The discovery that water microdroplets can replace potentially toxic agents in the creation of gold nanoparticles and nanowires could help usher in a new era of “green chemistry.”
An experiment that, by design, was not supposed to turn up anything of note instead produced a “bewildering” surprise, according to the Stanford scientists who made the discovery: a new way of creating gold nanoparticles and nanowires using water droplets.
The technique, detailed April 19 in the journal Nature Communications, is the latest discovery in the new field of on-droplet chemistry and could lead to more environmentally friendly ways to produce nanoparticles of gold and other metals, said study leader Richard Zare, a chemist in the School of Humanities and Sciences and a co-founder of Stanford Bio-X.
“Being able to do reactions in water means you don’t have to worry about contamination. It’s green chemistry,” said Zare, who is the Marguerite Blake Wilbur Professor in Natural Science at Stanford.
Gold is known as a noble metal because it is relatively unreactive. Unlike base metals such as nickel and copper, gold is resistant to corrosion and oxidation, which is one reason it is such a popular metal for jewelry.
Around the mid-1980s, however, scientists discovered that gold’s chemical aloofness only manifests at large, or macroscopic, scales. At the nanometer scale, gold particles are very chemically reactive and make excellent catalysts. Today, gold nanostructures have found a role in a wide variety of applications, including bio-imaging, drug delivery, toxic gas detection and biosensors.
Until now, however, the only reliable way to make gold nanoparticles was to combine the gold precursor chloroauric acid with a reducing agent such as sodium borohydride.
The reaction transfers electrons from the reducing agent to the chloroauric acid, liberating gold atoms in the process. Depending on how the gold atoms then clump together, they can form nano-size beads, wires, rods, prisms and more.
A spritz of gold
Recently, Zare and his colleagues wondered whether this gold-producing reaction would proceed any differently with tiny, micron-size droplets of chloroauric acid and sodium borohydide. How large is a microdroplet? “It is like squeezing a perfume bottle and out spritzes a mist of microdroplets,” Zare said.
From previous experiments, the scientists knew that some chemical reactions proceed much faster in microdroplets than in larger solution volumes.
Indeed, the team observed that gold nanoparticle grew over 100,000 times faster in microdroplets. However, the most striking observation came while running a control experiment in which they replaced the reducing agent – which ordinarily releases the gold particles – with microdroplets of water.
“Much to our bewilderment, we found that gold nanostructures could be made without any added reducing agents,” said study first author Jae Kyoo Lee, a research associate.
Viewed under an electron microscope, the gold nanoparticles and nanowires appear fused together like berry clusters on a branch.
The surprise finding means that pure water microdroplets can serve as microreactors for the production of gold nanostructures. “This is yet more evidence that reactions in water droplets can be fundamentally different from those in bulk water,” said study coauthor Devleena Samanta, a former graduate student in Zare’s lab and co-author on the paper.
If the process can be scaled up, it could eliminate the need for potentially toxic reducing agents that have harmful health side effects or that can pollute waterways, Zare said.
It’s still unclear why water microdroplets are able to replace a reducing agent in this reaction. One possibility is that transforming the water into microdroplets greatly increases its surface area, creating the opportunity for a strong electric field to form at the air-water interface, which may promote the formation of gold nanoparticles and nanowires.
“The surface area atop a one-liter beaker of water is less than one square meter. But if you turn the water in that beaker into microdroplets, you will get about 3,000 square meters of surface area – about the size of half a football field,” Zare said.
The team is exploring ways to utilize the nanostructures for various catalytic and biomedical applications and to refine their technique to create gold films.
“We observed a network of nanowires that may allow the formation of a thin layer of nanowires,” Samanta said.
The Latest on: Green chemistry
via Google News
The Latest on: Green chemistry
- Legislation improves CA program to ensure safer products on February 21, 2019 at 4:50 pm
The bill would amend California’s innovative “green chemistry” program to improve its functioning and ensure better oversight of toxic chemicals in consumer products that we all bring into our homes e... […]
- Commentary: ‘Green chemistry’ makes products safer. Here’s how California can do better on February 17, 2019 at 7:00 pm
Californians’ demand for healthier products is part of a trend toward healthy living that has changed our expectations of chemistry. We led the nation a decade ago by launching a Green Chemistry ... […]
- Cleaning businesses offering more green alternatives on February 15, 2019 at 1:19 pm
In an effort to keep the environment clean, she said she began using green chemistry about 15 years ago. According to the U.S. Environmental Protection Agency, green chemistry is the design of chemica... […]
- More green chemistry from Strem Chemicals –reusable catalysts available in the UK and Ireland on February 12, 2019 at 1:42 am
CO and CO2 processing with KCC-1 silica nanoparticles showing in the fibrous form of silica support In comparison to conventional porous silica, the internal volume and surface area of KCC-1 are highl... […]
- ‘Green chemistry will help in lowering waste, by-products’ on December 6, 2018 at 11:08 am
Trichy: The ‘green chemistry’ concept will play a major role in the future as it is of utmost importance to minimise waste and unwanted by-products, said G D Yadav, vice-chancellor of Institute of Che... […]
- A Roadmap for Advancing Green Chemistry in Washington State on December 3, 2018 at 4:00 pm
Description In 2011, the Washington State Department of Ecology initiated the development of a green chemistry “roadmap” project in partnership with business, educators, government, other states, and ... […]
- Rinskor™ active Earns Green Chemistry Challenge Award on October 14, 2018 at 5:00 pm
Corteva Agriscience™, Agriculture Division of DowDuPont, Makes Sustainability a Priority INDIANAPOLIS, Oct. 15, 2018 /PRNewswire/ -- Today, Corteva Agriscience™, Agriculture Division of DowDuPont, rec... […]
- LAUNCH Forum Features Breakthrough Green Chemistry Technologies on September 2, 2018 at 4:35 am
LAUNCH founders NASA, NIKE, Inc., the U.S. Agency for International Development (USAID) and the U.S. Department of State will host the LAUNCH Green Chemistry Forum at NASA's Kennedy Space Center on Ja... […]
- Safer by Design: ‘Meta’ Review Examines on June 20, 2018 at 7:37 am
Two decades after Paul Anastas introduced the 12 principles of green chemistry, a new review paper by Anastas and other Yale researchers documents the range of scientific research and innovation that ... […]
via Bing News