SERS Template Fabricated from Patterned Nanoporous Gold

Summary

Vanderbilt researchers have developed a technique that will amplify the Raman scattering signal from adsorbed molecules on a roughened metal surface to enable unique identification of the adsorbed molecules.

Description

Surface-Enhanced Raman Spectroscopy (SERS) is a surface sensitive technique that amplifies the Raman scattering signal from adsorbed molecules on a roughened metal surface enabling unique identification of the adsorbed molecules. Since the amplification can often be on the order of 1011 times, the technique affords the prospect for detection of single molecules; both chemical and biological. Current research-stage technologies only enable large amplifications at random locations on a SERS substrate, called hotspots, making reliable and cost-effective molecular identification challenging and commercialization improbable. The present invention provides a means to enhance the Raman scattering amplification over commercially available SERS substrates using an inexpensive imprinting process. Using this invention, sub-wavelength two-dimensional gratings are patterned into nanoporous gold (np-Au or NPG). Current experiments have demonstrated an enhancement of a few orders of magnitude over commercially available SERS substrates. While a number of companies are entering the field of supplying SERS substrates, at the present time the most readily available substrate is from Renishaw Diagnostics sold under the tradename of Klarite. Since the technique for patterning the gratings in the present invention is extremely simple, scaleable and inexpensive, the resulting substrates should be manufacturable at a fraction of the cost of manufacture of traditionally patterned substrates using electron beam lithography techniques.

Current Competitive Products

At the present time, Klarite substrates are sold for approximately $70 each while API Technologies' NanoLT sells for approximately $20 apiece. In the present invention, the NPG is made by acid-bath de-alloying of an Au-Ag leaf that sells for approximately $.06 per cm2. The NPG is then mounted on a substrate such as gold, silicon or glass. The grating pattern is then simply imprinted using a press. The silicon stamp (made by standard silicon lithography techniques) utilized as the template is reusable.

Current Status

The technology described in this invention has been used repeatedly at Vanderbilt's laboratories for over two years. The results of comparative tests conducted using the SERS substrates and commercially available Klarite substrates have been published (Y. Jiao, J. D. Ryckman, P. N. Ciesielski, C. A. Escobar, G. K. Jennings, and S. M. Weiss, "Patterned nanoporous gold as an effective SERS template," Nanotechnol. 22, 295302, 2011). Vanderbilt would be happy to make electronic copies of the publication available upon request.

Commercialization Issues and Plans

It is estimated that the SERS substrate market grew from approximately $1 million in 2005 to approximately $3 - 5 million in 2010. Vanderbilt believes this technology would be very competitive in this growing market and also that the barriers to entry (both technical and business) are quite low. As an academic institution, Vanderbilt seeks a commercialization partner to bring this technology to market via the licensing of the intellectual property. Ideally, the commercialization partner would collaborate with Vanderbilt researchers in the commercial packaging of the technology and sorting out the large-scale manufacturing issues. An attractive feature of this technology is that it uses simple, routinely used commercial techniques of manufacture.

In terms of intellectual property, Vanderbilt has applied for patent protection for both the substrate technology and the imprinting technology.