1. SERS Sensing Platforms and SERS Tags

Surface enhanced Raman spectroscopy (SERS) takes advantage of local electromagnetic field enhancements near metallic nanostructures. These enhancements are induced, among other factors, by the coherent oscillation of the conduction electrons on the surface of the nanoparticles, also called localized surface plasmons. SERS retains the fingerprinting capabilities of Raman, thus it is ideal for molecule identification at extremely low concentrations. In addition, the internal modes of a reporter molecule brought in close proximity to the metallic surface can act as diagnostic and tagging tools. Based on these considerations, we are interested in developing SERS platforms for chemical and biological sensing, both via direct and indirect approaches. For the direct implementation, we have recently developed and patented a chemical sensor based on gold nanostars (pictured in the TEM micrographs above) capable of detecting small molecule analytes, in multiplexed mode, up to low femtomolar concentrations (Nanoscale 2014, 6, 8891). In the indirect approach, we have pioneered the concept of dimer-based SERS tags, which we have employed for biosensing platforms (Adv. Funct. Mater. 2008, 18, 2518; Small, 2010, 6, 1550; Adv. Mater. 2010, 22, 4954) and for diseased cell identification (Adv. Healthcare Mater. 2013, 2, 1370). SERS tags can also be employed in a variety of other applications, for example in the identification and localization of pigments and proteinaceous materials in works of art, a project on which we are working in collaboration with Julie Arslanoglu of the Metropolitan Museum of Art of NYC (Analyst 2015, 140, 5971).

  1. 2.Computational Study of the Optical Properties of Plasmonic Nanoparticles

We are interested in studying computationally the optical properties of gold nanoparticles, especially those with complex morphology and high near field enhancement capability, such as gold nanostars. We are also interested in understanding the plasmonic properties of assembled nanostructures, such a nanostar-nanosphere core-satellite assemblies. Recently, we have been able to computationally predict, and experimentally verify, that core-satellite structures with a gold nanostar core and three spherical gold satellites can be regiospecifically synthesized from the bottom up, and display SERS enhancement factors equal to 10^11 at the interparticle junctions. By virtue of this enhancement, we were able to follow in real time the formation of the amide bond at the junction, which was employed to lock core and satellites together (Phys. Chem. Chem. Phys. 2015, Phys. Chem. Chem. Phys. 2015, 17, 21133).

  1. 3.Bottom up Synthesis of Novel Plasmonic Nanoparticles

We are currently working on the discovery and implementation of bottom up methodologies for the synthesis of non traditional plasmonic nanoparticles, specifically emphasizing on the search of hybrid, non-isotropic nanostructures that can be employed in various fields, but primarily in biomedical applications of SERS and photocatalysis. 

4. Effect of Interfacial Interactions at the Nanoscale on the Mechanical Properties of Bulk Polymers

It is well known and accepted that nanostructured fillers made of materials with high Young’s Modulus (e.g. ceramics, carbon nanotubes) can drastically improve the mechanical properties of bulk polymers, increasing significantly their strength. However, because of the intrinsic properties of these nanomaterials, whose morphology and surface chemistry cannot be easily tuned, it is difficult to incorporate in the polymer high volumes of fillers, making it difficult to tune their mechanical properties to the desired degree. We are interested in studying this possibility by taking advantage of anisotropic gold nanoparticles such as gold nanorods. Although gold cannot compare in its mechanical properties to ceramics and carbon nanotubes, it is relatively easy to modify the morphology and chemical properties of its derived nanoparticles, hence rendering it feasible to tune locally at the nanoscale the interactions between polymer chains and fillers. We believe with this approach we will be able to finely tune the mechanical properties of polymers in bulk and film.