the experimental extinction spectra show that the hybrid Au - Ag nanoparticles are useful for detecting the biomolecules. © Springer Science+Business Media, LLC 2008

Optical biochip with multi-channels for detecting biotin-streptavidin based on localized surface plasmon resonance

A rapid and accurate detection of molecular binding of antigen-antibody signaling in high throughput is of great importance for biosensing technology. We proposed a novel optical biochip with multichannels for the purpose of detection of biotin–streptavidin on the basis of localized surface plasmon resonance. The optical biochip was fabricated using photolithography to form the microarrays functioning with multichannels on glass substrate. There are different nanostructures in each microarray. Dry etching and nanosphere lithography techniques were applied to fabricate Ag nanostructures such as hemispheres, nanocylindricals, triangular, and rhombic nanostructures. We demonstrated that 100-nM target molecule (streptavidin) on these optical biochips can be easily detected by a UV-visible spectrometer. It indicated that period and shape of the nanostructures significantly affect the optical performance of the nanostructures with different shapes and geometrical parameters. Our experimental results demonstrated that the optical biochips with the multichannels can detect the target molecule using the microarrays structured with different shapes and periods simultaneously. Batch processing of immunoassay for different biomolecular through the different channels embedded on the same chip can be realized accordingly

Topical Review: Design, Fabrication, and Applications of Hybrid Nanostructured Array

Nanohybrid materials have been widely used in the material chemistry research areas. In this paper, we mainly discussed the hybrid nanostructures used for nanobiosensor applications. It is one of the most promising and rapidly emerging research areas in nanotechnology field. Design, fabrication, and applications of hybrid nanostructures are reviewed, respectively. Finite difference time domain (FDTD) methods are applied to design different materials of hybrid nanostructures. Nanosphere lithography (NSL) is used to fabricate our designed hybrid nanostructures. Moreover, protein A and staphylococcal enterotoixn B (SEB), an enterotoxin, are detected by our designed hybrid nanostructures. From all the experiment results, we can see that our designed hybrid nanostructures are one of important nanohybrid materials. They have many potential applications in the nanobiosensor in the future

Localized surface plasmon resonance-based hybrid Au-Ag nanoparticles for detection of Staphylococcus aureus enterotoxin B

A triangular hybrid Au-Ag nanoparticles array was proposed for the purpose of biosensing in this paper. Constructing the hybrid nanoparticles, an Au thin film is capped on the Ag nanoparticles which are attached on glass substrate. The hybrid nanoparticles array was designed by means of finite-difference and time-domain (FDTD) algorithm-based computational numerical calculation and optimization. Sensitivity of refractive index of the hybrid nanoparticles array was obtained by the computational calculation and experimental detection. Moreover, the hybrid nanoparticles array can prevent oxidation of the pure Ag nanoparticles from atmosphere environment because the Au protective layer was deposited on top of the Ag nanoparticles so as to isolate the Ag particles from the atmosphere. We presented a novel surface covalent link method between the localized surface plasmon resonance (LSPR) effect-based biosensors with hybrid nanoparticles array and the detected target molecules. The generated surface plasmon wave from the array carries the biological interaction message into the corresponding spectra. Staphylococcus aureus enterotoxin B (SEB), a small protein toxin was directly detected at nanogramme per milliliter level using the triangular hybrid Au-Ag nanoparticles. Hence one more option for the SEB detection is provided by this way. © 2009 Elsevier B.V. All rights reserved

Effect of nanoholes on the plasmonic properties of star nanostructures

The transmission and localized electric field distribution of nanostructures are the most important parameters in the plasmonic field for nano-optics and nanobiosensors. In this paper, we propose a novel nanostructure which may be used for nanobiosensor applications. The effect of nanoholes on the plasmonic properties of star nanostructure was studied via numerical simulation, using the finite-difference time-domain (FDTD) method. In the model, the material type and size of the nanostructures was fixed, but the distance between the monotor and the surface of the nanoholes was varied. For example, nanoholes were located in the center of the nanostructures. The simulation method was as follows. Initially, the wavelength of incident light was varied from 400 to 1200 nm and the transmission spectrum and the electric field distribution were simulated. Then at the resonance wavelength (wavelength where the transmission spectrum has a minimum), the localized electric field distribution was calculated at different distances from the surface of the nanostructures. This study shows that the position of nanoholes has a significant effect on the transmission and localized electric field distribution of star nanostructures. The condition for achieving the maximum localized electric field distribution can be used in nano-optics and nanobiosensors in the future

Tuning optical properties of rhombic hybrid Au-Ag nanoparticles: A discrete dipole approximation calculation

Optimization of metallic nanoparticles was presented in this paper by aid of computational numerical calculation. The optical extinction spectra of rhombic hybrid Au-Ag nanoparticles have been calculated by the discrete dipole approximation (DDA) aided design method. Both material and the thickness of the particles can be used to effectively tune localized surface plasmon resonance. On the basis of the calculated extinction spectra, the crucial parameters of the nanostructure arrays such as thickness can be determined. Using this DDA aided approach, a hybrid Au-Ag nanoparticles array is put forth and designed with the optimized parameter of thickness of metal thin films (h = 5 nm, and h = 25 nm). This study shows that the material of the particles have significant effect on the optical properties. The DDA aided design method can provide the optimized structure parameters for the hybrid nanostructures

Influence of Cr adhesion layer on detection of amyloid-derived diffusible ligands based on localized surface plasmon resonance

A Cr adhesion layer inserted between Ag nanoparticles and a glass substrate, for the purpose of improving the adhesion of Ag nanoparticles to glass, was observed to cause an abnormal peak shift of extinction spectra in non-specific reactions. The undesired peak shift misleads molecule detection in non-specific reactions. To solve this issue, a practical technique using n-propyl-trimethoxysilane-based passivation for the detection of amyloid-derived diffusible ligands was investigated as a route to eliminate the abnormal peak shifting observed in the non-specific reactions. To evaluate this passivation technique, localized surface plasmon resonance immunoassay experiments were conducted. Experimental results derived with and without the passivation process were investigated as a basis for comparative analysis. Our experimental results demonstrate that this passivation technique effectively eliminates the observed peak shift originating from the Cr adhesion layer. © 2009 Springer Science+Business Media, LLC

Biochemistry nanosensor based on hybrid metallic nanostructure array

A biochemistry nanosensor based on hybrid metallic nanostructure array was put forward in this paper. The hybrid metallic nanostructure array consists of two types Ag nanostuctures, spherical and pyramidal structures with the same period. A biochemistry sensor experiment is demonstrated by detecting the transmittance spectra of hybrid metallic nanostructure using Sciencetech spectrophotometer. The wave peaks of transmittance spectra have shifts when the metallic periods and the refractive index of Ag nanostuctures are different

Hybrid metallic nanoparticles for excitation of surface plasmon resonance

A Ag nanostructure was put forward in this paper. There are two types of Ag nanoparticles, spherical and pyramidal particles. Both of them have the same period, but different height and shapes. The hybrid nanoparticles can produce the localized surface plasmon resonance (LSPR), which couples each other and leads to an extra peak transmission. Our UV-visible-IR spectrophotometer measurement results show that some extra small and sharp peaks appear besides the normal LSPR wave peaks in the transmittance spectrum. The hybrid Ag nanoparticles being used as nanosensors will be more sensitive and selective than the conventional LSPR-based nanosensors. © 2007 American Institute of Physics

Effect of gold coating on sensitivity of rhombic silver nanostructure array

The sensitivity is the most important parameter in the sensing field. Effort was made to study the effect of gold coating on the sensitivity of rhombic silver nanostructure array through numerical simulation using the discrete dipole approximation method. This study shows that thickness of the gold coating can be varied to tune the sensitivity of the rhombic silver nanostructure array. The Au-Ag nanostructure array is found to possess the maximum refractive index sensitivity of 714 nm/RIU when thickness of gold is 20 nm, thickness of silver is 25 nm, and refractive index of the medium is around 1.35. The condition for achieving the maximum refractive index sensitivity can be used for detecting many species of biomolecules and drugs in the future