“What? Why? How?” All kinds of “wh” questions I bombarded at my buddy Marc when he apprised me that he is not going to make it to the long awaited trip. “Somebody tried to poison me” followed by guffaw was the jocular repartee from Marc. After a demented pause from my side, Marc cleared the air of confusion and sickeningly reported that he is suffering from food poisoning. The next morning I drove down to his place to see how he is doing. In one of the friendly banters which we always indulge into, he said” Non sense, this food poisoning man, I wish I could have some device like a phone which can detect the contaminants in food right away, so that I can make store owner eat that food once I find it’s contaminated” followed by burst of laughter. “Typical Marc” I muttered with smirk. But on my way back home that ‘device’ thought of Marc’s stuck in my head and being a chemist I started screening all the techniques used for the detecting chemicals and asked myself which technique can be exploited to make such a handy device to detect chemical contaminants. The answer came without a waste of second, its Surface Enhanced Raman Scattering(SERS)!
SERS is a result of the interaction of light(electromagnetic radiations) with the chemicals on nanostructured (of the size of nanometers) metal surface like silver and gold. Depending upon the composition and structure of the chemical, its interaction with the light is different. Interaction of light with chemical also depends on the metal nanosubstrate. After interaction with the light, interaction profile( spectrum) of light with chemical is generated. Every chemical has its own and unique interaction profile with light which can be called as fingerprint of that chemical. One can actually detect some unknown chemical just by interacting it with light and generate the interaction profile( fingerprint). Matching the profile with known chemicals, one can tell what chemical it is!
Though the phenomenon of SERS in well known, production of silver or gold nanostructure which can lead to very high interaction of light and chemical is not an easy task. Yan Zhou etal in one fine effort cited at very end have produced gold core silver shell nanoparticles with very high SERS activity. They have also examined the effect of thickness of the silver shell on SERS signals and developed a versatile SERS nanosubstrate. Method of synthesis of high quality gold core silver shell nanoparticles is very facile and structure can be maneuvered according to applications. Layer by layer approach of coating silver shell on gold core with Raman probe( chemical) inside is also reported here to have huge interaction between light and probe leading to high SERS activity.
Yan Zhou, Changwon Lee, Jinnan Zhang and Peng Zhang.
Padmanabh Joshi is a guest web writer for the Journal of Materials Chemistry blog. He currently works at the Department of Chemistry, University of Cincinnati.