Surface-enhanced Raman spectroscopy for trace detection on solids

  • Marienette Vega Department of Physics, Ateneo de Manila University


Raman scattering is the inelastic scattering of light upon interaction with a sample, and is the basis of Raman spectroscopy, an analytical technique that has been very useful in the analysis of materials. One general limitation of conventional Raman spectroscopy, however, has been the weakness of Raman scattering signals. It was observed in 1978 by Fleischmann, Van Duyne, Creighton, and their coworkers that when a molecule is next to certain metallic substrate, one may observe an enhancement of the Raman scattering intensity. This observation has brought forth what is known as surface-enhanced Raman spectroscopy (or SERS), which has a significantly extended the reach of Raman spectroscopy as an analytical tool. A critical requirement in this process is the presence of nanoparticles at the surface. As such, SERS is a truly nanoscience phenomenon as it relies on nanostructures for enhancement to occur.
In this work, the SERS technique is applied to the detection of extremely little amount of defects in bone implant prototypes. The nanoparticle-based substrate is composed of colloidal gold nanostars with localized surface plasmon resonance (LSPR) at 690 nm. Spectral maps, on clean and on nanostars covered surfaces, were obtained exactly at the same position using confocal Raman spectroscopy. Comparison of the two maps shows that there are more monoclinic phases detected in the nanostars-covered surface possibly due to the lightning rod effect in the nanostar tips. While SERS is a well-established detection technique and extensively being used for the detection of trace amounts and even single-molecule of chemical species, it has not been widely applied to detection in solids. Very little work has been done to exhibit SERS in solid materials and it remains a challenge to achieve SERS enhancement on dense and polished solids, such as zirconia implants. We report an unprecedented attempt on SERS on solid zirconia, which provides early evidence of the effectivity of the technique even on non-porous materials. With further improvement in sensitivity, SERS is a promising technique for the early detection of monoclinic phase in zirconia-based implants.

About the Speaker

Marienette Vega is an Assistant Professor at the Department of Physics of Ateneo de Manila University. She obtained both her Bachelors and Masters degree in Physics from the University of the Philippines Diliman. She then continued her graduate studies at the University of South Florida and obtained a second Masters degree in Physics. There she gained extensive experience on the preparation and analytical techniques involving magnetic materials, nanoparticles and ferrofluids. She pursued her PhD in Nanotechnology at the University of Trieste.   Her work on nanoparticles as substrates for surface-enhanced Raman spectroscopy has led to pioneering work on trace detection in solid materials. Immediately after her graduation, she returned to the Philippines and joined Ateneo de Manila University. Currently, she is actively building the nanoscience capabilities of the existing Materials Science Laboratory of the University. She is an active researcher in the field of nanotechnology. Her current projects are geared towards finding nanoparticle-based solutions for prevalent environmental problems, particularly the development of ultrasensitive chemical sensors for environmental contaminants and more efficient barrier fillers for alleviating air pollution and water contamination. She was also one of the recipients of the Australia-APEC Research Fellowship award.