Rice – MD Anderson use Fluorescent Carbon Nanotube probes to detect ovarian cancer – Achieve first In – Vivo Success


 

 

Rice CNTs 57f79f2812948

Abstract:
Researchers at Rice University and the University of Texas MD Anderson Cancer Center have refined and, for the first time, run in vivo tests of a method that may allow nanotube-based probes to locate specific tumors in the body. Their ability to pinpoint tumors with sub-millimeter accuracy could eventually improve early detection and treatment of ovarian cancer.

The noninvasive technique relies on single-walled carbon nanotubes that can be optically triggered to emit shortwave infrared light. The Rice lab of chemist Bruce Weisman, a pioneer in the discovery and interpretation of the phenomenon, reported the new results in the American Chemical Society journal ACS Applied Materials and Interfaces.

Rice Optical Sensor CNTs 0523_SPECTRAL-1-web-txhgun

For this study, the researchers used the technique to pinpoint small concentrations of nanotubes inside rodents. The lab of co-author Dr. Robert Bast Jr., an expert in ovarian cancer and vice president for translational research at MD Anderson, inserted gel-bound carbon nanotubes into the ovaries of rodents to mimic the accumulations that are expected for nanotubes linked to special antibodies that recognize tumor cells. The rodents were then scanned with the Rice lab’s custom-built optical device to detect the faint emission signatures of as little as 100 picograms of nanotubes.

The device irradiated the rodents with intense red light from an array of light-emitting diodes and read fluorescent signals with a specialized sensitive detector. Because different types of tissue absorb emissions from the nanotubes differently, the scanner took readings from many locations to triangulate the tumor’s exact location, as confirmed by later MRI scans.

Weisman said it should be possible to noninvasively find small ovarian tumors within rodents used for medical research by linking nanotubes to antibody biomarkers and administering the biomarkers intravenously. The biomarkers would accumulate at the tumor site. He said more refined versions of the optical scanner may then be able to locate a tumor within seconds, and further advances may extend the method’s application to human cancer detection. The new results suggested that antibody-nanotube probes could potentially detect tumors with as few as 100 ovarian cancer cells, which could make it a valuable tool for early detection. Rice MD Anderson Cancer CNTs 54864

Rice graduate student Ching-Wei Lin is lead author of the paper. Co-authors from the Bast group at MD Anderson are researcher Dr. Hailing Yang and senior research assistants Weiqun Mao and Lan Pang. Rice co-authors are chemistry graduate student Stephen Sanchez and Kathleen Beckingham, a professor of biosciences.

The research was supported by the National Science Foundation, the Welch Foundation, the National Institutes of Health, the John S. Dunn Foundation Collaborative Research Award Program, the National Cancer Institute, the Cancer Prevention and Research Institute of Texas, the National Foundation for Cancer Research, the Mossy Foundation, Golfers Against Cancer, the Roberson Endowment and Stuart and Gaye Lynn Zarrow.

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About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy.

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Rice U: Long Nanotube fibers for use in Large-Scale Aerospace, Consumer Electronics and Textile Applications


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Rice University researchers advance characterization, purification of Nanotube wires and films

RICE UNIVERSITY

To make continuous, strong and conductive carbon nanotube fibers, it’s best to start with long nanotubes, according to scientists at Rice University.

The Rice lab of chemist and chemical engineer Matteo Pasquali, which demonstrated its pioneering method to spin carbon nanotube into fibers in 2013, has advanced the art of making nanotube-based materials with two new papers in the American Chemical Society’s ACS Applied Materials and Interfaces.

The first paper characterized 19 batches of nanotubes produced by as many manufacturers to determine which nanotube characteristics yield the most conductive and strongest fibers for use in large-scale aerospace, consumer electronics and textile applications.

The researchers determined the nanotubes’ aspect ratio — length versus width — is a critical factor, as is the overall purity of the batch. They found the tubes’ diameters, number of walls and crystalline quality are not as important to the product properties.

Pasquali said that while the aspect ratio of nanotubes was known to have an influence on fiber properties, this is the first systematic work to establish the relationship across a broad range of nanotube samples. Researchers found that longer nanotubes could be processed as well as shorter ones, and that mechanical strength and electrical conductivity increased in lockstep.Rice II nanotubes

The best fibers had an average tensile strength of 2.4 gigapascals (GPa) and electrical conductivity of 8.5 megasiemens per meter, about 15 percent of the conductivity of copper. Increasing nanotube length during synthesis will provide a path toward further property improvements, Pasquali said.

The second paper focused on purifying fibers produced by the floating catalyst method for use in films and aerogels. This process is fast, efficient and cost-effective on a medium scale and can yield the direct spinning of high-quality nanotube fibers; however, it leaves behind impurities, including metallic catalyst particles and bits of leftover carbon, allows less control of fiber structure and limits opportunities to scale up, Pasquali said.

“That’s where these two papers converge,” he said. “There are basically two ways to make nanotube fibers. In one, you make the nanotubes and then you spin them into fibers, which is what we’ve developed at Rice. In the other, developed at the University of Cambridge, you make nanotubes in a reactor and tune the reactor such that, at the end, you can pull the nanotubes out directly as fibers.

“It’s clear those direct-spun fibers include longer nanotubes, so there’s an interest in getting the tubes included in those fibers as a source of material for our spinning method,” Pasquali said. “This work is a first step toward that goal.”

Q Flow MODEL-OF-CARBON-NANOTUBE-PAIDThe reactor process developed a decade ago by materials scientist Alan Windle at the University of Cambridge produces the requisite long nanotubes and fibers in one step, but the fibers must be purified, Pasquali said. Researchers at Rice and the National University of Singapore (NUS) have developed a simple oxidative method to clean the fibers and make them usable for a broader range of applications.

The labs purified fiber samples in an oven, first burning out carbon impurities in air at 500 degrees Celsius (932 degrees Fahrenheit) and then immersing them in hydrochloric acid to dissolve iron catalyst impurities.

Impurities in the resulting fibers were reduced to 5 percent of the material, which made them soluble in acids. The researchers then used the nanotube solution to make conductive, transparent thin films.

“There is great potential for these disparate techniques to be combined to produce superior fibers and the technology scaled up for industrial use,” said co-author Hai Minh Duong, an NUS assistant professor of mechanical engineering. “The floating catalyst method can produce various types of nanotubes with good morphology control fairly quickly. The nanotube filaments can be collected directly from their aerogel formed in the reactor. These nanotube filaments can then be purified and twisted into fibers using the wetting technique developed by the Pasquali group.”

Pasquali noted the collaboration between Rice and Singapore represents convergence of another kind. “This may well be the first time someone from the Cambridge fiber spinning line (Duong was a postdoctoral researcher in Windle’s lab) and the Rice fiber spinning line have converged,” he said. “We’re working together to try out materials made in the Cambridge process and adapting them to the Rice process.”

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Alumnus Dmitri Tsentalovich, currently an academic visitor at Rice, is lead author of the characterization paper. Co-authors are graduate students Robert Headrick and Colin Young, research scientist Francesca Mirri and alumni Junli Hao and Natnael Behabtu, all of Rice.

Thang Tran of Rice and NUS and Headrick are co-lead authors of the catalyst paper. Co-authors are graduate student Amram Bengio and research specialist Vida Jamali, both of Rice, and research scientist Sandar Myo and graduate student Hamed Khoshnevis, both of NUS.

The Air Force Office of Scientific Research, the Welch Foundation and NASA supported both projects. The characterization project received additional support from the Department of Energy. The catalyst project received additional support from the Temasek Laboratory in Singapore.

Influence of Carbon Nanotube Characteristics on Macroscopic Fiber Properties: http://pubs.acs.org/doi/abs/10.1021/acsami.7b10968

Purification and Dissolution of Carbon Nanotube Fibers Spun from Floating Catalyst Method: http://pubs.acs.org/doi/abs/10.1021/acsami.7b09287

This news release can be found online at http://news.rice.edu/2017/10/15/long-nanotubes-make-strong-fibers/

1-blind CNTWhat Are Carbon Nanotubes and What are some of their Applications

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure.

 

 

 

These cylindrical carbonmolecules have unusual properties, which are valuable for nanotechnologyelectronicsoptics and other fields of materials science and technology. Owing to the material’s exceptional strength and stiffness, nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] significantly larger than for any other material.

In addition, owing to their extraordinary thermal conductivity, mechanical, and electrical properties, carbon nanotubes find applications as additives to various structural materials. For instance, nanotubes form a tiny portion of the material(s) in some (primarily carbon fiber) baseball bats, golf clubs, car parts or damascus steel.

 

UC Riverside: Squeezing every drop (almost 100%) of fresh water from waste brine (salt solutions)


squeezingeveHot brines used in traditional membrane distillation systems are highly corrosive, making the heat exchangers and other system elements expensive, and limiting water recovery (a). To improve this, UCR researchers developed a self-heating …more

Engineers at the University of California, Riverside have developed a new way to recover almost 100 percent of the water from highly concentrated salt solutions. The system will alleviate water shortages in arid regions and reduce concerns surrounding high salinity brine disposal, such as hydraulic fracturing waste.

The research, which involves the development of a carbon nanotube-based heating element that will vastly improve the recovery of fresh during membrane distillation processes, was published today in the journal Nature Nanotechnology. David Jassby, an assistant professor of chemical and environmental engineering in UCR’s Bourns College of Engineering, led the project.

While reverse osmosis is the most common method of removing salt from seawater, wastewater, and brackish water, it is not capable of treating highly concentrated salt solutions. Such solutions, called brines, are generated in massive amounts during reverse osmosis (as waste products) and hydraulic fracturing (as produced water), and must be disposed of properly to avoid environmental damage. In the case of , produced water is often disposed of underground in injection wells, but some studies suggest this practice may result in an increase in local earthquakes.

One way to treat brine is membrane distillation, a thermal desalination technology in which heat drives water vapor across a membrane, allowing further water recovery while the salt stays behind. However, hot brines are highly corrosive, making the heat exchangers and other system elements expensive in traditional membrane distillation systems. Furthermore, because the process relies on the heat capacity of water, single pass recoveries are quite low (less than 10 percent), leading to complicated heat management requirements.

“In an ideal scenario, thermal desalination would allow the recovery of all the water from brine, leaving behind a tiny amount of a solid, crystalline salt that could be used or disposed of,” Jassby said. “Unfortunately, current processes rely on a constant feed of hot brine over the membrane, which limits water recovery across the membrane to about 6 percent.”

To improve on this, the researchers developed a self-heating carbon nanotube-based membrane that only heats the brine at the membrane surface. The new system reduced the heat needed in the process and increased the yield of recovered water to close to 100 percent.

In addition to the significantly improved desalination performance, the team also investigated how the application of alternating currents to the heating element could prevent degradation of the carbon nanotubes in the saline environment. Specifically, a threshold frequency was identified where electrochemical oxidation of the nanotubes was prevented, allowing the nanotube films to be operated for significant lengths of time with no reduction in performance. The insights provided by this work will allow carbon nanotube-based heating elements to be used in other applications where electrochemical stability of the nanotubes is a concern.

Explore further: Researchers develop hybrid nuclear desalination technique with improved efficiency

More information: Frequency-dependent stability of CNT Joule heaters in ionizable media and desalination processes, Nature Nanotechnology, nature.com/articles/doi:10.1038/nnano.2017.102

 

Making Solar Cells Obsolete with GIT’s Optical ‘Rectenna’ Technology ~ 40% to 90% Conversion Effciency: YouTube Video


Optical Rectenna download

Georgia Tech Professor of Mechanical Engineering, Dr. Bara Cola, shares how his childhood dreams of playing professional football turned into an exciting research career and important nanoengineering innovations. Dr. Cola’s breakthrough optical rectenna technology can be viewed here https://smartech.gatech.edu/handle/18….”

Watch the YouTube Video:

 

e9cf3-nanorectannaA new kind of nanoscale rectenna (half antenna and half rectifier) can convert solar and infrared into electricity, plus be tuned to nearly any other frequency as a detector.

Right now efficiency is only one percent, but professor Baratunde Cola and colleagues at the Georgia Institute of Technology (Georgia Tech, Atlanta) convincingly argue that they can achieve 40 percent broad spectrum efficiency (double that of silicon and more even than multi-junction gallium arsenide) at a one-tenth of the cost of conventional solar cells (and with an upper limit of 90 percent efficiency for single wavelength conversion).

It is well suited for mass production, according to Cola. It works by growing fields of carbon nanotubes vertically, the length of which roughly matches the wavelength of the energy source (one micron for solar), capping the carbon nanotubes with an insulating dielectric (aluminum oxide on the tethered end of the nanotube bundles), then growing a low-work function metal (calcium/aluminum) on the dielectric and voila–a rectenna with a two electron-volt potential that collects sunlight and converts it to direct current (DC).

“Our process uses three simple steps: grow a large array of nanotube bundles vertically; coat one end with dielectric; then deposit another layer of metal,” Cola told EE Times. “In effect we are using one end of the nanotube as a part of a super-fast metal-insulator-metal tunnel diode, making mass production potentially very inexpensive up to 10-times cheaper than crystalline silicon cells.”

Read the full Article Here: Solar Cells Will be Made Obsolete by 3D rectennas aiming at 40-to-90% efficiency

 

NASA and Rice U Collaborate on’Fuzzy Fibers’ (carbide nanotubes) that can take the Heat from NextGen Rockets


Space X Rocket 31E1F88F00000578-3477542-image-a-8_1457192298353Researchers create tough material for next generation of powerful engines

To stand up to the heat and pressure of next-generation rocket engines, the composite fibers used to make them should be fuzzy.

The Rice University laboratory of materials scientist Pulickel Ajayan, in collaboration with NASA, has developed “fuzzy fibers” of silicon carbide that act like Velcro and stand up to the punishment that materials experience in aerospace applications.

Fuzzy Fibers Rice NASA 170330153941_1_540x360Silicon carbide nanotubes attached to separate silicon carbide fibers, used by NASA, entangle each other in this electron microscope image. The material created at Rice University is intended for a ceramic composite that would make rocket engines stronger, lighter and better able to withstand extreme heat.
Credit: Ajayan Research Group/Rice University

 

 

The fibers strengthen composites used in advanced rocket engines that have to withstand temperatures up to 1,600 degrees Celsius (2,912 degrees Fahrenheit). Ceramic composites in rockets now being developed use silicon carbide fibers to strengthen the material, but they can crack or become brittle when exposed to oxygen.

The Rice lab embedded silicon carbide nanotubes and nanowires into the surface of NASA’s fibers. The exposed parts of the fibers are curly and act like the hooks and loops that make Velcro so valuable — but on the nanoscale.

The result, according to lead researchers Amelia Hart, a Rice graduate student, and Chandra Sekhar Tiwary, a Rice postdoctoral associate, creates very strong interlocking connections where the fibers tangle; this not only makes the composite less prone to cracking but also seals it to prevent oxygen from changing the fiber’s chemical composition.

The work is detailed in the American Chemical Society journal Applied Materials and Interfaces.

The work began when Hart, who had been studying the growth of carbon nanotubes on ceramic wool, met Michael Meador, then a scientist at NASA’s Glenn Research Center, Cleveland, at the kickoff reception for Rice’s Materials Science and NanoEngineering Department. (Meador is now nanotechnology project manager at NASA’s Game Changing Technologies program.)

That led to a fellowship in Cleveland and the chance to combine her ideas with those of NASA research engineer and paper co-author Janet Hurst. “She was partially converting silicon carbide from carbon nanotubes,” Hart said. “We used her formulation and my ability to grow nanotubes and figured out how to make the new composite.”

Back at Rice, Hart and her colleagues grew their hooks and loops by first bathing silicon carbide fiber in an iron catalyst and then using water-assisted chemical vapor deposition, a process developed in part at Rice, to embed a carpet of carbon nanotubes directly into the surface. These become the template for the final product. The fibers were then heated in silicon nanopowder at high temperature, which converts the carbon nanotubes to silicon carbide “fuzz.”

The researchers hope their fuzzy fibers will upgrade the strong, light and heat-resistant silicon carbide fibers that, when put in ceramic composites, are being tested for robust nozzles and other parts in rocket engines. “The silicon carbide fiber they already use is stable to 1,600 C,” Tiwary said. “So we’re confident that attaching silicon carbide nanotubes and wires to add strength will make it even more cutting-edge.”

The new materials should also make entire turbo engines significantly lighter, Hart said. “Before they used silicon carbide composites, many engine parts were made of nickel superalloys that had to incorporate a cooling system, which added weight to the whole thing,” she said. “By switching to ceramic matrix composites, they could take out the cooling system and go to higher temperatures. Our material will allow the creation of larger, longer-lasting turbo jet engines that go to higher temperatures than ever before.”

Friction and compression testing showed the lateral force needed to move silicon carbide nanotubes and wires over each other was much greater than that needed to slide past either plain nanotubes or unenhanced fibers, the researchers reported. They were also able to easily bounce back from high compression applied with a nano-indenter, which showed their ability to resist breaking down for longer amounts of time.

Tests to see how well the fibers handled heat showed plain carbon nanotubes burning away from the fibers, but the silicon carbide nanotubes easily resisted temperatures of up to 1,000 C.

Hart said the next step will be to apply her conversion techniques to other carbon nanomaterials to create unique three-dimensional materials for additional applications.


Story Source:

Materials provided by Rice University. Note: Content may be edited for style and length.


Journal Reference:

  1. Amelia H.C. Hart, Ryota Koizumi, John T Hamel, Peter Samora Owuor, Yusuke Ito, Sehmus Ozden, Sanjit Bhowmick, Syed Asif Syed Amanulla, Thierry Tsafack, Kunttal Keyshar, Rahul Mital, Janet Hurst, Robert Vajtai, Chandra Sekhar Tiwary, Pulickel M Ajayan. Velcro®-Inspired SiC Fuzzy Fibers for Aerospace Applications. ACS Applied Materials & Interfaces, 2017; DOI: 10.1021/acsami.7b01378

 

Nanotube-based Li-ion Batteries Can Charge to Near Maximum in Two Minutes but …


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Nanotube-based Li-ion Batteries Can Charge to Near Maximum in Two Minutes … but could our current grid system handle an ‘en masse’ switch to EV’s?

The prospects for ubiquitous all-electric vehicles (EVs) powered by lithium-ion (Li-ion) batteries took a bit of a hit back in 2010, when then U.S. Secretary of Energy Steven Chu addressed the United Nations Climate Change Conference in Cancun and suggested that, for battery powered cars to replace those powered by fossil fuels, some pretty significant improvements would need to be made to current technology.

Chu said at the time: “It will take a battery, first that can last for 15 years of deep discharges. You need about five as a minimum, but really six- or seven-times higher storage capacity and you need to bring the price down by about a factor of three.” Chu suggested it might take another five years before such a battery would be developed, and he was almost exactly right in his prediction.

Researchers at the Nanyang Technology University (NTU) in Singapore have achieved at least some of those criteria by developing a Li-ion battery capable of 20 years of deep discharges, more than 10 times that of existing Li-ion batteries.

In addition to longer battery life, the new battery design can be charged up quickly so that it can reach 70 percent of its maximum charge in just two minutes.

These features tick at least two of the metrics that Chu and others have indicated are key to making all-EVs compete with those running on fossil fuels. This would mean that EV owners would not have to spend roughly $5000 every two years for a completely new set of batteries. It could also allow for a quick stop of just a couple of minutes to significantly increase the driving range of the vehicle.

The key to the new Li-ion battery is the replacement of graphite at the anode with nanotubes synthesized from titanium dioxide. This is a departure from a lot of recent work toward improved anodes; other research teams have been using nanostructured silicon in place of graphite.

“With our nanotechnology, electric cars would be able to increase their range dramatically with just five minutes of charging, which is on par with the time needed to pump petrol for current cars,” said Chen Xiaodong, an associate professor at NTU Singapore, in a press release.

The new nanotube material, which is described in the journal Advanced Materials, is produced relatively easily, according to the researchers, by taking titanium dioxide nanoparticles and mixing them with sodium hydroxide. The real key to getting the long titanium dioxide nanotubes the nanoparticles yield is conducting the stirring process at the right temperature.

The technology has been patented and has been licensed by a company that says it could get a new generation of fast-charging batteries to market in two years.

While battery life and recharging have been significantly improved with the new battery design, it’s not clear that new batteries have a longer charge life, or what is known as gravimetric energy density (the amount of energy stored per unit mass). Instead, they have improved Li-ion’s relatively weak gravimetric power density (the maximum amount of power that can be supplied per unit mass) by eliminating the additives that are used to bind the electrodes to the anode. This allows the battery to transfer electrons and ions in and out of the battery more quickly. This translates into batteries that will last about the same amount of time on a charge as today’s current batteries, but can be charged up to near maximum very quickly.

NTU professor Rachid Yazami, who was the co-inventor of the lithium-graphite anode 34 years ago but not involved in this most recent research, has noted the significant improvement to Li-ion batteries this work represents.

Yazami said: “There is still room for improvement and one such key area is the power density—how much power can be stored in a certain amount of space—which directly relates to the fast charge ability. Ideally, the charge time for batteries in electric vehicles should be less than 15 minutes, which Prof Chen’s nanostructured anode has proven to do.”

Reusable carbon nanotubes could be the water filter of the future, says RIT study


Carbon NT Water Filter 136842_web

 

A new class of carbon nanotubes could be the next-generation clean-up crew for toxic sludge and contaminated water, say researchers at Rochester Institute of Technology.

Enhanced single-walled carbon nanotubes offer a more effective and sustainable approach to water treatment and remediation than the standard industry materials–silicon gels and activated carbon–according to a paper published in the March issue of Environmental Science Water: Research and Technology.

RIT researchers John-David Rocha and Reginald Rogers, authors of the study, demonstrate the potential of this emerging technology to clean polluted water. Their work applies carbon nanotubes to environmental problems in a specific new way that builds on a nearly two decades of nanomaterial research. Nanotubes are more commonly associated with fuel-cell research.

Graphene Mem 050815 3-anewapproachAlso Read About: UC BERKELEY: NANOTECHNOLOGY CAN HELP DELIVER AFFORDABLE, CLEAN WATER WITH GRAPHENE MEMBRANE: VIDEO

 

 

“This aspect is new–taking knowledge of carbon nanotubes and their properties and realizing, with new processing and characterization techniques, the advantages nanotubes can provide for removing contaminants for water,” said Rocha, assistant professor in the School of Chemistry and Materials Science in RIT’s College of Science.

Rocha and Rogers are advancing nanotube technology for environmental remediation and water filtration for home use.

“We have shown that we can regenerate these materials,” said Rogers, assistant professor of chemical engineering in RIT’s Kate Gleason College of Engineering. “In the future, when your water filter finally gets saturated, put it in the microwave for about five minutes and the impurities will get evaporated off.”

Carbon nanotubes are storage units measuring about 50,000 times smaller than the width of a human hair. Carbon reduced to the nanoscale defies the rules of physics and operates in a world of quantum mechanics in which small materials become mighty.

“We know carbon as graphite for our pencils, as diamonds, as soot,” Rocha said. “We can transform that soot or graphite into a nanometer-type material known as graphene.”

A single-walled carbon nanotube is created when a sheet of graphene is rolled up. The physical change alters the material’s chemical structure and determines how it behaves. The result is “one of the most heat conductive and electrically conductive materials in the world,” Rocha said. “These are properties that only come into play because they are at the nanometer scale.”

The RIT researchers created new techniques for manipulating the tiny materials. Rocha developed a method for isolating high-quality, single-walled carbon nanotubes and for sorting them according to their semiconductive or metallic properties. Rogers redistributed the pure carbon nanotubes into thin papers akin to carbon-copy paper.

“Once the papers are formed, now we have the adsorbent–what we use to pull the contaminants out of water,” Rogers said.

The filtration process works because “carbon nanotubes dislike water,” he added. Only the organic contaminants in the water stick to the nanotube, not the water molecules.

“This type of application has not been done before,” Rogers said. “Nanotubes used in this respect is new.”

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Co-authors on the paper are Ryan Capasse, RIT chemistry alumnus, and Anthony Dichiara, a former RIT post-doctoral researcher in chemical engineering now at the University of Washington.

Third-Generation Solar Cells using Metalorganic Perovskites Challenges silicon based Solar Cells


nanotubefilmAn illustration of a perovskite solar cell. Credit: Photo by Aalto University / University of Uppsala / EPFL

Five years ago, the world started to talk about third-generation solar cells that challenged the traditional silicon cells with a cheaper and simpler manufacturing process that used less energy.

Methylammonium lead iodide is a metal-organic material in the perovskite crystal structure that captures light efficiently and conducts electricity well—both important qualities in . However, the lifetime of solar cells made of metalorganic perovskites has proven to be very short compared to cells made of .

Now researchers from Aalto University, Uppsala University and École polytechnique fédérale de Lausanne (EPFL) in Switzerland have managed to improve the long term stability of solar cells made of perovskite using “random network” nanotube films developed under the leadership of Professor Esko Kauppinen at Aalto University. Random network nanotube films are films composed of single-walled carbon nanotubes that in an electron microscope image look like spaghetti on a plate.

‘In a traditional perovskite solar cell, the hole conductor layer consists of organic material and, on top of it, a thin layer of gold that easily starts to disintegrate and diffuse through the whole solar cell structure. We replaced the gold and also part of the organic material with films made of carbon nanotubes and achieved good cell stability in 60 degrees and full one sun illumination conditions‘, explains Kerttu Aitola, who defended her doctoral dissertation at Aalto University and now works as a researcher at Uppsala University

In the study, thick black films with conductivity as high as possible were used in the back contact of the solar cell where light does not need to get through. According to Aitola, nanotube films can also be made transparent and thin, which would make it possible to use them as the front contact of the cell, in other words as the contact that lets light through.

‘The solar cells were prepared in Uppsala and the long-term stability measurement was carried out at EPFL. The leader of the solar cell group at EPFL is Professor Michael Grätzel, who was awarded the Millennium Prize 2010 for dye-sensitised solar cells, on which the are also partly based on’, says Aitola.

Nanotube film may resolve longevity problem of challenger solar cells
Cross-section of the solar cell in an electron microscope image. The fluff seen in the front of the image is composed of bundles of nanotubes that have become half-loose when the samples have been prepared for imaging. Credit: Photo by Aalto University / University of Uppsala / EPFL

 

The lifetime of solar cells made of silicon is 20-30 years and their industrial production is very efficient. Still, alternatives are needed as reducing the silicon dioxide in sand to silicon consumes a huge amount of energy. It is estimated that a needs two or three years to produce the energy that was used to manufacture it, whereas a perovskite solar cell would only need two or three months to do it.

‘In addition, the silicon used in solar cells must be extremely pure’, says Aitola.

‘Perovskite solar cell is also interesting because its efficiency, in other words how efficiently it converts sunlight energy into electrical energy, has very quickly reached the level of silicon solar cells. That is why so much research is conducted on perovskite solar cells globally.’

The alternative solar cells are even more interesting because of their various application areas. Flexible solar cells have until now been manufactured on conductive plastic. Compared with the conductive layer of plastic, the flexibility of nanotube films is superior and the raw materials are cheaper. Thanks to their flexibility, solar cells could be produced using the roll-to-roll processing method known from the paper industry.

‘Light and would be easy to integrate in buildings and you could also hang them in windows by yourself’, says Aitola.

Explore further: New way to make low-cost solar cell technology

More information: Kerttu Aitola et al, High Temperature-Stable Perovskite Solar Cell Based on Low-Cost Carbon Nanotube Hole Contact, Advanced Materials (2017). DOI: 10.1002/adma.201606398

McMaster University: Researchers resolve problem holding back a Technology Revolution – Smaller, Nimbler Semiconductors that are expected to Replace Silicon – Carbon Nanotubes


 

mcmasterrese carbon nanotubes 081916Artistic rendition of a metallic carbon nanotube being pulled into solution, in analogy to the work described by the Adronov group. Credit: Alex Adronov, McMaster University

Imagine an electronic newspaper that you could roll up and spill your coffee on, even as it updated itself before your eyes.

It’s an example of the that has been waiting to happen, except for one major problem that, until now, scientists have not been able to resolve.

Researchers at McMaster University have cleared that obstacle by developing a new way to purify nanotubes – the smaller, nimbler semiconductors that are expected to replace silicon within computer chips and a wide array of electronics.

“Once we have a reliable source of pure nanotubes that are not very expensive, a lot can happen very quickly,” says Alex Adronov, a professor of Chemistry at McMaster whose research team has developed a new and potentially cost-efficient way to purify carbon nanotubes.

Carbon nanotubes – hair-like structures that are one billionth of a metre in diameter but thousands of times longer – are tiny, flexible conductive nano-scale materials, expected to revolutionize computers and electronics by replacing much larger silicon-based chips.

A major problem standing in the way of the new technology, however, has been untangling metallic and semiconducting carbon nanotubes, since both are created simultaneously in the process of producing the microscopic structures, which typically involves heating carbon-based gases to a point where mixed clusters of nanotubes form spontaneously as black soot.

Only pure semiconducting or metallic carbon nanotubes are effective in device applications, but efficiently isolating them has proven to be a challenging problem to overcome. Even when the nanotube soot is ground down, semiconducting and metallic nanotubes are knotted together within each grain of powder. Both components are valuable, but only when separated.

Researchers around the world have spent years trying to find effective and efficient ways to isolate carbon nanotubes and unleash their value.

While previous researchers had created polymers that could allow semiconducting carbon nanotubes to be dissolved and washed away, leaving metallic nanotubes behind, there was no such process for doing the opposite: dispersing the metallic nanotubes and leaving behind the semiconducting structures.Nanotubes images

Now, Adronov’s research group has managed to reverse the electronic characteristics of a polymer known to disperse semiconducting nanotubes – while leaving the rest of the polymer’s structure intact. By so doing, they have reversed the process, leaving the nanotubes behind while making it possible to disperse the metallic nanotubes.

The researchers worked closely with experts and equipment from McMaster’s Faculty of Engineering and the Canada Centre for Electron Microscopy, located on the university’s campus.

“There aren’t many places in the world where you can to this type of interdisciplinary work,” Adronov says.

The next step, he explains, is for his team or other researchers to exploit the discovery by finding a way to develop even more efficient polymers and scale up the process for commercial production.

The research is described in the cover story of Chemistry – A European Journal.

Explore further: Carbon nanotube ‘ink’ may lead to thinner, lighter transistors and solar cells

 

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Berkeley Lab Researchers: 5 Nanoscience Research Projects That Could Deliver Big Results


south-africa-ii-nanotechnology-india-brazil_261.jpgFrom energy efficiency to carbon capture, Berkeley Lab scientists are on it.

Berkeley Lab researchers are using the science of the very small to help solve big challenges. That’s because, at the nanoscale—the scale of molecules and proteins—new and exciting properties emerge that can possibly be put to use.

Here are five projects, now underway and recently highlighted in the News Center, which promise big results from the smallest of building blocks:

1. A DIY paint-on coating for energy efficient windows

This “cool” DIY retrofit tech could improve the energy efficiency of windows and save money. Researchers are developing a polymer-based heat-reflective coating that makes use of the unusual molecular architecture of a polymer.

It has the potential to be painted on windows at one-tenth the cost of current retrofit approaches. Window films on the market today reflect infrared solar energy back to the sky while allowing visible light to pass through, but a professional contractor is needed to install them. A low-cost option could significantly expand adoption and result in potential annual energy savings equivalent to taking 5 million cars off the road.

 

2. Nanowires that move data at light speed

Researchers have found a new way to produce nanoscale wires that can serve as tiny, tunable lasers. The excellent performance of these tiny lasers is promising for the field of optoelectronics, which is focused on combining electronics and light to transmit data, among other applications. Miniaturizing lasers to the nanoscale could further revolutionize computing, bringing light-speed data transmission to desktop, and ultimately, handheld computing devices.

 

3. Nano sponges that fight climate change

MOF

Scientists are developing nano sponges that could capture carbon from power plants before it enters the atmosphere. Initial tests show the hybrid membrane, composed of nano-sized cages (called metal-organic frameworks) and a polymer, is eight times more carbon dioxide permeable than membranes composed only of the polymer.

Boosting carbon dioxide permeability is a big goal in efforts to develop carbon capture materials that are energy efficient and cost competitive. Watch this video for more on this technology.

 

 

4. Custom-made chemical factories

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Scientists have recently reengineered a building block of a nanocompartment that occurs naturally in bacteria, greatly expanding the potential of nanocompartments to serve as custom-made chemical factories. Researchers hope to tailor this new use to produce high-value chemical products, such as medicines, on demand.

The sturdy nanocompartments are formed by hundreds of copies of just three different types of proteins. Their natural counterparts, known as bacterial microcompartments, encase a wide variety of enzymes that carry out highly specialized chemistry in bacteria.

 

5. Nanotubes that assemble themselves

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Researchers have discovered a family of nature-inspired polymers that, when placed in water, spontaneously assemble into hollow crystalline nanotubes. What’s more, the nanotubes can be tuned to all have the same diameter of between five and ten nanometers. Controlling the diameter of nanotubes, and the chemical groups exposed in their interior, enables scientists to control what goes through. Nanotubes have the potential to be incredibly useful, from delivering cancer-fighting drugs inside cells to desalinating seawater.

 

The Science of Small Revealed Using a Penny

Just how small can nanoscience get? Here’s a great example using an American penny from the Molecular Foundry.

In this video, the letters that spell Molecular Foundry were written with a beam of electrons fired at the surface. The smallest feature is 20 nanometers, or roughly 100 atoms. As the video zooms out, you lose sight of Molecular Foundry and see the Berkeley Lab logo, which was written with a beam of charged gallium atoms. As you continue to zoom out, you see an 18 hour timelapse of Abraham Lincoln’s face, again written with gallium atoms. Finally, all of this is done within the Lincoln Memorial side of the penny as it is removed from the focused ion beam.

Photolithography, which literally means writing with light, is the foundation for most top-down fabrication of things like microprocessors. However, because of something called the diffraction limit, photolithography is limited to devices that have features no smaller than the wavelength of the light used, often in the 100s of nanometers. As a result, things smaller than light like atoms and electrons must be used.

 

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