Deep-UV surface-enhanced resonance Raman scattering of adenine on aluminum nanoparticle arrays

The extreme accuracy and speed of NBA three-pointer Stephen Curry's long-range shots are well known to basketball fans around the world, but accuracy and speed are also a focus of research in biochemical testing. Dr. Yen Ta-Jen, professor in the Department of Materials Science and Engineering, National Tsing Hua University, Taiwan, has recently published a paper titled "Deep UV Surface-enhanced Resonance Raman Scattering of Adenine on Aluminum Nanoparticle Arrays" in the Journal of the American Chemical Society, in which he describes a new approach to light diffraction, also creating a spectral application with unmatched accuracy and speed. It is currently undergoing clinical trials for use in rapid screening for cancer and other diseases, and also has potential applications in such areas as genome screening, biomedical engineering, polymer synthesis, forensics, environmental and food safety, pharmaceuticals, and materials analysis.

Dr. Yen explains the key technology for changing normal light diffraction by referring to the opening and closing of a window blind. When the blind is closed, it prevents light from entering the room, causing it to darken. However, with the substrate Dr. Yen has developed, light is not impeded by such obstacles, instead becoming brighter. Dr. Yen said that his breakthrough is the result of 18 years of systematic and continuous research. The core technology is the nanoscale geometric cavities made on a single crystal aluminum plate substrate, which causes the light to behave in a way it can't normally do by resonant diffraction—making it possible to develop detection applications which are simple, fast, repeatable, label-free, and ultra-sensitive. What's more, whereas the other substrates reported in SERRS papers have only 1–4 Raman peaks, the substrate designed by Dr. Yen has 7–9, which greatly improves the results.

Amongst the many applications of detectors are pollution monitoring, food safety, biomedicine, and crime scene investigations; amongst the many detection methods is infrared. Raman spectroscopy is non-invasive and is less susceptible than infrared to external interference from such substances as water and carbon dioxide, but its sensitivity still had to be markedly improved. In addition, the cross section of Raman scattering is very small, so its spectroscopy analysis requires a large number of samples, which has hindered its practical application. In recent years, researchers have developed a technique called surface enhanced Raman scattering (SERS), which uses localized surface plasmon resonance to improve detection sensitivity by orders of magnitude through the interaction of light and matter. But for the detection of single molecules, SERS technology is still far from sufficient, which is what prompted Dr. Yen to come up with an innovative solution, consisting of increasing the excitation frequency of surface plasmon resonance so as to induce the Raman resonance scattering effect. In this way he succeeded in developing a surface enhanced resonant Raman scattering (SERRS) technique that can reach the deep ultraviolet band (DUV, wavelength of 266 nm).

This unique and ultra-sensitive detection technology is label-free, and has a strong local electromagnetic field and charge transfer effect, such that it can detect an extremely wide range of substances, including human nucleic acid, proteins, chemical substances, ultraviolet rays in outer space, and even the gunpowder being used in the Ukrainian-Russian War. Even with the monomer adenine (base A), with a thickness of only 1 nm, its Raman enhancement factor can be as high as ten-to-the-sixth-power times in the deep ultraviolet band, setting a new world record. The much enhanced SERRS signal of the 12-mer ss-DNA first proposed by Dr. Yen is suitable for use with all types of nucleic acid bases, as well as their sequential mutations; this mutation measured demonstrates a linear relationship to the quantity of its base A, which can be used as a quantitative detection application.

This groundbreaking technology is now being tested in clinical trials. Dr. Yen is also developing a low-cost version that can be used by consumers to test produce for excessive levels of residual agricultural chemicals.

More information:
Shankar K. Jha et al, Deep-UV Surface-Enhanced Resonance Raman Scattering of Adenine on Aluminum Nanoparticle Arrays, Journal of the American Chemical Society (2012). DOI: 10.1021/ja210446w

Provided by National Tsing Hua University