| Within the past two decades, chemical sensors have developed as viable alternatives to traditional methods of analysis. Optical lithium ion sensors that allow both direct and real-time detection are desirable for both biomedical and industrial purposes.; In terms of medical applications, patients suffering from manic depression and other neurological disorders consume lithium to treat the illness. Industrially, lithium is one of the least polluting and lightest elements that can be safely handled in electrochemical processes, and is thus used as an energy source in lithium ion batteries.; In order to monitor lithium ion concentration in complex environments we need to develop sensor compounds that change color or light up specifically when lithium bound.; By carefully taking into consideration the size of the lithium ion, we have designed compounds that are capable of binding selectively to the lithium ion, and when bound to lithium display an optical signal. These sensor molecules led us to develop the first fluorescence fiber-optic lithium ion sensor, which permits lithium detection in remote areas. The intensity of the color change in each of our studies indicates the lithium ion concentration.; In further research, we made use of nanotechnology to develop a lithium ion sensor for use in aqueous environments. The new strategy makes use of the unique optical properties of gold nanoparticles, which are dependent on their size and the proximity of the particles to each other. By modifying the gold nanoparticle surface with a molecule that binds selectively to lithium, we induced gold particle aggregation, which resulted in visible color changes.; Gold nanoparticles are not only useful for use in sensor applications, but they can also be employed as templates to prepare hollow nanoparticles. In an effort to design hollow nanotubes, we made use of gold nanorods and polymerized polystyrene and silica on their surface. The resulting polystyrene- and silica-coated gold particles were stable toward aggregation. Dissolution of gold from the core of the polymer-coated particles, resulted in hollow polystyrene and silica nanotubes. Hollow nanoparticles are expected to play an important role in gene therapy, drug delivery, contaminated waste removal, and cell and enzyme transplantation. |
