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

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

Characterization of Diamond-Like Film after Focused Ion Beam Processing

Optical properties (transmission and refractive index) and chemical structure (XPS) of diamond-like coating (DLC) film before and after focused ion beam milling (FIBM) process, were investigated in this paper. It is shown by our FIBM experiment that influence of FIBM on Optical properties and chemical structure of the DLC film is not apparent, especially in near-infra region. The film still can be used for optical applications. As an application example, diffractive optical element (DOE) was directly fabricated on the film by use of FIBM. Measured diffraction efficiency of the DOE is 73%, which is acceptable for conventional use.Singapore-MIT Alliance (SMA

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

Investigation of aspect ratio of hole drilling from micro to nanoscale via focused ion beam fine milling

Holes with different sizes from microscale to nanoscale were directly fabricated by focused ion beam (FIB) milling in this paper. Maximum aspect ratio of the fabricated holes can be 5:1 for the hole with large size with pure FIB milling, 10:1 for gas assistant etching, and 1:1 for the hole with size below 100 nm. A phenomenon of volume swell at the boundary of the hole was observed. The reason maybe due to the dose dependence of the effective sputter yield in low intensity Gaussian beam tail regions and redeposition. Different materials were used to investigate variation of the aspect ratio. The results show that for some special material, such as Ni-Be, the corresponding aspect ratio can reach 13.8:1 with Cl₂ assistant etching, but only 0.09:1 for Si(100) with single scan of the FIB.Singapore-MIT Alliance (SMA

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