Intellectual Merits: Fiber optic-based Surface-Enhanced Raman scattering (SERS) probe has many advantages, including immunity to electromagnetic interference, small and compact size, sensitivity, selectivity, multiplexing ability, remote sensing, the ability to be embedded into textile structure and detection of sub-monolayer coverage of molecules at inaccessible locations. A critical aspect of SERS fiber probe is the requirement of a specific surface morphology to achieve reproducible and high levels of enhancement. Most of the current fabrication techniques have difficulty in producing dependable, reproducible, rugged, easily fabricated and relatively inexpensive SERS probe. Recent the PIs have demonstrated that a nanofabrication technique based on glancing angle deposition (GLAD) produces Ag nanorod substrates that exhibit extremely high SERS enhancement factors. Also, in comparison with existing nanofabrication methods, the GLAD method offers several strategic advantages, including: (1) precise control of the size, shape, density, alignment, orientation and composition of the nanorod arrays, and (2) implementation of the method using relatively simple procedures. The overall objective of this project is two-fold: (1) to fundamentally understand how the nanostructural design of metallic nanorod arrays (i.e. their size, shape, orientation, lateral arrangement and composition) influences SERS enhancement; and (2) to develop optimized SERS substrates, including both planar and fiber substrates, and to integrate these substrates into fiber optic-based SERS probes. Broader Impacts: The successful development of a practical, simple and inexpensive technique for fabrication of novel nanostructures and integrated fiber Raman probes would have a large and immediate impact in the areas of: i) nanostructure fabrication and engineering, ii) fundamental surface science, iii) analytical spectroscopy, iv) chemical sensing, and v) bioanalytical applications. The PIs will also develop a lab-based nanotechnology course module to help undergraduate and high school students to obtain hands-on experience on nanofabrication.

Project Report

Fiber optic-based Surface-Enhanced Raman scattering (SERS) probes have many advantages, including immunity to electromagnetic interference, small and compact size, good sensitivity and selectivity, multiplexing ability, remote sensing, the ability to be embedded into textile structure and detection of sub-monolayer coverage of molecules at inaccessible locations. A critical aspect of a SERS fiber probe is the requirement of a specific surface morphology to achieve reproducible and high levels of enhancement. Most of the current fabrication techniques have difficulty producing dependable, reproducible, robust, easily fabricated and relatively inexpensive SERS probes. Recently the PIs have demonstrated that a nanofabrication technique based on glancing angle deposition (GLAD) produces Ag nanorod substrates that exhibit extremely high SERS enhancement factors. Also, in comparison with existing nanofabrication methods, the GLAD method offers several strategic advantages, including: (1) precise control of the size, shape, density, alignment, orientation and composition of the nanorod arrays, and (2) implementation of the method using relatively simple procedures. The overall objective of this project is two-fold: (1) to fundamentally understand how the nanostructural design of metallic nanorod arrays (i.e. their size, shape, orientation, lateral arrangement and composition) influences SERS enhancement; and (2) to develop optimized SERS substrates, including both planar and fiber substrates, and to integrate these substrates into fiber optic-based SERS probes. During the four-year NSF project period, we have focused on four aspects: (1) characterizing and optimizing the silver (Ag) nanorod SERS substrates; (2) understanding the origin of the SERS effect of these nanostructured substrates; (3) applying the SERS techniques for biological detection; and (4) integrating the Ag nanorod substrates for fiber optic sensor and microarray screening. For the SERS property characterization and substrate optimization, we have studied how different vapor incident angles, nanorod length, and underlayer thin films affect the SERS enhancement. We have found a particular structure design under a particular deposition conditions can give the maximum detection sensitivity. These optimized substrates have been routinely used for biological detection for this project and other related research projects. We have also investigated the effect of three dimensional structures on the SERS performance. In the meantime, we have looked into the fundamental mechanism of the SERS enhancement from these Ag nanorod structures. We have found that the thickness of the Ag nanorod layer plays an important role for SERS enhancement design, and the enhancement is mainly coming from the sidewall of the Ag nanorods. Based on a simple reflection and molecular orientation configuration on Ag nanorods, we have proposed a simple theoretical model that can explain many SERS phenomena related to incident laser configuration, such as polarization effect, laser incident angle effect, and the underlayer thin film effect. With the optimized SERS substrates and by collaborating with colleagues from Infectious Diseases, Food Science, and Microbiology, we have successfully applied the SERS technique for disease detection. Our experiments have demonstrated that the SERS detection technique based on the optimized Ag nanorod array substrates not only can differentiate different types of viruses and bacteria, but also distinguish different strains of virus and bacteria. The detection limit is very low and the time to obtain the detection results is within 30 s. This provides an ultrasensitive and fast sensing platform for disease diagnostics. Based on these exciting results, we have formed a start-up company named Argent Diagnostic Inc. The aim of the company is to commercialize the SERS diagnostic technology. Finally, we have investigated the possibility to integrate the Ag nanorods into different detection devices. We have shown that the Ag nanorod substrates can be directly used as a sensor chip for a fiber Raman system which makes the detection portable. We can also integrate the Ag nanorods directly onto a fiber tip to form a tiny sensing probe. The large area SERS substrate has also enabled us to design a SERS array chip for fast and reproducible screening. This project has trained one postdoctoral research associate, three graduate students, and involved four undergraduate students. Results from the project have been used in the PI’s physics lecture regarding bionanotechnology. It has produced 22 peer reviewed journal publications, 1 book chapter, 2 conference proceedings, and more than 20 conference talks and seminars.

Project Start
Project End
Budget Start
2007-07-01
Budget End
2011-06-30
Support Year
Fiscal Year
2007
Total Cost
$312,001
Indirect Cost
Name
University of Georgia
Department
Type
DUNS #
City
Athens
State
GA
Country
United States
Zip Code
30602