Highly responsive sensor on a nanostructured surface via the self-assembly of a biomolecule with an evanescent wave technique.

A self-assembled biomolecule was used to create a highly sensitive sensor surface for detecting toxic chemical species (polychlorinated biphenyls, PCBs). We fabricated the nanostructured sensor surface via the self-assembly of cytochrome c on a Au thin film. Surface plasmon resonance (SPR), an evanescent wave technique possessing maximum sensitivity on the surface and characterized by an exponential decay of sensitivity with distance from the surface, was utilized as the principle for signal transduction.

Investigation of adsorption behavior of bisphenol A on well fabricated organic surfaces using surface plasmon resonance spectroscopy.

Molecular adsorption of bisphenol A (BPA) on three types of self-assembled monolayers with different functionalities, such as -CH3, -SH, and -COOH, was examined using surface plasmon resonance (SPR) spectroscopy. BPA molecules in an aqueous solution were easily adsorbed onto a hydrophobic surface compared to a hydrophilic surface. Sorption behavior of BPA into poly(2-methoxyethyl acrylate) (PMEA) layer, which is known as a biocompatible polymer, was also investigated.

Mesoporous silica thin films as a spatially extended probe of interfacial electric fields for amplified signal transduction in surface plasmon resonance spectroscopy.

A new simpler concept about the signal amplification of surface plasmon resonance (SPR) that is based on the utilization of mesoporous silica thin films is demonstrated. As compared to monolayer based coatings, mesoporous silica thin films of approximately 200 nm extend the interaction arena away from the metal, thus permitting the integration of the change in optical contrast at different distances from the sensor surface.

In situ sensing of metal ion adsorption to a thiolated surface using surface plasmon resonance spectroscopy.

The kinetics of the adsorption of metal ions onto a thiolated surface and the selective and quantitative sensing of metal ions were explored using surface plasmon resonance (SPR) spectroscopy. The target metal ion was an aqueous solution of Pt2+ and a thin-gold-film-coated glass substrate was modified with 1,6-hexanedithiol (HDT) as a selective sensing layer. SPR spectroscopy was used to examine the kinetics of metal ion adsorption by means of the change in SPR angle.

Characterization of surface-confined alpha-synuclein by surface plasmon resonance measurements.

Urea-driven denaturation and renaturation of surface-bound alpha-synuclein are monitored by surface plasmon resonance (SPR) spectroscopy. The differential SPR angle shift (Delta Theta(SPR))(Net) enables us to estimate the Gibbs free energy change (DeltaG(o)) for the denaturation of the supported alpha-synuclein. DeltaG(o) for the denaturation of the supported alpha-synuclein, which is indirectly related to its biological activity can be increased significantly by the mixed self-assembled monolayers of 11-mercaptoundecanoic acid and 1,6-hexanedithiol.

Fabrication of reusable sensor for detection of Cu2+ in an aqueous solution using a self-assembled monolayer with surface plasmon resonance spectroscopy.

The proposed procedure for recycling the sensor surface consists of (1) the self-assembly of 2-aminoethanethiol hydrochloride (AET) on the Au substrate, (2) the neutralization of zwitterion-like species, -NH3+Cl- to -NH2 by treatment with a NaOH solution (pH 11), (3) the detection of Cu2+ on the NaOH-treated AET-Au substrate, and finally (4) regeneration of the sensor surface from [-NH2--> Cu2+] to [-NH3+Cl-] by treatment with 1 M HCl.

Facile synthesis of mesoporous silica sublayer with hierarchical pore structure on ceramic membrane using anionic polyelectrolyte.

A facile method for introducing mesoporous silica sublayer onto the surface of a ceramic membrane for use in liquid-phase separation is described. To reduce the electrostatic repulsion between the mesoporous silica sol and the ceramic membrane in highly acidic conditions (pH < 2), thus facilitating the approach of hydrolyzed silica sol to the surface of the membrane, poly(sodium 4-styrenesulfonate) (Na+PSS-, denoted as PSS-) was used as an ionic linker. The use of PSS- led to a significant reduction in positive charge on the ceramic membrane, as confirmed by experimental titration data.

Direct observation of a cooperative mechanism in the adsorption of heavy metal ions to thiolated surface by in-situ surface plasmon resonance measurements.

S-type adsorption kinetics, obtained by surface plasmon resonance spectroscopy measurements, suggest that the rate of Pt2+ adsorption on 1,6-hexanedithiol (HDT) on gold increases until the surface coverage reaches ca. 17%, after which, the adsorption profile of Pt2+ follows Langmuirian behavior for the surface coverage.