Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Silver Cycle: New Evidence for Natural Synthesis of Silver Nanoparticles

Nanoparticles of silver are being found increasingly in the environment — and in environmental science laboratories.

Because they have a variety of useful properties, especially as antibacterial and antifungal agents, silver nanoparticles increasingly are being used in a wide variety of industrial and consumer products. This, in turn, has raised concerns about what happens to them once released into the environment. Now a new research paper* adds an additional wrinkle: Nature may be making silver nanoparticles on its own.

A team of researchers from the Florida Institute of Technology (FIT), the State University of New York (SUNY), Buffalo, and the National Institute of Standards and Technology (NIST) reports that, given a source of silver ions, naturally occurring humic acid will synthesize stable silver nanoparticles.

“Our colleague, Virender Sharma, had read an article in which they were using wine to form nanoparticles. He thought that, based on the similar chemistry, we should be able to produce silver nanoparticles with humic acids,” explains FIT chemist Mary Sohn. “First we formed them by traditional methods and then we tried one of our river sediment humic acids. We were really excited that we could see the characteristic yellow color of the nanoparticles.” Samples were sent to Sarbajit Banerjee at SUNY Buffalo and Robert MacCuspie at NIST for detailed analyses to confirm the presence of silver nanoparticles.

“Humic acid” is a complex mixture of many organic acids that are formed during the decay of dead organic matter. Although the exact composition varies from place to place and season to season, humic acid is ubiquitous in the environment. Metallic nanoparticles, MacCuspie explains, have characteristic colors that are a direct consequence of their size**. Silver nanoparticles appear a yellowish brown.

The team mixed silver ions with humic acid from a variety of sources at different temperatures and concentrations and found that acids from river water or sediments would form detectable silver nanoparticles at room temperature in as little as two to four days. Moreover, MacCuspie says, the humic acid appears to stabilize the nanoparticles by coating them and preventing the nanoparticles from clumping together into a larger mass of silver. “We believe it’s actually a similar process to how nanoparticles are synthesized in the laboratory,” he says, except that the lab process typically uses citric acid at elevated temperatures.

“This caught us by surprise because a lot of our work is focused on how silver nanoparticles may dissolve when they’re released into the environment and release silver ions,” MacCuspie says. Many biologists believe the toxicity of silver nanoparticles, the reason for their use as an antibacterial or antifungal agent, is due to their high surface area that makes them an efficient source of silver ions, he says, but “this creates the idea that there may be some sort of natural cycle returning some of the ions to nanoparticles.” It also helps explain the discovery, over the past few years, of silver nanoparticles in locations like old mining regions that are not likely to have been exposed to man-made nanoparticles, but would have significant concentrations of silver ions.

* N. Akaighe, R.I. MacCuspie, D.A. Navarro, D.S. Aga, S. Banerjee, M. Sohn and V.K. Sharma. Humic acid-induced silver nanoparticle formation under environmentally relevant conditions. Environmental Science & Technology, Published online Apr. 1, 2011.

** The effect is called “surface plasmon resonance” and is caused by surface electrons across the nanoparticle oscillating in concert.

Michael Baum | Newswise Science News
Further information:

More articles from Life Sciences:

nachricht Molecular doorstop could be key to new tuberculosis drugs
20.03.2018 | Rockefeller University

nachricht Modified biomaterials self-assemble on temperature cues
20.03.2018 | Duke University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Physicists made crystal lattice from polaritons

20.03.2018 | Physics and Astronomy

Mars' oceans formed early, possibly aided by massive volcanic eruptions

20.03.2018 | Physics and Astronomy

Thawing permafrost produces more methane than expected

20.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>