A new nano material converts 97% of sunlight into heat

by Hansraj Agrawal | Oct 15, 2023 | Science

Scientists at the Indian Institute of Technology, Bombay, (IIT Bombay) have developed a new material that can convert sunlight into heat energy with unprecedented efficiency.

The material, called nanostructured hard-carbon florets (NCFs), is made by depositing carbon onto a substrate of amorphous dendritic fibrous nanosilica (DFNS), using a technique called chemical vapour deposition. The resulting material absorbs more than 97 per cent of the ultraviolet, visible and infrared light, and converts this them into thermal energy. The heat produced can be transferred to either air or water for practical applications.

The researchers have demonstrated that hollow copper tubes coated with NCFs can heat the air flown through them to over 346K. They have also demonstrated its ability to convert water into vapour with an efficiency of 186 per cent, the highest ever recorded. NCFs have outperformed all other competition when it comes to efficient conversion of the sun’s energy. “One metre square of NCF coatings converts 5 litres of water in an hour, that is at least 5 times better than commercial solar stills,” says Prof C Subramaniam.

What’s unique?

To efficiently harness solar thermal energy and convert it to usable heat, a material should possess two essential yet somewhat conflicting qualities. First, it should be able to effectively transform a significant portion of incoming light particles, known as photons, into heat in a process called photon thermalisation. Second, it must retain this heat without losing it through thermal conductivity and radiation.

When incoming photons strike a material, they set the material’s atoms into motion, creating oscillations called phonons, which then propagate through the material, spreading the heat. Materials with high phonon thermal conductivity transmit heat quickly but also tend to lose a significant portion of the absorbed heat. An ideal heat absorber should exhibit both high photon thermalisation and low phonon thermal conductivity. This is precisely what the NCFs offer.

The nanoparticle structure of NCFs resemble marigold flowers consisting of interconnected small carbon cones. This unique structure enables two crucial features: strong phonon activation when photons hit the material and low phonon thermal conductivity.

“NCF has ordered structure in short-range (shorter lengths) and disordered structure in long-range (longer distances). So, when light energy is absorbed by NCF, this short-range ordering causes strong phonon activation (oscillations in the ordered lattice). Anything that has strong phonons should also help in conducting the energy away. However, in NCF, the long-range disorder acts to scatter these phonon-waves. Therefore, the phonon thermal conductivity is low,” explains Subramaniam.

The NCF is highly efficient in converting sunlight into heat energy. The materials used to make NCFs are readily available, and the manufacturing technique easily scalable, making large-scale manufacturing of these florets commercially inexpensive. Once manufactured, NCFs can be spray-painted onto almost any surface, reducing the cost of application and maintenance as well.

Besting the best

According to the Ministry of New and Renewable Energy, an estimated 40 million or 2.5 per cent of households in India already use solar water heaters. However, commonly available solar heat absorbers are often expensive, bulky and potentially harmful to the environment. “Conventional coatings and materials for solar-thermal conversion are based on chromium or nickel films. While anodised chromium is a heavy metal and toxic to the environment, both Cr and Ni-films exhibit solar-thermal conversion efficiencies ranging between 60-70 per cent. In fact, the best commercial ones in the market operate at 70 per cent solar-thermal conversion efficiencies,” says Dr Ananya Sah, the lead author of the study that developed the NCF. The NCFs on the other hand, made primarily of carbon, are inexpensive to produce, environment-friendly and easy to use.

The team has already begun the process of commercialising the product by setting up a company at the Society for Innovation and Entrepreneurship (SINE) at IIT Bombay. The company will focus on scaling up the manufacturing of NCFs and developing NCF-based devices required for water heating and space-heating.

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IISc’s Materials Research Centre engineers enzyme mimetic to break down waste under sunlight

by Hansraj Agrawal | Oct 4, 2023 | Science

Scientists at the Indian Institute of Science’s Materials Research Centre (MRC) have pioneered the development of a novel nanozyme capable of effectively degrading toxic chemicals in industrial wastewater under sunlight.

Enzymes, vital for catalysing biological reactions, have long been challenged by issues such as sensitivity to damage, complex production processes, high costs, and impractical recycling.

Mass-producing natural enzymes, like laccase, extracted from fungi, are both costly and time-consuming, and their temperature-sensitive nature necessitates storage at extremely low temperatures.

Innovation

In response, the MRC research team crafted a platinum-based nanozyme, NanoPtA, that mimics the function of natural oxidases. This innovative nanozyme can be converted into a powdered form for industrial applications, is highly specific in substrate breakdown and remains robust across varying pH and temperature conditions.

In experimental trials, NanoPtA demonstrated remarkable efficiency in degrading common water pollutants like phenols and dyes within minutes when exposed to sunlight.

Furthermore, it exhibited outstanding stability, maintaining its effectiveness for up to 75 days at room temperature and remaining viable for over six months under similar conditions, explained Subinoy Rana, Assistant Professor at MRC and corresponding author of the paper published in Nanoscale.

Beyond wastewater treatment, the nanozyme also holds promise in healthcare applications. Researchers tested its ability to oxidise neurotransmitters such as dopamine and adrenaline, offering a potential diagnostic tool for neurological and neurodegenerative diseases, including Parkinson’s, Alzheimer’s and cardiac arrest, said Rohit Kapila, first author and PhD student at MRC, IISc.

Looking ahead, the team aims to patent this breakthrough nanozyme, believing it can be readily produced on an industrial scale. They are also exploring cost-effective alternatives to platinum for the nanozyme complex.

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Cancer killing nanoparticles

by Hansraj Agrawal | Oct 1, 2023 | Science

You can kill a cancer cell by sneaking nanoparticles inside it, or in its vicinity. When light shines on the nanoparticles, they absorb the light energy and give it back as heat — the heat kills the cancer cells. This mechanism is well understood, but the challenges are in designing a nanoparticle that is good at absorbing light and emitting heat, and is also small enough to crawl into the cancer cell.

Now a team of researchers led by Prof Jaya Prakash, Department of Instrumentation and Applied Physics, IISc, Bengaluru, has developed a hybrid nanoparticle of gold and copper sulphide for this purpose. Copper sulphide pinpoints the cancer cells and the gold destroys them, when light hits the nanoparticles.

A big challenge was to make the nanoparticle tiny enough to sneak into the cancer cell. To overcome this, the researchers used a novel ‘reduction’ method, using Tannic acid and sodium citrate to form gold nanoseeds, which were then deposited on a copper sulphide surface. The nanoparticle they got was 8 nm in size.

“The researchers believe that the nanoparticles’ small size would also allow them to leave the human body naturally without accumulating, although extensive studies have to be carried out to determine if they are safe to use inside the human body,” says a write-up in IISc’s in-house publication, Kernel.

“The researchers have tested their nanoparticles on lung cancer and cervical cancer cell lines in the lab. They now plan to take the results forward for clinical development,” Kernel says.

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Electric-solar hybrid oven

by Hansraj Agrawal | Oct 1, 2023 | Science

A team led by Prasant Saini of the IIT Mandi has developed an electric-solar hybrid oven. The Solar Thermal-Electric Powered Cooking Oven (STEPCO) can cook food in solar, electric or hybrid mode. The device, which has oven, toaster and griller features, costs around ₹12,000; the inventors say that the payback period is 2.3 years in hybrid mode and 3.7 years in only solar mode. It is good for a variety of foods, including cakes and pizza.

“The STEPCO oven demonstrated significantly higher energy efficiency in hybrid mode — 63 per cent — compared with 35 per cent in electric mode and 4 per cent in solar mode,” says a paper on the device, published in Energy.

The main heating chamber has three sides of aluminium alloy; the other three are of toughened glass. The three-glass sides are the top, bottom, and door (front side). The top and bottom surfaces of the heating chamber are made of transparent, toughened glass to allow entry of concentrated solar radiation. This ensures sufficient solar thermal heating of the oven when operating in solar or hybrid mode. “The heating elements present in the oven are responsible for providing electrical heating. They are used only when operating STEPCO in electric/hybrid mode. A microcontroller-based smart control system controls the operation of these elements,” the paper says.

Additionally, the STEPCO oven has the environmental benefit of emitting very little CO2 during the cooking process when used in hybrid mode and zero CO2 emissions when used in solar mode.

As many as 2.8 billion people did not have access to clean cooking in 2015, and this number is expected to decline only to 2.3 billion by 2030.

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Unveiling the secrets of the universe in radio waves

by Hansraj Agrawal | Oct 1, 2023 | Science

In 2018, Thoughtworks, a consultancy specialising in software and digital transformation, revealed a two-year collaboration with the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune. Their joint effort was aimed to create, assess, and implement automated data processing software tailored for the MeerKAT radio telescope. Now the efforts have borne fruit.

The MeerKAT Radio Telescope has gained prominence in recent years. Unlike optical telescopes, which capture signals only at night, MeerKAT, a radio telescope, receives signals throughtout the day and night.

Launched in 2018, MeerKAT is operated by the South African Radio Astronomy Observatory (SARAO), a national research facility funded by the Government of South Africa. MeerKAT was later integrated into the global Square Kilometre Array (SKA) initiative, which entails cooperation among numerous nations.

Comprising 64 antennas, MeerKAT plays a pivotal role as a precursor to the SKA, set to be the world’s most sensitive and powerful radio telescope, spanning two continents in the Southern Hemisphere — South Africa and Australia.

MeerKAT was originally named the Karoo Array Telescope (KAT) with 20 receptors. It was later renamed “MeerKAT” when the South African government expanded the budget to build 64 receptors.

The radio telescope showed promising results in February 2023 when scientists using the MeerKAT made a surprising discovery while studying a distant galaxy. They found large hydrogen atoms known as Rydberg atoms, which had never been observed in a distant galaxy before. (A Rydberg atom refers to an atom with an electron in a high energy state). These atoms appear to be scattered throughout the galaxy in ionised interstellar gas clouds. This discovery could provide insights into interstellar gas in galaxies and the formation of Rydberg atoms in space.

ThoughtWorks’ involvement revolves around the creation of an automated radio telescope image processing pipeline(ARTIP). “We have been collaborating with Dr Neeraj Gupta from IUCAA, and he put in a proposal to observe the sky for gas absorptions. This survey is called the MeerKAT Absorption Line Survey,” says Chhaya Dhanani, Portfolio Head Engineering for Research, Thoughtworks. MALS is now studying how active black holes interact with cold gas in galaxies, providing insights into black hole fuelling and galaxy evolution through absorption lines.

Dhanani says the ARTIP pipeline is completely automated. “In the past, processing a 1 TB dataset manually would take several months and could lead to errors. With automation, we can analyse such data in just 30 minutes to an hour, ensuring accurate results,” she adds. This has also led to critical discoveries. It helped identify a “OH radical” outside Milky Way galaxy. The finding hints at the possibility of finding water (H₂O) in outer space.

However, there is a long way to go. “The scientist has an observation time of about 1,600 hours (about 2 months). We are expecting our data size of around 1.7 beta byte to come along, and the pipeline is going to be used to process it,” says Dhanani.

Radio astronomy, a branch of astronomy focused on studying the sky using radio frequencies, involves handling large volumes of data. This presents a hurdle for radio astronomers as it demands substantial data processing and analysis to convey scientific findings effectively. “From a scientific perspective, it attempts to answer many theories around the origin of life and cosmology, and from a technological perspective, it has given rise to a lot of innovation in terms of high-end computers,” adds Dhanani.

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Making space on earth, for life on Mars

by Hansraj Agrawal | Oct 1, 2023 | Science

What does a human need to live on the Moon or Mars someday apart from rockets and stuff?

Practice!

For astronauts, or for those who want to pretend to be one, ‘spaces’ are being built on earth where conditions approximating the intended destination (Moon, Mars or a space station) are created. While you may not have conditions like weightlessness in these dwelling units, there will be plenty of make-believe features to fool you into trusting that you’re very far from home — like the ‘Mars-inside-a-tent’, pictured here.

Also Read: NASA plans ChatGPT-like AI assistant for astronauts

These ‘analogue space facilities’ — there are around 20 of them — are not for fun. While training astronauts, they also help researchers study things like how people behave in confined isolation in hostile and unpleasant settings. Studies even look at how their gut microbiome changes, stress levels and immune responses, from samples of spit, urine, blood and faecal matter.

Some of these analogue facilities are in desolate places on earth—one 1,200 sq ft analogue station is on a mountain desert in Hawaii, 8,200 ft above sea level, which resembles the Martian landscape. To give a real, out-of-the-world feel, dwellers sometimes communicate on the phone that sends and receives signals with a 20-minute delay; they eat frozen foods and compost their own poop. Tough life indeed. One lady volunteer, who lived in confinement in a Russian analogue facility for 8 months, had difficulty in re-integration, upon coming out, an article in Undark notes.

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