SERS as sensing method for bio-molecules on MBE-grown quantum dots

Using surface enhanced Raman spectroscopy (SERS), we have observed bio-molecules at extremely low concentration, adsorbed on self-organized semiconductor quantum dots, grown by molecular beam epitaxy. Quantum dots have found application in the field of biosensors, and the performance of these devices depends critically on the properties of the surface features. It is therefore of interest to explore useful and versatile spectroscopic sensing technique such as SERS to determine these properties. The SERS technique employs rough substrates with structures in the nanometer range to enhance Raman signals from adsorbed species. This spectroscopy has a number of important advantages: sensitivity, selectivity and non-destructive detection. In addition to this, SERS enables the determination of detailed information about adsorbed species such as molecular structure and orientation, while greatly increasing the Raman cross section and suppressing fluorescence. We show that the Raman signal observed from various biologically important molecules can be enhanced by up to six orders of magnitude by means of surface enhancement caused by adhesion to self-organized CdSe/CdZnSeMg quantum dots grown by molecular beam epitaxy.