| 摘要 |
A nanoparticle sensor is capable of detecting and recognizing single nanoparticles in an aqueous environment. Such sensor may find applications in broad areas of science and technology, from the analysis of diesel engine emissions to the detection of biological warfare agents. Particle detection is based on interferometric detection of multi-color light, scattered by the particle. On the fundamental level, the detected signal has a weaker dependence on particle size (ÿ R3), compared to standard detection methods (ÿ R6). This leads to a significantly larger signal-to-noise ratio for smaller particles. By using a multi-color or white excitation light, particle dielectric properties are probed at different frequencies. This scheme samples the frequency dependence of the particle's polarizability thereby making it possible to predict the composition of the particle material. The detection scheme also employs a heterodyne or pseudoheterodyne detection configuration, which allows it to reduce or eliminate noise contribution from phase variations, which appear in any interferometric measurements.
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