Tag Archives: selenium

Effects of soil contamination could be blunted with nanonutrients

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An October 15, 2024 news item on phys.org highlights research into soil remediation, Note: A link has been removed,

One of the pressing problems that the world faces in the era of climate change is how to grow enough healthy food to meet the increasing global population, even as soil contamination rises. Research recently published in Nature Food by an international team of scientists led by the University of Massachusetts Amherst, Guangdong University of Technology, and Central South University of Forestry and Technology, has shown that nutrients on the nanometer scale can not only blunt some of the worst effects of heavy metal and metalloid contamination, but increase crop yields and nutrient content.

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Caption: Nanomaterials can enter plants through above-ground tissues and root tissues. Soil rhizosphere microorganisms, soil particles, organic matter and rhizosphere deposits can also influence NM uptake in plants. Credit: 10.1038/s43016-024-01063-1 Courtesy of University of Massachusetts Amherst

An October 15, 2024 University of Massachusetts Amherst news release (also on EurekAlert), which originated the news item, describes the problem and the proposed solution, Note: Links have been removed,

“Much of the world’s arable soil is contaminated by heavy metals, like cadmium, lead and mercury, as well as metalloids, like arsenic and selenium,” says Baoshan Xing, University Distinguished Professor and director of the Stockbridge School of Agriculture at UMass Amherst. Xing, who is also the paper’s senior author, notes that such contamination puts severe stress on the ability to grow staple crops, which also affects the nutritional value of the crops that manage to survive. “We need to come up with solutions to reduce the heavy metals that wind up in our food,” says Xing, and one approach that has shown promise is the use of nutrients at nanoscale, or what he calls a “nano-enabled” agriculture.


The bulk fertilizers that you may be more familiar with are made up of large particles, which aren’t as readily absorbed by the crop. This means that farmers need to apply more, which then increases the levels of fertilizer runoff into streams, lakes and the ocean. However, crop nutrients at the nanometer scale can be specifically designed and mixed for particular crops, growing conditions and application methods, and engineered so that the target plant can most efficiently absorb the nutrients into its system, cutting down on the amount of fertilizer needed, keeping costs down and limiting runoff.

Though nanomaterials are already available on the agricultural market and have plenty of peer-reviewed science looking at their effect on the soil and crop growth, Xing and his colleagues’ research is the first comprehensive account of the effectiveness of nanomaterials as a class, with results that offer practical insights to help steer sustainable agriculture and global food safety.

“We collected data from 170 previous publications on the effectiveness of nanoparticles in reducing heavy metal and metalloid uptake,” says Chuanxin Ma, the paper’s co-lead author who completed his doctoral training at UMass Amherst’s Stockbridge School of Agriculture and is now a professor at China’s Guangdong University of Technology. “From those 170 papers, we collected 8,585 experimental observations of how plants respond to nanomaterials.”

The team then conducted a meta-analysis on this enormous trove of data, running it through a series of machine-learning models to quantify the effect of nanomaterials on crop growth and metal and metalloid uptake, before finally testing a flexible quantitative approach, known as the “IVIF-TOPSIS-EW method,” that can illuminate how to choose different types of nanomaterials according to a range of realistic agricultural scenarios.

The results show that nanomaterials are more effective than conventional fertilizers at mitigating the harmful effects of polluted soil (by 38.3%), can enhance crop yields (by 22.8%) and the nutritional value of those crops (by 30%), as well as combat plant stress (by 21.6%) due to metal and metalloid pollution. Nanomaterials also help increase soil enzymes and organic carbon, both of which help drive soil fertility.

“Of course, nanomaterials are not a silver bullet,” explains Xing. “They need to be applied in distinct ways based on the individual crop and soil.” Which is where the team’s IVIF-TOPSIS-EW method comes into play. “Our method can help policy makers choose the best course of action for their particular situation,” says Ma.

Yini Cao from Central South University of Forestry and Technology also contributed greatly to collecting and analyzing the data in this work.

This research was supported by the National Natural Science Foundation of China and the United States National Institute of Food and Agriculture (USDA).

Here’s a link to and a citation for the paper,

Engineered nanomaterials reduce metal(loid) accumulation and enhance staple food production for sustainable agriculture by Yini Cao, Chuanxin Ma, Jason C. White, Yuchi Cao, Fan Zhang, Ran Tong, Hao Yu, Yi Hao, Wende Yan, Melanie Kah & Baoshan Xing. Nature Food volume 5, pages 951–962 (2024) DOI: https://doi.org/10.1038/s43016-024-01063-1 Published: 11 October 2024 Issue Date: November 2024

This paper is behind a paywall.

The brittleness of molybdenum diselenide

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With the finding that molybdenum diselenide is not as strong as previously believed, industry may want to reconsider 2D materials before incorporating them in new products according to a Rice University (Texas, US) scientist. From a Nov. 14, 2016 news item on Nanowerk,

Scientists at Rice University have discovered that an atom-thick material being eyed for flexible electronics and next-generation optical devices is more brittle than they expected.

The Rice team led by materials scientist Jun Lou tested the tensile strength of two-dimensional, semiconducting molybdenum diselenide and discovered that flaws as small as one missing atom can initiate catastrophic cracking under strain.

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The finding may cause industry to look more carefully at the properties of 2-D materials before incorporating them in new technologies, he said.

 

A Nov. 14, 2016 Rice University news release (also on EurekAlert), which originated the news item, provides more insight into the research,

“It turns out not all 2-D crystals are equal,” said Lou, a Rice professor of materials science and nanoengineering. “Graphene is a lot more robust compared with some of the others we’re dealing with right now, like this molybdenum diselenide. We think it has something to do with defects inherent to these materials.”

The defects could be as small as a single atom that leaves a vacancy in the crystalline structure, he said. “It’s very hard to detect them,” he said. “Even if a cluster of vacancies makes a bigger hole, it’s difficult to find using any technique. It might be possible to see them with a transmission electron microscope, but that would be so labor-intensive that it wouldn’t be useful.”

Molybdenum diselenide is a dichalcogenide, a two-dimensional semiconducting material that appears as a graphene-like hexagonal array from above but is actually a sandwich of metallic atoms between two layers of chalcogen atoms, in this case, selenium. Molybdenum diselenide is being considered for use as transistors and in next-generation solar cells, photodetectors and catalysts as well as electronic and optical devices.

Lou and colleagues measured the material’s elastic modulus, the amount of stretching a material can handle and still return to its initial state, at 177.2 (plus or minus 9.3) gigapascals. Graphene is more than five times as elastic. They attributed the large variation to pre-existing flaws of between 3.6 and 77.5 nanometers.

Its fracture strength, the amount of stretching a material can handle before breaking, was measured at 4.8 (plus or minus 2.9) gigapascals. Graphene is nearly 25 times stronger.

Part of the project led by Rice postdoctoral researcher Yingchao Yang required moving molybdenum diselenide from a growth chamber in a chemical vapor deposition furnace to a microscope without introducing more defects. Yang solved the problem using a dry transfer process in place of a standard acid washing that would have ruined the samples.

To test samples, Yang placed rectangles of molybdenum diselenide onto a sensitive electron microscope platform invented by the Lou group. Natural van der Waals forces held the samples in place on springy cantilever arms that measured the applied stress.

Lou said the group attempted to measure the material’s fracture toughness, an indicator of how likely cracks are to propagate, as they had in an earlier study on graphene. But they found that pre-cutting cracks into molybdenum diselenide resulted in it shattering before stress could be applied, he said.

“The important message of this work is the brittle nature of these materials,” Lou said. “A lot of people are thinking about using 2-D crystals because they’re inherently thin. They’re thinking about flexible electronics because they are semiconductors and their theoretical elastic strength should be very high. According to our calculations, they can be stretched up to 10 percent.

“But in reality, because of the inherent defects, you rarely can achieve that much strength. The samples we have tested so far broke at 2 to 3 percent (of the theoretical maximum) at most,” Lou said. “That should still be fine for most flexible applications, but unless they find a way to quench the defects, it will be very hard to achieve the theoretical limits.”

 

When seen from above, the atoms in two-dimensional molybdenum diselenide resemble a hexagonal grid, like graphene. But in reality, the darker molybdenum atoms are sandwiched between top and bottom layers of selenide atoms. Rice University researchers tested the material for its tensile strength. Courtesy of the Lou Group

When seen from above, the atoms in two-dimensional molybdenum diselenide resemble a hexagonal grid, like graphene. But in reality, the darker molybdenum atoms are sandwiched between top and bottom layers of selenide atoms. Rice University researchers tested the material for its tensile strength. Courtesy of the Lou Group

Here’s a link to and a citation for the paper,

 

Brittle Fracture of 2D MoSe2 by Yingchao Yang, Xing Li, Minru Wen, Emily Hacopian, Weibing Chen, Yongji Gong, Jing Zhang, Bo Li, Wu Zhou, Pulickel M. Ajayan, Qing Chen, Ting Zhu, and Jun Lou. Advanced Materials DOI: 10.1002/adma.201604201 Version of Record online: 3 NOV 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.