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Som Tyagi Group – Drexel University

The molecular level specificity provided by Raman spectroscopy (RS) has made it a widely used spectroscopic tool for the determination of molecular structure and compound identification. Dr. Tyagi’s group has been studying Surface Enhanced Raman Scattering (SERS) in fractal aggregates fabricated from nano-particle printing inks. Fractal aggregates of metallic colloidal particles can provide hyper- enhancement for various linear and nonlinear optical responses, including RS. Such enhancement results from the localization of optical plasmon excitations within small parts (“hot-spots” a few to tens of nm in size) of a fractal aggregate. Since fractals are scale-invariant they, unlike translationally-invariant media, do not support propagating waves and hence can ‘trap’ electromagnetic field in very small volumes. When sufficiently concentrated, the large electromagnetic fields in the hot spots can result in very large SERS enhancement.

Why Is Small So Big?

Nanotechnology deals with products and processes that are measured in almost unbelievably small increments called “nanometers”—one billionth of a meter.

At the nanoscale, materials differ from larger objects in their physical, chemical and biological properties; therefore, they lend themselves to new and improved materials, systems and devices. Nanotechnology is behind the development of such diverse advancements as:

  1. Drug Delivery
  2. Biofiltration and Separation sciences
  3. Improved coatings for medical devices

Thanks to rapid advances in this exciting new field, we now have the tools and talents to manipulate materials on the molecular scale—a technology literally changing the world as we know it.


The NTI is an initiative of the Pennsylvania Department of Community and Economic Development and is funded by the Ben Franklin Technology Development Authority.