Surface-enhanced Raman scattering of 4-mercaptopyridine on thin films of nanoscale Pd cubes, boxes, and cages

We have synthesized a variety of Pd nanoparticles of 8–50 nm in size including solid cubes, hollow boxes, and porous cages. Using 4-mercaptopyridine (4MP) as a probe molecule, we have characterized thin films for surface-enhanced Raman scattering (SERS) activity, and have found a significant level of enhancement (with factors ranging from 170 for 8-nm cubes to 1.3 × 104 for boxes). For the cubes and boxes, we observed a trend of stronger enhancement with more red-shifted SPR bands. We evaluated the sensitivity of this approach, and also used SERS to monitor monolayer formation on these particles.