Since discovering porous gold nanoparticles three years ago, Wei-Chuan Shih continues to be busy in exploring its science and potential applications. Due to its porous nature, gold nanoparticles possess a larger surface area. Wei-Chuan Shih is an associate professor of electrical and computer engineering, and is being financially supported by the National Science Foundation to research electron oscillation in the nanoparticles and formulate methods to harness it.
Shih’s lab, the NanoBioPhotonics Group at University of Houston, has investigated the way porous gold nanoparticles react to light for many years, and last spring he claimed that the light-converted heat can be utilized to kill bacteria. Similarly, he also reported in Nano Letters, last month, that surface (plasmon)-enhanced near-infrared absorption was used for the first time to demonstrate chemical detection and identification.
We can generate hot electrons by shining light on these nanoparticles, so we are trying to take advantage of that, trying to find a way to make them work.
He explained that light at specific wavelengths tends to excite the electrons, or can cause them to move. In order to exploit the energy produced by the moving electrons, measuring what happened over minute fractions of time is required.
When the nanoparticle is exposed to light, the electrons begin to move within one quadrillionth of a second or a few femtoseconds. The electron oscillation starts to convert to heat after one trillionth of a second or a few picoseconds.
It is the hot electrons within the first few femtoseconds that we would like to harvest.
Shih and his team will make use of the NSF grant to explore if the hot electrons can be utilized to improve a catalyst that stimulates chemical reactions and boosts signaling. He will analyze ways to improve that signaling and establish methods to use it.
“There is some evidence to suggest plasmonic resonance can promote catalytic reactions,” he said of the interaction of light and the nanoparticles. “The light excites these electrons to oscillate within the nanoparticle.”
Plasmonic resonance expresses the way in which electrons present in a section of metallic nanomaterial respond to light, and Shih said it occurs only at specific wavelengths.
To discover ways to speed up chemical reactions will offer huge benefits in the petrochemical or oil industry, as minor enhancements can offer large impacts. However, Shih is keen on biosensing, utilizing the chemical reactions to generate a stronger signal from minuscule targets, more rapidly.
We are interested in ultrasensitive detection of disease, including cancer biomarkers such as nucleic acids and proteins.
Improved amplification of the signal is likely to yield several applications. Shih noted that enzyme-linked immunosorbent assay (ELISA) – a test frequently applied to measure proteins in research labs – relies on a catalysis reaction to enhance the signal. Finding a means to enhance the method’s efficiency would have a range of consequences, just one instance of how the research could be constructive, he said.