Tag Archives: nitrogen

Low-cost carbon sequestration and eco-friendly manufacturing for chemicals with nanobio hybrid organisms

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Years ago I was asked about carbon sequestration and nanotechnology and could not come up with any examples. At last I have something for the next time the question is asked. From a June 11, 2019 news item on ScienceDaily,

University of Colorado Boulder researchers have developed nanobio-hybrid organisms capable of using airborne carbon dioxide and nitrogen to produce a variety of plastics and fuels, a promising first step toward low-cost carbon sequestration and eco-friendly manufacturing for chemicals.

By using light-activated quantum dots to fire particular enzymes within microbial cells, the researchers were able to create “living factories” that eat harmful CO2 and convert it into useful products such as biodegradable plastic, gasoline, ammonia and biodiesel.

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A June 11, 2019 University of Colorado at Boulder news release (also on EurekAlert) by Trent Knoss, which originated the news item, provides a deeper dive into the research,

“The innovation is a testament to the power of biochemical processes,” said Prashant Nagpal, lead author of the research and an assistant professor in CU Boulder’s Department of Chemical and Biological Engineering. “We’re looking at a technique that could improve CO2 capture to combat climate change and one day even potentially replace carbon-intensive manufacturing for plastics and fuels.”

The project began in 2013, when Nagpal and his colleagues began exploring the broad potential of nanoscopic quantum dots, which are tiny semiconductors similar to those used in television sets. Quantum dots can be injected into cells passively and are designed to attach and self-assemble to desired enzymes and then activate these enzymes on command using specific wavelengths of light.

Nagpal wanted to see if quantum dots could act as a spark plug to fire particular enzymes within microbial cells that have the means to convert airborne CO2 and nitrogen, but do not do so naturally due to a lack of photosynthesis.

By diffusing the specially-tailored dots into the cells of common microbial species found in soil, Nagpal and his colleagues bridged the gap. Now, exposure to even small amounts of indirect sunlight would activate the microbes’ CO2 appetite, without a need for any source of energy or food to carry out the energy-intensive biochemical conversions.

“Each cell is making millions of these chemicals and we showed they could exceed their natural yield by close to 200 percent,” Nagpal said.

The microbes, which lie dormant in water, release their resulting product to the surface, where it can be skimmed off and harvested for manufacturing. Different combinations of dots and light produce different products: Green wavelengths cause the bacteria to consume nitrogen and produce ammonia while redder wavelengths make the microbes feast on CO2 to produce plastic instead.

The process also shows promising signs of being able to operate at scale. The study found that even when the microbial factories were activated consistently for hours at a time, they showed few signs of exhaustion or depletion, indicating that the cells can regenerate and thus limit the need for rotation.

“We were very surprised that it worked as elegantly as it did,” Nagpal said. “We’re just getting started with the synthetic applications.”

The ideal futuristic scenario, Nagpal said, would be to have single-family homes and businesses pipe their CO2 emissions directly to a nearby holding pond, where microbes would convert them to a bioplastic. The owners would be able to sell the resulting product for a small profit while essentially offsetting their own carbon footprint.

“Even if the margins are low and it can’t compete with petrochemicals on a pure cost basis, there is still societal benefit to doing this,” Nagpal said. “If we could convert even a small fraction of local ditch ponds, it would have a sizeable impact on the carbon output of towns. It wouldn’t be asking much for people to implement. Many already make beer at home, for example, and this is no more complicated.”

The focus now, he said, will shift to optimizing the conversion process and bringing on new undergraduate students. Nagpal is looking to convert the project into an undergraduate lab experiment in the fall semester, funded by a CU Boulder Engineering Excellence Fund grant. Nagpal credits his current students with sticking with the project over the course of many years.

“It has been a long journey and their work has been invaluable,” he said. “I think these results show that it was worth it.”

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

Nanorg Microbial Factories: Light-Driven Renewable Biochemical Synthesis Using Quantum Dot-Bacteria Nanobiohybrids by Yuchen Ding, John R. Bertram, Carrie Eckert, Rajesh Reddy Bommareddy, Rajan Patel, Alex Conradie, Samantha Bryan, Prashant Nagpal. J. Am. Chem. Soc.2019XXXXXXXXXX-XXX DOI: https://doi.org/10.1021/jacs.9b02549 Publication Date:June 7, 2019
Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Gold nanoparticles not always always biologically stable

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It’s usually silver nanoparticles (with a nod to titanium dioxide as another problem nanoparticle) which star in scenarios regarding environmental concerns, especially with water. According to an Aug. 28, 2018 news item on Nanowerk, gold nanoparticles under certain conditions could also pose problems,

It turns out gold isn’t always the shining example of a biologically stable material that it’s assumed to be, according to environmental engineers at Duke’s Center for the Environmental Implications of NanoTechnology (CEINT).

In a nanoparticle form, the normally very stable, inert, noble metal actually gets dismantled by a microbe found on a Brazilian aquatic weed.

While the findings don’t provide dire warnings about any unknown toxic effects of gold, they do provide a warning to researchers on how it is used in certain experiments.

Here’s an image of one of the researchers standing in the test bed where they made their discovery (the caption will help to make sense of the reference to mesocosms in the news release, which follows,,

Mark Wiesner stands with rows of mesocosms—small, manmade structures containing different plants and microorganisms meant to represent a natural environment with experimental controls. Courtesy: Duke University

An August 28, 2018 Duke University news release (also on EurekAlert) by Ken Kingery, which originated the news item, provides more detail about gold nanoparticle instability,

CEINT researchers from Duke, Carnegie Mellon and the University of Kentucky were running an experiment to investigate how nanoparticles used as a commercial pesticide affect wetland environments in the presence of added nutrients. Although real-world habitats often receive doses of both pesticides and fertilizers, most studies on the environmental effects of such compounds only look at a single contaminant at a time.

For nine months, the researchers released low doses of nitrogen, phosphorus and copper hydroxide nanoparticles into wetland mesocosms [emphasis mine]– small, manmade structures containing different plants and microorganisms meant to represent a natural environment with experimental controls. The goal was to see where the nanoparticle pesticides ended up and how they affected the plant and animal life within the mesocosm.

The researchers also released low doses of gold nanoparticles as tracers, assuming the biologically inert nanoparticles would remain stable while migrating through the ecosystem. This would help the researchers interpret data on the pesticide particles that partly dissolve by showing them how a solid metal particle acts within the system.

But when the researchers went to analyze their results, they found that many of the gold nanoparticles had been oxidized and dissolved.

“We were taken completely by surprise,” said Mark Wiesner, the James B. Duke Professor and chair of civil and environmental engineering at Duke. “The nanoparticles that were supposed to be the most stable turned out to be the least stable of all.”

After further inspection, the researchers found the culprit — the microbiome growing on a common Brazilian waterweed called Egeria densa. Many bacteria secrete chemicals to essentially mine metallic nutrients from their surroundings. With their metabolism spiked by the experiment’s added nutrients, the bacteria living on the E. densa were catalyzing the reaction to dissolve the gold nanoparticles.

This process wouldn’t pose any threat [emphasis mine] to humans or other animal species in the wild. But when researchers design experiments with the assumption that their gold nanoparticles will remain intact, the process can confound the interpretation of their results.

“The assumption that gold is inert did not hold in these experiments,” said Wiesner. “This is a good lesson that underscores how real, complex environments, that include for example the bacteria growing on leaves, can give very different results from experiments run in a laboratory setting that do not include these complexities.”

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

Gold nanoparticle biodissolution by a freshwater macrophyte and its associated microbiome by Astrid Avellan, Marie Simonin, Eric McGivney, Nathan Bossa, Eleanor Spielman-Sun, Jennifer D. Rocca, Emily S. Bernhardt, Nicholas K. Geitner, Jason M. Unrine, Mark R. Wiesner, & Gregory V. Lowry. Nature Nanotechnology (2018) DOI: https://doi.org/10.1038/s41565-018-0231-y Published

This paper is behind a paywall.

Boron nitride nanotubes

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Most of the talk about nanotubes is focused on carbon nanotubes but there are other kinds as a May 21, 2018 Rice University news release (also received via email and on EurekAlert and in a May 21, 2018 news item on ScienceDaily), notes,

Boron nitride nanotubes are primed to become effective building blocks for next-generation composite and polymer materials based on a new discovery at Rice University – and a previous one.

Scientists at known-for-nano Rice have found a way to enhance a unique class of nanotubes using a chemical process pioneered at the university. The Rice lab of chemist Angel Martí took advantage of the Billups-Birch reaction process to enhance boron nitride nanotubes.

The work is described in the American Chemical Society journal ACS Applied Nano Materials.

Boron nitride nanotubes, like their carbon cousins, are rolled sheets of hexagonal arrays. Unlike carbon nanotubes, they’re electrically insulating hybrids made of alternating boron and nitrogen atoms.

Insulating nanotubes that can be functionalized will be a valuable building block for nanoengineering projects, Martí said. “Carbon nanotubes have outstanding properties, but you can only get them in semiconducting or metallic conducting types,” he said. “Boron nitride nanotubes are complementary materials that can fill that gap.”

Until now, these nanotubes have steadfastly resisted functionalization, the “decorating” of structures with chemical additives that allows them to be customized for applications. The very properties that give boron nitride nanotubes strength and stability, especially at high temperatures, also make them hard to modify for their use in the production of advanced materials.

But the Billups-Birch reaction developed by Rice Professor Emeritus of Chemistry Edward Billups, which frees electrons to bind with other atoms, allowed Martí and lead author Carlos de los Reyes to give the electrically inert boron nitride nanotubes a negative charge.

That, in turn, opened them up to functionalization with other small molecules, including aliphatic carbon chains.

“Functionalizing the nanotubes modifies or tunes their properties,” Martí said. “When they’re pristine they are dispersible in water, but once we attach these alkyl chains, they are extremely hydrophobic (water-avoiding). Then, if you put them in very hydrophobic solvents like those with long-chain hydrocarbons, they are more dispersible than their pristine form.

“This allows us to tune the properties of the nanotubes and will make it easier to take the next step toward composites,” he said. “For that, the materials need to be compatible.”

After he discovered the phenomenon, de los Reyes spent months trying to reproduce it reliably. “There was a period where I had to do a reaction every day to achieve reproducibility,” he said. But that turned out to be an advantage, as the process only required about a day from start to finish. “That’s the advantage over other processes to functionalize carbon nanotubes. There are some that are very effective, but they may take a few days.”

The process begins with adding pure ammonia gas to the nanotubes and cooling it to -70 degrees Celsius (-94 degrees Fahrenheit). “When it combines with sodium, lithium or potassium — we use lithium — it creates a sea of electrons,” Martí said. “When the lithium dissolves in the ammonia, it expels the electrons.”

The freed electrons quickly bind with the nanotubes and provide hooks for other molecules. De los Reyes enhanced Billups-Birch when he found that adding the alkyl chains slowly, rather than all at once, improved their ability to bind.

The researchers also discovered the process is reversible. Unlike carbon nanotubes that burn away, boron nitride nanotubes can stand the heat. Placing functionalized boron nitride tubes into a furnace at 600 degrees Celsius (1,112 degrees Fahrenheit) stripped them of the added molecules and returned them to their nearly pristine state.

“We call it defunctionalization,” Martí said. “You can functionalize them for an application and then remove the chemical groups to regain the pristine material. That’s something else the material brings that is a little different.”

The researchers have provided this pretty illustration of boron nitride nanotube,

Caption: Rice University researchers have discovered a way to ‘decorate’ electrically insulating boron nitride nanotubes with functional groups, making them more suitable for use with polymers and composite materials. Credit: Martí Research Group/Rice University

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

Chemical Decoration of Boron Nitride Nanotubes Using the Billups-Birch Reaction: Toward Enhanced Thermostable Reinforced Polymer and Ceramic Nanocomposites by Carlos A. de los Reyes, Kendahl L. Walz Mitra, Ashleigh D. Smith, Sadegh Yazdi, Axel Loredo, Frank J. Frankovsky, Emilie Ringe, Matteo Pasquali, and Angel A. Martí. ACS Appl. Nano Mater., Article ASAP DOI: 10.1021/acsanm.8b00633 Publication Date (Web): May 16, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Graphene flakes bring spintronics a step closer?

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Italian researchers are hoping that graphene flakes will be instrumental in the development of spintronics according to a March 14, 2018 news item on phys.org,

Graphene nanoflakes are promising for possible applications in the field of nanoelectronics, and the subject of a study recently published in Nano Letters. These hexagonal nanostructures exhibit quantum effects for modulating current flow. Thanks to their intrinsic magnetic properties, they could also represent a significant step forward in the field of spintronics. The study, conducted via computer analysis and simulations, was led by Massimo Capone.

A March 14, 2018 Scuola Internazionale Superiore di Studi Avanzati (SISSA) press release (also on EurekAlert), which originated the news item, expands on the theme,

“We have been able to observe two key phenomena by analysing the properties of graphene nanoflakes. Both are of great interest for possible future applications” explain Angelo Valli and Massimo Capone, authors of the study together with Adriano Amaricci and Valentina Brosco. The first phenomenon deals with the so-called interference between electrons and is a quantum phenomenon: «In nanoflakes, the electrons interfere with each other in a “destructive” manner if we measure the current in a certain configuration. This means that there is no transmission of current. This is a typically quantum phenomenon, which only occurs at very reduced sizes. By studying the graphene flakes we have understood that it is possible to bring this phenomenon to larger systems, therefore into the nano world and on a scale in which it is observable and can be exploited for possible uses in nanoelectronics». The two researchers explain that in what are called “Quantum interference transistors” destructive interference would be the “OFF” status. For the “ON” status, they say it is sufficient to remove the conditions for interference, thereby enabling the current to flow.

Magnetism and spintronics

But there’s more. In the study, the researchers demonstrated that the nanoflakes present new magnetic properties which are absent, for example, in an entire sheet of graphene: «The magnetism emerges spontaneously at their edges, without any external intervention. This enables the creation of a spin current». The union between the phenomena of quantum interference and of magnetism would allow to obtain almost complete spin polarization, with a huge potential in the field of spintronics, explain the researchers. These properties could be used, for example, in the memorising and processing information technologies, interpreting the spin as binary code. The electron spin, being quantised and having only two possible configurations (which we could call “up” and “down”), is very well suited for this kind of implementation.

Next step: the experimental test

To improve the efficiency of the possible device and the percentage of current polarization the researchers have also developed a protocol that envisages the interaction of the graphene flakes with a surface made of nitrogen and boron. «The results obtained are really interesting. This evidence now awaits the experimental test, to confirm what we have theoretically predicted» concludes Massimo Capone, head of the research and recently awarded the title of Outstanding Referee by the American Physical Society journal; in this way, each year, the journal indicates the male and female scientists who have distinguished themselves for their expertise in collaborating with the journal.

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

Quantum Interference Assisted Spin Filtering in Graphene Nanoflakes by Angelo Valli, Adriano Amaricci, Valentina Brosco, and Massimo Capone. Nano Lett., 2018, 18 (3), pp 2158–2164 DOI: 10.1021/acs.nanolett.8b00453 Publication Date (Web): February 23, 2018

Copyright © 2018 American Chemical Society

This paper is behind a paywall.

Self-cleaning clothes

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There’s a new cotton fabric that will self-clean when exposed to sunlight. From the Dec. 14, 2011 news item on Nanowerk,

Mingce Long and Deyong Wu say their fabric uses a coating made from a compound of titanium dioxide, the white material used in everything from white paint to foods to sunscreen lotions. Titanium dioxide breaks down dirt and kills microbes when exposed to some types of light. It already has found uses in self-cleaning windows, kitchen and bathroom tiles, odor-free socks and other products. Self-cleaning cotton fabrics have been made in the past, the authors note, but they self-clean thoroughly only when exposed to ultraviolet rays. So they set out to develop a new cotton fabric that cleans itself when exposed to ordinary sunlight.

Their report describes cotton fabric coated with nanoparticles made from a compound of titanium dioxide and nitrogen. They show that fabric coated with the material removes an orange dye stain when exposed to sunlight. Further dispersing nanoparticles composed of silver and iodine accelerates the discoloration process. The coating remains intact after washing and drying.

It’s nice to see that the coating doesn’t wash or dry off easily. Long’s and Wu’s report appears in the ACS [American Chemical Society] Applied Materials & Interfaces (“Realizing Visible-Light-Induced Self-Cleaning Property of Cotton through Coating N-TiO2 Film and Loading AgI Particles”).  Mingce Long is from the  School of Environmental Science and Engineering, Shanghai Jiao Tong University, China  and Deyong Wu is from the School of Chemical and Environmental Engineering, Hubei University for Nationalities, China.

Dexter Johnson of the Nanoclast blog on the IEEE website (Institute of Electrical and Electronics Engineers) notes this in his Dec. 22, 2011 posting,

… This is not just cotton treated with TiO2 but cotton treated with a mix of silver iodide (Agl) along with Nitrogen (N)-TiO2. This combination increased the photocatalytic activities of the material.

So, this is what I find so infuriating about coverage of nanotechnology. Couldn’t someone (besides me) have said that researchers had found a way of improving the photocatalytic performance of TiO2 in textiles so as to make their self-cleaning properties X times better than previous methods?

There you have it from an engineer who’s been the nanotech scene for quite some time. The concept of coating a textile with nanoscale titanium dioxide so it self-cleans is not new; the discovery in this case is a refinement which increased the photocatalytic properties of the textile in question.