Resonant nano-cluster devices

Abstract

The resonance-enhanced absorption (REA) by metal clusters on a surface is an effective technique on which to base bio-optical devices. A four-layer device consisting of a metal mirror, a polymer or glass-type distance layer, a biomolecule interaction layer and a sub-monolayer of biorecognitively bound metal nano-clusters is reported. Experiments indicate a strong influence of the resonator homogeneity on the absorption maximum. Layer stability plays an important role in the overall performance of the device. Techniques and optimised lab protocols to set up biochips that use the REA process in the detection are presented. The sensors show one to three narrow reflection minima in the visible and or infra-red (IR) part of the spectrum and therefore they do not suffer from the spectral limitations associated with spherical gold colloids. Metal clusters (synthesised by thermal step reduction) as well as metal- dielectric shell clusters (synthesised by various shell deposition processes) are used to precisely shift the readout of the device to any frequency in the visible and near IR range. Disposable single-step protein chips, DNA assays as well as complex biochip arrays are established that use various DNARNA, antigen-antibody and protein-protein interaction systems.

Binding of Gold Clusters with DNA Base Pairs: A Density Functional Study of Neutral and Anionic GC−Aun and AT−Aun (n = 4, 8) Complexes

“…We found that hydrated base pairs have higher EAs than the corresponding gas-phase systems. Developments in this area have been reviewed recently. 2e,5b,8b,, DNA−metal, particularly DNA−gold, complexes appear to be good candidates for investigation of properties relevant to their use in nanobiotechnology. 2a,2d,,8b,− The binding of clusters of three and six gold atoms, from the catalytic point of view of Au particles, to the individual DNA bases and Watson−Crick AT and GC base pairs employing triangular T-shaped geometries was studied recently …”

Optical Resonance-Enhanced Absorption-Based Near-Field Immunochip Biosensor for Allergen Detection

“…Plasmon resonance properties 12 of biofunctionalized Au NPs allow biodetection based on interactions with electromagnetic waves in an advanced layered optical near-field setup. If metal (Au) NPs are undergoing an antigen−antibody binding process within a defined nanodistance (≤400 nm) to a highly reflective mirror and illuminated with white light of the visible and near-infrared spectrum from the particle side, they will generate a strong color effect (REA − ). This optical phenomenon was used to adjust a conventional enzyme-linked immunosorbent assay (ELISA) to a gold cluster-linked immunosorbent assay on a chip by conjugating a Au NP instead of an enzyme to the detector biomolecule .…”