UC San Diego

There remains a demand for inexpensive and reliable explosive sensors to be used in a field setting for identifying specific explosives. High explosives are considered to be organic and oxidizing, a relatively rare combination that makes them tractable for molecular recognition event. For this reason, fluorescent polymers have had favorable success in their use as sensors for high explosive. Here we report the use of fluorescent, silicon based copolymers, covalently linked to a silica TLC support. A thin layer of the polymer allows for a more efficient interaction with an analyte, thus yielding enhanced detection sensitivity. The attachment of the sensing polymers onto a chromatographic support allows for the separation of a mixture, as well as the identification of multiple explosives through the use of multiple sensing polymers. Hollow hard shell particles of 200 nm and 2 micron diameter with a 10 nm thick porous silica shell have also been synthesized using polystyrene templates and a sol-gel process. The template ensures that the hollow particles are monodispersed, while the charged silica surface ensures that they remain suspended in solution for weeks. When filled with perfluorocarbon gas, the particles behave as an efficient contrast agent for color Doppler ultrasound imaging in human breast tissue. The silica shell provides unique properties compared to conventional soft shell particles employed as ultrasound contrast agents: uniform size control, strong adsorption to tissue and cells immobilizing particles at the tissue injectionsite, a long imaging lifetime, and a silica surface that can be easily modified with biotargeting ligands or small molecules to adjust the surface charge and polarity