Great things from small things

Blog Archive

Home
Filter by: Breakthrough Discovery
Page 2

Nano LI Batt usc-lithium-ion-batteryDespite the recently reported battery-flaming problem of lithium-ion batteries (LIBs) in Boeing’s 787 Dreamliners and laptops (in 2006), LIBs are now successfully being used in many sectors. Consumer gadgets, electric cars, medical devices, space and military sectors use LIBs as portable power sources and in the future, spacecraft like James Webb Space Telescope are expected to use LIBs.

 

The main reason for this rapid domination of LIB technology in various sectors is that it has the highest electrical storage capacity with respect to its weight (one unit of LIB can replace two nickel-hydrogen battery units). Also, LIBs are suitable for applications where both high energy density and power density are required, and in this respect, they are superior to other types of rechargeable batteries such as lead-acid, nickel-cadmium, nickel-metal hydride, nickel-metal batteries, etc.

However, LIBs are required to improve in the following aspects: (i) store more energy and deliver higher power for longer duration of time, (ii) get charged in shorter period of time, (iii) have a longer life-time and (iv) be resistant to fire hazards. Figure 1 depicts the basic LIB Characteristics required for different applications and the respective properties that need to be improved.

Basic LIB characteristics required for different applicationsFig. 1:

Basic LIB characteristics required for different applications 1,2 (DOD: Depth of Discharge, SOC: State of Charge). (click on image to enlarge)

At present, there is a great deal of interest to upgrade the existing LIBs with improved properties and arrive at a battery technology that would permit smart-storage of electric energy. Futuristic smart electric grids that can provide an uninterruptible power supply to a household for 24 hours can replace the currently used lead acid battery systems by performing better in terms of longer back up time and reduced space requirements.

With the advent of next generation LIBs, electric vehicles are expected to cover longer distances with shorter charging times; mobile phones and laptops are expected to be charged within minutes and last longer.

What Nanotechnology can do to Improve the Performance of LIBs Nanotechnology has the potential to deliver the next generation LIBs with improved performance, durability and safety at an acceptable cost. A typical LIB consists of three main components: an anode (generally made of graphite and other conductive additives), a cathode (generally, a layered transition metal oxide) and electrolyte through which lithium ions shuttles between the cathode and anode during charging and discharging cycles.

On electrodes: The electrodes of LIB, both anode and cathode are made of materials that have the ability to be easily intercalated with lithium ions. The electrodes also should have high electrical conductivity so that the LIB can have high charging rates. Faster intercalation of Li ions can be facilitated by using nanosized materials for electrodes, which offer high surface areas and short diffusion paths, and hence faster storage and delivery of energy. One prominent example is the cathode material of A123 LIBs that use nanosized lithium iron phosphate cathode. Researchers have been trying to increase the electrical conductivity of lithium iron phosphate by doping it with metals.

However, without the need for doping, the conductivity and hence the performance of the cathode material could be improved significantly by using nano-sized lithium iron phosphate. One dimensional vanadium oxide materials, LiCoO2 nanofibers, nanostructured spinels (LiMn2O4) and phosphor-olivines (LiFePO4), etc., are being explored as cathode materials for the next generation LIBs. Similarly, nanosizing the anode materials can make the anode to have short mass and charge pathways (i.e allow easier transport of both lithium ions and electrons) resulting in high reverse capacity and deliver at a faster rate.

Nanostructured materials like silicon nanowires, silicon thin films, carbon nanotubes, graphene, tin-filled carbon nanotubes, tin, germanium, etc., are currently being explored as anode materials for the next generation LIBs.

On electrolyte: Electrolytes in LIB conduct lithium ions to and fro between two electrodes. Using solid electrolytes could render high-energy battery chemistries and better safety (avoids fire hazards) when compared to the conventionally used liquid electrolytes. However, achieving the optimal combination of high lithium-ion conductivity and a broad electrochemical window is a challenge. Also, reduction of interfacial resistance between the solid electrolyte and lithium based anodes also poses a formidable challenge3.

Nanostructuring of solid electrolytes has proven to improve the lithium ion conductivity, for example, when the conventional bulk lithium thiophosphate electrolyte was made nanoporous, it could conduct lithium ions 1000 times faster4. Another example is the nanostructured polymer electrolyte (NPE), which ensures safety. Main advantage of using this benign electrolyte is that it allows the use of lithium metal as anodes (instead of carbon based anodes) and contribute to the increase of energy density of the battery5.

On improving the performance of LIBs: The performance of the LIB is typically measured by its power and energy stored per unit mass or unit volume. The power density of the LIBs can be increased but often at an expense of energy density5. In order to achieve high power density as well as energy density, researchers are using nanotechnology to design electrodes with high surface area and short diffusion paths for ionic transport.

The high surface area provides more sites for lithium ions to make contact allowing greater power density and faster discharging and recharging. Another important parameter known as rate capability, indicates the maximum current output the LIB can provide and it plays an important role in deciding life-cycle of the LIB. In general, higher the rate capability, greater is the power density and longer the cycle-life.

Safety

The demand for the LIBs with increased power/energy density (P/E) ratio is accompanied by the greater safety risk of the battery. Preferably, a P/E ratio of roughly 0.5 along with uncomplicated heat management is proposed for the next generation LIBs. In order to avoid fire hazards, heat generated during the charging and discharging of the battery should be dissipated quickly and non-combustible materials should be used in LIBs.

In case of the LIBs with lithium metal as anodes, the so-called dendrite problem (growth of microscopic fibers of lithium across the electrolyte that leads to short circuits and overheating) remains to be solved. Separators with nanoporous structures can prevent the spreading of dendtrites by acting as a mechanical barrier without hindering the ion-transport during charging and discharging cycles.

Recently, a nanoporous polymer-ceramic composite separator that could prevent the spreading of dendrites has been reported. This novel separator consist of a laminated nanoporous gamma alumina sheet (pore size of 100 nm) sandwiched between macroporous polymer membranes. The nanoporous alumina in this layered composite could effectively impede the proliferation of dendrites and prevent cell failure that are caused by short circuits13. Thermally stable electrolytes, for example, nanoarchitectured plastic crystal polymer electrolytes (N-PCPE) can facilitate the development of safe LIBs.

Owing to its nanoarchitectural structure, N-PCPE is flexible while maintaining high ionic conductance and thermal stability. This makes the material to perform well with high electrochemical stability even in a wrinkled state. As it suffers no internal short-circuit problems even under severely deformed state, N-PCPE can be used in place of currently used flammable carbonate-based liquid electrolytes and polyolefin separator membranes to improve the safety of the LIBs14. In another context, it can be said that nanotechnology, in a way helps to use thermally stable advanced new materials as electrodes.

For example, Li4Ti5O12 spinel, which is a state-of-the-art anode material for LIBs has excellent safety and structural stability during cycling, but suffer from low ionic and electronic conductivities (in bulk form) that hampers the wide-spread use of this material. By making anodes with nanosized Li4Ti5O12 spinel and Li4Ti5O12/carbon nanocomposites, the safety as well as the electrochemical performance of the battery can be improved15. Also, nano-enabled separators with improved stability and low shrinkage properties at high temperatures have proved to improve the safety aspects as well as the performance of the LIBs16.

 For example, separators made of polymeric nanofibers (DuPont™ Energain™ battery separators) can allow automobile LIBs to accelerate quickly but safely due to their excellent stability at high temperatures.

Durability

The cycle life (number of times the LIB can be charged and discharged (one cycle together) by maintaining up to 70-80% of its original capacity) can be improved by the use of nanostructured electrodes.

New nanostructures like mesoporous CNT@TiO2-C nanocable having an inner core of carbon nanotubes encapsulating TiO2 nanoparticles, which are further covered by an outer carbon layer with mesoporous architectures provided superior electrochemical performance as anodes, hence achieving long-term cycling stability at high rates17. A high charge of 122 mA h g-1 even after 2000 cycles at 50 C could be achieved using this material.

Durable high rate LIB anodes, namely, carbon-encapsulated Fe3O4 nanoparticles homogeneously embedded in 2D porous graphitic carbon nanosheets present an excellent cycling performance (a capacity-loss of just 3.47% after 350 cycles at a high rate of 10 C). This is the highest among other conventional as well as nanostructured Fe3O4-based electrodes.

Here, Fe3O4 nanoparticles of size of about 18.2 nm were homogeneously coated with conformal and thin onion-like carbon shells and embedded into 2D carbon nanosheets (thickness <30 nm). The carbon shells prevent the exposure of Fe3O4 nanoparticles to the electrolyte and stabilize the electrode-electrolyte interface18. New 2D and 3D battery designs like forest of nanowires/rods on a thin film electrode and stacked nanorods in a ‘truck bed’ are also being explored to accommodate the volume expansion of new electrode materials and hence improve their stability.
Cost
By the year 2020, the cost of the LIBs for automotive applications are expected to come down by half [19] and almost 70% reduction in the lifetime cost of the LIBs (which brings down the cost of a battery by three times) [20] would be achieved by using nanomaterials (graphene coated silicon) for fabricating the LIB electrodes.
Nano LI Batt usc-lithium-ion-battery
In terms of using high energy electrode materials in a minimal quantity, nanotechnology can help reducing the cost of the next generation LIBs. Also, improvement in the durability (cycle life) of the LIBs using nanostructured components can improve their cost- benefit aspects.
Recent advances in paper-based batteries are attractive for consumer electronics as they enable low cost manufacturing of devices like transistors, smart displays, etc.[21]. Nanotechnology and nanomanufacturing techniques are expected to open up possibilities of low-energy processing methods for fabricating and stacking of the LIB components.

Challenges in Developing Nanoenabled LIBs

Though the LIB technology is about twenty years old now and even with the advent of nanotechnology, it is still a challenge to attain LIBs with optimal combination of energy, reliability, cost and safety[22]. With regard to the anode materials, lithium suffers from the dentrite-formation (leading to an explosion of the battery), high reactivity, etc. Hence, nanostructures of tin, silicon, etc., are being used as new anode materials.
LundFig. 2: Challenges in the development of nano-enabled LIBs.
Various strategies like (i) decreasing the particle size to nano-range (ii) employing hollow nanostructures (iii) making nanocomposites or nanocoatings with carbon and/or inert components, etc., are being used to achieve high capacity and stable cycle-life of electrodes.
However, these approaches reduce the overall energy density of the anode material due to the following reasons: (i) low packing -density of nanosized materials (ii) presence of large voids in the hollow structures (iii) increased weight -percentage of added carbon/or inert components. Lately, smartly-designed nanoparticle agglomerates in micron size range are proposed to be used to solve the above said technical drawbacks of using nano-enabled anodes and similar strategies can also be applied for designing efficient nano-sized cathode materials [23,24].
Other challenges such as lowering the high fabrication cost due to energy- consuming synthetic processes, avoiding undesired reactions at electrode/electrolyte interface that arise due to the large surface areas of nanomaterials, preventing the formation of agglomerates during the fabrication process, etc., can be overcome by careful selection of the fabrication procedure.
Commercialization of Nanoenabled LIBs: Current Scenario
LIBs have already penetrated the consumer electronics market and are now making the move into HEV/EV applications and grid-storage applications. By 2018, global market for LIBs is expected to grow strong and reach $24.2 billion. Unlike before, the industry is ready to develop improved LIBs for diverse and new applications, thanks to the growing knowledge on new materials/technologies.
At present, most of the research efforts to develop advanced electrodes, safe electrolytes, etc., employ nanomaterials/nanotechnology routinely. As discussed in the previous section, there are number of challenges that are yet to be met to achieve 100% reliability and the merit of using nanomaterials for next generation LIBs. Especially, in the case of LIBs for electric vehicles, which is considered as a golden ticket for the commercialization LIBs, some startup companies like A123, Ener1, etc., announced bankruptcies in the past few years in spite of receiving huge capital investment and producing batteries with exceptional properties.
Experts note that this downfall cannot be solely attributed to the new nanotech-enabled LIB technology but also to the issue of replacing internal combustion engine in vehicles [25,26]. At present, LIBs consume the 65% of the total cost of an electric vehicle, and hence in order to be cost-completive with gasoline, LIBs with twice the energy storage of state-of-art LIBs at 30 % of cost are required [27].
Thus, the successful commercialization of nano-enabled LIBs for all-electric vehicles depends on various factors as mentioned above. Apart from these automobile applications, nanoenabled LIBs for powering handheld gadgets and for stationary storage applications are more likely to depend on the improvement in the properties of the LIBs, volume production rates) and usage of abundant, low cost, high energy materials.
Conclusion
LIB technology is rapidly emerging as the most advantageous battery chemistry for transportation as well as consumer electronics. Various research efforts on nanotechnology based LIB technology has already led into the production and use of high performance LIBs (Toshiba, A123 Systems, Altair Nano, Next Alternative Inc., etc.) and yet more improvement with respect to the performance, durability and safety aspects, especially for automotive applications are more likely to be achieved in the future.
Acknowledgement
The author would like to thank Dr. Srinivasan Anandan of ARCI for the insightful discussions on the current research trends on LIBs and Dr. C.K. Nisha of CKMNT for her suggestions on enhancing the content of the article.
References 1. Walter Van Schalkwijk, “Advances in Lithium- Ion Batteries”, Springer (2002), ISBN 0-306-47356-9 2. Battery could find use in mobile applications (26 Feb 2014) 3. Liquid and solid electrolytes in lithium-ion batteries 4. Z. Liu, W. Fu, E.A. Payzant, et al., J. Am. Chem. Soc., 135 (2013) 975-978 5. Berkeley Lab’s Solid Electrolyte May Usher in a New Generation of Rechargeable Lithium Batteries For Vehicles 6. G. Kim, S. Jeong, J-H. Shin, et al., ACS Nano, 8 (2014) 1907-1912 13. Z. Tu, Y. Kambe, Y. Lu, et al., Adv. Energy Mater., 4 (2014) 1300654 14. K-Ho Choi, S-Ju Cho, S-H Kim, et al., Adv. Funct. Mater., 24 (2014) 44-52 15. T-F. Yi, L-J. Jiang, J. Shu, et al., J. Phys. Chem. Solids, 71 (2010) 1236 – 1242 16. DuPont Launches Energain™ Separators for High-Performance Lithium Ion Batteries 17. B. Wang, H. Xin, X. Li, et al., Scientific Reports, 4:3729 (2014) 1-7 18. C. He, S. Wu, N. Zhao et al., ACS Nano, 7 (2013) 4459-4469 19. Battery Executives See Price Drops Ahead (Sep 7 2013) 20. Nanostructured Silicon Li-ion Batteries’ Capacity Figures Are In (26 Oct 2012) 21. Nanotechnology researchers fabricate foldable Li-ion batteries (1 Oct 2013) 22. The Future Requires (Better) Batteries ( 11 Nov 2013) 23. A. Magasinki, P. Dixon, B. Hertzberg, et al., Nature Materials, 9 (2010) 353-358 24. W. Wei, D. Chen D, R. Wang., et al., Nanotechnology, 23 (2012) 475401 25. Is There a Future for Nano-Enabled Lithium Ion Batteries in Electric Vehicles? (14 Dec 2010) 26. Why Ener1 Went Bankrupt (27 Jan 2012) 27. Double Energy Density for Lithium-Ion Batteries By I. Sophia Rani, Centre for Knowledge Management of Nanoscience and Technology (CKMNT).
The full article has appeared in the April 2014 issue of “Nanotech Insights” and the above article is an abridged and revised version of the same.

Nano Cancer researchtest 030914Chemotherapy timing is key to success: Nanoparticles that stagger delivery of two drugs knock out aggressive tumors in mice.

Cambridge, MA | Posted on May 8th, 2014

 

 

Abstract:


MIT researchers have devised a novel cancer treatment that destroys tumor cells by first disarming their defenses, then hitting them with a lethal dose of DNA damage.

In studies with mice, the research team showed that this one-two punch, which relies on a nanoparticle that carries two drugs and releases them at different times, dramatically shrinks lung and breast tumors. The MIT team, led by Michael Yaffe, the David H. Koch Professor in Science, and Paula Hammond, the David H. Koch Professor in Engineering, describe the findings in the May 8 online edition of Science Signaling.

“I think it’s a harbinger of what nanomedicine can do for us in the future,” says Hammond, who is a member of MIT’s Koch Institute for Integrative Cancer Research. “We’re moving from the simplest model of the nanoparticle — just getting the drug in there and targeting it — to having smart nanoparticles that deliver drug combinations in the way that you need to really attack the tumor.”

BioGraphene-320

Doctors routinely give cancer patients two or more different chemotherapy drugs in hopes that a multipronged attack will be more successful than a single drug. While many studies have identified drugs that work well together, a 2012 paper from Yaffe’s lab was the first to show that the timing of drug administration can dramatically influence the outcome.

In that study, Yaffe and former MIT postdoc Michael Lee found they could weaken cancer cells by administering the drug erlotinib, which shuts down one of the pathways that promote uncontrolled tumor growth. These pretreated tumor cells were much more susceptible to treatment with a DNA-damaging drug called doxorubicin than cells given the two drugs simultaneously.

“It’s like rewiring a circuit,” says Yaffe, who is also a member of the Koch Institute. “When you give the first drug, the wires’ connections get switched around so that the second drug works in a much more effective way.”

Erlotinib, which targets a protein called the epidermal growth factor (EGF) receptor, found on tumor cell surfaces, has been approved by the Food and Drug Administration to treat pancreatic cancer and some types of lung cancer. Doxorubicin is used to treat many cancers, including leukemia, lymphoma, and bladder, breast, lung, and ovarian tumors.

Staggering these drugs proved particularly powerful against a type of breast cancer cell known as triple-negative, which doesn’t have overactive estrogen, progesterone, or HER2 receptors. Triple-negative tumors, which account for about 16 percent of breast cancer cases, are much more aggressive than other types and tend to strike younger women.

That was an exciting finding, Yaffe says. “The problem was,” he adds, “how do you translate that into something you can actually give a cancer patient?”

From lab result to drug delivery

To approach this problem, Yaffe teamed up with Hammond, a chemical engineer who has previously designed several types of nanoparticles that can carry two drugs at once. For this project, Hammond and her graduate student, Stephen Morton, devised dozens of candidate particles. The most effective were a type of particle called liposomes — spherical droplets surrounded by a fatty outer shell.

The MIT team designed their liposomes to carry doxorubicin inside the particle’s core, with erlotinib embedded in the outer layer. The particles are coated with a polymer called PEG, which protects them from being broken down in the body or filtered out by the liver and kidneys. Another tag, folate, helps direct the particles to tumor cells, which express high quantities of folate receptors.

Once the particles reach a tumor and are taken up by cells, the particles start to break down. Erlotinib, carried in the outer shell, is released first, but doxorubicin release is delayed and takes more time to seep into cells, giving erlotinib time to weaken the cells’ defenses. “There’s a lag of somewhere between four and 24 hours between when erlotinib peaks in its effectiveness and the doxorubicin peaks in its effectiveness,” Yaffe says.

The researchers tested the particles in mice implanted with two types of human tumors: triple-negative breast tumors and non-small-cell lung tumors. Both types shrank significantly. Furthermore, packaging the two drugs in liposome nanoparticles made them much more effective than the traditional forms of the drugs, even when those drugs were given in a time-staggered order.

As a next step before possible clinical trials in human patients, the researchers are now testing the particles in mice that are genetically programmed to develop tumors on their own, instead of having human tumor cells implanted in them.

The researchers believe that time-staggered delivery could also improve other types of chemotherapy. They have devised several combinations involving cisplatin, a commonly used DNA-damaging drug, and are working on other combinations to treat prostate, head and neck, and ovarian cancers. At the same time, Hammond’s lab is working on more complex nanoparticles that would allow for more precise loading of the drugs and fine-tuning of their staggered release.

“With a nanoparticle delivery platform that allows us to control the relative rates of release and the relative amounts of loading, we can put these systems together in a smart way that allows them to be as effective as possible,” Hammond says.

Morton and Lee are the lead authors of the Science Signaling paper. Postdocs Zhou Deng, Erik Dreaden, and Kevin Shopsowitz, visiting student Elise Siouve, and graduate student Nisarg Shah also contributed to the research. The work was funded by the National Institutes of Health, the Center for Cancer Nanotechnology Excellence, and a Breast Cancer Alliance Exceptional Project Grant.

Written by Anne Trafton, MIT News Office

####

 

Copyright © Massachusetts Institute of Technology

1x2 logo sm$5 Billion ‘Giga-Factory’ to Spark EV Uptake

 

 

Battery graphite demand could double in 6 years with no growth elsewhere US automotive giant, Tesla, has revealed plans to build a new $5bn lithium-ion battery (Li-ion battery) ‘gigafactory’ which could potentially increase natural graphite demand by up to 37% by 2020.   The factory, which is forecast to start production by 2017, is expecting to have an output of 35 gWh/year by as early as 2020, which would over double the size of the current market.

Its important to stress that the plant is in the planning stage and capacities depend strongly on market demand, but Tesla believes it can be the market leader by producing low cost batteries in the USA.

In IM Dataor synthetic materials remains unclear. Nonetheless, expansion of the battery market for electric vehicles (EVs) on this scale presents a valuable opportunity to graphite suppliers.

Seizing an opportunity
In 2012, consumption from the battery sector constituted 8% of global natural graphite demand.   For the natural graphite market to supply the type of market growth Tesla are forecasting, large flake graphite output will need to increase significantly over the coming years.  

IM Data estimates that large flake grades (+80 mesh and larger) only made up just over 20% of total flake graphite output of 375,000 tonnes in 2013, and with competition for these grades from other traditional markets (i.e. the refractories sector), new projects are likely to be required to meet the battery market demand.

A number of junior projects are aiming to reach production over the coming 2-3 years, many boasting large flake reserves capable of supplying new hi-tech markets.   With China’s large flake reserves depleting, and the efficiency of the country’s spherodization process under question, these projects have an opportunity to play a major role in supplying emerging markets.   Tesla’s rapid EV expansion plans are, however, centered around lowering Li-ion battery costs by over 30% per kWh, which will allow the company to bring a more price competitive product to market.
Raw material costs are therefore likely to be under close scrutiny as the company gears up for production, meaning any potential graphite suppliers will have to be competitive not only with other producers but also alternative carbon anode companies.   The FOB price of Chinese uncoated spherical graphite, 99.95% C, 15 microns stands at $3,400/tonne today, while prices of coated spherical graphite – the final material used in battery anodes – is valued at around three times this level.

 
From Ford to Tesla?

In 1913, Henry Ford introduced the use of an assembly line in the production of the Ford Model T motor car, which revolutionized the automobile industry and brought an affordable product to market in the US.   Over a century on and Tesla’s plans to internalise its Li-ion battery production could prove just as pivotal in the emergence of the EV market, unlocking a lucrative new layer of demand for natural graphite producers.

 

 
Although the use of graphite in Li-ion battery technologies is not a new concept, the quantities used in more developed portable device markets, such as phones or tablets, are not substantial enough to be a major source of demand for flake graphite.

 
As much as 56kg of graphite is, however, used per EV, making the market an exciting new prospect for the graphite community which has fueled a wave of interest in recent years.   While the market has failed to expand at the rate many had forecast –both the US and China have fallen short of government growth targets – EVs present the most feasible opportunity for graphite producers to diversify from traditional industrial markets.
If Tesla manages to meet its expansion plans over the coming six years, the company is likely to further the cause of not only the EV industry, but also the graphite market in its path.

How many graphite mines will Tesla need?

Should Tesla choose to use spherical graphite sourced from natural flake as its raw material of choice, at capacity the plant will need substantial volumes.

As outlined earlier, a conservative case will see the plant demanding 93,000 tonnes of flake graphite but in a bullish case this could rise as high as 140,000 tonnes. The challenge for the graphite industry will be not only the volumes but the sufficient quantity of medium and large flake graphite.
At present, medium flake (-100 mesh) graphite from China is used to produce spherical graphite which is then coated in Japan. Should the new, more economical processing techniques take off in the next two years as expected, a large portion of this demand will be for large flake (+80 mesh) and spherical graphite production hubs will emerge in Europe and North America.
The flake footprint of each mine varies quite significantly, each with its own blend of large and medium flakes in addition to fines. Therefore a number of mines will need to be built to satisfy a Tesla plant running at full capacity.
Below, IM Data offers the following consumption scenarios for Tesla’s battery plant by 2020:
Conservative case for Tesla plant running at capacity 

Spherical graphite demand = 28,000 tpa

Flake graphite demand = 93,000 tpa
New graphite mines needed (equivalent) = 6
Bullish case for Tesla plant at running capacity
Spherical graphite demand = 42,000 tpa
Flake graphite demand = 140,000 tpa
New graphite mines needed (equivalent) = 9

1x2 logo smA new study from Los Alamos National Laboratory and the University of Milano-Bicocca demonstrates that superior light-emitting properties of quantum dots can be applied in solar energy, boosting the output of solar cells and allowing for the integration of photovoltaic-active architectural elements into buildings.

A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by Los Alamos National Laboratory researchers in collaboration with scientists from University of Milano-Bicocca (UNIMIB), Italy. Their project demonstrates that superior light-emitting properties of quantum dots can be applied in solar energy by helping more efficiently harvest sunlight.

Photovoltaic-Solar-Panel-Windows-Made-Possible-by-Quantum-Dots

This schematic shows how the quantum dots are embedded in the plastic matrix and capture sunlight to improve solar panel efficiency.

“The key accomplishment is the demonstration of large-area luminescent solar concentrators that use a new generation of specially engineered quantum dots,” said lead researcher Victor Klimov of the Center for Advanced Solar Photophysics (CASP) at Los Alamos.

Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry. Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100 percent. These properties have recently become the basis of a new technology – quantum dot displays – employed, for example, in the newest generation of the Kindle Fire e-reader.

Light-harvesting antennas

A luminescent solar concentrator (LSC) is a photon management device, representing a slab of transparent material that contains highly efficient emitters such as dye molecules or quantum dots. Sunlight absorbed in the slab is re-radiated at longer wavelengths and guided towards the slab edge equipped with a solar cell.

Klimov explained, “The LSC serves as a light-harvesting antenna which concentrates solar radiation collected from a large area onto a much smaller solar cell, and this increases its power output.”

“LSCs are especially attractive because in addition to gains in efficiency, they can enable new interesting concepts such as photovoltaic windows that can transform house facades into large-area energy generation units,” said Sergio Brovelli, who worked at Los Alamos until 2012 and is now a faculty member at UNIMIB.

Because of highly efficient, color-tunable emission and solution processability, quantum dots are attractive materials for use in inexpensive, large-area LSCs. One challenge, however, is an overlap between emission and absorption bands in the dots, which leads to significant light losses due to the dots re-absorbing some of the light they produce.

“Giant” but still tiny, engineered dots

To overcome this problem the Los Alamos and UNIMIB researchers have developed LSCs based on quantum dots with artificially induced large separation between emission and absorption bands (called a large Stokes shift).

These “Stokes-shift” engineered quantum dots represent cadmium selenide/cadmium sulfide (CdSe/CdS) structures in which light absorption is dominated by an ultra-thick outer shell of CdS, while emission occurs from the inner core of a narrower-gap CdSe. The separation of light-absorption and light-emission functions between the two different parts of the nanostructure results in a large spectral shift of emission with respect to absorption, which greatly reduces losses to re-absorption.

To implement this concept, Los Alamos researchers created a series of thick-shell (so-called “giant”) CdSe/CdS quantum dots, which were incorporated by their Italian partners into large slabs (sized in tens of centimeters) of polymethylmethacrylate (PMMA). While being large by quantum dot standards, the active particles are still tiny – only about hundred angstroms across. For comparison, a human hair is about 500,000 angstroms wide.

“A key to the success of this project was the use of a modified industrial method of cell-casting, we developed at UNIMIB Materials Science Department” said Francesco Meinardi, professor of Physics at UNIMIB.

Spectroscopic measurements indicated virtually no losses to re-absorption on distances of tens of centimeters. Further, tests using simulated solar radiation demonstrated high photon harvesting efficiencies of approximately 10% per absorbed photon achievable in nearly transparent samples, perfectly suited for utilization as photovoltaic windows.

Despite their high transparency, the fabricated structures showed significant enhancement of solar flux with the concentration factor of more than four. These exciting results indicate that “Stokes-shift-engineered” quantum dots represent a promising materials platform. It may enable the creation of solution processable large-area LSCs with independently tunable emission and absorption spectra.

Funding: The Center for Advanced Solar Photophyscis (CASP) is an Energy Frontier Research Center funded by the Office of Science of the US Department of Energy.

The work of the UNIMIB team was conducted within the UNIMIB Department of Materials Science and funded by Fondazione Cariplo (2012-0844) and the European Community’s Seventh Framework Programme (FP7/2007-2013; grant agreement no. 324603).

Publication: Francesco Meinardi, et al., “Large-area luminescent solar concentrators based on ‘Stokes-shift-engineered’ nanocrystals in a mass-polymerized PMMA matrix,” Nature Photonics (2014); doi:10.1038/nphoton.2014.54

Source: Los Alamos National Laboratory

Image: Los Alamos National Laboratory

1x2 logo sm*** “Great Things from Small Things” has written and re-published many articles over the past several years on the “wee tiny” nano-materials called Quantum Dots. Their enabling applications across a broad spectrum of Markets & Industries from Electronics, Textiles, Drug Therapies, Bio-Medicines to Solar Energy Generation/ Storage and Display Screens, has been well documented. It would seem these new “wonder nano-materials” are poised to change the entire landscape of how we innovate and manufacture almost everything.

So what’s the catch? What has delayed a broader acceptance and integration of quantum dots into the marketplace? It would seem the answer lies not in the efficacy & validity of the new ‘nano-materials’ but more in the age old and time tested axiom of: “Low Cost + High Consistency + Ability to Mass Scale = Commercial Success.

A new company Nano Assembly has plans to change all that. Business Investigative writer Osama Natto highlights the High Profile Team and award winning company’s collaboration with KAUST (King Abdullah University of Science and Technology) to integrate these disruptive game changing materials in the broader marketplace for commercial success.

Article by Osama Natto

The Problem

Quantum dots are expensive enough to limit their otherwise broad applicability.

The standard way to make these semiconductor particles is to heat a solution to a high temperature in a small flask and inject a special agent. However, the solution will cool down naturally, and manual operation cannot maintain the high temperature needed for efficient production.

One can scale production of quantum dots up by using a larger flask, but this does not produce quality results. One can also use a continuous-flow reactor to benefit from higher consistency and automatic operation, as well as production of quantum dots in different sizes, but this still does not produce high-quality quantum dots.

The Solution

The Nano Assembly team has found a new method for producing quantum dots consistently and at a significantly lower price than competitors.

How the Product Works

The optical and electrical properties of quantum dots depend on their size and type. Different sizes emit different colors and exhibit a different absorption spectrum. Quantum dots must be produced according to careful standards.

The Technology Nano Assembly’s dual-stage servo control method allows the production of quantum dots without the broad peaks and troughs that come from other methods. The lower the absorption peak, the higher the quality of the quantum dots.

Where It Fits into the Market The quantum dots produced by Nano Assembly can be used anywhere that more expensively-produced quantum dots are utilized, allowing competing offerings to be replaced.

Patent Status The team has already filed for a patent and published their work in a high-impact journal.

Benefits to Saudi Economy These “low-cost and high quality quantum dots” could allow tech products already popular in Saudi Arabia, such as mobile phones, to include more efficient displays while remaining inexpensive. The team’s affordable quantum dots could also allow more people access to high-quality medical imaging, and improve solar cell technology to allow effective harvest of one of Saudi Arabia’s greatest natural resources: sunlight.

Usages

In part due to their ability to produce a rainbow of bright colors efficiently, quantum dots are used in display technologies. Since quantum dots are so tiny, they can also move anywhere in the human body, making them useful in the field of medical imaging as replacements for fluorescence-based biosensors that use organic dyes. Quantum dots can also be used as the absorbing photovoltaic material in solar cells.

Features and Benefits of the Product

  • High quality relative to competitors’ quantum dots
  • Low cost relative to competitors’ quantum dots

Market

Since quantum dots are used to make other products, Nano Assembly would be operating in the business-to-business market, although applications in fields like solar power also leave the door open for business-to-government sales.

Competitive Landscape

Current methods for producing quantum dots include high-temperature dual injection synthesis, molecular seeding, and a variation of the high-temperature dual injection method that incorporates a continuous flow system.

TeamNanoAssembly

(Image courtesy of King Abdullah University of Science and Technology)

Team

Names and Profiles of Team Members

Credentials Dr. Pan has earned both a Bachelor of Science and Master of Science from Anhui Polytechnic University, along with a Ph.D. in Chemistry from the University of Science and Technology of China. He is now participating in a post-doctoral fellowship at KAUST. Within the Nano Assembly team, Dr. Pan is in charge of production.

El-Ballouli holds a Bachelor of Science in Chemistry and a Master of Science in Organic Chemistry from the American University of Beirut. She is currently a Ph.D. student at KAUST. Her primary area of interest is continuous-flow synthesis and size separation of quantum dots for assembly in solar cells. El-Ballouli is in charge of product testing for the team.

Dr. Bakr has earned a Bachelor of Science in Materials Science and Engineering from the Massachusetts Institute of Technology (MIT), as well as both a Master of Science and Ph.D. in Applied Physics from Harvard University. He is currently an Assistant Professor of Materials Science and Engineering, and Principal Investigator at KAUST. Dr. Bakr acts as scientific adviser to the Nano Assembly team.

Dr. Sargent holds a Bachelor of Science in Engineering Physics from Queen’s University, along with a Ph.D. in Electrical and Computer Engineering (Photonics) from the University of Toronto. He is the Vice Dean of Research for the Faculty of Applied Science & Engineering, a Professor in the Department of Electrical & Computer Engineering (ECE), and a KAUST Investigator. Dr. Sargent is the technique and business adviser for the team.

Timeline

Nano Assembly has already begun the process of incorporating their company. Their immediate task is to set up the production line that they have prepared, test it, and scale it up. They are expecting significant annual growth through 2017.

Big-Picture Impact on the Saudi Economy   

The availability of high-quality quantum dots at a low price could help more tech-savvy companies and entrepreneurs enter the electronics, solar power, and medical imaging fields, among others. It could also help existing companies produce more cost-effective offerings within these fields. Either way, the end result would be a more technologically advanced and competitive Saudi Arabia

By Michael Berger. Copyright © Nanowerk

2x2-logo-sm.jpg

(Nanowerk Spotlight) Within the field of nanofluidics, the manipulation of liquids typically deals with volumes of femtoliters (10-15 L). A femtoliter is one quadrillionth of a liter or 1 µm3. To put that in perspective: that is less than one percent of the volume of an average human cell.

Existing nanofluidic approaches to facilitate the manipulation of ultra-small amounts of liquids usually require their confinement within quasi-1D nanochannels or nanopores. In these devices, the movement of the liquid objects must follow pre-designed routes. Researchers have now demonstrated a new platform for digital nanofluidics where water nanodroplets are trapped between a mica surface and graphene.

Here, with the assistance of a graphene protection layer and ice-like lubricant monolayer, water nanodroplets can be moved, merged, separated, and patterned into regular arrays freely within a two-dimensional channel. “This is the first demonstration of manipulating individual water nanodroplets of such low volumes on surfaces,” Guangyu Zhang, a professor at the Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, in Beijing, tells Nanowerk. “While our strategy demonstrates the extension of the manipulation freedom from 1D to 2D, we were also able to move water nanodroplets one by one, which means this nanofluidic process is ‘digital’.”

The work, reported in the March 19, 2014 online edition of ACS Nano (“A Route toward Digital Manipulation of Water Nanodroplets on Surfaces”), also demonstrates the ability to manipulate water nanodroplets with a volume down to the yoctoliter scale (10-24 L). Such small amount of liquid is of great importance not only on study of fundamental physics or chemistry related to its size confinement effect but also for various functional applications.

Manipulation of water nanodropetsManipulation of water nanodroplets (WNs). (a) Schematic for the manipulation of a WN by an AFM tip. Inset shows the sandwich structure of graphene/WN/mica. (b and c) With a multistep translation, the disordered nanodroplets are rearranged into an ordered 3×3 array. The blue dotted arrow (the same below) represents the path of the tip we preset. (d and e) Two nanodroplets are moved to the same location and merged. (f) An ultrasmall nanodroplet with volume as small as 1.2 yoctoliter is separated from a big one in (e). Inset images of (c), (e), and (f) are the sketches for corresponding processes of the manipulation. (Reprinted with permission from American Chemical Society) (click image to enlarge)

 

Generally, water nanodroplets are hard to form stably on certain surfaces. They are likely to evaporate unless being frozen or under moisture. Thus it’s difficult to manipulate them. “Intrigued by the recent discovery of 2D ice formation between graphene and mica surface by James R. Health’s group at Caltech (“Graphene Visualizes the First Water Adlayers on Mica at Ambient Conditions”), we started to use this mica-water-graphene sandwich structure to realize the water nanodroplets manipulation,” Zhang explains the motivation for this work. Specifically, the researchers put water nanodroplets on a mica surface and covered them with graphene to stabilize them.

like 2D buffer layer formed between the water nanodroplets and the mica surface, acting as a lubricant for the droplets. This made them very mobile and allowed to move them around freely upon applying an external force. The researchers used an atomic force microscope (AFM) to facilitate this manipulation, including moving, merging and separating of these individual water nanodroplets. Zhang points out that the volume of the smallest manipulable water nanodroplet in their system is around yoctoliter scale, which is a more than 5 orders of magnitude improvement over the existing micro/nanofluidic manipulation limits.

Practically, the demonstrated nanofluidic platform provides a relatively simple solution for lab-on-a-chip applications on which one could carry out molecular analysis, chemical reactions, as well as microelectronic and bioengineering applications. “The inertia and impermeability of graphene makes it suitable for bearing many kinds of chemical solvent or biological molecules,” says Zhang. “And since the typical volume of liquid in our samples is ∼1-100×10-24 L, the synthesis and analysis processes could be low-cost, fast response and environmentally friendly.” Going forward, the team will extend the current, relatively simple platform to a more complex one with liquids other than water. They are also planning to carry out prototype demonstrations of certain functionalities of this platform.

Read more: Digital nanofluidics – manipulating water droplets on surfaces http://www.nanowerk.com/spotlight/spotid=35011.php#ixzz2xfxTECYP

Nano Skin Sensors

Researchers have created a wearable device that is as thin as a temporary tattoo and can store and transmit data about a person’s movements, receive diagnostic information and release drugs into skin.

Similar efforts to develop ‘electronic skin’ abound, but the device is the first that can store information and also deliver medicine — combining patient treatment and monitoring. Its creators, who report their findings today in Nature Nanotechnology1, say that the technology could one day aid patients with movement disorders such as Parkinson’s disease or epilepsy.

The researchers constructed the device by layering a package of stretchable nanomaterials — sensors that detect temperature and motion, resistive RAM for data storage, microheaters and drugs — onto a material that mimics the softness and flexibility of the skin. The result was a sticky patch containing a device roughly 4 centimetres long, 2 cm wide and 0.003 millimetres thick, says study co-author Nanshu Lu, a mechanical engineer at the University of Texas in Austin.

“The novelty is really in the integration of the memory device,” says Stéphanie Lacour, an engineer at the Swiss Federal Institute of Technology in Lausanne, who was not involved in the work. No other device can store data locally, she adds.

Other Related Stories

The trade-off for that memory milestone is that the device works only if it is connected to a power supply and data transmitter, both of which need to be made similarly compact and flexible before the prototype can be used routinely in patients. Although some commercially available components, such as lithium batteries and radio-frequency identification tags, can do this work, they are too rigid for the soft-as-skin brand of electronic device, Lu says.

Even if softer components were available, data transmitted wirelessly would need to be converted into a readable digital format, and the signal might need to be amplified. “It’s a pretty complicated system to integrate onto a piece of tattoo material,” she says. “It’s still pretty far away.”

Surfer at Peahi Bay on Maui, Hawaii

Concern about the depletion of global water resources has grown rapidly in the past decade due to our increasing global population and growing demand for other diverse applications.

Since only 2.5% of the Earth’s water is fresh, it has been reported that almost half of the world’s population is at risk of a water crisis by the year 2025 [1]. Accordingly, significant research efforts have been focused on the desalination of brackish/seawater and the remediation and reuse of wastewater to meet the agricultural, industrial, and domestic water demands. While much progress has been made, the advent of membrane desalination techniques over fifty years ago has given significant impetus to the advancement of water purification technology. However, the need for improved membrane performance and lower operating costs have been a barrier for both researchers and consumers alike. Current water treatment technology Water purification membranes are typically divided into four categories according to pore size:

  • – microfiltration (MF, < few microns)
  • – ultrafiltration (UF, < 100 nm)
  • – nanofiltration (NF, < 10 nm)
  • – reverse osmosis (RO, < 1 nm)

Feed water quality is an important consideration when selecting a suitable membrane. NF and RO membranes have typically been designed for use of brackish water (2-5 g/L of salt), seawater (35 g/L of salt), and waste water (from agriculture and industry) treatments due to their separation capacity of ions (mono-/di-valent) and organic materials (macromolecules, proteins, glucose, and amino acids) from the water.

Of the various candidate materials, conventional desalination membranes are mainly fabricated using aromatic polyamide (PA) thin film composites on a polysulfone support and Loeb-Sourirajan-type cellulose acetate (CA) membranes to create desired architecture.

CA membranes exhibit a specific water flux of 1-20 L/m2/day/bar with an average NaCl rejection of > 98%. The advantage of CA membranes is that they are easy-to-make, fairly well priced, and offer excellent stability against mechanical stress and chlorine. However, an inherent weakness of CA membranes is their performance decrease due to changes in pH, temperature, hydrolysis, and fouling.        

reverse osmosis membrane(click image to enlarge)

PA membranes on the other hand exhibit a high flux (20-200 L/m2/day/bar) with a high salt rejection (> 99%) as well as increased stability against a wide range of pH and temperature. Unfortunately, despite having benefits, the extremely low resistance to chlorine and membrane fouling are construed as major obstacles for PA membranes. As a result, PA membranes are rendered uneconomical because of the high cost of pre-treatment steps prior to desalination membranes.

Most current desalination technologies on the market are based on energy-intensive processes such as multi-stage flash distillation (MSF; 35 kWh/m3) or a pressure-driven RO membranes (> 3 kWh/m3 for seawater and < 1 kWh/m3 for brackish water).

While membrane-based technology is more cost-effective than heat-based technology, the high cost for installation, operation, and maintenance are still major constraining factors for general use of membrane technologies in water treatment.

These costs (> 0.5 $/m3 for seawater and 0.2-0.3 $/m3 for brackish water [2]) are higher than the costs of obtaining fresh water from other sources. Furthermore, it has been predicted that current membrane technology is approaching the maximum performance achievable from CA and PA-based materials [3]. Considering that water treatment costs are directly related to the membrane performance, there is an increasing demand for innovative solutions that move beyond the modification of conventional materials, in order to meet scientific and economic requirements.

Aquaporin-embedded biomimetic membrane At Ingenuity Lab in Edmonton, Alberta, Dr. Carlo Montemagno and a team of world-class researchers have been investigating plausible solutions to existing water purification challenges. They are building on Dr. Montemagno’s earlier patented discoveries by using a naturally-existing water channel protein as the functional unit in water purification membranes [4].

Aquaporin-embedded biomimetic membrane

(click image to enlarge)

Aquaporins are water-transport proteins that play an important osmoregulation role in living organisms [5]. These proteins boast exceptionally high water permeability (~ 1010 water molecules/s), high selectivity for pure water molecules, and a low energy cost, which make aquaporin-embedded membrane well suited as an alternative to conventional RO membranes. Unlike synthetic polymeric membranes, which are driven by the high pressure-induced diffusion of water through size selective pores, this technology utilizes the biological osmosis mechanism to control the flow of water in cellular systems at low energy.

In nature, the direction of osmotic water flow is determined by the osmotic pressure difference between compartments, i.e. water flows toward higher osmotic pressure compartment (salty solution or contaminated water). This direction can however be reversed by applying a pressure to the salty solution (i.e., RO).

The principle of RO is based on the semipermeable characteristics of the separating membrane, which allows the transport of only water molecules depending on the direction of osmotic gradient. Therefore, as envisioned in the recent publication

“Recent Progress in Advanced Nanobiological Materials for Energy and Environmental Applications”

the core of Ingenuity Lab’s approach is to control the direction of water flow through aquaporin channels with a minimum level of pressure and to use aquaporin-embedded biomimetic membranes as an alternative to conventional RO membranes.

Ingenuity Lab’s ongoing research efforts Although introduced a decade ago, only recently has the proof-of-concept for aquaporin-based water purification membranes been demonstrated. Their ultimate success depends on improved membrane performance and membrane functionality which is affected by:

1) Activity of aquaporin in the membrane (rate of water transport)

2) Design concept of the protein-incorporated membrane matrix

3) Membrane manufacturability.

Since aquaporin-incorporated membranes are the key component to attaining higher levels of salt rejection and water flux, Ingenuity Lab has two intense research efforts underway.

The first is to improve the quality and properties of the materials used to produce aquaporin-based membranes. Both the production yield and the stability of the aquaporin is being improved through genetic modification. Additionally, new materials are being developed for use as the matrix to house the aquaporin molecules and form stable, biocompatible membranes that provide structural support for the protein and eliminate leakage around the protein. Efficient production of functional aquaporin and biomimetic materials with optimal protein compatibility guarantees the highest level of water purification capacity, which adds maximum economic benefits to the invention.

Ingenuity Lab’s second major research effort focuses on the development of new methods for assembling and fabricating water purification membranes using novel design concepts. The goal of this task is to develop a platform which protects aquaporin from mechanical and chemical stresses, while maintaining functionality, enabling low cost, scalable production.

The work being done at Ingenuity Lab holds great promise for our generation and those to come.  Ingenuity Lab’s water purification membranes will be applied to treat wastewater and seawater at a much lower pressure than current membranes. The low-energy requirement and high water flow rate of aquaporins are essential components to the realization of cost-effective water purification membranes. In addition to enhanced energy efficiency, unconventional manufacturability-driven membrane design contributes to cost-competitiveness, setting the membranes apart from traditional, more expensive, desalination processes.

In a unique approach,  Ingenuity Lab is applying technology and expertise from a variety of disciplines to actively solve some of the world’s most pressing environmental challenges; including here in Alberta, where this technology could be used to reduce the environmental impact of withdrawing bitumen from the oil sands. By reducing the environmental impact of oil sands mining it will allow us to continue to utilize this valuable resource for years to come.

References [1] Kulshreshtha, S. N. A global outlook for water resources to the year 2025. Water Resour. Manag. 1998, 12(3), 167-184. [2] Fritzmann, C.; Löwenberg, J.; Wintgens, T.; Melin T. State-of-the-art of reverse osmosis desalination. Desalination. 2007, 216, 1-76. [3] Elimelech, M.; Phillip, W.A. The future of seawater desalination: energy, technology, and the environment. Science. 2011, 333(6043), 712-717. [4] Montemagno, C.D.; Schmidt, J.J.; Tozzi, S.P. Biomimetic Membranes. U.S. Patent 7,208,089 B2, 24 April 2007. [5] Borgnia, M.; Nielsen, S.; Engel, A.; Agre, P. Cellular and molecular biology of the aquaporin water channels. Annu. Rev. Biochem. 1999, 68, 425–458.

Source: Ingenuity Lab
Read more: Novel water treatment technology surfaces at Ingenuity Lab http://www.nanowerk.com/spotlight/spotid=34964.php#ixzz2xB4hRpTp Follow us: @nanowerk on Twitter

Presented at a meeting of the American Chemical Society. March 16, 2014

1x2 logo sm

DALLAS, March 16, 2014 — Sunlight plus a common titanium pigment might be the secret recipe for ridding pharmaceuticals, pesticides and other potentially harmful pollutants from drinking water. Scientists combined several high-tech components to make an easy-to-use water purifier that could

work with the world’s most basic form of energy, sunlight, in a boon for water purification in rural areas or developing countries.

The talk was one of more than 10,000 presentations at the 247th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society, taking place here through Thursday.

Anne Morrissey, Ph.D., explained that the new technology could someday be incorporated into an easy-to-use consumer product that would remove these stubborn pollutants from drinking water as a final step after it has already been treated with conventional methods.

Her group at Dublin City University in Ireland started with a compound called titanium dioxide (TiO­2), a powder used to whiten paints, paper, toothpaste, food and other products. With the right energy, TiO2 can also act as a catalyst — a molecule that encourages chemical reactions — breaking down unwanted compounds in drinking water like pesticides and pharmaceuticals. Morrissey explained that modifying current water treatment methods to get rid of these potentially harmful species can be costly and energy-intensive, and often, these modifications don’t completely eliminate the pollutants.

But Morrissey said TiO2 is usually only activated by ultraviolet light, which is produced by special bulbs. To access titanium dioxide’s properties with the sun’s light, Morrissey and her group experimented with different shapes of TiO2 that would better absorb visible light. She found that nanotubes about 1,000 times thinner than a human hair were best, but they couldn’t do it on their own.

That’s why she turned to graphene, a material made of sheets of carbon just one atom thick. “Graphene is the magic material, but its use for water treatment hasn’t been fully developed,” she said. “It has great potential.” Morrissey put the TiO2 nanotubes on these graphene sheets. Pollutants stuck to the surface of the graphene as they passed by, allowing TiO2 to get close enough to break them down.

Her research group successfully tested the system on diclofenac, an anti-inflammatory drug notorious for wiping out nearly an entire vulture population in India.

“We’re looking at using the graphene composite in a cartridge for one-step drinking water treatment,” said Morrissey. “You could just buy a cartridge off the shelf and plop it into the pipe where the drinking water comes into your house.” The cartridge system would also ensure that the graphene stays immobilized and does its job without contaminating the clean water.

Morrissey noted, however, that the technology will never be strong enough to completely clean drinking water on its own. Rather, she sees it as a polishing step after traditional water treatment processes to mop up the most insidious pollutants.

That could be especially useful in her home country, where she said many rural communities use small water treatment systems that only supply a few dozen homes. Because they don’t have the infrastructure that large-scale urban treatment plants do, she thinks that a cartridge that could clean with only the sun’s energy could help make their water safer.

Ultimately, Morrissey said there are still many questions to answer before declaring her TiO2-graphene system a success. One of the biggest is making sure that when it breaks down pollutants, it is producing harmless byproducts. She also wants to make sure that the energy required for the system compares favorably to simply using TiO2 with ultraviolet light. But so far, she reported, her design seems to be easier to make and dispose of than other visible-light activated TiO2 purifiers.

The authors wish to acknowledge the financial support of the Marie Curie Initial Training Network funded by the EC FP7 People ProgrammeATWARM (Advanced Technologies for Water Resource Management)Tyndall National Institute, Ireland, for their support through the SFI-funded National Access Programme (NAP407); and the Environmental Protection Agency STRIVE program.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 161,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

1x2 logo smNi3S2/carbon nanotube nano composite as electrode material for hydrogen evolution reaction in alkaline electrolyte and enzyme-free glucose detection.

 

 

Highlights

  • The Ni3S2/CNT nanocomposite can be easily synthesized using hydrothermal method.
  • The HER performance of Ni3S2/CNT nanocomposite is activated by base treatment.
  • The HER activity of nanocomposite is correlated to Ni3S2 morphology on CNTs.
  • Ni3S2 and conductive CNTs impart high HER activity and stability to the catalyst.
  • The composite electrode exhibits high catalytic activity toward glucose oxidation.


Abstract

In this study, the nanocomposite of Ni3S2 and multi-walled carbon nanotubes (MWCNTs) with the high catalytic activities toward hydrogen evolution reaction (HER) and glucose oxidation was synthesized using glucose-assisted hydrothermal method. Ni3S2 nanoparticles with the diameters ranging from 10 to 80 nm were highly dispersed over conductive MWCNT surface.

A series of linear polarization measurements suggested that the HER activity of nanocomposite of Ni3S2 and MWCNTs was increased with decreasing the loading amount of Ni3S2 on MWCNTs and the optimal Ni3S2 loading on MWCNTs was 55 wt%. Furthermore, the immersion of the composite catalyst in a concentrated KOH solution induced the morphological change of the Ni3S2 nanoparticles on MWCNTs, which increases the active surface area of the composite electrode.

As a result, the KOH-treated composite electrode showed a higher HER activity than other electrodes. For example, the value of exchange current density of the KOH-treated composite electrode was ca. 395 times and 1.6 times larger than that of Ni3S2 electrode and as-synthesized composite, respectively. Furthermore, the impedance measurements showed the KOH-treated composite electrode had the smaller charge transfer resistance of the HER than Ni3S2 electrode.

Based on the slopes obtained from Arrhenius curves of the electrodes, the estimated HER activation energy (71.8 kJ/mol) of KOH-treated composite electrode was only one-third of that of the pure Ni3S2 electrode. The high catalytic activity of the KOH-treated composite electrode was stemmed from the synergistic effect of the large active surface area of Ni3S2 nanoparticles and the excellent electrical coupling to the conductive MWCNT network.

More importantly, the current density of KOH-treated composite electrode showed no sign of degradation after the continuous 1000 cycling in a 1 M KOH solution at the temperature of 323 K. On the other hand, the nanocomposite of Ni3S2 and MWCNTs was proposed for the first time as an enzyme-free sensor for glucose.

The Ni3S2 nanoparticles on MWCNTs exhibited high electrocatalytic activity toward glucose oxidation and were insensitive to uric acid and ascorbic acid. Furthermore, the composite electrode exhibited that its catalytic current was linearly dependent on the concentration of glucose in the range from 30 to 500 μM and its sensitivity was as high as 3345 μA/mM.

The present work suggested that the nanocomposite of Ni3S2 and MWCNTs not only served as an inexpensive, highly active and stable electrode material for alkaline water electrolysis, but also showed a great potential application as a highly sensitive and selective biosensor for glucose.


Keywords

  • Nickel sulfide;
  • Carbon nanotubes;
  • Nanocomposite;
  • Electrocatalyst;
  • Hydrogen evolution

1 2 3 4 5 8
Recent Posts

Categories

Search

Nano Enabled Super Capacitors and Batteries for the Future of Energy Storage

Follow Us on Twitter @Genesisnanotech


Could not authenticate you.