Surface-enhanced spectroscopy, nanostructure fabrication and sensor applications

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Molecules are the building blocks of everything we breathe, drink or eat. However, until very recently, the detection of a single molecule was more fiction than science. The present proposal is about receiving the fingerprint signals from a single molecule using metal nanoparticles as transmitters. The detection of single molecules is achieved with metallic nanostructures of silver and gold, and a great deal of effort is dedicated to the fabrication of such structures and to the study of their optical properties. Thus, the first step in this project is the fabrication of silver or gold nanostructures (about 100 times bigger than the molecule under investigation) used in the detection of molecular species. In addition, if we can detect one, it would be easy to detect a bunch of them and we are developing analytical protocols to detect very small amounts of molecules using the same method. The latter is known as trace analysis, and can involve the detection of small amounts of pollutants in the environment, contaminants in pharmochemicals, or the detection of micro-organisms and toxins. The potential for applications is so evident that the race for patenting specific detection systems is on, and many small companies are flourishing profiting from trace analysis. In this research proposal we explore two techniques that can provide single molecule detection (SMD) using metallic nanostructures; they are surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF). We hope to provide pattern recognition for SMD. Therefore, when a single molecule send out information about its environment, or changes in it, a proper interpretation can be given. Developing the methods for SMD is equivalent to finding the ultimate sensor element for applications in biological, chemical and physical sciences. This explains the enormous interest in detecting the signal coming from a single molecule.