Optical and biological sensing capabilities of Au2S/AuAgS coated gold nanorods

Gold nanorods coated with a multiplex component, namely Au(2)S/AuAgS coated gold nanorods, are produced without precipitation and aggregation among the nanorods. Both the thickness of the shell and size of the core can be readily controlled by this technique allowing one to tune the plasmon resonance of the nanocomposites over a range of several hundred nanometers. These Au(2)S/AuAgS coated gold nanorods exhibit interesting optical properties and are suitable for many biological sensing applications. Functionalization of the Au(2)S/AuAgS coated gold nanorods is achieved by manipulating the affinity between the Au(2)S/AuAgS and thiol compounds. Biomolecules can be covalently attached via the NH(2) bond of the antibodies to the NHS-terminated nanorods. The longitudinal peaks of the Au(2)S/AuAgS coated gold nanorods are extremely sensitive to the refractive index changes induced by target binding, suggesting that they are excellent sensors for target-specific binding events and have the potential to achieve single-molecule sensitivity in microspectroscopy.