The impact of nanotechnologies on the global divide

carbon-nanotube(Nanowerk News) Nanotechnologies are capable of introducing promising applications that could impact upon our daily lives; it is through the visualisation and control of matter at the scale of a billionth of a metre that allows nanotechnologies to modify and enhance the properties of products across all industry sectors. Even though nanotechnologies have immense potential, they are only in their infancy and have yet to reach full maturity. When considering the changes they could bring, it must be asked: are nanotechnologies going to reduce the rich-poor divide, or will they have the opposite effect?
Closing the Gap: The Impact of Nanotechnologies on the Global Divide


In light of debates that make nanotechnologies responsible for a further widening of the aforementioned divide, the Nanotechnology Industries Association (NIA) has published a report analysing this Nano-Gap, or Nano-Divide, by examining the pros and cons of nanotechnologies and their impact global development and the on-going fight against poverty.
Entitled “Closing the Gap: The Impact of Nanotechnologies on the Global Divide” (pdf), this report looks at how nanotechnology-based inventions and their potential applications could be implemented in developing counties, and whether they could benefit the most underprivileged populations. Obstacles and problematic issues that could arise are also scrutinised, with the following more fully addressed:

  • – Will nanotechnologies reach the populations they wish to assist?
  • – What impact could they have on world trade and already weak economies?
  • – What of the unprecedented nature and uncertainties surrounding the risks of nanotechnology?
  • – Will inventors from the developing world have to circumvent challenging intellectual property rules in order to make full use of the technology?
This subsequently leads the report into looking at the possible ways forward for the fair development of nanotechnologies. Finally, the report looks at the possibilities for scientists and entrepreneurs from low- and middle-income countries to scale-up the benefits for their countries with the help of international cooperation and global dialogue.
Source: Nanotechnology Industries Association

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Graphene Improves Oil Exploration

carbon-nanotube(Nanowerk News) Graphene holds potential for diverse applications, including battery materials, electrodes, high-speed electronics, water filtration, and solar energy harvesting. We’ve discussed most of those applications in earlier blog posts, and not a day passes without some progress in one of those directions hitting the world headlines. Little media attention, however, has been paid to a young and exciting application of graphene – oil exploration.
Most of the world’s growing energy demand is fulfilled from some form of fossil fuel, like coal and oil. It is well known that oil exploration and the energy sector are big business, but also potentially damaging to the environment. Oil spills and uncontrolled oil well explosions form just a part of the risk involved in oil exploration. Another cause for concern is the efficiency of extraction, and potential losses, or leaks of oil into the environment. Graphene is being explored for its use in various stages of the exploration and extraction process.
Much of the research on graphene for oil has come out of the lab of Prof. James Tour at Rice University. In their early work (published in 2012: “Graphene Oxide as a High-Performance Fluid-Loss-Control Additive in Water-Based Drilling Fluids”), the group first showed that adding platelets of graphene oxide to a common water-based drilling fluid decreased the losses of the fluid to the surrounding rock, as compared to a standard mixture of clays and polymers used in the drilling industry today.
Graphene platelet plugging a nanopore
Graphene platelet plugging a nanopore (from ACS Applied Materials and Interfaces 4, 222 (2012))
These fluids are pumped downhole as part of the process to keep drill bits clean and remove cuttings. With traditional clay-enhanced fluids, differential pressure forms a layer on the wellbore called a filter cake, which both keeps the oil from flowing out and drilling fluids from invading the tiny, oil-producing pores.
When the drill bit is removed and drilling fluid displaced, the formation oil forces remnants of the filter cake out of the pores as the well begins to produce. But sometimes the clay won’t budge, and the well’s productivity is reduced.
The Tour Group discovered that microscopic, pliable flakes of graphene can form a thinner, lighter filter cake (“Functionalized graphene oxide plays part in next-generation oil-well drilling fluids”). When they encounter a pore, the flakes fold in upon themselves and look something like starfish sucked into a hole. But when well pressure is relieved, the flakes are pushed back out by the oil. The thinner graphene layer budged much more easily than the the layer which would remain after a traditional clay-enhanced liquid was used. A drilling fluid with 2 percent functionalized graphene oxide formed a filter cake an average of 22 micrometers wide — substantially smaller than the 278-micrometer cake formed by traditional drilling fluids. GO blocked pores many times smaller than the flakes’ original diameter by folding.
Graphene can also be put to use for well logging. Well logging techniques provide data on the geological properties of reservoirs of interest to the oil and gas exploration industry. A commonly used logging technique uses wirelines to provide information about an oil or gas well. Wirelines are long wires with sensors attached to them, which are lowered into an exploration hole to provide information about the hole and its contents. An extension of wireline logging is logging-while-drilling, which relies on sensors at the end of the drill itself. Both methods utilize oil-based fluids for drilling and lubrication. Oil-based fluids, however, are not very good conductors of electricity, which is where graphene enters the scene. The group of Tour developed a solution that contains magnetic graphene nanoribbons (MGNRs). The MGNRs form part of a conductive coating in oil-based drilling fluids, improving the reliability of the information that is sent back up the hole by the sensors. Furthermore, the magnetic properties of the ribbons could also be exploited for using the ribbons themselves as advanced sensors. The Tour group filed a patent for this application.
Finally, since graphene nanoribbons can be made small enough to pass into tiny crevices of the rock which holds precious oil, some envision little graphene-based robots creeping through rocks, sending wireless data which contains information on oil location and concentration.
Source: By  Marko Spasenovic, Graphenea

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Quantum Dots from a Familiar Energy Source, Coal: Video

201306047919620The prospect of turning coal into fluorescent particles may sound too good to be true, but the possibility exists, thanks to scientists at Rice University.

The Rice lab of chemist James Tour found simple methods to reduce three kinds of coal into graphene quantum dots (GQDs), microscopic discs of atom-thick graphene oxide that could be used in medical imaging as well as sensing, electronic and photovoltaic applications.

Coal yields production of graphene quantum dots

Band gaps determine how a semiconducting material carries an electric current. In quantum dots, band gaps are responsible for their fluorescence and can be tuned by changing the dots’ size. The process by Tour and company allows a measure of control over their size, generally from 2 to 20 nanometers, depending on the source of the coal.


An illustration shows the nanostructure of bituminous coal before separation into graphene quantum dots. Courtesy of the Tour Group

There are many ways to make GQDs now, but most are expensive and produce very small quantities, Tour said. Though another Rice lab found a way last year to make GQDs from relatively cheap carbon fiber, coal promises greater quantities of GQDs made even cheaper in one chemical step, he said.

“We wanted to see what’s there in coal that might be interesting, so we put it through a very simple oxidation procedure,” Tour explained. That involved crushing the coal and bathing it in acid solutions to break the bonds that hold the tiny graphene domains together.

“You can’t just take a piece of graphene and easily chop it up this small,” he said.

Tour depended on the lab of Rice chemist and co-author Angel Martí to help characterize the product. It turned out different types of coal produced different types of dots. GQDs were derived from bituminous coalanthracite and coke, a byproduct of oil refining.

Graphene quantum dots

An electron microscope image shows the stacking layer structure of graphene quantum dots extracted from anthracite. The scale bar equals 100 nanometers. Courtesy of the Tour Group.

The coals were each sonicated in nitric and sulfuric acids and heated for 24 hours. Bituminous coal produced GQDs between 2 and 4 nanometers wide. Coke produced GQDs between 4 and 8 nanometers, and anthracite made stacked structures from 18 to 40 nanometers, with small round layers atop larger, thinner layers. (Just to see what would happen, the researchers treated graphite flakes with the same process and got mostly smaller graphite flakes.)

Tour said the dots are water-soluble, and early tests have shown them to be nontoxic. That offers the promise that GQDs may serve as effective antioxidants, he said.

Medical imaging could also benefit greatly, as the dots show robust performance as fluorescent agents.

“One of the problems with standard probes in fluorescent spectroscopy is that when you load them into a cell and hit them with high-powered lasers, you see them for a fraction of a second to upwards of a few seconds, and that’s it,” Martí said. “They’re still there, but they have been photo-bleached. They don’t fluoresce anymore.”

Testing in the Martí lab showed GQDs resist bleaching. After hours of excitation, Martí said, the photoluminescent response of the coal-sourced GQDs was barely affected.

Rice University chemist James Tour, left, and graduate student Ruquan Ye show the source and destination of graphene quantum dots extracted from coal in a process developed at Rice. Tour said the fluorescent particles can be drawn in bulk from coal in a one-step process. Photo by Jeff Fitlow

That could make them suitable for use in living organisms. “Because they’re so stable, they could theoretically make imaging more efficient,” he said.

A small change in the size of a quantum dot – as little as a fraction of a nanometer – changes its fluorescent wavelengths by a measurable factor, and that proved true for the coal-sourced GQDs, Martí said.

Low cost will also be a draw, according to Tour. “Graphite is $2,000 a ton for the best there is, from the U.K.,” he said. “Cheaper graphite is $800 a ton from China. And coal is $10 to $60 a ton.

“Coal is the cheapest material you can get for producing GQDs, and we found we can get a 20 percent yield. So this discovery can really change the quantum dot industry. It’s going to show the world that inside of coal are these very interesting structures that have real value.”

Co-authors of the work include graduate students Ruquan Ye, Changsheng Xiang, Zhiwei Peng, Kewei Huang, Zheng Yan, Nathan Cook, Errol Samuel, Chih-Chau Hwang, Gedeng Ruan, Gabriel Ceriotti and Abdul-Rahman Raji and postdoctoral research associate Jian Lin, all of Rice. Martí is an assistant professor of chemistry and bioengineering. Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science.

The Air Force Office of Scientific Research and the Office of Naval Research funded the work through their Multidisciplinary University Research Initiatives.

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Microscale garbage “collectors” cleans polluted water

By Michael Berger. Copyright © Nanowerk

3D rendered Molecule (Abstract) with Clipping Path(Nanowerk Spotlight) The construction of artificial micro- and nanomotors is a high priority in the nanotechnology field owing to their great potential for diverse potential applications, ranging from targeted drug delivery, on-chip diagnostics and biosensing, or pumping of fluids at the microscale to environmental remediation.

Particular attention has been given to self-propelled chemically-powered micro/nanoscale motors, such as catalytic nanowires (read more: “”Another nanotechnology step towards ‘Fantastic Voyage'”), microtube engines (read more: “Microbots transport, assemble and deliver micro- and nanoscale objects”) or spherical Janus microparticles (read more: “Novel motor system powered by polymerization”). In new work, researchers in Germany have now reported the first example of micromotors for the active degradation of organic pollutants in solution.

The novelty of this work lies in the synergy between internal and external functionality of the micromotors. “Previously, some groups tried to demonstrate the use of catalytic nanomotors for biomedical applications – including ours – on-chip biosensors and capture of bio species,” Dr. Samuel Sánchez, Group Leader Smart Nano-Bio-Systems, Max Planck Institute for Intelligent Systems, tells Nanowerk. “However, the toxicity of the fuel employed still limits their real applications. We imagined that environmental applications might be another field to explore, where the use of hydrogen peroxide is not controversial.” In that direction, Wang’s group reported the removal of oil droplets (“‘Microsubmarines’ designed to help clean up oil spills”) from solution, not degrading them.

Now, Sánchez and his collaborators went one step beyond that and demonstrated the total removal of contaminants using micromotors. Indeed, the chemical is used for the self-propulsion and for the remediation when interacts with the outer layer of the micromachine. “We have demonstrated the ability of self-propelled micromotors to oxidize organic pollutants in aqueous solutions through a Fenton process,” explains Sánchez.

“The combination of mixing and releasing iron ions in liquids results in a rate of removal of model pollutant (rhodamine 6G) ca. 12 times higher than when the Fenton oxidation process is carried out with nonpropelling metallic iron tubes.” Reporting their results in The November 1, 2013 online edition of ACS Nano (“Self-Propelled Micromotors for Cleaning Polluted Water”), the research team from Max Planck, the Leibniz Institute for Solid State and Materials Research Dresden, and the Chemnitz University of Technology demonstrates that micromotors boost the Fenton oxidation process (read more about Fenton reactions at the bottom of this article) without applying external energy, and complete degradation of organic pollutants is achieved.


          Schematic process for the degradation of polluted water into inorganic products by multifunctional micromotors

Schematic process for the degradation of polluted water (rhodamine 6G as model contaminant) into inorganic products by multifunctional micromotors. The self propulsion is achieved by the catalytic inner layer (Pt), which provides the motion of the micromotors in H2O2 solutions. The remediation of polluted water is achieved by the combination of Fe2+ ions with peroxide, generating OH• radicals, which degrade organic pollutants. (Reprinted with permission from American Chemical Society)

Sánchez notes that, if desired, the micromotors can be easily recovered using a magnet once the water purification process has been completed and the excess of hydrogen peroxide can be easily decomposed to pure water and oxygen under visible light. The team fabricated their tubular bubble-propelled micromotors containing small amounts of metallic iron (from 20 to 200 nm layer thickness) as outer layer and platinum as inner layer. The mechanism of degradation is based on Fenton reactions relying on spontaneous acidic corrosion of the iron metal surface of the micromotors in the presence of hydrogen peroxide, which acts both as a reagent for the Fenton reaction and as main fuel to propel the micromotors.

Moreover, the ability of self-propelled, tubular micromotors to improve mixing results in a synergetic effect that enhances water remediation without applying external energy. This work can pave the way for the use of multifunctional micromotors for environmental applications where the use of hydrogen peroxide is not a major drawback but a co-reagent. Sánchez adds that the high efficiency of the oxidation of organic pollutants achieved by the Fe/Pt catalytic micromotors reported in this work is of importance for the design of new and faster water treatments, such as the decontamination of organic compounds in wastewaters and industrial effluents. The aim of this study was to fabricate an autonomous microscopic cleaning system that is working without external energy input in a much faster and convenient way.

The micromotors offer this ability to move the catalyst around without external actuation or addition of catalyst (iron salts) to achieve water remediation, removal of organic dyes, etc. However, as the researchers point out, this is an application especially for microscale environments. “It is, unfortunately, clear that we would not use the micromotors in a large reactor vessel to clean huge amounts of water,” says Sánchez. Nevertheless, the high efficiency of the oxidation of organic pollutants achieved by the Fe/Pt catalytic micromotors reported here is of importance for the design of new and faster water treatments, such as the decontamination of organic compounds in wastewaters and industrial effluents.

“We have proven that the usefulness of the micromotors lies not solely in their capacity to move, but to exploit their motion using their external surface to enhance useful catalytic reactions,” says Sánchez. “This work could open a new research line towards coupling a variety of catalytic reactions in self-propelled devices where the presence of hydrogen peroxide is not a disadvantage. We expect that a rich variety of contaminants can be in the next years be cleaned.”

Watch the micromotor in action. A synergetic effect is achieved taking advantage of the release of the iron ions from the outer layer of the micromotors and their active motion in the solution.

About Fenton reactions The Fenton method is one of the most popular advanced oxidation processes for the degradation of organic pollutants, utilizing the hydroxyl radical (OH•) as its main oxidizing agent. The generation of OH• in the Fenton method occurs by reaction of H2O2 in the presence of Fe(II). However, one disadvantage of these processes is that Fe ions in solution must be removed after the treatment to meet regulations for drinking water. In order to diminish and, in the best scenario, solve the problems caused by the presence of Fe ions in treated effluents and decrease the costs of recovery, the use of heterogeneous Fenton catalysts is a promising strategy that could allow for the degradation of pollutants by Fenton processes without the requirement of dissolved iron salts. The micromotors fabricated in this work can be included as a new type of heterogeneous Fenton catalyst. With this method the remaining iron in the solution is one to three orders of magnitude lower than in conventional Fenton processes.

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