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

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

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

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

Rapid approach for cloning bacterial single-genes directly from soils

Obtaining functional genes of bacteria from environmental samples usually depends on library-based approach which is not favored as its large amount of work with small possibility of positive clones. A kind of bacterial single-gene encoding glutamine synthetase (GS) was selected as example to detect the efficiency of cloning strategy in this study. Five GS genes were directly cloned from soils using degenerate primers with two steps of nested polymerase chains reactions. The genes showed 94 to 99% amino acid identities to the homologs in the known database, and encoded proteins affiliated to GS I and GS II families, respectively. All the five genes could rescue the growth of Escherichia coli glutamine auxotroph mutant ET6017 in minimum medium (ammonium chloride was sole nitrogen source in this medium). This study develops one rapid approach for cloning bacterial single-genes directly from soils. Comparing with the conventional strategies for gene cloning from complex environmental samples, this method did not need making genomic library and isolating target genes from large amount of library clones. This approach distinctively demonstrates its advantages of rapidity and effectiveness particularly when it aims at cloning short single-genes that had known homologs in all kinds of nucleic acid databases.Keywords: Gene cloning, soil, glutamine synthetase, nested PCR, single-geneAfrican Journal of Biotechnology Vol. 12(32), pp. 5029-503

Entanglement Creation and Storage in Two Qubits Coupling to an Anisotropic Heisenberg Spin Chain

The time evolution of the entanglement of a pair of two spin qubits is investigated when the two qubits simultaneously couple to an environment of an anisotropic Heisenberg XXZ spin chain. The entanglement of the two spin qubits can be created and is a periodic function of the time if the magnetic field is greater than a critical value. If the two spin qubits are in the Bell state, the entanglement can be stored with relatively large value even when the magnetic field is large.Comment: 4figures

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