IIT Bombay uses mango leaves to make fluorescent graphene quantum dots 


The quantum dots can be used for bioimaging and measuring intracellular temperature

Using mango leaves to synthesise fluorescent graphene quantum dots (nanocrystals of semiconductor material), researchers from the Indian Institute of Technology (IIT) Bombay have been able to produce cheap probes for bioimaging and for intracellular temperature sensing.

Unlike the currently used dyes, quantum dots synthesised from mango leaves are biocompatible, have excellent photostability and show no cellular toxicity. The results were published in the journal ACS Sustainable Chemistry & Engineering.

Green route

To synthesise quantum dots, the researchers cut mango leaves into tiny pieces and froze them using liquid nitrogen. The frozen leaves were crushed into powder and dipped in alcohol. The extract was centrifuged and the supernatant evaporated in an evaporator and then heated in a microwave for five minutes to get a fine powder.

Using mice fibroblast cells, a team led by Rohit Srivastava from the Department of Biosciences and Bioengineering at IIT Bombay evaluated the potential of quantum dots for bioimaging and temperature-sensing applications. In mice cell in vitro studies, the graphene quantum dots were able to get into the cells easily without destroying the integrity, viability and multiplication of the cells. The quantum dots get into the cytoplasm of the cell.

The quantum dots, 2-8 nanometre in size, were found to emit red luminescence when excited by UV light. “Even when the excitation wavelength was 300-500 nanometre, the emission from the quantum dots was at 680 nanometre. The quantum dots exhibited excitation-independent emission,” says Mukeshchand Thakur from the Department of Biosciences and Bioengineering at IIT Bombay, one of the authors of the paper.

The quantum dots have smaller and larger fluorescent units. When the excitation is at lower wavelength, the smaller units transfer energy to the larger units and there is red emission. And when the excitation is at higher wavelength, the red emission comes directly from the larger units, thus remaining excitation-independent.

The quantum dots that Mukesh Kumar Kumawat (left) and Rohit Srivastava have fabricated can be used for bioimaging.

Nanothermometer

“Since the quantum dots get into the cytoplasm of the cell, the graphene quantum dots can be used for cell cytoplasm labelling applications,” says Mukesh Kumar Kumawat from the Department of Biosciences and Bioengineering, IIT Bombay and the first author of the paper.

The quantum dots found inside the cells showed intense florescence at 25 degree C. As the temperature rises to 45 degree C, the intensity of fluorescence tends to decrease.

As a result, the researchers found up to 95% reduction in fluorescence intensity when the temperature was increased by 20 degree C. “So quantum dots can be used for detecting temperature variation in the intracellular environment,” says Thakur.

“The graphene quantum dots can be used as a nanothermometre. Besides measuring intracellular temperature increase, they can be used for measuring temperature increase in cancer cells and when there is inflammation,” says Prof. Srivastava. “We are seeing interest by companies making imaging probes. There is also interest to use it as a temperature probe.”

“Since the quantum dots emit red light, they can be used for making organic light-emitting diodes as well,” says Kumawat.

Source:thehindu.com

Scientists have invented a graphene-based sieve that turns seawater into drinking water.


Researchers have achieved a major turning point in the quest for efficient desalination by announcing the invention of a graphene-oxide membrane that sieves salt right out of seawater.

At this stage, the technique is still limited to the lab, but it’s a demonstration of how we could one day quickly and easily turn one of our most abundant resources, seawater, into one of our most scarce – clean drinking water.

 

The team, led by Rahul Nair from the University of Manchester in the UK, has shown that the sieve can efficiently filter out salts, and now the next step is to test this against existing desalination membranes.

“Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology,” says Nair.

“This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.”

Graphene-oxide membranes have long been considered a promising candidate for filtration and desalination, but although many teams have developed membranes that could sieve large particles out of water, getting rid of salt requires even smaller sieves that scientists have struggled to create.

One big issue is that, when graphene-oxide membranes are immersed in water, they swell up, allowing salt particles to flow through the engorged pores.

The Manchester team overcame this by building walls of epoxy resin on either side of the graphene oxide membrane, stopping it from swelling up in water.

 This allowed them to precisely control the pore size in the membrane, creating holes tiny enough to filter out all common salts from seawater.

The key to this is the fact that when common salts are dissolved in water, they form a ‘shell’ of water molecules around themselves.

“Water molecules can go through individually, but sodium chloride cannot. It always needs the help of the water molecules,” Nair told Paul Rincon from the BBC.

“The size of the shell of water around the salt is larger than the channel size, so it cannot go through.”

Not only did this leave seawater fresh to drink, it also made the water molecules flow way faster through the membrane barrier, which is perfect for use in desalination.

“When the capillary size is around one nanometre, which is very close to the size of the water molecule, those molecules form a nice interconnected arrangement like a train,” Nair explained to Rincon.

“That makes the movement of water faster: if you push harder on one side, the molecules all move on the other side because of the hydrogen bonds between them. You can only get that situation if the channel size is very small.”

There are already several major desalination plants around the world using polymer-based membranes to filter out salt, but the process is still largely inefficient and expensive, so finding a way to make it quicker, cheaper, and easier is a huge goal for researchers.

Thanks to climate change, seawater is something we’re going to have plenty of in the future – Greenland’s coastal ice caps which have already passed the point of no return are predicted to increase sea levels by around 3.8 cm (1.5 inches) by 2100, and if the entire Greenland Ice Sheet melts, future generations will be facing oceans up to 7.3 metres (24 feet) higher.

But at the same time, clean drinking water is still incredibly hard to come by in many parts of the world – the UN predicts that by 2025, 14 percent of the world’s population will encounter water scarcity. And many of those countries won’t be able to afford large-scale desalination plants.

The researchers are now hoping that the graphene-based sieve might be as effective as large plants on the small scale, so it’s easier to roll out.

Graphene oxide is also a lot easier and cheaper to make in the lab than single-layers of graphene, which means the technology will be affordable and easy to produce.

“The selective separation of water molecules from ions by physical restriction of interlayer spacing opens the door to the synthesis of inexpensive membranes for desalination,” Ram Devanathan from the Pacific Northwest National Laboratory, who wasn’t involved in the research, wrote in an accompanyingNature News and Views article.

“The ultimate goal is to create a filtration device that will produce potable water from seawater or wastewater with minimal energy input.”

He added that the next step will be to test how durable the membranes are when used over long periods of time, and how often they need to be replaced.

Source: Nature Nanotechnology.

Luminescence switchable carbon nanodots follow intracellular trafficking and drug delivery


Tiny carbon dots have, for the first time, been applied to intracellular imaging and tracking of drug delivery involving various optical and vibrational spectroscopic-based techniques such as fluorescence, Raman, and hyperspectral imaging. Researchers have demonstrated, for the first time, that photo luminescent carbon nanoparticles can exhibit reversible switching of their optical properties in cancer cells.

‘Caged’ non-fluorescent carbon dot enters the cancer cell, loses its caging and lights up.

Tiny carbon dots have, for the first time, been applied to intracellular imaging and tracking of drug delivery involving various optical and vibrational spectroscopic-based techniques such as fluorescence, Raman, and hyperspectral imaging. Researchers from the University of Illinois at Urbana-Champaign have demonstrated, for the first time, that photo luminescent carbon nanoparticles can exhibit reversible switching of their optical properties in cancer cells.

“One of the major advantages of these agents are their strong intrinsic optical sensitivity without the need for any additional dye/fluorophore and with no photo-bleaching issues associated with it,” explained Dipanjan Pan, an assistant professor of bioengineering and the leader of the study. “Using some elegant nanoscale surface chemistry, we created a molecular ‘masking’ pathway to turn off the fluorescence and then selectively remove the mask leading to regaining the brightness.

“Using carbon dots for illuminating human cells is not new. In fact, my laboratories, and several other groups around world, have shown that these tiny dots represent a unique class of luminescent materials with excellent biocompatibility, degradability, and relatively facile access to large-scale synthesis in comparison to other popular luminescent materials such as quantum dots,” added Pan.

And, the entire process of is highly controlled and can be observed in living cells as they reported in the group’s study, “Macromolecularly ‘Caged’ Carbon Nanoparticles for Intracellular Trafficking via Switchable Photoluminescence,” appearing in the Journal of the American Chemical Society.

“We can apply this technique for intracellular trafficking by means of switchable photo-luminescence in mammalian cells in vitro, wherein the endocytic membrane-abundant anionic amphiphilic molecules participates in the ‘de-caging’ process,” stated Pan. “The carbon dots, each measuring less than 50 nanometers in diameter, are derived from agave nectar and are highly luminescent. The in situ nanoscale chemical exchange further probed into the mechanistic understanding of the origin of carbon luminescence and indicated that it is primarily a surface phenomenon.

“This can be reversibly turned on and off by a simple counter-ionic nanoscale chemistry,” Pan said. “These results can become the basis for new and interesting designs for carbon-based materials for intracellular imaging probing cellular function and to study other biological processes.”

Has Nanotechnology Already Reached Its Limit?


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What’s the Latest Development?

Professor Mike Kelly at Cambridge University’s Centre for Advanced Photonics and Electronics has stunned a budding nanotechnology industry by saying that structures with a diameter of three nanometres or less cannot be mass-produced. “This statement raises a major question concerning the billions of dollars that are poured into nanotechnology each year in the hope that the latest technology developed in the lab can make the transition to a manufactured product on the market,” according to Phys Org.

What’s the Big Idea?

Nanotechnology is built on the ability to control and manipulate matter at the atomic and molecular level and has already had far reaching applications including helping drugs to be delivered into patients’ bodies, improving food packaging and increasing the efficiency of solar panels. It is a budding industry that, given recent success in the laboratory—the 2010 Nobel Prize was given to two scientists for their experiments with graphene, an extremely tough one-atom-think nanostructure—holds large commercial potential.

Acne spot treatment: Latest in nanotechnology, transdermal drug delivery to take on an old problem


Acne, a scourge of adolescence, may be about to meet its ultra high-tech match. By using a combination of ultrasound, gold-covered particles and lasers, researchers have developed a targeted therapy that could potentially lessen the frequency and intensity of breakouts, relieving acne sufferers the discomfort and stress of dealing with severe and recurring pimples.

The particles are delivered into the sebaceous gland by the ultrasound, and are heated by the laser. The heat deactivates the gland.

Acne, a scourge of adolescence, may be about to meet its ultra high-tech match. By using a combination of ultrasound, gold-covered particles and lasers, researchers from UC Santa Barbara and the private medical device company Sebacia have developed a targeted therapy that could potentially lessen the frequency and intensity of breakouts, relieving acne sufferers the discomfort and stress of dealing with severe and recurring pimples.

“Through this unique collaboration, we have essentially established the foundation of a novel therapy,” said Samir Mitragotri, professor of chemical engineering at UCSB.

Pimples form when follicles get blocked by sebum, an oily, waxy substance secreted by sebaceous glands located adjacent to the follicle. Excretion of sebum is a natural process and functions to lubricate and waterproof the skin. Occasionally, however, the openings of the follicles (pores) get blocked, typically by bits of hair, skin, dirt or other debris mixed in with the sebum. Overproduction of sebum is also a problem, which can be caused by hormones or medications. Changes in the skin, such as its thickening during puberty, can also contribute to follicle blockage. Whatever the cause, the accumulating sebum harbors bacteria, which results in the inflammation and local infection that we call acne.

The new technology builds on Mitragotri’s specialties in targeted therapy and transdermal drug delivery. Using low-frequency ultrasound, the therapy pushes gold-coated silica particles through the follicle into the sebaceous glands. Postdoctoral research associate Byeong Hee Hwang, now an assistant professor at Incheon National University, conducted research at UCSB.

“The unique thing about these particles is that when you shine a laser on them, they efficiently convert light into heat via a process called surface plasmon resonance,” said Mitragotri. This also marks the first time ultrasound, which has been proved for years to deliver drugs through the skin, has been used to deliver the particles into humans.

These silica and gold particles are exceedingly tiny — about a hundredth of the width of a human hair — but they are key to the therapy. Once the particles are deposited in the target areas, lasers are aimed at them and, because the gold shells are designed specifically to interact with the near-infrared wavelengths of the lasers, the light becomes heat. The heated particles essentially cause deactivation of the sebaceous glands. The sebum, pore-blocking substances and particles are excreted normally.

“If you deactivate these overproducing glands, you’re basically treating the root cause of the acne,” said Mitragotri.

According to the research, which is published in the Journal of Controlled Release, this protocol would have several benefits over conventional treatments. Called selective photothermolysis, the method does not irritate or dry the skin’s surface. In addition, it poses no risk of resistance or long-term side effects that can occur with antibiotics or other systemic treatments.

“It’s highly local but highly potent as well,” Mitragotri said of the treatment. “I think this would be beneficial in addressing the concerns regarding other, conventional treatments.” According to Mitragotri, this photothermolysis method is particularly suited to patients with advanced, severe or difficult-to-treat acne. The research has gone from concept to clinical trials in a relatively short amount of time. However, other more long-term elements of this therapy have yet to be studied, such as the extent of follicular damage, if any; what the most effective and beneficial parameters of this treatment may be; and what contraindications exist.

Nanotechnology Could Cure Teenage Acne Forever


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Scientists at UC Santa Barbara have created the most high-tech solution to teenage anxiety yet: a treatment for acne that uses a combination of ultrasound, gold-covered nanoparticles, and lasers.

The research is unique because it has created what amounts to a therapeutic regimen that works in three distinct steps. And rather than treating the symptoms of acne, like medications that can dry the face and cause extreme sensitivity to sunlight, the nanotechnology treatment attacks acne at its source.

First, golden nanoparticles, whose width is less than one-hundredth that of a human hair, are applied to the skin. Then, ultrasound pushes the particles through the hair follicle into the sebaceous gland, which releases the oily substance responsible for causing acne. Finally, a laser is shined on the skin that turns the gold particles into heat, disabling the glands

Published in the Journal of Controlled Release, researchers explain that the treatment would not cause the skin to dry out since the blocking of follicles would simply be prevented:

“Called selective photothermolysis, the method does not irritate or dry the skin’s surface. In addition, it poses no risk of resistance or long-term side effects that can occur with antibiotics or other systemic treatments.”

The extremely small size of the golden particles that penetrate hair follicles is the key to the treatment, an advance brought about by the development of nanotechnology, or the ability to control physical elements at the nanoscale. The future for this technology is promising, particularly regarding the treatment of medical conditions located in the brain.

An obstacle called the blood-brain barrier currently prevents most medications from treating the brain directly, but nanotechnology can overcome those obstacles. More interesting still is the technology’s potential to aid learning by carrying encoded information directly to memory centers in the brain. It’s a technology currently beyond the horizon, to be sure, but Nicholas Negroponte explains how it would work in his Big Think interview:

“The best way to interact with the brain is from the inside, from the bloodstream. Because if you inject tiny robots into the bloodstream, they can get very close to all the cells and nerves and things in your brain, really close. So if you want to input information or read information, you do it through the bloodstream. So by extension … you could in theory load Shakespeare into your bloodstream and as the little robots get to the various parts of the brain, they deposit little pieces of Shakespeare or little pieces of French if you want to learn how to speak French.”

MIT Freezes Water At Boiling Point


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This photo shows a glaciologist removing a core of ice to study the chemical make-up of its body dating back to 1840, in Law Dome Camp, Antartica, 1993. The 2016 MIT study in question happened at a nano-scale – so it’ll be a while (or never) before they c

Quick, what temperature does water boil or freeze at? You probably know this like the back of your hand, 100 and 0 degrees Celsius or 212 and 32 Fahrenheit. Well, now we can freeze water above the boiling point. If you feel like your head’s about to explode with that image, don’t worry. We’ll explain.

It is known to anybody who is familiar with the laws of pressure, or who has tried to cook in the mountains, that the boiling and freezing points of water change when the water is exposed to differing pressures. Normally this effect is small, and only has causes differences of a few degrees. Researchers at MIT found that if water is placed inside a tiny enough space, a space only slightly larger than the water molecules themselves, then the freezing point can be raised to above its boiling point. This is done by means of carbon nanotubes, small straw-shaped structures that are the workhorse of nanotech.

The team of researchers published their findings in the journal Nature Nanotechnology, and include Michael Strano, Kumar Agrawal, Steven Shimizu, Lee Drahushuk, and Daniel Kilcoyne among other partners and assistants. Dr. Strano is especially excited by the results, and remarks on how unexpected they are:

The effect is much greater than anyone had anticipated,” he says. The effects were also in an unexpected direction; the researchers had anticipated that the freezing point would go down.

But, what use could this possibly have, other than just being a curiosity? More than you might suppose. Because of the high freezing point, the technology could be used to make ice wires, taking advantage of the extremely high conductivity of water and the stability of the ice at room temperature. Dr. Strano mentioned that application specifically, “This gives us very stable water wires, at room temperature.”  Nanotechnology is a new field, with many possible applications, ranging from computers, to medicine of all kinds, and even to facial care.

There is still a great deal about this process that remains unknown. Chief among them is how the water even gets into the tubes; the researches set the water in place for this experiment, but carbon nanotubes are considered to be water repellent, and the entry of the water in the tubes is difficult to explain logistically. Dr. Strano also notes that the word “ice” is too precise to use to describe the water in the tubes. While it is solid, it may not have the crystalline structure of ice at the molecular level.

What brave new world do we live in, where water can freeze above 100 degrees? One where nanotech is king? Or is nanotech past its prime already? This discovery is new, and further research is needed, but what is certain is that exciting developments await.

Nanotechnology Accelerates Green Energy Production


Nanotechnology is a field that’s receiving a lot of attention at the moment as scientists learn more every day about the benefits it can bring to both the environment and our health. There are various ways in which nanotechnology has proved itself useful including in developing enhanced solar cells and more efficient rechargeable batteries, and in saving raw materials and energy.

When it comes to nanotechnology, even the smallest achievements make huge differences, and on November 23, 2016, future technologies were presented to the international congress as part of the “Next Generation Solar Energy Meets Nanotechnology.” Out of the ten projects, three of them were located in Wurzburg and are explained in a little more detail below:

  • Eco-friendly inks for organic solar cells: Over at the University of Erlangen-Nuremberg, Professors Vladimir Dyakonov and Christoph Brabec have created eco-friendly photovoltaic inks using nanomaterials and have developed a new simulation process at the same time. Dyakonov explains, “They allow us to predict which combinations of solvents and materials are suitable for the eco-friendly production of organic solar cells.”
  • Nanodiamonds for ultra-fast electrical storage: If we want to have powerful, yet highly efficient electric vehicles then we need some way of storing the energy as a standard battery couldn’t handle it. Supercapacitors are great regarding acting as an efficient energy storage system. But, because their energy density is so low they need to be quite large in order to deliver any reasonable amount of energy. However, further work is being done in this area currently, and progress is promising.  Professor Anke Kruger, head of the project, says “Based on these findings, it is now possible to build application-oriented energy stores and test their applicability.”
  • Increased storage capacity of hybrid capacitors: Better energy storage systems were also the focus of Professor Gerhard Sextl and his team’s project. Their hybrid capacitors can store more energy due to the embedded lithium ions and can do it quickly through the use of a supercapacitor. Sextl says, “We have managed to develop a material that combines the advantages of both systems. This has brought us one step closer to implementing a new, fast and reliable storage concept.”

Next Generation Carbon Nanotube Computer Memory is on the Way to Take on Memory Market


Founded back in 2001, and most well known for being pioneers in semiconductors and nanotechnology, Nantero is making the headlines again as they secure $21 million for their next big venture. The nanotech company has set out to develop a new type of computer memory that’s stronger than steel but less dense than aluminum.

In the fifteen years Nantero has been in operation, it’s managed to secure $110 million in funding. With this new round of funding the team at the nanotech company is looking to get their lead product, NRAM (non-volatile random-access memory), out to a host of new customers including Fujitsu Semiconductor and Mie Fujitsu Semiconductor as well as introduce other products into the market too. Much of the new funding came from Globespan Capital Partners, with some anonymous new and existing investors too. Some of the company’s previous investors include Harris & Harris Group, Draper Fisher Jurvetson, and CRV.

This new type of technology is all set to replace flash memory and dynamic random-access memory (DRAM). It’s got better storage capabilities and better density and speed than anything that’s currently on the market, and sales are expected to take off quite quickly. The chips have much better thermal and electrical conductivity properties than any other material as are made using carbon nanotubes. Greg Schmergel, co-founder and CEO of Nantero said, “With this additional funding, we will be able to help these existing customers speed their time to market while also supporting the many other companies that have approached us about using Nantero NRAM in their next generation products.”

Revolutionizing the World with Genetic Material Computers


A new nanostructure has been created by researchers for conducting electricity using DNA and gold plating. The new nanostructure has the potential to be used for future electronics after improvements. These DNA origami nanostructures are fascinating. Using DNA as construction material capable of holding scar folds of molecules and atoms has been a huge step for modern nanostructures.

Scientists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Paderborn University recently developed gold-platted nanowires. As published in the journal Langmuir, the gold plated nanowires independently assemble themselves from single DNA strings.

Artur Erbe from the institute of Icon Beam Physics and Material Research explained that nanowires are able to conduct electricity because of their gold-platting. Two electrical contacts connected the Nano-sized structures. What is even more intriguing is the use of modified DNA strings. These were used as stable double strands combined through their base pairs. Thus, they allowed structures to independently take any desired form. Therefore, complex structures were developed.

Credits: B. Teschome, A. Erbe, et al.
According to Erbe, using this approach (which resembles Japanese paper folding technic origami hence the name DNA-origami) will allow the creation of tiny patterns. The ‘top down’ method i.e. developing Nano sockets using base material that is chiseled until desired structure is formed. The new ‘bottom up’ method is set to change the usual method of making these electric components.

However, there is a stumbling block. Erbe pointed out that “Genetic matter doesn’t conduct a current particularly well.” Furthermore, conductive materials need better melding. Not to mention the use of cheaper standard wire coating and not gold. Overall, this is a promising research. If successful, this Nanowire technology could become the future of electronics.

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