Abstract: A method and apparatus with the sensitivity to detect and identify single target molecules through the localization of dual, fluorescently labeled probe molecules. This can be accomplished through specific attachment of the taget to a surface or in a two-dimensional (2D) flowing fluid sheet having approximate dimensions of 0.5 ?m×100 ?m×100 ?m. A device using these methods would have 103-104 greater throughput than previous one-dimensional (1D) micro-stream devices having 1 ?m3 interrogation volumes and would for the first time allow immuno- and DNA assays at ultra-low (femtomolar) concentrations to be performed in short time periods (˜10 minutes). The use of novel labels (such as metal or semiconductor nanoparticles) may be incorporated to further extend the sensitivity possibly into the attomolar range.

Abstract: Surface-Enhanced Raman Spectroscopy (SERS) is a vibrational spectroscopic technique that utilizes metal surfaces to provide enhanced signals of several orders of magnitude. When molecules of interest are attached to designed metal nanoparticles, a SERS signal is attainable with single molecule detection limits. This provides an ultrasensitive means of detecting the presence of molecules. By using selective chemistries, metal nanoparticles can be functionalized to provide a unique signal upon analyte binding. Moreover, by using measurement techniques, such as, ratiometric received SERS spectra, such metal nanoparticles can be used to monitor dynamic processes in addition to static binding events. Accordingly, such nanoparticles can be used as nanosensors for a wide range of chemicals in fluid, gaseous and solid form, environmental sensors for pH, ion concentration, temperature, etc., and biological sensors for proteins, DNA, RNA, etc.