Sensors Mostafa A. El-Sayed, Georgia Tech Research Corporation, DMR 0906822 Sensing of biological materials, dangerous substances or explosive substances is presently a very important field of research. Although many sensing techniques have been used, improving the accuracy and sensitivity is still in need. Each molecule has a Raman fingerprint, but the challenge in using Raman measurement is to enhance its weak signal. Silver and gold nanoparticles have plasmon fields which are responsible for greatly enhancing the Raman signal. During our research in this current grant we prepared gold nanocages which we have shown to have the strongest plasmon field ever reported for a nanoparticle. We used these nanoparticles to sense thiophenol vapor with very great sensitivity. Our theoretical calculations show gold nanocages to have a high plasmon field. Many sizes and shapes of nanoparticles have been used as a Raman substrate. Some conditions have to be met to observe a strong Raman signal quantitatively. The plasmonic nanoparticles should be kept at fixed separation distances during the measurement. The plasmon field intensity depends on the inter-particle separation, so if the distance is varied during the SERS measurement or from one analyte to another, the SERS spectrum Mahmoud M A, Snyder, B., El-Sayed, M A; J Phys. Chem.(2010), 114, 7436. Surface-enhanced Raman Scattering of Thiophenol vapor adsorbed on gold nanocages monolayer of different percent surface coverage by using the Langmuir- Blodgett technique. 40 60 80 100 40 60 80 100 Y ou tsid e 5 0 n m x 5 nm 0.1000 0.3858 1.4 8 9 5.7 4 3 22 .1 6 85 .5 0 329.9 1273 2500 K IE I 2 X SEM images of 50 nm gold nanocages monolayer assembled on the surface of quartz substrate by use of the Langmuir-Blodgett. The field enhancement map contour for 50 nm gold nanocage with wall thickness of 5 nm as calculated by the DDA method.