Nav: Home

Dose of vitamin C helps gold nanowires grow

February 19, 2019

HOUSTON - (Feb. 19, 2019) - A boost of vitamin C helped Rice University scientists turn small gold nanorods into fine gold nanowires.

Common, mild ascorbic acid is the not-so-secret sauce that helped the Rice lab of chemist Eugene Zubarev grow pure batches of nanowires from stumpy nanorods without the drawbacks of previous techniques.

"There's no novelty per se in using vitamin C to make gold nanostructures because there are many previous examples," Zubarev said. "But the slow and controlled reduction achieved by vitamin C is surprisingly suitable for this type of chemistry in producing extra-long nanowires."

Details of the work appear in the American Chemical Society journal ACS Nano.

The Rice lab's nanorods are about 25 nanometers thick at the start of the process - and remain that way while their length grows to become long nanowires. Above 1,000 nanometers in length, the objects are considered nanowires, and that matters. The wires' aspect ratio - length over width - dictates how they absorb and emit light and how they conduct electrons. Combined with gold's inherent metallic properties, that could enhance their value for sensing, diagnostic, imaging and therapeutic applications.

Zubarev and lead author Bishnu Khanal, a Rice chemistry alumnus, succeeded in making their particles go far beyond the transition from nanorod to nanowire, theoretically to unlimited length.

The researchers also showed the process is fully controllable and reversible. That makes it possible to produce nanowires of any desired length, and thus the desired configuration for electronic or light-manipulating applications, especially those that involve plasmons, the light-triggered oscillation of electrons on a metal's surface.

The nanowires' plasmonic response can be tuned to emit light from visible to infrared and theoretically far beyond, depending on their aspect ratios.

The process is slow, so it takes hours to grow a micron-long nanowire. "In this paper, we only reported structures up to 4 to 5 microns in length," Zubarev said. "But we're working to make much longer nanowires."

The growth process only appeared to work with pentahedrally twinned gold nanorods, which contain five linked crystals. These five-sided rods -- "Think of a pencil, but with five sides instead of six," Zubarev said -- are stable along the flat surfaces, but not at the tips.

"The tips also have five faces, but they have a different arrangement of atoms," he said. "The energy of those atoms is slightly lower, and when new atoms are deposited there, they don't migrate anywhere else."

That keeps the growing wires from gaining girth. Every added atom increases the wire's length, and thus the aspect ratio.

The nanorods' reactive tips get help from a surfactant, CTAB, that covers the flat surfaces of nanorods. "The surfactant forms a very dense, tight bilayer on the sides, but it cannot cover the tips effectively," Zubarev said.

That leaves the tips open to an oxidation or reduction reaction. The ascorbic acid provides electrons that combine with gold ions and settle at the tips in the form of gold atoms. And unlike carbon nanotubes in a solution that easily aggregate, the nanowires keep their distance from one another.

"The most valuable feature is that it is truly one-dimensional elongation of nanorods to nanowires," Zubarev said. "It does not change the diameter, so in principal we can take small rods with an aspect ratio of maybe two or three and elongate them to 100 times the length."

He said the process should apply to other metal nanorods, including silver.

The National Science Foundation and Welch Foundation supported the research.
-end-
David Ruth: 713-348-6327?david@rice.edu
Mike Williams: 713-348-6728?mikewilliams@rice.edu

Read the abstract at https://pubs.acs.org/doi/10.1021/acsnano.8b09203.

This news release can be found online at https://news.rice.edu/2019/02/19/dose-of-vitamin-c-helps-gold-nanowires-grow/

Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials:

Zubarev Research Group: http://www.owlnet.rice.edu/~zubarev/

Rice Department of Chemistry: https://chemistry.rice.edu

Wiess School of Natural Sciences: https://naturalsciences.rice.edu

Images for download:

https://news-network.rice.edu/news/files/2019/02/0225_NANOWIRE-1-WEB-1pi3kxq.jpg
Gold nanowires grown in the Rice University lab of chemist Eugene Zubarev promise to provide tunable plasmonic properties for optical and electronic applications. The wires can be controllably grown from nanorods, or reduced. (Credit: Zubarev Research Group/Rice University)

https://news-network.rice.edu/news/files/2019/02/0225_NANOWIRE-2-WEB-24vyjgb.jpg
Gold nanowires grown from nanorods show promise for sensing, diagnostic, imaging and therapeutic applications. The process discovered by the Rice University lab of chemist Eugene Zubarev is fully controllable and reversible. The scale bar equals 300 nanometers. (Credit: Zubarev Research Group/Rice University)

Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,962 undergraduates and 3,027 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 2 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

Rice University

Related Nanowires Articles:

Nanowires, the future of electronics
The current demand for small-sized electronic devices is calling for fresh approaches in their design.
Improving silver nanowires for FTCEs with flash light interactions
A Korean research team led by Professor Keon Jae Lee of the Materials Science and Engineering Department at KAIST and Dr.
UC researchers use gold coating to control luminescence of nanowires
In electronics, the race for smaller is huge. Physicists at the University of Cincinnati are working to harness the power of nanowires, microscopic wires that have the potential to improve solar cells or revolutionize fiber optics.
Obtaining of silicon nanowires becomes eco-friendly
Scientists from the Faculty of Physics, the Lomonosov Moscow State University have devised a technique of silicon nanowires synthesis.
Nanowires as sensors in new type of atomic force microscope
A new type of atomic force microscope (AFM) uses nanowires as tiny sensors.
Tiny crystals and nanowires could join forces to split water
Scientists are pursuing a tiny solution for harnessing one of the world's most abundant sources of clean energy: water.
A versatile method to pattern functionalized nanowires
A team of researchers from Hokkaido University has developed a versatile method to pattern the structure of 'nanowires,' providing a new tool for the development of novel nanodevices.
Newly discovered organic nanowires leave manmade technologies in their dust
A microbial protein fiber discovered by a Michigan State University scientist transports charges at rates high enough to be applied in manmade nanotechnologies.
New research shows how nanowires can be formed
In an article published in Nature today, researchers at Lund University in Sweden show how different arrangements of atoms can be combined into nanowires as they grow.
New type of nanowires, built with natural gas heating
A new simple, cost-effective approach that may open up an effective way to make other metallic/semiconducting nanomaterials.

Related Nanowires Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".